Author(s)

S. Sinkunas, J. Gylys & A. Kiela

Abstract

This paper is concerned with heat transfer calculation in a liquid film falling down a vertical surface. Heat transfer in laminar film flow is influenced by the cross curvature of the wetted surface, heat flux on the film surface and boundary conditions on the wetted wall. The analytical study evaluating the influence of cross curvature on heat transfer in laminar film has been carried out. Equations using correction factors for the calculation of heat transfer in laminar liquid film with respect to the cross curvature for different boundary conditions were established. An experimental investigation of heat transfer in the entrance region of the turbulent film has also been performed. The description of the experimental set-up is presented in the paper. The research has been carried out on a water film flowing down a surface of vertical tube with the Reynolds number ranging from 9.2·103 to 10.5·103. The results of experiments are discussed with respect to the local heat transfer dependence on the Reynolds number and initial velocity of the film. Heat transfer stabilization length was determined experimentally. Keywords: heat transfer, laminar film, cross curvature, correction factor, turbulent film, entrance region. 1 Introduction In many technological processes that deal with heat and mass transfer, gravity driven liquid films are widely used. With liquid falling films one can obtain comparatively high heat transfer coefficient. This approach is employed for cooling and heating processes in chemical, food, pharmaceutical and other

Keywords

heat transfer, laminar film, cross curvature, correction factor, turbulent film, entrance region.