ISBN 978-3-8439-4413-7

978-3-8439-4413-7, Reihe Thermodynamik

Stefan Brack
Time-resolved Transient Convective and Conjugate Heat Transfer Experiments Using IR Thermography

249 Seiten, Dissertation Universität Stuttgart (2020), Softcover, A5

Zusammenfassung / Abstract

Renewable energy sources represent an ever-increasing but over a day strongly fluctuating part of the energy supply. The associated change in the operating conditions of stationary gas turbines towards more operating point variations requires detailed consideration, prediction and evaluation of transient processes in the area of cooling. Such transient operating point changes are characterized by changes in the heat load, varying cooling air mass flows as well as cooling air temperatures. In addition to the numerical simulation of such processes, the experimental generation, acquisition and evaluation of such transient processes is of particular interest.

This thesis presents an experimental setup which enables transient and independent changes of the airflow temperature and the airflow velocity. In addition to the experimental setup, a measurement and evaluation methodology was developed, which allows a temporally and spatially resolved acquisition with infrared thermography and an evaluation of the heat transfer under consideration of 3D heat conduction effects.

The validation of the measurement and evaluation methodology was carried out by a comparison with the simultaneously applied transient thermochromic liquid crystal (TLC) heat transfer measurement methodology. In the wake of a tetrahedral vortex generator, both evaluation methods delivered the same results within their measurement uncertainty, except for areas strongly influenced by lateral heat conduction effects or with a very fast indication of the TLC.

Selected application experiments are presented. The transient heat transfer at a pulsating airflow temperature and a constant airflow velocity as well as vice versa are discussed. A further experiment shows the heat transfer at a modeled operating point change, which consists of several linear changes of the airflow temperature and the airflow velocity. Finally, the applicability of a global wall shear stress determination method is shown.