HYBRID FREE COOLING WITH CONDENSER SURFACE CONTROL

FIELD

[0001]This disclosure is directed to systems and methods for performing hybrid mechanical and free cooling, particularly controlling the condenser surface to maintain pressure differential(s) while ensuring utilization of available free cooling.

BACKGROUND

[0002]Free cooling systems can utilize the condenser fans of the mechanical cooling system to drive air over the process fluid to be cooled. Condenser fans are controlled to at least maintain suitable pressure differentials within the mechanical cooling circuit for operation of the compressor.

SUMMARY

[0003]This disclosure is directed to systems and methods for performing hybrid mechanical and free cooling, particularly controlling the condenser surface to maintain pressure differential(s) while ensuring utilization of available free cooling.

[0004]In embodiments, a mechanical cooling circuit can be operated while also utilizing free cooling to cool a process fluid. The mechanical cooling circuit can be configured such that a total size of the condensing surface of the condenser of the working fluid can be controlled. For example, valves can selectively permit or restrict flow to certain portions of the condenser, thereby varying the surface area of the condenser that is being utilized. By allowing the total condensing surface of the condenser to be adjusted, the pressure differential in the mechanical cooling circuit can be controlled to suitable levels while allowing the airflow over free cooling heat exchanger to be increased, thereby increasing potential utilization of free cooling. This can enable or improve the efficiency of hybrid operating modes where mechanical cooling is required but where free cooling can at least partially meet cooling demand, thereby reducing energy consumption to achieve desired temperatures.

[0005]In an embodiment, a condensing and free cooling system for a heating, ventilation, air conditioning, and refrigeration (HVACR) system includes a working fluid inlet, a first heat exchange portion including a first condensing surface, a second heat exchange portion including a second condensing surface, a working fluid outlet, and a valve. The valve is configured to receive working fluid from the first heat exchange portion and selectively direct said received working fluid to at least one of the second heat exchange portion and the working fluid outlet. The condensing and free cooling system further includes one or more free cooling heat exchangers and a fan configured to direct an airflow over the at least one free cooling heat exchanger and at least one of the first condensing surface and the second condensing surface.

[0006]In an embodiment, the condensing and free cooling system includes a controller configured to receive a pressure differential of the HVACR system and to control the valve based on the pressure differential.

[0007]In an embodiment, the condensing and free cooling system includes a second fan configured to direct a second airflow over the second condensing surface at least one of the one or more free cooling heat exchangers.

[0008]In an embodiment, the condensing and free cooling system includes a third heat exchange portion including a third condensing surface, and a second valve, wherein the second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet.

[0009]In an embodiment, a heating, ventilation, air conditioning, and refrigeration (HVACR) system includes a mechanical cooling circuit. The mechanical cooling circuit includes a compressor, a condenser, an expander, and an evaporator. The condenser includes a working fluid inlet, a first heat exchange portion including a first condensing surface, a second heat exchange portion including a second condensing surface, a working fluid outlet, and a valve configured to receive working fluid from the first heat exchange portion and selectively direct said received working fluid to at least one of the second heat exchange portion and the working fluid outlet. The HVACR system further includes a process fluid circuit including one or more free cooling heat exchangers and one or more fans each configured to direct air over at least one of the first condensing surface and the second condensing surface and at least one of the one or more free cooling heat exchangers.

[0010]In an embodiment, the HVACR system further includes a controller configured to operate one or more of the valves and the one or more fans based on a pressure differential in the mechanical cooling circuit. In an embodiment, the controller is configured to operate one or more of the valves and the one or more fans such that the pressure differential is maintained above an operational threshold of the mechanical cooling circuit.

[0011]In an embodiment, the condenser further includes a third heat exchange portion including a third condensing surface, and a second valve. The second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet.

[0012]In an embodiment, the one or more free cooling heat exchangers includes at least a first free cooling heat exchanger and a second free cooling heat exchanger. The one or more fans includes at least a first fan configured to direct a first airflow over the first condensing surface and the first free cooling heat exchanger and a second fan configured to direct a second airflow over the second condensing surface and the second free cooling heat exchanger.

[0013]In an embodiment, a method of controlling a heating, ventilation, air conditioning, and refrigeration (HVACR) system includes circulating a process fluid in a process fluid circuit, wherein the process fluid circuit includes one or more free cooling heat exchangers and circulating a working fluid in a mechanical cooling circuit, wherein the mechanical cooling circuit includes a compressor and a condenser. The method further includes operating at least one fan so as to direct an airflow over at least one of the one or more free cooling heat exchangers and at least a portion of the condenser. The method also includes controlling at least one valve condenser so as to allow or prevent flow of the working fluid from a first portion of the condenser to a second portion of the condenser, based on a pressure differential in the mechanical cooling circuit.

[0014]In an embodiment, controlling the at least one valve reduces an effective condensing surface of the condenser when the pressure differential in the mechanical cooling circuit is at or below a threshold pressure differential value. In an embodiment, the threshold pressure differential value is a minimum pressure differential for operation of the compressor.

[0015]In an embodiment, operating the at least one fan includes operating a first fan at a first speed and a second fan at a second speed. The first fan directs a first airflow over at least one of the one or more free cooling heat exchangers and the first portion of the condenser when the first portion of the condenser has working fluid flowing therethrough. The second fan directs a second airflow over at least one of the one or more free cooling heat exchangers and the second portion of the condenser when flow of the working fluid to the second portion of the condenser is prevented by the valve. The second speed is greater than the first speed. In an embodiment, the first speed is determined based on the pressure differential in the mechanical cooling circuit. In an embodiment, the method further includes determining the second speed based on a desired outlet temperature of the one or more free cooling heat exchangers.

DRAWINGS

[0016]FIG. 1 shows a heating, ventilation, air conditioning, and refrigeration (HVACR) system according to an embodiment.

[0017]FIG. 2 shows a condenser and free cooling system for an HVACR system according to an embodiment.

[0018]FIG. 3 shows a method of operating an HVACR system according to an embodiment.

DETAILED DESCRIPTION

[0019]This disclosure is directed to systems and methods for performing hybrid mechanical and free cooling, particularly controlling the condenser surface to maintain pressure differential(s) while ensuring utilization of available free cooling.

[0020]FIG. 1 shows a heating, ventilation, air conditioning, and refrigeration (HVACR) system according to an embodiment. HVACR system 100 includes working fluid circuit 102 and process fluid circuit 104. HVACR system 100 further includes one or more fan(s) 120. HVACR system 100 also includes a controller 122.

[0021]In an embodiment, working fluid circuit 102 can include a compressor 106, a condenser 108, an expander 110, and an evaporator 112.

[0022]In an embodiment, the process fluid circuit 104 can include the evaporator 112, pump 114, load 116, and one or more free cooling heat exchanger(s) 118.

[0023]HVACR system 100 is a system configured to provide at least cooling to a conditioned space by circulating a process fluid to absorb heat from the conditioned space. The HVACR system 100 can optionally be configured to further provide heating, for example by having the working fluid circuit 102 further including components for operation as a heat pump, one or more boilers or any other suitable additions for such functionality. The HVACR system 100 can optionally further include any suitable components for servicing ventilation and/or refrigeration demands. HVACR system 100 is configured to be operated in operating modes including at least a free cooling mode where the process fluid is cooled by the ambient environment, a mechanical cooling mode where the process fluid is cooled by operation of working fluid circuit 102, and a hybrid cooling mode where the process fluid is cooled by a combination of the ambient environment and operation of the working fluid circuit 102.

[0024]Working fluid circuit 102 is configured to provide at least mechanical cooling to the process fluid of the process fluid circuit 104. Working fluid circuit 102 is configured to circulate a working fluid, such as a refrigerant or a blend thereof. Working fluid circuit 102 can include any suitable components in a suitable arrangement to circulate a working fluid such that the working fluid can exchange heat with the process fluid to provide cooling to the process fluid in mechanical cooling or hybrid cooling modes.

[0025]Working fluid circuit 102 includes compressor 106. Compressor 106 can be any suitable compressor for compressing the working fluid, such as a screw compressor, a scroll compressor, a centrifugal compressor, or the like. Compressor 106 can have a pressure differential requirement that is to be maintained to ensure operation of the compressor 106 or the efficiency thereof.

[0026]Condenser 108 is configured to allow the working fluid from compressor 106 to exchange heat with an ambient environment. Condenser 108 can also be referred to as a first heat exchanger or an outdoor heat exchanger. Condenser 108 includes a plurality of condenser segments 124 each including a condensing surface 126. In an embodiment, condenser 108 includes at least three condenser segments 124. Each condensing surface 126 is a surface of a heat exchanger allowing the working fluid in the respective condenser segment 124 to exchange heat with the ambient environment. Each of condenser segments 124 is separated by at least one of the valves 128. Valves 128 are each configured to control flow of the working fluid from one condenser segment 124 to another, such that the working fluid can be directed either to a successive condenser segment 124 or to a fluid line configured to convey the working fluid to expander 110. In an embodiment, valves 128 are three-way valves. In an embodiment, the valves 128 are combined with check valves as shown in FIG. 2 and described below to provide control of the flow of the working fluid.

[0027]Expander 110 is configured to expand the working fluid. Expander 110 can be any suitable expander for expanding the working fluid. Non-limiting examples of expander 110 include one or more expansion orifices, expansion valves, orifice plates, controllable expansion valves such as electronic expansion valves, combinations thereof, and the like. Expander 110 can be downstream of condenser 108, such that expander 110 receives the working fluid leaving condenser 108.

[0028]Evaporator 112 is a heat exchanger where the expanded working fluid from expander 110 exchanges heat with the process fluid of process fluid circuit 104, thereby cooling the process fluid. The working fluid leaving evaporator 112 can return to the compressor 106.

[0029]Process fluid circuit 104 is configured to circulate a process fluid to service at least a cooling demand at load 116. The process fluid circulated by process fluid circuit 104 can be any suitable process fluid suitable for absorbing and rejecting heat to provide cooling at the load 116, such as water, glycol, combinations thereof, and the like. Process fluid circuit 104 includes the evaporator 112, where the process fluid is placed in a heat exchange relationship with the working fluid. Process fluid circuit 104 can further include one or more pump(s) 114 configured to drive the process fluid to circulate through the process fluid circuit 104. Process fluid circuit 104 is configured to service at least cooling needs at load 116. Load 116 includes one or more conditioned spaces, such as a building or portions thereof. The working fluid can exchange heat with air to be cooled at load 116 by way of one or more terminals or the like.

[0030]Process fluid circuit 104 is configured to be able to utilize free cooling under suitable conditions. Process fluid circuit 104 includes one or more free cooling heat exchanger(s) 118. At each of free cooling heat exchanger(s) 118, the process fluid can reject heat to the ambient environment, thereby cooling the process fluid. In an embodiment, free cooling heat exchanger(s) 118 are located at or near the condenser segments 124. In an embodiment, a free cooling heat exchanger 118 is provided for each of the condenser segments 124. In an embodiment, each free cooling heat exchanger 118 is provided at or near a corresponding condenser segment 124. In an embodiment, process fluid circuit 104 can include suitable piping and valves configured to control flow to each of the free cooling heat exchanger(s) 118, such that the flow of process fluid to each of the free cooling heat exchanger(s) 118 can be controlled.

[0031]Fans(s) 120 are configured to each direct airflow over at least one of the one or more free cooling heat exchanger(s) 118 and at least one of the condenser segments 124. The fans 120 can be configured to draw air through or drive air over the one or more free cooling heat exchanger(s) 118 and at least one of the condenser segments 124. In an embodiment, a fan 120 can be provided for each of one respective free cooling heat exchanger 118 and one respective condenser segment 124. In an embodiment, the fans 120 can be controlled to provide airflow at a speed determined by controller 122. In an embodiment, the fans 120 can each be individually controlled to a determined speed. The airflow provided by fans 120 can facilitate heat exchange between the ambient environment and the process and working fluids respectively in the one or more free cooling heat exchanger(s) 118 and at least one of the condenser segments 124.

[0032]Controller 122 is configured to control one or more elements of the HVACR system 100. Controller 122 can be configured to control valves 128 and/or fans 120. Controller 122 can be configured to control the control valves 128 and/or fans 120 based on a pressure differential in the working fluid circuit 102. The pressure differential in the working fluid circuit 102 can be maintained at or above a threshold value, or within a desired range of pressure differentials by controlling valves 128 and/or fans 120 when in a hybrid mode where free cooling and mechanical cooling are used together. The controller 122 can control the pressure differential by controlling the valves 128 to adjust a number of condenser segments 124 at which working fluid can reject heat at the condensing surfaces 126 thereof. For example, when the pressure differential is at or below a threshold value or a lower boundary of a range, the valves 126 can be adjusted to reduce the number of condenser segments 124 receiving working fluid. In an embodiment, the threshold value or lower boundary of the range of pressure differentials can be a minimum pressure differential required for operation of the compressor 106, the minimum required pressure differential as adjusted by a safety factor, a value set based on efficiency calculations and/or an operating map of the compressor, or the like. In an embodiment, the valves 126 can be operated to increase the number of condenser segments 124 receiving working fluid to thereby increase an effective condensing surface of the condenser 108, for example when the pressure differential is above a threshold value, above a required minimum pressure differential for compressor 106 by a predetermined amount, or the like. Controller 122 can further control the operation of fans 120. For example, controller 122 can select or adjust a fan speed based on the pressure differential. Fans 120 can be set to a slower speed or the speed of fans 120 can be adjusted downwards when the pressure differential is at or below a threshold value or a lower boundary of a range. Fans 120 can be set to a higher speed or adjusted upwards when the pressure differential is above a second threshold value or an upper boundary of a range. In the hybrid operation, increasing the speed of fans 120 can increase the utilization of available free cooling by increasing airflow over the free cooling heat exchanger(s) 118. In an embodiment, the controller 122 can be configured to control the fans 120 according to whether a respective condenser segment 124 associated with the particular fan 120 is receiving working fluid. In an embodiment, condenser segments 124 receiving working fluid can have the associated fans 120 controlled according to the pressure differential(s) in the working fluid circuit 102, whereas the fans 120 associated with condenser segments 124 that are not receiving working fluid can be operated based on a desired speed for utilization of available free cooling. For example, condenser segments 124 receiving working fluid can have the associated fans 120 operated at relatively lower speeds than the fans 120 associated with condenser segments 124 that are not receiving working fluid.

[0033]Pressure sensors 130 can be included in or along the working fluid circuit 102. Pressure sensors 130 can determine a pressure differential across the working fluid circuit 102. The pressure differential determined using pressure sensors 130 can be a pressure differential between any two suitable points on working fluid circuit 102 such that the pressure differential is indicative of an ability to operate or an efficiency of operating the working fluid circuit 102. For example, the pressure sensors 130 can be positioned such that the pressure differential across compressor 106 can be determined. In embodiments, more than two pressure sensors 130 can be provided, and pressure differentials can be determined based on the respective pressures measured at each. Pressure sensors 130 can be connected to controller 122 such that the controller 122 can receive the readings from the pressure sensors 130 and determine the pressure differentials between the pressure sensors 130. The pressure differentials determined based on the readings from pressure sensors 130 can be used by controller 122 to control the valves 128 and/or the fans 120 so as to maintain suitable pressure differential(s) while taking advantage of available free cooling to support operation in a hybrid mode including mechanical cooling and free cooling being performed together.

[0034]FIG. 2 shows a condenser and free cooling system for an HVACR system according to an embodiment. Condenser and free cooling system 200 includes condenser 202 including a working fluid inlet 204, a plurality of condenser segments 206, one or more valve(s) 208, check valve(s) 210 and a working fluid outlet 212. The condenser and free cooling system 200 further includes a process fluid inlet 214, one or more free cooling heat exchanger(s) 216, and a process fluid outlet 218. The condenser and free cooling system 200 also includes one or more fan(s) 220 and a controller 222.

[0035]Condenser and free cooling system 200 can be an outdoor portion of an HVACR system such as HVACR system 100 described above and shown in FIG. 1. Condenser and free cooling system 200 can include condenser 202, where working fluid of a working fluid circuit can exchange heat with an ambient environment, and can include free cooling heat exchanger(s) 216, where a process fluid of a process fluid circuit can also exchange heat with the ambient environment to perform free cooling. The condenser and free cooling system 200 can be, for example, included in a rooftop unit or other suitable outdoor unit of the HVACR system.

[0036]Condenser 202 provides the condenser of a working fluid circuit. Condenser 202 includes working fluid inlet 204. At working fluid inlet 204, working fluid is received from a compressor of a working fluid circuit, such as compressor 106 of working fluid circuit 102 described above and shown in FIG. 1. From working fluid inlet 204, the received working fluid can pass to a first condenser segment 206.

[0037]Condenser segments 206 are a plurality of heat exchangers each configured to allow heat exchange between an ambient environment and the working fluid, for example at a condensing surface thereof. Each condenser segment 206 can include one or more heat exchanger coils. In an embodiment, each condenser segment 206 includes a pair of heat exchange coils angled to form a V-shape. In an embodiment, the condenser segments 206 are arranged in series.

[0038]Valves 208 are configured to control the flow of working fluid to condenser segments 206. In the embodiment shown in FIG. 2, a valve 208 is provided between each of the successive condenser segments 206 in series, such that each valve 208 can obstruct flow to all downstream condenser segments 206. The valves 208 can be controlled such that the number of condenser segments 206 is adjustable, thereby allowing the overall condensing surface provided by condenser 202 to be adjustable based on operation of the valves 208. In an embodiment, at least some of valves 208 are two-way valves configured to allow or prohibit flow therethrough. In an embodiment, at least some of valves 208 are three-way valves configured to receive a flow from a first condenser segment 206 and selectively direct the working fluid to one of a subsequent condenser segment(s) 206 or to a return line extending to the working fluid outlet 212.

[0039]Check valves 210 can optionally be included to control flow in the condenser 202, such that working fluid does not flow backwards to condenser segments 206 that would be excluded from receiving working fluid flow based on the position of valves 208. For example, the check valves can be positioned between connections of respective condenser segments 206 to a return line leading to the working fluid outlet 212.

[0040]Working fluid outlet 212 allows the working fluid leaving the condenser segments 206 to continue passing through the working fluid circuit, for example to an expander such as the expander 110 described above and shown in FIG. 1. The working fluid outlet 212 can receive fluid flow from the most downstream condenser segment 206 that is allowed to receive working fluid by way of the valves 208. In an embodiment, the valves 208 can be configured to direct the working fluid to the working fluid outlet 212 when preventing flow to any of the following condenser segment(s) 206.

[0041]Process fluid inlet 214 is configured to receive process fluid from a process fluid circuit, such as the process fluid circuit 104 described above and shown in FIG. 1. The process fluid inlet 214 can receive the process fluid when the HVACR system including condenser and free cooling system 200 is in a free cooling mode or a hybrid cooling mode. The process fluid received at process fluid inlet 214 is directed to one or more free cooling heat exchanger(s) 216. The free cooling heat exchangers 216 are one or more heat exchangers configured to allow the process fluid to exchange heat with the ambient environment, thereby cooling the process fluid under particular ambient conditions. In an embodiment, the free cooling heat exchangers 216 are located at or near corresponding condenser segments 206. In an embodiment, the free cooling heat exchangers 216 include a plurality of heat exchange coils. In such an embodiment, at least some of the heat exchange coils are located at or near corresponding heat exchange coils of condenser segments 206. In such an embodiment, the plurality of heat exchange coils includes pairs of heat exchange coils arranged in a V-shape and located adjacent to a V-shaped pair of heat exchange coils of one of the condenser segments 206. In embodiments including a plurality of free cooling heat exchangers 216, the free cooling heat exchangers 216 can be arranged in series. The free cooling heat exchangers can be connected to a process fluid outlet 218. The process fluid can continue through a process fluid circuit, for example passing to one or more pumps such as pump 114 described above and shown in FIG. 1, to a process fluid side of an evaporator such as evaporator 112 described above and shown in FIG. 1, or any other suitable part of the process fluid circuit.

[0042]Fan(s) 220 are configured to each direct airflow over at least one of the one or more free cooling heat exchanger(s) 216 and at least one of the condenser segments 206. The fans 220 can be configured to draw air through or drive air over the one or more free cooling heat exchanger(s) 216 and at least one of the condenser segments 206. In an embodiment, a fan 220 can be provided for each of one respective free cooling heat exchanger 216 and one respective condenser segment 206. In an embodiment, the fans 220 can be controlled to provide airflow at a speed determined by controller 222. In an embodiment, the fans 220 can each be individually controlled to a determined speed. The airflow provided by fans 220 can facilitate heat exchange between the ambient environment and the process and working fluids respectively in the one or more free cooling heat exchanger(s) 216 and at least one of the condenser segments 206.

[0043]Controller 222 is a controller configured to control at least the valves 208 and/or the fans 220. Controller 222 can be configured to receive pressure values from pressure sensors (as a non-limiting example, the pressure sensors 130 described above and shown in FIG. 1) within the working fluid circuit and to control the valves 208 and/or fans 220 based on a pressure differential within the working fluid circuit. The pressure differential can be maintained at or above a threshold value, or within a desired range of pressure differentials by controlling valves 208 and/or fans 220 when in a hybrid mode, where free cooling and mechanical cooling are used together. The controller 220 can control the pressure differential by controlling the valves 208 to adjust a number of condenser segments 206 at which working fluid can reject heat to the ambient environment. For example, when the pressure differential is at or below a threshold value or a lower boundary of a range, the valve(s) can be adjusted to reduce the number of condenser segments 206 receiving working fluid. In an embodiment, the threshold value or lower boundary of the range of pressure differentials can be a minimum pressure differential required for operation of the working fluid circuit or components thereof, such as for example, but not limited to a compressor. In some embodiments, the threshold value or lower boundary can be a minimum required pressure differential as adjusted by a safety factor, a value set based on efficiency calculations and/or an operating map of the compressor, or the like. In an embodiment, the valves 208 can be operated to increase the number of condenser segments 206 receiving working fluid to thereby increase the effective condensing surface of the condenser 202, for example when the pressure differential is above a threshold value, above a required minimum pressure differential for the compressor by a predetermined amount, or the like. Controller 222 can further control the operation of fans 220. For example, controller 222 can select or adjust a fan speed based on the pressure differential, activate one or more of fans 220, deactivate one or more of fans 220, or the like. Fans 220 can be set to a slower speed or the speed of fans 220 can be adjusted downwards when the pressure differential is at or below a threshold value or a lower boundary of a range. Fans 220 can be set to a higher speed or adjusted upwards when the pressure differential is above a second threshold value or an upper boundary of a range. In the hybrid operation, increasing the speed of fans 220 can increase the utilization of available free cooling by increasing airflow over the free cooling heat exchanger(s) 216. In an embodiment, the controller 222 can be configured to control the fans 220 according to whether a respective condenser segment 206 associated with the particular fan 220 is receiving working fluid. In an embodiment, condenser segments 206 receiving working fluid can have the associated fans 220 controlled according to the pressure differential(s) in the working fluid circuit, whereas the fans 220 associated with condenser segments 206 that are not receiving working fluid can be operated based on a desired speed for utilization of available free cooling. For example, condenser segments 206 receiving working fluid can have the associated fans 220 operated at relatively lower speeds than the fans 220 associated with condenser segments 206 that are not receiving working fluid.

[0044]FIG. 3 shows a method of operating an HVACR system according to an embodiment. Method 300 includes circulating a process fluid in a process fluid circuit 302, circulating a working fluid in the mechanical cooling circuit 304, operating a fan 306, and controlling at least one valve based on a pressure differential in the mechanical cooling circuit 308. In an embodiment, the method according to FIG. 3 can be carried out in HVACR system 100 as shown in FIG. 1 and described above. In an embodiment, the method according to FIG. 3 can be carried out in an HVACR system including the condenser and free cooling system 200 as shown in FIG. 2 and described above.

[0045]Method 300 can be performed during a hybrid cooling operation of the HVACR system. The hybrid cooling operation can be an operation where the HVACR system is providing cooling to a conditioned space utilizing a combination of mechanical cooling provided by operation of a working fluid circuit and by utilizing free cooling by having a process fluid reject heat to an ambient environment.

[0046]The process fluid is circulated at 302. The circulation of the process fluid at 302 includes flow to a cooling load where the process fluid absorbs heat to thereby cool the cooling load, and also flow of the process fluid through one or more free cooling heat exchangers where the process fluid can reject heat to an ambient environment. The circulation of the process fluid at 302 further includes flow of the process fluid through an evaporator of the working fluid circuit, where the working fluid can absorb heat from the process fluid, thereby cooling the process fluid. In an embodiment, the circulation of the process fluid at 302 can be driven by one or more suitable pumps. The one or more free cooling heat exchangers through which the process fluid is circulated at 302 can be located at or near segments of the condenser of the working fluid circuit, such that ambient air is directed over both at least one of the one or more free cooling heat exchangers and at least one segment of the condenser when driven by a fan.

[0047]The working fluid is circulated at 304. The circulation of the working fluid at 304 includes flow through a circuit so as to provide cooling to the process fluid. The circulation of working fluid at 304 and the circulation of process fluid at 302 can be performed at overlapping periods of time during the method 300. The circulation of the working fluid at 304 can include compressing the working fluid at any suitable one or more compressors, directing the compressed working fluid to a condenser, directing the working fluid from the condenser to an expander, and directing the working fluid from the expander to an evaporator. At the evaporator, the working fluid can absorb heat from the process fluid being circulated at 302, thereby cooling the process fluid. The working fluid from the evaporator can pass back to the compressor to continue being circulated at 304. The condenser in the working fluid circuit includes a plurality of segments, each including a condensing surface where the working fluid can exchange heat with the ambient environment. The segments can be selectively included or excluded from the fluid path through which the working fluid is circulated at 304 by operation of the valves at 308, thereby modifying the condensing surface at which the working fluid can exchange heat with the ambient environment.

[0048]One or more fans are operated at 306. The operation of the fans at 306 can direct airflow over or through one or more segment(s) of the condenser of the working fluid circuit and/or over or through the free cooling heat exchanger(s) of the process fluid circuit. In an embodiment, the operation of fans at 306 includes operation of a plurality of fans, where each fan of the plurality of fans provides airflow over or through one free cooling heat exchanger and one corresponding segment of the condenser. In an embodiment, all fans being operated at 306 can be operated at the same speed. In an embodiment, the speed can be determined independently for each of the fans being operated at 306. In an embodiment, at least one of the one or more fans can be operated at 306 at a speed determined based on one or more free cooling parameters, such as ambient temperature, inlet temperature, desired outlet temperature, or the like. In an embodiment, at least one of the one or more fans can be operated at a speed determined based on a pressure differential within the working fluid circuit. For example, one or more fans associated with segments of the condenser where working fluid is being circulated at 304 can be operated at speeds selected so as to avoid reducing a pressure differential within the working fluid circuit below an operational threshold of the working fluid circuit. Fans associated with segments of the condenser where working fluid is not being circulated at 304 can be operated 306 at different speeds, for example at speeds higher than those associated with segments where working fluid is being circulated at 304. In an embodiment, the speeds of the fans being operated at 306 can be determined based on the effects of the fan speed on pressure differential in the mechanical cooling circuit as a function of the effective condensing surface of the condenser resulting from operation of valves at 308.

[0049]At least one valve is controlled based on a pressure differential in the mechanical cooling circuit at 308. The control of the valve(s) at 308 can control the number of segments of the condenser receiving working fluid. For example, the valve(s) located at 308 can allow or permit flow from one segment of the condenser to a successive segment of the condenser. In an embodiment, the valve(s) operated at 308 can be variable flow valves configured to regulate an amount of working fluid flowing from one segment of the condenser to a successive segment of the condenser. The working fluid that is not directed to a successive segment of the condenser can, by any suitable valves and/or piping, bypass the remainder of the condenser and flow to the expander as the working fluid is circulated 304. The control of valves at 308 can thereby control the effective condensing surface of the condenser by controlling the number of condenser segments where the working fluid can exchange heat with the ambient environment. The control of the valve(s) at 308 can be based on, for example, pressure differential(s) within the working fluid circuit, thresholds for such pressure differential(s), and the like. For example, the valves can be controlled at 308 so as to maintain at least a threshold pressure differential within the working fluid circuit such that the working fluid circuit can be operated. The threshold pressure differential can be based on the operating characteristics of the working fluid circuit or components thereof, such as for example but not limited to the compressor. The threshold pressure differential can, in embodiments, include a safety factor for maintaining the pressure differential above an operational requirement for the working fluid circuit. In an embodiment, the valves can be controlled at 308 to reduce the condensing surface of the condenser when the pressure differential within the working fluid circuit is at or below the threshold pressure differential. In an embodiment, the valves can be controlled at 308 based on predicted values of the pressure differential based on the operating parameters of the working fluid circuit, ambient temperatures, cooling demand, process fluid temperatures, speed of the operation of fans at 306, or any other suitable parameters capable of affecting the pressure differential within the working fluid circuit. The control according to predicted values can be such that the pressure differential is maintained at or above the threshold pressure differential. In an embodiment, the valves are controlled at 308 to maintain the pressure differential in a range including a lower threshold and an upper threshold. In an embodiment, the valves can be controlled at 308 to increase the number of condenser segments receiving working fluid to thereby increase the effective condensing surface of the condenser, for example when the pressure differential is above the threshold value, above a required minimum pressure differential for the compressor by a predetermined amount, or the like.

Aspects

[0050]It is understood that any of aspects 1-4 can be combined with any of aspects 5-9 or 10-15. It is understood that any of aspects 5-9 can be combined with any of aspects 10-15.

[0057]Aspect 2. The condensing and free cooling system according to aspect 1, further comprising a controller configured to receive a pressure differential of the HVACR system and to control the valve based on the pressure differential.

[0058]Aspect 3. The condensing and free cooling system according to any of aspects 1-2, further comprising a second fan configured to direct a second airflow over the second condensing surface and at least one of the one or more free cooling heat exchangers.

[0059]Aspect 4. The condensing and free cooling system according to any of aspects 1-3, further comprising a third heat exchange portion including a third condensing surface, and a second valve, wherein the second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet.

[0074]Aspect 6. The HVACR system according to aspect 5, further comprising a controller configured to operate one or more of the valve and the one or more fans based on a pressure differential in the mechanical cooling circuit.

[0075]Aspect 7. The HVACR system according to aspect 6, wherein the controller is configured to operate one or more of the valve and the one or more fans such that the pressure differential is maintained above an operational threshold of the mechanical cooling circuit.

[0076]Aspect 8. The HVACR system according to any of aspects 5-7, wherein the condenser further comprises a third heat exchange portion including a third condensing surface, and a second valve, wherein the second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet.

[0077]Aspect 9. The HVACR system according to any of aspects 5-8, wherein the one or more free cooling heat exchangers includes at least a first free cooling heat exchanger and a second free cooling heat exchanger, and the one or more fans includes at least a first fan configured to direct a first airflow over the first condensing surface and the first free cooling heat exchanger, and a second fan configured to direct a second airflow over the second condensing surface and the second free cooling heat exchanger.

[0083]Aspect 11. The method according to aspect 10, wherein controlling the at least one valve reduces an effective condensing surface of the condenser when the pressure differential in the mechanical cooling circuit is at or below a threshold pressure differential value.

[0084]Aspect 12. The method according to aspect 11, wherein the threshold pressure differential value is a minimum pressure differential for operation of the compressor.

[0085]Aspect 13. The method according to any of aspects 10-12, wherein operating the at least one fan includes operating a first fan at a first speed and a second fan at a second speed, wherein the first fan directs a first airflow over at least one of the one or more free cooling heat exchangers and the first portion of the condenser when the first portion of the condenser has working fluid flowing therethrough, the second fan directs a second airflow over at least one of the one or more free cooling heat exchangers and the second portion of the condenser when flow of the working fluid to the second portion of the condenser is prevented by the valve, and wherein the second speed is greater than the first speed.

[0086]Aspect 14. The method according to aspect 13, wherein the first speed is determined based on the pressure differential in the mechanical cooling circuit.

[0087]Aspect 15. The method according to any of aspects 13-14, further comprising determining the second speed based on a desired outlet temperature of the one or more free cooling heat exchangers.

[0088]The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.