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 consi sting of an upper evaporation chamber and lower condensation chamber, has b een recently proposed. The principle of operation of such a still, the main design parameters and the results of solar still performance tests are pre sented in this paper. The present discussion is restricted to the performan ce testing of a solar still with a nominal still area of 1 m(2), 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 c onstant feedstock flow-rare, 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-stat e 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 f low-rate in the range from 2.8 to 3.44 x 10(-4) kg m(-2) s(-1). The experim ental results indicate that the still performance can be enhanced further b y increasing the linear air stream velocity in the lower chamber by decreas ing its cross-sectional flow area. (C) 1998 Elsevier Science Ltd All rights reserved.