Heat exchanger and related exchange module
A heat exchanger, includes modules defining a first path for a first fluid, each having two metal sheets forming between them a network of channels which are located in parallel with each other from the fluidic point of view, each channel interposed between two neighbouring channels of the network being, over the whole of its developed length, adjacent to these two neighbouring channels from which it is isolated by two respective weld lines connecting the two metal sheets; a second path for a second fluid is defined between the modules; and an overall variation in the passage cross-section over the length of at least one of the paths with continuity of profiles of the channels.
This invention relates to a heat exchanger and a heat exchange module intended to form part of such an exchanger.
A heat exchanger is known from WO 98/16786 in which modules define a first path for a first fluid, each one comprising two metal sheets defining between them a network of channels arranged mutually in parallel from the fluidic point of view. Each channel interposed between two neighbouring channels of the network is, over the whole of its developed length, adjacent to these two neighbouring channels, from which it is isolated by two respective weld lines joining the two metal sheets. A second path for a second fluid is defined between the modules, in the internal volume of a casing enclosing the modules.
According to this document, the modules are manufactured from two flat sheets, which are joined together by weld lines comprising the above-mentioned lines isolating the neighbouring channels from each other, then a pressurised liquid is introduced between the metal sheets, producing an inflation of the two metal sheets between the weld lines, thereby to form the channels. The channels of a same module are in parallel from a fluidic point of view between two distribution zones common to all the channels of a same module, themselves connected to connecting boxes.
During the hydroforming step, i.e. the above-mentioned inflation step, the inflation in the distribution zones is limited so that when in operation the second fluid more easily enters into pseudo-channels formed between the neighbouring modules in the troughs between the successive inflated zones. Apart from these zones of limited inflation, the profile of the channels is continuous and even uniform. Thus the fluid passage cross-sections are only modified locally at the inlet and outlet. The transition between the modified passage cross-section zone and the zone with a constant passage cross-section along the channels, is abrupt and localised.
WO 01/07 854 describes an improvement according to which the channels are U-shaped instead of rectilinear. In a variant illustrated in
DE-A1-19639115 describes a heat transfer element in the form of a plate constituted by two metal sheets defining between them channels for an exchange fluid. In embodiments described with reference to
Such an exchanger is particularly complex to produce and its flow rate is very limited.
The object of this invention is to propose a heat exchanger which without significant extra expense allows the progress of the flow rates of at least one of the exchange fluids to be controlled, in particular when this fluid undergoes at least a partial change of state, for example condensation, while flowing.
Another object of the invention is to produce a heat exchanger with low pressure losses distributed in a controlled manner.
Another object of the invention is to propose a heat exchange module which can be part of such an exchanger.
According to the invention, the heat exchanger in which modules define a first path for a first fluid and each module comprises two metal sheets forming between them a network of channels which are in parallel with each other from the fluidic point of view, wherein each channel which is interposed between two neighbouring channels of the network is, over the whole of its developed length, adjacent to these two neighbouring channels and is separated therefrom by two respective weld lines joining the two metal sheets, and a second path for a second fluid is defined between the modules, is characterised by an overall variation in passage cross-section along at least one of the paths, with the channels having continuity of profile.
It has been found according to the invention that a structure of the type described in WO 98/16 786 or WO 01/07 854, i.e. with channels isolated from each other which are adjacent over their whole developed length, is particularly suitable for implementation of overall variations in passage cross-section along at least one of the paths.
By “overall” variation is understood a variation other than the localised path-end variations described above in relation to the prior art, and other than the local variations due for example to the fact that the second exchange fluid, if circulating transversally to the channels, experiences for example a reduction in passage cross-section each time it passes an inflated part of one of the two adjacent modules.
By “continuity of profile of the channels” is indicated that the variations in passage cross-section are not due to profile discontinuities such as cross-sectional variations due to abrupt widening or narrowing, variations due to bifurcation of a single channel into two channels.
The overall variations in cross-section may be obtained according to the invention by channels of different hydraulic diameters, by channels the hydraulic diameter of which varies progressively from one end to the other, and/or by a relative arrangement of the modules which varies the hydraulic diameter between the modules for the second fluid and/or etc.
The hydraulic diameter of a passage for a fluid is the diameter of a theoretical cylindrical tube offering the same flow resistance as the passage in question having a profile other than a circular cylinder.
According to a second aspect of the invention, the heat exchange module comprising two metal sheets forming between them a network of channels with continuous profile arranged in parallel to each other from a fluidic point of view, each channel interposed between two neighbouring channels of the network being adjacent over the whole of its developed length to these two neighbouring channels from which it is isolated respectively by two weld lines joining the two metal sheets; is characterised by an overall variation in the passage section defined by these channels with continuity of profile of the channels.
Other features and advantages of the invention will become apparent in the following description, which relates to non-limitative examples.
In the attached drawings:
Generally, in the interests of clarity, all the drawings of this application are very diagrammatic, the number of channels in a module being markedly lower than would be found in most real situations, and the metal sheet thickness is represented as unduly large.
In the example shown in
Each channel extends with a continuous profile over the whole height of the module 2. All the channels 6 open at each upper and respective lower end, into an upper connection chamber 7 defined in an upper connecting box 8 or respectively in a lower connection chamber 9 defined in a lower connecting box 11. Thus the channels 6 together constitute a first exchange path for a first fluid and this first exchange path may, in operation, be connected by the connecting boxes 8 and 11 to an external circuit for this first fluid. The sealed connection of the channels 6 to the chambers 7 and 9 is provided by bars 12 of a suitable shape which are inserted between the ends of the modules 2 and together form a base for the connecting box 8 or 11 respectively. The channels 6 are thus in parallel from a fluidic point of view with each other between the two connection chambers 7 and 9. Each channel 6 apart from the two end channels of the network of channels of each module is adjacent over its whole developed length to two neighbouring channels, while being isolated from these two neighbouring channels by a respective weld line 4 which is continuous over the whole developed length of the channel. In the case illustrated here where the channels are rectilinear, the developed length is the same as the overall length. In other cases where the channels are curved and for example have a U-shape as in WO 0107854, the developed length is of course very different to the bulk length.
A second path for a second exchange fluid is defined between the modules 2. The inlet and the outlet in this second path are by means of second connecting boxes 13 and 14 located on the side wall of the casing 1 to enable their internal chambers 16 and 17 respectively to communicate with the gaps 18 between the edges of modules 2, on the side of the ends 19 of the bars 12 which faces away from the connection chamber 7 or 9. In the example of the connecting box 13, its periphery is leak-tightly welded to periphery 22 of a rectangular opening formed in casing 1. One side 21 of the periphery 22 is formed by the aligned ends 19.
Thus a second exchange fluid flows between the connecting boxes 13 and 14, passing through a second exchange path constituted by the internal space of casing 1 located between modules 2.
In the example shown, the lateral connecting box 13 is located in the upper part close to the upper connecting box 8 for the first path, while the lateral connecting box 14 is located on the lower part of casing 1 close to the lower connecting box 11 of the first path. The second fluid enters laterally between the modules, flows between the modules parallel to the channels 6, then exits laterally by the other connecting box. Each of these two fluids may flow upwards or downwards according to the application. The name “counter-current exchanger” describes an exchanger with parallel currents in which the two fluids flow in opposite directions, one upwards and the other downwards in this example. The name “co-current exchanger” describes an exchanger in which the two fluids flow not only parallel, but also in the same direction.
The example shown in
In this example, the lateral connecting boxes for the second path 13 and 14 completely cover two opposite sides of the casing 1; these sides then being entirely open such that the second fluid flows in a horizontal direction parallel to the planes of modules 2. Such an exchanger where the two fluids flow in different directions is known as a “cross-current” exchanger.
The example in
In such a condenser, the second fluid has a volume flow rate which decreases from the inlet 23 to the outlet 24, as the initial volume of gas decreases to the extent that a part of the gas condenses.
Consequently, if the passage cross-section of the second path is approximately the same for the whole length of this second path between the inlet connecting box 13 and the outlet connecting box 14, the speed of flow will decrease. If this is an appropriate speed at the inlet of the second path, it will be too slow for effective exchange near the outlet. If, on the other hand, the speed is appropriate in the region of the outlet, it will be too high at the inlet and the gas will have a tendency to carry droplets along with it towards the outlet, contrary to the separation effect sought.
This example of a condenser has been chosen to clearly demonstrate the advantages of a different passage cross-section in different zones of the same path, but other examples can be envisaged, in particular in an evaporator, or also to adapt the speeds in the meaning of an optimisation of the result obtained, in particular in terms of heat exchanges.
In the example shown in
In the example of
When two modules 102 as described are placed side-by-side in parallel planes P, with the modules of the same hydraulic diameter placed facing each other, the available hydraulic diameter in the second path 28 between these modules 102 in a direction perpendicular to that of channels 6a to 6d varies overall from one end to the other of the second path. If for example the second path is ascending, in the configuration shown where the channels have a hydraulic diameter increasing from bottom to top, the hydraulic diameter of the second path decreases from its beginning to its end. This corresponds to the desired characteristics in the condenser in
In the example shown in
In the example in
In all the examples described up to this point the pitch Po between the weld lines 4 was the same for all the weld lines for one module and for all of the modules. In the example shown in
The example shown in
For the upper die 32 (not shown in
In all the examples described with reference to
In the example represented in
Such a module is useful in order to produce a condenser in a configuration according to
Such a module can also be arranged with the large end of the channels downwards in order to produce, for example, a reflux condenser; i.e. as described above with reference to
The inflation of the channels may be constant along each channel, or alternatively may increase from the narrower end to the wider end of each channel.
If, moreover, the inflations of the channels are variable as illustrated in
In the example shown in
In a way which is not shown, it is also possible to position the modules in relation to each other in a fan shape by relative pivoting about an axis parallel to the weld lines, thus to the longitudinal direction of the channels, in order to produce a variable hydraulic diameter of the second path when the exchanger is the cross-current type.
In the examples in
The invention is particularly applicable with the following dimensions:
- developed length of channels: 0.5 to 10 m
- width of the network of channels: 0.15 to 2 m
- pitch sequence of modules: 8 to 105 mm
- pitch sequence of weld lines: 10 to 100 mm
- inflation of channels: 5 to 80 mm measured inside the channels.
The metal sheets are typically of stainless steel of a thickness of a few tenths of a millimetre (no upper limit at 10/10) with the understanding that a thin sheet is preferable for thermal exchange but that the pressure differences between the two fluids and the thermal stresses must also be taken into account.
Of course, the invention is not limited to the examples described and represented. The means of varying the hydraulic diameter described may be combined in very many ways.
It is conceivable to produce channels which have a constant hydraulic diameter over one part of their length and a progressively variable hydraulic diameter over another part of their length.
The exchangers described with reference to
The invention is compatible with non-rectilinear channels, for example the U-shaped channels of WO 01/07 854.
With respect to the example in
-
- the inflation varies progressively along each channel;
- the pitch between weld lines, on the other hand, is constant.
Claims
1. A heat exchanger comprising:
- modules defining a first path for a first fluid, each comprising two metal sheets forming between them a network of channels which are located in parallel with each other from the fluidic point of view, each channel interposed between two neighbouring channels of the network being, over the whole of its developed length, adjacent to these two neighbouring channels from which it is isolated by two respective weld lines connecting the two metal sheets;
- a second path for a second fluid is defined between the modules; and an overall variation in a passage cross-section over the length of at least one of the paths with continuity of profiles of the channels.
2. A heat exchanger according to claim 1, characterised in that the pitch between the neighbouring weld lines varies progressively over at least part of the length of the channels of one module.
3. A heat exchanger according to claim 1, characterised in that the inflation of the metal sheets of a module varies progressively over at least part of the length of the channels.
4. A heat exchanger according to claim 1, characterised in that the pitch between neighbouring weld lines varies from one channel to the other of a module.
5. A heat exchanger according to claim 1, characterised in that the inflation of the metal sheets of a module varies from one channel to another.
6. A heat exchanger according to claim 1, characterised in that the arrangement of the modules in relation to each other produces an overall variation in the passage cross-section over the length of the second path.
7. A heat exchanger according to claim 1, characterised in that the overall variation in the cross-section of one of the paths is in the same direction as a variation in the flow rate of gas in this path intended for a phase change process.
8. A heat exchanger according to claim 1, characterised in that the modules are in parallel planes.
9. A heat exchanger according to claim 1, characterised in that the modules are in convergent planes.
10. A heat exchanger according to claim 1, characterised in that the modules have longitudinal edges forming an angle with each other, each being almost parallel to a respective outside weld line.
11. A heat exchange module comprising two metal sheets which between them form a network of channels located in parallel to each other from a fluidic point of view, each channel interposed between two neighbouring channels of the network being adjacent over its whole developed length to these two neighbouring channels from which it is isolated by two respective weld lines joining the two metal sheets, and wherein an overall variation in the passage cross-section is defined by the channels with continuity of profile of the channels.
12. A heat exchange module according to claim 11, characterised in that the pitch between neighbouring weld lines varies progressively over at least part of the length of the channels.
13. A heat exchange module according to claim 11, characterised in that the inflation of the metal sheets varies progressively over at least part of the length of the channels.
14. A heat exchange module according to claim 11, characterised in that the pitch between the neighbouring weld lines varies from one channel the other.
15. A heat exchange module according to claim 11, characterised in that the inflation of the metal sheets varies from one channel to the other.
16. A heat exchange module according to claim 11, characterised in that it comprises longitudinal edges each forming an angle with the other, each being almost parallel to a respective outside line of weld.
Type: Application
Filed: Jan 12, 2005
Publication Date: Jul 23, 2009
Inventors: Sylvain Benezech (Beaune), Pierre-Xavier Bussonnet (Dracy Le Fort), Michel Claudel (Sarrebourg), Florent Noel (Harskirchen)
Application Number: 10/585,601
International Classification: F28F 3/12 (20060101);