Experimental study on evaporative heat transfer and pressure drop of R-134a flowing downward through vertical corrugated tubes with different corrugation pitches
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Author list: Aroonrat K., Dalkilic A.S., Wongwises S.
Publisher: Taylor and Francis Group
Publication year: 2013
Journal: Experimental Heat Transfer (0891-6152)
Volume number: 26
Issue number: 1
Start page: 41
End page: 63
Number of pages: 23
ISSN: 0891-6152
eISSN: 1521-0480
Languages: English-Great Britain (EN-GB)
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Abstract
This study reports an experimental investigation of evaporative heat transfer and pressure drop of R-134a flowing downward inside vertical corrugated tubes with different corrugation pitches. The double tube test section is 0.5 m long with refrigerant flowing in the inner tube and hot water flowing in the annulus. The inner tubes are comprised of one smooth tube and three corrugated tubes with different corrugation pitches of 6.35, 8.46, and 12.7 mm. The test runs are performed at evaporating temperatures of 10ฐC, 15ฐC, and 20ฐC; heat fluxes of 20, 25, and 30 kW/m2; and mass fluxes of 200, 300, and 400 kg/m2s. The experimental data obtained from the smooth tube are plotted with flow pattern map for vertical flow. Comparisons between smooth and corrugated tubes on the heat transfer and pressure drop are also discussed. It is observed that the heat transfer coefficient and frictional pressure drop obtained from the corrugated tubes are higher than those from the smooth tube. Furthermore, the heat transfer coefficient and frictional pressure drop increase as the corrugation pitch decreases. The maximum heat transfer enhancement factor and penalty factor are up to 1.22 and 4.0, respectively. ฉ 2013 Taylor and Francis Group, LLC.
Keywords
corrugated tube, evaporative, vertical
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