Deformable Exchanger
A heat exchanger includes two mutually isolated fluid circuits in close thermal contact, a first fluid circuit, or bundle (3), consisting of a helical winding of two walls and the second circuit consisting of a chamber containing the bundle (3), each circuit including its own fluid input and output elements. The heat exchanger is characterized in that the bundle is elastically deformable under the effect of excess pressure or low pressure.
The present invention relates to exchangers and notably to exchangers for providing heat exchange between two fluids.
Generally, it is known that heat exchangers applying fluids consist of two mutually isolated circuits but which are in thermal contact as close as possible, and through which travel both fluids respectively.
It is also known that maintenance of the heat exchangers and in particular their cleaning, is generally a long operation, difficult to perform efficiently or even sometimes impossible. Finally it is known that such cleaning sometimes consists of removing for example scale which was deposited in the exchanger along with the use of the latter.
Exchangers of the so-called plate and gasket type formed from more metal sheets may be disassembled plate by plate, so that it is thereby possible to access their circuits, even if this is a long operation to implement. However, these exchangers, because of their actual design, are therefore costly to utilize.
Moreover exchangers of the brazed plate type cannot be disassembled and therefore their circuits are also difficult to clean.
This is why focus was on helical exchangers which are made from two metal sheets which are wound and maintained spaced apart from each other by pins. After winding them, one proceeds with welding of the metal sheet edges in order to generate two independent fluid circuits, i.e. a first circuit comprised between both wound and welded metal sheets and a second circuit comprised between the different turns of the winding. For reasons related to the construction method, the user does not have access both to the space between both wound sheets and to the one between the various turns of the winding, so that it is impossible to achieve efficient mechanical cleaning of this exchanger and that one must content oneself with chemical type cleaning, which is often insufficient for certain applications.
Now these exchangers, because of their constitution, require that for proper effective maintenance, access be provided not only to the actual winding but also to their spaces between the turns. Now these are all the more reduced which makes cleaning of the exchangers even more problematic especially when dealing with removal of deposits such as scale from the latter.
However, a certain number of applications which would be open to this type of exchangers, such as uses in the food industry field, the medical field, the pharmaceutical field and in fine chemistry, or notably in electronics, involve periodical cleanings with high efficiency.
The object of the present invention is to propose means with which a user may carry out such cleaning and this in a simple and fast way.
Thus, the object of the invention is a heat exchanger comprising two mutually isolated fluid circuits in intimate thermal exchange contact, a first fluid circuit or bundle, being formed by a helical winding of two walls and the second circuit being formed by an chamber containing the bundle, each circuit including its own fluid input and output means, characterized in that the bundle is elastically deformable under the effect of excess pressure or low pressure.
According to the invention, the chamber will preferentially be of a tubular shape and, when the internal pressure of the bundle will be equal to its external pressure, its outer diameter will be slightly less than or equal to the inner diameter of the chamber. The diameter difference between the inner face of the chamber and the outer face of the bundle will be less than 6% of the diameter of the latter.
The tubular casing may include two bottoms, at least one of which may be removable, these bottoms being respectively crossed by the fluid input and output means, and means capable of providing the seal between the bottoms and the fluid input and output means of the bundle. These input and output means may respectively consist of two longitudinal tubes and the means capable of providing the seal between the tubes and the bottoms may consist of O-ring gaskets or a stuffing box.
The object of the present invention is also a method for intervening, such as for example for cleaning, on a bundle of a helical type exchanger including two mutually isolated fluid circuits in intimate thermal exchange contact, a first fluid circuit, or bundle, being formed by a helical winding of two walls, or bundle, and the second circuit being formed by a space delimited by a casing containing the bundle, each circuit including its own fluid input or output means, characterized in that it includes the steps of:
submitting before its removal, the bundle to low pressure, and/or to cooling relatively to its casing, so as to cause it to contract,
once the bundle is extracted from its casing, interrupting the low pressure,
proceeding with intervention on the bundle,
again submitting the bundle to low pressure and/or to cooling relatively to its casing, so as to cause it to contract before it being placed in the casing,
setting the bundle back to pressure and/or to room temperature as soon as it has been placed back in its casing.
According to the invention, the bundle may be made so that it is deformable under the effect of a pressure difference between the bundle and the chamber, of excess pressure or low pressure and it may be provided with an outer diameter less than the inner diameter of the casing, and periodical excess pressures and/or low pressures may be applied to the bundle in order to change its outer diameter and break the brittle components which may have adhered to the walls (scale) which are deposited on it.
The method may include a preliminary step consisting of disconnecting the bundle from its circuit.
It is also possible according to the invention to promote the intervention operation by submitting the bundle, once the latter is extracted from its casing, and before the intervention, to excess pressure and/or to heating relatively to the casing, which will have the effect of spacing out the turns of the winding from each other.
In order to avoid submitting the bundle to too strong pressure with the consequences of deforming the metal forming the winding beyond its elastic limit, a limiter, the diameter of which will be equal to the maximum diameter which should not be exceeded as desired, will be positioned around the bundle. This limiter may consist of a ring or sheath.
An embodiment of the present invention will be described hereafter as a non-limiting example, with reference to the appended drawing wherein:
An exchanger according to the invention which essentially consists of a casing 1 which is intended to receive a bundle 3, is illustrated in
The bundle 3 consists of a helical winding of two metal sheets 5 which are spaced apart from each other and welded so as to provide between them a fluid circuit. Spacing out these two metal sheets 5 is provided by a series of “pins” 7 which are generated and distributed over the surface of the metal sheets before folding the latter. These pins 7, once the winding has been carried out, also provide regular and controlled spacing between the turns. The space between both folded metal sheets includes a supply conduit 9 and a discharge conduit 11.
The casing 1 consists of a cylindrical tube 13, the inner diameter of which corresponds to the outer diameter of the bundle 3, so as to be able to receive the latter. The casing 1, as illustrated in
Thus, by simply disassembling the removable bottom 25, access is provided to the bundle 3, after having either disconnected the latter from the supply pipes connected to its conduits 9 and 11, or by positioning an outlet 11 with sufficient length.
It is known that this type of exchangers requires minimum play between the bundle 3 and the inner face of the tube in which it is positioned. Now, in certain exchangers, notably in stainless steel, which are intended for applications which require particular attention, notably in the field of pharmacy or in the food industry field, it is required that the bundle be able to be removed from its casing without forming scratches on the inner wall of the tube during this operation, such scratches notably forming nesting locations for bacteria.
In order to solve this problem, the bundle 3 is caused to be deformable at its diameter under the effect of a stress. In order to thereby make the bundle deformable, the thickness and the nature of the steel used will be varied.
On an assembled exchanger intended to be disassembled, retraction of the bundle 3 will be caused by connecting one of the inlets 9 or 11 to the latter, to a vacuum pump, after having blocked the other inlet, in order to create partial vacuum. The bundle may then be disassembled without any risk of scratching the inner face of the casing 1. Once the bundle 3 has been disassembled, the vacuum will be suppressed so that it will expand and resume its initial natural diameter, and then one will proceed with the intervention (notably with mechanical cleaning) on the latter.
The intervention may be made easier and more efficient if the bundle 3 is expanded beyond its rated diameter, by this time applying excess pressure to it. During this operation care will be taken in order not to deform it beyond the elastic limit of the material used, so that it may resume its rated diameter as soon cleaning and interruption of the excess pressure has been completed.
In order to limit the deformation to a maximum controlled value of the bundle 3, the latter may be surrounded, as illustrated in
Once the intervention on the bundle is finished, a vacuum is again established in the latter so as to be able to easily place it in the casing 1, and the vacuum pump is then disconnected so that the bundle resumes its rated dimensions and shape.
It is also possible according to the invention to resort to a change in relative temperature in order to cause the bundle to contract or to expand. Thus, before disassembling the bundle from its casing, a strongly cooled liquid notably close to or even less than 0° C. may be caused to flow in the bundle, so as to cause it to contract, and at the same time the casing may be submitted to a higher temperature than room temperature so as to cause it to expand.
Of course, according to the invention, it is possible to have either the low pressure and cooling, or the excess pressure and heating, act on the bundle simultaneously.
For certain applications, it is possible to provide the bundle 3 with a diameter less than the inner diameter of the casing 1. Such an arrangement is particularly interesting in that it provides automatic or quasi-automatic removal of brittle (limestone for example) deposits which occur on the walls of the bundle. Indeed, it is sufficient to submit the bundle, for example during its operation, to an excess pressure (or a low pressure) of the fluid which flows through it in order to deform and cause the bursting of the scale platelets which cover it. These operations may even be performed automatically.
Claims
1-12. (canceled)
13. A heat exchanger comprising two mutually isolated fluid circuits in intimate thermal exchange contact, a first fluid circuit, or bundle (3) being formed by a helical winding of two walls and the second circuit being formed by an chamber containing the bundle (3), each circuit including its own fluid input and output means, characterized in that the bundle is elastically deformable under the effect of excess pressure and low pressure.
14. The exchanger according to claim 13, characterized in that said chamber is of a tubular shape and when the internal pressure of the bundle is equal to external pressure, its outer diameter is slightly less than or equal to the inner diameter of the chamber.
15. The exchanger according to claim 14, characterized in that the diameter difference between the inner face of the chamber and the outer face of the bundle is less than at most 6% of the diameter of the latter.
16. The exchanger according to claim 13, characterized in that the tubular casing (1) includes two bottoms (19, 25) at least one of which is removable and which are respectively crossed by fluid input (9) and output (11) means, and means capable of providing the seal between the bottoms and the fluid input and output means of the bundle (3).
17. The exchanger according to claim 16, characterized in that the means capable of providing the seal between the tubes and the bottom consist of O-ring gaskets (23, 31) or a stuffing box.
18. A device for limiting an external diameter of a bundle (3) of an exchanger according to claim 13, characterized in that it consists of least one calibrated component (20) the inner diameter of which is equal to the maximum outer diameter which is intended to be admissible and which is intended to be positioned around the latter after having taken it out of the casing (1) in order to control the diameter thereof when it is submitted to excess pressure and/or to a controlled rise in temperature.
19. The device according to claim 18, characterized in that the aforesaid component consists of a ring or sheath (20).
20. A method for intervening, such as notably for cleaning, on a bundle of a heat exchanger of the helical type including two mutually isolated fluid circuits in intimate thermal exchange contact, a first fluid circuit being formed by a helical winding of two walls, or bundle, and the second circuit being formed by a space delimited by a casing containing the bundle, each circuit including its own fluid input and output means, characterized in that it includes the steps of:
- submitting, before its removal, the bundle to low pressure and/or cooling relatively to its casing, so as to cause it to contract,
- setting back the bundle to pressure and/or room temperature once it has been extracted from its casing, in order to cause it to recover its initial dimensions,
- proceeding with intervention on the bundle,
- again submitting the bundle to low pressure and/or cooling relatively to its casing, in order to cause it to contract before it is placed in the casing,
- setting back the bundle to pressure and/or room temperature once it has been placed back in its casing.
21. The method according to claim 20, characterized in that it includes a preliminary step consisting of disconnecting the bundle from its circuit.
22. The method according to claim 20, characterized in that it includes an intermediate step before the step for intervening on the bundle, consisting of submitting the bundle to excess pressure and/or an increase in temperature relatively to room temperature, in order to cause it to expand.
23. The method according to claim 22, characterized in that, before applying to the bundle (3) said excess pressure and/or said increase in temperature, a device for limiting its diameter according to any claim 4 is positioned around the latter.
24. The method according to claim 20, characterized in that it consists of producing the bundle (3) so that it is deformable under the effect of a pressure difference between the bundle and the chamber, and of providing it with an outer diameter less than the inner diameter of the casing (1) and of applying to the bundle periodical excess pressures and/or low pressures, in order to change its other diameter.
Type: Application
Filed: Aug 9, 2005
Publication Date: Mar 27, 2008
Inventor: Jean-Marie Gueguen (Maison Laffitte)
Application Number: 11/659,615
International Classification: F28G 13/00 (20060101); F28D 9/04 (20060101);
