Modelling and Analysis of Laminar Flow and Heat Transfer in the Double Pass Solar Air Heater

摘要

The purpose of the present paper is to investigate the theoretical performance and thermal behavior of double pass flat plate solar air heaters. Under studying solar air heater, is a unit in which the air is first passed between the glass cover and absorber plate and preheated at this passage, then is passed in the passage between the absorber plate and insulated plate for final heating. The flow of air in passages is assumed to be laminar. In order to accurate estimation of performance and thermal behavior of solar air heater, the laminar boundary layer equations for flowing air between collector plates are used. The implicit finite difference scheme is applied to solve the governing differential equations. The effects of absorber plate length and space between collector plates on the exit air mean temperature and collector performance are studied. It is found that the glass cover temperature is lowered and operated near the ambient temperature. As a result, the losses were reduced and the collector performance goes up.