JPH01150798A - Heat transfer pipe support structure - Google Patents

Abstract

PURPOSE:To improve heat exchange performance, by a method wherein a spacer is formed by a sheet, heat transfer pipes are supported in linear contact, and at least one of the upper stream side and the downstream side of the sheet is formed in a shape having low fluid resistance against fluid on the drum side. CONSTITUTION:In a heat pipe support material 15, spacers 15a are combined together in the shape of a lattice, and the surroundings thereof are secured to a ring 15b. An inner cylinder 16 is secured to a drum body 2 through inner cylinder support members 17, and heat transfer pipes 3 are extended through the inner cylinder 16 and supported by means of heat transfer pipe support members 15. Fluid flowing in a drum body 2 through an inlet nozzle 6 on the drum side flows, as shown by an arrow mark B, along the heat transfer pipes 3, and flows through an outlet nozzle 7 on the drum side to the outside. In this case, by forming the spacer 15a of the heat transfer pipe support member 15 in a shape, for example, a streamline shape, in which the upper stream side and the downstream side are decreased in fluid resistance against the flow of fluid on the drum side, a compact heat exchanger which extremely sharply reduces incurring of a pressure loss and increases an integrated performance index to a maximum value is provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat exchanger tube support structure, and particularly to a heat exchanger tube support that can reduce pressure loss and increase heat transfer efficiency in a multi-tubular heat exchanger. Regarding structure.

[Conventional technology]

In general, a shell-and-tube heat exchanger 1 has a large number of heat exchanger tubes 3 arranged in a cylindrical body 2, as shown in FIG. is supported by a notch baffle 5.

A body-side inlet nozzle 6 and a body-side outlet nozzle 7 are provided on the side surface of the body 2, and the fluid flowing in from the body-side inlet nozzle 6 flows as shown by arrow A in the figure, and flows through the body-side outlet nozzle 7. It is designed to leak out to the outside. Further, a pair of tube-side heads 8 and 9 are provided at both ends of the body 2, and the tube-side head 8 is provided with a tube-side inlet nozzle 10, and the tube-side head 8 is provided with a tube-side outlet nozzle 11, respectively. . The fluid flowing in from the tube-side inlet nozzle 1o flows inside the heat transfer tube 3, and then flows out to the outside via the tube-side outlet nozzle 11.

However, when the above-mentioned notch baffle 5 is provided in the body 2, the fluid is bent before and after the notch baffle 5, and flows perpendicularly to the heat exchanger tube 3. For this,
Although the heat transfer performance between the shell side and the tube side was good, there was a drawback that the pressure loss on the shell side was large.

Therefore, as disclosed in Japanese Unexamined Patent Publication No. 56-94195, instead of the notched baffle, a large number of ronds with a circular cross section are provided in the direction across the heat exchanger tube, and the heat exchanger tube is supported by these ronds. A shell-and-tube heat exchanger designed to reduce pressure loss on the shell side is known.

[Problem that the invention seeks to solve]

If the above-mentioned Rondo is used, the shell side fluid becomes a completely parallel flow along the heat transfer tube, so it is possible to reduce the shell side pressure loss, but on the other hand, there is no turbulence in the shell side fluid, and the transfer A new problem occurred in that the thermal boundary M around the heat tube became thicker and the heat transfer performance deteriorated. Moreover, since the rod cross section is circular, the pressure loss on the shell side has not been sufficiently reduced.

An object of the present invention is to provide a heat exchanger tube support structure that significantly reduces shell-side pressure loss without reducing heat transfer performance and improves overall heat exchange performance.

[Means for solving problems]

In order to achieve the above object, the heat exchanger tube support structure of the present invention installs a plurality of heat exchanger tube supports in which rod-shaped spacers are assembled in a lattice shape in a cylindrical body perpendicular to the axis, In the heat exchanger tube support structure that supports the heat exchanger tubes by individually inserting the heat exchanger tubes into each lattice of the heat exchanger tube support material, the spacer is formed of a thin plate to support the heat exchanger tubes in line contact. At least one side of the upper fluid side and the downstream side of the thin plate relative to the body side fluid,
It is characterized by being formed into a shape with low flow resistance.

[Effect]

In order to further improve the performance of the shell side compared to the conventional multi-tube heat exchanger, the heat exchange method should be a counter-flow type, in which the shell side fluid flows in parallel along the heat exchanger tubes. In order for the shell side fluid to flow parallel to the heat exchanger tubes, a certain heat exchanger tube support material is installed instead of the conventional notched baffle, and the shell side fluid flows parallel to the heat exchanger tubes between the heat exchanger tube supports and the heat exchanger tubes. Make it flow.

Considering this, when calculating the shell side heat transfer coefficient hs, it is possible to use the equation (1) below for estimating the inside of a smooth circular pipe, and use the hydraulic diameter de of the shell side instead of the pipe inner diameter di as the representative diameter. can.

a However, Ks: body side fluid thermal conductivity (W/mK) Cn: heat transfer performance coefficient (-) Prs: body side fluid plan l-function (-) m, n: constant (-).

Here, by simply increasing the shell side flow velocity Vs, in other words, the shell side Reynolds number Res, the apparent (operational) heat transfer performance h
Improving s is not considered to be a very effective means. Therefore, in order to evaluate the overall performance of the shell side, the heat transfer coefficient hs
If we focus on the original performance improvement method expressed as the ratio of the loss coefficient fs and the loss coefficient fs, there should be an optimal shape for the structure of the heat exchanger tube support material.

In other words, if a heat exchanger tube support material having a certain shape is installed in the shell side flow, the local flow velocity in this part will increase, and moreover, there will be an obstacle that will disturb the downstream flow.

Therefore, with the above structure of the present invention, by installing the heat transfer tube support members at certain intervals on the shell side, the shell side fluid flows almost parallel to the tube side fluid, and the pressure loss of the shell side fluid is reduced. . In addition, by installing this heat exchanger tube support material, turbulence is particularly promoted in the downstream part of the fluid on the shell side, and the flow velocity on the shell side locally increases, compared to the case without the heat exchanger tube support material. Heat transfer coefficient improves performance by 20-50%.

Furthermore, since the shell-side fluid continues to flow in parallel even if the heat exchanger tube support material is inserted, this is advantageous in terms of fluid-coupled vibrations occurring in the heat exchanger tubes.

〔Example〕 An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1(a), the heat exchanger tube support material 15 according to the present invention has bar-shaped spacers 15a combined in a lattice shape or an elliptical crate shape, and the periphery thereof is fixed to a ring 15b. In order to actually manufacture such a heat exchanger tube support material 15, each spacer 15a is cut into grooves, fitted into each other, and then welded. And this heat exchanger tube support material 1
A plurality of 5 are installed at certain intervals in the body side flow path.

By the way, the feature of the present invention is the shape of the cross section of the spacer 15a (there are various types of shapes as shown in the same figure (b).
S is the case without the heat exchanger tube support material 15, and SD is the standard type spacer 15a. Below, the first symbol R represents a semi-cylindrical shape, E represents a blunt edge shape, F represents a streamline shape, and HP represents a sharp edge shape, and the second symbol U represents these shapes installed on the upstream side of the flow. In this case, B indicates the case where the device is installed on both the upstream and downstream sides, and D indicates the case where the device is installed on the downstream side. Note that CD is the case of the cylindrical rod shown in the conventional example.

Next, FIG. 2 shows an example in which the heat exchanger tube support material 15 of this embodiment is actually applied to a shell-and-tube heat exchanger. Here, the same parts as in the prior art are denoted by the same reference numerals. In the figure, an inner cylinder 16 is disposed within the body 2, and the inner cylinder 16 is fixed to the body 2 via an inner cylinder support member 17. Further, the heat exchanger tube 3 is provided so as to pass through the interior of the inner cylinder 16, and several places of the heat exchanger tube are supported by the heat transfer support member 15 shown in FIG. The fluid flowing into the body 2 from the body side inlet nozzle flows along the heat transfer tube 3 as shown by arrow B, and flows out from the body side outlet nozzle. The rest of the configuration is the same as the conventional one shown in FIG. 9, so the explanation will be omitted here.

Here, FIG. 3 shows changes in the local heat transfer coefficient hdx and static pressure Px of the shell-side fluid along the flow when the heat exchanger tube support material 15 is installed. When the heat exchanger tube support material 15 is arranged between the three groups of heat exchanger tubes, the local flow velocity in this part increases, stirring occurs upstream and downstream, especially on the downstream side, and heat from the surface of the heat exchanger tubes 3 increases. The transmissibility hdx is improved. On the other hand, the static pressure distribution along these lines causes a sudden pressure drop ΔPs due to the installation of the heat exchanger tube support material 15, and the value of the pressure loss ΔPs due to the installation of the heat exchanger tube support material 15 is the friction loss ΔPf on the surface of the heat exchanger tube. It is quite large compared to .

Figure 3 shows a conceptual diagram of the local heat transfer coefficient distribution and static pressure distribution, and from the same figure, it can be seen that when the heat exchanger tube support material 15 is present, heat transfer is promoted compared to the case without the heat exchanger tube support material 15. Material 15
It can be clearly seen that the pressure loss caused by the spacer 15a is large.

Therefore, in order to verify the above conceptual model, a simulation test was conducted using air as the fluid, and the results are shown in FIG. Figure (a) shows the local heat transfer coefficient distribution, and Figure (b) shows the static pressure distribution.

In this case, the conditions are as follows: protrusion ratio ε = 0.5°, clearance ratio between heat transfer surface and spacer α = 0.25, spacer length ratio (spacer length/equivalent diameter) β = 1.56°. The turbulent flow range (10'<Re), the Reynolds coefficient Re of the shell side fluid, is 2.7×10', and the Prandtl number P r of the shell side fluid is 0.72. Also, as a parameter,
The standard spacer (SD) in Fig. 1(b), the semi-cylindrical spacer (RU) on the upstream side, the semi-cylindrical spacer (RB) on the upstream and downstream sides, the semi-cylindrical spacer (RD) on the downstream side, and the conventional example Column spacer (rondo baffle type)
(CD) was used. In the experiment, in order to establish similarity between the temperature field and the velocity field, a sufficient temperature run-up section was taken, and the region in which the heat transfer and pressure drop effects due to spacer installation were investigated was a region of uniformly developed flow.

Looking at the local heat transfer coefficient distribution in Figure 4, the installation of the spacer causes a speed-increasing effect within the spacer region and further heat transfer promotion due to turbulence on the downstream side of the spacer, resulting in a sudden increase in heat transfer compared to the case without a spacer. An increase in heat transfer coefficient has been obtained. Considering each type of spacer, CD, SD,
R.U., R.B.

Performance decreases in RD order. However, when comparing the average heat transfer coefficients, the difference between them is not very large. On the other hand, when looking at the static pressure distribution shown in FIG. 6(b), a rapid pressure drop occurs between the upstream side and the downstream side of the spacer. This is because the spacer is installed in the middle of the flow path, which causes the flow to suddenly expand and contract. in this case,
Comparing the size of spacer loss ΔPs, CD, RD,
R.U.

The pressure loss ΔPs becomes smaller in the order of RB. This result shows that when the upstream side of the spacer has a smooth shape, the pressure loss is significantly reduced.

The above data are graphs showing local changes along the flow direction. Therefore, using these data, we defined the average and practical heat transfer and pressure drop characteristics below.

As a heat transfer characteristic, the average heat transfer coefficient hdm was determined from the following equation (2) using the data of the local heat transfer coefficient hdx obtained above.

However, L e (=XIXs) is the heat transfer improvement range (m).

Further, as a pressure loss characteristic, the equivalent friction loss coefficient fe for the entire pressure loss APL between one pitch including the spacer loss ΔPs and the pipe friction loss ΔPi was determined using the following equation (3).

ΔPt, =ΔPs+ΔPf Plotting the values obtained from equations (2) and (3) means:
When hdm is expressed dimensionless according to the general definition,
It was calculated based on the fact that hdm and N u d m are in a proportional relationship.

Next, heat transfer and pressure loss characteristics will be explained using FIG. 5.

First, looking at the heat transfer characteristics shown in FIG.
It can be seen that the heat transfer performance can be improved approximately twice as much as that obtained from the following equation (4) when the Boelter equation is applied outside the tube.

Nus=0.023ResO・8Prso, 4-(4
) vs evs Re=-.

Here, since the equivalent diameter de is an equilateral triangle, the equivalent diameter de is as follows.

π dO Note that the symbols used in formulas (3) to (5) are as follows.

h s CJllii side heat transfer coefficient (W/mK) ks: Shell side fluid thermal conductivity (W/mK) vs: Shell side fluid dynamic viscosity coefficient (I/s) vs: Shell side fluid flow velocity (m/5) Pt : Pipe pitch (m) dO: Pipe outer diameter (m) Furthermore, heat transfer is promoted by about 30% compared to the case without a spacer. However, the difference in heat transfer coefficient between various spacer shapes is not significant. This is thought to be because the local flow velocity in this part increases by installing the spacer, and because the spacer is inserted as an obstacle into the flow, a turbulence promoting effect remains in the downstream part.

On the other hand, as for the pressure loss characteristics, as shown in FIG. 2(b), the pressure loss is about 4 to 8 times as much as the conventional pipe friction loss (Blasius equation) shown in equation (6).

fs”0.3164Re5-0-25-(6)
This is considered to be the sum of the friction loss along the outer surface of the spacer, the contraction and expansion loss of the body fluid due to the insertion of the spacer, and the mixing loss on the downstream side of the spacer.

From this result, as in FIG. 14, if the upstream side of the spacer is made smooth, the equivalent friction loss coefficient fe decreases significantly.

For example, if you use a standard spacer (S D
) has a thicker FE of approximately 7.5 times, and both have a semi-cylindrical spacer on the upstream side.

In RB, fe is approximately 4.5 times, and a sharp drop in loss coefficient can be seen.

FIG. 6 shows changes in heat transfer and pressure loss characteristics depending on the arrangement direction of the spacer shape with respect to the standard spacer (SD).

Figure (a) shows the change in average heat transfer coefficient of various spacers with respect to the standard spacer (SD).
d m *, and (b) of the same figure shows t! Semi-spacer S
D) shows the change in the equivalent Ila friction loss coefficient of various spacers f e / f e *. In both cases, the * mark may be a standard spacer. Further, the range of Reynolds number Re is 1.80 x 10'<Re <4.60 x 10' in the case of a highly turbulent flow.

First, looking at the change in the average heat transfer coefficient in Fig. 6(a), when using the standard spacer (SD) as a reference, the value is approximately 90% regardless of the spacer shape and arrangement direction. A decrease in heat transfer coefficient of about 10% is observed. However, the same figure (
Looking at the change in the uniform friction loss coefficient in b), the basic i%I' value f e/f e = 1.
0, approximately 45% if the upstream side is a semi-cylindrical spacer.
, approximately 40% if the upstream and downstream sides are semi-cylindrical spacers.
When the downstream side is a semi-cylindrical spacer, the value is about 80%. From these results, if at least the upstream side is a semi-cylindrical spacer, the pressure loss can be reduced by about 55 to 60% compared to a standard spacer.

Next, FIG. 7 shows a schematic diagram of the flow around the spacer. As shown in this figure, the shape of the spacer is U.

We will divide it into three areas, P and D, and consider the role of each.

U on the upstream side of the spacer is important to function as a flow resistance reducing part, D on the downstream side of the spacer becomes a heat transfer promoting part to generate turbulence on the downstream side, and P between these is the original heat exchanger tube support part. becomes. Therefore, the spacer 15 shown in FIG.
Using sample a as a sample, a modified version of these with the downstream side slightly cut may also be considered.

Expanding the case of the semi-cylindrical spacer obtained above, the first
Comprehensive performance evaluation is performed for the various spacers shown in Figure (b).

First, in evaluating the overall performance of the shell side, the following equation is defined in consideration of the heat transfer coefficient hs and the loss coefficient fe of the shell side fluid.

It is.

Therefore, the changes in η for the overall performance evaluation index η of the standard spacer (SD) were determined using the various spacer shapes, arrangements, and directions shown in FIG. 1(b), and will be explained with reference to FIG. 8. Here, the larger the value of η/η* on the vertical axis, the greater the overall performance including heat transfer and pressure drop characteristics, and η
The size of /η represents the compactness of the heat exchanger. The results are summarized as follows.

1) In the case of streamlined spacers (FB) on both the upstream and downstream sides, a very significant reduction in pressure loss can be achieved, so a compact heat exchanger with the highest overall performance index can be obtained.

2) Semi-cylindrical shape only on the upstream side or on the upstream and downstream sides,
When using sharp etch, dull etch, or streamlined spacers, the spacer is approximately 70 to 130% smaller than standard spacers (SD).
This will improve the overall performance of the system. However, since there is no significant difference between the case of only the upstream side and the case of both the upstream and downstream sides, the case of only the upstream side is sufficient from the viewpoint of manufacturing cost 1~. Note that among these, the spacer shape with the highest overall performance is preferably a sharp etch shape such as HPU or FU, or a streamlined shape.

3) If a semi-cylindrical, streamlined, sharp or blunt etched spacer is used only on the downstream side, it will not be possible to achieve a significant pressure loss reduction, and the pressure loss will be approximately 10 to 5
Only a 0% overall performance improvement can be achieved.

4) In the case of the conventional cylindrical bar-shaped spacer (CD), the overall performance is better than the case of only the downstream side, but compared to the case of only the upstream side or both the upstream and downstream sides, the overall performance is the worst. It can be seen that the spacer shape is better.

〔Effect of the invention〕

As explained above, according to the present invention, the cross-sectional shape of the spacer of the heat exchanger tube support material is formed to have a shape with small flow resistance on at least one of the upstream side and the downstream side with respect to the flow of the body side fluid. It is possible to reduce the pressure loss of the shell side fluid before and after the pipe support material, thereby increasing the flow velocity on the shell side and promoting turbulence.The overall performance of the shell side can be evaluated by the ratio of the shell side heat transfer coefficient and pressure loss. By doing so, heat transfer can be promoted in the original sense. Moreover, if the overall performance of the circular side improves as shown in 2 below, since the overall performance of the pipe side using smooth tubes is originally high, the overall heat transfer coefficient of the heat exchanger as a whole will increase, resulting in high performance and Miniaturization is achieved.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of a heat exchanger tube support material according to the present invention, FIG. 1(b) is a cross-sectional view of a spacer of the heat exchanger tube support material, and FIG.
Figure (a) is a longitudinal sectional view when the present invention is applied to a shell-and-tube heat exchanger, Figure 2 (b) is a sectional view taken along the line ■-■ in Figure (a), and Figure 3 is An explanatory diagram of the local heat transfer coefficient and static pressure distribution with respect to the position along the fluid flow direction on the shell side, FIG. 4 is a graph showing the behavior of the local heat transfer coefficient and static pressure distribution according to the present invention,
Fig. 5 is a graph showing the behavior of heat transfer/pressure drop characteristics according to the present invention, Fig. 6 is a graph showing changes in heat transfer/pressure drop characteristics with respect to the standard shape with respect to the installation direction of the heat transfer tube support material, and Fig. 7 is a graph showing the behavior of heat transfer/pressure drop characteristics according to the present invention. A schematic diagram of the flow around the heat tube support material, FIG. 8 is a graph of comprehensive property evaluation for the structure of the heat transfer tube support material, and FIG. 9 is a vertical cross-sectional view of a conventional multi-tube heat exchanger. 1...Multi-tube heat exchanger, 2...Body, 3...Heat transfer tube, 4...Tube plate, 6...Body side nozzle, 7...Body side outlet nozzle, 8.9 ...Tube side head, 10...Tube side inlet nozzle, 11...Tube side outlet nozzle, 15...Heat exchange tube support material, 15a...Spacer, 15b...Link, 1
6... Inner cylinder, 17... Inner cylinder support member.

Claims (1)

[Claims] 1. A plurality of heat exchanger tube supports in which bar-shaped spacers are assembled in a lattice shape are installed in a cylindrical body perpendicular to the axis, and heat exchanger tubes are individually placed in each lattice of the heat exchanger tube support members. In the heat exchanger tube support structure that supports the heat exchanger tube by inserting the spacer, the spacer is formed of a thin plate, supports the heat exchanger tube in line contact, and provides an upper fluid and a downstream side for the body side fluid of the thin plate. A heat exchanger tube support structure characterized in that at least one side thereof is formed into a shape with low flow resistance.