Investigation of Thermal and Energy Characteristics in an R152a Vapor Compression Refrigeration System Employing Graphene Nanolubricant
摘要
The present work investigates the effect of graphene nanoparticles appended with the R152a refrigerant-based vapor compression refrigeration cycle on the overall performance of the system. R152a, with an ozone depletion potential (ODP) of 0 and a global warming potential (GWP) of 140, has been targeted as a base refrigerant. The effect of graphene nanoparticles with varying volume fractions (0.1–0.3 Vol.%) has been experimentally investigated on different refrigeration system parameters, such as compressor suction and discharge pressure, compressor discharge temperature, compressor energy consumption, and system performance coefficient. The thermophysical characteristics, such as thermal conductivity, density, and viscosity, of lubricants and graphene nanolubricants, have also been investigated. The thermal conductivity of nanolubricant is improved by the compactness of specific nano-oil fractions. At a temperature of 65 °C, the lubricant density was measured to decrease by 0.8925 g/m3 when the nanolubricant volume fraction was 0.1 Vol.% and by 0.8909 g/m3 when the volume fraction was 0.2%. As compressor oil density decreased, compressor pressure and energy consumption decreased for all nanolubricant suspensions in the refrigeration cycle. The most notable decreases in suction and discharge pressure, around 50% and 19.23%, respectively, are observed when the nanolubricant concentration is set at 0.3 Vol.% and a 75 g charge of R152 is employed. Compared to the base refrigerant, a maximum COP of about 3.21 is attained with a 75 g charge and a graphene volume fraction of 0.3 Vol.%. Furthermore, the lowest discharge temperature is observed for a graphene volume fraction of 0.3 Vol.%.