Patent Application
20190063843
The invention relates to a helically coiled heat exchanger.
Such helically coiled heat exchangers are used in a wide variety of processes, for example in ethylene or natural gas plants (LNG plants for short).
In the case of such heat exchangers, the coolant in the shell space of the heat exchanger is usually applied to a bundle of tubes which is arranged in the shell space and comprises tubes which are helically coiled on a core tube and in which the process stream to be cooled is conducted. The coolant is in this case introduced into the heat exchanger in a two-phase state, the liquid phase being separated from the gaseous phase in a distributor and distributed to the bundle of tubes by way of distributor arms.
During the operation of the heat exchanger, gas vortices may occur in the shell space. If such vortices are in the upper portion of the heat exchanger, in the region of the upper side of the bundle of tubes, they may divert the liquid phase flowing out from the distributor arms in a direction transverse to the longitudinal axis of the shell or of the bundle of tubes, which has the consequence that the liquid phase can longer be applied to the bundle of tubes in an equally distributed manner. Such an uneven distribution of the liquid phase or the coolant reduces the effectiveness of the heat exchanger significantly.
Against this background, the present invention is therefore based on the object of providing a heat exchanger that is improved with regard to the aforementioned problem.
This object is achieved by a heat exchanger with the features of claim 1.
Advantageous configurations of the invention are provided in the corresponding subclaims and are described below.
According to claim 1, heat exchanger for indirect heat exchange between a first and a second medium is provided, having
It is then provided according to the invention that, from an underside of the bottom of the at least one distributor arm that is facing the upper side of the bundle of tubes, at least one directing element projects in the direction of the upper side of the bundle of tubes or extends along the longitudinal axis toward the upper side of the bundle of tubes, the at least one directing element extending in a circumferential direction of the bundle of tubes at least over half of a width of the bottom of the at least one distributor arm and/or the at least one directing element projecting along the longitudinal axis into a gap of the bundle of tubes between two tube layers of the bundle of tubes.
Said upper side of the bundle of tubes is formed by the uppermost tube portions of the tubes of the bundle of tubes that are coiled around the core tube and extends along a horizontal plane or along a plane that runs perpendicularly in relation to the longitudinal axis. However, said upper side does not have to run completely flat or parallel to this plane, but may have curvatures and a varying height profile (with respect to the longitudinal axis). The reason for this is in particular that the individual tubes or tube portions on said upper side of the bundle of tubes have a circular cross section. It is also provided in particular that, on said upper side, upper end portions of the tubes of the bundle of tubes are gathered into tube clusters, which project from the upper side and are led through gaps between distributor arms that are neighboring in the circumferential direction. The tube clusters in this case end in each case in a tubesheet, in which the individual tubes are anchored, the respective tubesheet being fixed on the cylindrical shell of the heat exchanger. The upper side of the bundle of tubes also deviates from a horizontal path due to the tube clusters that are led away from the bundle of tubes. The tubes of the bundle of tubes may in particular be coiled onto the core tube or fixed thereon in such a way that the core tube can bear the load of the bundle of tubes. As an alternative to this, the weight of the bundle may be borne by so-called bearing webs, which are arranged between the tube layers and are connected to them. The bearing webs may in this case project beyond the upper side of the bundle of tubes and may be welded on or fixed there on bearing arms. The bearing arms may in particular be fixed both on the core tube and on the shell; they consequently connect the core tube and the shell above the bundle of tubes in the form of spokes. In the case of this variant, the bearing arms ultimately bear the bundle of tubes and the core tube by way of the shell. This upper part in the heat exchanger forms the so-called fixed bearing, since the shell and the core tube are fixedly connected to one another here, while at the bottom of the heat exchanger the core tube is connected to the shell in particular by way of a sliding bearing.
The fact that the at least one directing element projects in the direction of the upper side of the bundle of tubes or extends toward the upper side of the bundle of tubes may mean in particular that the at least one directing element ends before or at the upper side of the bundle of tubes, there preferably being a clearance between the directing device and the upper side, or specifically enough clearance to avoid mechanical contact with the bundle of tubes, in order to protect the bundle of tubes from leakages.
It may also be provided that the at least one directing element projects into the bundle of tubes along the longitudinal axis, in particular into a gap (or a number of gaps) between two tube layers of the bundle of tubes. These tube layers may be for example tube layers of the bundle of tubes that are neighboring in the radial direction. In this case, the at least one directing element may project into the bundle of tubes only by a certain portion or over its entire length in a plane running perpendicular to the longitudinal axis. A suitable gap into which the at least one directing element can project may also be present between two tube layers that are not directly neighboring in the radial direction. Thus, because of the tubes being led out into the clusters, the tube layers end at different heights along the longitudinal axis of the shell (these differences may be for example 100 mm to 150 mm). Thus, for example at a specific location along the circumference, the nth tube layer may end high, but the (n+1)th tube layer low, and the (n+2)th tube layer high again. These gaps between every second layer (here above the (n+1)th tube layer) may also be used.
In the embodiments described herein, in particular concerning those embodiments in which the respective directing element is not formed as a tube, it may be provided that the respective directing element does not extend in the axial direction, i.e. along the longitudinal axis, downward as far as the upper side of the bundle of tubes or beyond (for example into a gap of the bundle of tubes), but ends above the upper side. The respective directing element may in this case extend over at least 70%, in particular at least 80%, in particular at least 90%, in particular at least 95% or in particular at least 99%, of the vertical distance between the upper side of the bundle of tubes and the underside of the bottom of the respective distributor arm.
In all of the embodiments, the at least one directing element is preferably formed separately from the core tube, i.e. in other words the core tube is not understood as meaning a directing element projecting from the bottom of the at least one distributor arm.
The at least one directing element is formed so as to prevent a cross flow of the gaseous and/or liquid phase of the first medium on the upper side of the bundle of tubes (for example because of gas vortices), or performs this function because of its arrangement with respect to the upper side of the bundle of tubes. Understood here as a cross flow is in particular a flow that takes place in a direction which runs along the upper side of the bundle of tubes or the direction of which has at least one component that runs perpendicularly to the longitudinal axis.
The directing element may in this case either shield the liquid phase from gas vortices, in particular cross flows on the upper side of the bundle of tubes, or by its arrangement between the bottom of the at least one distributor arm and the upper side of the bundle of tubes, suppress or at least reduce such cross flows, so that the liquid phase can be distributed directly in the downward direction by following gravitational force.
According to a particularly preferred embodiment of the invention, it is provided that the at least one directing element is formed as a directing plate, in particular a baffle plate, which is connected in particular by way of an upper peripheral region to the bottom of the at least one distributor arm, an opposite lower periphery extending, as described above, at least down as far as the upper side of the bundle of tubes. The at least one directing element or the directing plate is preferably disposed perpendicularly on the underside of the bottom of the at least one distributor arm. The directing plate forms in particular a closed surface area without apertures/holes.
It is also provided according to one embodiment of the invention that the at least one directing element extends along a circumferential direction of the bundle of tubes and also in particular along the longitudinal axis of the shell.
It is also provided according to one embodiment of the invention that the at least one distributor arm has two side walls, which lie opposite one another in the circumferential direction of the bundle of tubes or the shell, extend in each case along the radial direction of the bundle of tubes from the inside to the outside toward the shell of the heat exchanger and also in each case along the longitudinal axis from the bottom upward to a roof of the at least one distributor arm.
It is also provided according to one embodiment of the invention that the at least one directing element extends in the circumferential direction of the shell or the bundle of tubes from one side wall to the other side wall. This means in other words that the directing element extends in the circumferential direction over an entire width of the bottom of the respective distributor arm.
It is also provided according to one embodiment of the invention that the at least one directing element has in a plane running perpendicularly to the longitudinal axis a curvature, in particular a curvature with a constant radius of curvature, so that in particular an inner side of the directing element that is facing the core tube is at a constant distance overall from the longitudinal axis. In this embodiment, the at least one directing element therefore has at least a concavely curved inner side, which is facing the core tube, and an outer side, facing away from the core tube or the inner side, that has a convex curvature.
Furthermore, said radius of curvature of the at least one or the respective directing element may lie between the radius of curvature of the tubes of a tube layer lying further inward in the radial direction and the radius of curvature of the tubes of a tube layer lying further outward in the radial direction.
It is also provided according to one embodiment of the invention that the heat exchanger has a number of directing elements, which project in each case from the underside of the bottom of the at least one distributor arm that is facing the upper side of the bundle of tubes in the direction of the upper side of the bundle of tubes or extend along the longitudinal axis toward the upper side of the bundle of tubes (also see above), the directing elements extending in each case in a circumferential direction of the bundle of tubes at least over half of the width of the bottom of the at least one distributor arm and/or the directing elements projecting in each case along the longitudinal axis into a gap of the bundle of tubes between two tube layers of the bundle of tubes.
These multiple directing elements may be in particular a number of the (in particular curved) directing plates described above, which may in each case be disposed in particular with a lower periphery in gaps between neighboring tube layers.
The heat exchanger may of course also have a plurality of distributor arms, which extend in each case in a radial direction from the core tube toward the shell, there being between every two distributor arms that are neighboring in the circumferential direction of the shell an intermediate space through which tubes, or in each case a tube cluster, of the bundle of tubes are led past the distributor arms to an assigned tubesheet, which is fixed on the shell. In principle, at least one or more directing elements according to the invention may be provided on all of the distributor arms.
The at least one distributor arm or the respective distributor arm may have—with respect to a horizontal plane or plane made to extend perpendicularly to the longitudinal axis—a cross section in the form of a sector of a circle, i.e. like a piece of pie. Correspondingly, the respective bottom of a distributor arm is preferably formed correspondingly in the form of a sector of a circle.
If a number of directing elements, in particular directing plates (see above), are provided, it is preferably provided that the directing elements are arranged next to one another in a radial direction along which the at least one distributor arm extends from the core tube toward the shell. In particular, in this case all of the directing plates may extend along the circumferential direction of the shell, in particular along the underside of the bottom from one side wall to the other side wall of the distributor arm concerned. The individual directing elements or directing plates may in this case project in each case into a gap between neighboring tube layers of the bundle of tubes.
The directing plates that are situated further inward in the radial direction, i.e. situated closer to the core tube, may have a smaller length in the circumferential direction of the shell than the peripheral plates situated further outward, for example if the respective distributor arm has a cross-sectional form of a sector of a circle (see above) and the respective directing plate extends from one side wall of the distributor arm concerned to the other side wall of the distributor arm.
In an alternative embodiment, the at least one directing element or the number of directing elements is or are formed in each case as a tube that is in flow connection with an assigned through-opening of the bottom. The respective tube may in this case adjoin an assigned through-opening of the bottom of the respective distributor arm. In particular, each through-opening of the respective distributor arm may be connected to such a tube in the way described above. It is also conceivable that a number of tubes are provided as directing elements, a number of through-openings opening out into the same tube, which then has a correspondingly greater diameter.
In this case, the tubes do not necessarily have to have a circular cross section. Rather, here the directing elements may also be formed in each case by a channel that extends in the direction of the longitudinal axis, with a wall running around, the channel being in flow connection with at least one through-opening of the bottom.
According to a further alternative embodiment, it is provided that the at least one directing element forms a plurality of channels that extend in the direction of the longitudinal axis and have respective walls, neighboring channels forming common walls or the walls of neighboring channels being adjacent to one another, the respective wall bounding a region of the shell space between the bottom of the at least one distributor arm and the upper side of the bundle of tubes into which at least one through-opening of the bottom of the at least one distributor arm opens out.
It is in this case provided according to one embodiment that the channels are formed in cross section in an n-gonal manner, n being greater than or equal to 3, in particular 4 or 6. The channels may therefore be formed in particular in a rectangular (n=4) or honeycomb (n=6) manner in cross section. It may also be provided according to one embodiment of the invention that the at least one directing element is formed by a wall which extends along a periphery of the bottom and surrounds a region of the shell space between the bottom of the at least one distributor arm and the upper side of the bundle of tubes into which the through-opening of the bottom of the at least one distributor arm opens out. The wall may extend in particular from the core tube along said periphery in the radial direction as far as the end-face wall of the distributor arm, from there in the circumferential direction of the shell to the opposite side wall of the distributor arm and from there along the radial direction back to the core tube.
In other words, in the case of this embodiment, in particular a channel that is made to extend in the direction of the longitudinal axis is therefore bounded by the wall, it being possible for the wall to form a continuation of the side walls of the distributor arm in the direction of the longitudinal axis, projecting from the bottom of the distributor arm.
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 also has at least one distributor arm 21, preferably a number of distributor arms 21, which serve(s) for distributing a liquid phase F of the first medium M to an upper side 3a of the bundle of tubes 3 facing the respective distributor arm 21, the respective distributor arm 21 having opposite from the upper side 3a a bottom 200 with through-openings 205, so that the liquid phase F can be passed to the upper side 3a of the bundle of tubes 3 by way of the through-openings 205. As a difference from
The respective distributor arm 21 projects in particular in a radial direction R, which is disposed perpendicularly on the longitudinal axis z, from the core tube 300 and is preferably in flow connection with it. The core tube 300 in turn projects from a pre-distributor 20, which is arranged above the bundle of tubes 3 and the distributor arms 21 and in which the first medium M is collected and in particular degassed. The liquid phase F can correspondingly flow from the pre-distributor 20 into the core tube 300 and subsequently into the respective distributor arm 21. Instead of the core tube 100, the liquid phase F may also be fed into the respective distributor arm 21 by way of an annular channel, which for example runs around the inside of the shell 5. Then, from an underside 200a of the bottom 200 of the respective distributor arm 21 that is facing the upper side 3a of the bundle of tubes 3, at least one directing element 22 projects in the direction of the upper side 3a of the bundle of tubes 3 and thereby extends in each case along the longitudinal axis z toward the upper side 3a of the bundle of tubes 3. Preferably, the at least one directing element 22 extends in a circumferential direction U of the bundle of tubes 3 at least over half of the width B of the bottom 200 of the at least one distributor arm 21 (cf.
According to the embodiment shown in
The directing elements or plates 22 are preferably arranged next to one another in the radial direction R, along which the respective distributor arm 21 extends from the core tube 300 toward the shell 5, one or more of the through-openings 205 in each case opening out into an intermediate space between two directing plates 22 that are neighboring in the radial direction R, so that the liquid phase F can be discharged into the respective intermediate space above the upper side 3a of the bundle of tubes 3.
The directing elements 22 configured in such a way serve in this case for preventing a cross flow of the gaseous phase G of the first medium M on or along the upper side 3a of the bundle of tubes 3 or along the radial direction R. As a result, the liquid phase F can be discharged undisturbed by way of the distributor arms 21 along the longitudinal axis z in the downward direction, and an uneven distribution of the liquid phase F is prevented.
As can be seen from
The respective distributor 21 has furthermore two side walls 203, 204, which lie opposite one another in the circumferential direction U of the bundle of tubes 3 or the shell 5, extend in each case along the radial direction R of the bundle of tubes 3 from the inside to the outside toward the shell 5 of the heat exchanger 1 and in each case project upward along the longitudinal axis z from a periphery 200b of the bottom 200 of the respective distributor arm 21.
The respective distributor arm 21 has furthermore an end-face wall 201, which lies opposite the shell 5 in the radial direction R and connects the two side walls 203, 204 to one another. In the upward direction, the respective distributor arm 21 is preferably closed by a roof 206, which is connected to the respective side walls 203, 204 and the end-face wall 201 and slopes up toward the core tube 300, so that the gaseous phase G of the first medium M can rise up along the ridge 206 to the core tube 300.
It is preferably also provided (cf. in particular
Between every two distributor arms 21 that are neighboring in the circumferential direction U of the shell 5 there is a gap through which a tube cluster 33 of the bundle of tubes 3, formed by end portions of the tubes 3, is in each case led past the distributor arms 21 to an assigned tubesheet 34, which in each case is fixed on the shell 5.
The individual running-around walls 22b are formed in particular hexagonally in cross section (with respect to a cross-sectional plane made to extend parallel to the respective bottom 200) and are connected in each case to neighboring walls 22b, so that the respective directing element 22 forms overall a honeycomb structure, as can be seen from
According to a further embodiment, shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 17020369.9 | Aug 2017 | EP | regional |
