The Next Generation of Refrigerants — Historical Review, Considerations, and Outlook

FORUM The next generation of refrigerants — Historical review, considerations, and outlook James M. Calm, Engineering Consultant ABSTRACT This article reviews the progression of refrigerants, from early uses to the present, and then addresses future directions and candidates. The article breaks the history into four refrigerant generations based on defining selection criteria. It discusses displacement of earlier working fluids, with successive criteria, and how interest in some early refrigerants re-emerged, for example renewed interest in those now identified as “natural refrigerants.” The paper examines the outlook for current options in the contexts of existing international agreements, including the Montreal and Kyoto Protocols to avert stratospheric ozone depletion and global climate change, respectively. It also examines other environmental concerns and further international and local control measures. The discussion illustrates how isolated attention to individual environmental issues or regulatory requirements, in contrast to coordinated responses to the several issues together, can result in unintended environmental harm that almost certainly will require future reversals. It identifies pending policy and regulatory changes that may impact the next generation of refrigerants significantly. Keywords — refrigerants, environmental impacts, ozone depletion, climate change, global warming, history, status, outlook 1. REFRIGEraNT Jacob Perkins and Richard Trevithick. industrial solvent that Perkins used in his The latter proposed an air-cycle system business as a printer and therefore had PROGRESSION for refrigeration in 1828, but again did available. Refrigeration goes back to ancient not build one. Perkins, however, did times using stored ice, vaporization of so with his invention of the vapor- Figure 1 depicts the progression of water, and other evaporative processes. compression machine in the 1830s, and refrigerants from their advent through Numerous investigators in different thus introduced actual refrigerants as we four generations. countries studied phase-change physics in know them. His 1834 patent describes the 1600s and 1700s; their fundamental a cycle using a “volatile fluid for the 1.1 First Generation findings set the foundation for “artificial” purpose of producing the cooling and — Whatever Worked (man-made) refrigeration. Oliver Evans freezing … and yet at the same time first proposed the use of a volatile fluid condensing such volatile fluids, and The most common refrigerants for the in a closed cycle to freeze water into ice bringing them into operation without first hundred years were familiar solvents [1]. He described a system that produced waste” [2]. Many refrigeration experts and other volatile fluids; they constituted refrigeration by evaporating ether under recognize his landmark contribution with the first generation of refrigerants, a vacuum, and then pumped the vapor identification of this mechanical vapor- effectively including whatever worked to a water-cooled heat exchanger to compression approach as the Perkins and was available. Nearly all of these early condense for re-use. While there is no Cycle. Although designed to use sulfuric refrigerants were flammable, toxic, or record that he built a working machine, (ethyl) ether as the refrigerant, the first both, and some were also highly reactive. his ideas probably influenced both tests actually used caoutchoucine, an Accidents were common. For perspective, This article was originally published as: J. M. Calm, “The Next Generation of Refrigerants – Historical Review, Considerations, and Outlook,” International Journal of Refrigeration, 2008(7):1123-1133, 2008, as a requested expansion and update to “The Next Generation of Refrigerants,” paper ICR07-B2-534, Refrigeration Creates the Future (proceedings of the 22nd International Congress of Refrigeration, Beijing, People’s Republic of China, 21-26 August 2007), Chinese Association of Refrigeration (CAR), Beijing, PRC, and International Institute of Refrigeration (IIR), Paris, France, 2007 24 EcOLIBRIUm • N OVE MBE R 20 0 8 FORUM eight elements remained, namely carbon, fourth generation nitrogen, oxygen, sulfur, hydrogen, 2010 fluorine, chlorine, and bromine [6]. global warming Within three days of starting, in 1928, zero/low, ODP, Midgley and his colleagues made critical low GWP, short atm observations regarding flammability high efficiency third generation and toxicity of compounds consisting 1990–2010s of these elements. They also noted that ozone protection every known refrigerant at the time (HCFCs), HFCs, NH3, H 0, HCs, C0 , . combined just seven of these elements — second generation 2 2 all but fluorine. Their first publication 1930–1990s on fluorochemical refrigerants shows safety and durability how variation of the chlorination and ethers, CFCs, HCFCs, fluorination of hydrocarbons influences HFCs, NH , H 0, . first generation 3 2 the boiling point, flammability, and 1830–1930s toxicity [7]. whatever worked Commercial production of R-12 began ethers, C02, NH3, S02, HC00CH3, HCs, H20, in 1931 followed by R-11 in 1932 [8- CCI4, CHCS, . 9]. Chlorofluorocarbons (CFCs) and later — especially starting in the 1950s in residential and small commercial Figure 1: Refrigerant Progression air conditioners and heat pumps — hydrochlorofluorocarbons (HCFCs) dominated the second generation of a number of companies marketed rejected sulfur dioxide (R-764) for safety refrigerants. Ammonia continued as, propane (R-290) as the “odorless safety reasons and carbon tetrachloride (R-10) and remains today, the most popular refrigerant” in promoting it over for incompatibility with metals, especially refrigerant in large, industrial systems ammonia (R-717) [3]. A telling, historic in the presence of water. They finally especially for food and beverage advertisement claimed that propane selected dielene (1,2-dichloroethene, processing and storage. “is a neutral chemical, consequently no R-1130) for the first centrifugal machine, corrosive action occurs” and “is neither though this selection then required an deleterious nor obnoxious and should international search to find a source [5]. 1.3 Third Generation occasion require, the engineer can work — Ozone Protection in its vapor without inconvenience” 1.2 Second Generation Linkage of released CFCs — including [3]. Continued preference, even today, — Safety and Durability CFC refrigerants — to depletion of of ammonia over hydrocarbons in protective ozone catalyzed the third The second generation was distinguished industrial applications suggests that high generation with focus on stratospheric by a shift to fluorochemicals for safety flammability was and remains a greater ozone protection. The Vienna and durability. Repeated leaks, of then concern in large systems. Convention and resulting Montreal prevalent methyl formate (R-611) and Protocol forced abandonment of The first documented, systematic search sulfur dioxide (R-764), retarded early ozone-depleting substances (ODSs). for a refrigerant offering a practical efforts to market domestic refrigerators Fluorochemicals retained the primary design with improved performance to replace iceboxes. With direction focus, with emphasis on HCFCs came in the 1920s, with examination that “the refrigeration industry needs for interim (transitional) use and of refrigerants for chillers [4]. Willis a new refrigerant if they expect to get hydrofluorocarbons (HFCs) for the longer H. Carrier, known for his advances in anywhere,” Thomas Midgley, Jr., and his term. The shifts sparked renewed interest psychrometrics and air conditioning, associates Albert L. Henne and Robert R. in “natural refrigerants” — particularly and R. W. Waterfill investigated a range McNary first scoured property tables to ammonia, carbon dioxide, hydrocarbons, of candidate refrigerants for suitability find chemicals with the desired boiling and water — along with expanded use in positive-displacement and centrifugal point. They restricted the search to of absorption and other not-in-kind (radial turbo) compression machines those known to be stable, but neither (those not using vapor-compression with focus on developing the latter. They toxic nor flammable. The published systems with fluorochemical refrigerants) concluded (without analysis of trans- boiling point for carbon tetrafluoride approaches. Public and private research critical cycles) that the performance of (R-14) drew attention to the organic programs systematically examined both carbon dioxide (R-744) would depend fluorides, but they correctly suspected additional non-fluorochemical and on the cycle and amount of liquid the actual boiling temperature to be hydrofluoroether (HFE) candidates, but subcooling, but that it yielded the lowest much lower than published. Turning to yielded few promising options. predicted performance of the fluids the periodic table of elements, Midgley analyzed. They also noted that ammonia quickly eliminated those yielding Manufacturers commercialized the first and water (R-718) would require excessive insufficient volatility. He then eliminated alternative refrigerants in late 1989 and, stages for centrifugal compressors for the those resulting in unstable and toxic within 10 years, introduced replacements conditions sought, and that water “gives compounds as well as the inert gases, for most ozone-depleting refrigerants. a low efficiency of performance.” They based on their low boiling points. Just Non-Article 5 (mostly-developed) NOVEmbER 2008 • EcOLIbrIUM

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