An air-conditioning apparatus is able to ensure an appropriate flow rate of refrigerant and an appropriate amount of oil returned to a compressor that match operation conditions regardless of an operating state of a refrigerant circuit and a change in an operation condition. The air-conditioning apparatus includes: a first detector configured to detect a refrigerant temperature within an accumulator; a storage unit configured to store information regarding a two-layer separation temperature of refrigerant and refrigerating machine oil; a determiner configured to compare the refrigerant temperature with the two-layer separation temperature and determine a two-layer separation state of the refrigerant and the refrigerating machine oil; a second detector configured to detect a state of the refrigerant sucked by the compressor; and a control unit configured to adjust an opening degree of a flow control valve on the basis of the two-layer separation state and a state of the sucked refrigerant.

To improve the heat exchange efficiency of a heat exchanger that includes an upstream heat exchange unit and a downstream heat exchange unit. When the heat exchanger functions as an evaporator, a gas outlet pipe is an upstream refrigerant outlet that is located adjacent to the other end of upstream flat pipes of the upstream heat exchange unit, and a gas outlet pipe is a downstream refrigerant outlet that is located adjacent to the other end of downstream flat pipes of the downstream heat exchange unit. First resistance to refrigerant flow in the upstream heat exchange unit and second resistance to refrigerant flow in the downstream heat exchange unit are adjusted in order that the degree of superheating of refrigerant at the downstream refrigerant outlet is smaller than the degree of superheating of refrigerant at the upstream refrigerant outlet.

A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor that is a variable speed compressor, a second expansion device, and an evaporator. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. A controller stages operation of the first and second compressors and runs the second compressor at an initial speed less than a maximum speed initially when a staging protocol is performed during start up or re-starting of the refrigeration system.

A vapor-compression system includes a centrifugal compressor configured to increase a pressure of a refrigerant based on at least one of an activation of a device or the device being equal to or above a first threshold temperature. A fluid communication system is configured to provide, to the device, a portion of the refrigerant in a liquid state. The portion of the liquid refrigerant in a liquid state is configured to have a saturation temperature equal to or below the first temperature threshold.

An air-conditioning apparatus includes a suction-injection pipe that introduces a refrigerant in a liquid or two-phase state into a suction side of a compressor, an expansion device that is arranged at the suction-injection pipe, and a controller that regulates the suction-injection flow rate of a refrigerant introduced into the suction side of the compressor through the suction-injection pipe by controlling the opening degree of the expansion device.

An air-conditioning apparatus includes a temperature sensor for detecting a temperature of the heat medium sent from each of the intermediate heat exchangers to each of the use-side heat exchangers, and a temperature of the heat medium that has exited each of the use-side heat exchangers, an opening degree controller for regulating a flow rate of the heat medium through each of the heat medium flow control devices, and a computing unit for computing a usage capacity of each of the indoor units from a rotation speed of the pump, an opening degree of each of the heat medium flow control devices, temperatures detected by the temperature sensors, and power consumption of each of the indoor units, and proportionally dividing the power consumption for a common portion among each of the indoor units based on the computed usage capacity and the power consumption of the common portion.

A method for controlling a vapor compression system during start-up is disclosed. The rate of change, ΔT.sub.1, of the temperature of refrigerant entering the evaporator, and the rate of change, ΔT.sub.2, of the temperature of refrigerant leaving the evaporator are compared. Based on the comparing step, a refrigerant filling state of the evaporator is determined. The opening degree of the expansion device is then controlled according to a first control strategy in the case that it is determined that the evaporator is full or almost full, and according to a second control strategy in the case that it is determined that the evaporator is not full. Thereby it is ensured that a maximum filling degree of the evaporator is quickly reached, without risking that liquid refrigerant passes through the evaporator.

An air-conditioning apparatus includes a refrigerant circuit in which a compressor, an indoor heat exchanger, a first expansion device, an outdoor heat exchanger, and a flow switching device are sequentially connected to each other; a hot gas bypass pipe coupling a discharge port of the compressor and the flow switching device to each other; and a controller. The outdoor heat exchanger includes an upper heat exchanger and a lower heat exchanger having passages in parallel with each other. The outdoor heat exchanger includes a plurality of hairpin pipes, which are part of a heat transfer pipe. When the upper heat exchanger is defrosted, all hairpin pipes that are located at a lowermost step of the upper heat exchanger are used as refrigerant inlets. When the lower heat exchanger is defrosted, all hairpin pipes that are located at an uppermost step of the lower heat exchanger are used as refrigerant inlets.

A refrigerator is provided that may include at least one compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed in the at least one compressor, a refrigerant tube that guides the refrigerant condensed in the condenser, a plurality of evaporation passages, in which expansion devices may be respectively disposed, the plurality of evaporation passages branching from the refrigerant tube, a flow adjuster disposed in the refrigerant tube to supply the refrigerant into at least one evaporation passage of the plurality of evaporation passages, a plurality of evaporators, respectively, connected to the plurality of evaporation passages to evaporate the refrigerant decompressed in the plurality of expansion devices, and a liquid refrigerant supply device disposed at an outlet-side of the condenser to separate a liquid refrigerant of the refrigerant heat-exchanged in the condenser, thereby supplying the liquid refrigerant into the flow adjuster.

An air conditioner may prevent a refrigerant stored in a refrigerant storage from rapidly flowing into a main refrigerant circuit when the type of operation is switched.

The air conditioner may include a refrigerant circuit provided with a compressor, a condenser, an expansion valve and an evaporator; a refrigerant amount detection device configured to determine whether a refrigerant state in an outlet of the compressor is a supercooled state or a gas-liquid two phase state, and configured to calculate a refrigerant amount ratio in the refrigerant circuit, based on a predetermined set value according to at least one of a temperature and a pressure detected in the refrigerant circuit, and the refrigerant state; and a controller configured to control the refrigerant circuit according to the refrigerant amount ratio calculated by the refrigerant amount detection device.