Design And Experimental Research Of Multi-temperature Zone Tube Thermocouple Verification Furnace

The verification furnace is an important constant temperature device in the thermocouple verification process.The quality of the high temperature field provided by the verification furnace will directly affect the verification results of the thermocouple.In the high-precision calibration of temperature sensors,there is no other equipment that can replace the role of the verification furnace,so it is of great significance to improve the quality of the temperature field of the verification furnace.At present,most of the verification furnaces used in my country are single-temperature zone verification furnaces,which have shortcomings such as too short temperature field length,large temperature field fluctuations,and low verification efficiency,resulting in low reliability of measurement results.Aim to further explore the working mechanism of the thermocouple verification furnace and optimize the internal structural parameters,in order to solve the problems of poor reliability and low production efficiency caused by the short length of the temperature field and the slow cooling of the furnace tube,this paper studies and designs an attached air The main research contents of the multi-temperature zone tubular thermocouple verification furnace with cold cooling function are as follows:(1)Aiming at the problems of poor temperature field quality and low verification efficiency existing in the current single-temperature zone verification furnace,according to the requirements of national technical specifications,an air-cooled multi-zone temperature control verification furnace was designed.The basic structure and working principle of the verification furnace were described,and the design and research of key components such as the furnace barrel,air duct,frame,etc.were carried out,and the production materials and design parameters of the core components were confirmed.(2)A simulation model of the temperature field and air duct flow field of the verification furnace was established,and the unstructured grid was divided.Based on the CFD theory,the optimal air duct shape was determined,and the internal insulation structure of the furnace barrel was analyzed and researched;based on the thermodynamic theory,the length distribution and power distribution of the furnace barrel heating wire were simulated and analyzed,and the furnace barrel and the air duct were finally determined The best structural parameters.(3)The temperature field parameters of the multi-temperature zone verification furnace prototype are measured,including temperature field deviation,uniform temperature field length and uniform temperature field temperature gradient.The deviation distance of the temperature field of the sample machine is less than or equal to 1mm;the length of the uniform temperature field is 100mm;the maximum temperature deviation in the uniform temperature field is 0.165℃.All performance parameters are in line with the requirements of the national JJF1184-2007 calibration furnace temperature field technical regulations and specifications,and are better than similar products.(4)The uncertainty evaluation of the temperature field test results of the thermocouple verification furnace has been completed,and the uncertainty of the experimental results that may be caused by the systematic and random errors in the experiment process is analyzed.After calculation,the final expanded uncertainty is 0.2°C.The uncertainty evaluation result meets the requirements of the corresponding national regulations,which improves the reliability of the performance parameters of the verification furnace prototype.