Patent Application
20180195782
The disclosure herein relates generally to a heat exchanger, such as for example, a condenser coil constructed fins and microchannel tubes. The heat exchanger is fluidly connected with a volume constructed and configured to store refrigerant in certain operations, such as for example during a pump down operation.
In a cooling system, such as for example a fluid chiller, e.g., water chiller, it may be desired to remove enough refrigerant out from the evaporator and out of contact with water tubes in the evaporator. This can avoid water tubes in the evaporator from freezing due to refrigerant migration from the evaporator to the condenser, such as at low ambient conditions. A pump down operation may be used to remove refrigerant out from the evaporator to address this problem, and the refrigerant is then stored for a period of time.
In a cooling system that uses microchannel tubes in its heat exchanger construction, such as for example in a condenser coil, the internal volume of such a heat exchanger may be relatively small. In the removal of refrigerant from the evaporator, such as for example in the pump down operation, such a heat exchanger with microchannel tubes may not provide sufficient storage for the refrigerant.
The disclosure herein relates generally to a heat exchanger, such as for example, a condenser coil constructed with fins and microchannel tubes. The heat exchanger is fluidly connected with a volume constructed and configured to store refrigerant in certain operations, such as for example during a pump down operation.
In an embodiment, a heat exchanger includes a microchannel coil, the microchannel coil includes flattened tubes with ends connected to headers, and includes fins between the flattened tubes. The flattened tubes include multiple channels fluidly connected with the headers to pass a working fluid, such as for example a refrigerant mixture, through the multiple channels of the flattened tubes and through the headers. The flattened tubes and fins are constructed and arranged to pass a heat exchange fluid, such as for example air, through the microchannel coil externally of the flattened tubes and fins so as to have a heat exchange relationship with the working fluid. The microchannel coil includes a first fluid port fluidly connected with one of the headers, and a second fluid port fluidly connected with one of the headers. In an embodiment, the first fluid port is arranged relatively at a higher location than the second fluid port. In a cooling mode, the first fluid port receives the working fluid, and the second fluid port exits the working fluid after the working fluid has passed through the flattened tubes and the headers. In a mode other than the cooling mode, such as for example in a mode to store refrigerant, which in some circumstances is a pump down mode, the second fluid port receives the working fluid, and the first fluid port exits the working fluid after the working fluid has passed through the flattened tubes and headers. The heat exchanger further includes a volume fluidly connected with the first fluid port. In the cooling mode, the volume is constructed and arranged to pass the working fluid through the volume and to the first fluid port into the header fluidly connected with the first fluid port. In the mode other than the cooling mode, the volume is constructed and arranged to receive the working fluid from the first fluid port and to store the working fluid.
In an embodiment, the heat exchanger further includes a flow control device fluidly connected with the volume. In the cooling mode, the flow control device is open to pass the working fluid through the volume and into the first fluid port and into the microchannel coil. In the mode other than the cooling mode, the volume stores the working fluid received from the first fluid port, where the flow control device may be closed.
In an embodiment, the first fluid port is fluidly connected to a condensing section of the microchannel coil. In an embodiment, the first fluid port is connected to an inlet of the condensing section.
In an embodiment, the second fluid port is fluidly connected to a sub-cooling section of the microchannel coil. In an embodiment, the second fluid port is connected to an outlet of the microchannel coil, such as for example an outlet of the liquid and/or sub-cooled liquid section of the microchannel coil.
In an embodiment, the volume is constructed to receive a substantial amount of the working fluid charge designed for a cooling system in which the heat exchanger is implemented.
In an embodiment, a fan is assembled with the heat exchanger to draw the heat exchange fluid over the microchannel coil.
In an embodiment, the volume is disposed within a perimeter defined by an arrangement of the microchannel coil, the fan, and another coil, which in some circumstances is also a microchannel coil.
In an embodiment, a cooling system, which in some instances is a fluid chiller such as for example a water chiller where water is the working fluid, includes a heat exchanger as per any one or more of the paragraphs [0005] to [0011] above. The cooling system includes a compressor fluidly connected with the heat exchanger, an expansion device fluidly connected with the heat exchanger, and another heat exchanger fluidly connected with the expansion device. The heat exchanger is a condenser and the other heat exchanger is an evaporator. In an embodiment, the fluid chiller is an air-cooled chiller, for example where the heat exchanger is an air-cooled condenser.
In an embodiment, a method of operating a cooling mode of a cooling system includes compressing a working fluid, directing the working fluid to a heat exchanger as per any one or more of the paragraphs [0005] to [0012] above, directing the working fluid from the heat exchanger to an expansion device, and directing the working fluid from the expansion device to another heat exchanger, and returning the working fluid to the compressor. In an embodiment, the heat exchanger is a condenser, the another heat exchanger is an evaporator. The step of directing the working fluid from the compressor to the heat exchanger includes directing the working fluid through a volume prior to the working fluid flowing into the first fluid port. In an embodiment, the step of directing the working fluid from the compressor to the heat exchanger includes directing the working fluid from the compressor to flow control device and, from the flow control device, to the heat exchanger.
In an embodiment, a method of storing a working fluid, such as a refrigerant mixture, in a cooling system includes directing the working fluid into a heat exchanger as per any one or more of the paragraphs [0005] to [0011] above by directing the working fluid through the second fluid port. The method further includes directing the working fluid out of the microchannel coil and out of the first fluid port, directing the working fluid into a volume, and storing the working fluid in the volume.
In an embodiment, a method of retrofitting an existing cooling system includes fluidly connecting a volume to a fluid line fluidly connecting a compressor to a microchannel heat exchanger. The method further includes fluidly connecting the volume to a fluid port, which is fluidly connected to the microchannel heat exchanger, and installing a valve on the fluid line.
These and other features, aspects, and advantages of the heat exchanger, cooling system, and methods of use thereof will become better understood when the following detailed description is read with reference to the accompanying drawing, wherein:
While the above figures set forth embodiments of the heat exchanger, cooling system, and methods of use thereof, other embodiments are also contemplated, as noted in the following descriptions. In all cases, this disclosure presents illustrated embodiments of the heat exchanger, cooling system, and methods of use thereof by way of representation but not limitation. 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 heat exchanger, cooling system, and methods of use thereof described herein.
The disclosure herein relates generally to a heat exchanger in a cooling system, such as for example, a condenser coil constructed as a fin and microchannel tube. The heat exchanger is fluidly connected with a volume constructed and configured to store refrigerant in certain operations, such as for example during a pump down operation.
The cooling system 10 directs a working fluid, which in some cases is a refrigerant mixture, through the circuit of
The compressor 12 compresses the working fluid, and directs the working fluid to the condenser 14. The condenser 14 condenses the working fluid from a vapor to a liquid and directs the working fluid to the expansion device 16. The condenser 14 in some cases can employ a fan 20 which draws a heat exchange fluid, such as for example air, across the condenser 14 to condense the working fluid. The condenser 14 may include one or more heat exchanger coils which pass the working fluid through the condenser 14. The expansion device 16 expands the working fluid to further cool the working fluid, where the working fluid can become a mixed vapor liquid phase fluid. The working fluid is directed to the evaporator 18, where the working fluid is evaporated into a vapor. The working fluid may then return to the compressor 12 and be recirculated through the circuit.
One example of a heat exchanger coil may be a microchannel heat exchanger coil (microchannel coil). A microchannel coil in some instances has flattened tubes that extend from one or more headers. A microchannel coil may have one or more rows of flattened tubes, be folded on itself, and may use the same header or have different headers connected to the ends of the flattened tubes. A microchannel coil has multiple channels within each of the flattened tubes and fins between the flattened tubes.
As shown in
A heat exchange fluid, such as for example air, e.g., ambient air, may be drawn through and across the microchannel coil 200, as indicated by the direction arrows 212. As shown, relatively cooler air may pass through the microchannel coil 200, cool the working fluid flowing through the flattened tubes 202 and header(s) 206, and exit the microchannel coil 200 as relatively warmer air. The air passing through the coil passes externally of the flattened tubes 202 and fins 204, and is in a heat exchange relationship with the working fluid. In an embodiment, it will be appreciated that the overall structure of the microchannel coil may have tubes that extend straight from one end to another end (e.g. from one header to another header) or may have tubes that are folded, bent, or rolled, and may have for example a single header or more than one header on the same side or end.
The condenser 300 includes one or more condensing units 302, which includes one or more heat exchanger coils 304 (coils 304) and can have one or more fans (not shown in
In an embodiment, one or both of the coils 304 of a condensing unit 302 are microchannel coils. In an embodiment, the coils 304 may be microchannel coils similar to the microchannel 200 coil illustrated in
The condenser 300 by way of inlet(s) 314 and one or more fluid ports 314a is fluidly connected with a line 312 to receive the working fluid, and by way of one or more fluid ports 318, is fluidly connected with a line 316 to exit the working fluid after having passed through the microchannel tubes and headers of the coils 304. In an embodiment, the fluid port 314a is arranged relatively at a higher location than the fluid port 318. In an embodiment, the line 312 is a discharge line from a compressor, and in an embodiment, the line 316 is a line to an evaporator. In an embodiment, any of lines 312, 316 in some circumstances are in fluid communication with other components of the fluid circuit. For example, the line 316 in some instances is fluidly connected with another component such as for example an expansion device, e.g. 16 in
In an embodiment, the condenser 300 includes one or more inlets 314 to feed the working fluid from the line 312 into the coils 304 by way of one or more fluid ports 314a. It will be appreciated that one or more fluid ports 314a may be employed to support the inlet(s) present. In the embodiment shown, two inlets 314 are shown entering the coil 304. It will be appreciated that one inlet or more than two inlets may be employed. It will also be appreciated that more than one fluid port 318 may be employed.
In an embodiment, a volume 310 is between the line 312, and along one of the inlets 314. Fluid port 314a is fluidly connected with the volume 310 and provides access into the coil 304, such as for example into a header of microchannel coil 304. In an embodiment, the fluid port 314a is fluidly connected with the condensing section 306 on the inlet side entering the coil 304. It will be appreciated that the other inlet 314, as well as other inlets which may be implemented with the coil 304, may also be fluidly connected with the volume 310 and include a similar fluid port as fluid port 314a to provide access into the coil 304 via the volume 310.
In an embodiment, the volume 310 is a receiver or other suitably constructed container, vessel, or the like, which is suitable to hold, contain, or otherwise store a fluid such as for example a refrigerant mixture therein. It will also be appreciated that the volume may not be a separately dedicated volume, for example where the volume in some circumstances is an oversized discharge line (e.g. a “gas” line between the compressor and condenser), so the diameter and/or length of the discharge line is relatively larger than other fluid lines and can hold a substantial charge of refrigerant relative to normally constructed fluid lines in the system. It will be appreciated that the volume 310 includes openings for fluid flow to enter and exit the volume 310. It will be appreciated that the volume 310 is designed to meet regulatory standards, such as for example being a Pressure Equipment Directive (PED) compliant vessel according, for example, to European standards, and/or being an American Society of Mechanical Engineers ASME compliant vessel according to U.S. standards. It will also be appreciated that, depending on the compressor type, one or more lubricant (e.g. oil) separators may be between the compressor and condenser (see e.g. 526 in
In an embodiment, such as shown in
In an embodiment, the volume 310 is disposed in the fluid circuit in lines that pass vapor during for example the cooling mode. In the embodiment shown, the volume is along inlet 314 which is fluidly connected with the line 312, which can be, e.g., the compressor discharge line.
In an embodiment, the volume 310 is not disposed in the fluid circuit in lines that would be characterized as liquid lines of the cooling system. In an embodiment, the volume is not connected between vapor lines and liquid lines, but only within vapor lines.
As shown, the volume 310 is disposed on the outside of the arrangement of the coils 304. It will be appreciated that the volume 310 may be located in various locations of the condenser 300. For example, the volume 310 can be disposed on any of the condensing units 302 of the cooling system, may be inside or outside the perimeter defined by the coils and fan(s) (e.g. inside or outside V shaped coil), and with respect to any of the fan(s), and does not necessarily have to be located with respect to the last or end condensing unit (e.g. does not have to be located with last condensing unit and fan or set of fans that may stop last, such as during a pump down operation).
In an embodiment, the condenser includes one or more flow control devices 320 located prior to the inlet(s) 314.
In an embodiment, the flow control device 320 is a valve which can be automatically and/or actively controlled by the controller of a unit (cooling system e.g., fluid chiller) or a system controller, which controls multiple units and/or devices (e.g. in a building). It will be appreciated that unit and system controllers are well known, for example to control a pump down operation and to control the normal operation (e.g. cooling mode) of the cooling system. It will be appreciated that the flow control device 320 can be any suitable valve whether controlled or manually operated. In some circumstances, the flow control device 320 is a manually operated valve, for example in a system which uses maintenance pump down and not operational pump down.
In an embodiment, the flow control device 320 is a solenoid valve which is controllable to an open and closed state. For example, in the activated state the solenoid valve is closed, and in the non-activated state the solenoid valve is open. It will be appreciated that the flow control device 320 can be automatically controlled, e.g., activated about a few seconds before cooling system shutdown. It will also be appreciated that the flow control device 320 can be deactivated to open to start up the cooling system with no issue, for example after the working fluid has been removed from the volume 310. hi some examples, removing the working fluid from the volume 310 may take a certain amount of time, such as about a few minutes, depending on the size of the volume 310.
In an embodiment, the flow control device 320 is in the open state, but not during pump down. The flow control device 320 activates or closes when a pump down is to be initiated, which may be controlled to a set point based on an ambient temperature or system pressure or temperature. The flow control device 320 deactivates or opens when the compressor shuts down. In an embodiment, the flow control device 320 may be activated or closed just before or after starting a pump down cycle, and then deactivated or opened after compressor shutdown.
In an embodiment, in a cooling mode the compressor is on and the flow control device is open. In an embodiment, in a non-cooling mode such as during a pump down operation, the compressor may be on and the flow control device is closed. In an embodiment, in a non-cooling mode such as when the compressor is off or on standby, the flow control device may be open or closed.
In an embodiment, when the compressor is off, the volume may still store fluid even if the flow control device is open. The flow control device in some circumstances isolates the volume from the discharge side and the goal of a pump down is to empty the evaporator (refrigerant moved to the condenser and volume).
In an embodiment, the pump down cycle can include closing the expansion device, e.g. expansion valve, which is upstream of the evaporator. In some circumstances, the compressor is also unloaded. Unloading the compressor can help to avoid high pressure limits before filling of the condenser where the gas refrigerant has relatively less condenser area (e.g. in a microchannel coil) to condense the fluid so it may be desirable to reduce refrigerant flow to the condenser. Closing the expansion device and unloading of the compressor can be a simultaneous operation to help speed up the pump down process.
As shown in
With specific reference to
As shown, the volume 310 is located outside the V shaped coils, but it will be appreciated that the volume 310 can be located inside the V (see e.g.,
With specific reference to
It will be appreciated that the flow control device(s), e.g. 320, herein is closed in modes intended to fill the volume, e.g. 310, such as, for example, in a pump down operation. It will be appreciated that the flow control device(s) can be closed in other non-cooling modes, while it will also be appreciated that in certain non-cooling modes other than a pump down operation, the flow control device(s) may be opened or closed, such as, for example, when the compressor is off.
Some cooling system designs may employ an evaporator that is a flooded type of evaporator, which in some instances may be a shell and tube type of construction. In some instances, a flooded evaporator can have a relatively high ratio of refrigerant volume (e.g. shell side) to water volume (e.g. tube side). The relatively high ratio potentially makes the water inside the evaporator water tubes susceptible to freezing, such as for example if the refrigerant is allowed to migrate and the ambient temperature is below 30° F. (may be lower temperature if a freeze inhibitor is applied). It will be appreciated that such circumstances can apply to other types of evaporators, such as a falling film evaporator, where the ratio of refrigerant volume to water volume may not be as high, as long as there may be risk of pooling refrigerant at the bottom of the evaporator, which can affect some of the tubes of the evaporator. Refrigerant migration may occur in conditions where there is refrigerant in the evaporator, and the condenser is colder than the evaporator. Freezing may be a concern upon shutdown of the cooling system, such as in relatively cold conditions, for example when the condenser rapidly changes from a high to a low temperature. Refrigerant migration can also be an issue after long periods of off time when there is a rapid drop in ambient temperature.
To avoid evaporator water tubes from freezing due to refrigeration migration from the evaporator to the condenser at low ambient conditions, refrigerant is removed from the evaporator, such as for example to a level below the water tubes. Refrigerant is then stored in another volume of the condenser, e.g., a vessel, container, reservoir, receiver, holding structure, or the like. Such a process can be involved in what is called a pump down operation. It will be appreciated that the volume 310 herein may be sized, constructed, arranged, and/or otherwise configured to hold a substantial amount of the working fluid charge of the system. This amount can be the entire charge of the cooling system or any amount less than the entire charge that would be sufficient in various operations, such as in a pump down operation. It will be appreciated that the some of the charge may suitably be retained by the coils, in which case not all of the volume is employed or the size of the volume may be designed according to the capacity of the coil, e.g. microchannel coil.
A goal of the pump down operation is to empty an amount of refrigerant from the evaporator, e.g., to avoid evaporator water tubes freezing due to refrigerant migration from evaporator to condenser such as for example at low ambient conditions, or to remove enough of an amount of refrigerant from the evaporator to not have refrigerant in contact with the water tubes. It will be appreciated that pump down can also be done for maintenance or service, e.g., when there is a need and/or desire to open a low pressure side of the cooling circuit and remove refrigerant from the low pressure side. Generally, the amount of refrigerant to be removed from the evaporator can vary depending on the cooling system design. Generally, at least a sufficient amount of refrigerant is removed so as not to be susceptible to freezing or to a level of freezing which may be harmful and/or undesired. The volume 310 can be sized and located appropriately to meet the system design, and may include more than one volume (e.g. multiple 310s).
Cooling system designs with microchannel coils in some instances can present a challenge for storing refrigerant, as the volume available in a microchannel coil is relatively very low compared to the volume amount of refrigerant that may need to be stored.
The additional volume 310 for liquid storage, e.g., available for a pump down operation, and which does not affect normal operation, e.g., cooling mode of a water chiller is useful to supplement what volume condensing unit(s) may provide (e.g. the liquid lines, the coils, headers, etc.). In an embodiment, the volume 310 can be implemented as a refrigerant storage vessel in a condenser of a cooling system such as for example a chiller, where the refrigerant storage vessel is in fluid communication with the microchannel coil. The refrigerant storage vessel provides system volume for non-cooling mode operations, e.g., for pump down operations to store refrigerant.
The condenser 500 includes condensing units 502. As shown, there are multiple condensing units, for example seven, as counted by the number of V shaped configurations of the condenser 500. The condenser 500 is shown as part of a cooling system which includes compressor 522 and evaporator 518, and fans 506. It will be appreciated that a cooling system, such as the cooling system shown in
As shown, the volume 510 is within the perimeter defined by the coil and fan arrangement. Two volumes 510 are shown, one to serve each circuit of the cooling system. It will be appreciated that the volumes 510 may be placed at various locations of the condenser and on any of the condensing units, taking into account various factors, such as for example production cost and convenience. In an embodiment, the fan(s) may be on or off during a pump down operation. In an embodiment, when the fan(s) are off, there is no forced air flow used to facilitate movement of the working fluid through the circuit. In an embodiment, when the fan(s) are on, forced air flow is used to facilitate movement of the working fluid through the system which under certain circumstances can make pump down operation run faster. In an embodiment, the volume can also be in another location without fan or “out of forced airflow” location (for example volume is an oversized discharge line(s), which are not placed within the airflow path.
Flow control device 520, which in an embodiment is a solenoid valve, is disposed on the line 512 prior to the split into the inlets 514. The flow control device 520 may operate similar to the flow control device 320 described above with respect to
The cooling systems herein including the implementation of the volume and flow control device for working fluid storage can enjoy many advantages. Such advantages include for example: little or no risk of having vapor in the liquid line (e.g., vapor or non-subcooled liquid in the liquid outlet); little to no risk to trap refrigerant (bottom of the heat exchanger is not closed); no risk to store refrigerant or oil in the volume during operation e.g. cooling mode; liquid sub-cooling level can be insured or maintained; in case of failure of the flow control device; the cooling system may still operate with the same or reduced operating map so there is little to no impact; the flow control device may be controlled automatically (e.g. by an active system) and used for example in a pump down operation, and depending on the mode of operation of the cooling system.
Additional advantages can include for example: good reliability; relatively simple to control; little to no impact on operating performance; relatively easy to integrate in a new or existing cooling system as a retrofit application; without the need to modify the microchannel heat exchanger.
Any of aspects 1 to 8 may be combined with any of aspects 9 to 19, any of aspects 9 to 15 may be combined with any of aspects 16 to 19, and any of aspects 16 to 18 may be combined with aspect 19.
Aspect 1. A heat exchanger comprising:
a microchannel coil, the microchannel coil includes flattened tubes fluidly connected to a header, and fins between the flattened tubes,
the microchannel coil includes a first fluid port fluidly connected with the header, and a second fluid port fluidly connected with the header,
in the mode other than the cooling mode, the volume is constructed and arranged to receive the working fluid from the first fluid port, and to store the working fluid.
Aspect 2. The heat exchanger of Aspect 1, further comprising a flow control device fluidly connected with the volume, wherein, in the cooling mode, the flow control device is open to pass the working fluid through the volume and into the first fluid port and into the microchannel coil, and in the mode other than the cooling mode, the flow control device is closed, so that the volume stores the working fluid received from the first fluid port.
Aspect 3. The heat exchanger of Aspect 1 or 2, wherein the microchannel coil includes a condensing section, the first fluid port is fluidly connected to an inlet of the condensing section.
Aspect 4. The heat exchanger of any of Aspects 1 to 3, wherein the microchannel coil includes a sub-cooling section, the second fluid port is fluidly connected to an outlet of the sub-cooling section.
Aspect 5. The heat exchanger of any of Aspects 1 to 4, wherein the volume includes a capacity to receive a substantial amount of an operating charge of the working fluid designed for a cooling system in which the heat exchanger is implemented.
Aspect 6. The heat exchanger of any of Aspects 1 to 5, further comprising a fan assembled with the microchannel coil to draw the heat exchange fluid over the microchannel coil.
Aspect 7. The heat exchanger of Aspect 6, wherein the volume is disposed within a perimeter defined by an arrangement of the microchannel coil, the fan, and another coil.
Aspect 8. A cooling system comprising:
a compressor to compress a working fluid;
a first heat exchanger to condense the working fluid, the heat exchanger is fluidly connected with the compressor to receive the working fluid compressed by the compressor;
an expansion device to expand the working fluid, the expansion device is fluidly connected with the first heat exchanger to receive the working fluid condensed by the first heat exchanger; and
a second heat exchanger to evaporate the working fluid, the second heat exchanger is fluidly connected with the expansion device to receive the working fluid expanded by the expansion device,
the first heat exchanger including:
a microchannel coil, the microchannel coil includes flattened tubes extending between two headers, and fins between the flattened tubes,
the microchannel coil includes a first fluid port fluidly connected with one of the headers, and a second fluid port fluidly connected with one of the headers,
compressing a working fluid with a compressor;
directing the working fluid to a first heat exchanger according to claim 1 to condense the working fluid;
directing the working fluid from the first heat exchanger to an expansion device to expand the working fluid;
directing the working fluid from the expansion device to a second heat exchanger; and returning the working fluid to the compressor,
the step of directing the working fluid from the compressor to the first heat exchanger includes directing the working fluid through a volume prior to the working fluid flowing into a microchannel coil of the first heat exchanger.
Aspect 17. The method of Aspect 16, further comprising storing the working fluid, the step of storing includes directing the working fluid into the first heat exchanger, directing the working fluid from the microchannel coil and out of a fluid port; and directing the working fluid into a volume, and storing the working fluid in the volume.
Aspect 18. The method of Aspect 17, wherein the step of storing the working fluid is during a pump down operation.
Aspect 19. A method of retrofitting an existing cooling system comprising:
fluidly connecting a volume to a fluid line fluidly connecting a compressor to a microchannel heat exchanger;
fluidly connecting the volume to a fluid port, which is fluidly connected to the microchannel heat exchanger; and
installing a valve on the fluid line between the compressor and the volume.
The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. The terms “a,” “an,” and “the” include the plural forms as well, unless clearly indicated otherwise.
While the embodiments have been described in terms of various specific embodiments, those skilled in the art will recognize that the embodiments can be practiced with modification within the spirit and scope of the claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2015/001912 | 6/29/2015 | WO | 00 |
