Geometric Parameters And Enhanced Internal Evaporation Heat Transfer Mechanism Of Micro-Fin Tubes

As an effective approach to giving high heat transfer coefficients,tubes with their geometries enhanced and optimized are routinely used in industrial applications.With the development of air conditioning industry,tubes for heat transfer in evaporation and condensation units continue to reduce to a smaller size.Experimental investigations of evaporation heat transfer of R22 and R410A inside a horizontal micro-fin cooper tube have been conducted and are reported here.Nine micro-fin tubes with inner diameter ranging from 7.14mm to 8.8mm have different geometric parameters,such as the apex angle,the helical angle,fin height,fin pitch and starts.The evaporation experiments were taken at a constant temperature of 6?.Moreover,working conditions of the experiments varied with the mass flux ranging from 100 kg/(m2.s)to 400 kg/(m2.s).For the evaporation experiments of Tube 1 to Tube 6 with R22,the inlet and outlet vapor quality is set as 0.1 and 0.9,respectively.For the evaporation experiments of Tube 7 to Tube 9 with R410A,the inlet and outlet vapor quality is set as 0.2 and 0.9,respectively.The heat transfer coefficients and the changing trend of the heat transfer coefficients vary among these tubes.The influence of each geometric parameter on the heat transfer performance of the micro-fin tube has been analyzed and is reported.Besides,correlations of evaporation heat transfer inside 8.8mm or less horizontal round micro-fin tubes were developed.