Combined free and forced convective heat transfer and fluid flow in a rotating curved circular tube

Abstract

A study is made of the combined free and forced convective heat transfer and fluid flow in a rotating curved circular tube for the fully developed flow with the thermal boundary condition of constant heat flux per unit length of tube. The heat-transfer and flow-friction characteristics are determined by the five non-dimensional parameters, i.e. the radius ratio B, the Prandtl number Pr, a parameter Ro which represents the effects of Coriolis forces, the Grashof number Gr 2 and the Dean number K 1. The governing equations are solved by finite difference method, and the results of computations are presented for the axial velocity and temperature distributions, the streamlines and isothermals, the local f and Nu, and the mean f and Nu. The effects of B is minor. Pr has substantially no effect on f, but increases Nu greatly when a strong secondary current is present. The increase in the last three parameters of secondary-flow-inducing forces enhance both f and Nu significantly. The rate of increase in f and Nu due to the force parameters is higher for a circular tube than for rectangular tubes. Their effects commence to be pronounced at smaller values of them which are Ro ≈ 2, Gr 2 ≈ 100 and K 1 ≈ 100, while those for a square tube are Ro ≈ 10, Gr 2 ≈ 1000 and K 1 ≈ 100.