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A Study of a Water-To-Water Heat Pump Using Hydrocarbon and Hydrofluorocarbon Zeotropic Mixtures



William V. Payne, Piotr A. Domanski, J Muller


This investigation compared the performance of R22 to the performance of propane (R290) and zeotropic mixtures of HFC's and hydrocarbons in a water-to-water heat pump. Baseline testing began with R22 and proceeded to R290, R32/290, R32/152a, and R290/600a. The use of brazed plate heat exchangers arranged in counterflow for both heating and cooling allowed glide matching using the zeotropic refrigerant mixtures. The performance of the system was characterized by air-side capacity, air-side coefficient of performance (COP), compressor RPM, and refrigerant conditions. Testing showed that the R32/290 (50/50 by mass) mixture produced the highest cooling COP for a given capacity averaging 17% higher than R22 at standard conditions. When compared to the simulated direct expansion R22 system, the R32/290 cooling COP averaged 11% lower. Heating tests showed that propane (R290) COP averaged 3% lower than R22 in the direct expansion simulation and 5% higher than R22 in the water-to-water tests. R32/290 heating COP averaged 10% lower than R22 in the simulated direct expansion configuration.
NIST Interagency/Internal Report (NISTIR) - 6330
Report Number


coefficient of performance, COP, flammable, glide matching, water-to-water heat pump, zeotropic mixtures


Payne, W. , Domanski, P. and Muller, J. (1999), A Study of a Water-To-Water Heat Pump Using Hydrocarbon and Hydrofluorocarbon Zeotropic Mixtures, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed February 20, 2024)
Created April 30, 1999, Updated October 12, 2021