Development of a modular zeolite-water heat pump

The working pair zeolite-water has very good characteristics for the heat pump application. It is nonpoisonous, non-flammable and low-corrosive so that the use of a zeolite-water heat pump in the large field of domestic heating is very promising. The poor heat and mass transfer of the zeolite has to be considered by an appropriate design of the adsorber heat exchanger. Compact zeolite layers directly linked with the heat exchanger enable a high specific thermal output (thermal output related, to the mass of zeolite) which is the main shortcoming of these machines. Additionally the coefficient of performance (COP) can be improved significantly by a modular design of the machine consisting of six to eight heat pump modules. Due to the periodical operating mode which is required by the zeolite-water pair the single module is built up in a simple way without amy moving parts. The different modules, each of them operating in another phase of the sorption cycle, are connected in series by a heat transfer medium circuit so that a continuous thermal output together with high COP is achieved by this zeolite-water heat pump. First experimental investigations focus on the layout of the different components of the heat pump, e.g. the single module, the adsorber/desorber and the evaporator/condenser. The paper will present the design of these components as well as the design of the entire modular machine. Furthermore there will be a theoretical discussion of the COPs of the modular heat pump depending on the ambient temperature, on the number of modules and on the heating system.