Effects of Oil Compressibility on the Thermal Performances of Diaphragm Compressors Used in the Hydrogen Refuelling Station with a Mathematical Method

The diaphragm compressor is one of the most commonly utilized compressor types in hydrogen refuelling stations. When employed at high pressure, oil expansion produces significant volume loss in the diaphragm compressor. Oil compressibility effects must be considered when designing the high-pressure diaphragm compressor, else the real flow rate will be much lower than expected. To further understand the effects of oil compressibility on the thermal performance of the compressor, a mathematical model that took oil compressibility into account was given in this work to mimic the thermodynamic process, and experiments were conducted to validate this model. The results indicate that lowering the oil compressibility is a good way to improve the thermal performance of the diaphragm compressor. When the oil bulk modulus rose from 800 to 1200 MPa, the volumetric efficiency grew by 10%, the isentropic indicated efficiency increased by 1.7%, and the minimum suction pressure reduced by 2.1 MPa.