Refrigerant charge reduction in R600a domestic refrigerator-freezer by optimizing hot-wall condenser geometry

ABSTRACT The objective of this study is to investigate the effects of hot-wall condenser geometry on domestic refrigerator-freezers (RFs) in terms of refrigerant charge reduction. A transient simulation model for an R600a domestic RF is developed and validated to capture the dynamic performance at various operating conditions. The hot-wall condenser in the domestic RF is determined to store excess refrigerant charge. The effects of the hot-wall condenser geometry on the performance of the RF are analyzed according to the total refrigerant charge. The coefficient of performance (COP) decreases with decreasing hot-wall condenser length and diameter; however, the decrease in the COP of the RF is compensated by the decreased energy consumption. Based on the global minimum energy consumption, the optimum hot-wall condenser design is achieved when the tube length is reduced to 70% of its original size and the tube outer diameter is decreased to 3.75 mm. Furthermore, the total refrigerant charge in the RF corresponding to the optimized hot-wall condenser geometry is shown to be 14% lower compared to the rated charge amount.