Experimental performance evaluation and refrigerant charge optimization of a dehumidifier with 5 mm diameter finned tube evaporator

This study investigates the feasibility of replacing the conventional 7 mm finned-tube evaporators used in domestic vapor compression-based dehumidifiers with smaller-diameter 5 mm evaporator, with the aim of addressing critical challenges in refrigerant reduction, system compactness and cost. Small-diameter heat exchangers have been developed significantly in the air conditioning or refrigeration field due to their advantages of high heat exchange efficiency, low cost and low refrigerant charge. Therefore, there is still potential for the application of small-diameter heat exchangers in dehumidifiers. This paper evaluates the feasibility of replacing the Φ7 mm evaporator of a dehumidifier with a Φ5 mm evaporator. Through comparative experiments, it is demonstrated that the Φ5 mm evaporator configuration achieves significant benefits: It reduces refrigerant charge by 26.7 % (from 150 g to 110 g) while maintaining comparable dehumidification performance; Enhances energy factor by 3.9 % under standard operating conditions (27.0 °C/21.2 °C) with a 2.37 % small decrease in dehumidification capacity; Lowers total system cost by 15.29 % through combined evaporator material savings and refrigerant reduction. Notably, the Φ5 mm evaporator system reaches the prototype's performance at the 18.3 °C/13.7 °C condition, achieving a dehumidification capacity of 0.710 kg/h with an energy factor of 1.924 kg/kW h. These findings establish small-diameter evaporator as a viable alternative in dehumidifier application that addresses environmental concerns through reduced refrigerant requirements while providing economic benefits through cost-effective design. They provide critical insights for the implementation of next-generation eco-friendly refrigerants, such as hydrocarbon-based refrigerant R290, in mechanical dehumidification system.