JPH1038490A - Finned heating tube for high-temperature heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide finned heating tube for high-temperature heat exchanger, securing the optimum heat absorbing capacity in respective positions from the heat source inlet port of a heat exchanger to the outlet port of the same and high in reliability without having any possibility of deterioration or the like due to employing under high-temperature atmosphere. SOLUTION: A finned heating tube is constituted of a mother tube, employing a flat heating tube 5 having a wide plane as a heating tube increased in the heat transfer area thereof, and a multitude of fins 8, which are brazed to the mother tube. The length and pitch of the fins is longer at the inlet port side of a heat source 3 while the length is reduced gradually and the pitch is reduced toward the outlet port side of the heat source. A multitude of stages of fins, whose length are different sequentially, are formed and worked by one sheet of thin material sheets 11a, 11b so as to be classified in accordance with the size of the fin pitches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finned heat transfer tube for a high temperature heat exchanger, and more particularly to a finned heat transfer tube for a high temperature heat exchanger suitable for a heat exchanger used in a high temperature range, such as a boiler. Used in high temperature heat exchangers.

[0002]

2. Description of the Related Art Generally, various types and shapes of heat transfer tubes and fins for heat exchangers are widely used. From the viewpoint of the temperature range of the heat source to be handled, these can be classified as a heat exchanger used in a relatively high temperature range or a heat exchanger used in a low temperature range. And
Typical products include a boiler for exchanging heat with high-temperature hot air, and an air conditioner and a refrigerator for exchanging heat by cooling air by creating a flow of air.

[0003] As a heat exchanger for an evaporator used in a refrigerator, for example, one described in Japanese Patent Application Laid-Open No. 61-285395 is known. In the heat exchanger described in the publication, a plurality of parallel members are stacked at an appropriate interval to form a flat refrigerant flow path, and the flat refrigerant flow paths are arranged in parallel in the airflow direction, and A plurality of fin members whose intervals are narrower toward the downstream side of the airflow and whose dimensions in the airflow direction are long are attached to the outer wall of the flat refrigerant flow path in parallel with the airflow direction.

That is, the fin length is increased in the later stage with respect to the flow direction of the air flow to secure an electric heating area, and the fin is not adversely affected by the dead water area in the refrigerant flow path, and the air flow due to the frosting phenomenon is prevented. The passage is prevented from being blocked.

On the other hand, the present invention is directed to a heat exchanger for a high temperature region, such as an air conditioner, a refrigerator, etc., in which the temperature of a heat source is completely different from that for cooling a refrigerant and exchanging heat by producing an air flow. . In the above-mentioned boiler, the heat source heat generated in the combustion chamber is guided to the inside of the flue-type heat transfer tube, and heat exchange is performed so as to increase the water temperature outside the heat transfer tube. Such a technique is described in, for example, “Machine Engineering Essentials”, edited by Akibarou Baba, 19
Published by Sanseido in February 1976, Chapter 3, P820-P821,
These are described in FIGS. 3-3, 3-4, and 3-5.

Focusing on this heat transfer tube, a relatively thick finless bare tube has conventionally been used. This is because the use of the finless thick-walled tube prevents the heat transfer tube from being melted and deteriorated at the inlet of the heat exchanger exposed to a high-temperature heat source, even if the heat absorbing ability is reduced. After that, the amount of heat from the heat source, which was absorbed at the entrance and decreased,
The heat transfer operation continues to reach the middle portion of the heat transfer tube, but after the middle portion, the finned heat transfer tube having the increased heat transfer area can obtain higher heat absorption capacity. In this regard, a bare tube having no fins is disadvantageous in that it has a low heat absorption capacity.

Next, as an example in which fins are spirally wound around a heat transfer tube, see, for example, "Introduction to Heat Exchange Technology for Energy Engineering" by Tsune Nakayama, published by Ohmsha, December 1981, No. 2, Chapter, P45, FIG. 2.6. This is a heat transfer tube that puts a heat source inside the heat transfer tube and heats or cools the gas or liquid outside. However, even in this case, since the heat transfer capacity of the fin-wrapped heat transfer tube is uniform, no measures are taken to increase the heat transfer area in response to the gradually decreasing heat source temperature. Had not been absorbed yet.

[0008] On the other hand, although the temperature range to be used is different, a plate-fin type heat exchanger in which many fine fins are provided on a thin aluminum plate is used in an outdoor unit of an air conditioner. However, the use temperature is outside the range required by the present invention.

[0009]

It is not an exaggeration to say that the performance of the heat exchanger is, of course, affected by the heat transfer coefficient of the heat transfer tube, and is greatly influenced by an appropriate heat transfer area. Therefore, with respect to the heat source, the heat transfer tubes or the fins do not melt and deteriorate on the upstream side of the heat exchanger, and have a heat transfer area as large as possible and high efficiency from the middle to the downstream of the heat exchanger. Preferably, fins are provided. That is, the main point of the heat exchanger is to increase the heat transfer area effectively and improve the heat absorption capacity in inverse proportion to the decrease in the temperature of the supplied heat source.

From such a viewpoint, how to arrange the fins provided on the heat transfer tube from the inlet side to the outlet side of the heat source at each position, how to design the arrangement, shape, quantity and size of the fins, and The optimal shape of the heat transfer tube having the fins can be said to be an important issue of the finned heat transfer tube for achieving high performance.

The present invention has been made in order to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide an optimum heat absorbing capacity at each position from a heat source inlet to an outlet of a heat exchanger. An object of the present invention is to provide a highly reliable finned heat transfer tube for a high-temperature heat exchanger, which is secured and free from deterioration due to use in a high-temperature atmosphere.

Next, paying attention to the fins to be connected to the heat transfer tubes as the heat flow path of the supply heat source, fins having as high a precision as possible such as fin dimensions, pitch, interval, and position are prepared. It is important to connect to the heat transfer tube surface. The reason is that the heat transfer surface composed of the heat transfer tubes and the fins avoids the influence of the boundary layer described later, and a high heat transfer coefficient can be obtained only by constantly touching the heat source.
Even if a large number of fins are prepared, the accuracy is poor, and if the fins are misaligned and the fin surfaces overlap each other, the heat transfer surface is reduced accordingly and the heat transfer coefficient is reduced. Therefore, it is necessary to consider a method of manufacturing a finned heat transfer tube having high dimensional accuracy.

Further, the fuel used to supply the heat source is
Generally, a clean gas is often used,
In rare cases, it may be oil. In this case, if the operation time is long, the combustion scum sticks to the fins and reduces the heat transfer coefficient. Therefore, cleaning work is forced at that time.
That is, in the fin-wrapped heat transfer tubes disclosed in the above-mentioned prior art, brushing cleaning is almost impossible because of the dense heat transfer tube group.

Therefore, another object of the present invention is to provide a finned heat transfer tube for a high-temperature heat exchanger which is suitable for mass production, contributes to improvement of accuracy for guaranteeing performance, and is easy to maintain such as cleaning work. Is to provide.

[0015]

Means for Solving the Problems To achieve the above object, a first configuration of a finned heat transfer tube for a high-temperature heat exchanger according to the present invention supplies heat from a heat source to the inside of the heat transfer tube,
A heat transfer tube for a high-temperature heat exchanger that raises the temperature of a fluid outside the heat transfer tube by a heat exchange effect, wherein the heat transfer tube has a temperature gradient from a heat source inlet to a heat source outlet generated in the heat transfer tube performing the heat exchange effect. On the inner surface of the heat transfer tube, from the heat source inlet to the heat source outlet, from the heat source inlet to the heat source outlet, provided fins formed in a multi-stage from a single plate so as to sequentially change in inverse proportion to the temperature drop of the heat source. The heat transfer tube as a whole is configured to maintain the required heat absorption capacity.

In order to achieve the above object, a second structure of the finned heat transfer tube for a high-temperature heat exchanger according to the present invention is to supply heat from a heat source to the outside of the heat transfer tube, In a heat transfer tube for a high-temperature heat exchanger that changes a fluid temperature by a heat exchange effect, the outer surface of the heat transfer tube with respect to a temperature gradient from a heat source inlet to a heat source outlet generated in the heat transfer tube performing the heat exchange, From the heat source inlet to the heat source outlet, the heat transfer tube is provided with a plurality of fins formed from a single plate so as to sequentially change in inverse proportion to the temperature drop of the heat source from the heat source inlet to the heat source outlet. It is configured to maintain the heat absorption capacity of the helium.

In the first and second configurations, the heat absorption capacity of the heat transfer tube is formed from a single plate in multiple stages from the heat source inlet to the heat source outlet so as to be sequentially changed in inverse proportion to the temperature decrease of the heat source. The fin has a fin length and a fin pitch that are increased on the inlet side of the heat source, the fin length is gradually reduced toward the outlet side of the heat source, and the fin pitch is formed to be small. From a plurality of fins having different fin lengths.

The heat transfer tube is a flat tube having a substantially parallel elliptical cross section and a parallel flat surface portion. The heat transfer tube has an outer surface or an inner surface extending from the heat source inlet of the heat transfer tube to the heat source outlet. A plurality of fins formed from a single plate are connected to each other so as to change the heat absorbing ability.

Here, the concept of developing the present invention and the function of the above configuration will be described. In order to increase the heat transfer coefficient of the finned heat transfer tube, it is necessary to first increase the heat transfer area, and the means is to provide as many surfaces as possible in the heat transfer tube that directly contact the flow of the heat source. On the other hand, in the cylindrical heat transfer tube, the front half has a heat exchange effect, but the rear half has a disadvantage that the effect is reduced by half. Therefore, by adopting a flat tube having a parallel elliptical structure as a mother tube as a shape obtained by combining the tube groups established for the flow of the heat source, the number of components is reduced while securing a heat transfer area.

Next, increasing the heat transfer area of the fins is the same, but if the amount of heat absorption at the inlet of the heat source becomes excessive, there is a risk of fin melting as described above. Therefore, the inventors decided to find a fin that increased in heat absorption capacity in inverse proportion to the temperature decrease of the heat source from the heat source inlet side to the outlet side. In designing the fins, refer to the above-mentioned document "Introduction to heat exchange technology for energy engineering"
The development was promoted based on Chapters, P19, and FIGS.

FIGS. 5 and 6 show FIGS. 1 and 12 and FIGS.
13 is shown. FIG. 5 is a diagram showing the relationship between the length of a general flat plate and the heat transfer coefficient, and FIG. 6 is an explanatory diagram showing the boundary layer and the thickness of the boundary layer. In FIG. 5, the horizontal axis represents the length L (mm) of the flat plate (fin), and the vertical axis represents the average heat transfer coefficient (W / m ^2).
k) and the thickness (mm) of the boundary layer at the trailing edge. In FIG. 6, L indicates the length of the flat plate (fin), 1 indicates the boundary layer, and 2 indicates its thickness.

The relationship between the length L of the flat plate (fin) and the average heat transfer coefficient with respect to the flow direction of the heat source is shown as a solid line in FIG. Further, a flat plate (fin) indicated by a broken line in FIG.
The shorter the fin length L is, as shown in FIG. 6, the better the boundary layer thickness at the trailing edge. Therefore, the arrangement of the fins with respect to the supply heat source is such that the fin pitch and the fin length are increased in the inlet-side high-temperature section, gradually reduced from the center of the heat transfer tube, and are shortened with the finest possible pitch in the outlet-side low-temperature section. The above conditions are achieved by setting the fin length.

Next, in order to manufacture a highly reliable finned heat transfer tube, it is necessary to increase the precision of parts before joining. Here, the heat transfer tube has a flat surface (parallel elliptical structure) having a wide flat surface to secure a mounting surface, and fins of various dimensions to be joined to the heat transfer tube are made of a single sheet material ( A fin structure with high accuracy and high productivity that can be formed by one shot (for each fin pitch described later).

Further, there are a method of brushing the fin surface with a wire brush or the like and a method of decomposing the combustion scum using a chemical cleaning liquid in order to remove the combustion scum adhered to the fin. In the former case, an extra-fine brush is inserted into the fin gap from the heat source outlet side to the heat source side for cleaning, so that a structure considering the arrangement of the fins is required. In the latter case, there are no particular restrictions, and there is no problem as long as the brushing method is possible.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view schematically showing a configuration of a smoke tube type heat transfer tube for passing a heat source according to an embodiment of the present invention through a heat transfer tube. FIG. 2 is a perspective view showing a heat source according to another embodiment of the present invention. FIG. 3 is a perspective view schematically showing a configuration of a liquid tube type heat transfer tube passing outside the heat transfer tube, and FIG. 3 is a diagram showing the shape and arrangement of fins formed on the heat transfer tube of FIGS. 1 and 2;
Is a plan view, (b) is a side view, (c) is a sectional view taken along line (a), (d) is a sectional view taken along line (a), and FIG. 4 is a fin before forming. 7A is a development view of a fin material on the heat source inlet side, and FIG. 7B is a development view of a fin material on the heat source passage (exit) side.

In FIG. 1, 5 is a flat heat transfer tube, 8 is a fin formed on the inner surface of the flat heat transfer tube 5, and 6 is a smoke tube type heat transfer tube relating to a finned heat transfer tube. 9 is a brazing part,
Reference numeral 10 denotes a weld. The finned heat transfer tube shown in FIG.
The heat source 3 (hot air) indicated by a thick arrow is introduced into the inside of the flue-tube type heat transfer tube 6, and heat is exchanged with the liquid or gas 4 shown by a thin arrow outside the flue-tube type heat transfer tube 6. The flue-tube type heat transfer tubes 6 are used in combination in a real machine to constitute a heat exchanger.

The flat heat transfer tube 5 is a parallel elliptical shape having a wide flat surface so as to improve the reliability of the joining quality in the work of brazing with the fins 8 shown in the brazing portion 9 and to secure a heat transfer surface. Is a flat heat transfer tube. The flat heat transfer tube 5 is formed by joining thin bent steel plates 5a and 5b to a welded portion 10a.
The front and both side surfaces can be effective heat transfer surfaces of the heat source 3 as shown in FIG. 1, and contribute to the improvement of the heat transfer coefficient greatly compared with the conventional cylindrical heat transfer tube. I have.

The fins 8 to be soldered to the inner surface of the flat heat transfer tube 5 have the dimensions and arrangement shown in FIG.
One of the design principles of the fins 8 is to sequentially change the heat absorption capacity of the fins 8 in inverse proportion to the temperature decrease of the heat source caused by the heat exchange action of the heat source 3. Another design principle of the fins 8 is that, as shown in FIGS. 5 and 6, the shorter the length of the fin (flat plate), the higher the heat transfer coefficient and the smaller the thickness of the boundary layer. It is a thing.

That is, at the inlet side of the heat source 3, a fin size 8a having a heat absorption amount that does not cause the fin 8 to melt.
８8d (the fin lengths l ₁ to l ₄ shown in FIG. 3 (b) and the fin pitch X shown in FIG. 3 (c) as viewed from the II ′ plane are both large), and pass through the intermediate portion, respectively. fin length l ₅ to l ₇ shown in fin dimensions 8e~8g [3 (b) along the temperature drop of the heat source, and b - 3 viewed from b 'plane
The fin pitch X / 2 shown in (d) is small),
In the outlet from the latter half, since the heat source temperature is considerably lowered and there is no fear of fin melting, the fin 8h has an increased heat transfer area in order to secure the maximum heat absorption, and the fin pitch is X / 2. , it is performed fin design fins length as the shortest l _8. Further, with respect to the heat flux from the heat source 3, the fins 8 are arranged in a staggered arrangement so as to avoid a decrease in the heat transfer coefficient due to the thickness of the boundary layer.

On the other hand, in the heat transfer tube with fins shown in FIG. 2, the heat source 3 indicated by a thick arrow is introduced outside the liquid tube type heat transfer tube 7,
The heat exchange is performed with the liquid 4 indicated by a thin arrow inside the liquid tube type heat transfer tube 7. The liquid tube type heat transfer tubes 7 are used in combination in a real machine to constitute a heat exchanger.

The flat heat transfer tube 5 shown in FIG. 2 is different from that of FIG. 1 only in the direction of the welded portion 10, and improves the reliability of the joining quality in the work of brazing with the fins 8 shown in the brazing 9. In addition, the front and both side surfaces are parallel elliptical flat heat transfer tubes each having a wide plane that can be an effective heat transfer surface of the heat source 3. Further, the fins 8 to be soldered to the outer surface of the flat heat transfer tube 5 adopt the dimensions and arrangement shown in FIG. 3, and are completely equivalent to those described in the embodiment of FIG. , The description of which is omitted.

Even with the high performance smoke tube type heat transfer tube 6 and liquid tube type heat transfer tube 7 designed according to the above-mentioned policy, a highly accurate manufacturing method is required to guarantee the performance. next,
A method of manufacturing the fin 8 which can be used in each of the embodiments shown in FIGS. 1 and 2 will be described with reference to FIG. FIG. 4 is a development view of a fin material before forming, and FIG.
FIG. 4B is a material development view in a range of a to 8d, and FIG.

The fins 8 are made of one thin steel plate (having a thickness of 0.5
１．０1.0 mmt), and the fin materials 11a, 11b are formed in the first step from the fin materials 11a, 11b of one thin steel plate for each fin pitch X, X / 2. The cutting process is performed on a large number of cutting lines 12 indicated by solid lines in the middle, and the bending process of the bending lines 13 indicated by broken lines is performed in the second step.

At the time of mass production, the fin length and the fin pitch are set to standard dimensions, a total cutting and bending die is prepared, and the fin blanks 11a and 11b are supplied. Do. As a result, the fins 8 of various sizes can be soldered to the flat heat transfer tubes 5 with accurate arrangement dimensions, and the occurrence of defective products such as a decrease in the heat transfer coefficient due to the overlapping of the fins can be prevented.

Regarding the consideration of the combustion waste due to the difference in fuel, an extra fine wire-brush is inserted between the fins to periodically perform the cleaning operation. The work method is to insert a very fine wire-brush from the heat source outlet side with a small fin pitch and put the brush in and out toward the inlet side. And the exit side is set to X twice as large as that of the exit side, and the gap is formed in a staggered arrangement based on the fin thickness. The staggered arrangement of the fin length not only facilitates the brushing work of the combustion scum adhering to the fin surface (the scum easily falls off),
The fact that the heat transfer coefficient can be made within the range of the fin length that can take a high heat transfer coefficient is also a great feature as a high-performance finned heat transfer tube.

According to each of the above embodiments, the following effects can be obtained. Conventionally, most of the heat transfer tubes of a heat exchanger used in a relatively high temperature region are formed of cylindrical tubes, and only about half the heat amount of the supplied heat source is used for heat exchange. Therefore, the flat heat transfer tube with fins provided here has the following features: (1) the flat tube and the fin increase the heat transfer area;
(2) The fins have different heat absorption capacities corresponding to the heat source temperatures from the inlet to the outlet. (3) The fin dimensions and arrangement are designed to be optimal values in consideration of the boundary layer and thickness. For this reason, the heat transfer tube has a heat transfer coefficient approximately twice that of the conventional heat transfer tube.

Further, the fin structure can be machined from one sheet of steel and is not only high in mass productivity, but also contributes to improvement of accuracy for guaranteeing performance. In the cleaning operation of the combustion scum, the brushing operation, which was impossible with the conventional spiral fin winding tube, can be sufficiently performed by arranging short fins in a staggered manner.

[0038]

As described above in detail, according to the present invention, the optimum heat absorption capacity at each position is secured from the heat source inlet to the outlet of the heat exchanger, and the heat exchanger is deteriorated by use in a high-temperature atmosphere. A highly reliable finned heat transfer tube for a high-temperature heat exchanger without fear of the like can be provided. Further, according to the present invention, it is possible to provide a finned heat transfer tube for a high-temperature heat exchanger that is suitable for mass production, contributes to improvement in accuracy for guaranteeing performance, and is easy to maintain such as cleaning work. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating a configuration of a smoke tube type heat transfer tube that passes a heat source through the heat transfer tube according to one embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a configuration of a liquid tube type heat transfer tube for passing a heat source outside a heat transfer tube according to another embodiment of the present invention.

FIG. 3 is a view showing the shape and arrangement of fins formed on the heat transfer tubes of FIGS. 1 and 2;

FIG. 4 is a development view of a fin material before forming processing.

FIG. 5 is a diagram showing the relationship between the length of a general flat plate and the heat transfer coefficient.

FIG. 6 is an explanatory diagram showing a boundary layer and a boundary layer thickness.

[Explanation of symbols]

3 ... heat source, 4 ... gas or liquid, 5 ... flat heat transfer tube, 6 ...
Smoke tube type heat transfer tube, 7 ... liquid tube type heat transfer tube, 8, 8a to 8h ... fin, 9 ... brazing portion, 10 ... welding portion, 11, 11a,
11b: fin material, 12: cut line, 13: bending line.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasushi Senba 603 Kandamachi, Tsuchiura-shi, Ibaraki Pref.

Claims (6)

[Claims] 1. A heat transfer tube for a high-temperature heat exchanger that supplies heat from a heat source to the inside of the heat transfer tube and raises the temperature of a fluid outside the heat transfer tube by a heat exchange effect, wherein the heat transfer tube performing the heat exchange operation is provided. For the temperature gradient from the heat source inlet to the heat source outlet, the heat absorption capacity of the heat transfer tube on the inner surface of the heat transfer tube from the heat source inlet to the heat source outlet is inversely proportional to the temperature drop of the heat source. A finned heat transfer tube for a high-temperature heat exchanger, wherein a plurality of fins formed from a single plate are provided so as to be changed so as to maintain a required heat absorption capacity as a whole of the heat transfer tube. 2. A heat transfer tube for a high-temperature heat exchanger that supplies heat from a heat source to the outside of the heat transfer tube and changes a fluid temperature inside the heat transfer tube by a heat exchange effect, wherein the heat transfer tube performing the heat exchange operation is provided. In response to the temperature gradient from the heat source inlet to the heat source outlet, the heat absorption capacity of the heat transfer tube on the outer surface of the heat transfer tube from the heat source inlet to the heat source outlet is inversely proportional to the temperature decrease of the heat source. A finned heat transfer tube for a high-temperature heat exchanger, wherein a plurality of fins formed from a single plate are provided so as to be changed so as to maintain a required heat absorption capacity as a whole of the heat transfer tube. 3. The heat transfer tube according to claim 1, wherein the heat absorption capacity of the heat transfer tube is sequentially changed in inverse proportion to the temperature decrease of the heat source from the heat source inlet to the heat source outlet. The fins formed in multiple stages have a fin length and a fin pitch that are increased on the inlet side of the heat source, the fin lengths are gradually reduced toward the outlet side of the heat source, and the fin pitch is formed smaller. A heat transfer tube with fins for a high-temperature heat exchanger, wherein a plurality of fins having different fin lengths are formed and formed from a thin sheet material. 4. The heat transfer tube according to claim 1, wherein the heat transfer tube is a flat tube having a substantially parallel elliptical cross section and a parallel flat portion, and an outer surface of the flat tube. Or a fin for a high-temperature heat exchanger, wherein a plurality of fins formed from a single plate are joined to the inner surface so as to change the heat absorption capacity from the heat source inlet to the heat source outlet of the heat transfer tube. With heat transfer tube. 5. The heat transfer tube according to claim 1, wherein the heat transfer tube is a cylindrical tube, and heat is absorbed on an outer surface or an inner surface of the cylindrical tube from a heat source inlet to a heat source outlet of the heat transfer tube. A finned heat transfer tube for a high-temperature heat exchanger, wherein a plurality of fins formed from a single plate are joined to change the capacity. 6. The fin arrangement according to claim 1, wherein the fins are arranged in a staggered arrangement, and an ultrafine brush can be inserted into a fin gap from the heat source outlet side of the heat transfer tube to the heat source outlet side. A heat transfer tube with fins for a high-temperature heat exchanger, characterized in that: