Abstract

In this paper, the condensation heat transfer characteristics of R134a inside enhanced tubes using two type of surface structures with different materials was investigated, which were then compared with plain tubes under the same test conditions. The enhanced tubes were: EHT tube with dimpled and petal arrays structure and 1EHTb tube with protrusion and similar petal arrays structure. The experiment was conducted for a mass flux ranging from 100 to 200 kg m^-2^ s^-1^ with saturation temperature of 318 K. The inlet and outlet vapor qualities were fixed at 0.8 and 0.2, respectively. The test tubes had the same outer diameter of 12.7 mm. Results showed that the dimpled and protruded surface tubes enhanced the convection condensation heat transfer and the heat transfer coefficient was 1.4 to 1.6 times higher than that of the smooth tube. Heat transfer enhancement of the 1EHTa and 1EHTb tube was mainly due to the complex roughness surface structures that created swirling and increased the interface turbulence. Enhanced tubes exhibited higher performance factors compared to the smooth tube. The average performance factor was 1.3-1.5. The condensation heat transfer coefficient had slight increase with mass flux. The pressure drop penalty increased with mass flux. Compared with smooth tube, the pressure drop penalty of enhanced tube was larger.

 

*Key words:* condensation, heat transfer coefficient, pressure drop, enhanced tube.


An Experimental Study of R134a Condensation Heat Transfer in Horizontal Smooth and Enhanced Tubes

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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