Computation of solar radiation distribution in a solar still with internal and external reflectors

摘要

A model that calculates the distribution of solar radiation inside a basin-type solar still with plane reflectors has been proposed. In this model, both surface finish and optical view factors are taken into consideration in the computation of solar radiation that effectively reaches the surface of saline water in the distillation system. The model was applied to a conventional solar still and an advanced solar still with separate condenser. The conventional solar still was tested at New Delhi (28°35'N, 77°12'E) in previous work while the advanced distillation system was developed in this investigation and it comprised three basins with saline water. Basin 1 was fitted horizontally in the evaporator chamber, with the condenser chamber housing basins 2 and 3. The top part of the evaporator unit was covered with glass to allow solar radiation to reach water in basin 1. In addition, the internal surfaces of the walls of the evaporator and external surface of the front wall of the condenser unit reflected part of the incoming solar radiation onto the surface of saline water in basin 1. The distillation system was tested outdoors at the Malawi Polytechnic (15°48'S, 35°02'E). Under the prevailing meteorological conditions, it is found that the computed solar load on the surface of saline water in the evaporator basin is lower than that observed on a horizontal plane outside each energy system. The new model exhibited a higher degree of accuracy than the previous one. Other results are presented and discussed in this paper.