HEAT PUMPS
change the direction of the refrigerant fl ow, enabling it to heat or cool the space. Heat pumps transfer heat energy from one place to another. Chillers remove heat from a space or process stream, making it cooler and
rejecting heat to the environment whereas heat pumps either extract heat from the environment and use it to provide useful heat, or reject heat just like a chiller, when ‘reversed’ in cooling mode. Furthermore, heat pump water heaters typically use the environment as a relatively low-temperature heat source, while chillers use the environment as a heat sink. Indeed, the biggest advantage that heat pumps have over chillers is their ability to integrate simultaneous heating and cooling to deliver environmental and energy system benefi ts. HVAC technology that can heat and cool – also known as a polyvalent system – is an intelligent solution to air conditioning requirements in systems where the heating demand is simultaneously or independently combined with a cooling request from the building. Polyvalent heat pumps can provide an extremely versatile solution to the
problem of decarbonising heat. They can heat or cool but are most eff ective when operating in simultaneous heating and cooling mode, making use of the otherwise rejected heat produced from the production of chilled water.
Polyvalent versus four-pipe systems
Polyvalent and four-pipe heat pump systems both off er simultaneous or synchronised heating and cooling which makes them versatile and effi cient indoor temperature control devices. They are also ecologically impressive. REHVA – the Federation of European Heating, Ventilating and Air Conditioning Associations says polyvalent heat pumps are sustainable solutions, and their main benefi t is an ability to meet contemporary heating and cooling demands. It adds: “The capability of this solution to exploit the potential free energy derived from the heat recovery can lead to signifi cant savings in terms of energy consumption and fuel expenditure... Convenience increases when the hours of simultaneous request for heating and cooling grow.” The vocabulary we use for these systems is important and is still
developing and coalescing around diff erent terms. All polyvalent heat pumps are four-pipe systems, but not all four-pipe systems are polyvalent. Essentially, polyvalent heat pumps can achieve both heating and cooling simultaneously and independently, with both sides under control.
A four-pipe system could also use a heat pump that can switch between the two modes, delivering either heating or cooling which is used in reversed or diverted systems, but not at the same time, or traditional heat recovery machine that is doing either heating or cooling as its primary job, with recovery of the other side of the process as a byproduct but not under control against a specifi c setpoint or demand. A traditional four-pipe fan coil unit system, for example, contains distinct fl ow and return pipe-lines for the heating system and separate fl ow and return pipe-lines for the cooling system. If there is any concurrent heating and cooling requirements, for example on a deep-plan building or a mixed use development, or if there is a regular demand for domestic / sanitary hot water at the same time as cooling, these systems would work more energy effi ciently with a polyvalent unit.
years
Glycol Experts since 1998
& Expert Engineering Services Unrivalled Heat Transfer Fluids
Since 1998, Hydratech's key objective has been the establishment of technical partnerships with those responsible for cooling system design, installation and operation. By understanding their exact application requirements, Hydratech’s team of chemical, mechanical and sales engineers can deliver a fluid solution that improves system efficiency, extends system life, and saves energy.
Hydratech Fluids Hydratech’s market leading heat transfer fluids, glycols, antifreeze, corrosion inhibitors and water treatment chemicals are proven to provide precise, stable temperature control, and comprehensive system protection.
Hydratech Services The Hydratech Services division provides specialist engineering and maintenance services to maximise the potential for optimised system performance and reduced operational costs.
Coolflow DTX
High efficiency non-toxic glycol, suitable for replacing propylene glycol. DTX represents a major step forward in heat transfer and pumping efficiency, providing >10% reduction in operating costs when compared with propylene glycol based fluids.
Contact us today
find out how Hydratech can help your business improve system efficiency and save energy.
01792 586800
www.hydratech.co.uk info@hydratech.co.uk
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www.acr-news.com • November 2024 13 Manufactured in U.K
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