RU2413152C2 - Heat exchanger from hollow flat sections - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: in heat exchanger with small weight and high volume conductivity, which operates with fluid media at high pressure drop and high temperatures, hollow flat sections are assembled in a pack, located at equal intervals one from the other and connected to outer headers; at that, the above flat sections include relief central section, and side edges of two walls of hollow flat section are welded; at that, walls of each hollow flat section are rigid, their relief central section has one or several rows of periodically changing convexities located on one and the same line and equipped with steep surfaces which form many sharp edges directed at an angle and/or perpendicular to the line along which the convexities are located; besides, gap between opposite surfaces is equal, known and invariable in the area of expected pressure drops.

EFFECT: possible manufacture of lighter, thinner and cheaper metal, glass or polymer heat exchangers with hollow flat sections, which have relief walls and outer headers.

12 cl, 8 dwg

Description

This invention, in particular, relates to a heat exchanger assembled from a package of hollow flat sections and having a very high level of performance, namely a very high volumetric conductivity combined with a small front surface area, low cost of mechanical energy to drive the involved fluids and the possibility work with liquid and / or gaseous media at relatively high pressure drops and temperatures.

Secondly, the invention relates to heat exchangers, which are similar to the aforementioned heat exchanger, in comparison with it, in general, have a lower level of performance, but may be better suited to certain special applications.

Heat exchangers from hollow flat sections have a much higher level of performance than heat exchangers with solid fins on radiators for heat engines. In fact, with the same bulk conductivity in such liquid-gas heat exchangers, the gap between adjacent hollow planar sections is much larger than the gap between solid fins. As a result, the weight of the first heat exchangers, their volume, the front surface area and the energy consumed to supply the liquid / liquids and / or gas is significantly lower than in the last heat exchangers. Nevertheless, heat exchangers with solid metal fins continue to be used universally in a number of areas. In these circumstances, if the heat engines are equipped with conventional water-air radiators, the front surface area (main section) of these radiators is about 0.3 dm ² per kW output, while their operation requires mechanical energy (gas and liquid supply) , constituting up to 10% of the dissipated thermal energy, and in the case of small temperature differences - even more. This indicates the advantage of hollow flat section heat exchangers.

Heat exchangers made from a single package of hollow flat sections made of polymer, glass or metal are described in European patent EP 1,579,163 B1, obtained by TET. A method of manufacturing one of these heat exchangers consists in manufacturing, by means of high temperature blow molding, a polymer draft form. In this case, a harmonic-type preform is obtained, equipped with a biconvex corrugated casing, with embossed walls having steep periodically varying convexities, and then controlled compression of this preform is performed. After compression, this corrugated casing takes the final form of a single package of rigid hollow flat sections with a thin inner channel connected to two internal collectors. Such integral polymer heat exchangers give quite satisfactory results in many applications, since the required volumetric conductivity remains in the average range (no more than 20 W / ° C / dm ³ ), and the fluids that the heat exchanger operates with are under a moderate pressure drop (not more than 0.1 MPa) and have a not very high temperature (less than 100 ° C). Indeed, in some special cases, the advantages of these heat exchangers in terms of weight, cost, volume and energy consumption (from 3 to 5% of the extracted heat energy) largely compensate for their limited performance, in particular, if the initial temperature difference between two fluids, which are in question, is relatively small (less than 60 ° C).

This one-piece heat exchanger, assembled from hollow flat sections with embossed polymer walls, has many advantages. The walls of such a heat exchanger combine a certain rigidity and a certain fineness, that is, mutually conflicting characteristics, so that it has a small weight, cost and volume. Despite the laminar flow of coolant, the thin internal channel of the heat exchanger makes possible good thermal conductivity between the liquid and the wall of the hollow flat section. On the other hand, the relief walls of the heat exchanger create a relatively significant turbulence in the air flow between the flat sections, which can significantly increase the gap between them. This significantly reduces the energy needed to propel the air between the flat sections. In addition, the significant turbulence of the air circulating between the flat sections increases the apparent thermal conductivity of the air and, consequently, the overall thermal conductivity of the heat exchanger.

Nevertheless, experience has shown that this two-stage method of high-temperature blow molding with subsequent controlled compression of a biconvex corrugated casing of a polymer billet leads to a limited result if they seek to increase the required level of productivity and, in particular, the volume conductivity of the heat exchanger manufactured in this way. Indeed, with this method, full control of the two-stage process of manufacturing an integral package of hollow flat sections with respect to the thickness of the internal channel and the walls of the flat sections is not possible, although these thicknesses are crucial parameters for the total volumetric conductivity of the heat exchanger. As a result, in practice, with regard to the internal channel of the hollow flat sections, this gives an average thickness of about 2 millimeters with a spread of at least 30%. As for the wall thickness of the flat sections, the average value is about 1 millimeter and the spread is about 50%, and this spread is mainly due to the uneven narrowing of the wall during high-temperature blow molding of the workpiece.

It should be noted that the presence of internal collectors of a package of hollow flat sections adds to the performance limitation that can be attributed to these problems with thickness another aspect: the creation of a central channel common to all of these hollow flat sections, which makes it possible to direct fast fluid flow between these two collectors. As a result, this relatively large central channel hardly contributes to the necessary heat transfer.

International application WO 2006/010822, filed by TET, describes high-performance cooling devices for various applications. In these devices, radiators are heat exchangers made in accordance with the method described in the European patent TET. For one of the special applications (cooling the exhaust gases of a diesel engine for reuse), the invention provides the possibility of using a one-piece heat exchanger having hollow metal flat sections capable of withstanding a higher pressure drop and temperature than the pressure and temperature to which the whole can be subjected polymer heat exchanger. For this, by hydroforming, it is necessary to produce a metal billet of a heat exchanger of the harmonic type. This known method seems promising in the field of solid heat exchangers with hollow metal flat sections, but at present it is not yet possible to properly apply it. Moreover, this method per se is limited in terms of its theoretical effectiveness. Indeed, since the specific thermal resistance of cooling liquids, i.e., water or oil, is high, the thermal resistance of the liquid layer flowing in the laminar flow in such hollow flat sections is inevitably high, provided that the average thickness is at least 2 mm This eliminates much of the advantage of the low thermal resistance that could be provided by the considered metal walls.

Therefore, it is necessary to develop another method of manufacturing heat exchangers for various special applications, in particular for the application that was discussed above, and, more broadly, for any device that includes the possibility of having a very highly efficient heat exchanger. To this end, these new metal heat exchangers should have the same small weight, volume, front surface area and mechanical energy consumption as in the above-described whole heat exchangers. They must satisfy this requirement with much greater bulk conductivity (for example, at least 100 W / ° C / dm ³ ). In addition, they, first of all, must work accordingly at high pressure drops and temperatures, for example 1 MPa and 600 ° C. In addition, based on these first metal heat exchangers, other less productive polymer or glass heat exchangers are also possible, related to special applications, especially those that use corrosive liquids.

For this, in contrast to the solid metal heat exchangers originally designed for cooling the exhaust gases of diesel engines, new heat exchangers, in particular, designed for this specific application, should be equipped with hollow metal flat sections having the thinnest and most accurate internal channel, and also the walls are rigid and at the same time very thin. As for the general characteristics of such a heat exchanger, it is obvious that they will be completely different from the characteristics of previous heat exchangers. They will be borrowed from heavy, volumetric heat exchangers, which are designed to cool electrical transformers in distribution networks and are described in patents US 3153447 from 1964 and US 3849851 from 1974. This device is assembled from large hollow metal flat sections with embossed walls, by welding connected to two external collectors that can be mounted vertically and cooled by air circulating due to natural convection.

The first subject of the invention is a high-performance heat exchanger composed of hollow flat sections with thin metal walls reinforced with the corresponding relief, at the same time having low weight, volume, surface area and mechanical energy consumption, as well as high bulk conductivity, and at the same time suitable for failure-free, easily controlled industrial production, in addition, capable of working with liquid and / or gaseous media at high temperatures and / or pressure drops.

The second subject of the invention relates to an improved heat exchanger, similar to the previous heat exchanger, with a lower performance than the previous heat exchanger, but better suited to the special applications under consideration, different from the previous heat exchanger, and containing a package of hollow flat sections with thin polymer or glass walls reinforced with appropriate relief.

A third subject of the invention is a compact radiator with a small front surface area made of these advanced heat exchangers, having high thermal conductivity and requiring very little energy for pumping and ventilation.

In accordance with the invention, a heat exchanger with low weight and volume and very high volumetric conductivity, capable of working with fluids at high pressure drops and temperatures, in which:

hollow metal flat sections with a thin inner channel are assembled in a bag, arranged at equal intervals from each other and attached to the external collectors;

these flat sections comprise a raised central portion located between two connecting portions provided with thin holes with an area approximately equal to the cross-sectional area of the central portion;

the walls of these flat sections are made by stamping and cutting a metal sheet;

the side edges of the two walls of the hollow flat section are welded;

characterized in that:

the walls of each hollow flat section are both rigid and very thin, their embossed central section has one or more sets of periodically changing bulges located on the same line, provided with steep riveted surfaces that create a large number of sharp edges directed at an angle or perpendicular to the line along which the bulges are located;

the gap between the opposite surfaces is the same, very small, precisely known and practically unchanged in the field of the provided pressure drops;

the gaps separating the flat sections are comparatively thin.

Before explaining the benefits of these new arrangements, it should be noted that in the American patents in question, the walls of the flat sections should not be thin and their stiffness is not a particular problem, so the relief of the central portion of the walls is not a solution to the problem of stiffness. which in this case is unlikely to exist. The considerable thickness of the walls made of ordinary metal sheets easily meets this requirement. The relief is designed to easily increase the heat transfer surface of flat sections without increasing their size. This is achieved due to longitudinal undulations resulting from relatively thin recesses evenly spaced in the walls at a certain distance from each other. A specific profile of these undulations is shown; it is ordinary and can hardly be characterized as to some extent original, since in this type of heat exchanger this aspect is not of interest. Nevertheless, due to these undulations, the internal channel of the hollow flat sections has either increasing or decreasing thickness, symmetrically changing around a relatively high average value. In addition, the walls of the inner channel do not contain opposite inclined surfaces.

According to a first embodiment of the invention, the device, firstly, comprises flat sections with very thin rigid walls (for example, 0.15 mm for certain steels) that have extremely high hardness and limited elasticity due to the hardening obtained as a “bonus” during standard (cold) stamping; each surface of these concavities and bulges serves as a rigid strip, in addition, each sharp edge acts as an edge in which these stripes are embedded. Consequently, these bands under the action of the applied pressure drop can bend only very limitedly. In particular, if the overpressure acts externally, this deflection always remains significantly less than the internal thickness of the hollow flat section, the thickness of which, measured between the surfaces of the convexes, is precisely known and extremely small (for example, 0.3 mm) in accordance with the design. This prevents any contact between the walls of opposing surfaces, so that the heat transfer function between two fluids is always carried out appropriately.

Under these conditions, each embossed hollow flat section in accordance with the invention has significant initial stiffness due to the fact that the metal constituting its walls is riveted, and also due to the fact that periodically varying bulges significantly increase the moment of inertia of the flat section. Thus, these doubly rigid, very thin strips are able to perfectly function as an efficient heat exchanger between two fluids circulating along the two surfaces of these strips, even if there is a high pressure drop between these fluids. The immediate properties of these stamped periodically varying bulges, which should provide this rigidity, determine the basis of the invention. They take the form of steep riveted surfaces formed by significant local elongations of the initially flat sheet, which, thus, creates a number of very thin, very rigid strips, all of whose edges are embedded in the ribs formed by the sharp edges of the bulges.

The sharp edges of the dihedrons that form these steep surfaces between themselves have a second known effect - the effect of increasing the apparent thermal conductivity of air; faces oriented at an angle and / or perpendicular to the direction of air flow have the effect of creating significant turbulence, in general, rapid air flow passing through relatively thin gaps separating the flat sections. Such an arrangement in the case of vertically mounted undulating flat sections in the considered US patents would not matter, since the slow air flow passes through the gaps separating them with inaccurate sizes, circulating due to natural convection.

If now, to complete this argument, we turn to the European patent TET, then we can see that all of the above reasons that limit productivity in the new heat exchanger are eliminated and replaced by their opposites: the walls and inner channel have a very small, accurate and known thickness, and the central channel, as will be described in detail below, can be removed. On the contrary, all the positive properties related to the embossed walls of the hollow flat sections of the whole polymer heat exchanger described in this European patent are preserved. These properties are complemented by characteristics arising from hardening of the used metal sheets. By combining these properties with the advantages of the heat exchanger described in the American patent, together with the use (in the context of the envisaged high pressure drops a priori impractical) of very thin walls and the creation of a very thin internal channel, a new, non-obvious heat exchanger is obtained. Consequently, this new heat exchanger has a performance level that far exceeds the performance level of the already highly efficient one-piece polymer heat exchanger, which complies with the European TET patent.

In accordance with special characteristics that complement the basic properties described above,

each hollow flat section contains at least two rows of periodically varying bulges;

two adjacent rows are separated by a thin, straight partition formed by two stamped inner protrusions connected by welding;

the height of these protrusions is equal to half the internal width of the flat sections at the vertices of their bulges.

These latter measures, taken due to the possibility outlined in the American patent in question, in order to improve the stiffness of the flat sections, if they are large (m ² ), give two extremely useful results for the proposed heat exchanger. Firstly, under the influence of a relatively high internal overpressure applied to the hollow planar sections of such a heat exchanger, the direct inner partition retains a value of the inner thickness of the embossed central portion that is practically independent of the pressure drop acting on the thin walls of the flat sections. As a result, hollow flat sections with very thin walls, reinforced by the corresponding relief, are able to withstand relatively high internal overpressure without damage. Without such welded inner protrusions, adjacent rows of very rigid periodically varying bulges would be separated by flexible zones acting as a hinge. In response to such excess pressure, this would lead to a slight bulging of the flat sections, causing a significant reduction in heat transfer in the spaces between them or even rapid wear of the flat sections. However, with such partitions formed by these two welded inner protrusions, it is not necessary to systematically increase the thickness of the very thin walls of the hollow flat sections so that they can withstand temporary high internal overpressure. This means that lighter, less expensive heat exchangers can be manufactured.

A second advantage of these welded inner protrusions is the greater efficiency of the required heat transfer. The inner partition, thus formed between two adjacent rows of periodically varying bulges, creates a barrier to the flow of fluid entering the hollow flat section. The first effect of each barrier is to prevent a significant direct flow between two external collectors, along a smooth wall with a small surface area, which is therefore ineffective for the required heat transfer, since this surface is not covered by a strong air stream, because it is located in the rear area of the collector located upstream. On the other hand, the second effect of this barrier is the direction of the incoming flow to two rows of periodically varying bulges, which have high heat transfer efficiency and, thus, maximize the heat transfer.

It should be noted that for the heat exchanger with large hollow flat sections with relatively thick walls, described in the US patents under consideration, these two advantages are not of great interest. In this heat exchanger, the maximum pressure drop that occurs at the bottom of large vertical flat sections is the low hydrostatic overpressure created by the cooling oil. The proposed heat exchanger does not apply to this; it is clear that this heat exchanger can be installed in any relevant position, in addition, it can operate at very high pressure drops. Moreover, since the oil circulates from the top to the bottom due to natural convection in hollow flat sections, the dimensions of which are much larger than the size of the external manifolds, the low dynamic pressure upstream due to the low circulation speed prevents the oil from choosing a fast straight path from one reservoir to another .

In accordance with properties that complement the previous characteristics:

the angles formed by the normals to two adjacent surfaces of periodically varying convexities are at least 30 °, so that the sharp edges of these surfaces can be effective in creating turbulence and commensurate with the ribs into which the surfaces of these convexes are embedded;

the maximum normal angle to two adjacent surfaces is limited by the constraints dictated by the conditions under which the considered metal sheet is stamped.

In accordance with the properties that complement the previous characteristics, the opposite surfaces of the flat section have parallel walls, and the gap separating these walls is constant and has a value of the same order as the wall thickness.

In accordance with properties that complement the previous characteristics:

periodically varying bulges have in themselves two surfaces in the form of an isosceles trapezoid, having a common longitudinal face and two joint rhomboid surfaces;

the long diagonal of the diamond-shaped surfaces can have a size several tens of times greater than the wall thickness of the flat sections.

According to properties that are alternative to the previous characteristics:

periodically varying bulges themselves have two triangular surfaces and two joint hexagonal surfaces having a common transverse face;

the distance between the transverse faces of the hexagonal surfaces may be several tens of times greater than the wall thickness of the flat section.

In accordance with properties that complement the previous characteristics, the embossed central portion of each hollow flat section is connected to the external manifolds by two connecting sections having two lateral edges with smooth walls with a significant slope, containing parts of truncated cones.

According to properties that complement the previous characteristics, external collectors have an aerodynamic profile that can minimize their flow resistance.

In accordance with possible properties that complement the previous characteristics, symmetrical convex surfaces seem to be cut by a diamond-shaped pattern and contain several secondary surfaces equipped with additional sharp edges.

As a result of these various measures, the bulk conductivity of the heat exchanger manufactured in this way is extremely high. There are several reasons for this. Firstly, flat sections have metal walls with insignificant thermal resistance, secondly, the thermal resistance of a very thin layer of water or oil inside the flat sections is small despite the laminar flow of this layer and the relatively high thermal resistance of the mentioned liquids, thirdly, turbulence and the apparent thermal conductivity of the air circulating between the flat sections increases with the height of the bulges and the total number of sharp edges contained in them. Thanks to at least two rows, each of which comprises several periodically varying bulges, provided with surfaces inclined at an angle of about 45 °, an advantageous compromise is reached between the various parameters involved. Stamping of bulges whose surfaces are inclined at an angle of less than about 50 ° is a common operation that does not pose any problems in manufacturing. A minimum angle of 30 ° between the normals to two adjacent surfaces provides sufficient turbulence in the air flow and a minimum width for each row of bulges in the central portion of the flat sections if the height of these cavities and bulges is fixed. In addition, the minimum angle of 30 ° between the normals to two adjacent surfaces gives the face under consideration sufficient rigidity comparable with the rigidity of the rib, in this case the faces are jointly comparable with the network of ribs.

In addition, due to the heat exchanger formed by packing a large number of such identical flat sections connected to two external collectors, it is possible to significantly reduce the pressure drop of the fluid circulating in them at a constant speed and in a laminar flow, the speed of which, depending on the circumstances, can be relatively high. In any case, such a package significantly reduces the energy that is needed to pump the liquid. In addition to the use of external collectors with an aerodynamic profile, despite the relatively large gap separating the flat sections, their largest size, set parallel to the flow rate of two intersecting fluids, leads to a significant reduction in the aerodynamic resistance of the radiator and / or the energy required for its ventilation.

As for the metals that can be used to make the walls of hollow flat sections in accordance with the invention, it should be noted that there are few of them, but they are well known to stamping specialists, and the choice (for example, steel or aluminum) is ultimately determined by the mechanical characteristics of these metals in the operating temperature range of heat exchangers incorporating such flat sections.

As a result of these various measures, the industrial production of the proposed very high-performance heat exchangers includes a number of completely controllable operations that are relatively easy to automate. As a result, the mass production achieves the beneficial cost of such heat exchangers. These operations are as follows:

1) stamping and cutting from a thin metal sheet of identical walls of a flat section;

2) turning one wall upside down;

3) the assembly of two adjacent walls by welding their side flanges and protrusions of their inner central section;

4) mounting and fastening by welding these hollow flat sections to their two outer manifolds.

According to the invention, a compact radiator with a very high bulk conductivity is characterized by the following:

the radiator contains two identical groups of heat exchangers made of thin metal hollow sheets, related to the two main collectors located upstream and downstream, which are equipped with flat rectangular trapezoidal surfaces, slightly separated from each other, and arranged so that their right angles are located against a friend;

individual heat exchanger collectors in each group, located upstream and downstream, respectively, at constant intervals slightly larger than the width of the central portion of the heat exchangers, are attached to two surfaces of two main collectors located upstream and downstream.

Thanks to these measures, the radiator can be constructed with a very high volumetric conductivity and the minimum possible main cross-section (should be allocated up to 0.10 dm ² per kW). A large number of heat exchangers, in turn formed by a large number of metal hollow flat sections packaged in accordance with the invention, can be attached to either of the two sides of the two main collectors. This compact radiator also requires very little energy to pump and vent, about five times lower than the energy needed for radiators with solid fins with the same thermal conductivity.

The properties and advantages of the invention will become more apparent after reading the following description of a non-limiting embodiment of the invention, which is accompanied by links to the accompanying drawings. The drawings depict the following.

Figure 1. Top view of the first embossed wall of the proposed hollow flat section.

Figa. Top view of the second embossed wall of the proposed hollow flat section.

Figv and 2C. Views of the individual surfaces of this wall.

Figure 3. A longitudinal section of periodically varying bulges on the first wall.

Figure 4. A longitudinal section of one of the ends of a hollow flat section welded to the collector.

Figure 5. Isometric perspective of a heat exchanger with fifteen hollow flat sections.

6. Top view of the proposed radiator designed using these heat exchangers.

Figure 1 shows a first embodiment of a thin metal wall 10 of a hollow flat section. This wall was stamped and then cut so as to obtain a relief central section 13, placed between the two connecting sections. As an example, this wall is made of aluminum and has a thickness of 0.3 mm; the width of the relief central section of the wall is 60 mm, the length is 76 mm. The central portion 13 is composed of two adjacent identical rows 12 and 14 of periodically varying bulges separated by a thin non-curved zone 16 with a width of 4 mm. Two connecting sections 18 and 20 have smooth walls. Each row contains two identical regions of alternating relief composed of bulges and concavities, namely for rows 12-14 of four bulges 22 _1-2 and 24 _1-2 on one side and four concavities 22 ' _1-2 and 24' _{1- 2} on the other hand. Concavities are depicted in gray. Each bulge 22 _1-2 -24 _1-2 or each concavity 22 ' _1-2 -24' _1-2 has a panniform shape with four slopes having very sharp sharp edges, that is, for each periodically varying bulge in row 12: -first, in itself, two symmetrical trapeziums 26 _1-2 and 28 _1-2 for convexities and 26 ' _1-2 and 28' _1-2 for concavities, each of which has a large base 19 mm long, secondly, together with the adjacent bulge in the same row, two isosceles triangles 30 _1-2 and 32 _1-2 for the bulges and 32 ' _1-2 for concavities, all with a base of 28 mm, thirdly, longitudinal the ridge is 34 _1-2 for the bulges and 34 ' _1-2 for the concavities, all 5 mm long; fourth, the same height 5 mm. It should be noted that two pairs of isosceles triangles 30 ₂ -30 ' ₁ and 30' ₂ -32 ₁ in row 12 (and similarly in row 14), which relate to two successive alternations of two periodically changing reliefs, form two flat rhombuses .

In the center of a thin straight section 16, which divides in two the embossed central section 13 of the depicted wall 10, the inner protrusion 36 is made by stamping 2 mm wide, with symmetrical sides and such rigidity as the stamping technology allows. The protrusion 36 has a height equal to half the maximum gap separating the ridges on the two walls of the fabricated hollow flat section (i.e., as indicated below, 0.2 mm). Two lines 38-40 separate the parallel outer edges of two rows 12-14 of periodically varying bulges on the wall of the hollow flat section from a pair of parallel outer flanges 42-44, forming part of the sealing surface of the two walls of the flat section. Lines 38-40 and flanges 42-44 have a width of 1 mm and form a thin ledge with a height of 0.2 mm, defining half the internal thickness of the flat section on the skates of its bulges. These two flat lines 38-40 end in two flat parts 46-48 of the two connecting sections 18-20 of the wall 10, and two parallel flanges 42-44 end with two pairs of oblique outer flanges 50 ₁ -50 ₂ and 52 ₁ -52 _{2 of} the same connecting sections. They form another part of the sealing surface of the walls of the flat section. Each flange 50 _1-2 or 52 _1-2 forms an angle of 60 ° with the longitudinal line of symmetry of the wall 10. The end of each connecting section 18-20 contains an almost flat part 54-56 in the form of a truncated cone, half the angle of the cone solution is 87.5 °. This conical part is bounded by two pairs of arcs 58 _1-2 and 60 _1-2 , the last pair has a length of 8 mm. Their ends are connected to each other by means of two steps 1.5 mm high, so that the area of each of the holes located upstream or downstream and thus made for a hollow flat section is 24 mm ² , which is approximately equal to the cross-sectional area the inner space of the embossed central section 13 of the flat section.

On figa shows a stamped and then cut a thin metal wall 11, which forms a second embodiment of the proposed hollow flat section. The wall 11 differs from the previous wall 10 only in relation to its relief section, which contains only one row of bulges 15 with a width of 26 mm, and the shape of its periodically varying bulges. A single row contains three bulges 22b _1-3 and three concavities 22'b _1-3 , the concavities are indicated in gray. Each bulge 22b _1-3 and each concavity 22'b _1-3 has a roof-like shape with four steep slopes. As a result, each of the three periodically varying bulges in row 15 has: first, by itself, a pair of symmetrical side triangles 25b _1-2 , 27b _1-2 , 29b _1-2 for the bulges and similar triangles 25'b _1-2 , 27'b _1-2 , 29'b _1-2 for concavities, the base of each triangle being 14 mm, and secondly, together with the adjacent convexity, the central hexagons 31 _1-5 , all hexagons having a transverse ridge 18 mm long and the same height of 5 mm.

In FIGS. 2B and 2C, as variants of the convex surfaces shown in FIGS. 1 and 2A, two of the main surfaces (see FIG. 2A) have secondary surfaces. FIG. 2B shows a triangular lateral surface 25 having three secondary surfaces 37 _1-3 , which form a relatively flat trihedron with three sharp edges, with a pyramidal tip 39 located in the center of gravity of this triangle. On figs shows a hexagonal longitudinal surface 31, equipped with six triangles with coplanar sides 41 _1-6 , with a central pyramidal tip 43 _1-6 , similar to the tip 39 in figv. The height of points 39 and 43 _1-6 is determined by the limitations of sheet metal stamping technology.

1 and 2A show two possible shapes that can take on bulges on the embossed walls of the proposed hollow flat sections. On figv and 2C depicts possible options for the main surfaces of these bulges, allowing to improve their ability to produce turbulence in the air flow between the flat sections.

Figure 3 shows an enlarged longitudinal section along the axis AA '(see figure 1) of one of the ends of the part of the hollow flat section before attaching it to the collector. This flat section is the result of welding two walls 10a and 10b, the wall 10b being a wall 10a turned upside down around the transverse axis of symmetry BB ′ (see FIG. 1). Section AA 'is made along the ridges 35 ₂ and 35' _{2 of the} periodically varying relief formed by the bulge 24 ₂ and concavity 24 ' ₂ in row 14, it passes through the connecting section 18 of the wall 10a of this flat section. Figure 4 shows an enlarged section of the same end of the flat section, made along the longitudinal line of symmetry CC '(see figure 1) of rows 12 and 14 of periodically varying bulges and connecting sections 18 and 20 of the wall 10a.

In FIG. 3, the convexities and concavities of the first embodiment of the lower wall 10b and the upper wall 10a of the flat section are inverted, so that the parts 24 ₂ and 24 ′ _{2 of the} upper wall 10a, which are visible in the profile in FIG. 3, are concave and convex, respectively. The bulge 24 ' ₁ and the concavity 24 ₁ on the wall 10b, which are defined above, are placed respectively in the concavity and bulge. The thickness of the portion 62 of the inner channel of the hollow flat section located between the embedded skates 34 ₁ -35 ' ₂ or 34' ₁ -35 _{2 of the} relief zone of the flat section is 0.4 mm, and the thickness of the portion 64 of the inner channel located between the slopes of 45 ° or the drooping sides of the bulges, equal to 0.28 mm. The thickness of the inner channel 66 between the flat parts of the connecting sections 18 and 20 is 0.4 mm

In accordance with figure 3 in the right part of the section along the line AA ', firstly, shows the beginning of the 68 gradual separation of the walls from two opposite conical sections 54-56 of the walls 10a-10b, which end these two connecting sections, secondly, two symmetrical ledges of these walls, which begin with circles 58 ₂ and 58 ₁ , and thirdly, two symmetrical outer flanges 52 ₂ and 50 ₁ defining the sealing surface of the walls 10a and 10b.

Figure 4 shows a section along the longitudinal axis of symmetry CC 'of the end of one hollow flat section, coupled, welded by a shoulder 70 into the edges and ends of the groove 72 in the form of an arc of 120 °, made in the connecting casing 74 of the external manifold 75, formed by two welded to each other oblong casings. The sectional view shows two parallel sections 16a and 16b of the thin central portion of the walls 10a and 10b, separated by a gap of 0.4 mm, and two other diverging sections 54 and 56, corresponding to the opposite sections of the connecting sections of the two walls 10a and 10b of the hollow flat section. The gap between the extreme edges of these two diverging sections is 3 mm, and the arc length is 120 ° 60 ₂ and 60 ₁ (see figure 1) - 8 mm. As a result, the area of direct cross sections of the internal channel with embossed walls and the area of the holes at the ends of the ribs are approximately equal.

Figure 5 shows an elementary heat exchanger 76 containing fifteen thin hollow metal sections 78 _1-15 with embossed walls. The ends of these hollow flat sections, as shown above, are inserted and welded into grooves with circular edges that have a width of 3.5 mm, spaced 8 mm apart and are made in the outer manifolds 80-82, with the formation of an aerodynamic profile. To make it possible to easily produce such welded joints, the collectors 80-82 are composed of two elongated casings having a U-shaped cross section and welded to each other along line 83. They are made of metal strips cut from sheets identical to those sheets that are used for the production of walls from stamped sheets. Grooves with an appropriate width, length and gap are made into half of these strips, then two types of strips prepared in this way are converted into front cover and connecting shrouds 75 using two corresponding templates with protruding and hollow profiles. After this, the holes are welded in various hollow flat sections to the grooves in the connecting covers. Then, two front closing covers are alternately welded to the previous two, and one of their ends is sealed tightly to form both two streamlined external collectors and the heat exchanger itself.

Figure 6 shows a top view of a compact radiator 81. Six identical heat exchangers 76 _1-6 can be mounted in parallel on one side of two flat main collectors 84-86, having the form of a rectangular trapezoid and mounted with a jack, to form a compact radiator with the corresponding total thermal conductivity . These two collectors 84-86 have parallel sides 88 _1-2 and 90 _1-2 and a thickness approximately equal to the maximum size of the straight cross sections of the outer collectors 80 _1-2 . Two adjacent heat exchangers are mounted so that the lateral edges of their flat sections practically adjoin each other, or install them with slight interleaving. In the first case, the lower parts of the external collectors located upstream (80 _1-6 ) upstream and downstream (82 _1-6 ) upstream are inserted at the same depth into the corresponding round holes 94 _1-6 and 96 _1-6 located at regular intervals along the longitudinal sides of the 92-93 front surfaces of the main collectors, then they are welded. In the second case, the insertion depth of the collectors is different for heat exchangers in uneven and even rows. The length of the longer 88 ₂ -90 ₂ parallel sides of the two main collectors 84-86 is determined by the number of heat exchangers 76 mounted. The short sides of the two main collectors 84-86 have lengths defined by the interval between the external collectors 80-82 and the gap 100 (usually 5 mm), dividing the inclined sides of the main collectors.

Such an arrangement of heat exchangers formed by packages of thin hollow metal flat sections with very thin walls reinforced with relief makes it possible to form a compact radiator, which is highly preferred for cooling large-capacity heat engines (more than 100 kW). It has a small main cross section, very high thermal conductivity, low power consumed for pumping and ventilation, limited volume and weight. The radiator is suitable for the treatment of exhaust gases of diesel engines, after cooling used to improve engine performance at low speeds. In a more general sense, using such a compact metal device, efficient heat transfer between two fluids, in particular between a liquid and a gas having a high temperature and / or pressure drop (up to about 600 ° C. and 1 MPa) can be effected.

The invention is not limited to the described examples. The length and width of the hollow flat sections can be significantly larger than shown in figure 1, and be several decimeters. The same can be said for periodically varying bulges in each row and the number of rows in each flat section. In practice, the maximum dimensions of a flat section are determined by the dimensions of the table of the available stamping presses. As for the number of hollow flat sections in the heat exchanger, it can reach several tens. The same can be said for the total number of heat exchangers assembled in a compact radiator.

It should also be noted that the proposed hollow flat sections can be manufactured using two corresponding embossed walls - similar to each other, but not identical due to the fact that they have different side ribs. Instead of two identical walls with side flanges that contain a small ledge that defines the half-thickness of the inner channel of the central section, flat sections can have one wall with flanges having a ledge with a height twice as high as the height of the previous ledge, and the second wall without any any ledge. This will require the use of two different pairs of stamp matrices, but with large volumes of output this will not have a large economic impact.

The drawings above show hollow flat sections for a liquid-gas heat exchanger. Fluid circulates in these metal flat sections with a very thin inner channel (0.3 mm). Obviously, in the case of gas-gas heat exchangers, the thickness of this inner channel is much larger (usually more than 1 mm), and the gap between the flat sections is generally smaller than in the illustrated heat exchanger. This is due to the fact that the mass flow rates and velocities of two gases on one or the other side of the walls of the hollow flat sections are comparable.

Moreover, for special applications, especially in chemistry and some other areas in which corrosive fluids are used, it is often desirable, and sometimes necessary, to have access to high-performance glass heat exchangers that are excellently suited for the respective operating conditions. To this end, these glass heat exchangers can be provided with high volumetric conductivity, but in the middle between the conductivities indicated above for plate heat exchangers made either from a whole polymer or from the metal of the type proposed in the invention (20 or 100 W / ° C / dm ³ ). As for the maximum temperatures and pressure drops that can be applied to these glass heat exchangers, they are lower than the values that can withstand the proposed metal heat exchangers, but higher than the values relating to solid polymer heat exchangers in accordance with the European patent TET. Thus, for applications of this type, it can be advantageous to have access to polymer heat exchangers with volumetric conductivity of about 50% higher than the conductivity of solid heat exchangers, while maintaining their temperature and differential pressure ranges.

To this end, they can apply a new technology to the proposed metal heat exchangers, and instead of a metal sheet, simply apply a glass or polymer sheet and process it by hot stamping or high-temperature shaping. The manufacturing methods used in these two technologies for forming products from sheet materials are similar to each other: in the first technology, mechanical pressure and two forms consistent with each other, containing concavities and / or protrusions, are used, in the second technology, a single form with concavities and / or protrusions. Both technologies use appropriate heating. However, no freewheeling is performed.

The thickness of the walls and internal channels of such glass or polymer heat exchangers with hollow flat sections having embossed walls and external collectors will inevitably increase in accordance with the specific mechanical properties of the type of glass or polymer used. Their performance will directly depend on these properties, as explained above.

Claims (12)

1. A heat exchanger (76) with low weight and high bulk conductivity, capable of working with fluids at high pressure drop and high temperatures, in which:
hollow flat sections (78 _1-15 ) with a thin internal channel are assembled in a bag, arranged at equal intervals from each other and connected to external collectors (80-82);
these flat sections contain a relief central section (13) located between two connecting sections (18-20) provided with thin holes (60 _1-2 ), with an area approximately equal to the cross-sectional area of the central section;
moreover, the side edges (42-44) of the two walls (10-11) of the hollow flat section (78) are welded;
characterized in that
the walls (10-11) of each hollow flat section (78 _1-15 ) are rigid, their embossed central section (13) has one or more aggregates (12-14) periodically changing, located on the same line of the bulges (22-22 ', 24-24 ') provided with steep surfaces (24, 26, 28, 30) that create a large number of sharp edges directed at an angle and / or perpendicular to the line along which the bulges are located;
the gap (64-66) between the opposite surfaces is the same, precisely known and unchanged in the area of the provided pressure drops. 2. The heat exchanger according to claim 1, characterized in that
hollow flat sections are made of metal; wherein
the walls of these hollow flat sections (78) are made by stamping and cutting a metal sheet; steep surfaces of periodically varying bulges are riveted. 3. The heat exchanger according to claim 1, characterized in that the hollow flat sections are made of glass or polymer;
the walls of these hollow flat sections are made by hot stamping or high-temperature shaping, and then cutting out a sheet of glass or polymer. 4. The heat exchanger according to any one of claims 1 to 3, characterized in that
each hollow flat section (78) contains at least two rows (12-14) of periodically varying bulges;
two adjacent rows are separated by a thin straight partition (36) formed by two stamped or thermoformed internal protrusions assembled by welding;
the height of these protrusions is equal to half the maximum value of the internal width of the hollow flat sections. 5. A heat exchanger according to any one of claims 1 to 3, characterized in that the angles formed by the normals to two adjacent surfaces of periodically varying convexities are at least 30 °, so that the sharp edges of these surfaces effectively create turbulence and withstand pressure drops between fluids;
the maximum normal angle to two adjacent surfaces is limited by the constraints dictated by the conditions under which the material in question is stamped or hot formed. 6. A heat exchanger according to any one of claims 1 to 3, characterized in that the periodically varying convexes themselves have two side surfaces in the form of an isosceles trapezoid (26 _1-2 , 26 ' _1-2 ) having a common longitudinal face (34 ₁ , 34 ' ₁ ), and two joint diamond-shaped surfaces (30 ₂ -30' ₁ );
the long diagonal of the diamond-shaped surfaces can have a size several tens of times greater than the wall thickness of the flat sections. 7. The heat exchanger according to any one of claims 1 to 3, characterized in that the periodically varying convexes themselves have two side surfaces in the form of an isosceles triangle (25b _1-2 , 27b _1-2 , 29b _1-2 ) for the convexities and ( 25'b _1-2 , 27'b _1-2 , 29'b _1-2 ) for concavities and two joint central hexagonal surfaces for convexities (22b _1-3 ) and for concavities (22'b _1-3 ) having common transverse face;
the gap between the transverse faces of the hexagonal surfaces can be several tens of times the wall thickness of the flat sections. 8. A heat exchanger according to any one of claims 1 to 3, characterized in that the embossed central section (13) of each hollow flat section is connected to the external collectors by means of two connecting sections (18-20) having two side edges with smooth walls with a significant slope containing parts of truncated cones (54-56). 9. The heat exchanger according to any one of claims 1 to 3, characterized in that the opposite surfaces of the hollow flat section have parallel walls, and the gap (64) separating these walls is constant and has a value of the same order as the wall thickness. 10. The heat exchanger according to any one of claims 1 to 3, characterized in that the symmetrical convex surfaces are cut by a diamond-shaped pattern (25-31), contain several secondary surfaces (37 _1-3 -41 _1-5 ) and are provided with additional sharp edges. 11. The heat exchanger according to any one of claims 1 to 3, characterized in that the external collectors (80-82) of the hollow flat sections have an aerodynamic profile that can minimize the resistance of the heat exchanger;
each collector is composed of two elongated casings, of which one casing (75) is designed to connect to the flat sections, and the other casing is designed to be closed in front, the cross section of the collectors is U-shaped, and the collectors are connected to each other via a line (83) weld. 12. A compact lightweight radiator with high or very high thermal conductivity, characterized in that
contains two identical groups of heat exchangers (76) with hollow flat sections (781.15) made of metal, glass or polymer, as disclosed in claim 5;
these two groups of heat exchangers are interfaced with two thin main collectors, one of which - the collector (84) - is located upstream, and the other - the collector (86) - is located downstream, which are equipped with flat rectangular trapezoidal surfaces, slightly separated from each other gap (100) and placed so that their right angles are located against each other;
individual heat exchanger collectors in each group, namely, collectors (80 _1-6 ) located upstream and collectors (82 _1-6 ) located downstream, respectively, at constant intervals greater than the width of the central section (13) heat exchangers attached to two respective surfaces of two main collectors located upstream and downstream.

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