A multistage compression system uses refrigerant and oil. The multistage compression system includes a low-stage compressor that compresses the refrigerant, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, refrigerant pipes that introduce the refrigerant compressed and discharged by the low-stage compressor into a suction part of the high-stage compressor, an intercooler, and an oil discharge pipe. The intercooler cools the refrigerant discharged by the low-stage compressor before the refrigerant is sucked into the high-stage compressor. The intercooler is disposed between the refrigerant pipes. The oil discharge pipe discharges the oil in the low-stage compressor. The oil discharge pipe connects the low-stage compressor and a portion of the refrigerant pipes. The portion of the refrigerant pipes is on an upstream side of the intercooler.

A refrigerant circuit of a refrigeration apparatus performs a refrigeration cycle in which a high pressure is equal to or greater than the critical pressure of a refrigerant. The refrigeration apparatus performs at least a heat application operation in which an indoor heat exchanger of the refrigerant circuit functions as a radiator. A controller of the refrigeration apparatus controls the opening degree of the indoor expansion valve of the refrigerant circuit so that the temperature of the refrigerant at the outlet of the indoor heat exchanger reaches a predetermined reference temperature, in the heat application operation.

A refrigeration apparatus is of a two-stage compression type for compressing a refrigerant to a supercritical region. The refrigeration apparatus includes a lower stage-side compression unit, a higher stage-side compression unit, an intermediate cooler, a heat source-side heat exchanger, a utilization-side heat exchanger, an economizer circuit, and a control unit. During a first operation in which the heat source-side heat exchanger functions as a radiator and the utilization-side heat exchanger functions as an evaporator, in a case where a discharge temperature which is a temperature of the refrigerant discharged from the higher stage-side compression unit is more than a first temperature, the control unit increases a cooling capacity of the intermediate cooler without increasing a refrigerant flow rate of the economizer circuit on condition that the intermediate cooler does not reach a maximum cooling capacity.

A refrigerant control system includes: a storage part which stores a first refrigerant; a first sub-pipe which is connected to an outlet side pipe of a first circulation flow path; a second sub-pipe which is connected to an inlet side pipe of the first circulation flow path; a third sub-pipe which is connected to the inlet side pipe and is formed so that heat of the third sub-pipe lower than heat of the outlet side pipe is able to be transferred to the first refrigerant in the storage part a first opening and closing valve which is provided in the first sub-pipe; a second opening and closing valve which is provided in the second sub-pipe; a third opening and closing valve which is provided in the third pipe; and an opening and closing control unit which performs opening and closing control of the first opening and closing valve, the second opening and closing valve, and the third opening and closing valve on the basis of a set temperature of a second refrigerant.

A multistage compression system uses refrigerant and oil. The multistage compression system includes a low-stage compressor that compresses the refrigerant, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, refrigerant pipes that introduce the refrigerant compressed and discharged by the low-stage compressor into a suction part of the high-stage compressor, an intercooler, and an oil discharge pipe. The intercooler cools the refrigerant discharged by the low-stage compressor before the refrigerant is sucked into the high-stage compressor. The intercooler is disposed between the refrigerant pipes. The oil discharge pipe discharges the oil in the low-stage compressor. The oil discharge pipe connects the low-stage compressor and a portion of the refrigerant pipes. The portion of the refrigerant pipes is on an upstream side of the intercooler.

A refrigerant vapor compression system includes a compression device having at least a first compression stage and a second compression stage arranged in series refrigerant flow relationship. A first refrigerant heat rejection heat exchanger is disposed downstream with respect to refrigerant flow of the second compression stage. A first refrigerant intercooler is disposed intermediate the first compression stage and the second compression stage. The first refrigerant intercooler is disposed downstream of the first refrigerant heat rejection heat exchanger with respect to the flow of the first secondary fluid. An economizer includes a vapor line in fluid communication with a suction inlet to the second compression stage. A second refrigerant heat rejection heat exchanger is disposed intermediate with respect to refrigerant flow of the second compression stage and the first refrigerant heat rejection heat exchanger. A second refrigerant intercooler is disposed intermediate the first compression stage and the second compression.

This disclosure relates to cold-chain transportation, and more particularly to a refrigerated container refrigeration system capable of preventing freezing of container door, including compressors, oil separators, gas coolers, regenerators, electronic expansion valves, gas-liquid separators, an evaporator, suction pressure regulating valves, oil-level solenoid valves, gas cooler pressure regulating valves, differential pressure regulating valves, an evaporation pressure regulating valve, solenoid valves, check valves, flow meters, pressure sensors, temperature sensors, a door anti-freezing area, a refrigerated container shell, refrigerated container doors, a refrigeration unit, an anti-freezing pipeline and fastening components. Carbon dioxide is selected as refrigerant. A flow two-stage cycle compression refrigeration system with switchable operation pipeline is adopted, and the outlet pipeline of a high-pressure compressor is extended for preventing freezing of container door.

The present invention relates to a gas heat pump system. The gas heat pump system, according to one embodiment of the present invention, comprises: an air conditioning module comprising a compressor, an outdoor heat exchanger, an expansion apparatus, an indoor heat exchanger and a refrigerant line; and an engine module comprising an engine for combusting a mixture of fuel and air, thereby providing power for driving the compressor. The engine module comprises: a mixer for mixing and discharging the air and fuel; a supercharging means for receiving the mixture discharged from the mixer, compressing same, and then discharging same; an intercooler for receiving the mixture compressed in the supercharging means, cooling same by a heat exchange method, increasing the density thereof, and then discharging same; an adjustment means for receiving the mixture discharged from the intercooler, adjusting the quantity thereof, and then supplying same to the engine; and an exhaust gas heat exchanger for exchanging heat between a coolant and exhaust gas discharged from the engine, wherein the exhaust gas heat exchanger is directly connected to an exhaust manifold of the engine.

An apparatus includes a high side heat exchanger, a flash tank, a first load, a first compressor, an auxiliary cooling system, and a first check valve. The high side heat exchanger removes heat from a refrigerant. The flash tank stores the refrigerant from the high side heat exchanger. The first load uses the refrigerant to remove heat from a space proximate the first load. The first compressor compresses the refrigerant from the first load. The auxiliary cooling system removes heat from the refrigerant stored in the flash tank during a power outage. The first check valve directs the refrigerant between the first load and the first compressor back to the flash tank when the pressure of the refrigerant between the first load and the first compressor exceeds a threshold during the power outage.

A refrigerant control system includes: a storage part which stores a first refrigerant; a first sub-pipe which is connected to an outlet side pipe of a first circulation flow path; a second sub-pipe which is connected to an inlet side pipe of the first circulation flow path; a third sub-pipe which is connected to the inlet side pipe and is formed so that heat of the third sub-pipe lower than heat of the outlet side pipe is able to be transferred to the first refrigerant in the storage part a first opening and closing valve which is provided in the first sub-pipe; a second opening and closing valve which is provided in the second sub-pipe; a third opening and closing valve which is provided in the third pipe; and an opening and closing control unit which performs opening and closing control of the first opening and closing valve, the second opening and closing valve, and the third opening and closing valve on the basis of a set temperature of a second refrigerant.