HEAT PUMPS 1 SORPTION TECHNOLOGY FIRED UP
Gas-fi red heat pumps using adsorption have been developed only for commercial use – until now. A system that is small enough for domestic applications has been developed as a prototype. Tim Dwyer explains how the technology works
T
he development and application of sorption heat pumps have been part of the heating and refrigeration scene for many years,
and in recent times several manufacturers have produced gas-fi red heat pumps aimed principally at the commercial market. But such technologies have been too large to use in a domestic setting. Now a research team led by Professor
Bob Critoph of the University of Warwick’s School of Engineering has taken a well-tried concept and developed it into an affordable air source sorption heat pump that is small enough to be used domestically and could replace a conventional gas-fi red boiler. Modelling of the new concept, which is now at prototype stage, suggests that the heat pump could be produced at a realistic cost and reduce gas consumption by over one third, thus providing good payback on the investment. The system evolved by Critoph uses
ammonia as the working fl uid, as it is able to work well below zero and, in compact equipment, has comparatively low fl ow pressure drops, so improving the effectiveness of the overall system. The sorbent itself is solid active carbon, although other solids (such as silica gel or
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zeolite) or liquid sorbents may have been used. The basic principles of the resulting
adsorption heat pump system are shown in Figure 1 – active carbon has an enormous surface area allowing the attachment of many molecules of the ammonia refrigerant. This basic process is clearly not
An artist’s impression of the air source sorption heat pump concept developed by Warwick University
August 2011 CIBSE Journal 29
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All images and illustrations Sorption Energy Ltd/University of Warwick
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