Optimal Reynolds number of laminar forced convection in a helical tube subjected to uniform wall temperature

In this study, fully developed laminar flow and heat transfer in a helically coiled tube with uniform wall temperature have been investigated analytically based on minimal entropy generation principle. The influence of coil curvature ratio and fluid properties, β1 and β2 on the optimum Reynolds number have been investigated for two well-known fluids viz. air and water. It was revealed that optimum Reynolds numbers decrease as curvature ratio increases except in the low ranges of curvature ratio where transition to turbulent flow occurs. In the range of the present study, a correlation predicting optimal Reynolds number was proposed for each fluid using least square analysis.