Abstract: In a refrigeration cycle system, switching is allowed between a parallel operation mode and a series operation mode. In the parallel operation mode, a refrigerant, upon leaving a load side heat exchanger, parallelly flows through a high-pressure side passage of each of a first internal heat exchanger and a second internal heat exchanger and then flows into an expansion valve. In the series operation mode, the refrigerant, upon leaving the load side heat exchanger, flows through the high-pressure side passage of the first internal heat exchanger, further flows through the high-pressure side passage of the second internal heat exchanger, and then flows through a high-pressure side bypass pipe into the expansion valve.

Abstract: A refrigerating and air-conditioning apparatus suppresses liquid backflow to a compressor with a simple configuration, and reduces annual power consumption. An outdoor unit and an indoor unit are connected to each other by a gas-side connecting pipe and a liquid-side connecting pipe to form a refrigerant circuit in which a compressor, a four-way valve, an indoor heat exchanger, a refrigerant heat exchanger, an expansion valve, an outdoor heat exchanger, and an accumulator are sequentially connected. The refrigerant heat exchanger transfers heat between a high-pressure-side refrigerant flowing between the expansion valve and an outdoor-unit liquid pipe connecting portion and a low-pressure-side refrigerant on an outlet side of the accumulator.

Abstract: It is aimed to enhance the strength of a plate heat exchanger while maintaining the heat exchange capability of the plate heat exchanger. A plate heat exchanger 20 is configured with a plurality of stacked plates 2 and 3. Each of the plates 2 and 3 includes at four corners thereof a first inlet hole 5 which acts as an inlet for a first fluid, a first outlet hole 6 which acts as an outlet for the first fluid, a second inlet hole 7 which acts as an inlet for a second fluid, and a second outlet hole 8 which acts as an outlet for the second fluid. Each of the plates 2 and 3 and an adjacent plate define therebetween a first flow path for passing the first fluid and a second flow path for passing the second fluid, so as to exchange heat between the first fluid and the second fluid. In each of the plates 2 and 3, a longitudinal length L1 is 4 or more times a lateral length L2.

Abstract: An air conditioner that can perform defrosting efficiently while heating or the like is continued even if the air conditioner is configured by one outdoor unit is obtained.