Abstract: A method of operating a refrigeration system is disclosed. The method comprises cooling a refrigerant using a first high side heat exchanger, and reducing the pressure of a first portion of the refrigerant received from the first high side heat exchanger using a first expansion valve in a first low side heat exchanger unit. The method further comprises cooling a first space with the refrigerant received from the first expansion valve using a first low side heat exchanger in the first low side heat exchanger unit, and reducing the pressure of a second portion of the refrigerant received from the high side heat exchange using an expander of an expansion-compression unit. The method further comprises compressing the refrigerant received from the first low side heat exchanger using a compressor of the expansion-compression unit.

Abstract: A method of operating a refrigeration system is disclosed. The method comprises cooling a refrigerant using a first high side heat exchanger and reducing a pressure of a first portion of the refrigerant received from the first high side heat exchanger using a first expansion valve. The method comprises separating the refrigerant received from the first expansion valve into a liquid refrigerant and a vapor refrigerant using a receiver tank. The method comprises cooling a first space with the liquid refrigerant received from the receiver tank using a first low side heat exchanger, and recycling the refrigerant exiting the first low side heat exchanger to the receiver tank.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: The disclosure provides a method of operating a refrigeration system. The method includes operating a first low-temperature evaporator in a refrigeration mode, where the first low-temperature evaporator receives refrigerant from a flash tank. The method includes operating a second low-temperature evaporator in a refrigeration mode, where the first low-temperature evaporator receives refrigerant from the flash tank. The method includes causing the first low-temperature evaporator to operate in the defrost mode by: closing a first controllable valve in a refrigerant conduit that couples the first low-temperature evaporator to a low-temperature compressor of the refrigeration system, and directing the refrigerant exiting the first low-temperature evaporator to be received by the second low-temperature evaporator.

Abstract: A cooling system partially floods the low temperature low side heat exchangers (e.g., freezers) in the system. An accumulator is positioned between the low temperature low side heat exchangers and the low temperature compressor. The accumulator collects the refrigerant (both liquid and vapor) from the flooded low temperature low side heat exchangers. Refrigerant discharged by the low temperature compressor is fed through the accumulator so that heat can be transferred to the refrigerant collected in the accumulator. As a result, the temperature of the refrigerant discharged by the low temperature compressor drops before that refrigerant reaches the medium temperature compressor.

Abstract: A refrigeration system includes pressure-regulating valve positioned between two flash tanks and a heat exchanger is positioned downstream from a medium temperature compressor. After determining that operation of an evaporator in a defrost mode is indicated, the system causes the evaporator to operate in the defrost mode by adjusting the pressure-regulating valve to increase a pressure of a first flash tank relative to a pressure of a second flash tank, allowing flow of refrigerant from the first flash tank to the heat exchanger, and allowing refrigerant heated by the heat exchanger to flow to the first evaporator.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system can operate in any number and combination of three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates any number and combination of three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: An apparatus includes a high side heat exchanger, a flash tank, a load, a compressor, and a heat exchanger. The high side heat exchanger removes heat from a refrigerant. The flash tank stores the refrigerant from the high side heat exchanger and to discharge a flash gas. The load uses the refrigerant from the cool a space proximate the load. The compressor compresses the refrigerant from the load. The heat exchanger transfers heat from the refrigerant from the compressor to the flash gas before the refrigerant from the compressor reaches the high side heat exchanger. The heat exchanger directs the flash gas to the compressor after heat from the refrigerant from the compressor is transferred to the flash gas and directs the refrigerant from the compressor to the high side heat exchanger after heat from the refrigerant from the compressor is transferred to the flash gas.

Abstract: A refrigeration system includes a controllable valve positioned downstream from one or more low-temperature compressors. The controllable valve receives compressed refrigerant from the low-temperature compressors and directs flow of the refrigerant to one or both of (i) medium-temperature compressors downstream from the controllable valve and (ii) one or more evaporators based on an operation mode of the evaporators. A pressure-regulating valve is disposed in refrigerant conduit coupling a first flash tank to a second flash tank. After determining to operate a first evaporator in a defrost mode, a controller adjusts the controllable valve to direct a portion of refrigerant to the first evaporator and adjusts the pressure-regulating valve to increase a pressure of the first flash tank relative to that of the second flash tank.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: An apparatus includes a high side heat exchanger, a flash tank, a load, a compressor, and a heat exchanger. The high side heat exchanger removes heat from a refrigerant. The flash tank stores the refrigerant from the high side heat exchanger and to discharge a flash gas. The load uses the refrigerant from the cool a space proximate the load. The compressor compresses the refrigerant from the load. The heat exchanger transfers heat from the refrigerant from the compressor to the flash gas before the refrigerant from the compressor reaches the high side heat exchanger. The heat exchanger directs the flash gas to the compressor after heat from the refrigerant from the compressor is transferred to the flash gas and directs the refrigerant from the compressor to the high side heat exchanger after heat from the refrigerant from the compressor is transferred to the flash gas.

Abstract: A cooling system partially floods the low temperature low side heat exchangers (e.g., freezers) in the system. An accumulator is positioned between the low temperature low side heat exchangers and the low temperature compressor. The accumulator collects the refrigerant (both liquid and vapor) from the flooded low temperature low side heat exchangers. Refrigerant discharged by the low temperature compressor is fed through the accumulator so that heat can be transferred to the refrigerant collected in the accumulator. As a result, the temperature of the refrigerant discharged by the low temperature compressor drops before that refrigerant reaches the medium temperature compressor.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system can operate in any number and combination of three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

Abstract: A cooling system partially floods the low temperature low side heat exchangers (e.g., freezers) in the system. An accumulator is positioned between the low temperature low side heat exchangers and the low temperature compressor. The accumulator collects the refrigerant (both liquid and vapor) from the flooded low temperature low side heat exchangers. Refrigerant discharged by the low temperature compressor is fed through the accumulator so that heat can be transferred to the refrigerant collected in the accumulator. As a result, the temperature of the refrigerant discharged by the low temperature compressor drops before that refrigerant reaches the medium temperature compressor.

Abstract: A refrigeration system includes at least one low-temperature evaporator, at least one medium-temperature evaporator, one or more low-temperature compressors, and one or more medium-temperature compressors. A controllable valve positioned downstream from the one or more low-temperature compressors directs flow of refrigerant from the low-temperature compressor(s) to one or both of (i) the medium-temperature compressor(s) and (ii) one or more evaporators based on an operation mode of evaporators. A controller is communicatively coupled to the controllable valve. A controller determines that operation of a first evaporator in a defrost mode is indicated and causes the first evaporator to operate in the defrost mode by adjusting the controllable valve to direct a portion of the received compressed refrigerant to the first evaporator.

Abstract: A refrigeration system includes evaporators, one or more medium temperature compressors, and a three-way valve positioned downstream from the one or more medium temperature compressors. The three-way valve receives the compressed refrigerant from the medium temperature compressors and directs flow of the received compressed refrigerant to (i) a gas cooler and/or (ii) one or more of the evaporators based on an operation mode of the evaporators. A controller determines that operation of a first evaporator in a defrost mode is indicated and causes the first evaporator to operate in the defrost mode by adjusting the three-way valve to direct a portion of the received compressed refrigerant to the first evaporator.

Abstract: A refrigeration system includes a controllable valve positioned downstream from one or more low-temperature compressors. The controllable valve receives compressed refrigerant from the low-temperature compressors and directs flow of the refrigerant to one or both of (i) medium-temperature compressors downstream from the controllable valve and (ii) one or more evaporators based on an operation mode of the evaporators. A pressure-regulating valve is disposed in refrigerant conduit coupling a first flash tank to a second flash tank. After determining to operate a first evaporator in a defrost mode, a controller adjusts the controllable valve to direct a portion of refrigerant to the first evaporator and adjusts the pressure-regulating valve to increase a pressure of the first flash tank relative to that of the second flash tank.

Abstract: A refrigeration system includes pressure-regulating valve positioned between two flash tanks and a heat exchanger is positioned downstream from a medium temperature compressor. After determining that operation of an evaporator in a defrost mode is indicated, the system causes the evaporator to operate in the defrost mode by adjusting the pressure-regulating valve to increase a pressure of a first flash tank relative to a pressure of a second flash tank, allowing flow of refrigerant from the first flash tank to the heat exchanger, and allowing refrigerant heated by the heat exchanger to flow to the first evaporator.