JPH061156B2 - Heat exchanger - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger, and more particularly to a shell-and-tube type shell-side fluid passage that changes the flow direction from the axial direction of the shell to the radial direction of the shell. With respect to the heat exchanger.

[Conventional technology]

The symmetrical heat exchanger of the present invention is a heat exchanger used in a scientific plant such as a styrene monomer reactor.
The structure of this styrene monomer reactor will be described with reference to FIG. Combustion gas flows into the shell 2 from the cylindrical inlet pipe 1 as the high temperature side fluid. Inside the shell 2, the combustion gas is redirected by the baffle plate 3 from the axial direction of the shell 2 to the radial direction of the shell 2. A process gas containing ethylbenzene as a main component flows as a fluid on the low temperature side in the plurality of heat transfer tubes 5 packed with the catalyst 4. The large number of heat transfer tubes 5 are arranged in the shell 2 in the axial direction thereof. The combustion gas radially spreads from the center of the shell 2 to the outside between the heat transfer tube groups,
Flows through the gap 6 formed between the baffle plate 3 and the baffle plate 3 to the lower side, flows again between the heat transfer tube groups from the outside toward the shell center, and flows into the outlet pipe 7 provided in the lower portion of the shell 2. Then, it is guided to the outside of the shell 3.

This heat exchanger produces styrene monomer in the heat transfer tube 5 by a dehydrogenation reaction which is an endothermic reaction of ethylbenzene. Therefore, improving the heat exchange efficiency between the combustion gas and the process gas leads to improving the production efficiency of the styrene monomer. In order to improve the heat exchange efficiency, it is necessary to make the flow velocity distribution of the combustion gas flowing between the heat transfer tube groups uniform and obtain a flow velocity distribution with less uneven flow.

As a method of reducing the uneven flow that occurs when the direction of the fluid flow is suddenly changed, a method of installing some object in the flow path is known. The first of such methods
As a conventional example, as shown in FIG. 5, in a T-shaped branch pipe in which the main flow direction changes, a streamlined guide vane is formed in a branch pipe extending in both directions from a portion forming an angle intersecting at right angles with the T-shaped branch portion. Some are provided (Japanese Patent Laid-Open No. 58-39993).
Issue).

As a second conventional example, a plurality of heat transfer tubes surrounding an introduction tube of an object that exchanges heat with another fluid outside the heat transfer tube are supported by a tube plate with both ends opened to respective plenums. In the plenum part on the end side of the introduction pipe, the fluid introduced into the plenum reverses in the heat transfer pipe and flows out from another plenum. There is one (Japanese Patent Publication No. 52-165)
No. 80).

[Problems to be solved by the invention]

In the conventional heat exchanger shown in FIG. 7, when the combustion gas flows from the cylindrical pipe to the radial portion of the shell 2, the flow direction is changed at right angles, so that the heat transfer tube group region of the shell side fluid passage is formed. Uneven flow occurs near the inlet, reducing heat exchange efficiency.
FIG. 8 shows the flow velocity distribution of the combustion gas in the heat exchanger, and FIG. 9 shows the detailed flow velocity distribution of the fuel gas in the heat transfer tube group region above the baffle plate 3. As can be seen from these two figures, a vortex is generated in the portion of the shell 2 where the flow direction changes, and as a result, a large drift is generated at the heat transfer tube group region inlet of the shell side fluid passage.

In order to prevent such a drift, it is possible to apply the structure of the first conventional example to the heat exchanger of FIG. However, as shown in FIG. 10, the first conventional example is intended to prevent the separation of the boundary layer at an angle that intersects the T-shaped branch at a right angle, but in order to maintain the rectification effect regardless of the magnitude of the flow rate. In this case, it is necessary to change the shape depending on the flow rate. In addition, when applied to an existing heat exchanger, it is difficult to install the guide vanes without disassembling the shell portion.

Further, application of the second conventional example is also conceivable. But the second
When the structure in the lower plenum of the conventional example is applied to the heat exchanger of FIG. 7, as shown in FIG. 11, a ring is formed concentrically with the inlet pipe 1 on the upstream side of the heat transfer tube group region in the fluid passage. The structure has a porous plate 12 in the shape of a circle. The ring-shaped porous plate 12 is a cylinder. In such a second conventional example, since a resistance is installed in the shell side fluid passage, pressure loss increases, and another power source such as a combustion gas pump or blower may be required. .

An object of the present invention is to provide a heat exchanger capable of preventing uneven flow of fluid at the inlet of the heat transfer tube group area and uniformly distributing the flow rate of the fluid to the heat transfer tube group area with a low pressure loss.

[Means for Solving the Problems] The above object is to arrange a shell, a plurality of heat transfer tubes provided in the shell in the axial direction and through which a first fluid flows, and the plurality of heat transfer tubes. And a fluid passage in the shell for guiding a second fluid that exchanges heat with the first fluid by changing a flow direction from an axial direction of the shell to a direction intersecting with the plurality of heat transfer tubes. In the heat exchanger having
This can be achieved by arranging a means for diverting the second fluid and merging the diverted second fluid on the upstream side of the heat transfer tube group region in a portion of the fluid passage where the flow direction changes.

[Operation] In the present invention, in the portion where the flow direction changes from the axial direction of the shell in the fluid passage to the direction intersecting with the plurality of heat transfer tubes,
Since the means for diverting the second fluid is arranged, the rectifying action of the means prevents uneven distribution of the second fluid in the fluid passage on the downstream side of the portion where the flow direction changes, and the heat transfer tube group region with low pressure loss. The flow rate can be evenly distributed. Further, since the means for merging the second fluid is arranged on the upstream side of the heat transfer tube group area, the second fluid can be further mixed by this merging, and the flow rate distribution to the heat transfer tube group area can be further uniformized.

〔Example〕

A preferred embodiment of the present invention will be described by taking a styrene monomer reactor used in a chemical plant as an example. As shown in FIG. 1, the heat exchanger 10 of the present embodiment has a shell 2, a baffle plate 3, a heat transfer tube 5 and a ring-shaped distribution plate 8. An inlet pipe 1 and an outlet pipe 7 are provided at an upper portion and a lower portion at the axial center of the shell 2. The upper tube sheet 9A is provided in the shell 2 and attached to the inlet pipe 1 so as to surround the inlet pipe 1. The inside surrounded by the inlet pipe 1, the shell 2 and the upper tube sheet 9A is the upper plenum 13. The lower tube sheet 9B is provided in the shell 2 and attached to the outlet pipe 7 so as to surround the outlet pipe 7. A lower plenum 14 is formed inside the shell 2, the outlet pipe 7 and the lower tube sheet 9B. Both ends of the heat transfer tube 5 have an upper tube sheet 9
A and the lower tube sheet 9B are attached respectively. The baffle plate 3 is installed so as to intersect the heat transfer tube 5 at the central portion in the axial direction of the heat transfer tube 5. The heat transfer tube 5 penetrates the baffle plate 3. A large number of heat transfer tubes 5 are arranged inside the shell 2 in the peripheral portion of the shell 2 to form an annular heat transfer tube group region. Heat transfer tube 5, upper plenum 13 and lower plenum 1
The inside of 4 is filled with the catalyst 4. The perforated plate 15B provided in the lower plenum 14 prevents the catalyst 4 from falling. A perforated plate 15A is installed near the upper surface of the catalyst layer in the upper plenum 13 to prevent the catalyst 4 from being raised by the fluid.

Inlet piping 1, passage 16A formed between baffle plate 3 and upper tube sheet 9A, passage 16B formed between shell 2 and baffle plate 3, and between baffle plate 3 and lower tube sheet 9B The passage 16C formed and the combustion gas passage 16 formed by the outlet pipe 7 are formed in the shell 2. The passages 16A and 16C are spaces formed between the heat transfer tubes 5 in the heat transfer tube group region. The circular ring-shaped plate 8 is arranged in the bent portion 16D whose flow direction changes from the inlet pipe 1 extending in the axial direction of the shell 2 of the combustion gas passage 16 to the passage 16A extending in the radial direction of the shell 2. The ring-shaped plate 8 is located at the center of the passage 16A in the vertical direction,
It is installed on a support 17 attached to the baffle plate 3. The ring-shaped plate 8 has an opening 19 in the center, is arranged concentrically with the annular heat transfer tube group region, and is arranged so as to be perpendicular to the axial center of the shell 2. An annular gap 18 is formed between the outer circumference of the ring-shaped plate 8 and each heat transfer tube 5 located at the innermost circumference of the heat transfer tube group region.

The process gas containing ethylbenzene as a main component is introduced into the inlet 2
It flows from 0A into the upper plenum 13, passes through the heat transfer tube 5 and the lower plenum 14, and flows out from the outlet 20B.
The process gas contacts the catalyst 4 while passing through the upper plenum 13, the heat transfer tubes 5 and the lower plenum 14.

The high-temperature combustion gas is introduced into the shell 2 from the inlet pipe 1, passes through the bent portion 16, the passages 16A, 16B and 16C, and flows out of the shell 2 from the outlet pipe 7. The combustion gas heats the process gas flowing in the heat transfer tube 5 while passing through the passages 16A and 16C.

The flow of combustion gas in the bent portion 16D will be described in detail. The flow direction of a part of the combustion gas flowing from the inlet pipe 1 is changed in the radial direction of the shell 2 by the ring-shaped plate 8 and flows toward the passage 16A along the upper surface of the ring-shaped plate 8. After passing through the opening 19 of the ring-shaped plate 8, the remaining combustion gas is redirected in the radial direction of the shell 2 by the baffle plate 3 and flows under the ring-shaped plate 8 toward the passage 16. The distribution of the flow rate of the combustion gas above and below the ring-shaped plate 8 depends on the opening ratio, which is the ratio of the area of the opening 19 of the ring-shaped plate 8 to the cross-sectional area of the inlet pipe 1. A part of the combustion gas divided up and down by the ring-shaped plate 8 is merged again in the annular gap 18 and the divided combustion gas is mixed. That is, the flow rate of the combustion gas flowing in the inlet pipe 1 is distributed above and below the ring-shaped plate 8 as described above, but when the opening ratio deviates from the optimum due to the change in the flow rate of the combustion gas, the ring-shaped plate 8 The flow rate ratio above and below is deviated from 1. However, in such a case, since the flow of the upper and lower combustion gases is mixed in the annular gap 18 by the pressure difference caused by the difference in the distribution of the combustion gas flow above and below the ring-shaped plate 8, the distribution of the upper and lower flow rates of the combustion gas is distributed. The difference becomes smaller and the rectification is promoted.

The flow in the combustion gas passage 16 in this example was simulated using a three-dimensional heat-fluid analysis program. The simulation will be described with reference to FIGS. 2, 3, and 4. FIG. 2 shows the shape parameters of the combustion gas passage 16 and the ring-shaped plate 8 which are the objects of the simulation. In this simulation, the opening ratio, which is the ratio of the opening area Ai of the disc to the cross-sectional area Ap of the cylindrical pipe, and the outer diameter D of the disc.
Analysis was performed using the ratio of o and the inner diameter Dt of the tube group region as a parameter. FIG. 3 shows a bird's-eye view of the coordinate grid of the combustion gas passage 16 used in the numerical analysis. The effect of the heat transfer tube group on the flow in the heat transfer tube group region was treated as the flow resistance to the flow. In FIGS. 4 and 5, Ai / Ap = 0.8,
The flow velocity distribution when Do / Dt = 0.9 and the average Reynolds number in the cylindrical inlet pipe 1 = 10 ⁶ is shown. Fourth
By comparing FIG. 8 with FIG. 8 and FIG. 5 with FIG. 9, by providing the ring-shaped plate 8 at the bent portion 16D, the drift at the inlet of the heat transfer tube group region is improved, and the maximum velocity (V _max ) It can be seen that the average velocity (V _av ) ratio decreases at all positions in the heat transfer tube group region. FIG. 6 shows the relationship between the opening ratio of the ring-shaped plate 8 and the combustion gas flow rate ratio, with the horizontal axis as the r direction of the heat exchanger. W _up is the flow rate of the combustion gas flowing above the ring-shaped plate 8, and Wt is the total flow rate of the combustion gas. Here, the combustion gas flow rate ratio means the combustion gas flow rate (W _up ) flowing between the ring-shaped plate 8 and the upper tube sheet 9A and the total combustion gas flow rate (W
It is the ratio (W _up / Wt) of t). Therefore, the condition of the rectification ratio is that the combustion gas flow rate ratio becomes 0.5. The result in the case where the ring-shaped plate 8 is not shown in FIG. 6 shows the analysis result for the conventional example. From FIG. 6, Ai / Ap = 0.
It can be seen that the case of 8 has the largest rectification effect. Further, the pressure loss is 99% when Ai / Ap = 0.5, Ai / Ap when 100% without the ring-shaped plate 8.
= 0.6, 95%, Ai / Ap = 0.8, 88
It turned out to be%.

According to the present embodiment, by installing the ring-shaped plate 8, it is possible to reduce uneven flow at the inlet portion of the heat transfer tube group region, improve heat exchange efficiency, and reduce pressure loss. When applied to a new heat exchanger, only the ring-shaped plate 8 needs to be additionally installed without significantly changing the conventional structure. Further, in the existing heat exchanger, the ring-shaped plate 8 is divided and inserted from the inlet pipe 1 and then welded inside to manufacture the ring-shaped plate 8 and installed, and the shell 2 needs to be disassembled. There is no.

Another embodiment of the ring-shaped plate is shown in FIG. The ring-shaped plate 8A of the present embodiment has a circular shape and is provided with a large number of holes 21 in the outer peripheral portion. When the ring-shaped plate 8A is used instead of the ring-shaped plate 8 in the heat exchanger of FIG. 1, when the combustion gas flow rates above and below the ring-shaped plate 8A become unbalanced near the outer peripheral portion, the combustion gas flow rate The combustion gas flows from the larger amount of gas to the smaller amount of gas through the holes 21, thereby mixing the upper and lower flows, which has the effect of further homogenizing the flow rate distribution shown in FIG. The same effect is
The ring-shaped plate 8B shown in the figure can also be obtained in a heat exchanger using the ring-shaped plate 8 instead. The ring-shaped plate 8B is provided with a gear-shaped notch 22 on the outer peripheral portion.

Another embodiment of the present invention is shown in FIG. The same components as those in the embodiment of FIG. 1 are designated by the same reference numerals. The heat exchanger 25 of the present embodiment is different from the heat exchanger 10 in that three circular ring-shaped plates 8 are arranged in the bent portion 16D of the combustion gas passage 16. The three ring-shaped plates 8 are provided with passages 16
They are arranged parallel to each other toward A and perpendicular to the axis of the shell 2. The outer diameter and the inner diameter of each ring-shaped plate 8 become larger as they go from the baffle plate 3 toward the inlet pipe 1. Further, the outer diameter of the ring-shaped plate 8 located below is larger than the inner diameter of the ring-shaped plate 8 adjacent immediately above it. Therefore, the ring-shaped plates 8 arranged adjacent to each other
Partially overlap each other in the axial direction of the shell 2. Although not shown, each ring-shaped plate 8 supports 17
Are fixed to the baffle plate 3 respectively. The outer diameter of the ring-shaped plate 8 arranged at the top is larger than the inner diameter of the inlet pipe 1. The opening area of the opening 19 located in the center is set to 1/4, 2/4, and 3/4 from the lowermost ring-shaped plate 8 to make the mutual intervals of the ring-shaped plates 8 equal. Each ring-shaped plate 8
Similar to the heat exchanger 10, an annular gap 18A is formed between the outer circumference of the heat transfer tube and the heat transfer tube located at the innermost circumference of the heat transfer tube group region. The width of each annular gap 18A in the radial direction is wider as it corresponds to the lower ring-shaped plate 8.

The heat exchanger 25 of this embodiment in which the ring-shaped plate 8 is arranged in the curved portion 16D can have the same function as the heat exchanger 10 and can obtain the same effect. Further, this embodiment is
Since the plurality of ring-shaped plates 8 are arranged in the bent portion 16D, a more uniform combustion gas velocity distribution can be obtained at the inlet of the heat transfer tube group region than that of the heat exchanger 10, and the most desirable rectification state can be obtained. .

A heat exchanger 26 according to another embodiment of the present invention is shown in FIG. In the heat exchanger 26 of this embodiment, two ring-shaped plates 8 are arranged in the bent portion 16D of the combustion gas passage 16. The two ring-shaped plates 8 have the same outer diameter and different inner diameters. The inner diameter of the upper ring-shaped plate 8 is larger than that of the lower ring-shaped plate 8. This embodiment produces the same effect as the heat exchanger 25.

A heat exchanger 27 which is another embodiment of the present invention is shown in FIG. The present heat exchanger 27 is obtained by replacing the three ring-shaped plates 8 of the heat exchanger 25 with three ring-shaped bodies 8D. Each ring-shaped body 8D includes a ring-shaped plate portion 8E and a cylindrical portion 8F. The ring-shaped plate portion 8E has an opening 1 at the center.
9A is a circular ring-shaped plate having 9A. The cylindrical portion 8F is
It is attached to the ring-shaped plate portion 8E so as to surround the opening 19A. The three ring-shaped bodies 8D include the combustion gas passage 16
The ring-shaped plate portion 8E is vertically arranged on the bent portion 16D (above the baffle plate 3). Each cylindrical portion 8F faces the axial direction of the shell 2. The three ring-shaped bodies 8D are
The intervals between the ring-shaped plate portions 8E adjacent to each other are equal. The outer diameters of the three ring-shaped bodies 8D are the same. However, the inner diameter of the opening 19A, that is, the cylindrical portion 8F
The inner diameter of the ring-shaped member 8D is larger toward the upper side.

Also in the heat exchanger 27 of this embodiment, similarly to each of the above-described embodiments, the bent portion 16D of the combustion gas passage 16 outside the heat transfer tube group region is perpendicular to the axial center of the shell 2, that is, the heat transfer tube 5
The ring-shaped plate portion 8E is arranged in a direction intersecting with (specifically, also perpendicular to the heat transfer tube 5), and the annular gap 18 is provided between the outer periphery of the ring-shaped plate portion 8E and the inner peripheral surface of the heat transfer tube group region. Since the heat exchanger 25 is formed, the same effect as the heat exchanger 25 can be obtained.
Furthermore, in this embodiment, since the ring-shaped body 8D has the cylindrical portion 8F, the flow rate distribution of the combustion gas to the heat transfer tube group region is made more uniform in the axial direction of the shell 2.

Another embodiment of the ring-shaped body is shown in FIG. The ring-shaped body 8G includes a ring-shaped plate portion 8E and a taper portion 8H having a loop shape. Both the inner diameter and the outer diameter of the tapered portion 8H increase from the upper side to the lower side. An opening is formed at the upper end of the tapered portion 8H. Even if the heat exchanger 27 uses a ring-shaped body 8G instead of the three ring-shaped bodies 8D, the same effect as that of the heat exchanger 27 can be obtained.

EFFECTS OF THE INVENTION According to the present invention, the fluid is split at the upstream side of the heat transfer tube group region and then merged to prevent uneven distribution of the fluid at the inlet of the heat transfer tube group region and to transfer the fluid with low pressure loss. The flow rate can be evenly distributed to the heat pipe group region.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a heat exchanger according to an embodiment of the present invention,
2 is an explanatory view showing the shape parameters of the ring-shaped plate of the heat exchanger of FIG. 1, FIG. 3 is a bird's eye view of the coordinate grid of the combustion gas passage of FIG. 1 used for three-dimensional analysis, and FIG. Explanatory drawing which shows the flow velocity vector of the fluid in the heat exchanger of the Example of FIG.
FIG. 5 is an explanatory view of the flow velocity vector in the heat transfer tube group region in the heat exchanger of FIG. 1, FIG. 6 is a characteristic diagram showing the relationship between the opening ratio and the flow rate ratio of the ring-shaped plate, and FIG. FIG. 8 is a longitudinal sectional view of the exchanger, FIG. 8 is an explanatory view showing a flow velocity vector of a fluid in the conventional heat exchanger shown in FIG. 7, and FIG. 9 is a heat transfer tube group region in the heat exchanger of FIG. FIG. 10 is an explanatory view showing a flow velocity vector, FIG. 10 is a configuration diagram showing a guide vane in a conventional T-shaped branch pipe, and FIG. 11 is obtained by applying a conventional ring-shaped porous plate to the heat exchanger of FIG. Longitudinal section of the heat exchanger, FIG. 12 and FIG.
FIG. 3 is a plan view of another embodiment of the ring-shaped plate of FIG.
4, 15 and 16 are longitudinal sectional views of a heat exchanger which is another embodiment of the present invention, and FIG. 17 is a longitudinal sectional view which is another embodiment of the ring-shaped body of FIG. is there. DESCRIPTION OF SYMBOLS 1 ... Inlet piping, 2 ... Shell, 3 ... Baffle plate, 4 ... Catalyst, 5 ... Heat transfer tube, 7 ... Exit piping, 8, 8A, 8B ... Ring plate, 8D ... Ring body, 9A ... Upper tube plate, 9B ... Lower tube sheet, 16 ... Combustion gas passage, 18 ... Annular gap.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Harada 1168 Moriyama-cho, Hitachi-shi, Ibaraki Hiritsu Seisakusho Co., Ltd.Energy Research Institute (72) Inventor Hirotomo 794 Higashi-Toyoi, Shimomatsu-shi, Yamaguchi Niitsu Seisakusho Co., Ltd. In the Kasado Plant (72) Inventor Motomasa Fuse 1168 Moriyama-cho, Hitachi, Hitachi, Ibaraki Energy Research Institute, Hitachi, Ltd. (72) Fumio Takahashi 1168 Moriyama-cho, Hitachi, Ibaraki Energy Research, Hitachi, Ltd. In-house (56) References JP 54-24353 (JP, A) JP 58-39993 (JP, A) JP 49-30181 (JP, B1) JP 52-16580 (JP, B2)

Claims (4)

[Claims] 1. A shell, a plurality of heat transfer tubes provided in the shell in an axial direction thereof through which a first fluid flows, and a heat transfer tube group region configured by arranging the plurality of heat transfer tubes, A heat exchanger having a fluid passage in the shell that guides a second fluid that exchanges heat with the first fluid by changing the flow direction from the axial direction of the shell to a direction intersecting with the plurality of heat transfer tubes; A heat exchanger characterized by arranging means for diverting the second fluid and merging the diverted second fluid on the upstream side of the heat transfer tube group region in a portion in which the flow direction changes. . 2. A shell, a plurality of heat transfer tubes arranged in a peripheral portion of the shell such that an axial center thereof is parallel to an axial center of the shell and in which a first fluid flows, and a central portion of the shell. A baffle plate which is disposed at a peripheral portion and through which the plurality of heat transfer tubes pass, and in which a flow direction is changed along the baffle plate in a central portion of the shell from an axial direction of the shell to a radial direction, and the first fluid and heat. In a heat exchanger having a fluid passage for guiding a second fluid to be exchanged to a gap between the plurality of heat transfer tubes, a plurality of the drift prevention means having a portion perpendicular to an axis of the shell at least on a downstream side is provided. A heat exchanger, wherein the heat exchanger is arranged at a portion of the fluid passage where the flow direction changes so as to form a gap between the heat exchanger tube and the inside of the heat exchanger tube group region. 3. The heat exchanger according to claim 2, wherein the uneven flow preventing means is a ring-shaped plate. 4. A plurality of the ring-shaped plates are arranged in parallel with each other in a portion where the flow direction changes, and the inner diameter of the ring-shaped plates increases as the gap between the outer periphery of the ring-shaped plates and the heat transfer tube group region increases. 4. The heat exchanger according to claim 3, wherein the adjacent ring-shaped plates are partially overlapped with each other in the axial direction of the shell.