Evaporation heat transfer and pressure drop of HFC-134a in a helically coiled concentric tube-in-tube heat exchanger |
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| Affiliation: | 1. School of Chemical Engineering, Sichuan University, Chengdu, 610065, China;2. School of Mechanical Engineering, Sichuan University of Science and Engineering, Zigong, 643000, China;3. Sichuan Provincial Key Lab of Process Equipment and Control, Zigong, 643000, China;1. Department of Mechanical Engineering, Benha Faculty of Engineering, Benha University, Benha, 13511 Qalyubia, Egypt;2. Department of Mechanical Power Engineering, Faculty of Engineering, Mansoura University, 35516 El-Mansoura, Egypt;3. Department of Mechanical Engineering, Faculty of Engineering at Shoubra, Benha University, 11629 Cairo, Egypt;4. Department of Mechanical Engineering, Faculty of Engineering, University of Jeddah, 21589 Jeddah, KSA;1. Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran;2. Laboratory for Alternative Energy Conversion (LAEC), School of Mechatronic Systems Engineering, Simon Fraser University, Surrey, BC, Canada |
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| Abstract: | The two-phase heat transfer coefficient and pressure drop of HFC-134a during evaporation inside a smooth helically coiled concentric tube-in-tube heat exchanger are experimentally investigated. The test section is a 5.786-m long helically coiled tube with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tube is made from copper tubing of 9.52 mm outer diameter and 7.2 mm inner diameter. The heat exchanger is fabricated by bending a straight copper tube into a spiral coil. The diameter of coil is 305 mm. The test run are done at average saturated evaporating temperatures ranging between 10 and 20 °C. The mass fluxes are between 400 and 800 kg m?2 s?1 and the heat fluxes are between 5 and 10 kW m?2. The inlet 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 directly measured by a differential pressure transducer. The effects of heat flux, mass flux and, evaporation temperature on the heat transfer coefficients and pressure drop are also discussed. The results from the present experiment are compared with those obtained from the straight tube reported in the literature. New correlations for the convection heat transfer coefficient and pressure drop are proposed for practical applications. |
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