微细金属丝在空气中的自然对流换热的实验研究  

EXPERIMENTAL STUDY ON HEAT TRANSFER OF NATURAL CONVECTIVE FLOW BETWEEN MICRO-WIRE AND AIR

作　　者：侯亚丽[1] 王秀春[1] 张承武[2] 刘志刚[2] 

机构地区：[1]河北工业大学能源与环境工程学院,天津300130 [2]山东省科学院能源研究所,山东济南250014

出　　处：《工程热物理学报》2007年第3期460-462,共3页Journal of Engineering Thermophysics

摘　　要：对直径分别39．9～350．1μm的微细金属丝水平和垂直放置在空气中时的自然对流换热系数进行了实验测量。实验中对细丝采用焦耳加热。并通过标定金属丝电阻与温度的关系,精确测定了金属细丝的表面平均温度。将测得的实验值与经典关联式的预测值进行了比较,实验结果表明:随着细丝直径的减小,实验值与理论计算值的差别越来越大。这可能由于尺度的缩小,使得细丝的边缘效应加强,边界层变薄,从而强化了换热;水平放置的细丝表面的自然对流换热要强于垂直放置的细丝,这是由于竖丝表面受到流体的冲刷作用,边界层厚度大于横丝表面边界层厚度的缘故。The heat transfer of natural convection between air and micro-wires with outer diameters ranging from 39.9 μm to 350.1 μm, placed at horizontally and vertically, is experimentally investigated. Using the Joule heating, the wire is heated and its average temperature can be obtained exactly according to the relations between the wire resistance and the temperature. The experimental results show that the deviation between the experimental Nusselt number and the values of the classical correlations will be larger with decrease of the wire diameter due to the thinner boundary layer caused from the edge effect when the wire diameter become smaller. Because of the thicker boundary layer resulted from a scouring effect of water at vertical orientation, the experimental data at horizontal orientation is larger than those at veridical orientation.

关 键 词：焦耳加热 微细金属丝 自然对流换热 努谢尔特数 边界层 

分 类 号：TK124[动力工程及工程热物理—工程热物理]