NL8700261A - STACK OF HEAT EXCHANGE PLATES. - Google Patents

Description

* N034193 ι

Stack of heat exchange plates.

Description

The invention relates to a stack of plates of plastic, which are suitable as an accumulator material for the heat transfer between gas flows in heat exchangers. The basis of the invention is a simplified method for manufacturing the Tasable plates together and for joining them into a stack of plates.

International patent application WO 83/02997 discloses a storage material of plastic which, in particular for reheating the gases discharged from a boiler 10 removed from a boiler in a wet cleaning step, by heat transfer of the gases to the device for the addition of uncleaned gases discharged from the boiler is suitable for wet cleaning. A number of stacks of plates are placed in a rotor, which protrudes into two flue gas flows in such a way that the separate stacks of plates are alternately guided through the two flue gas flows during rotation. They absorb heat from the hotter flue gas flow and give it back to the colder flue gas flow. A cleaning liquid, in particular water, flows through the stacks of plates between the passages through the flue gas flows to remove the solids deposited from the flue gas on the surface of the plates. The stacks of plates are alternately exposed to high temperature stress and the corrosive effect of the flue gases as well as the mechanical stress due to the cleaning fluid flowing in at high speed and its corrosive effect. Polyphenylene oxide is mentioned as material which can withstand this load.

In order to manufacture the stack of plates serving as a heat accumulator in a cheap and simple manner, it is proposed to ultrasonically weld flat plates of plastic with spacers placed between them. In this method, the spacers must be laid separately on each plate surface. In order to avoid this operation, it has further been proposed to form the spacing profiles as partial areas of the plate-shaped accumulator elements. This requires an additional operation. Furthermore, the plate surface on each of the spacers formed is interrupted by a corresponding bulge. This embodiment has several drawbacks. For example, the mechanical strength of the plate surfaces is reduced by the interruptions. The spacers formed by deforming part of the sheet surfaces are necessarily thinner than the sheet material and internally hollow. Therefore, they 8700261 2-22 have only limited strength. When stacking equal plate elements, there is a further drawback that the formed spacers of one plate always engage in the hollow back of the spacers of the next plate, so that the conditions for welding in this place are unfavorable. If the spacers are arranged in separate planes offset from each other, then a lower strength of the entire stack of plates is obtained, than when all corresponding spacers lie one above the other in a continuous column.

The object of the invention is to avoid the above-mentioned drawbacks. In particular, the production of the mutually tangible plate elements used for the construction of the stack of plates must be simplified and the use of spacers manufactured separately must be avoided. Furthermore, the aim is to reduce the number of work operations when the individual plate elements are joined together into stacks of plates welded together.

These objects are achieved according to the invention in that the stack of plates is built up from a number of plates of thermoplastic, Tasbare plastic, with a number of projections connected in one piece with the plate bodies. The separate plates are placed in the stack of plates parallel to each other and the top ends of the protrusions are welded to the face of the adjacent plate. The protrusions are distributed in the unbroken plate surfaces.

Figures 1 to 12 serve for further explanation.

Figure 1 shows a cross section of a plate element with projections mounted thereon.

Figures 2 to 4 show perspective views of various embodiments of plate elements.

Figure 5 shows how a plurality of plate surfaces with a rectified flow pattern are assembled into a DC heat exchanger.

Figure 5 shows the cross-shifted arrangement of two plate elements to form a cross-flow heat exchanger.

Figures 7 to 9 show cross sections through different embodiments of the protrusions, each of which is adapted to different shaft processes.

Figure 10 shows a cross-section through a finished 1 axle joint.

Figure 11 shows a cut section of a cross section through a finished stack of plates.

Figure 12 schematically shows a device for manufacturing 8700261 3 the plate elements according to the invention.

Characteristic of the plates, from which the stack of plates is composed, is a continuous plate body 1, which is not interrupted at the location where the protrusions are located and wherein the side opposite the protrusions has at most a flat recess 3.

Although it is possible to provide projections on both plate sides in connection with joining other plates, it is preferred that all projections provided for connection to other plates are provided on one side of the plate in each case. In order to arrange the plates in the stack of plates parallel to each other, it is expedient that all protrusions serving for the 1-axis connection have the same height h. Apart from protrusions serving for welding, further protrusions with a smaller height may be present on one or both sides of the plates, which serve, for example, for the flow conduction or to make the flowing gases swirl. In the following, "protrusions" are understood to mean protrusions serving only for welding to adjacent plates.

These protrusions are conveniently spaced from 20 to 200 mil-20 meters apart. It is advantageous, both for manufacture and to increase strength, that the projections at the base, where they rest on the actual sheet bodies, have a larger diameter than at the tip. They preferably have a wedge-shaped cross-section which merges arcuately into the surface of the plate body. This transition preferably has a radius of curvature r of at least 1, preferably 2 to 10 millimeters.

If spot welds are sufficient, the plates - as shown in Figure 2 - can have separate protrusions in the form of obtuse pyramids or cones 4. This embodiment has a particularly low flow resistance. It may be expedient to provide a projection in the edge area, which is designed as a continuous dam 5, with which the stack of plates can be sealed laterally. The projections can also be designed in the form of shorter or longer sheet pieces 6 in accordance with Figure 3. In a flow view it is advantageous if the dams run parallel to each other and are pointed or rounded at the ends in a flow-favorable manner. Corrugated dams 7 or dams 8 40 of periodically varying diameter can serve to generate a strong swirl in the flow in the same or preferably opposite direction. Swirling promotes heat transfer 8700261 4 and inhibits dust deposition. The highest strength of the plate tape is achieved with dams continuing along the entire plate length 9.

The plate body generally has a thickness of 0.5 to 3 ran. Regardless of the protrusions and the transition region at their base, the sheet body preferably has a uniform thickness with, of course, manufacturing-dependent deviations. If, exceptionally, this is not the case, then the plate thickness in the thinnest places is taken as the basis for the following dimensions. The invention makes it possible to provide protrusions that are higher than the sheet thickness. Their height h is preferably more than double, in particular 2 to 10 times the plate thickness. For example, the protrusions have a height of 1 to 10, preferably 3 to 6 ran.

The invention further makes it possible to provide protrusions with a considerable thickness. The diameter d at half the height of the protrusions is generally larger than the plate thickness and is, for example, 1.5 to 3 times the plate thickness.

The optimal shape of the head of the protrusions is directed to the 1 axis method. A pointed head 10 according to Figure 7 is advantageous for ultrasonic welding. The angle of the striker alpha is preferably between 70 and 110 degrees. On a dam-shaped projection, the head has the shape of a continuous cutting edge.

For the friction welding method, a rounded head 11 according to Figure 8 is better suited.

It is particularly advantageous if the friction welding connection is provided between the head 11 and a flat cavity 3 in the surface 2 to be joined. Since, as a rule, the same plates are welded together into a stack, a head 11 of a projection of one plate always comes onto the back of the base surface of the corresponding projection of the next plate. In this place, as a rule, there is a flat cavity. This cavity automatically forms when the bottom side 12 of the plate runs over a conventional cooling roll or smoothing roll without recesses and the projection has a considerable height and / or thickness. In this case, a flat cavity 3 is created by thermal vibration during cooling.

When the projections consist of the dams 13, which run from one side of the plate to the opposite side, the 1-axis method with a heating wire can be used. For that purpose, the heating wire 14 is inserted into the head of the projection 13.

The stack of plates according to the invention or the plates used for the construction thereof 870 025 1 5 consist of thermoplastic, Tasbare synthetic material. The plastic must be able to be processed by extrusion and, when heated to the melting temperature, optionally under a low pressure, be welded such that after cooling there is a connection provided by the material. For the rest, the material properties of the plastic depend on the application conditions. For the heat exchange with air at temperatures in the range between minus 20 and 80 ° C, a number of thermoplastic plastics that are technically suitable for this purpose can be used, such as poly-10 vinyl chloride, polystyrene, acrylic glass or polycarbonate. For the preferred application in flue gas cleaning plants, plastics with a hot deformation resistance above 12 ° C are used, for example polyphenylene oxide, polyether sulfone or polyetherimide. Polyphenylene oxide is preferred.

15 Manufacture of the plate elements.

It is essential for the economical manufacture of the new plates that they can be produced in one operation. The installation schematically shown in Figure 12 is suitable for this purpose. A plasticized molding compound is fed from an extruder 20 into the crevice nozzle 21 and extruded as a flat web 22 therefrom. The still plastic web is led in the cal formed by the rollers 23 and 24 otherwise. The extrusion speed and the rotational speed of the calender rollers are coordinated in such a way that a thickening 25 consisting of the molten pre-mass is formed in front of the cal, otherwise. At least one calender roll 23 has in its surface a number of recesses 26 for forming the protrusions in the extruded plate. Under the mass pressure prevailing in cal differently, the plastic molding material is pressed into the recesses 26, whereby projections 2 are formed. A conical shape of the recesses 26 and the shaped protrusions 2 facilitates their de-molding. The calender rolls are cooled to below the melting temperature of the plastic, so that the protrusions 2 retain the shape assumed in the recesses 26 after taking them out of the mold. Coolant elements 27 serve to cool the calender rollers 23, 24, through which coolant flows in a manner known per se, through the hollow shafts of the rollers.

To form the conical projections 4, the surface of the roller 23 is provided with corresponding conical recesses 26. Edge dams 5 can be manufactured with an annular slot 40 circumferentially cut. Similarly, recesses 26b 87 0 o 2β? τ 6 formation of sheet-like projections 6, 7 in the surface of the roller. A continuous dam 5, 9 may be equipped either with a circumferential annular slot or with a slot cut in the surface parallel to the axis. In the first case, an endless dam is created in the extrusion direction, while in the second case a dam is created transversely to the extrusion direction over the entire sheet width. In both cases, a heating wire 14 can be incorporated in the head of the projection by inserting a heating wire into the slot of the calender roll before entering the roll gap, which should, if possible, be located on the base of the slot and possibly is held there by magnets. When the slot is filled with the molding compound, the heating wire is embedded therein.

The material 15 necessary for filling the recesses is taken from the bead 25, which must be of sufficient size for this purpose. When manufacturing dams in the top direction of the extruded sheet, it is advantageous to make the strand 22 slightly thicker at the places where a dam is to be formed, by correspondingly widening the exit slot of the nozzle 21, to continuously provide the amount of material necessary to form the dam. The continuously produced protruding web is divided into separate plates as required in a manner known per se.

The stack of plates.

A stack of plates according to the invention is shown in cross-section in figure 11. A number of plate elements (31a, 31b, 31c ...) with protrusions are arranged parallel to each other, the upper ends of the protrusions being welded to the bottom of the next higher plate. A typical cross section 30 through a welded joint is shown in Figure 10. The molding compound applied during welding in the molten state has formed a bead 15 which connects the head of the projection to the plane of the next sheet through the material. Preferably, all the separate plates 31a, 31b, 31c ... are the same size and welded together so that corresponding edges are always in one plane. The base of the stack of plates is usually rectangular. When each plate of the stack on two opposite edges each has a continuous edge dam 5, the entire stack of plates on this side is closed to the flowing medium.

40 The size of the individual plates depends on the intended 87 0 0 2 6 1 7 application and is practically limited only by the width of the extrusion nozzle. Therefore, the width is generally between 0.1 and 2 m and the length in the extrusion direction is between 0.1 and 10 m. The stack of plates may, for example, have a height of 0.1 and 2 mm, which corresponds to a number of 10 to 200 separate plates arranged one above the other. When determining the dimensions of a number of plates necessary for a given stack height, it must be taken into account that the height of the protrusions may decrease by approximately one millimeter during welding.

When welding by the ultrasonic method, high-frequency vibration energy is applied under pressure to the contact site between the tip of a projection and a smooth plate back. With a suitable shape of the vibration transducer, an entire line of spindle axis locations or a line-shaped weld seam can be produced along a continuous dam in a single pass. By placing the 1 axis device further line by line, all projections in a plate plane can be welded step-by-step to the next plate. In this way a stack of plates can be increased layer by layer with one layer of plates each time.

In the frictional welding process, an entire plate is vibrated parallel to its base, whereby all protrusions are simultaneously melted by the frictional heat that occurs and are welded to the back of the adjacent plate surface. Therefore, this method is considerably faster than the ultrasonic welding method. An even higher working speed is possible with the hot wire welding method, wherein the heating wires 14 embedded in the tip of the continuous dam 13 in accordance with Figure 9 are heated by applying a precisely metered electric voltage, the tips of the protrusion and the abutting face of the next plate are simultaneously melted and welded together. In this method, a complete stack of plates can be welded in one pass when all heating wires are connected to the heating voltage at the same time. Also in this method, separate plates are held together with light pressure until completing the 1 axis process.

The stack of plates of direct current construction manufactured according to the invention is used, for example, as a heat accumulation material in heat exchangers of waste gas cleaning installations. Other applications are air-conditioning systems for buildings, greenhouses, stables and the like, which can be heated or cooled as required. The heat exchange between fresh air flowing in and exhaust air flowing out is carried out. In addition to the regenerator principle in which the stack of plates alternately absorbs and gives off heat, the recuperator principle can also be used, in which the heat-exchanging flows flow equally through alternating layers of the stack of plates; the cross-flow recuperators built up according to figure 6 are particularly suitable for this purpose. Although the heat exchange between air and flue gases is also the most important, such heat exchangers can also be used for other gaseous or liquid media, such as for instance water.

870 02a 1

Claims (27)

1. Stack of plates, consisting of a number of plates of thermoplastic, Tasbare plastic, with a number of protrusions connected in one piece with the plate body, which are arranged distributed in the continuous plate surface, the plate surfaces in the pile of plates being parallel to each other and the upper ends of the protrusions are welded to the face of the adjacent plate. 2. Stacking plates according to claim 1, characterized in that all protrusions of each separate plate are arranged on one side of the plate. Stacking plates according to claims 1 or 2, characterized in that many or all protrusions of each separate plate have the same height. Stacking plates according to claims 1 to 3, characterized in that the protrusions of each separate plate have mutual distances of 20 to 200 mm. Stacking plates according to claims 1 to 4, characterized in that the protrusions at the base have a larger diameter than at the tip. Stack of plates according to claim 5, characterized in that the protrusions have a wedge-shaped cross section. Stack of plates according to claims 5 or 6, characterized in that the plate surfaces transition into the surface of the protrusions with a radius of curvature of at least 1, preferably 2, 25 to 10 mm. Stack of plates according to claims 1 to 7, characterized in that the plates have flat recesses where the protrusions are welded to an adjacent plate. 9. Stacking plates according to claims 1 to 8, characterized in that the protrusions have a height of more than double, in particular 2 to 10 times the thickness of the plate. Stack of plates according to claim 9, characterized in that the protrusions are 1 to 10 mm high. Stack of plates according to claim 10, characterized in that the protrusions are 3 to 6 mm high. Stack of plates according to claims 1 to 11, characterized in that the protrusions at half height have a diameter greater than the plate thickness. Stack of plates according to claim 12, characterized in that the diameter of the protrusions at half height is 1.5 to 3 times the thickness of 8700261 V the plate thickness. Stacking plates according to claims 1 to 13, characterized in that the protrusions have an approximately square or circular base and the shape of pyramids or cones. Stack of plates according to claims 1 to 14, characterized in that the protrusions are in the form of approximately parallel arranged dams. Stack of plates according to claim 15, characterized in that the dams in the longitudinal direction have a periodically varying diameter. Stack of plates according to claim 15, characterized in that the dams are corrugated in the longitudinal direction. Stacking plates according to claims 15 to 17, characterized in that the dams have distances of 20 to 250 mm. 19. Stacking plates according to claims 15 to 18, characterized in that the dams are advantageously pointed or rounded at least on a front side in flow view. Stack of plates according to claims 15 to 19, with the dams continuing over the entire plate length. Stack of plates according to claim 20, characterized in that the dams have a heating wire on the weld with the neighboring plate. Stack of plates according to claims 1 to 21 consisting of a plastic with a resistance to hot forming above 150eC. Stack of plates according to claim 22 consisting of polyphenylene-25 oxide, polyether sulfone or polyetherimide. Stack of plates according to claim 23, characterized in that it is composed of equally large separate plates, the corresponding sides of which lie in one plane. 25. Stack of plates according to claim 24, characterized in that each plate located in the stack has a continuous edge dam on two opposite edges. Stack of plates according to claim 25, characterized in that the edge dams of all separate plates are arranged in the same direction. Stack of plates according to claim 25, characterized in that the edge-dams of successive plates each run at right angles to one another. 870 026 1