Design parameters, performance testing and analysis of a double-glazed, air-blown solar still with thermal energy recycle

An air-blown, multiple-effect solar still with thermal energy recycle consisting of an upper evaporation chamber and lower condensation chamber, has been recently proposed. The principle of operation of such a still, the main design parameters and the results of solar still performance tests are presented in this paper. The present discussion is restricted to the performance testing of a solar still with a nominal still area of 1 m², utilizing a solar simulator providing a constant radiation intensity of 630±39 W m^-2. The solar still performance was monitored under the conditions: of a constant feedstock flow-rate, 8.22 x 10^-4 kg m^-2 s^-1, and varying air flow-rate, ranging from 0.89 x 10^-4 to 12.53 x 10^-4 kg m^-2 s^-1. It was observed, under these conditions, that the thermal energy recycle began to be effective after about 30 min and that the still achieved steady-state after approximately 1 h of operation. The steady-state distillation rate exhibits an optimum (of the order of 3.06 x 10^-4 kg m^-2 s^-1) at air flow-rate in the range from 2.8 to 3.44 x 10^-4 kg m^-2 s^-1. The experimental results indicate that the still performance can be enhanced further by increasing the linear air stream velocity in the lower chamber by decreasing its cross-sectional flow area.