Heat transfer during condensation of HFC-134a and R-404A inside of a horizontal smooth and micro-fin tube
Heat transfer during condensation of HFC-134a and R-404A inside of a horizontal smooth and micro-fin tube
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DOI：
10.1016/j.expthermflusci.2010.03.013
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发表时间：
2010-11
影响因子：
3.2
通讯作者：
S. N. Sapali;P. Patil
中科院分区：
文献类型：
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作者：
S. N. Sapali;P. Patil
在最近的中小容量制冷系统中，冷凝器管从内部设置有微型翅片。压缩机出口和冷凝器入口处的蒸汽制冷剂处于冷凝状态。当它在冷凝器中前进时，它处于两个阶段，并且在出口处，它处于过冷液体中。对HFC-134 a和R-404 A在内径为8.56mm的光滑管和内径为8.96mm的微肋管中的凝结换热系数进行了实验研究。与以往的研究不同，本实验是在不同的冷凝温度下进行的，有过热和过冷，并使用密封压缩机。在35°C至60°C的平均饱和冷凝温度下进行测试运行。质量通量在90到800 kgm −2s−1之间。实验结果表明，光滑管和微肋管的平均传热系数均随质量流量的增大而增大，随冷凝温度的升高而减小。HFC-134 a和R-404 A在微肋管中的平均冷凝热温度分别是光管的1.5-2.5倍和1.3 ~ 2倍。R-404 A的HTC小于HFC-134 a。新的关联式的基础上收集的数据，在实验中预测冷凝HTCs提出了广泛的操作条件。
In recent small and medium capacity refrigeration systems, the condenser tubes are provided with micro-fins from inside. The vapour refrigerant at the compressor outlet and the condenser inlet is in superheat state. As it advances in the condenser it is in two phases and at the outlet it is in sub cooled liquid. The heat transfer coefficient (HTC) during condensation of HFC-134a and R-404A in a smooth (8.56mm ID) and micro-fin tubes (8.96mm ID) are experimentally investigated. Different from previous studies, the present experiments are performed for various condensing temperatures, with superheating and sub cooling and using hermetically sealed compressor. The test runs are done at average saturated condensing temperatures ranging from 35°C to 60°C. The mass fluxes are between 90 and 800kgm−2s−1. The experimental results indicate that the average HTC increases with mass flux but decreases with increasing condensing temperature for both smooth and micro-fin tubes. The average condensation HTCs of HFC-134a and R-404A for the micro-fin tubes were 1.5–2.5 and 1.3–2 times larger than that in smooth tube respectively. The HTCs for R-404A are less than that of HFC-134a. New correlations based on the data gathered during the experimentation for predicting condensation HTCs are proposed for wide range of operating conditions.