Operating characteristics and design optimization of a heat pump clothes dryer using R290 as an alternative refrigerant to R134a

A Heat Pump Clothes Dryer (HPD) typically uses R134a as the working fluid; however, R134a must be replaced with a refrigerant with a low global warming potential. While R290 presents a promising alternative to R134a in HPDs, component optimization, which has not yet been addressed in existing studies, is essential because the refrigerant charge must be restricted to less than 150 g due to flammability concerns. In this study, drop-in tests of R290 were performed on an HPD designed for R134a, and component optimization was carried out to enhance the performance of the HPD with R290 while complying with refrigerant charge regulations. At a charge of 150 g, the Specific Moisture Extraction Rate (SMER) and Moisture Extraction Rate (MER) of the original HPD using R290 were 15.3 % and 7.7 % lower, respectively, than those using R134a. To achieve improved drying performance, the optimal charge amount of R290 was determined to be 210 g, which exceeds the 150 g safety limit for flammable refrigerants. Therefore, the heat exchangers in the HPD were optimized to reduce the refrigerant charge to below 150 g while maintaining performance. The SMER of the optimized HPD using R290 (charge = 150 g) was 2.2 % higher than that of the original HPD using R290 (charge = 210 g), whereas the MERs of both HPDs were equivalent. Furthermore, based on the Life Cycle Climate Performance (LCCP) analysis, the LCCP of the optimized HPD using R290 (charge = 150 g) was 6 % lower than that of the original HPD using R134a. This study offers a valuable guideline for designing HPDs using eco-friendly refrigerants, ensuring compliance with safety regulations while maintaining system performance.