翅片管空气冷却器传热系数模型
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摘要
以管内介质有相变的翅片管空气冷却器为研究对象,采用量纲分析、泛函分析等方法,构建了一个合理的翅片管空气冷却器传热系数关联式。以氨泵供液型空气冷却器为实验研究对象,设计了结构参数、迎面风速、库温、驱动温差和供液倍率等多因素、多水平的实验方案,并采用校准箱法测得不同测点下的传热系数。采用测试数据并以关联式为目标函数,通过非线性拟合方法建立了适用于氨泵供液空气冷却器传热系数计算的关联式。关联式计算值与实测值相对误差在±10%之间,且分项管内换热系数大于管外换热系数,符合空气冷却器换热系数分布的一般规律,证明了传热关联式是合理准确的。在氨泵供液空气冷却器常用设计点,关联式计算值约为设计经验值1.11~1.30倍,这表明采用关联式设计该类型空气冷却器可节约11%~30%的换热面积,提高了经济效益。
A reasonable heat transfer coefficient correlation for a finned-tube air cooler was established by applying the methods of dimensional analysis and function analysis. This approach focused on an air cooler design in which the refrigerant phase changes in the tube. A pump-feeding ammonia air cooler was chosen as the experimental study object. Further,a multi-factor and multi-level experimental scheme was designed for this machine type. The scheme included the structure parameters,face velocity,ambient temperature,driving temperature,and circulation ratio. The heat transfer coefficients were tested under various conditions using a calibrated-box method according to the scheme. Moreover,the heat coefficient correlation of the pump-feeding ammonia air cooler was obtained through a nonlinear fitting method based on the test results. It was found that the relative errors between the calculated correlation values and the test values range from -10% to + 10%. Furthermore,the tube side heat coefficient is larger than the outside heat coefficient,which is consistent with practical experiments. These results show that the established correlation is reasonable and sufficiently accurate for use in practice.The calculated correlation values are 1. 11 to 1. 30 times the experimental values at the common design points for the pump-feeding ammonia air cooler. Thus,the heat transfer surface can be reduced by 11%-30% when the correlation is applied in the design of this type of air cooler. This correlation is helpful for reduction of the machine dimensions and to enhance its economic efficiency.
A reasonable heat transfer coefficient correlation for a finned-tube air cooler was established by applying the methods of dimensional analysis and function analysis. This approach focused on an air cooler design in which the refrigerant phase changes in the tube. A pump-feeding ammonia air cooler was chosen as the experimental study object. Further,a multi-factor and multi-level experimental scheme was designed for this machine type. The scheme included the structure parameters,face velocity,ambient temperature,driving temperature,and circulation ratio. The heat transfer coefficients were tested under various conditions using a calibrated-box method according to the scheme. Moreover,the heat coefficient correlation of the pump-feeding ammonia air cooler was obtained through a nonlinear fitting method based on the test results. It was found that the relative errors between the calculated correlation values and the test values range from -10% to + 10%. Furthermore,the tube side heat coefficient is larger than the outside heat coefficient,which is consistent with practical experiments. These results show that the established correlation is reasonable and sufficiently accurate for use in practice.The calculated correlation values are 1. 11 to 1. 30 times the experimental values at the common design points for the pump-feeding ammonia air cooler. Thus,the heat transfer surface can be reduced by 11%-30% when the correlation is applied in the design of this type of air cooler. This correlation is helpful for reduction of the machine dimensions and to enhance its economic efficiency.
引文
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[12]李锐.冷风机翅片管的数学模型及性能的比较法辨析[J].制冷与空调(四川),2014,28(2):211-214.(LI Rui.The mathematical correlation of cooling fan finned tube and its performance analysis using comparison methods[J].Refrigeration and Air Conditioning,2014,28(2):211-214.)
[2]兰州石油机械研究所.换热器[M].北京:中国石化出版社,2013:680-718.(Lanzhou Petroleum Machinery Research Institute.Heat exchangers[M].Beijing:China Petrochemical Press,2013:680-718.)
[3]HOLMAN J P.Heat Transfer[M].Beijing:China Machine Press,2011:227-258.
[4]彦启森.空气调节用制冷技术[M].北京:中国建筑工业出版社,2010:76-110.(YAN Qisen.Air conditioning refrigeration technologies[M].Beijing:China Building Industry Press,2010:76-110.)
[5]余建祖.换热器原理与设计[M].北京:北京航空航天大学出版社,2006:131-170.(YU Jianzu.Heat exchanger principle and design[M].Beijing:Beijing University of Aeronautics and Astronautics Press,2006:131-170.)
[6]陈江平,穆景阳,刘军朴,等.二氧化碳跨临界汽车空调系统开发[J].制冷学报,2002,23(3):14-17.(CHEN Jiangping,MU Jingyang,LIU Junpu,et al.Development of the trans-critical carbon-dioxide automotive air-conditioning system[J].Journal of Refrigeration,2002,23(3):14-17.)
[7]ZHAO X,BANSAL P K.Flow boiling heat transfer characteristics of CO2at low temperatures[J].International Journal of Refrigeration,2007,30(6):937-945.
[8]OZAWA M,AMI T,ISHIHARA I,et al.Flow pattern and boiling heat transfer of CO2in horizontal small-bore tubes[J].International Journal of Multiphase Flow,2009,35(8):699-709.
[9]YUN R,KIM Y,MIN S K.Flow boiling heat transfer of carbon dioxide in horizontal mini tubes[J].International Journal of Heat&Fluid Flow,2005,26(5):801-809.
[10]CHOI K I,PAMITRAN A S,OH C Y,et al.Boiling heat transfer of R-22,R-134a,and CO2,in horizontal smooth minichannels[J].International Journal of Refrigeration,2007,30(8):1336-1346.
[11]申江.制冷装置设计[M].北京:机械工业出版社,2010:26.(SHEN Jiang.Refrigeration Units Design[M].Beijing:China Machine Press,2010:26.)
[12]李锐.冷风机翅片管的数学模型及性能的比较法辨析[J].制冷与空调(四川),2014,28(2):211-214.(LI Rui.The mathematical correlation of cooling fan finned tube and its performance analysis using comparison methods[J].Refrigeration and Air Conditioning,2014,28(2):211-214.)