文档介绍：Solar aspects of papers
A SIMPLIFIED MODEL FOR ESTIMATING DISTILLATE YIELD IN LARGE SOLAR STILLS
Arturo Palacio, Alejandro Rodríguez, Italia Millan, Jose L. Fernández
Engineering Institute, National University Autonomous of Mexico
Apartado Postal 70-472, Coyoacan, 04510, Mexico, .
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ABSTRACT
A simplified one-phase model based which considers an homogeneous gas mixture with an “apparent diffusion coefficient”, has been developed to represent the flow characteristics inside a double slope solar still. Its application for the calculation of the heat flow and therefore of the distillate yield shows good agreement with experimental data. Preliminary results about the asymmetry of the flow patterns attained for symmetrical boundary conditions is presented and discussed.
INTRODUCTION
The use of solar energy in engineering applications has gained more importance over the last decades. Several studies, theoretic as well as experimental, have been realized on the heat transfer mechanisms that take place in triangular cavities, which is the typical shape in the X-Y plane geometry of a solar still. Convection has been proven to be the main heat transfer phenomenon in the water distillation process, as concluded by several authors.
In 1979, Flack, Konopnicki and Rooke described an experimental study of the heat transfer due to convection in a laminar flow contained in a triangular cavity (isothermal walls, hot and cold, and adiabatic base). The results are similar to those shown in rectangular cavities with the exception of the apex, where conduction is proven to be the predominant heat transfer mechanism due to temperature difference and the proximity of the walls. A second study realized by Flack et al. [1980] concludes that under summer conditions (hot top, cold base) the air flow remains laminar, convection near the walls is minimum and the aspect ratio at a given Gr has very little influence over Nu. As for the winter conditio