Quantification of the Surface Temperature Discrepancy Caused by Subsurface Thermocouples and Methods for Compensation

In the study of boiling water heat transfer, temperature measurements via subsurface thermocouples are often used in conjunction with inverse heat conduction (IHC) models to evaluate the heat-transfer boundary conditions at the surface. It has been documented in previous studies that the presence of a subsurface thermocouple causes a disturbance in the local temperature field surrounding the thermocouple. If not accounted for, such discrepancies will lead to errors when evaluating the surface heat flux histories and surface temperatures via IHC models. A technique called the “equivalent depth” technique is proposed as a method to offset the location of the thermocouple and thereby compensate for the effect the thermocouple hole has on the measured temperature. Although the use of the equivalent depth technique results in the correct prediction of the surface heat flux without including the thermocouple hole in the IHC analysis, it does not allow the correct calculation of the surface temperature. This article outlines the simulations and procedure to derive a correlation to determine the correct surface temperature. By quantifying the surface temperature discrepancy between regions with thermocouples and regions without, a correlation is developed and can be used in conjunction with an IHC analysis to correctly predict the surface temperature. A verification of this technique for the characterization of the surface boundary condition using an IHC model with experimentally measured thermal history data is also presented.