板翅式换热器热通道结霜过程的数值模拟
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摘要
为了研究板翅式换热器热通道在不同工况下的霜层生长规律以及霜层对板翅式换热器的影响,建立了基于Lewis传热传质类比理论的结霜模型,并将该模型与板翅式换热器非稳态传热模型相结合。首先借助平板结霜可视化观测实验台验证了该模型的准确性,然后主要计算对比了湿空气进口流速分别为0.8、1.2、2 m/s,相对湿度分别为60%、70%、80%时换热器热通道结霜量的大小,以及结霜起点位置的变化。结果表明:空气流速越大,霜层增长的速率越大,结霜区域越小;空气相对湿度越大,霜层增长的速率越大,结霜区域越大。并且,随着霜层厚度增长通道压降持续增大,板翅式换热效率持续下降,当热通道内霜层平均厚度累积到1.5 mm时换热器效率下降约10%。
To study the frost growth rule in the hot channel of plate-fin heat exchangers under different working conditions, a frosting model based on Lewis heat and mass transfer analogy theory is established and then combined with the unsteady heat transfer model of plate-fin heat exchanger. First, the accuracy of the model is verified on the test rig for frosting visualization on flat surface. Then, the mass and starting positions of frost at inlet humid air flowing speeds of 0.8 m/s, 1.2 m/s and 2.0 m/s and relative humidities of 60%, 70% and 80% are compared, respectively. The results show that the higher the air velocity, the faster the frost growth rate and the smaller the frost area. Also, the higher the relative humidity of air, the faster the frost growth rate and the larger the frost area. Meanwhile, with the increase of the frost layer thickness, the pressure drop of the channel continues to increase, and the efficiency of the plate-fin heat exchanger decreases. When the average thickness of the frost layer accumulates to 1.5 mm in the hot channel, the efficiency of the heat exchanger decreases by about 10%.
To study the frost growth rule in the hot channel of plate-fin heat exchangers under different working conditions, a frosting model based on Lewis heat and mass transfer analogy theory is established and then combined with the unsteady heat transfer model of plate-fin heat exchanger. First, the accuracy of the model is verified on the test rig for frosting visualization on flat surface. Then, the mass and starting positions of frost at inlet humid air flowing speeds of 0.8 m/s, 1.2 m/s and 2.0 m/s and relative humidities of 60%, 70% and 80% are compared, respectively. The results show that the higher the air velocity, the faster the frost growth rate and the smaller the frost area. Also, the higher the relative humidity of air, the faster the frost growth rate and the larger the frost area. Meanwhile, with the increase of the frost layer thickness, the pressure drop of the channel continues to increase, and the efficiency of the plate-fin heat exchanger decreases. When the average thickness of the frost layer accumulates to 1.5 mm in the hot channel, the efficiency of the heat exchanger decreases by about 10%.
引文
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[2] KIM D, KIM C, LEE K S. Frosting model for predicting macroscopic and local frost behaviors on a cold plate [J]. International Journal of Heat and Mass Transfer, 2015, 82: 135-142.
[3] SONG M, DANG C. Review on the measurement and calculation of frost characteristics [J]. International Journal of Heat and Mass Transfer, 2018, 124: 586-614.
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[5] ZENDEHBOUDI A, WANG B, LI X. Application of smart models for prediction of the frost layer thickness on vertical cryogenic surfaces under natural convection [J]. Applied Thermal Engineering, 2017, 115: 1128-1136.
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[8] LIU Z, DONG Y, LI Y. An experimental study of frost formation on cryogenic surfaces under natural convection conditions [J]. International Journal of Heat and Mass Transfer, 2016, 97: 569-577.
[9] 赵祥雄, 孙皖, 刘炅辉, 等. 逆布雷顿空气制冷机动态降温特性数值研究 [J]. 低温工程, 2013, 192(2): 46-51. ZHAO Xiangxiong, SUN Wan, LIU Jionghui, et al. Numerical study on dynamic cooling performance of reverse Brayton cycle air cryocooler [J]. Cryogenics, 2013, 192(2): 46-51.
[10] 杨山举, 陈兴亚, 张兴群, 等. 逆布雷顿空气制冷机透平膨胀特性研究 [J]. 工程热物理学报, 2016, 37(2): 245-249. YANG Shanju, CHEN Xingya, ZHANG Xingqun, et al. Study on the turbo expansion characteristic of a reverse Brayton air refrigerator [J]. Journal of Engineering Thermophysics, 2016, 37(2): 245-250.
[11] FELZIN A E, BENTON D. A more exact representation of cooling tower theory [J]. Journal of Cooling Tower Institute, 1991, 12(2): 8-26.
[12] 蔡君伟, 孙皖, 李斌, 等. -150 ℃逆布雷顿空气制冷机动态温降特性研究 [J]. 西安交通大学学报, 2013, 47(3): 60-63. CAI Junwei, SUN Wan, LI Bin, et al. Study on the dynamic cooling performance of a -150 ℃ reverse Brayton cycle air cryocooler [J]. Journal of Xi’an Jiaotong University, 2013, 47(3): 60-63.
[13] óNEAL D, TREE D. Measurement of frost growth and density in a parallel plate geometry [J]. ASHRAE Journal, 1984, 90(2): 278-290.
[14] 王军, 陈雁, 高才. 准稳态结霜模型求解与分析 [J]. 制冷, 2010, 29(4): 16-20. WANG Jun, CHEN Yan, GAO Cai. Resolution and analysis for quasi-stable frost forming model [J]. Refrigeration, 2010, 29(4): 16-20.
[15] SILVA D L D, HERMES C J L, MELO C. First-principles modeling of frost accumulation on fan-supplied tube-fin evaporators [J]. Applied Thermal Engineering, 2011, 31(14/15): 2616-2621.
[16] 连之伟, 陈宝明. 热质交换原理与设备 [M]. 北京: 中国建筑工业出版社, 2001: 43-45.
[2] KIM D, KIM C, LEE K S. Frosting model for predicting macroscopic and local frost behaviors on a cold plate [J]. International Journal of Heat and Mass Transfer, 2015, 82: 135-142.
[3] SONG M, DANG C. Review on the measurement and calculation of frost characteristics [J]. International Journal of Heat and Mass Transfer, 2018, 124: 586-614.
[4] 童治文, 王志远, 郭鹏, 等. 换热器低温结霜工况性能实验研究 [J]. 低温与超导, 2014, 42(8): 63-68. TONG Zhiwen, WANG Zhiyuan, GUO Peng, et al. Experimental study on heat exchanger performance under low-temperature frosting condition [J]. Cryogenics & Superconductivity, 2014, 42(8): 63-68.
[5] ZENDEHBOUDI A, WANG B, LI X. Application of smart models for prediction of the frost layer thickness on vertical cryogenic surfaces under natural convection [J]. Applied Thermal Engineering, 2017, 115: 1128-1136.
[6] 陈叔平, 来进琳, 殷劲松, 等. 空温式深冷翅片管气化器表面结霜特性实验研究 [J]. 制冷学报, 2010, 31(4): 26-30. CHEN Shuping, LAI Jinlin, YIN Jingsong, et al. Experiment on frost characteristic of air-warmed cryogenic finned-tube vaporizer [J]. Journal of Refrigeration, 2010, 31(4): 26-30.
[7] KIM K H, KO H J. Analysis of heat transfer and frost layer formation on a cryogenic tank wall exposed to the humid atmospheric air [J]. Applied Thermal Engineering, 2009, 29: 2072-2079.
[8] LIU Z, DONG Y, LI Y. An experimental study of frost formation on cryogenic surfaces under natural convection conditions [J]. International Journal of Heat and Mass Transfer, 2016, 97: 569-577.
[9] 赵祥雄, 孙皖, 刘炅辉, 等. 逆布雷顿空气制冷机动态降温特性数值研究 [J]. 低温工程, 2013, 192(2): 46-51. ZHAO Xiangxiong, SUN Wan, LIU Jionghui, et al. Numerical study on dynamic cooling performance of reverse Brayton cycle air cryocooler [J]. Cryogenics, 2013, 192(2): 46-51.
[10] 杨山举, 陈兴亚, 张兴群, 等. 逆布雷顿空气制冷机透平膨胀特性研究 [J]. 工程热物理学报, 2016, 37(2): 245-249. YANG Shanju, CHEN Xingya, ZHANG Xingqun, et al. Study on the turbo expansion characteristic of a reverse Brayton air refrigerator [J]. Journal of Engineering Thermophysics, 2016, 37(2): 245-250.
[11] FELZIN A E, BENTON D. A more exact representation of cooling tower theory [J]. Journal of Cooling Tower Institute, 1991, 12(2): 8-26.
[12] 蔡君伟, 孙皖, 李斌, 等. -150 ℃逆布雷顿空气制冷机动态温降特性研究 [J]. 西安交通大学学报, 2013, 47(3): 60-63. CAI Junwei, SUN Wan, LI Bin, et al. Study on the dynamic cooling performance of a -150 ℃ reverse Brayton cycle air cryocooler [J]. Journal of Xi’an Jiaotong University, 2013, 47(3): 60-63.
[13] óNEAL D, TREE D. Measurement of frost growth and density in a parallel plate geometry [J]. ASHRAE Journal, 1984, 90(2): 278-290.
[14] 王军, 陈雁, 高才. 准稳态结霜模型求解与分析 [J]. 制冷, 2010, 29(4): 16-20. WANG Jun, CHEN Yan, GAO Cai. Resolution and analysis for quasi-stable frost forming model [J]. Refrigeration, 2010, 29(4): 16-20.
[15] SILVA D L D, HERMES C J L, MELO C. First-principles modeling of frost accumulation on fan-supplied tube-fin evaporators [J]. Applied Thermal Engineering, 2011, 31(14/15): 2616-2621.
[16] 连之伟, 陈宝明. 热质交换原理与设备 [M]. 北京: 中国建筑工业出版社, 2001: 43-45.