HEAT PUMPS
Hot tips and cold facts about heat pumps
Heat pumps can be used for cooling as well as heating, a feature that will become ever more important as the eff ect of global warming (or, more accurately, heating) increases. Tim Mitchell, sales director of Klima-Therm, explains the implications.
Chillers
are cooling specialists, designed for that one useful and controlled output, whereas reversible heat pumps can heat or cool as required.
H
otter summers are likely to become more common as we deal with the mounting impact of the climate emergency, according to the UK’s Met
Offi ce. The current UK annual average temperature is roughly 8.8°C, but by 2050, this will probably rise to between 9.1 and 11.7°C, and the likelihood of heatwaves could increase fi ve-fold. As global temperatures rise, the number of days the UK observes 25°C or more will increase. Despite a relatively cool summer here, globally, 2024 was the hottest year on record. On 19 July 2022, a temperature of 40.3°C (104.5 °F) was recorded at Coningsby in Lincolnshire, the hottest temperature ever recorded in the UK and 1.6°C higher than the previous maximum temperature recorded in 2019. While most people can adapt biologically and physically
to incremental increases in average temperatures, children, pregnant women, and older adults are more susceptible to adverse eff ects because they are less able to regulate their body temperatures.
The health impacts of extreme heat can be signifi cant. As the body gets hotter, blood vessels open up, which lowers blood pressure. This means the heart must pump harder to push blood around the body. In older people with weaker hearts, this can pose a real danger. For younger people, too, there are risks. Heat stress is the leading cause of weather- related deaths, according to the World Health Organisation (WHO). It cautions that this can exacerbate underlying illnesses, including cardiovascular disease, diabetes, mental health issues, and asthma, and can increase the risk of accidents and transmission of some infectious diseases. Heatstroke is a medical emergency with a high fatality rate. The number of people exposed to extreme heat is growing
exponentially due to climate change in all world regions, according to the WHO. It estimates that heat-related mortality for people over 65 years of age increased by around 85% between 2000–2004 and 2017–2021. This has signifi cant implications for the development of cooling technology to protect people from the eff ects of extreme heat, typically in the form of chillers and heat pumps (in reverse mode to provide cooling rather than heating). Broadly, both chillers and heat pumps operate on the basis of one of two types of refrigeration cycle: ■ Vapour compression – using a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and rejects that heat elsewhere.
■ Vapour absorption – using the absorption and desorption of a refrigerant by an absorbent to provide cooling.
Both aff ect the temperature of water or air, which then circulates through a building’s HVAC system to create comfortable indoor conditions. But, although both technologies boast the same key components – compressor, condenser, expansion device, and evaporator – chillers and heat pumps remain distinct from each other. Chillers are cooling specialists, designed for that one useful and controlled output, whereas reversible heat pumps can heat or cool as required. This is because the latter can also include a reversing valve which allows the heat pump to
12 November 2024 •
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