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强化传热期刊
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ISSN 打印: 1065-5131
ISSN 在线: 1026-5511

强化传热期刊

DOI: 10.1615/JEnhHeatTransf.2017019585
pages 221-239

INVESTIGATION OF THERMAL-HYDRODYNAMIC HEAT TRANSFER PERFORMANCE OF R-1234ZE AND R-134A REFRIGERANTS IN A MICROFIN AND SMOOTH TUBE

Kaggwa Abdul
Department of Mechanical Engineering, National Chiao Tung University, Hsinchu, Taiwan
Chi-Chuan Wang
Department of Mechanical Engineering Chiao Tung University, Hsinchu 300, Chinese Taipei

ABSTRACT

This research is based on R-1234ze that is considered a substitute for R-134a due to its low global warming potential in a microfin tube with outer diameter 9.52 mm, the number of fins 70, and fin height 0.17 mm. In comparison, a smooth tube with similar geometries was used to study pressure drop and heat transfer coefficients related to the two fluids. The microfin tube was brazed inside a stainless steel tube and heated electrically. T-type thermocouples were used to measure the temperature distribution during the phase change process. The experimental saturation temperatures and refrigerant mass velocities varied from 10–20°C and 50–300 kg/m2s, respectively. The vapor quality ranged from 0.1 to 0.9 and heat flux from 5 to 11 kW/m2. The results showed that heat transfer performance of R-134a in both microfin and a smooth tube was better than R-1234ze, especially at mass velocities above G = 100 kg/m2s. However, R-1234ze yielded better heat transfer coefficients at mass velocities lower than G = 100 kg/m2s. The pressure gradient of R-1234ze was markedly higher than that of R-134a at all mass flow rates.


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