This application claims priority to German Patent Application No. DE 10 2017 215 617.1, filed on Sep. 5, 2017 and German Patent Application No. DE 10 2018 212 820.0, filed on Aug. 1, 2018, the contents of both of which are incorporated herein by reference in their entirety.
The present invention relates to a sorption heat transfer module.
Thermally driven sorption refrigeration systems have a high energy saving potential since inexpensive waste and excess heat is as used as drive energy and as a result, the pressure on the electrical networks can be reduced, particularly in hot time and climate zones with a high refrigeration requirement. These installations can also be used as heat pumps which by means of burner heat raise additional environmental heat to a temperature level sufficient for heating purposes, with the result that the fuel requirement can be reduced.
Of particular interest here are adsorption systems in which porous solids are used and which have no moving parts which are therefore liable to wear in the working medium area. The greatest obstacle to the introduction of these systems on the market can be attributed to the relatively low power densities hitherto achieved and the still too-high power costs.
The published German Patent Application DE 10 2011 079 586 A1 describes such a sorption module whose housing design is however still very complex and is a source of some loss mechanisms. A disadvantage is the complex design with a fairly large number of joints to be sealed hermetically.
A further development for the solution of these problems is disclosed with the published German Patent Application DE 10 2014 223 040 A1 in which a housing wall is configured as a heat transfer structure, with the result that the number of passive housing walls is reduced. As a result, some loss effects are reduced. Due to a largely cylindrical formation of the housing structure, support means for receiving pressure differential forces can be dispensed with, which brings with it cost advantages.
A disadvantage of the proposed cylindrical module concept however is the quality of the thermal connection of the phase change structures to a fluid heat transfer medium and the comparatively large thermal mass, which has a harmful effect on the power density and the efficiency of the sorption module. Furthermore, there is the problem that depending on the installation position of the cylinder module, it can occur that condensate bound in the capillary structure can be displaced in the entire structure due to gravitational and acceleration effects. For example, condensed working medium can accumulate in low-lying regions, with the result that conversely high-lying regions of the capillary structure dry out too rapidly during the evaporation phase.
Another weak point of the said embodiment of the housing jacket carrying this capillary structure is the difficulty of applying the internal capillary structure with very good thermal contact. For this a metal firmly bonded connection preferably by soldering should be strived for, which is made difficult by the protective oxide layer of stainless steel.
A third weak point of the last-mentioned module design is the heat transfer coefficient k on the side of the heat transfer agent, which serves to remove or supply the condensation heat and the heat of evaporation with the smallest possible driving temperature difference.
The present invention is concerned with the problem of providing an improved cylindrical sorption module with thermally activatable housing. This problem is solved according to the invention by the subject matter of the independent claim(s). Advantageous embodiments are the subject matter of the dependent claim(s).
The present invention is based on the general idea that a housing with suitable structures simultaneously provides a heat transfer surface in order to transfer condensation heat and/or evaporation heat with very good heat transfer to a or from a fluid heat transfer medium. By multiple usage of components and structures, a substantial contribution can thus be made to increasing the volumetric power density, the efficiency and also to reducing the manufacturing costs. The first two optimization criteria in this case require a structure combination by means of which a total heat transfer coefficient from the heat transfer medium to the phase change structure and from there to the saturation temperature of the working medium vapour of overall 1500 W/m2*K is exceeded. The individual thermal resistances of the heat transfer path must therefore be minimized under the boundary condition of minimal production costs for material and joining processes.
For this purpose a sorption heat transfer module having a thermally activatable housing is provided which encloses a sorption zone through which a working medium can flow, and in which the housing according to the invention comprises a gastight inner wall made of a corrosion-protected material, the internal surface of which is adjoined by a capillary structure which consists of at least one corrugated fin package which is connected in a firmly bonded manner to the internal surface of the inner wall. This results in an extremely efficient phase change structure which is particularly easy to manufacture and at the same time very well connected, which provides a sorption heat transfer module having a high efficiency. The term “gas-tight” should not be understood to be absolute in the present connection but relative, i.e. related to the present case of application. In other words, the gas-tight inner wall is substantially tight for the gases which usually occur in such a sorption heat module whereas tightness e.g. with respect to hydrogen gas is not required.
In a preferred embodiment of the sorption heat transfer module according to the invention, it is provided that the thermally activatable housing comprises an outer wall which encloses the gas-tight inner wall and together with the inner wall forms an annular channel for a heat transfer agent through which axial flow can take place. Via this annular channel, a heat transfer agent can flow particularly simply and specifically through the sorption heat transfer module according to the invention and the condensation heat can be efficiently removed.
A particularly compact design can be achieved if the inner wall and the outer wall are each configured cylindrically, if the inner wall is arranged coaxially and concentrically in the outer wall and if the annular channel is arranged radially between inner wall and outer wall.
This compact design can be assisted by the fact that the annular channel has smaller dimensions in the radial direction than the capillary structure.
Expediently it can be provided that the annular channel has respectively one inlet-side and/or outlet-side annular beading. The inlet-side annular beading can serve as a distribution box whilst the outlet-side annular beading can serve as a collecting box.
The solution according to the invention consists in particular in using corrosion-protected steel such as, for example, stainless steel, zinc-plated, nickel-plated or particularly preferably tin-plated steel (tin sheet) as material for a gas-tight housing wall. Additionally preferred is a cylindrical housing geometry fabricated from longitudinally welded or optionally formed steel tubes. The capillary structure is preferably made of optionally tin-plated copper strip as phase change structure for condensation, capillary binding of condensed working medium, preferably methanol and re-evaporation of the condensate, wherein closed corrugated fin annular packages are provided for soldering to the inner wall of the corrosion-protected housing. In a first embodiment of the sorption heat transfer module according to the invention, the application of the corrugated fin packages is provided here in such a manner that the tips of these corrugated fin packages are soldered to an internal surface of the inner wall. In a particularly preferred second embodiment of the sorption heat transfer module according to the invention, the application of the corrugated fin packages is additionally provided in such a manner that the front faces of the corrugated fin packages are soldered to the internal surface of the inner wall.
Accordingly, in a production process firstly a soft-soldered assembly can be created consisting of a gas-tight cylinder with internally soldered-on capillary structures and externally soldered-on corrugated fins and in a second step this assembly can be completed by an outer wall which with the gas-tight inner wall forms an annular channel through which axial flow can take place so that the inner assembly can be thermally activated by flow with a heat transfer agent.
The term ‘corrugated fins” and fin packages made from these are understood as continuously rollable zig-zag structures made of thin-walled metal strip which can be formed very differently in detail, for example with or without gills.
In a further preferred embodiment of the sorption heat transfer module according to the invention, it is provided that a heat-conducting structure adjoins an external surface of the gas-tight inner wall, which is connected in a firmly bonded manner to the inner wall and which preferably consists of at least one corrugated fin package. This heat-conducting structure appreciably increases the efficiency of the sorption heat transfer module and can be produced in a modular manner similar to the capillary structure. It is preferred here that a thermally insulating layer, preferably a silicone foam mat, is inserted between the heat-conducting structure and the outer wall in order to ensure thermal insulation of the annular channel towards the outside and to minimize the connected thermal mass. A silicone foam mat is specifically available as prefabricated material in different dimensions and is particularly easy to process. Particularly preferably the annular channel has respectively one inlet-side and/or outlet-side annular beading which is used for a homogeneous distribution of the axially directed volume flow of a heat transfer agent in the circumferential direction.
It is particularly advantageous here if the heat-conducting structure is arranged here in the aforesaid annular channel. By this means the heat can be efficiently transferred between the fluidic heat transfer agent flowing in the annular channel and the inner wall.
Advantageous here is a further development in which the heat-conducting structure extends in an annular manner in the annular channel. By this means a large volume of the annular space can be used by the heat-conducting structure which improves the efficiency of the heat transfer.
Another further development additionally or alternatively proposes that the heat-conducting structure extends starting from the inner wall in the annular channel over at least 80%, preferably over at least 90% of a radial channel width of the annular channel. This also improves the utilization of the space present in the annular channel.
The efficiency of the heat transfer between the heat transfer agent and the inner wall can also be improved whereby a thermally insulating layer, preferably a silicone foam mat, is arranged in the annular channel radially between the heat-conducting structure and the outer wall. This reduces any heat transfer between the heat-conducting structure and the outer wall or between heat transfer agent and outer wall.
Particularly advantageous is a further development in which the individual components are matched to one another so that the thermally insulating layer abuts radially inwards against the heat-conducting structure and radially outwards against the outer wall. By this means the space provided in the annular channel is maximally utilized radially by the heat-conducting structure without there being any radial contact between the heat-conducting structure and the outer wall.
The compact design can also be assisted if according to one embodiment, the heat-conducting structure has smaller dimensions in the radial direction than the capillary structure.
In an even further preferred embodiment of the sorption heat transfer module according to the invention, it is provided that tips or front faces of individual corrugated fin packages of the capillary structure and/or heat-conducting structure are connected in a firmly bonded manner to the inner wall and are preferably located opposite the corrugated fin packages of the capillary structure and the heat-conducting structure so that they overlap. The firmly bonded connection of tips or front faces and preferred opposite position of the two structures here ensures a particularly good thermal contact via the inner wall. Preferably the corrugated fin packages of the capillary structure which are connected in a firmly bonded manner on the front side have through-openings in a rolling plane, which allow an axial passage of the working medium between the inner wall and the corrugated fin packages arranged thereon. This results in the advantage that the individual corrugated fin packages can easily be applied and at the same time there is an axially assisted vapour flow with external gas flushing effect. Particularly preferably here at least two of the through openings are arranged between two axially adjacent corrugated fin packages of the capillary structure offset with respect to one another in the circumferential direction in order to enable a flushing transport of undesirable non-condensable external gases in the principal flow direction. Alternatively or additionally at least two of the axially adjacent corrugated fin packages connected in a firmly bonded manner on the front side are arranged offset with respect to one another in the circumferential direction. However, the corrugated fin packages of the capillary structure connected in a firmly bonded manner on the front side can also be arranged axially parallel and spaced apart from one another in the circumferential direction, preferably arranged spaced apart from one another in a contact-free manner, so that wedge-shaped axial flow channels are formed between the individual corrugated fin packages. As a result of the contact-free arrangement, a capillary contact between individual corrugated fin packages is avoided, whilst at the same time a tight occupancy of the phase change zone is ensured and furthermore, external gases can be flushed out in an axially parallel manner and can accumulate in a passive axial end region of the phase change structure.
In yet another preferred embodiment of the sorption heat transfer module according to the invention, it is provided that individual corrugated fin packages of the capillary structure are arranged spaced apart from one another in the circumferential direction and axial direction on the gastight inner wall, preferably at an axial distance between 1 mm and 4 mm, particularly preferably at an axial distance between 2 mm and 3 mm. Specifically with the choice of these distances, in practice displacement effects of condensate due to gravity and accelerations can be avoided and a particularly high flushing capacity for external gases of the sorption heat transfer module can be established without adversely affecting its efficiency.
In yet another preferred embodiment of the sorption heat transfer module according to the invention, it is provided that the corrugated fin packages of the capillary structure have a fin density between 200 Ri/dm and 400 Ri/dm, and/or a width of the corrugated fin packages of the capillary structure lies between 10 mm and 30 mm, preferably between 15 mm and 25 mm. With the choice of these dimensions, in practice a particularly high efficiency of the sorption heat transfer module can be demonstrated.
In yet another preferred embodiment of the sorption heat transfer module according to the invention, it is provided that the gas-tight inner wall is made of a corrosion-protected steel material, in particular a zinc-plated, nickel-plated or tin-plated steel, and/or the capillary structure and/or the heat-conducting structure is made of a copper material, in particular a tin-plated copper strip, which is preferably soft soldered to the gas-tight inner wall and the working medium is an alcoholic fluid, in particular methanol or ethanol. The said combination of materials is due to the alcoholic working media such as methanol or ethanol. If water is used as working medium, aluminium-based materials can also be used. However, the preferred materials have the advantage that these can be soft-soldered cost-effectively.
In yet another preferred embodiment of the sorption heat transfer module according to the invention, it is provided that the thermally activatable housing is designed to be cylindrical and is preferably made of longitudinally welded, particularly preferably formed steel tubes. A cylindrical design has a high differential compressive strength and merely requires forming steps which can be implemented cost-effectively.
In yet another preferred embodiment of the sorption heat transfer module according to the invention, it is provided that the thermally activatable housing has a dividing wall provided with at least one through opening which extends between the capillary structure and the sorption zone. The dividing wall is used here for thermal separation of the two different temperature-controlled zones of the sorption heat transfer module, wherein transport of the vaporous working medium between the zones takes place via the at least one through opening.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the relevant description of the figures with reference to the drawings.
It is understood that the features mentioned previously and to be explained further hereinafter can be used not only in the respectively given combination but also in other combinations or alone without departing from the scope of the present invention.
A preferred exemplary embodiment of the invention is shown in the drawings and will be explained in detail in the following description, wherein the same reference numbers relate to the same or similar or functionally the same components.
In the figures, in each case schematically:
In this first embodiment as a phase change structure, an annular corrugated fin package 5 rolled from tin-plated copper strip is applied by soft soldering with good thermal contact to the internal surface of a gas-tight inner wall 4 which here consists of tin plate. This corrugated fin package 5 here represents a capillary structure 18. The width of the at least one annular corrugated fin package 5 is dimensioned so that with a preferred fin density between 200 Ri/dm and 400 Ri/dm, the capillary force is sufficient to hold condensed working medium in a fixed position against gravity and optionally predictable acceleration forces. The width of a corrugated fin package 5 lies between 10 mm and 30 mm, preferably between 15 mm and 25 mm.
The housing 2 also comprises an outer wall 6 which together with the gas-tight inner wall 4 forms an annular channel 7 which has a fluidic, i.e. liquid and/or gaseous heat transfer agent flowing through it in the axial direction. In order to increase the thermal conductivity, a heat-conducting structure 19 in the form of another corrugated fin package 8 is provided, which is soft-soldered to the inner wall 4. For thermal insulation the outer wall 6 is separated from the heat-conducting structure 19 by an insulating layer 9.
In the axial direction of this inner wall 4, which is designed to be cylindrical here merely as an example, a plurality of such annular closed corrugated fin packages 5 are arranged axially at a distance from one another in such a manner that no capillary bridges are formed between the annular packages 5. This is achieved by axial spacings between 1 and 4 mm. Particularly preferred spacings lie in the range between 2 mm and 3 mm.
It can be further deduced from
The entire gas chamber between the central sorption zone 3 operated at higher temperature levels and the external phase change zone which can be activated via the temperature-controllable inner wall 4′ is here divided into two partial chambers by another cylindrical dividing wall 16. This dividing wall 16 is provided with a through opening 15, via which the vaporous working medium is transported between the two zones. The intermediate cylinder is used for thermal separation of the two differently temperature-controlled zones of the sorption heat transfer module 1′. The annular channel 7′ has respectively one inlet-side and one outlet-side annular beading 10, which is used for a homogeneous distribution of the axially directed volume flow in the circumferential direction.
Preferably the corrugated fin packages 5″ which are soldered on annularly on the inside have spaced-apart openings in the circumferential direction which enable a small axially parallel gas transport. These serve the purpose that non-condensable external gases which accumulate there are flushed away in the axially parallel direction and can accumulate in an axial end region in order to be sucked away there in concentrated form as required according to the prior art.
The lower half of
The through openings 13, 13′ for axial gas transport serve the purpose that non-condensable gases accumulating between the corrugated fin packages 5″ cannot accumulate there in harmful concentration but are transported following the principal direction of flow in the direction of that axial end of the housing 2″ which has a displacement chamber and/or a blow-off or extraction opening through which these harmful gases can be removed from the housing 2″ as required.
The structure applied to the outside of the gas-tight inner wall 4″ to improve the heat transfer on the heat transfer agent side can be designed in a similar manner to the first embodiment of
According to the depicted fundamental embodiments of a front-side or tip-side application of the corrugated fin packages 5 . . . 5′″, the thermally activatable housing implemented according to the invention affords manifold advantages compared to known solutions. Thus, the very high attainable heat transfer coefficient between fluid temperature and saturated vapour temperature of the working medium only requires very small driving temperature differences for the removal of condensation heat and supply of evaporation heat and thereby increases the efficiency and the power density of the sorption heat transfer module. In addition, the optionally tin-plated semi-finished product materials such as for example tin plate for the gas-tight inner wall and optionally tin-plated copper strip for fabricating the phase change structure in the form of corrugated fin packages having a high fin density and thus attainable capillary condensate retaining function and the surface-enlarging fin system of the annular channel for fluidic flow enable a very cost-effective and thermally very good conducting joining process of the three required structure components. In particular, the particularly preferred second embodiment of a sorption heat transfer module according to the invention in
The axial flow through the housing 2 . . . 2′″ is however not necessarily advantageous. The material combination based on steel materials is due to the favoured alcohol working media (methanol, ethanol). When using water as working medium, aluminium-based materials can also be used but these cannot be soft-soldered cost-effectively. In general purely cylindrical designs can also be avoided but these have a lower differential compressive strength and require more complex forming methods and/or thicker wall thicknesses such as, for example, internal high-pressure forming.
Number | Date | Country | Kind |
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102017215617.1 | Sep 2017 | DE | national |
102018212820.0 | Aug 2018 | DE | national |