THERMOHYDRAULIC PERFORMANCE OF SOLAR AIR HEATERS WITH ROUGHENED ABSORBER PLATES

Artificial roughness has been found to enhance the heat transfer from the absorber plate to the air in a solar air heater duct. However, thi s improvement is invariably accompanied by increased pumping power. In this work, the effect of roughness and operating parameters on the th ermal as well as the hydraulic performance of roughened solar air heat ers is discussed and the thermohydraulic performance of roughened sola r air heaters is compared with that of conventional smooth solar air h eaters. The optimum design and operating conditions have been determin ed. On the basis of thermohydraulic considerations it has been found t hat the systems operating in a specified range of Reynolds number show better thermohydraulic performance depending upon the insolation. A r elationship between the system and operating parameters that combine t o yield optimum performance has been developed. (C) 1997 Elsevier Scie nce Ltd.