A multi-temperature air conditioning system, a control method thereof and a transport refrigeration vehicle. The multi-temperature air conditioning system includes an outdoor unit; a first type indoor unit; and a second type indoor unit; a number of a first type four-way valves corresponds to the number of the first type indoor units, and a number of a second type four-way valves corresponds to the number of the second type indoor units; and a section flow path which could be conducted or disconnected is further included, which connects the first type indoor unit between the first throttling element and the first on-off valve, and connects the second type indoor unit between the second throttling element and the second on-off valve.

Disclosed is an air conditioner. The air conditioner of the present disclosure for achieving the above or other object, there is provided an air conditioner including: a compressor which compresses refrigerant; an accumulator which supplies refrigerant to the compressor; a condenser which condenses refrigerant discharged from the compressor; an expansion valve which expands refrigerant passing through the condenser; an evaporator which has a heat exchange pipe through which refrigerant passing through the expansion valve flows, and evaporates refrigerant flowing through the heat exchange pipe; a gas-liquid separation pipe which connects a first point and a second point located between one end and the other end of the heat exchange pipe; and a bypass pipe which has one end connected to the gas-liquid separation pipe and the other end connected to the accumulator, wherein the gas-liquid separation pipe comprises: a first part which has one end connected to the first point and the other end connected to one end of the bypass pipe; and a second part which extends from the first part at between one end and the other end of the first part, and is connected to the second point.

A refrigeration cycle apparatus includes; a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a first expansion device, a second expansion device, and a load-side heat exchanger are sequentially connected by refrigerant pipes and in which refrigerant is circulated; a controller that controls the refrigerant circuit; a bypass pipe extending from a liquid pipe between the first expansion device and the second expansion device toward a suction side of the compressor; a third expansion device provided at the bypass pipe to decompress the refrigerant that flows through the bypass pipe; and a refrigerant cooler provided at the bypass pipe and downstream of the third expansion device to cause heat exchange to be performed between the refrigerant decompressed by the third expansion device and heat generated from the controller.

An air conditioner has a refrigerant circuit in which a refrigerant circulates and a controller, and is configured to condition air in an indoor space. A countermeasure device is provided against leakage of the refrigerant to the indoor space. A detector is configured to detect a concentration of the refrigerant in the indoor space. A first relay is connected to the controller and the countermeasure device. The controller closes the first relay when the concentration of the refrigerant detected by the detector exceeds a predetermined allowable concentration. The countermeasure device operates when the first relay is closed.

A heat source controller performs a first operation when a compression element is in a stopped state and a pressure in a receiver exceeds a predetermined first pressure. The heat source controller allows an inlet of the compression element to communicate with the receiver, and drives the compression element in the first operation.

A multi-type air conditioner may include three pipes, including a high-pressure pipe, a low-pressure pipe, and a liquid line which may be connected to a plurality of indoor units, in which some of the indoor units may be operated in a cooling mode and the rest of the indoor units may be operated in a heating mode, such that waste heat from the indoor units operated in the heating mode may be recovered to be used for the indoor units operated in the cooling mode.

In an air-conditioning apparatus including a refrigerant circulating circuit A and a heat medium circulating circuit B that performs passing of heat to and from the refrigerant circulating circuit A, the heat medium circulating circuit is a closed circuit, the maximum pump head Pp of a pump of the heat medium circulating circuit is 150 kPa or more, and a pressure near at least a suction side of the pump is set to a charged pressure that is maintained equal to or higher than the atmospheric pressure during operation of the pump.

An air conditioner may include a plurality of indoor units and a plurality of outdoor units connected to the plurality of indoor units. Each of the plurality of outdoor units may include a plurality of outdoor heat exchangers. Each of the outdoor heat exchangers may include a plurality of heat exchanger parts. When a defrosting operation condition is satisfied during a heating operation, indicating that a defrosting operation should be performed the plurality of heat exchanger parts of the plurality of outdoor heat exchangers may successively perform the defrosting operation.

A multi-type air conditioner may include three pipes, including a high-pressure pipe, a low-pressure pipe, and a liquid line which may be connected to a plurality of indoor units, in which some of the indoor units may be operated in a cooling mode and the rest of the indoor units may be operated in a heating mode, such that waste heat from the indoor units operated in the heating mode may be recovered to be used for the indoor units operated in the cooling mode.

A cooling and heating control method of a multi type air conditioner in which a target pressure of a compressor is adjusted based on conditions of respective indoor units so as to reduce power consumption is provided. The cooling control method includes determining the indoor unit desired to execute power saving control, judging whether or not a difference between a temperature of a space in which the indoor unit desired to execute power saving control is located and a set temperature of the indoor unit is less than a reference value, raising a target evaporation temperature of the indoor unit upon judging that the difference is less than the reference value, comparing an evaporation temperature of the indoor unit with the raised target evaporation temperature, and raising an evaporation pressure of a compressor, when the evaporation temperature of the indoor unit is lower than the raised target evaporation temperature.