Heat exchanger

Abstract

This heat exchanger is capable of mutually transferring heat between a first heat medium and a second heat medium. This heat exchanger includes: a tube through which the first heat medium flows; and a housing which includes a housing inner surface surrounding the tube, and in which the second heat medium flows between a tube outer surface, which is the outer surface of the tube, and the housing inner surface. The tube includes: an inlet into which the first heat medium flows and which is formed at a first end in an axial direction in which the center axis of the tube extends; an outlet from which the first heat medium flows out and which is formed at a second end, which is opposite to the first end, of the tube; and a tube inner surface which extends along the axial direction from the inlet to the outlet and surrounds the flow path of the first heat medium. In the case where the area of a cross-sectional region surrounded by the tube inner surface when the tube is cut along a plane perpendicular to the central axis is defined as a flow path cross-sectional area, the tube includes a narrowing part in which the flow path cross-sectional area decreases as the distance to the outlet in the axial direction decreases.

Description

heat exchanger

[0001] The present disclosure relates to a heat exchanger.

[0002] A so-called shell-and-tube heat exchanger is known (see, for example, Patent Document 1). In this type of heat exchanger, the internal space of the shell and the internal space of the tube are separated from each other, and heat is exchanged between the medium flowing through the tube and the medium flowing through the shell via the wall surfaces of the tube.

[0003] Chinese Patent Application Publication No. 114166043

[0004] A heat exchanger includes, for example, a shell through which a heat-receiving medium flows and tubes through which a heat-transferring medium flows. The heat-transferring medium can be, for example, steam. For example, when steam comes into contact with a tube through which a heat-receiving medium flows, the heat of the steam is transferred to the heat-receiving medium via the tube wall. As a result of this heat exchange, a liquid film may form on the tube wall, and the liquid film may accumulate inside the tube as a liquid pool. The tube wall functions as a heat transfer surface that forms a path for heat transfer. If a liquid pool exists inside the tube, the liquid pool creates thermal resistance, making it difficult for heat to transfer through the tube wall. As a result, the efficiency of the heat exchanger may decrease.

[0005] The present disclosure describes a heat exchanger that can increase the efficiency of heat exchange.

[0006] A heat exchanger according to the present disclosure is capable of transferring heat between a first heat medium and a second heat medium. The heat exchanger includes a tube through which the first heat medium flows and a housing including an inner surface of a housing surrounding the tube, the housing having a second heat medium flowing between the tube outer surface and the inner surface of the housing. The tube includes an inlet formed at a first end in an axial direction along which a central axis of the tube extends and through which the first heat medium flows, an outlet formed at a second end of the tube opposite the first end and through which the first heat medium flows, and a tube inner surface extending axially from the inlet to the outlet and surrounding a flow path of the first heat medium. When the flow path cross-sectional area is defined as the area of ​​a cross-sectional region surrounded by the inner surface of the tube when the tube is cut along a plane perpendicular to the central axis, the tube includes a constriction portion whose flow path cross-sectional area decreases toward the outlet in the axial direction.

[0007] In the heat exchanger described above, the tubes include a constriction portion in which the cross-sectional area of ​​the flow path decreases toward the outlet in the axial direction. When a first heat medium is introduced into the tubes, heat exchange occurs between the first heat medium and a second heat medium outside the tubes. As a result of this heat exchange, condensate is generated in the tubes. This condensate flows through the tubes from the inlet to the outlet in accordance with the flow of the first heat medium. When the tubes include a constriction portion, as in the heat exchanger described above, the flow velocity of the first heat medium increases as the first heat medium flows through the constriction portion. As a result, the condensate generated in the tubes is dragged toward the outlet by the fast-flowing first heat medium. In other words, the condensate is quickly discharged to the outside of the tubes without stagnation, following the flow of the first heat medium. Therefore, in the heat exchanger described above, the inner surface of the tubes can continue to function as a heat transfer surface. Furthermore, when the first heat medium flows through a tube including a constriction portion, a larger portion of the first heat medium can directly contact the inner surface of the tube as it flows from the inlet to the outlet of the tube, compared to when the first heat medium flows through a tube with a constant inner diameter. In this case, heat exchange between the first heat medium flowing through the tubes and the second heat medium flowing outside the tubes can be performed more efficiently, thereby improving the heat exchange efficiency of the heat exchanger.

[0008] In the heat exchanger described above, the inner surface of the tube may be formed with a plurality of fins extending upright from the inner surface of the tube. The fins may extend along the axial direction or may be arranged circumferentially around the tube. In this case, by forming a plurality of fins on the inner surface of the tube, the area of ​​the inner surface of the tube that functions as a heat transfer surface, i.e., the heat transfer area, can be increased. Furthermore, by extending the fins along the axial direction, the condensate of the first heat medium can be made to flow in the axial direction and be easily discharged to the outside of the tube. Therefore, with the above configuration, the heat transfer area can be increased while maintaining the function of the inner surface of the tube as a heat transfer surface, thereby further improving the heat exchange efficiency.

[0009] In the heat exchanger described above, the multiple fins may be formed at least on the inner surface of the tube in the constricted portion. The height of each of the multiple fins from the inner surface of the tube may be decreased as the fins are positioned closer to the outlet in the axial direction. As the first heat medium flows toward the outlet of the tube, heat exchange between the first heat medium and the second heat medium outside the tube progresses, so that the first heat medium flows near the outlet after much heat exchange has taken place. Therefore, near the outlet, it is not necessary to increase the heat transfer area more than necessary to promote heat exchange. In the above configuration, the height of each of the multiple fins is decreased as the fins are positioned closer to the outlet in the axial direction. As a result, the volume of the tube can be kept small, thereby reducing the material cost of the tube.

[0010] In the heat exchanger described above, the tube may further include a first body extending axially between the inlet and the throttle portion and a second body extending axially between the throttle portion and the outlet. The cross-sectional flow area of ​​the first body and the second body may be constant at each position along the axial direction. The cross-sectional flow area of ​​the second body may be smaller than that of the first body. In this case, the first heat medium flows through the tube in the order of the first body, the throttle portion, and the second body, and then is discharged from the outlet of the tube. Because the first heat medium flows through the second body near the outlet after extensive heat exchange, the cross-sectional flow area of ​​the second body does not need to be reduced more than necessary to promote heat exchange. In contrast, in the above configuration, the cross-sectional flow area of ​​the second body is constant, thereby preventing the cross-sectional flow area of ​​the second body from being excessively reduced. Furthermore, in the above configuration, the cross-sectional flow area of ​​the first body between the inlet and the throttle portion is constant. If the first body were not provided and the throttled portion extended from the tube inlet, the first heat medium would flow through the throttled portion before heat exchange of the first heat medium progressed (i.e., before the first heat medium changed phase). This would increase the likelihood of erosion by the first heat medium occurring on the inner surface of the tube in the throttled portion. In contrast, if a first body with a constant flow path cross-sectional area is provided between the inlet and the throttled portion, heat exchange of the first heat medium can proceed until a phase change occurs in the first body, and then the first heat medium that has begun to change phase can flow through the throttled portion. This prevents erosion from occurring on the inner surface of the tube in the throttled portion.

[0011] In the heat exchanger described above, the tube may include a first region disposed at any position along the axial direction and a second region disposed closer to the outlet in the axial direction than the first region and having a flow path cross-sectional area smaller than the flow path cross-sectional area of ​​the first region. The thickness of the second region from the outer surface of the tube to the inner surface of the tube may be equal to or greater than the thickness of the first region from the outer surface of the tube to the inner surface of the tube. In this case, the flow velocity of the first heat medium flowing through the second region is higher than the flow velocity of the first heat medium flowing through the first region. As a result, erosion of the inner surface of the tube due to condensate of the first heat medium is more likely to occur in the second region than in the first region. In the above configuration, the thickness of the second region is equal to or greater than the thickness of the first region, making it possible to prevent a decrease in the mechanical strength of the second region due to erosion.

[0012] In the heat exchanger described above, the thickness of the tube from the outer surface to the inner surface may be constant at each position along the axial direction from the inlet to the outlet, which makes it easy to manufacture the tube using, for example, three-dimensional molding technology.

[0013] In the heat exchanger described above, the thickness of the second region may be greater than the thickness of the first region, which more reliably prevents the mechanical strength of the second region from being reduced due to erosion.

[0014] In the heat exchanger described above, the tubes may be formed integrally with the housing, in which case the tubes can be easily manufactured using, for example, three-dimensional modeling technology.

[0015] The heat exchanger may include a first tube and a second tube as the tubes. The first tube and the second tube may extend along the axial direction or may be aligned along a direction perpendicular to the axial direction. In this case, the amount of the first heat medium can be increased, thereby making it possible to perform heat exchange between the first heat medium and the second heat medium more efficiently.

[0016] In the heat exchanger described above, the housing may include a first manifold section that distributes a first heat medium and supplies it to the first tube and the second tube. The first manifold section may include an inlet through which the first heat medium flows, a first outlet connected to the inlet of the first tube and through which a portion of the first heat medium flows out from the inlet, a second outlet connected to the inlet of the second tube and through which at least a portion of the remaining first heat medium flows out from the inlet, and an inner wall surface that surrounds a flow path of the first heat medium extending from the inlet to the first outlet and the second outlet. A plurality of fins extending along the flow direction of the first heat medium are formed on the inner wall surface of the first manifold section. When a plurality of fins are formed on the inner wall surface of the first manifold section, the area of ​​the inner wall surface of the first manifold section that can function as a heat transfer surface, i.e., the heat transfer area, can be secured larger than when a plurality of fins are not formed on the inner wall surface. This can further improve the efficiency of heat exchange. Furthermore, when the fins formed on the inner wall surface of the first manifold section extend along the flow direction of the first heat medium, the first heat medium flowing in from the inlet can flow more easily in the flow direction than when the fins extend in a direction perpendicular to the flow direction, which makes it easier for the condensate of the first heat medium flowing through the tubes to be discharged to the outside.

[0017] In the heat exchanger described above, the housing may include a second manifold section that joins and discharges the first heat medium from the first tube and the second tube. The second manifold section may include a first inlet connected to the outlet of the first tube and through which the first heat medium flows from the outlet of the first tube, a second inlet connected to the outlet of the second tube and through which the first heat medium flows from the outlet of the second tube, an outlet through which the first heat medium flows from the first inlet and the second inlet, and an inner wall surface that surrounds the flow path of the first heat medium extending from the first inlet and the second inlet to the outlet. The inner wall surface of the second manifold section may be formed with a plurality of fins extending in the flow direction of the first heat medium. When a plurality of fins are formed on the inner wall surface of the second manifold section, the area of ​​the inner wall surface of the second manifold section that can function as a heat transfer surface, i.e., the heat transfer area, can be secured larger than when a plurality of fins are not formed on the inner wall surface. This allows for increased heat exchange efficiency. Furthermore, when the fins formed on the inner wall surface of the second manifold section extend along the flow direction of the first heat medium, the condensate of the first heat medium that has flowed into the first inlet and the second inlet can flow in the flow direction and be more easily discharged to the outside from the outlet, compared to when the fins extend perpendicular to the flow direction, which makes it possible to prevent the condensate from the first tubes and the second tubes from accumulating in the second manifold section.

[0018] The heat exchanger of the present disclosure can increase the efficiency of heat exchange.

[0019] FIG. 1 is a perspective view showing the appearance of a heat exchanger according to one embodiment. FIG. 2 is a cross-sectional view of the heat exchanger taken along line A1-A1 in FIG. 1. FIG. 3 is a cross-sectional view of the heat exchanger taken along line A2-A2 in FIG. 1. FIG. 4 is a cross-sectional view showing the tube of FIG. 3. FIGS. 5(a), 5(b), 5(c), and 5(d) are alternative cross-sectional views showing the tube of FIG. 4. FIG. 6 is a cross-sectional view showing the first manifold section of FIG. 3. FIG. 7 is a cross-sectional view showing the second manifold section of FIG. 3. FIG. 8 is a cross-sectional view showing a modified example of the tube. FIGS. 9(a), 9(b), and 9(c) are alternative cross-sectional views showing the tube of FIG. 8.

[0020] Hereinafter, the heat exchanger of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted.

[0021] FIG. 1 is a perspective view showing the appearance of a heat exchanger 1 of this embodiment. As shown in FIG. 1, the heat exchanger 1 receives steam 91 (first heat medium). Furthermore, the heat exchanger 1 receives a heat medium 92 (second heat medium). The heat medium 92 may be, for example, an organic solvent or acetone. The heat exchanger 1 removes heat from the received steam 91. As a result, some or all of the water contained in the steam 91 condenses. The condensed water will be referred to as "condensate" in the following description. The heat exchanger 1 discharges condensate 93 as a result of the heat exchange.

[0022] The heat exchanger 1 includes a steam inlet 11 (inlet), a condensate outlet 12 (outlet), a heat transfer medium inlet 13, and a heat transfer medium outlet 14. The steam inlet 11 is connected to, for example, a boiler. The steam inlet 11 receives steam 91 provided from the boiler. The steam inlet 11 is connected to a condensate outlet 12. The condensate outlet 12 discharges condensate 93. The condensate outlet 12 is connected to, for example, a flash tank. The condensate outlet 12 provides the condensate 93 to the flash tank. The heat transfer medium inlet 13 is connected to, for example, a raw material tank. The heat transfer medium inlet 13 receives a heat transfer medium 92 provided from the raw material tank before heat exchange. The heat transfer medium inlet 13 is connected to the heat transfer medium outlet 14. The heat transfer medium outlet 14 discharges the heat transfer medium 92 after heat exchange. The heat transfer medium outlet 14 is connected to, for example, a reactor. The heat transfer medium outlet 14 provides the heat transfer medium 92 after heat exchange to the reactor.

[0023] As an example, the heat exchanger 1 is disposed so that its central axis L4 is parallel to the vertical direction. The central axis L4 is an axis passing through the center of the housing body 4 (described later). This type of arrangement can be referred to as "disposing the heat exchanger 1 vertically." In this arrangement, the steam inlet 11 is disposed vertically above the condensate outlet 12. Therefore, the steam 91 and condensate 93 move from top to bottom due to gravity. In contrast, the heat transfer medium inlet 13 is disposed vertically below the heat transfer medium outlet 14. Therefore, the heat transfer medium 92 moves from bottom to top against gravity. In other words, the direction of movement of the steam 91 and condensate 93 along the central axis L4 is opposite to the direction of movement of the heat transfer medium 92. This type of flow is referred to as "counterflow" or "complete counterflow."

[0024] The direction in which the heat medium 92 moves may be the same as the direction in which the steam 91 moves. For example, the heat medium 92 may be introduced from a portion called the heat medium outlet 14 and discharged from a portion called the heat medium inlet 13. This type of flow is called "parallel flow." The direction in which the heat medium 92 flows does not make any essential difference to the structure of the heat exchanger 1. In other words, the heat exchanger 1 of this embodiment can be used as either a counterflow type or a parallel flow type.

[0025] Fig. 2 is a cross-sectional view of the heat exchanger 1 taken along line A1-A1 in Fig. 1. Fig. 3 is a cross-sectional view of the heat exchanger 1 taken along line A2-A2 in Fig. 1. Fig. 2 shows a cross-section of the heat exchanger 1 taken along a plane perpendicular to the central axis L4. Fig. 3 shows a cross-section of the heat exchanger 1 taken along a plane including the central axis L4. As shown in Figs. 2 and 3, the heat exchanger 1 includes, for example, a housing 2 and a plurality of tubes 3. The housing 2 includes, for example, a housing main body 4, a first manifold section 5, and a second manifold section 6.

[0026] The housing body 4 is, for example, a cylindrical member centered on the central axis L4. The housing body 4 extends along the axial direction D1 along which the central axis L4 runs. When the heat exchanger 1 is disposed vertically, the axial direction D1 is a direction along the vertical direction. A heat medium inlet pipe 41 is connected to the housing body 4. The heat medium inlet pipe 41 is a tubular portion including the heat medium inlet 13 described above. The heat medium inlet pipe 41 extends, for example, in a direction inclined with respect to the central axis L4. Furthermore, a heat medium discharge pipe 42 (see FIG. 1 ) is connected to the housing body 4. The heat medium discharge pipe 42 is a tubular portion including the heat medium outlet 14 described above. The heat medium discharge pipe 42 extends, for example, in the same direction as the heat medium inlet pipe 41.

[0027] As shown in FIG. 2 , the housing body 4 includes a support 43 extending along a central axis L4 therein. The support 43 may be, for example, a cylinder centered on the central axis L4. A plurality of tubes 3 are arranged inside the housing body 4. Each of the plurality of tubes 3 is, for example, a cylindrical member centered on a central axis L3 extending along the axial direction D1. The central axis L4 is an axis passing through the center of the tube 3. The central axis L3 of the tube 3 extends, for example, parallel to the central axis L4 of the housing body 4. As shown in FIG. 2 , for example, four tubes 3 are arranged around the support 43 at an angle of 90 degrees. The individual configurations of the tubes 3 may be, for example, identical to each other.

[0028] The housing body 4 includes a housing inner surface 44 that surrounds the plurality of tubes 3. The tubes 3 include a tube outer surface 31 that faces the housing inner surface 44. The tube outer surface 31 is spaced apart from the housing inner surface 44. That is, a gap G is formed between the tube outer surface 31 and the housing inner surface 44. The heat medium 92 received from the heat medium inlet pipe portion 41 passes through the gap G between the tube outer surface 31 and the housing inner surface 44 and reaches the heat medium outlet pipe portion 42. Steam 91 introduced from the steam inlet 11 described above flows through the tubes 3. The steam 91 flowing through the plurality of tubes 3 exchanges heat with the heat medium 92 flowing through the gap G outside the tubes 3. Heat is removed from the steam 91 as it flows through the tubes 3. As a result, some or all of the steam 91 becomes condensed liquid 93.

[0029] FIG. 3 shows two of the four tubes 3, namely, tubes 3A and 3B, which are aligned in a direction D3 perpendicular to the axial direction D1. For simplicity, fins 35, 54, and 64, which will be described later, are omitted from FIG. 3 . In the following description, one of the two tubes 3A and 3B may be referred to as the "first tube 3A," and the other of the two tubes 3A and 3B may be referred to as the "second tube 3B." The first tube 3A and the second tube 3B are disposed on either side of the central axis L4 of the housing main body 4 in the direction D3. Hereinafter, when the first tube 3A and the second tube 3B are described without distinguishing between them, the first tube 3A and the second tube 3B will be simply referred to as the "tube 3."

[0030] FIG. 4 is a cross-sectional view showing the tube 3. As shown in FIG. 4, the tube 3 includes a tube inner surface 34 extending along the axial direction D1 from a first end 32 to a second end 33. The first end 32 may be one end of the tube 3 along the axial direction D1. The second end 33 may be the other end of the tube 3 opposite the first end 32. An inlet 32a is formed at the first end 32, through which a portion of the steam 91 flows in. The inlet 32a may be, for example, a substantially circular opening. An outlet 33a is formed at the second end 33, through which the condensate 93 flows out. The outlet 33a may be, for example, a substantially circular opening. The area of ​​the outlet 33a is smaller than the area of ​​the inlet 32a, for example. The area of ​​the inlet 32a may be the area of ​​an area surrounded by the tube inner surface 34 at the first end 32. The area of ​​the outlet 33a may be the area of ​​an area surrounded by the tube inner surface 34 at the second end 33.

[0031] As shown in FIG. 2 , multiple fins 35 are formed on the tube inner surface 34. Each of the multiple fins 35 is a protrusion that rises from the tube inner surface 34 toward the central axis L3. The multiple fins 35 are arranged at regular intervals along the circumferential direction D2 and extend linearly along the axial direction D1. The circumferential direction D2 is a direction along a ring centered on the central axis L3. The steam 91 and condensate 93 flowing through the tube 3 flow along the axial direction D1 from the inlet 32a to the outlet 33a. Therefore, it can be said that the multiple fins 35 extend along the flow direction of the steam 91 and condensate 93. The multiple fins 35 do not necessarily have to be formed on the tube inner surface 34. For example, the tube inner surface 34 may be a smooth surface without any protrusions.

[0032] In the present disclosure, the surfaces of the multiple fins 35 are described as being configured as part of the tube inner surface 34. Therefore, the tube inner surface 34 includes fin surfaces 34a, which are the surfaces of the multiple fins 35, and a base surface 34b, which is the portion other than the fin surfaces 34a (see FIG. 5 ). The fin surfaces 34a are portions of the tube inner surface 34 that protrude from the base surface 34b toward the central axis L3. The base surface 34b is a portion of the tube inner surface 34 that is connected to the base of the fin surfaces 34a, i.e., a portion other than the fin surfaces 34a. The tube inner surface 34 surrounds the flow path of the steam 91. In other words, the area surrounded by the tube inner surface 34 forms the flow path through which the steam 91 flows.

[0033] Figure 2 shows a flow path cross section F surrounded by the tube inner surface 34. In Figure 2, the flow path cross section F is indicated by dotted hatching. The flow path cross section F is the cross-sectional area surrounded by the tube inner surface 34 when the tube 3 is cut along a plane perpendicular to the central axis L3. In the present disclosure, the area of ​​the flow path cross section F is defined as the area of ​​the cross-sectional area surrounded by the tube inner surface 34, i.e., the "flow path cross-sectional area."

[0034] As shown in FIG. 4 , the tube 3 includes, for example, a first body portion P1, a second body portion P2, and a tapered portion P3. The tapered portion P3 is a central portion of the tube 3 between the inlet 32a and the outlet 33a. The first body portion P1 is a portion of the tube 3 extending along the axial direction D1 between the inlet 32a and the tapered portion P3. The second body portion P2 is a portion of the tube 3 extending along the axial direction D1 between the tapered portion P3 and the outlet 33a. A plurality of fins 35 are formed on the tube inner surface 34 of at least the tapered portion P3. In the present disclosure, the multiple fins 35 are formed across the first body portion P1, the tapered portion P3, and the second body portion P2. In other words, the multiple fins 35 extend continuously on the tube inner surface 34 from the inlet 32a to the outlet 33a.

[0035] The inner diameter of the constricted portion P3 becomes smaller as it is positioned closer to the outlet 33a in the axial direction D1. In other words, the tube inner surface 34 of the constricted portion P3 has a tapered surface that becomes smaller in diameter as it approaches the outlet 33a in the axial direction D1. The inner diameter may be the inner diameter of the base surface 34b of the tube inner surface 34. As a result, the area of ​​the flow path cross section F (see FIG. 2) surrounded by the tube inner surface 34 of the constricted portion P3 decreases as it is positioned closer to the outlet 33a in the axial direction D1. Therefore, the area of ​​the flow path cross section F in a region closer to the outlet 33a in the axial direction D1 than in any region of the constricted portion P3 along the axial direction D1 is smaller than the area of ​​the flow path cross section F in that region.

[0036] 4 shows a first body region R1, a second body region R2, a first throttling region R31 (first region), and a second throttling region R32 (second region). The first body region R1 is a partial region of the first body portion P1 at an arbitrary position along the axial direction D1. The second body region R2 is a partial region of the second body portion P2 at an arbitrary position along the axial direction D1. The first throttling region R31 is a partial region of the throttling portion P3 at an arbitrary position along the axial direction D1. The second throttling region R32 is a partial region of the throttling portion P3 located closer to the outlet 33a in the axial direction D1 than the first throttling region R31.

[0037] 5A is a cross-sectional view showing the flow path cross section F1 of the first body region R1. FIG. 5B is a cross-sectional view showing the flow path cross section F31 of the first throttle region R31. FIG. 5C is a cross-sectional view showing the flow path cross section F32 of the second throttle region R32. FIG. 5D is a cross-sectional view showing the flow path cross section F2 of the second body region R2. As shown in FIGS. 5B and 5C, the area of ​​the flow path cross section F32 of the second throttle region R32 is smaller than the area of ​​the flow path cross section F31 of the first throttle region R31. Therefore, it can be seen from FIGS. 5B and 5C that the area of ​​the flow path cross section F of the throttle portion P3 decreases as it moves closer to the outlet 33a in the axial direction D1.

[0038] Furthermore, in the constricted portion P3, the height of each fin 35 formed on the tube inner surface 34 decreases as it approaches the outlet 33a in the axial direction D1. The height of the fin 35 is the radial distance from the base surface 34b to the tip of the fin surface 34a. The radial direction is the direction perpendicular to the central axis L3. The height H32 of the fin 35 in the second constricted region R32 shown in Figure 5(c) is lower than the height H31 of the fin 35 in the first constricted region R31 shown in Figure 5(b).

[0039] The thickness T32 of the second throttle region R32 shown in Figure 5(c) is equal to or greater than the thickness T31 of the first throttle region R31 shown in Figure 5(b). In the present disclosure, the thickness T32 of the second throttle region R32 is the same as the thickness T31 of the first throttle region R31. In other words, the thickness T (see Figure 3) of the throttle portion P3 is constant at each position along the axial direction D1. The "thickness T" refers to the thickness of the tube 3 at any position along the axial direction D1, i.e., the distance between the tube outer surface 31 and the base surface 34b of the tube inner surface 34.

[0040] The flow passage cross section F of the first body portion P1 is constant at each position along the axial direction D1. The flow passage cross section F1 of the first body region R1 shown in FIG. 5(a) is, for example, equal to the maximum value of the area of ​​the flow passage cross section F of the throttle portion P3. The maximum value of the area of ​​the flow passage cross section F of the throttle portion P3 is the area of ​​the flow passage cross section F at the connection portion P3a (see FIG. 4) of the throttle portion P3 to the first body portion P1. The flow passage cross section F of the second body portion P2 is constant at each position along the axial direction D1. The flow passage cross section F2 of the second body region R2 shown in FIG. 5(b) is, for example, equal to the minimum value of the area of ​​the flow passage cross section F of the throttle portion P3. The minimum value of the area of ​​the flow passage cross section F of the throttle portion P3 is the area of ​​the flow passage cross section F at the connection portion P3b (see FIG. 4) of the throttle portion P3 to the second body portion P2. Therefore, the area of ​​the flow passage cross section F2 of the second body region R2 is smaller than the area of ​​the flow passage cross section F1 of the first body region R1.

[0041] The height of each fin 35 formed in the first body portion P1 and the second body portion P2 is constant at each position along the axial direction D1. The height H1 of each fin 35 in the first body region R1 shown in Fig. 5(a) is, for example, the same as the maximum height of each fin 35 in the tapered portion P3. The height H2 of each fin 35 in the second body region R2 shown in Fig. 5(b) is the same as the minimum height of each fin 35 in the tapered portion P3. Therefore, the height H2 of each fin 35 in the second body region R2 is lower than the height H1 of each fin 35 in the first body region R1.

[0042] The thickness T of each of the first body portion P1 and the second body portion P2 is the same as the thickness T of the tapered portion P3. The thickness T1 of the first body region R1 shown in Figure 5(a), the thickness T31 of the first tapered region R31 shown in Figure 5(b), the thickness T32 of the second tapered region R32 shown in Figure 5(c), and the thickness T2 of the second body region R2 shown in Figure 5(d) are all the same. Therefore, the thickness T (see Figure 3) of the tube 3 is constant at each position along the axial direction D1 from the inlet 32a to the outlet 33a. In other words, the tube inner surface 34 and the tube outer surface 31 extend parallel to each other, and the distance between the base surface 34b of the tube inner surface 34 and the tube outer surface 31 is constant.

[0043] In the above description, the first throttle region R31 is considered to be an example of the "first region" of the present disclosure, and the second throttle region R32 is considered to be an example of the "second region" of the present disclosure. However, as long as the flow path cross-sectional area of ​​one of the two regions of the tube 3 aligned along the axial direction D1 is smaller than the flow path cross-sectional area of ​​the other region, regions other than the first throttle region R31 and the second throttle region R32 may be considered to be the "first region" and the second throttle region R32 or the second throttle region R2 may be considered to be the "second region." For example, the first body region R1 may be considered to be the "first region," and any one of the first throttle region R31, the second throttle region R32, and the second body region R2 may be considered to be the "second region." Alternatively, the first throttle region R31 may be considered to be the "first region," and the second throttle region R32 or the second body region R2 may be considered to be the "second region." Alternatively, the second throttle region R32 may be considered to be the "first region," and the second body region R2 may be considered to be the "second region."

[0044] Referring again to Figure 3, the first manifold section 5 is a cover section disposed to close one end of the housing body 4. The first manifold section 5 is connected to the first ends 32 of the plurality of tubes 3. The first manifold section 5 distributes steam 91 received from the steam inlet 11 and supplies it to each tube 3. The second manifold section 6 is a cover section disposed to close the other end of the housing body 4. The second manifold section 6 is connected to the second ends 33 of each tube 3. The second manifold section 6 combines condensate 93 from each tube 3 and discharges it from the condensate outlet 12.

[0045] Fig. 6 is a cross-sectional view showing the first manifold section 5. As shown in Fig. 6, the first manifold section 5 includes the above-mentioned steam inlet 11 and a plurality of steam outlets 15 through which steam 91 flows from the steam inlet 11. The inner wall surface 53 of the first manifold section 5 extends from the steam inlet 11 to the plurality of steam outlets 15. The inner wall surface 53 surrounds a flow path of the steam 91 flowing from the steam inlet 11 to the plurality of steam outlets 15.

[0046] The first manifold section 5 includes, for example, one inlet pipe section 51 including a steam inlet 11, and multiple branch pipe sections 52 each including multiple steam outlets 15. The steam inlet 11 is formed at the outer end of the inlet pipe section 51. The inlet pipe section 51 is a tubular section extending along the central axis L4. The inner end of the inlet pipe section 51 is connected to the multiple branch pipe sections 52. Each branch pipe section 52 includes a connecting pipe section 521 extending in a direction inclined with respect to the central axis L4, and a parallel pipe section 522 extending parallel to the central axis L4.

[0047] The connecting pipe section 521 is a tubular section connected to the inner end of the inlet pipe section 51. The connecting pipe section 521 is disposed between the inlet pipe section 51 and the parallel pipe section 522, and connects the inlet pipe section 51 and the parallel pipe section 522. The parallel pipe section 522 is a tubular section that extends coaxially with the tubes 3. The inner end of the parallel pipe section 522 is connected to the connecting pipe section 521. Steam outlets 15 are formed at the outer end of the parallel pipe section 522. Each steam outlet 15 is connected to the inlet 32 ​​a of each tube 3. Therefore, the first manifold section 5 can guide the steam 91 received from the steam inlet 11 from each steam outlet 15 to each tube 3.

[0048] 6 shows, among the multiple branch pipe sections 52, a first branch pipe section 52A including a first steam outlet 15A (first outlet) and a second branch pipe section 52B including a second steam outlet 15B (second outlet). The first branch pipe section 52A is connected to the inlet 32a (see FIG. 3) of the first tube 3A. The second branch pipe section 52B is connected to the inlet 32a (see FIG. 3) of the second tube 3B. A portion 91A of the steam 91 that flows from the steam inlet 11 into the introduction pipe section 51 passes through the first branch pipe section 52A and flows from the first steam outlet 15A to the first tube 3A. A remaining portion 91B of the steam 91 passes through the second branch pipe section 52B and flows from the second steam outlet 15B to the second tube 3B. The other portion of the steam 91 passes through another branch pipe section 52 and flows from another steam outlet 15 to another tube 3.

[0049] A plurality of fins 35 extending in the flow direction of the steam 91 are formed on the inner wall surface 53 of each branch pipe section 52. For example, on the inner wall surface 53 of the connecting pipe section 521 of each branch pipe section 52, the plurality of fins 35 extend in the direction in which the connecting pipe section 521 extends, i.e., in a direction inclined with respect to the central axis L4. On the inner wall surface 53 of the parallel pipe section 522 of each branch pipe section 52, the plurality of fins 54 extend in the direction in which the parallel pipe section 522 extends, i.e., in a direction along the central axis L4. The height and spacing of the plurality of fins 54 formed on the inner wall surface 53 of each branch pipe section 52 may be the same as the height and spacing of the plurality of fins 35 formed on the first body portion P1 of the tube 3, for example.

[0050] Figure 7 is an enlarged cross-sectional view of the second manifold section 6 of Figure 3. As shown in Figure 7, the second manifold section 6 includes a plurality of condensate inlets 16 into which condensate 93 flows from the plurality of tubes 3, and the above-mentioned condensate outlet 12. The inner wall surface 63 of the second manifold section 6 extends from the plurality of condensate inlets 16 to the condensate outlet 12. The inner wall surface 63 surrounds a flow path for the condensate 93 that flows from the plurality of condensate inlets 16 to the condensate outlet 12.

[0051] The second manifold section 6 includes, for example, a plurality of branch pipe sections 61 each including a plurality of condensate inlets 16, and one discharge pipe section 62 including a condensate outlet 12. Each branch pipe section 61 includes a parallel pipe section 611 extending parallel to the central axis L4 and a connecting pipe section 612 extending in a direction inclined with respect to the central axis L4. The parallel pipe section 611 is a tubular section extending coaxially with the tube 3. The condensate inlet 16 is formed at the outer end of the parallel pipe section 611. The connecting pipe section 612 is a tubular section connected to the inner end of the parallel pipe section 611. The connecting pipe section 612 is disposed between the parallel pipe section 611 and the discharge pipe section 62, and connects the parallel pipe section 611 and the discharge pipe section 62. The discharge pipe section 62 is a tubular section extending along the central axis L4. The inner end of the discharge pipe section 62 is connected to the connecting pipe section 612. The outer end of the discharge pipe section 62 is formed with a condensate outlet 12. Therefore, the second manifold section 6 can guide the condensate 93 discharged from each tube 3 to the outside through the condensate outlet 12.

[0052] 7 shows, among the multiple branch pipe sections 61, a first branch pipe section 61A including a first condensate inlet 16A (first inlet) and a second branch pipe section 61B including a second condensate inlet 16B (second inlet). The first branch pipe section 61A is connected to the outlet 33a (see FIG. 3) of the first tube 3A. The second branch pipe section 61B is connected to the outlet 33a (see FIG. 3) of the second tube 3B. The condensate 93 that flows from the first tube 3A through the condensate inlet 16 into the first branch pipe section 61A passes through the discharge pipe section 62 and is discharged from the condensate outlet 12 to the outside. The condensate 93 that flows from the second tube 3B through the condensate inlet 16 into the second branch pipe section 61B passes through the discharge pipe section 62 and is discharged from the condensate outlet 12 to the outside. The condensate 93 that flows from the other tubes 3 into the other branch pipe section 61 via the other condensate inlet 16 passes through the discharge pipe section 62 and is discharged to the outside from the condensate outlet 12 .

[0053] A plurality of fins 64 extending in the flow direction of the condensate 93 are formed on the inner wall surface 63 of each branch pipe section 61. For example, on the inner wall surface 63 of the parallel pipe section 611 of each branch pipe section 61, the plurality of fins 64 extend in the direction in which the parallel pipe section 611 extends, i.e., along the central axis L4. On the inner wall surface 63 of the connecting pipe section 612 of each branch pipe section 61, the plurality of fins 64 extend in the direction in which the connecting pipe section 612 extends, i.e., in a direction inclined with respect to the central axis L4. The height and spacing of the plurality of fins 64 formed on the inner wall surface 63 of each branch pipe section 61 may be the same as, for example, the height and spacing of the plurality of fins 35 formed on the second body portion P2 of the tube 3.

[0054] The heat exchanger 1 is formed by integrally forming a plurality of tubes 3, a housing body 4, a first manifold section 5, and a second manifold section 6. There are no explicit boundaries, such as joint surfaces, between the respective components. In other words, the heat exchanger 1 is not obtained by manufacturing the plurality of tubes 3, the housing body 4, the first manifold section 5, and the second manifold section 6 as separate parts and then combining them. Such a heat exchanger 1 can be manufactured by so-called three-dimensional modeling technology.

[0055] <Points to Note When Designing a Heat Exchanger> Points to note when designing a heat exchanger will be described before describing the effects of the heat exchanger 1. First, points to note when designing a so-called full condensation type heat exchanger will be described, and then points to note when designing a so-called partial condensation type heat exchanger will be described.

[0056] Assume that a full condensing heat exchanger is placed horizontally and condensation occurs outside the tubes. In this case, the baffle cuts are vertical to prevent condensate from accumulating inside the shell. If the baffle cuts were horizontal, the baffles could act as weirs, causing condensate to accumulate. Areas where condensate accumulates do not function as condensation surfaces (heat transfer surfaces). Furthermore, the flow of the medium may become unstable. The above considerations are not required when a full condensing heat exchanger is placed horizontally and condensation occurs inside the tubes. Furthermore, the above considerations are not required when a full condensing heat exchanger is placed vertically and condensation occurs outside the tubes.

[0057] On the other hand, when a full condensation type heat exchanger is arranged vertically and condensation occurs inside the tubes, the inner diameter of the tubes 3 needs to be appropriately set so as not to be affected by the growth of a condensate film at the bottom of the tubes 3. Ideally, it is desirable to set the flow rate of the medium so as not to cause the growth of a condensate film on the inner surface 34 of the tubes 3. However, because the volume of the medium decreases due to condensation, it is difficult to set the flow rate so as to be uniform throughout the entire tube 3. Therefore, design strategies that suppress the growth of the condensate film (thinning the film) are not often adopted.

[0058] Next, consider a case where a partial condensing heat exchanger is installed horizontally or vertically and condensation occurs outside the tubes. In this case, non-condensable gas may accumulate inside the shell. Therefore, measures must be taken to prevent non-condensable gas from accumulating. For example, a mechanism for discharging accumulated non-condensable gas is provided. Furthermore, in the case of a downflow, the upward flow of non-condensable gas increases the possibility of non-condensable gas accumulating.

[0059] Even heat exchangers designed with these considerations in mind have had the following problems. First, shell-and-tube heat exchangers do not have a mechanism for actively removing the condensed liquid film. As a result, a liquid film forms on the condensation surface, reducing the effective heat transfer surface area that contributes to heat exchange. Second, adopting a design that overcomes this problem places restrictions on the medium flow conditions, making highly efficient operation in complete counterflow difficult. Third, when condensation occurs in the shell-side space, non-condensable gases accumulate. This accumulation of non-condensable gases can also reduce the efficiency of heat exchange.

[0060] <Functions and Effects of Heat Exchanger> The heat exchanger 1 of the present disclosure solves the above-described problems by providing the following functions and effects.

[0061] A heat transfer medium 92 flows from bottom to top in the gap G outside the tubes 3. Steam 91 is introduced into the heat exchanger 1 from the steam inlet 11. The steam 91 has a certain amount of kinetic energy that can be defined by pressure and flow velocity. This steam 91 flows into the tubes 3. The tube inner surfaces 34 are an area that is affected by the heat transfer medium 92, and therefore function as a heat transfer surface. The steam 91 that comes into contact with the tube inner surfaces 34 loses heat, reaches its saturation limit, and condenses. Furthermore, the steam 91 present near the tube inner surfaces 34 also loses heat, reaches its saturation limit, and condenses. As a result of the condensation, condensed liquid is produced. The condensed liquid is, for example, water.

[0062] Because the tubes 3 are arranged such that their central axes L3 are aligned vertically, the tube inner surfaces 34 also extend vertically downward. Therefore, the condensate 93 condensed on the tube inner surfaces 34 moves vertically downward due to the action of gravity and is discharged to the outside through the condensate outlet 12. The amount of condensate 93 condensing increases toward the downstream side of the tubes 3, and the level of the condensate 93 accumulated in the tubes 3 rises. In other words, the area in contact with the condensate 93 gradually increases toward the downstream side. The area in contact with the condensate 93 does not function as a heat transfer surface for condensation. Therefore, the area functioning as a heat transfer surface tends to decrease toward the downstream side.

[0063] In the heat exchanger 1 of the present disclosure, the tube 3 includes a constriction portion P3 in which the area of ​​the flow passage cross section F decreases toward the outlet 33a in the axial direction D1. In this case, as the steam 91 flows through the tube 3, the steam 91 passes through the constriction portion P3, increasing the flow velocity of the steam 91. As a result, the condensate 93 generated in the tube 3 is dragged by the fast-flowing steam 91 and flows toward the outlet 33a. In other words, the condensate 93 follows the flow of the steam 91 and is quickly discharged to the outside of the tube 3 without stagnation. Therefore, the tube inner surface 34 can continue to function as a heat transfer surface. In other words, in the heat exchanger 1 of the present disclosure, the condensate 93 generated by condensation is less likely to remain in the portion functioning as a heat transfer surface. As a result, heat transfer is not hindered by the condensate 93, and a decrease in the efficiency of the heat exchanger 1 can be suppressed.

[0064] Furthermore, when the tubes 3 include the constricted portions P3, a larger portion of the steam 91 can be in direct contact with the inner surface 34 of the tubes 3 as the steam 91 flows from the inlet 32a to the outlet 33a of the tubes 3, compared to when the steam 91 flows through tubes 3 having a constant inner diameter. In this case, heat exchange between the steam 91 flowing through the tubes 3 and the heat medium 92 flowing outside the tubes 3 can be performed more efficiently. Therefore, the heat exchanger 1 of the present disclosure can improve the efficiency of heat exchange. The driving force for moving the condensate 93 through the tubes 3 does not need to be gravity, and may be a driving force other than gravity.

[0065] In short, the heat exchanger 1 of the present disclosure utilizes the increased flow velocity of the steam 91 at the throttle portion P3 to eliminate liquid films that may form on the tube inner surfaces 34, which are heat transfer surfaces. The heat exchanger 1 of the present disclosure is equipped with a mechanism for actively eliminating liquid films in this manner. As a result, it is possible to suppress a reduction in the effective heat transfer surface due to the formation of liquid films on the tube inner surfaces 34. Furthermore, the heat exchanger 1 of the present disclosure can promote heat exchange between the steam 91 and the heat medium 92 by having the steam 91 flow through the throttle portion P3. Furthermore, the heat exchanger 1 of the present disclosure can perform complete counterflow operation. Furthermore, the heat exchanger 1 of the present disclosure flows the steam 91 and condensate 93 through the relatively thin tubes 3 including the throttle portion P3, thereby suppressing the accumulation of incompressible gas.

[0066] As in the heat exchanger 1 of the present disclosure, multiple fins 35 may be formed on the tube inner surface 34. The multiple fins 35 may extend along the axial direction D1 or may be arranged along the circumferential direction D2. In this case, forming multiple fins 35 on the tube inner surface 34 can ensure a larger area of ​​the tube inner surface 34 that functions as a heat transfer surface, i.e., a larger heat transfer area. Furthermore, extending the multiple fins 35 along the axial direction D1 can facilitate the condensate 93 flowing in the axial direction D1 and being discharged to the outside of the tube 3. Therefore, with the above configuration, a larger heat transfer area can be ensured while maintaining the function of the tube inner surface 34 as a heat transfer surface, thereby further improving the heat exchange efficiency.

[0067] As in the heat exchanger 1 of the present disclosure, the multiple fins 35 may be formed on at least the tube inner surface 34 of the constricted portion P3. The height of each of the multiple fins 35 from the tube inner surface 34 may decrease as the fins are positioned closer to the outlet 33a in the axial direction D1. As the steam 91 flows toward the outlet 33a of the tube 3, heat exchange between the steam 91 and the heat medium 92 outside the tube 3 progresses, so the steam 91 flows near the outlet 33a after a significant amount of heat exchange has occurred. Therefore, the heat transfer area near the outlet 33a does not need to be larger than necessary to promote heat exchange. In the above configuration, the height of each of the multiple fins 35 decreases as the fins are positioned closer to the outlet 33a in the axial direction D1. As a result, the volume of the tube 3 can be kept small, thereby reducing the material cost of the tube 3.

[0068] As in the heat exchanger 1 of the present disclosure, the tube 3 may include a first body portion P1 extending along the axial direction D1 between the inlet 32a and the throttle portion P3, and a second body portion P2 extending along the axial direction D1 between the throttle portion P3 and the outlet 33a. The area of ​​the flow path cross section F at each position of the first body portion P1 along the axial direction D1 may be constant. The area of ​​the flow path cross section F at each position of the second body portion P2 along the axial direction D1 may be constant. The area of ​​the flow path cross section F of the second body portion P2 may be smaller than the area of ​​the flow path cross section F of the first body portion P1. In this case, the steam 91 flows through the tube 3 in the order of the first body portion P1, the throttle portion P3, and the second body portion P2, and is then discharged from the outlet 33a of the tube 3. Because the steam 91 flows through the second body portion P2 closer to the outlet 33a after undergoing a large amount of heat exchange, the area of ​​the flow path cross section F of the second body portion P2 does not need to be reduced more than necessary to promote heat exchange. In contrast, in the above configuration, the area of ​​the flow path cross section F of the second body portion P2 is constant, thereby preventing the area of ​​the flow path cross section F of the second body portion P2 from being excessively small. Furthermore, in the above configuration, the area of ​​the flow path cross section F of the first body portion P1 between the inlet 32a and the throttle portion P3 is constant. If the first body portion P1 were not provided and the throttle portion P3 extended from the inlet 32a of the tube 3, for example, the steam 91 could flow through the throttle portion P3 without condensing at all. In this case, the steam 91 is more likely to erode the inner surface 34 of the tube in the throttle portion P3. In contrast, if the first body portion P1 having a constant area of ​​the flow path cross section F is provided between the inlet 32a and the throttle portion P3, heat can be removed from the steam 91 in the first body portion P1 up to a temperature range where a phase change of the steam 91 occurs, and the steam 91 can flow through the throttle portion P3 only after the steam 91 begins to condense. This makes it possible to prevent erosion from occurring on the tube inner surface 34 of the narrowed portion P3.

[0069] As in the heat exchanger 1 of the present disclosure, the tube 3 may include a first throttle region R31 disposed at any position along the axial direction D1, and a second throttle region R32 disposed closer to the outlet 33a in the axial direction D1 than the first throttle region R31 and having a flow path cross-sectional area F smaller than the flow path cross-sectional area F of the first throttle region R31. The thickness T32 of the second throttle region R32 may be equal to or greater than the thickness T31 of the first throttle region R31. In this case, the flow velocity of the steam 91 flowing through the second throttle region R32 is higher than the flow velocity of the steam 91 flowing through the first throttle region R31. As a result, erosion (corrosion) of the tube inner surface 34 by the condensate 93 is more likely to occur in the second throttle region R32 than in the first throttle region R31. In the above configuration, the thickness T32 of the second throttle region R32 is equal to or greater than the thickness T31 of the first throttle region R31, making it possible to prevent a decrease in the mechanical strength of the second throttle region R32 due to erosion.

[0070] As in the heat exchanger 1 of the present disclosure, the thickness T of the tube 3 may be constant at each position along the axial direction D1 from the inlet 32 ​​a to the outlet 33 a. In this case, the tube 3 can be easily manufactured using, for example, three-dimensional molding technology.

[0071] As in the heat exchanger 1 of the present disclosure, the tubes 3 may be formed integrally with the housing 2. In this case, the tubes 3 can be easily manufactured using, for example, three-dimensional modeling technology.

[0072] Like the heat exchanger 1 of the present disclosure, the heat exchanger 1 may include first tubes 3A and second tubes 3B. The first tubes 3A and the second tubes 3B may extend along the axial direction D1 or may be aligned along the direction D3. In this case, the amount of steam 91 can be increased, thereby enabling more efficient heat exchange between the steam 91 and the heat medium 92.

[0073] As in the heat exchanger 1 of the present disclosure, the housing may include a first manifold section 5 that distributes steam 91 and supplies it to the first tubes 3A and the second tubes 3B. A plurality of fins 54 extending along the flow direction of the steam 91 may be formed on the inner wall surface 53 of the first manifold section 5. When a plurality of fins 54 are formed on the inner wall surface 53 of the first manifold section 5, the area of ​​the inner wall surface 53 of the first manifold section 5 that can function as a heat transfer surface, i.e., the heat transfer area, can be secured larger than when a plurality of fins 54 are not formed on the inner wall surface 53. This allows for more efficient heat exchange. Furthermore, when a plurality of fins 54 formed on the inner wall surface 53 of the first manifold section 5 extend along the flow direction of the steam 91, the steam 91 flowing in from the steam inlet 11 can flow more easily in the flow direction than when a plurality of fins 54 extend perpendicular to the flow direction. As a result, condensate 93 formed on the tubes 3 can be more easily discharged to the outside.

[0074] As in the heat exchanger 1 of the present disclosure, the housing 2 may include a second manifold section 6 that joins and discharges the steam 91 from the first tubes 3A and the second tubes 3B. The inner wall surface 63 of the second manifold section 6 may be formed with a plurality of fins 64 extending along the flow direction of the steam 91. When the plurality of fins 64 are formed on the inner wall surface 63 of the second manifold section 6, the area of ​​the inner wall surface 63 of the second manifold section 6 that can function as a heat transfer surface, i.e., the heat transfer area, can be secured larger than when the plurality of fins 64 are not formed on the inner wall surface 63. This allows for more efficient heat exchange. Furthermore, when the plurality of fins 64 formed on the inner wall surface 63 of the second manifold section 6 extend along the flow direction of the steam 91, the condensate 93 that flows into the first condensate inlet 16A and the second condensate inlet 16B can flow in the flow direction and be more easily discharged to the outside through the condensate outlet 12 than when the plurality of fins 64 extend perpendicular to the flow direction. This makes it possible to prevent the condensed liquid 93 from the first tube 3A and the second tube 3B from accumulating in the second manifold portion 6.

[0075] <Modifications> The heat exchanger of the present disclosure is not limited to the embodiments described below, and various modifications are possible without departing from the gist of the present invention.

[0076] FIG. 8 is a cross-sectional view showing a modified example of the tube. In the above-described embodiment, the thickness T of the tube 3 is constant. The thickness TA of the tube 300 shown in FIG. 8 varies. "Thickness TA" refers to the thickness of the tube 300 at any position along the axial direction D1, i.e., the distance between the tube outer surface 31 and the base surface 34b of the tube inner surface 34. The tube 300 includes a constricted portion P3A and a second body portion P2A instead of the constricted portion P3A and the second body portion P2A. The thickness TA of the constricted portion P3A increases as it is positioned closer to the outlet 33a in the axial direction D1. The thickness TA of the second body portion P2A is equal to the maximum value of the thickness TA of the connecting portion P3b of the constricted portion P3A.

[0077] 8 shows a first throttle region R31A (first region), a second throttle region R32A (second region), and a second body region R2A. The first throttle region R31A is a partial region of the throttle portion P3A at an arbitrary position along the axial direction D1. The second throttle region R32A is a partial region of the throttle portion P3A located closer to the outlet 33a in the axial direction D1 than the first throttle region R31A. The second body region R2A is a partial region of the second body portion P2A at an arbitrary position along the axial direction D1.

[0078] Fig. 9(a) is a cross-sectional view showing the flow path cross section F31A of the first throttle region R31A. Fig. 9(b) is a cross-sectional view showing the flow path cross section F32A of the second throttle region R32A. Fig. 9(c) is a cross-sectional view showing the flow path cross section F2A of the second body region R2A. As shown in Fig. 9(a) and Fig. 9(b), the thickness T32A of the second throttle region R32A is thicker than the thickness T31A of the first throttle region R31A.

[0079] Even when the tube 300 shown in FIG. 9 is used, the same effects as those of the above-described embodiment can be obtained. Furthermore, when the thickness T32A of the second throttle region R32A is greater than the thickness T31A of the first throttle region R31A, as in the tube 300, a decrease in the mechanical strength of the second throttle region R32A due to erosion can be more reliably prevented. In this modification, as long as the flow path cross-sectional area of ​​one of the two regions of the tube 300 aligned along the axial direction D1 is smaller than the flow path cross-sectional area of ​​the other region, the regions other than the first throttle region R31A and the second throttle region R32A may be considered the “first region” and the “second region.” For example, the first throttle region R31A may be considered the “first region,” and the second throttle region R32A or the second body region R2A may be considered the “second region,” or the second throttle region R32A may be considered the “first region,” and the second body region R2A may be considered the “second region.”

[0080] The heat exchanger of the present disclosure may have the following configuration, for example.

[0081] The present disclosure is [1] "a tube used in a heat exchanger, characterized in that the cross-sectional area, when cut vertically in the direction of fluid flow in the flow path, decreases from one end of the flow path to the other end of the flow path."

[0082] The present disclosure is [2] "A heat exchanger according to the above [1], characterized in that the inside of the flow path has a fin structure."

[0083] The present disclosure is [3] "a heat exchanger as described in [1] or [2] above, in which the thickness of the portion where the cross-sectional area of ​​the flow path is reduced is equal to or greater than the thickness of the portion where the cross-sectional area of ​​the flow path is larger than that portion."

[0084] The present disclosure is [4] "A heat exchanger according to any one of the above [1] to [3], wherein the thickness of the tube is constant throughout the tube."

[0085] The present disclosure is [5] "A heat exchanger according to any one of the above [1] to [3], characterized in that it has a portion where the thickness of the portion where the cross-sectional area of ​​the flow path is smaller is greater than the thickness of the portion where the cross-sectional area of ​​the flow path is larger than that portion."

[0086] The present disclosure is [6] "A heat exchanger described in any one of [1] to [5] above, characterized in that the tubes are manufactured using a 3D printer."

[0087] The present disclosure is [7] "A heat exchanger characterized by including a plurality of tubes according to any one of [1] to [6] above."

[0088] 1...heat exchanger, 2...casing, 3, 3A, 3B, 300...tubes, 3A...first tube, 3B...second tube, 5...first manifold section, 6...second manifold section, 11...steam inlet (inlet), 12...condensate outlet (outlet), 15A...first steam outlet (first outlet), 15B...second steam outlet (second outlet), 16A...first condensate inlet (first inlet), 16B...second condensate inlet (second inlet), 31...tube outer surface, 32...first end , 32a...inlet, 33...second end, 33a...outlet, 34...inner surface of tube, 35, 54, 64...fins, 44...inner surface of housing, 53, 63...inner wall surface, 91...steam (first heat medium), 92...heat medium (second heat medium), D1...axial direction, D2...circumferential direction, D3...direction, L3...central axis, P1...first body portion, P2, P2A...second body portion, P3, P3A...throttling portion, R31, R31A...first throttle region (first region), R32, R32A...second throttle region (second region).

Claims

1. A heat exchanger capable of transferring heat between a first heat medium and a second heat medium, comprising: a tube through which the first heat medium flows; and a casing including an inner surface of a casing surrounding the tube, the second heat medium flowing between a tube outer surface that is the outer surface of the tube and the inner surface of the casing, the tube including: an inlet formed at a first end in an axial direction along which a central axis of the tube extends, through which the first heat medium flows; an outlet formed at a second end of the tube opposite to the first end, through which the first heat medium flows out; and a tube inner surface extending along the axial direction from the inlet to the outlet and surrounding a flow path of the first heat medium, wherein when a flow path cross-sectional area is defined as an area of ​​a cross-sectional region surrounded by the tube inner surface when the tube is cut by a plane perpendicular to the central axis, the tube includes a constriction portion where the flow path cross-sectional area decreases the closer to the outlet in the axial direction.

2. A heat exchanger as described in claim 1, wherein a plurality of fins are formed on the inner surface of the tube, the fins extending along the axial direction and arranged along the circumferential direction of the tube.

3. A heat exchanger as described in claim 2, wherein the plurality of fins are formed at least on the inner surface of the tube in the constricted portion, and the height of each of the plurality of fins decreases as they are positioned closer to the outlet in the axial direction.

4. A heat exchanger as described in any one of claims 1 to 3, wherein the tube further includes a first body portion extending along the axial direction between the inlet and the throttle portion, and a second body portion extending along the axial direction between the throttle portion and the outlet, wherein the flow path cross-sectional area at each position of the first body portion and the second body portion along the axial direction is constant, and the flow path cross-sectional area of ​​the second body portion is smaller than the flow path cross-sectional area of ​​the first body portion.

5. A heat exchanger as described in any one of claims 1 to 4, wherein the tube includes a first region arranged at an arbitrary position along the axial direction, and a second region arranged at a position closer to the outlet in the axial direction than the first region and having a flow path cross-sectional area smaller than the flow path cross-sectional area of ​​the first region, and a thickness of the second region from the outer surface of the tube to the inner surface of the tube is greater than or equal to a thickness of the first region from the outer surface of the tube to the inner surface of the tube.

6. A heat exchanger as claimed in claim 5, wherein the thickness of said tube from the outer surface of said tube to the inner surface of said tube is constant at each position along said axial direction from said inlet to said outlet.

7. The heat exchanger of claim 5, wherein said thickness of said second region is greater than said thickness of said first region.

8. A heat exchanger according to any one of claims 1 to 7, wherein the tubes are integrally formed with the housing.

9. A heat exchanger according to any one of claims 1 to 8, comprising a first tube and a second tube as the tubes, the first tube and the second tube extending along the axial direction and aligned along a direction perpendicular to the axial direction.

10. A heat exchanger as described in claim 9, wherein the housing includes a first manifold portion which distributes the first heat medium and supplies it to the first tube and the second tube, the first manifold portion including: an inlet through which the first heat medium flows in; a first outlet connected to the inlet of the first tube and through which a portion of the first heat medium flows out from the inlet; a second outlet connected to the inlet of the second tube and through which at least a portion of the remainder of the first heat medium flows out from the inlet; and an inner wall surface extending from the inlet to the first outlet and the second outlet and surrounding a flow path of the first heat medium, and a plurality of fins extending along a flow direction of the first heat medium are formed on the inner wall surface of the first manifold portion.

11. A heat exchanger as described in claim 9 or 10, wherein the housing includes a second manifold portion that joins and discharges the first heat medium from the first tube and the second tube, the second manifold portion including: a first inlet connected to the outlet of the first tube and through which the first heat medium flows in from the outlet of the first tube; a second inlet connected to the outlet of the second tube and through which the first heat medium flows in from the outlet of the second tube; an outlet through which the first heat medium flows out from the first inlet and the second inlet; and an inner wall surface extending from the first inlet and the second inlet to the outlet and surrounding a flow path of the first heat medium, and a plurality of fins extending along the flow direction of the first heat medium are formed on the inner wall surface of the second manifold portion.

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