Heat Pump Test Apparatus for the Evaluation of Low Global Warming Potential Refrigerants
Harrison M. Skye
International efforts to reduce man-made global warming include restrictions on the use of chemicals with a high global warming potential (GWP). The heating, ventilation, air- conditioning, and refrigeration (HVAC&R) industry subsequently faces a phasedown of many commonly used hydrofluorocarbon (HFC) refrigerants that have a high GWP. A new family of refrigerants known as hydrofluoroolefins (HFOs), including their mixtures with HFCs, show promise as replacements. The overall GWP impact of refrigerants includes both the direct GWP related to inadvertent release of the fluid into atmosphere, as well as and indirect GWP caused by emissions from the power source used to energize the associated HVAC&R equipment. The indirect emissions far outweigh the direct emissions, so the efficiency of candidate replacements must be carefully quantified to guide the selection of fluids that actually achieve a reduction in the overall GWP. A 3.4 kW (1 ton) heat pump test apparatus has been constructed and instrumented for measuring the cycle performance of low-GWP refrigerants; the description of that apparatus is the focus of this report. Details are described for the system components, instrumentation, data reduction, and uncertainty analysis. Results from baseline experiments with R134a were used to test and verify the apparatus and data reduction procedure. The data will be used to provide a relative comparison between the low-GWP refrigerants quantified by metrics including capacity, coefficient of performance and volumetric capacity. Future tests with low-GWP refrigerants will be compared with those from baseline refrigerants R134a and R410A. Additionally, the test data will be used to verify a new NIST heat pump modeling tool, CYCLE_D-HX, which captures both thermodynamic and heat transfer processes in HVAC&R equipment. Refrigerants, refrigerant mixtures, and cycle configurations that are difficult and/or time consuming to test can be rapidly explored using the model.
Heat Pump Test Apparatus for the Evaluation of Low Global Warming Potential Refrigerants, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.TN.1895
(Accessed June 9, 2023)