THEORETICAL AND EXPERIMENTAL ANALYSIS OF EVAPORATOR­ CONDENSER TUBE

Abstract

The behavior and mechanism of simultaneous evaporation­ condensation process are very important for the design of horizontal evaporator condenser tube (spray film evaporator), which is widely used in desalination field. In the present work, evaporation - condensation heat transfer in a thin film in horizontal tube is investigated experimentally and theoretically. Evaporation takes place over the tube and condensation is inside it the effect of the operating parameters on evaporation - condensation heat transfer coefficient is experimentally and numerically analyzed hence, the optimum operating conditions are obtained. For such tube, the condensation of steam inside tube imparts its latent heat to the evaporating liquid film, which is sprayed above the tube. Two models are tested, from the liberated steam point of view. The first one, is the open-loop model, where the produced steam and heating steam are independent, while the other one is the closed loop model, where the produced steam is compressed inside the tube and there it loses heat required for evaporating process.

In experimental work a horizontal copper tube with

0.0375/0.038 m diameter and 1.2 m length is tested. The parameters affecting the evaporation-condensation process are heat flux, flow rate of falling film, evaporation pressure, condensate pressure, and the temperature of sub-cooled falling film. Average and local Nusselt number and average and local coefficient of friction are evaluated. Throughout, this work, the range of Reynolds number of the falling­ water film is 100 to 800, while that of condensate inside the tube takes