Experimental study of momentum and heat transfer in the entrance region of vertical film flow

This paper reports the experimental research of fluid flow and heat transfer on wetted surface of vertical tubes. In many engineering applications an estimation of the entrance region is required. Therefore, the alteration of hydromechanic parameters of liquid film in the entrance region was investigated. The detailed description of experimental set-up is presented in the study. The method for the shear stress measurement on wetted surface of a vertical tube was proposed. Values of shear stress for the turbulent liquid film flow in the range of Reynolds numbers from 103 to 105 were determined. It was noticed that shear stress close to the liquid distributor depends upon the initial velocity of the film. Experimental investigation of heat transfer in the entrance. region for the turbulent film was performed as well. The research has been carried out in water film failing down a surface of a vertical tube as Reynolds number ranged from 3300 to 3800. The experimental results of local heat transfer variation are discussed in the paper. Heat transfer stabilization length was established experimentally. Evaluation of heat losses in the test section is presented.