A method of initiating a low-energy cooling mode using a controller of an HVAC system includes measuring a temperature of ambient air proximal to a condenser coil and determining whether the temperature of the ambient air proximal the condenser coil is less than a temperature threshold. If the temperature of the ambient air is less than the temperature threshold, the HVAC system is configured to operate in a low-energy cooling mode. In the low-energy cooling mode, the controller opens a first bypass valve to allow a refrigerant to bypass a compressor and the compressor is powered off. The HVAC system is operated until a cooling demand has been met.

A multi-type air conditioner is provided that includes an outdoor unit having a liquid pipe through which a liquid refrigerant flows, and a gas pipe through which a gas refrigerant flows; a plurality of indoor units including a first indoor unit and a second indoor unit each connected to the liquid pipe and the gas pipe to circulate a refrigerant; a gas pipe connecting tube connecting the gas pipe and the plurality of indoor units so that a gas refrigerant flows therethrough; and a liquid pipe connecting tube connecting the liquid pipe and the plurality of indoor units so that a liquid refrigerant flows therethrough.

A method of initiating a low-energy cooling mode using a controller of an HVAC system includes measuring a temperature of ambient air proximal to a condenser coil and determining whether the temperature of the ambient air proximal the condenser coil is less than a temperature threshold. If the temperature of the ambient air is less than the temperature threshold, the HVAC system is configured to operate in a low-energy cooling mode. In the low-energy cooling mode, the controller opens a first bypass valve to allow a refrigerant to bypass a compressor and the compressor is powered off. The HVAC system is operated until a cooling demand has been met.

A heat exchanger includes a first-row heat exchange module through which a refrigerant is introduced from the outside, a second-row heat exchange module through which the refrigerant is discharged to the outside, a third-row heat exchange module through which the refrigerant is discharged to the outside, and a flow-splitting module that splits the refrigerant from the first-row heat exchange module into the second-row heat exchange module and the third-row heat exchange module, wherein the refrigerant reciprocates one time in a flow path, the first-row heat exchange module constitutes a forward path of the flow path, and both the second-row heat exchange module and the third-row heat exchange module constitute backward paths of the flow path.

A sensor control system includes: a refrigerant leak sensor configured to, when powered, measure an amount of a refrigerant present in air outside of a heat exchanger of a refrigeration system, where the heat exchanger is located within a building that is at least one of heated and cooled by the refrigeration system; and a power control module configured to one of: continuously power the refrigerant leak sensor; and disconnect the refrigerant leak sensor from power when a blower that moves air past the heat exchanger is on.

A refrigeration cycle apparatus includes a refrigeration cycle circuit, a bypass flow path, a first valve provided in the refrigeration cycle circuit, a second valve provided at the bypass flow path, a first temperature sensor configured to detect a temperature of an indoor space, a second temperature sensor configured to detect a temperature of refrigerant on a liquid side of an indoor heat exchanger, and a notification part. The refrigeration cycle apparatus is able to operate in an operation state where the compressor operates, the indoor heat exchanger functions as an evaporator, and the first valve is open while the second valve is closed. In the operation state, the notification part issues notification of an abnormality of an electronic expansion valve or the first valve when a temperature detected by the second temperature sensor is higher than an evaporation temperature of refrigerant in the refrigeration cycle circuit.

A refrigeration cycle apparatus includes a hot water tank, a heat source for heating water in the hot water tank, and a refrigeration cycle circuit that includes an indoor heat exchanger, a heat-source heat exchanger, and a water heat exchanger. The indoor heat exchanger may operate as a condenser. When an outside temperature is greater than a specified temperature, the refrigeration cycle apparatus operates in a first state in which the heat-source heat exchanger operates as an evaporator and the water heat exchanger does not operate. When the outside temperature is less than the specified temperature, the refrigeration cycle apparatus operates in a second state in which the water heat exchanger operates as an evaporator and refrigerant therein absorbs heat from water in the hot water tank heated by the heat source and the heat-source heat exchanger does not operate.

An air-conditioner includes: a refrigerant circuit through which a refrigerant flows, the refrigerant circuit being formed of a compressor, a switching valve, a first heat exchanger, an expansion valve, and a second heat exchanger connected to one another by a first pipe; a heat-transfer medium circuit through which a heat-transfer medium flows, the heat-transfer medium circuit being formed of a pump, the first heat exchanger, and a third heat exchanger connected to one another by a second pipe; and control device that controls the compressor and the pump. In an operation of the air-conditioner performed before entering a defrosting operation, the control device increases a frequency of the compressor, as compared to the frequency of the compressor in a heating operation, and reduces a rotational speed of the pump, as compared to the rotational speed of the pump in the heating operation.

The refrigerant device includes a refrigerant circuit, an injection circuit, an inlet temperature sensor, an outlet temperature sensor, and a controller configured to control the operation of the refrigerant circuit. The controller includes an evaluation value calculation unit and a refrigerant amount detection unit. The evaluation value calculation unit calculates an evaluation value indicating a capability of a subcooling heat exchanger in accordance with an inlet temperature detected by the inlet temperature sensor and an outlet temperature detected by the outlet temperature sensor. The refrigerant amount detection unit determines whether there is a shortage of refrigerant in accordance with the evaluation value calculated by the evaluation value calculation unit.

The invention is an impulse system and a method for heat transfer in thermal nonequilibrium state through a heat-transferring wall of a heat transferring volume. The system is based on a heat transferring volume and an impulse device in fluid, pressure and thermal communication with each other, where the impulse device delivers a heat load to the heat transferring volume through a working medium in condensed phase impulses. The impulse device controls the rate of delivery of impulses such that each subsequent impulse is received before the heat capacity of the heat transferring wall returns to an equilibrium state thereby resulting in an accumulation of the changes in heat capacity of the heat transferring wall and subsequent changes in the temperature of the heat-transferring wall above or below the wall thermal equilibrium state to increase the heat transfer flow through the wall.