Mutrees - Heat Pumps

Heat Pumps

Heat pumping technologies are widely used for upgrading low-temperature (free heat from renewable sources, such as air, water, ground and waste heat) to useful temperatures. Heat pumps are used for residential and commercial space and water heating, cooling, refrigeration and in industrial processes.

Conventional Heat Pumps

The great majority (45% of the industrial heat pump installations) of heat pumps work on the principle of the vapour compression cycle. The main components in such a heat pump system are the compressor, the expansion valve and two heat exchangers referred to as evaporator and condenser. The components are connected to form a closed circuit, as shown in the figure below. A volatile liquid, known as the working fluid or refrigerant, circulates through the four components. Closed compression cycle systems can be powered by an electrical or a diesel engine.


Open-cycle Mechanical Vapour Recompression heat pumps (O-MVR) use a process vapour or gas as the working “fluid”. This process vapour is compressed so that the temperature increases. The compressed process vapour is then condensed just as in a closed system. For an open-cycle system no evaporator is required, but the use of a process vapour directly influences the process, making this more complicated, since both systems (heat pump and process) are directly connected.

Enhanced Heat Pumps

Metal hydride heat pumps are a type of dry adsorption systems (so a type of chemical heat pumps in fact). In such a system the working fluid (gas or vapour) is adsorbed by a solid, hence these systems are also known as solid sorption systems. The dry adsorption systems based on hydrogen-metal hydrides are relatively recent. Van Mal has first suggested the concept of metal hydride heat pumps in 1974. In metal hydride heating and cooling systems, hydrogen gas is used as the working fluid and metals or alloys are used as adsorbents and desorbents. The use of hydrogen makes the metal hydride system environmentally safe.

Since hydrogen adsorption and desorption by metal hydrides are followed by heat generation and heat adsorption respectively, metal hydrides can be used for heating and cooling by allowing them to adsorb or desorb hydrogen at required temperatures and pressures. This is the principle behind the hydride heating systems. Hydride heating systems normally consist of a pair of reactors filled with alloys of different chemical stabilities. These two reactors are connected in such a way that hydrogen gas can flow between them.



Mutrees can offer consultancy in the implementation of conventional heat pumps. Further, due to our expertise in chemical heat pumps, we can assist in the development of enhanced heat pumps based on this principle.

© 2010 D.F.Mulder