Parametric Analysis of the Transient Conjugated Downward Laminar Mixed Convection in A Vertical Pipe

Abstract

Transient conjugated downward laminar mixed-convection heat transfer in a vertical pipe, submitted partially to a constant heat flux, is investigated computationally. The governing equations are solved by a developed code using the finite-volume method and Boussinesq's assumptions. Solutions are obtained for (Re, Gr) = (1, 5 × 10³) and (100, 5 × 10⁵) and wall-to-fluid conductivity ratios K = 10, 50, 100, and 500. From a parametric study, transient distribution of the normalized interfacial heat flux, of the friction coefficient as a function of the axial coordinates, as well as transient evolution of the vector velocities are obtained and the effects of Gr, Re, and K investigated.