ENHANCED HEAT TRANSFER IN SOLAR AIR HEATERS

摘要

The use of artificial roughness in solar air heaters owe their origin to several investigations carried out in connection with the enhancement of heat transfer in nuclear reactors and turbine blades. For this work a solar air heater with its absorberplate roughened with V-shaped ribs has been considered for performance investigation. The thermo-hydraulic performance ratio, (St ysts)3 / (f. / fs) has been considered as was described by some authors for this study for different rib configuration. It can be concluded that in the entire range of flow Reynolds number, the pitch ratio of 10 yields the best performance. The experimental correlations for heat transfer and friction factor were developed experimentally and were given in by some authors for such a system in the range of parameters given as 0.02 ￡ e/Dh< 0.034, 30°Sa^ 90 "and 2500 Re < 18000. The maximum heat transfer occurs for the angle of attack of 60 degrees.