For many years, air-conditioning units were relatively stable in terms of operating temperatures and pressures, until the introduction of R-410A refrigerant. At the same temperatures, R-410A required systems to operate at 50% higher pressure than R-22 systems. With this came the redesign of the compressors, condensers, and other materials used in the pressure/temperature loop. This paper provides the science behind the development of tube and fittings qualified to be used in the R-410A systems. The baseline for copper refrigeration tube material properties and operating pressures can be found in ASME B31.5 Table 502.3.1 (see Table 1) and ASTM B280. The baseline for copper fittings material properties and operating pressure can be found in ASME B16.22. Using these standards as the basis for calculation, the yield and maximum allowable stress provides operating pressures for copper tube and fittings that are deemed insufficient for R-410A applications. The rated internal working pressures for copper fittings and the R-410A pressure are provided in Figure 1. The maximum rated internal working pressure at 100°F (37.7°C) for 7/8 in. (22.2 mm) refrigeration fittings is 580 psi (4.00 MPa), where the maximum operating pressure for R-410A at 150°F (65.6°C) is 613 psi (4.23 MPa).
According to ASME B 16.22 (2001), none of the operating limits for copper fittings are sufficient. A similar deduction can be made for refrigeration tube. With the consensus standards in play, a development team set out to develop products that would accommodate the use of R-410A.
Citation: ASHRAE Transactions, Volume 117, Part 2, Montreal, QC
Product Details
- Published:
- 2011
- Number of Pages:
- 10
- File Size:
- 1 file , 4.3 MB
- Product Code(s):
- D-ML-11-022
