Effect of Biodegradable Refrigeration oil on the Tribological Behaviour of Liner/Ring Tribo pair material of Hermetically Sealed Compressors

Abstract

Abstract An improvement in co-efficient of performance (COP) of a vapour compression refrigeration (VCR) system is largely depends upon the work of compression which in turn rely on the quality of lubricants. Further the compatibility of cylinder liner/piston ring tribo pair material of a hermetically sealed compressor is another vital aspect to consider during the development of refrigeration oil. The base oil, which has been used for the formulation of refrigeration oil, is derived from petroleum products. However the depletion of petroleum reserves, uncertainty in crude oil prices, energy demand and increased environmental awareness has promoted the crucial requirement to synthesize refrigeration oil from environmentally friendly energy resources. The present investigation is intended to formulate a rapeseed oil based trimethylolpropane tri ester as biodegradable refrigeration oil with good thermo-oxidative stability and cold flow behaviour via chemical modifications. Thermo gravimetric Analysis (TGA) and Differential Thermal Analyses (DTA) were performed to study the thermo-oxidative stability of biodegradable refrigeration oil. This investigation is also addressing the issue of the tribological behaviour of cylinder liner/piston ring material of a hermetically sealed compressor in VCR system under the influence of biodegradable refrigeration oil and synthetic refrigeration oil (ISO 68 grade-POE oil) using a pin-on-disc tribometer. The surface morphology analysis of tested pin materials was also carried out using scanning electron microscope. The tribological experiments were carried out in accordance with ASTM G99. Under similar experimental conditions, biodegradable refrigeration oil exhibited good friction reduction behaviour and inferior wear reduction behaviour as compared to synthetic refrigeration oil.