Rinnai’s Pete Seddon details the workings of a commercial heat pump
Heat pumps have a leading position in the pecking order of appliances that can work on commercial sites and property and drive towards NetZero and decarbonisation. The ever-growing interest in heat pump technology means an equal amount of curiosity is devoted to how a heat pump works.
What are the main internal mechanisms that enable a smooth operational product life cycle of a heat pump? And what are the inner mechanisms that provide product functionality?
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A commercial heat pump operates and uses similar technology in a similar way to an everyday consumer product, a common refrigerator. A “fridge” operates by extracting heat from within the fridge cabinet and exhausts this heat into the room. A heat pump follows a similar process however it is installed outside and extracts heat from the outside air and then transfers the heat generated into a body of water.
A heat pump has four main components within the closed circuit which is also known as the refrigerant circuit.
These components are:
- The Compressor. A compressor is used to move gaseous refrigerant through the refrigeration circuit, and a heat exchanger, which extracts heat from the source. The heat is then passed on to a heat sink through another heat exchanger.
- The Condenser. The condenser is a form of heat exchanger and is used to transfer the heat from the hot compressed gas into the water without coming directly in to contact with each other. As a lot of the heat is removed from the gas it will now change state from a gas to a liquid but will still be high pressure.
- The Expansion Device. The expansion device allows the pressure of the refrigerant to be lowered which in turn will allow its state to be changed at lower temperatures which is crucial for the whole process.
- The Evaporator. The evaporator is the component that starts the process all over again and is another form of heat exchanger. By using a fan, it draws air across the Evaporator which allows the refrigerant to change state back into a low-pressure gas ready to go back into the compressor. This then goes back to the compressor to continue to the cycle.
There are of course a lot more components within the heat pump that are integral to its operation and the overall heat pump efficiency such as thermistors to monitor the temperature of the refrigerant and the Control Board to ensure the desired output is achieved.
Commercial heat pumps can transfer heat even in minus temperatures, air source and ground source heat pumps could generate heat as low as -20°C ambient temperature. Conversely, they also create heat at extremely high temperatures. This is achieved because of the low boiling point of the refrigerant gases.
Commercial heat pumps generally use less energy to operate than they output in heat energy, making them extremely efficient – however when the temperature lift for commercial water heating or space heating is substantial (Temperature lift = outdoor air temperature and the temperature heat is delivered at within the building).
The heat pump efficiency i.e., COP or SCOP will reduce, therefore many heat pumps work at their optimum with low temperature heat distribution systems (such as underfloor heating) and why performance reduces dramatically when a heat pump is required to supply heat at high temperature for conventional domestic hot water.
Rinnai’s H3 range of products include domestic and commercial heat pumps that offer immediate property decarbonisation. Rinnai is determined to provide UK customers with cost effective low carbon solutions towards domestic and commercial hot water and building heating provision.