热线风速仪温度补偿方法的研究

A Study of Temperature Compensation Methods for a Hot Wire

本文通过对热线风速仪三种温度补偿方法(恒定温度法、恒定过热度和恒定加热比法)的考察,指出热线与流体间温差对换热关系中速度指数会产生一定的影响。文中还分析了热线在低风速测量时的特性,提出了修正的恒定过热度法和恒定加热比法,提高了原方法的补偿精度,扩展了补偿范围。

The three methods of temperature compensation,constant temper-ature,constant overheat and constant overheat ratio,are widely investiga-ted in this paper.It is pointed out that the temperature difference between asensor and fluid may exert some effects on the value of exponent of velocityfactor in the heat transfer correlation of a hot wire,when the parameterGr_d/Re^8d is over 1.After experiment and analysis are made for low velocity mea-surments,it is found out that why theprevious methods have poor accuracy andsmall valid range is that those only have the changes of temperature diffe-rence in the heat transfer correlation compensated and fail to compensate thechanges of fluid properties with temperature changes.Having measured theparameters of heat transfer where velocity is zero,we put forward correctionsfor the previous methods of constant overheat and constant overheat ratio.Themodified methods improve the accuracy and give wider applicable range.