JP2020016393A - Heat exchanger - Google Patents

Abstract

To provide a heat exchanger capable of being more easily manufactured than the prior art and high in heat exchange efficiency.SOLUTION: A heat exchanger according to the present invention has a pipe that is wound in coil form around a central shaft. In regard to pipe parts adjacent to each other in an axial direction of the central shaft, radii of curvature are different from each other, and images projected on a surface perpendicular to the central shaft overlap each other. In a preferable embodiment, the radius of curvature of the pipe part is increased or decreased along the axial direction of the central shaft, or alternately increased or decreased. In a more preferable embodiment, the pipe part is at least partially made as a metallic corrugated pipe.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat exchanger that performs heat exchange between two types of fluids having different temperatures.

  A heat exchanger for exchanging heat between a first fluid flowing inside a coiled tube and a second fluid flowing outside the tube and having a different temperature from the first fluid is known. Have been. For example, Patent Document 1 filed by the applicant earlier describes an invention of a heat exchanger in which a metal corrugate tube is wound in a coil shape.

  When heat is exchanged between the first fluid and the second fluid using the heat exchanger described in Patent Document 1, the second fluid is parallel to the central axis of the coiled tube. Since the fluid flows, the fluid flowing at a position close to the center axis of the coil among the second fluids does not come into contact with the pipe, and hardly contributes to heat exchange. Therefore, a heat exchanger devised so that a fluid flowing at a position close to the center axis of the coil of the second fluid can be brought into contact with the pipe has been conventionally known.

  For example, Patent Literature 2 discloses a heat exchanger in which a refrigerant pipe is bent in a spiral shape and formed in a conical shape. In this heat exchanger, the refrigerant pipes are arranged at intervals so that they do not overlap one another. For this reason, since the refrigerant pipe does not interfere with the hot air flow during cooling or the cold air flow during heating between the upper and lower portions, the efficiency of heat exchange is improved.

  Further, for example, Patent Document 3 discloses a heat transfer tube for an exhaust heat recovery system including a plurality of conical spiral heat transfer portions. In this heat transfer tube, the exhaust gas is discharged so as to diffuse from the outer periphery of the small diameter portion toward the inner peripheral surface of the flue. Therefore, the exhaust gas can be more uniformly diffused to the inner peripheral surface and the outer peripheral surface of the heat transfer section, and the efficiency of heat recovery is improved.

JP, 2017-44416, A Japanese Utility Model Publication No. 58-124762 Registered Utility Model No. 3176771

  A metal, an alloy, a resin, or the like can be used as a material forming the pipe through which the first fluid flows. Some materials that make up the tube do not allow the minimum radius of curvature of the tube to be too small. In the case where a tube made of such a material is used, there is a possibility that the tube may be damaged if the tube is processed into a shape described in Patent Document 2 or Patent Document 3.

  Also, when processing a pipe into a shape as described in Patent Literature 2 or Patent Literature 3, depending on the material, it is necessary to bend the pipe strongly even if the pipe is not damaged, so it takes time to process. In addition, it is necessary to maintain and fix the pipe in a strongly bent state, which causes a problem that the manufacturing cost increases.

  The present invention has been made in consideration of the problems of the above-described conventional technology, and has as its object to provide a heat exchanger that can be easily manufactured and has high heat exchange efficiency.

  The heat exchanger according to the present invention is a heat exchanger having tubes that are wound in a coil shape around a central axis, and for tubes adjacent to each other in the axial direction of the central axis, the radii of curvature are different, and , The images projected on the plane perpendicular to the central axis overlap.

  For this reason, the change in the radius of curvature of the tube is smaller than that of the heat exchanger according to the prior art, and there is no need to bend and process the tube strongly, so that the production is easy. In addition, since the fluid flowing at a position close to the center axis of the coil among the second fluids is more likely to come into contact with the pipe, heat exchange between the first fluid and the second fluid can be performed efficiently. .

  In a preferred embodiment of the invention, the tube is a metal corrugated tube. The metal corrugated tube has irregularities on its surface. Therefore, the first fluid and the second fluid flowing near the surface of the tube become turbulent, and the efficiency of heat exchange is improved. Further, since the heat exchanger according to the present invention does not need to bend the tube strongly, there is little possibility that the metal corrugated tube is damaged by the bending process.

  According to the heat exchanger according to the present invention, the second fluid flowing near the center axis of the coil is brought into contact with the tube without strongly bending the tube, thereby improving the heat exchange efficiency without increasing the manufacturing cost. Can be done. Further, the efficiency of heat exchange can be further increased by using a metal corrugated tube as the tube.

It is a perspective view showing the heat exchanger concerning a 1st embodiment of the present invention. It is a perspective view showing other examples of the heat exchanger concerning a 1st embodiment of the present invention. It is a perspective view showing the heat exchanger concerning a 2nd embodiment of the present invention. It is a perspective view which shows the heat exchanger which concerns on a prior art.

  An embodiment for carrying out the present invention will be described in detail below with reference to the drawings and tables. Note that the embodiment described here is merely an example, and the embodiment of the present invention is not limited to the embodiment described here.

<Basic configuration of heat exchanger>
The present invention is an invention of a heat exchanger 1 having a tube P wound in a coil shape around a central axis. In the heat exchanger 1 according to the present invention, between the first fluid flowing inside the pipe P and the second fluid flowing outside the pipe P and having a different temperature from the first fluid, Heat exchange takes place through the P wall. The first fluid and the second fluid may both be liquid or gas, or one of them may be liquid and the other may be gas. In the heat exchanger 1 according to the present invention, the flow directions of the first fluid and the second fluid may be the same direction, or may be opposite directions. The temperature of the first fluid and the second fluid supplied to the heat exchanger 1 may be constant or may change.

  In the heat exchanger 1 according to the present invention, the flow path through which the second fluid flows is a space having an area where the pipe P wound in a coil shape can be installed. The cross-sectional area of the flow path through which the second fluid flows is larger than the cross-sectional area inside the pipe through which the first fluid flows. Therefore, as a preferable use of the heat exchanger 1 according to the present invention, it is conceivable to heat or cool the first fluid by using heat of the second fluid. However, it is also possible to use the heat exchanger 1 according to the present invention to heat and cool the second fluid using the heat of the first fluid, contrary to the above.

  In the heat exchanger 1 according to the present invention, the pipe P is wound in a coil shape around a central axis. The coil shape refers to a three-dimensional helical shape or a helical shape, and as described later in detail, the distance from the central axis to the tube P may not be constant but may vary. Further, it is preferable that the direction in which the pipe P is wound in a coil shape around the central axis be a constant direction in the entire heat exchanger in both the circumferential direction and the axial direction in view of facilitating manufacture. The heat exchanger 1 may have one pipe P or two or more pipes. From the viewpoint of facilitating production, it is preferable that the tube is constituted by one tube.

  In the heat exchanger 1 according to the present invention, the radii of curvature of the pipes P adjacent to each other in the axial direction of the central axis are different. The portions of the tubes P that are adjacent to each other in the axial direction of the central axis refer to a portion of the tube P wound in a coil shape and a portion of the tube P that is different in position by one turn in the axial direction. Since the radius of curvature of the pipe P is different between these adjacent portions, the diameter of the coil is different. When the radius of curvature changes in a direction to decrease, the position of the pipe P approaches the central axis. If the radius of curvature changes in the direction of increasing, the position of the pipe P moves away from the central axis. This makes it possible to effectively use both the fluid flowing at a position close to the central axis and the fluid flowing at a position distant from the central axis in the second fluid, so that the efficiency of heat exchange is improved.

  In the heat exchanger 1 according to the present invention, the difference in the radius of curvature between the portions of the tubes P adjacent to each other in the axial direction of the central axis means that the radius of curvature is not constant over the entire tube P wound in a coil shape. Say. When the radius of curvature is constant over the entire tube P wound in a coil shape, that is, when the diameter of the coil is constant and the distance from the central axis to the tube P is constant, all of the second fluid is removed. It cannot be used effectively. Even if there is a pair of pipes P having the same radius of curvature in a part of the pipe P wound in a coil shape, the axis of the central axis is used in other parts except the part. If the radii of curvature of the pipes P adjacent to each other in the directions are different, the effect of the present invention can be obtained. Therefore, the embodiment of the present invention does not completely exclude the existence of a portion where the radius of curvature of adjacent pipes P is the same.

  In the heat exchanger 1 according to the present invention, for the portions of the pipes P adjacent to each other in the axial direction of the central axis, the images projected on the plane perpendicular to the central axis overlap. The projected image is an image in which a shadow formed when a parallel ray parallel to the central axis is applied to the tube P is projected on a plane perpendicular to the central axis. In the present invention, a projected image of one portion of the tube P and a projected image of another portion of the tube P adjacent thereto overlap in a plane perpendicular to the central axis. In other words, for adjacent pipes P, the change in the radius of curvature does not exceed the outer diameter of the pipes P.

  When only the efficiency of heat exchange is emphasized, it is preferable to arrange the projected images so as not to overlap each other, for example, as in a refrigerant pipe described in Patent Document 2. However, for portions of the pipes P adjacent to each other in the axial direction of the central axis so that the images projected on the plane perpendicular to the central axis do not overlap, the pipe P is strongly bent and the radius of curvature is reduced. It must be extremely changed to exceed the outer diameter of P. Then, problems such as breakage of the pipe P and time required for processing the pipe P occur. In the heat exchanger 1 according to the present invention, the pipe P is wound in a coil shape by causing a gradual change in the radius of curvature such that the images projected on the plane perpendicular to the central axis are overlapped. Can be solved.

  In the present invention, it is preferable that the overlapping of the images projected on the plane perpendicular to the central axis is realized in the entire circumferential direction of the tube P wound in a coil shape. If there is a portion where the projected images do not overlap even in a part of the pipe P in the circumferential direction, the portion will be strongly processed, and the above-described manufacturing problem will occur.

  In the present invention, the degree of overlapping of images projected on a plane perpendicular to the central axis is not particularly limited. When the ratio of the area of the overlapping portion in the projected image is 10% or more, the change in the radius of curvature is small, so that it is not necessary to bend the pipe P too strongly. Risks such as time-consuming processing can be more reliably reduced. When the ratio of the area of the overlapping portion is 90% or less, since the change in the radius of curvature is not zero, the length measured in the axial direction of the central axis of the tube P wound in a coil shape does not need to be too long. Since the position of the pipe P can be moved closer to or away from the central axis, the length of the heat exchanger 1 can be made more compact. Therefore, in the present invention, the proportion of the area of the overlapping portion in the projected image is preferably 10% or more and 90% or less. A more preferable range of the ratio of the area of the overlapping portion is 20% or more and 80% or less.

  In a preferred embodiment of the present invention, the radius of curvature of the portions of the pipes P adjacent to each other in the axial direction of the central axis is equal to or larger than the minimum radius of curvature of the pipe. The minimum radius of curvature of the pipe P refers to the minimum radius of curvature that cannot be bent further without breaking the pipe P. The minimum radius of curvature of the pipe P is an amount determined by the mechanical properties of the material constituting the pipe P, the dimensions of the pipe P, the processing history of the pipe P, and other conditions. If it is desired to effectively use the second fluid in the heat exchanger 1, the pipe P may be strongly bent to partially reduce the diameter of the coil so that the pipe P approaches the center axis of the coil as much as possible. Conceivable. However, depending on the material and shape of the pipe P, when strong bending is performed, the pipe P may be easily damaged, or it may take time to bend the pipe P. Therefore, it is preferable that the radius of curvature of the pipe P does not fall below the minimum radius of curvature in the entire heat exchanger.

<First embodiment>
In a preferred embodiment of the invention, the radius of curvature of the section of the tube P increases or decreases along the axis of the central axis. FIG. 1 is a perspective view showing an example of a heat exchanger 1 according to the first embodiment of the present invention. In this embodiment, the radius of curvature of the portion of the tube P wound in a coil shape is the minimum at the minimum radius of curvature S located at both ends and the maximum at the maximum radius of curvature L located at the center. That is, the radius of curvature of the portion of the pipe P initially increases along the axial direction of the central axis, and decreases when the radius exceeds the central portion. In the center, the change in the radius of curvature is small, and there is a pair of pipes P having the same radius of curvature. In other portions, the pipe P approaches or moves away from the central axis, so that the second fluid can be effectively used. The second fluid flowing at a position far from the central axis of the heat exchanger 1 shown in FIG. 1 flows through the gap between the coils to a position near the central axis, and then flows out again to a position far from the central axis. Thereby, the second fluid is stirred by the heat exchanger 1, so that the efficiency of heat exchange is improved. Further, since the shape of the heat exchanger 1 is symmetric in the axial direction, it is not necessary to select the installation direction with respect to the direction in which the second fluid flows.

  FIG. 2 is a perspective view showing another example of the heat exchanger 1 according to the first embodiment of the present invention. In this embodiment, the radius of curvature of the portion of the tube P wound in a coil shape is maximum at the maximum radius of curvature L located at the upper end, and then decreases to the minimum value at the minimum radius of curvature S, and then again. It starts to increase and then starts to decrease again after passing through the maximum value at the maximum radius of curvature L located below, and the radius of curvature at the lower end is an intermediate value between the maximum value and the minimum value. At the minimum radius of curvature S and the maximum radius of curvature L, there is a pair of pipes P having the same radius of curvature. In other portions, the pipe P approaches or moves away from the central axis, so that the second fluid can be effectively used. Further, as in the case of the heat exchanger 1 shown in FIG. 1, the second fluid is stirred by flowing out from a position close to the center axis of the coil to a position far from the center axis, or by repeating the reverse movement. Therefore, the efficiency of heat exchange is improved. Further, since the diameter of the coil is maximum at two places, the heat exchanger can be stably fixed to the flow path of the second fluid.

<Second embodiment>
In a preferred embodiment of the invention, the radius of curvature of the portion of the tube P alternates between increasing and decreasing along the axial direction of the central axis. FIG. 3 is a perspective view illustrating an example of the heat exchanger 1 according to the second embodiment of the present invention. In this embodiment, a portion l of a large radius of curvature and a small portion s of a portion of a tube P wound in a coil shape are provided alternately. The respective radii of curvature in the large radius l and the small radius s are the same throughout the heat exchanger. In this embodiment, since there are only two types of large and small radii of curvature, manufacturing is easy. Note that the second embodiment is not limited to the embodiment shown in FIG. 3, and the radius of curvature of the pipe P may be increased or decreased alternately along the axial direction of the central axis. It is not always necessary to limit the size to two types, large and small. Even in this case, a portion having a large diameter of the coil can be provided at an arbitrary position, so that the heat exchanger can be stably fixed to the flow path of the second fluid.

<Tube shape>
The pipe P constituting the heat exchanger 1 according to the present invention allows the first fluid to flow therein, and any pipe having thermal conductivity can be used. Since it is necessary to wind the coil around the central axis, it is preferable that the tube be capable of being bent with a small force and is not easily damaged by bending. As a material forming the tube P, for example, a metal, an alloy, a resin, or the like can be used. Specifically, it can be made of a material such as copper, steel, stainless steel, or polyethylene. The diameter and thickness of the pipe P can be appropriately designed according to the material and the flow rate of the first fluid flowing inside. The diameter and wall thickness of the tube P may be constant over the entire tube, or may vary from part to part. With respect to the inner diameter and the outer diameter of the pipe P or both of them, a coating for the purpose of corrosion prevention or the like may be applied to the surface.

  In a preferred embodiment of the present invention, at least a part of the pipe P is a metal corrugated pipe. The metal corrugated pipe is a pipe formed by applying a stepping process to a pipe made of a thin metal plate to provide unevenness in a longitudinal direction, and has an advantage that bending can be performed extremely easily. When a metal corrugated pipe is used for the pipe P constituting the present invention, since a step is provided perpendicular to the flow direction of the first fluid flowing through the pipe P, a turbulent flow is generated near the inner wall of the pipe P. This has the effect of improving the efficiency of heat exchange with the second fluid. The metal constituting the corrugated tube is preferably copper, copper alloy, stainless steel or the like.

  In a preferred embodiment of the present invention, the pipe P constituting the heat exchanger 1 is formed by using, for example, a frame 2 having an upper plate 21, a lower plate 22, and a column 23, as in the comparative example shown in FIG. It is fixed to the flow path of the second fluid. A pipe for supplying or discharging the first fluid is connected to both ends of the pipe P. The pipe P and the pipe can be directly connected using welding or the like. Further, the connection can be made indirectly using a pipe joint.

<How to use the heat exchanger>
In the heat exchanger 1 according to the present invention, the efficiency of heat exchange is improved by effectively utilizing both the fluid flowing at a position near the central axis and the fluid flowing at a position far from the central axis among the second fluids. I do. That is, the heat exchanger 1 according to the present invention is basically configured on the assumption that the second fluid flows in the axial direction of the central axis. Specific installation locations include, for example, wells from which groundwater spouts and rivers through which river water flows. Above all, groundwater that springs out from a depth exceeding 10 m is suitable as a second fluid used for heat exchange because it maintains a temperature of about 15 ° C. throughout the year. Since the heat exchanger 1 according to the present invention can be configured to have a small coil size and a compact size, the heat exchanger 1 can be easily installed in a small well having an outer diameter of about 300 mm in the vertical direction, for example. On the other hand, when installed in a river, for example, it can be installed horizontally in the riverbed such that the central axis matches the direction of the flow of the river water.

<Reference example>
In order to compare the heat exchange efficiency of the heat exchanger according to the present invention with that of the prior art, the temperature was analyzed by computer simulation. The shape of the heat exchanger was the shape illustrated in FIG. The flow path through which the second fluid flows had a cylindrical shape with a diameter of 300 mm. The heat exchanger installed in the flow path was constituted by a tube having an inner diameter of 15 mm and a length of 14.5 m, and the diameter of the coil was 250 mm at the maximum and 100 mm at the minimum. In the heat exchanger of the comparative example, the diameter of the coil was constant and 250 mm. The distance between adjacent pipe portions, that is, the pitch, was 60 mm as the distance between the centers of the pipes. In both the reference example and the comparative example, the second fluid was water having a temperature of 21.0 ° C. and a flow rate of 1.4 m per minute. The first fluid was water having an inlet temperature of 23.0 ° C. and a flow rate of 50 m / min, and the flow direction of the first fluid was the same as that of the second fluid. In the simulation, the temperature when the temperature on the outlet side of the first fluid gradually decreased and became stable was measured, and the temperature difference between the inlet side and the outlet side of the first fluid was determined by comparing the temperature difference between the first fluid and the second fluid. The percentage of the value divided by the temperature difference of the fluid was determined as the efficiency of heat exchange. Further, the temperature distribution of each portion when the temperature was stabilized was displayed in color. The results of temperature measurement by simulation are shown in Reference Example 1 and Comparative Example 1 in Table 1.

  According to the simulation results shown in Table 1, the heat exchange efficiency of Reference Example 1 was improved as compared with the conventional technique shown in Comparative Example 1. In order to consider the cause, when observing the temperature distribution indicated by color, in the heat exchanger of Comparative Example 1, the second fluid flowing at a position far from the central axis and heated by the upstream pipe was By contacting the downstream tube at the same position, the temperature difference between the first fluid and the second fluid is reduced, while the temperature of the second fluid flowing near the center axis is hardly changed, It was recognized that the efficiency of heat exchange was not good as a whole. On the other hand, in the heat exchanger according to the present invention, since the heat exchange between the first fluid and the second fluid is performed with a wider cross-sectional area than the heat exchanger of the comparative example, the heat exchange efficiency is improved. Was admitted.

  Next, analysis was performed using the same model as in Reference Example 1 and Comparative Example 1 for the purpose of estimating the influence of the flowing direction of the fluid when the temperature difference between the first fluid and the second fluid was enlarged. Was. That is, the temperature of the first fluid is set to 25.0 ° C., the temperature of the second fluid is set to 15.0 ° C. assuming self-injecting groundwater, and the flow direction of the second fluid is the same as or opposite to that of the first fluid. The simulation was performed under the same conditions as in Table 1 except that the direction was changed. The results of temperature measurement by simulation are shown in Reference Example 2, Reference Example 3, and Comparative Example 2 in Table 1.

  According to the simulation results shown in Table 1, the heat exchange efficiencies in Reference Example 2 and Comparative Example 2 in which the temperature difference between the first fluid and the second fluid was increased were higher than those in Reference Example 1 and Comparative Example 1, respectively. It was not different from the result. On the other hand, in the case of Reference Example 3 in which the flowing direction of the fluid was reversed, the heat exchange efficiency was slightly higher than the results of Reference Examples 1 and 2. This is considered to be because in the reverse direction, the temperature of the second fluid does not increase so much because the first fluid that the second fluid contacts first has already been cooled upstream.

  Next, in order to estimate the thermal efficiency when the flow rate of the second fluid was increased from 1.4 m / min to 60 m / min, analysis was performed using the same model as Reference Example 1 and Comparative Example 1. That is, the simulation was performed under the same conditions as above except that the flow rate of the second fluid was set to 60 m per minute. The results of temperature measurement by simulation are shown in Reference Example 4 and Comparative Example 3 in Table 1.

  According to the simulation results shown in Table 1, even when the flow rate of the second fluid was greatly increased, the heat exchange efficiency was significantly different between Reference Example 4 according to the present invention and Comparative Example 3 according to the related art. It was noted that there was a difference.

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Frame 21 Upper plate 22 Lower plate 23 Prop P pipe L Maximum radius of curvature S Minimum radius of curvature l Part with large radius of curvature s Part with small radius of curvature

Claims (6)

A heat exchanger having a coiled tube around a central axis,
A heat exchanger in which tubes adjacent to each other in the axial direction of the central axis have different radii of curvature and images projected on a plane perpendicular to the central axis overlap. 2. The heat exchanger according to claim 1, wherein a ratio of an area of a portion of the tube where an image projected on a plane perpendicular to a central axis overlaps is 10% or more and 90% or less. The heat exchanger according to claim 1 or 2, wherein a radius of curvature of the portion of the tube increases or decreases along an axial direction of a central axis. The heat exchanger according to claim 1, wherein a radius of curvature of the tube portion increases and decreases alternately along an axial direction of a central axis. 5. The heat exchanger according to claim 1, wherein the radius of curvature of the portion of the tube is greater than or equal to the minimum radius of curvature of the tube. The heat exchanger according to any one of claims 1 to 5, wherein at least a part of the tube is a metal corrugated tube.