Experimental Study of Falling Film Heat Transfer on a Horizontal Tube of an Evaporative Tubular Heat Dissipator

Abstract

The present article deals with the experimental investigation of onset and permanent dry out heat flux and mass transfer coefficient at which dry patch formation just starts and permanent condition of dry patch takes place over the surface of a tube of evaporative tubular heat dissipator. A single horizontal tube of evaporative tubular heat dissipator through which hot fluid is flowing is subjected to simultaneous flows of water from the top and air flow from underneath the test unit, with controlled amount of moisture. The primary objective of the present study is to derive the correlations of onset and permanent dry out heat flux and mass transfer coefficients in terms of dimensionless numbers, using the multiple regression analysis of the experimental observations at a wide range of operating variables. The present empirical results show good agreement with the experimental results. Derived correlations from experimental data show that as the film flow rate increases, heat flux needed to cause a permanent or temporary dry patch formation increases provided that the air flow rate is constant. Mass transfer coefficients pertaining to onset and permanent dry patches are also estimated over a wide range of operating conditions. Correlations derived are helpful in improvement of the design of heat transfer devices and many other engineering applications.