Patent Grant
11022376
The present invention relates to a heat exchanger, and more particularly, it relates to a heat exchanger that performs heat exchange between a first fluid and a second fluid.
Conventionally, a heat exchanger that performs heat exchange between a first fluid and a second fluid is known. Such a heat exchanger is disclosed in Japanese Patent Laid-Open No. 2010-101617, for example.
Japanese Patent Laid-Open No. 2010-101617 discloses a plate-fin heat exchanger including a layer through which no fluid flows between heat exchange passage packages in which first passages through which a first fluid flows and second passages through which a second fluid flows are alternately disposed. In the heat exchange between the first fluid and the second fluid, the thermal stress increases as the temperature gradient increases. Therefore, in Japanese Patent Laid-Open No. 2010-101617, the layer through which no fluid flows is disposed between the heat exchange passage packages such that the temperature gradient is significantly reduced, and the thermal stress is reduced. The heat exchanger disclosed in Japanese Patent Laid-Open No. 2010-101617 is particularly used for applications such as liquefaction or vaporization of a natural gas having a large temperature difference with a fluid.
Patent Document 1: Japanese Patent Laid-Open No. 2010-101617
When the low-temperature first fluid is a cryogenic liquefied gas and the high-temperature second fluid is water or antifreeze, for example, there is a possibility that the passages are clogged by solidifying (freezing).
In the heat exchanger disclosed in Japanese Patent Laid-Open No. 2010-101617, although it is possible to reduce the thermal stress by providing the layer through which no fluid flows and significantly reducing or preventing excessive heat transfer between the flow paths, no consideration is given to the risk of occurrence of freezing in the flow paths, and there is a problem that the flow paths may be clogged by occurrence of freezing. In addition, simply providing the layer through which no fluid flows between the flow paths reduces the heat exchange performance, and thus there is a problem that the size of the heat exchanger is increased due to an increase in flow path length, for example.
The present invention has been proposed in order to solve the aforementioned problems, and one object of the present invention is to provide a heat exchanger in which an increase in its size can be significantly reduced or prevented while fluid freezing is significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference.
In order to attain the aforementioned object, a heat exchanger according to the present invention includes a first flow path through which a first fluid flows, a second flow path through which a second fluid flows, and an adjustment layer disposed between the first flow path and the second flow path adjacent to each other and that adjusts an amount of heat exchange between the first flow path and the second flow path, and the adjustment layer includes a first portion and a second portion having a heat transfer performance lower than that of the first portion, and has a heat transfer performance varied depending on a position in the adjustment layer.
As described above, the heat exchanger according to the present invention includes the adjustment layer disposed between the first flow path and the second flow path adjacent to each other and that adjusts the amount of heat exchange between the first flow path and the second flow path. Accordingly, the adjustment layer between the first flow path and the second flow path can significantly reduce or prevent excessive heat transfer between the first flow path and the second flow path. Consequently, fluid freezing can be significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference. Furthermore, the adjustment layer includes the first portion and the second portion having a heat transfer performance lower than that of the first portion, and has a heat transfer performance varied depending on the position in the adjustment layer 30. Accordingly, the second portion is disposed in a portion in which freezing is likely to occur in the flow path to sufficiently decrease the heat transfer performance while the first portion is disposed in a portion in which freezing is unlikely to occur to relatively increase the heat transfer performance such that the high heat exchange performance can be ensured. Accordingly, an increase in a flow path length required to realize a desired amount of heat exchange can be significantly reduced or prevented. Thus, an increase in the size of the heat exchanger can be significantly reduced or prevented while fluid freezing is significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference.
According to the present invention including the aforementioned configuration, even when there is a possibility of fluid boiling due to heat exchange, the fluid boiling can be significantly reduced or prevented. Occurrence of unintentional boiling in the flow path may increase the load related to the strength of the heat exchanger, and may not be acceptable due to the specification of the heat exchanger. According to the present invention, the second portion is disposed in a portion in which boiling is likely to occur in the flow path such that the heat transfer performance can be sufficiently decreased while the first portion is disposed in a portion in which boiling is unlikely to occur such that the heat transfer performance can be relatively increased. Accordingly, an increase in a flow path length required to realize a desired amount of heat exchange can be significantly reduced or prevented. Thus, an increase in the size of the heat exchanger can be significantly reduced or prevented while unintentional fluid boiling is significantly reduced or prevented.
In the aforementioned heat exchanger according to the present invention, in the adjustment layer, the second portion is preferably provided within a predetermined range including a portion that overlaps a vicinity of an inlet or a vicinity of an outlet of the second fluid. According to this configuration, when the temperature of the second fluid monotonously decreases along the second flow path, for example, the second portion includes the portion that overlaps the vicinity of the outlet of the second fluid, which is highly likely to freeze such that occurrence of freezing can be effectively and significantly reduced or prevented. When the temperature of the first fluid becomes cryogenic in the vicinity of the inlet of the second fluid in a parallel-flow heat exchanger and the inner surface temperature of the second flow path is close to the freezing temperature, for example, the second portion includes the portion that overlaps the vicinity of the inlet of the second fluid, which is highly likely to freeze such that occurrence of freezing can be effectively and significantly reduced or prevented.
In the aforementioned heat exchanger according to the present invention, the second flow path preferably includes a risk area in which an inner surface temperature of the second flow path is closest to a temperature of the first fluid, and in the adjustment layer, the second portion is preferably disposed within a predetermined range including a portion that overlaps the risk area of the second flow path. According to this configuration, the second portion overlaps the risk area such that occurrence of freezing can be more reliably and significantly reduced or prevented. The risk area can be set as an area in which the inner surface temperature of the second flow path obtained by calculating the temperature distribution of the inner surface of the second flow path when the adjustment layer is not provided (when the first flow path and the second flow path are directly adjacent to each other), for example, is closest to the temperature of the first fluid.
In the aforementioned heat exchanger according to the present invention, the adjustment layer preferably includes heat conduction portions that make a connection between the first flow path and the second flow path adjacent to each other, and the first portion and the second portion preferably include the heat conduction portions having different heat transfer performances. According to this configuration, the shape and dimensions of the adjustment layer itself are not adjusted, but the number, size, material, etc. of the heat conduction portions are changed such that the distribution of the heat transfer performances in the first portion and the second portion can be easily adjusted. Consequently, the appropriate distribution of the heat transfer performances according to the risk of occurrence of fluid freezing in the adjustment layer can be easily realized.
In this case, a density per unit area of the heat conduction portions in the adjustment layer is preferably varied such that the heat conduction portions have the different heat transfer performances. According to this configuration, unlike the case in which a plurality of types of heat conduction portions made of different materials are provided, for example, the number of heat conduction portions per unit area is changed or a plurality of heat conduction portions having different sizes are arranged at an equal pitch, for example, such that the heat transfer performances of the heat conduction portions can be easily varied.
In the aforementioned configuration in which the adjustment layer includes the heat conduction portions, each of the first flow path, the second flow path, and the adjustment layer preferably includes a planar flow path layer, and includes a heat transfer fin inside the planar flow path layer, the heat conduction portions are preferably constituted by the heat transfer fin disposed in the adjustment layer, and at least one of intervals between fin sections of the heat transfer fin and thicknesses of the fin sections are preferably different from each other such that the heat conduction portions have the different heat transfer performances. According to this configuration, the first flow path, the second flow path, and the adjustment layer can share a similar basic structure, and thus each of the first flow path, the second flow path, and the adjustment layer can be each of the flow path layers of the so-called plate-fin heat exchanger. Consequently, unlike the case in which a special structure is used for the adjustment layer, the heat exchanger can be easily constructed even when the adjustment layer is provided. In addition, the heat transfer performance of the adjustment layer can be varied by a simple configuration in which the intervals between the fin sections or the thicknesses of the fin sections are simply different from each other.
In the aforementioned heat exchanger according to the present invention, the adjustment layer preferably has a hollow flow path structure disposed between the first flow path and the second flow path and through which a fluid can flow except during the heat exchange. According to this configuration, the hollow structure can easily decrease the heat transfer performance of the adjustment layer, and thus occurrence of freezing can be effectively and significantly reduced or prevented. In addition, the adjustment layer has a hollow flow path structure through which a fluid can flow except during the heat exchange such that as a measure against occurrence of fluid freezing, a heat medium having a temperature higher than the freezing temperature can flow through the adjustment layer except during the heat exchange between the first fluid and the second fluid so as to quickly eliminate freezing.
In the aforementioned heat exchanger according to the present invention, the first fluid is preferably a low-temperature liquefied gas evaporated in the first flow path, and the second fluid is preferably a liquid heat medium cooled by the liquefied gas. In such a configuration, there is a possibility of freezing on the second fluid side by heat exchange between the cryogenic first fluid and the second fluid. Even in this case, the first portion and the second portion are provided to vary the heat transfer performance of the adjustment layer such that the heat transfer efficiency can be increased as much as possible within a range in which freezing of the second fluid can be significantly reduced or prevented, and thus an increase in the size of the heat exchanger can be effectively and significantly reduced or prevented.
In this case, in the adjustment layer, the first portion is preferably disposed within a range that overlaps a vapor phase region of the first fluid that flows through the first flow path, and in the adjustment layer, the second portion is preferably disposed within a range that overlaps a vapor-liquid mixed phase region of the first fluid that flows through the first flow path. According to this configuration, in the vapor-liquid mixed phase region in which the heat transfer coefficient of the first fluid is high, freezing of the second fluid is significantly reduced or prevented by the second portion having a low heat transfer performance, and in the vapor phase region in which the heat transfer coefficient of the first fluid is low, heat exchange can be efficiently performed by the first portion having a high heat transfer performance. Consequently, the heat exchanger can be made as compact as possible while freezing of the second fluid is significantly reduced or prevented.
In the aforementioned structure in which the adjustment layer has a hollow flow path structure through which a fluid can flow except during the heat exchange, when freezing of the second fluid occurs in the second flow path, a heat medium is preferably supplied to the adjustment layer except during the heat exchange so as to eliminate the freezing of the second fluid. According to this configuration, even when freezing occurs in the second flow path, the heat medium for eliminating freezing is supplied to the adjustment layer after the heat exchange (supply of the first fluid and the second fluid) is stopped such that freezing can be easily and quickly eliminated.
According to the present invention, as described above, the heat exchanger in which an increase in its size can be significantly reduced or prevented while fluid freezing is significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference can be provided.
An embodiment of the present invention is hereinafter described on the basis of the drawings.
The configuration of a heat exchanger 100 according to the present embodiment is now described with reference to
The heat exchanger 100 shown in
The liquefied gas is hydrogen, oxygen, nitrogen or a natural gas, for example. The heat medium used for a liquefied gas evaporator is varied, but from the viewpoint of availability (low cost) etc., a liquid such as water, seawater, or antifreeze, air, or the like is used. These liquids and air (moisture in the air) have the property of freezing at a temperature higher than the supply temperature of the liquefied gas.
In the first embodiment, the heat exchanger 100 includes a plate-fin core 1. The plate-fin core 1 is a heat exchanging portion having a stacked structure in which a plurality of planar flow path layers 2 are stacked. In the following description, for convenience, the stacking direction of the flow path layers 2 is defined as a Z direction (or an upward-downward direction), a longitudinal direction along one side of the core 1 in a horizontal plane orthogonal to the Z direction is defined as an X direction, and a short-side direction along another side of the core 1 in the horizontal plane orthogonal to the Z direction is defined as a Y direction.
The flow path layers 2 of the core 1 each have a planar (flat plate) structure including a heat transfer fin 3 and side bars 4 that constitute the outer peripheral wall of the heat transfer fin 3. In addition, each flow path layer 2 is divided by tube plates 5, which are partition walls on the stacking direction side. The heat transfer fin 3 is a corrugated fin having a corrugated shape, and contacts the upper and lower tube plates 5 at the peak portions of the corrugated portions. The corrugated heat transfer fin 3 divides the inside of the flow path layer 2 to create a plurality of flow paths (channels). The tube plates 5 and the heat transfer fin 3 function as heat transfer surfaces that transmit heat in the core 1. In the core 1, a stacked body of the stacked flow path layers 2 is sandwiched by a pair of side plates 6 and is bonded by brazing or the like such that the core 1 has a rectangular box shape (rectangular parallelepiped shape) as a whole. The core 1 is made of a material such as stainless steel, for example.
The core 1 includes first flow paths 10 through which a first fluid 7 flows and second flow paths 20 through which a second fluid 8 flows. In the present embodiment, the first fluid 7 is a low-temperature fluid, and the second fluid 8 is a high-temperature fluid. That is, the first fluid 7 is a low-temperature liquefied gas evaporated in the first flow paths 10, and the second fluid 8 is a liquid heat medium cooled by the liquefied gas. It is assumed that the first fluid 7 and the second fluid 8 are fluids, one of which may be frozen by heat exchange with the other. In the present embodiment, among the first fluid 7 and the second fluid 8, the second fluid 8 is a fluid having a risk of occurrence of freezing in the flow path. As an example in the present embodiment, the liquefied gas is liquid hydrogen, for example, and the heat medium is antifreeze, for example. The antifreeze is a liquid that mainly contains water and a freezing point depressant (such as ethylene glycol). The first fluid 7 is an example of a “liquefied gas” in the claims. The second fluid 8 is an example of a “heat medium” in the claims.
In the present embodiment, the core 1 further includes an adjustment layer 30 disposed between the first flow path 10 and the second flow path 20 adjacent to each other and that adjusts the amount of heat exchange between the first flow path 10 and the second flow path 20. The adjustment layer 30 is disposed between all the first flow paths 10 and the second flow paths 20. That is, in the core 1, the flow path layers are stacked in the order of the first flow path 10, the adjustment layer 30, the second flow path 20, the adjustment layer 30, . . . . Therefore, in the present embodiment, the first flow path 10 and the second flow path 20 are not directly adjacent to each other (with the tube plate 5 interposed therebetween).
As shown in
The structure of each of the flow path layers 2 (the first flow path 10, the second flow path 20, and the adjustment layer 30) is now described with reference to
<First Flow Path>
As shown in
The heat transfer fin 3 provided in the first flow path 10 is hereinafter referred to as the heat transfer fin 13. The heat transfer fin 13 of the first flow path 10 extends from the inlet 11 to the outlet 12 of the first flow path 10. In
Header tanks or the like (not shown) are attached to the inlet 11 and the outlet 12, respectively. The first fluid 7 in the liquid phase is supplied from the outside to the inlet 11 via the header tank, and the first fluid 7 (gas 7a) after heat exchange (after vaporization) is discharged from the outlet 12 via the header tank. Therefore, the first flow path 10 includes a liquid phase region (L), a vapor-liquid mixed phase region (L+V), and a vapor phase region (V) from the inlet 11 side toward the outlet 12 side based on phase changes in the first fluid 7 that flows through the first flow path 10.
<Second Flow Path>
As shown in
The heat transfer fin 3 provided in the second flow path 20 is hereinafter referred to as the heat transfer fin 23. The heat transfer fin 23 of the second flow path 20 extends from the inlet 21 to the outlet 22 of the second flow path 20. In
Header tanks or the like (not shown) are attached to the inlet 21 and the outlet 22, respectively. The second fluid 8 is supplied from the outside to the inlet 21 via the header tank, and the second fluid 8 after heat exchange is discharged from the outlet 22 via the header tank.
<Adjustment Layer>
As shown in
Returning to
In this specification, the heat transfer performance of the adjustment layer 30 indicates the ease of heat transmission when heat is transmitted between the first flow path 10 and the second flow path 20 via the adjustment layer 30. The heat transfer performance can be considered as total performance including heat transmission due to each of heat conduction, heat transfer (convection heat transfer), and heat radiation.
In a configuration example shown in
In the present embodiment, in the adjustment layer 30, the second portion 32 is disposed within the predetermined range including a portion that overlaps a risk area RA of the second flow path 20. The risk area RA is an area of the second flow path 20 in which the inner surface temperature is closest to the temperature of the first fluid 7. The inner surface temperature of the second flow path 20 is the surface temperatures of the tube plates 5 that define the second flow path 20. The inner surface temperature of the second flow path 20 is influenced by the temperature of the low-temperature first fluid 7 and the heat transfer performance on the first flow path 10 side, and thus the positions and ranges of the first portion 31 and the second portion 32 are set by the relationship between the first fluid 7 that flows through the first flow path 10 and the second fluid 8 that flows through the second flow path 20.
Specifically, referring to
The heat transfer performance in the first flow path 10 varies with phase changes in the liquefied gas that flows through the first flow path 10. The vapor-liquid mixed phase region (L+V) is a region in which the heat transfer coefficient of the first fluid 7 becomes the highest and the inner surface temperature of the second flow path 20 becomes closest to the temperature of the first fluid 7 with heat exchange. That is, the risk area RA in which the risk of occurrence of freezing of the second fluid 8 in the second flow path 20 is the highest is an area that overlaps the vapor-liquid mixed phase region (L+V) of the first flow path 10. Furthermore, in the second flow path 20, a region that overlaps the liquid phase region (L) of the first flow path 10 is on the downstream side (outlet 22 side) of the risk area RA, and thus in the region, the risk of occurrence of freezing is the second highest next to that in the vapor-liquid mixed phase region (L+V). On the other hand, the vapor phase region (V) is a region in which the temperature of the first fluid 7 increases in the first flow path 10, and in the region, the heat transfer coefficient of the first fluid 7 is the lowest. In addition, as compared with the remaining regions, the inner surface temperature of the second flow path 20 is not decreased. Therefore, a region that overlaps the vapor phase region (V) is a region in which the first portion 31 with a low risk of occurrence of freezing and a high heat transfer performance can be placed.
The liquid phase region (L), the vapor-liquid mixed phase region (L+V), and the vapor phase region (V) in the first flow path 10 can be analytically determined based on the type of fluid, the flow rate, the inlet temperature and outlet temperature, the working pressure, and design information about the structure of each flow path, for example.
In the configuration examples shown in
In the present embodiment, the adjustment layer 30 includes heat conduction portions 33 that make a connection between the first flow path 10 and the second flow path 20 adjacent to each other. The heat conduction portions 33 contact the tube plate 5 (see
The adjustment layer 30 has a hollow structure through which no fluid flows, and thus most of heat transmission is due to heat conduction through the heat conduction portions 33 while heat transmission due to heat transfer (convection heat transfer) and heat radiation is slight as compared with heat conduction. Therefore, in the adjustment layer 30, it is possible to vary the heat transfer performance depending on the structure, arrangement, and number of the heat conduction portions 33.
The heat conduction portions 33 are not particularly restricted as long as the same each have a structure that makes a connection between the first flow path 10 and the second flow path 20 (between the tube plates 5). The heat conduction portions 33 may be columnar or block-shaped members, or may be plate-shaped or lattice-shaped members, for example. In the present embodiment, the heat conduction portions 33 are constituted by the heat transfer fin 34 (heat transfer fin 3) disposed in the adjustment layer 30. The heat transfer fin 34 is a corrugated fin similar to the heat transfer fins 13 and 23 of the other flow path layers 2. In this case, as shown in
In the present embodiment, the first portion 31 and the second portion 32 include the heat conduction portions 33 having different heat transfer performances. Specifically, the density per unit area of the heat conduction portions 33 in the adjustment layer 30 is varied such that the heat conduction portions 33 have different heat transfer performances. In the present embodiment in which the heat conduction portions 33 are constituted by the heat transfer fin 34, intervals between the longitudinal plates 35 of the heat transfer fin 34 are different from each other such that the heat conduction portions 33 have different heat transfer performances. That is, the pitches of the heat conduction portions 33 (the longitudinal plates 35 of the heat transfer fin 34) are different between the first portion 31 and the second portion 32. The longitudinal plates 35 are examples of a “fin section” in the claims.
That is, as shown in
For example, a configuration example in
The thickness of each of the longitudinal plates 35 may be different between the first portion 31 and the second portion 32. That is, the thickness t1 in the heat transfer fin 34a of the second portion 32 and the thickness t2 in the heat transfer fin 34b of the first portion 31 may be different from each other such that the heat conduction portions 33 may have different heat transfer performances. Both the pitch and the thickness of the longitudinal plates 35 may be different between the first portion 31 and the second portion 32. In this case, the density of the longitudinal plates 35 per unit area may be relatively low in the second portion 32 and may be relatively high in the first portion 31.
With such a configuration, the heat transfer performance of the second portion 32 of the adjustment layer 30 is relatively low. Consequently, the second portion 32 significantly reduces or prevents freezing of the second fluid 8 of the second flow path 20 even when the cryogenic first fluid 7 flows in through the inlet 11 of the first flow path 10.
On the other hand, the heat transfer performance of the first portion 31 of the adjustment layer 30 is relatively high. Consequently, the first portion 31 promotes heat exchange between the first flow path 10 and the second flow path 20 as compared with the second portion 32.
According to the present embodiment, the following effects are achieved.
According to the present embodiment, as described above, the adjustment layer 30 disposed between the first flow path 10 and the second flow path 20 adjacent to each other and that adjusts the amount of heat exchange between the first flow path 10 and the second flow path 20 is provided. Accordingly, the adjustment layer 30 between the first flow path 10 and the second flow path 20 can significantly reduce or prevent excessive heat transfer between the first flow path 10 and the second flow path 20. Consequently, fluid freezing can be significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference. Furthermore, the adjustment layer 30 includes the first portion 31 and the second portion 32 having a heat transfer performance lower than that of the first portion 31, and has a heat transfer performance varied depending on the position in the adjustment layer 30. Accordingly, the second portion 32 is disposed in a portion in which freezing is likely to occur in the flow path to sufficiently decrease the heat transfer performance while the first portion 31 is disposed in a portion in which freezing is unlikely to occur to relatively increase the heat transfer performance such that the high heat exchange performance can be ensured. Accordingly, an increase in a flow path length required to realize a desired amount of heat exchange can be significantly reduced or prevented. Thus, an increase in the size of the heat exchanger 100 can be significantly reduced or prevented while fluid freezing is significantly reduced or prevented even when heat exchange is performed between fluids having a large temperature difference.
According to the present embodiment, as described above, in the adjustment layer 30, the second portion 32 is provided within the predetermined range (the range of the distance D1) including the portion that overlaps the vicinity of the inlet 21 or the vicinity of the outlet 22 of the second fluid 8. Accordingly, when the temperature of the second fluid 8 monotonously decreases along the second flow path 20, for example, the second portion 32 includes the portion that overlaps the vicinity of the outlet 22 of the second fluid 8, which is highly likely to freeze such that occurrence of freezing can be effectively and significantly reduced or prevented.
According to the present embodiment, as described above, in the adjustment layer 30, the second portion 32 is disposed within the predetermined range (the range of the distance D1) including the portion that overlaps the risk area RA (the area in which the inner surface temperature of the second flow path 20 is closest to the temperature of the first fluid 7) of the second flow path 20. Accordingly, the second portion 32 overlaps the risk area RA such that occurrence of freezing can be more reliably and significantly reduced or prevented.
According to the present embodiment, as described above, the adjustment layer 30 includes the heat conduction portions 33 that make a connection between the first flow path 10 and the second flow path 20 adjacent to each other, and the first portion 31 and the second portion 32 include the heat conduction portions 33 having different heat transfer performances. Accordingly, the shape and dimensions of the adjustment layer 30 itself are not adjusted, but the number, size, material, etc. of the heat conduction portions 33 are changed such that the distribution of the heat transfer performances in the first portion 31 and the second portion 32 can be easily adjusted. Consequently, the appropriate distribution of the heat transfer performances according to the risk of occurrence of fluid freezing in the adjustment layer 30 can be easily realized.
According to the present embodiment, as described above, the density per unit area of the heat conduction portions 33 (the pitch of the longitudinal plates 35) in the adjustment layer 30 is varied such that the heat conduction portions 33 have different heat transfer performances. Accordingly, the heat transfer performances of the heat conduction portions 33 can be easily varied depending on their positions in the flowing direction, unlike the case in which a plurality of types of heat conduction portions 33 made of different materials are provided, for example.
According to the present embodiment, as described above, the first flow path 10, the second flow path 20, and the adjustment layer 30 each include the planar flow path layer 2. Furthermore, the heat conduction portions 33 are constituted by the heat transfer fin 34 (heat transfer fin 3) disposed in the adjustment layer 30, and at least one of the pitches (P3, P4) between the longitudinal plates 35 of the heat transfer fin 34 (34a, 34b) and the thicknesses (t1, t2) of the longitudinal plates 35 are different from each other such that the heat conduction portions 33 have different heat transfer performances. Accordingly, the first flow path 10, the second flow path 20, and the adjustment layer 30 can share a similar basic structure, and thus each of the first flow path 10, the second flow path 20, and the adjustment layer 30 can be each of the flow path layers 2 of the plate-fin heat exchanger 100. Consequently, unlike the case in which a special structure is used for the adjustment layer 30, the heat exchanger 100 can be easily constructed even when the adjustment layer 30 is provided. In addition, the heat transfer performance of the adjustment layer 30 can be varied by a simple configuration in which the pitches between the longitudinal plates 35 or the thicknesses of the longitudinal plates 35 are simply different from each other.
According to the present embodiment, as described above, the first fluid 7 is a low-temperature liquefied gas evaporated in the first flow path 10, and the second fluid 8 is a liquid heat medium cooled by the liquefied gas. In such a configuration, there is a possibility of freezing on the second fluid 8 side by heat exchange between the cryogenic first fluid 7 and the second fluid 8. Even in this case, the first portion 31 and the second portion 32 are provided to vary the heat transfer performance of the adjustment layer 30 such that the heat transfer efficiency can be increased as much as possible within a range in which freezing of the second fluid 8 can be significantly reduced or prevented, and thus an increase in the size of the heat exchanger 100 can be effectively and significantly reduced or prevented.
According to the present embodiment, as described above, in the adjustment layer 30, the first portion 31 is disposed within the range that overlaps the vapor phase region (V) of the first fluid 7 that flows through the first flow path 10, and in the adjustment layer 30, the second portion 32 is disposed within the range that overlaps the vapor-liquid mixed phase region (L+V) of the first fluid 7 that flows through the first flow path 10. Accordingly, in the vapor-liquid mixed phase region (L+V) in which the heat transfer coefficient of the first fluid 7 is high, freezing of the second fluid 8 is significantly reduced or prevented by the second portion 32 having a low heat transfer performance, and in the vapor phase region (V) in which the heat transfer coefficient of the first fluid 7 is low, heat exchange can be efficiently performed by the first portion 31 having a high heat transfer performance. Consequently, the heat exchanger 100 can be made as compact as possible while freezing of the second fluid 8 is significantly reduced or prevented.
The effects of the heat exchanger 100 according to the present embodiment are now described using simulation results with reference to
The simulation was performed on Comparative Example 1 in which the adjustment layer 30 was not provided (in which the first flow path 10 and the second flow path 20 are divided by the tube plate 5), Comparative Example 2 in which only the low-density heat transfer fin 34a was provided over the entire adjustment layer 30 (in which the heat transfer performance of the entire adjustment layer 30 corresponded to the heat transfer performance of the second portion 32), and Comparative example 3 in which only the high-density heat transfer fin 34b was provided over the entire adjustment layer 30 (in which the heat transfer performance of the entire adjustment layer 30 corresponded to the heat transfer performance of the first portion 31) in addition to the heat exchanger 100 according to the present embodiment described above.
In the simulation, hydrogen (liquid hydrogen) was used as the first fluid 7, antifreeze was used as the second fluid 8, and a calculation was performed with the same conditions such as the flow rate and the pressure. As the simulation conditions, the inlet temperature of the liquid hydrogen was −253° C., the boiling point thereof was −242.5° C., and the outlet temperature thereof was −50° C. The freezing point of the antifreeze was −50° C., the inlet temperature thereof was −39° C., and the outlet temperature (target temperature) thereof after cooling with hydrogen was −43° C. In the simulation, the average of the surface temperature (the surface temperature on the second flow path 20 side; see
<Risk of Occurrence of Freezing>
As a common trend in
In the heat exchanger 100 (see
In the heat exchanger 100 according to the present embodiment and Comparative Example 2, it has been found that the surface temperature is −50° C. or higher, and thus freezing of the antifreeze hardly occurs. On the other hand, in Comparative Example 1 and Comparative Example 3, it has been found that the surface temperature is lower than −50° C., and thus freezing of the antifreeze occurs.
<Flow Path Length>
When the flow path length of the heat exchanger 100 according to the present embodiment was 1, the flow path length was 0.38 in Comparative Example 1, 1.18 in Comparative Example 2, and 0.99 in Comparative Example 3. That is, the flow path length required to move the same amount of heat is in the order of Comparative Example 1<Comparative Example 3<the present embodiment<Comparative Example 2.
The simulation results together indicate that although the heat transfer performance is high and the flow path length can be reduced in Comparative Example 1 in which the adjustment layer 30 is not provided and Comparative Example 3 in which only the high-density heat transfer fin 34b is provided in the adjustment layer 30, freezing occurs in the second flow path 20, and thus there is a risk of clogging the flow path. On the other hand, the simulation results together indicate that although freezing in the second flow path 20 can be prevented in Comparative Example 2 in which only the low-density heat transfer fin 34b is provided in the adjustment layer 30, the flow path length is 1.18 times that in the present embodiment, and the size of the heat exchanger is increased.
On the other hand, the simulation results together indicate that in the heat exchanger 100 according to the present embodiment, freezing in the second flow path 20 can be prevented similarly to Comparative Example 3, and the temperature of the liquid hydrogen can be increased to the target temperature with the same flow path length as that in Comparative Example 2. Therefore, in the heat exchanger 100 according to the present embodiment, it has been confirmed that an increase in its size can be significantly reduced or prevented while fluid freezing is significantly reduced or prevented.
In the heat exchanger 100, the risk area RA and the position and range of the second portion 32 in the adjustment layer 30 can be set based on the temperature distribution in Comparative Example 1 (in which the adjustment layer 30 is not provided) shown in
[Modified Examples]
The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is not shown by the above description of the embodiment but by the scope of claims for patent, and all modifications (modified examples) within the meaning and scope equivalent to the scope of claims for patent are further included.
For example, while the example in which the low-temperature liquefied gas is used as the first fluid 7 and the liquid heat medium for vaporizing the liquefied gas is used as the second fluid 8 has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the first fluid 7 may be a high-temperature gas such as exhaust gas after combustion or after reaction, and the second fluid 8 may be a liquid refrigerant (such as water) for cooling the high-temperature gas. That is, the first flow path 10 may be a flow path on the high-temperature side, and the second flow path 20 may be a flow path on the low-temperature side. In this case, boiling of the second fluid 8 may occur in the second flow path 20 due to heat exchange. The occurrence of unintentional boiling in the flow path may increase the load related to the strength of the heat exchanger, and may not be acceptable due to the specification of the heat exchanger. In the present invention, even when there is a possibility of fluid boiling, boiling of the second fluid 8 in the second flow path 20 can be significantly reduced or prevented by the adjustment layer 30. Furthermore, the adjustment layer 30 includes the first portion 31 and the second portion 32 having different heat transfer performances such that the high heat exchange performance can be ensured, and thus an increase in the size of the heat exchanger can be significantly reduced or prevented.
While the example in which the plate-fin heat exchanger 100 is provided has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, a heat exchanger other than the plate-fin heat exchanger may be used.
For example, the present invention may be applied to a multi-tube heat exchanger 200 as in a modified example shown in
Besides this, the heat exchanger according to the present invention may be a plate heat exchanger in which corrugated metal plates including flow paths integrally formed on the front and back sides are stacked and bonded by seal, welding, or the like such that flow path layers are formed between the metal plates. Alternatively, the heat exchanger may be a diffusion-bonded heat exchanger in which metal plates including flow paths formed by grooving are stacked and integrated by diffusion-bonding, for example, such that flow path layers are provided between the metal plates.
While the example in which the flow path layers are alternately stacked one by one in the order of the first flow path 10, the adjustment layer 30, the second flow path 20, the adjustment layer 30, . . . has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, a plurality of same flow path layers may be successively stacked. That is, a plurality of first flow path layers 10 may be successively stacked in such a manner that the first flow path 10, the first flow path 10, the adjustment layer 30, the second flow path 20, the adjustment layer 30, the first flow path 10, the first flow path 10, . . . are stacked. Alternatively, a plurality of adjustment layers 30 may be successively stacked in such a manner that the first flow path 10, the adjustment layer 30, the adjustment layer 30, the second flow path 20, the adjustment layer 30, the adjustment layer 30, . . . are stacked.
While the example in which the adjustment layer 30 is a layer through which no fluid flows has been shown in the aforementioned embodiment, the present invention is not restricted to this. For example, as shown in a modified example of
When the adjustment layer 130 having a hollow flow path structure through which a fluid can flow except during heat exchange is provided as described above, the hollow structure can easily decrease the heat transfer performance of the adjustment layer 130, and thus occurrence of freezing and boiling can be effectively and significantly reduced or prevented. In addition, as a measure against occurrence of fluid freezing, a heat medium having a temperature higher than the freezing temperature can flow through the adjustment layer 130 except during heat exchange between the first fluid 7 and the second fluid 8 so as to quickly eliminate freezing.
That is, when freezing of the second fluid 8 occurs in the second flow path 20, a heat medium is supplied to the adjustment layer 130 except during heat exchange so as to eliminate the freezing of the second fluid 8. Accordingly, even when freezing occurs locally in the second flow path 20 after heat exchange, the heat medium for eliminating freezing is supplied to the adjustment layer 130 after the heat exchange (supply of the first fluid 7 and the second fluid 8) is stopped such that freezing can be easily and quickly eliminated.
While the example in which the adjustment layer 30 includes the same flow path layer 2 as those of the first flow path 10 and the second flow path 20 has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the adjustment layer need not include the flow path layer, and may have a layer structure other than the flow path layer. For example, as in a modified example shown in
While the counter-flow heat exchanger 100 in which the flowing direction of the first fluid 7 and the flowing direction of the second fluid 8 are opposite to each other has been shown as an example in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the heat exchanger may be a parallel-flow heat exchanger other than the counter-flow heat exchanger. In the case of the parallel-flow heat exchanger, the inlet 11 of the first flow path 10 and the inlet 11 of the second flow path 20 are disposed on the same side. Therefore, when the risk of freezing the second fluid 8 is high, the temperature of the second fluid 8 can be increased in a region near the inlet at which the temperature of the first fluid 7 is the lowest, and thus the risk of freezing can be further significantly reduced or prevented. On the other hand, when the temperature difference between the first fluid 7 and the second fluid 8 is large near the outlet of the first flow path 10, the counter-flow heat exchanger is preferable because the heat exchange efficiency is increased and the size thereof can be reduced. Alternatively, the heat exchanger may be a cross-flow heat exchanger in which the flowing direction of the first fluid 7 and the flowing direction of the second fluid 8 are orthogonal to each other.
While the heat exchanger 100 including the plurality of first flow paths 10 and the plurality of second flow paths 20 has been shown as an example in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the numbers of first flow paths and second flow paths are not particularly restricted. One first flow path and one second flow path may be provided, or two or more first flow paths and two or more second flow paths may be provided.
While the example in which the adjustment layer 30 is divided into two regions of the first portion 31 and the second portion 32, and the first portion 31 and the second portion 32 have different heat transfer performances has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the adjustment layer 30 may include three or more portions having different heat transfer performances. For example, in the adjustment layer, three portions of a portion adjacent to the liquid phase region (L) of the liquefied gas, a portion adjacent to the vapor-liquid mixed phase region (L+V), and a portion adjacent to the vapor phase region (V) may have different heat transfer performances. Alternatively, in the adjustment layer 30, the heat transfer performance may continuously change, instead of including a plurality of regions having different heat transfer performances. For example, the density of the heat conduction portions 33 may be continuously increased from the upstream side to the downstream side in the flowing direction of the first fluid.
While the example in which the hollow adjustment layer 30 is provided has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, the inside of the adjustment layer 30 may be filled with a fluid or a solid such as a powder (particulate material) or a porous material. In this case, these fillers may function as heat conduction portions. The heat transfer performance can be varied by changing a material (thermal conductivity) of the filler, the particle diameter of the filler, the porosity of the filler, etc.
While the example in which the first fluid 7 in the first flow path 10 undergoes a phase change has been shown in the aforementioned embodiment, the present invention is not restricted to this. According to the present invention, as shown in
2, 102: flow path layer
7: first fluid (liquefied gas)
8: second fluid (heat medium)
10: first flow path
20: second flow path
30, 130: adjustment layer
31: first portion
32: second portion
33: heat conduction portion
(34a, 34b): heat transfer fin
35: longitudinal plate (fin section)
50: risk area
100, 200, 300: heat exchanger
P3, P4: pitch between the longitudinal plates (interval between the fin sections)
t1, t2: thickness of the longitudinal plate
X: flowing direction of the first fluid
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/079980 | 10/7/2016 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/066128 | 4/12/2018 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5341769 | Ueno et al. | Aug 1994 | A |
| 9927184 | Fujita | Mar 2018 | B2 |
| 10465991 | Van Bockryck | Nov 2019 | B2 |
| 20080308264 | Antonijevic | Dec 2008 | A1 |
| 20100139901 | Takada | Jun 2010 | A1 |
| 20100181053 | Hecht et al. | Jul 2010 | A1 |
| 20150316326 | Choi | Nov 2015 | A1 |
| 20170108284 | Fujita | Apr 2017 | A1 |
| 20170162884 | Shimada | Jun 2017 | A1 |
| 20180073811 | Taras | Mar 2018 | A1 |
| 20190056164 | Yamada | Feb 2019 | A1 |
| 20200064083 | Mitsuhashi | Feb 2020 | A1 |
| Number | Date | Country |
|---|---|---|
| 10 2006 017 434 | Feb 2007 | DE |
| 1 054 225 | Nov 2000 | EP |
| 2531945 | May 2016 | GB |
| 62-28693 | Feb 1987 | JP |
| 5-164482 | Jun 1993 | JP |
| 8-159683 | Jun 1996 | JP |
| 2002-323295 | Nov 2002 | JP |
| 2010-101617 | May 2010 | JP |
| 2016-503483 | Feb 2016 | JP |
| WO 2015141634 | Sep 2015 | WO |
| Entry |
|---|
| International Search Report (PCT/ISA/210) issued in PCT Application No. PCT/JP2016/079980 dated Dec. 13, 2016 with English translation (four (4) pages). |
| Japanese-language Written Opinion (PCT/ISA/237) issued in PCT Application No. PCT/JP2016/079980 dated Dec. 13, 2016 (four (4) pages). |
| Extended European Search Report issued in counterpart European Application No. 16918324.1 dated Sep. 17, 2019 (seven (7) pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20200049411 A1 | Feb 2020 | US |
