The invention relates to heat exchangers for the indirect heat exchange between at least one first and one second medium. Such heat exchanger can, for example, include: a tube bundle formed from a plurality of tubes, helically coiled around a core pipe, for receiving the first medium, a shell (or jacket), enclosing the tube bundle and defining a shell space (or jacket space) surrounding the tube bundle, for the reception of the second medium, and a liquid distributor for distributing a stream (S) of the second medium in the form of a liquid (F) in the shell space (200),
Such a heat exchanger permits the indirect heat exchange between a first and a second medium and comprises at least one tube bundle for receiving the first medium, a shell enclosing the at least one tube bundle, which shell defines a shell space surrounding the tube bundle for receiving the second medium in the form of a liquid, and a liquid distributor, which is designed to distribute a stream (main stream) of the second medium over a cross-section of the shell space. The tube bundle is preferably formed from a plurality of tubes, which are helically coiled around a core tube which extends along the longitudinal axis (cylinder axis) of the shell in the shell space.
Such a heat exchanger is known from DE 10 2004 040 974 A1.
In heat exchangers that operate by falling film evaporation, i.e. the liquid to be evaporated flows down from the top through the evaporation space (shell space) and is partially evaporated in the process, heat transfer between shell side (shell space) and tube side (tube bundle) is based on a steady heat quantity supply from both sides. On the tube side the streams are distributed uniformly to all layers. However, this uniform distribution may be impaired by external conditions, for example by gas entrainment in an otherwise purely liquid stream. On the shell side the liquid distributor systems are designed such that a two-phase liquid/gas mixture (second medium) is calmed and degassed in a predistributor system. The degassed liquid is then accumulated via a downcomer to generate pressure and supplied to the actual main distributor system. The liquid is braked by a fixedly installed flow retarder in the lower part of the downcomer and degassed further. The main distributor system is load-independent and static, whereby changes arising in the overall system (e.g. gas content, load) may have an effect on distribution quality.
Taking this as a basis, the problem underlying the present invention is that of improving a heat exchanger of the above-mentioned type with regard to the distribution quality.
Thus, an aspect of this invention is therefore to provide a heat exchanger system of the above-mentioned type with improved distribution quality.
Upon further study of the specification and appended claims, other aspects and advantages of the invention will become apparent.
This problem is solved by a heat exchanger having a control means for controlling distribution in the shell space of an additional, further stream, conveyed in the shell space, of the liquid, and/or to control distribution of the stream of the liquid in the shell space.
According thereto, a control means is provided, which is designed to control distribution in the shell space of an additional, further stream (sub-stream), conveyed in the shell space parallel to the stream (main stream), of the liquid, and/or to control distribution of the stream (main stream) of the liquid in the shell space.
According to the invention, the quantity of heat supplied is thus influenced in particular on the shell side (and optionally on the tube side, see below), in order to thus be able to respond to the respectively prevailing conditions. To this end, distribution and feed of a part of the liquid (further stream) is conducted parallel to the (main) stream in particular on the shell side. In this way, liquid distribution may be purposefully adapted from outside to the conditions prevailing in the heat exchanger.
Through separate shell-side control of the sub-stream or further stream of the liquid, it is possible purposefully to counteract maldistribution and/or discontinuities, which may be detected by temperature measurements. Such maldistribution or discontinuities may be brought about by conditions external to the heat exchanger or result from thermodynamic processes within the tube bundle of the heat exchanger. As a result of the controlled shell-side liquid distribution, the heating surface of the heat exchanger may be put to optimum use and performance kept higher, even under unfavorable conditions, than without the above-stated control.
To distribute the liquid to be distributed of the (main) stream, the liquid distributor comprises a main distributor above the tube bundle, which is provided with passage openings (perforated plate) through which the liquid may rain down onto the tube bundle.
There is preferably provided at least one additional line controllable with the control means and having at least one outlet arranged above the tube bundle, via which outlet the further stream of the liquid may be fed controllably onto the tube bundle. In this case, to control distribution of the further stream of the liquid to the tube bundle, the control means comprises at least one valve of the additional line, with which for example the effective cross-section of that line may be varied.
Furthermore, the main distributor comprises at least one passage region, through which tubes of the tube bundle may pass, wherein the passage region is defined in particular by two distributor arms of the main distributor, via which the liquid may be fed onto the tube bundle. The at least one line is preferably also passed through this passage region, in order to be able to distribute the further stream (sub-stream) predefinably to the tube bundle arranged below the main distributor.
Of course, to convey the further stream or further streams it is also possible to provide a plurality of lines each with at least one outlet, via which liquid may additionally be fed controllably onto the tube bundle. The outlets are preferably distributed in such a way over the cross-section (oriented perpendicular to the longitudinal axis of the shell) of the shell space that the further stream of the liquid is variably distributable in a radial direction of the shell at least to two (or indeed a plurality of) sections of the tube bundle and/or in a circumferential direction of the shell, i.e. distribution of the further stream to the sections may be separately controlled for each section.
To distribute the stream (main stream) of the liquid the main distributor preferably comprises a plurality of distributor arms, which in particular each extend in the radial direction of the shell. In this case, the distributor arms in particular each exhibit a pie-slice shape, i.e. take the form of a sector of a circle (the base of the distributor arm being in the shape of a truncated triangle). The passage regions are then preferably shaped accordingly.
To supply the main distributor with the stream (main stream) of the liquid to be distributed, the liquid distributor comprises at least one downcomer, which is preferably arranged in the core tube of the tube bundle and in particular comprises an external diameter which is smaller than the internal diameter of the core tube. The main distributor is in this case connected via the at least one downcomer to a predistributor (preliminary distributor) of the liquid distributor, which serves to collect and calm the liquid.
In a variant of the invention, the distributor arms are subdivided for variable (controllable) distribution of the stream (main stream) of the liquid in the radial direction into at least two separate (or a plurality of) segments, which each comprise at least one passage opening through which liquid may rain onto the tube bundle. The control means is set up and provides control of a feed of liquid into the two (or plurality of) segments separately for each segment, such that the liquid is variably distributable in the radial direction of the shell onto at least two (or accordingly a plurality of) sections of the tube bundle. To this end downcomers (e.g. with valves) may be associated with the individual segments, via which downcomers the segments may be controllably charged with liquid from the stream (main stream), such that distribution of the liquid to the two sections (or indeed plurality of sections) is separately controllable for each section.
In a further exemplary embodiment provision is made for at least two (or a plurality of) distributor arms to be designed to supply liquid to in each case different sections of the tube bundle in the radial direction of the shell. In the process, the distributor arms each comprise at least one passage opening for distributing the liquid of the stream (main stream) to the sections, through which passage opening liquid may be fed onto the tube bundle, wherein the passage openings are differently positioned in the radial direction, such that sections of the tube bundle may be selectively (controllably) supplied with liquid by the distributor arms. To charge the distributor arms with the liquid to be distributed, a plurality of downcomers are preferably provided, wherein each downcomer supplies at least one, in particular two distributor arms with liquid. In this respect, the downcomers are in particular arranged in the core tube or are formed by subdivision of the core tube into sections. Control of the liquid feed through the downcomers (e.g. by means of valves) may likewise control distribution of the stream (main stream) of the liquid to the sections of the tube bundle separately for each section.
Control may also be performed on the tube-side, the tube-side control cooperating with the shell-side control in that the tubes of the tube bundle or tube space are helically coiled around the core tube so as to form at least the above-stated first and second sections of the tube bundle (or indeed a plurality of sections). In this case, the sections are formed separately from one another and each surround the core tube, wherein the second section encircles the first section of the tube bundle, i.e. the sections subdivide the tube bundle in the radial direction of the shell, whose longitudinal axis or cylinder axis coincides with the longitudinal axis (cylinder axis) of the core tube. More than two sections, e.g. three sections, can be present.
The first and the second section penetrate each other when the two hollow cylinders, formed by the sections, overlap each other at least partially. In such a case, the radially innermost section extends away from the core pipe up to a given radius R1. The second section extends from the core tube from a radius R2 up to a radius R3. If the second section surrounds the first section, the radius R2 is at least as large as the radius R1. If the second section penetrates the first section, the radius R2 is smaller than R1. The two hollow cylinders, which are formed by the sections, consequently overlap at least partially. Within the framework of the invention, it is also possible for the two sections to overlap in a complete manner.
In accordance with further embodiments of the invention, 3 or more sections may also be advantageous, in which the individual sections surround or penetrate each other. In an analogous manner to the preceding, it is advantageous when a third section surrounds a second section, which, in its turn, surrounds a first section. It is also advantageous in an alternative embodiment when a third section penetrates a second section, which penetrates a first section. Combinations of sections being surrounded with sections being penetrated just as more than 3 sections are also alternative expedient developments of the invention.
The separate (hollow-cylindrical) sections each further comprise at least one associated inlet, such that they may each be separately charged with the first medium. In this respect, a further control means may be provided, with which feed of the first medium via the respective inlet of a section may be controlled separately from feed of the first medium via the inlets of the other sections (e.g. by means of valves associated with the inlets). The individual sections each further comprise at least one associated outlet for outlet of the first medium from the tube space or shell.
In a preferred manner the flow through the tubes and/or the flow at the shell side are controlled depending on the measured temperature at one or more points of the heat exchanger. Advantageously the heat exchanger comprises at least one optical fiber connected to equipment suitable for determining a temperature from the signals of the optical fiber. The use of an optical fiber provides the opportunity to determine the temperature at any point or various given points of the optical fiber by the analysis of optical signals originating of Raman scattering, Brillioun scattering or of the scattering of a Bragg grating. All these signals are temperature depending and therefore suitable for the determination of the temperature. The optical fibers are preferably fastened on or inside the tubes.
Further features and advantages of the invention are to be explained with the following description of the Figures of exemplary embodiments by way of the Figures, in which:
At least one first medium is fed into the tube space (tube bundle 10) and flows upwards in the vertical direction Z. The shell space 200 serves to accommodate a second medium in the form of a liquid F, which is fed onto the at least one tube bundle 10 and flows downwards in the vertical direction Z in the shell space. Because the tube bundle 10 takes the form of a helically coiled tube bundle, the first medium is thus conveyed in cross-countercurrent relative to liquid F.
To distribute the liquid F in the shell space 200, a stream S of the liquid F introduced into the shell 20 is collected, calmed and degassed in a predistributor 43. To accommodate the liquid F, the predistributor 43 here comprises a peripheral wall, which extends upward from a base, the base extending transversely to the longitudinal axis of the shell 20. The base predistributor 43 is connected via a downcomer 380 extending into the core tube 100 to a main distributor 44, and supplies the latter with the stream S of the liquid F. Main distributor 44 comprises a plurality of distributor arms 300 (cf.
The distributor arms 300 each comprise a base with a plurality of passage openings (“perforated plates”), through which liquid F introduced into the distributor arms 300 may rain onto the tube bundle 10 arranged therebelow in the vertical direction Z.
To be able to influence distribution of the liquid F in the shell space and optionally, for example, counteract uneven distribution, distribution and feed of a part of the liquid F then proceeds on the shell side in the form of at least one further stream S′ parallel to the (main) stream S.
To this end, additional lines 330 are provided for conveying the further stream S′ (or the further streams). The further stream S′ is introduced into the additional lines 330 and shell space 200 via corresponding inlets/ports 332. The additional lines 330 in each case have at least one outlet 331, via which the liquid F may be fed with additional control onto the at least one tube bundle 10. The lines 330 therefore each have a valve 333. To be able to feed the liquid F in a controlled manner via the additional lines 330 onto the tube bundle 10, the additional lines 330 pass through the passage regions 45 of the main distributor 44 and the outlets 331 thereof are arranged above the tube bundle 10, in particular such that the tube bundle 10 may be supplied with the liquid F in the radial direction R of the shell 20 in separately controllable sections. The sections of the shell in this case each surround the core tube 100 and are in this case of hollow (circular) cylindrical construction. The individual sections thus each engage around the sections which are radially further towards the inside.
As an alternative, the distributor arms 300 may be designed to supply different sections of the tube bundle 10 with liquid F, for example by corresponding distribution of the passage holes 371 of the distributor arms 300 in the radial direction R according to
Advantageously, one or more optical fibers 387 are fastened on the tubes (or within the tubes) of the tube bundle 10. The temperature of the tubes can be determined from the signals of the optical fibers.
The entire disclosure[s] of all applications, patents and publications, cited herein and of corresponding German Application No. 10 2011 017 029.4 filed Apr. 14, 2011, are incorporated by reference herein.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
Number | Date | Country | Kind |
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10 2011 017 029 | Apr 2011 | DE | national |
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