Determination of heat transfer coefficient maps using an inverse bem algorithm

Abstract

This chapter provides an algorithm designed to extract accurate multidimensional heat transfer coefficient maps from surface temperature measurements, which are provided by non-invasive techniques, such as infrared tomography or thermo chromic liquid crystals. Determination of convective heat transfer coefficients is important in the design and analysis of thermal systems exposed to convective heat transfer. The approach is based on a boundary element method (BEM) which uses either transient or steady temperature inputs, and incorporates a smoothing technique borrowed from inverse problem methods to provide robustness to input temperature uncertainties. As it requires only surface mesh, the method is flexible and easy to implement for examination of arbitrarily complex geometries encountered in engineering practice. Following this, a common approach for measurements of convective heat transfer coefficients relies on thermochromic liquid crystal (TLC) thermography, thermographic phosphor (TOP) thermography, and temperature-sensitive paints (TSP). Temperature levels are indicated by: color (for TLC), intensity of fluorescent emissions (for TGP and TSP). These methods can provide a broadband response or narrow-band response. Diagnostic applications of TLC, TGP, or TSP-based methods usually rely on transient measurements where the temperature is measured twice by detection of color or fluorescence intensity, in quick succession at two different times over such a short interval from the beginning of the transient process that heat conduction into the surface is assumed as one-dimensional.