Prediction of heat transfer coefficient for laminar flow in a heated circular tube with a distribution of heat flux near the entrance

Abstract

A desiccant air conditioning system which can handle the sensible and latent heats in the air separately is generally composed of a dehumidifying rotor with desiccant material, a heat source for regeneration of the material and a heat exchanger controlling the dehumidified air temperature. We proposed a desiccant rotor heated by solar irradiation, concentrated by Fresnel lens, impinging the rotor directly. The irradiation has a distribution along the channel on the wall in a rotor. This study presents local heat transfer coefficient on the wall by performing a CFD simulation assuming laminar forced convection heat transfer in a circular channel. The results showed that the coefficients decreased along the channel. Comparing with the result considering uniform heat flux condition, the decreasing rate was large, and it didn't reach a constant value obtained at the fully developed flow region.