Effect of an Air Cavity Appended to the Solar Still: A Computational Approach

In recent years, saline water distillation using solar energy has been identified as a high renewable energy need. Despite the fact that numerous researchers have taken varied techniques in this area, this work presents a novel design and its computational analysis which is an essential criterion in improving the performance of a solar still. An air cavity is added to the passive still in this investigation to prevent heat loss to the atmosphere. To explore the effect of the air cavity in the heat transfer phenomena within the solar still, a finite volume technique based on the SIMPLE algorithm is used in Ansys Fluent software to solve the governing equations. The findings of this process include Nusselt number (Nu), Reynolds number (Re), and variation of total heat flux with respect to the variation of the height of an air cavity while holding Prandtl (Pr = 0.712). The findings showed that reducing the height of an air cavity resulted in a significant increase in mass and heat transfer rates inside the air cavity. The temperature gradient between the glass cover and the saline water plays a critical role in the optimisation of the design parameters of the solar still. From the CFD simulations, a height of 20 cm of an air cavity is determined to be the optimum height for improving the solar still performance in terms of the evaporation rate inside the still.