换热器热力学计算中平均温差计算方法

对算术平均温差和对数平均温差的计算方法进行分析.分别采用对数平均温差法(LMTD)与测壁温法进行换热计算,分析二者计算结果的差别.通过实验进一步验证,认为在计算对流表面换热系数时,采用两种数据处理方法所得结果不同,特别当雷诺数较小时二者差距较大,二者的差别主要来自于对数平均温差和算术平均温差;而在紊流区,二者相差不大,可以用算术平均温差代替对数算法.在工程计算中可以采用LMTD来分析紊流区内的对流换热特性.

Investigation on Calculation Method of Mean Temperature Difference in Heat Exchanger Thermodynamic Calculation

The calculation method for the logarithm mean temperature difference(LMTD) and the arithmetic temperature difference was analyzed.Heat exchange is calculated by two methods of logarithm mean temperature difference and measuring of wall temperature,and calculation results were analyzed.Ex-periment showed that in the calculation of the convective heat transfer coefficient,the results gained by these two methods had large differences,especially in low Reynolds number region.The difference of the calcula-tion results came from the distinctness between LMTD and AMTD.In the turbulent flow area,the difference became small and LMTD can be adopted to analyze the convective heat transfer characteristics in the turbu-lent flow area in the engineering calculation.