A microchannel refrigeration evaporator and a freeze-drying system using the same

Abstract

This invention relates to an evaporator and a freeze-drying system, and more particularly to a microchannel refrigeration evaporator and a freeze-drying system using the evaporator. It includes a rectangular flat tube structure that is circular along its length, and a first microchannel structure that is circumferentially parallel to each other within the flat tube structure. One end of the flat tube structure is connected to a first inlet manifold extending along its width, and the other end is connected to a first outlet manifold extending along its width. The first inlet manifold and the first outlet manifold are interconnected with the first microchannel structure. The inlet manifold and the first outlet manifold are respectively connected to an inlet and an outlet. By employing a rectangular metal flat tube structure with a microchannel structure in the middle, the flat tube structure completely fits the surrounding drying chamber without any hollow structure in the middle, maximizing the coverage area and increasing the heat exchange efficiency.

Description

Technical Field

[0001] This invention relates to an evaporator and a freeze-drying system, and more particularly to a microchannel refrigeration evaporator and a freeze-drying system using the evaporator. Background Technology

[0002] Vacuum freeze dryers are suitable for drying high-grade raw materials, Chinese herbal medicine slices, seafood, wild vegetables, dehydrated vegetables, food, fruits, chemical pharmaceutical intermediates, and other materials.

[0003] Currently, the freeze dryer housing and the refrigeration evaporator are two separate components in vacuum freeze dryers. The freeze dryer housing is mainly used to withstand the pressure generated by the vacuum, while the refrigeration evaporator is mainly used for refrigeration. The refrigeration evaporator is installed on the outer wall of the freeze dryer housing, and heat transfer mainly relies on the contact between the outer wall of the freeze dryer housing and the refrigeration evaporator, resulting in low heat transfer efficiency.

[0004] As physics tells us, water has three phases, known as the triple point. Based on the principle that boiling point decreases with decreasing pressure, as long as the pressure is below the triple point pressure (below 611.657), the water in the material can sublimate directly into water vapor without passing through a liquid phase. Based on this principle, the material can be frozen below its freezing point, turning the water into solid ice. Then, under a suitable vacuum environment, the ice can be directly heated and sublimated into steam to remove it. The water vapor is then condensed using a water vapor condenser in the vacuum system, thus drying the material. The vacuum freeze dryer integrates the refrigeration system, vacuum system, heat transfer oil heating system, and dehumidification system into a new type of cabinet structure. This structure makes greater use of the material storage space within the drying chamber for freeze-vacuum drying. Currently, the refrigeration system of vacuum freeze dryers uses an evaporator to achieve the refrigeration function. The evaporator is made of copper tubing in a spiral shape. During manufacturing, the copper tubing is manually coiled around the outside of the vacuum freeze dryer's drying chamber and fitted onto the outer wall of the chamber, making installation time-consuming and labor-intensive.

[0005] Regarding improvements in heat transfer efficiency, prior art patent application number CN201410332136.2, entitled "Heat Exchanger," provides a heat exchanger comprising: multiple horizontally arranged pipes; a pair of vertical manifolds connected to the pipes; and at least one flow distribution baffle installed at one set of the multiple pipes in the manifolds, such that the flow distribution baffles are arranged between the pipes in the set. Each of the at least one flow distribution baffles is provided with at least one distribution hole to allow refrigerant flow. When the heat exchanger operates as an evaporator for an outdoor unit, it prevents unbalanced refrigerant distribution. It utilizes flow distribution baffles within the manifolds to achieve series flow of the refrigerant. However, it does not fully consider the problem of resistance generated during liquid flow; during upward flow, some pipes may experience refrigerant blockage.

[0006] Prior art patent application number: CN201420324502.5, patent title: Heat exchanger for heat pump water heater and heat pump water heater, provides a heat exchanger including multiple flat tubes, which are spaced apart from each other between a first manifold and a second manifold, and both ends of each flat tube are connected to the first manifold and the second manifold respectively. The inner cavities of the first manifold, the second manifold, and the flat tubes form a refrigerant flow channel, wherein the spacing between adjacent flat tubes decreases from the refrigerant inlet along the refrigerant flow channel to the refrigerant outlet. The heat exchanger according to this utility model can increase the heat exchange area covered by the high-pressure gaseous refrigerant section, improve the heat exchanger efficiency, and ensure uniform water temperature. Figure 1 As shown, the pipes are modified into a flat tube shape, but the spaces between the flat tubes are still open, which increases the coverage area of ​​the heat exchanger pipes to a certain extent, thereby enhancing the heat exchange efficiency. However, this structure still has the problem of refrigerant flowing upwards and potentially being obstructed, preventing complete flow throughout the entire pipe. Summary of the Invention

[0007] This invention provides a refrigeration evaporator with a larger heat exchange coverage area, higher refrigerant flow efficiency, and more comprehensive flow.

[0008] The specific plan is as follows: A microchannel refrigeration evaporator, The invention includes a rectangular flat tube structure, which is circumferential along its length and contains a first microchannel structure that is circumferentially parallel to each other. One end of the flat tube structure is connected to a first inlet manifold extending in the width direction, and the other end is connected to an outlet manifold extending in the width direction. The first inlet manifold and the first outlet manifold are interconnected with the first microchannel structure. The inlet manifold and the first outlet manifold are respectively connected to an inlet and an outlet.

[0009] Furthermore, the center point of the microchannel structure is closer to the inner wall side after the flat tube structure is surrounded.

[0010] Furthermore, the distance between the inner wall of the flat tube structure and the boundary of the microchannel structure is set as the microchannel wall thickness, and the microchannel wall thickness is between 0.3mm and 5mm, preferably between 0.3mm and 1mm.

[0011] Furthermore, a flow-boosting structure is provided on the inner wall of the first microchannel structure.

[0012] Furthermore, the flow-boosting structure is a protruding piece distributed in the first microchannel.

[0013] Furthermore, the cross-section of the first microchannel structure is rectangular, and the protruding pieces are located at the four vertices and extend towards the center of the rectangle.

[0014] Furthermore, the flow-boosting structure causes the inner wall of the first microchannel structure to have a mesh-like recessed structure.

[0015] Furthermore, a control valve is provided on the side of the first microchannel structure that is parallel to each other and close to the first outlet manifold.

[0016] Furthermore, the control valves have an interlocking function; the refrigerant flows sequentially from the first inlet manifold into the first parallel microchannel structures, at which time all the control valves are in the closed state; a pressure sensor is installed on the control valve in the last first microchannel structure, and when the pressure sensor senses the refrigerant flow, all the control valves are opened to allow the refrigerant to flow.

[0017] Furthermore, the flat tube structure is divided into uniformly segmented structures along the direction of its first inlet manifold and first outlet manifold. The first inlet manifold and the first outlet manifold are provided with spaced-apart baffles. The baffles are located at the same positions as the segments of the flat tube structure, so that the first inlet manifold, the first microchannel structure and the first outlet manifold form a series path.

[0018] Furthermore, the three segments in the flat tube structure are connected in parallel as a whole channel, and then connected in series to the next set of three segment channels, repeating in sequence.

[0019] Furthermore, a second inlet manifold is provided on one side of the flat tube structure perpendicular to the first inlet manifold, and a second outlet manifold is provided on the other side of the flat tube structure perpendicular to the first inlet manifold. The flat tube structure is provided with a second microchannel structure that is longitudinally parallel to each other, and the second microchannel structure is interconnected with the second inlet manifold and the second outlet manifold. The first inlet manifold and the second inlet manifold share the same inlet. The first outlet manifold and the second outlet manifold share the outlet. The first microchannel structure and the second microchannel structure are staggered.

[0020] Furthermore, the first inlet manifold is provided with a first clamping lug, and the first outlet manifold is provided with a matching second clamping lug; a stirrup is inserted between the first clamping lug and the second clamping lug.

[0021] A freeze-drying system includes any of the microchannel refrigeration evaporators, a compressor, a drying chamber, a vacuum device, and a heating device as described above; the microchannel refrigeration evaporator is arranged around the side wall of the drying chamber; the vacuum device is connected to the bottom of the drying chamber; the heating device is located on one side of the feed inlet of the drying chamber; and the compressor is connected to the microchannel refrigeration evaporator.

[0022] Furthermore, the compressor is an air-cooled compressor, and it is connected to the microchannel refrigeration evaporator on the other side away from the drying chamber, so that the layout of the entire freeze-drying system is a regular polygon.

[0023] Furthermore, the drying oven is cylindrical in shape, and the flat tube structure is made of aluminum.

[0024] The beneficial effects of this plan are: 1) By adopting a rectangular metal flat tube structure with a microchannel structure in the middle, the flat tube structure fits perfectly with the surrounding drying box without any hollow structure in the middle, maximizing the coverage area and increasing the heat exchange efficiency.

[0025] 2) A flow-boosting structure is set within the microchannel structure to increase the refrigerant flow rate within the microchannel structure.

[0026] 3) Two inlet manifolds and an outlet manifold are set up in a horizontal and vertical configuration to further increase the range of refrigerant flow, thereby making up for the areas where refrigerant cannot flow in the traditional series structure and enhancing heat exchange efficiency. Attached Figure Description

[0027] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a flat tube in the prior art of the present invention. Figure 2 This is a schematic diagram of the microchannel refrigeration evaporator in an embodiment of the present invention; Figure 3 This is a schematic diagram of the microchannel structure in an embodiment of the present invention; Figure 4 This is a schematic diagram of the microchannel wall thickness H in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the first type of protruding piece in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the second type of protruding piece in an embodiment of the present invention; Figure 7 This is a schematic diagram of the flow collector baffle in an embodiment of the present invention; Figure 8This is a schematic diagram of liquid flow in the first form of the series structure in an embodiment of the present invention; Figure 9 This is a schematic diagram of liquid flow in the second form of the series structure in an embodiment of the present invention; Figure 10 This is a schematic diagram of liquid flow in an embodiment of the present invention, showing the coexistence of series and parallel structures. Figure 11 This is a schematic diagram of the freeze-drying system in an embodiment of the present invention; Figure 12 This is a schematic diagram of the mesh-like recessed structure in an embodiment of the present invention; Figure 13 The figure shows the test results of the copper tube evaporator in the freeze-drying effect test; Figure 14 The figure shows the test results of the evaporator of this invention with H=0.3mm in the freeze-drying effect test; Figure 15 This is a simplified structural diagram of the parallel structure in an embodiment of the present invention; Explanation of reference numerals in the attached figures: 1. Flat tube structure; 11. First microchannel structure; 12. First inlet manifold; 121. First clamping lug; 13. First outlet manifold; 14. Inlet; 15. Outlet; 2. Flow enhancement structure; 21. Protruding plate; 22. Mesh recessed structure; 23. Manifold baffle; 31. Second inlet manifold; 32. Second clamping lug; 33. Second outlet manifold; 34. Second microchannel structure; 4. Compressor; 5. Drying oven; 6. Vacuum device; 7. Heating device; 8. Control valve; Microchannel wall thickness: H. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0030] like Figure 2 , 3As shown, a microchannel refrigeration evaporator includes a rectangular flat tube structure 1, which can also be square. The flat tube structure 1 is circumferential along its length, and a first microchannel structure 11 is provided inside the flat tube structure 1, which are circumferentially parallel to each other. In this embodiment, the flat tube structure 1 is made of a rectangular metal plate with a certain thickness for opening microchannel structures inside the flat tube structure 1. The contact area between the metal plate and the drying chamber 5 is significantly larger than that of parallel pipe structures with gaps in the middle. Even if the pipe structure is flat tube in shape, there are still many hollow areas between the pipes, which cannot be used to exchange heat with the drying chamber 5.

[0031] The total heat transfer formula between the evaporator and the drying oven 5 is: q△T / R_t,total in: R_t,total: Thermal resistance (k / w); q: Heat (w); ΔT: Temperature difference (k) According to R_t,total = R_t,cond + R_t,conv R_t,cond: Thermal resistance (kW) between drying oven 5 and evaporator. R_t,conv: Thermal convection resistance (k / w) between the refrigerant and the evaporator copper tubes. R_t,cond=L / (kA); L: thickness (m); K: thermal conductivity [w / (m•k)]; A: contact area (m²).

[0032] Based on the above formula, theoretically, it's possible to test and calculate the thermal resistance value R_t,total of a material. However, this formula is idealized; it assumes that the contact surface is perfectly smooth and flat, and all heat is conducted through the material to the other end. This is practically impossible. Therefore, the measured and calculated thermal resistance value is not entirely the material's inherent thermal resistance, but rather the material's inherent thermal resistance plus the so-called contact surface thermal resistance. Because the smoothness, roughness, or flatness of the contact surface, as well as the pressure applied during installation, will result in different contact surface thermal resistance values, leading to different total thermal resistance values. In short: a. For the same material, the thermal conductivity is a constant value, while the thermal resistance R_t,total will change with the thickness L.

[0033] b. For the same material, the larger the thickness L, the longer the heat has to travel through the material, the more time it takes, and the worse the efficiency.

[0034] c. For thermally conductive materials, the selection of appropriate thermal conductivity K and thickness L has a significant impact on performance. Choosing a material with very high thermal conductivity K but a large thickness L will also result in insufficient performance. The ideal choice is: high thermal conductivity K and thin thickness L, ensuring perfect contact pressure and optimal interfacial contact, i.e., a large contact area A.

[0035] As shown in the formula, thermal conductivity K is an inherent property parameter of the material, used to describe its thermal conductivity. This characteristic is independent of the material's size, shape, and thickness; it is solely related to the material's inherent properties. Therefore, materials of the same type have the same thermal conductivity, which does not change due to variations in thickness. Under the same conditions, the larger the heat transfer contact area A, the higher the heat transfer efficiency between the evaporator and the drying chamber 5.

[0036] Because existing designs often use copper tubes, which have a small contact area with the drying oven 5 due to the line contact, the thermal resistance of the system, especially the resistance conducted from the copper tube to the stainless steel cylinder, increases. Therefore, using the flat tube structure 1 and microchannel structure in this embodiment can greatly increase the contact area, thereby reducing the thermal resistance R_t,cond.

[0037] In this embodiment, the flat tube structure 1 unfolds into a metal plate with a certain thickness. The outer wall of the metal plate in the length direction is a flat surface to ensure that the contact area A with the drying chamber 5 is as large as possible. Microchannels are distributed inside the metal plate. The wall thickness of the microchannels is as thin as possible on the side that contacts the freeze dryer drying chamber 5 to ensure that the heat conduction thickness L is as small as possible. Multiple flat tube structures 1 are connected by 2 manifolds.

[0038] According to the formula R_t,cond=L / (kA), as the contact area A between the drying oven 5 and the evaporator increases, R_t,cond decreases.

[0039] One end of the flat tube structure 1 is connected to a first inlet manifold 12 extending in the width direction, and the other end is connected to an outlet manifold extending in the width direction. The first inlet manifold 12, the first outlet manifold 13, and the first microchannel structure 11 are interconnected. The inlet manifold and the first outlet manifold 13 are respectively connected to an inlet 14 and an outlet 15. In this embodiment, the first inlet manifold 12 is connected to one end of the flat tube structure 1; the other end of the flat tube structure 1 is connected to the first outlet manifold 13. The first inlet manifold 12 and the first outlet manifold 13 are interconnected in series or in parallel through multiple flat tube structures 1, allowing refrigerant to circulate among the first inlet manifold 12, the first outlet manifold 13, and the microchannel structure. The inlet 14 is connected to the front end face of the first inlet manifold 12, allowing refrigerant to be introduced into the first inlet manifold 12. The front end face of the first outlet manifold 13 is connected to the outlet 15, allowing refrigerant to be led out of the first outlet manifold 13.

[0040] like Figure 4 As shown, further, the center point of the microchannel structure is closer to the inner wall side after the flat tube structure 1 is surrounded. In this embodiment, the microchannel structures distributed within the flat tube structure 1 are positioned as close as possible to the inner wall side after the flat tube structure 1 is surrounded, reducing the heat conduction thickness L in the thermal resistance formula, thereby reducing thermal resistance and achieving better heat transfer efficiency and cooling effect.

[0041] Further, the distance between the inner wall of the flat tube structure 1 and the boundary of the microchannel structure is set as the microchannel wall thickness H, and the microchannel wall thickness H is between 0.3mm and 5mm, preferably between 0.3mm and 1mm. In this embodiment, the freeze-drying effect is tested by comparing the evaporator of the first microchannel structure 11 and the evaporator of the parallel copper tubes with a hollow center, with a 4kg water replenishment capacity of the freeze dryer. The drying chamber 58 used has the same structural dimensions; the thermal resistance of the copper tube is K=385 W / mK, and the thermal resistance of the aluminum tube is K=210 W / mK; the copper tube has a size of φ9.5*0.7 and a length of 22 meters, and the microchannel wall thickness H is 0.3mm; the contact area between the copper tube and the drying chamber 5 is approximately A=220cm², and the contact area between the microchannel flat tube and the drying chamber 5 is approximately A=2246cm²; and the refrigerant charge through the copper tube and the first microchannel structure is the same.

[0042] In this freeze-drying test, water was first frozen to ice, and a certain vacuum was created in the channel. The ice was then heated according to a specific pattern, causing it to sublimate into gas. This gas then re-solidified into ice upon contact with a cooled evaporator, releasing heat and transferring water to the evaporator to achieve freeze-drying. Freeze-drying was considered complete when the heating temperature reached a certain value and the vacuum level dropped to a certain value. After testing, the results were presented as follows: Figure 13 , 14 As shown, using a copper tube evaporator as the test object, the total freeze-drying time is approximately 1750 minutes. Freeze-drying begins at 650 minutes and is completed when the vacuum degree no longer changes significantly at 2400 minutes. Using the evaporator of this invention, the total freeze-drying time is shortened to 1210 minutes. Freeze-drying begins at 570 minutes and is completed when the pressure no longer changes significantly at 1780 minutes. The total freeze-drying time is reduced by 540 minutes, and the efficiency is improved by 30%.

[0043] Furthermore, a flow-enhancing structure 2 is provided on the inner wall of the first microchannel structure 11. In this embodiment, the flow-enhancing structure 2 is provided in the microchannel structure. The function of the flow-enhancing structure 2 is not only to increase the heat exchange area of ​​the refrigerant, but also to increase the turbulence of the fluid. The increase in fluid turbulence increases the Reynolds number RE of the fluid, which in turn increases the Nusselt number (a disorder constant describing the fluid), thereby increasing the convective heat transfer coefficient h of the fluid, and ultimately achieving the purpose of increasing the heat exchange efficiency.

[0044] like Figure 5 As shown, the flow-boosting structure 2 further comprises protruding pieces 21 distributed within the first microchannel. In this embodiment, the contact area between the refrigerant and the evaporator is increased by adding protruding pieces 21 inside the first microchannel structure 11, i.e.: Nu=hL / K h: Convective heat transfer coefficient K: Thermal conductivity According to R_t,conv=dT / q=l / (hS), as h increases, R_t,conv decreases. After adding the protruding fins, the contact area between the refrigerant and the evaporator increases, that is, S increases and R_t,conv decreases.

[0045] like Figure 6 As shown, the first microchannel structure 11 has a rectangular cross-section, and the protruding pieces 21 are located at the four vertices and extend towards the center of the rectangle. In another embodiment of the present invention, the protruding pieces 21 are located at the corners of the rectangle and extend towards the center. This arrangement, compared to the protruding pieces 21 extending upwards along the long side of the rectangle, reduces resistance to refrigerant flow and increases the heat exchange area between the refrigerant and the evaporator, thereby increasing heat transfer efficiency.

[0046] like Figure 12 As shown, further, the flow-enhancing structure 2 makes the inner wall of the first microchannel structure 11 form a mesh-like recessed structure 22. In another embodiment of the present invention, the inner wall of the first microchannel structure 11 is recessed downwards, and a mesh structure is further provided downwards on the surface of the recessed structure. The downwardly recessed structure increases the contact area between the first microchannel structure 11 and the refrigerant. Compared with the protruding sheet 21, this can save material, maintain the flow rate of the refrigerant in the microchannel, and increase the heat transfer efficiency.

[0047] like Figure 15As shown, further, a control valve 8 is provided on the side of the first microchannel structure that is parallel to each other near the first outlet manifold. In the embodiments of the present invention, the direct flow between the first inlet manifold, the first microchannel structure and the first outlet manifold is commonly referred to as a parallel path. In traditional parallel structures, when the refrigerant flows, due to the problem of liquid resistance, the refrigerant in the microchannel structure far from the inlet will have difficulty flowing, resulting in uneven distribution of cooling capacity, affecting the overall cooling efficiency of the evaporator, and also causing uneven ice capture. By setting control valves, the flow rate of refrigerant within the microchannel plates is adjusted according to the valve opening degree, ensuring a consistent flow rate and thus maintaining uniform cooling capacity within each microchannel plate. Adjustment can be performed manually or automatically, with valve configurations tailored to individual needs. If proportional control valves are used, a corresponding control system is required. When there is no refrigerant or only a small amount of refrigerant flowing in the microchannel structure far from the inlet, the upstream control valve 8 is closed, stopping the refrigerant flow to the first outlet manifold. Simultaneously, the refrigerant flows towards the downstream microchannel structure until it is fully circulated. Then, the upstream control valve is opened, ensuring full refrigerant flow in each of the first microchannel structures. By adjusting the valves, the uniformity of cooling capacity within the microchannel plates is improved, enhancing refrigeration efficiency.

[0048] Furthermore, the control valves 8 have an interlocking function; refrigerant flows sequentially from the first inlet manifold into the first parallel microchannel structures, at which time all control valves 8 are in the closed state; a pressure sensor is installed on the control valve in the last first microchannel structure. When the pressure sensor senses the refrigerant flow, all control valves are opened to allow the refrigerant to flow. In this embodiment, an interlocking control valve is used, which can be a solenoid valve. A pressure sensor is installed on the last solenoid valve, and the pressure sensor is connected to the solenoid valve through a circuit and equipped with a corresponding control system. Initially, all solenoid valves are in the closed state. When the refrigerant flows into the last microchannel structure, it triggers the pressure sensor on the solenoid valve, opening all solenoid valves to allow the refrigerant to flow simultaneously. This structure fully considers the insufficient refrigerant flow in the evaporator and the complexity of manual control, providing a control valve interlocking device that can both control the sufficient flow of refrigerant between them and automatically complete related adjustments, making it convenient and efficient.

[0049] like Figure 7As shown, further, the flat tube structure 1 is divided into uniformly segmented structures along the direction of its first inlet manifold 12 and first outlet manifold 13. The first inlet manifold 12 and first outlet manifold 13 are provided with spaced-apart baffles 23. The positions of the baffles 23 are the same as the segmentation points of the flat tube structure 1, forming a series path between the first inlet manifold 12, the first microchannel structure 11, and the first outlet manifold 13. In this embodiment, the first inlet manifold 12 and first outlet manifold 13 are regularly separated by the baffles 23, realizing the interconnection and series connection of the multiple segments of the flat tube structure 1, such as... Figure 8 As shown, when a single segment of the microchannel structure forms a flow path, the refrigerant enters the first inlet manifold 12 through the inlet 14. Upon encountering the obstruction of the manifold baffle, it then flows in a different direction into the first microchannel structure 11. After reaching the end of the microchannel, it enters the first outlet manifold 13. In the first outlet manifold 13, it encounters the obstruction of the manifold baffle 23. The refrigerant then flows in a different direction from the first outlet manifold 13 into the next segment of the microchannel flat tube. After reaching the end of the microchannel, it enters the first inlet manifold 12. This process repeats multiple times, finally flowing into the outlet manifold and exiting through the outlet 15. During this process, the refrigerant absorbs heat from the drying chamber 5, lowering its temperature and achieving the purpose of freezing and drying the items inside. The series flow compensates for the problem of insufficient flow within the manifold during parallel flow, resulting in a better cooling effect.

[0050] like Figure 9 Furthermore, when the volume of the drying oven 5 is large, the three segments in the flat tube structure 1 can be connected in parallel as a whole channel, and the flow can be connected in series to the next set of three segment channels, and so on; when the volume of the middle surrounding box is large, it can achieve a better cooling effect.

[0051] like Figure 10Furthermore, the flat tube structure has a second inlet manifold 31 on one side perpendicular to the first inlet manifold, and a second outlet manifold 33 on the other side perpendicular to the first inlet manifold. The flat tube structure contains longitudinally parallel second microchannel structures 34, which are interconnected with the second inlet manifold and the second outlet manifold. The first inlet manifold and the second inlet manifold share the inlet 14; the first outlet manifold and the second outlet manifold share the outlet 15; and the first microchannel structure and the second microchannel structure are staggered. In this embodiment, in the series flow structure, a second inlet manifold 31 and a second outlet manifold 33 are added vertically, and a second microchannel structure 34 is connected in parallel with them. The first microchannel structure 11 and the second microchannel structure 34 are both located within the flat tube structure 1 and do not interfere with each other. The parallel structure allows refrigerant to flow from the inlet side to the other, addressing the issue of insufficient flow due to flow obstruction in the first microchannel. This also compensates for the uneven flow caused by upward backflow obstruction in the series structure. By simultaneously using both series and parallel microchannel mechanisms, the refrigerant flow in both structures is mutually compensated for potential insufficient flow, especially when the intermediate drying chamber 5 has a large volume, as the refrigerant's path is longer, making insufficient flow more likely. This structure significantly improves refrigeration efficiency.

[0052] Furthermore, the first inlet manifold 12 is provided with a first clamping lug 121, and the first outlet manifold 13 is provided with a matching second clamping lug 32; a stirrup is inserted between the first clamping lug 121 and the second clamping lug 32. In this embodiment, since the evaporator is wrapped around the outside of the drying chamber 5, in order to better fit the outer wall of the drying chamber 5, clamping lugs are provided on the first inlet manifold 12 and the first outlet manifold 13, and they are tightened with stirrups, so that after the evaporator wraps around and fits tightly against the drying chamber 5, its shape is fixed and it will not be deformed by external force, thus affecting the heat transfer efficiency.

[0053] like Figure 11The freeze-drying system includes any of the microchannel refrigeration evaporators described above, a compressor 4, a drying chamber 5, a vacuum device 6, and a heating device 7. The microchannel refrigeration evaporator is arranged around the side wall of the drying chamber 5. The vacuum device 6 is connected to the bottom of the drying chamber 5. The heating device is located on the feed inlet side of the drying chamber 5. The compressor is connected to the microchannel refrigeration evaporator. In this embodiment, the freeze-drying chamber 5, refrigeration device, vacuum device 6, and heating device are included. The refrigeration system includes a microchannel refrigeration evaporator and a compressor 4. The compressor is a driven fluid machine that raises low-pressure gas to high-pressure gas and is the core of the refrigeration system. The microchannel refrigeration evaporator is attached to the outer wall of the drying chamber 5. The refrigeration device is used to lower the temperature of the drying chamber 5, freezing the material into a solid state. The vacuum device 6 is connected to the drying chamber 5 and is used to evacuate the drying chamber 5. The heating device is used to heat the material inside the drying chamber 5. The heating method of the heating device can be existing technologies such as hot air, heating blanket, and microwave.

[0054] Furthermore, the compressor 4 is an air-cooled compressor, connected to the side of the microchannel refrigeration evaporator away from the drying chamber 5, making the entire freeze-drying system's layout a regular polygon. In this embodiment, the air-cooled compressor has excellent cooling performance. Limiting its installation position avoids the air-cooled compressor drawing in high temperatures discharged from the drying chamber, which could lead to excessively high exhaust temperatures and affect the normal operation of the entire freeze-drying system. Additionally, designing the entire freeze-drying system's layout as a regular polygon can reasonably save space, making the system more versatile.

[0055] Furthermore, the drying chamber 5 is cylindrical, and the flat tube structure 1 is made of aluminum. In this embodiment, depending on the shape of the drying chamber 5, when it is cylindrical or rectangular, the shapes of the flat tube and the manifold will change, and the angle and position during bending will also change. Optimally, the drying chamber 5 is cylindrical, ensuring that the evaporator fits better against the outside of the drying chamber 5. The optimal evaporator is made of aluminum, is a microchannel flat tube with the above-described structure, and the flow-boosting structure 2 is provided within the microchannel. Based on design experience, a suitable evaporator structure is selected according to the size of the drying chamber 5: Small drying chambers 5 are suitable for configuration with a series structure of microchannel flat tube evaporators, so that the refrigeration capacity of the refrigeration unit meets the needs of the freeze dryer and the refrigeration efficiency is optimal. If a parallel structure is used, the refrigerant flows through the evaporator quickly and flows out before it has time to exchange heat, which is not conducive to the refrigeration of the refrigeration unit. Large drying chambers 5 are suitable for configuration with microchannel flat tube evaporators that can be configured in both series and parallel structures. This avoids excessively long pipelines and excessive impact from flow resistance. The parallel structure ensures the refrigeration capacity of the refrigeration unit and optimizes the refrigeration efficiency, while ensuring that the flow resistance is not too high, thus optimizing the refrigeration efficiency.

[0056] Working Principle: The substance to be frozen is placed on the tray of freeze-drying chamber 5. The freeze dryer is started, and the refrigeration system begins to work. The freeze dryer first pre-freezes the substance containing a large amount of water into a solid state. Then, the vacuum system is activated, and chamber 5 is evacuated. Under vacuum conditions, the heating device is activated, causing the solid water to sublimate directly, while the substance itself remains in the ice rack from when it was frozen. This is the drying process, and the volume of the substance remains unchanged after drying. Solid water absorbs heat during sublimation, causing the temperature of the substance itself to drop and slowing down the sublimation rate. To increase the sublimation rate and shorten the drying time, the product must be appropriately heated. After freezing and drying are completed, the substance is removed from the drying chamber, completing the freeze-drying process.

[0057] The refrigeration unit uses a compressor and other tools to deliver refrigerant into the flat tube structure 1. The refrigerant enters the first inlet manifold from the inlet pipe; the refrigerant then enters multiple flat tubes and flows into the outlet manifold. When it is necessary to discharge the refrigerant, the refrigerant in this unit is discharged from the outlet pipe, thus completing the freezing of the substance.

[0058] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A microchannel refrigeration evaporator, characterized in that, The invention includes a rectangular flat tube structure, which is circumferential along its length and contains a first microchannel structure that is circumferentially parallel to each other. One end of the flat tube structure is connected to a first inlet manifold extending in the width direction, and the other end is connected to a first outlet manifold extending in the width direction. The first inlet manifold and the first outlet manifold are interconnected with the first microchannel structure. The first inlet manifold and the first outlet manifold are respectively connected to an inlet and an outlet. The flat tube structure is divided into uniformly distributed multi-segment structures along the direction of its first inlet manifold and first outlet manifold. The first inlet manifold and the first outlet manifold are provided with spaced-apart manifolds. The positions of the manifolds are the same as the segmentation points of the flat tube structure, so that the first inlet manifold, the first microchannel structure and the first outlet manifold form a series path. The flat tube structure has a second inlet manifold on one side perpendicular to the first inlet manifold, and a second outlet manifold on the other side perpendicular to the first inlet manifold. The flat tube structure is provided with a second microchannel structure that is longitudinally parallel to each other, and the second microchannel structure is interconnected with the second inlet manifold and the second outlet manifold. The first inlet manifold and the second inlet manifold share the same inlet. The first outlet manifold and the second outlet manifold share the outlet. The first microchannel structure and the second microchannel structure are staggered.

2. The microchannel refrigeration evaporator according to claim 1, characterized in that, The center point of the first microchannel structure is closer to the inner wall side after the flat tube structure is surrounded.

3. A microchannel refrigeration evaporator according to claim 2, characterized in that, The distance between the inner wall of the flat tube structure and the boundary of the first microchannel structure is set as the microchannel wall thickness, and the microchannel wall thickness is 0.3mm to 5mm.

4. A microchannel refrigeration evaporator according to claim 1, characterized in that, The inner wall of the first microchannel structure is provided with a flow-boosting structure.

5. A microchannel refrigeration evaporator according to claim 4, characterized in that, The flow-boosting structure is a protruding piece distributed in the first microchannel structure.

6. A microchannel refrigeration evaporator according to claim 5, characterized in that, The first microchannel structure has a rectangular cross-section, and the protruding pieces are located at the four vertices and extend toward the center of the rectangle.

7. A microchannel refrigeration evaporator according to claim 4, characterized in that, The flow-boosting structure causes the inner wall of the first microchannel structure to have a mesh-like concave structure.

8. A microchannel refrigeration evaporator according to claim 1, characterized in that, A control valve is provided on the side of the first microchannel structure that is parallel to each other and close to the first outlet manifold.

9. A microchannel refrigeration evaporator according to claim 8, characterized in that, The control valves are interconnected; the refrigerant flows sequentially from the first inlet manifold into the first parallel microchannel structures, at which time all the control valves are closed; a pressure sensor is installed on the control valve in the last first microchannel structure, and when the pressure sensor senses the refrigerant flow, all the control valves are opened to allow the refrigerant to flow.

10. A microchannel refrigeration evaporator according to claim 1, characterized in that, The three segments in the flat tube structure are connected in parallel as a whole channel, and then connected in series to the next set of three segment channels, and so on.

11. A microchannel refrigeration evaporator according to claim 1, characterized in that, The first inlet manifold is provided with a first clamping lug, and the first outlet manifold is provided with a matching second clamping lug; a stirrup is inserted between the first clamping lug and the second clamping lug.

12. A freeze-drying system, characterized in that, The device includes a microchannel refrigeration evaporator, a compressor, a drying oven, a vacuum device, and a heating device as described in any one of claims 1 to 9; the microchannel refrigeration evaporator is arranged around the side wall of the drying oven; the vacuum device is connected to the bottom of the drying oven; the heating device is located inside the drying oven; and the compressor is connected to the microchannel refrigeration evaporator.

13. A freeze-drying system according to claim 12, characterized in that, The compressor is an air-cooled compressor, which is connected to the microchannel refrigeration evaporator on the side away from the drying chamber, so that the layout of the entire freeze-drying system is a regular polygon.

14. A freeze-drying system according to claim 12, characterized in that, The drying oven is cylindrical in shape, and the flat tube structure is made of aluminum.

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