Assessment of the performance of ultralow‐<scp>GWP</scp> refrigerants in a two‐stage heat pump system using simulation and <scp>MCMD</scp>

Abstract The Kigali Amendment's mandate to phase down high‐GWP refrigerants highlights the urgent need for sustainable alternatives in cold climate heat pumps, which are critical for delivering efficient heating in severely cold regions. This study evaluates ultralow‐GWP refrigerants—R‐290, R‐152a, R‐161, R‐1234yf, and R‐1234ze(E)—for application in a two‐stage vapor injection heat pump operating at outdoor temperatures as low as −20 °C and a condenser temperature of 52 °C. The methodology integrates modeling and simulation with thermodynamic and exergy analyses, total equivalent warming impact (TEWI) assessment, and a TOPSIS‐based multicriteria decision‐making (MCDM) approach. Results show that R‐152a achieves the highest COP (2.92) and the lowest TEWI (9078.78 kg CO 2 e), followed by R‐290 (COP = 2.81, TEWI = 9345.6 kg CO 2 e), while R‐161 shows the lowest COP (2.64). A trade‐off in volumetric heating capacity is observed: R‐152a delivers 3.2 MJ/m 3 versus 3.78 MJ/m 3 for R‐161. Exergy efficiency increases with ambient temperature; for example, R‐152a improves from 0.355 to 0.383 as temperature rises from −20 °C to 0 °C. The TOPSIS ranking confirms R‐152a as the top performer (score = 0.642), closely followed by R‐290 (0.637). All refrigerants evaluated show acceptable performance for cold‐climate use. Notably, R‐152a and R‐290 emerge as climate‐friendly, high‐performance candidates. Unlike prior studies that rely primarily on single‐criterion comparisons, this work introduces a novel integrated framework combining thermodynamic, exergy, environmental, and MCDM analyses to guide refrigerant selection for sustainable heating in cold climates.