Cyclic pressure fatigue property of copper tube for air conditioner

摘要

Air-conditioner manufactures have been applying new HFC refrigerant R410A due to global environmental issues. R410A has about 1.5 times higher operating pressure than currently used HCFC refrigerant R22. It was examined that the Japan Refrigeration and Air conditioning Industry Association (JRAIA) had made a recommendable safety test procedure standard which incorporates with an additional cyclic pressure fatigue test. However, cyclic pressure fatigue property data of thinner copper tube for heat exchanger application had not been reported yet. We conducted several cyclic pressure fatigue tests about thinner straight copper tubes and hair-pin fabricated tubes. The thinner straight copper tube completely satisfied cyclic pressure fatigue test. But hair-pin fabricated thinner copper tube sometimes did not satisfy the cyclic pressure fatigue test due to crack at deformation point of hair-pin top. Several deformation grade straight tubes were experimented with the cyclic pressure fatigue tests for relationship analysis between the deformation ratio and the cyclic pressure fatigue life. Also we simulated the stress distribution of the hair-pin fabricated tubes under maximum pressure added by Finite Element Method. It indicated that the deformation ratio of hair-pin fabricated top portion have relation with concentrated stress. And it seems that these fatigue cracks are apparently effected by grain boundary with low cyclic fatigue from the fracture surface observation.