An Experimental Study ON Heat Transfer and Pressure Drop of Air-Solids Turbulent Flow inside a Horizontal Tube with Different Entrance Angle.(Dept.M)

The present work deals with The effect of turbulent air-sand suspension flow on heat transfer and pressure drop in horizontal tube with a uniform heat flux at different entrance angles. four different inlet bend angles in addition to the case of plain tube (θ=oo were studied at different Reynolds numbers, sand particles of different average-sizes and different mass loading ratios. It was obtained for the plain tube flow that the presence of the solid particles in turbulent flow enhances the heat transfer coefficient giving an enhancement ratio of the Nusselt number of 1.'5 at M=O.4 and Re=35,000 for particles of 120 microns. Moreover, at higher Reynolds numbers (over 64, 000 slightly enhancement in the heat transfer coefficient was observed. For the flow with different entrance angles. the heat transfer coefficient enhances in the upstream portion of the fest-section. The results of clean-air flow show that about 1.18 fold increase in average Nusselt number was corresponding to about 1.5 fold increase in the pressure drop along the test-section. The presence of the solid particles in the flowing air enhances the heat transfer coefficient up to mass-loading ratio of M=O.15 and further addition of solids affects slightly the heal transfer coefficient. New correlations for the Nusselt number and its enhancement ratio were obtained for both cases of plain tube and for the tube with different entrance angles.