Gas Cooler Assembly for Transcritical Refrigeration System

This application is a continuation of U.S. application Ser. No. 18/074,979 filed Dec. 5, 2022 for “GAS COOLER ASSEMBLY FOR TRANSCRITICAL REFRIGERATION SYSTEM” by S. Jarvie.

The disclosed subject matter relates to a refrigeration system, and more particularly, to a simultaneous heating and cooling refrigeration system.

Heat pumps are efficient alternatives to furnaces, boilers, chillers, and air conditioners for heating and cooling buildings. In order to heat a primary environment, a heat pump must absorb heat from a secondary environment. To accomplish this, a refrigeration system must create a temperature differential with the ambient temperature of the secondary environment. Heat pump heating systems designed for elevated discharge temperatures typically cannot utilize all of their waste heat and have to reject some to of the waste heat to the secondary environment or another environment external to the system. This rejected energy is wasted energy, especially if the system is actively trying to extract heat from the secondary environment. Thus, a need for a more efficient system is desirable.

A transcritical refrigeration gas cooler assembly comprises at least one gas cooler-condenser having an inlet and an outlet, the inlet configured to receive a carbon dioxide (CO) refrigerant from a discharge line of a refrigeration system, at least one evaporator having an inlet and an outlet, the inlet fluidly connected to and downstream of the outlet of the at least one gas cooler-condenser, and an expansion valve positioned upstream of the inlet of at least one evaporator.

A method of operating a transcritical refrigeration gas cooler assembly to recover energy from excess heat comprises receiving a carbon dioxide (CO) refrigerant at a first refrigerant temperature at an inlet of at least one gas cooler-condenser of the gas cooler assembly, flowing an external airflow through the gas cooler assembly, rejecting heat from the COrefrigerant within the at least one gas cooler-condenser to the external airflow to increase an air temperature of the external airflow, and rejecting heat from the external airflow to the COrefrigerant within at least one evaporator to increase a temperature of the COrefrigerant within the evaporator.

While the above-identified figures set forth one or more embodiments of the present disclosure, 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 and components not specifically shown in the drawings.

is a schematic illustration of refrigeration system. Refrigeration systemoperates in a transcritical state using an R-744 carbon dioxide (CO) refrigerant as a working fluid. Thus, refrigeration systemcan be considered a transcritical refrigeration system. R-744 COrefrigerant has a critical point at 87.8° F. (31° C.) and 1070 psia (7.4×10kPa). The various components of refrigeration systemare discussed herein with reference to the refrigeration cycle.

Refrigeration systemincludes primary compressors, which form a first suction group, for compressing the refrigerant to increase its pressure and temperature. In the embodiment shown, there are two primary compressors, but there can be a single primary compressor, or more than two (e.g., four) primary compressorsin alternative embodiments. In one example the temperature of the compressed refrigerant ranges from about 90° F. to 325° F. (32.2° C. to 162.8° C.) such that the refrigerant is supercritical. Primary compressorscan be medium temperature compressors with a lower suction temperature threshold of about 0° F. (−17.8° C.). One liquid accumulatoris fluidly connected to each primary compressor. Liquid accumulatorsact as a safety device to prevent any entrained liquid droplets in suction gases from entering primary compressors. In an alternative embodiment, a single liquid accumulatorcan be fluidly connected to multiple primary compressors. After compression, refrigerant traverses oil separator, positioned downstream of compressorsalong discharge line. Oil separatorremoves oil and other contaminants from the compressed refrigerant, and these contaminants can be collected in oil receiver. Oil separatorcan be bypassed in certain situations, such as to perform maintenance.

Downstream of oil separatoralong discharge lineare first and second heat reclaim circuitsand, respectively. First heat reclaim circuitcan include heat exchangerthrough which the refrigerant, at a temperature of around 90° F. to 325° F., can reject heat to a working fluid (e.g., water, a glycol-water mixture, etc.) of an associated system requiring elevated temperatures, such as a boiler (e.g., steam, electric, hot water, etc.), hot water heater, in-floor heating system, district heating system, thermal mass storage system, phase change materials (PCM) storage systems, etc. Accordingly, refrigerant exits first heat reclaim circuitat a reduced temperature ranging from 88° F. to 300° F. (31.1° C. to 148.9° C.) depending on the refrigerant temperature entering first heat reclaim circuitand the extent of heat exchange with the circuit's working fluid. Second heat reclaim circuitcan be optionally included in refrigeration system, and similarly includes heat exchangerthrough which the refrigerant, at a reduced temperature of 88° F. to 300° F. can reject heat to the working fluid of an associated system, such as any of those listed above with respect to first heat reclaim circuit. Second heat reclaim circuittherefore further reduces the temperature of the refrigerant to about 88° F. to 290° F. (31.1° C. to 143.3° C.). Heat exchangersandcan be brazed plate, shell-tube, and/or coaxial heat exchangers to name a few non-limiting embodiments. Bypass valvesat the inlet to each of heat reclaim circuitsandallow for one or both circuits to be bypassed depending on the operation mode of refrigeration system.

Downstream of heat reclaim circuitsandis gas cooler assembly. Gas cooler assemblyincludes bypass valve, gas cooler-condenser, evaporator, expansion valve, adiabatic precooler, and fan(s). Bypass valveis positioned upstream of gas cooler assemblyand is operable to block refrigerant flow into gas cooler-condenserin a bypass state. In such a state, refrigerant is bypassed to liquid receiver. Evaporatoris fluidly connected to and downstream of gas cooler-condenser, with various intervening components discussed below. Optional dampercan be included in gas cooler assemblyto allow auxiliary heat into gas cooler assembly, as is discussed in greater detail below with respect to. Refrigerant circulates through gas cooler-condenserand is discharged at a reduced temperature. Accordingly, liquid receiveris positioned downstream of gas cooler-condenserfor receiving the refrigerant. After pressure drop from high pressure control valve, liquified refrigerant collects at the bottom of liquid receiver, and gaseous refrigerant (i.e., “flash gas”) rises to the top of liquid receiverwhere it can be extracted along parallel compressor suction lineand provided to parallel compressor, a flash gas compressor positioned in parallel with primary compressors, and compresses gaseous refrigerant for recirculation through discharge line. Parallel compressorcan be similarly fluidly connected to liquid accumulatorfor preventing liquid from entering a respective parallel compressor. An alternative embodiment can include more than one parallel compressor. Intermediate heat exchangercan optionally be positioned along suction lineto superheat suction flash gas and further sub-cool liquid refrigerant.

Linefluidly connects liquid receiverto evaporatorof gas cooler assemblyvia expansion valve. Expansion valvereduces the pressure and temperature of the refrigerant upstream of evaporator. The refrigerant circulates through and is discharged from evaporatoralong primary compressor suction lineand returns to primary compressors. At least a portion of liquified refrigerant from liquid receivercan be provided to optional cooling circuit. Expansion valvereduces the temperature and pressure of the liquified refrigerant, and it circulates through heat exchangerof cooling circuitto absorb heat from and cool a working fluid of the associated system, such as a chiller, cooler, freezer, chilled water system, cooling system, etc., used to cool commercial, industrial, or residential spaces, server rooms, data centers, medical facilities, indoor agricultural facilities, thermal mass storage systems, PCM storage systems, or to refrigerate food, medicine, etc. Refrigerant circulated through cooling circuitcan be returned to primary compressorsalong primary suction line. Systemcan, therefore, advantageously operate in simultaneous heating and cooling modes such that heat reclaims circuit(s)and/orand cooling circuitare energized and operating to exchange heat without the need for a flow reversing valve to change the direction of flow through system.

Gas cooler assemblycan be configured as horizontal assembly (as depicted in) or a v-bank assembly.is a schematic illustration of gas cooler assemblyA, andis a schematic illustration of alternative gas cooler assemblyB, each shown in isolation from the remainder of refrigeration system.are discussed below with continued reference to.

Referring first to, gas cooler assemblyA, as shown, is a horizontal gas cooler assembly with the various subcomponents stacked along the y-axis to receive fluid along the x-axis. If rotated 90° in either direction such that the various components are instead stacked along the x-axis, gas cooler assembly can alternatively be a vertical gas cooler assembly. Gas cooler-condenserA is fluidly connected to discharge lineand receives the refrigerant post-circulation through heat reclaims circuits,(if included and not bypassed) at inletA and discharges the refrigerant at outletA. In an exemplary operation mode, the refrigerant temperature coming into inletA can range from 88° F. to 300° F. Such inlet temperatures can be achieved, for example, by only circulating the refrigerant through a single heat reclaim circuit (e.g., first heat reclaim circuit). While refrigerant is circulating through gas cooler assemblyA, fanA can be operated to draw an external (i.e., outdoor) airflow Fthrough gas cooler assemblyA. Adiabatic precoolerA can cool the incoming airflow Fvia evaporative means if the temperature of the incoming airflow is at or above a threshold condition. Accordingly, adiabatic precoolerA can include adiabatic cooling pads or a nozzle misting system. As airflow Fflows across gas cooler-condenserA, it absorbs heat from the refrigerant circulating through gas cooler-condenserA if a temperature differential exists between the two fluids. In this way, gas cooler-condenser operates as a heat exchanger, operating in series with upstream heat exchangersand. In one example with a relatively cold outdoor temperature between 10° F. and 20° F. (−12.2° C. to −6.7° C.) and a refrigerant temperature between 88° F. and 300° F. at gas cooler-condenserA, airflow Fcan absorb an amount of heat from the refrigerant to generate a relatively warm microclimate downstream of gas cooler-condenserA and upstream of evaporatorA (i.e., in the space between the two), relative to airflow F. Airflow Ftraverses evaporatorA before being exhausted by fan(s)A back to the external environment, often at a higher temperature than that at which it was ingested into gas cooler assemblyA. Under certain microclimate conditions, bypass valve() can be operated to bypass refrigerant to liquid receiver. Such conditions can include the microclimate capacity (i.e., temperature) exceeding an upper threshold, or when 100% of the usable heat is extracted from the refrigerant, such that no further heat rejection is required.

EvaporatorA includes inletA and outletA. Expansion valveA is positioned upstream of inletA. As discussed above, refrigerant from liquid receiveris cooled and expanded by expansion valveA. In one example, the liquid refrigerant can be cooled, by expansion valveA from around 90° F. (32.2° C.), to less than 32° F. (0° C.). The relatively warmer airflow Ffrom the microclimate downstream of gas cooler-condenserA rejects an amount of heat to the refrigerant circulating through evaporatorA such that the refrigerant is discharged generally above the lower suction temperature threshold of primary compressors(i.e., 0° F.), and in an exemplary embodiment, above 32° F. (0° C.). In this manner, the microclimate generated by airflow Ffirst traversing gas cooler-condenserA acts to prevent frost formation on downstream evaporatorA, as the relatively warmer airflow rejects heat to evaporatorA and maintains the surrounding temperature above the freezing point of water (i.e., 32° F.). Gas cooler assemblyA can optionally include damperA fluidly connected to a source of auxiliary/waste heat from a separate system. DamperA is operable to permit the auxiliary heat into the microclimate space between gas cooler-condenserA and evaporatorA.

Referring to, gas cooler assemblyB, as shown, is a v-bank gas cooler assembly with two sets of subcomponents generally symmetrically disposed about midline M, and gas cooler-condensersB and evaporatorsB angled with respect to midline M to form a “V”. Gas cooler assemblyB can alternatively be an angled gas cooler assembly with only a single set of subcomponents on either side of midline M. Gas cooler assemblyB is substantially similar to gas cooler assemblyA, with refrigerant provided to inletB of gas cooler-condensersB and being discharge through outletsB. EvaporatorsB includes inletsB at which cooled refrigerant is provided via expansion valvesB. Refrigerant is discharged from outletsB of evaporatorsB. Fan(s)B draw external airflow Fserially across adiabatic precoolersB, gas cooler-condensersB, and evaporatorsB before exhausting airflow Fback to the external environment. Gas cooler-condensersB are similarly configured to generate a microclimate for preventing frost accumulation on evaporatorsB. Gas cooler assemblyB can also optionally include dampersB for permitting auxiliary heat into the microclimate space between each gas cooler-condenserB and evaporatorB.

Referring back to, in some modes of operation, frost can still form and be detected on evaporator. In such case, refrigeration systemcan initiate the first step of a defrost sequence, which operates gas cooler-condenserin a maximum discharge gas temperature state to increase the heat of rejection capacity and elevate the microclimate temperature above 32° F. to defrost evaporator. If stepalone is not sufficient to defrost evaporator, stepcan be initiated at which system control means throttle the heating output to increase the heating capacity of gas cooler-condenser. If defrosting needs are still not met, stepcan be initiated in which an outdoor cooling coil of gas cooler assemblyis turned off and the indoor cooling circuit is engaged while systemis still rejecting heat via gas cooler-condenser. The defrost sequence can end after a predetermined amount of time or after a “clear” reading from the frost detection system.

is a schematic illustration of alternative refrigeration system, configured for operation at low ambient temperatures. Refrigeration systemsimilarly includes medium temperature, primary compressors, forming a first suction group, for compressing the refrigerant to a supercritical state. Primary compressorscan have a lower suction temperature threshold of about 0° F. One liquid accumulatoris fluidly connected to each primary compressor, and alternatively, to the entire first suction group. Oil separatorremoves oil and other contaminants from the compressed refrigerant, and these contaminants can be collected in oil receiver.

Refrigeration systemfurther includes first heat reclaim circuitand optional second heat reclaim circuit, with heat exchangersand, respectively. First and second heat reclaims circuits,can be bypassed through operation of bypass valves. Gas cooler assemblyis downstream of first and second heat reclaims circuits,on discharge line. Gas cooler assemblycan be arranged as a horizontal, vertical, angled, or v-bank gas cooler assembly. Gas cooler assemblyincludes bypass valve, gas cooler-condenser(s)fluidly connected to and upstream of a pair of expansion valves, each upstream of a respective associated evaporator. Fan(s)operate to draw air across adiabatic precooler(s)and into gas cooler assembly. Evaporatorscan be placed in series and can increase heat absorption of refrigeration system. Bypass valveis operable to bypass gas cooler assemblyand divert refrigerant to liquid receiver. Gas cooler assemblyfurther includes bypass valvedownstream of evaporatorsfor bypassing the low temperature suction group, as is discussed in greater detail below. Dampercan be positioned within or proximate gas cooler assemblyto supply auxiliary heat to the microclimate area. Systemcan further be operable to run a defrost sequence substantially similar to that discussed above with respect to system.

Gas cooler-condenserdischarges refrigerant to liquid receiver. Any gaseous refrigerant can be provided to one or more parallel compressorsvia parallel compressor suction line. Accumulatorcan be fluidly connected to one or more parallel compressors. Intermediate heat exchangercan optionally be positioned upstream of liquid receiverto superheat suction flash gas and further sub-cool liquid refrigerant.

Linefluidly connects liquid receiverto evaporatorsof gas cooler assemblyvia expansion valves. The refrigerant is discharged from evaporatorsalong primary compressor suction lineand returns to primary compressors. At least a portion of liquified refrigerant from liquid receivercan be provided to first cooling circuitand second cooling circuit. First cooling circuitincludes heat exchangerand second cooling circuitincludes heat exchangers. Expansion valvesandreduce the temperature and pressure of the liquified refrigerant, for circulation through heat exchangersand, respectively, to absorb heat from and cool a working fluid of the associated cooling systems, such as those listed above with respect to cooling circuitof system. Refrigerant circulated through first cooling circuitand/or second cooling circuitcan be returned to primary compressorsalong suction line.

Refrigeration systemadditionally includes low temperature compressorsand associated liquid accumulators. Low temperature compressorsform a second (i.e., low temperature) suction group. Low temperature compressorscan operate simultaneously with primary compressorsto “boost” refrigerant to a suitable pressure and temperature for primary compressorsduring low ambient operating conditions with an outside air temperature ranging from −40° F. to −0° F. (−40° C. to −17.8° C.). Low temperature compressorshave a low threshold suction temperature as low as −50° F. (−45.5° C.) in an exemplary embodiment, and as low as −69.7° F. (−56.5° C.) in an alternative embodiment. Bypass valveallows for refrigerant to be provided to low temperature compressorsduring low ambient operating conditions, and for low temperature compressorsto be bypassed when not operating in low ambient conditions. Low temperature discharge lineprovides “boosted” refrigerant to suction lineand back to primary compressors. Desuperheat exchangercan be positioned in thermal communication with low temperature discharge lineand desuperheats the refrigerant to a temperature suitable for primary compressorsto recompress the refrigerant.

Refrigeration systems,can be in wired or wireless communication with controllers,respectively, to control various systems operating modes, microclimate generation, valves, compressors, dampers, fans, etc. Systems,can be electrically powered systems, configured to receive electrical power from one or more sources such as fuel, solar, wind, hydro-electric, off grid energy, etc. Controllers,can be configured to switch between power sources in some embodiments.

Further alternative embodiments of the disclosed refrigeration systems can include more than two heat reclaim circuits, more than two cooling circuits, more than one gas cooler assembly, and various other associated hardware, to name a few, non-limiting examples.

The disclosed refrigeration systems have many benefits. First, transcritical R-744 COcan achieve relatively high temperatures, with the ability to reject heat to various heating systems and having sufficient “waste” heat to generate a microclimate to prevent frost accumulation on the evaporator. The systems can operate simultaneously in heating and cooling modes without the need to reverse refrigerant flow. The gas cooler assemblies operate to recover energy from waste heat in a refrigerant-to-air, then air-to-refrigerant manner by flowing outside air over the gas cooler-condenser to elevate the air temperature to create a microclimate which then elevates the refrigerant temperature in the evaporator. Many existing refrigeration systems recover energy from waste heat in a refrigerant-to-refrigerant manner, which can lead to detrimental superheating of the refrigerant. Finally, the COrefrigerant is non-flammable and more environmentally friendly than fluorocarbon-based refrigerants, as it is not an ozone-depleting substance, has a low global warming potential (GWP), and does not degrade into “forever chemicals” like PFAS (per/polyfluoroalkyl substances) refrigerants and other synthetic refrigerants.

The following are non-exclusive descriptions of possible embodiments of the present invention.

A gas cooler assembly comprises at least one gas cooler-condenser having an inlet and an outlet, the inlet configured to receive a carbon dioxide (CO) refrigerant from a discharge line of a refrigeration system, at least one evaporator having an inlet and an outlet, the inlet fluidly connected to and downstream of the outlet of the at least one gas cooler-condenser, and an expansion valve positioned upstream of the inlet of at least one evaporator.

The gas cooler assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

The above gas cooler assembly can further include at least one adiabatic precooler.

Any of the above gas cooler assemblies can further include at least one fan configured to draw an external airflow into the gas cooler assembly.

Any of the above gas cooler assemblies can further include a bypass valve positioned upstream of the inlet of the at least one gas cooler-condenser.

In any of the above gas cooler assemblies, an external airflow can flow serially across the at least one gas cooler-condenser and the at least one evaporator.

In any of the above gas cooler assemblies, the at least one gas cooler-condenser can receive the COrefrigerant at a first refrigerant temperature ranging from 88° F. to 300° F.

In any of the above gas cooler assemblies, the at least one gas cooler assembly can be configured as a horizontal gas cooler assembly.

In any of the above gas cooler assemblies, the at least one gas cooler assembly can be configured as a vertical gas cooler assembly.

In any of the above gas cooler assemblies, the at least one gas cooler assembly can be configured as a v-bank gas cooler assembly.

In any of the above gas cooler assemblies, the at least one gas cooler assembly can be configured as an angled gas cooler assembly.

Any of the above gas cooler assemblies can further include a damper fluidly connected to a source of auxiliary heat, the damper being configured to allow an amount of the auxiliary heat into the gas cooler assembly between the at least one gas cooler-condenser and the at least one evaporator.

Any of the above gas cooler assemblies can further include a bypass valve positioned downstream of the outlet of the at least one evaporator.

In any of the above gas cooler assemblies, the at least one evaporator can include a plurality of evaporators arranged in series.

A method of operating a gas cooler assembly to recover energy from excess heat comprises receiving a carbon dioxide (CO) refrigerant at a first refrigerant temperature at an inlet of at least one gas cooler-condenser of the gas cooler assembly, flowing an external airflow through the gas cooler assembly, rejecting heat from the COrefrigerant within the at least one gas cooler-condenser to the external airflow to increase an air temperature of the external airflow, and rejecting heat from the external airflow to the COrefrigerant within at least one evaporator to increase a temperature of the COrefrigerant within the evaporator.

The method 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 the above method, the first refrigerant temperature can range from 88° F. to 300° F.

In any of the above methods, flowing the external airflow through the gas cooler assembly can include operating at least one fan of the gas cooler assembly to draw the external airflow serially across the at least one gas cooler-condenser and the at least one evaporator.

Any of the above methods can further include drawing the external airflow across at least one adiabatic precooler, and operating the adiabatic precooler above a threshold condition of the external airflow.

In any of the above methods, rejecting heat from the COrefrigerant within the at least one gas cooler-condenser to the external airflow can generate a microclimate downstream of the at least one gas cooler-condenser and upstream of the at least one evaporator, relative to a direction of the external airflow.

Any of the above methods can further include preventing frost accumulation on the at least one evaporator using the microclimate when a temperature of the microclimate is at least 32° F.

Any of the above methods can further include bypassing the at least one cooler condenser when a temperature of the microclimate exceeds an upper threshold.

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.