ISBN 9783843936866

978-3-8439-3686-6, Reihe Thermodynamik

Meriam Axtmann
Investigations on Heat Transfer and Pressure Loss in Staggered Pin Fin Cooling Arrays

144 Seiten, Dissertation Universität Stuttgart (2018), Softcover, A5

Zusammenfassung / Abstract

The durability of thermally highly loaded components, such as combustion chambers or turbine blades, is increased by applying cooling solutions, such as pin fin arrays. These induce turbulence and increase coolant mixing. Previous studies focused on conventional pin fin patterns. Future research should concentrate on the development of new cooling technologies to decrease the required mass flow rate of cooling air and total pressure loss. In this thesis, elongated regular and irregular pin fin arrays are investigated experimentally and supported with numerical simulations.

The objective of this work is to define the characteristics of various staggered pin fin arrays with respect to heat transfer enhancement and total pressure loss augmentation.

The transient technique using thermochromic liquid crystals is applied to determine highly-resolved heat transfer distributions on the endwall and pin fin surfaces. Additionally, the lumped capacitance method is used to determine the integral heat transfer on the pin fin itself. Therefore, a sensitivity coefficient is introduced to analyze the time dependent result of the heat transfer coefficient. The quality of the measurements is ensured by verifying the model assumptions experimentally and numerically. The measurement of the fluid reference temperature is assessed towards thermocouple specific aspects, such as thermal inertia and stem effect.

An elementary comprehension of the heat transfer is established for regularly staggered pin fin arrays. Detailed highly resolved distributions of the heat transfer on the endwall and on the pin fins are obtained from TLC measurements. Secondary flow features driving the heat transfer are identified. In particular, the influence of the horseshoe vortex and mixing in wake regions are determined. In general, mainly at high Reynolds numbers, the effect of the Reynolds number is stronger than the configuration effect.

Improvements of pin fin arrays may be possible through local modifications of the current configurations. Therefore, irregular pin fin patterns are investigated. The suggested alternative configurations of staggered arrays can be applied in modern component cooling.