Experimental characterization of heat transfer in the components of a small hermetic reciprocating compressor

Gas superheating is responsible for almost half of the thermodynamic energy loss in small reciprocating compressors adopted for household refrigeration. This is a direct effect of heat transfer between the gas and solid components along the suction system and inside the compression chamber. An experimental study was conducted into heat transfer in the components of a small reciprocating compressor under three operating conditions. Measurements were carried out with thin film heat flux sensors and thermocouples on the surfaces of the suction muffler, discharge chamber, electrical motor and compressor shell. Local thermal conductances were estimated from the experimental data and allowed further insight into different phenomena associated with the heat transfer process. It is shown that such thermal conductances are also useful as boundary conditions for heat transfer modeling and an example of application is provided for the three-dimensional heat conduction in the compressor shell. The measurements reveal the strong influence of the lubricating oil on the heat transfer inside the compressor.