RU2639439C1 - Tube-and-shell heat exchanger with curved tubes - Google Patents

Abstract

FIELD: heating system.SUBSTANCE: in the heat exchanger, consisting of a housing, tube grids, partitions and tubes, the tubes are installed with a preliminary deflection. Preliminary deflection is carried out by means of displacing holes for tubes in the partitions or by means of displacing the partitions by displacement mechanism, and the partitions are installed with the possibility of displacement in the direction of preliminary displacement. The partitions in the middle part of the heat exchanger are rigidly fixed with the displacement of the holes for the tubes, and the housing can be made with a deflection. The remaining partitions are installed with the possibility of further displacement in the direction of the preliminary displacement of the tubes to compensate for their elongation at temperature deformation. The preliminary deflection of the tubes is carried out during the assembly of the heat exchanger from straight tubes which are bent within elastic deformation.EFFECT: ensuring compensation of tube elongation at temperature deformation.6 cl, 5 dwg

Description

The invention relates to heat exchange and reactor equipment and can be used in the energy, chemical, petrochemical industries, power equipment of vehicles and other industries where heat exchange is carried out.

Shell-and-tube heat exchangers with compensating devices are known: with a lens compensator, with a floating head, with U-shaped tubes. The first has a complex structure, does not have a rigid body and does not work at high pressures, the second is not reliable enough when working with aggressive environments and environments that do not allow cavities to communicate, the third has low maintainability, and it is difficult to use, in particular, in a vertical version.

Known heat exchanger according to patent No. 2451889. Inside the casing of the heat exchanger is a tube bundle, which consists of at least two rows of cone-shaped pipes, fixed with ends in the holes of the gratings along concentric circles. The pipes are inclined simultaneously in two directions: inclined to the vertical axis of the body and with an additional inclination made by shifting the ends in the circumferential direction, i.e. along arcs of circles placing them in tube sheets. In this case, the slope angles are made in the range of 0.5-50.0 degrees from the vertical plane passing through the vertical axis of the housing. The heat exchanger has a complex tube design and low maintainability.

The heat exchanger according to patent No. 2451889 adopted as a prototype.

The purpose of the invention is the provision of compensation for elongation of pipes during temperature deformation in the heat exchanger using straight tubes.

This goal is achieved by the fact that in the heat exchanger, consisting of a housing, tube sheets, partitions and pipes, the pipes are installed with a preliminary deflection with the possibility of further deflection during temperature deformation.

Preliminary deflection is carried out due to the displacement of the holes for pipes in the partitions, as well as due to the displacement of the partitions by the movement mechanism, and two partitions with cutouts in opposite directions in the middle part of the heat exchanger are fixedly displaced, the remaining partitions are installed with the possibility of further displacement in the direction of the preliminary displacement.

The preliminary deflection of the pipes is carried out in the process of assembling the heat exchanger from straight pipes that bend within the elastic deformation.

The housing can be made with a deflection, while two partitions with cutouts in opposite directions in the middle part of the heat exchanger are fixedly mounted in the housing, the remaining partitions are installed with the possibility of further displacement in the direction of preliminary deflection of the housing.

Thus, significant differences are made in the design of the heat exchanger, namely: straight pipes are installed with a deflection, which is formed by a preliminary displacement of the holes in the partitions in the transverse direction relative to the rectilinear initial position of the pipe axis or by a preliminary displacement of the partitions themselves with the pipes in the transverse direction in the manufacture of the heat exchanger. When elongating due to thermal deformation of the tubes, they are displaced in the same transverse direction, dragging along the partitions installed with the possibility of further displacement and providing synchronous displacement of the pipes, the elongation of the pipes occurs without their mutual touching and touching the heat exchanger body. In this case, the displacement is carried out within the elastic deformation of the pipes. This difference is significant, as it allows to achieve the purpose of the invention:

- providing compensation for pipe elongation during temperature deformation;

- manufacture of a heat exchanger with curved tubes from straight pipes.

The preliminary displacement of the pipes with a further displacement during elongation during thermal deformation corresponds to the case when, when the temperature changes, the deformation of the pipes is greater than the deformation of the heat exchanger body. If, when the temperature changes, the deformation of the pipes is less than the deformation of the heat exchanger body, the pipes are installed by means of partitions with the maximum possible displacement, and when the temperature changes, the displacement decreases, the deformed pipes straighten out within the elastic deformation.

The proposal is illustrated by drawings, where in FIG. 1 shows a heat exchanger with a deflection with one bend of pipes, which is a half-wave. The axis of the pipes at the junction with the tube plate is inclined at an angle β _about to the perpendicular to the tube plate, where:

- 1 - heat exchanger housing;

- 2, 3 - pipe boards;

- 4 - pipes in the lower part of the heat exchanger;

- 5 - pipes in the middle of the heat exchanger;

- 6 - pipes in the upper part of the heat exchanger;

- 7 - a partition with a cutout from above;

- 8 - partition with a cutout from below;

- L is the distance between the tube plates;

- e is the length of the quarter wave with the displacement of the pipes;

- l is the distance from the tube plate to the partition;

- i - partition number;

- h is the total transverse displacement within the quarter-wave;

- β is the angle of inclination of the axes of the pipes from the initial position to the position of the axes with the displacement of the pipes;

- β _about - the angle of inclination of the axis of the pipe to the perpendicular to the tube plate of the heat exchanger at the junction of the pipe with the tube plate;

- p - index at preliminary transverse displacement;

- t is the index for lateral displacement at temperature deformation.

The housing 1 has a cylindrical surface.

In FIG. 2 shows a heat exchanger, where during bending three bends of pipes are formed, which are a full wave, the angle of inclination of the axes of the pipes at the junction with the tube plate β _о is equal to:

β _about = 0,

Where:

- 9 - curtains;

- 10 - a device for lateral displacement of partitions;

- N - total lateral displacement.

The housing 1 has a cylindrical surface.

The rest - see FIG. one.

In FIG. 3 shows a section AA of the heat exchanger in FIG. 2. Partitions 7 and 8 are shown at maximum displacement, where:

- 11 - guides;

- δ is the distance between the housing and the partition in a direction perpendicular to the displacement of the partition, the rest - see FIG. 1 and 2.

In FIG. 4 shows a heat exchanger where two deflections are formed with two pipe bends and a fixed middle, which are a complete wave, where:

- 12 - fixed partition with a cutout from above;

- 13 - fixed partition with a cutout from below;

- γ is the angle of inclination of the original pipe axes to the axis of the heat exchanger;

- ϕ is the angle of inclination of the tube plate to the axis of the heat exchanger.

The composite housing 1 consists of articulated shells with cylindrical surfaces. The rest - see FIG. 1 ... 3.

In FIG. 5 shows a heat exchanger where a preliminary displacement is formed due to the bending of the housing, the preliminary bending of the pipes is a half-wave, consisting of two quarter-waves, the closures 12 and 13 closest to the middle of the heat exchanger with the upper and lower cutouts are fixed.

The rest - see FIG. 1 ... 4.

Various combinations of the heat exchanger designs shown in FIG. 1-5.

In FIG. 1, the heat exchanger consists of a housing 1, at the ends of which pipe boards 2 and 3 are installed, in which pipes 4, 5 and 6 are installed, between the pipe boards the pipes are held by partitions 7 and 8, the partitions 7 hold the pipes 4 and 5, the partitions 8 hold the pipes 5 and 6. The holes for pipes 4, 5 and 6 in the partitions 7 and 8 are made with a preliminary displacement h _Pi relative to the initial axis of the pipes, depending on the distance l _i from the tube plate to the i-th partition. The preliminary deflection of the pipes is a half-wave, consisting of a convex rising and convex decreasing wormholes:

n _P = 2,

where n _P - the number of quarter-waves with a preliminary offset between the tube plates,

L = 2e _P.

The initial axis of the pipes are parallel to the axis of the heat exchanger.

The value of the preliminary transverse displacement h _P for pipes is selected from the condition under which the stress at mechanical compression is not more than the stress during pipe bending and is determined by the formula:

h _P ≥d / 4,

where d is the diameter of the pipes, mm

The ends of the pipes are embedded in the pipe boards at an angle β ₀ :

β _max ≥β ₀ > 0.

Between the pipe boards there must be at least two partitions. The value of the movement within the quarter-wave - h _P for the i-th partition is equal to h _Пi and depends on the distance from the tube plate to the i-th partition l _i , with a convex rising wave:

h _Пi = 2h _П l _i / e (el _i / 2e).

The bending of pipes during thermal deformation is a complete wave, consisting of a concave increasing, convex increasing, convex decreasing, concave decreasing quarter-waves, which are superimposed on quarter-waves upon preliminary displacement:

n _T = 4,

where n _T is the number of quarter-waves when displaced by thermal deformation of pipes.

The total transverse displacement h is determined by the formula:

The maximum value of the displacement h within the quarter-wave is determined by the formula:

h _max = 2dEΔtαk / (1-c) [σ],

where - E is the modulus of elasticity of the material, MPa;

- Δt is the difference in the temperature of the pipes and the body, ° C;

- α is the coefficient of linear expansion of the material, mm / ° C;

- k - the coefficient depends on the ratio of e _P and e _T , h _P and h _T ;

- c - pipe load factor from the action of forces during preliminary displacement and other loads in the heat exchanger, except for bending loads during temperature deformation.

The displacement of the pipes during thermal deformation is superimposed on the preliminary displacement, the presence of two additional bends depends on the ratio of the displacement values h _P and h _T.

The heat exchanger is manufactured and operates as follows.

The pipes are welded into the tube sheets at an angle β _about with the installed partitions, forming a tube bundle, which is installed in the housing. The pipes in the partitions are installed with an offset so that when installed in the tube bundle body, the pipes are previously displaced by the value of h _P. Tube boards are fixed to the body. When heated, the pipes lengthen and shift further in the direction of preliminary displacement within the elastic deformation by the value of h _T.

The minimum quarter- _wavelength e _Tmin is determined by the formula:

where - [σ] _D is the permissible stress of the pipe material, MPa.

The maximum value of the angle of inclination of the axis of the pipe during the transition from a concave to convex quarter to the angle of inclination of the pipe is determined by the formula:

β _max = arctg2 (Δtα) ^1/2

In this case, the following conditions are met:

0≤β≤arctg 2h / e.

If the elastic moduli and linear expansion coefficients of the material of the casing and pipes are different, formula (2) changes depending on the characteristics of the materials.

Otherwise, existing technologies are used in the manufacture.

If heat treatment of the heat exchanger is not provided, bending within the elastic deformation is carried out by a total value of h.

In FIG. 2 and 3, the heat exchanger is additionally equipped with shutters 9 for blocking the gap formed when the partitions are displaced, for the pipes to be displaced in the transverse direction; there are transverse displacement devices for the partitions 10 and guides 11. The distance between the guides of one partition must exceed the maximum size of the partition to prevent jamming. If the change in the minimum distance 8 between the body and the partition during the movement of the latter is significantly less than the displacement h, (h> 5δ), the guides 11 are not provided. If the cross-sectional area of the cutouts of the partitions significantly exceeds the cross-sectional area of the gaps and the latter do not significantly affect heat transfer, shutters 9 are not provided.

When the pipes are displaced, three bends are formed. The bends of the pipes during preliminary displacement and elongation during thermal deformation coincide and are a complete wave, consisting of a concave rising (first bend), convex rising and convex decreasing (second bending), concave decreasing (third bending) wormholes:

n _P = n _T = 4;

L = 4e _P = 4e _T.

The initial axis of the pipes are parallel to the axis of the heat exchanger,

The heat exchanger of FIG. 2 and 3 is manufactured and operates as follows.

Pipes are installed in pipe boards and partitions, forming a tube bundle, which is installed in the housing. The tube bundle is installed in the housing and is displaced by the displacement devices of the partitions 10, after bending the pipe by an amount of h _P. Tube boards are fixed to the body. When heated, the pipes lengthen and shift further in the direction of preliminary displacement within the elastic deformation by the value of h _T. The total displacement is determined by the formula (1). Shutters 9 provide overlap of the gap between the housing 1 and the partitions 7 and 8 with their lateral displacement.

The heat exchanger may contain several successive deflections. In this case, the role of the second tube plate is played by two stationary partitions with different cutouts that are closest to the place of transition from one deflection to another.

In FIG. 4 in the heat exchanger between the tube plates two deflections are formed, which are one wave, the angle of inclination of the axis of the pipes to the axis of the heat exchanger is determined by the formula

0≤β≤arctg 2.33h / e.

The angle of inclination of the axes of the pipes at the junction with the pipe board β _about equal to:

β ₀ = 0.

The tube plate is inclined to the axis of the heat exchanger at an angle ϕ;

90 ° ≥ϕ≥90 ° -β _max ;

- γ is the angle of inclination of the original axes of the pipes to the axis of the heat exchanger - to reduce the dimensions of the heat exchanger by minimizing the space for lateral displacement of the pipes.

Partitions 12 and 13 closest to the middle of the heat exchanger with the upper and lower cutouts are fixed motionless. The displacement of two pairs of partitions holding the pipes is carried out in two places at a distance closest to 1 / 4L and 3 / 4L from the tube plates, while the greatest displacement h _P should be at a distance of 1 / 4L and 3 / 4L from the tube plates.

With a preliminary displacement of the pipes, two bends are formed, consisting of a convex rising (first bending), convex decreasing, concave decreasing (second bending) and concave rising quarter-waves:

L = 4e _P.

During thermal deformation, 6 quarter-waves are formed with two different values of e _T , which are superimposed on four quarter-waves of length e _П. The holes in the partitions of the pipes 12 and 13 are made in an oval cross-section so that at the maximum displacement of the pipes they occupy a position if there was one partition holding the pipes 4, 5 and 6, located at a distance of 1/2 L from the tube plates. The holes in the partitions 12 and 13 can be round, in this case the length of the bent part and the maximum possible elongation are reduced, and there is also a non-synchronization of the bends of the pipes 4, 5 and 6.

In the manufacture of the heat exchanger, it is necessary to provide for the possibility of passing partitions through the joints, if the case is composite.

In FIG. 5 in the heat exchanger, with a preliminary bias between the tube sheets, one bend and one half-wave length e _{П are formed} . Partitions 12 and 13 closest to the middle of the heat exchanger with the upper and lower cutouts are fixed motionless.

With temperature deformation, 5 bends and 8 quarter-waves of length e _{T are formed} , which are two full waves, consisting of concave rising, convex rising, convex decreasing, concave decreasing waves each:

n _T = 8,

where n _T is the number of quarter-waves at a displacement during thermal deformation of pipes,

4e _T = e _P.

The greatest displacement of pipes during thermal deformation occurs at a distance of 1 / 4L and 3 / 4L from the tube plates.

When applying a preliminary displacement and displacement during thermal deformation of the pipes, three to five bends are formed depending on the ratio of the displacement values h _П and h _T.

Possible construction of a composite housing 14, consisting of cylindrical sectors with stationary in the middle of the partitions 12 and 13.

A housing design from a cylindrical shell with stationary partitions 12 and 13 in the middle part with previously displaced holes in the partitions is possible.

Claims (6)

1. The heat exchanger, consisting of a housing, tube sheets, partitions, pipes, characterized in that the pipes are installed with a preliminary deflection with the possibility of further deflection during temperature deformation. 2. The heat exchanger according to claim 1, characterized in that the preliminary deflection is carried out by displacing the holes for the pipes in the partitions. 3. The heat exchanger according to claim 1, characterized in that the preliminary deflection is carried out due to the displacement of the partitions by the movement mechanism. 4. The heat exchanger according to claim 1, characterized in that two partitions with cutouts in opposite directions in the middle part of the heat exchanger are fixedly displaced, the remaining partitions are installed with the possibility of further displacement in the direction of preliminary displacement. 5. The heat exchanger according to claim 1, characterized in that the preliminary deflection of the pipes is carried out in the process of assembling the heat exchanger from straight pipes, which are bent within the elastic deformation. 6. The heat exchanger according to claim 1, characterized in that the body is deflected, two partitions with cutouts in opposite directions in the middle part of the heat exchanger are fixedly mounted in the body, the remaining partitions are installed with the possibility of further displacement in the direction of preliminary deflection of the body.

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