COMPARISON OF THE PERFORMANCE OF ENHANCED SOLAR AIR HEATERS HAVING TURBULENCE PROMOTERS

A solar air heater is a simple device to heat air by utilizing solar energy. The main drawback of a solar air heater is that the heat transfer coefficient between the absorber plate and the air stream is low, which results in a lower thermal efficiency of the heater. To overcome the low value of heat transfer between the absorber plate and the air stream, the underside of the absorber plate is roughened with artificial roughness elements, which act as turbulence promoters. Use of these turbulence promoters improves the convective heat transfer by creating turbulence in the flow. However, it would result in an increase in friction losses and hence greater power requirements from a fan or blower. In this study a comparison of two solar air heaters having expanded metal mesh and transverse wire roughness is made on the basis of reduced heat transfer surface for fixed heat duty and pressure drop, increased heat duty for fixed surface area, and reduced pumping power for fixed heat duty and surface area.