Evaluation of mechanical integrity on the brazing joint of a tube-type heat exchanger with considering local material properties

Abstract

Recently, the demands for eco-friendly and effective energy systems have rapidly increased due to global environment problems. A heat exchanger is a well-known mechanical rig that has been used for a long time in many energy systems to reduce heat energy loss and to increase energy efficiency. However, till now, there have been few attempts to install a heat exchanger inside of an airliner engine. In such a case, the heat exchanger should be designed to be compact, lightweight, and highly reliable; therefore, the issue of the mechanical integrity of the heat exchanger becomes very important. In this study, we suggest a method by which it is possible to evaluate the mechanical integrity of a tube-type heat exchanger using global and local analysis. In the global analysis, fluid–structure interaction was introduced to get global behavior of a tube, which was used as boundary conditions in the local analysis. Also, local material properties near a brazing joint were measured using a nano-indentation test, and then they were utilized in the local analysis to evaluate clearly stress distribution around the joint. Through this study, a U-shaped single tube brazed on a manifold, which is a segment of a tube-type heat exchanger, was used as an example; its fatigue limit and stress concentration on the joint depending on the change of fillet radius were estimated by the proposed approach.

Keywords

Brazing joint mechanical integrity fluid–structure interaction fatigue limit global and local analysis tube-type heat exchanger

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