Effect of non-uniform heat flux on wall frinction and convection heat trasfer coefficient in atrapezoidal channel

Turbulent wall friction and forced convection heat transfer in a water-cooled trapezoidal channel were experimentally investigated. The parameter ranges were: Reynolds number = 10 super(4)-8.6 x 10 super(4), and Prandtl number = 2.2-5.5. The channel hydraulic diameter was 1.14 cm, and its total and heated lengths were 139.4 and 60.9 cm, respectively. The Colebrook correlation predicted the unheated channel friction factors well. It, however, systematically over predicted the measured friction factors obtained with the test section non-uniformly heated. Perimeter-average convective heat transfer coefficients for laterally non-uniform imposed heat fluxes were compared with the predictions of three widely-used correlations for turbulent flow in circular channels. All the correlations under predicted the data, typically by 11-28%. copyright 2001 Elsevier Science Ltd. All rights reserved.