GB1595120A

GB1595120A - Heat exchanger

Info

Publication number: GB1595120A
Application number: GB23629/78A
Authority: GB
Original assignee: Interatom Internationale Atomreaktorbau GmbH
Current assignee: Interatom Internationale Atomreaktorbau GmbH
Priority date: 1977-06-08
Filing date: 1978-05-26
Publication date: 1981-08-05
Also published as: FR2394051A1; NL7805595A; DE2725877A1

Description

(54) HEAT EXCHANGER (71) We, INTERATOM, INTERNA TIONALE ATOMREAKTORBAU GmbH, a German company of Bergisch Gladbach 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a heat exchanger.

According to the present invention, there is provided a heat exchanger comprising: a) a vessel for containing a first exchange medium; b) at least one bundle of tubes within the vessel for containing a second exchange medium; and c) a pressure relief and instrumentation tube also within the vessel, which tube is normally closed off from the interior of the vessel and is capable of being withdrawn from the vessel to enable the interior of the vessel to be inspected, but which does not contain a tube bundle.

In order that the present invention may be more fully understood, an embodiment of heat exchanger according to the present invention will be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a vertical longitudinal section through the heat exchanger, taken along the line I-I in Figure 2; and Figure 2 is a horizontal cross-section through the heat exchanger, taken along the line 11-Il in Figure 1.

A heat exchanger or steam generator vessel containing a plurality of vertical, upwardly extractable tube bundles may be required to be capable of being used with at least one corrosive medium, such as liquid metal or various organic substances having low pressures and/or good thermal properties at high temperatures, but which, on contact with the oxygen of the air with water, may react extremely violently. These media must therefore be very carefully enclosed. Possible lack of fluid-tightness or cases of damage in such vessels are, therefore, to be as far as possible prevented.

Thus, it is particularly desirable that such vessels and the tube bundles therein should be capable of being tested at regular intervals and with the least possible expenditure of time.

In Specification No. 1,514,831, there is proposed a liquid metaVwater heat exchanger, wherein a plurality of vertical tube bundles are arranged in a vessel in such a manner as to be removable therefrom.

Each of the tube bundles has at its centre a central tube in which are contained inter alia downwardly extending feed water pipes and in which there may be arranged leakage or oscillation monitoring probes. The provision of monitoring probes in each individual tube bundle is naturally associated with considerable outlay and each probe can be employed only for monitoring the tube bundle with which it is accociated. If the vessel itself is to be monitored or inspected, it is necessary either to provide supplementary probes or to remove one or more of the tube bundles in order.that the vessel may be inspected from the interior.

The embodiment of heat exchanger according to the present invention shown in Figures 1 and 2 is a liquid sodium/water heat exchanger for a sodium-cooled nuclear reactor installation. The exchanger comprises a cylindrical vessel I having circular cross-section for containing liquid sodium as the first exchange medium sealed at its upper end with a rounded lid 2 and having a rounded end wall 3 at it slower end.

A horizontal intermediate partition 4 is provided towards the upper end of the vessel I and a horizontal intermediate partition 5 is provided towards the lower end of the vessel 1. These horizontal intermediate partitions 4 and 5 are formed with a plurality of cylindrical apertures extending therethrough in which there are inserted sligingly but almost in fluid-tight manner a plurality of tube bundles 6 for containing water-steam as the second exchange medium, a pressure relief and instrumentation tube 7 and a pump housing 8. The tube 7 is closed off from the interior of the vessel and is capable of being withdrawn from the vessel to enable the interior of the vessel to be inspected, but does not contain a tube bundle.As shown only with respect to one of the tube bundles 6 n Figure 1, all these parts 6, 7, 6r are welded in fluidtight manner to the lid 2 such that the weld seam can, with only slight expenditure, be opened up and subsequently closed again by welding. Thus the vessel 1 is absolute, fluid-tight, but the various parts 6, 7, 8 can nevertheless be released and moved upwardly out of the vessel 1 with only a slight outlay. The tube 7 is of substantially smaller diameter than the tube bundles 6 and can therefore be more readily extracted from the vessel 1 for purposes of inspection.

The tube 7 extends along the axis of the vessel and each tube bundle extends parallel to the axis of the vessel, as does the pump housing 8.

Arranged in the tubular wall of the tube 7, respectively in the vicinity of the end wall 3 and in the vicinity of the lid 2, there is in each case at least one rupture or safety disc 16 which, in the event of damage, for example in the event of a pressure increase due to a sodium-water reaction occurring as a result of damage to the tubes of the tube bundles 6, rapidly and reliably releases a large cross-section and conveys a mixture of sodium and various reaction products initially to a separator (not shown) which separates the reaction products and then to a relief vessel (also not shown). In the event of such a sodium-water reaction, the path from the location of damage to a disc 16 should be as short as possible, in order that the rupture disc may be able to respond rapidly.Due to the arrangement of the discs 16 in the retractable tube 7, the discs 16 can be tested or replaced with only slight outlay and it is not necessary to provide special apertures or pipelines on the vessel for this purpose. Additionally, by attachment of suitable probes, the discs 16 can be monitored electrically. A suitable monitoring device for this purpose is disclosed in British Patent Specification No.

1,374,296. The discs 16 are useful mainly in sodium/water heat exchangers, such as that illustrated, but can also be employed in sodium/sodium heat exchangers for protection of the vessel 1 in the event of power excursions of the reactor.

In operation of the heat exchanger illustrated, the primary coolant constituted by liquid sodium flows through an inlet 9 into a first chamber between the upper intermediate partition 4 and the lid 2, and from there through lateral apertures in casings of the tube bundles 6 and downwardly within the casings and through further lateral apertures into a second chamber between the lower intermediate portion 5 and the end wall 3. From there it is sucked into the pump housing 8 via a pump inlet 11 and expelled into a third chamber between the two intermediate partitions 4 and 5, from where it flows between the inner wall of the vessel 1 and guiding means in the form of a cylindrical wall 12 secured to the upper intermediate partition 4 to an outlet 10.The purpose of the cylindrical wall 12 is to ensure that the temperature of the inner wall of the vessel 1 in the vicinity of the wall 12 continuously corresponds to the outflow temperature of the sodium (which is less than the inflow temperature), so that the thermal loading of the vessel 1 is minimised.

The secondary coolant, which in the case of the illustrated embodiment is water/steam but which may also be sodium, enters the tube bundles 6 at their upper ends and flows through vertical down tubes 13 to the lower ends of the tube bundles 6 where it reverses its direction of flow and flows through a plurality of thin-walled tubes 14 back to the upper ends of the tube bundles 6 and out through an outlet 15. In the course of flowing through the tubes 14 the secondary coolant is heated by the primary coolant flowing between the outsides of the tubes 14 and the casings.

Figure 2 in particular shows how the tube bundles 6, the pressure relief and instrumentation tube 7 and the pump housing 8 are arranged in space-saving manner in the cylindrical vessel 1 so that the heat exchanger is particularly compact. Due to the eccentric arrangement of the pump housing 8 and due to the arrangement of the tube 7 (having a diameter very much smaller than that of the tube bundles 6) substantially in the centre of the vessel 1, the number of tube bundles which are to be provided and their diameter can be chosen almost at will without wasting space. The eccentric arrangement does not lead to substantially non-uniform temperatures about the periphery of the vessel and to resultant peripheral stressing of the vessel since the major portions of the tube bundle casings and the pump housings 8 are surrounded only by a medium which has already discharged its heat to the tube bundles. The eccentric arrangement of the pump housing 8 which has a substantially larger diameter than the tube 7 affords an extremely spacesaving arrangement.

Instrumentation 17 is disposed in the tube 7 so as to be accessible for maintenance.

Such instrumentation 17 may comprise, for example, devices for detecting boiling noises in the sodium and providing a warning of approaching damage to the tube bundles and/or leakage detection devices and/or oscillation metering devices and/or temperature metering devices. The tube 7 may be removed and replaced by an observation or manipulator tube in cases of damage so that the instrumentation can be tested after extraction of the tube 7. In the case of a sodium-cooled nuclear reactor installation, the tube 7 can be pulled into an exchange tank which is sealed on all sides and is filled with an inert gas, so that the extracted tube 7 does not come into contact with the atmosphere. The tube bundles 6 can be treated in the same manner.

The heat exchanger described above with reference to the drawing is particularly advantageous since it may be employed with corrosive media and since the tube bundles may be extracted from the vessel.

Furthermore the heat exchanger is capable of being tested from the interior of the vessel with the minimal outlay and minimal expenditure of time. Also the wall of the vessel is provided with only a small number of welded connections which prejudice rigidity of the vessel and make testing with the known ultrasound and eddy current processes more difficult.

WHAT WE CLAIM IS: 1. A heat exchanger comprising: a) a vessel for containing a first exchange medium; b) at least one bundle of tubes within the vessel for containing a second exchange medium; and c) a pressure relief and instrumentation tube also within the vessel, which tube is normally closed off from the interior of the vessel and is capable of being withdrawn from the vessel to enable the interior of the vessel to be inspected, but which does not contain a tube bundle.

2. A heat exchanger according to claim 1 wherein the vessel is substantially cylindrical and has a circular cross-section and the pressure relief and instrumentation tube extends along the axis of the vessel.

3. A heat exchanger according to claim 2, wherein the or each tube bundle is elongate and extends parallel to the axis of the vessel.

4. A heat exchanger according to claim 3, wherein the pressure relief and instrumentation tube and the tube bundle(s) are connected to the vessel in such a manner that they may be withdrawn from the vessel parallel to their lengths.

5. A heat exchanger according to claim 4, wherein the pressure relief and instrumentation tube is suspended from one end of the vessel.

6. A heat exchanger according to any preceding claim, wherein the pressure relief and instrumentation tube has one or more rupture discs disposed in its tubular wall, the rupture disc(s) being adapted to be ruptured when an excess pressure prevails in the vessel.

7. A heat exchanger according to any preceding claim, wherein the pressure relief and instrumentation tube is adapted to be connected to a separator and/or a relief vessel.

8. A heat exchanger according to any preceding claim, wherein the vessel also contains a pump connected to the vessel in such a manner that it may be withdrawn from the vessel.

9. A heat exchanger according to claim 8 8 when appended directly or indirectly to claim 2, wherein the pump is elongate and extends parallel to the axis of the vessel.

10. A heat exchanger according to any preceding claim, wherein the or each bundle is contained within a tubular casing having at least one opening at each end region.

11. A heat exchanger according to claim 10 when appended to claim 8 or 9, wherein the interior of the vessel is divided into three chambers by two partitions, a first of the chambers being in fluid communication with an inlet of the vessel and the opening(s) at one end of the or each tube bundle, a second of the chambers being in fluid communication with the opening(s) at the other end of the or each tube bundle and an inlet of the pump, and a third of the chambers intermediate the first and second chambers being in fluid communication with an outlet of the pump and an outlet of the vessel.

12. A heat exchanger according to claim 11, wherein means are provided for guiding the flow of first exchange medium towards the outlet of the vessel by way of a region adjacent a wall of the vessel.

13. A heat exchanger according to claim 8, 9, 11 or 12 or claim 10 when appended to claim 8 or 9, wherein the tube bundle(s), the pressure relief and instrumentation tube and the pump are suspended from a lid of the vessel.

14. A heat exchanger according to any preceding claim, wherein the pressure relief and instrumentation tube contains at least one monitoring device.

15. A heat exchanger substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawing.

16. A nuclear reactor installation incorporating a heat exchanger according to ahy preceding claim.

17. An installation according to claim 16, adapted to be operated with liquid sodium as the first exchange medium and water/steam as the second exchange medium.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. warning of approaching damage to the tube bundles and/or leakage detection devices and/or oscillation metering devices and/or temperature metering devices. The tube 7 may be removed and replaced by an observation or manipulator tube in cases of damage so that the instrumentation can be tested after extraction of the tube 7. In the case of a sodium-cooled nuclear reactor installation, the tube 7 can be pulled into an exchange tank which is sealed on all sides and is filled with an inert gas, so that the extracted tube 7 does not come into contact with the atmosphere. The tube bundles 6 can be treated in the same manner. The heat exchanger described above with reference to the drawing is particularly advantageous since it may be employed with corrosive media and since the tube bundles may be extracted from the vessel. Furthermore the heat exchanger is capable of being tested from the interior of the vessel with the minimal outlay and minimal expenditure of time. Also the wall of the vessel is provided with only a small number of welded connections which prejudice rigidity of the vessel and make testing with the known ultrasound and eddy current processes more difficult. WHAT WE CLAIM IS:

1. A heat exchanger comprising: a) a vessel for containing a first exchange medium; b) at least one bundle of tubes within the vessel for containing a second exchange medium; and c) a pressure relief and instrumentation tube also within the vessel, which tube is normally closed off from the interior of the vessel and is capable of being withdrawn from the vessel to enable the interior of the vessel to be inspected, but which does not contain a tube bundle.

18. A compact heat exchanger or steam

generator vessel for corrosive media, containing a plurality of perpendicular heat exchanger or steam generator tube bundles adapted to be extracted from above, and, apart from the tube bundles, a central pressure relief and instrumentation tube which is sealed below and adapted to be extracted upwardly.