基于传热原理的热电偶测温误差模型及应用

Error model and application of temperature measure about thermo-couple based on heat transfer principle

应用传热学原理研究了热电偶静态测温误差和动态响应模型及减少测温误差的方法。热电偶测温误差是由热电偶与周围环境净热辐射引起,对流传热系数大小决定性地影响测温误差。带遮热套热电偶高速抽气时能有效减少测温误差,裸装和不抽气的热电偶不能直接应用于气体温度在线检测;动态响应过程误差还受时间常数0τ影响,30τ可视为动态响应结束时间。此研究结果不仅可用于裸偶信号校正、高精度温度信号获取及动态读数时间选取,也可为温度在线控制提供科学依据。

The error model of static temperature measurement, the model of dynamic response and methods of reducing the error of temperature measurement about thermocouple are studied based on principle of heat transfer. The error of temperature measurement about thermocouple results from net radiant heat transfer between thermoeouple and surroundings. The coefficient of heat transfer in the process of convection has great influence on the error of temperature measurement. The error of therm-ocouple with cover of heat insulation is decreased evidently when gas is pumped with very great velocity. The naked thermo-couple and the thermocouple without pump are not used directly to on-line temperature measurement of gas. To the dynamic process, error is also influenced by their time constant τ0. When ＇r is equal to 3τ00,the process of dynamic response could be considered to have been finished. The results of study will not only be used to correct reading error of signal of naked thermocouple, acquire signal of the higher precision temperature and select appropriate dynamic reading time, but also be supplied scientific basis for on-line temperature control.