TWI784433B - Regenerator structure design - Google Patents

Abstract

The present disclosure provides a regenerator that extends in the axial direction and has porous structure. Two ends of the regenerator in the axial direction respectively have a high-temperature fluid inlet and a low-temperature fluid outlet. The porosity of the regenerator in the radial direction, from the outside of the regenerator to the inside of the regenerator, has a gradient from low to high.

Description

Regenerator Structure Design

This case is about the structural design of a regenerator, especially a regenerator with high heat transfer efficiency.

"Regenerator" is an important component of many engines and cycle machines such as refrigerators, and its main purpose is to recover heat energy. Taking the Stirling Engine as an example, when the high-temperature gas flows into the regenerator from one end of the regenerator, the gas will transfer heat energy to the heat-absorbing material in the regenerator, so that the gas is pre-cooled into a low-temperature gas and then enters the low-temperature gas. Relatively, when the low-temperature gas flows into the regenerator from the other end of the regenerator, it will absorb the heat energy originally stored in the heat-absorbing material, so that the gas is preheated into a high-temperature gas before entering the high-temperature zone. In this way, the heat discharged during the process of equal-volume heat removal of the gas can be used to provide the heat required by the gas during the process of equal-volume heat absorption and temperature rise, so as to achieve the effect of pre-cooling and pre-heating the gas, thereby reducing the external energy consumption of the cycle machine. demand and losses to improve overall device efficiency.

Therefore, following the above, the regenerator has an important influence on the efficiency of the cycle machine. For an ideal regenerator, it is necessary to transfer fluid as quickly as possible and reduce the loss of its own heat energy, so as to perform heat exchange more effectively, improve heat transfer efficiency and reduce the demand for external energy of the cycler.

In view of the above, this case provides a regenerator, which extends in the axial direction and has a porous structure. The regenerator has a high-temperature fluid inlet and a low-temperature fluid inlet and outlet, which are respectively located at both ends of the regenerator in the axial direction; wherein, the regenerator is in its The porosity in the radial direction has a gradient from low to high in the direction from the outside of the regenerator to the inside of the regenerator.

By making the regenerator extending in the axial direction, the porosity in the radial direction presents a gradient change from low to high (that is, dense to loose) from the outer circumference to the center, so that the distribution of the fluid inside the regenerator can be determined by the flow resistance. The difference of the regenerator is controlled so that the fluid can be concentrated in the central part of the regenerator instead of the area near the outer periphery when flowing through the regenerator. Therefore, when the regenerator is used in the pipe body, since the fluid flow in the outer area of the regenerator is reduced, the heat generated by the fluid flowing near the outer wall due to contact with the pipe wall or radiated to the outside can be reduced. lost.

In addition, in other embodiments, in addition to having a gradient change in porosity in the radial direction, the porosity in the axial direction of the regenerator may also have a gradient change. Specifically, the porosity of the regenerator in its radial direction has a gradient from low to high except that it has a gradient from low to high in the direction from the outside of the regenerator to the inside of the regenerator, and the porosity of the regenerator in its axial direction is In the direction from the low-temperature fluid inlet and outlet to the high-temperature fluid inlet and outlet, there may also be a gradient change from low to high.

By further making the axial porosity of the regenerator change from low to high (that is, dense to loose) from the low temperature end to the high temperature end, the flow rate of the fluid in the regenerator can be increased under the premise of retaining heat transfer , and further improve the overall efficiency of the regenerator.

This case provides a regenerator whose porosity in the radial direction has a gradient from low to high (that is, dense to loose) from the outside to the center, so that the fluid can be concentrated in the central part of the regenerator instead of The area close to the pipe wall reduces the heat loss of the fluid in the regenerator to improve the heat transfer efficiency of the regenerator.

Please refer to Figure 1 first. FIG. 1 is a schematic perspective view of a regenerator 1 drawn according to an embodiment of the present invention. The regenerator 1 can be cylindrical and has an extension axis A. In some embodiments, the cross-sectional shape of the regenerator 1 perpendicular to the extension axis A can be other shapes such as rectangle, polygon, ellipse, etc. besides the circle as shown in FIG. 1 . In this case, in order to make the description more concise, the cylindrical regenerator 1 will be used for description. Wherein, the direction parallel to the extension axis A is called "axial direction"; the direction from the outside of the regenerator 1 to the extension axis A and perpendicular to the extension axis A is called "radial direction". Therefore, reference can be made to Fig. 2A. Fig. 2A is a schematic front view of the regenerator 1 shown in Fig. 1. When the cross-sectional shape of the regenerator 1 is circular, "radial" is equivalent to the direction R from the circumference to the center of the circle. Or the direction R' from the center of the circle to the circumference.

Please refer back to Figure 1. The regenerator 1 will be set in a pipe body during use, and the fluid (such as gas) will enter the pipe body and flow through the regenerator 1, so that the heat exchange between the fluid and the regenerator 1, and then flow out of the regenerator 1 . The regenerator 1 is a porous structure with a plurality of holes, and has a high-temperature fluid inlet and outlet H1 and a low-temperature fluid inlet and outlet L1 at both ends in the axial direction. The high-temperature fluid enters the regenerator 1 from the high-temperature fluid inlet H1, transfers heat to the regenerator 1 and cools down to a relatively low-temperature low-temperature fluid, and then leaves the regenerator 1 through the low-temperature fluid inlet L1. In contrast, the low-temperature fluid enters the regenerator 1 from the low-temperature fluid inlet and outlet L1, obtains heat from the regenerator 1 and heats up to a relatively high-temperature high-temperature fluid, and then leaves the regenerator 1 through the high-temperature fluid inlet and outlet H1. For the convenience of description, the end of the regenerator 1 with the high-temperature fluid inlet and outlet H1 is called the high-temperature end H, and the end with the low-temperature fluid inlet and outlet L1 is called the low-temperature end L.

As shown in Figure 1, the porosity of the regenerator 1 in its radial direction is from low to low in the direction from the outside of the regenerator 1 to the inside of the regenerator 1 (extension axis A) (that is, in the direction R). Highest gradient change. That is to say, the porous structure of the regenerator 1 has a lower porosity (more dense) on the outside and a higher porosity (looser) on the inside.

For further description of the "radial porosity gradient" of the regenerator 1, please refer to FIG. 2A. FIG. 2A is a schematic front view of the regenerator 1 shown in FIG. 1 . In some embodiments, the regenerator 1 may have a multi-layer structure in the radial direction, and the porosity of the regenerator 1 in the radial direction may have a gradient change by using the multi-layer structure. In the embodiment shown in FIG. 2A , the regenerator 1 has a three-layer structure in the radial direction, which are respectively a first layer 101 , a second layer 102 , and a third layer 103 from inside to outside. The innermost first layer 101 has the loosest structure and the highest porosity. The outermost third layer 103 has the densest structure and the lowest porosity. The porosity of the second layer 102 is in between. Therefore, in the direction from the outside of the regenerator 1 to the inside of the regenerator 1 (ie in the direction R), the porosity has a gradient change from low to high.

It should be noted that “the porosity has a gradient change in the radial direction” mentioned in this case only needs to mean that the porosity “at least partially” has a gradient change in the radial direction of the regenerator 1 . As long as the porosity at least partially has a gradient change in the radial direction, the effect of reducing the flow of fluid to the outside of the regenerator 1 and concentrating it in the center can be achieved. Therefore, when a cavity 2 is further provided inside the porous structure of the regenerator 1 shown in FIG. 2A (as shown in FIG. 2B ), since the cavity 2 does not have holes, it will be considered as having no porosity in this case, but Because the first layer 101, the second layer 102, and the third layer 103 of the regenerator 1 still constitute a gradient change, although the regenerator 1 shown in Figure 2B does not have a porosity gradient change from the outermost to the center, However, there are still some porosity gradients in the radial direction. Therefore, the regenerator 1 shown in FIG. 2B still complies with "the porosity in the radial direction has a gradient change".

On the other hand, as mentioned above, since the porosity only needs to have a "at least partial" gradient change in the radial direction of the regenerator 1, the porosity of the outermost layer of the regenerator 1 may not be the lowest (not the densest). ), and the porosity of the innermost layer of the regenerator 1 may not be the highest (not the most porous). For example, as shown in FIG. 2C , the regenerator 1 may have a four-layer structure, which is a first layer 101 , a second layer 102 , a third layer 103 , and a fourth layer 104 in sequence from inside to outside. Wherein, similar to the configuration in FIG. 2A , the porosity of the first layer 101 is higher than that of the second layer 102 , and the porosity of the second layer 102 is higher than that of the third layer 103 . But the porosity of the third layer 103 is lower than that of the fourth layer 104 . That is to say, compared with the third layer 103 , the fourth layer 104 of the outermost layer is looser. In this way, the effect of reducing the flow of fluid to the outside of the regenerator 1 and concentrating it toward the center can still be achieved.

When the outermost side of the regenerator 1 has the lowest radial porosity (the densest), and the innermost side of the regenerator 1 has the highest radial porosity (the loosest), the regenerator 1 can be placed close to the outer part of the pipe body Having the least amount of fluid passing through and allowing the maximum amount of fluid to pass through the center of the regenerator 1 allows the regenerator 1 to have the lowest heat loss.

In addition, the number of layers of the regenerator 1 shown in FIG. 2A to FIG. 2C is only an example. In other embodiments, the regenerator 1 may only have a structure of two or more layers. The thickness of each layer in the multilayer structure can be the same or different, and two adjacent layers can be in contact with each other or not. As long as "in the direction from the outside of the regenerator 1 to the inside of the regenerator 1, the porosity in the radial direction has a gradient change from low to high" will suffice.

The "porosity" (or "average porosity") of a region mentioned in this case can be determined by measuring the total area of the pores contained in the region and the total area of the region on the cross-section. The total area of the holes in the area/the total area of the area; or by measuring the total volume of the holes in the area and the total volume of the area if it is a solid (abbreviated as "the total volume of the area") ), obtained as the total volume of holes in the region/total volume of the region. For example, if it is desired to calculate the average porosity of each layer of the regenerator 1 shown in FIG. 2A by the area, then the cross-sectional view of the regenerator 1 can be judged by software or manual methods, for example, where is a hole in each layer, Then add up the area of each hole to get the total area of the hole. Then, the average porosity of the layer can be obtained by dividing the total area of the holes by the total area of the layer. If it is desired to calculate the average porosity of each layer of the regenerator 1 shown in FIG. 2A by volume, the actual volume occupied by each layer can be obtained by using, for example, the drainage method, and the actual volume can be divided by the total volume of the layer. Get a ratio, then subtract the ratio from 1 to get the average porosity of the layer. In addition, if the material density of each area is known, the actual volume occupied by the area can also be obtained by measuring the weight of the area and dividing it by the material density, and then the average porosity can be obtained in the aforementioned manner.

The material used for each layer in the regenerator 1 is not particularly limited, as long as it can be used to form a stable porous structure. For example, the materials used may be ceramics, metals, plastics, or combinations thereof. The porous structure of each layer in the regenerator 1 can be made in any way suitable for the material of the layer, and then the layers with different porosities are nested to form the regeneration of "the porosity has a gradient change in the radial direction" described in this case. Device 1. For example, porous metal bodies with different porosity can be produced by adding different proportions of blowing agents to molten metal. Alternatively, plastic particles or wax particles with different particle sizes and contents are placed in the mold first, and then molten metal is injected into the mold to obtain porous metal bodies with different porosity. Then, the obtained porous metal body is cut and trimmed by means such as laser to form layers with different porosities, and then the obtained layers are nested to form a "porosity with a gradient change in the radial direction" Regenerator 1.

In some other embodiments, the regenerator 1 can also be directly formed in the pipe body. For example, taking the three-layer structure of the regenerator 1 shown in Figure 2A as an example, a metal rod can be inserted into the tube body first, and sinterable powder ( Such as metal particles or ceramic particles) are then rapidly sintered to form a porous structure of the outermost layer of the regenerator 1 , the denser third layer 103 . Then, take out the metal rod, replace it with another metal rod with a smaller diameter, and then fill the space between the metal rod and the third layer 103 with sinterable powder with a particle size larger than before and perform rapid sintering to form a regenerator The porous structure of the second layer 102 of 1. Then, take out the metal rod with smaller diameter, fill the remaining space with sinterable powder with larger particle size and perform rapid sintering to form the porous structure of the first layer 101 of the innermost layer of the regenerator 1 . Finally, the whole body is sintered at a higher temperature to obtain the three-layer structure of the regenerator 1 as shown in FIG. 2A .

In some embodiments, three-dimensional printing can also be used to manufacture the porous structure of each layer, and then the layers are nested to form the regenerator 1; The whole regenerator 1 with gradient change. When the regenerator 1 with radial gradient changes is directly manufactured by 3D printing, since no additional assembly is required, the thickness of each layer of the multilayer structure can be relatively small, thereby forming a finer radial porosity change.

The method of forming a porous structure by 3D printing, in addition to directly forming a porous structure, can also use a material mixed with plastic particles and metal particles to print a block containing both, and then pass the block through The sintering step, which removes the plastic contained therein and allows bonding between the metal particles, also results in a porous metal body. By adjusting the size of plastic particles and the ratio between plastic and metal, the porosity of the resulting porous metal body can be regulated.

In some embodiments, instead of using a three-dimensional porous structure to form the regenerator 1 , a two-dimensional sheet mesh material may be used to form the regenerator 1 . For example, the structure of the regenerator 1 shown in Figure 3 can first be stacked into blocks with metal mesh sheets with lower porosity (denser), and then cut and trimmed by means such as laser And at the same time welding, in order to obtain the structure of the outermost layer (that is, the third layer 103 in Fig. 3). Then, in a similar manner, the second layer 102 and the third layer 103 are formed by using metal mesh sheets with higher porosity and higher (looser) respectively. Then, the first layer 101 , the second layer 102 and the third layer 103 are sequentially nested to form the regenerator 1 as shown in FIG. 3 .

Next, please refer back to FIG. 1 and FIG. 2A , and refer to FIG. 4 together. FIG. 4 is an explanatory diagram of porosity changes drawn by the regenerator 1 according to an embodiment of the present invention. As mentioned above, the regenerator 1 may have a multi-layer structure in the radial direction (similarly, as long as at least part of the radial direction has a multi-layer structure), and the multi-layer structure is used to make the porosity of the regenerator 1 have a gradient change in the radial direction. In some embodiments, three adjacent layers in the multilayer structure have the same thickness in the radial direction, and the porosities of the three layers jointly exhibit a linear relationship. That is, in the three adjacent layers, their respective porosity values will fall on a straight line.

For example, in some embodiments, the structure of the regenerator 1 shown in FIG. 1 can be shown in FIG. 4, which has a three-layer structure, and the innermost first layer 101 is located at a radius of 0 to 1/3 in the radial direction. In between, the second layer 102 is located between 1/3 radius and 2/3 radius in the radial direction, and the outermost third layer 103 is located between 2/3 radius and the outer circumference. Wherein, if the relative value of the porosity of the first layer 101 is 1 (the loosest), the relative value of the porosity of the second layer 102 can be 0.5, and the relative value of the porosity of the third layer 103 can be 0.25 (the densest). Therefore, the porosity of the three adjacent layers in the multilayer structure exhibits a linear relationship.

In addition, compared to the above-mentioned "porosity in the radial direction shows a "linear" gradient", in other embodiments, the three adjacent layers in the multilayer structure each have the same thickness in the radial direction, but each of the three layers has the same thickness. There is a non-linear relationship between the porosity. That is, in the three adjacent layers, their respective porosity values will not fall on a straight line at the same time. For example, refer to FIG. 5 . Fig. 5 is an explanatory diagram of porosity change drawn by a regenerator according to another embodiment of the present application. Fig. 5 is similar to Fig. 4, both are explanatory diagrams of porosity changes, but in order to make the drawing more concise, the relative values of porosity at each position are not drawn in Fig. 5, but only the layers of the regenerator 1 are marked Relative porosity. Wherein, the line segment 51 is the oblique straight line in FIG. 4 , which is used as a comparison object.

In some embodiments, the three-layer structure of the regenerator 1 shown in FIG. 1 can be shown as the line segment 52 in FIG. 5, and the innermost first layer 101 is located between 0 and 1/3 of the radius , the second layer 102 is located between 1/3 radius and 2/3 radius in the radial direction, and the outermost third layer 103 is located between 2/3 radius and the outer circumference. Among them, the relative porosity values of the first layer 101, the relative porosity values of the second layer 102, and the relative porosity values of the third layer 103 do not fall on a straight line at the same time, so the three have a nonlinear relationship.

In some embodiments, in addition to presenting a non-linear relationship among the porosities corresponding to the adjacent three layers, further, there may also be a relationship in which the porosity change rate outside the regenerator 1 is greater than the porosity change rate inside the regenerator 1 . For example, as shown by the line segment 52 in Fig. 5, the porosity change rate (i.e. the absolute value of the slope between two points) between the outermost third layer 103 and the second layer 102 of the regenerator 1 is greater than that of the innermost third layer 102. The porosity change rate between the first layer 101 and the second layer 102 . It should be noted that the “outside” and “inside” only represent the relative positional relationship between the two areas for comparison, one is closer to the outer periphery of the regenerator 1 , and the other is closer to the extension axis A of the regenerator 1 . Therefore, "outside" does not mean that the outermost part of the entire regenerator 1 must be included; "inner side" does not mean that the innermost part of the entire regenerator 1 must be included. Similarly, "outer" does not mean that the outermost of three adjacent layers must be included; "inner" does not mean that the innermost of three adjacent layers must be included.

As a form of "the porosity change rate on the outside is greater than the porosity change rate on the inside", as shown in the line segment 52 of Figure 5, the relative value of the porosity of the first layer 101 of the regenerator 1, the second layer 102 The relative value of porosity and the relative value of porosity of the third layer 103 fall on a parabola with the opening facing downward.

By making the outer porosity change rate greater than the inner porosity change rate in at least part of the regenerator 1, the regenerator 1 can further increase the fluid flow rate while maintaining low heat loss. Specifically, when the outer porosity change rate is greater than the inner porosity change rate, the value of the porosity in the outer area (relatively denser area with lower porosity) will rapidly increase as it gets closer to the inside of the regenerator 1. increase, so that the proportion of the dense area in the regenerator 1 is low, that is, most of the regenerator 1 is a relatively loose area. As long as a part of the outside has a dense area (area with low porosity), the movement of fluid from the inside to the outside of the regenerator 1 can be effectively reduced, so the configuration can achieve the effect of reducing heat loss. In addition, since the regenerator 1 designed according to this configuration has a relatively high proportion of the porous area, the fluid can have a higher flow rate in this type of regenerator 1, and the heat transfer efficiency between the regenerator 1 and the fluid can be further improved .

Therefore, if the radial direction of the regenerator 1 is in the direction from the outside of the regenerator 1 to the inside of the regenerator 1, the whole (the part containing the porosity) shows a gradient from low to high, and the regenerator 1 contains the outermost The porosity change rate of the region is greater than the porosity change rate of the innermost region of the regenerator 1, then at this time, in addition to having a better effect of reducing heat loss (because the region near the pipe body can have the least flow rate), Because the regenerator 1 as a whole has a relatively high proportion of the porous area, the regenerator 1 can have a better fluid flow rate and a better heat transfer efficiency.

By using the above-mentioned various structures, the porosity of the regenerator in its radial direction presents a gradient change from low to high (that is, dense to loose) from the outside (or the pipe wall of the pipe body) to the center, so that the fluid in the The distribution inside the regenerator is controlled by the difference of flow resistance, so that when the fluid flows through the regenerator, it can be concentrated in the central part of the regenerator instead of the area close to the pipe wall. Since the fluid flow in the outer area of the regenerator is reduced, the heat loss generated by the contact with the tube wall or radiation to the outside when the fluid flows near the outer wall can be reduced.

In addition, since the fluid is concentrated in the central part of the regenerator, the fluid near the pipe wall will be reduced. Therefore, the friction between the fluid and the pipe wall can also be reduced, so that the overall average flow rate of the fluid in the regenerator can be further increased. When the flow rate increases, the Reynolds number _{(Re number, R e =} ρvd/μ, where v, ρ, and μ are the flow rate, density, and viscosity of the fluid, respectively, and d represents the diameter of the pipe in a circular pipe) will also increase . When the Reynolds number increases, the fluid can change from laminar flow to turbulent flow. In turbulent flow, the fluid flow is disturbed and many small eddies are formed, and the thickness of the laminar boundary layer will decrease at this time. The thermal resistance is mainly concentrated in the laminar boundary layer, so when the boundary layer is thinner, the thermal resistance is smaller and the heat transfer coefficient is larger. Therefore, the heat transfer efficiency between the regenerator and the fluid can be further improved.

Furthermore, if the radial direction of the regenerator further has a non-linear gradient porosity change, especially if the porosity change rate outside the regenerator is greater than the porosity change rate inside the regenerator, the regenerator can maintain low heat loss. Next, further increase the fluid flow rate.

Next, please refer to Figure 6. Fig. 6 is a schematic perspective view of a regenerator 1 drawn according to some embodiments of the present application. In these embodiments, the porosity of the regenerator 1 not only has a gradient change in the radial direction, but also has a gradient change in the porosity in the axial direction. Specifically, as shown in FIG. 6, the porosity of the regenerator 1 in the axial direction has a gradient from low to high in the direction from the low-temperature fluid inlet L1 to the high-temperature fluid inlet H1. That is, the structure of the low-temperature end L of the regenerator 1 is denser, while the structure of the high-temperature end H is relatively loose.

By making the porosity of the regenerator 1 in the axial direction, from the low-temperature end L to the high-temperature end H, there is a gradient change from low to high (that is, dense to loose), so that the internal porosity of the regenerator 1 can be improved under the premise of retaining heat transfer. The flow rate of the fluid further improves the overall efficiency of the regenerator 1 . Regarding the part of the increase of the fluid flow rate in the regenerator 1, the flow resistance is reduced due to the increase of the porosity of some areas in the regenerator 1, so the flow rate and flow rate of the fluid in the regenerator 1 can be further increased; and the part about the retained heat transfer , because the loose zone is set at the high temperature end H, and because there is a large temperature difference between the fluid and the regenerator 1 at the high temperature end H, even if there is a high flow rate in the loose zone, the fluid and the regenerator 1 can still have a high heat transfer rate to complete the heat transfer. When the fluid gradually cools down to the low-temperature end L, although the temperature difference between the fluid and the regenerator 1 is small at this time, the heat transfer rate decreases, but because the low-temperature end L is set as a dense area, the flow rate of the fluid in this area is low And it needs to go through a long path, so there is more time for heat transfer between the two. Therefore, the overall heat transfer rate of the regenerator 1 can still be maintained.

Please continue with Figure 6. The aforementioned "the porosity of the regenerator 1 has a gradient change in its axial direction" can be achieved by using a multi-stage structure in the regenerator 1 . For example, as shown in FIG. 6 , the regenerator 1 may have a three-stage structure. In the direction from the high temperature end H to the low temperature end L, there are the first section A1, the second section A2, and the third section A3 in sequence. Wherein, the porosity of the third section A3 is smaller than that of the second section A2, and the porosity of the second section A2 is smaller than that of the first section A1. Thereby, the porosity of the regenerator 1 can have a gradient change in its axial direction.

However, it should be understood that the number of stages shown in FIG. 6 is only an example, and in other embodiments, the regenerator 1 may only have a structure of two or more stages. The axial thicknesses of each segment in the multi-segment structure can be the same or different, and some adjacent segments may not be in contact with each other. As long as "in the direction from the low-temperature fluid inlet L1 (or low-temperature end L) to the high-temperature fluid inlet H1 (or high-temperature end H), the porosity in the axial direction has a gradient from low to high."

In a multi-segment structure, the porosity of each segment (or "average porosity") can be measured by measuring the total volume of the pores contained in the segment and the total volume of the segment if it is a solid (hereinafter referred to as "total volume of the segment"), obtained in the form of total volume of holes in the segment/total volume of the segment. For example, the actual volume occupied by each section can be obtained by using the drainage method, and a ratio can be obtained after dividing the actual volume by the total volume of the section, and then subtracting the ratio from 1 is the average porosity of the section . In addition, if the density of the material used in each segment is known, the actual volume occupied by the segment can be obtained by measuring the weight of the segment and dividing it by the material density, and then the average porosity can be obtained in the aforementioned manner.

In some embodiments, the multi-stage structure of the regenerator can be obtained by stacking a plurality of regenerators 1 (such as the structure shown in FIG. 1 ) with different porosities, each of which only has a radial porosity gradient form. For example, please refer to FIG. 7 . Fig. 7 can be regarded as a schematic cross-sectional top view drawn according to the regenerator in Fig. 6 . The structure shown in FIG. 7 can be formed by first forming a first-stage regenerator with a higher overall porosity, a first-stage regenerator with a second-highest overall porosity, and a first-stage regenerator with the lowest overall porosity in the aforementioned manner. Then, the three sections are arranged and combined in order to form the first section A1, the second section A2, and the third section A3 of the regenerator, and the structure shown in FIG. 7 can be obtained.

It should be noted that although the structure shown in FIG. 7, the first section A1, the second section A2, and the third section A3 all have a three-layer structure with the same thickness configuration (that is, in the second section A2 The thickness of the outer layer is the same as the thickness of the outer layer of the first section A1 and the thickness of the outer layer of the third section A3, the thickness of the middle layer of each section is the same, and the thickness of the inner layer of each section is the same), but in fact the sections do not need to have the same The structure, as long as it can comply with "in the direction from the low-temperature fluid inlet and outlet L1 (or low-temperature end L) to the high-temperature fluid inlet and outlet H1 (or high-temperature end H), the porosity of each section makes the regenerator 1 axially have from low to high gradient change".

In the case that each section has the same structure, the two adjacent sections in the multi-section structure can make the porosity of the innermost layer of one section the same as the porosity of the outer layer of the other section, so that the minimum materials and processing steps can be used. To complete the regenerator with both radial and axial gradient changes. Specifically, taking the inner layer 101A1 and the middle layer 102A1 of the first section A1 in FIG. 7 and the inner layer 101A2 and the middle layer 102A2 of the second section A2 as examples, the inner layer 101A1 of the first section A1 has the highest porosity ( The most porous), the middle layer 102A1 of the first section A1 has the second highest porosity. And in order to make the porosity of the whole section of the second section A2 lower than the porosity of the first section A1 as a whole, and have a porosity gradient change in the radial direction, the inner layer 101A2 of the second section A2 can be made to have the same shape as the first section A1. The middle layer 102A1 of section A1 has the same porosity, and the middle layer 102A2 of the second section A2 has the third highest porosity. Since materials with the same porosity can be used in two regions, a regenerator with both radial and axial gradients can be completed with fewer materials and fewer processing steps.

In some embodiments, if each stage has the same structure, the multi-stage structure of the regenerator 1 can also be formed by first forming the outermost layer of each stage at the same time, and then forming the inner layers sequentially. For example, in the structure shown in Figure 7, a metal rod can be placed in the tube body first, and in the gap between the metal rod and the tube body, sinterable powders with different particle sizes can be filled in three batches. Then perform rapid sintering to form the outermost layers of the first segment A1, the second segment A2, and the third segment A3. Then, in a similar manner, the middle and inner layers of the first section A1, the second section A2, and the third section A3 are formed. Finally, the whole body is sintered at a higher temperature to obtain the structure of the regenerator 1 as shown in FIG. 7 .

In some embodiments, the regenerator 1 "in the direction from the low-temperature fluid inlet and outlet L1 (or low-temperature end L) to the high-temperature fluid inlet and outlet H1 (or high-temperature end H), the porosity in the axial direction has a gradient from low to high ” can have various implementations. For example, the regenerator may have a multi-segment structure in the axial direction, and each segment in the multi-segment structure has the same thickness in the axial direction. Among them, the three porosities corresponding to three adjacent segments in the multi-segment structure have a linear or nonlinear relationship.

In some embodiments, when the three porosities corresponding to three adjacent segments in the multi-segment structure have a nonlinear relationship, compared with a linear relationship, the heat transfer efficiency may be better. For example, when the porosity change rate at the low temperature end L is greater than the porosity change rate at the high temperature end H among the three porosities corresponding to three adjacent segments in the multi-stage structure, since the low temperature end L The porosity at the position (relatively dense area with low porosity) will increase rapidly as it approaches the high temperature end H of regenerator 1, so that the proportion of the dense area in regenerator 1 is low, that is, regeneration Most of the device 1 is a relatively loose area. Therefore, the fluid can have a higher flow rate in the regenerator 1, and the heat transfer efficiency between the regenerator 1 and the fluid can be further improved.

In summary, by making the porosity of the regenerator radially change from low to high (that is, dense to loose) from the pipe wall to the center, the fluid can be concentrated in the regenerator when it flows through the regenerator. Its central part rather than the area close to the tube wall, thereby reducing the heat loss of the fluid. In addition, since the friction between the fluid and the pipe wall can also be reduced, the overall average flow velocity of the fluid can be increased, so the heat transfer efficiency between the regenerator and the fluid can be further improved. Therefore, combining the above two points, by making the porosity of the regenerator in its radial direction have a gradient change from low to high (that is, dense to loose) from the tube wall to the center, a high heat transfer efficiency can be obtained. Regenerator.

In addition, in addition to the gradient change in porosity in the radial direction, if there is also a gradient change in the axial direction of the regenerator, the flow rate of the fluid in the regenerator can be increased under the premise of retaining heat transfer, thereby further improving regeneration. overall efficiency of the device.

1: Regenerator 101: first floor 102: second floor 103: third floor 104: fourth floor 51, 52: line segment 2: cavity A: Extension shaft A1: first paragraph 101A1: inner layer 102A1: middle layer A2: Second paragraph 101A2: inner layer 102A2: middle layer A3: The third paragraph H: high temperature end H1: High temperature fluid inlet and outlet L: low temperature end L1: Cryogenic fluid inlet and outlet R, R': Direction

Fig. 1 is a three-dimensional schematic diagram of a regenerator drawn according to an embodiment of the present invention. FIG. 2A is a schematic front view of the regenerator shown in FIG. 1 . Fig. 2B is a schematic front view of a regenerator drawn according to an embodiment of the present invention. Fig. 2C is a schematic front view of a regenerator drawn according to another embodiment of the present application. Fig. 3 is a schematic front view of a regenerator drawn according to another embodiment of the present application. Fig. 4 is an explanatory diagram of porosity change drawn by the regenerator according to an embodiment of the present invention. Fig. 5 is an explanatory diagram of porosity change drawn by a regenerator according to another embodiment of the present application. Fig. 6 is a perspective view of a regenerator drawn according to some embodiments of the present application. Fig. 7 is a schematic cross-sectional top view drawn according to the regenerator in Fig. 6 .

1: Regenerator A: Extension shaft H: high temperature end H1: High temperature fluid inlet and outlet L: low temperature end L1: Cryogenic fluid inlet and outlet

Claims (8)

A regenerator, which extends along an axial direction and has a porous structure, and the regenerator has a high-temperature fluid inlet and a low-temperature fluid inlet and outlet, respectively located at both ends of the regenerator in the axial direction; wherein, the regenerator The porosity in the radial direction has, at least in part, a gradient from low to high in the direction from the outside of the regenerator to the inside of the regenerator; and the porosity of the outermost layer of the regenerator is not the lowest. The regenerator as claimed in claim 1, wherein the regenerator has a multi-layer structure in the radial direction, at least partially adjacent three layers in the multi-layer structure have the same thickness in the radial direction, and each layer has a corresponding layer porosity ; wherein, the three adjacent layers in the multi-layer structure have the gradient change in the direction from the outside of the regenerator to the inside of the regenerator, and the three layers of pores corresponding to the three adjacent layers in the multi-layer structure The rate has a linear relationship. The regenerator as claimed in claim 1, wherein the regenerator has a multi-layer structure in the radial direction, at least partially adjacent three layers in the multi-layer structure have the same thickness in the radial direction, and each layer has a corresponding layer porosity ; wherein, the three adjacent layers in the multi-layer structure have the gradient change in the direction from the outside of the regenerator to the inside of the regenerator, and the three layers of pores corresponding to the three adjacent layers in the multi-layer structure rate exhibits a non-linear relationship. The regenerator as described in claim 3, wherein the porosity change rate outside the regenerator is greater than the porosity change rate inside the regenerator; wherein the outside and the inside are used to represent the relative positional relationship between the two regions , the outer side is closer to the outer periphery of the regenerator than the inner side. The regenerator as claimed in claim 1, wherein the axial porosity of the regenerator has a gradient from low to high in the direction from the low-temperature fluid inlet to the high-temperature fluid inlet. The regenerator as described in claim 5, wherein the regenerator has a multi-stage structure in the axial direction, and three adjacent stages in the multi-stage structure have the same thickness in the axial direction, and each stage has a corresponding porosity; The porosity of the three segments corresponding to the three adjacent segments in the multi-segment structure has a linear relationship. The regenerator as described in claim 5, wherein the regenerator has a multi-stage structure in the axial direction, and three adjacent stages in the multi-stage structure have the same thickness in the axial direction, and each stage has a corresponding porosity; The porosity of the three segments corresponding to the three adjacent segments in the multi-segment structure has a non-linear relationship. The regenerator as described in claim 5, wherein the regenerator has a multi-stage structure in the axial direction, and the two adjacent stages in the multi-stage structure are respectively the first section and a second section, each of the adjacent two sections has an inner layer and an outer layer closer to the outside of the regenerator than the inner layer; wherein, the inner layer of the first section and the inner layer of the second section the layers have the same thickness in the radial direction; the outer layer of the first section and the outer layer of the second section have the same thickness in the radial direction; the outer layer of the first section has a first porosity; and the inner layer of the second section has A second porosity; wherein, the first porosity is the same as the second porosity.

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