A piston compressor is a mechanical type of compressor that compresses gases by reducing volume through piston-driven motion. In industrial high-temperature heat pumps (HTHPs), it plays a key role: it boosts the pressure and temperature of the circulating refrigerant to levels that allow process heat to be delivered at temperatures of up to 200 °C.

Compression takes place in one or more cylinders ,where pistons move in a cyclical motion. During the intake stroke, refrigerant is drawn into the cylinder; during the compression stroke, it is compressed by the rising piston and discharged into the high-pressure side of the system. This principle allows for a staged and highly controlled pressure increase, making it particularly well-suited for applications involving large pressure differentials.

One example of a piston compressor used in high-temperature industrial heat pumps is SPH’s ThermBooster™, which features a custom-designed, four-cylinder piston compressor running at 1,500 rpm. Engineered for compatibility with both natural refrigerants and environmentally friendly synthetic HFOs, it delivers optimum performance and high efficiency.

Compared to other compressor types—such as screw or scroll compressors—piston compressors offer superior pressure flexibility and mechanical durability. This allows for high efficiency and substantial temperature lifts, even under part-load conditions—where screw compressors, for instance, often fall short. These characteristics make piston compressors an excellent choice for demanding industrial heating applications that require both high temperatures and high pressures. However, due to their intermittent compression cycle, they can be more susceptible to vibration, necessitating careful system design and effective sound and vibration insulation.

The energy efficiency of a piston compressor significantly impacts the overall coefficient of performance (COP) of the heat pump. Ongoing improvements in valve technology, lubrication systems, and motor efficiency continue to reduce energy consumption and enhance the cost-effectiveness of the entire system