Heat Transfer in Liquid-Film Flow

Abstract

Measurements have been made of local heat transfer coefficients to liquid-vapor mixtures flowing upwardinside vertical tubes at atmospheric pressure. Four tube sizes and six liquids were tested with a 10 to 1 range in feed rates. The heat transfer coefficient has been found to depend mainly on the vapor velocity when liquid-film (generally known as "climbing film") conditions have been established, For any one liquid the heat transfer in the liquid-film region is dependent solely on the vapor velocity and independent of the liquid feed rate. An equation has been derived which correlates our data and those of other authors for liquid-film conditions, irrespective of whether the film b e moving upward or downward in vertical tubes, or on the inside of a horizontal tube.N RECENT years, considerable attention has been paid to the

Thin-Film Evaporation Enhancement by Finned Surfaces

“…Wilke (1962) conducted an extensive study of heat transfer to falling liquid films and recommended correlations of the form nNu = A(Nner (NPX™ (3) Values of the coefficient, A, and exponent, a, depended on the film Reynolds number-i.e., for (NRe)u < 400, A = 0.0614 and a = 8/15; for 400 < NRe < 800, A = 0.00112 and a = 6/5; and for iVRe < 800, A = 0.0066 and a = 14/15. Wallgren (1967) integrated an empirical equation for the local heat-transfer coefficient in liquid film flow presented by Penman and Tait (1965) and obtained the following expression for the average heat-transfer coefficient:…”