2016 ASHRAE Annual Conference

This paper addresses the challenge of improving the performance of Heat Pumps (HPs) in cold climate condition by applying refrigerant mixtures. The potential benefits of implementing R32/CO2 zeotropic refrigerant mixtures in three different residential air-source HPs for cold climates is studied. The cases studied are: conventional residential HP, HP with variable mixture control system and HP with variable compressor speed. The seasonal performance of a heating system with these air-source HPs, supplemented with an auxiliary electric heater is studied in the cold climate city of Montreal. To this aim, a detailed screening HP model previously developed is modified and used. The obtained results highlight the potential HP performance improvement of applying refrigerant mixtures.

Instances of counterfeit refrigerants causing violent and unexpected explosions, resulting in multiple fatalities, have been reported in mobile refrigeration units around the world. In addition, counterfeit refrigerants have caused system reliability issues in numerous air-conditioning applications. It was initially believed the inclusion of methyl chloride (R40) in the refrigerant composition caused these explosions and reliability issues. ASHRAE research project RP-1665 was commissioned to examine reactivity of R40 with R134a refrigeration system materials. R40 reactivity, in concentration ranges of 0.01 to 10 percent, was studied in the presence of R134a, polyolester lubricant (POE), aluminum 1100 metal, aluminum 380 metal, in the presence of iron metal, copper metal, sodium aluminum silicate zeolite and alumina catalysts. R40 was shown to have varying levels of reactivity, generally mild, but showing the potential for catastrophic reactivity. This paper contains a summary of the work from ASHRAE Research project 1665 and will provide insights into the impact of R40 contamination, by providing the chemistry of the reactions, preventative safeguards, threshold levels, and assessment procedures. RP-1665 was conducted by McCampbell Analytical Inc., located in Pittsburg, California.

The presence of unsaturated fluorocarbon contaminants in the refrigerants used in HVAC&R systems may result in reaction products that could potentially cause problems in system performance or reliability. Since 2007, the 40 ppm limit for unsaturated halogenated contaminants in new and reclaimed refrigerants set by AHRI 700 has proven to be more restrictive to reclaimers, recyclers and HVAC&R system providers than previously thought. In addition, compounds such as hydro-fluoro-olefins (HFO) have been tested as low global warming potential (GWP) alternative refrigerants and shown to have acceptable stability in some applications. So, it may not be appropriate to classify all unsaturated compounds as unstable and blanket them under the same restrictive limit.
This research project aimed at determining the effects of halogenated unsaturated contaminants present in refrigerants on the stability of refrigerant/lubricant systems and recommending a concentration limit specific to the unsaturated contaminant below which the refrigerant/lubricant system is thermally stable. The following refrigerant/lubricant mixtures with their corresponding contaminants were selected for stability study in sealed tube tests: (1) R-134a/POE with with 1,1-dichloroethylene, 1,2-dichloroethylene, R-1131 and HFO-1234yf; (2) R-1234yf/POE with HFO-1225ye(Z), HCFC-1233xf and HFC-1243zf; (3) R-123/Mineral Oil with R-1122, R-1123 and R-1131.
 Based on criteria such as visual changes, Total Acid Numbers (TAN), organic anion and dissolved metal concentrations after aging, it was concluded that the R-134a/POE system was as stable as the control (without contaminant) when the concentration of its contaminants was less than 1000 ppm. The R-1234yf/POE system was stable when its contaminants were less than 5000 ppm, while the R-123/Mineral Oil system was stable when its contaminants were less than three weight-%. These maximum concentration limits were however based on sealed tube stability tests and would need to be balanced against other safety concerns, such as toxicity, flammability, handling and recycling practices.