JP2000121284A - Heat transfer tube and heat conveying system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce in size a heat exchanger without lowering heat transfer characteristics even in the case of using an aqueous solution obtained by adding a surfactant as a heat conveying medium by providing an agitating means for agitating by applying a shearing force to a heat conveyor flowing in a heat transfer tube. SOLUTION: A twisted flat plate 13 having a width equal to an inner diameter of the cylindrical heat transfer tube 12 is inserted fixedly into inside of the tube 12. The plate 13 is obtained by twisting a tape-like flat plate and twisting it at a predetermined pitch. A heat conveying medium flowing in the tube 12 is agitated by the plate 13, and a heat transfer performance of the medium is improved. Generally, in the solution, a surfactant having a hydrophobic base part and a hydrophilic base part is self-gathered so that the hydrophilic part of a center is surrounded on its outer periphery with the hydrophobic part to form a bar-like micell. Thus, this is entangled in a high order to exhibit a viscoelasticity. However, a shearing force is applied to the medium by the plate 13 to agitate the medium, the entangled micell is disentangled so that no viscoelasticity is developed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer system including a heat transfer tube and a heat exchanger using the same.
The present invention relates to a heat transfer tube using an aqueous solution containing a surfactant for reducing frictional resistance as a heat transfer medium and a heat transfer system including a heat exchanger using the heat transfer tube.

[0002]

2. Description of the Related Art In a conventional district heating and cooling system, the length of a pipe for circulating water as a heat transfer medium from a heat supply side plant to a building as a heat utilization side plant is several kilometers or more. The transport power is quite large. For this reason, the cost used for conveying water accounts for about 60% to 70% of the electricity cost in the running cost of the district heating and cooling system.

Recently, as an effective method of reducing the power of water transport, a method has been proposed in which an aqueous solution containing a surfactant exhibiting viscoelasticity is used as a heat transport medium to significantly reduce the flow frictional resistance in a pipe. I have.

It is said that the above-described effect of reducing the flow frictional resistance is caused by the following. That is, when several tens to several thousand ppm of a predetermined cationic surfactant and a counter ion such as sodium salicylate are dissolved in water flowing in the pipe, the surfactant becomes hydrophilic around the hydrophobic base in the water. It is said that the base is arranged to form micelles (associates), and the micelles are entangled in a higher order in a rod-like form and exhibit viscoelasticity.

[0005] As a method for reducing the friction in the surface-active agent and water conveying pipe exhibiting such characteristics, for example, Japanese Patent Publication No. 3-7 / 1995
No. 6360, Japanese Patent Publication No. 4-6231, Japanese Patent Publication No. 5
And Japanese Patent Application Laid-Open No. 8-31431.

[0006]

However, it is known that the properties of an aqueous solution to which the above-mentioned surfactant is added are such that the heat transfer characteristics are reduced as the flow friction resistance is reduced. For this reason, when the aqueous solution to which the above-mentioned surfactant is added is used for a heat transfer system such as a district heating / cooling system or a building air conditioning system, the water transfer power is reduced due to a decrease in flow friction resistance, and an energy-saving heat transfer system is constructed. However, the heat transfer performance of the heat exchangers installed in the air conditioners of the heat supply-side plant and the heat utilization-side plant is reduced. As a result, in a heat transfer system using an aqueous solution to which a surfactant is added, a conventional aqueous solution in which an additive that prevents corrosion of equipment materials such as water or pipes to which no surfactant is added is dissolved in a heat transfer medium. As compared with the heat transfer system used in the above, there is a problem that the area of the heat transfer portion of the heat exchanger in the heat supply side plant and the heat utilization side plant becomes large, and the heat exchanger becomes large.

An object of the present invention is to improve the heat transfer characteristics in a heat exchanger while reducing the frictional resistance in piping even when an aqueous solution containing a surfactant for reducing frictional resistance is used for the heat transfer medium. An object of the present invention is to provide a heat transfer tube capable of reducing the size of a heat exchanger without lowering the heat exchanger, and a heat transfer system including a heat exchanger using the same.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies and conducted various experiments. As a result, the heat transfer performance of the aqueous solution to which the surfactant was added greatly changed depending on the internal shape of the heat transfer tube. This led to the completion of the present invention.

That is, the heat transfer tube of the present invention is a heat transfer tube using an aqueous solution to which a surfactant for reducing frictional resistance is added as a heat transfer medium, wherein the heat transfer medium flowing in the heat transfer tube is subjected to a shear force. And a stirring means for stirring.

It is preferable that the stirring means is a twisted flat plate fixed inside the heat transfer tube.

Further, the heat transfer system of the present invention is a heat transfer system using an aqueous solution to which a surfactant for reducing frictional resistance is added as a heat transfer medium, wherein a heat supply side for supplying heat to the heat transfer medium. A plant that uses heat from the heat transfer medium, and a pipe that circulates the heat transfer medium between the heat supply side plant and the heat use side plant, wherein the heat supply side plant And at least one of the heat utilization side plants includes any one of the heat transfer tubes described above, and includes a heat exchanger that heats or cools the heat transfer medium formed by the heat transfer tubes via the pipes. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a heat transfer system having a heat exchanger having heat transfer tubes according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a heat transfer system including a heat exchanger having a heat transfer tube according to an embodiment of the present invention. In the following description, an air-conditioning system for air-conditioning a building or the like will be described as an example. However, the heat transfer system of the present invention is not particularly limited to this example, and is not limited to a district cooling and heating system, a waste incineration plant, a factory, or the like. The present invention can be similarly applied to a heat system, a heat utilization system utilizing temperature difference energy of river water, seawater, sewage treatment water, and the like.

As shown in FIG. 1, the heat transfer system includes a heat supply side plant 1, a heat utilization side plant 2 such as a building, and a pipe 3. The heat supply-side plant 1 includes a refrigerator 4. A heat transfer medium, which is an aqueous solution to which a cationic surfactant having a property of reducing frictional resistance is added, flows inside the pipe 3, and the heat transfer medium is cooled inside the refrigerator 4, It is transported from the plant 1 to the heat utilization side plant 2. The cooled heat transfer medium is supplied to the heat utilization side plant 2
Is used as cooling heat for cooling, and then the heated heat transfer medium is again transferred to the heat supply side plant 1 and circulates between the heat supply side plant 1 and the heat use side plant 2.

Next, the heat exchanger provided inside the refrigerator 4 will be described in detail. FIG. 2 is a partial cross-sectional perspective view showing the structure of the heat exchanger provided inside the refrigerator 4.

[0015] The portion for transmitting the cold generated in the refrigerator to the heat transfer medium is generally called an evaporator.
A heat exchanger that is a shell and tube heat exchanger is provided. As shown in FIG. 2, the heat exchanger 10 includes a shell 1
1. A heat transfer tube 12 is provided. The inside of the shell 11 of the heat exchanger 10 is kept under reduced pressure, and a number of heat transfer tubes 12 are installed in parallel in a certain direction. The heat transfer medium continuously flows inside each of the heat transfer tubes 12, and in the shell 11, water in the case of the absorption refrigerator and Freon liquid in the case of the electric turbo refrigerator continuously flow. The water or the chlorofluorocarbon liquid evaporates (vaporizes) while dripping on the outside of the heat transfer tube 12.
The heat transfer medium in the heat transfer tube 12 is cooled by the heat of vaporization at this time. The cooled heat transfer medium is supplied to a heat exchanger of the heat utilization side plant 2 by a pump (not shown) via a pipe 3 connected to the heat transfer pipe 11, and is supplied to the heat utilization side plant 2.
It is used as cooling for cooling.

Next, the heat transfer tube 12 will be described in detail. FIG. 3 is a partially sectional perspective view showing the structure of the heat transfer tube shown in FIG. FIG. 4 is a diagram illustrating a cross section taken along line II of the heat transfer tube illustrated in FIG. 3. In addition, fins and the like for radiating heat are provided on the outer periphery of the heat transfer tube in the same manner as a normal heat transfer tube, but illustration and description are omitted for simplification.

As shown in FIGS. 3 and 4, a torsion flat plate 13 having a width equal to the inner diameter of the heat transfer tube 12 is inserted and fixed inside the cylindrical heat transfer tube 12. The twisted flat plate 12 is formed by twisting a tape-shaped flat plate,
It is twisted at a predetermined pitch. The twist pitch of the twisted flat plate 13 is not particularly limited, but is preferably 200 mm or less, more preferably 100 mm or less, and further preferably 65 mm or less, as the pitch at which the twisted state rotates half a turn. preferable. The length of the twisted flat plate 13 is not particularly limited, but is preferably in the range of 1/10 to 1 times the length of the heat transfer tube, and is preferably in the range of 1/10 to 1/2 time. More preferably, it is more preferably in the range of 1/10 to 1/4. Further, the material and thickness of the torsion flat plate 13 are not particularly limited, and various types can be adopted according to the specifications of the heat transfer plant used.

With the above configuration, the heat transfer medium flowing through the heat transfer tube 12 is agitated by the twisted flat plate 13, and the heat transfer performance of the heat transfer medium is improved. This is presumed to be due to the following reasons. In general, in an aqueous solution to which a surfactant is added, a surfactant consisting of a hydrophobic base and a hydrophilic base is self-assembled to form a rod-shaped micelle so that the hydrophilic base surrounds the periphery of the hydrophobic base, and the rod-shaped micelle is formed. It shows viscoelasticity by being entangled in high order. However, heat transfer tube 1
Due to the twisted flat plate 13 provided in the tube 2, a considerable shear force is applied to the heat transfer medium flowing in the tube and the heat transfer medium is stirred. For this reason, the entanglement of the micelles is loosened, and as a result, the viscoelasticity does not appear and the heat transfer performance does not decrease.

Therefore, the pipe diameter (inner diameter) generally used for the refrigerator of the plant on the heat supply side of the air conditioning system is 10 to 2 mm.
1.0 to 2.5 m / s using a heat transfer tube within the range of 0 mm
Even when an aqueous solution to which a surfactant is added is used as the heat transfer medium within the flow rate range of, the same heat transfer performance (heat transfer coefficient) as when water is used as the heat transfer medium can be obtained. As a result, the heat transfer tube 1 having the twisted flat plate 13 as described above
1 is used in the heat transfer system shown in FIG. 1, the pipe 3 other than the heat transfer pipe has a water transfer power due to the effect of reducing the flow frictional resistance of the aqueous solution to which the surfactant has been added as in the conventional case. Can be reduced, and the heat transfer tubes 12 in the heat exchanger 10 of the heat supply-side plant 1
Since the heat transfer performance does not decrease, heat can be efficiently exchanged from the heat transfer medium, and the heat exchanger can be downsized.

Further, the state in which the entanglement of the micelles is unraveled by the above-mentioned twisted flat plate continues for several seconds without the twisted flat plate in the heat transfer tube. The molecules self-assemble again to form rod-like micelles, and viscoelasticity is restored. On the other hand, the residence time of the heat transfer medium in a heat exchanger in a general refrigerator is
Because it is several tens of seconds, if a twisted flat plate is provided in front of the heat exchange part of the heat exchanger tubes of the heat exchanger, the micelles will pass through the heat exchanger with the entanglement untangled, and then And the viscoelasticity is restored.
For this reason, if a twisted flat plate is provided at least in front of the heat exchange part of the heat transfer tube of the heat exchanger, the heat transfer medium will not be in a viscoelastic state in which the heat transfer performance is reduced in the heat exchanger, and the heat transfer performance will be reduced. Does not drop. Therefore, the position at which the torsion plate 13 is fixed to the heat transfer tube 12 is not particularly limited, and the torsion plate may be provided on the entire heat transfer tube, or may be provided upstream of the heat exchange portion of the heat transfer tube where heat exchange is performed. Or a portion immediately before the heat exchange portion of the heat transfer tube.

As a heat transfer tube having the above-mentioned twisted flat plate therein, a static mixer commercially available and mainly used for mixing, stirring, or accelerating a chemical reaction, such as Noritake Co., Ltd. N10-
331-1 may be used. In this static mixer, a twisted flat plate of metal or the like is inserted and fixed in a circular tube, and a shear force is applied to the heat transfer tube 12 shown in FIG. Can be added and stirred, and the same effect can be obtained.

In the above embodiment, the case where the heat transfer tube of the present invention is used for the heat exchanger 10 of the heat supply side plant 1 has been described. The same can be applied to the exchanger, and the same effects as above can be obtained.

[0023]

EXAMPLES Hereinafter, the heat transfer characteristics of the heat transfer tube of the present invention will be specifically described with reference to examples. Note that the present invention is not limited to the following embodiments.

FIG. 5 is a diagram showing a configuration of an evaluation device for evaluating the heat transfer characteristics of the heat transfer tube. As shown in FIG.
The heat transfer medium adjusted to 10 ° C. is filled in the medium tank 21, and the heat transfer medium in the medium tank 21 is introduced into the heat transfer characteristic measuring unit 26 via the pipes 23 to 25 by the pump 22. The heat transfer characteristic measuring unit 26 includes the heat transfer tube 12 and the heat transfer tube 12.
And a circular pipe 27 covering the periphery of the circular pipe. The circular pipe 27 is a circular pipe made of stainless steel and having a nominal diameter of 40A. Heat transfer tube 12 and circular tube 2
7, that is, an annular portion between the circular tube 27 and the heat transfer tube 12, about 2-3 ° C. so that the temperature of the tube wall of the heat transfer tube 12 becomes 8 ° C. Of cold water always flows in. 10 ° C. flowing into the heat transfer tube 12 by the cold water
Is cooled.

By the above operation, the evaluation apparatus calculates the heat transfer coefficient as the heat transfer characteristic inside the heat transfer tube 12 during cooling. The method of cooling the heat transfer medium flowing in the heat transfer tube differs between the actual evaporator in the refrigerator and the above-described evaluation device. This difference relates to the outside of the heat transfer tube. It has no effect on the heat transfer characteristics of the heat transfer medium flowing inside the heat transfer tube discussed in the above.

As a heat transfer medium to be compared, an aqueous solution (hereinafter, referred to as a conventional medium) in which 750 ppm of a nitrous acid-based pipe corrosion inhibitor, Kurisawa I-108 (manufactured by Kurita Industry Co., Ltd.) is dissolved in tap water, In this conventional medium, 750 ppm of surfactant Esocard O-12 (manufactured by Lion Corporation) containing oleyl-bis (2-hydroxyethyl) methylammonium chloride as a main component and 450 ppm of sodium salicylate (manufactured by Wako Pure Chemical Industries) were dissolved. An aqueous solution (hereinafter referred to as a surfactant medium) was used, and the difference in heat transfer characteristics between the two was evaluated.

(Example 1) As a heat transfer tube, a tube inner diameter of 14.0 mm, which is generally used as a heat transfer tube of a refrigerator,
A smooth copper tube having a length of 1000 mm was used. Inside this heat transfer tube, a width of 14.0 mm, a thickness of 1.0 mm, and a length of 300 m were used.
A stainless steel plate having a thickness of 50 m was twisted so as to have a half-rotation pitch of 50 mm, and was fixed to the upstream entrance of the heat transfer tube with reference to the flow direction of the heat transfer medium, and installed in the above-described evaluation device. In this heat transfer tube, a surfactant medium is caused to flow, and the heat transfer coefficient (W / m ² · ° C.) and the flow rate (m /
s), and the results are shown in FIG. 6 by black circles.

(Example 2) As a heat transfer tube, a ridge having a rectangular cross section of 0.5 mm in height and 0.7 mm in width, which is generally used as a heat transfer tube of a refrigerator, is 1.7 mm in inner circumferential surface. Spiral tube diameter 1 formed at equal intervals
4.6mm (excluding ridge height) copper tube, width 1
Except that the torsion plate was fixed in the same manner as in Example 1 except that it was 3.6 mm, the heat transfer coefficient, the flow rate, and the flow rate when a surfactant medium was used as the heat transfer medium under the same conditions as in Example 1. Was measured, and the results are shown by black circles in FIG.

(Comparative Example 1) A heat transfer tube similar to that of Example 1 was installed in the above-described evaluation apparatus except that the twisted flat plate was not used, and a heat transfer medium using a conventional medium and a heat transfer medium using a surfactant medium were used. The heat transfer coefficient and the flow rate were measured when the conventional medium was used, and a white circle when the conventional medium was used and a white triangle when the surfactant medium was used, respectively, are shown in FIG.

(Comparative Example 2) A heat transfer tube similar to that of Example 2 was installed in the above-described evaluation apparatus except that there was no twisted flat plate, and a conventional medium was used as a heat transport medium and a surfactant medium was used. The heat transfer coefficient and the flow rate were measured when the conventional medium was used, and a white circle when the conventional medium was used, and a white triangle when the surfactant medium was used, are shown in FIG.

As shown in FIGS. 6 and 7, a surfactant medium was used under the conditions of Comparative Examples 1 and 2 in a flow rate range of 1.0 to 2.5 m / s generally used in a heat transfer system. However, when the surfactant medium was used under the conditions of Examples 1 and 2, the heat transfer characteristics did not decrease, and under the conditions of Comparative Examples 1 and 2. The same heat transfer characteristics as when using a conventional medium can be obtained,
Even when a surfactant medium was used, it was confirmed that the use of a twisted flat plate did not reduce the friction reducing effect and did not lower the heat transfer characteristics.

[0032]

According to the heat transfer tube of the present invention, the heat transfer medium flowing in the heat transfer tube is agitated by applying a shearing force. Since the heat transfer characteristics of the heat tube do not deteriorate, the heat exchanger can be downsized.

Further, the heat transfer system of the present invention uses the above-mentioned heat transfer tube for a heat exchanger, so that the pipes other than the heat transfer tube use the water transfer power due to the effect of reducing the flow frictional resistance of the aqueous surfactant solution as in the conventional case. Can be reduced, and the heat transfer performance of the heat transfer tubes in the heat exchanger does not decrease. Therefore, a heat transfer system can be constructed using a downsized heat exchanger.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a heat transfer system including a heat exchanger having heat transfer tubes according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional perspective view showing a structure of a heat exchanger provided inside the refrigerator shown in FIG.

FIG. 3 is a partially sectional perspective view showing the structure of the heat transfer tube shown in FIG.

FIG. 4 is a view showing a cross section taken along line II of the heat transfer tube shown in FIG. 3;

FIG. 5 is a block diagram showing a configuration of an evaluation device for evaluating the heat transfer characteristics of the heat transfer tube.

FIG. 6 is a graph showing heat transfer characteristics of Example 1 and Comparative Example 1.

FIG. 7 is a graph showing heat transfer characteristics of Example 2 and Comparative Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat supply side plant 2 Heat utilization side plant 3 Piping 4 Refrigerator 10 Heat exchanger 11 Shell 12 Heat transfer tube 13 Twisted flat plate

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masaaki Yoshikawa 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. 1-2 1-2 Osaka Gas Co., Ltd. No. 33 Obayashi Gumi Co., Ltd. (72) Inventor Hajime Onojima 4-33 Kitahama Higashi, Chuo-ku, Osaka

Claims (3)

[Claims] 1. A heat transfer tube using an aqueous solution to which a surfactant for reducing frictional resistance is added as a heat transfer medium, wherein a stirring means for applying a shearing force to the heat transfer medium flowing in the heat transfer tube and stirring the heat transfer medium. Heat transfer tube with. 2. The heat transfer tube according to claim 1, wherein said stirring means is a twisted flat plate fixed inside said heat transfer tube. 3. A heat transfer system that uses, as a heat transfer medium, an aqueous solution to which a surfactant that reduces frictional resistance is added, wherein a heat supply side plant that supplies heat to the heat transfer medium; A heat utilization side plant utilizing heat, and a pipe for circulating the heat transfer medium between the heat supply side plant and the heat utilization side plant, wherein at least the heat supply side plant and the heat utilization side plant 3. A heat transfer system comprising: the heat transfer tube according to claim 1; and a heat exchanger configured to heat or cool the heat transfer medium formed by the heat transfer tube via the pipe.