The tube-fin heat exchanger is the core equipment in the whole air-conditioning system, the thermal resistance of copper tube and fin contact accounts for 10%-20% of the total thermal resistance of the heat exchanger, and the thermal contact with the fin increases. Therefore, reducing the contact gap of the heat exchanger is extremely important to improve the overall heat exchange efficiency. In this paper, for the high-efficiency heat exchanger composed of seamless internal thread copper pipe, the heat exchange tube and the fin are expanded by hydraulic expansion and the liquid pressure range, reasonable pressure holding time and pull-off force are guaranteed by a large number of experiments. In this paper, the heat transfer tube and the fins are expanded by hydraulic expansion, and the relationship between the liquid pressure range, the reasonable pressure holding time and the pull-off force and the dwell time is measured through a large number of experiments. Finally, the effect of different liquid pressure expansion joints on the contact gap was further observed by a microscope.
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