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Content archived on 2024-05-14

Advanced cycles and replacement working fluids in heat pumps


This project aims at developing the use of refrigerant mixtures and the ammonia-water cycle as substitutes for CFC working fluids, in buildings and in high temperature industrial applications. Heat-pumps for buildings will be developed for increased coefficient of performance and heat pump equipment suitable for heat recovery in industrial food production and drying processes will be investigated at temperatures between 40°C and 120° C.
Technical Approach
The ammonia-water cycle is of interest because it allows higher temperatures to be achieved than are possible using ammonia alone. Problems of water migration, lubrication and materials compatibility have to be addressed. Lorenz cycles used for their wide temperature glides will be studied. New heat exchangers will be developed for Lorenz Cycles.
A major concern of the project is the properties of the working fluids and their mixtures: thermo-physical properties, flammability, chemical stability, miscibility with the lubricating oil. In order to identify methods of dynamically measuring actual refrigerant composition at key points in the cycle a "smart" control will be developed to adjust the mixture composition as to match the heat pump performance to the particular application. The safety aspects of flammable refrigerant mixtures and the implications of flammable mixtures appearing on a temporary basis at different places within the system will be investigated.
Expected Achievements and Exploitation
The outputs of the project will include:
. Design of ammonia-water absorber and desorber units to suit large temperature glides.
. Evaluation of lubricants, oil-water solubilities and influence of mixture properties on lubrication and stability of working fluids. . Methods to measure continuously ammonia-water concentrations. . Process integration aspects of heat pumps with large temperature glides. . Report on refrigerant mixture selection for operation between 40°C and 120°C, including the thermophysical and transport properties and chemical stability of the mixtures.
. Experimental investigation of split evaporator system behaviour with different refrigerant mixtures (range 40-120°C).
. Production and testing of smart controller for dynamically controlling mixture composition.
. New heat-exchanger designs to achieve counter- or pseudo-counter-current operation.
. Report on application of Lorenz cycle machines in a food processing plant and in buildings with experimental validation of performance on test facilities.

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Cromore Road
United Kingdom

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Participants (11)