CFD models are used to analyze the development and depletion of secondary flow in high aspect ratio cooling channels. New correlations for the heat transfer coefficient depletion of various surfaces of rectangular cooling as functions of radius of curvature and distance from entrance to the curve region are developed. It was determined that the changes in the coolant heat transfer due to the diminishment of the secondary flow is influenced by the radius of curvature and the distance from the end of the curved regions. Nomenclature A, α, β = correlation coefficients and exponentsD h = hydraulic diameter h = heat transfer coefficient L e = distance from exit of the curvature L m = distance from middle of the curvature H = cooling channel height Nu c = Nusselt number for the curved section Nu s = Nusselt number for the straight section R = radius of curvature W = cooling channel width