FR2469684A1 - Heat exchanger for two fluids - has modular construction of stacked flat plastics sheets with interposed partitions to form passages - Google Patents

Abstract

The heat exchanger comprises sets of modules arranged to form the required configuration e.g. cross flow or opposing flow. Each module (1) is in the form of two flat sheets (2,3) of a suitable plastics material, these being separated by partitions (4) fixed between them. The partitions are spaced apart to form passages (5), sealed to isolate the fluids passing through them. The complete modules are assembled by stacking one on the other to provide the required effect and heat transfer capacity. The modular construction provides an increased efficiency for reduced weight and requires less space.

Description

 Heat exchanger.

 The present invention relates generally to heat exchangers.

These devices are intended, in a manner well known per se, to achieve a heat exchange between two fluids separated from each other by a wall 8 through which this heat exchange occurs.

 It is known that the efficiency of a heat exchanger depends, to a large extent, on the exchange surface and on the fractionation of the fluid streams, no tan. ment in the gas phase.

 Consequently, in heat exchangers, attempts have been made to increase the exchange surface and the fractionation of the veins of fluid, in particular by the presence, on the surfaces separating the fluids, of fins, spikes or analogous profiling.

An object of the invention is to provide improvements to heat exchangers of known type by increasing the exchange surface and consequently the efficiency of the exchanger, without increasing its size.

 Another object of the invention is to provide a reduced weight heat exchanger.

 Another difficulty which arises in heat exchangers, in particular of the "cross-current" type, is the realization of the seal between the fluid streams at the corners of the stack of plates of the exchanger.

I1 is known for example, in the case of an exchanger usable in a static recuperator, to produce this bundle i from aluminum plates which are joined together by crimping on alternating sides, in order to thus form a stack or bundle of cross current plates. However, in addition to the high price of such an exchanger, which results from both the material used and the operations necessary for its manufacture, there is a risk of leakage at the corners of the stack and poor sealing when crimping, peculiarities which harm , as is easily understood, the efficiency of the heat exchanger thus produced.

Yet another object of the invention is to create a heat exchanger overcoming these drawbacks by allowing a substantially perfect seal to be obtained.

 The invention is embodied, in one of its aspects, in a heat exchanger characterized in that it consists of a tubular structure formed by sheets, sheets or the like kept in a spacing relationship by a sparse partitioning between these sheets fluids flow channels, in combination with collectors connecting between them alternating intervals provided between these sheets for the flow of two fluids on either side of each sheet separating two intervals.

This tubular structure can be of any material, in particular metal, plastic or other material. It can be obtained by extrusion or by assembly by gluing, welding, etc.
A plate-shaped material existing on the market consists of a tubular plastic structure comprising two sheets of plastic material held in a spacing relationship by a multitude of bars or partitions extending between the sheets and integral with them. this. Such a tubular plastic structure can be manufactured by extrusion.

 According to a preferred embodiment, the heat exchanger consists of the union of at least two tubular structure plates, in particular of plastic material of the type known per se, each comprising two parallel sheets kept apart from one another by bars forming a partition, these two plates being joined against one another so that a heat exchange is ensured between the fluids passing through the channels or passages formed in these plates between the bars or partitions, through the sheets in contact each time forming one face of the tubular structure plate, means forming collectors being provided at the ends of the channels or passages formed by these plates for the arrival and the exit of the fluids between which the heat exchange must take place.

The research which led to the invention has shown that such a tubular structure and in particular this material in the form of plates known per se for producing a heat exchanger makes it possible to obtain an inexpensive and light exchanger, due to the low weight. elements involved in its realization, as well as an increase in the heat exchange surface, resulting from the presence of numerous bars or partitions, and an increase in the heat exchange efficiency resulting from the increase in turbulence in the flow of fluids, also due to partitioning. It has been found that this turbulent regime is reached very quickly and is preserved, whatever the flow rate of the fluids. Furthermore, given that tubular structure plates of the indicated type are made of plastic by extrusion, a very good fluid tightness.

The connection of the collectors with the plates can be carried out in a simple manner, since it is then a question of sealing with planar plate surfaces formed by the sheets of the tubular structure.

The number of plates thus juxtaposed can be any. It will depend on the capacity desired for the heat exchanger, that is to say the flow of fluids.

 According to one possible embodiment, the heat exchanger consists of a stack of tubular structure plates of the above type, alternately offset by 90 "so as to produce a cross-current exchanger.

According to another possible embodiment, the heat exchanger comprises a stack of plates in which the partitions are oriented in the same direction, means being provided for making each second plate communicate with each other in order to produce a heat exchanger with opposite currents. case, one can in particular cut obliquely one of the two ends of each plate and arrange the bevels thus formed alternately, which ensures the entry and exit of the two fluids between which the heat exchange must take place maintaining the required seal.

In the case of a heat exchanger with opposite currents of this type, a preferential arrangement consists in placing the plates of tubular structure by alternately shifting them by a distance corresponding to half the spacing between the bars or partitions, which provides a further improvement in the heat exchange effect.

 The invention also relates, in another aspect, to a static recuperator constituting an application of the heat exchanger described above. Such a static recuperator can be used in particular in a ventilation installation for premises or construction, by being interposed in the outlet current of the stale air for its exhaust to the outside and in the fresh air intake stream for its introduction into the room, so as to ensure, by heat exchange, the recovery of calories from the stale air before its evacuation and their transfer to the fresh air admitted inside the room.

 According to an embodiment which seems judicious, this static recuperator can be constituted by a box provided with the required inlet and outlet orifices and inside which is placed a stack or bundle formed of plates of tubular structure offset alternately by 90 , this stack being arranged inside this box so that its angles are in contact with the walls of said box, thus providing diametrically opposite collecting chambers two by two for the entry and exit of the two fluids, l sealing between the chambers being ensured at the points of contact of the vertices of the stack with the walls of the box.

According to an embodiment which appears to be advantageous, the box is internally lined with a heat-insulating coating, for example in glass wool.

According to another particularity, it is judiciously provided at the tops of the stack of plates of pieces in the form of squares which, by a wing, isolate the channels from the adjacent plates and, by their other wing, can be fixed to the wall of the box.

Such a static recuperator is of simple construction and consequently inexpensive and of very low weight. Taking into account in particular the lightness of the stacking of plates constituting the heat exchange element that properly speaking it is possible to produce a box in which the glass wool or the similar heat-insulating coating is simply covered with a plate protective, for example of an aluminum plate.

 The description which follows, made with reference to the appended drawings, given without limitation, will allow a better understanding of the invention.

Fig. 9 is a perspective view of a tubular structure plate usable according to the invention.

Fig. 2 is a partial perspective representation, showing the alternating arrangement of successive plates for producing a cross-flow heat exchanger
Fig. 3 is a schematic elevational view showing an arrangement usable for constituting a heat exchanger with opposite currents.

Fig. 4 is a vertical sectional view showing the application of a heat exchanger according to the invention for the production of a static recuperator.

 Fig. 5 is a corresponding horizontal section view.

The tubular structure plate shown in FIG. 1 and generally designated by the reference 1 corresponds to a commercial product known per se.

It is made of plastic and comprises two sheets 2 and 3 forming its faces and kept apart by bars or partitions 4, thus providing between the sheets 2 and 3 channels or passages 5 of small section. Such material can be produced by extrusion. It is light and has good resistance to crushing.

It has been shown schematically in FIG. 2 the way in which a heat exchanger can be produced from plates 1 of the aforementioned type. In the present case, the plates are arranged alternately with an offset of 90 ', so as to ensure cross flows. The directions of flow of the fluid are indicated by arrows 6 and 7.

 We see that the plates i are joined so as to constitute a stack or bundle of plates. The heat exchange is ensured for each of the plates through the two sheets constituting its faces, which are attached to the adjacent sheets of the neighboring plates, the heat exchange surface being increased due to the presence of the bars or partitions. having led to the invention have further shown that the efficiency of a heat exchanger of this type is further increased as a result of the turbulent regime which is created due to the presence of partitioning, this turbulent regime being reached very quickly and being retained whatever the flow rate. The combination of this turbulent flow regime with the increase in the heat exchange surface provides a significant increase in the efficiency of a heat exchanger of this type compared to known exchangers, this advantage is also combined with the lightness of the assembly resulting from the use of plastic. This high efficiency allows the exchanger to be produced in a lower volume for a given heat exchange capacity.

As can easily be seen in FIG. 2, it can be seen that the seal between the sets of perpendicular channels between them of the exchanger can be easily ensured at the angles or tops of the stack, which avoids any mixing between the fluids and also any heat loss.

 We have shown in FIG. 3 a heat exchanger 8 which here again consists of a stack formed by the juxtaposition of plates 1 of the type visible in FIG.

 1.

 However, in the present case, as opposed to FIG. 2, the plates are arranged so that the bars or partitions 4 are parallel to each other.

Thus, the channels formed by the plates can be traversed by the fluids in opposite directions to carry out the heat exchange.

 In order to solve the problem of sealing between the channels or plates ensuring the delivery of different fluids, each second plate is, in the stack considered, bevelled towards its end, as indicated in 9 and 10. On will understand that each second plate is provided with a bevel 9, while the other plates are provided with a bevel 10 at the opposite end of the exchanger.

 It is thus possible to admit a fluid through the upper part of the exchanger, as indicated by arrow 11, and to evacuate it at the opposite end of this exchanger, as indicated by arrow 12, while the other fluid is also admitted through the upper part of the exchanger, as indicated in 13, and is discharged at the end opposite to its admission, as indicated by arrow 14. No mixing can thus occur. The nature of the plates allows an easy cutting of their ends, so that a heat exchanger of this type can here again be produced without significant means.

 The static recuperator which is shown in 1Q Fig. 4 and 5 constitute an application of a cross-flow heat exchanger produced according to the invention, as shown in FIG. 2. Such a static recuperator can be used for example in a heating system. ventilation or air renewal of a room or a building to recover the heat from the stale air by transferring it to the fresh air for its preheated heat.

This static recuperator comprises a box generally designated by the reference 15, which is formed from insulating panels of very high density mineral wool, therefore self-supporting, provided with a reflective aluminum film to perfect the insulation. The lower part 16 is made of stainless steel sheet so as not to retain the condensates. The box 15 has an orifice 18 for entering the fresh air, an orifice 19 for leaving the preheated fresh air, an orifice 20 for entry of the stale air and an orifice 21 for the outlet of the stale air having given up a large part of its heat to the fresh air admitted. I1 is provided inside this box 15 a stack or bundle of plates forming a heat exchanger, indicated at 22, of the type visible in FIG. 2, that is to say in which the plates are offset alternately by 90 "to form a cross-current exchanger. Brackets 23 are arranged at the tops of this exchanger 22, a wing 24 of each bracket penetrating into each vertex of the exchanger, while the other wing 25 is used for fixing, for example by gluing, against the underside of the glass wool coating 17 or of the wall 16 of the box. This arrangement thus creates chambers 26 of triangular section, which form collectors - isolated from each other by the brackets 23. The arrows in Fig. 4 indicate the mode of flow of the two streams of fluids between which heat exchange must take place.

We see that the heat exchanger which is the subject of the invention thus allows the realization of a static recuperator of simple and particularly effective construction. Due to the yield obtained, this recuperator can be reduced to a small volume for a large heat exchange capacity. I1 is also of light weight due to the nature of the material constituting the exchanger. The means necessary to isolate the two streams of fluids are also extremely simple.

It goes without saying that the invention could be applied to many other technical fields and that modifications can be made to the embodiments described, in the field of technical equivalences, without departing from the invention.

Thus, although the description relates more particularly to the use of tubular plastic plates, it will be understood that such plates could also be made of any other material, for example extruded aluminum.

Claims (10)

 1. Heat exchanger, characterized in that it is constituted by a tubular structure formed by sheets, sheets or the like, maintained in a spacing relationship by a partitioning between these sheets of fluid flow channels, in combination with collectors connecting alternating intervals between these sheets for the flow of two fluids on either side of each Zeual separating two intervals. 2.- heat exchanger according to claim 9, characterized in that it is constituted by the meeting of at least two tubular structure plates (1), in particular of plastic, each comprising two parallel sheets (2, 3) kept apart from one another by bars (4) forming a partition, these two plates being placed side by side so that a heat exchange is ensured between the fluids passing through the passages in these plates between the bars or partitions, through the sheets in contact each time forming one face of the tubular structure plate, means forming collectors (9, 10, 26) being provided at the ends of the channels or passages formed by these plates for the inlet and outlet of the fluids between which the heat exchange must take place.  3.- Heat exchanger according to claim 1 or 2, characterized in that it consists of a stack or bundle of plates (1) of tubular structure offset alternately by 90C so as to produce a cross-current exchanger.  4. Heat exchanger according to claim 1 or 2, characterized in that it consists of a stack of plates (1) in which the partitions are oriented in the same direction, means (9, 10) being provided to make communicate with each other plate in order to produce a heat exchanger with opposite currents.  5. Heat exchanger according to claim 4, characterized in that one of the two ends (9, 10) of each plate (1) is cut obliquely, the bevels formed being arranged alternately in the stack.  6.- Heat exchanger according to claim 4 or 5, characterized in that the plates (I) of tubular structure are offset alternately by a distance corresponding to half the spacing between the bars or partitions (4).  7.- Static recuperator usable in particular in ventilation and air renewal installations for premises and buildings, with a view to recovering at least in part the heat contained in the stale air evacuated from the premises towards the outside in transferring it to the fresh air admitted from the outside into this room, characterized in that it comprises a heat exchanger according to any one of claims 1 to 6, interposed in the flow of stale air and air fresh. 8. Static recuperator according to claim 7, characterized in that it is constituted by a box (15) provided with inlet (18, 20) and outlet (19, 21) and inside which is placed a stack (22) of plates (1) of tubular structure offset alternately by 90, this stack being arranged inside this box so that its angles or vertices are in contact with the walls (16, 17 ) of said box, thus providing collecting chambers (26) diametrically opposite two by two for the entry and exit of the two fluids, the sealing between the chambers being ensured at the points of contact of the angles or vertices of the stack with the walls of the box.  9. Static recuperator according to claim 8, characterized in that the box is formed of self-supporting insulating panels.  10. Static recuperator according to claim 8 or 9, characterized in that there are provided, at the angles or tops of the stack (22), pieces in the form of brackets (23) insulating by a wing (24) the channels of the adjacent plates and fixed by their other wing (25) on the wall (16, 17) of the box (15).