Thermocouple error analysis of the gas temperature measurement in porous materials at high temperatures

The error analysis of gas temperature measurement in porous materials using thermocouples was investigated by simulating the heat transfer process for the thermocouple junction. Firstly, the local thermal non-equilibrium model with Monte Carlo method (MCM) was used to solve the coupled heat transfer in porous material. The temperature and velocity fields of porous material were obtained and the heat transfer model of thermocouple junction was built based on a lumped energy balance. Then, MCM was adopted for the radiation simulation between the junction and solid matrix. The junction temperature was computed and compared with the local gas temperature at steady state. The temperature difference and effects of wall temperature, inlet velocity and the emissivity and diameter of junction were analysed. The results showed that the measurement errors increase with the increasing of wall temperature. The maximum error is 10.4% at the wall temperature 1500 K. As the inlet velocity increases, the discrepancy between the junction temperature and gas temperature decreases. The maximum discrepancy occurs in the region r/R=0.6 to 0.8. In addition, measurement errors can be reduced by using small diameter and low emissivity of junction.