Hybrid heat pump and desiccant space conditioning system and control method

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG.
1 there is shown in schematic form a multi wheel desiccant/water vapor exchange system integrated into a heat pump, which may be controlled according to the present invention.
Two air flow paths are defined through the system, one of which is air taken from an enclosed conditioned space.
This air stream will typically contain large amounts of water vapor and will be warmer than the desired temperature at which the conditioned space is to be maintained.
In a supermarket, for instance, evaoporation of water from goods, and exhaled and perspired moisture contribute to high humidity.
Operation of refrigeration equipment, lights, and other machinery, as well as heat given off by humans and heating from insolation raise the temperature as well.
Typical direct expansion types of space conditioning systems use evaporator coils to both condense moisture from the air stream (the latent load), and to cool the airstream (the sensible load).
Such systems typically use chlorofluorocarbon (CFC) refrigerants which are now known to be harmful to the environment.
There have also been employed desiccant systems which first adsorb water vapor from the air stream using an inorganic material with a high K value for more hydrated states.
After adsorption of water vapor (an exothermic process which yields dry, but extremely hot air), a cooling step is required which may be carried out using a heat exchanger to recover the thermal energy and recycle it for us in regenerating the desiccant by heating to drive off adsorbed water.
The present invention combines these two approaches to yield a highly efficient system which is capable of heating, cooling, and dehumidifying an enclosed space.
Compressor 50 which is typically driven by an electric motor (not shown), serves to compress gaseous refrigerant which has absorbed heat from an air stream.
Coils 10, 20, and 30 may either be evaporation coils in which a liquid refrigerant is allowed to expand (thereby absorbing heat from the ambient surrounding the coil), or in which a compressed stream of high temperature refrigerant is allowed to condense to a liquid (thus liberating heat which is transferred to the ambient surrounding the coil)