# US 11,441,824 B2 · Subcritical CO2 refrigeration system using thermal storage > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,441,824 B2 - Document ID: US11441824B2 - Status: Granted - Kind: B2 - Application number: 16/763,089 - Filed: 2017-11-10 - Published: 2020-11-05 - Granted: 2022-09-13 - Earliest claimed: 2017-11-10 - Assignees: Hussmann Corporation - Applicants: Hussmann Corporation - Inventors: Norman E. Street; Tobey D. Fowler; Neil Monson; Wayne G. Schaeffer - Web page: https://patentgrep.com/patent/US11441824B2 ## CPC - F25B 25/005: {using primary and secondary systems} - A47F 3/04: air-conditioned, refrigerated (refrigerators F25D; heating arrangements specially adapted for transparent or reflecting areas H05B3/84) - F25B 1/10: with multi-stage compression (with cascade operation F25B7/00) - F25B 5/02: arranged in parallel - F25B 6/04: arranged in series - F25B 9/008: {the refrigerant being carbon dioxide} - F25B 2339/047: Water-cooled condensers - F25B 2400/13: Economisers - F25B 2400/22: Refrigeration systems for supermarkets - F25B 2400/23: Separators - F25B 2400/24: Thermal storage element - F25B 2600/2501: Bypass valves - F25B 2600/2507: Flow-diverting valves - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS - A47F: SPECIAL FURNITURE, FITTINGS, OR ACCESSORIES FOR SHOPS, STOREHOUSES, BARS, RESTAURANTS OR THE LIKE; PAYING COUNTERS ## Abstract A refrigeration system includes a primary refrigeration circuit configured to circulate a CO2 primary refrigerant and a secondary refrigeration circuit separate from the primary refrigeration circuit. The primary refrigeration circuit includes a compressor assembly, a condenser assembly, a receiver, and one or more refrigeration loads having an evaporator assembly. The secondary refrigeration circuit includes a thermal storage unit and a heat exchanger. The thermal storage unit contains a phase change material. The secondary refrigeration circuit is in thermal communication with the primary refrigeration circuit through the heat exchanger. The primary refrigerant includes a critical temperature. The primary refrigeration circuit is configured for subcritical operation. The primary refrigeration circuit and the secondary refrigeration circuit are configured such that the phase change material provides cooling to the primary refrigerant during a first operating condition. The phase change material is configured to maintain subcritical operation of the primary refrigeration circuit during the first operating condition when the primary refrigerant is above the critical temperature. ## Claims ### Claim 1 A refrigeration system comprising: a primary refrigeration circuit configured to circulate a CO2 primary refrigerant, the primary refrigeration circuit including a compressor assembly, a condenser assembly, a receiver, and one or more refrigeration loads having an evaporator assembly; and a secondary refrigeration circuit separate from the primary refrigeration circuit and including a thermal storage unit and a heat exchanger, the thermal storage unit containing a phase change material, wherein the secondary refrigeration circuit is in thermal communication with the primary refrigeration circuit through the heat exchanger, wherein the primary refrigerant includes a critical temperature, wherein the primary refrigeration circuit is configured for subcritical operation such that the CO2 primary refrigerant remains at or below a critical temperature, wherein the primary refrigeration circuit and the secondary refrigeration circuit are configured such that the phase change material provides cooling to the primary refrigerant during a first operating condition, and wherein the phase change material is configured to maintain subcritical operation of the primary refrigeration circuit during the first operating condition when the primary CO2 refrigerant would otherwise be above the critical temperature. ### Claim 2 (depends on 1) The refrigeration system of claim 1, wherein the one or more refrigeration loads includes a low temperature refrigerated merchandiser and a medium temperature refrigerated merchandiser. ### Claim 3 (depends on 1) The refrigeration system of claim 1, wherein the secondary refrigeration circuit is configured to circulate a secondary refrigerant and the phase change material contained in the thermal storage unit is separate from the secondary refrigerant. ### Claim 4 (depends on 1) The refrigeration system of claim 1, wherein the heat exchanger is a discharging heat exchanger and the secondary refrigeration circuit includes a charging heat exchanger. ### Claim 5 (depends on 4) The refrigeration system of claim 4, wherein the primary refrigeration circuit and the secondary refrigeration circuit are configured such that the primary refrigerant provides cooling to the phase change material through the charging heat exchanger. ### Claim 6 (depends on 1) The refrigeration system of claim 1, wherein the primary refrigeration circuit is configured for subcritical operation in a first ambient temperature range and a second ambient temperature range, and is configured for transcritical operation in a third ambient temperature range. ### Claim 7 (depends on 6) The refrigeration system of claim 6, wherein the first ambient temperature range is below approximately 77° F., the second ambient temperature range is above approximately 95° F., and the third ambient temperature range is between approximately 77° F. and approximately 95° F. ### Claim 8 (depends on 1) The refrigeration system of claim 1, wherein the primary refrigeration circuit includes a condenser conduit, wherein the condenser conduit is in communication with the heat exchanger. ### Claim 9 (depends on 8) The refrigeration system of claim 8, wherein the condenser conduit is connected to an inlet conduit by a valve positioned between the condenser assembly and the receiver. ### Claim 10 (depends on 8) The refrigeration system of claim 8, wherein the condenser conduit is connected to an adiabatic cooler in communication with the condenser assembly. ### Claim 11 A refrigeration system comprising: a CO2 refrigerant having a critical temperature; a receiver configured to retain the CO2 refrigerant; one or more refrigeration loads having an evaporator assembly and in fluid communication with the receiver; a compressor assembly in fluid communication with the refrigeration loads; a condenser assembly in fluid communication with the compressor assembly; and a thermal storage unit in fluid communication with the condenser assembly and the receiver, wherein the thermal storage unit includes a heat exchanger and phase change material, wherein the phase change material provides cooling to the CO2 refrigerant during a first operating condition when the CO2 refrigerant would otherwise be above the critical temperature, and wherein the CO2 refrigerant is configured to cool the phase change material during a second operating condition when the CO2 refrigerant is below the critical temperature. ### Claim 12 (depends on 11) The refrigeration system of claim 11, wherein during the first operating condition the CO2 refrigerant is directed from the condenser assembly to the thermal storage unit prior to entering the receiver. ### Claim 13 (depends on 11) The refrigeration system of claim 11, wherein the heat exchanger includes a fin-tube heat exchanger. ### Claim 14 (depends on 11) The refrigeration system of claim 11, wherein in a third operating condition the CO2 refrigerant is directed from the condenser assembly to the receiver and from the receiver to the one or more refrigeration loads without entering the thermal storage unit. ### Claim 15 (depends on 11) The refrigeration system of claim 11, wherein during the second operating condition the CO2 refrigerant is directed from the receiver to the thermal storage unit. ### Claim 16 (depends on 15) The refrigeration system of claim 15, wherein during the second operating condition the CO2 refrigerant is directed from the thermal storage unit to a secondary compressor assembly. ### Claim 17 A method of controlling a refrigeration system including a CO2 refrigerant having a critical temperature, a receiver configured to retain the CO2 refrigerant, one or more refrigeration loads having an evaporator assembly and in fluid communication with the receiver, a compressor assembly in fluid communication with the refrigeration loads, a condenser assembly in fluid communication with the compressor assembly, and a thermal storage unit in fluid communication with the condenser assembly and the receiver, wherein the thermal storage unit includes a heat exchanger and phase change material, the method comprising: directing the CO2 refrigerant to the thermal storage unit to cool the CO2 refrigerant with the phase change material during a first operating condition when the CO2 refrigerant would otherwise be above the critical temperature; and directing the CO2 refrigerant to the thermal storage unit to charge the phase change material during a second operating condition when the CO2 refrigerant is below the critical temperature. ### Claim 18 (depends on 17) The method of claim 17, wherein during the first operating condition the CO2 refrigerant is directed from the condenser assembly to the thermal storage unit prior to entering the receiver. ### Claim 19 (depends on 17) The method of claim 17, wherein in a third operating condition the CO2 refrigerant is directed from the condenser assembly to the receiver and from the receiver to the one or more refrigeration loads without entering the thermal storage unit. ### Claim 20 (depends on 17) The method of claim 17, wherein during the second operating condition the CO2 refrigerant is directed from the receiver to the thermal storage unit. ### Claim 21 (depends on 20) The method of claim 20, wherein during the second operating condition the CO2 refrigerant is directed from the thermal storage unit to a secondary compressor assembly.