JP4508450B2 - Heat transfer tube and heat transfer system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat transfer performance that is manifested simultaneously with friction reduction in a heat exchanger in a method of reducing flow friction by adding a surfactant to water in a system that conveys cold and warm heat by sensible heat of water. The present invention relates to a heat exchanger tube for heat exchanger that prevents a decrease and a heat transfer system using the same.
[0002]
[Prior art]
For example, in a district cooling and heating system, the length of a pipe for circulating water as a heat transfer medium from a heat supply side plant to a heat utilization side building is several kilometers or more, and the water transfer power is considerably large. It is also said to be about 60% to 70% of the running cost of the system.
[0003]
Recently, as an effective method for reducing the water conveyance power, a method of remarkably reducing the fluid friction resistance by using a surfactant aqueous solution exhibiting viscoelasticity as a heat conveyance medium has been proposed.
[0004]
This is because when a specific cationic surfactant and sodium salicylate are dissolved in water flowing through the pipes in the range of several tens to several thousand ppm, the surfactant is in water and the hydrophilic base is centered around the hydrophobic base. It is said that it is arranged to form micelles (aggregates), and the micelles form a rod-like form and are entangled in high order to exhibit viscoelasticity.
[0005]
As a surfactant exhibiting such characteristics and a method for reducing the frictional resistance in the water conveyance pipe, for example, Japanese Patent Publication No. 3-76360, Japanese Patent Publication No. 4-6231, Japanese Patent Publication No. 5-47534, Japanese Patent Application Laid-Open No. Hei 8- There is a method described in Japanese Patent No. 311431.
[0006]
However, it is known as a characteristic of these aqueous solutions that the heat transfer characteristics are lowered at the same time as the flow frictional resistance is reduced. In other words, when considering using these aqueous solutions in heat transfer systems such as district cooling and heating and building air conditioning, the flow friction resistance is certainly reduced, and the transfer power is reduced accordingly, and an energy-saving heat transfer system is built. However, on the other hand, the heat transfer performance in the heat exchangers installed in the heat supply side plant and the heat utilization side air conditioner respectively decreases. Therefore, compared with the conventional system using water or an aqueous solution in which additives that prevent corrosion of equipment materials such as pipes are used as the heat transfer medium, the heat transfer part of the heat supply side plant and the heat utilization side heat exchanger It will be necessary to increase the area.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to use a conventional aqueous heat transfer system while making the area of the heat transfer part of the heat exchanger unit the same as that of a system using a conventional aqueous heat transfer medium when a viscoelastic surfactant aqueous solution is used as a heat transfer medium. It is an object of the present invention to provide a heat transfer tube and a heat transfer system using the heat transfer tube in which the heat transfer characteristics in the heat exchanger section do not deteriorate as compared with the case of using a transfer medium.
[0008]
[Means for Solving the Problems]
In the transport power reduction type heat transport system using a viscoelastic surfactant aqueous solution as a heat transport medium, the present inventors transmit heat to the heat transport medium in the heat supply side plant (heat or cool the heat transport medium). ) Concerning heat exchangers and heat exchangers that transfer heat from the heat transfer medium (heating or cooling the heat transfer medium) in the heat utilization side plant, heat is transferred to the heat transfer tubes used in those heat exchangers. It has been found that the above object can be achieved by inserting a cylindrical packing closely contacting the inner surface of the pipe into a part of the upstream portion of the heat transfer pipe along the central axis inside the pipe where the carrier medium flows.
[0009]
That is, the present invention provides a heat transfer tube as shown below and a heat transfer system using the heat transfer tube.
Item 1. A heat transfer tube of a heat exchanger that uses an aqueous surfactant solution as a heat transfer medium, and a cylindrical packing closely contacting the inner surface of the heat transfer tube along a central axis inside the tube through which the heat transfer medium flows. A heat transfer tube inserted in a part of the upstream part.
Item 2. A heat transfer system that uses an aqueous surfactant solution as a heat transfer medium, a heat supply side plant that supplies heat to the heat transfer medium, a heat use side plant that uses heat of the heat transfer medium, and the heat supply The heat supply side plant and the heat utilization side plant are provided with a pipe that circulates the heat transfer medium between the side plant and the heat utilization side plant, and at least one of the heat supply side plant and the heat utilization side plant is heat having the heat transfer tube according to Item 1. Heat transfer system with an exchanger.
Item 3. Item 2. The heat transfer system according to Item 2, wherein the surfactant according to Item 2 is a mixture of oleyl trihydroxyethylammonium salt and salicylate.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The heat transfer performance of the viscoelastic surfactant aqueous solution varies greatly depending on the processing shape inside the heat transfer tube. Then, when a cylindrical packing that is in close contact with the inner surface of the heat transfer tube along the central axis inside the heat transfer tube through which the viscoelastic surfactant aqueous solution flows is inserted into a part of the upstream portion of the heat transfer tube, for example, district heating and cooling Within the range of the pipe diameter (inner diameter) of 10 to 20 mm, such as the heat transfer pipe of a refrigerator that is actually used in the heat supply side plant of the system, the flow velocity range area that is actually used is 1 to 2 m / s. Thus, it is possible to provide the same heat transfer performance (heat transfer coefficient) as in conventional water conveyance.
[0011]
As described above, when a cylindrical filler that is in close contact with the inner surface of the tube along the central axis inside the heat transfer tube is inserted into a part of the upstream portion of the heat transfer tube, the viscoelastic surfactant aqueous solution is used as a heat transfer medium. Even if it is used, the heat transfer performance does not deteriorate. When the surfactant aqueous solution flows into the cavity of the cylindrical packing, the flow path of the surfactant aqueous solution is abruptly reduced, and then the cavity of the cylindrical packing When the surfactant flows out from the section, the flow path of the surfactant aqueous solution is rapidly expanded. Therefore, the surfactant aqueous solution is subjected to strong loss energy of contraction and expansion flow, and the higher order structure of the rod-like micelle. This is considered to be because viscoelasticity disappears when the cylindrical packing is passed and for a while after passing.
[0012]
The cross-sectional shape of the inner surface cavity of the cylindrical filler in the heat transfer tube of the present invention is not particularly limited, and examples thereof include a circle, a square, a triangle, and a semicircle. Preferably, it is circular or the like.
[0013]
Also, the cross-sectional area of the inner cavity of the cylindrical packing is not particularly limited, but if it is large, there is no effect because the loss energy of the contraction / expansion flow given to the surfactant aqueous solution is small, and conversely small. And it is not good because it will hinder the flow itself. Therefore, it is preferably 10 to 90% of the cross-sectional area inside the heat transfer tube, more preferably 15 to 80%, and particularly preferably 18 to 75%.
[0014]
Further, the length of the cylindrical packing is not particularly limited. However, if the length is short, there is no effect because the time for giving the loss energy of the contraction / expansion flow to the surfactant aqueous solution is shortened. Is wasteful. The length of the heat transfer tube is preferably inserted in the length of 0.1 to 10%, more preferably 0.5 to 5%, and particularly preferably 0.7 on the upstream side of the heat transfer tube. It is ~ 2% long.
[0015]
The material of the cylindrical filling is not particularly limited, but synthetic resin or metal is preferable. Examples of the synthetic resin include acrylic resin, polypinyl chloride, melamine resin, and polyethylene, and acrylic resin and polyethylene are preferable. Examples of the metal include iron, copper, gold, silver, stainless steel, brass and the like, and iron, copper, stainless steel and the like are preferable from the viewpoint of cost.
[0016]
The cylindrical packing is fixed in a state of being inserted into the heat transfer tube. The fixing means is not particularly limited. For example, the outside of the cylindrical packing and the inner surface of the heat transfer tube may be adhered and fixed with an adhesive.
[0017]
The surfactant contained in the surfactant aqueous solution used as the heat transfer medium is not particularly limited and may be a conventionally used one. For example, a mixture of oleylhydroxyethyldimethylammonium salt and salicylate, oleylbishydroxyethylmethyl Examples thereof include a mixture of ammonium salt and salicylate, a mixture of oleyl trihydroxyethylammonium salt and salicylate, a mixture of cetyltrimethylammonium salt and salicylate, a mixture of stearyltrimethylammonium salt and salicylate, and the like. Preferably, it is a mixture of oleyl trihydroxyethyl ammonium salt and salicylate. These mixtures are presumed to undergo salt exchange in the system to produce the corresponding quaternary ammonium cation salicylates.
[0018]
The concentration of the surfactant in the surfactant aqueous solution is not particularly limited. The concentration of the quaternary ammonium salt is preferably 50 to 50000 ppm, more preferably 100 to 30000 ppm, and particularly preferably 200 to 10000 ppm. The concentration of salicylate is preferably 0.1 to 5 times the molar amount of the quaternary ammonium salt used simultaneously, more preferably 0.3 to 3 times the molar amount, and 0.5 to 2 times the molar amount. Is particularly preferred.
[0019]
When the heat transfer pipe of the present invention is used for heat transfer of district air conditioning systems and building air conditioning systems, transfer of waste heat from garbage incineration plants and factories, or transfer of temperature difference energy such as river water, seawater, sewage treated water, etc. In addition, not only water transport power is reduced by reducing the flow frictional resistance of the viscoelastic surfactant aqueous solution, but also heat exchange that transfers heat to the heat transport medium in the heat supply side plant and the heat utilization side plant, respectively. It is no longer necessary to increase the size of the vessel or improve the vessel, and it can be handled with conventional water-use devices.
[0020]
【Example】
First, as an example of a heat exchanger used in a heat transfer system, a structure of a refrigerator in a heat supply plant of a district cooling and heating system will be described.
[0021]
A portion that transmits the cold heat generated in the refrigerator to the heat transfer medium is generally called an evaporator, and includes a shell-and-tube heat exchanger as shown in FIG. As shown in FIG. 1, the heat exchanger 10 includes a shell 11 and a heat transfer tube 12. The inside of the shell is held under reduced pressure, and a large number of heat transfer tubes (tubes) 12 are installed in parallel in a certain direction. While the heat transfer medium continuously flows inside each heat transfer tube 12, in the shell 11, water is absorbed continuously in the case of an absorption refrigeration machine, and chlorofluorocarbon liquid in the case of an electric turbo chiller. The liquid evaporates (vaporizes) while dripping down 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 that time. The cooled heat transfer medium is supplied to the heat utilization side through a pipe by a pump and used as cooling heat.
[0022]
FIG. 2 is a diagram illustrating a configuration of an evaluation apparatus for evaluating the heat transfer characteristics of the heat transfer medium. As shown in FIG. 2, the heat transfer medium adjusted to 10 ° C. is filled into the medium tank 21, and the heat transfer medium in the medium tank 21 is introduced into the heat transfer characteristic measurement unit 26 through the pipes 23 to 25 by the pump 22. To do. The heat transfer characteristic measuring unit 26 includes a heat transfer tube 12 and a circular tube 27 that covers the periphery of the heat transfer tube 12, and the circular tube 27 is a stainless tube having a nominal diameter of 40A. Inside the double pipe (double pipe heat exchanger) composed of the heat transfer tube 12 and the circular tube 27, that is, in the annular portion between the circular tube 27 and the heat transfer tube 12, the tube wall of the heat transfer tube 12 is provided. Cold water of about 2 to 3 ° C. is constantly introduced so that the temperature becomes 8 ° C. With this cold water, the 10 ° C. heat transfer medium flowing into the heat transfer tube 12 is cooled.
[0023]
With this configuration, the evaluation apparatus calculates the heat transfer coefficient as the heat transfer characteristic inside the heat transfer tube 12 during cooling. In addition, although the method for cooling the heat transfer medium flowing in the heat transfer tube is different between the actual refrigerator internal evaporator and the evaluation device, both are related to the outside of the heat transfer tube, and the heat transfer tube discussed in the present invention There is no effect on the heat transfer characteristics (heat transfer coefficient) of the heat transfer medium flowing inside.
(Comparative Example 1)
A smooth copper tube having a tube inner diameter of 14 mm was used as the heat transfer tube of the evaluation device described above. This heat transfer coefficient was measured using clean water as a heat transfer medium.
Example 1
As the heat transfer tube of the above-described evaluation apparatus, an acrylic resin cylindrical packing having an outer diameter of 13.9 mm and an inner diameter of 10 mm is inserted into only 1% of the upstream portion of the pipe along the inner central axis of a smooth copper tube having an inner diameter of 14 mm. And fixed one was used.
[0024]
A cross-sectional view of the heat transfer tube 12 is shown in FIG. FIG. 4 shows a longitudinal sectional view (longitudinal sectional view) of the upstream portion of the heat transfer tube 12. 3 and 4, reference numeral 13 denotes a cylindrical packing.
[0025]
This heat transfer tube is installed in the apparatus, and 500 ppm of oleylbishydroxyethylmethylammonium chloride and 300 ppm of sodium salicylate are added to water as a heat transfer medium, and a surfactant aqueous solution consisting of salicylate of oleylbishydroxyethylmethylammonium salt ( This heat transfer coefficient was measured using OBHE.
(Comparative Example 2)
In Example 1, the heat transfer coefficient of the heat transfer medium was measured under the same conditions except that the cylindrical packing was not used.
(Example 2)
In Example 1, a surfactant aqueous solution consisting of salicylate of oleyl trihydroxyethylammonium (abbreviated as OTHE) was added as a heat transfer medium by adding 500 ppm of oleyltrihydroxyethylammonium chloride and 275 ppm of sodium salicylate to clean water. The heat transfer coefficient of the heat transfer medium was measured under the same conditions except for use.
(Comparative Example 3)
In Example 2, the heat transfer coefficient of the heat transfer medium was measured under the same conditions except that the cylindrical packing was not used.
[0026]
FIG. 5 shows the heat transfer coefficients of the clean water and the surfactant aqueous solution in each heat transfer tube thus obtained.
[0027]
As can be seen from FIG. 5, the heat transfer coefficient of the surfactant aqueous solution is the same as that of clean water at the same flow rate in the heat transfer tube in which the cylindrical packing is not inserted in the flow rate range of 1 to 2 m / s in the actual machine. It is more reduced. However, in the heat transfer tube in which the cylindrical packing is inserted, the heat transfer coefficient of the surfactant aqueous solution is almost the same as that of clean water measured using the heat transfer tube in which the cylindrical packing is not inserted. In other words, it has been found that even if an aqueous surfactant solution is used, the heat transfer characteristics can be prevented from deteriorating with respect to the clean water in the rod-like filled heat transfer tube.
[0028]
【The invention's effect】
According to the heat transfer tube of the present invention, when the viscoelastic surfactant aqueous solution is used as the heat transfer medium, the conventional water-based heat transfer medium is used while the area of the heat transfer portion of the heat exchanger is the same as the conventional type. Compared to the case, the heat transfer characteristics in the heat exchanger section do not deteriorate.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a shell-and-tube heat exchanger.
FIG. 2 is a diagram showing a configuration of an evaluation apparatus for evaluating heat transfer characteristics of a heat transfer tube.
FIG. 3 is a cross-sectional view showing an example of a heat transfer tube of the present invention.
FIG. 4 is a longitudinal sectional view (longitudinal sectional view) showing an example of the heat transfer tube of the present invention.
FIG. 5 is a graph showing heat transfer coefficients in Examples and Comparative Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Heat exchanger 11 ... Shell 12 ... Heat transfer tube 13 ... Cylindrical filling 21 ... Medium tank 22 ... Pumps 23, 24, 25 ... Pipe 26 ... Heat transfer characteristic measuring unit 27 ... circular pipe

Claims (3)

A heat exchanger tube of a heat exchanger that uses a surfactant aqueous solution as a heat carrier medium,
In a heat transfer tube in which a cylindrical packing that is in close contact with the inner surface of the tube is inserted into a part of the upstream portion of the heat transfer tube along a central axis inside the tube in which the heat transfer medium flows , an inner surface cavity of the cylindrical packing The cross-sectional shape of the portion is circular, the cross-sectional area of the inner cavity of the cylindrical packing is 18 to 75% of the cross-sectional area inside the heat transfer tube, and the length of the cylindrical packing is the length of the heat transfer tube Heat transfer tube that is 0.7-2% of the total length .   A heat transfer system that uses an aqueous surfactant solution as a heat transfer medium, a heat supply side plant that supplies heat to the heat transfer medium, a heat use side plant that uses heat of the heat transfer medium, and the heat supply A heat transfer medium according to claim 1, wherein at least one of the heat supply side plant and the heat use side plant includes a pipe that circulates the heat transfer medium between the side plant and the heat use side plant. Heat transfer system with heat exchanger.   The heat transfer system according to claim 2, wherein the surfactant according to claim 2 is a mixture of oleyl trihydroxyethylammonium salt and salicylate.

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