Research On Temperature Uniformity Of Tubular Resistance Furnace Used In Metrology And Testing

In the temperature measurement field, tubular resistance furnace for measurement (Abbreviated as tubular furnace) is a very important equipment to provide a constant temperature, it is mainly used in calibration or verification of thermocouple, RTD and other temperature sensors in measurement industry, it is also a key equipment for thermocouple and RTD materials manufacturers to set the value. Its temperature uniformity will directly affect testing results accuracy of the thermocouple, RTD and other sensors; it has a huge impact on product quality. At present, in our temperature-measuring field, this tubular furnace is very extensive, and no other devices can replace its role till now.Nowadays, in our measurement industry and thermocouple, RTD national standards, all of the tubular furnace temperature indicators of measurement are in the case of no-load (that is, the measuring thermocouple did not put in the furnace) to calibrate, its temperature field testing has been in use is the no-load testing. However, the actual of the operation, the tubular furnace must be with loads (that is, the furnace is equipped with the measuring thermocouple) to use, then the temperature field can compliance is the key. Therefore, the study of its temperature field uniformity, especially with loads, it is very necessary.The people’s republic of China national measurement specification JJF1184-2007"Testing Specification of Temperature Uniformity in Thermocouple Calibration Furnaces" provides that:"Within the tubular furnace uniform temperature field length of not less than60mm, radius of14mm, temperature difference between any two points less than1℃."The temperature field of existing tubular furnace in no-load testing can generally be compliance, however, when it’s with loads, the temperature is difficult to compliance. If you use the tubular furnace which is not up to the standards to measure the thermocouple, which will cause the measurement uncertainty too large, result in unreliable measurement; but if replacement the equipment, it will increase the testing cost.This paper, aiming at the existing metrology and testing tubular resistance furnace, has carried on research from following aspects.Through consulting documents extensively, I initially learned that the structure of the tubular furnace, the measuring methods of the tubular furnace temperature field, and the testing methods of thermocouple.Considering a variety of factors that can affect the temperature field in the tubular furnace, use the software "FLUENT" to simulate the temperature field of the tubular furnace in different situations, and aiming at the existing tubular furnace, proposing feasible experimental programs to verify the simulation results.Testing the temperature field of the existing tubular furnace, proposing that place a mega-thermal alloy uniform temperature block at the center of the tubular furnace uniform temperature field, experiments to compare the furnace temperature differences before and after place the block in the furnace.Use different type and different diameter sheathed thermocouples to test their repeatability, compare the experimental standard deviation, evaluate the measurement uncertainty, and investigate the impact on the thermocouple measurement result from the tubular furnace temperature field.