Comparative thermal model analysis and experimental validation for predicting performance of a pyramidal solar still with integrated pulsating heat pipe

Developing nations face a dire situation as water scarcity and pollution significantly impact various aspects of life. It's crucial to take action now to address these pressing issues and ensure a sustainable future for all. Solar desalination processes emerge as a promising solution to these pressing problems in water purification technologies. This paper reports the thermal modeling and experimental results of two solar still designs, namely (i) Pyramidal solar still with pulsating heat pipe (PHP), Modified pyramidal solar still (MPSS), and (ii) conventional pyramidal solar still (CPSS). This study uses energy balance equations to focus on MPSS and CPSS thermal modeling. In the MPSS, a PHP, in conjunction with a solar collector, provides external heat to basin water. Several models, including Dunkel, Kumar and Tiwari, Chen, and Zheng Hongfei, are utilized to estimate the performance of both MPSS and CPSS. Extensive experiments have been conducted for validation purposes. Key parameters considered for prediction and comparison include evaporative heat transfer coefficient, convective heat transfer coefficient, total heat transfer coefficient, and hourly yield. It is noted that the Kumar and Tiwari model demonstrates a superior ability to predict cumulative yield, with a percentage error of 5.81 % and 5.9 % for MPSS and CPSS, respectively, compared to the experimental cumulative yield. The theoretical average basin water temperature observed in MPSS is 64.56 degrees C, and CPSS is 58.8 degrees C. The enhancement in temperature is attributed to the supplementary heat provided by the PHP.