AU2006275171A1

AU2006275171A1 - Coiled heat exchanger having different tube diameters

Info

Publication number: AU2006275171A1
Application number: AU2006275171A
Authority: AU
Inventors: Markus Hammerdinger; Christiane Kerber; Manfred Schonberger; Manfred Steinbauer
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2005-07-29
Filing date: 2006-07-06
Publication date: 2007-02-08
Anticipated expiration: 2026-07-06
Also published as: AU2006275171B2; CN101233378A; WO2007014618A1; RU2402733C2; NO20081063L; US20080271880A1; CN101233378B; BRPI0614910A2; RU2008107273A

Description

ox 259. Hynoton, Vic 3444 AUSTRALIA * www.academyXL.com e InfoeocodmyXL.com o a business of Tonco Services Pty Ltd * ABN 72 892 315 097 Free 1800637640 Inter M +61 3 54 232558 Fox E 03 54 232677 inter . +61 3 54 232677 TRANSLATION VERIFICATION CERTIFICATE This is to certify that the attached document is an English translation of the -- German-language Patent Application PCT/EP2006/006626 and Academy Translations declare that the translation thereof is to the best of their knowledge and ability true and correct. Academy ronslotions PO Box 259, Kyneton VIC 3444 AUSTRAUR January 25, 2008 Date Stamp/Signature: AT Ref.: ddc-2082 Multilingual Technical Documentation Translation from German of PCT Application PCT/EP2006/006626 COILED HEAT EXCHANGER HAVING DIFFERENT TUBE DIAMETERS 5 Description The invention relates to a coiled heat exchanger having a plurality of tubes which are wound around a core tube, 10 having a casing that delimits an outer space around the tubes. In LNG baseload plants, natural gas is continuously liquefied in large quantities. The liquefaction of 15 natural gas is mainly accomplished by heat exchange with a coolant in coiled heat exchangers. Many other applications of coiled heat exchangers, however, are also known. 20 In a coiled heat exchanger, many layers of tubes are coiled around a core tube in a screw-like manner. A first medium is introduced into the interior of at least a part of the tubes, which exchanges heat with a second medium that flows between the tubes and a surrounding casing. 25 The tubes are collected into several groups at the end of the heat exchanger, and are led out of the outer space in a bundle. Coiled heat exchangers of this type and their 30 application, for example for the liquefaction of natural gas, are described in each of the following publications: - Hausen/Linde, Low Temperature Engineering, 2nd Edition, 1985, pp. 471-475 2 - W. Scholz, "Gewickelte Rohrwirmetduscher [Coiled Tube Heat Exchangers]", Linde-Berichte aus Technik und Wissenschaft, [Linde Reports on Science and Technology], No. 33 (1973), pp. 34-39 5 - W. Bach, "Offshore-Erdgasverflissigung mit Stickstoffkilte - Prozessauslegung und Vergleich von Gewickelten Rohr- und Plattenwirmetduschern [Offshore Natural Gas Liquefaction with Nitrogen Coolant Process Design and Comparison of Coiled Tube and Plate 10 Heat Exchangers", Linde-Berichte aus Technik und Wissenschaft, [Linde Reports on Science and Technology, No. 64 (1990), pp. 31-37 - W. F6rg et al., "Ein neuer LNG Baseload Prozess und die Herstellung der Hauptw&rmetiuscher", Linde-Berichte aus 15 Technik und Wissenschaft No. 78 (1999), pp3-11 (English edition: W. F6rg et al., "A New LNG Baseload Process and the Manufacturing of the Main Heat Exchanger", Linde Reports on Science and Technology, No. 61 (1999), pp. 3-11) 20 - DE 1501519 A - DE 1912341 A - DE 19517114 A - DE 19707475 A - DE 19848280 A 25 Tubes with uniform cross section are used in the known coiled heat exchangers. 30 The object of the invention is to further optimize coiled heat exchangers of this type, especially with regard to weight, number of tubes, process conditions, and/or operational reliability.

3 The object is achieved in that the tubes have at least two tube groups with different outer diameter and/or different inner diameter. A "tube group" consists of at 5 least one, preferably a plurality of tubes. The tubes in a tube group can, but need not, be adjacent to one another in a tangential and/or radial direction. Both tube groups are preferably located in the same tube bundle. A "tube bundle" describes the entirety of an 10 internal component of a coiled heat exchanger, comprising core tube, tube layers wound around it, and any accessory items located between them, such as supports, etc., which is manufactured in a coiling process. A coiled heat exchanger has one or several tube bundles of this type 15 within a casing. In this manner, the tube geometry can be better adapted to the specific technical process requirements. Such specific requirements may, for example, consist of 20 different thermal properties of different process fractions that flow through the associated tube groups, or in the different length of tubes in the different tube layers. A further advantage consists in that the wall thicknesses can be adapted to different process pressures 25 of the media flowing through the tubes, and thus weight can be saved. Within the scope of the invention, the following combinations of geometric parameters for the tubes in the 30 two tube groups are possible: 4 Outer diameter Inner diameter Wall thickness Same Different Different Different Same Different Different Different Same or different "Different" here is understood to mean a deviation in the associated dimension that is significantly larger than the applicable manufacturing tolerance. One parameter is 5 considered especially to be different from another if its value differs by at least 2%, preferably at least 5%. Within the scope of the invention, the inner diameter especially can be varied, preferably while the outer 10 diameter remains the same. By varying the inner diameter, for example, the pressure drop along the tubes can be influenced. Two different tube groups can thus be optimized independently of one 15 another for two different process fractions. This can be done, fundamentally, with the same wall thickness; that is, both tube groups also have different outer diameters. Alternatively, all tubes can have the same outer diameter; then only the wall thickness and inner diameter 20 vary. Within the scope of the invention, it is therefore useful in many cases to provide the same outer diameter for the two tube groups, and to achieve the inner diameter by 25 using different wall thicknesses. Two tube groups with different inner diameters can then be coiled in the same tube layer, and can have two different process fractions flowing through them. Compared to an arrangement with different process fractions in different tube layers, 5 this provides improved uniformity of distribution of heat flows in the heat exchanger. A difference in the wall thickness can be implemented 5 with the use of the same material, or also with the use of different materials (for example, aluminium and steel) for the two tube groups. The use of different materials is described in detail in the German patent application 102005036413.6 (applicant's internal reference P05164 10 DE/AVA) , which was submitted at the same time as this application, and in the corresponding applications. The two tube groups can be arranged in the same or in different tube layers. Of course, more than two tube 15 groups with different dimensions can also be provided. For example, a first and a second tube group can be arranged within a first tube layer, and a third tube group in a second tube layer. 20 It is useful, especially to adapt to process fractions with different pressures for which the two tube groups are intended, if two tube groups have different wall thicknesses. For the tube group with the lower internal design pressure, a smaller wall thickness is used, and 25 thus weight is saved. Depending on the pressure loss desired and technical manufacturing capabilities, either the inner diameter or the outer diameter of the two tube groups can be different; alternatively, both diameters can be different. 30 It is fundamentally also possible to vary the inner and/or outer diameter of the same tube within the heat exchanger, for example in order to achieve better 6 adaptation to the volume of an evaporating or condensing process flow. In this case, the first tube group comprises, for example, a first section of tubes and the second tube group comprises another section of the same 5 tube, for example one that connects to the first section. The invention also relates to the application of a heat exchanger of this type to the implementation of an indirect heat exchange between a hydrocarbon flow and at 10 least one heating or cooling fluid. The hydrocarbon flow thereby comprises, for example, natural gas. 15 The hydrocarbon flow is liquefied, cooled, heated, and/or evaporated in the course of the indirect heat exchange. The heat exchanger is preferably used to liquefy or evaporate natural gas. 20 The invention, as well as further details of the invention, is described in more detail in the following, with the application example shown schematically in the drawing. Shown is a coiled heat exchanger 1 according to the invention for the liquefaction of a natural gas flow 25 2 to produce liquefied natural gas (LNG - liquid natural gas) 3, by means of indirect heat exchange with three coolant flows, a low-pressure coolant 4, a first high pressure coolant 5, and a second high-pressure coolant 6. 30 The coiled heat exchanger here has a single tube bundle with three tube groups. The tubes in the tube groups are coiled alternately in different layers in a screw pattern around a common core tube. (The tube coil corresponds to 7 the generally known principle of a coiled heat exchanger; the geometric arrangement is thus not shown in the schematic drawing.) The tube groups in this example are divided according to process flows. Natural gas 2 flows 5 through the tube of a first tube group 7; one each of the two high-pressure coolants 5, 8 flows through the tubes of a second and third tube group 8, 9 respectively. The high-pressure coolants are thereby fed from bottom to top; that is, in the same direction as the natural gas. 10 The low-pressure coolant 4 flows from top to bottom; that is, in the counterflow direction to the natural gas, in the outer space of the tubes, and thereby evaporates. Evaporated low-pressure coolant 10 is drawn off of the outer space at the bottom end of the heat exchanger. 15 In a concrete example with numbers, the process pressures are: Natural gas 2 ..................... 120 bar Low-pressure coolant 4 .............15 bar 20 First high-pressure coolant 5 ..... 60 bar Second high-pressure coolant 6 .... 60 bar The tubes are made of a light metal material, such as aluminium or an aluminium alloy, and have different wall 25 thicknesses for the different tube groups. The outer diameters of the tubes in all tube groups are the same. In a first variant, which is optimized for weight, the wall thicknesses are: 30 Tube group 7 ...................... 1.4 mm Tube groups 8 and 9 ............... 0.9 mm 8 In a further variant, the wall thicknesses were optimized with regard to the thermal and hydraulic design, and with regard to as a homogeneous a tube bundle construction as possible, whereby process-driven parameters (e.g., 5 prescribed maximum pressure drops in individual process flows) needed to be maintained. In this second variant, the wall thicknesses are: Tube group 7 ...................... 1.4 mm 10 Tube groups 8 and 9 ............... 1.2 mm In the second variant, identical tube lengths were achieved in the individual tube groups, whereby the heat exchanger was optimized both with regard to heat transfer 15 and with regard to cost-effectiveness.

Claims

1. Coiled heat exchanger having a plurality of tubes which are wound around a core tube, having a casing 5 that delimits an outer space around the tubes, wherein the tubes of a first tube group (7) have a first inner diameter and a first outer diameter, and the tubes of a second tube group (8, 9) have a second inner diameter and a second outer diameter, characterized in 10 that the second inner diameter is different from the first inner diameter, and/or the second outer diameter is different from the first outer diameter.

2. Heat exchanger as in claim 1, characterized in that 15 the second inner diameter is different from the first inner diameter, and the second outer diameter is the same as the first outer diameter.

3. Heat exchanger as in claim 1 or 2, characterized in 20 that the first and the second tube groups (7, 8, 9) are arranged within the same tube layer.

4. Heat exchanger as in claim 1 or 2, characterized in that the first and the second tube groups (7, 8, 9) 25 are arranged in different tube layers.

5. Heat exchanger as in one of the claims 1 through 4, characterized in that the tubes in the first tube group (7) have a first wall thickness, and tubes in 30 the second tube group (8, 9) have a second wall thickness, and the first wall thickness is different from the second wall thickness. 10

6. Heat exchanger as in one of the claims 1 through 5, characterized in that the tubes in the first tube group (7) and the tubes in the second tube group (8, 9) are located in the same tube bundle. 5

7. Application of the heat exchanger in accordance with one of the claims 1 through 6 for carrying out indirect heat exchange between a hydrocarbon flow (2) and at least one heating or cooling fluid (4, 5, 6). 10

8. Application as in claim 7, characterized in that the hydrocarbon flow (2) comprises natural gas.

9. Application as in claim 7 or 8, characterized in that 15 the hydrocarbon flow (2) is liquefied, cooled, heated, and/or vaporized due to the indirect heat exchange.