FR2572798A1 - Heat exchanger with plates of the <<fin-plates>> type and its method of manufacture - Google Patents

Abstract

The invention relates to a heat exchanger consisting only of a stacking of plates formed by stamping, which have the distinctive feature of creating, in one single piece, two distinct elements such as the plate and the fin. These plates comprise a series of packing elements 1 which fit into each other over a limited depth, so as to form the channels for the liquid 2 and gas 3 circuits. The parts between the packing elements form the fins 4 which may or may not be equipped with shutters 5. Two end plates make up the casing 6 and 7. The assembly is simple and is carried out in one single operation of soldering or welding, in particular for aluminium, stainless steel, plasticised steel. Heating convectors, exchangers having a large exchange surface for air conditioning or for recovering heat over air or smoke, exchanger for the motor or other industries.

Description

 The present invention relates to a new type of heat exchanger, which is intermediate between the finned tube and the conventional heating radiator.

 It is also close to the types of plate heat exchangers equipped with heat sinks or certain types of finned exchangers for the automotive field.

The finned tubes, widely used for thermal exchanges between liquids and gases, nevertheless pose some problems, explained below, which limit their efficiency or their field of application:
- In a finned tube, the heat exchange is with cross flows, therefore less effective than with countercurrent flows.

 - The fins are usually crimped on the tube for a cost, which creates resistance to the conduction of heat at their contact on the tube; phenomenon accentuated in cases of gas cooling, where the fins then expand more than the tube.

The finned extruded tubes solve this problem, but are expensive with a limited surface (liquid / gas) ratio.

 - The system of collectors required for the battery-packed finned tubes is bulky and expensive.

The pressure drop on the liquid circuit increases significantly when the number of rows of finned tubes is increased, with significant repercussions, especially on operating costs.
Conventional heating radiators perform a countercurrent exchange, but have equal or nearly equal exchange surfaces on the gas side and the liquid side. the new models feature either mass-cast or welded-on fins, which improves efficiency, but at a cost that remains high.

 Plate heat exchangers used for the heat exchange between gas and liquid, in particular for automobile radiators, comprise heat sinks, constituted by corrugated sheets, sandwiched between plates, in the gas circuit, and which fulfill the role of fins.

The technology of these devices, based on the interposition of strips intended to maintain the spacing of the plates and to determine the circulation channels of the two fluids, gives a more heterogeneous apparatus than the exchanger according to the invention.

 The exchangers consist of pressed fins where the tubes are replaced by collets nested in each other, have substantially the same characteristics as the conventional finned tubes including cross flow.

 The originality of the heat exchanger according to the invention is in the design of the plates that constitute it. This design is based on a selective composition of principles developed for the devices mentioned above, its purpose is to maximize the benefits and eliminate or reduce the disadvantages that these devices.

 In the following description, the shapes of the plates shown in the accompanying drawings are given by way of non-limiting examples.

 The heat exchanger according to the invention is characterized in that it consists solely of a stack of plates having a series of parts in disbursement intended to form the liquid circuit, alternating with flat parts, generally provided with louvers and constituting the gas circuit.

 The essential feature of the plates constituting the exchanger according to the invention is to produce with a single piece, two distinct elements, such as the plate and the fin.

In this configuration, the plate allows the counter-current heat exchange and the possibility of a long contact between the fluids, and the fin has a large exchange surface. In addition, all the functions necessary for the development of the device are also ensured, conferring on it a great efficiency and a particularly low cost for the devices resulting from the stamping standard and especially for the manufacture in gold2n - series
LaFig. 1 is a perspective representation of one of these plates, which are all identical, outside the two end plates.

 Fig. 2 is a transverse section of the exchanger according to the invention, showing the stacking of the plates and showing 11 interlocking parts disbursed 0. These disbursements have a deflection angle () on their lateral sides, which limits the depth of the interlockings, so that their lateral sides ensure: the maintenance of the spacing of the plates, the separation of the liquid / gas circuits, which results, on the one hand the formation of the channels of the liquid circuit t in the intervals thus produced between the disbursement funds and on the other hand, the formation of the channels of the gas circuit in the intervals produced: - between the fins.

Finally, these lateral sides ensure the contact surface between the plates allowing the tight assembly of llen- seems by a simple operation of brazing, welding or gluing depending on the nature of the materials constituting the plates
The plane parts alternating with the channels, constitute the fins &commat; dissipating or receiving heat in the gas circuit. In the cases of application, they may include 0 shutters obtained in the stamping operation and which have the triple aim of improving the efficiency of the heat exchange. and to reduce the expansion stresses, the latter being sensitive for the cases of high temperatures or long channels, and to facilitate the stamping of disbursements, by allowing the fins to release part of their material.

 Fig. 3 is a longitudinal section of the fins showing the profile of the louvers and in particular their alternation on either side of the plane of the fin. This profile can be parallel to the plate or with a slight angle of incidence.

 Fig. 4 is a cross-section showing louver shapes in 4 non-limiting solutions.

Solutions a and b have a profile parallel to the plate, solutions c and d derived from the previous 2, provide a slight angle of incidence creating turbulence in the gas flow to improve the efficiency of the fins. Solution e is simply a wave that increases the surface of the fin and facilitates the stamping operation of the disbursement.

 In cases where it is feared fouling1 with need for sweeping, the fins may comprise only corrugations obtained during stamping.

 The depth of the disbursements can be increased so that the interlocking takes place over a length greater than the spacing pitch of the plates, in order to obtain an overlap of the lateral sides, creating a multi-thickness wall, brazed, welded or bonded and shrunk by the plates themselves, substantially increasing the resistance to liquid circuit pressure. This arrangement is particularly advantageous in the case of thin plates (for example 0.1 mm or more). It is highlighted in Fig.5.

 Fig. 6 is a longitudinal section on the liquid circuit. It shows the channels (21 provided at their ends with the orifices which constitute the secondary distribution manifolds Q8.

The stacking of the plates causes the bottoms of the channels, in turn, to constitute fins for the dissipation or reception of heat in the liquid, as shown in FIGS. 2 and 6
Figs. 2 and 6, also show that all the plates constituting the exchanger according to the invention are identical outside the two end plates) and G
These include the main collectors G
Go back and return of the liquid circuit, provided with orifices for the connection of the exchanger. These collectors are obtained by stamping, either directly in the plates or in patches and brazed on the plates.

The position of the general collectors can be on the opposite sides of the exchanger, for an equiristant distribution in the channels, or on the same side for ease of installation.

The end plates 06 and G also constitute the shell of the exchanger, either alone with a bend, or in combination with two other sheets having two collapsed edges. This envelope is then a cladding that can be provided at each end of fastening means, including flanges, allowing its connection to another device or a network of ducts ventilation for example The plate &commat; has disbursements G whose purpose is to equalize the last interval between plates
Fig.2, and to fret the last channels of the liquid circuit
This envelope may also constitute the jacket of a heating convector, represented by FIGS. 10 abc and whose description is detailed as application of the invention in chapter "Manufacturing process
The alternation of the channels and fins can be repeated as many times as is necessary to obtain large exchange surfaces. Their dimensions and proportions can also be adapted, during the design of the exchanger, to the characteristics of the fluids, the materials constituting the plates and dimensional dimensions imposed. The length of the channels is calculated according to the data of the exchange problem posed. They can in particular be of great length for the cases of exchange with weak At; however, for common problems, these lengths will be standardized for reasons of stamping cost. Finally the number of plates is the third variable allowing the adjustment of the power of the exchanger to the data of the problem.

 According to a variant, the support between the disbursements for maintaining the spacing of the plates can be done on the inner and outer roundings thereof, as indicated in FIG. 8.

 The application examples, constitution materials and manufacturing process, given below, are not limiting.

 The manufacturing process begins with the stamping of the plates which can be carried out on an automatic press from rolled sheets, the width corresponding to the length of the plates taken in the longitudinal direction of the channels.

Fig.9 shows the principle of the phases of the stamping operation without extending on this well known technique. The press tool used is of the "Tool to follow" type, with belt positioner, it carries out at each positioning the following 4 phases
Phase 1 - Downgrading of the maintenance matrix in the previous disbursement, to ensure a precise separation of disbursements.

Phase 2 - Descent of the flank guides 02w and matrices W for the execution of the louvers or the wave on the future fins, then immediate release of the masters these
Phase 3 - Descent of the flank guide &commat; and matrix 0 for executing the disbursement; the call of matter being fed by the decrease in the amplitude of the louvers, or the wave on the fins, the sheet sliding under the flank guides.

Phase 4 - Strip debugging and repositioning to resume Phase 1
Depending on the size of the series and the size of the plates, the press tool may include the number of dies required to execute all louvers, then all disbursements in a single descent.

 The shearing of the plates according to the number of planned disbursements will be done.

The operations of degreasing, assembly, brazing, or welding, or gluing, depend on the nature of the material constituting the plates, and the intended applications; these materials can be, in particular:
- Aluminum in thickness from 0.1 to 2mm.

with solder coating on one or both sides (type 3003- 4343 10% H 14 PECHINEY, for example); press tool perfectly polished to prevent deterioration of the solder layer, degreasing, assembly and maintenance of the plates, in a clamping jig, then soldering in a single operation in a salt bath, or in a vacuum oven, or in a neutral atmosphere, for applications such as
Heating convector, shown Fig.lo a and allowing large exchange surfaces, in a low volume and low price, advantageously supplied with fluid at low temperature, but also allowing water supply at the conventional temperature of 90 / 70. The fins may have louvers &commat; or one or more waves 4 e. The jacket 6 of this convector forms one of the two end plates of the heat exchanger, allowing it to be emitted by convection and radiation. The other end plate Q has the main head-and-return manifolds (9 with connection sleeves A and
R and bleeding air Fig. 10 b. The jacket t is provided with two bars on the rear face for fixing the convector, Fig.10 c, it can receive a grid 10 at the top, and a baked paint application.

Note that the penultimate plate, which is brazed with the end plate forming the jacket (6, may be of reinforced thickness for better resistance to the pressure of the liquid.

The configuration of the heating body allows the denomination of: "plate-fin convector
Heat exchanger for heating or cooling air in air conditioning, heat recovery or other non-corrosive gases in the industry.

 Radiator for cooling or heating in the automobile field.

- Steel or copper, or their respective alloys, in particular stainless steel, in thickness of 1/10 to 1 mm, for example, with solder paste made of copper, or copper alloy, or special solders, applied mechanically in the contact area of the plates, before the operations of assembly and maintenance of the plates, soldering being carried out in the oven under a neutral atmosphere, for applications such as
Exchanger for air or gas at high temperature, or corrosive, with primer such as: water, oil other liquid.

 .Recoveror of heat on smoke etc ..

 - Tinned steel, the brazing being ensured by the tin layer in the tinning bath.

 - Steel or aluminum or copper, or their respective alloys, protected by applying a plastic film on both sides, especially (polyethylene or polypropilene thin: 50 to 200 microns for example), after assembly and maintenance of the plates, the Plastic films are welded to each other at the contact surfaces of the plates, by circulating hot air in the liquid circuit of the exchanger, at a temperature which is a function of the nature of the plastics material used.

Plastic films can also be welded by an ultrasonic process or glued.

 The protection of the plates can also be ensured by a varnish, in particular based on epoxy resin, or polyester, or acrylic, applied on both sides by dipping before assembly of the plates or after their assembly, the varnish ensuring the bonding of the plates between they, their anti-corrosion protection, and the sealing of liquid / gas circuits.

 The reactions due to the pressure which tend to spread the plates can be balanced by a system of rods and counter plates made of folded sheet according to an example shown in Fig.ll. These composite plate-fin heat exchangers have an application for heating or cooling air or corrosive gases, for temperatures compatible with the material constituting the protection, generally less than 100

Claims (9)

 1 - Heat exchanger with counterflow circulation adapted mainly for heat exchanges between liquid and gas, characterized in that it consists exclusively of a stack of plates formed by stamping, that these plates have a series of parts in disbursement ( 1) forming the channels of the liquid circuit (2) and which alternate with planar portions forming the fins of the gas circuit (4), these disbursements (1) have a relief angle (o ()) on their lateral sides, which they fit together to a depth limited by this clearance angle, so that their lateral sides ensure: the maintenance of the spacing of the plates, the separation of the liquid / gas circuits, which results, on the one hand, forming the channels of the liquid circuit (2) in the gaps produced between the funds of the disbursements (1), and on the other hand, forming the channels of the gas circuit (3) in the intervals produced between the fins (4), e t finally that said lateral sides provide the contact surface between the plates for sealing assembly, by a simple operation of brazing, welding or gluing depending on the nature of the materials constituting the plates.  2 - Heat exchanger according to claim (l) characterized in that the flat portions of the plates, alternating with the disbursements (1), constitute the vanes (4) for dissipating or receiving heat in the gas circuit (3), they may be smooth, or comprise louvers (5), intended to improve the efficiency and reduce the expansion stresses, that the plane of these louvers may be parallel to the plane of the plates, or have an angle of incidence, that the fins (4) may simply comprise corrugations parallel to the channels and obtained in the stamping operation.  3 - heat exchanger according to claims 1 and 2, characterized in that the depth of the disbursements (1) can be increased, so that the nesting takes place over a length greater than the spacing no. plates, in order to obtain an overlap of the lateral sides of the disbursements creating a multi-thickness wall brazed, welded or glued and fretted by the plates themselves, in order to increase the resistance to the pressure of the liquid circuit (2), particularly in cases with thin plates, for example of 0, lmm  4 - Heat exchanger according to claims 1,2 and 3, characterized in that the liquid supply of the channels is provided by orifices (8) located at each end of the disbursements, that these orifices are obtained in the operation d stamping out disbursements and constituting the secondary manifolds (8) Return and return of the liquid circuit; and in that the bottoms of the channels (2,) constitute fins for dissipating or receiving heat in the liquid circuit.  5 - Heat exchanger according to claims 1,2,3 and 4, characterized in that all the plates which constitute it are identical, apart from the 2 end plates (6) and (7), the latter two comprise the collectors main (9) Flow and return of the liquid circuit, that said collectors can be positioned on one side or on opposite sides of the exchanger, and that they are obtained by stamping either directly in the plates or in the parts reported and brazed on these plates, and that they are provided with the connection ports of the exchanger; in that these two end plates (6) and (7) constitute the envelope of the exchanger, either alone, with a fold and a dropped edge, to form two Darplaque sides, or in association with two other plates each provided with two collapsed edges; that the envelope thus created has the configuration of a cladding that can be provided at both ends, fixing means, in particular flanges for its connection to a network of ventilation ducts, or on an apparatus, in particular, in that the plate (7) comprises disbursements intended to equalize the last gap between plates, and to shrink the last channels of the liquid circuit.  6 - Application of the heat exchanger according to claims 1,2,3,4 and 5, to a heating convector shown in FIG. 10 a, b, c, characterized in that it is made entirely of aluminum sheet with solder coating on one or two sides, that the brazing is carried out in a single operation in a salt bath or in a vacuum oven or under neutral atmosphere; in that its jacket (6) forms one of the two end plates of the exchanger, joined by brazing with the other plates, that it participates in the emission of heat by convection and radiation, and that the other end plate (7) comprises the main manifolds (9) Return and Return, with connection sleeves and air purge; in that the jacket is provided with a removable grid (10) in the upper part, and 2 bars (11) on the rear face Fig.10 c, for fixing the convector, and that it can receive an application of baked paint;  7 - "heat exchanger according to claims 1, 2,3,4,5 and 6, characterized in that it consists solely of plates whose particularity is to achieve with one piece, two separate elements, such as the plaque and fin, that in this configuration the plates act in 3 ways  a) - As separating plates of the two fluids determining the channels of the two respective circuits, and having in particular the advantages of countercurrent flows, and the possibility of a long contact between the fluids.  b) - As receiving fins or heat dissipators in the gas circuit and the liquid circuit, ensuring most of the exchange, including continuity of the conduction of heat in the mass of the fins and plates which are of a single piece.  c) - As essential elements ensuring, in association with the 2 extreme plates, all the functions necessary for the development of the exchanger, in order to improve its efficiency and to reduce the cost.  8 - Heat exchanger according to claims 1,2,3,4,5,6 and 7, characterized in that the contact between the disbursements for maintaining the spacing of the plates can be done on the inner and outer roundings of these.  in that the sheet used may be aluminum originally coated with a solder film on one or on both sides (for example, type 3003 -4343-10% H14 PECHINEY), soldering the whole of the exchanger being carried out in a single operation, in a salt bath or in a vacuum oven or in a neutral atmosphere; the parts being held in a clamping jig for applications such as convectors, exchanger for heating or air cooling in particular.  in that the material call for the stamping of the disbursement is compensated by the reduction in the amplitude of the louvers, or the undulation on the part forming the air lette, the sheet sliding under the flank guides  9 - A method of manufacturing a heat exchanger according to claims 1,2,3,4,5,6,7 and 8, characterized in that the fin plates are made by stamping on automatic press from sheet metal a coil of thickness from 0.1 to 2 mm, in particular with a ".Use to follow" equipped with a positioner or with a tool comprising all the dies necessary for the execution of the plate in a single descent;  in that the sheet used can be, in particular of stainless steel, or of copper with braze paste based in particular on copper or cuprous alloy, applied mechanically in the contact zone of the plates, the brazing being carried out in the furnace under neutral atmosphere; for applications such as high temperature gas exchanger, such as smokes, in particular.  - In that the sheet may be steel, tin, brazing being provided by the tin layer in the tin plating bath.  - In that the sheet may be steel, aluminum, copper, or their respective alloys, the plates being protected by applying a plastic film on both sides, in particular Polyethylene or polypropylene, thin: 50 200 microns for example, after assembly and maintenance of the parts, the plastic films being welded together at the contact surfaces of the plates, in particular by means of a hot air circulation in the liquid circuit, and at a temperature compatible with the plastic material used; films can also be glued.  in that the protection of the plates can also be ensured by a varnish, in particular based on epoxy resin, or polyester, or acrylic, applied on both sides, by dipping before assembling the plates or after their assembly, the varnish ensuring the bonding the plates together, their anti-corrosion protection, and the sealing of the liquid / gas circuits. Application to exchangers for corrosive gases at a temperature <100, in particular.  in that, depending on the case, the reactions due to the pressure of the liquid tending to move the plates apart can be compensated by a system of rods and plywoods made of folded sheet metal (in particular Fig. 11).