Experimental Study of Heat Transfer on the Internal Surfaces of a Double-Wall Structure with Pin Fin Array

Wei Zhang,Guangchao Li,Huiren Zhu

doi:10.3390/en13246573

Wei Zhang, Guangchao Li + Show 1 more

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https://doi.org/10.3390/en13246573

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Abstract

The double-wall structure is one of the most effective cooling techniques used in many engineering applications, such as turbine vane/blade, heat exchangers, etc. Heat transfer on the internal surfaces of a double-wall structure was studied at impinging Reynolds numbers ranging from 1 × 104 to 6 × 104 using the transient thermochromic liquid crystal (TLC) technique. The two-dimensional distributions of Nusselt numbers and their averaged values were obtained on the impingement surface, target surface and the pin fin surface. The Nusselt number correlations on the surfaces mentioned above were determined as a function of Reynolds number. The results show that the second peak values of the Nusselt number distribution appear on the target surface at all Reynolds numbers studied in this paper for a short distance of the target surface to impingement surface. This phenomenon becomes significant with the further increase of the Reynolds number. The difference between the Nusselt number at the second peak and the stagnation point decreases with the increasing Reynolds number. The maximal Nusselt number regions on the impingement surface appear at the left and right sides of the pin fins between the two impingement holes. The Nusselt numbers of the pin fin surfaces are highly dependent on their various locations in the double-wall structures. The contributions of the impingement surface, pin fin surface and target surface to the overall heat transfer rate are analyzed. The target surface contributed the largest amount of heat transfer rate with a value of about 62%. The heat transfer contribution is from 18% to 21% for the impingement surface and 16% to 18% for the pin fin surfaces within the studied Reynolds numbers.

Highlights

In order to increase the propulsion thrust and the thermal efficiency of the advanced gas turbine, the turbine inlet temperature was continuously increased and has been higher than the melting point of the turbine material
The double-wall structure combined with internal jet impingement [1,2], pin fins [3,4,5] and the external film cooling [6,7,8] is one of the most effective cooling techniques used in many engineering applications, such as turbine vane/blade, power electronics, heat exchangers, etc. [9]
The impingement-enhanced heat transfer region is mainly located of the Nusselt number, as the temperature cannot be converted by the hue

Summary

Introduction

In order to increase the propulsion thrust and the thermal efficiency of the advanced gas turbine, the turbine inlet temperature was continuously increased and has been higher than the melting point of the turbine material. An effective cooling technique is required to ensure the normal work of the engine. The double-wall structure combined with internal jet impingement [1,2], pin fins [3,4,5] and the external film cooling [6,7,8] is one of the most effective cooling techniques used in many engineering applications, such as turbine vane/blade, power electronics, heat exchangers, etc. The cooling performance is a key parameter on cooling structures. The convection cooling in the holes and film cooling was the dominant factors affecting the overall effectiveness [10]. When the hole spacing was sufficiently wide, the through-hole convection was not dominant [11]

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