An Experimental Investigation to Determine the Effect of Tube Material on the Tubeside Heat Transfer Performance of the Enhanced 1EHT Three Dimensional Heat Transfer Tube

Abstract

Condensation heat transfer characteristics were experimentally investigated over a wide range of operating conditions in order to determine the heat transfer performance inside horizontal, smooth and enhanced heat transfer tubes; using R410A in tubes produced of copper and stainless steel. Experimental data was verified and results were compared to the performance measured in a smooth tube. Results indicate that the condensation heat transfer coefficient (HTC) enhancement ratio is in the range from 1.15 to 2.05 for the 1EHT tube and for the HX tube it ranged from 1.18 to 1.69. Smooth tube heat transfer performance was slightly affected by the thermal conductivity of the tube; however, larger enhancements are found in the enhanced tubes.
Heat transfer coefficients increase with an increase of mass velocities. When the mass flux increases, the liquid flow becomes more turbulent and the liquid film becomes thinner; this reduces the thermal resistance and enhances the heat transfer. Heat transfer performance for low mass velocities rise slowly, showing only a small difference in magnitude. Performance increase is larger at high mass flux rates than that those found at low mass fluxes. The influence of thermal conductivity on the condensation heat transfer of the enhanced horizontal tubes was discussed. Better heat transfer performance occurs in tubes produced of a higher thermal conductivity material (copper) or in tubes with a smaller diameter.