May 2021

24 | Plant & Works Engineering www.pwemag.co.uk May 2021 Energy & Environmental Management Focus on: HVAC Industrial chiller refrigerants I ndustrial chillers remove heat from liquid via vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. Refrigerants, or working fluids, are the substances used in refrigeration cycles where in most cases they transition from a liquid to a gas and back again. Fluorocarbons, especially chlorofluorocarbons, became commonplace refrigerants in the 20th century, but are now being phased out because of their ozone depletion effects. Other common refrigerants are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane. Ideal refrigerant properties The ideal refrigerant would be non-toxic, non-flammable, non-explosive, non-corrosive, not harmful to the environment, cheap and easy to produce and work with and have good thermodynamic properties operating at low pressures. The desired thermodynamic properties are a boiling point somewhat below the target temperature and a high latent heat of vaporization to move more heat per volume when it boils. Ideally, the refrigerant should have moderate density in liquid form, a relatively high density in gaseous form, and evaporate and condenses at temperatures easily manipulated with compression. Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by appropriate choice of operating pressures. Lastly, refrigerants should mix well with oil, so that the oil can effectively lubricate the compressor. In reality, different refrigerants have varying degrees of these desired properties making choice a matter of trade off. The change in priorities over the last century from safety to environmental protection continues to drive change in refrigerant choice. Richard Payne* takes a look at industrial chiller refrigerants. History & regulation of refrigerants The first commercial refrigerants used toxic or flammable gases, such as ammonia, methyl chloride, or propane that could result in fatal accidents when they leaked. A non-toxic and non-flammable chlorofluorocarbon (CFC) gas was developed in 1928 (R-12) and branded Freon by DuPont later replaced by hydrochlorofluorocarbon (HCFC) commonly R-22 and hydrofluorocarbon (HFC) refrigerants. These refrigerants were frequently used for industrial purposes as they delivered a high level of safety and efficiency combined with low installation costs. Most of these common CFC, HCFC, and HFC refrigerants are greenhouse gases that contribute to global warming and may deplete the ozone layer when leaked to the atmosphere. R-22 for example has a global warming potential (GWP) about 1,800 times higher than CO2. Regulations have become increasingly strict with the Montreal Protocol in 1987 and the Kyoto Protocol in 1997 resulting in a shift to refrigerants with even lower environmental impact. In the UK, regulations came into force in 2002 banning the use of ozone-depleting HCFC refrigerants such as R-22 in new systems. Legacy chillers that use this refrigerant however can still be serviced and maintained. EU F-gas regulations came into force in 2015 to reduce emissions of fluorinated greenhouse gases (F Gases) through phasedown quotas, bans and maintenance requirements. Limiting the amount of F-gases sold in the EU from 2015 phasing down in steps to one-fifth of 2014 sales in 2030. Banning F-gases in many new types of equipment Preventing emissions of F-gases from existing equipment by requiring checks, servicing and recovery of the gases at the end of the equipment’s life These regulations and market demand for more environmentally friendly solutions has driven much innovation in industrial process and HVAC temperature control with many new refrigerants such as R-454b and R- 513a being adopted. Refrigerant safety classifications Refrigerants are categorised according to toxicity and flammability. There are two classes for toxicity; lower toxicity (Class A) where toxic concentrations are less than or equal to 400 parts per million (PPM) by volume and higher toxicity (Class B). There are four classes of flammability: 1, 2L, 2 or 3. Class 1 is for refrigerants that show no flame propagation at 140°F (60°C) ranging to class 3 highly flammable. The purpose of the 2L subclass is to reflect the lower flammability properties of the new low-GWP refrigerants, such as hydrofluoro-Olefins (HFOs), like R-1234yf and R-1234ze. QRSH$ QRSW$ #('8=$ RH`1$ L(&0$ RH`1$ QRRW$ GHHG$ GHH[$ GHQH$ GHQG$ GHQZ$ GHQZC GHGQ$ !"##$ %&'()*+,-*$ !".#$/$!"..$ ,)00)&12$ +3-*$ 4)&'(-51$ 6()'),)1$ !".#7$ (-815,-*$!" ..$ !"9:;,$ (-815,-*$!" ##$ <2)')$ 6()'),)1$ !"##$=5&&-*$ %&$>-?$ @A+%80-&'$ B()?'C$%&$ +3-$)D$!" 9.:5$$ E-(F%,-$G5&$ )&$!"##$ !".#79H-$ %&'()*+,-*$ I"B53$ !-J+15'%)&3$K$ 6C53-$L)?&$ !"M.75$ ! "M.MG$ !"9M9G$ !"9M#G$ !"7#$ N&'()*+,-*$ Time line