Vegetable Oil based Biodegradable Refrigeration Oil - An Optimization of Tribological Characteristics Using D-optimal Design

The present study investigates the tribological behaviour of vegetable oil-based polyolester refrigeration oil using the pin-on-disc tribometer. Experiments were carried out choosing the load and sliding velocity as a function of rotational speed as the numerical factor and refrigeration oil as the categorical factor. Response surface methodology (RSM) based D-optimal design was utilized for modelling and optimization of friction and wear characteristics. The tribological characteristics of a lubricant-material combination of hermetically sealed compressor was observed with synthetic refrigeration oil (POE68), vegetable oil based polyolester (BIO) and blended refrigeration oil i.e., (BIO50) 50% by vol. of vegetable oil based refrigeration oil & 50% by vol. of POE68. The results showed that the application of blended refrigeration oil (BIO50) leads to the improved tribological behaviour in terms of coefficient of friction of 0.02742 and specific wear rate of 1.98x10-4 mm3/Nm at a speed of 1160 rpm and load of 7.44 kg. The surface morphology analysis of worn pin surfaces showed that the compressor material lubricated with blended refrigeration oil was glossier than synthetic and vegetable oil based polyolester refrigeration oil.