Investigation of heat transfer in straight and curved rectangular ducts using liquid crystals thermography

Abstract

A rectangular cross section channel with both straight and curved test sections was used to investigate the effect of Taylor-Goertler vortices on the heat transfer from the curved section by comparing the results with those obtained in the straight section The flow was heated through the Joulean heating of one of the walls which was made of Temsheet. Liquid crystals were applied on the surfaces of both test sections. Experiments were run for several values of the volumetric flow rate corresponding to Reynolds numbers between 258 and 920. The average Nusselt number was calculated for each experiment and plotted as function of both the Reynolds and Dean numbers. Three distinct regions of the average Nusselt number were observed in the curved section when compared with the straight section. The presence of Taylor-Goertler votices in the curved section was verified from the distribution of the liquid crystal color bands. It was concluded that the overall effect of the vortices whenever they occurred was to improve the heat transfer process from the curved section.