Feature capacities from a couple of kW to over a thousand kW , and coefficient of performance ( COP ) that can be as much as 4 or 5 ( dependent on source conditions ). Noise levels and energy classes also need to be considered .
HEAT PUMP HISTORY It is still widely believed that heat pump technology is a recent invention , and because of this there are concerns that the systems may be unproven or at the early stage of development , however this technology was actually established more than 150 years ago . The first ground source heat pump was brought into use around 70 years ago .
As early as 1852 , Lord Kelvin produced ideas regarding what today is known as the heat pump . In his works he noted that a ‘ reverse heat engine ’ could in fact be used not only for cooling but also for heating applications . He also pointed out that such a device would need less primary energy due to the extraction of heat from the environment . For space heating however , it took about 85 years until the first commercial heat pumps were incorporated into buildings , and for the purpose of heating only .
In the period before 1875 heat pumps were primarily applied for heating purposes in industrial applications where the savings and advantaged over coal or wood energy sources were obvious . This period also saw the common use of steam systems for central heating . On a domestic level the heat pump technology used for the first hot water systems were driven by natural convection . They operated only above feed temperatures of about 50 ° C .
" In South Africa , the inclusion of heat pumps is considered essential in any commercial and retail project as they offer significant energy savings ."
Heat pumps for heating and domestic hot water purposes were unfortunately not attractive at that time because of the already low efficiency of the steam system it was in competition with , and so initial acceptance was low . The continual development of the heat pump technology was further based on inventions to cover the huge demand for cooling , particularly in the food supply chain industries .
Artificial cooling technology , with the exception of evaporative cooling employed by Indian and Egyptian civilizations , did not surface until the invention of refrigeration machines came about as the advancement of
Creative Commons
An example of an air source heat pump installation .
food supply grew , also around the 1870s . Natural ice was transported around to meet cooling needs until shortages became a persisting problem and a shift took place to focus priority on development of the refrigeration cycle to meet cooling and refrigeration demands .
APPLICATIONS Heat pumps are used today in many scenarios for both heating and air conditioning applications , and on largely different scales . The technology of compressed refrigerant cycles and various valve inclusions have made it possible to engineer a bi-directional flow to generate cooling or heat as required making the heat pump a truly versatile device .
In South Africa their inclusion is considered essential in any
commercial and retail project as they offer significant energy savings and are also making a comeback on the industrial side where savings of any kind have become critical for businesses operational costs . Heat pumps can be applied to space heating / cooling , process water heating / cooling , steam production , drying , dehumidification , evaporation and distillation , and concentration processes , to name a few .
These devices can further be used in a system through recovery of waste heat to use at highly beneficial levels . Recent research and development has indicated that heat pump performance is likely to further improve over the coming years . Improvements in component design and in the use of waste heat sources are further expected to raise overall heat pump performance .
HEAT PUMP FUNCTION AND SYSTEM TYPES To illustrate the principle of heat pump function , one needs to understand the process of “ change of state ” well . Change of state refers to the events of a substance changing from gas to liquid , or from liquid to solid , or vice versa . Water , an example that everyone is familiar with can exist in different states as a vapour , or as a liquid , or as a solid . When water is in each of these states , it still contains the same molecules , being H₂O .
www . hvacronline . co . za RACA Journal I October 2021 21