# US 2009/0260389 A1 · Co2 refrigeration unit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260389 A1 - Document ID: US20090260389A1 - Status: Published application - Kind: A1 - Application number: 12/425,719 - Filed: 2009-04-17 - Published: 2009-10-22 - Earliest claimed: 2008-04-18 - Inventors: Serge DUBE - Web page: https://patentgrep.com/patent/US20090260389A1 ## CPC - C09K 5/041: {for compression-type refrigeration systems} - F25B 7/00: Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit (F25B9/00 takes precedence) - F25B 9/008: {the refrigerant being carbon dioxide} - F25B 5/02: arranged in parallel - F25B 47/022: {hot gas defrosting} - F25B 2309/061: with cycle highest pressure above the supercritical pressure - F25B 2400/075: with parallel compressors - F25B 2400/22: Refrigeration systems for supermarkets - F25B 2400/23: Separators - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract A refrigeration unit comprises a CO2 refrigeration circuit having a CO2 compression stage in which CO2 refrigerant is compressed, a CO2 condensation stage having a tank in which CO2 refrigerant is accumulated in a liquid state, at least one of pressuring means and an expansion stage to direct the CO2 refrigerant from the CO2 condensation stage to a CO2 evaporation stage in which CO2 refrigerant absorbs energy to refrigerate. A condensation circuit has a second refrigerant being circulated between a second compression stage, a second condensation stage, a second expansion stage and a second evaporation stage. A heat-exchanger unit by which the CO2 refrigerant from the CO2 refrigeration circuit is in heat exchange with the second refrigerant in the second evaporation stage such that the second refrigerant absorbs heat from the CO2 refrigerant to at least partially liquefy the CO2 refrigerant for the CO2 condensation stage. A defrost circuit directing defrost CO2 refrigerant from the CO2 compression stage to the CO2 evaporation stage to defrost at least one evaporator of the CO2 evaporation stage, the defrost CO2 refrigerant being subsequently returned to the CO2 refrigeration circuit. ## Claims ### Claim 1 A refrigeration unit comprising: a CO2 refrigeration circuit having a CO2 compression stage in which CO2 refrigerant is compressed, a CO2 condensation stage having a tank in which CO2 refrigerant is accumulated in a liquid state, at least one of pressuring means and an expansion stage to direct the CO2 refrigerant from the CO2 condensation stage to a CO2 evaporation stage in which CO2 refrigerant absorbs energy to refrigerate; a condensation circuit having a second refrigerant being circulated between a second compression stage, a second condensation stage, a second expansion stage and a second evaporation stage; a heat-exchanger unit by which the CO2 refrigerant from the CO2 refrigeration circuit is in heat exchange with the second refrigerant in the second evaporation stage such that the second refrigerant absorbs heat from the CO2 refrigerant to at least partially liquefy the CO2 refrigerant for the CO2 condensation stage; and a defrost circuit directing defrost CO2 refrigerant from the CO2 compression stage to the CO2 evaporation stage to defrost at least one evaporator of the CO2 evaporation stage, the defrost CO2 refrigerant being subsequently returned to the CO2 refrigeration circuit. ### Claim 2 (depends on 1) The refrigeration unit according to claim 1, wherein the CO2 evaporation stage has at least medium-temperature evaporators and low-temperature evaporators, with a line directing CO2 refrigerant exiting the low-temperature evaporators to the CO2 compression stage, and with the pressuring means upstream of the medium-temperature evaporators to feed CO2 refrigerant to the medium-temperature evaporators, with another line directing CO2 refrigerant exiting the medium-temperature evaporators to the CO2 condensation stage. ### Claim 3 (depends on 1) The refrigeration unit according to claim 1, wherein the CO2 evaporation stage has at least medium-temperature evaporators and low-temperature evaporators, with a line directing CO2 refrigerant exiting the low-temperature evaporators to the CO2 compression stage, and with the expansion stage upstream of the medium-temperature evaporators to feed CO2 refrigerant to the medium-temperature evaporators, with another line directing CO2 refrigerant exiting the medium-temperature evaporators to the CO2 compression stage. ### Claim 4 (depends on 1) The refrigeration unit according to claim 1, further comprising a defrost reservoir between the CO2 evaporation stage and the CO2 compression stage to collect the defrost CO2 refrigerant exiting the defrost circuit, a suction of the CO2 compression stage connected to the defrost reservoir to collect CO2 refrigerant in a gas state for the CO2 refrigeration circuit. ### Claim 5 (depends on 4) The refrigeration unit according to claim 4, wherein a discharge line extends from the CO2 compression stage to the defrost reservoir to selectively flush CO2 refrigerant from the defrost reservoir through another line extending from the defrost reservoir to the tank in the CO2 condensation stage. ### Claim 6 (depends on 1) The refrigeration unit according to claim 1, further comprising at least one dedicated compressor in the CO2 compression stage to collect at least part of the defrost CO2 refrigerant exiting the defrost circuit, to compress and discharge the defrost CO2 refrigerant to the CO2 refrigeration circuit. ### Claim 7 (depends on 1) The refrigeration unit according to claim 1, further comprising a pressure-reducing valve on a discharge line of the CO2 compression stage, downstream of a defrost line feeding defrost CO2 refrigerant to the defrost circuit, to maintain a pressure of the CO2 refrigerant in the CO2 refrigeration circuit downstream of the pressure-reducing valve lower than the pressure of the defrost CO2 refrigerant. ### Claim 8 (depends on 1) The refrigeration unit according to claim 1, wherein the defrost CO2 refrigerant is circulated in the CO2 evaporation stage of the defrost circuit at a pressure below 700 Psi. ### Claim 9 (depends on 1) The refrigeration unit according to claim 1, wherein the condensation circuit has a pressure-maintaining line extending from a discharge of the second compression stage to a suction of the second compression stage, the pressure-maintaining line being selectively opened to maintain a minimum operating pressure at a suction of the second compression stage. ### Claim 10 (depends on 1) The refrigeration unit according to claim 1, further comprising a line extending from the CO2 evaporation stage to the CO2 condensation stage to direct defrost CO2 refrigerant from the defrost circuit to the refrigeration circuit. ### Claim 11 A refrigeration unit comprising: a casing; a CO2 refrigeration circuit having a CO2 compression stage in which CO2 refrigerant is compressed, a CO2 condensation stage having a tank in which CO2 refrigerant is accumulated in a liquid state, at least one of pressuring means and an expansion stage to direct the CO2 refrigerant from the CO2 condensation stage to a CO2 evaporation stage in which CO2 refrigerant absorbs energy to refrigerate, with at least the CO2 compression stage, and the CO2 condensation stage being in the casing; a condensation circuit having a second refrigerant being circulated between a second compression stage, a second condensation stage, a second expansion stage and a second evaporation stage, at least the second compression stage, the second expansion stage and the second evaporation stage being in the casing; and a heat-exchanger unit in the casing by which the CO2 refrigerant from the CO2 refrigeration circuit is in heat exchange with the second refrigerant in the second evaporation stage such that the second refrigerant absorbs heat from the CO2 refrigerant to at least partially liquefy the CO2 refrigerant for the CO2 condensation stage. ### Claim 12 (depends on 11) The refrigeration unit according to claim 11, further comprising a defrost circuit directing defrost CO2 refrigerant from the CO2 compression stage to the CO2 evaporation stage to defrost at least one evaporator, the defrost CO2 refrigerant being subsequently returned to the CO2 refrigeration circuit. ### Claim 13 (depends on 11) The refrigeration unit according to claim 11, wherein the at least one of pressuring means and expansion stage are in the casing. ### Claim 14 (depends on 11) The refrigeration unit according to claim 11, further comprising a ventilation circuit in which circulates a third refrigerant between a third compression stage, a third condensation/gas cooling stage, a third expansion stage and a third evaporation stage, at least the third compression stage, the third condensation/gas cooling stage, and the third expansion stage being in the casing, with the third evaporation stage adapted to be in a ventilation duct to absorb heat from ventilation air. ### Claim 15 (depends on 14) The refrigeration unit according to claim 14, further comprising a heat reclaim stage in a discharge line of the CO2 compression stage to reclaim heat from the CO2 refrigerant, the heat reclaim stage comprising a coil adapted to be in said ventilation duct to heat ventilation air. ### Claim 16 (depends on 11) The refrigeration unit according to claim 11, further comprising at least an other one of the refrigeration unit in another one of the casing, the other one of the refrigeration unit being without one of the condensation circuit, and being in heat-exchange relation with the heat-exchange unit of the first one of the refrigeration unit. ### Claim 17 A refrigeration unit of the type having a CO2 refrigeration circuit with a CO2 compression stage in which CO2 refrigerant is compressed, a CO2 condensation stage having a tank in which CO2 refrigerant is accumulated in a liquid state, an expansion stage to direct the CO2 refrigerant from the CO2 condensation stage to a CO2 evaporation stage in which CO2 refrigerant absorbs energy CO2 refrigerate, the CO2 evaporation stage having at least two evaporators, the refrigeration unit comprising at least one line connected from the CO2 condensation stage to one expansion valve of the expansion stage, the line diverging into at least two lines each connected to a balancing valve and an own one of the evaporators, such that CO2 refrigerant expanded by the one expansion valve is directed to the at least two evaporators through the balancing valves. ### Claim 18 (depends on 17) The refrigeration unit according to claim 17, wherein the expansion stage is in a casing with the CO2 compression stage and the CO2 condensation stage at a distal location from the CO2 evaporation stage. ### Claim 19 (depends on 18) The refrigeration unit according to claim 18, wherein the refrigeration unit is retrofitted to existing evaporators. ### Claim 20 (depends on 17) The refrigeration unit according to claim 17, further comprising a defrost circuit directing defrost CO2 refrigerant from the CO2 compression stage to the CO2 evaporation stage to defrost the evaporators, the defrost refrigerant being subsequently returned to the CO2 refrigeration circuit.