Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube
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Author list: Aroonrat K., Wongwises S.
Publisher: Elsevier
Publication year: 2011
Journal: Experimental Thermal and Fluid Science (0894-1777)
Volume number: 35
Issue number: 1
Start page: 20
End page: 28
Number of pages: 9
ISSN: 0894-1777
eISSN: 1879-2286
Languages: English-Great Britain (EN-GB)
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Abstract
Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated tube are experimentally investigated. The double tube test sections are 0.5m long with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tubes are one smooth tube and two corrugated tubes, which are constructed from smooth copper tube of 8.7mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20ฐC, heat fluxes of 20, 25, and 30kW/m2, and mass fluxes of 200, 300, and 400kg/m2s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat flux, mass flux, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated tubes compared with those of the smooth tube are approximately 0-10% and 70-140%, respectively. ฉ 2010 Elsevier Inc.
Keywords
Two-phase friction factor
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