ACR Journal

December 2020 | January 2021 The science behind heat pumps is no mystery; indeed, it has been known for more than 250 years. William Cullen, a Scottish physician, chemist and agriculturalist, demonstrated artificial refrigeration – which is eectively the foundation of the heat pump’s operating principle – as far back as 1748. The theory underpinning heat pumps (essentially mechanical devices that extract low-grade heat from one source and transfer it to another) is relatively simple. However, their operational characteristics have come on leaps and bounds since Cullen’s discovery all those years ago. The latest heat pumps are compact, exceptionally eˆcient and eective in both cold and warm climates. A typical heat pump system is designed around the concept of the latent heat of vaporisation. Thermal energy from the outside environment is moved into the air or water systems inside a building through the evaporation of a working fluid. The vapour produced is then condensed, releasing thermal energy into the system. HEAT PUMPS 38 Reclaiming more energy output than is put in sounds impossible, but it’s something that, to the layman, heat pumps appear to achieve. And the latest models offer even greater efficiencies. Tim Mitchell, Sales Director of Klima-Therm, looks at what’s hot in heat pump technology. Something for nothing Perhaps the single most important advantage of a heat pump used for heating is that it upgrades the heat and delivers it at a higher temperature than the source from which the heat was extracted. The biggest benefits, however, revolve around heat pumps’ environmental performance – they are exceptionally eˆcient and therefore reduce carbon emissions compared to the traditional burning of fossil fuels. Reverse cycle A bonus of heat pumps is that reverse cycle models can also provide cooling in summer. Using heat pumps for heating involves collecting low grade heat from the air, water (for example, lakes or rivers) or from the ground. This heat is then upgraded by using a refrigerant circuit incorporating an electrically driven compressor. It can then be delivered at a suitable temperature for space heating or for the heating of sanitary hot water. For cooling, this process is simply reversed. So, low-temperature heat is Volume 7 No.1 Modern heat pumps are compact, exceptionally efficient and effective in both cold and warm climates Tim Mitchell Klima-Therm.indd 38 03/12/2020 11:59

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