FR2519579A1 - Heat exchanger plates made by assembling polymer modules - where module ends are placed in mould filled with polymer to join modules together - Google Patents

Abstract

Each plate consists of a frame made by assembling at least two different types of module. Adjacent ends of two modules which are to be joined together are located in a mould to leave a space; and the two ends of the modules are clamped in position by pegs. The mould is next heated to near the m.pt. of the modules, and a liq. with the same compsn. as the modules is injected into the mould to join the modules together. The adjacent ends of two modules to be joined together pref. contain holes, grooves, or tongue and groove joints to improve the strength of the moulded joints. In an embodiment, the modules are made of polyethylene or polypropylene, the same polymer being used to make the moulded joints. Only two moulds are needed to make heat exchanger plates of different length, so mfr. costs are reduced.

Description

 The present invention relates to a method of manufacturing the plates of a heat exchanger by assembling elements end to end.

 Plate heat exchangers constitute an advantageous type of exchanger because of their simplicity, their very good exchange coefficient, their ease of maintenance, their compactness and the possibilities of varying the exchange surface without modify the frame. Such devices consist of a stack of planar elements assembled to determine separate flow circuits traversed by fluids of different temperatures between which heat exchange takes place.

 Numerous embodiments of plate exchangers are contacted, for example exchangers in which the planar elements consist of stamped metal plates.

 French patent 2,290,646 also discloses a plate heat exchanger made of molded material constituted by a succession of adjoining plates communicating two by two to delimit separate flow circuits. Each plate comprises at least one planar frame surrounding a central cavity, at least two orifices formed in the frame for the inlets and outlets of the fluid media which pass through the central cavity, and openings formed in the frame for the passage of the fluids to a neighboring module. The frames are isolated from each other by a thin waterproof sheet which separates the fluid media in two adjacent frames. The heat transfer between the fluids takes place through this thin sheet from one plate to the next.

 The plates of an exchanger of this type are produced by pressure molding. As the plates are generally of large dimensions, it is necessary that the mold also has a large tension, and therefore its production is expensive.

 Furthermore, when it is desired to vary the parameters of the exchanger, for example the flow rate of one or the other of the fluids, or the exchange surface between these two fluids, a plate of different geometry is required. It is therefore necessary to make a different mold for each type of plate.

 The process of the invention overcomes these drawbacks. It makes it possible to produce a molded material plate for heat exchanger by means of a mold of small dimensions, therefore of a low cost price. On the other hand, it makes it possible to produce plates of variable shapes and dimensions by means of a single mold. It therefore avoids having to make a different mold for each type of plate.

 According to the invention, each plate of the exchanger is constituted by two distributor blocks connected by longitudinal walls. The plate produced according to the method of the invention is characterized in that it consists of several modular elements which are assembled end to end.

 More specifically, the method of manufacturing, according to the invention, a plate of an exchanger from modular elements of molded material, each plate of this exchanger being constituted by two distributor blocks connected by longitudinal walls, is characterized in that each plate is produced by assembling end to end at least two constituent parts, the end-to-end assembly being carried out by introducing the ends to be assembled in a press leaving a space between them, whose shape is that which must take the joint of the two modular elements to be assembled, and by blocking the ends in this position with a fixed side, by bringing the mold to a temperature close to the melting temperature of the material of the constituent parts of the plate, by injecting the same liquid material in the space left free between the ends to be assembled.

 Preferably, the ends of the parts to be assembled have ribs, notches or holes which improve their connection. This makes it possible to increase the contact surface between the ends to be assembled and the material injected, and therefore to improve the solidity of the connection.

 The invention also relates to the exchanger plate obtained by means of the method of the invention.

Other characteristics and advantage # s of the invention will become apparent on reading the description which follows, given by way of indication and in no way limiting, with reference to the appended drawings, in which
- Figure 1 shows a perspective view of a heat exchanger plate of the prior art
- Figures 2a and 2b show two examples of heat exchanger plate produced by the method of the invention;
- Figures 3a and 3b show a mold for implementing the method of the invention;
- Figure 4 shows various embodiments for improving the connection of the ends to be assembled.

 - Figure 5 shows a perspective view of another embodiment of a plate exchanger obtained by the method of the invention.

 FIG. 1 shows a perspective view of a plate heat exchanger plate produced according to the prior art, for example according to the teachings of French patent 2,290,646. This part is molded from a single piece holding. It comprises two distributor blocks 2 and two longitudinal walls 4 which connect the distributor blocks 2 so as to form a planar frame surrounding a central cavity 6.

Four orifices for the passage of fluids are provided in the frame, respectively two orifices 8 for the entry and exit of a first fluid and two orifices 10 for the passage of a second fluid through the plate. The heat exchanger consists of a superimposition of plates identical to plate 1 separated by a thin waterproof sheet which acts as an exchange surface. The heat exchange between the fluids takes place through this thin sheet. The first fluid enters through one of the holes 8, passes through the central cavity 6 and exits through the second outlet orifice 8. The second fluid, which exchanges calories with the first, does not pass through the central cavity 6 of the plate shown , but crosses the cavities of the plates located above and below. The circulation of these two fluids can be done in co-current or against-current. Generated scraping, an element such as a mesh, is placed in the central cavity 6 in order to cause a turbulent flow.

dans laquelle Tepp désigne la température d'entrée du fluide froid dans l'échangeur, Ts sa température de sortie, Tep la température d'entrée du fluide chaud, et TSFC sa température de sortie.However, to obtain a large exchange surface, it is necessary to have large plates. The production of such plates requires according to the prior art dime molds - equivalent sions, therefore a very high cost price. On the other hand, when it is desired to produce heat exchangers which have a clearly determined exchange power as a function of the inlet and outlet temperatures of the fluids, it is often necessary to have plates not only of large dimensions, but also of different geometry, which requires, according to the prior art, to manufacture a different plate mold for each type of exchanger. More specifically, the heat exchange power of an exchanger is characterized by number of transfer units, (NUT), given by the formula

in which Tepp designates the inlet temperature of the cold fluid into the exchanger, Ts its outlet temperature, Tep the inlet temperature of the hot fluid, and TSFC its outlet temperature.

 The method of the invention, illustrated in Figures 2 to 4 overcomes this drawback.

 In FIGS. 2a and 2b there are shown two alternative embodiments of plates obtained by this method. Figure 2a shows a plate 14 consisting of four parts, respectively two distributor blocks 2 and two side walls 4 assembled by the method of the invention. Thus, thanks to this process, it suffices to have two molds of small dimensions which make it possible, one of the modular distribution elements 2, and the other, the longitudinal modular elements, the respective sizes of which are obviously much smaller. to that of the entire plate. This significantly reduces the cost price of the plate and consequently of the exchanger. In addition, the length of the longitudinal walls 4 can be varied as desired. This makes it possible to produce, by means of a single mold, plates of different lengths but which include the same distributor block 2.

 There is shown in Figure 2b a variant 14 'of the plate of Figure 2a. For this plate, the longitudinal edges 4 were made up of several parts 4a, 4b, 4c assembled by the method of the invention. A very long plate is thus obtained.

 In the case of plate 14 (FIG. 2a), four operations make it possible to produce the plate.

The ends to be assembled 16, are constituted by the two arms of the modular distribution elements 2, and by the longitudinal modular elements 4.

 In the case of the plate 14 in FIG. 2b, eight connection operations are necessary since it is also necessary to assemble the parts 4a, 4b, 4c together.

 Figures 3a and 3b illustrate in more detail the steps of carrying out the method of the invention. The ends 16 to be assembled are placed end to end inside a small overmolding mold 20 composed of two parts 22 and 24 and the internal shape of which corresponds to that of the parts to be assembled.

These ends 16 may for example be the end of a longitudinal wall 4 and the start of an exchange block 2. It may also be two ends of longitudinal walls, like the walls 4a and 4b shown on Figure 2b. A space 26 is left between the two ends 16 and they are blocked in this position, by clamping screws 28 which pass through corresponding holes 27, made in the ends 16. The space 26 left between the two ends has for purpose of allowing the injection of material. The mold 20 includes heating means 30 which make it possible to bring it to a temperature close to the melting temperature of the material of the two modular elements. In FIG. 3a, the heating means 30 have been symbolized by an electrical resistance surrounding the mold 20.

 Among the materials commonly used to make the parts of the plate 14 of the exchanger, mention may be made of polyethylene and polypropylene, the melting temperatures of which are 200 and 2300C respectively.

 Through an orifice 32, the same material is injected into space 26 in the liquid phase as that which constitutes the parts to be assembled.

 One thus obtains, after cooling, an intimate connection of the same nature and defined geometry between the two modular elements.

 Figure 3b shows a practical embodiment of the device of Figure 3a. The heating means 30 are made up, in this embodiment, by a resistor 30 integrated in the bottom of the mold 24, which avoids having to unroll it when the ends 16 to be assembled are introduced. The mold can be opened and closed quickly thanks to the quick cam clamping device 33. In addition, cooling ducts 34 are provided for the part of the mold 20.

 Note that the holes 27 for the passage of the screws 28 remain in the parts. However, these orifices are not annoying because they do not communicate with the central cavity 6. Consequently, they cannot give rise to any leakage of liquid.

 There are shown in Figure 4 various embodiments of the ends 16 intended to improve their connection. In FIG. 4a, the ends have longitudinal holes 36 into which the molten material penetrates, which increases the bonding surface.

 FIG. 4b shows an end 16 or 18 comprising a rib 38.

 FIG. 4c shows ends comprising tenons 40 which also have the aim of increasing the length of the connection and therefore the contact surface between the parts.

 There is shown in Figure 5 a third embodiment of a plate 1 of heat exchanger E obtained by the manufacturing method of the present invention, and the exchanger obtained by the superposition of these plates. An exchange surface constituted by a thin sheet of plastic or metallic material is interposed between two plates.

Tie rods 36 placed in the holes 37 provided in the longitudinal edges 4 and at the ends of the distributor blocks 2 ensure the alignment of the plates and their tightening between two end plates (not shown). The height of the exchanger can be varied as desired by increasing or reducing the number of plates. The plates are inverted alternately from 1800 before being stacked alternately. The distribution and evacuation channels 38 are located from one plate to another, in a symmetrical position on either side of the longitudinal axis of a plate.

 Note the orifices 27 which were necessary to maintain a suitable spacing between the ends of the parts to be assembled (ends 16) during the injection of the plastic material in which the plates 1 are made. Note also the trace 26 left by the junction of the two plates.

 Thus, the invention indeed allows the inexpensive production of heat exchanger plates in molded material without requiring the use of a different mold for each dimension, or each form of the plate.

Claims (3)

 1. A method of manufacturing plates of a heat exchanger by assembling modular elements end to end, characterized in that each plate (14) is produced by assembling end to end at least two constituent parts, the assembly butt with the end being produced by introducing the ends to be assembled (16) into a press (20) leaving a space (26) between them, the shape of which is that which the joint of the two modular elements (16) to be assembled must take, and by blocking the ends (16) with fixed side in this position by bringing the mold (20) to a temperature close to the melting temperature of the material of the component parts of the plate (14), by injecting the same liquid material into the space (26) left free between the ends (16) to be assembled.  2. Method according to claim 1, characterized in that the ends (16) have holes (36), ribs (38) or tenons (40) intended to improve their connection.  3. Heat exchanger plate (14, 14 ') obtained by the method of claims 1 and 2.