Cooling of a reciprocating compressor through oil atomization in the cylinder

An analysis of the influence of oil atomization in the cylinder of a reciprocating compressor is presented in this paper. During compression, oil atomization enhances heat removal from the refrigerant gas. This cooling effect, which eventually results in a global temperature decrease of the compressor parts, aims primarily at reducing the refrigerant superheating in the suction system and inside the cylinder, which is largely responsible for overall energy losses and a decrease of the volumetric efficiency. A prototype was constructed and tested with R-134a in a hot gas-cycle calorimeter. A significant reduction of the compressor thermal profile has been achieved, with the largest variations of 30.9°C (55.6°F) and 23.6°C (42.5°F) in the discharge chamber and cylinder wall, respectively. A major dependence of the compressor efficiency parameters on the refrigerant solubility in the oil has been observed. A simulation model using an integral control volume formulation for mass and energy conservation in the cylinder and in other compressor components is proposed. Based on this model, the effect of oil atomization on the compressor performance is presented and discussed in terms of oil injection parameters, such as nozzle position, oil temperature and flow rate.

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