PRESSURE DROP AND CONVECTION HEAT TRANSFER CORRELATIONS IN DOUBLE PASS SOLAR COLLECTOR WITH POROUS MEDIA

摘要

The correlation of the pressure drop with heat transfer in a double pass solar collector with porous media was determined. The collector dimensions were 1.2 m wide and 2.4 m long, with flow channel of variable height from 0.07 to 0.35 m. The lower channel was filled with 0.8 to 3.2 kg of steel wool as the porous media. Pressure drop and temperatures were measured for several airflow rates, porosities and heights of solar collector lower channel. Both pressure drop and efficiency were found to depend on the air flowrates and porosity. Several friction factor models namely Petukhove, Blasius, Colburn and Haaland were applied in analyzing the pressure drop using the model suggested by Darcy-Weisbach. The hydraulic diameter of conduct with porous media was derived from compressed particle theory by considering steel wool as a porous media of cylindrical shape. The Halaand friction factor model gave the best fit to the experimental data with average SME of 11.02%. The cylinder factor of 3.3 was used in the hydraulic model and roughness factor of 3.8mm were used in Halaand friction factor model.