Numerical Calculation of the Heat Transfer Coefficients in Multi-Thermocouple Probes by the Reconstruction Temperature Method

Abstract

The numerical simulation of the heat transfer problem of the quenching process requires an accurate characterization of the heat transfer coefficient dependence on surface temperature, which is usually determined by measuring the cooling curve and applying an inverse method. In most cases, the thermocouple is located at the center of the probe (ISO 9950, Industrial Quenching Oils — Determination of Cooling Characteristics — Nickel-Alloy Probe Test Method), but, in recent years, probes with several thermocouples have been developed (e.g., Tensi test) and the process to estimate the coefficients turned out to be more complex. The proposed methodology has considered the numerical reconstruction of the temperature field of the probe using multi-thermocouple measurements, actual material properties, and heat transfer equations. The heat transfer coefficients are directly obtained from the numerically reconstructed thermal field based on the fact that its gradient at the boundaries is proportional to the heat flux transferred. It is important to remark that neither parameter optimization nor curve fitting is needed.