COMBINED CONVECTION AND WALL CONDUCTION EFFECTS IN LAMINAR PIPE-FLOW - NUMERICAL PREDICTIONS AND EXPERIMENTAL VALIDATION UNDER UNIFORM WALLHEATING

Laminar combined convection in horizontal circular ducts is investigat ed both numerically and experimentally, under uniform wall heating. A series of experiments for the heating of water in a long horizontal co pper tube are simulated numerically in order to assess the reliability of the theoretical results. Peripheral and axial wall conduction effe cts, inherently present in the experiments, are accounted for in the n umerical model. The cross validation of experimental and numerical dat a allows significant conclusions to be reached on conjugate conduction and convection with buoyancy effects in horizontal duct flows. Buoyan cy is considered for values of the modified Rayleigh number, Ra-q0, up to 5 . 10(6); the forced convection contribution is considered for tw o values of the entry Reynolds number, Re-0 = 500 and 1000.