UBC Theses and Dissertations
Combined free and forced convection in a horizontal tube under uniform heat flux Kupper, Arthur K.
This thesis presents experimental results of combined free aid forced convection laminar heat transfer for water flowing through a circular horizontal tube with uniform wall heat flux. The Reynolds number ranged from 100 to 2000, and changes in heat transfer rate allowed a variation, of Grashof number from 300 to 30,000. The Prandtl number ranged from 4 to 9. The effect of secondary flow created by free convection occurring at higher Grashof number indicates an increase in Nusselt number up to 200 per cent. For the fully-developed region two tentative correlations are given. The expression Nu = 48/11 + 0.047 Pr¹′³(Re Ra)¹′⁵correlates 53 per cent of the data to within ± 10 per cent. Another slightly more accurate expression which correlates 68 per cent of the data to within ± 10 per cent, but does not satisfy the pure forced convection, is Nu = 2.41 + 0.082 Pr¹′³ (Re Ra)¹′⁵.