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暖通空调杂志社>期刊目次>2017年>第10期

双排椭圆孔肋片管式换热器的换热和压降特性数值研究

Numerical study on heat transfer and pressure drop characteristics of double-row finned-tube heat exchangers with elliptical holes

[1]朱荣鑫 [1]王厚华 [2]王清勤 [2]叶 凌 [2]吴伟伟
[1]重庆大学 [2]中国建筑科学研究院

摘要:

基于正交试验法,以孔径和两个位置为变量,对空气源热泵用肋片管式换热器的肋片进行了开椭圆孔研究。利用CFD对平肋片和椭圆孔肋片进行了不同雷诺数Re下的三维数值模拟,并对空气侧流动和换热性能进行了对比分析。经验证,模拟结果与相关文献试验数据吻合得很好,证明了模拟方法的正确性。与平肋片相比,在所研究Re范围内,9种椭圆孔肋片传热因子j提升了4%~25%,摩擦因子f变化范围为-7.5%~7.9%。对综合性能评价指标j/f,j/f1/2,j/f1/3进行了计算,在相同流量、压降、泵功耗下,椭圆孔肋片的综合换热能力均优于平肋片。肋片开椭圆孔可有效阻碍其表面温度和速度边界层的发展,增强气流扰动,在阻力变化不大的情况下,可有效强化肋片换热性能。与椭圆孔位置相比,孔径对肋片换热性能的影响较大。

关键词:椭圆孔,肋片管式换热器,正交试验,换热,压降,传热因子,摩擦因子

Abstract:

Based on the methodology of orthogonal experiment, taking the hole diameter and two positions as variable parameters, designs the finned-tube heat exchangers which use elliptical hole fins for air-source heat pump (ASHP). Implements three dimensional (3D) numerical simulation on flat fins and elliptical hole fins by CFD with different Re values, analyses and compares their air-side flow and heat transfer performance. The simulation results are in correspondence with the referenced experiment data, which verifies the correct simulation method. Compared with the results of flat fins, the heat transfer factor (j) values of nine elliptical hole fins are increased by 4% to 25% and the friction factor (f) values vary in the range of -7.5% to 7.9%, within the studied Re scope. The calculation results of performance evaluation index of j/f, j/f12, j/f13 show that comprehensive heat transfer performance of elliptical hole fins is better than that of flat fins under the identical flow rate, pressure drop and pump power. Elliptical hole fins can effectively prevent the boundary layers development of surface temperature and velocity, enhance flow turbulence and strengthen heat transfer performance of fins in a case of the resistance force with a little change. Compared with the positions of elliptical hole, the hole diameter has a greater effect on heat transfer.

Keywords:ellipticalhole,finned-tubeheatexchanger,orthogonalexperiment,heattransfer,pressuredrop,heattransferfactor,frictionfactor

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