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Performance of R32/R1234yf blends as potential lower GWP replacements for R410A in a 3 RT rooftop heat pump.

Number: 2191

Author(s) : SCHULTZ K., PETERSEN M., NAYAK G.

Summary

R410A (GWP1 ~ 2088) is imminently being replaced mainly by R454B (GWP ~ 465) and R32 (GWP ~ 675) in residential and light commercial air-conditioning and heat pumping equipment. R454B is a binary blend of R32 (68.9%)2 and R1234yf (31.1%). However, there continues to be regulatory and societal pressure to further reduce the direct global warming potential (GWP) of refrigerants used in these products. One path to lower GWP in unitary-type products is to employ other compositions in the R454 (R32/R1234yf) series. In particular, the composition of 43.5% R32 and 56.5% R1234yf, known as DR-4 (predecessor to newly designated R454D, 43%/57%), has a GWP ~ 300, identified at one time as a potentially practical long-term limit for unitary-type equipment. Additionally, the composition of 21.5% R32 and 78.5% R1234yf (R454C) has a GWP ~ 150, a limit set in early evaluations of alterna-tives to R134a in automotive systems and now an upper bound in newly passed future regulations.
This paper reports measurements of performance made on a commercial 10.5 kW (3 RT) rooftop unit (RTU) heat pump. The unit was run with R410A and R454B as baselines and with DR-4 and R454C. The original compressor was replaced with a compressor of larger displacement for the DR-4 and R454C tests. An AFD was also used to adjust the compressor speed to achieve similar capacities with all refrigerants. Measurements were made in both cooling and heating modes; only the cooling performance is presented here due to space limitations. The measured performance of the RTU with each refrigerant is compared with predictions based on a simple thermodynamic cycle model. The capacity and efficiency with R454B were about as expected relative to R410A. Performance with DR-4 was close to the simplified predictions with deviations due mainly to performance differences between the original compressor and the larger replacement as well as slightly better evaporator performance with DR-4. Performance with R454C fell short of the simplified model expectations, especially in cooling mode. This was mainly due to poor performance of the indoor coil operating as the evaporator. Overall, it was determined that DR-4 is a very suitable replacement for R454B if the GWP limit were to be set at 300. R454C is a feasible alternative to R454B if the GWP limit were to be set at 150. However, R454C’s larger temperature glide and lower gas density present engineering design challenges to replacing R454B. Other fluids with GWP < 150 that have higher operating pressures and smaller temperature glides would be better candidates.

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  • Original title: Performance of R32/R1234yf blends as potential lower GWP replacements for R410A in a 3 RT rooftop heat pump.
  • Record ID : 30033072
  • Languages: English
  • Subject: Environment
  • Source: 2024 Purdue Conferences. 20th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2024/07/17

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