VAPOR COMPRESSION SYSTEMS INCLUDING LIQUID REFRIGERANT ATOMIZER, AND METHODS OF OPERATING AND CONTROLLING THE SAME

Information

  • Patent Application
  • 20240328690
  • Publication Number
    20240328690
  • Date Filed
    April 03, 2024
    10 months ago
  • Date Published
    October 03, 2024
    4 months ago
Abstract
A vapor compression system includes a compressor including a compression stage for compressing a working fluid, a first heat exchanger downstream from the compressor that receives and cools the working fluid, a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid, and an accumulator positioned between the second heat exchanger and the compression stage. The accumulator defines an interior volume for containing a vapor phase and a liquid phase of the working fluid, and the accumulator includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the accumulator and flow towards the compression stage. The accumulator atomizes the liquid phase of the working fluid into droplets and introduces the droplets into the vapor phase of the working fluid exiting the accumulator.
Description
FIELD

The field is vapor compression systems, and more specifically, vapor compression systems including an atomizer for controlled introduction of liquid phase working fluid into a low-pressure vapor phase working fluid stream.


BACKGROUND

Vapor compression systems are widely used in climate control applications to provide heat pump, refrigeration, and/or air conditioning capabilities. A typical vapor compression system includes a fluid circuit having a first heat exchanger (e.g., a condenser that changes a phase of refrigerant from gas/vapor phase to a liquid), a second heat exchanger (e.g., evaporator that changes of a phase of refrigerant from liquid to gas/vapor phase), an expansion device disposed between the first and second heat exchangers, and a compressor that operates to circulate and pressurize a gas/vapor phase working fluid (and optional lubricant oil) between the first and second heat exchangers (e.g., condenser and evaporator). The compressor is typically a mechanical compressor that serves to pressurize the working fluid, which can be subsequently condensed and evaporated as it is circulated within the system to transfer heat into or out of the system.


The working fluid in many vapor compression systems is a refrigerant capable of undergoing the requisite phase changes of the vapor compression cycle. A challenge of vapor compression technology is lowering the impact of the refrigerant on the environment. Recently, new lower global warming potential refrigerants (GWP) have been introduced. The new low GWP refrigerant (especially the blends) may introduce various challenges on the system that may need to be mitigated. Some of the potential challenges, for example, include: (1) that the newer refrigerants typically have higher discharge temperatures; (2) the sub-150 GWP options (e.g., R454C, R455A, R457A, R468A) have higher glide than R410A, and some blends have an overweighted portion of the glide in the last 5-10% of the phase change region; (3) the sub-150 GWP options (e.g., R454C, R455A, R457A, R468A) have a lower density than R410A, and R1234ze is a lower density than R134a. The portion of the evaporator required to perform the superheating function with the new refrigerant may be increased with the new refrigerant driving a lower evaporator performance; and the natural option CO2 has a higher discharge temperature because it is supercritical at discharge.


Another challenge of vapor compression technology is that it only takes a few milliseconds for vapor to be compressed and passed across the compressor. There is little time (or area) for the gas to exchange the heat with the environment. For this reason, the compression process is assumed to be adiabatic. From a thermodynamic perspective, however, isothermal (constant temperature) compression could be as much as about 30% more efficient than adiabatic compression.


A need exists for improvements in vapor compression technology that overcome the above-described technical challenges in a cost-effective manner and limit, or even prevent, negative environmental impact, increase compression efficiency, reduce the complexity and number of parts of the system, reduce overall footprint of the system, among other advantages.


This section is an introduction to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion provides supporting information for better understanding the various aspects of the present disclosure. Accordingly, these statements are to be read in this light, and not as admissions of prior art.


SUMMARY

One aspect is a vapor compression system that circulates a working fluid. The system includes a compressor including a compression stage for compressing the working fluid, a first heat exchanger downstream from the compressor that receives and cools the working fluid, a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid, and an accumulator positioned between the second heat exchanger and the compression stage. The accumulator defines an interior volume for containing a vapor phase and a liquid phase of the working fluid, and the accumulator includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the accumulator and flow towards the compression stage. The accumulator is operable to atomize the liquid phase of the working fluid into droplets and introduce the droplets into the vapor phase of the working fluid exiting the accumulator.


Another aspect is a method of operating a vapor compression system that includes a compressor, a first heat exchanger, a second heat exchanger, and an accumulator. The method includes compressing a working fluid at a compression stage of the compressor; cooling the working fluid at the first heat exchanger downstream from the compressor; heating the working fluid at the second heat exchanger downstream from the first heat exchanger; channeling the working fluid into an interior volume of the accumulator downstream from the second heat exchanger and upstream from the compression stage, where the working fluid in the interior volume includes a liquid phase and a vapor phase; channeling the vapor phase of the working fluid from the accumulator towards the compression stage; and using the accumulator, atomizing the liquid phase of the working fluid into droplets and introducing the droplets into the vapor phase being channeled towards the compression stage.


Another aspect is a vapor compression system that circulates a working fluid including a vapor phase and a liquid phase. The system includes a scroll compressor including a compression stage for compressing the working fluid, a first heat exchanger downstream from the compressor that receives and cools the working fluid, a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid, an atomizer configured to generate droplets of the liquid phase of the working fluid and positioned to introduce the droplets into the vapor phase of the working fluid upstream from the compression stage, and a controller connected to the atomizer and configured to control an amount of the droplets introduced into the vapor phase of the working fluid based on a volume ratio of the scroll compressor.


Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.





BRIEF DESCRIPTION OF THE DRAWINGS

Features and aspects of embodiments are described below with reference to the accompanying drawings, in which elements are not necessarily depicted to scale.



FIG. 1 is a schematic of an example of a vapor compression system;



FIG. 2 is a section of a scroll compressor used with the vapor compression system of FIG. 1;



FIG. 3 is a schematic of another example of a vapor compression system;



FIG. 4 is a schematic section of an example of an accumulator or vapor-liquid separation vessel that may include in the vapor compression systems of FIGS. 1 and 3;



FIG. 5 is a schematic section of another example of an accumulator or vapor-liquid separation vessel that may include in the vapor compression systems of FIGS. 1 and 3;



FIG. 6 is an example of a method of operating a vapor compression system;



FIG. 7 is a schematic block diagram of an example of a controller used in the vapor compression systems of FIGS. 1 and 3; and



FIGS. 8-10 are various examples of control algorithms that may be implemented using the controller of FIG. 7.





Corresponding reference characters indicate corresponding parts throughout the figures.


DETAILED DESCRIPTION


FIG. 1 is a schematic diagram of a vapor compression system 100. In some examples, the vapor compression system 100 is implemented as or as part of a heating, ventilation, and air conditioning (HVAC) system, a refrigeration system, and/or a heat pump. The system 100 includes a first heat exchanger 102, a second heat exchanger 104, a compressor 106, and an expansion device 108. The system 100 also includes a working fluid loop 110 that circulates a working fluid, such as a refrigerant, between the first heat exchanger 102, the compressor 106, the second heat exchanger 104, and the expansion device 108. The system 100 may include additional components or other components than those shown and described with reference to FIG. 1.


The working fluid includes at least one refrigerant that is suitable for use in a vapor compression cycle. Non-limiting examples of suitable refrigerants include natural refrigerants (e.g., carbon dioxide, water, ammonia, hydrocarbons, and the like), fluorocarbon-based refrigerants, and refrigerants that have a low global warming potential, such as ASHRAE classified A1 and A2L refrigerants. Non-limiting examples of A1 refrigerants include carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1-difluoroethane (R152a), 1,1,1,2-tetrafluoroethane (R134A), and R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125)), and trifluoro, monochloropropenes (R-1233), including cis- and trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd) isomers (HFO-1233zd (Z) and HFO-1233zd (E)), and hexafluorobutenes (HFO-1336, including HFO-1336mzz (Z), 1336mzz (E)). Non-limiting examples of A2L refrigerants include difluoromethane (R-32) and hydrofluorolefins (HFOs). Suitable HFO refrigerants are described, for example, in U.S. Pat. No. 4,788,352 to Smutny and U.S. Pat. No. 8,444,874 to Singh et al., the relevant portions of which are incorporated by reference. HFOs may include 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) and trans-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234zc). Non-limiting suitable examples of specific HFO refrigerants include 3,3,3-trifluoropropene (HFO-1234zf), HFO-1234 refrigerants like 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ze), cis- and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), pentafluoropropenes (HFO-1225) such as 1,1,3,3,3, pentafluoropropene (HFO-1225zc), hexafluorobutenes (HFO-1336), such as cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z) and trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz (E)), or those having a hydrogen on the terminal unsaturated carbon such as 1,2,3,3,3, pentafluoropropene (HFO-1225yez), fluorochloropropenes such as trifluoro, monochloropropenes (HFO-1233) like CF3CCl═CH2 (HFO-1233xf) and CF3CH═CHCl (HFO-1233zd) (including trans (E) and cis (Z) isomers (HFO-1233zd (E) and HFO-1233zd (Z)), (E)-1,2-difluoroethene (R-1132 (E)), and any combinations thereof. In certain aspects, the HFO refrigerant may be selected from the group consisting of: R-1234yf, R-1234ze, R1233zd (E), R1233zd (Z), R1336mzz (Z), R1336mzz (E), R-1132 (E), and combinations thereof. In some examples, these refrigerants are used in combination with other A1 or A2L refrigerants or yet other refrigerants, such or A3 or B1 or B2 refrigerants, including natural or flammable refrigerants (e.g., dimethyl ether (R-E170) or propane (C3H8 or R-290)).


The vapor compression system 100 in some examples operates using a working fluid that includes a refrigerant blend of at least two refrigerants. Suitable refrigerant blends and suitable climate control systems for use with such refrigerant blends are described, for example, in U.S. patent application Ser. No. 17/507,403 to Welch et al., filed on Oct. 21, 2021, and published as U.S. Publication No. 2023/0130167 on Apr. 27, 2023, the entire disclosure of which is incorporated by reference. Features of the vapor compression system 100, as well as the vapor compression system 300 shown in FIG. 3 and described below, can be used in any combination with the systems described in U.S. Publication No. 2023/0130167 in any combination. In certain examples, the refrigerant blend includes an A1 refrigerant, e.g., carbon dioxide (R-744), mixed with at least one other refrigerant. The carbon dioxide refrigerant is desirably used in a sub-critical system design. One example of a suitable, non-limiting refrigerant blend includes CO2 (R-744) as the more volatile, high-pressure refrigerant mixed with an HFO refrigerant (e.g., R-1233zd (E)) as the less volatile, low-pressure fluid. The refrigerant blend may be a “high glide” refrigerant blend that has a first refrigerant (e.g., CO2) with a relatively lower normal boiling point (at 1 atmosphere (atm.) of pressure)) and a second refrigerant with a relatively higher normal boiling point. A difference between normal boiling points of the first and second refrigerants is greater than or equal to 25° C. As a non-limiting example, where the refrigerant blend includes CO2 having a normal boiling point of approximately −78° C. at 1 atm and R-1233zd (E) having a normal boiling point of approximately 18° C. at 1 atm, a difference in boiling points is about 96° C.


Suitable working fluid refrigerant blends include a refrigerant selected from the group consisting of: R-744, R-22, R134A, R410A, R-1234yf, R-1234zc, R1233zd (E), R1233zd (Z), R1336mzz (Z), R1336mzz (E), and combinations thereof. Alternatively, a first refrigerant and a second refrigerant included in the refrigerant blend are independently selected from the group consisting of: R-744, R-22, R152a, R134A, R410A, R-E170, R-32, HFOs, R-290, and combinations thereof. In some examples, the first refrigerant is selected from the group consisting of: R-744, R-22, R134A, R410A, R-E170, R-32, HFOs, and combinations thereof, and the second refrigerant is selected from the group consisting of: 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf), 1,3,3,3-tetrafluoroprop-1-ene (R-1234ze), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd (E)), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd (Z)), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and combinations thereof.


The working fluid may include one or more refrigerants, such as those described above, in combination with a refrigeration lubricant oil. For example, the working fluid may include a synthetic oil. The lubricant oil may in some examples include a polyvinyl ether (PVE) oil, a polyalphaolefin (PAO), a polyalkylene glycol (PAG), alkylbenzene, mineral oil, or an ester-based oil, such as polyol ester (POE) oil. POE oils may suitably be used where carbon dioxide (R-744) is present in the working fluid (e.g., in a refrigerant blend). Suitable POE oils may include a compound formed from a carboxylic acid and a polyol. Such POE compounds may be formed from a carboxylic acid selected from a group consisting of: n-pentanoic acid, 2-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, 3,3,5-trimethylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, and isononanoic acid, and combinations thereof and a polyol selected from a group consisting of: pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylpropanol, and combinations thereof.


The first and second heat exchangers 102, 104 are each operable to transfer heat between the working fluid in the loop 110 and another fluid (e.g., air surrounding the respective heat exchanger 102, 104). The heat exchangers 102, 104 each include a heat exchange coil 112, 114, respectively, through which the working fluid in the loop 110 is routed. Alternatively, one or both heat exchangers 102, 104 may include a concentric tube (or shell and tube), finned tube, brazed plate, plate and frame, microchannel, or any other suitable heat exchanger design to enable the heat exchangers to function as described. The heat exchangers 102, 104 are equipped with or used in conjunction with one or more fans or blowers (not shown) that operate to force fluid (e.g., air) streams 116, 118 to pass across the coils 112, 114, respectively. One of the first and second heat exchangers 102, 104 is located indoors and one of the heat exchangers 102, 104 is located outdoors. In this example, the first heat exchanger 102 is an indoor unit that operates to exchange heat between an indoor air stream 116 and the working fluid in the coil 112 and the second heat exchanger 104 is an outdoor unit that operates to exchange heat between an outside air stream 118 and the working fluid in the coil 114.


In operation of the vapor compression system 100, the first heat exchanger 102 operates as an evaporator, transferring heat from a first fluid (e.g., air) stream 116 flowing over the coil 112 to the working fluid. The second heat exchanger 104 operates as a condenser, transferring heat from the working fluid flowing through the coil 114 to a second fluid (e.g., air) stream 118. In some examples, the operational mode of the vapor compression system 100 is reversible, such that the first heat exchanger 102 operates as a condenser and the second heat exchanger 104 operates as an evaporator.


The expansion device 108 is positioned between the second heat exchanger 104 and the first heat exchanger 102 and operates to expand or de-pressurize the working fluid at this stage of the vapor compression system 100. The expansion device 108 is an expansion valve (e.g., a thermal expansion valve). Alternatively, the expansion valve 108 is any suitable expansion device, such as an orifice or capillary tube for example.


Conditions (e.g., temperature and pressure) of the working fluid are monitored at one or more stages of the loop 110. For example, conditions of the working fluid are monitored upstream from the compressor 106 (or a compression stage 120) using one or more sensors 130 and downstream from the compressor 106 (or a compression stage 120) using one or more sensors 132. The sensors 130 and 132 include temperature sensors and pressure sensors. Each sensor 130, 132 may be used to monitor both temperature and pressure, or each of the sensors 130, 132 may include separate equipment (e.g., separate sensors) for monitoring temperature and pressure. The sensors 130, 132 may additionally and/or alternatively include any suitable equipment for monitoring conditions of the working fluid, such as flow meters for example. The location of the sensors 130, 132 in FIG. 1 is not limiting. The sensors 130, 132 may be located at any suitable location on the loop 110, such as along conduits connecting working components of the vapor compression system 100. In some examples, the vapor compression system 100 includes sensors (e.g., the sensors 130, 132) positioned for monitoring conditions of the working fluid at two or more stages of the loop 110. In various examples, the vapor compression system 100 includes sensors (e.g., the sensors 130, 132) positioned for monitoring conditions of the working fluid upstream and downstream from one, some, or each working component of the vapor compression system 100 (e.g., the first heat exchanger 102, the second heat exchanger 104, the compressor 106, and/or the expansion device 108).


The vapor compression system 100 also includes a controller 134 communicatively connected to various components of the system 100, such as the compressor 106 and the sensors 130, 132, for example, and other components of the system. Although a single controller 134 is shown and described, the controller 134 in some examples includes multiple controllers 134. The multiple controllers 134 may be centralized or decentralized. The controller 134 controls various aspects and parameters of the vapor compression system 100 during operation. Some of the control functions of the controller 134 will be described below.


The controller 134 receives feedback and monitored process information from one or more sensors, such as the sensors 130, 132, for continuous, periodic, or intermittent monitoring of conditions within the vapor compression system 100 (e.g., the temperature and/or pressure of the working fluid at one or more stages of the vapor compression cycle), among other information. The controller 134 includes a communication interface to communicatively couple the controller 134, via one or more connections 136, to one or more components of the vapor compression system 100. The one or more connections 136 communicatively couple the controller 134 to the compressor 106, the sensors 130, 132, and/or other components of the system 100. The communication interface includes, for example, a wired or wireless network adapter and/or a wireless data transceiver for use with a mobile telecommunications network. In this way, the one or more connections 136 communicatively couple the controller 134 to the one or more components of the system 100 via a wired and/or wireless connection.


The compressor 106 is positioned between the first heat exchanger 102 and the second heat exchanger 104 and includes one or more compression stages 120 that operates to compress or pressurize the working fluid at this stage of the vapor compression system 100. The compressor 106 may be any suitable compressor including, but not limited to, scroll, reciprocating, rotary, screw, and centrifugal compressors. In various examples, the compressor 106 is a scroll compressor. Scroll compressors are known and are commercially available, for example, from Copeland LP (Sidney, OH, US).


Referring to FIG. 2, a simplified schematic of a non-limiting example of a scroll compressor 200 is shown. The scroll compressor 200 includes a compressor housing 202 that forms a sealed cavity within which compression of the working fluid is accomplished. The compressor housing 202 includes a shell 204, an end cap 206 positioned at one end of the shell 204, and a base 210 positioned at an opposite end of the shell 204. The scroll compressor 200 has any suitable scroll compressor design, such as a floating orbit design, a floating non-orbit design, a co-rotating design, or another suitable scroll compressor design.


The compressor 200 includes a compression stage 212 at which compression of the working fluid is accomplished. The compression stage 212 includes a non-orbiting scroll 214 and an orbiting scroll 216 operably engaged with a motor assembly 218. The compression stage is connected with a first chamber 208 and a second chamber 220 of the compressor housing 202. The first chamber 208, which is at a first pressure (e.g., suction pressure), is defined by the shell 204. The second chamber 220, which is at a second pressure (e.g., discharge pressure), is defined by the end cap 206. A partition 222 (e.g., a muffler plate) separates the first chamber 208 and the second chamber 220. In some examples, the partition 222 limits or prevents working fluid from prematurely flowing between the first chamber 208 and the second chamber 220 without first being compressed via the compression stage 212.


The motor assembly 218 includes a stator 224 and a rotor 226. The compressor 200 also includes a driveshaft 228 that may be press fit within the rotor 226. The rotor 226 transmits rotational power to the driveshaft 228. The motor assembly 218 is a variable-speed motor for rotating the driveshaft 228 at any of a plurality of speeds. Alternatively, the motor assembly 218 is a fixed-speed motor. In the example compressor 200, the motor assembly 218 is positioned within the shell 204. The compressor 200 alternatively is an open drive compressor driven by a motor assembly that is positioned outside of the compressor housing 202. The driveshaft 228 is rotationally supported in the compressor housing 202 by bearing assemblies (not shown), such as rolling element bearings, journal bearings, or another suitable bearing type.


The non-orbiting scroll 214 and the orbiting scroll 216 include spiral wraps that engage (or mesh) with one another, thereby creating a series of moving fluid pockets. The fluid pockets defined by the scrolls 214, 216 decrease in volume as they move from a radially outer position (e.g., at a suction pressure) to a radially inner position (e.g., at a discharge pressure that is higher than the suction pressure) throughout a compression cycle. A discharge passage 230 extends through the non-orbiting scroll 214 and the partition 222. The discharge passage 230 is in communication with at least one of the fluid pockets at the radially inner position and allows compressed working fluid, such as refrigerant or a mixture of refrigerant and lubricant, (at or near the discharge pressure) to flow therethrough and into the second chamber 220.


The orbiting scroll 216 further includes a cylindrical hub 232 that projects downward and interfaces with a main bearing housing 234. The cylindrical hub 232 includes or defines a drive bearing (not shown). The driveshaft 228 is drivingly engaged to the cylindrical hub 232, and the drive bearing transmits rotational motion from the driveshaft 228 to the orbiting scroll 216.


The main bearing housing 234 is positioned within the shell 204 and is fixed relative to the compressor housing 202 (e.g., by press fit within the shell 204 or another suitable fixation means). The non-orbiting scroll 214 is connected to the main bearing housing 234. Additionally or alternatively, the non-orbiting scroll 214 is connected to the partition 222. The main bearing housing 234 receives a bearing assembly (not shown) and cooperates with the bearing assembly to support the driveshaft 228 for rotational motion relative thereto. The main bearing housing 234 also receives the cylindrical hub 232 of the orbiting scroll 216. The main bearing housing 234 includes a thrust surface that supports the cylindrical hub 232, and more particularly provides axial support for orbital motion of the orbiting scroll 216 relative to the main bearing housing 234, with the drive bearing positioned inside the cylindrical hub 232. A coupling (not shown), such as an Oldham coupling, is engaged with the orbiting scroll 216 and the non-orbiting scroll 214, or the main bearing housing 234, to prevent relative rotation therebetween.


An inlet fitting 236 is positioned on the compressor housing 202 and defines an inlet 238 for drawing the working fluid into the fluid pockets defined by the scrolls 214, 216, where the working fluid is compressed. In the example compressor 200, the inlet fitting 236 is positioned on the shell 204 and connects the inlet 238 to the first chamber 208. After the working fluid is compressed, the compressed working fluid exits the compression stage 212 through the discharge passage 230 and enters the second chamber 220 at discharge pressure. The compressed working fluid exits the second chamber 220 through a discharge outlet 242 defined by a discharge fitting 240. The discharge fitting 240 is attached to the end cap 206 of the compressor housing 202. In some examples, a discharge valve assembly (not shown) is positioned within the discharge fitting 240 and inhibits or prevents a reverse flow condition through the discharge fitting 240.


Referring again to FIG. 1, in operation of the vapor compression system 100, working fluid in the loop 110 is compressed at the compression stage 120 of the compressor 106, which raises the pressure of the working fluid. Upstream from the compressor 106, the working fluid flows towards the compressor 106 via line 122. The working fluid in the line 122 is at a low pressure and is substantially in a vapor phase, having been heated by the first heat exchanger 102. Some of the working fluid that enters the compression stage 120 is in a liquid phase, and more particularly in the form of atomized droplets of liquid phase working fluid to limit, or even prevent, an increase in temperature superheat experienced across the compression stage 120 as described below. Pressurized working fluid exits the compressor 106 and is channeled via line 124 toward the second heat exchanger 104, where the working fluid is condensed to a high pressure, substantially liquid phase state. The working fluid exiting the second heat exchanger 104 is channeled via line 126 toward the expansion device 108 that reduces the pressure of the working fluid. The working fluid exiting the expansion device 108, which is a mixture of a vapor phase and a liquid phase, is channeled toward the first heat exchanger 102 via line 128. The working fluid is heated in the first heat exchanger 102 and substantially evaporates into a vapor phase. The working fluid is then channeled back toward the compressor 106 via the line 122, where the working fluid is again compressed and the process repeats. Circulation of the working fluid in the loop 110 is driven by the compressor 106, and, optionally, one or more additional fluid displacement devices (e.g., pumps). The direction of flow of the working through the loop 110, as shown in FIG. 1, is reversible in some examples to switch the heat transfer functions of the first heat exchanger 102 and the second heat exchanger 104, and enable the vapor compression system 100 to operate in various operating modes. To enable reversing flow of the working fluid in the loop 110, the vapor compression system 100 in some examples includes one or more reversing valves or four-way valves.


As shown in FIG. 1, the vapor compression system 100 also includes an atomizer 138 connected to a source 140 of liquid phase working fluid and operable to introduce atomized or micron-sized droplets of the liquid phase working fluid into vapor phase working fluid being channeled to the compression stage 120 of the compressor 106. The atomized droplets transfer heat from the vapor phase of the working fluid across the compression stage 120, as the atomized droplets evaporate during compression which extracts heat by heat of evaporation. As described below, the atomizer 138 and source 140 are operated and controlled to reduce heat generation across the compression stage 120 using the heat of evaporation of the droplets, and improve compressor efficiency, reduce the opportunity for compressor lift, and reduce load on the compressor and energy consumption. The atomizer 138 and source 140 are also operated and controlled such that the atomized liquid phase droplets also reduce compressor noise while limiting or preventing the risk of liquid slugging at the compressor 106. Liquid slugging occurs when liquid phase working fluid accumulates at or near an inlet of the compression stage 120 (i.e., at the suction side of the compressor 106), and strains the compressor 106 and potentially leads to compressor damage or failure.


The atomizer 138 is positioned for introducing the droplets upstream of the compression stage 120. As shown in FIG. 1, the atomizer 138 is positioned for introducing the droplets into the line 122. Alternatively, the atomizer 138 is located at any suitable position in the vapor compression system 100 to enable the atomizer 138 to function as described. In some examples, the atomizer 138 is located in the first heat exchanger 102 or in a housing of the compressor 106 upstream from the compression stage 120. With reference to FIG. 2, the atomizer 138 is shown located within the first chamber 208 of the scroll compressor 200 and is indicated at 244. The atomizer 138/244 at this location is operable to introduce atomize droplets of liquid phase working fluid that pools proximate the base 210 of the compressor housing 202.


The source 140 of the liquid phase working fluid used with the atomizer 138 is part of the loop 110 and located at any suitable position on the loop 110. In some examples, the source 140 is a pool of liquid phase working fluid in one or both of the heat exchangers 102 and 104. Additionally or alternatively, the source 140 is a pool of liquid phase working fluid in an accumulator positioned on the loop 110. An example accumulator 302 positioned between the first heat exchanger 102 and the compressor 106 and used as the source 140 is described below with reference to FIG. 3. Additionally or alternatively, an accumulator (e.g., the receiver 312 in FIG. 3) that is positioned between the second heat exchanger 104 and the first heat exchanger 102 is used as the source 140. The accumulator source 140 in some examples is part of the compressor 106, upstream from the compression stage 120. For example, referring to FIG. 2, the accumulator source 140 is a region of the first chamber 208 of the scroll compressor housing 202 proximate the base 210 where liquid phase working fluid entering via the inlet 236 pools by gravity upstream from the compression stage 212. In yet other examples, the source 140 is a pool of the liquid phase working fluid that settles in the line 122 upstream from the compressor 106. Additionally or alternatively, the source 140 of the liquid phase working fluid is an external source, separate from the loop 110, such as an external source of the liquid phase working fluid used to charge the working fluid into the loop 110.


The atomizer 138 includes any suitable mechanism for generating atomized droplets of the liquid phase working fluid from the source 140. The atomized droplets are suitably micron-sized, for example, between about 1 micrometers (μm) to about 20 μm in size. The micron-sized droplets provide a relatively large heat and mass transfer surface area for transferring heat across the compression stage 120 by heat of evaporation. The relatively small size of the droplets also limit, or even prevent, liquid slugging that may be caused by liquid phase working fluid introduced into the vapor phase upstream from the compression stage 120. Larger sized droplets, for example, droplets exceeding 100 μm, may have the propensity to accumulate at the inlet of the compression stage 120, which may cause liquid slugging. Additionally or alternatively, larger sized droplets may not sufficiently evaporate during compression and/or may decrease a flow rate of the working fluid across the compression stage 120, which may negatively affect compressor efficiency.


The atomizer 138 includes one or more acoustic energy devices that are in direct contact with a volume of the liquid phase working fluid. The acoustic energy device(s) operate to atomize the droplets of the liquid phase working fluid by generating acoustic energy (e.g., ultrasonic waves) and directly imparting the acoustic energy on the volume of the liquid phase working fluid. In some examples, the acoustic energy devices include ultrasonic transducers. Any number of acoustic energy devices (e.g., ultrasonic transducers) can be included in the atomizer 138, such as one, two, or more than two acoustic energy devices. The acoustic energy device(s) are positioned at any suitable location within the source 140 and in direct contact with the liquid phase working fluid to enable the atomizer 138 to function as described. For example, the acoustic energy device(s) are positioned within a pool of liquid phase working fluid in an accumulator (e.g., the accumulator 302 in FIG. 3 or within the first chamber 208 of the scroll compressor housing in FIG. 2). Referring again to FIG. 2, the atomizer 244 in this example is an ultrasonic transducer positioned proximate the base 210 of the compressor housing 202. The atomizer 244 imparts ultrasonic waves to liquid phase working fluid that accumulates proximate the base 210 in the first chamber 208, thereby generating atomized droplets of the liquid phase working fluid and introducing the droplets into the vapor phase working fluid entering the compression stage 212. The atomizer 244 in this example provides an additional advantage of providing a cost-effective and efficient means of separating liquid phase working fluid from oil or other lubricant that pools proximate the base 210 in the first chamber 208 and re-introducing such working fluid into the vapor phase and the compression stage 212.


In alternative examples, the atomizer 138 includes a nozzle, such as a spray nozzle, swirl nozzle, or ultrasonic nozzle, that operates to generate atomized droplets of the liquid phase working fluid delivered to the nozzle from the source 140. The atomizer 138 implemented as a nozzle is used in conjunction with a source 140 of the liquid phase working fluid that is remote from the atomizer 138. For example, the source 140 is a pool of liquid phase working fluid within the first heat exchanger 102, the second heat exchanger 104, a remote accumulator, or an external source and the nozzle/atomizer 138 is located on the line 122 or within the compressor 106 upstream from the compression stage 120. In these examples, the liquid phase working fluid is delivered from the source 140 to the atomizer 138 using a pump or other displacement device.


In an example operation of the vapor compression system 100, the atomizer 138 generates the droplets of liquid phase working fluid and introduces the droplets into vapor phase working fluid upstream of the compression stage 120 (e.g., within the line 122 and/or within the compressor 106 upstream from the compression stage 120). The droplets are carried by the vapor phase flow across the compression stage 120, and evaporate during compression to promote heat transfer and reduce temperature superheat of the compressed working fluid. In some examples, the droplets facilitate a substantially isothermal compression process, whereby the working fluid experiences a change of temperature across the compression stage 120 within a range of +/−5° C. of saturated vapor temperature, such as within a range of +/−1° C. of saturated vapor temperature.


The controller 134 controls the atomizer 138 to adjust (e.g., increase or decrease) the amount of droplets introduced into the vapor phase based on one or more monitored conditions of the working fluid in the loop 110. The monitored conditions are provided to the controller 134 as inputs from one or more sensors of the vapor compression system 100 (e.g., the sensors 130, 132). Example control algorithms implemented by the controller 134 for controlling the atomizer 138 are described in detail below. In various examples, the controller 134 causes the atomizer 138 to increase or decrease the amount of droplets introduced into the vapor phase to control a discharge temperature of the working fluid exiting the compression stage 120, a volume ratio of the compressor 106 (e.g., the scroll compressor 200), and/or a concentration of the working fluid (e.g., where the working fluid includes a blend of two or more refrigerants having different boiling points).


In examples where the atomizer 138 (e.g., an ultrasonic transducer) is in direct contact with the liquid phase working fluid in the source 140 (e.g., an accumulator), the controller 134 controls the amount of droplets introduced into the vapor phase by adjusting the amount of energy (e.g., ultrasonic waves) imparted on the liquid phase by the atomizer 138. For example, the controller 134 adjusts the operational frequency of the ultrasonic transducer to generate more or less atomized droplets that are introduced into the vapor phase working fluid.


In examples where the source 140 of the liquid phase working fluid is remote from the atomizer 138 (e.g., a nozzle), the controller 134 controls the amount of droplets introduced into the vapor phase by adjusting a flow rate of the liquid phase supplied to the atomizer 138 from the source 140. For example, the amount of the liquid phase working fluid supplied to the atomizer 138 from the source 140, and thus an amount of droplets introduced into the vapor phase working fluid being channeled to the compression stage 120, is controlled by adjusting the speed of the pump that supplies the liquid phase from the source 140. Alternatively, in some examples, a flow metering valve or another flow control device is used to adjust the amount of the liquid phase working fluid supplied to the atomizer 138.


Referring now to FIG. 3, another example vapor compression system 300 is shown. The vapor compression system 300 includes corresponding elements and components as the vapor compression system 100 of FIG. 1, which are indicated using corresponding reference numerals. The vapor compression system 300 also includes an accumulator 302 disposed on the working fluid loop (indicated at 320 in this example). The accumulator 302 operates as the source 140 of liquid phase working fluid and the atomizer 138 as described below. The accumulator 302 is positioned between the first heat exchanger 102 and the compressor 106, and contains the working fluid in two distinct phases—a liquid phase 304 and a vapor phase 306. The accumulator 302 is a vapor-liquid separation vessel (e.g., a flash tank, a cyclone separator, a cold trap, and the like) that separates the liquid phase 304 and the vapor phase 306. The vapor compression system 300 in this example also includes a condensed working fluid receiver 312 and a liquid-to-suction heat exchanger 314 upstream from the receiver 312. The receiver 312 is a tank or vessel that stores or contains a volume of condensed working fluid upstream from the expansion device 108. In some examples, a control valve (not shown) is positioned upstream from the receiver 312 to limit or inhibit backflow of working fluid. A filter-drier (not shown) may be positioned downstream of the receiver 312 and operates to remove contaminants (e.g., corrosive materials) from the working fluid. The liquid-to-suction heat exchanger 314 receives the high pressure working fluid from the second heat exchanger 104 in a first flow direction and the low pressure working fluid from the first heat exchanger 102 in a second flow direction to transfer heat between the low pressure and high pressure working fluid upstream from the accumulator 302 and the receiver 312. The liquid-to-suction heat exchanger 314 includes any suitable heat exchanger design including those described above for the first and second heat exchangers 102, 104.


As shown in FIG. 3, the liquid phase 304 collects in an interior volume of the accumulator 302 proximate a bottom and the vapor phase 306 within the interior volume is proximate a top of the accumulator 302, above the liquid phase 304. The vapor phase 306 is channeled from the accumulator 302 towards the compression stage 120 via a line 308. Some of the liquid phase 304 in the accumulator 302 is atomized using the accumulator 302 into droplets and the droplets are introduced into the vapor phase 306 exiting the accumulator 302. The droplets of the liquid phase 304 are introduced into the vapor phase 306 to provide the advantages described above, such as, inter alia, promoting heat transfer during compression, reducing a temperature superheat of the compressed working fluid, and improving compressor efficiency. Examples of atomizing of the liquid phase 304 using the accumulator 302 are described below with reference to FIGS. 4 and 5.


In operation of the vapor compression system 300, working fluid is channeled to the compressor 106 from the accumulator 302 via the line 308, and includes the vapor phase 306 and droplets of the liquid phase 304 introduced by the accumulator 302. The working fluid is compressed at the compression stage 120 of the compressor 106, which raises the pressure of the working fluid. The atomized droplets of the liquid phase 306 suitably limit, or even prevent, an increase in temperature superheat of the working fluid to improve compressor efficiency. Pressurized working fluid exits the compressor 106 and is channeled via line 316 toward the second heat exchanger 104, where the working fluid is condensed to a high pressure, substantially liquid phase state. The working fluid exiting the second heat exchanger 104 is channeled via line 318 toward the liquid-to-suction heat exchanger 314, where the high pressure working fluid transfers heat with low pressure working fluid from the first heat exchanger 102. The high pressure and low pressure working fluid exit the liquid-to-suction heat exchanger 314 via lines 322, 324, respectively. The high pressure working fluid exiting the liquid-to-suction heat exchanger 314 is channeled via the line 322 toward the receiver 312 and the low pressure working fluid is channeled via the line 324 toward the accumulator 302. The liquid phase 304 and vapor phase 306 streams of the working fluid in the line 324 separate in the accumulator 302, which also operates to atomize some of the liquid phase 304 into droplets and introduce the droplets into the vapor phase 306 that is drawn through the line 308 towards the compression stage 120. The high pressure working fluid is temporarily contained in the receiver 312 before being channeled toward the expansion device 108 via line 326.


The liquid-to-suction heat exchanger 314 operates to transfer heat between relatively higher temperature liquid working fluid exiting the second heat exchanger 104 and relatively lower temperature, biphasic working fluid exiting the first heat exchanger 102. Such intercooling reduces power consumption and/or otherwise improve performance of the first and/or second heat exchangers 102, 104, for example, by permitting incomplete evaporation at the first heat exchanger 102 and/or incomplete condensation at the second heat exchanger 104. For example, the relatively higher temperature liquid working fluid in the line 318 increases the temperature and vapor quality of the working fluid in line 330 from the first heat exchanger 102 while providing a higher level of sub-cooling or a lower temperature and lower vapor quality of the liquid working fluid in the line 318. Thus, the liquid-to-suction heat exchanger 314 provides certain advantages in the vapor compression system 300, including further cooling the liquid working fluid prior to it entering expansion device 108, which can increase system efficiency, can reduce possible flashing in the liquid line and enable the expansion device 108 to operate with greater stability. In this manner, the partially evaporated working fluid is further evaporated by heat transfer with slightly warmer partially condensed (or performs subcooling of) working fluid from the same cycle. In some examples, the liquid-to-suction heat exchanger 314 also enables the first heat exchanger 102 to evaporate the working fluid without superheat, which may improve performance of the compressor 106.


The working fluid exiting the expansion device 108 is channeled via line 328 towards the first heat exchanger 102, where the working fluid is heated in the first heat exchanger 102 and then channeled to the liquid-to-suction heat exchanger 314 via the line 330. As described above for the system 100, the direction of flow of the working through the loop 320 in some examples is reversible to switch the heat transfer functions of the first heat exchanger 102 and the second heat exchanger 104, and enable the vapor compression system 300 to operate in various operating modes.


The vapor compression system 300 is operable using a “high glide” refrigerant blend as the working fluid. High glide refrigerant blends include a first refrigerant and a second refrigerant, where a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C. In certain examples, the vapor compression system 300 is operable using a high glide refrigerant blend in which the first refrigerant and the second refrigerant are independently selected from the group consisting of: carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1,1,2-tetrafluoroethane (R134A), R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125), 1,1-difluoroethane (R152a), dimethyl ether (R-E170), propane (R-290), 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf), cis- and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), cis- and trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234zc), 3,3,3-trifluoropropene (HFO-1234zf), trifluoromonochloropropenes (HFO-1233), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (E)), cis-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (Z)), 2-chloro-3,3,3-trifluoropropene (HFO-1233xf), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (E)), pentafluoropropenes (HFO-1225), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,2,3,3,3-pentafluoropropene (HFO-1225yez), hexafluorobutenes (HFO-1336), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz (E)), trans-1,2-difluoroethene (R-1132 (E)), and any isomers or combinations thereof. Although refrigerant blends may be described herein as including a first refrigerant blend and a second refrigerant blend, the refrigerant blend includes more than two refrigerants in some examples.


One or more components (e.g., the liquid-to-suction heat exchanger 314 and the accumulator 302) of the vapor compression system 300 enable the use of high glide refrigerant blends by permitting partial phase change of the refrigerant blend at an evaporation stage (e.g., the first heat exchanger 102) and a condensation stage (e.g., the second heat exchanger 104) of the vapor compression system 300 and changing relative proportions of the first refrigerant and the second refrigerant in the working fluid blend at different points in the system 300. For example, a substantial proportion of the liquid phase 304 in the accumulator 302 is one of the first refrigerant and the second refrigerant, whichever has the higher boiling point, while a substantial proportion of the vapor phase 306 in the accumulator 302 is the one of the first and second refrigerant having the lower boiling point. The accumulator 302, by introducing droplets of the liquid phase 304 into the vapor phase 306, operates to change the proportions of the first and second refrigerants in the blend without negatively impacting performance and efficiency of the compressor 106. Additional components are included and implemented in some examples to enable the use of such high glide refrigerant blends, such as those described in U.S. Publication No. 2023/0130167 to Welch et al., the entire disclosure of which is incorporated by reference. For example, one or more additional accumulators (e.g., the receiver 312) are included in the system 300 at any suitable location on the loop 320. In this way, a resulting density of the compressor suction (upstream from the compression stage 120) is modified by preferentially storing and introducing concentrated amounts of first refrigerant or second refrigerant in one or more select regions of the system. In some such examples, one or more of the additional accumulators function as described for the accumulator 302, by preferentially introducing liquid phase droplets of the first refrigerant or second refrigerant to change the concentration of the working fluid blend at the respective location.


Referring now to FIG. 4, an example of the accumulator 302 used in the system 300 is shown schematically and indicated at 400. In some examples, the accumulator 400 is included in the vapor compression system 100 (FIG. 1), such as on the line 122 upstream from the compression stage 120. The accumulator 400 operates as a flash tank or other vapor-liquid separation vessel, and includes a body 402 defining an interior volume 404 in which a liquid phase 406 of the working fluid separates from a vapor phase 408 of the working fluid. The body 402 is cylindrical in shape in this example, but may have any suitable shape to enable the accumulator 400 to function as described. In some examples, as described above, the working fluid is a refrigerant blend including a first refrigerant and a second refrigerant, where a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C. In these examples, a substantial proportion of the liquid phase 406 is one of the first refrigerant and the second refrigerant, whichever has the higher boiling point, while a substantial proportion of the vapor phase 408 is the one of the first and second refrigerant having the lower boiling point. Alternatively, the working fluid includes a single refrigerant in a biphasic state, and the two phases separate into the liquid phase 406 and the vapor phase 408. The biphasic state is the result of partial or incomplete evaporation at the first heat exchanger 102, and/or the introduction the liquid phase 406 into the working fluid at or upstream from the accumulator 400 for economization of the vapor compression system 100/300. In some examples, the liquid phase 406 also includes a lubricant oil that is present in the working fluid. The collection of the liquid phase 406 in the accumulator, in some such examples, limits, or even prevents, liquid slugging at the compression stage 120 (FIGS. 1 and 3). Additional, non-limiting advantages of the accumulator 400 include, for example, storing additional working fluid charge to compensate for operational variations of the vapor compression system 100/300 (e.g., variation in the tubing length in the field and/or variations of the operational mode), and controlling the oil return to the compressor 106.


The working fluid enters the interior volume 404 via an inlet 412 defined by an inlet fitting 414 positioned on the body 402. The inlet fitting 414 is located on a sidewall 416 of the body 402, proximate a top 424 of the body 402, but may be positioned at other locations on the body 402. In the example shown in FIG. 5 and described below, the inlet fitting 414 is located proximate a bottom 426 of the body 402. The liquid phase 406 settles proximate the bottom 426 of the body 402, forming a pool 410 in the interior volume 404. The vapor phase 408 is located above a surface 418 of the pool 410 in the interior volume 404 and is channeled through an internal conduit 420 to an outlet 422 of the body 402. The outlet 422 is defined by an outlet fitting 436 located on the sidewall 416 of the body 402 proximate the top 424 and diametrically opposite the inlet fitting 414. The outlet fitting 436 is positioned at other locations on the body 402 in other examples. The internal conduit 420 is U-shaped in this example, defining a conduit inlet 428 that is located above the surface 418 of the pool 410. The internal conduit 420 may have any suitable shape to function as described. The conduit inlet 428 is positioned to receive the vapor phase 408 without receiving a volume of the liquid phase 406 in the pool 410. As shown in FIG. 4, the conduit 420 extends initially downward from the conduit inlet 428 into the pool 410 and turns to extend upward towards and eventually connect to the outlet 422 of the body 402. The conduit 420 operates to control the phase state proportions of the working fluid being channeled to the compressor 106. In some examples, the conduit 420 is omitted.


The accumulator 400 also includes atomizers 430 (labeled as 430a-430c in FIG. 4) positioned and operable to atomize the liquid phase 406 into atomized or micron-sized droplets 432 and introduce the droplets 432 into the vapor phase 408. The droplets 432 are sized (e.g., between about 1 μm to about 20 μm in size) such that the vapor phase 408 carries the droplets 432 into the internal conduit 420 and towards the compressor 106, where the droplets 432 operate to transfer heat across the compression stage 120 as described above. Larger sized droplets 434 (e.g., exceeding about 100 μm in size) are suitably not carried by the vapor phase 408 and instead fall into the pool 410 as a consequence of their terminal velocity. As a result, the larger sized droplets 434 are inhibited from flowing towards the compressor 106, which is advantageous since these larger sized droplets 434 may not sufficiently evaporate across the compression stage 120 and/or may cause liquid slugging.


In the example accumulator 400, the atomizers 430 are ultrasonic transducers that directly contact the liquid phase 406 of the working fluid. The ultrasonic transducers 430 operate by generating ultrasonic waves and directly imparting the ultrasonic energy on the liquid phase 406, thereby creating the atomized droplets 432. Any number of the ultrasonic transducers 430 may be included with the accumulator 400, for example, one, two, or more than two ultrasonic transducers (e.g., three, four, five, six, seven, eight, nine, ten, or more than ten). The positions of the ultrasonic transducers 430 in this example are described below. In other examples, the ultrasonic transducers are at any suitable position to function as described. In some examples, one or more ultrasonic transducers 430 are positioned on a line upstream from the accumulator 400 (e.g., the line 326 in FIG. 3) and/or downstream from the accumulator (e.g., the line 308 in FIG. 3). In the vapor compression system 100 of FIG. 1, the accumulator 400 may be located on the line 122 and one or more ultrasonic transducers 430 may be positioned on the line 122 upstream and/or downstream from the accumulator 400.


As shown in FIG. 4, in this example, there are five ultrasonic transducers 430 (labeled 430a-430e) included in the accumulator 400. A first ultrasonic transducer 430a is positioned within the inlet fitting 414 proximate the inlet 412. A second ultrasonic transducer 430b is positioned on an interior surface of the sidewall 416 proximate the surface 418 of the pool 410. The three remaining ultrasonic transducers 430c-430e are located within the internal conduit 420. In particular, a third ultrasonic transducer 430c is positioned along the downward extent of the conduit 420, a fourth ultrasonic transducer 430d is positioned proximate a bottom turn of the conduit 420, and a fifth ultrasonic transducer 430e is positioned along the upward extent of the conduit 420. In some examples, an ultrasonic transducer 430 is additionally or alternatively positioned within the outlet fitting 436.


In operation of the accumulator 400, working fluid enters the interior volume 404 via the inlet 412, indicated by the flow line 440. The working fluid 440 at this stage is a biphasic mixture of the vapor phase 408 and the liquid phase 406. The working fluid 440 is supplied from the first heat exchanger 102 (e.g., an evaporator) of FIGS. 1 and 3 and/or from the liquid-to-suction heat exchanger 314 of FIG. 3. The first ultrasonic transducer 430a positioned in the inlet fitting 414 operates to generate the droplets 432 before the working fluid 440 enters the interior volume 404. When the working fluid 440 enters the interior volume 404, non-atomized liquid phase 406 and larger sized droplets 434 collect in the pool 410 which the atomized droplets 432 remain within the vapor phase 408 and are carried to the conduit inlet 428 of the internal conduit 420. The second ultrasonic transducer 430b operates to generate atomized droplets 432 from the pool 410 proximate the surface 418, and these droplets 432 are also carried by the vapor phase 408 towards the conduit inlet 428. The vapor phase 408 and the atomized droplets 432 are channeled through the internal conduit 420 towards the outlet 422. The ultrasonic transducers 430c-430e in the conduit 420 operate to generate the droplets 432 within the conduit 420 and/or maintain the atomized size of the droplets 432 through the conduit 420 to prevent agglomeration and settling of the liquid phase 406 therein. The vapor phase 408 and the atomized droplets 432 are then channeled out of the accumulator 400 via the outlet 422 and towards the compression stage 120 of the compressor 106, indicated by the flow line 442. Here again, in some examples, an ultrasonic transducer is positioned in the outlet fitting 436 as well and operates to generate the droplets 432 proximate the outlet 422 and/or prevent agglomeration and settling of the liquid phase 406 therein.



FIG. 5 is another example of the accumulator 302 used in the system 300, shown schematically and indicated at 500. The accumulator 500 is similar to the accumulator 400 described above with reference to FIG. 4, and corresponding elements and components are indicated using corresponding reference numerals. Like the accumulator 400, the accumulator 500 can also be used in the vapor compression system 100 of FIG. 1 and operates as a flash tank or other vapor-liquid separation vessel. The description of the accumulator 400 above applies equally to the accumulator 500 unless expressly stated otherwise or the context clearly indicates otherwise. The atomizers 430 are omitted from FIG. 5, but the atomizers 430 may also be included with the accumulator 500 and the description of the atomizers 430 above applies equally to the accumulator 500.


In the example accumulator 500, the inlet fitting 414 is located proximate the bottom 426 of the body 402 and the outlet fitting 436 is located proximate the top 424 and diametrically opposite the inlet fitting 414. The relative positioning of the inlet fitting 414 and the outlet fitting 436 causes the vapor phase 408 to flow generally upwards in the interior volume 404 between the inlet 412 and the outlet 422. The inlet fitting 414 is also positioned such that the inlet 412 is at least partially below the surface 418 of the pool 410 of the liquid phase 406.


In an example operation of the accumulator 500, the working fluid 440 enters the interior volume 404 via the inlet 412. The working fluid 440 flows through the pool 410 and the vapor phase 408 flows generally upwards through the surface 418 towards the conduit inlet 428 while the liquid phase 406 at least partially collects in the pool 410. The velocity of the working fluid 442 drives some of the liquid phase 406 out of the pool 410 with the vapor phase 408, resulting in atomized droplets 432 and larger sized droplets 434 above the surface 418. Due to the difference in terminal velocity of the atomized (smaller sized) droplets 432 and the larger sized droplets 434, the droplets 432, 434 separate with the atomized droplets 432 being carried with the vapor phase 408 to the conduit inlet 428 and the larger droplets 434 falling or settling back into the pool 410. The conduit inlet 428 is at a suitable height H1 above the surface 418 of the pool 410 to allow for the separation of the droplets 432, 434 by their terminal velocities. The vapor phase 408 and the atomized droplets 432 are channeled through the internal conduit 420 towards the outlet 422. The vapor phase 408 and the atomized droplets 432 are then channeled out of the accumulator 400 via the outlet 422 and towards the compression stage 120 of the compressor 106, indicated by the flow line 442. Here again, in some examples, one or more ultrasonic transducers (e.g., the ultrasonic transducers 430a-430c) are included in the accumulator 500 and positioned to operate as described above with reference to the accumulator 400 of FIG. 4.



FIG. 6 is an example of a method 600 of operating a vapor compression system, such as the vapor compression system 100 of FIG. 1 and/or the vapor compression system 300 of FIG. 3. The method 600 includes compressing 602 a working fluid at a compression stage of a compressor (e.g., the compression stage 120 of the compressor 106). The method 600 also includes cooling 604 the working fluid at a condenser downstream from the compressor (e.g., the second heat exchanger 104) and heating 606 the working fluid at an evaporator downstream from the condenser (e.g., the first heat exchanger 102). In some examples of the method 600, the working fluid is expanded or depressurized between the condenser and the evaporator using an expansion device (e.g., the expansion device 108).


The method 600 also includes channeling 608 a vapor phase of the working fluid from the evaporator towards the compressor. In some examples, the vapor phase is separated from a liquid phase of the working fluid within an interior volume of an accumulator (e.g., the accumulator 302, 400, 500) downstream from the evaporator and upstream from the compression stage. Alternatively, the working fluid is substantially entirely vapor phase exiting the evaporator and a liquid phase may be sourced from another source (e.g., one of the sources 140 described above with reference to FIG. 1). The liquid phase is partially atomized 610 (e.g., using an atomizer 138, 430 and/or an accumulator 400, 500) and atomized liquid phase droplets are introduced into the vapor phase being channeled towards the compression stage. In some examples of the method 600, atomizing 610 the liquid phase of the working fluid into droplets includes contacting the liquid phase with an ultrasonic transducer (e.g., an ultrasonic transducer 430) that is positioned in an interior volume of an accumulator. Alternatively, the ultrasonic transducer may be positioned as an in-line ultrasonic transducer along a line (e.g., the line 122 in FIG. 1 or the line 308 in FIG. 3) upstream from the compression stage. In some examples of the method 600, atomizing 610 the liquid phase into droplets includes flowing the vapor phase of the working fluid generally upwards within an interior volume of an accumulator such that the vapor phase carries relatively smaller droplets of the liquid phase and relatively larger droplets of the liquid phase separate from the vapor phase and pool within the interior volume. With the atomized droplets introduced into the vapor phase being channeled towards the compression stage, the method 600 also includes transferring heat during compression via a heat of evaporation of the droplets of the liquid phase introduced into the vapor phase.


The method 600 also includes controlling 612 an amount of the droplets of the liquid phase that are introduced into the vapor phase based on one or more characteristics of the working fluid in the vapor compression system. The one or more characteristics of the working fluid are indicative of operational performance and/or efficiency of the vapor compression system. For example, the one or more characteristics of the working fluid include any one or more of a degree of temperature superheat of the working fluid exiting the compressor, a volume ratio of the compressor, relative concentrations or proportions of the working fluid at different stages of the vapor compression system (e.g., where the working fluid includes a high glide refrigerant blend), among other characteristics. The characteristics of the working fluid are determined using a controller (e.g., the controller 134) using monitored conditions (e.g., temperature and/or pressure) of the vapor compression system at one or more stages. For example, the vapor compression system includes sensors (e.g., the sensors 130, 132) positioned for monitoring conditions (e.g., temperature and/or pressure) of the working fluid upstream and downstream from one, some, or each working component of the vapor compression system (e.g., the evaporator, the condenser, the compressor, the expansion device, the accumulator, among other components). In some examples of the method, the controller receives information related to monitored conditions of the vapor compression system at two or more stages, determines one or more characteristics of the working fluid at each stage based on the monitored information and compares the characteristics at the different stages, and controls 612 the amount of the liquid phase droplets introduced into the vapor phase based on the comparison. Example control schemes that may be implemented in the method 600 are described below with reference to FIGS. 7-10.


Controlling 612 the amount of liquid phase droplets introduced into the vapor phase includes increasing or decreasing the amount of droplets introduced. The manner in which the amount of liquid phase droplets introduced into the vapor phase is controlled 612 varies depending on the manner in which the droplets are atomized 610 and introduced into the vapor phase. For example, the amount of droplets introduced into the vapor phase is controlled 612 by controlling a flow rate of the liquid phase supplied to an atomizer from a remote source of liquid refrigerant (as described with reference to FIG. 1). Alternatively, the amount of droplets introduced into the vapor phase is controlled 612 by adjusting the amount of energy (e.g., ultrasonic waves) imparted on the liquid phase by an atomizer in direct contact with the liquid phase (e.g., by adjusting an operational frequency of an ultrasonic transducer used to atomize the liquid phase). Any suitable means may be used to control 612 the amount of droplets introduced into the vapor phase depending on the particular configuration of the vapor compression system and atomizer used.



FIG. 7 is an example block diagram of the controller 134 used in the vapor compression systems described (e.g., the vapor compression system 100 of FIG. 1 and/or the vapor compression system 300 of FIG. 3). The controller 134 is a computer system that includes at least one processor 706 and at least one memory device 708. The memory device 708 includes a non-transitory computer-readable medium and program that are accessed by the processor 706 and executable to perform the functions described for the controller 134. The controller 134 receives inputs 702 that include monitored conditions of the vapor compression system. For example, the inputs 702 include monitored temperature and pressure information from one or more stages of the vapor compression. In some examples, the inputs 702 include monitored conditions (e.g., temperature and/or pressure) received from two or more stages of the vapor compression system. The monitored conditions are measured or detected using suitably located sensors (e.g., the sensors 130, 132 in FIGS. 1 and 3). The controller 134 is operable to process the inputs 702 using one or more control algorithms and generate an output 704 for controlling an amount of liquid phase droplets introduced into the vapor phase being channeled to the compressor 106 as described above. The output 704 is continuously, periodically, or intermittently generated. The controller 134 executes one or more control algorithms (e.g., stored in the memory device 708) to determine one or more characteristics of the working fluid based on the inputs 702 and to generate the output 704 based on the one or more characteristics of the working fluid determined using the inputs 702. The characteristic(s) of the working fluid are determined based on inputs 702 related to monitored condition(s) at a single stage of the vapor compression system or at multiple stages. Depending on the control algorithm employed, the controller 134 controls the amount of liquid phase droplets introduced into the vapor phase based on determined characteristic(s) of the working fluid at a single stage or at multiple stages.



FIG. 8 is one example of a control algorithm 800 that is implemented by the controller 134. In this example, the control algorithm 800 is implemented to control the amount of liquid phase droplets introduced to the vapor phase being channeled towards the compression stage based on a monitored temperature at the discharge of the compression stage 120, or compressor discharge temperature (i.e., a temperature of the compressed working fluid at the outlet of the compressor). The compressor discharge temperature is monitored using a sensor (e.g., the sensor 132 in FIGS. 1 and 3) located downstream from the compression stage 120. The compressor discharge temperature is received at operation 802 by the controller 134 as an input 702 and the controller 134 determines at operation 804 a degree of temperature superheat of the compressed working fluid based on the input 702. In this example, the compressor discharge temperature is the monitored condition and the degree of temperature superheat is the determined characteristic of the working fluid. The controller 134 also compares at operation 806 the degree of temperature superheat to a compressor protection limit, which is determined empirically or based on simulated operational cycles of the vapor compression system. If the degree of temperature superheat is above the compressor protection limit, this indicates that more atomized liquid should be introduced to increase heat transfer across the compression stage to reduce temperature superheat of the compressed working fluid. In response to such a determination at operation 806, the controller 134 at operation 808 generates an output 704 causing more liquid phase working fluid to be atomized and introduced into the vapor phase. If the degree of temperature superheat is below the compressor protection limit, this indicates that less atomized liquid should be introduced since the reduction of temperature superheat is more than enough to satisfy system requirements. In response to such a determination at operation 806, the controller 134 at operation 810 generates an output 704 causing less liquid phase working fluid to be atomized and introduced into the vapor phase.



FIG. 9 is another example of a control algorithm 900 that is implemented by the controller 134. In this example, the control algorithm 900 is implemented to control the amount of liquid phase droplets introduced to the vapor phase being channeled towards the compression stage based on a monitored temperature and pressure at discharge and suction of the compression stage 120, that is, based on compressor discharge temperature and pressure and compressor suction temperature and pressure. The compressor discharge temperature and pressure are monitored using one or more sensors (e.g., the sensor 132 in FIGS. 1 and 3) located downstream from the compression stage 120. The compressor suction temperature and pressure are monitored using one or more sensors (e.g., the sensor 130 in FIGS. 1 and 3) located upstream from the compression stage 120. These temperatures and pressures are received at operation 902 by the controller 134 as an input 702 and the controller 134 determines at operation 904 a density of the working fluid at each stage (i.e., a density at compressor suction, ρsuc, and a density at compressor discharge, ρdis). In this example, the compressor discharge and suction temperatures and pressures are the monitored conditions and the working fluid densities are the determined characteristics of the working fluid. The density of the working fluid at compressor suction and compressor discharge are used to gauge the operational volume ratio of the compressor vs. the intended or desired volume ratio. Volume ratio is a performance characteristic for certain types of compressors, such as scroll compressors and/or screw compressors. Accordingly, in some examples where the control algorithm 900 is implemented, the compressor 106 is the scroll compressor 200 (FIG. 2).


To gauge volume ratio performance of the compressor, the controller 134 compares at operation 906 the compressor suction density, ρsuc, and the compressor discharge, ρdis, to determine a ratio ρdissuc. This ratio is then compared, at operations 906 and 910, against predetermined range of values that are indicative of desirable volume ratio performance. If the determined ratio ρdissuc exceeds a predetermined upper range value, the controller 134 at operation 908 generates an output 704 causing more liquid phase working fluid to be atomized and introduced into the vapor phase. If the determined ratio ρdissuc is below a predetermined lower range value, the controller 134 at operation 912 generates an output 704 causing less liquid phase working fluid to be atomized and introduced into the vapor phase. If, as determined at operations 906 and 910, the determined ratio ρdissuc is within the predetermined range, then the controller 134 maintains the amount of liquid phase working fluid presently being atomized and introduced into the vapor phase.



FIG. 10 is another example of a control algorithm 1000 that is implemented by the controller 134. In this example, the control algorithm 1000 is implemented to control the amount of liquid phase droplets introduced to the vapor phase being channeled towards the compression stage based on a monitored temperature at the outlet of the condenser (Tc) and a monitored temperature at the inlet of the evaporator (Te). This control algorithm 1000 is suitably implemented in examples where the working fluid is a high glide refrigerant blend and partial phase change and separation occurs between the condenser and the evaporator (e.g., as described above with reference to FIG. 3). Based on empirical or simulated data, a function ƒ(Tc, Te) is derived to estimate relative proportions of the refrigerants in the working fluid at each of the two stages (i.e., exiting the condenser and entering the evaporator). This equation is used by the controller 134 to determine whether additional liquid phase refrigerant should be added to the vapor phase in order to adjust the relative proportions of the refrigerants in the working fluid entering the compression stage. Equation 1 below is an example of a general equation that can be derived and used in this control algorithm 1000 as the function ƒ(Tc, Te), with the coefficients A, B, C, D, and E and the constant F being determined using empirical or simulated data of the vapor compression system:










AT
c
2

+

BT
e
2

+

CT
c

+

DT
e

+


ET
c



T
e


+
F




(

Equation


1

)







The temperatures Tc and Te are monitored using one or more sensors located downstream of the condenser (e.g., second heat exchanger 104) and upstream of the evaporator (e.g., first heat exchanger 102), respectively. These temperatures are received at operation 1002 by the controller 134 as an input 702 and the controller 134 determines at operation 1004 an output value using the function ƒ(Tc, Te). The output value is indicative of a concentration or relative proportions of the refrigerants in the working fluid blend, and is compared at operations 1006, 1010 against a predetermined range of values that are indicative of desirable proportions in the blend at the two stages monitored. In this example, the temperatures Tc, Te are the monitored conditions and the output value determined using the function ƒ(Tc, Te) is the determined characteristic of the working fluid. If the output value exceeds a predetermined upper range value, the controller 134 at operation 1008 generates an output 704 causing more liquid phase working fluid to be atomized and introduced into the vapor phase. If the output value is below a predetermined lower range value, the controller 134 at operation 1012 generates an output 704 causing less liquid phase working fluid to be atomized and introduced into the vapor phase. If, as determined at operations 1006 and 1010, the output value is within the predetermined range, then the controller 134 maintains the amount of liquid phase working fluid presently being atomized and introduced into the vapor phase.


Various examples of vapor compression systems, and methods of operating and controlling such systems, are described above. Advantages of the above described systems and methods will be understood and appreciated by reading this disclosure in its entirety. Non-limiting advantages and technical benefits of the systems and methods described above include: i) reducing lift of the vapor compression system; ii) providing compressor intercooling to improve evaporator and/or condenser performance and reduce total energy consumption; iii) reducing compressor noise without sacrificing compressor efficiency and/or without increasing the propensity for compressor damage or failure (e.g., by liquid slugging); iv) enabling the use of high glide refrigerant blends while allowing for phase separation between two refrigerants in the blend and re-introduction to control refrigerant proportions; v) reducing the degree of temperature superheat of compressed working fluid exiting the compressor; vi) reducing the opportunity for damage to lubricants and/or to mechanical parts as a result of temperature superheat; vii) facilitating easier, faster, and more reliable liquid refrigerant injection mass flow into the compression stage; vii) allowing efficient and reliable removal of refrigerant from accumulated oil in the vapor compression system; viii) enabling the evaporator to run in a flooded or near-flooded state to increase system capacity and efficiency; ix) providing a flash tank economizer that can efficiently and reliably perform wet injection of liquid refrigerant without causing damage to the compressor or negatively impacting compressor efficiency; x) preventing liquid floodback in the compressor; xi) enhancing the flow rate of working fluid across the compression stage thus increasing capacity of the compressor; xii) reducing overall energy consumption of the vapor compression system; xiii) enabling the use of low GWP refrigerants; xiv) reduction in the size of the components (e.g., heat exchangers) and overall footprint of the vapor compression system; and xv) enabling the above advantages i)-xiv) and reducing the complexity of the system while doing so.


Example embodiments of vapor compression systems and methods as described above. The systems and methods can be implemented in any application suitable for use with a vapor compression system. For example, the vapor compression systems and methods can be used in climate control systems (e.g., HVAC systems), refrigeration systems, and/or heat pumps. The systems and methods are not limited to the specific embodiments described herein. Components of the system and methods may be used independently and separately from other components described herein. For example, the atomizers and accumulators described herein may be used in any suitable vapor compression system.


When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.


Unless otherwise indicated, approximating language, such as “generally,” “substantially,” and “about,” as used herein indicates that the term so modified may apply to only an approximate degree, as would be recognized by one of ordinary skill in the art, rather than to an absolute or perfect degree. Accordingly, a value modified by a term or terms such as “about,” “approximately,” and “substantially” is not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Additionally, unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, for example, a “second” item does not require or preclude the existence of, for example, a “first” or lower-numbered item or a “third” or higher-numbered item.


As used herein, the terms “processor” and “computer” and related terms, e.g., “processing device,” “computing device,” and “controller” are not limited to just those integrated circuits referred to in the art as a computer, but instead refer broadly to a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and/or other programmable circuits, and such terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, a computer-readable medium, such as a random access memory (RAM), and a computer-readable non-volatile medium, such as flash memory. Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to only being, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used such as, but not limited to, a scanner. Furthermore, in the embodiments described herein, additional output channels may include, but are not limited to only being, an operator interface monitor.


As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims
  • 1. A vapor compression system that circulates a working fluid, the system comprising: a compressor including a compression stage for compressing the working fluid;a first heat exchanger downstream from the compressor that receives and cools the working fluid;a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid; andan accumulator positioned between the second heat exchanger and the compression stage, wherein the accumulator defines an interior volume for containing a vapor phase and a liquid phase of the working fluid, wherein the accumulator includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the accumulator and flow towards the compression stage, and wherein the accumulator is operable to atomize the liquid phase of the working fluid into droplets and introduce the droplets into the vapor phase of the working fluid exiting the accumulator.
  • 2. The vapor compression system of claim 1, wherein the accumulator includes an ultrasonic transducer positioned in the interior volume to contact the liquid phase of the working fluid and operable to atomize the liquid phase of the working fluid.
  • 3. The vapor compression system of claim 2, wherein the accumulator includes two or more ultrasonic transducers.
  • 4. The vapor compression system of claim 1, wherein the inlet is positioned proximate a bottom of the accumulator and the outlet is positioned proximate a top of the accumulator, such that the vapor phase of the working fluid flows generally upwards within the interior volume towards the outlet and carries relatively smaller droplets of the liquid phase, and relatively larger droplets of the liquid phase separate from the vapor phase and pool within the interior volume.
  • 5. The vapor compression system of claim 1, wherein the droplets of the liquid phase of the working fluid introduced into the vapor phase transfer heat via a heat of evaporation of the droplets during compression.
  • 6. The vapor compression system of claim 5, further comprising a controller connected to the accumulator for controlling an amount of the droplets introduced into the vapor phase of the working fluid.
  • 7. The vapor compression system of claim 6, further comprising temperature sensors and pressure sensors connected to the controller and positioned for monitoring a temperature and pressure of the working fluid, wherein the controller is configured to: determine one or more characteristics of the working fluid at two or more stages of the vapor compression system based on the monitored temperature and pressure, andcontrol, based on the determined one or more characteristics, the amount of the droplets introduced into the vapor phase of the working fluid.
  • 8. The vapor compression system of claim 7, wherein the compressor is a scroll compressor, and wherein the one or more characteristics include a density of the working fluid.
  • 9. The vapor compression system of claim 7, wherein the working fluid is a refrigerant blend comprising a first refrigerant and a second refrigerant, wherein a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C., and wherein the one or more characteristics are indicative of a concentration of the first and second refrigerants in the working fluid.
  • 10. The vapor compression system of claim 9, wherein the first refrigerant and the second refrigerant are independently selected from the group consisting of: carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1,1,2-tetrafluoroethane (R134A), R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125), 1,1-difluoroethane (R152a), dimethyl ether (R-E170), propane (R-290), 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf), cis- and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), cis- and trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze), 3,3,3-trifluoropropene (HFO-1234zf), trifluoromonochloropropenes (HFO-1233), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (E)), cis-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (Z)), 2-chloro-3,3,3-trifluoropropene (HFO-1233xf), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (E)), pentafluoropropenes (HFO-1225), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,2,3,3,3-pentafluoropropene (HFO-1225yez), hexafluorobutenes (HFO-1336), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz (E)), trans-1,2-difluoroethene (R-1132 (E)), and any isomers or combinations thereof.
  • 11. A method of operating a vapor compression system that includes a compressor, a first heat exchanger, a second heat exchanger, and an accumulator, the method comprising: compressing a working fluid at a compression stage of the compressor;cooling the working fluid at the first heat exchanger downstream from the compressor;heating the working fluid at the second heat exchanger downstream from the first heat exchanger;channeling the working fluid into an interior volume of the accumulator downstream from the second heat exchanger and upstream from the compression stage, wherein the working fluid in the interior volume includes a liquid phase and a vapor phase;channeling the vapor phase of the working fluid from the accumulator towards the compression stage; andusing the accumulator, atomizing the liquid phase of the working fluid into droplets and introducing the droplets into the vapor phase being channeled towards the compression stage.
  • 12. The method of claim 11, wherein atomizing the liquid phase of the working fluid into droplets comprises contacting the liquid phase with an ultrasonic transducer in the interior volume.
  • 13. The method of claim 11, further comprising flowing the vapor phase of the working fluid generally upwards within the interior volume from an inlet towards an outlet of the accumulator such that the vapor phase carries relatively smaller droplets of the liquid phase and relatively larger droplets of the liquid phase separate from the vapor phase and pool within the interior volume.
  • 14. The method of claim 11, further comprising transferring heat during compression via a heat of evaporation of the droplets of the liquid phase introduced into the vapor phase.
  • 15. The method of claim 14, further comprising: monitoring a temperature and a pressure of the working fluid at two or more stages of the vapor compression system;determining one or more characteristics of the working fluid based on the monitored temperatures and pressures; andcontrolling, based on the determined one or more characteristics, an amount of the droplets introduced into the vapor phase of the working fluid.
  • 16. The method of claim 15, wherein the compressor is a scroll compressor, and wherein the one or more characteristics include a density of the working fluid.
  • 17. The method of claim 15, wherein the working fluid is a refrigerant blend comprising a first refrigerant and a second refrigerant, wherein a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C., and wherein the one or more characteristics are indicative of a concentration of the first and second refrigerants in the working fluid.
  • 18. A vapor compression system that circulates a working fluid including a vapor phase and a liquid phase, the system comprising: a scroll compressor including a compression stage for compressing the working fluid;a first heat exchanger downstream from the compressor that receives and cools the working fluid;a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid;an atomizer configured to generate droplets of the liquid phase of the working fluid and positioned to introduce the droplets into the vapor phase of the working fluid upstream from the compression stage; anda controller connected to the atomizer and configured to control an amount of the droplets introduced into the vapor phase of the working fluid based on a volume ratio of the scroll compressor.
  • 19. The vapor compression system of claim 18, further comprising one or more sensors connected to the controller and positioned for monitoring one or more conditions of the working fluid at a first stage upstream from the compression stage and a second stage downstream from the compression stage, and wherein the controller is configured to: determine a density of the working fluid at each of the first and second stages based on the monitored conditions of the working fluid;compare a ratio of the densities to a target volume ratio of the scroll compressor; andbased on the comparison, control the amount of the droplets introduced into the vapor phase of the working fluid.
  • 20. The vapor compression system of claim 19, wherein the one or more sensors include a temperature sensor and a pressure sensor positioned at each of the first stage and the second stage.
  • 21. The vapor compression system of claim 18, wherein the atomizer is positioned within a housing of the scroll compressor.
CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application No. 63/493,878, filed Apr. 3, 2023, the entire disclosure of which is incorporated by reference.

Provisional Applications (1)
Number Date Country
63493878 Apr 2023 US