INVESTIGATION OF THE PERFORMANCE OF SOME SOLAR-THERMAL CONVERSION

Abstract

The main purpose of this work is the investigation and optimization of the thermal performance of flat-plate solar air heaters. To achieve this goal, I have designed and constructed two units of solar air heaters. They have been tested experimentally and theoretically under Tanta's (Lat. 30° 47' N) prevailing weather conditions. The first one is a double-glass double-pass solar air heater (DGDPSAH) used as a reference unit [117). The second is a double­ glass double-pass solar air heater with packed bed (DGDPSAHPB) as a modified unit [120). These units were constructed using locally available materials in the Solar Energy Laboratory, Physics Department, .Faculty of Science, Tanta University. The DGDPSAHPB is used with some materials as packed beds above or/and under the absorber plate. Suitable mathematical models for the DGDPSAH and DGDPSAHPB were formulated based on the energy balance equations for the various elements of the two systems. Computer programs were developed based on the solution of the energy balance equations for the various elements of the considered units. Another computer program was used for calculating the total solar radiation incident on the glass covers of the heaters using the hourly measured values of •solar radiation incident on a horizontal surface during the test period. Numerical calculations were carried out to study the effect of different operational and configurational parameters on the performances of the heaters. Temperatures of different elements of the heaters, various heat transfer coefficients, fan Ptan and flow Pflow pumping powers, pressure drop I!.P and thermal output power Q, as well as the thermal 1'/r and thermohydraulic 17TH efficiencies were investigated.