heat exchanger

Abstract

To provide a heat exchanger which may inhibit pressure fluctuation in a passage when used in a situation where fluctuation of a fluid pressure easily occurs.SOLUTION: A heat exchanger 100 includes: a first pipe 10; a second pipe 20 into which the first pipe 10 is inserted; and a third pipe 30 into which the first pipe 10 and the second pipe 20 are inserted. A first passage 41 is formed between the first pipe 10 and the second pipe 20 to allow a first fluid 1 to circulate therebetween, and a second passage 42 for allowing a second fluid 2 which conducts heat exchange with the first fluid 1 to circulate is formed between the second pipe 20 and the third pipe 30. The first pipe 10 includes: a passage 11 which communicates with the second pipe 20 at both ends; and a pressure fluctuation suppression part 12 which limits circulation of the first fluid 1 in the passage 11 and releases a pressure fluctuated in the first passage 41 from an end of the passage 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a heat exchanger, and particularly to a multi-tube heat exchanger.

Background Art

[0002] Conventionally, a multi-tube heat exchanger has been known (see, for example, Patent Document 1).

[0003] In the above Patent Document 1, a double-tube heat exchanger is disclosed, which includes an outer tube, an inner tube, and a masking tube provided inside the inner tube. A first flow path is formed between the outer tube and the inner tube, and a second flow path is formed between the inner tube and the masking tube. Both ends of the masking tube are closed, and the inside of the masking tube is filled with a heat insulating material. One end of the second flow path and one end of the first flow path are connected to a catalyst section. A raw material gas is supplied into the second flow path from a supply section connected to the other end of the second flow path. The raw material gas is supplied from the second flow path to the catalyst section. The raw material gas is reformed by a catalytic reaction, and the reformed gas is supplied from the catalyst section to the first flow path. The reformed gas is discharged from a discharge section connected to the other end of the first flow path. Heat exchange is performed between the raw material gas flowing through the second flow path and the reformed gas flowing through the first flow path.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The double-tube heat exchanger described in Patent Document 1 above is used as a heat exchanger for gas reforming. However, when such a heat exchanger is used in applications where fluid pressure fluctuations are likely to occur, the heat exchange performance may become unstable due to pressure fluctuations in the flow path, or repeated stress caused by the pressure fluctuations may occur, negatively affecting the durability (long-term reliability) of the heat exchanger. Therefore, when using such a heat exchanger in applications where fluid pressure fluctuations are likely to occur, it is desirable to suppress pressure fluctuations in the flow path.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a heat exchanger that can suppress pressure fluctuations within the flow path, even when used in applications where fluid pressure fluctuations are likely to occur. [Means for solving the problem]

[0007] To achieve the above objective, the heat exchanger according to this invention comprises a first pipe, a second pipe into which the first pipe is inserted, and a third pipe into which both the first and second pipes are inserted, wherein a first flow path is formed between the first pipe and the second pipe for the circulation of a first fluid, and a second flow path is formed between the second pipe and the third pipe for the circulation of a second fluid that exchanges heat with the first fluid, and the first pipe includes a passage whose both ends are in communication with the second pipe, and a pressure fluctuation suppression section that restricts the flow of the first fluid in the passage and releases pressure fluctuations in the first flow path from the ends of the passage. The first fluid is a liquid that is vaporized by heat exchange with the second fluid, and the pressure fluctuation suppression section restricts the flow of the first fluid, causing the vaporized gas of the first fluid to accumulate in the passage, and includes holes that allow the vaporized gas to flow in response to pressure fluctuations in the first flow path. nothing.

[0008] In this invention, "restricting the flow of the first fluid in the passage" is a broad concept that includes not only restricting the flow of the first fluid so that it does not flow when there are no pressure fluctuations, but also restricting the flow in the passage so that the first fluid flows at a flow rate that is sufficiently small compared to the flow rate of the first fluid in the first flow path (increasing the flow resistance).

[0009] In the heat exchanger according to this invention, the first pipe includes passages that communicate with the second pipe at both ends, so that the first flow path and the passage within the first pipe are provided in parallel between one end and the other end of the second pipe. Here, the first pipe includes a pressure fluctuation suppression section that restricts the flow of the first fluid within the passage. The first fluid is a liquid that is vaporized by heat exchange with the second fluid, and the pressure fluctuation suppression section restricts the flow of the first fluid, causing the vaporized gas of the first fluid to accumulate in the passage, and includes holes that allow the vaporized gas to flow in response to pressure fluctuations in the first flow path. Therefore, even when a passage is provided within the first pipe, the first fluid is actively directed to flow through the first flow path rather than the passage, allowing heat exchange between the first fluid flowing through the first flow path and the second fluid flowing through the second flow path. Furthermore, since the pressure fluctuation suppression unit releases the pressure fluctuations in the first flow path from the end of the passage, when pressure fluctuations occur in the first flow path due to heat exchange, the passage within the first pipe acts as a bypass path for releasing the pressure, reducing the pressure difference between one end and the other end of the second pipe. As a result, pressure fluctuations within the flow path can be suppressed even when used in applications where fluid pressure fluctuations are likely to occur.

[0010] Heat exchanger according to the above invention So As the liquid first fluid boils and vaporizes within the first channel, the pressure within the first channel fluctuates according to the boiling conditions. Even in such cases, the pressure fluctuation suppression unit restricts the flow of the first fluid, causing the vaporized gas of the first fluid to accumulate in the passage. By allowing the vaporized gas to flow in accordance with the pressure fluctuations within the first channel, pressure fluctuations can be suppressed by allowing the vaporized gas to pass through the passage in accordance with the pressure changes on the first channel side. As a result, even in an unstable boiling state, instability in heat exchange performance can be suppressed, and the generation of repeated stress (pulsation) caused by pressure fluctuations can be effectively suppressed.

[0011] In the heat exchanger according to the above invention, preferably, the pressure fluctuation suppression section has a throttling member provided in the passage. With this configuration, by narrowing the inner diameter of the passage with the throttling member, the flow resistance of the passage can be made sufficiently higher than the flow resistance of the first passage. As a result, a pressure fluctuation suppression section can be realized with a simple structure in which the first fluid flows in and out of the passage in a state where almost no first fluid flows into the passage (a state where it flows substantially only on the first passage side), and in an amount that eliminates the pressure difference when a pressure difference occurs at both ends.

[0012] In the heat exchanger according to the above invention, preferably, one end of the passage is open into the second pipe, and the pressure fluctuation suppression section is provided so as to cover the other end of the passage. With this configuration, unlike a configuration in which the pressure fluctuation suppression section is placed inside the first pipe, for example, the pressure fluctuation suppression section can be easily provided.

[0013] In a configuration where the first fluid is a liquid that is vaporized by heat exchange with the second fluid, preferably, the first, second, and third pipes are provided to extend vertically, with an inlet for the first fluid at the lower end of the second pipe, an outlet for the vaporized gas at the upper end of the second pipe, and a pressure fluctuation suppression section at the upper end of the first pipe. With this configuration, the first fluid introduced from the inlet at the lower end is vaporized as it flows upward, and the vaporized gas of the first fluid flows out from the outlet at the upper end. Therefore, the difference in specific gravity can be used to move the vaporized gas of the first fluid upward, allowing the vaporized gas to flow smoothly. Furthermore, the lower end of the passage in the first pipe is in contact with the liquid of the first fluid, and the upper end of the passage is in contact with the vaporized gas of the first fluid. When a pressure fluctuation occurs, the liquid of the first fluid or the vaporized gas flows into the passage temporarily, thereby suppressing the pressure fluctuation between the inlet and the outlet.

[0014] In the heat exchanger according to the above invention, preferably, fins are further provided in the first flow path so as to abut against the outer surface of the first pipe and the inner surface of the second pipe, respectively, and the fins have portions where the materials of the first pipe and the second pipe and the fin are integrated at the abutment points with the first pipe and the second pipe, respectively. With this configuration, heat from the second fluid supplied from the outer side of the first flow path can be efficiently transferred by the fins to the inner side of the first flow path (outer surface of the first pipe). Furthermore, since the fins have portions where the materials of the first pipe and the second pipe and the fin are integrated at the abutment points with the first pipe and the second pipe, the contact area between the fin and the first pipe (second pipe) at the abutment points can be increased compared to the case where the surface of the fin and the surface of the first pipe (second pipe) are in contact without being integrated. The increased contact area reduces thermal resistance and improves heat exchange performance by making it easier to transfer heat. Therefore, the temperature difference between the outer surface of the first pipe and the inner surface of the second pipe can be reduced, and variations in the radial heat exchange performance of the first flow path can be reduced. [Effects of the Invention]

[0015] According to the present invention, as described above, it is possible to provide a heat exchanger that can suppress pressure fluctuations within the flow path, even when used in applications where fluid pressure fluctuations are likely to occur. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic longitudinal cross-sectional view showing the entire heat exchanger. [Figure 2] This is a schematic horizontal cross-sectional view of a heat exchanger. [Figure 3] This is a schematic enlarged cross-sectional view showing the pressure fluctuation suppression section. [Figure 4] This is a schematic diagram illustrating the structure of an offset fin. [Figure 5] This is a schematic diagram illustrating the flow of the first fluid through the offset fins. [Figure 6] This is a horizontal cross-sectional view showing an enlarged view of the contact area between the first and second tubes and the fins. [Figure 7] It is a schematic diagram for explaining the operation of the heat exchanger. [Figure 8] It is a schematic diagram for explaining the manufacturing method of the heat transfer tube. [Figure 9] It is a schematic diagram showing the pressure fluctuation suppression part according to the modification example. [Figure 10] It is a schematic diagram showing a modification example in which the pressure fluctuation suppression part is provided at the lower end of the first tube.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0018] First, referring to FIGS. 1 to 6, the heat exchanger 100 according to an embodiment will be described.

[0019] (Overall Configuration of the Heat Exchanger) As shown in FIG. 1, the heat exchanger 100 is a multi-tube type heat exchanger. The heat exchanger 100 of the present embodiment circulates the first fluid 1 and the second fluid 2 to exchange heat between the first fluid 1 and the second fluid 2. As an example, the first fluid 1 is a fluid at a lower temperature than the second fluid 2. The second fluid 2 is a fluid at a higher temperature than the first fluid 1. The first fluid 1 receives heat from the second fluid 2 by heat exchange. The second fluid 2 gives heat to the first fluid 1 by heat exchange.

[0020] Specifically, the heat exchanger 100 of the present embodiment is configured as a vaporizer for the first fluid 1. The first fluid 1 is a liquid that is vaporized by heat exchange with the second fluid 2. In the present embodiment, the first fluid​​​The heat exchanger 100 has an inlet 3a and an outlet 3b for the first fluid 1, and an inlet 4a and an outlet 4b for the second fluid 2. The first fluid 1 is introduced into the inlet 3a in a liquid state. As the first fluid 1 passes through the heat exchanger 100, it is vaporized and discharged from the outlet 3b in a gaseous state (referred to as vaporized gas). The second fluid 2 is introduced into the inlet 4a, releases heat as it passes through the heat exchanger 100, and is discharged from the outlet 4b in a liquid state at a temperature lower than the inlet temperature.

[0022] The heat exchanger 100 has a cylindrical shape that extends in a straight line overall. The heat exchanger 100 comprises a first pipe 10, a second pipe 20, and a third pipe 30. The first pipe 10 is inserted into the second pipe 20. The first pipe 10 and the second pipe 20 are inserted into the third pipe 30. The diameters increase in the order of the first pipe 10, the second pipe 20, and the third pipe 30. The first pipe 10, the second pipe 20, and the third pipe 30 are all cylindrical in shape. The heat exchanger 100 (i.e., the first pipe 10, the second pipe 20, and the third pipe 30) is installed to extend in the vertical direction.

[0023] (First and second pipes) A first flow path 41 is formed between the first pipe 10 and the second pipe 20 through which the first fluid 1 flows. Fins 50 are provided in the first flow path 41. A second flow path 42 is formed between the second pipe 20 and the third pipe 30 through which the second fluid 2, which exchanges heat with the first fluid 1, flows. The first flow path 41 and the second flow path 42 are separated so as not to communicate with each other. The second pipe 20 acts as a partition wall separating the first flow path 41 and the second flow path 42. The heat exchanger 100 has a structure in which an assembly for the flow of the first fluid 1, including the first pipe 10, the second pipe 20, and the fins 50, is placed inside the third pipe 30 through which the second fluid 2 flows. Hereinafter, the assembly of the first pipe 10, the second pipe 20, and the fins 50 will be referred to as the "heat transfer tube HT".

[0024] The first pipe 10 extends from near the inlet 3a to near the outlet 3b. The lower end 10b of the first pipe 10 faces the inlet 3a. The upper end 10a of the first pipe 10 faces the outlet 3b. The first pipe 10 is a single pipe member that extends continuously from the upper end 10a to the lower end 10b.

[0025] In this embodiment, the first pipe 10 includes a passage 11. The passage 11 is the internal space of the first pipe 10, partitioned by the inner circumferential surface 10d of the first pipe 10. The passage 11 extends continuously from the upper end 10a to the lower end 10b. Therefore, both ends of the passage 11 communicate with the inside of the second pipe 20.

[0026] The second pipe 20 extends vertically while housing the first pipe 10 inside. The second pipe 20 is a single pipe member that extends continuously from the upper end 20a to the lower end 20b. An inlet 3a for the first fluid 1 is provided at the lower end 20b of the second pipe 20, and an outlet 3b for vaporized gas is provided at the upper end 20a of the second pipe 20. The inlet 3a is a through hole formed in the lower end 20b. The outlet 3b is a through hole formed in the upper end 20a.

[0027] The first pipe 10 and the second pipe 20 are arranged so that their central axes coincide. As shown in Figure 2, the space between the outer surface 10c of the first pipe 10 and the inner surface 20d of the second pipe 20 is the first flow path 41. As shown in Figure 1, the first flow path 41 is a cylindrical space that extends vertically with a flow path height corresponding to the difference between the outer diameter D1 of the first pipe 10 and the inner diameter D2 of the second pipe 20.

[0028] The first flow path 41, which passes through the outer circumference of the first pipe 10, and the passage 11, which passes through the inside of the first pipe 10, are arranged in parallel between the inlet 3a and outlet 3b of the heat transfer tube HT. However, the flow rate of the first fluid 1 passing through the passage 11 is very small compared to the flow rate of the first fluid 1 flowing through the first flow path 41, so that the first fluid 1 hardly flows through the passage 11.

[0029] (Pressure fluctuation suppression unit) Specifically, as shown in Figure 3, the first pipe 10 includes a pressure fluctuation suppression section 12. The pressure fluctuation suppression section 12 is configured to restrict the flow of the first fluid 1 in the passage 11 and to release the pressure that has fluctuated in the first flow path 41 from the end of the passage 11.

[0030] The pressure fluctuation suppression section 12 is configured to restrict the flow of the first fluid 1, causing the vaporized gas of the first fluid 1 to accumulate in the passage 11. One end (lower end) of the passage 11 is open into the second pipe 20 (see Figure 1), and the pressure fluctuation suppression section 12 is provided to cover the other end (upper end) of the passage 11. In other words, the pressure fluctuation suppression section 12 is provided at the upper end 10a of the first pipe 10. Therefore, the upper end of the passage 11 of the first pipe 10 is connected to the outlet 3b side via the pressure fluctuation suppression section 12, and the lower end is an opening that is open to the inlet 3a. The pressure fluctuation suppression section 12 restricts the flow of the first fluid 1 in the passage 11 by covering the upper end of the passage 11.

[0031] More specifically, the pressure fluctuation suppression unit 12 has a throttling member 12a provided in the passage 11. In this embodiment, the throttling member 12a is a cover that closes the upper end 10a of the first pipe 10. The throttling member 12a has a disc shape, and its peripheral edge is joined to the upper end 10a of the first pipe 10. The throttling member 12a has a throttling hole 12b that penetrates the throttling member 12a in the thickness direction.

[0032] The diaphragm hole 12b has an opening area (see Figure 2) that is sufficiently smaller than the cross-sectional area of ​​the first flow path 41. Note that the cross-sectional area of ​​the flow path and the opening area are areas in a plane perpendicular to the direction in which the first flow path 41 extends (vertical direction). Also, the inner diameter of the diaphragm hole 12b is smaller than the inner diameter of the first pipe 10 (inner diameter of passage 11). For example, the inner diameter of the diaphragm hole 12b is 1 / 20 or less of the inner diameter of the first pipe 10.

[0033] As a result, the passage 11 has a significantly larger flow resistance than the first passage 41 because its flow path cross-sectional area is reduced at the throttling hole 12b. Therefore, the flow of the first fluid 1 in the passage 11 is restricted by the throttling hole 12b. The passage 11 is mostly filled with vaporized gas of the first fluid 1, and is never filled with liquid first fluid 1. Even when liquid first fluid 1 flows into the passage 11, it only flows to a small area near the lower end of the passage 11. The liquid first fluid 1 present near the lower end of the passage 11 vaporizes at a slower pace compared to the first passage 41 and flows out little by little towards the outlet 3b through the throttling hole 12b. As a result, the pressure fluctuation suppression unit 12 restricts the flow rate of the first fluid 1 in the passage 11 to a level that can be considered virtually nonexistent (negligible) compared to the flow rate in the first passage 41.

[0034] On the other hand, the pressure fluctuation suppression unit 12 is configured to circulate vaporized gas in response to pressure fluctuations in the first flow path 41. That is, at the upper end of the first pipe 10, the passage 11 below the throttling member 12a and the space near the outlet 3b above the throttling member 12a are in communication via a small throttling hole 12b. Therefore, when a pressure difference occurs between the upper and lower sides of the throttling member 12a, vaporized gas of the first fluid 1 circulates through the throttling hole 12b to reduce this pressure difference. As a result, pressure fluctuations caused by the unstable phenomenon of boiling of the first fluid 1 in the first flow path 41 are suppressed by the pressure fluctuation suppression unit 12.

[0035] (fin) As shown in Figure 1, the fin 50 is provided within a predetermined range in the first flow path 41. One end of the fin 50 (upper end 50a) is positioned in the vertical direction between the outlet 3b of the first fluid 1 and the outlet 4b of the second fluid 2. The other end of the fin 50 (lower end 50b) is positioned in the vertical direction between the inlet 3a of the first fluid 1 and the inlet 4a of the second fluid 2.

[0036] As shown in Figure 2, the fin 50 is formed of a corrugated fin. The fin 50 includes a plurality of vertical plate portions 51 extending radially between the first pipe 10 and the second pipe 20, and horizontal plate portions 52 connecting the ends of adjacent vertical plate portions 51 along the circumferential direction. The fin 50 is provided in the first flow path 41 so as to abut against the outer circumferential surface 10c of the first pipe 10 and the inner circumferential surface 20d of the second pipe 20, respectively. By connecting the first pipe 10 and the second pipe 20, the fin 50 transfers heat between the first pipe 10 and the second pipe 20 by heat conduction. The fin 50 has the function of increasing the heat transfer area (surface area) within the first flow path 41 by the plurality of vertical plate portions 51 that extend to partition the inside of the first flow path 41.

[0037] As shown in Figure 4, the fin 50 is an offset fin formed such that the position of the vertical plate portion 51 is shifted in the circumferential direction of the first flow path 41 (direction B in Figure 4) at predetermined length L intervals in the direction along the first flow path 41 (vertical direction, direction A in Figure 4). Note that Figure 4 is a perspective view showing a simplified version of the corrugated fin of Figure 2 unfolded on a plane. As shown in Figure 5, in the offset fin, at predetermined length L intervals in direction A along the flow path, another vertical plate portion 51 appears where there was a gap between the vertical plate portions 51. Therefore, the first fluid 1 is likely to collide with the vertical plate portions 51 of the fin 50, generating turbulence.

[0038] Furthermore, in this embodiment, the fin 50 has portions where the materials of the first pipe 10 and the second pipe 20 and the fin 50 are integrated at the contact portion CP with the first pipe 10 and the contact portion CP with the second pipe 20. As shown in Figure 6, the fin 50 has an inner circumferential horizontal plate portion 52 that contacts the outer circumferential surface 10c of the first pipe 10, and the contact portion between this horizontal plate portion 52 and the outer circumferential surface 10c is the contact portion CP. Similarly, the fin 50 has an outer circumferential horizontal plate portion 52 that contacts the inner circumferential surface 20d of the second pipe 20, and the contact portion between this horizontal plate portion 52 and the inner circumferential surface 20d is the contact portion CP.

[0039] Here, the heat transfer tube HT is manufactured by heat treatment with fins 50 pressed between the outer surface 10c of the first tube 10 and the inner surface 20d of the second tube 20. As a result of the heat treatment, atomic diffusion occurs in at least a portion of each contact area CP, and the materials become integrated as shown in Figure 6. In Figure 2, for convenience, the boundaries between the first tube 10, the second tube 20 and the fins 50 are clearly shown. Note that the first tube 10, the second tube 20 and the fins 50 are made of the same material. Specifically, the first tube 10, the second tube 20 and the fins 50 are all made of stainless steel.

[0040] (3rd tube) Returning to Figure 1, the third pipe 30 has an inner diameter larger than the outer diameters of the first pipe 10 and the second pipe 20. The inner diameter D3 of the third pipe 30 is, for example, about twice the outer diameter of the second pipe 20 in the example of Figure 1. The upper end 30a and the lower end 30b of the third pipe 30 are closed. The third pipe 30 is provided with an inlet pipe 31 connected from the side near the lower end 30b of the third pipe 30, and an outlet pipe 32 connected from the side near the upper end 30a of the third pipe 30. The inlet pipe 31 has an inlet 4a for the second fluid 2. The outlet pipe 32 has an outlet 4b for the second fluid 2.

[0041] The introduction pipe 31 is connected to the third pipe 30 so as to face the outer surface of the heat transfer tube HT near the inlet 3a. As a result, the introduction pipe 31 causes the second fluid 2, which is at its highest temperature immediately after flowing from the introduction pipe 31 into the third pipe 30, to collide with the portion of the heat transfer tube HT near the inlet 3a, which is prone to being at its lowest temperature. Consequently, the heat transfer coefficient near the inlet 3a of the heat transfer tube HT becomes locally higher compared to other parts of the heat transfer tube HT, and the surface temperature of the second pipe 20 becomes locally higher, thereby suppressing the freezing of the second fluid 2 near the inlet 3a.

[0042] The outlet pipe 32 is configured to discharge the second fluid 2, which has released heat through the second flow path 42 between the third pipe 30 and the second pipe 20, from the outlet section 4b.

[0043] The upper end 30a and lower end 30b of the third pipe 30 are provided so that a heat transfer tube HT passes through them, and the outer surface of the heat transfer tube HT is fixed to the upper end 30a and lower end 30b. The third pipe 30 and the heat transfer tube HT (first pipe 10 and second pipe 20) are provided so that their central axes coincide. The space between the outer surface 20c of the second pipe 20 and the inner surface 30d of the third pipe 30 is the second flow path 42. The second flow path 42 is a cylindrical space that extends vertically with a flow path height corresponding to the difference between the outer diameter of the second pipe 20 and the inner diameter D3 of the third pipe 30. In this embodiment, unlike the first flow path 41, the second flow path 42 is not provided with fins.

[0044] (Heat exchanger operation) Next, the operation of the heat exchanger 100 in this embodiment will be described.

[0045] First, as shown in Figure 7, the first fluid 1 and the second fluid 2 are introduced into the heat exchanger 100, respectively. In Figure 7, the liquid first fluid 1 and the vaporized gas first fluid 1 are illustrated with different hatching.

[0046] In this embodiment, the first fluid 1 is supplied from a storage unit, such as a liquid nitrogen tank. The first fluid 1 flows into the inlet 3a of the heat transfer tube HT via piping (not shown) connected to the inlet 3a of the heat transfer tube HT. The first fluid 1 flows upward through the inside of the heat transfer tube HT, from the inlet 3a at the lower end to the outlet 3b at the upper end. The temperature of the first fluid 1 at the inlet 3a (inlet temperature) is, for example, -180°C.

[0047] The second fluid 2 flows from the hot water supply equipment into the inlet 4a (inlet pipe 31) of the third pipe 30 via piping (not shown) connected to the inlet 4a. The temperature of the second fluid 2 at the inlet 4a (inlet temperature) is, for example, 30°C or higher and 80°C or lower. The heat exchanger 100 is configured to create turbulence in the flow of the second fluid 2 by causing the second fluid 2 to collide with the outer surface 20c of the second pipe 20 from the inlet 4a. For this purpose, the second fluid 2 is supplied from the inlet 4a at a flow velocity that can create turbulence. By creating turbulence, the heat transfer coefficient near the inlet 3a becomes locally higher, and the surface temperature of the second pipe 20 near the inlet 3a can be increased, thereby suppressing the freezing of the second fluid 2 near the inlet 3a.

[0048] The second fluid 2 flows from the outlet of the inlet pipe 31 towards the heat transfer tube HT inside the third pipe 30, then flows upward through the second flow path 42 inside the third pipe 30, flows into the outlet pipe 32 near the upper end 30a inside the third pipe 30, and flows out from the outlet 4b.

[0049] The first fluid 1 that flows into the second pipe 20 from the inlet 3a flows through the first flow path 41 between the first pipe 10 and the second pipe 20. As described above, the passage 11 inside the first pipe 10 has a sufficiently high flow resistance compared to the first flow path 41 due to the pressure fluctuation suppression section 12 (throttling hole 12b), so the first fluid 1 hardly flows into the passage 11.

[0050] The first fluid 1 flowing through the first channel 41 exchanges heat with the second fluid 2 flowing through the second channel 42. The first fluid 1 in the first channel 41 receives heat from the second fluid 2 in the second channel 42, which surrounds the outer circumference of the first channel 41. For this reason, heat transfer usually decreases as you move radially inward from the inner surface 20d of the second pipe 20. In this embodiment, the first pipe 10 is placed inside the second pipe 20, and the first channel 41 is made into a cylindrical space. As a result, the first channel 41 is not formed near the central axis (where the first pipe 10 is formed) away from the inner surface 20d of the second pipe 20. Therefore, the channel height of the first channel 41 is sufficiently small, and the temperature distribution inside the first channel 41 (inside the second pipe 20) is made more uniform compared to the case where the first pipe 10 is not provided.

[0051] The first fluid 1 flowing through the first channel 41 receives heat from the second fluid 2, using the inner circumferential surface 20d of the second pipe 20 and the surface of the fins 50 as heat transfer surfaces. In this embodiment, because the temperature difference between the first fluid 1 and the second fluid 2 is large (the heat transfer surface becomes hotter than the boiling point of the first fluid 1), a phenomenon called film boiling may occur, in which the heat transfer surface is covered by a continuous vapor film of the first fluid 1.

[0052] Normally, in a film boiling state, the presence of a vapor film prevents direct contact between the liquid first fluid 1 and the heat transfer surface. Furthermore, when the first fluid 1 flows in a laminar flow, the liquid first fluid 1 flows by sliding along the surface of the vapor film. Therefore, the heat transfer coefficient is lower compared to when the liquid and the heat transfer surface are in direct contact.

[0053] In contrast, in this embodiment, since the fins 50 in the first flow channel 41 are offset fins (see Figures 4 and 5), the flow is disturbed when the first fluid 1 collides with the end face of the vertical plate portion 51. As a result, the vapor film is disturbed, making it easier for the liquid first fluid 1 and the heat transfer surface to come into direct contact even in a film boiling state. Therefore, even when there is a large temperature difference between the first fluid 1 and the second fluid 2, the effect of film boiling is suppressed and a high heat transfer coefficient can be obtained.

[0054] The vaporized gas of the first fluid 1 in the first flow path 41 moves upward and flows out from the upper end of the first flow path 41, and flows out from the heat exchanger 100 through the outlet 3b of the second pipe 20. In this way, the first fluid 1 is vaporized and sent to the destination of the vaporized gas through piping (not shown) connected to the outlet 3b.

[0055] <Function of the pressure fluctuation suppression unit> Because the first flow path 41 is in an unstable boiling state, pressure fluctuations (pulsations) are easily generated. Pressure fluctuations generated in the first flow path 41 are suppressed by the pressure fluctuation suppression unit 12. That is, when a pressure difference occurs between the upper and lower sides of the throttling hole 12b, this pressure difference is reduced as the vaporized gas moves through the throttling hole 12b.

[0056] For example, if the pressure P2 at the outlet 3b becomes lower than the pressure P1 inside the passage 11, the vaporized gas of the first fluid 1 inside the passage 11 flows out to the outlet 3b through the throttling hole 12b, thereby reducing the pressure difference. Liquid phase first fluid 1, corresponding to the amount flowing out from the throttling hole 12b, temporarily flows into the passage 11 from the lower end of the passage 11. If the pressure P2 at the outlet 3b becomes higher than the pressure P1 inside the passage 11, the vaporized gas of the first fluid 1 at the outlet 3b flows into the passage 11 through the throttling hole 12b, thereby reducing the pressure difference.

[0057] If the pressure fluctuation suppression unit 12 is not provided and pressure fluctuations are not suppressed, for example, if the pressure temporarily drops, the boiling point of the first fluid 1 will decrease. If the evaporation rate of the first fluid 1 temporarily increases due to the decrease in the boiling point, the pressure in the first flow path 41 will increase. The flow rate of the first fluid 1 will also fluctuate in response to the change in pressure. These fluctuations will cause instability in the state of the first flow path 41, leading to instability in heat exchange performance and the generation of repeated stress due to pulsation.

[0058] In this embodiment, pressure fluctuations that cause such instability in heat exchange performance and the generation of repeated stress due to pulsation are suppressed by the pressure fluctuation suppression unit 12.

[0059] (Method of manufacturing a heat exchanger) Next, the manufacturing method of the heat exchanger 100 of this embodiment will be described.

[0060] First, the heat transfer tubes (HT) are fabricated. The fabrication of the heat transfer tubes (HT) includes the following steps S1 to S4, as shown in Figure 8. (Step S1) A fin 50 is placed on the outer surface 10c of the first pipe 10. (Step S2) The first assembly of the first tube 10 and fin 50 is placed inside the second tube 20. (Step S3) The diameter of the second tube 20 is reduced by drawing the second assembly in which the first tube 10 and fin 50 are placed inside the second tube 20, and the fin 50 is pressed and fixed between the outer surface 10c of the first tube 10 and the inner surface 20d of the second tube 20. (Step S4) The second assembly after drawing is subjected to heat treatment to form a portion where the materials of the first pipe 10 and the second pipe 20 and the fin 50 are integrated at the contact portion CP (see Figure 6) between the fin 50 and the first pipe 10 and the contact portion CP between the fin 50 and the second pipe 20.

[0061] Step S1 is performed by wrapping the corrugated fin sheet FS, on which the fins 50 are formed, around the outer surface 10c of the first tube 10.

[0062] In step S2, a second tube 20 is prepared, having an inner diameter larger than the maximum outer diameter of the first assembly of the first tube 10 and fin 50, and the first assembly is inserted into the inside of this second tube 20. In other words, the inner diameter D2a of the second tube 20 in step S2 (see step S3 in Figure 8) is larger than the inner diameter D2 of the second tube 20 shown in Figure 1.

[0063] In process S3, as a result of the cold drawing process, the second tube 20 is reduced in size from an inner diameter D2a to an inner diameter D2. Due to this reduction in diameter, the inner circumferential surface 20d of the second tube 20 comes into contact with the outer lateral plate portion 52 of the fin 50, which is positioned on the outer circumferential surface 10c of the first tube 10. The fin 50 is firmly sandwiched between the first tube 10 and the second tube 20, thereby compressing and fixing the first tube 10, the fin 50, and the second tube 20 together.

[0064] In step S4, the second assembly after drawing is heated in a heating furnace 90 at a predetermined holding temperature for a predetermined holding time. In this embodiment, where the first tube 10, the second tube 20, and the fins 50 are made of stainless steel, the holding temperature for the heat treatment is a predetermined temperature of approximately 900°C to approximately 1200°C. The holding time for the heat treatment is a predetermined time of, for example, 1 hour to 10 hours.

[0065] Heat treatment causes atomic diffusion at the interface of the contact points CP (see Figure 6) between the fin 50 and the first tube 10 and the second tube 20. As a result, at least a portion of the contact point CP between the inner circumferential lateral plate portion 52 of the fin 50 and the outer circumferential surface 10c of the first tube 10 becomes integrated. Similarly, at least a portion of the contact point CP between the outer circumferential lateral plate portion 52 of the fin 50 and the inner circumferential surface 20d of the second tube 20 becomes integrated. Note that the entire contact point CP between the fin 50 and the first tube 10 and the second tube 20 may be integrated, but only a portion may be integrated to account for uneven heating.

[0066] As a result of processes S1 to S4, the heat transfer tube HT is manufactured. The heat transfer tube HT is inserted into the third tube 30 and fixed to the third tube 30. The manufacturing process of the third tube 30 is omitted from this explanation. This completes the manufacture of the heat exchanger 100.

[0067] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0068] In this embodiment, as described above, the first pipe 10 includes passages 11 that communicate with the second pipe 20 at both ends. Therefore, between one end and the other end of the second pipe 20, the first flow path 41 and the passage 11 in the first pipe 10 are provided in parallel. Here, since the first pipe 10 includes a pressure fluctuation suppression unit 12 that restricts the flow of the first fluid 1 in the passage 11, even if a passage 11 is provided in the first pipe 10, the first fluid 1 is actively allowed to flow more through the first flow path 41 than through the passage 11, allowing heat exchange between the first fluid 1 flowing through the first flow path 41 and the second fluid 2 flowing through the second flow path 42. Furthermore, since the pressure fluctuation suppression unit 12 releases the pressure that has fluctuated in the first flow path 41 from the end of the passage 11, when a pressure fluctuation occurs in the first flow path 41 due to heat exchange, the passage 11 in the first pipe 10 acts as a bypass path for releasing the pressure, thereby reducing the pressure difference between one end and the other end of the second pipe 20. As a result, pressure fluctuations within the fluid path can be suppressed even when used in applications where fluid pressure fluctuations are likely to occur.

[0069] Furthermore, in this embodiment, as described above, the first fluid 1 is a liquid that is vaporized by heat exchange with the second fluid 2. Therefore, the liquid first fluid 1 boils and vaporizes in the first flow path 41, causing the pressure in the first flow path 41 to fluctuate according to the boiling conditions. Even in such cases, in this embodiment, the pressure fluctuation suppression unit 12 is configured to restrict the flow of the first fluid 1, causing the vaporized gas of the first fluid 1 to accumulate in the passage 11, and to allow the vaporized gas to flow in accordance with the pressure fluctuations in the first flow path 41. By allowing the vaporized gas in the passage 11 to pass through in accordance with the pressure changes on the first flow path 41 side, pressure fluctuations can be suppressed. As a result, even in an unstable boiling state, instability in heat exchange performance can be suppressed, and the generation of repeated stress (pulsation) caused by pressure fluctuations can be effectively suppressed.

[0070] In particular, the effect of pressure fluctuations occurring during boiling increases as the supply pressure of the first fluid 1 decreases. Therefore, the configuration of this embodiment, in which pressure fluctuations can be suppressed by the pressure fluctuation suppression unit 12, is particularly effective when the first fluid 1 is supplied to the heat transfer tube HT at a relatively low pressure (for example, less than 1 MPa).

[0071] Furthermore, in this embodiment, as described above, the pressure fluctuation suppression unit 12 has a throttling member 12a provided in the passage 11. By narrowing the inner diameter of the passage 11 with the throttling member 12a, the flow resistance of the passage 11 can be made sufficiently higher than the flow resistance of the first passage 41. As a result, a pressure fluctuation suppression unit 12 can be realized with a simple structure in which the first fluid 1 flows in and out of the passage 11 in a state where almost no first fluid 1 flows in (a state where it flows substantially only to the first passage 41 side), and when a pressure difference occurs at both ends, the amount of first fluid 1 that flows in and out is sufficient to eliminate that pressure difference.

[0072] Furthermore, in this embodiment, as described above, one end of the passage 11 is open into the second pipe 20, and the pressure fluctuation suppression unit 12 is provided to cover the other end of the passage 11. Therefore, unlike a configuration in which the pressure fluctuation suppression unit 12 is placed inside the first pipe 10, for example, the pressure fluctuation suppression unit 12 can be easily provided.

[0073] Furthermore, in this embodiment, as described above, the first pipe 10, the second pipe 20, and the third pipe 30 are provided to extend in the vertical direction, an inlet 3a for the first fluid 1 is provided at the lower end 20b of the second pipe 20, an outlet 3b for vaporized gas is provided at the upper end 20a of the second pipe 20, and the pressure fluctuation suppression unit 12 is provided at the upper end 10a of the first pipe 10. Therefore, the first fluid 1 introduced from the inlet 3a at the lower end is vaporized as it flows upward, and the vaporized gas of the first fluid 1 flows out from the outlet 3b at the upper end. For this reason, the difference in specific gravity can be used to move the vaporized gas of the first fluid 1 upward, so that the vaporized gas can flow smoothly. Furthermore, the lower end of the passage 11 within the first pipe 10 is in contact with the liquid of the first fluid 1, and the upper end of the passage 11 is in contact with the vaporized gas of the first fluid 1. When pressure fluctuations occur, the liquid of the first fluid 1 or the vaporized gas of the first fluid 1 temporarily flows into the passage 11, thereby suppressing pressure fluctuations between the inlet 3a and the outlet 3b.

[0074] Furthermore, in this embodiment, as described above, the first flow path 41 is further provided with fins 50 that are in contact with the outer circumferential surface 10c of the first pipe 10 and the inner circumferential surface 20d of the second pipe 20, respectively. The fins 50 have portions where the materials of the first pipe 10 and the second pipe 20 are integrated at the contact portion CP with the first pipe 10 and the contact portion CP with the second pipe 20. As a result, heat from the second fluid 2 supplied from the outer circumferential side of the first flow path 41 can be efficiently transferred by the fins 50 to the inner circumferential side of the first flow path 41 (the outer circumferential surface 10c of the first pipe 10). Furthermore, since the fin 50 has portions where the materials of the first pipe 10 and the second pipe 20 are integrated at the contact portion CP with the first pipe 10 and the second pipe 20, the contact area between the fin 50 and the first pipe 10 (second pipe 20) at the contact portion CP can be increased compared to the case where the surface of the fin 50 and the surface of the first pipe 10 (second pipe 20) are in contact without being integrated. By increasing the contact area, the thermal resistance decreases and heat is transferred more easily, improving the heat exchange performance. As a result, the temperature difference between the outer surface 10c of the first pipe 10 and the inner surface 20d of the second pipe 20 can be reduced, and variations in the radial heat exchange performance of the first flow path 41 can be reduced.

[0075] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims.

[0076] For example, the above embodiment shows an example in which the heat exchanger 100 is configured as a vaporizer for the first fluid 1, but the present invention is not limited to this. In the present invention, the heat exchanger 100 may be a heat exchanger that performs functions other than vaporization of the fluid. In other words, a phase change of the fluid does not need to occur in the flow path. The first fluid 1 may be on the high-temperature side and the second fluid 2 may be on the low-temperature side.

[0077] Furthermore, although the above embodiment shows an example in which the pressure fluctuation suppression section 12 is a throttling member 12a having a throttling hole 12b that closes the end of the first pipe 10, the present invention is not limited to this. For example, in the example of Figure 9, the pressure fluctuation suppression section 12 includes a throttling member 112 having a throttling hole 12b and a cover 113 having a mounting hole 113a for the throttling member 112. The cover 113 is joined to the end of the first pipe 10 so as to close the end opening of the first pipe 10. The mounting hole 113a is a threaded hole (female thread) that penetrates the cover 113 in the thickness direction. A threaded portion (male thread) that engages with the threaded portion of the mounting hole 113a is formed on the outer circumferential surface of the throttling member 112. The throttling member 112 is detachably attached to the mounting hole 113a. In this configuration, by providing multiple types of aperture members 112 with different diameters of aperture holes 12b, the diameter of the aperture hole 12b can be changed (adjusted) to an appropriate size by changing the aperture member 112.

[0078] Furthermore, although the above embodiment shows an example in which the throttling member 12a is joined to the end of the first pipe 10 by welding or the like, the present invention is not limited thereto. A screw groove (female thread) may be formed on the inner circumferential surface 10d of the end of the first pipe 10, and the throttling member 12a, which has a screw groove (male thread) formed on its outer circumferential surface, may be screw-fixed to the inner circumferential surface 10d of the first pipe 10.

[0079] Furthermore, although the above embodiment shows an example in which the pressure fluctuation suppression section 12 is a throttling member 12a joined to the end of the first pipe 10, the present invention is not limited thereto. In the present invention, the pressure fluctuation suppression section 12 may be integrally formed with the first pipe 10. For example, the pressure fluctuation suppression section 12 may be formed on the first pipe 10 by tapering the end of the first pipe 10 and reducing the inner diameter of the passage 11 at the end of the first pipe 10 to a size corresponding to the diameter of the throttling hole 12b.

[0080] Furthermore, although the above embodiment shows an example in which the pressure fluctuation suppression section 12 is a throttling member 12a having a throttling hole 12b, the present invention is not limited thereto. In the present invention, the pressure fluctuation suppression section 12 does not have to have a throttling hole 12b. The pressure fluctuation suppression section 12 may include a filter member made of, for example, a porous material or fibers and provided to block the passage 11, and the filter member may be configured to release the fluctuating pressure while restricting the flow of the first fluid 1 in the first pipe 10.

[0081] Furthermore, although the above embodiment shows an example in which the pressure fluctuation suppression unit 12 is provided at the upper end 10a of the first pipe 10, the present invention is not limited to this. As shown in Figure 10, the pressure fluctuation suppression unit 12 may be provided at the lower end 10b of the first pipe 10. Also, the pressure fluctuation suppression unit 12 may be provided at an intermediate position within the first pipe 10 between one end (upper end 10a) and the other end (lower end 10b), rather than at the end of the first pipe 10. The pressure fluctuation suppression unit 12 may be provided at multiple locations among one end, the other end, and intermediate positions of the first pipe 10.

[0082] Furthermore, although the above embodiment shows an example in which fins 50 are provided in the first channel 41, in the present invention, fins 50 may not be provided in the first channel 41. Also, although the above embodiment shows an example in which fins are not provided in the second channel 42, in the present invention, fins may be provided in the second channel 42.

[0083] Furthermore, in the above embodiment, an example was shown in which the fin 50 has a portion where the materials of the first pipe 10 and the second pipe 20 and the fin 50 are integrated at the contact portion CP with the first pipe 10 and the second pipe 20, respectively, but the present invention is not limited to this. It is not necessary for the materials of the first pipe 10 and the second pipe 20 and the fin 50 to be integrated at the contact portion CP. In other words, it is not necessary to perform heat treatment in the manufacturing process of the heat transfer tube HT.

[0084] Furthermore, in the above embodiment, an example of manufacturing a heat transfer tube HT was shown by performing a drawing process S3 on the second assembly and a heat treatment process S4 on the second assembly after drawing, but the present invention is not limited thereto. In the present invention, drawing (process S3) does not need to be performed. In this case, in the heat treatment process S4, the process of pressing the outer peripheral plate portion 52 of the fin 50 against the inner peripheral surface 20d of the second tube 20 and the process of integrating the materials at the contact portion CP by heating may be performed in a single step by pressurizing the inside of the first tube 10 to expand it, or by sealing an expanding substance inside the first tube 10 and then performing a heat treatment.

[0085] Furthermore, although the above embodiment shows an example in which the first pipe 10, the second pipe 20, and the third pipe 30 are provided to extend in the vertical direction, the present invention is not limited thereto. The first pipe 10, the second pipe 20, and the third pipe 30 may be provided to extend horizontally or diagonally in the vertical direction. When each pipe is provided in the horizontal direction, different temperature distributions and gas-liquid distributions are formed on the upper and lower sides of the first flow path 41. Therefore, when the heat exchanger 100 is configured as a vaporizer for the first fluid 1, a configuration in which each pipe extends in the vertical direction is preferable. [Explanation of Symbols]

[0086] 1 1st fluid 2 Second fluid 3a Entrance 3b Exit section 4a Entrance 4b Exit section 10 1st tube 10a Upper end 10b Bottom end 10c Outer surface 10d Inner surface 11 aisles 12 Pressure fluctuation suppression unit 12a, 112 Restriction member 20 2nd pipe 20a Upper end 20b Bottom end 20d Inner surface 30 3rd tube 30d inner surface 41 First channel 42 Second channel 50 fins 100 heat exchanger CP contact part HT heat transfer tube

Claims

1. It comprises a first pipe, a second pipe into which the first pipe is inserted, and a third pipe into which both the first and second pipes are inserted. A first flow path is formed between the first pipe and the second pipe for the flow of a first fluid, and a second flow path is formed between the second pipe and the third pipe for the flow of a second fluid that exchanges heat with the first fluid. The first pipe includes a passage whose both ends are connected to the second pipe, and a pressure fluctuation suppression section that restricts the flow of the first fluid in the passage and releases pressure fluctuations in the first flow path from the end of the passage. The first fluid is a liquid that is vaporized by heat exchange with the second fluid. The pressure fluctuation suppression unit is a heat exchanger that includes holes that restrict the flow of the first fluid to cause vaporized gas of the first fluid to accumulate in the passage, and allow the vaporized gas to flow in response to pressure fluctuations in the first flow path.

2. The heat exchanger according to claim 1, wherein the pressure fluctuation suppression unit has a throttling member provided in the passage.

3. The passage has one end that is open into the second pipe, The heat exchanger according to claim 1 or 2, wherein the pressure fluctuation suppression section is provided so as to cover the other end of the passage.

4. The first pipe, the second pipe, and the third pipe are provided so as to extend in the vertical direction. An inlet for the first fluid is provided at the lower end of the second pipe, and an outlet for the vaporized gas is provided at the upper end of the second pipe. The heat exchanger according to claim 1, wherein the pressure fluctuation suppression unit is provided at the upper end of the first pipe.

5. The first flow path further includes fins provided so as to abut the outer surface of the first pipe and the inner surface of the second pipe, respectively. The heat exchanger according to any one of claims 1 to 4, wherein the fin has portions in contact with the first pipe and the second pipe where the materials of the first pipe and the fin are integrated.

Images