Impact of rotating fan and ultrasonic humidifier on the thermal performance of pyramidal solar still

Abstract

Abstract This study investigates the performance enhancement of a pyramidal solar still by integrating two active techniques: a low-power fan and an ultrasonic humidifier. Baseline experiments were first conducted using a static pyramidal solar still and compared with results from a fan-assisted configuration and a unit equipped with an ultrasonic humidifier. The fan promoted faster vapor circulation, while the humidifier produced fine mist particles that accelerated evaporation. Experiments carried out under Dubai’s climatic conditions showed that the system achieved a maximum efficiency of 57%, with corresponding values of heat transfer rate, evaporative heat transfer coefficient, and condensation heat transfer coefficient of 148.43 W, 20.38 W/m²°C, and 1.64 W/m²°C, respectively. The maximum partial vapor pressures at the basin and glass surfaces were 18,626.71 Pa and 15,276.53 Pa. At peak heating around 3:00 PM, the ultrasonic humidifier-based system recorded significantly higher partial vapor pressures—38.04% at the basin surface and 23.87% at the glass surface—compared to the static still, highlighting the effectiveness of active enhancements in accelerating vapor generation. Overall, the ultrasonic-based system demonstrated the highest performance, while the static unit produced the lowest output. The distillate yields were 90 ml, 180 ml, and 330 ml for the static, dynamic, and ultrasonic systems, respectively. Also, it is found that, the system yielded energy and exergy efficiencies equal to 25.11% and 1.75%.