Hydride heat pump with heat regenerator
Regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided.
Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.
Conventional dual metal hydride heat pumps comprise canisters containing two chemically different hydrides, one canister operates over a relatively lower temperature range, and the other canister operates over a relatively higher temperature range. The first or lower temperature performing hydride cools greatly, when providing hydrogen to the second or higher temperature performing hydride, and therefore can be used as a heat sink for cooling a room. The second or higher temperature performing hydride, when heated by an external source of heat desorbs hydrogen, which is used as a hydrogen source to the lower temperature performing hydride. Since higher temperature performing hydride take up hydrogen when cooled and desorb the hydrogen when heated, the higher temperature performing hydride side is heat driven usually by a relatively inexpensive source of heat such as natural gas or waste heat.
If the lower and higher temperature performing hydride canisters are cycled merely by exhausting their heat to the environment, no heat is regenerated. Consequently some regeneration schemes thermally link two low temperature canisters to each other and two high temperature canisters to each other thereby halving the sensible heat requirements. Net heating and cooling is then required to bring the canisters to the next required cycling temperatures.
Unfortunately regeneration schemes such as this have raised the coefficient of performance or COP of hydride heat pumps to only about 0.5 to 0.6, i.e. for every 1000 watts of heat delivered to the hydride heat pump only 500 to 600 watts of heat is removed at a lower temperature. If the system were able to regenerate all of the sensible heat, the COP would be almost 1.0. It is therefore desirable to regenerate more of the sensible heat in hydride heat pumps.
In air conditioning systems the efficiency of the apparatus is usually measured by its coefficient of performance or COP. By the term COP as used herein is meant the ratio of heating or cooling work performed divided by the amount of power required to do the work. Since cooling is generally the primary object of heat pumps, many systems are rated on their cooling COPs.
It is an objective of this invention to provide a system and process improving the efficiency of regenerative hydride heat pump operations. It is also an object of this invention to provide a system and process for regenerating a large portion of the sensible heat.
By the term sensible heat as used herein is meant the mass times specific heat times temperature change. Therefore, unless otherwise specified, the term sensible heat as used herein does not include latent heat or heat of adsorption or chemisorption.
Another object of this invention is to provide a regenerative hydride heat pump system and process having an enhanced coefficient of performance. Still another object of this invention is to provide a regenerative sorbent heat pump system and process which can be used for cooling chambers, rooms or interior spaces. Yet another object of this invention is to provide such systems and processes which can operate using hydride/hydrogen gas systems which have very low or no atmospheric ozone-depletion-potential or ODP. It is a further object of this invention to provide a system which can be used for heating and cooling rooms and buildings in which the heating can be for comfort or space heating in the winter or for producing hot water year around.
There is also provided by the principles of this invention a regenerative temperature hydride heat pump system for cooling a chamber, room or interior space comprising a plurality of first or low temperature canisters. The number of first canisters is at least four. Each of the first canisters has a first or lower temperature performing hydride contained therein, and a first heat conductive passageway for indirectly transferring heat between the first hydride and a heat transfer fluid in the passageway without direct contact between the heat transfer fluid and the first hydride.
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