Study on Forced Convective Heat Transfer in Curved Pipes : 1st Report, Laminar Region

Abstract

The effect of curvature on heat transfer for fully developed laminar flow in curved pipes on the condition of constant wall temperature gradient is studied theoretically and experimentally. For the case of large Dean numbers R_e√(a/R), a boundary layer is considered to exist along the pipe wall. The momentum and energy integral equations of the boundary layer are solved to the second approximation, and theoretical formulae for resistance coefficient and Nusselt number are obtained for a range of large Dean numbers. In order to ascertain the theoretical result, velocity and temperature distributions are measured in air flow through the pipe of radius ratio R/a=40 and of an inside diameter of 35.6 mm. From this experiment it is assured that the boundary layer approximation may be applicable to our case. Nusselt numbers obtained by the experiment are in good agreement with the theoretical results.