WO1999010694A2 - Method for producing a heat exchanger - Google Patents

Abstract

Method for producing a heat exchanger (WT) for recovering heat energy during air exchange in housing or office space. Said heat exchanger contains a stack-like arrangement of equal, narrow air chambers which are constructed by spacers (A, B) and a metal foil (F) laid around said spacers. Said method comprises the following steps: (a) application of a heated, liquefied thermoplastic corresponding to the shape of the spacers (A, B) directly onto the foil (F); (b) folding the foil (F) along an exterior longitudinal edge of the spacer (A1, B1) over the constructed coating; (c) pressing the foil (F) on said constructed coating; (d) application of another coating with spacers (A, B) arranged in a laterally reversed manner to the previous layer; (e) repetition of the folding and coating steps with spacers (A, B) arranged in alternating positions until the final stack height is obtained.

Description

 Process for manufacturing a heat exchanger

The present invention relates to a method for producing a heat exchanger according to the preamble of claim 1.

For example, from European Patent Application 0 040 890 a heat exchanger is known which consists of spacers stacked on top of one another and a film which winds in a zigzag pattern around the individual spacers, the film separating the individual spacers from one another by a film layer.

This type is shown in Figure 1. The heat exchanger according to FIG. 1 has a stack of many narrow air chambers. These are each formed by two layers of a zigzag-shaped folded film (F), in the folds of which spacers A, B are inserted according to FIG. 2 for the lateral limitation of the air chambers. The spacers A, B consist of a U-shaped spacer AI, Bl and a straight spacer A2, B2. These together form the edges of a rectangle, which has a gap to the spacer AI, Bl at both ends of the spacer A2, B2. These gaps each form two openings a, b at the ends of a long side of the respective air chamber when the spacer is inserted into the film. The openings a, b of the odd-numbered air chamber units of the stack are all on one long side, and those of the even-numbered air chamber units are on the opposite long side.

Figure 3 shows an overall arrangement of the heat exchanger device. The heat exchanger stack is located in a housing G. The housing G has an inlet opening with a pollen filter 18 and an outlet opening. Electronics E is also provided, which is accommodated in the housing G. Small fan motors 15 are arranged in front of the openings a, b of the heat exchanger stack.

The fan motors force air flows through the chambers. The streams of some Side, then flow along the chamber walls of the air chambers on the other side, in which air flows move in the opposite direction

Since the chamber walls are made of thin metal foil (e.g. 12 μm), there is very good heat coupling between the chambers on two sides, with the exception of the first and last chamber, which each have only one neighboring chamber. The height of the air chamber is determined by the height of the spacers A, B. The smaller their thickness, the more air chambers can be formed for a certain stack height.

The heat exchanger described can be operated highly efficiently in countercurrent and can therefore be used in particular to recover the thermal energy which is contained in used room air and escapes when ventilated outdoors.

In order to achieve the highest possible heat exchanger capacity, it is necessary to keep the distance between the individual film layers as small as possible and thus to keep the height of the spacers as low as possible. At the same time, the tightness of the air chambers formed by the spacers and the film layers must be ensured, particularly since the air resistance in the heat exchanger increases because of the narrowing of the flow cross section.

Due to the difficult handling of the thin spacers, the low tear strength of the film and the increasing demands on the tightness of the heat exchanger, these requirements can no longer be met by simply stacking them together and possibly gluing the spacers to the film.

It is therefore the task of creating a manufacturing method for such a heat exchanger in such a way that a precise and fast manufacture is made possible.

The object is achieved with the features of claim 1. Advantageous Refinements can be found in the subclaims. The method is described below using exemplary embodiments. The figures show:

Fig. 4 flow in the inlet / outlet area of the heat exchanger

Fig. 5 cross section through the heat exchanger in the inlet / outlet area of the heat exchanger

The heat exchanger described is manufactured as follows:

On a rectangular base plate, which has a stabilizing and protective function, spacers of arrangement A or B are alternately placed on top of one another and welded point by point, whereby after each spacer A, B the metal foil F around the long, closed side of the U-shaped spacer AI or Bl is folded and comes to rest between the spacers A and B, or between B and A. The film should be wrapped tightly so that the air chambers are as uniform as possible across the entire width of the stack.

The winding process is repeated as often as necessary up to the intended stack height and is completed with a further rectangular plate, the film F being cut off before this end plate is applied.

For additional stabilization, the finished stack can be wrapped with a suitable adhesive tape next to the openings. The respective air chambers are clearly and reliably separated from each other by the winding method, so that no losses occur due to leaks. Aluminum foil is preferably used as the foil material. The spacer frames can be punched out of plastic film tapes, preferably from recycling material.

Instead of the manufacturing method described using punched or cut spacers, other methods are also conceivable: Using a controllable heating device mounted on a positioning unit in 3 axes, thermoplastics are sprayed directly onto the film layer as a thin and uniform material application in the arrangement forms A and B. After coating, the unit moves into a temporary resting position so that the film roll can be tilted onto the opposite shelf. The film F is folded over the coating just created. A press plate then presses the film firmly onto the still sticky coating. The plate is removed and the next coating can begin, now with the mirror-image arrangement of spacers to the previous position etc. until the final stack height is reached. The stack is also started here with a rectangular base plate made of plastic and completed with a similar one.

Instead of using thermoplastic material, a suspension of multicomponent thermosets and a suitable filler material can also be used, the suspension being adjusted so that it does not flow away. Hardening takes place very slowly at normal temperature. It can be accelerated by heating the controllable injection unit or by heating the finished heat exchanger stack in the furnace. The manufacturing procedure for the stack is analogous to alternative 1.

Another manufacturing method comes from the powder sintering method. Here, a uniformly high layer of thermoplastic powder is spread onto the respective film layer, then the powder is irradiated using a highly concentrated heat source (eg laser beam) in a raster process according to the arrangement A or B, so that the powder melts at these points and becomes intimately associated with the film F. connects. When the entire layer has been scanned, the non-liquefied powder is sucked off again. The film is folded as for I and II.

Production method III can be combined with version II in such a way that a suspension according to II is applied and immediately thereafter with a concentrated heat source, for example a laser beam, is heated with the aid of a deflection system and thus experiences faster curing.

Another type of production of the heat exchanger stack can be carried out using the screen printing method. In this case, by means of two screen printing rollers, a paste-like suspension of heat-hardening components, provided with suitable filling materials, is applied to the film which runs endlessly between the rollers. A matching folding mechanism causes the film, which is coated with the paste on each side, to bend at the right place, so that a Z-Z fold is created. With the help of appropriately shaped pressure frames or plates, the film sections are lightly pressed from the uncoated side onto the stack growing in this way. When the specified stack height is reached, the film is separated on a folded edge, the finished stack is covered with a cover plate, the stack is transported further to a hardening furnace and the next stack is restarted by inserting a base plate.

FIG. 4 shows the flow conditions in a heat exchanger according to FIG. 1 in its inlet / outlet area. The air flows according to the flow lines L from the inlet opening a in a semicircular flow into the fuselage W of the heat exchanger. At the same time, the air of the counterflow flows along the flow lines L 'in the heat exchanger chamber underneath from the fuselage W of the heat exchanger in a semicircular flow out of the outlet opening b.

While the heat exchanger operates over its predominant length as a counterflow heat exchanger, there is rather a crossflow in the inlet / outlet area according to FIG. 3, since the flows are deflected here by an angle of 90 °. Cross-flow heat exchangers have poorer efficiencies than counter-flow heat exchangers. The efficiency of the heat exchanger is therefore impaired in the deflection area. The loss that occurs in this area can no longer be compensated. In order to increase the efficiency of the heat exchanger, it is therefore advantageous to completely exclude the heat exchanger's inlet / outlet area from the heat transfer. For this purpose, the area on the film F, which forms the inflow / outflow area of the heat exchanger, is covered on at least one side of the film F with a heat insulator.

This is advantageously applied before the film is folded. The insulator can be a plastic film, for example, which is applied to one side or to both sides of the metal film. Self-adhesive film can be useful for the production. A coating of the metal foil with paint or the like is also possible for thermal insulation.

With a heat exchanger, the flow resistance increases with decreasing height of the air chambers. In order to reduce the flow resistance to an acceptable level, the heat exchanger therefore advantageously has the cross section shown in FIG. 5 in the inflow / outflow area.

Accordingly, the solid lines, the film F runs here zigzag-fb ^'RMIG with sharp, acute-angled creases at folded edges. The individual film layers connect the folded edges opposite one another in a substantially straight line. In cross-section, a stack of alternately stacked acute angles is formed, so that the longitudinal edges 11 of the inlet / outlet openings a, b are flattened at an acute angle.

In the fuselage W of the heat exchanger, the foil layers of foil F run parallel to one another in accordance with the dashed lines. The sharp crease is no longer available here.

With this arrangement, the inlet / outlet openings a, b and the deflection region causing the resistance are made more aerodynamically efficient. This allows the same stack height and slot width reduce the flow resistance to almost half.

In use, the heat exchanger stack is used in semi or fully automatic ventilation devices to largely avoid thermal energy losses when exchanging air, for example in living rooms and at workplaces. However, such a device does not only have a positive effect during the cold seasons, but also in summer, living rooms and work rooms can be kept cool for a long time, provided the outer walls and windows are designed for low thermal conductivities and sufficient cooling is possible at night.

Claims

claims 1.Procedure for the production of a heat exchanger (WT) for the recovery of thermal energy during air exchange in living / working rooms, with a stacked arrangement of a large number of similar, narrow air chambers, which consist of spacers (A, B) and a metal foil wrapped around the spacers ( F) are formed with the following process steps: (a) applying a heated, liquefied thermoplastic according to the shape of the spacers (A, B) directly on the film (F); (b) folding the film (F) over the created coating along an outer longitudinal edge of the spacers (AI, Bl); (c) pressing the film (F) onto the coating just created; (d) applying the next coating with a mirror-image arrangement of the spacers (A, B) to the previous layer; (e) Repeating the folding and coating steps with alternating layers of the spacers (A, B) up to the final stack height. 2.Procedure for the production of a heat exchanger (WT) for the recovery of thermal energy during air exchange in living / working spaces, with a stacked arrangement of a large number of similar, narrow air chambers, which consist of spacers (A, B) and a metal foil wrapped around the spacers ( F) are formed with the following process steps: (f) applying a pulpy suspension of thermosetting components mixed with suitable filler material directly to the film (F) according to the shape of the spacers (A, B); (g) folding the film (F) over the created coating along an outer Long edge of the spacers (AI, Bl); (h) pressing the film (F) onto the coating just created; (i) Applying the next coating with a mirror image arrangement of the Spacers (A, B) to the previous layer; (j) repeating the folding and coating steps with alternating layers of Spacers (A, B) up to the final stack height. 3. The method according to claim 2, characterized by the step (k) Accelerate the curing of the thermoset by heating the heat exchanger (WT). 4. The method according to claim 3, characterized in that the heating of the heat exchanger (WT) is carried out by means of a laser beam. 5.Procedure for the production of a heat exchanger (WT) for the recovery of thermal energy during air exchange in living / working rooms, with a stacked arrangement of a large number of similar, narrow air chambers, which consist of spacers (A, B) and a metal foil wrapped around the spacers ( F) are formed with the following process steps: (1) Apply a powdery thermoplastic according to the shape of the Spacers (A, B) directly on the film (F); (m) Liquefying the applied powder / granular thermoplastic with a Heat source at the points corresponding to the arrangement of the spacers (A, B) (n) suctioning off the thermoplastic powder that is not required (o) folding the film (F) over the created coating along an outer Long edge of the spacers (AI, Bl); (p) pressing the film (F) onto the coating just created; (q) Apply the next coating with a mirror image arrangement of the Spacers (A, B) to the previous layer; (r) Repeating the folding and coating steps with alternating layers of the spacers (A, B) up to the final stack height. 6.Procedure for producing a heat exchanger (WT) for recovering thermal energy during air exchange in living / working rooms, with a stacked arrangement of a large number of similar, narrow air chambers, which consist of spacers (A, B) and a metal foil wrapped around the spacers ( F) are formed with the following process steps: (s) rolling a paste-like suspension consisting of heat-curing components with a suitable filling material by means of a modified screen printing process onto both sides of the endless film (F) alternately in the shapes of the spacers (A or B); (t) folding the film (F) over the created coating along an outer longitudinal edge of the spacers (AI, Bl); (u) and zigzag-shaped folding of the film (F) into a stack. 7.Procedure for the production of a heat exchanger (WT) for the recovery of thermal energy during air exchange in living / working rooms, with a stacked arrangement of a large number of similar, narrow air chambers, which consist of spacers (A, B) and a metal foil wrapped around the spacers ( F) are formed with the following process steps: (v) Apply heated, liquefied wax according to the shape of the Spacers (A, B) directly on the film; (w) folding the film (F) over the created coating along an outer Long edge of the spacers (AI, Bl); (x) pressing the film (F) onto the coating just created; (y) applying the next coating with a mirror image arrangement of the Spacers (A, B) to the previous layer; (z) repeating the folding and coating steps with alternating layers of Spacers (A, B) up to the final stack height. 8. A method for producing a heat exchanger (WT) for recovering thermal energy during air exchange in residential workrooms, with a stacked arrangement of a large number of similar, narrow air chambers, which are formed from spacers (A, B) and a metal foil (F) wrapped around the spacers with the following process steps: (aa) placing a spacer (A, B) on the film; (bb) folding the film (F) around an outer, closed longitudinal edge of the spacers (A1, B1); (cc) placing another spacer (A, B) in mirror image with respect to the previous spacer (A, B) on the film, the film (F) coming to rest between the two spacers (A, B); (dd) repeating the folding and inserting steps with alternating layers of Spacers (A, B) up to the final stack height. 9. A method for producing a heat exchanger (WT) for recovering thermal energy in the exchange of air from living / working spaces, among others, according to one of the above methods, with a stacked arrangement of a plurality of similar, narrow chambers, which consist of spacers (A, B) and a folded metal foil (F) are formed, characterized in that the area of the foil (F) which forms the inflow / outflow area of the heat exchanger (WT) is covered on at least one side of the foil (F) with a heat insulator. 10. The method according to claim 9, characterized in that the heat insulator is applied to both sides of the film (F). 11. Heat exchanger (WT) for the recovery of thermal energy in the air exchange of living / working spaces, with a stacked arrangement of a plurality of similar, narrow chambers, which consist of spacers (A, B) and one around the spacers beaten metal foil (F) are formed, characterized in that the area of the foil (F) which forms the inflow / outflow area of the heat exchanger (WT) is covered on at least one side of the foil (F) with a heat insulator. 12. Heat exchanger (WT) according to claim 11, characterized in that the Thermal insulator is a plastic film. 13. Heat exchanger (WT) for the recovery of thermal energy when air is exchanged from living / working spaces, with a stacked arrangement of a large number of similar, narrow chambers which are formed from spacers (A, B) and a metal foil (F) wrapped around the spacers , characterized in that the longitudinal edges (11) of the inlet / outlet openings (a, b) are flattened at an acute angle.