Experimental Investigation of Overall Heat Transfer Coefficientin Drop wise Condensation

Abstract

The experiments are performed to study the heat transfer characteristics over a drop wise condensation. The phenomenon of drop wise condensation is in which the condensate forms into drops rather than covering the entire cooling surface with a continuous film. In drop wise condensation, heat transfer coefficient produced is 2 to 10 times greater than those produced by film wise condensation. Hence drop wise condensation is desirable as it is more effective method of heat transfer than that of film wise condensation. Drop wise condensation can be promoted by applying: (i) Suitable organic promoter; (ii) Thin layer of special metal; or (iii) Coating with chrome plating on condenser surface. Special treatment like chrome plating on condenser surface is required for drop wise condensation. Highly polished surfaces also practice drop wise condensation. The experiments covered the following ranges: Plating Thickness (t) 20, 30 and 40 µm, surface finish (Ra) 5, 10 and 15 µm, and mass flow rate of water (Mw) 16.66, 22.33 and 28 kg/sec. Overall heat transfer coefficient is considered as performance parameter. The sequence of experimental trialsis based on full factorial method of design of experiment (DOE) with three factors and two levels. Regression method is used for analysis, and by using estimated effects and coefficient analysis, correlation equation is obtained.