Patent Application
20120222847
The invention relates to heat exchangers.
It relates more particularly to exchangers the core of which is produced from a three-dimensional hollow laminated panel, obtained from a three-dimensional weaving comprising two parallel layers linked together by a weaving of orthogonal fibres defining a hollow intercalated space between the two layers. After resin impregnation and curing, each of the layers is transformed into a hardened and impervious skin and the orthogonal fibres, also stiffened, keep these two stiff layers at a uniform distance. A solar panel produced in this way is for example described in EP 0 047 443 A2. Another type of exchanger, which can be used as a cooler, is described in DE 199 21 688 A1. DE 91 07 320 U1 describes an isothermal container produced with such laminated panels.
These laminated panels have a structural feature based on the fact that the orthogonal fibres are not distributed in an isotropic manner over the entirety of the layers, but in parallel rows: the central hollow space between the stiff layers is thus divided into a plurality of flow passages forming parallel channels. The walls defining the channels however have a certain porosity in the transversal direction and therefore between adjacent channels, because of the non-continuous distribution of the orthogonal fibres along the rows.
As with any heat exchanger, an exchanger produced in this way is connected to a fluid inlet and to a fluid outlet making it possible to connect the network of channels to an external circuit, so as to circulate a heat transfer fluid in the assembly, in order to receive heat from or transfer heat to the external environment.
A first possibility, disclosed in particular in EP 0 047 443 A2 mentioned above, consists of providing inlets/outlets for the supply/draw-off of fluid which are substantially based at points arranged at two diagonally opposite angles of the panel. This technique uses the fact that, as explained above, a part of the flow occurs in a subsidiary fashion through the porous walls, leading to a progression of the fluid front combining the flows following the two directions, preferred (in the direction of the channels) and subsidiary (through the porous walls).
Such a configuration for the supply/draw-off of fluid is simple to produce, but it is not always optimal from the point of view of the homogeneity of the circulation of fluid in the panel. Moreover, the efficiency of the circulation is very dependent on the geometry of the panel (more or less elongated in one direction or the other) which therefore very seriously limits the possibilities of its use.
Another possibility, described for example in DE 199 21 688 A1 mentioned above, consists of adding “manifolds” or “header tanks” for the distribution and collection of the fluid at the two ends of the network of channels for the circulation of the heat transfer fluid, as in the case of traditional heat exchangers. These manifolds extend over the entire length of the panel and serve on one side for the distribution of fluid, on the opposite side for its collection.
The circulation of the fluid is of course much more homogeneous than in the previous case, as it does not depend on the flow in the transversal direction between channels, and therefore provides a better heat exchange for the same surface area of panels. It is on the other hand more complex and expensive to implement: the manifolds must be produced separately, attached and assembled onto the panel, with risks to sealing (bonding defect for example). The presence of the manifolds involves moreover an additional space requirement on both sides of the panel, which makes their incorporation more difficult, for example in the form of discrete roof panels, imitating traditional coverings such as slate, corrugated iron, tiles, etc.
One of the purposes of the invention is to resolve all the above problems, by proposing a novel structure for heat exchangers produced from laminated panels.
The exchanger is of the general type disclosed by DE 199 21 688 A1 mentioned above, i.e. an exchanger comprising a network of channels extending between two parallel faces, in order to allow the circulation of a heat transfer fluid in the channels and the heat exchange between this heat transfer fluid and the outside through at least one of the faces. The network of channels is formed by a three-dimensional hollow laminated panel based on fibres hardened by the impregnation of a resin, comprising two two-dimensional woven layers which are impervious and stiff forming the parallel faces, and a stiff weaving of orthogonal fibres, connecting the two layers together by providing a hollow intercalated space by forming rows of parallel walls between them defining the channels. Moreover, the exchanger comprises means for the distribution of fluid, arranged between a fluid inlet and one of the ends of each of the channels of the network, and means for collecting fluid, arranged between a fluid outlet and the opposite end of each of the channels of the network.
In a manner that characterizes the invention, this exchanger does not have attached elements forming manifolds for the distribution of fluid, and the means for the distribution, respectively collection, of fluid are means incorporated into the hollow laminated panel, comprising a longitudinal recess produced in the laminated panel along a longitudinal edge of the latter forming an angle with the direction of the channels, this recess (i) opening onto the inner side of the longitudinal edge on the channels, (ii) being closed on the outer side of this same edge, and (iii) being in fluidic communication with the inlet, respectively outlet of fluid.
In a first embodiment, the recess is defined by a gap reserved between the longitudinal edge of the laminated panel and an outer covering extending over one of the faces of the laminated panel and opening onto the longitudinal edges of the latter.
In a second embodiment, the recess is formed by removing material in a region of one of the faces of the laminated panel along the longitudinal edge of the latter, so as to define a U-section groove directed perpendicularly to the plane of the faces and opening onto the face. The outlet of the U-section groove can in particular be closed by an outer covering of the panel, extending over the face where the recess is formed.
In a third embodiment, the recess is defined by removing material from the sheared edge of the laminated panel along the longitudinal border of the latter, so as to define a U-section groove directed parallel to the plane of the faces and opening towards the outside of the sheared edge. The outlet having a U-section groove can in particular be closed by an edging profile arranged along the sheared edge of the laminated panel.
In all cases, the exchanger is advantageously provided with an insert for guiding fluid and/or creating turbulence, housed in the longitudinal recess, in particular a twisted tape with a helical configuration.
In a specific application, the laminated panel has a non-rectangular shape of a parallelogram, this panel being arranged vertically with the means of distribution and collection of fluid inclined with respect to the horizontal, and with the fluid inlet placed in a low position and the fluid outlet placed in high position, so as to allow a natural circulation of the heat transfer fluid in the exchanger by the thermosiphon effect.
In another application, the exchanger comprises several triangular or trapezoid panels assembled in roof panels, these panels being arranged with the channels oriented in a vertical plane, the recesses forming means for the distribution of fluid and the fluid inlet being situated in the lower part of the panel, and the recesses forming means for the collection of fluid and the fluid outlet being situated in the upper part of the panel and along the crests of the roof, so as to allow a natural circulation of the heat transfer fluid in the panels by the thermosiphon effect.
An example of an embodiment of the invention will now be described, with reference to the attached drawings where the same numerical references denote identical or functionally similar elements in all figures.
a), 5(b) and 5(c) are views of a first embodiment of a heat exchanger according to the invention produced from a panel such as that in
a), 6(b) and 6(c) are similar to the previous ones for a second embodiment of the invention, respectively in plan view, in exploded cross-section before moulding and after machining of the laminated panel, and in cross-section in its final configuration.
a), 7(b1), 7(b2) and 7(c) are similar to the previous ones for a third embodiment, respectively in plan view, in cross-section before machining, in exploded cross-section after machining and before installing the border profiles, and in cross-section in its final configuration.
a), 8(b) and 8(c) are similar to
This laminated panel is obtained from a three-dimensional weaving comprising two parallel layers 10, 12 linked together by a weaving of orthogonal fibres 14 so as to define between these two layers a hollow intercalated space 16.
The product is initially presented in the form of rolls of fabric, which can be cut and shaped to the desired dimensions and configuration. The fibres, generally glass fibres, are then impregnated with a resin (polyester, epoxide, phenolic, etc.) which after curing transforms each of the layers into a hard and impervious skin. The orthogonal fibres, also stiffened, keep these two stiff layers at a uniform distance, externally in the form of a stiff and hollow laminated panel having two parallel faces.
The product is commercially available under the name Parabeam 3D Glass Fabrics from the company Parabeam Industrie-Handelsonderneming B.V., Helmond, Netherlands. Different thicknesses are available from 3 to 22 mm, and the final product obtained has excellent properties in terms of lightness, compressive strength and shear, as well as a low thermal resistance.
This product also has a structural feature based on the fact that the orthogonal fibres 14 are not distributed in an isotropic fashion over the entirety of the layers, but in parallel rows. The weaving of the orthogonal fibres is sufficiently tight along these rows so that the latter define the parallel walls 20 dividing the central hollow space 16 into a plurality of flow passages or parallel channels 18. It should be noted that the orthogonal threads are distributed along these rows in a discontinuous fashion, which results in a certain amount of porosity of the walls 20 in the transversal direction, i.e. between two adjacent flow passages 18.
This panel can be used as a heat exchanger by circulating a heat transfer fluid in the hollow intercalated space. This circulation is shown diagrammatically in
a), 5(b), 5(c), illustrate a first embodiment of the invention.
The invention resides in the way in which the heat transfer fluid arriving via an inlet 26 and leaving via an outlet 28 is distributed within the panel 30.
This embodiment utilizes a mould 32, the width of which is slightly greater than that of the panel 30, the difference being for example of the order of 10 to 20 mm with respect to the overall width of the panel (for a typical width of panel of 0.60 m). The panel 30, the dimensions of which can for example reach 4.50×0.60 m, is sandwiched between an outer skin 34, in particular a black outer skin for a face which will be exposed to solar radiation in the case of a solar collector, and an inner skin 36. The assembly formed by the laminated panel 30 and the inner and outer skins 36, 34 is placed in the mould 32, in the configuration illustrated in exploded view in
The two gaps 38 thus defined are connected, one to a fluid inlet 42, the other to a fluid outlet 44, this inlet and outlet being preferably diagonally opposite in order to allow a flow of fluid in the panel 30 that is as homogeneous as possible.
For a panel 40 used as a solar collector, the panel is mounted with the cold water feed 26 in the lower part and the hot water draw-off 28 in the upper part, so as to allow the hot water to rise by natural convection in the panel mounted vertically (or inclined, with the side of the outlet 28 at the top).
The inlet and outlet 42 and 44 can be produced by simple drilling, equipped with a connection to a pipe, respectively for the supply or draw-off of fluid.
a), 6(b), 6(c), illustrate a second embodiment of the invention.
In this embodiment, the configuration of the different elements is comparable, but the gaps 38 which serve for the distribution and collection of the fluid are produced not by blocking-out a gap at the time of moulding, but by machining the panel 30, as can be seen in particular in the exploded view in
a), 7(b1), 7(b2) and 7(c) illustrate a third embodiment of the invention.
In this embodiment, the recesses 38 are also formed by machining, but this machining is not carried out by the removal of material from one of the faces of the panel, but by the removal of material directly from the sheared edge, over a width slightly less than the total thickness of the panel, so as to leave the two existing parallel faces 10, 12, the removal of material being carried out only in the region of the orthogonal fibres situated between these two parallel faces. In this way a U-section groove is obtained, directed parallel to the plane of the faces and opening towards the outside of the sheared edge of the panel 30. The imperviousness of this groove is obtained on the outer side by a simple border profile 46 attached along the sheared edge of the laminated panel, optionally on the four sides of the panel 30 so as to form a stiff frame for holding and protecting this panel.
a), 8(b) and 8(c) illustrate a variant of the first embodiment in
It is possible to combine or modify several single collectors such as those that have just been described, for example by placing them in series or in parallel, superposition and/or juxtaposition of collectors with several passes in cross flow or counterflow, partial paths in opposite directions, etc., according to techniques which are known per se.
Moreover, although a collector has been described which is produced from a flat panel, this shape is in no way limitative, and the technique implemented makes it possible to very easily obtain very varied shapes: a panel that is curved, corrugated, etc.
In general, the heat exchanger that has just been described is suitable for a very large number of other applications, among which there can be mentioned in a non limitative fashion:
Very advantageously, the panel 30 does not have a rectangular shape, as in the examples disclosed above, but a parallelogram shape, the panel being placed vertically and produced so that the parallel channels, and therefore the main direction of flow of the fluid, extends vertically. The gaps or recesses 38 for the collection and distribution of the fluid are then, due to the parallelogram shape, inclined with respect to the horizontal, the fluid inlet 42 is placed in a low position in the recess or inclined lower gap, and the fluid outlet 44 in a high position of the recess or inclined upper gap. In fact, this configuration will have a tendency to promote a natural circulation of the heat transfer fluid in the exchanger by natural convection and the thermosiphon effect, without the need to provide additional means of pumping. It will then be sufficient to connect the hot water outlet pipe 28 and the cold water inlet pipe 26 to an appropriate exchanger 50 such as a domestic hot water tank or a heat exchanger for the water of a swimming pool in order to obtain a simple, effective and inexpensive heating device.
The heat exchanger 40 thus produced can be for example incorporated in an enclosure element 52 or similar, so as integrate it invisibly into the domestic environment, by giving the visible face of the laminated panel a material effect (imitation wood, etc.) and by adding to it attached pieces 54, 56 making it possible to conceal the parallelogram shape of the actual heat exchanger, and to give the assembly a shape similar to that of an enclosure panel or similar.
The roof has the general shape of a pyramid, produced from heat exchangers 40 produced for example in accordance with the embodiment in
The upper side of the trapezium and its lateral sides (the inclined sides) are also provided with a recess 38, which acts as a collector for the fluid that is heated as it passes through the panel 30. The recess 38 formed on the upper side of the trapezium is provided with apertures 44 in fluidic communication with a hot water outlet pipe 28.
As can be seen in
The assembly thus constituted is completed by a pyramidal ridge element 66 defining a cavity 68 in communication with the apertures 44, for the recovery and collection of the hot water after the latter has passed through the channels of the different panels forming the heat exchangers from bottom to top, by natural convection.
This roof structure can be produced very simply, essentially by bonding and by screwing, therefore at low cost. Moreover, the use of the laminated panels makes this structure extremely light, and it can be simply installed on support pillars 70, without the need to provide reinforcement or additional carpentry items.
Moreover, it is extremely easy to give the visible face a material effect (imitation tiles or slates) so that it can be discretely integrated with the surrounding landscape.
