JP2747662B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tubular cylindrical heat exchanger having a plurality of baffles directly involved in heat transfer in a shell, and more particularly, to a gap between the shell and the baffles. The present invention relates to a multi-tubular cylindrical heat exchanger in which leak flow is prevented for a long period of time.

[0002]

2. Description of the Related Art In a multi-tubular cylindrical heat exchanger usually used for industrial purposes, a baffle is installed in a body of a heat exchanger shown in FIG.
As shown in the figure, it is common to manufacture the outer diameter of the baffle 10 smaller than the inner diameter of the barrel 12.
There is a gap 14 between 2 and baffle 10. 16 is a tube. In the TEMA standard, standard dimensions for the difference between the inner diameter of the trunk and the outer diameter of the baffle are shown for each size of the inner diameter of the trunk (TEMA standard heat exchanger).

Further, Japanese Utility Model Laid-Open Publication No. Sho 60-105988 discloses that an elastic seal plate (a seal plate in which thin plates of stainless steel or the like are stacked) is provided in a gap between a body and a baffle, and a bolt is attached to the baffle. A multi-tube heat exchanger attached by fastening or the like is described.

[0004]

In the operation of the conventional heat exchanger shown in FIG. 5, the gap 1 between the shell 12 and the baffle 10
Since the flow component passing through 4 is in a direction substantially parallel to the tube and hardly comes into contact with the tube, the flow component becomes a leak flow (bypass flow) on heat transfer, which has an effect of obstructing heat transfer in the heat exchanger. Decreases overall heat transfer performance.
Furthermore, since such a leak flow component affects heat transfer in a complicated manner, when designing a heat exchanger, calculation accuracy for estimating the degree of influence of the leak flow component on heat transfer is important, In particular, in the case of large heat exchangers with a body diameter exceeding 2500 mm, the effect of this leak flow component on heat transfer increases dramatically, and the actual heat transfer performance is significantly lower than the calculation result and is ignored in operation. Insufficient heat transfer may occur.

[0005] Apart from the TEMA standard heat exchanger described above, for specific industrial applications, the baffle outer diameter is made slightly smaller than the body inner diameter, and these baffles are attached to the inside of the body, or the heat exchanger or baffle is welded. (1) In order to enable the baffle to be inserted into the inside of the body, it is necessary to finish the inside of the body to strict dimensional accuracy by machining, etc. It becomes an expensive heat exchanger. (2) Even when the baffle is directly welded to the inner surface of the body, the gap between the baffle and the body must be made sufficiently small in order to ensure welding quality, and thus has the same problem as (1). In particular, in the case of a large-sized heat exchanger, the tendency to be economically expensive becomes remarkable.

In the shell-and-tube heat exchanger disclosed in Japanese Utility Model Application Laid-Open No. Sho 60-105988, the seal plate is only in close contact with the inner surface of the body due to elasticity. Fluid leakage cannot be completely stopped. In addition, there are some places where the seal plate does not come into close contact with the inner surface of the body due to unevenness of the inner surface of the body or the like. In this case, leakage increases. The elastic seal plate structure described in Japanese Utility Model Laid-Open Publication No.
Basically, it is a method of providing a baffle in the longitudinal direction inside the trunk and sealing a gap between the longitudinal baffle and the trunk of the heat exchanger (the trunk classification F according to TEMA) having two passes on the trunk side. (lamiflex) seal.
However, such a seal plate structure in which thin plates such as stainless steel are stacked,
It is known that the loss of elasticity relatively early causes a significant reduction in the sealing effect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a multi-tube cylindrical heat exchanger having a plurality of baffles directly involved in heat transfer in a body thereof, particularly a large heat exchanger. In the exchanger, easy to manufacture and economically inexpensive,
In order to prevent the leak flow through the gap between the body and the baffle for a long period of time, and to solve the problem of a significant heat transfer shortage due to a decrease in heat transfer performance due to the influence of the leak flow and / or a deterioration in calculation accuracy. To provide an improved heat exchanger.

[0008]

In order to achieve the above object, a heat exchanger according to the present invention is provided in a multi-tube cylindrical heat exchanger having a plurality of baffles in a body thereof, the heat exchanger being provided outside the baffles. The diameter is smaller than the inside diameter, and the baffle is cut off on one side.
And have a segmental type, gaps <br/> infarction Ide, welded to one end of the barrel inner surface of the seal plate against the outer periphery of the baffle so as to prevent fluid leakage baffle outer periphery attachment between the cylinder and the baffle And the other end of the seal plate
The seal is welded to the outer periphery of the baffle . That is, one end of the seal plate is attached to the inner surface of the body by welding, and a baffle plate is provided so as to overlap and contact the seal plate. The other end of the seal plate is sealed welded to the outer peripheral portion of the baffle
You . This makes it possible to completely prevent fluid leakage at the outer peripheral portion of the baffle. The opening of the baffle (window portion) is small, and when mounting the seal plate over a wide range, the case of providing a sealing strip into the cylinder, mounting the seal plate is divided into a suitable number in the circumferential direction of the cylinder inner surface Is preferred. In this way, the divided pieces of the seal plate can be easily brought into the body, and can be easily fitted to the inner surface of the body for welding, so that good welding quality can be obtained. Also, if there is a sealing strip inside the torso,
In this case, as shown in FIG.
The sealing strip is attached
You.

FIG. 6 is a temperature curve in the heat exchanger showing an influence of a leak flow component flowing through the gap in the heat exchanger having a gap between the shell and the baffle. The basic equation in the heat transfer calculation of the heat exchanger is represented by the following equation. Q = UAΔt Here, Q: heat exchange amount between the shell side and the tube side U: overall heat transfer coefficient A: heat transfer area Δt: average temperature difference between the shell side fluid and the tube side fluid, and Δt is represented by the following equation. Is represented. Δt = k {(t _i −T ₀ ) − (t ₀ −T _i )} / l
_n (t _i −T ₀ ) / (t _o −T _i ) where (t _i −T ₀ )> (t ₀ −T _i ), and k takes into account the structure of the heat exchanger. Coefficient (<1.
0).

In the above calculation of Δt, the temperature difference serving as the driving force for the main heat transfer is essentially the difference between the tube side fluid temperature and the body side main flow temperature. Therefore, unlike the case of FIG. 6, when there is no leak flow on the trunk side, or when there is a leak flow and it is sufficiently mixed with the main flow in the heat exchanger, T ₀ ≒ T ₁ , and according to the above equation, Calculating Δt does not cause a large error from the actual value. However, as shown in FIG. 6, when a leak flow component exists on the barrel side and hardly mixes with the main flow in the heat exchanger and mixes with the main flow for the first time after passing through the final baffle, the barrel side outlet temperature Calculating Δt using T ₀ gives a result as if the shell-side fluid temperature in the heat exchanger was indicated by a broken line. Therefore, the amount of heat exchanged is calculated based on Δt which is originally larger than the actual Δt and should be calculated using the outlet temperature T ₁ of the main flow.
In actual operation, there is a problem of insufficient heat transfer that cannot be ignored.
Normally, in the heat transfer calculation performed, the degree of mixing of the main flow and the leak flow is theoretically evaluated in the coefficient k of the Δt calculation, and the effect is incorporated in the calculation. , The overall calculation accuracy is reduced, and in particular, the degree of the influence of the leak flow component is greatly increased, so that the calculation accuracy is further reduced.

[0011]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples, and can be implemented with appropriate modifications. FIG. 1 shows a heat exchanger in the present embodiment, FIG. 2 shows an enlarged view of an example of a portion provided with a seal plate in a gap between the trunk and the baffle in FIG. 1, and FIG. 4 is an enlarged view of another example in which a seal plate is provided in the gap, and FIG. 4 is an enlarged view of a cross section taken along line AA in FIG.

10 is a baffle (baffle plate), 1
2 is a torso, 14 is a gap between the torso and the baffle, 16 is a tube, 18 is a front tubesheet, 20 is a rear tubesheet, 22 is a channel, and a front tubesheet 18
A large number of tubes (heat transfer tubes) 16 are arranged between the rear tube sheet 20 and the rear tube sheet 20 in the horizontal direction. 24 is a tie rod, 26 is a spacer covering the tie rod, 28 is a sealing strip, 30 is a fluid inlet nozzle, and 32 is a fluid outlet nozzle. FIG. 1 shows, as an example, a case in which a high-temperature fluid flows on the tube side and a low-temperature fluid flows in a countercurrent direction on the barrel side, and the baffle is a segmental type with one side notched, and the tube sheet is a fixed type. Shows the case.

The baffle 10 is constructed such that the outer diameter of the baffle is sufficiently smaller than the inner diameter of the barrel to allow easy insertion into the barrel 12 (it may be in accordance with the standard dimensions set forth in the TEMA standard or slightly smaller). A seal plate 34 is attached in contact with the baffle 10 so as to close the gap 14 between the baffle 12 and the baffle 10. The seal plate is manufactured using the same material as the body, so that when the heat exchanger is operated, There is no problem of stress generated due to the difference in thermal expansion between the body and the body.Specifically, as shown in Fig. 2, one end of the seal plate 34 is attached to the inner surface of the body 12 by welding. Therefore, a complete seal is provided between the seal plate 34 and the inner surface of the body 12. This welding is performed by, for example, making a groove on the portion of the seal plate that contacts the inner surface of the body. In addition, as shown in Fig. 3, if a portion where the baffle 10 and the seal plate 34 overlap with each other is further sealed and welded as shown in Fig. 3, the fluid at the outer peripheral portion of the baffle 10 is formed. Leakage is completely prevented 38 is a seal weld.

As shown in FIG. 4, when the sealing strip 28 is provided in the body, the sealing plate 34 is attached in order to facilitate the mounting of the sealing plate 34.
Is preferably divided into a plurality in the circumferential direction.

Next, an example of a manufacturing procedure will be described. After attaching the front tube sheet 18 (left side) to the body 12, the tie rods 24 are attached to the front tube sheet 18.
After that, the baffles 10 are inserted one by one into the body 12 one by one from the right side, and attached at a predetermined position. Each time the baffle 10 is attached, the seal plate 34 is attached so as to be in contact with the baffle 10. The rear tubesheet 20 (right side) is finally attached to the torso 12. The tube 16 is inserted into the body after both the tube sheets 18 and 20 are mounted on the body 12, but the baffle is mounted within a range that does not hinder the internal operation for mounting the baffle 10 and the seal plate 34. Some of the tubes may be inserted from the beginning for the guide. In a conventional heat exchanger, usually, the tube sheets 18, 20, the tie rod 24, and the baffle 10 are assembled outside the body,
Insert into the torso.

In the multi-tube heat exchanger described in Japanese Utility Model Application Laid-Open No. Sho 60-105988, the seal plate is attached to the baffle by bolting before the tube bundle is incorporated into the body due to the characteristics of the seal plate. In the example heat exchanger, due to structural characteristics, the seal plate 34 is welded in the cylinder for each baffle when the bundle is incorporated into the cylinder 12.

[0017]

As described above, the present invention has the following effects. (1) Since the gap between the body and the baffle is closed by the attachment of the seal plate, the leak flow component originally passing through this gap is eliminated or extremely reduced. For this reason, since the heat transfer performance is not reduced by the influence of the leak flow, the heat transfer area can be reduced, and the heat exchanger can be manufactured economically and at low cost. In addition, since the influence of the leak flow component is eliminated, especially in a large heat exchanger, the decrease in heat transfer calculation accuracy is greatly improved,
Accurate design can be performed. (2) The outer diameter of the baffle can be made sufficiently smaller than the inner diameter of the body to be about the same as the TEMA standard heat exchanger. Therefore, it is not necessary to finish the inner surface of the body to strict dimensional accuracy by machining, etc., and it is easy to install the inside of the body. And the cost of manufacturing the heat exchanger is economically low. (3) Since the seal plate is attached to the inner surface of the body by welding, the seal plate and the inner surface of the body are physically completely sealed , and the fluid leakage in the gap between the body and the baffle is completed.
Ru can be stopped in all. As long as the shape of the seal plate substantially conforms to the shape of the inner surface of the cylinder, any unevenness of the inner surface of the cylinder does not cause any problem for welding the seal plate. (4) Since the portions where the baffle and seal plate overlaps seal welding, it is possible to physically completely prevent fluid leakage baffle outer circumference. (5) In the seal plate structure described in Japanese Utility Model Application Laid-Open No. Sho 60-105988, the elasticity of the seal plate is lost relatively early after the start of operation due to aging and the sealing effect is greatly reduced. In this heat exchanger, the seal plate does not need to have elasticity.Therefore, a seal plate having a thickness sufficient to withstand the pressure difference between the fluids before and after the baffle is directly and firmly welded to the body, so that this is achieved. Such early deterioration of the sealing effect can be eliminated. (6) Divide the seal plate in the circumferential direction
When attaching, each piece of the divided seal plate
Can be easily brought into the fuselage and to the fuselage inner surface for welding.
Can be easily adjusted, and good welding quality can be obtained.
You.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the heat exchanger of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an example of a portion in which a seal plate is provided in a gap between a body and a baffle in FIG.

FIG. 3 is an enlarged sectional view showing another example of a portion in which a seal plate is provided in a gap between a body and a baffle in FIG. 1;

FIG. 4 is an enlarged sectional view taken along line AA in FIG.

FIG. 5 is a cross-sectional view illustrating a structure of a conventional heat exchanger in which a gap remains between a body and a baffle.

FIG. 6 is a temperature curve diagram in a heat exchanger showing an influence of a leak flow in a heat exchanger having a gap between a body and a baffle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Baffle 12 Body 14 Gap 16 Tube 18 Front tube sheet 20 Rear tube sheet 22 Channel 24 Tie rod 26 Spacer 28 Sealing strip 30 Fluid inlet nozzle 32 Fluid outlet nozzle 34 Seal plate 36 Welded part 38 Seal welded part

Claims (2)

(57) [Claims] 1. A multi-tube cylindrical heat exchanger having a plurality of baffles inside a body, wherein the outer diameter of the baffle is smaller than the inner diameter of the body, and the baffle is a segmental type with one side cut away.
And, Ide busy the gap between the cylinder and the baffle, the baffle periphery
If one end of the seal plate is welded to the inner surface of the body in contact with the outer periphery of the baffle to prevent fluid leakage
In both cases, seal the other end of the seal plate to the outer periphery of the baffle.
Welded heat exchanger . 2. When a sealing strip is provided in the body.
In both cases, the seal plate is divided and attached in the circumferential direction of the inner surface of the body , and the divided seal plate is penetrated and sealed.
The heat exchanger of claim 1, wherein the ring strip is attached.