Convective boiling of R-134a on enhanced-tube bundles

Date

2016-08-01

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Abstract

The current paper presents the experimental investigation of the heat transfer performance and effect of tube pitch on highly enhanced surface tube bundles. The fluid–tube combination used was R-134a and the enhanced tube TBIIHP. Three pitch-to-diameter ratios were studied: 1.167, 1.33, and 1.5; all with a staggered triangle arrangement. Twenty enhanced tubes were used in each bundle; the tube outer diameter and length are 19.05 mm (3/4 inch) and 1 m (39.36 inch), respectively. Three input variables were investigated: heat flux (5–60 kW/m2), mass flux (15–55 kg/m2.s), and quality (10–70%). The test saturation temperature was 4.44 °C. A local method employing the EBHT technique was implemented in data reduction. All tube bundles showed strong dependency on heat flux. The smallest P/D bundle showed a considerably lower performance than the other two. When compared to the pool boiling performance, the smallest P/D bundle was lower while the other two showed a closer performance. The P/D 1.33 bundle outperforms P/D 1.167 bundle and provide quite similar performance to the P/D 1.5. When considering the refrigerant quantity, the P/D 1.5 bundle uses more refrigerant compared to the P/D 1.33; the latter proves to be the optimum. Finally, a new enhanced tube heat transfer coefficient bundle model was proposed based on the extensive data collected and the studied bundle phenomena.

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Citation: Gorgy, E., & Eckels, S. (2016). Convective boiling of R-134a on enhanced-tube bundles. International Journal of Refrigeration, 68, 145–160. https://doi.org/10.1016/j.ijrefrig.2016.04.010

Keywords

Bundle void fraction, Boiling heat transfer, Convective boiling, EBHT analysis, Enhanced tubes, Tube bundle prediction

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