Detailed multiphysics modeling and validation of thermocouple readings in fires

Abstract

Detailed CFD models of mineral-insulated metal-sheathed (MIMS) thermocouples are discussed and thermocouple readings in fire environment are validated against experimental thermocouple data for a Hencken burner flame. Thermocouple readings are presented as functions of equivalence ratio, thermocouple diameter, thermocouple orientation, position of the junction, depth of insertion into fire, and sheath surface emissivity. Effects of surface oxidation, sheath diameter, and insertion depth on thermocouple response time are analyzed in detail. Computational results are compared with published experimental data. Overall, predictions showed excellent agreement with experimental data. Small deviations occurred in the case of insertion depths due to axial heat losses.