A liquid slug protector device for air conditioning and heat pump systems includes a housing having an inlet port, an outlet port, and a cavity. The device further includes a piston disposed in the cavity. The piston has an inflow channel. The device also includes a backing structure disposed in the cavity. The backing structure has an outflow channel, where a first refrigerant flow path from the inlet port to the outlet port includes the inflow channel and the outflow channel. The device further includes a peripheral channel that is at least partially bound by the piston. A second refrigerant flow path from the inlet port to the outlet port includes the peripheral channel and the outflow channel. The second refrigerant flow path is closed when the piston abuts against the backing structure.

A heat transfer system includes a first two-phase heat transfer fluid vapor/compression circulation loop including a compressor, a heat exchanger condenser, an expansion device, and a heat absorption side of a heat exchanger evaporator/condenser. A first conduit in a closed fluid circulation loop circulates a first heat transfer fluid therethrough. A second two-phase heat transfer fluid circulation loop transfers heat to the first heat transfer fluid circulation loop through the heat exchanger evaporator/condenser, including a heat rejection side of the heat exchanger evaporator/condenser, a liquid pump, a liquid refrigerant reservoir located upstream of the liquid pump and downstream of the heat exchanger evaporator/condenser, and a heat exchanger evaporator. A second conduit in a closed fluid circulation loop circulates a second heat transfer fluid therethrough having an ASHRAE Class A toxicity and a Class 1 or 2L flammability rating.

A refrigerant pump and a data center cooling system. The data center cooling system includes a refrigerant connected between a condenser and an evaporator. The refrigerant includes a housing, a partition plate, and a pump head. The housing is provided with a liquid inlet and a liquid outlet. The partition plate is disposed inside the housing, and they jointly form first space and second space. A pump body includes the pump head and a motor. An inlet of the pump head is located at the bottom of the first space in a gravity direction. The motor is located in the second space. The pump head is configured to transfer refrigerant in the first space to the second space. The liquid inlet is directly connected to the condenser by using a pipeline. The first space is configured to store refrigerant of the data center cooling system.

A cooling system includes a compressor, a condenser, an evaporator, a first one-way valve, and a second one-way valve. The compressor includes a compressor inlet and a compressor outlet. The condenser includes a condenser inlet and a condenser outlet, and the compressor outlet communicates with the condenser inlet. The evaporator includes an evaporator inlet and an evaporator outlet, the condenser outlet communicates with the evaporator inlet, and the evaporator outlet communicates with the compressor inlet and the condenser inlet. The first one-way valve is disposed on a first flow path between the compressor outlet and the condenser inlet. The second one-way valve is disposed on a second flow path between the evaporator outlet and the condenser inlet.