Accurate Temperature Measurement during Water Quench Operations Characterized by Boiling Water Heat Transfer

摘要

Mathematical models are taking on an increased role in process design, optimization and in some cases process control. Inherent to the accuracy of the model predictions is accurate knowledge of the boundary conditions in the process. In situations where water quenching is used to control the temperature of the product being produced, it is important to quantitatively understand the heat transfer at the surface of the product during the quench operation (typically expressed as a boiling water curve). Often these boiling curves are determined by using experimental measurements of temperature-time data in the product during a quench operation in conjunction with Inverse Heat Conduction (IHC) models. The experimental data used is usually measured using thermocouples installed in the sample being cooled at a known sub-surface location. This paper outlines the influence of the thermocouple hole on boiling water heat transfer predictions using and inverse conduction model. The study showed that, in some circumstances - high heat flux in combination with low thermal conductivity - the hole or void used to install the thermocouple has to be included in the analysis in order to obtain accurate boiling curves. The paper also outlines the use of a general criterion to determine if the thermocouple hole needs to be included in the analysis based on a Biot number. This work was done as part of a collaborative research agreement with The TIMKEN Company with partial funding from the U.S. Department of Energy under award #DE-FC36-99ID13819.