A numerical study of condensation heat transfer and pressure drop in horizontal round and flattened minichannels

作者：Zhang, Jingzhi; Li, Wei^*; Sherif, S. A.

来源：International Journal of Thermal Sciences, 2016, 106: 80-93.

DOI：10.1016/j.ijthermalsci.2016.02.019

• Condensation
• Flattened tube
• Numerical simulation
• Heat transfer
• Pressure drop

Condensation heat transfer and pressure drop characteristics for R410A and R134a in horizontal round (d(h) = 3.78 mm) and flattened tubes [aspect ratio (AR) = 3.07, 4.23, and 5.39] at saturation temperature T-sat = 320 K were investigated numerically. Liquid-vapor interfaces and stream traces are also presented to give a better understanding of the condensation process inside these tubes. The results indicate that local heat transfer coefficients and pressure gradients increase with increasing mass flux, vapor quality, and aspect ratio. The enhancement of the flattened tube is more pronounced at higher mass flux and vapor quality. The liquid film thickness decreases with increasing aspect ratio, mass flux, and vapor quality. The average liquid film thickness of R134a is about 40% thinner than R410A. For round tubes, a vortex with its core lying at the bottom of the tube is observed in the vapor phase region, while this vortex is only noticeable at lower mass flux in flattened tubes. The transportation of vapor phase from the core region to the wall region, like the flow pattern of longitudinal vortex, will also enhance heat transfer. The numerically-computed heat transfer coefficients and frictional pressure gradients for flattened tubes are compared with their counterparts from empirical correlations.

• 出版日期2016-8
• 单位浙江大学