# US 11,029,068 B2 · Systems and methods for pressure control in a CO2 refrigeration system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,068 B2 - Document ID: US11029068B2 - Status: Granted - Kind: B2 - Application number: 14/787,666 - Filed: 2014-04-30 - Published: 2016-04-14 - Granted: 2021-06-08 - Earliest claimed: 2013-05-03 - Assignees: Hill Phoenix, Inc. - Applicants: Hill Phoenix, Inc. - Inventors: Kim G. Christensen; Jeffrey Newel; John D. Bittner - Web page: https://patentgrep.com/patent/US11029068B2 ## CPC - F25B 49/022: {Compressor control arrangements} - F25B 9/008: {the refrigerant being carbon dioxide} - F25B 1/10: with multi-stage compression (with cascade operation F25B7/00) - F25B 5/02: arranged in parallel - F25B 40/00: Subcoolers, desuperheaters or superheaters - 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 - F25B 2500/07: Exceeding a certain pressure value in a refrigeration component or cycle - F25B 2600/2509: Economiser valves - F25B 2700/13: Mass flow of refrigerants - F25B 2700/198: Intermediate pressures - F25B 2700/21163: of the refrigerant at the outlet of the condenser - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract Systems and methods for controlling pressure in a CO2 refrigeration system are provided. The pressure control system includes a pressure sensor, a gas bypass valve, a parallel compressor, and a controller. The pressure sensor is configured to measure a pressure within a receiving tank of the CO2 refrigeration system. The gas bypass valve is fluidly connected with an outlet of the receiving tank and arranged in series with a compressor of the CO2 refrigeration system. The parallel compressor is fluidly connected with the outlet of the receiving tank and arranged in parallel with both the gas bypass valve and the compressor of the CO2 refrigeration system. The controller is configured to receive a pressure measurement from the pressure sensor and operate both the gas bypass valve and the parallel compressor, in response to the pressure measurement, to control the pressure within the receiving tank. ## Claims ### Claim 1 A system for controlling pressure in a CO2 refrigeration system having a receiving tank, a compressor and a gas cooler/condenser, the system for controlling pressure comprising: a gas bypass valve fluidly connected with an outlet of the receiving tank and arranged in series with the compressor; a parallel compressor fluidly connected with the outlet of the receiving tank and arranged in parallel with both the gas bypass valve and the compressor, the parallel compressor receiving the CO2 refrigerant at a first pressure higher than a second pressure at which the CO2 refrigerant is received by the compressor; and a controller configured to: receive an indication of a CO2 refrigerant flow rate through the gas bypass valve wherein the indication of the CO2 refrigerant flow rate is one of a position of the gas bypass valve, a volume flow rate of the CO2 refrigerant through the gas bypass valve, or a mass flow rate of the CO2 refrigerant through the gas bypass valve; compare the indication of the CO2 refrigerant flow rate with a threshold value indicating a threshold flow rate through the gas bypass valve; control a pressure of the CO2 refrigerant within the receiving tank using only the gas bypass valve in response to the indication of the CO2 refrigerant flow rate not exceeding the threshold value, wherein controlling the pressure within the receiving tank using only the gas bypass valve comprises operating the gas bypass valve to reach an intermediate position between fully open and fully closed to adjust the pressure within the receiving tank to achieve a pressure setpoint or a pressure range; and activate the parallel compressor in response to the indication of the CO2 refrigerant flow rate exceeding the threshold value. ### Claim 2 (depends on 1) The system of claim 1, wherein the controller is configured to cause the gas bypass valve to close upon activating the parallel compressor. ### Claim 3 (depends on 1) The system of claim 1, further comprising a pressure sensor configured to measure the pressure within the receiving tank; wherein, upon receiving the indication of the CO2 refrigerant flow rate exceeding the threshold value, the controller is configured to control the pressure within the receiving tank using only the gas bypass valve, only the parallel compressor, or both the gas bypass valve and the parallel compressor, depending on the pressure within the receiving tank. ### Claim 4 (depends on 3) The system of claim 3, wherein, upon receiving the indication of the CO2 refrigerant flow rate exceeding the threshold value, the controller is configured to: compare the pressure within the receiving tank to a first threshold pressure and a second threshold pressure higher than the first threshold pressure; and deactivate the parallel compressor and control the pressure within the receiving tank using only the gas bypass valve in response to a determination that the pressure within the receiving tank is between the first threshold pressure and the second threshold pressure. ### Claim 5 (depends on 4) The system of claim 4, wherein, upon comparing the pressure within the receiving tank to the first threshold pressure and the second threshold pressure, the controller is configured to control the pressure within the receiving tank using both the gas bypass valve and the parallel compressor in response to a determination that the pressure within the receiving tank exceeds the second threshold pressure. ### Claim 6 (depends on 4) The system of claim 4, wherein, upon comparing the pressure within the receiving tank to the first threshold pressure and the second threshold pressure, the controller is configured to increase the first threshold pressure to a first adjusted threshold pressure higher than the second threshold pressure in response to a determination that the pressure within the receiving tank exceeds the second threshold pressure. ### Claim 7 (depends on 6) The system of claim 6, wherein after increasing the first threshold pressure to the first adjusted threshold pressure, the controller is configured to: compare the pressure within the receiving tank to the first adjusted threshold pressure and the second threshold pressure; and close the gas bypass valve and control the pressure within the receiving tank using only the parallel compressor in response to a determination that the pressure within the receiving tank is between the second threshold pressure and the first adjusted threshold pressure. ### Claim 8 (depends on 7) The system of claim 7, wherein the controller is configured to reset the first threshold pressure downward from the first adjusted threshold pressure to an initial value of the first threshold pressure in response to a determination that the pressure within the receiving tank is less than the second threshold pressure. ### Claim 9 A method for controlling pressure in a CO2 refrigeration system using a controller, the method comprising: receiving, at the controller, an indication of a CO2 refrigerant flow rate through a gas bypass valve of the CO2 refrigeration system, wherein the indication of the CO2 refrigerant flow rate is one of a position of the gas bypass valve, a volume flow rate of the CO2 refrigerant through the gas bypass valve, or a mass flow rate of the CO2 refrigerant through the gas bypass valve; comparing, by the controller, the indication of the CO2 refrigerant flow rate with a threshold value indicating a threshold flow rate through the gas bypass valve; controlling, by the controller, a pressure of the CO2 refrigerant using only the gas bypass valve in response to the indication of the CO2 refrigerant flow rate not exceeding the threshold value, wherein controlling the pressure using only the gas bypass valve comprises operating the gas bypass valve to reach an intermediate position between fully open and fully closed to adjust the pressure to achieve a pressure setpoint or a pressure range; and activating, by the controller, a parallel compressor of the CO2 refrigeration system in response to the indication of the CO2 refrigerant flow rate exceeding the threshold value, the parallel compressor receiving the CO2 refrigerant at a first pressure higher than a second pressure immediately downstream of the gas bypass valve. ### Claim 10 (depends on 9) The method of claim 9, further comprising causing the gas bypass valve to close upon activating the parallel compressor. ### Claim 11 (depends on 9) The method of claim 9, further comprising: comparing the pressure within a receiving tank of the CO2 refrigeration system to a first threshold pressure and a second threshold pressure higher than the first threshold pressure upon receiving the indication of the CO2 refrigerant flow rate exceeding the threshold value; and deactivating the parallel compressor and controlling the pressure within the receiving tank using only the gas bypass valve in response to a determination that the pressure within the receiving tank is between the first threshold pressure and the second threshold pressure. ### Claim 12 (depends on 11) The method of claim 11, further comprising controlling the pressure within the receiving tank using both the gas bypass valve and the parallel compressor in response to a determination that the pressure within the receiving tank exceeds the second threshold pressure. ### Claim 13 (depends on 11) The method of claim 11, further comprising increasing the first threshold pressure to a first adjusted threshold pressure higher than the second threshold pressure in response to a determination that the pressure within the receiving tank exceeds the second threshold pressure. ### Claim 14 (depends on 13) The method of claim 13, further comprising, after increasing the first threshold pressure to the first adjusted threshold pressure: comparing the pressure within the receiving tank to the first adjusted threshold pressure and the second threshold pressure; and closing the gas bypass valve and controlling the pressure within the receiving tank using only the parallel compressor in response to a determination that the pressure within the receiving tank is between the second threshold pressure and the first adjusted threshold pressure.