Archives of Current Research International

In closed-loop low-temperature drying systems, evaporator dehumidification efficiency is strongly governed by the refrigerant evaporation temperature. Although numerous international studies have examined moisture condensation in heating, ventilation and air-conditioning systems and dehumidification systems, most have focused on airflow modelling, fin-surface design or control optimisation. Experimental investigations linking evaporation temperature to real-time condensation dynamics remain limited, especially for small- and medium-scale closed-loop dryers commonly used in Vietnam. This study experimentally investigated the influence of three evaporation temperatures, t₀ = 5 °C, 0 °C and –5 °C, on the dynamic behaviour of moisture condensation during operation. Experiments were conducted on the same evaporator coil, with constant fin spacing and constant air velocity across the coil, over a 120-minute cycle for each t₀ condition. The results indicated that moisture removal increased rapidly during the first 20–30 minutes because of the large temperature gradient between humid air and the coil surface. When t₀ decreased from 5 °C to 0 °C, the total condensed moisture increased from 2,615 g to 3,025 g after 120 minutes. However, at t₀ = –5 °C, dehumidification performance declined sharply after the initial stage because frost accumulation reduced airflow rate and heat-transfer efficiency. These findings indicate that lower evaporation temperatures enhance initial moisture removal but require appropriate control and defrost cycles to maintain long-term system stability and energy efficiency.