Device for closing inner tubes in a tubular heat exchanger

Abstract

A device for closing at least one inner tube in a tubular heat exchanger. The device comprises a main body provided with inner tube through holes and at least one plug configured to be inserted into the at least one inner tube.

Claims

1. A tubular heat exchanger comprising: a tube case, a bend pipe, a plurality of inner tubes and a device for closing at least one of the plurality of inner tubes in the tubular heat exchanger; said device comprising a main body provided with inner tube through holes and at least one plug; each plug configured to be inserted into one of said plurality of inner tubes to completely block flow through the one of said inner tubes, wherein said main body is clamped between the tube case and the bend pipe and is provided with bolt openings for fixing the device to the tube case and the bend pipe using bolts through the bolt openings.

2. The tubular heat exchanger according to claim 1, wherein said at least one plug is provided with a gasket in order to provide a tight fitting between said plug and said one of said plurality of inner tubes.

3. The tubular heat exchanger according to claim 2, wherein said gasket is placed such that, when said at least one plug is inserted in said one of said plurality of inner tubes, said gasket provides for that no gap is formed between said plug and said one of said inner tubes.

4. The tubular heat exchanger according to claim 3, wherein said gasket is placed such that, when said at least one plug is inserted in said one of said plurality of inner tubes, said gasket is placed next to an outer end of said one of said inner tubes.

5. The tubular heat exchanger according to claim 1, said device further comprising at least one sensor placed on said at least one plug such that a leakage in said one of said plurality of inner tubes can be detected.

6. The tubular heat exchanger according to claim 1, wherein said device is made in one piece.

7. The tubular heat exchanger according to claim 1, wherein said at least one plug is screwed onto said main body.

8. The tubular heat exchanger according to claim 1, wherein a front side of said tube case is provided with a recess.

9. A kit of parts comprising a number of tubular heat exchangers according to claim 1.

10. A method for evaluating the performance of a tubular heat exchanger according to claim 1, said method comprising closing said one of said plurality of inner tubes by installing said device between said bend pipe and said tube case, and measuring performance in terms of formation of fouling, energy consumption and/or aggregation of fibers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, wherein:

(2) FIG. 1a and FIG. 1b illustrate an example of a tubular heat exchanger.

(3) FIG. 2 illustrates an example of an interface between a bend pipe and a tube case in a cross sectional view.

(4) FIG. 3 illustrates in a cross sectional view an example of an interface between a bend pipe and a tube case with a device provided with plugs placed in between.

(5) FIG. 4 illustrates in a cross sectional view another example of an interface between a bend pipe and a tube case with a device provided with plugs placed in between.

(6) FIG. 5 illustrates in a cross sectional view yet another example of an interface between a bend pipe and a tube case with a device provided with plugs placed in between.

(7) FIG. 6 illustrates an example of a device for closing inner tubes of a tubular heat exchanger.

(8) FIG. 7a illustrates in a cross sectional view a further example of an interface between a bend pipe and a tube case with a device provided with plugs placed in between.

(9) FIG. 7b illustrates in a cross sectional view yet an example of an interface between a bend pipe and a tube case with a device provided with plugs placed in between.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) FIG. 1a illustrates an example of a tubular heat exchanger 100, more particularly a Tetra Spiraflo marketed by Tetra Pak. As illustrated in FIG. 1b, inner tubes 102 placed inside an outer tube 104, often referred to as a shell, are connected to each other by bend pipes 106. In this way a compact and energy efficient design can be achieved.

(11) In order to keep the inner tubes bundled together a set of inner tubes placed inside the same shell can be attached in each of their ends to a tube case 200 as illustrated in FIG. 2. By having the inner tubes bundled together in this way the set of inner tubes can easily be pulled out from the shell if needed for inspection or the set of inner tubes should be replaced by another set of inner tubes, e.g. because another kind of product is to be processed. Today it is a common approach to weld the inner tubes to the tube case.

(12) Even though tubular heat exchangers are flexible in the way that the set of inner tubes can be replaced easily there is still a need to further improve the flexibility. For instance, the inner tubes have in many cases a length in the range of 3 to 6 meters, thereby requiring both space and proper equipment when replacing one set of inner tubes with another set.

(13) In order to improve the flexibility it is suggested to have a device 300 that can be placed between the tube case 200 and the bend pipe 106 as illustrated in FIG. 3. The device 300 can comprise a main body having through holes 302a, 302b such that product can flow through a first set of the inner tubes 102 and one or several plugs 304a, 304b arranged to be placed into a second set of the inner tubes, thereby making sure that no product is fed into this second set of inner tubes.

(14) When one or a number of inner tubes are blocked the flow pattern may be altered. A readily appreciated result is that if a total mass flow is maintained in a lower number of tubes the fluid velocity will increase, and this will in turn change the flow pattern where individual flows meet. There will also be a direct change in an outflow or inflow pattern as a liquid enters the inner pipes depending on which pipes are blocked. These alterations of flow properties may be beneficially used when optmizing a heat exchanger for a particular liquid product. The effect of using a device in accordance with any embodiment of the invention may be evaluated by visually observing parameters such as fouling and aggregation of fibers by dismantling the device and visually observing any sign of characteristic signs, such as material build-up etc. A typical example of aggregation of fibers may be that the ends of one elongate fiber enters one inner pipe each, meaning that the fiber as such will be prevented from entering the heat exchanger. As this continues for further fibers there will be an unwanted aggregation. Other effects such as energy consumption, or energy efficiency may be monitored or measured by non-intrusive techniques, e.g. by measuring the energy consumed and relating it to a measure of the liquid processed in the heat exchanger. A method of measuring the aggregation of fibers or fouling non-intrusively may be to monitor the pressure drop over the entire heat exchanger or over a portion thereof.

(15) As illustrated, in order to provide a tight fitting between the inner tubes and the plugs 304a, 304b one or several gaskets 306 may be used. In the example illustrated two O-rings for each of the plugs 304a, 304b are used.

(16) An advantage of having the possibility to easily close the second set of inner tubes is that the velocity in the first set of inner tubes will be increased, which can be an advantage in case it is known for a specific product that increased velocity reduces amount of fouling.

(17) In the example illustrated in FIG. 3, the inner tubes 102 are received in the tube case 200. In many cases the inner tubes 102 are welded to a front 5 side of the tube case, i.e. in this case a side closest to the device 300.

(18) In FIG. 4 another example having an alternative arrangement of a tube case 400 and inner tubes 402 is illustrated. Unlike the example illustrated in FIG. 3, the inner tubes 402 are not received by the tube case 400, instead the inner tubes 402 are attached, e.g. by welding, to a back side of the tube case. Although not illustrated, in order to provide for an easier manufacturing process the inner tubes may be fed in a few millimeters into the tube case such that they are kept in place while attaching the inner tubes to the tube case. Herein, when attaching inner tubes to the back side of the tube case, the through holes of the tube case is considered to be part of the inner tubes.

(19) An advantage of attaching the inner tubes to the back side of the tube case instead of in the front side is that a planar front side of the tube case 400 is achieved. This in turn implies that it is easier to provide a tight fitting between the device 300 and the tube case 400. Having a more tight fitting implies increased food safety since the risk that food residues will get caught in gaps or dead ends is reduced.

(20) As illustrated in FIG. 4, in order to provide for a tight fitting between the plugs 304a, 304b and the tube case 400 gaskets can be placed on the plugs such that, when the plugs are inserted in the inner tubes, they are close to the outer ends of the inner tubes. Since attaching the inner tubes in the back side of the tube case provides for a more well defined edge on the front side of the tube case (since the edge is not affected by the welding), the combination of having back side weldings and gaskets close to the outer ends is advantageous.

(21) When closing an inner tube in both ends a closed space is formed. In order to make sure that there is no leakage in this closed space sensors 500a, 500b may be provided on the plugs as illustrated in FIG. 5. The sensors may be leakage detection sensors having an open circuit that is closed when water or product is present due to the electrical conductivity of water or product. Alternatively, the sensors may be light based sensors having a transmitter for transmitting light and a receiver for receiving reflected light. If there is a leakage the reflected light is affected and thus the leakage can be detected by continuously analyzing the reflected light. The transmitter and the receiver may be placed on the same plug or, alternatively, the transmitter may be placed on one plug and the receiver may be placed on the corresponding plug in the other end of the inner tube.

(22) In order to analyze sensor signal data this may be transmitted via wires 502a, 502b or wireless to a control device 504 provided with data processing capability. Although not illustrated, the control device 504 and/or the sensors 500a, 500b may transmit data to a computer or the like placed at a remote location, e.g. a service central, using available data communications network.

(23) FIG. 6 illustrates a device 600 having through holes 602, providing for that product can flow through, plugs 604 arranged to be inserted in inner tubes and bolt openings 606 providing for that the device can be fastened using bolts.

(24) As illustrated, the plugs may be provided with gaskets in the form of O-rings providing for that there is a tight fitting with the inner tubes to be closed.

(25) As illustrated in FIGS. 7a and 7b by examples the tube case may be provided with a recess 700 providing for that there is a space formed between the device and the tube case. By having the recess there is no small gap formed between the tube case and the device that is difficult to keep clean using available cleaning in place (CIP) technologies. Since the space is keeping the device and the inner tubes apart the through holes of the device do not have be aligned with the inner tubes. Instead the through holes in the device may be chosen in a way such that an optimal flow profile is formed. Further, which inner tubes to close and which to be keep open may also depend on the flow profile.

(26) In order to influence the flow front side flow influence elements 702a, 702b may be provided on the device. By having these the flow may be influenced such that aggregation of fibers is reduced and/or such that a proper mixing occur and/or such that less fouling is formed. As illustrated in FIGS. 7a and 7b, the front side flow influence elements 702a, 702b may have the form of semispheres, but other forms may be used as well.

(27) In order to influence the flow inside the space formed due to the recess 700 of the tube case, plug flow influence elements 704 may be used. The plug flow influence elements 704 may have different shapes. By having these the flow may be influenced such that aggregation of fibers is reduced and/or such that a proper mixing occur and/or such that less fouling is formed.

(28) As illustrated in FIG. 7a, the inner tubes may be received via through holes of the tube case and attached in the front side. Though, as explained above and illustrated in FIG. 7b, the inner tubes may as an alternative be attached in the back side of the tube case.

(29) Although not illustrated, in order to keep a tight fit between the tube case and the device a gasket may be used. Similarly, in order to keep a tight fit between the device and the bend pipe a gasket may be used. Due to that a tubular heat exchanger may easily be reconfigured by using the device mentioned above, this suits well for testing out new configurations of the tubular heat exchanger if this does not perform according to expectations or if a new product should be processed by the heat exchanger. More particularly, in order to evaluate a configuration of the tubular heat exchanger, a first step may be to theoretically determine the optimal solution in terms of open and closed inner tubes, and optionally front side flow influence elements and/or plug flow influence elements. This step may be based on simulation technology and/or test data collected beforehand.

(30) A second step may be to choose a device according to an outcome of the first step, or to modify the device to be according to the outcome.

(31) A third step may be to install the device in the tubular heat exchanger.

(32) A fourth step may be to evaluate the performance of the tubular heat exchanger. The performance may be evaluated based on aggregation of fibers. This may be of interest since a reduced aggregation of fibers implies an increased running time between cleaning. The performance may also be based on fouling. This is of interest since less fouling implies increased running time between cleaning. The performance may also be based on energy consumption, since energy consumption is directly linked to cost of production. Energy consumption can be measured in terms of pressure drop.

(33) The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.