Distortion in the Thermal Field Around Inserted Thermocouples in Experimental Interfacial Studies—Part 3: Experimental and Numerical Verification

Abstract

Using the electrostatic analog method, the authors have investigated in earlier publications the disturbance in a two-dimensional steady temperature field due to the presence of a thermocouple void and the measurement error due to the heat transfer along the thermocouple leads. Those results pertaining to a perfectly insulated thermocouple void are verified in the present study, using the finite element method and a well-controlled experiment in which the thermocouple hole is scale-modelled. The numerical and experimental results are found to be in good agreement with those predicted by the electrostatic analog method. The numerical solution of the case in which the thermocouple leads act as heat sink indicated the inherent deficiency of the analog method in modelling the path of the heat flow lines from the zone surrounding the thermocouple hole into the leads. The previously published data on the effect of the heat losses through the leads on the temperature measurement error are therefore revised. The characteristic features of the disturbed temperature field, in terms of its symmetry, the existence of neutral points and the sinusoidal variation of the temperature along the periphery of the hole are quantitatively confirmed.