A Review on CFD Simulation of Modified Solar Stills for Improved Evaporation, Condensation, and Exergy Efficiency

Solar stills are known to offer a sustainable and cost-effective way to produce fresh water, although their efficiency still remains limited due to low rates of evaporation and condensation. The use of current Computational Fluid Dynamics (CFD) technology has provided a significant discovery to accelerate understanding of the inherent heat and mass transfer mechanisms and to offer an opportunity for design optimization to physical dimensions. This review explores thee CFD-based improvements in artificial solar stills for better design of condensation, evaporation, and general thermal performance. Different geometrical templates such as conical, hemispherical, stepped, and the use of fins are evaluated on their influence upon solar radiation absorption, vapor room creation, and condensate collection. The review also identifies the respective roles putative phase change materials, nanofluid-based enhancers, wick setups, external condensers, and active cooling systems play in improving productivity of the system. Three available CFD methods in bulk-field domains are used to model viscous multiphase interaction using two phases: (i) Volume Flow of Fluid model (VOF), (ii) prediction of solar radiation, and (iii) selection of the turbulence model as its motion. Important in predicting vapor liquid interfaces, temperature stratification, and fluid flow patterns. Different in that optimized geometrical shapes can reduce the rate at which thermal energy is lost, thereby reducing entropy production and enhancing the quality of the utilization of energy. According to available studies, conical and hemispherical absorption still—backed by PCM, fins, or nanofluids are deemed to hold the best prospect for yield enhancement, thereby registering the highest improvement of exergy efficiency because of better temperature stratification and better condensation. Research gaps include not having dynamic coupling of CFD with real-time weather data, nor have transient exergy modelling, and hybrid desalination–energy-recovery systems been sufficiently explored. In essence, an optimization driven by CFD is the best way to design better-performing solar stills suitable for decentralized desalination.