Spiral pipe phase-change heat exchange device with perforated fins

Abstract

The invention relates to the technical field of phase change heat storage, in particular to a spiral tube phase change heat exchange device with perforated fins, which comprises a shell, heat exchange tubes, fins and a phase change material, the heat exchange tubes are arranged in the shell and are stacked and encircled; the fins are arranged in the shell and connected with the heat exchange tubes, and the plane where the fins are located is parallel to the length direction of the shell. Through holes are formed in the fins; and the phase-change material is filled in the shell and outside the heat exchange tube. According to the heat exchanger, the heat exchange tubes are arranged in the shell in the length direction of the shell in a stacked and surrounding mode so as to have a larger surface area, and the fins and the heat exchange tubes are connected into a whole so as to further enlarge the heat transfer area. Moreover, the plane where the fins are located is parallel to the length direction of the shell, so that the phase-change material can flow in the length direction of the shell, the phase-change material can flow in the direction perpendicular to the length direction of the shell through the through holes in the fins, and therefore the obstruction of the fins to natural convection of the phase-change material is reduced; the melting heat storage process of the phase-change material is accelerated, and the heat exchange efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of phase change heat storage, and in particular to a spiral tube phase change heat storage device with perforated fins. Background Art

[0002] Phase change heat storage technology uses phase change materials as thermal energy storage media to store or recover heat energy during the phase change of the material. The phase change involved is mostly solid-liquid phase change. Since substances absorb or release latent heat when they undergo phase change, this technology is also called latent heat storage technology. Compared with sensible heat storage technology, phase change latent heat has greater energy storage density and smaller temperature change; compared with thermochemical heat storage technology, phase change latent heat has good repeatability and controllability. Phase change heat storage technology is an effective and practical way to reduce the mismatch between energy supply and energy demand. In the past few decades, phase change heat storage technology has been widely studied and applied in many important fields, such as solar thermal storage systems, electronic cooling, building envelope structures, refrigeration, and waste heat recovery.

[0003] Since the density of the phase change material changes with the temperature during the solid-liquid phase change, the liquid phase change material encapsulated in the heat storage tank has a certain flow rate. Although the flow rate is small, the fluidity of the phase change material always exists during the entire heat storage process. In order to improve the heat transfer effect of the phase change material in the heat storage tank, many researchers have added fins to the outside of the heat exchange tube. The plane where these fins are located is set perpendicular to the length direction of the heat storage tank. Although the addition of fins expands the heat transfer area and increases the thermal conductivity, the presence of fins hinders the natural convection heat transfer of the phase change material to a certain extent, making the phase change material take more time in the middle and late stages of melting in the heat storage device. Summary of the invention

[0004] In view of this, the present invention provides a spiral tube phase change heat transfer device with perforated fins, which aims to expand the heat transfer area while reducing the obstruction to the natural convection of the phase change material during the solid-liquid phase change by adjusting the arrangement of the fins.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A spiral tube phase change heat exchange device with perforated fins comprises a shell, a heat exchange tube, a fin and a phase change material; the heat exchange tube is arranged in the shell and is stacked and wrapped along the length direction of the shell, and the openings at both ends of the heat exchange tube extend to the outside of the two ends of the shell; the heat exchange tube is used for circulating a heat exchange fluid; the fin is arranged in the shell and connected to the heat exchange tube, and the plane where the fin is located is arranged parallel to the length direction of the shell; the fin has through holes; the phase change material is filled in the shell and outside the heat exchange tube.

[0007] In some optional embodiments, the fin is elliptical in shape.

[0008] In some optional embodiments, the through hole is in an elongated strip shape and is arranged along the length direction of the shell.

[0009] In some optional embodiments, when there are more than two fins, the fins are circumferentially dispersed along the center line of the shell.

[0010] In some optional embodiments, the heat exchange tube is generally rectangular in a direction perpendicular to the center line of the shell.

[0011] In some optional embodiments, when there are more than two heat exchange tubes, adjacent heat exchange tubes are arranged in an annular layered array in a direction perpendicular to the center line of the shell.

[0012] In some optional embodiments, the fin has the through holes at locations between adjacent heat exchange tubes.

[0013] In some optional embodiments, the winding directions of adjacent heat exchange tubes are opposite.

[0014] In some optional embodiments, the flow direction of the heat exchange fluid in at least one of the heat exchange tubes is opposite to the flow direction of the heat exchange fluid in the other heat exchange tubes.

[0015] In some optional implementations, the shell is made of quartz glass, and a thermal insulation material is wrapped outside the shell.

[0016] In summary, compared with the prior art, the present invention has the following advantages and beneficial effects: the present invention has a compact structure, is easy to process, and is low in cost. The heat exchange tubes are stacked and arranged in the shell along the length direction of the shell to have a larger surface area, and the fins are connected to the heat exchange tubes as a whole to further expand the heat transfer area. In addition, the plane where the fins are located is arranged parallel to the length direction of the shell to facilitate the flow of the phase change material along the length direction of the shell. The through holes on the fins can facilitate the flow of the phase change material in a direction perpendicular to the length direction of the shell, thereby reducing the obstruction of the fins to the natural convection of the phase change material, accelerating the melting and heat storage process of the phase change material, and improving the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the present invention, for the convenience of showing the internal structure, Figure 1 Part of the housing is omitted.

[0018] Figure 2 It mainly illustrates the structural schematic diagram when the winding directions of two adjacent heat exchange tubes in the present invention are opposite.

[0019] Figure 3 for Figure 2 Side view of.

[0020] Figure 4 It is a schematic diagram of the structure of the fin in the present invention.

[0021] The meanings of the symbols in the figure are: shell 1, heat exchange tube 2, opening 3, fin 4, through hole 5, hole 6. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0023] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0024] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there are any descriptions of "first", "second" and the like, they are only used for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0025] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0026] The applicant found in the research that during the heat storage process, the heat exchange fluid in the heat exchange tube transfers heat to the heat exchange tube wall and fins. At the initial stage of melting of the phase change material, the phase change material close to the heat exchange tube wall and fins melts first, and the melted phase change material continues to absorb the heat from the heat exchange tube wall and fins and transfers it to the unmelted phase change material. In the middle and late stages of melting, the phase change material in the heat storage tank is a solid-liquid mixed phase. As the density of the phase change material changes during the solid-liquid phase change, the phase change material has a certain flow rate, forming natural convection, so the heat exchange method at this time is mainly convective heat exchange.

[0027] When the phase change material changes from solid to liquid, the first melted liquid part will disperse and flow around. Since the width of the heat storage tank is small and the flow distance is limited, the flow of the phase change material mainly occurs in the length direction of the heat storage tank. When the plane where the fins are located is set perpendicular to the length direction of the heat storage tank, it will hinder the phase change material from flowing along the length direction of the heat storage tank, thereby affecting the heat exchange effect.

[0028] Based on this research finding, the present application embodiment proposes a spiral tube phase change heat exchange device with perforated fins, such as Figure 1 As shown, the device includes a shell 1, a heat exchange tube 2, a fin 4 and a phase change material.

[0029] The shell 1 can be a hollow cavity with a cylindrical or rectangular outer contour, with a cavity inside to accommodate the heat exchange tube 2, the fin 4 and the phase change material. The two ends of the shell 1 have detachable end covers, and the detachable seal between the shell 1 body can be achieved by bolts and sealing rings. The shell 1 can be made of quartz glass, and thermal insulation materials (such as glass fiber wool, glass wool and other insulation wool) can also be wrapped outside the shell 1 to reduce the heat loss of the phase change material. Quartz glass is made by melting various pure natural quartz (such as crystal, quartz sand, etc.), with a very small linear expansion coefficient, which is 1 / 10 to 1 / 20 of ordinary glass, and has good thermal shock resistance; it has high heat resistance, and the regular use temperature is 1100℃ to 1200℃, and the short-term use temperature can reach 1400℃.

[0030] The heat exchange tube 2 is usually a hollow tube made of a metal material (such as copper) so that the heat exchange fluid (usually water) can flow in the tube. The heat exchange tube 2 is arranged in the shell 1 and the heat exchange tube 2 itself is stacked and surrounded along the length direction of the shell 1. The heat exchange tube 2 has openings 3 at both ends, and the two openings 3 extend to the end caps at both ends of the shell 1 respectively. The heat exchange tube 2 can be supported in the shell 1 by the end caps at both ends of the shell 1.

[0031] The fin 4 is arranged in the shell 1 and can be connected to the heat exchange tube 2 by welding or other methods. For example, a hole 6 is provided on the fin 4 for the heat exchange tube 2 to pass through. After the heat exchange tube 2 passes through the hole 6, the fin 4 is welded to the heat exchange tube 2. The fin 4 is usually made of a metal material (such as copper) in the form of a thin sheet or plate, which can expand the heat exchange area and quickly exchange heat with the phase change material. In order to reduce the influence of the fin 4 on the flow of the phase change material along the length direction of the shell 1, the embodiment of the present application innovatively sets the plane where the fin 4 is located parallel to the length direction of the shell 1. In this way, the phase change material will not be hindered by the fin 4 when it flows along the length direction of the shell 1, and the natural flow is smoother and the heat exchange effect is better. In the width direction of the shell 1, due to the limited distance, the flow phenomenon is not significant. Therefore, setting the plane where the fin 4 is located parallel to the length direction of the shell 1 has little effect on it. After simulation and observation, it is found that it has little effect on the overall heat exchange effect. However, in order to improve the heat exchange effect of the entire device as much as possible, the embodiment of the present application still opens a plurality of through holes 5 on the fins 4 to facilitate the phase change material to flow in a length direction perpendicular to the shell 1, thereby reducing the influence of the fins 4 on the flow of the phase change material in the width direction of the shell 1. Studies have shown that opening through holes 5 on the fins 4 can enhance heat transfer and facilitate natural convection of the phase change material. The fins 4 can not only increase the heat transfer surface and enhance the thermal conductivity of the phase change material in the early stage of melting, but also in the later stage of melting of the phase change material, due to the presence of the through holes 5, the liquid phase change material can pass through the through holes 5, reducing the obstruction to natural convection.

[0032] At the same time, the fins 4 can also be used to support the heat exchange tubes 2. On the one hand, the fins 4 are connected to the heat exchange tubes 2. On the other hand, the ends of the fins 4 away from the center line of the shell 1 can be abutted against the inner wall of the shell 1 or connected by methods such as welding, thereby stably supporting the heat exchange tubes 2 in the shell 1 and improving its stability.

[0033] The phase change material is filled inside the shell 1 and wrapped around the outside of the heat exchange tube 2 and the fin 4. The phase change material can be paraffin, molten salt or a composite material formed by the two, preferably paraffin, the phase change temperature of paraffin is 48.3℃~62℃, and the solid density is 860kg / m 3 , liquid density is 780kg / m 3 , solid thermal conductivity is 0.13W / m / K, liquid thermal conductivity is 0.11W / m / K, solid specific heat capacity is 2.18kJ / kg / K, liquid specific heat capacity is 2.39kJ / kg / K, phase change latent heat is 114.5kJ / kg, thermal expansion coefficient is 0.001K -1 .

[0034] When the high-temperature heat exchange fluid flows through the heat exchange tube 2, it transfers heat to the heat exchange tube 2 and the fin 4. The solid phase change material near the heat exchange tube 2 and the fin 4 first melts into a liquid state. As the heat exchange continues, the temperature of the liquid phase change material continues to rise, and the solid phase change material in contact with the liquid phase change material gradually melts. The phase change material continuously stores heat energy through sensible heat and latent heat of phase change until all the solid phase change material melts into liquid phase change material. At the same time, the liquid phase change material near the heat exchange tube 2 and the fin 4 has a higher temperature, resulting in a lower density. There is a density difference in the liquid phase change material due to the temperature difference, which triggers the natural convection of the liquid phase change material, thereby enhancing the opportunity for the high-temperature liquid phase change material to contact the solid phase change material, thereby improving the melting efficiency of the phase change material.

[0035] The heat exchange fluid in the heat exchange tube 2 is stacked and rotated along the length direction of the shell 1, and the plane where the fins 4 are located is set parallel to the length direction of the shell 1, so that the liquid phase change material will not be hindered by the fins 4 when flowing along the length direction of the shell 1, and the heat of the heat exchange fluid in the heat exchange tube 2 can be transferred to the fins 4 more quickly and transferred along the fins 4. At the same time, this structure can also enhance the flow performance of the phase change material due to density changes, so that it can continuously transfer heat and change phases along the length direction of the shell 1, avoiding the obstruction and compression loss of the phase change material when it flows along the length direction of the shell 1 when the plane where the fins are located is set perpendicular to the length direction of the shell 1. In addition, setting the plane where the fins 4 are located parallel to the length direction of the shell 1 is also convenient for processing and installation, with a relatively simple structure and easier to clean than vertical installation.

[0036] At the same time, the through holes 5 on the fins 4 can also allow the liquid phase change material to flow in a direction perpendicular to the length of the shell 1, so that the fins 4 have almost no negative impact on the heat transfer area of ​​the heat exchange tube 2 while expanding the heat transfer area, thereby improving the heat transfer efficiency. During the melting process of the phase change material, the melted liquid phase change material can pass through the through holes 5 to transfer heat to the solid phase change material, thereby enhancing the fluidity of the phase change material.

[0037] When the low-temperature heat exchange fluid flows through the heat exchange tube 2, the heat energy stored in the phase change material can be released. In the embodiment of the present application, heat exchange fluids of different temperatures are circulated in the heat exchange tube 2 to transfer heat to the phase change material for heat storage or absorb the heat of the phase change material for heat release. During the heat exchange process, the phase change material undergoes a solid-liquid phase change, and uses sensible heat and latent heat for storage and release.

[0038] As an optional implementation, the applicant has found through repeated research, calculation and testing that the fluidity of the liquid phase change material can be further improved when the shape of the fin 4 is designed to be elliptical. This is because the solid phase change material in each corner of the shell 1 melts very slowly due to being away from the heat exchange tube 2 and the fin 4. After the shape of the fin 4 is designed to be elliptical, there is a channel between the edge of the fin 4 and the inner wall of the shell 1 for the liquid phase change material to flow, especially the four corners of the fin 4, which have larger channels, which are more conducive to the flow of liquid phase change material, thereby effectively improving the overall melting rate of the phase change material.

[0039] In addition, in order to reduce the obstruction of the main part of the fin 4 to the flow of the liquid phase change material, as an optional embodiment, the through hole 5 on the fin 4 can be designed to be a long strip and arranged along the length direction of the shell 1, so that the through hole 5 has a longer size and a larger flow range, which is conducive to the flow of liquid phase change material.

[0040] There can be one fin 4, or more than two fins 4 can be provided. When there are more than two fins 4, the fins 4 are dispersedly arranged along the circumferential direction of the center line of the shell 1. For example, when there are four fins 4, the four fins 4 are respectively arranged at the left, right, top and bottom positions of the cross section of the shell 1, and two adjacent fins 4 are perpendicular to each other, and two relative fins 4 are parallel to each other. Each fin 4 can also be connected to each other as a whole near the center by, for example, welding. The through holes 5 on each fin 4 are arranged along the length direction of the fin 4 itself, that is, along the length direction of the shell 1. Multiple fins 4 are dispersedly arranged in the shell 1. On the one hand, it is conducive to uniform and sufficient contact with the phase change material. On the other hand, because the fins 4 are not in contact with each other, or the contacting parts are small, more channels are left to facilitate the flow of liquid phase change materials.

[0041] As mentioned above, the heat exchange tube 2 is stacked and wound in the shell 1 along the length direction of the shell 1, for example, it can be wound in a spiral form, the cross section of the heat exchange tube 2 is circular, and the overall shape is like a spring. The heat exchange tube 2 can also be generally rectangular in the direction perpendicular to the center line of the shell 1. When the side length of the rectangle is equal to the diameter of the circle, the heat exchange tube 2 can have a longer length in the shell 1 than the circular one, that is, it has a larger heat exchange area, which can make the heat exchange area of ​​the phase change material wider, reduce the temperature gradient in the shell 1, and thus make the heat transfer more uniform.

[0042] Only one heat exchange tube 2 may be provided in the shell 1, but in order to further improve the heat exchange efficiency, the embodiment of the present application also considers that multiple heat exchange tubes 2 may be provided in the shell 1. When there are more than two heat exchange tubes 2, adjacent heat exchange tubes 2 are arranged in a circular layered array in a direction perpendicular to the center line of the shell 1. For example, when there are two heat exchange tubes 2, one heat exchange tube 2 is located inside the other heat exchange tube 2, and there is no contact between the two heat exchange tubes 2. Both heat exchange tubes 2 are connected to the fins 4, and the two heat exchange tubes 2 are kept apart by the fins 4. Increasing the number of heat exchange tubes 2 can significantly increase the heat exchange area and heat exchange efficiency.

[0043] Furthermore, when there are more than two heat exchange tubes 2, a high-temperature heat exchange fluid may be introduced into a portion of the heat exchange tubes 2, and a low-temperature heat exchange fluid may be introduced into another portion of the heat exchange tubes 2, thereby achieving heat storage and heat release simultaneously.

[0044] For example, when heat storage is required, such as storing solar heat, a heat exchange fluid heated by solar energy flows through all heat exchange tubes 2, and the heat is stored in the phase change material in the shell 1. When heat release is required, such as power generation, a normal temperature heat exchange fluid flows through all heat exchange tubes 2 to absorb the heat in the phase change material in the shell 1 to form steam to drive the steam turbine to generate electricity. Since there are multiple heat exchange tubes 2 in the embodiment of the present application, a heat exchange fluid heated by solar energy can be circulated through a part of the heat exchange tubes 2 to allow the phase change material to store heat, and at the same time, a normal temperature heat exchange fluid flows through another part of the heat exchange tubes 2 to form steam to release heat, so as to achieve heat storage and heat release at the same time.

[0045] At the same time, however, the increase in the number of heat exchange tubes 2 will also affect the natural convection of the liquid phase change material to a certain extent. Although this effect is very limited, in order to eliminate this effect as much as possible, the embodiment of the present application also provides through holes 5 in the parts of the fins 4 between adjacent heat exchange tubes 2 to prevent obstruction of the flow of the liquid phase change material. These through holes 5 are also long and are arranged along the length direction of the shell 1.

[0046] The winding directions of adjacent heat exchange tubes 2 can also be set in opposite directions. For example, among two adjacent heat exchange tubes 2, one is wound in a clockwise direction and the other is wound in a counterclockwise direction. In this way, the adjacent heat exchange tubes 2 are staggered with each other so that the heat exchange surface is evenly distributed. The liquid phase change material will swirl when flowing through the heat exchange tube 2, thereby fully exchanging heat with the heat exchange tube 2.

[0047] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The above preferred embodiments shall not be regarded as limiting the present invention, and the protection scope of the present invention shall be subject to the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications shall also be regarded as the protection scope of the present invention.

Claims

1. A spiral tube phase change heat exchange device with perforated fins, characterized in that: It comprises a shell (1), a heat exchange tube (2), fins (4) and a phase change material; The heat exchange tube (2) is arranged in the shell (1) and is stacked and wrapped around the shell (1) in a longitudinal direction. The openings (3) at both ends of the heat exchange tube (2) extend outside the two ends of the shell (1). The heat exchange tube (2) is used for circulating a heat exchange fluid. The fin (4) is arranged in the shell (1) and connected to the heat exchange tube (2); the plane where the fin (4) is located is arranged parallel to the length direction of the shell (1); the fin (4) has a through hole (5); The phase change material is filled inside the shell (1) and outside the heat exchange tube (2).

2. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 1, characterized in that: The fin (4) is elliptical in shape.

3. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 1, characterized in that: The through hole (5) is in the shape of an elongated strip and is arranged along the length direction of the housing (1).

4. A spiral tube phase change heat exchange device with perforated fins according to any one of claims 1 to 3, characterized in that: When there are more than two fins (4), the fins (4) are dispersedly arranged along the circumferential direction of the center line of the shell (1).

5. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 1, characterized in that: The heat exchange tube (2) is generally rectangular in a direction perpendicular to the center line of the shell (1).

6. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 1, characterized in that: When there are more than two heat exchange tubes (2), adjacent heat exchange tubes (2) are arranged in a ring-shaped layered array in a direction perpendicular to the center line of the shell (1).

7. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 6, characterized in that: The fin (4) has the through hole (5) at a position between adjacent heat exchange tubes (2).

8. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 6, characterized in that: The winding directions of adjacent heat exchange tubes (2) are opposite.

9. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 6, characterized in that: The flow direction of the heat exchange fluid in at least one of the heat exchange tubes (2) is opposite to the flow direction of the heat exchange fluid in the other heat exchange tubes (2).

10. A spiral tube phase change heat exchange device with perforated fins as claimed in claim 1, characterized in that: The shell (1) is made of quartz glass, and a thermal insulation material is wrapped around the outside of the shell (1).

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