Heat and mass transfer during evaporation from a free surface of water flowing through fibrous sheet in an inclined enclosure.

Abstract

The simultaneous phenomenaof heat and mass transfer from water flowing through a fibrous sheet attached below the upper boundary of an inclined enclosure have been studied as a fundamental work for developing a new type of solar still. Experimental work was carried out with two kinds of fibres, two angles of inclination, and different feed rates at various heat inputs. The maximum temperature at the upper wall of the enclosure increased linearly with applied heat flux and was almost independent of the feed rate and the kind of fibre. Experiments with high-permeability sheet showed an increase in evaporation rate of about 16 %at a 10-degree angle and 30 % at a 36-degree angle. Thermal convection in the enclosure became evident at a low feed rate and declined with increase in feed rate. A mathematical model for the temperature distribution in the preheating zone was formulated and the heat transfer properties were studied by curve-fitting with the experimental data. The result provides useful data for designing the newtype of solar still.