Patent Application
20190137185
The invention relates to a heat exchanger according to claim 1 and to a method for arranging flow obstacles in a heat exchanger according to claim 14.
Such a heat exchanger has a pressure-bearing shell, which extends along a preferably vertically oriented longitudinal axis and bounds a shell space for receiving a first fluid. A bundle of tubes comprising a plurality of tubes for receiving at least one second fluid is arranged in the shell space, wherein the tubes form a number of tube layers of the bundle of tubes that are arranged one above the other in the radial direction of the bundle of tubes. The at least one second fluid can consequently enter into an indirect heat exchange with the first fluid carried in the shell space. Such a heat exchanger also has a shroud, which is arranged in the shell space, surrounds the bundle of tubes and preferably takes the form of a cylinder jacket, wherein spacers that are made to extend parallel to the longitudinal axis are arranged between the shroud and the outermost tube layer. By means of the spacers, which can be used to fix the shroud on the outermost tube layer, in particular thermally induced stresses between the shroud and the bundle of tubes can be reduced. For this purpose, the spacers may be formed as elastically deformable in the radial direction of the bundle of tubes. However, on account of the spacers, between every two spacers adjacent to one another in the circumferential direction of the shroud and the shroud and the uppermost tube layer there is a small intermediate space, which in particular has in each case the form of a partial shell of the cylinder jacket. These intermediate spaces reduce the effect of the shroud, which is that of suppressing an excessive bypass flow of the first fluid past the bundle of tubes, since such flows would have an adverse effect on the effectiveness of the heat exchanger. On the one hand, in the case of a falling film evaporator, an excessive bypass flow may lead to an increased occurrence of liquid in the sump of the heat exchanger. If that makes the liquid level rise too high, the output of such a heat exchanger must be reduced or the liquid (first fluid) must be extracted from the system, in order in particular to prevent a shutdown of the installation. On the other hand, because of this bypass flow, the exchanged heat output of the exchanger may be reduced.
On this basis, the present invention therefore addresses the problem of providing a heat exchanger and a method that reduce the disadvantage described at the beginning of a bypass flow.
This problem is solved by a heat exchanger with the features of claim 1 and by a method with the features of claim 14. Advantageous refinements of these aspects of the present invention are specified in the corresponding subclaims and will be described below.
According to claim 1, it is provided according to the invention that a flow obstacle is arranged in the respective intermediate space and is designed to hinder or suppress a flow of the first fluid in the respective intermediate space at least over a partial portion of the respective intermediate space that is made to extend along the longitudinal axis.
According to a preferred embodiment of the heat exchanger according to the invention, it is also provided that the respective intermediate space has a cross-sectional area perpendicularly to the longitudinal axis, wherein, along its entire length in the direction of the longitudinal axis, the respective flow obstacle takes up over 50%, preferably over 60%, preferably over 70%, preferably over 80%, preferably over 90%, preferably over 95%, preferably over 99%, in particular 100%, of the cross-sectional area of the assigned intermediate space.
According to a preferred embodiment of the heat exchanger according to the invention, it is also provided that the flow obstacle comprises a flexible layer of material, so that it can be placed around a comparatively more rigid support structure, for example produced from a metal. According to preferred embodiments, such a layer of material may for example have a modulus of elasticity in compression (for example in accordance with DIN EN ISO 604) of less than 10000 MPa (MegaPascals), preferably of less than 2000 MPa, particularly preferably of less than 1000 MPa, more particularly preferably in the range from 100 to 1000 MPa and in particular particularly preferably in the range from 300 to 1000 MPa.
According to one embodiment, the flexible layer of material may comprise PTFE (polytetrafluoroethylene) or be formed from PTFE.
In order in particular to make it easier for the respective flow obstacle to be pushed into the assigned intermediate space, according to one embodiment it is preferably provided that the respective flow obstacle has a supporting structure. Here, the supporting structure may also be integrally formed on the layer of material, or the layer of material may be integrally formed on the supporting structure.
Here, the supporting structure may for example be formed in the manner of a plate. If the distance between adjacent spacers in the circumferential direction of the shroud is sufficiently small, the supporting structure may for example be formed as a flat or planar plate, in particular as a metal sheet. When there are greater distances between adjacent spacers, from one to the other, such a supporting structure may also have a curvature that corresponds to a curvature of the outermost tube layer in the circumferential direction of the shroud or follows the same path.
In principle, the supporting structure according to one embodiment may comprise metal or may be formed from a metal.
Furthermore, according to a preferred embodiment of the heat exchanger according to the invention, it is provided that, with respect to a vertically aligned longitudinal axis of the shell, the layer of material of the respective flow obstacle is placed or guided (for example when there is an integrally formed supporting structure/layer of material, see above) around an upper edge of the supporting structure of the flow obstacle, so that the layer of material at least in certain portions, preferably completely, covers this upper edge and a front side of the supporting structure and a rear side of the supporting structure facing away from the front side. The front side of the respective supporting structure is in this case facing the shroud and facing away from the outermost tube layer.
Furthermore, according to a preferred embodiment of the heat exchanger according to the invention, it is provided that, with respect to a vertically aligned longitudinal axis of the shell, the respective flow obstacle is in each case pushed into the respective intermediate space from below. This allows in particular an already constructed heat exchanger also to be retrofitted with a flow obstacle according to the invention (also see below). Here, for example, an existing opening in the shell of the heat exchanger, for example in the form of a manhole, may be used to obtain access to the heat exchanger.
Furthermore, according to a preferred embodiment of the heat exchanger according to the invention, it is provided that the respective flow obstacle is pushed into the assigned intermediate space, or arranged there, with a portion of the layer of material that is placed around the upper edge out in front. The supporting structure advantageously serves here for stiffening the layer of material, which is preferably configured to seal off the respective intermediate space. In this way, a comparatively extremely flexible sealing material or a corresponding layer of material can also be pushed into the comparatively narrow intermediate space between the shroud and the outermost tube layers. Preferably, the supporting structure remains in the heat exchanger. However, it is also conceivable in principle to use the supporting structure merely as a positioning aid and to remove it again after arranging the respective layer of material.
With regard to the sealing of the existing intermediate spaces, it is in particular important to protect a lower portion of the bundle of tubes from bypass flows. According to one embodiment of the heat exchanger according to the invention, it is therefore provided that, with respect to a vertical alignment of the longitudinal axis of the shell, the respective flow obstacle only extends along a lower portion of the bundle of tubes in the respective intermediate space. This lower portion extends in particular in an upward direction from a lowermost end of the bundle of tubes (with respect to a heat exchanger arranged ready for operation, in the case of which the longitudinal axis extends parallel to the vertical). This lower portion preferably has in this case an extent or length in the direction of the longitudinal axis that is in particular less than 50%, 30%, 20%, 10% or 5% of the overall length of the bundle of tubes along the longitudinal axis.
Furthermore, according to one embodiment of the invention, it is provided that the respective flow obstacle extends in the circumferential direction of the shroud over the entire circumferential extent of the respective intermediate space between the spacers, and completely fills the respective intermediate space, in particular also in the radial direction. This allows a flow in the respective intermediate space to be suppressed at least over the partial portion of the intermediate space over which the respective flow obstacle extends along the longitudinal axis.
Furthermore, according to a preferred embodiment of the heat exchanger according to the invention, it is provided that, for forming the tube layers, the tubes are in each case coiled helically onto or around a core tube of the heat exchanger that is designed for the purpose of absorbing the load of the tubes. Here, it is preferably provided that the heat exchanger has further spacers between the respective tube layer and the tube layer lying thereunder in each case, arranged further inward in the radial direction, wherein the spacers extend in each case along the longitudinal axis. The individual tube layers are in this case preferably supported on the tube layer respectively arranged thereunder by way of a constant number of spacers per tube layer, and consequently ultimately on the core tube. The latter preferably extends along the longitudinal axis of the shell and furthermore is preferably arranged coaxially in relation to the shell in the shell space.
Said spacers are preferably in each case arranged in the radial direction exactly over an assigned spacer lying thereunder. Furthermore, the outermost spacers (in the radial direction of the bundle of tubes) are preferably formed as elastically deformable in the radial direction. So that they can compensate for thermally induced stresses between the shroud and the bundle of tubes. For this purpose, the spacers may be produced from a corresponding material or have separate spring means (for example helical springs).
A further aspect of the invention relates to a method for arranging, in particular retrofitting, flow obstacles in a heat exchanger, which has a shell that is made to extend along a longitudinal axis and surrounds a shell space for receiving a first fluid, wherein the heat exchanger also has a bundle of tubes arranged in the shell space and comprising a plurality of tubes for receiving at least one second fluid, which form a number of tube layers, and also a shroud, which is arranged in the shell space and encloses an outermost tube layer of the bundle of tubes in the radial direction of the bundle of tubes, wherein spacers that are made to extend along the longitudinal axis are arranged between the shroud and the outermost tube layer, wherein between every two spacers adjacent to one another in the circumferential direction of the shroud and the shroud and the uppermost tube layer there is an intermediate space, and wherein a flow obstacle is pushed into the respective intermediate space and is designed to hinder or suppress a flow of the first fluid along the longitudinal axis in the respective intermediate space at least over a partial portion of the respective intermediate space that is made to extend along the longitudinal axis.
In individual embodiments of the method according to the invention, the flow obstacles may be designed in the ways described above.
The flow obstacles are in each case preferably inserted into the respective intermediate space from below and then pushed in the upward direction along the (preferably vertical) longitudinal axis in the shell of the heat exchanger.
As already mentioned above, according to one embodiment of the method, an already operationally ready heat exchanger is retrofitted in this way for better suppression of the bypass flows in the intermediate spaces.
In particular, the respective flow obstacle, which is preferably pushed in along the longitudinal axis from below into a lower portion of the respective intermediate space, has a supporting structure with an upper edge, around which a layer of material is placed (the layer of material may also be integrally formed on the supporting structure, see above), so that a portion of the layer of material surrounds this upper edge, wherein the flow obstacle is pushed into the respective intermediate space from below with this portion out in front. The layer of material or the supporting structure may comprise the materials respectively described above or be formed from the materials respectively described above.
Further details and advantages of the invention are to be explained by the following description of the figures of an exemplary embodiment by reference to the figures:
in which:
The heat exchanger 1 is designed for the indirect exchange of heat between a first fluid S and at least one second fluid S′ and has a shell 10, which surrounds a shell space M for receiving the first fluid S, which can be introduced into the shell space M by way of an inlet nozzle 101 on the shell 10 and can be drawn off again from the shell space M by way of a corresponding outlet nozzle 102 on the shell 10, wherein the first fluid S acts from above on a bundle of tubes 2 of the heat exchanger arranged in the shell space M.
The shell 10 of the heat exchanger 1 extends along a longitudinal axis z, which runs along the vertical with respect to a state of the heat exchanger 1 arranged as intended. The bundle of tubes 2 has a plurality of tubes 20 for receiving the at least one second fluid S′. Various second fluids S′ may be carried in assigned tubes or groups of tubes of the bundle of tubes 2, i.e. the bundle of tubes 2 is divided in a way corresponding to the number of second fluids S′ to be carried. The tubes 20 are coiled helically onto a core tube 21 so as to form a number of layers of tubes 200, 201, which are arranged one above the other in a radial direction R, which is perpendicular to the longitudinal axis z, wherein the core tube 21 likewise extends along the longitudinal axis z and is arranged concentrically in the shell space M. Furthermore, the individual tube layers 200, 201 are fixed to one another by way of spacers 6 made to extend along the longitudinal axis z, wherein in each case a number of spacers 6 are arranged one above the other in the radial direction R of the bundle of tubes 2. In this case, a constant number of spacers 6 is preferably provided between the adjacent tube layers.
A number of tubes 20 may be respectively brought together in a tubesheet 104, wherein the second fluid S′ or a number of second fluids S′ can be introduced into each tube 20 by way of inlet nozzles 103 on the shell 10 and can be drawn off from the tubes 20 by way of outlet nozzles 105. Consequently, heat can be exchanged indirectly between the first fluid S and the at least one second fluid S′, wherein these fluids S, S′ are for example passed through the heat exchanger 1 in countercurrent.
The shell 10 and the core tube 21 are at least in certain portions configured in the form of a cylinder, so that the longitudinal axis z forms a cylinder axis of the shell 10 and of the core tube 21 running concentrically therein. Also arranged in the shell space M is a preferably hollow-cylindrically formed shroud 3, which encloses the bundle of tubes 2, so that an annular gap surrounding the bundle of tubes 2 is formed between the bundle of tubes 2 and each shroud 3. Arranged in this gap are spacers 60, which are made to extend along the longitudinal axis z and are used to fix the shroud 3 to the bundle of tubes 2, in particular to the outermost tube layer 200. Said spacers 60 preferably extend along the longitudinal axis z over the entire length of the bundle of tubes 2 and are in each case preferably formed so as to be elastically deformable in the radial direction R, in order to be able to compensate for thermally induced stresses between the bundle of tubes 2 and the shroud 3. On account of the spacers 60, between the shroud 3 and the outermost tube layer 200 there is between every two spacers 60 adjacent to one another in the circumferential direction U of the shroud 3 an intermediate space M′, which is made to extend along the longitudinal axis z.
Preferably arranged in these intermediate spaces M′ are flow obstacles 300, which in the ideal case completely prevent a bypass flow of the first fluid S in the intermediate spaces M′ in the region of the flow obstacles 300, or in particular at least hinder these flows in such a way that a significant increase in the effectiveness of the heat exchanger 1 is achieved, or it is provided that at least part of the fluid S (preferably the entire fluid S) is returned into the bundle 2 from the respective intermediate space M′.
According to one embodiment, the flow obstacles 300 have a supporting structure 302 (for example in the form of a rectangular metal sheet) and a layer of material 301, which for example consists of PTFE and is placed around an upper edge 302b of the supporting structure 302, so that the layer of material 301 covers this upper edge 302b and a front side 302a of the supporting structure 302 that is facing the shroud 3 and a rear side 302c of the supporting structure 302 that is facing away from the front side 302a with corresponding portions 301a, 301b, 301c. Here, the supporting structure 302 serves for stiffening the layer of material 301 of the respective flow obstacle 300, which is inserted, preferably in each case from below, in a direction of insertion E (cf.
Such sealing can be advantageously provided as a retrofit on already existing helically coiled heat exchangers 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 005 838.2 | May 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/025120 | 5/11/2017 | WO | 00 |
