A numerical study on the effect of oil lubricant on the heat transfer and efficiency of a vapour compression refrigeration system. (May 2022) - Li, Zhaohua
Abstract: The involvement of oil lubricants in vapour compression refrigeration (VCR) systems could adversely influence the flow, heat transfer and efficiency of refrigeration. A numerical model for a VCR system using linear compressor, R1234yf, and POE oil is developed in this study to investigate the effect of oil lubricant on the flow and heat transfer as well as the system performance including cooling capacity and coefficient of performance (COP). The proposed model is validated by measurements of a prototype oil-free VCR system with most of the simulated data falling within ±20% of measurements. The evaporator heat transfer coefficient, cooling capacity, and COP for the system from the proposed model show a positive correlation with oil circulation rate (OCR). The COPs and pressure losses for oil-free system are 15–28% higher and 36–60% lower than that of oil-lubricated system respectively. Highlights: Numerical model of oil-free VCR system was validated by measurements. Presence of oil lubricant in the compressor cylinder reduces the in-cylinder temperature. higher OCR tends to have a lower vapour quality at the evaporator outlet. COPs and pressure losses for oil-free system are 15–28% higher and 36–60% lower. Heat transfer and COP show negative correlation with OCR.