An air-conditioning system that performs a refrigeration cycle in a refrigerant circuit includes: an outdoor unit; a plurality of indoor units; a refrigerant connection pipe that connects the outdoor unit and the indoor units; and a first control valve disposed in the refrigerant connection pipe and that blocks a flow of refrigerant. The refrigerant connection pipe includes: a plurality of indoor-side pipes that each communicate with one of the indoor units; an outdoor-side pipe that communicates with two or more of the indoor-side pipes from an outdoor unit side; and a branch that connects the outdoor-side pipe and a group of two or more of the indoor-side pipes.

A heat exchanger includes: a heat exchange element including flat tubes spaced from each other; and a first header in which one end portion of each of the flat tubes is inserted. The first header includes: a first main header portion in which some of the flat tubes are inserted; a first sub-header portion in which others of the flat tubes are inserted such that the number of the flat tubes inserted in the first sub-header portion is smaller than that of the flat tubes inserted in the first main header portion; and a partition plate provided between the first main header portion and the first sub-header portion, and joined to the first main header portion and the first sub-header portion. The partition plate has a surface area that is larger than a sectional area of the first main header portion and a sectional area of the first sub-header portion.

In a power converter, an inductance L of a reactor and a capacitance C of a capacitor satisfy a condition of the expression (1) below. In the power converter, a current-limiting circuit between an AC power source and the capacitor is unnecessary. Herein, αm ([A.Math.s]) is a value of a ratio of a maximum rated current squared time product to a maximum rated output current of diodes of a rectifier circuit, Pmax is a maximum power consumption of the motor, Vac is a voltage value of a three-phase AC voltage, and a value of a constant a is 4.3 $\begin{array}{cc}a.Math.C.Math.\sqrt{\frac{C}{L}}.Math.\frac{{\mathrm{Vac}}^3}{P_{\max }}\le {\alpha }_m.& \left(1\right)\end{array}$

A fresh-air air conditioning system comprises: a first electromagnetic valve connected to a first interior heat exchanger, and the first electromagnetic valve is connected via a first accumulator to a compressor and a third electromagnetic valve; the third electromagnetic valve is connected via a second accumulator to the compressor and a second electromagnetic valve; and the second electromagnetic valve is connected to a second interior heat exchanger. When the first interior heat exchanger or the second interior heat exchanger is closed, the third electromagnetic valve opens so that the first accumulator and the second accumulator simultaneously communicate with the open one of the first interior heat exchanger or the second interior heat exchanger, avoiding poor oil return as a result of prolonged single-cylinder operation of the compressor, and ensuring the reliability of the compressor as well as interior comfort.

An air-conditioning system includes an outdoor unit, a plurality of indoor units, and one or more refrigerant leak sensors. The outdoor unit is configured to exchange heat between outdoor air and refrigerant in a refrigerant circuit in which the refrigerant is circulated. The plurality of indoor units are each configured to exchange heat between the refrigerant and air inside a room in the refrigerant circuit and to perform air-conditioning inside the room. The one or more refrigerant leak sensors are each configured to detect a leak of the refrigerant from the refrigerant circuit. The one or more refrigerant leak sensors are each arranged separately from the outdoor unit and the plurality of indoor units.

A refrigeration cycle apparatus (1) is capable of performing a refrigeration cycle using a small-GWP refrigerant. The refrigeration cycle apparatus (1) includes a refrigerant circuit (10) and a refrigerant enclosed in the refrigerant circuit (10). The refrigerant circuit includes a compressor (21), a condenser (23), a decompressing section (24), and an evaporator (31). The refrigerant contains is a small-GWP refrigerant.

Upon detection of a leakage of refrigerant, a refrigerant recovery operation is performed for operating a compressor in a state where an outdoor expansion valve is closed. The refrigerant suctioned from an indoor unit passes through an outdoor heat exchanger so as to be liquefied and accumulated in an outdoor unit. When a low-pressure detection value by a pressure sensor decreases below a reference value, a termination condition for the refrigerant recovery operation is satisfied, and the compressor is stopped. Furthermore, when an abnormality in the refrigerant recovery operation is detected based on a behavior of the low-pressure detection value obtained until the termination condition is satisfied, the compressor is stopped to thereby end the refrigerant recovery operation. Also, guidance information for notification about an abnormality is output to a user.

An air conditioner including a refrigerant circuit including a compressor, an outdoor heat exchanger, an outdoor expansion valve, an indoor expansion valve, and an indoor heat exchanger. The refrigerant circuit including an auxiliary heat exchanger provided on a refrigerant pipe between the outdoor heat exchanger and the indoor expansion valve and connected in series with the outdoor expansion valve, and a rectifier configured to allow a refrigerant flowing from the outdoor heat exchanger toward the indoor expansion valve in a cooling operation or a refrigerant flowing from the indoor expansion valve toward the outdoor heat exchanger in a heating operation to sequentially flow through the auxiliary heat exchanger and the outdoor expansion valve.

A refrigerant cycle apparatus, that circulates a flammable refrigerant in a refrigerant circuit, includes: a gas-side cutoff valve; a liquid-side cutoff valve, where the gas-side cutoff valve and the liquid-side cutoff valve are disposed on opposite sides of a first portion of the refrigerant circuit; a detection unit that detects refrigerant leakage from the first portion into a predetermined space; and a control unit that sets a cutoff state in the gas-side cutoff valve and the liquid-side cutoff valve when the detection unit detects the refrigerant leakage from the first portion into the predetermined space. The cutoff leakage rate at the gas-side cutoff valve is higher than the cutoff leakage rate at the liquid-side cutoff valve.

A refrigeration cycle apparatus includes an outdoor unit a plurality of indoor units a relay unit a refrigerant circuit and a controller The relay unit includes a plurality of high-pressure valves and a plurality of low-pressure valves The controller when an operation state of at least one of the indoor units is changed from a first state to a second state, judges, based on a degree of supercooling of an outlet of the outdoor heat exchanger or the indoor heat exchanger or based on a degree of superheating of a suction side of the compressor, whether an abnormality is present in the plurality of high-pressure valves or the plurality of low-pressure valves.