Effect of Soft Metal Plating on the Thermal Contact Conductance of Finned-Tube Heat Exchangers

Abstract

This paper presents the experimental results of thermal contact conductance, heat transfer, and interfacial temperature drop of finned tube heat exchanger test specimens. The results were based on the measured temperatures at several locations on the test specimen so that the thermal contact conductance could be directly determined. Each test specimen was assembled by mechanically expanding seven tubes into a single fin. The geometry of the specimens was based on a commonly used model of heat exchangers. The specimens included one bare tube (uncoated) specimen and three electroplated tube specimens. The plating materials were zinc, silver, and gold. The thickness of the plating in each case was 5 micrometers.Experiments have been conducted in both vacuum and nitrogen. The results show that the highly conductive plating material enhances the thermal contact conductance. The effect of interstitial gas such as nitrogen is beneficial for the heat transfer and the thermal contact conductance. The interfacial temperature drop alone does not fully reflect the efficiency of the heat exchanger.