The
objective of this research project was to develop an optimized process that
makes use of low-grade heat provided from solar irradiation to drive a
distillation-desalination process. An efficient distillation process re-uses
input heat, by using the heat-of-condensation as the heat source for
pre-heating the incoming cold saline water. This research project was
concerned with examining the physical and thermodynamic characteristics of this
process so as to optimize the efficiency of a solar powered water distiller
employing heat recovery. The study was primarily concerned with understanding
the natural convection driving the evaporation-condensation process and the
other physical and geometric considerations that affect the distillation
process. In contrast to other projects investigating low temperature
distillation devices employing regeneration, this research project incorporated
a CFD (Computational Fluid Dynamics) analysis that formed the base for the
optimization process. By using such an analysis the optimum geometry for a
distillation enclosure was determined to be an “ovalized rectangle”. This basic
geometry with CFD-optimized dimensions, along with some additional features was
incorporated into a fully operational laboratory distillation system. The
distillation system was tested experimentally and its thermal efficiency was
determined. The device tested is capable of distilling water to levels of ~ 17
ppm dissolved salt content at thermal efficiencies comparable to the
theoretical possible. These findings, incorporated into solar distiller design
will assist the designer in choosing optimized parameters to maximize the
device’s efficiency.
