RU2402733C2 - Helical-coil heat exchanger with pipes of various diametre - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: in helical-coil heat exchanger with multiple pipes wound around central pipe and jacket that limits external space around pipes, some of which make the first group of pipes with the first inner diametre and the first outer diametre, and other ones make the second group of pipes with the second inner diametre and with the second outer diametre, the second inner diametre differs from the first inner diametre and/or the second outer diametre differs from the first outer diametre, and the second thickness of pipes wall differs from the first thickness of pipes wall.

EFFECT: optimisation of helical-coil heat exchangers, from the point of view of their mass, number of helical-coil pipes, modes of operation and operational reliability.

8 cl, 1 dwg

Description

The present invention relates to a coil heat exchanger with a plurality of pipes wound around a central pipe and a casing restricting the external space around the pipes.

In facilities designed for a base load for liquefying natural gas, it is continuously liquefied in large volumes. Natural gas is liquefied mainly due to its heat exchange with a coolant in coil (coil) heat exchangers. However, many other applications of coil heat exchangers are known.

In a coil heat exchanger, its pipes are wound in several layers in a spiral around the central pipe. At least in part of the pipes, a first medium is passed, between which and a second medium flowing in the external space between the pipes and the casing enclosing them, heat exchange occurs. At the ends of the heat exchanger, its pipes are combined into several groups and in the form of bundles are removed from the external space surrounding them.

Such coil heat exchangers and their use, for example, for liquefying natural gas, are described in each of the following publications:

- Hausen / Linde, Tieftemperaturtechnik, 2nd ed., 1985, pp. 471-475,

- W. Scholz, "Gewickelte Rohrwärmeaustauscher", Linde-Berichte aus Technik und Wissenschaft, No. 33, 1973, pp. 34-39,

- W. Bach, "Offshore-Erdgasverflüssigung mit Stickstoffkälte - Prozessauslegung und Vergleich von Gewickelten Rohr- und Plattenwärmetauschern", Linde-Berichte aus Technik und Wissenschaft, No. 64, 1990, pp. 31-37,

- W.Förg et al., "Ein neuer LNG Baseload Prozess und die Herstellung der Hauptwärmeaustauscher, Linde-Berichte aus Technik und Wissenschaft", No. 78, 1999, pp. 3-11 (publication in English: W.Förg et al. ., "A New LNG Baseload Process and Manufacturing of the Main Heat Exchanger", Linde Reports on Science and Technology, No. 61, 1999, pp. 3-11),

- DE 1 501 519 A,

- DE 1912341 A,

- DE 19517114 A,

- DE 19707475 A,

- DE 19848280 A.

Known coil heat exchangers use pipes of the same cross section.

The basis of the present invention was the task of further optimization of such coil heat exchangers, primarily in terms of their mass, number of coil pipes, operating modes and / or operational reliability.

This problem is solved due to the fact that the pipes of at least two of their groups have different outer diameters and / or different inner diameters. In this case, the “pipe group” consists of at least one pipe, preferably a plurality of pipes. Pipes of the same group may, but need not necessarily, be adjacent to each other in the tangential direction and / or radial direction. Both groups of pipes are preferably in the same tube bundle. By “pipe bundle” is meant a structurally unified internal unit of a coil heat exchanger consisting of a central pipe, wound on it with layers of pipes and auxiliary means located between them, such as jumpers and other structural elements, and made in one cycle of the pipe winding process. The coil heat exchanger has one or more similar tube bundles inside its casing.

The solution proposed in the invention makes it possible to better coordinate the geometric parameters of the coil pipes with specific technological needs. Such specific technological needs can be based, for example, on differences in the thermal properties of various technological fractions flowing through the corresponding groups of pipes, or on the need to use pipes of different lengths in different layers formed by them. Another advantage is the possibility of matching the wall thickness of the pipes with different values of the working pressure of the media flowing through them and thereby reducing the mass of the heat exchanger as a whole.

According to the invention, the following combinations of geometric parameters of pipes of their two groups are possible:

Outside diameter Inner diameter Wall thickness same different different different same different different different the same or different

The term “different” in this context means a difference in the values of the corresponding size, which is significantly more than the production tolerances established for it. Two values of the same parameter or of the same value are considered different primarily when they differ from each other by at least 2%, preferably at least 5%.

According to the invention, it is possible to vary primarily the inner diameter of the pipes, preferably with a constant outer diameter.

The use of pipes with different inner diameters allows, for example, setting the magnitude of the pressure drop along their length. In this way, two different groups of pipes can be independently optimized for two different process fractions. In principle, the same result can be achieved with the same pipe wall thickness, i.e. both groups of pipes may also have different outer diameters. In another embodiment, all pipes may have the same outer diameter, and in this case, only their wall thickness and inner diameter will vary.

Therefore, according to the invention, in many cases it is advisable to use pipes in both groups with the same outer diameter and with a different inner diameter, which can be varied due to their implementation with different wall thicknesses. Due to this, two groups of pipes with different inner diameters can be wound into the same layer and two different technological fractions can be passed through them. As a result, in comparison with the transmission of different technological fractions through pipes located in different layers, the uniformity of the distribution of the heat flux in the heat exchanger improves.

Pipes with different wall thicknesses can be manufactured using the same material to make pipes of both of their groups or from different materials (for example, aluminum and steel). The use of different materials for the manufacture of coil heat exchanger tubes is described in more detail in the simultaneously filed application DE 102005036413.6 (applicant's internal case number P05164-DE / AVA) and other related patent applications.

Both groups of pipes can be located in the same or in different layers of pipes. Obviously, more than two groups of pipes with different sizes can be provided in the heat exchanger. So, for example, the first and second groups of pipes can be located in the first layer of pipes, and the third group of pipes can be located in the second layer of pipes.

It is advisable to use two groups of pipes with different thicknesses of their walls, first of all, to coordinate different pressure fractions with different pressure values for the passage of which both of these groups of pipes are intended. To pass the technological fraction of a lower design pressure, a group of pipes with a smaller wall thickness is used, thereby reducing the weight of this group of pipes. Moreover, depending on the required pressure loss in the pipes or in each pipe of one of their groups and depending on the technological capabilities, the pipes of both of their groups can differ either in their inner or their outer diameter or in their inner and their outer diameters.

In principle, it is also possible to vary the inner and / or outer diameter of the same pipe within the heat exchanger, for example, to better match the volume of the vaporized or condensed process stream. In this case, the first group of pipes will be, for example, the first sections of pipes, and the second group will be other sections of the same pipes, for example, adjacent to their first sections.

Another object of the present invention is the use of such a heat exchanger for indirect heat exchange between a hydrocarbon-containing stream and at least one heat or coolant.

The hydrocarbon containing stream may be, for example, natural gas.

In indirect heat exchange, a hydrocarbon-containing stream is liquefied, cooled, heated and / or evaporated. In a preferred embodiment, the inventive heat exchanger is used to liquefy or vaporize natural gas.

Below the invention is described in more detail on the example of one of the variants of its implementation with reference to the only schematic drawing attached to the description. The drawing shows the inventive coil heat exchanger 1, designed to liquefy a stream of natural gas 2 to produce liquefied natural gas 3 by indirect heat exchange with three flows of refrigerants, namely: with low-pressure refrigerant 4, with the first high-pressure refrigerant 5 and with the second high pressure refrigerant 6.

In this example, the coil heat exchanger has a single bundle of coil pipes with three groups of coil pipes. Pipes of their individual groups are alternately spirally wound in different layers onto a common central pipe (Pipe winding corresponds to the well-known principle of coil winding of a coil heat exchanger, and therefore the exact mutual geometric arrangement of the pipes is not shown in the schematic drawing). In this example, the coil pipes are distributed in groups in accordance with the flow of process flows through them. Natural gas 2 is passed through the pipes of their first group 7, and one of the two high pressure refrigerants 5, 6, respectively, is passed through the pipes of the second, respectively, third groups 8, 9. At the same time, high pressure refrigerants are passed from the bottom up, i.e. in direct flow with natural gas. Low pressure refrigerant 4 flows from top to bottom through the outer space surrounding the pipe, i.e. in countercurrent to natural gas, and thus evaporates. The evaporated low pressure refrigerant 10 exits the surrounding outer pipe at the lower end of the heat exchanger again.

In one specific example, process streams passed through a heat exchanger may have the following operating pressure values:

natural gas 2 120 bar low pressure refrigerant 4 15 bar first high pressure refrigerant 5 60 bar second high pressure refrigerant 6 60 bar

Pipes (coils) are made of light metal, for example, aluminum or its alloy, and have in each group wall thickness different from other groups. Moreover, in all layers of the pipe have the same outer diameter.

In the first embodiment, aimed at optimizing the mass of the heat exchanger, the pipes have the following wall thickness:

group 7 pipes 1.4 mm pipes of groups 8 and 9 0.9 mm

In another embodiment, the wall thickness of the pipes can be optimized with respect to thermal and hydraulic parameters and with respect to the maximum possible uniformity of the arrangement of the pipes in the bundle, taking into account the necessary process parameters (for example, given maximum pressure drops in individual process streams). In this second embodiment, the pipes have the following wall thickness:

group 7 pipes 1.4 mm pipes of groups 8 and 9 1.2 mm

In the second embodiment, pipes of the same length were used in their individual groups, which made it possible to optimize the heat exchanger in terms of heat transfer and economic efficiency.

Claims (8)

1. A coil heat exchanger with a plurality of pipes wound around a central pipe and a casing restricting the external space around the pipes, one of which makes up the first group (7) of pipes with a first inner diameter, with a first outer diameter and with an equal difference between them with the first wall thickness and the others constitute the second group (8, 9) of pipes with a second inner diameter, with a second outer diameter and with equal difference between them a second wall thickness, characterized in that the second inner diameter is different from the first inner the diameter and / or the second outer diameter is different from the first outer diameter and the second pipe wall thickness is different from the first pipe wall thickness. 2. The heat exchanger according to claim 1, characterized in that the second inner diameter is different from the first inner diameter, and the second outer diameter is equal to the first outer diameter. 3. The heat exchanger according to claim 1 or 2, characterized in that the first and second groups (7, 8, 9) of pipes are located in the same pipe layer. 4. The heat exchanger according to claim 1 or 2, characterized in that the first and second groups (7, 8, 9) of pipes are located in different layers of pipes. 5. The heat exchanger according to claim 1 or 2, characterized in that the pipes of their first group (7) and pipes of their second group (8, 9) are in the same tube bundle. 6. The use of a heat exchanger according to one of claims 1 to 5 for indirect heat exchange between a hydrocarbon-containing stream (2) and at least one heat or coolant (4, 5, 6). 7. The use according to claim 6, characterized in that the hydrocarbon-containing stream (2) is natural gas. 8. The use according to claim 6 or 7, characterized in that the hydrocarbon-containing stream (2) is liquefied, cooled, heated and / or evaporated by indirect heat exchange.

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