Effect of non-uniform heat flux on wall friction and convection heat transfer coefficient in a trapezoidal channel

Turbulent wall friction and forced convection heat transfer in a water-cool ed trapezoidal channel were experimentally investigated. The parameter rang es were: Reynolds number = 10(4)-8.6 x 10(4), and Prandtl number = 2.2-5.5. The channel hydraulic diameter was 1.14 cm, and its total and heated lengt hs were 139.4 and 60.9 cm, respectively. The Colebrook correlation predicte d the unheated channel friction factors well. It, however, systematically o ver predicted the measured friction factors obtained with the test section non-uniformly heated. Perimeter-average convective heat transfer coefficien ts for laterally non-uniform imposed heat fluxes were compared with the pre dictions of three widely-used correlations for turbulent flow in circular c hannels. All the correlations under predicted the data, typically by 11-28% . (C) 2001 Elsevier Science Ltd. All rights reserved.