Forced-convective internal cooling of a horizontal equilateral-triangle cross-sectioned duct

An experimental determination of the steady-state forced convection from the internal surfaces of a horizontal, uniformly heated electrically, equilateral-triangle cross-sectioned duct with sharp corners has been undertaken. The average Nusselt number D, using the hydraulic diameter as the characteristic physical dimension, is a constant if the flow in the duct is laminar, but a function of the airʹs Reynolds number, when the flow is turbulent. Non-dimensional correlations, which can be used for predicting the value of the steady-state rate of convective heat transfer from such a triangular duct into the airflow, have been deduced, viz. D = 3•25 for laminar flows, i.e. ReD < 1450; and D = 0•012 ReD0•83 for turbulent flows, i.e. ReD ≥ 1450.