Refrigeration – Refrigeration producer – Sorbent type
Reexamination Certificate
2002-06-28
2004-01-06
Doerrler, William (Department: 3744)
Refrigeration
Refrigeration producer
Sorbent type
C062S484000, C062S485000, C062S487000, C062S494000
Reexamination Certificate
active
06672103
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a high power density sorption heat store, in particular for the temporal-periodical storage of available heat, and to a method of heat storage.
2. Description of Related Art
Sorption heat stores are used to temporally and locally store periodically recurring heat energies with the help of a working fluid, in a targeted and user-friendly way allowing the power to be unloaded again, in a sorption-active micro-porous solid matter storage material. Preferred applications concern the seasonal or short-term storage of heat in housing and building technologies for heating and air-conditioning of rooms or to heat service water. Modern systems of sorption storage consist, as a rule, of a heat-insulated container that is periodically loaded with heat power in a targeted manner, and is again unloaded upon recall. For this purpose, the working fluid is periodically transformed in a gaseous state by means of vaporizers, and is bound to suitable porous sorbents during the storage unloading process. During this, sorption heat is released, which can be supplied to further liquid or gaseous heat exchangers via circuits for the available heat. In the loading process of the stores, a removal of the working fluid from sorbents is carried out through means of desorption. This ensues by feeding heat from power supply networks or, preferably, from other locally available sources of heat, such as devices for obtaining solar power or geothermal heat, with the working fluid being again liquefied in associated condensers. Less expensive thermal or electric forms of power may thus be stored during slack periods in power supply networks, with the advantage of then having additional amounts of available heat to be drawn on in periods of increased power demand.
According to “
Sorptionsspeicher—Saisonale Wärmespeicherung mit hohen Energiedichten
” (Sorption stores—seasonal heat storage with high power densities), a company publication of UFE SOLAR GmbH, Alfred-Nobel-Strasse 1, D-16225 Eberswalde/Brandenburg, written by W. Mittelbach and H.-M. Henning, the power densities exceed those of a conventional water storage unit by four to five times, depending on the depth and range of the storage state created.
In more recent proposals concerning sorption stores, it is asserted to increase the power storage densities and the thermal efficiency initially by introducing verbal concepts such as “compact store” or “high-performance store” and the technical measures derived therefrom, in that, on the whole, in a space delimited due to the geometric dimensions of the apparatus, the at least three, originally spatially separated areas sorption area, vaporizer and/or condensation area, and an area for stocking the working fluid, normally water, are united in one common container. Solutions like this (cf. DE 40 19 669, DE 198 11 302, and EP 0 897 094) are relatively simple to manufacture and can be installed in secondary rooms of buildings, e.g., of houses, and may be operated with a certain expenditure for the regulation and control alone of valves, serving the purpose of heating, air-conditioning and preparing service water.
As a rule, the vaporizer and condenser are arranged below the sorbent chamber, and are periodically successively flowed through in most cases by two circuits representing alternatingly switched heat exchange circuits of fossil fuel-operated heating means and solar or geothermal circuits. The sorption-active store volume must be capable of being evacuated and hermetically sealed, in order to make maximum use of the cyclically reversible loading cycle existing between the loading and unloading process. Hence, the task of any development of a sorption store is to maximize this loading cycle that is determined pressure-dependent by two separated isotherms involved in the adsorption and desorption process.
In this process, however, basic problems arise in conjunction with the transport processes for fluid and heat with regard to the heating, cooling and working fluids both in the inner container volume, as well as via the surfaces of the conduit systems providing for said transport:
The sorbents exhibit a markedly restricted heat conductivity, so that the desired positive heat balance is impeded in a preferred direction of the container, but also in one of its transverse directions. As a rule, the sorbents consist of granulized or pelletized particles, which, in the form of grain beds, are present between the heat and flow conducting equipment. For increasing the storage density, high filling portions are sought, whereby necessary installations imparting the heat restrict the storage-active space.
The free paths for the transport of the working fluid are reduced within the beds due to the desired higher filling proportions with sorbents. Moreover, the sorbents have outer and inner pore systems, which have to be filled with working fluid as completely as possible, so as to achieve a high storage density.
By combining vaporizer and condenser parts within one receptacle and in a narrow space, “bridges” short-circuiting the transport processes arise across the heat and flow conducting equipment within the receptacle, which shorten the desired course of the balance processes throughout the entire sorbent space and contribute to a flow bypass formation reducing the efficiency.
In a configuration of the sorption store in a compactness which is not optimally high, the proportion of the external heat insulation has to be relatively large, so as to achieve that a sufficient power density remains maintained over a longer period of time. Internal insulations between the vaporizer and condenser, however, would additionally reduce the storage density. Accordingly, with an increase of the dimensional scale, the proportion of the external insulation may be reduced in that a temperature gradient is established from the inner and warmer to the outer and cooler spaces.
The more recent approaches scarcely furnish indications as to how to solve these problems, either.
It is, however, known that usual modern heat exchangers, e.g. designed as tube bundle or jacketed heat exchangers, are able to limit and even reduce these problems to a high degree with an optimal formation and configuration of up to several meters in diameter. Heat exchangers are available in standardized constructions and series established, for example, by norms for tubular bundle heat exchangers, such as the German Standards DIN 28 182
: Rohrleitungen, Durchmesser der Bohrungen in Rohrböden, Umlenksegmenten und Stützplatten
; DIN 28 185
: Rohrbündel-Einbauten
or DIN 28 008
: Abma&bgr;e und Toleranzen
. The correspondingly highly sophisticated knowledge on their design and dimensions is likewise contained in standard works, such as in the handbooks “
Verfahrenstechnische Berechnungsmethoden” Teil
1
—
Wärmeübertrager; Teil
5
—
Chemische Reaktoren; Apparate, Ausrüstung und ihre Berechnung
, published by Deutscher Verlag für Grundstoffindustrie, Leipzig, 1981.
Furthermore, it is known from DE 39 25 704 that using ribbed tubes as inner tubes, a relatively long travel path and a large transfer surface for the second heat transfer medium around the inner tube, and hence a good heat transmission is achieved in that, for example, a flexible hose structure forming a flow channel is shrunk onto the ribs. Such modified ribbed tubes, however, do not yet allow a suitable guidance of the flow of working medium which must be in connection with the sorbent via openings. For this reason, more recent arrangements as in DE 195 39 105 relate to so-called sorption heat exchangers, in which the channels for the working fluid flowing in vapor form and the inner heat-conducting elements are largely matched to one another in one of the transverse dimensions. So as to increase the dimensional scale, a favorable guidance of the working fluid may also ensue in a preferred longitudinal direction (the main axis of the apparatus), which guidance, however, is not yet assured with the chosen known arrangement o
Fuesting Bernd
Muenn Peter
Stach Helmut
Welke Hartmut
Doerrler William
Shulman Mark
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