Pull-Down Characteristics and Sustainable Cooling Performance of an Eco-Friendly R600a Vapour Compression Refrigeration System Using Graphene Oxide Nanolubricant

Abstract

Pull-down time is a critical transient performance parameter for vapour compression refrigeration (VCR) systems with low Global Warming Potential (GWP) R600a refrigerant, representing the system’s ability to rapidly achieve the desired cooling temperature. Faster pull-down time leads to reduced compressor operating duration, lower energy consumption and improved user comfort. This paper presents an experimental investigation on pull-down time and cooling effect of a VCR system operating with eco‑friendly R600a refrigerant using graphene oxide (GO) based nano‑lubricant. Graphene oxide nanoparticles were dispersed in polyolester (POE) oil at concentrations of 0.1 gram/L, 0.2 gram/L and 0.3 gram/L. Experiments were conducted at varying refrigerant mass charges of 40 gram, 50 gram and 60 gram. The cooling effect and transient pull‑down characteristics were evaluated and compared. Results indicate a significant reduction in pull‑down time and enhancement in cooling effect, reduction in power consumption and improvement in coefficient of performance with GO nano‑lubrication compared to pure POE oil. An optimum performance was observed at 0.2 gram/L GO concentration with a 50 gram refrigerant charge. The findings demonstrate the potential of graphene oxide nano-lubricants to enhance transient cooling performance and improve energy efficiency in a vapour compression refrigeration system using low-GWP R600a refrigerant.