Performance Parameter Study of R32 for Low Temperature Cold Storage

Abstract

R32 refrigerant has attracted increasing attention as a more environmentally friendly and efficient alternative to R404a, R407a, and R507a in low-temperature cold storage applications. This study evaluates the performance of R32 in a cold storage system, beginning at an ambient temperature of 32°C and continuing until the chamber reaches −18°C to −20°C, with evaporator temperatures down to −28°C. The methodology combines steady-state simulations conducted via an Excel VBA interface (“The Poci”) with experimental validation using a standard cold-storage setup (compressor, condenser, expansion valve, and evaporator). Test conditions included ambient temperatures of 25 °C, 30 °C, 35 °C, and 40 °C, and condensing temperatures of 45 °C, 50 °C, 55 °C, and 60 °C. Temperature and pressure were recorded every minute using K-type thermocouples and pressure transmitters; compressor power consumption was logged with a power-meter data logger; and mass flow rates were measured with a Coriolis data logger. Model validation employed the Mean Absolute Percentage Error (MAPE). Results show a MAPE deviation of 2.11 %, indicating high simulation accuracy. At a constant cooling load, R32 achieved the lowest compressor power consumption (0.65–0.68 kW) and the highest coefficient of performance (COP = 2.8) among the refrigerants. Lowering the condensing temperature improved the thermal efficiency of all refrigerants, but R32 remained superior, particularly under ambient conditions of 30 °C–35 °C. Pressure–enthalpy (P–h) diagram analysis confirmed that R32 exhibits a higher evaporation enthalpy and a shorter compression path, contributing to its superior COP. These findings demonstrate that R32 is highly suitable for cold storage applications at −18°C to −20°C, replacing R404a, R407a, and R507a, offering enhanced energy efficiency and potential reductions in global warming potential (GWP). Further research is recommended to conduct long-term studies on refrigerant–material compatibility and to perform fire risk assessments associated with R32’s A2L flammability classification.