Modeling an active solar still for sea water desalination process optimization

• Comprehensive numerical modeling of an active solar still was performed.
• All the design parameters with those of the heat transfer fluid were included in the model.
• Validation of the modeling was assessed by comparison to an exact 2-D model of a humid-air cavity.
• Adequacy of the correlations used for the heat transfer coefficients was verified.
• Extensive parametric studies enabled to determine the relative influence of the key factors.

Active solar stills can provide enhanced distillate productivity, as saline water is circulated and put in contact with an additional heat source which supplies extra heat to the system. In this work, a single slope solar still having a transparent glass cover is considered to be heated at its bottom by a circulating heat transfer fluid. The rate of this flow and the temperature at the inlet of the still are assumed to be controlled such that they are adjusted to the desired values. A modeling based on relevant correlations giving the heat transfer coefficients and the vaporization heat flux as function of Rayleigh number was derived. This takes the form of a set of highly coupled nonlinear ordinary differential equations in terms of time-dependent temperatures of the still components. The obtained model enabled to take into account the effects of heat transfer fluid rate, inlet temperature, sea water rate, basin depth, ambient temperature, wind speed and relative humidity of ambient air. Extensive parametric studies were performed and optimization of the rate and yield of distilled water was discussed.