JPS6036895A - Heat exchanger - Google Patents

Abstract

PURPOSE:To reduce the sticking of marine organism and facilitate their removal, by polishing to a mirror-like finish the surface of heat exchanging tube or plate with which a cooling fluid contacts. CONSTITUTION:A seamless tube can be finished by an electrolytic polishing, a chemical polishing procedure and the like. As for a welded tube, a buffing, or an electrolytic polishing, a chemical polishing procedure is applied on a longitudinally extending titanium plate or a titanium strip produced in a manufacturing step and then the plate or the strip is bent in its widthwise direction for joint by a butt welding. The welded tube cannot avoid the sticking of marine organism on the bead area of its welded portion, but can reduce the quantity of such sticking by polishing other areas to a mirror-like surface. The surface roughness of polished area should be approximately 0.15mum or less in terms of Ra system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger equipped with a heat exchange tube or a heat exchange plate, and particularly relates to heat transfer performance when titanium material is used as the heat exchange tube or heat exchange plate. This relates to technology for suppressing the decline in

Traditionally, aluminum, arsenic, and other silicones have been added to brass as heat exchange tubes or heat exchange plate materials for condensers and other heat exchangers in thermal power plants, chemical factories, ships, etc. Heat exchangers made of so-called special brass or cupronickel made of copper, nickel, and iron mainly use seawater or river-seawater as the cooling fluid, so depending on the quality of the seawater or river-seawater, corrosion may occur. It has been experienced that corrosion tends to occur, and deposits containing corrosion products adhere to the surface, causing problems such as deterioration of heat transfer performance.

In recent years, titanium materials with excellent seawater corrosion resistance have been evaluated. Its use as a heat exchange tube or G-type exchange plate is being considered.

However, in comparison with the above-mentioned special brass or copper alloy, such heat exchange tubes or heat exchange plates made of titanium materials tend to have creatures in seawater attached to their surfaces, and the adhesion of attached substances is strong. This has the inherent problem that it is difficult to remove. Moreover, once the surface of the titanium tube or titanium plate has deposits attached to it, it becomes easy for the deposits to re-attach after the deposits have been removed, increasing the rate of attachment and increasing the amount of deposits over time. It is. and,.

Such deposits on the inner surface of the heat exchange tube or the surface of the heat exchange plate deteriorate the heat transfer performance and increase the water head loss.

Therefore, when using titanium tubes as heat exchange tubes,
It is common practice to remove deposits by passing a sponge ball 2 to 3 l'1 m larger than the inner diameter of the pipe through the pipe together with cooling water during operation of the heat exchanger. requires almost continuous cleaning.

On the other hand, there are water jet cleaning methods, wire brush cleaning methods, and the like as cleaning methods that have stronger cleaning power than sponge ball cleaning, but both require the heat exchanger to be stopped. Furthermore, in the case of heat exchange plates, the mechanical cleaning method described above cannot be applied due to their structure. There are methods to sterilize seawater used as a cooling fluid by chlorinating it or raising the temperature of the seawater, but these methods have become difficult to implement in recent years due to environmental protection.

Therefore, the present inventors conducted various studies and investigations into the adhesion of marine organisms to titanium, and discovered that the surface properties of titanium are significantly related to the adhesion of marine organisms. Table 1 shows the samples used by the inventors in their research.1. In addition, both trials *'1 are 50m+nX100a
It is a plate-shaped sample of m×0.7 mm.

Sample A in Table 1 is annealed after rolling and is generally used as a welded pipe or plate. Sample B has a surface that has been somewhat roughened by vapor polishing. The surfaces of the sample, qc, and sample were polished to a mirror finish by separate cloth polishing or electrolytic polishing. The surface roughness was measured using Surfizer manufactured by Tokyo Seimitsu Co., Ltd. (needle tip radius: 2 μm, pressing force: 70 mg).
) 1, Ra (center line roughness)
, Ilmax (maximum height) are each JIS-B-0
This is based on the provisions of 601.

Then, the above sample was placed in a 700mm
The specimens were immersed in a 600mm x 1000mm water tank for 6 months, and the state of biofouling was investigated. The results are shown in Table 2. It can be seen that the amount of deposits is significantly smaller in sample 0.D compared to samples A and B. The measurements were conducted with Fujibbo removed.

Table 2 From the results in Tables 1 and 2 above, it is clear that the surface roughness of the titanium plate has a large effect on the adhesion of marine organisms and mud, and it is clear that the surface roughness of the titanium plate has a large effect on the adhesion of marine organisms and mud. It can be seen that the amount of deposits decreases as the temperature increases.

This is because the surface of titanium used as a conventional tube or plate has a depth of 0.2 to 2.5 μm at a pitch of 5 to 10 μm.
There is a μI11 indentation on the male side, and this indentation is said to play the role of an anchor when attached to marine organisms. In other words, the surface of titanium is covered with a stable oxide film, so even after being immersed in seawater for an extended period of time, the surface shape remains the same as before immersion, and titanium does not exhibit toxicity to living organisms. This is because the anchor effect of the four parts is maintained together.

Note that this dent is due to manufacturing defects such as rolls during the previous process of making the board.
It is thought that this is caused by various factors such as localized destruction of the oxide film, non-uniform formation, or non-uniform dissolution during acid cleaning, but in normal products, unevenness of this degree is avoided and the thickness is 1 m < . Moreover, it is not harmful in terms of quality.

On the other hand, if the titanium having the above-mentioned irregularities is subjected to cloth polishing, electrolytic polishing, chemical polishing, etc., until the surface roughness becomes about 0.01 to 0.1571 m in Ra, it becomes a mirror surface. , the recesses that serve as anchors, which serve as starting points for marine life, are significantly reduced.
It is thought that the adhesion of marine organisms, etc. will be reduced.

Here, the present invention has been completed based on the following knowledge, and its purpose is to reduce the amount of deposits on marine organisms and to reduce the amount of deposits on marine organisms. It is an object of the present invention to provide a heat exchanger equipped with a heat exchange tube or a heat exchange plate using a hard material that is easy to remove.

In order to achieve this object, the present invention uses a titanium material manufacturing method as a heat exchange tube or heat exchange plate, and cooling water such as seawater, river seawater, river, lake water, etc. is brought into contact with the surface of one side as a cooling fluid. In the heat exchanger to be used, the surface of the heat exchange tube or heat exchanger (opposite surface) with which the cooling fluid comes into contact was polished to a surface roughness of about 0.15 tt m or less in Ra.

If the heat exchange tube or heat exchange plate made of titanium material according to the present invention is used in a heat exchanger that uses seawater, river seawater, etc. as a cooling fluid, it will prevent marine organisms, mud, etc. from forming on the surface of the heat exchanger. This reduces adhesion, suppresses deterioration in heat transfer performance and increase in water head loss, and together with the original 7F+J water corrosion resistance, reliability as a heat exchange tube or heat exchange plate is greatly improved. That's what I do.

Moreover, because the surface is smoothly polished, the adhesion of marine organisms, etc. is weak, and the adhesion can be removed well even with the conventional sponge ball cleaning method, and it is difficult to re-clean after removing the adhesion. As a result, maintenance work for the heat exchanger becomes extremely easy.

Here, examples of titanium tubes to which the present invention can be applied include those conventionally provided as titanium tubes for heat exchangers, such as JIS-1 (-4631 Jun), and
As a titanium plate, JIS-〇-A (: n (+
', Last-/+Z %--P+, as a means of polishing the helical tube or titanium plate, split cloth polishing, electrolytic 01 polishing, chemical polishing, or any of these polishing methods are used. be able to. In other words, for seamless pipes formed by drawing, methods such as electrolytic polishing and chemical polishing can be used, and for welded pipes, the manufacturing process involves After subjecting the titanium plate or titanium strip to cloth polishing, electrolytic polishing, chemical polishing, or a combination of these polishing processes, curve the pieces in the width direction, butt them together, and then weld the butted parts. . In addition, 71 is added to the titanium tube after welding, and 'I
Polish the inner surface of the tube by performing rL depolishing, chemical polishing, etc.
Vff can also be applied. In addition, for titanium plates,
Any of the polishing means described in 1 above may be employed.

Here, in the case of a welded pipe, a bead is formed at the welded portion. Therefore, in order to make the inner surface of a welded pipe completely mirror-finished, it is necessary to first perform cutting to remove large irregularities on the inner surface of the tube, and then perform electrolytic polishing, chemical polishing, etc. Heat exchange tubes generally have a length of 1
~501TI- is a long thin tube with an inner diameter of 10 to 40 mm, so it is economically unrealistic to perform such troublesome processing. Therefore, for welded pipes,
It is assumed that the adhesion of marine organisms and the like in the bead area of the weld is unavoidable, and by mirror-finishing the other parts, the amount of adhesion can be reduced, thereby achieving the primary purpose of the present invention. Note that if the mirror surface area of the inner surface of the tube is too small, a sufficient effect of reducing the amount of deposits cannot be obtained, so it is desirable that the width of the welded portion is 20 mm or less in the circumferential direction of the tube.

The surface roughness of the thus polished inner surface of the titanium tube or titanium plate is required to be approximately 0.15 μm or less in terms of Ra. This is based on the previous research data Table 1
And as is clear from Table 2, the higher the degree of mirror polishing of the surface, that is, the lower the value in the Ra display, the more the amount of deposits decreases and the more effective the effect is obtained. A certain effect can be obtained with a thickness of 0.15 μm or less. Note that this mirror polishing does not necessarily need to be performed over the entire tube inner surface or plate surface, but as described above, if the mirror polished area is too small, a sufficient effect cannot be obtained.

When heat exchange tubes or heat exchange plates made of titanium materials such as those described above are used in a heat exchanger, it is highly effective to use seawater, river seawater, etc. as the cooling fluid that is circulated within or on the surface of the tubes. However, it is of course possible to use other cooling water such as river water or lake water. In addition, heat exchangers using titanium heat exchange tubes or Gj heat exchange plates are used not only for atomic coupler condensers that require high reliability, but also for other various types of heat exchangers. In addition, the cleaning methods used in maintenance work include not only the sponge ball cleaning method, but also various cleaning methods such as carborundum ball cleaning, brush cleaning, and cleaning. 4).

Next, in order to make the present invention more concrete,
Several embodiments of the present invention will be shown and explained, but it goes without saying that the present invention is not subject to any restrictions by these embodiments.

Example 1 Width 79.3 mm1, thickness 0.7 mm, length approximately 5 mm
A 0 m titanium strip was polished on only one side using a cloth polishing machine with separate rolls.

The polishing conditions were as follows: After repeating the polishing three times with open Xyzal Chofu (made of hemp) using oil-based Xyzal as the abrasive,
Furthermore, polishing was repeated four times with a cotton M4 cloth using a blue rod (chromium oxide) as a polishing ion. The titanium strip was fed at a speed of 800 marks/min while the Chofu was being rocked. After polishing, roll forming with the polished surface facing inside.
A titanium tube was manufactured by TIG welding. For comparison, a welded titanium tube manufactured from unpolished titanium strip, an aluminum brass tube manufactured by a drawing method, and a 10% cupronickel tube were prepared.

Next, clean seawater without chlorine treatment was passed through the above four types of pipes at a flow rate of 2 m/sec for 6 months from March to August, which corresponds to the breeding season of living organisms, and the water adhered to the inner surface of the pipes. The type of kimono and the state of adhesion were visually observed, and the amount of kimono, zgh, and strength (density A) were measured. The results are shown in Table 3.

Furthermore, in order to evaluate the adhesion of the attachment to the inner surface of the pipe, a sponge ball 2 towns larger than the inside diameter of the pipe was passed through the pipe five times at a flow rate of 2 m/sec. ) The sound volume (mg/cnl) was measured. 4th result
Shown in the table. Note that the numbers in parentheses indicate the removal rate (%) of deposits corresponding to the amount of deposits of cleaning +) iJ.

The titanium tube was passed through a sponge ball 300 times, and after it was thought that all the deposits had been removed, the titanium tube was passed through a sponge ball twice a week for seven months from October to April of the following year. (5 pieces/time), 131 times of FFRJ water under the same conditions as the two tests was applied, and the amount of deposits and staining coefficient after the test were determined. The results are shown in Table @5.

It is clear from the results of Tables 3 to 5 that the polished titanium tube according to the present invention has the following effects: Although it is slightly inferior to aluminum brass tubes and Gypronickel tubes, it shows significantly superior results compared to J6 and 11 FIff5 titanium tubes (Table 3). In addition, even when removing such deposits with sponge cleaning, approximately 55% of the unpolished titanium tube is removed after 5 cleanings.
However, the polished titanium tube is about 89
%, which is close to that of the aluminum brass tube14), and it can be seen that the adhesion of deposits becomes weaker after 4r (Table 4).

Furthermore, the reattachment of marine organisms ≦ near after the removal of materials is also shown to be significantly suppressed on polished titanium tubes compared to unpolished titanium tubes (Table 5). .

\1, ゝ1, ゛・2,\ \\\ \, \, \ Table 3 Table 4 Table 5 Example 2 A polished titanium tube with a length of 15 m was manufactured in the same manner as in Example 1,
A conventional unpolished titanium tube was also prepared for comparison. and,
These two types of titanium tubes were cleaned and the seawater temperature was 1.
In No. 19, the steam temperature was 14-29°C1, 27-42°C, and the flow velocity in the pipe was 2 m/sec. Also, during test) 9r, 10 sponge balls 2 mm larger than the inner diameter of the tube were passed through the tube at a frequency of 1 time per death.

Then, the soiling coefficient was measured every 31 months after the start of water flow, and the soiling coefficient was also measured in the same manner one week later.

The results are shown in Table 6. From this result, it can be seen that the adhesion of deposits on polished Fg' titanium tubes is 1 bit weaker than that of unpolished titanium tubes, and that the fouling coefficient (heat transfer performance) is maintained well by sponge ball cleaning. .

Table 6

Claims (2)

[Claims] (1) In a heat exchange Rg in which a titanium material is used as a heat exchange tube or a heat exchange plate, and cooling water such as sea water, river sea water, river, lake water, etc. is brought into contact with the surface of one side as a cooling fluid, the cooling A heat exchanger characterized in that the surface of the heat exchange tube or the heat exchange plate with which the fluid comes into contact is polished so as to have a surface roughness of about 15 μm or less in terms of Ra. (2) The heat exchange tube is a welded tube made by bending longitudinal titanium plates in the width direction and butting them together, and welding the butted portions, and the welded portion has a diameter of 20 mm or less in the circumferential direction of the tube. The heat exchanger according to claim 1, wherein the inner surface of the tube except for the width region is polished.