Abstract

This paper presents a theoretical analysis of a novel solar still system, which was previously explored through experimental studies. The experimental results demonstrate that integrating phase change material (PCM) to store latent heat from vapor condensed on sidewalls during sunlight exposure, along with the use of pulsating heat pipes (PHPs) to recover this stored energy after sunset, and cooling the condenser sidewalls with PCM, significantly boosts the system's efficiency from 23.7 % to 48.5 %. These innovative features, applied for the first time in a single-stage passive solar still, are thoroughly examined using a groundbreaking mathematical model. This model is the first to uniquely account for heat transfer and condensation on sidewalls and to accurately simulate the function of pulsating heat pipes (PHPs) within a passive solar still setup. By incorporating measured radiation intensity and ambient temperatures, the model applies an exhaustive energy balance, utilizing heat transfer correlations and resistances for precise temperature predictions of each component. This detailed analysis highlights the system's innovative aspects and identifies areas for further refinement, shedding light on potential improvements and the system's limitations. The results show a water production of 6.7931 kg/m2 and an efficiency of 52.2 %, with a discrepancy of 7.8 % compared to experimental findings. Notably, 37.6 % of the total freshwater production is derived from sidewall condensation, significantly reducing heat loss by capturing latent heat. Additionally, by reallocating 9.3 % of stored energy, the PHPs maintain the saline water temperature 6.2 degrees higher at night, thereby sustaining elevated production rates.