AIR-BLOWN SOLAR STILL WITH HEAT RECYCLING

摘要

A laboratory-scale solar still of 1 m~2 area, designed to recycle the condensation heat of the distillate has been constructed and tested through in-door experiments, using incandescent lamps for irradiation. In this still a considerable fraction of the exothermal enthalpy of condensation and the sensible heat of the warm condensate are successfully recycled and reused for preheating and evaporating the feedstock via a much simpler technique, relative to that used in either multi-stage distillation or multi-flash systems. For heat transfer the most effective processes, forced thin layer evaporation and film condensation, have been applied in counter-flow of the heat exchanging fluids. As a result, about a threefold increase in yield could be achieved, compared with that of a basin-type still of the same area and with the same irradiation. The variation of the yield and the steady-state local temperatures with regard to the variations in the air and feedstock flow rates are discussed in detail. Optimum conditions, together with the heat and mass balance calculations are also given. The effect of scale-up on the still productivity is estimated. These estimations promise enhanced thermal efficiency with increase in size, and thus a further increase in the productivity per unit area.