A new approach in evaluation of thermal contact conductance of tube–fin heat exchanger

This paper presents a new method in evaluating the thermal contact conductance (TCC) of tube–fin heat exchanger, which makes it possible to improve the tube–fin TCC performance at the stage of forming process design. Firstly, the tube–fin contact status is studied with a finite element (FE) model of tube expansion process. The simulation result shows that the tube–fin joining is far form full contact and a gap exists at the interface, which is confirmed by experimental observation. Distribution of the contact pressure along the tube–fin interface is obtained from the numerical results. Then, an experiment for the relationship between the contact pressure and the TCC is carried out. Combining the experiment result with the contact pressure distribution from the simulation, the tube–fin TCC can be evaluated. This evaluation results agree well with thermal measurement of the whole heat exchanger. Based on the method, effect of key factors of the expansion forming process, such as expanding ratio and die geometry, are optimized.