Patent Application
20250155172
The present disclosure is directed generally to cooling systems and more particularly to oil recovery for a compressor of a vapor compression cycle (VCC) with direct pumped two-phase cooling.
In a conventional two-fluid cooling cycle, indirect cooling of components is provided by a closed vapor compression cycle loop thermally connected to a liquid coolant loop as illustrated in
Two-fluid cooling cycle 100 includes coolant loop 106 and refrigerant loop 108. In some configurations, two-fluid cooling cycle 100 may be described as a vapor cycle loop that is thermally connected to a liquid loop. Coolant loop 106 is a closed-loop system that includes cold sink 102, evaporator 110, and pump 112. Coolant loop 106 includes a coolant fluid, which can be continuously cycled through a closed-loop flow path through cold sink 102, evaporator 110, and pump 112. Coolant liquid passes through cold sink 102 where it picks up heat from heat load 104 and increases in temperature. The heated coolant enters evaporator 110 where excess heat is extracted and the coolant is cooled.
Refrigerant loop 108 includes evaporator 110, compressor 114, condenser 116, and expansion valve 118. Refrigerant loop 108 is a closed-loop system through which a refrigerant can be continuously cycled. Evaporator 110 is part of both coolant loop 106 and refrigerant loop 108. Evaporator 110 receives, as a first working fluid, the coolant of coolant loop 106 and, as a second working fluid, a refrigerant of refrigerant loop 108. The refrigerant picks up heat from the coolant of coolant loop 106 within evaporator 110 and enters a vapor phase. The refrigerant is supplied to compressor 114 as a saturated or superheated vapor, is cooled to a liquid state by condenser 116, is expanded to an evaporator pressure through expansion valve 118 and returned to evaporator 110 as a two-phase fluid where it will pick up heat and vaporize as it absorbs heat from the coolant of coolant loop 106.
The closed-loop system of two-fluid cooling cycle 100 allows for the use of compressors (e.g., scroll compressors) that require lubrication for operation. A lubricant is mixed with the refrigerant in refrigerant loop 108 which continuously cycles through compressor 114. While two-fluid cooling cycle 100 is capable of providing thermal management of temperature sensitive components, it does so at the expense of system efficiency, size, and weight due to the required components and inefficiencies thereof.
A cooling system includes a liquid loop, a vapor compression loop, and a heat exchanger in fluid communication with each of the liquid loop and the vapor compression cycle loop. The liquid loop includes a cold sink for cooling a heat load. The vapor compression cycle loop is fluidly coupled to the liquid loop by a separator, which is configured to separate a two-phase form of a working fluid received from the cold sink into a vapor form of the working fluid and a liquid form of the working fluid.
A method of recovering a lubricant in a hybrid vapor compression cooling system includes separating, by a separator, a vapor form of a working fluid from a liquid form of a working fluid, wherein the working fluid comprises the lubricant and wherein the lubricant is preferentially separated with the liquid form of the working fluid; delivering the liquid form of the working fluid from the separator to a liquid loop, the liquid loop comprising a pump and a cold sink fluidly coupled in flow series, the cold sink in fluid communication with a separator inlet; delivering the vapor form of the working fluid from the separator to a vapor compression cycle loop, the vapor compression cycle loop comprising a compressor, a condenser, and an expansion valve fluidly coupled in flow series, the expansion valve fluidly coupled to a separator inlet; delivering a first portion of the working fluid in the liquid loop to the cold sink; and delivering a second portion of the working fluid in the liquid loop to the vapor compression cycle loop.
The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims and accompanying figures.
While the above-identified figures set forth embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.
Systems 200 and 300 are configured to operate with a single working fluid (refrigerant), which is supplied to a cold sink 202, 302 (e.g., cold plates) that can be thermally coupled to one or more heat loads (not shown) to provide cooling thereto. Heat loads can be, for example and without limitations, power electronics, electronic devices, a working fluid line of a cooling loop/cycle, or the like, and/or portions thereof as will be appreciated by those of skill in the art.
The working fluid used in systems 200 and 300 can be a refrigerant, for example and without limitation, 1,1,1,2-Tetrafluoroethane (R-134a) or 2,3,3,3-Tetrafluoropropene (R-123yf). Other refrigerants may be used without departing from the scope of the present disclosure. The working fluid is cycled through systems 200 and 300 as a liquid, two-phase fluid, and saturated vapor as shown in
As illustrated in
Within liquid loop 204, outlet 238 of separator 210 is fluidly coupled to inlet 240 of pump 208, as shown by fluid line 224. Outlet 242 of pump 208 is fluidly coupled to one or more inlets 244 of cold sink 202 via one or more metering elements 220, as illustrated by fluid line 225. One or more outlets 246 of cold sink 202 are fluidly coupled to inlet 236 of separator 210, as illustrated by fluid line 226. Outlet 242 of pump 208 is additionally fluidly coupled to vapor loop 206 via heat exchanger 218. Outlet 242 of pump 208 is fluidly coupled to inlet 248 of heat exchanger 218, as illustrated by fluid line 227. Outlet 252 of heat exchanger 218 is fluidly coupled to inlet 256 of compressor 212 of vapor loop 206, as illustrated by fluid line 228.
Within vapor loop 206, outlet 239 of separator 210 is fluidly coupled to inlet 256 of compressor 212, as illustrated by fluid line 229. Outlet 258 of compressor 212 is fluidly coupled to inlet 260 of condenser 214, as illustrated by fluid line 230. Outlet 262 of condenser 214 is fluidly coupled to inlet 250 of heat exchanger 218, as illustrated by fluid line 231. Outlet 254 of heat exchanger 218 is fluidly coupled to inlet 264 of expansion valve 216, as illustrated by fluid line 232. Inlet 250 of heat exchanger 218 is fluidly coupled to outlet 254 of heat exchanger. Inlet 250 and outlet 254 of heat exchanger 218 are fluidly separated from inlet 248 and outlet 252 of heat exchanger 218. Outlet 266 of expansion valve 216 is fluidly coupled to inlet 237 of separator 210, as illustrated by fluid line 233. In some embodiments, inlets 236 and 237 of separator can be a single inlet fed by fluid lines 226 and 233, which can be combined upstream of separator 210.
The flow of fluid (liquid, two-phase, and vapor) between components of system 200 is illustrated by arrows. As previously discussed, system 200 utilizes a single working fluid (e.g., refrigerant) and separator 210, which divides the flows of working fluids (vapor and liquid) between liquid loop 204 and vapor loop 206.
Separator 210 receives the working fluid in the two-phase state from cold sink 202 of liquid loop 204 and expansion valve 216 of vapor loop 206. The two-phase working fluid is separated into liquid and vapor components within separator 210. The liquid portion of the working fluid is delivered to liquid loop 206 for cooling a thermal load in thermal communication with cold sink 202. The vapor portion of the working fluid is directed to vapor loop 206 wherein it is returned to a two-phase state via compressor 212, condenser 214, and expansion valve 216.
Separator 210 may be a gravity driven component configured to separate the denser liquid phase from the less dense gaseous vapor phase. Compressor 212 arranged downstream of separator 210 can pull the vapor phase of the working fluid out of separator 210 while gravity acts to pull the liquid portion of the working fluid away from the vapor portion of the working fluid. Pump 208, arranged downstream of separator 210, may be used to aid in pulling the liquid working fluid from separator 210 through liquid loop 204. It will be appreciated that separator 210 is not limited to a gravity-type separator. For example, centrifugal gas-liquid separators may be used without departing from the scope of the present disclosure.
The liquid portion of the working fluid received in liquid loop 204 from separator 210 is increased in pressure through pump 208 and provided to cold sink 202 for cooling purposes. The working fluid within liquid loop 406 is maintained in liquid form as it enters cold sink 202, which may include pressure regulating elements associated with each heat load that is thermally coupled to cold sink 202.
In some embodiments, an inlet manifold associated with the cold sink 202 may be arranged between the pump 208 and cold sink 202 to receive the liquid working fluid. Similarly, a downstream outlet manifold may be arranged at the downstream end of cold sink 202 to receive and combine the working fluid as it exits cold sink 202. The working fluid may be in liquid form, two-phase form, or vapor form as it exits the cooling sink 202. The working fluid can be joined with the fluid from vapor loop 206 before, at, or in separator 210.
Heat exchanger 219 can be a thermal energy storage device arranged in liquid loop 204 between cold sink 202 and separator 210. Heat exchanger 219 can be, for example and without limitation, a phase change heat exchanger (PCMHX).
A vapor portion of the working fluid within separator 210 is directed into vapor loop 206. The vapor portion of the working fluid is compressed by compressor 212 and then condensed to a liquid state within condenser 214. Condenser 214 can be fluidly coupled to a ram air duct of an aircraft. The liquid working fluid is directed through a first flow path of heat exchanger 218 where it can heat liquid working fluid received from pump 208 in a separate flow path. The resulting cooled liquid working fluid is then expanded into a two-phase state by expansion valve 216. The two-phase fluid from each of liquid loop 204 and the vapor loop 206 are received by separator 210.
Compressor 212 is lubricated using a lubricant (e.g., oil) suspended in the working fluid of system 200. Lubricant entrained in the two-phase fluid entering separator 210 from expansion valve 216 and cold sink 202 is preferentially separated with the liquid portion of the working fluid separated in separator 210 and delivered to liquid loop 204. As such, compressor 212 may receive insufficient amounts of lubricant from separator 210 to maintain operation. Over time, compressor 212 loses lubrication due to accumulation of lubricant in liquid loop 204 without replacement. To prevent lubricant from accumulating in liquid loop 204, a portion of lubricant laden liquid working fluid exiting pump 208 in liquid loop 204 is pumped through heat exchanger 218 where it is vaporized and fed directly into compressor 212 downstream of separator 210. The lubricant is entrained in the vaporized fluid and can lubricate compressor 212 during operation.
Heat exchanger 218 places the liquid working fluid with lubricant received from pump 208 in liquid loop 204 in thermal communication with the liquid working fluid received from condenser 214 in vapor loop 206. Heat exchanger 218 can be for example and without limitation, a shell and tube heat exchanger or other liquid-to-liquid heat exchanger known in the art. The liquid working fluid received in heat exchanger 218 from condenser 214 heats the liquid working fluid received in heat exchanger 218 from pump 208 to convert the liquid working fluid received from pump 208 to a vapor phase suitable for delivery to and operation of compressor 212. The vaporized working fluid exiting heat exchanger 218 (via outlet 252) can be combined with the vaporized working fluid exiting separator (via outlet 239) upstream of or at an inlet of compressor 212. Since cooling is applied to the liquid working fluid received from condenser 214 in vapor loop 206, the efficiency of the cycle is not significantly reduced. Heat exchanger 218 is arranged between condenser 214 and expansion valve 216 such that the cooled liquid working fluid is received by expansion valve 216. Lubricant entrained in the vaporized working fluid delivered to compressor 212 cycles through vapor loop 206 and is returned to liquid loop 204 via separator 210.
The amount of lubricant delivered to compressor 212 can be determined by the amount of liquid working fluid directed from pump 208 to heat exchanger 218. Flow of liquid working fluid from pump 208 is split between cold sink 202 and heat exchanger 218. One or more metering elements 220 disposed in fluid line 225 and in fluid communication with fluid line 227 can meter fluid flow of working fluid delivered to cold sink 202. Metering element 222 disposed in fluid line 227 can modulate fluid flow or change a volume of working fluid delivered to heat exchanger 218. The volume of working fluid delivered to heat exchanger 218 can be set based on a lubricant load (amount of lubricant in the working fluid) and a predetermined lubricant demand for operation of compressor 212. In some embodiments, the lubricant load can be increased over lubricant loads of a conventional refrigerant system to reduce the amount of liquid working fluid delivered to heat exchanger 218 and thereby increase the amount of working fluid available for cooling via cold sink 202.
One or both metering elements 220 and 222 can be a valve electronically controlled by a controller (not shown). One or both metering elements 220 and 222 can be controlled to modulate fluid flow to heat exchanger 218 and cold sink 202 based on lubricant load and the predetermined lubricant demand for operation of compressor 212.
System 300 shown in
As illustrated in
Within liquid loop 304, outlet 338 of separator 310 is fluidly coupled to inlet 340 of pump 308 as shown by fluid line 324. Outlet 342 of pump 308 is fluidly coupled to one or more inlets 344 of cold sink 302 via one or more metering elements 320 as illustrated by fluid line 325. One or more outlets 346 of cold sink 302 are fluidly coupled to inlet 336 of separator 310 as illustrated by fluid line 326. Outlet 342 of pump 308 is additionally fluidly coupled to vapor loop 306 via evaporator 318. Outlet 342 of pump 308 is fluidly coupled to inlet 348 of evaporator 318 as illustrated by fluid line 327. Outlet 350 of evaporator 318 is fluidly coupled to inlet 352 of compressor 312 of vapor loop 306 as illustrated by fluid line 328.
Within vapor loop 306, outlet 339 of separator 310 is fluidly coupled to inlet 356 of compressor 312 as illustrated by fluid line 329. Outlet 358 of compressor 312 is fluidly coupled to inlet 360 of condenser 314 as illustrated by fluid line 330. Outlet 362 of condenser 314 is fluidly coupled to inlet 364 of expansion valve 316 as illustrated by fluid line 331. Outlet 366 of expansion valve 316 is fluidly coupled to inlet 337 of separator 310 as illustrated by fluid line 332. In some embodiments, inlets 336 and 337 of separator can be a single inlet fed by fluid lines 326 and 332, which can be combined upstream of separator 310.
The flow of fluid (liquid, two-phase, and vapor) between components of system 300 is illustrated by arrows. As previously discussed, system 300 utilizes a single fluid (e.g., refrigerant) and separator 310, which divides the flows of fluids of the refrigerant (vapor and liquid) between liquid loop 304 and vapor loop 306.
Components of system 300 operate in substantially the same way as similar components of system 200 described with respect to
Evaporator 318 is a heat exchanger. Evaporator 318 places the liquid working fluid with lubricant received from pump 308 in liquid loop 304 in thermal communication with a heat load (e.g., electronics) requiring cooling. Thermal energy is transferred from the heat load to the liquid working fluid received in evaporator 318 from pump 308 to convert the liquid working fluid received from pump 308 to a vapor phase suitable for delivery to and operation of compressor 312. The vaporized working fluid exiting evaporator 318 (via outlet 350) can be combined with the vaporized working fluid exiting separator (via outlet 339) upstream of or at an inlet of compressor 312. Lubricant entrained in the vaporized working fluid delivered to compressor 312 cycles through vapor loop 306 and is returned to liquid loop 304 via separator 310.
Although a specific type of heat exchanger (evaporator 318) is described, those of skill in the art will appreciate that embodiments of the present disclosure may incorporate other types of heat exchangers thermally coupled to a heat load without departing from the scope of the present disclosure.
The amount of lubricant delivered to compressor 312 can be determined by the amount of liquid working fluid directed from pump 308 to evaporator 318. Flow of liquid working fluid from pump 308 is split between cold sink 302 and evaporator 318. One or more metering elements 320 disposed in fluid line 325 and in fluid communication with fluid line 327 can meter fluid flow of working fluid delivered to cold sink 302. Valve 322 disposed in fluid line 327 can modulate fluid flow or change a volume of working fluid delivered to evaporator 318. The volume of working fluid delivered to evaporator 318 can be set based on a lubricant load and a predetermined lubricant demand for operation of compressor 312. As described with respect to system 200, in some embodiments, the lubricant load can be increased over lubricant loads of a conventional refrigerant system to reduce the amount of liquid working fluid delivered to evaporator 318 and thereby increase the amount of working fluid available for cooling via cold sink 302.
One or both metering elements 320 and 322 can be a valve electronically controlled by a controller (not shown), and one or both metering elements 320 and 322 can be controlled to modulate fluid flow to heat exchanger 318 and cold sink 302 based on a lubricant load of the refrigerant and the predetermined lubricant demand for operation of compressor 312.
Advantageously, embodiments disclosed herein provide for improved efficiency cooling systems and cycles. Embodiments of the present disclosure provide for single-fluid, multi-phase cooling systems that efficiently separate liquid and vapor loops to reduce inefficiencies introduced by having a multi-phase fluid in such cooling cycles. The addition of the disclosed heat exchanger or evaporator to deliver vaporized working fluid with entrained lubricant to the compressor of the vapor loop enables the single-fluid, two-phase cooling cycle to operate with compressors, such as scroll compressors, that require lubrication to function.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A cooling system includes a liquid loop, a vapor compression loop, and a heat exchanger in fluid communication with each of the liquid loop and the vapor compression cycle loop. The liquid loop includes a cold sink for cooling a heat load. The vapor compression cycle loop is fluidly coupled to the liquid loop by a separator, which is configured to separate a two-phase form of a working fluid received from the cold sink into a vapor form of the working fluid and a liquid form of the working fluid.
The cooling system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In an embodiment of the preceding cooling system, each of the cold sink and the heat exchanger can be disposed to receive a liquid form of the working fluid from the separator.
In an embodiment of any of the preceding cooling systems, the liquid loop can further include a pump disposed in fluid communication between the separator outlet and each of a cold plate inlet and a heat exchanger inlet.
In an embodiment of any of the preceding cooling systems, the liquid loop can further include a first fluid metering element disposed in a fluid line fluidly coupling the cold sink inlet and a pump outlet, the first fluid metering element configured to meter a flow of the working fluid delivered to the cold sink.
In an embodiment of any of the preceding cooling systems, the liquid loop can further include a second fluid metering element disposed in a fluid line fluidly coupling the heat exchanger inlet and the pump outlet, the second fluid metering element configured to meter a flow of the working fluid delivered to the heat exchanger.
In an embodiment of any of the preceding cooling systems, at least one of the first and second fluid metering elements can be an electronically controlled valve.
In an embodiment of any of the preceding cooling systems, the vapor compression cycle loop can include a compressor, the compressor fluidly coupled to a heat exchanger outlet and the separator outlet to receive a vapor form of the working fluid from each of the heat exchanger and the separator.
In an embodiment of any of the preceding cooling systems, the heat exchanger can be configured to provide thermal communication between the working fluid in the liquid loop and the working fluid in the vapor compression cycle loop.
In an embodiment of any of the preceding cooling systems, the vapor compression cycle loop can further include a condenser disposed downstream of the compressor and an expansion valve disposed downstream of the condenser and upstream of the separator. The heat exchanger is disposed between the condenser and the expansion valve and configured to place the working fluid received from the condenser in thermal communication with the working fluid received from the pump.
In an embodiment of any of the preceding cooling systems, the vapor compression cycle loop can further include a condenser disposed downstream of the compressor and an expansion valve disposed downstream of the condenser and upstream of the separator. The heat exchanger is configured to place the working fluid received from the pump in thermal communication with a heat load external to the vapor compression cycle loop.
In an embodiment of any of the preceding cooling systems, the heat exchanger can be an evaporator.
In an embodiment of any of the preceding cooling systems, the working fluid comprises a refrigerant and a lubricant.
In an embodiment of any of the preceding cooling systems, the separator can be configured to preferentially separate the lubricant from the vapor form of the working fluid and deliver the lubricant in the liquid form of the working fluid to the liquid loop.
In an embodiment of any of the preceding cooling systems, each of the heat exchanger and the cold plate can be arranged to receive a portion of the working fluid from the pump.
In an embodiment of any of the preceding cooling systems, the heat exchanger can be configured to place the working fluid received from the pump in thermal communication with a heat sink to vaporize the working fluid received from the pump.
A method of recovering a lubricant in a hybrid vapor compression cooling system includes separating, by a separator, a vapor form of a working fluid from a liquid form of a working fluid, wherein the working fluid comprises the lubricant and wherein the lubricant is preferentially separated with the liquid form of the working fluid; delivering the liquid form of the working fluid from the separator to a liquid loop, the liquid loop comprising a pump and a cold sink fluidly coupled in flow series, the cold sink in fluid communication with a separator inlet; delivering the vapor form of the working fluid from the separator to a vapor compression cycle loop, the vapor compression cycle loop comprising a compressor, a condenser, and an expansion valve fluidly coupled in flow series, the expansion valve fluidly coupled to a separator inlet; delivering a first portion of the working fluid in the liquid loop to the cold sink; and delivering a second portion of the working fluid in the liquid loop to the vapor compression cycle loop.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, additional components, and/or steps:
In an embodiment of the preceding method, delivering the second portion of the working fluid to the vapor compression cycle loop can include delivering the second portion of the working fluid to a heat exchanger upstream of the compressor of the vapor compression cycle loop.
In an embodiment of any of the preceding methods, the heat exchanger places the second portion of the working fluid in thermal communication with a heat load to vaporize the second portion of the working fluid.
In an embodiment of any of the preceding methods, the heat exchanger places the second portion of the working fluid in thermal communication with working fluid received from the condenser of the vapor compression cycle loop to vaporize the second portion of the working fluid.
In an embodiment of any of the preceding methods, controlling a volume of the second portion of the working fluid based on a lubricant load and a predetermined lubricant demand for operation of the compressor.
