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Accelerated fatigue testing of aluminum refrigeration press fittings for HVAC & R applications.

Number: pap. 2438

Author(s) : ELBEL S., DUGGAN M., LAGROTTA T., et al.

Summary

Components of HVAC and refrigeration systems are subjected to various parameters and conditions that affect their operating life. Rapid changes in pressure and temperature along with mechanical vibrations caused by rotating equipment such as compressors and fans induce fatigue in the components. Additionally, freezing and thawing of ice between the joints of fittings can also be a factor leading to failure of couplings and joints. Aluminum is being more widely used in the refrigeration industry as a replacement for copper due to economics of lower cost and easy manufacturing. A series of tests were conducted to simulate conditions experienced by fittings in a real life refrigeration system at an accelerated rate. The aluminum fittings of this study are subjected to same accelerated fatigue test conditions which the copper fittings were earlier subjected to. The test methodology is identical to the one developed and performed on copper fittings in an earlier study by Wilson and Bowers (2014). Because the fitting manufacturer and the test lab are the same, it is possible to fairly compare the results between the two studies. The first test is a rapid pressure-temperature cycling test where the fittings are subjected to rapid changes in pressure and temperature which occur due start/stop cycles and during frost/defrost modes of a residential R410A heat pump system. The second test is a vibration test which subjects the fittings to vibration loads experienced due to rotating components in the system. The third test is a freeze/thaw test which simulates ice buildup and melting at the joints during frost/defrost cycles. The test were conducted on flame free aluminum press fittings which are designed to be used with R410A. Aluminum press fittings of six different sizes (9.5 mm to 28.3 mm) were exposed and investigated according to the accelerated tests described above. Pressure, temperature, strains and acceleration were measured and analyzed and compared to the earlier copper fitting results obtained by Wilson and Bowers (2014) where possible. At the end of each test the exposed specimen were carefully investigated for possible damage and leak tightness was confirmed. The main contribution of the work is to extend the previously established test method to evaluate a family of new aluminum press fittings at identical conditions as the earlier study that used copper fittings. It was found that both fitting materials, when exposed to identical accelerated test conditions, were able to withstand all tests without showing any signs of premature failure. It was concluded that the aluminum version of the fittings is a suitable alternative to the earlier copper connectors, giving manufacturing a reliable, yet low-cost alternative.

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Pages: 10

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Details

  • Original title: Accelerated fatigue testing of aluminum refrigeration press fittings for HVAC & R applications.
  • Record ID : 30018857
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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