ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai 37 REFRIGERANTS Operational properties: working examples R404A R448A R449A R452A R407F R744 (CO2) Global Warming Potential 3922 1387 1397 2140 1825 1 Relative Cooling Capacity 100% 104% 102% 102% 106% 101% Relative Mass Flow 100% 80% 79% 102% 106% 88% Volumetric Capacity KJ/m3 100% 104% 102% 102% 106% 407% Coefficient of Performance 4.1% 4.23% 4.24% 4.14% 4.25% 2% Total Equivalent Warming Impact (relative to R404A) 100% 86% 86% 91% 88% 181% *Evaporating temperature 2oC, Condensing temp 35oC, 7K superheat, 5k subcooling The following information applies to the figures in this table: evaporating temperature 2°C, condensing temperature 35°C, 7K superheat, 5k subcooling. not necessarily mean that they will be a more efficient refrigerant in a particular application. This needs to be modelled on the demands of a specific system. Naturals can also bring into play safety concerns. The likes of propane or propylene have flammability issues which you don’t have with typical HFC refrigerants. There can be toxicity issues with carbon dioxide and ammonia. For example, from an energy perspective, in a warm climate, carbon dioxide can be a very inefficient gas because it needs far more power than an equivalent HFC system. In the case of chillers, my recommendation would always be to take the advice of the manufacturer. The chiller manufacturer will give very specific guidance on how the system will react with individual refrigerants. As a chiller is a self-contained system, the manufacturer will have a very good idea and give very accurate advice on what will happen if you change the refrigerant. The operational properties of gases relating to heat pumps is an area where the spotlight will only grow larger. The operational properties of the gas are critical here as they define the types of heat pump system to be used in a specific application. For example, with monobloc heat pump systems, the key parts are outside the building, and in this instance, flammable refrigerants are an option because the risk is lower. But if the refrigerant circuit enters the building itself, the refrigerant’s flammability is a key property that needs to be understood. So, again, consult the heat pump manufacturer on this one. They will have a good idea about what works for their systems and, equally importantly, what is safe. Generation of heat An important issue around heat pumps and the operational properties of gases is the heat aspect. For example, how hot you can warm the water in the house? Natural gas water temperatures operate significantly higher than they do for heat pumps, but depending on the gas used in the heat pump; you can vary the water temperature. A major change is happening in our industry in how jobs are defined. Heating and plumbing are converging as new green technologies as heat pumps grow in popularity. Skill crossovers are happening more and more. However, care must be taken to ensure that the right people – and rightly qualified people – are doing the job at hand. As a rule of thumb, if you have concerns about operational properties, make your refrigerant supplier your first port of call. Talk to them about the issues you have. They will have detailed information on refrigerants and how they will operate. Of course, with those really big jobs involving chillers engage with the manufacturer too – they will also have the insight needed to steer you in the right direction.

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