INVESTIGATION OF PERFORMANCE OF ARTIFICIALLY ROUGHENED SOLAR DRYER

Abstract

The conventional solar air-heating collector used in solar dryer has low thermal efficiency leading to slow drying rate. In the recent past, several investigations have been carried out to enhance the energy collection efficiency of solar air heater and one of the efficient method of enhancement is the use of artificial roughness on the underside of absorber plate. It has been proposed to investigate the enhancement in the performance of a forced convection solar dryer using artificial roughness in the solar air heater. The artificial roughness proposed to be used, comprise of wedge shaped integral ribs because such a geometry has been found to be optimum from heat and fluid flow consideration. The experimental set up comprising of solar air heater, dryer, blower, and instrumentation for various measurements was designed, fabricated and tested. The data on the performance of both solar air heater and the dryer was collected as a function of mass flow rate and relative roughness height of the ribs of artificial roughness. This data has been processed to obtain the major performance ' parameters i.e., the collector efficiency, drying . efficiency and efficiency ratio (ratio of drying efficiency for dryer using air heater with artificial roughness to that of dryer with conventional solar air heater). It has been found that in general an increase in mass flow rate and relative roughness height increases the drying efficiency. iii