WO2024012442A1

WO2024012442A1 - Micro-channel refrigerating evaporator and freeze-drying system using evaporator

Info

Publication number: WO2024012442A1
Application number: PCT/CN2023/106754
Authority: WO
Inventors: 张文锋
Original assignee: 东富龙科技集团股份有限公司
Priority date: 2022-07-15
Filing date: 2023-07-11
Publication date: 2024-01-18
Also published as: CN115143667A; CN116717929A

Abstract

A micro-channel refrigerating evaporator and a freeze-drying system using the evaporator. The micro-channel refrigerating evaporator comprises a rectangular flat tube structure, wherein the flat tube structure is arranged in a surrounding manner in the lengthwise direction thereof; first micro-channel structures, which are parallel to each other in a circumferential direction, are arranged in the flat tube structure; one end of the flat tube structure is connected to a first inlet flow collecting pipe which extends in a widthwise direction, and the other end thereof is connected to a first outlet flow collecting pipe which extends in the widthwise direction; the first inlet flow collecting pipe, the first outlet flow collecting pipe and the first micro-channel structures are in communication with one another; and the first inlet flow collecting pipe and the first outlet flow collecting pipe are respectively connected to an inlet port and an outlet port. By means of using a rectangular metal flat tube structure and arrangement of the micro-channel structures in the middle thereof, the flat tube structure is completely attached to a surrounding drying box, such that no hollow structure is disposed in the middle, the coverage area is thus increased to the maximum extent and the heat exchange efficiency is improved.

Description

Microchannel refrigeration evaporator and freeze-drying system using the evaporator

Technical field

The present invention relates to an evaporator and a freeze-drying system, and in particular to a micro-channel refrigeration evaporator and a freeze-drying system using the evaporator.

Background technique

The vacuum freeze dryer is suitable for drying high-grade raw materials, traditional Chinese medicine pieces, seafood, wild vegetables, dehydrated vegetables, food, fruits, chemical drug intermediates and other materials.

At present, the freeze dryer box and the refrigeration evaporator used in vacuum freeze dryers are two separate components. The freeze dryer box is mainly used to withstand the pressure generated by the vacuum, and the refrigeration evaporator is mainly used for refrigeration. A refrigeration evaporator is installed on the outer wall of the freeze-drying cabinet. The heat transfer mainly relies on the contact between the outer wall of the freeze-drying cabinet and the refrigeration evaporator, and the heat transfer efficiency is low.

It can be known from physics that water has three phases, which are called three-phase common points. According to the principle of reduced pressure and lower boiling point, as long as the pressure is below the triple point pressure (the pressure is below 611.657), the moisture in the material can be obtained from the water It sublimates directly into water vapor without passing through the liquid phase. According to this principle, the material can be frozen below the freezing point to turn the moisture in the material into solid ice. Then, in an appropriate vacuum environment, the ice can be directly heated and sublimated into steam to remove it, and then the water vapor in the vacuum system can be used. The condenser condenses water vapor to dry the material. The vacuum freeze dryer combines a refrigeration system, a vacuum system, a thermal oil heating system, and a moisture dehumidification system into a new box structure. This structure makes maximum use of the material storage space in the drying box for freeze vacuum drying. At present, the refrigeration system of the vacuum freeze dryer uses an evaporator to achieve the refrigeration function. The evaporator is made of copper tubes in a spiral shape. During processing, the copper tubes are manually coiled around the drying box of the vacuum freeze dryer and set in the drying box of the vacuum freeze dryer. On the outer wall, installation is time-consuming and laborious.

In order to improve the heat transfer efficiency, the prior art patent application number: CN201410332136.2, patent name: heat exchanger, provides a heat exchanger, including: multiple pipes, arranged horizontally; a pair of vertical headers, Connected to the pipes; at least one flow distribution baffle mounted to the header at a group of the plurality of pipes such that the flow distribution baffle is arranged between the pipes of the group. described Each of the at least one flow distribution baffle is provided with at least one distribution hole to allow refrigerant to flow therethrough. The heat exchanger prevents unbalanced distribution of refrigerant when operating as the evaporator of the outdoor unit. It realizes the series flow of refrigerants by setting flow distribution baffles in the header pipes. However, it does not fully consider the problems caused by the resistance when the liquid flows. During the upward flow process, there will be a problem that the refrigerant cannot flow into some pipes.

Prior art patent application number: CN201420324502.5, patent name: heat exchanger for heat pump water heater and heat pump water heater, provides a heat exchanger, including a plurality of flat tubes, the plurality of flat tubes are spaced apart from each other is provided between the first header and the second header, and both ends of each flat tube are connected to the first header and the second header respectively. The first header The flow tube, the second header tube and the inner cavity of the flat tube form a refrigerant flow channel, wherein the spacing between adjacent flat tubes extends from the refrigerant inlet along the refrigerant flow channel to the refrigeration decreases in the direction of the agent outlet. The heat exchanger according to the utility model can increase the heat exchange area covered by the high-pressure gas refrigerant section, improve the heat exchanger efficiency and make the water temperature uniform. As shown in Figure 1, the pipe is improved into a flat tube shape, but the hollow design is still between the flat tubes, which increases the coverage area of the heat exchanger pipe to a certain extent, thereby enhancing the efficiency of heat exchange. However, this structure still has the problem that the refrigerant flows back upward, the flow may be blocked, and the entire pipeline cannot be completely circulated.

Contents of the invention

The invention provides a refrigeration evaporator with a larger heat exchange coverage area, higher refrigerant circulation efficiency, and more comprehensive circulation.

The specific plans are as follows:

A microchannel refrigeration evaporator,

It includes a rectangular flat tube structure, the flat tube structure is circumferential along its length direction, and the flat tube structure is provided with a first microchannel structure that is parallel to each other in the circumferential direction;

One end of the flat tube structure is connected to a first inlet header extending along the width direction, and the other end is connected to an outlet header extending along the width direction;

The first inlet header, the first outlet header and the first microchannel structure are interconnected;

The first inlet header and the first outlet header are respectively connected with an inlet and an outflow port.

Further, the center point of the first microchannel structure is closer to the inner wall side surrounded by the flat tube structure.

Further, the boundary distance between the inner wall side of the flat tube structure and the microchannel structure is set to the microchannel wall thickness, and the microchannel wall thickness ranges from 0.3mm to 5mm, preferably from 0.3mm to 1mm.

Further, a flow-increasing structure is provided on the inner wall of the first microchannel structure.

Further, the flow-increasing structure is a protruding piece distributed in the first microchannel structure.

Further, the cross section of the first microchannel structure is rectangular, and the protruding pieces are provided at four vertices and extend toward the center of the rectangle.

Furthermore, the flow-increasing structure causes the inner wall of the first microchannel structure to form a reticular concave structure.

Further, a control valve is provided on a side of the mutually parallel first microchannel structures close to the first outlet header.

Further, the control valves have a linkage function; the refrigerant will flow from the first inlet header to the first micro-channel structures that are parallel to each other. At this time, all of the control valves are in a closed state; A pressure sensor is provided on the control valve in the final first microchannel structure. When the pressure sensor senses the flow of refrigerant, all control valves are opened to allow the refrigerant to flow.

Further, the flat tube structure is divided into uniform multi-section structures along the direction of the first inlet header and the first outlet header. The first inlet header and the first outlet header are There are spaced collecting partitions arranged in the tube, and the position of the collecting partitions is the same as the segment of the flat tube structure, so that the first inlet collecting tube and the first microchannel structure A series path is formed between the first outlet header and the first outlet header.

Further, the three segments in the flat tube structure are connected in parallel as an integral channel, and the flow flows in series to the next group of three segmented channels, and the sequence is repeated.

Further, a second inlet header is provided on one side of the flat tube structure perpendicular to the first inlet header, and a second inlet header is provided on the other side of the flat tube structure perpendicular to the first inlet header. There is a second outlet header;

A second microchannel structure longitudinally parallel to each other is provided in the flat tube structure, and the second microchannel structure interconnects the second inlet header and the second outlet header;

The first inlet header and the second inlet header share the inlet;

The first outlet header and the second outlet header share the outflow port;

The first microchannel structure and the second microchannel structure are staggered from each other.

Further, the first inlet header is provided with a first tightening lug, and the first outlet header is provided with a matching second tightening lug; the first tightening lug is provided A stirrup is provided inside between the ear and the second tightening lug.

A freeze-drying system, including any one of the above-mentioned micro-channel refrigeration evaporator, a compressor, a drying box, a vacuum device, and a heating device; the micro-channel refrigeration evaporator is arranged around the side wall of the drying box; the vacuum The device and the bottom of the drying box are connected to each other; the heating device is located on one side of the feed port of the drying box, and the compressor is connected to the micro-channel refrigeration evaporator.

Furthermore, the compressor is an air-cooled compressor and is connected to the other side of the micro-channel refrigeration evaporator away from the drying box, so that the device layout of the entire freeze-drying system is a regular polygon.

Further, the drying box adopts a cylindrical shape, and the flat tube structure is made of aluminum material.

The beneficial effects of this program are:

1) By using a rectangular metal flat tube structure and setting a micro-channel structure in the middle, the flat tube structure is completely fit with the surrounding drying box. There is no hollow structure in the middle, which maximizes the coverage area and increases the heat exchange efficiency.

2) Set up a flow-increasing structure in the microchannel structure to increase the rate of refrigerant circulation in the microchannel structure.

3) Set up two inlet headers and outlet headers that match horizontally and vertically to further increase the range of refrigerant circulation to make up for the inability to circulate in the traditional series structure and enhance heat exchange efficiency.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of the non-limiting embodiments with reference to the following drawings:

Figure 1 is a schematic structural diagram of a flat tube in the prior art in the background technology of the present invention;

Figure 2 is a schematic structural diagram of a microchannel refrigeration evaporator in an embodiment of the present invention;

Figure 3 is a schematic structural diagram of a microchannel structure in an embodiment of the present invention;

Figure 4 is a schematic diagram of the microchannel wall thickness H in the embodiment of the present invention;

Figure 5 is a schematic structural diagram of a first form of protruding piece in an embodiment of the present invention;

Figure 6 is a schematic structural diagram of a second form of protruding piece in an embodiment of the present invention;

Figure 7 is a schematic structural diagram of a current collecting partition in an embodiment of the present invention;

Figure 8 is a schematic diagram of the liquid flow of the first form of series structure in the embodiment of the present invention;

Figure 9 is a schematic diagram of the liquid flow of the second form of series structure in the embodiment of the present invention;

Figure 10 is a schematic diagram of liquid flow in which a series structure and a parallel structure coexist in an embodiment of the present invention;

Figure 11 is a schematic structural diagram of a freeze-drying system in an embodiment of the present invention;

Figure 12 is a schematic structural diagram of a reticular recessed structure in an embodiment of the present invention;

Figure 13 shows the test results of the copper tube evaporator in the freeze-drying effect test;

Figure 14 is a test result diagram of the evaporator H=0.3mm of the present invention in the freeze-drying effect test;

Figure 15 is a schematic structural diagram of a parallel structure in an embodiment of the present invention;

Explanation of reference symbols:
1. Flat tube structure; 11. First microchannel structure; 12. First inlet header; 121. First tightening lug; 13. First outlet header; 14 Inlet; 15. Outlet; 2. Flow-enhancing structure; 21. Protruding piece; 22. Mesh-shaped concave structure; 23. Collection partition; 31. Second inlet header; 32. Second tightening arm; 33. Second outlet collector Tube; 34. Second microchannel structure; 4. Compressor; 5. Drying box; 6. Vacuum device; 7. Heating device; 8. Control valve;
Microchannel wall thickness: H.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Other embodiments of the invention will be readily apparent to those skilled in the art from 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 technical means in the technical field that are not disclosed in the present disclosure. .

As shown in Figures 2 and 3, a micro-channel refrigeration evaporator includes a rectangular flat tube structure 1, which can also be in a square shape; the flat tube structure 1 is circumferential along its length direction, and the flat tube structure 1 1 is provided with first microchannel structures 11 that are circumferentially parallel to each other; in this embodiment, the flat tube structure 1 adopts a rectangular metal plate, and the rectangular plate has a certain thickness for use inside the flat tube structure 1 A micro-channel structure is provided; the contact area between the metal plate and the drying box 5 is significantly larger than the pipe structure that is parallel to each other and spaced in the middle. Even if the pipe structure adopts the shape of a flat tube, there are still many hollow areas between the pipes. The intermediate area cannot be used for heat exchange with the drying box 5 .

The total heat transfer formula between the evaporator and drying box 5 is:
q△T/R_t,total

in:

R_t,total: thermal resistance (k/w); q: heat (w); △T: temperature difference (k)

According to R_t,total=R_t,cond+R_t,conv

R_t,cond: Thermal conduction resistance between drying box 5 and evaporator (k/w)

R_t,conv: Thermal convection resistance between the refrigerant and the evaporator copper tube (k/w)

R_t,cond=L/(kA); L: thickness (m); K: thermal conductivity [w/(m·k)]; A: contact area (㎡).

Based on the above formula, the thermal resistance value R_t,total of a material can theoretically be tested and calculated. But this formula is only an idealized formula. The conditions he sets are: the contact surface is completely smooth and flat, and all heat passes through the material through thermal conduction and reaches the other end. In fact, this is an impossible condition, so the thermal resistance value tested and calculated is not entirely the thermal resistance value of the material itself, but should be the thermal resistance value of the material itself + the so-called thermal resistance value of the contact surface. Because the flatness, smoothness or roughness of the contact surface, and the different installation and tightening pressures, different thermal resistance values of the contact surface will be produced, and different total thermal resistance values will also be obtained. In summary:

a. For the same material, the thermal conductivity is a constant value, but the thermal resistance value R_t,total changes with the thickness L.

b. For the same material, the greater the thickness L, it can be simply understood that the more distance the heat has to travel through the material, the more time it takes, and the worse the efficiency.

c. For thermally conductive materials, selecting appropriate thermal conductivity K and thickness L has a great relationship with performance. Choose a material with high thermal conductivity K, but the thickness L is very large, and the performance is not good enough. The most ideal choice is: high thermal conductivity K, thin thickness L, perfect contact pressure to ensure the best interface contact, that is, a large contact area A.

It can be seen from the formula that thermal conductivity K is an inherent performance parameter of the material itself, which is used to describe the thermal conductivity of the material. This characteristic has nothing to do with the size, shape, or thickness of the material itself, but is related to the properties of the material itself. Therefore, the thermal conductivity of similar materials is the same and will not change due to different thicknesses. Under the same conditions, the larger the heat transfer contact area A, the greater the heat transfer between the evaporator and drying box 5. The higher the efficiency.

Since copper tubes are often used in existing designs, the copper tubes are in line contact with the drying box 5 and the contact area is small, resulting in an increase in the thermal resistance of the system, especially the resistance from the copper tubes to the stainless steel cylinder; therefore, using the method in this embodiment The flat tube structure 1 and microchannel structure can greatly increase the contact area, thereby reducing the thermal resistance R_t,cond.

In this embodiment, the flat tube structure 1 is expanded 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 box 5 is as large as possible. Microchannels are distributed in the metal plate. , the microchannel wall thickness is as thin as possible on the side in contact with the drying box 5 of the freeze dryer to ensure that the heat conduction thickness L is as small as possible. Multiple flat tube structures 1 are connected through 2 headers.

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

One end of the flat tube structure 1 is connected to a first inlet header 12 extending in the width direction, and the other end is connected to an outlet header extending in the width direction; the first inlet header 12, the first The outlet header 13 is interconnected with the first microchannel structure 11; the first inlet header 12 and the first outlet header 13 are connected to an inlet 14 and an outflow port 15 respectively; this embodiment , the first inlet header 12 is connected to one end of the flat tube structure 1; the other end of the flat tube structure 1 is connected to a first outlet header 13; the first inlet header 12 and the first outlet header The flow tubes 13 are connected in series or in parallel through the plurality of flat tube structures 1, and the refrigerants can circulate with each other in the first inlet header 12, the first outlet header 13 and the microchannel structure. The inlet 14 is connected to the front end surface of the first inlet header 12 and can introduce refrigerant into the first inlet header 12; the front end surface of the first outlet header 13 is connected to an outflow port 15; The refrigerant can be led out of the first outlet header 13 .

As shown in Figure 4, further, the center point of the first microchannel structure is closer to the inner wall side surrounded by the flat tube structure 1. In this embodiment, the microchannel structures distributed in the flat tube structure 1 are located as close as possible to the surrounding inner wall side of the flat tube structure 1 to reduce the heat conduction thickness L in the thermal resistance formula, correspondingly Reduce thermal resistance to achieve better heat transfer efficiency and cooling effect.

Further, the boundary distance between the inner wall side of the flat tube structure 1 and the first microchannel structure is set to the microchannel wall thickness H, and the value of the microchannel wall thickness H is 0.3mm~5mm, preferably 0.3mm~ between 1mm. In this embodiment, the evaporator of the first microchannel structure 11 and the mutual A parallel copper tube evaporator with a hollow in the middle was used as a comparison to test the freeze-drying effect, and the freeze-drying machine was tested with a 4kg water supply; the drying box 58 used in it had the same structural dimensions; the thermal resistance of the copper tube was K = 385W/mK, and the aluminum heat Resistance K = 210W/mK; copper tube size φ9.5*0.7, length 22 meters, microchannel wall thickness H is 0.3mm; the contact area between the copper tube and the drying box 5 is about A = 220cm2, the microchannel flat tube and the dryer The contact area of box 5 is approximately A=2246cm2; and the amount of refrigerant passing through the copper tube and the first microchannel structure is consistent.

When freeze-drying in this test, the water is first frozen to ice, and the channel is evacuated to a certain degree of vacuum. The ice is heated according to a certain rule to make the ice sublime into gas. The gas re-solidifies when it encounters the cooled evaporator and becomes Ice and release heat, the water is transferred to the evaporator to achieve freeze-drying. The end of freeze-drying is determined when the heating temperature reaches a certain value and the vacuum degree drops to a certain value. After the test, the test results are shown in Figures 13 and 14. Taking the copper tube evaporator as the actual measurement object, the total freeze-drying time is about 1750 minutes. Freeze-drying starts at the 650th minute, and the vacuum degree no longer changes significantly at the 2400th minute. That is, freeze-drying is completed; actual measurement using the evaporator of the present invention shows that the total freeze-drying time is shortened to 1210 minutes. Freeze-drying begins at the 570th minute. By the 1780th minute, the pressure no longer changes significantly, that is, the freeze-drying is completed, and the total freeze-drying time is reduced. 540 minutes, efficiency increased by 30%.

Furthermore, a flow-enhancing structure 2 is provided on the inner wall of the first microchannel structure 11 . In this embodiment, the microchannel structure is provided with a flow increasing structure 2. The function of the flow increasing structure 2 can not only increase the heat exchange area of the refrigerant, but also increase the turbulence of the fluid; the increase in the fluid turbulence increases the Reynolds number of the fluid. The number RE increases, which in turn increases the Nusselt number (which describes the chaos constant of the fluid), thus increasing the convective heat transfer coefficient h of the fluid, ultimately achieving the purpose of increasing heat transfer efficiency.

As shown in FIG. 5 , further, the flow-increasing structure 2 is a protruding piece 21 distributed in 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, that is:

Nu＝hL/K

h: convection heat transfer coefficient

K: thermal conductivity

According to R_t,conv=dT/q=l/(hS), h becomes larger and R_t,conv becomes smaller. After adding the protruding piece, the contact area between the refrigerant and the evaporator increases, that is, S increases and R_t,conv becomes smaller; As shown in Figure On, after adding the protruding pieces, R_t,conv becomes smaller and the heat transfer efficiency increases.

As shown in FIG. 6 , further, the cross section of the first microchannel structure 11 is rectangular, and the protruding pieces 21 are provided at four vertices and extend toward the center of the rectangle. In another embodiment of the present invention, the protruding pieces 21 are arranged at the corners of the rectangle and extend toward the center. This arrangement can reduce the impact on the refrigerant compared to the protruding pieces 21 arranged on the long sides of the rectangle and extending upward. It can also increase the heat exchange area between the refrigerant and the evaporator and increase the heat transfer efficiency.

As shown in FIG. 12 , further, the flow-enhancing structure 2 causes the inner wall of the first microchannel structure 11 to form a mesh-like depression structure 22 . In another embodiment of the present invention, the inner wall of the first microchannel structure 11 is recessed downward, and a mesh structure is provided downward on the surface of the recessed structure. The downward recessed structure is used to increase the size of the first microchannel structure. Compared with the protruding piece 21, the contact area between the channel structure 11 and the refrigerant can save material, maintain the flow rate of the refrigerant in the microchannel, and increase the heat transfer efficiency.

As shown in Figure 15, further, a control valve 8 is provided on one side of the mutually parallel first microchannel structures close to the first outlet header. In the embodiment of the present invention, the direct communication method between the first inlet header, the first microchannel structure and the first outlet header is commonly known as a parallel path. In a traditional parallel structure, the refrigerant During circulation, due to the problem of liquid resistance, the refrigerant in the microchannel structure far away from the inlet will be difficult to circulate, and the cooling capacity will be unevenly distributed, which will affect the cooling efficiency of the overall evaporator and also cause uneven ice capture. By setting a control valve, the flow of refrigerant in the microchannel plate is adjusted through the opening of the valve. The flow rate is consistent, so that the cooling capacity is maintained uniformly in each microchannel plate; it can be adjusted manually or automatically. Adapt the valve configuration. If a proportional regulating valve is used, a corresponding control system needs to be added; when there is no refrigerant or only a small amount of refrigerant flowing in the microchannel structure away from the inlet, the front control valve 8 is in a closed state, so that The refrigerant in the front stops flowing to the first outlet header. At the same time, the refrigerant will flow toward the microchannel structure in the rear. After the microchannel structure in the rear has fully circulated the refrigerant, the control valve in the front is opened, and each third The refrigerant is fully circulated in the micro-channel structure, and the uniformity of the cooling capacity of the micro-channel plate is adjusted through the valve to improve the refrigeration efficiency.

Furthermore, the control valves 8 have a linkage function; the refrigerant will flow from the first inlet header to the parallel first microchannel structures in sequence. At this time, all the control valves 8 are closed. State; a pressure sensor is provided on the control valve in the last first microchannel structure. When the pressure sensor senses the flow of refrigerant, all control valves are opened to allow the refrigerant to flow. Book In the embodiment, a linkage control valve is used, which can be a solenoid valve. A pressure sensor is provided on the last solenoid valve. The pressure sensor is connected to the solenoid valve through a circuit and is equipped with a corresponding control system. First, all the solenoid valves are closed. When the refrigerant flows into the final microchannel structure, the pressure sensor on the solenoid valve is triggered, all the solenoid valves are opened, and the refrigerant flows together. This structure fully takes into account the insufficient circulation of refrigerant in the evaporator and the complexity of manual control, and provides a control valve communication device that can control sufficient mutual circulation between refrigerants and automatically complete relevant adjustments, which is convenient and efficient.

As shown in Figure 7, further, the flat tube structure 1 is divided into a uniform multi-section structure along the direction of the first inlet header 12 and the first outlet header 13. The first inlet header The pipe 12 and the first outlet header 13 are provided with spaced collecting partitions 23. The position of the collecting partitions 23 is the same as the segment of the flat tube structure 1, so that all the collecting partitions 23 are arranged at intervals. A series path is formed between the first inlet header 12 , the first microchannel structure 11 and the first outlet header 13 . In this embodiment, the first inlet header 12 and the first outlet header 13 are regularly separated by the header partition 23 to realize that the multi-section structures of the flat tube structure 1 are interconnected and connected in series, as shown in Figure 8 As shown, when a single segment of the microchannel structure is a circulation channel, the refrigerant enters the first inlet header 12 from the inlet 14, encounters the obstruction of the header partition, and then changes direction and flows into The first microchannel structure 11 flows to the end of the microchannel and enters the first outlet header 13. In the first outlet header 13, it encounters the obstruction of the header partition 23, and the cooling The agent changes direction from the first outlet header 13 and flows into the next section of microchannel flat tube. After flowing to the end of the microchannel, it enters the first inlet header 12. After many repetitions, it finally flows into the outlet header and flows to the Outlet 15 discharges. During this process, the refrigerant absorbs the heat of the drying box 5 and reduces the temperature of the drying box 5 to achieve the purpose of freeze-drying the items in the box 5; series flow can make up for the problem of insufficient circulation in the header during parallel flow, achieving better results. Ground cooling effect.

As shown in Figure 9, further, when the volume of the drying box 5 is large, the three segments in the flat tube structure 1 can be connected in parallel as an integral channel, and the next group of three segments can be flowed in series. The channels are repeated in sequence; when the volume of the box surrounding the middle is larger, it can achieve better cooling effect.

As shown in Figure 10, further, a second inlet header 31 is provided on the side of the flat tube structure that is perpendicular to the first inlet header. The other vertical side of the tube is provided with a second outlet header 33; the flat tube structure is provided with a third longitudinally parallel Two microchannel structures 34, the second microchannel structure interconnects the second inlet header and the second outlet header; the first inlet header and the second inlet header The inlet 14 is shared; the first outlet header and the second outlet header share the outflow port 15; the first microchannel structure and the second microchannel structure are staggered from each other. In this embodiment, on the series flow structure, the second inlet header 31 and the second outlet header 33 are added in the vertical direction, and the second microchannel structure is connected in parallel with them. 34. The first microchannel structure 11 and the second microchannel structure 34 are jointly arranged in the flat tube structure 1 and do not interfere with each other. The parallel structure flows from one side of the inlet to the other side, solving the problem that the first microchannel may be blocked, resulting in insufficient flow, and making up for the problem in the series structure that the upward reverse flow is easily blocked, resulting in unbalanced flow. In this way, series connection is used at the same time. The micro-channels and the parallel micro-channel mechanism mutually compensate for the possible insufficient flow of refrigerant in both structures. Especially when the volume of the intermediate drying box 5 is large, the circulation distance of the refrigerant is lengthened, and the problem of insufficient flow is more likely to occur. . This structure can greatly improve refrigeration efficiency.

Further, the first inlet header 12 is provided with a first tightening lug 121, and the first outlet header 13 is provided with a matching second tightening lug 32; A stirrup is provided inside between one tightening lug 121 and the second tightening lug 32 . In this embodiment, since the refrigeration evaporator is surrounding the outside of the drying box 5, in order to better fit the outer wall of the drying box 5, the first inlet header 12 and the first outlet header 13 are provided There are hoop ears, and they are tightened with stirrups to make the evaporator surround and stick to the drying box 5 to fix its shape and not be deformed by external force and affect the heat transfer efficiency.

As shown in Figure 11, a freeze-drying system includes any one of the above-mentioned micro-channel refrigeration evaporators, a compressor 4, a drying box 5, a vacuum device 6, and a heating device 7; the micro-channel refrigeration evaporator surrounds is provided on the side wall of the drying box 5; the vacuum device 6 and the bottom of the drying box 5 are connected to each other; the heating device is provided on one side of the feed port of the drying box 5, and the compressor and the micro-channel refrigeration evaporation device connected. In this embodiment, the freeze-drying drying box 5, refrigeration device, vacuum device 6, and heating device are included. The refrigeration system includes a micro-channel refrigeration evaporator and a compressor 4. The compressor is a device that elevates low-pressure gas to high-pressure gas. The dynamic fluid machinery is the core of the refrigeration system. The microchannel refrigeration evaporator is attached to the outer wall of the drying box 5 . The refrigeration device is used to reduce the temperature of the drying box 5 to freeze the material into a solid; the vacuum device 6 is connected to the drying box 5 and is used to vacuum the drying box 5; the heating device is used to The material in the drying box 5 is heated; the heating method of the heating device can be hot air, heating blanket, microwave and other existing technologies.

Furthermore, the compressor 4 is an air-cooled compressor and is connected to the other side of the micro-channel refrigeration evaporator away from the drying box 5, so that the device layout of the entire freeze-drying system is a regular polygon. In this embodiment, the air-cooled compressor has excellent refrigeration effect. Limiting its installation position can prevent the air-cooled compressor from inhaling the high temperature discharged from the drying box, causing the exhaust temperature to be too high and affecting the entire freeze-drying system. of normal operation. In addition, the device layout of the entire freeze-drying system is designed as a regular polygon, which can reasonably save the space occupied by the freeze-drying system and make the entire system more applicable.

Furthermore, the drying box 5 adopts a cylindrical shape, and the flat tube structure 1 adopts aluminum material. In this embodiment, according to the different shapes of the drying box 5, when the drying box 5 is cylindrical or rectangular, the shapes of the flat tubes and headers will change, and the angles and positions during bending will also change. The best , the shape of the drying box 5 is cylindrical, ensuring that the evaporator can better fit outside the drying box 5. The best evaporator is made of aluminum and is a micro-channel flat tube with the above-mentioned structure, and the flow-increasing structure 2 is provided in the micro-channel. Through design experience, select the appropriate evaporator structure according to the size of the drying box 5 cylinder: the small drying box 5 is suitable for configuring a series structure micro-channel flat tube evaporator, so that the cooling capacity of the refrigeration device meets the needs of the freeze-drying machine, and the refrigeration efficiency is optimal. If used In the parallel structure, the refrigerant flows through the evaporator quickly, and the refrigerant flows out before it has time to exchange heat, which is not conducive to the refrigeration of the refrigeration device; the large drying box 5 is suitable for configuring micro-channel flat tube evaporators common in series and parallel structures to avoid If the pipeline is too long, it will be greatly affected by the flow resistance. The parallel structure ensures the cooling capacity of the refrigeration device and optimizes the refrigeration efficiency; it ensures that the flow resistance is not too large and optimizes the refrigeration efficiency.

Working principle: The material to be frozen is placed on the tray of the freeze-drying drying box 5, the freeze-drying machine is started, and the refrigeration system starts to work. The freeze-drying machine first cools down and freezes the material containing a large amount of moisture into a solid, and then starts the vacuum system. The drying box 5 is evacuated, and the heating device is started under vacuum conditions to directly sublimate the solid water, while the material itself remains in the ice shelf during freezing. This is the drying process, and the volume of the material does not change after drying. Solid water absorbs heat during sublimation, causing the temperature of the substance itself to drop and slowing down the sublimation speed. In order to increase the sublimation speed and shorten the drying time, it is necessary to The product is properly heated. After the freezing and drying are completed, the material is taken out of the drying box to complete the freeze-drying of the material.

The refrigeration device uses tools such as a compressor to transport the refrigerant into the flat tube structure 1. The refrigerant enters the first inlet header from the inlet tube; the refrigerant then enters multiple flat tubes and then flows into the outlet header. When it needs to be discharged When refrigerant is used, discharge the refrigerant in the device from the outlet pipe to complete the freezing of the substance.

It is to be understood that the present invention is not limited to the precise construction described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

A micro-channel refrigeration evaporator, characterized by:

It includes a rectangular flat tube structure, the flat tube structure is circumferential along its length direction, and the flat tube structure is provided with a first microchannel structure that is parallel to each other in the circumferential direction;

One end of the flat tube structure is connected to a first inlet header extending along the width direction, and the other end is connected to a first outlet header extending along the width direction;

The first inlet header, the first outlet header and the first microchannel structure are interconnected;

The first inlet header and the first outlet header are respectively connected with an inlet and an outflow port.
The microchannel refrigeration evaporator according to claim 1, wherein the center point of the first microchannel structure is closer to the inner wall side surrounded by the flat tube structure.
The microchannel refrigeration evaporator according to claim 2, wherein the boundary distance between the inner wall side of the flat tube structure and the first microchannel structure is set to the microchannel wall thickness, and the microchannel wall The thickness ranges from 0.3mm to 5mm, preferably from 0.3mm to 1mm.
A microchannel refrigeration evaporator according to claim 1, characterized in that a flow increasing structure is provided on the inner wall of the first microchannel structure.
The microchannel refrigeration evaporator according to claim 4, wherein the flow-increasing structure is a protruding piece distributed in the first microchannel structure.
The microchannel refrigeration evaporator according to claim 5, wherein the cross section of the first microchannel structure is rectangular, and the protruding pieces are provided at four vertices and extend toward the center of the rectangle.
The microchannel refrigeration evaporator according to claim 1, wherein the flow-increasing structure causes the inner wall of the first microchannel structure to form a reticular concave structure.
A microchannel refrigeration evaporator according to claim 1, characterized in that a control valve is provided on a side of the mutually parallel first microchannel structures close to the first outlet header.
A micro-channel refrigeration evaporator according to claim 8, characterized in that the control valves have a linkage function; the refrigerant will flow into the parallel first parallel tubes sequentially from the first inlet header. Microchannel structure, at this time, all the control valves are in a closed state; a pressure sensor is set on the control valve in the last first microchannel structure, when the pressure sensor senses After the refrigerant has circulated, open all control valves and circulate the refrigerant.
A microchannel refrigeration evaporator according to claim 1, characterized in that the flat tube structure is divided into multiple uniform sections along the direction of the first inlet header and the first outlet header. structure, the first inlet header and the first outlet header are provided with collection partitions distributed at intervals, and the positions of the collection partitions are the same as the segments of the flat tube structure. , forming a series path between the first inlet header, the first microchannel structure and the first outlet header.
A micro-channel refrigeration evaporator according to claim 10, characterized in that three segments in the flat tube structure are connected in parallel as an integral channel, and flow to the next group of three segmented channels in series, repeating in sequence. .
A microchannel refrigeration evaporator according to claim 10, characterized in that:

The flat tube structure is provided with a second inlet header on one side perpendicular to the first inlet header, and a second inlet header is provided on the other side of the flat tube structure perpendicular to the first inlet header. outlet header;

A second microchannel structure longitudinally parallel to each other is provided in the flat tube structure, and the second microchannel structure interconnects the second inlet header and the second outlet header;

The first inlet header and the second inlet header share the inlet;

The first outlet header and the second outlet header share the outflow port;

The first microchannel structure and the second microchannel structure are staggered from each other.
A microchannel refrigeration evaporator according to claim 1, characterized in that the first inlet header is provided with a first tightening lug, and the first outlet header is provided with a corresponding Matching second tightening lugs; stirrups are inserted inside between the first tightening lugs and the second tightening lugs.
A freeze-drying system, characterized in that it includes the micro-channel refrigeration evaporator according to any one of claims 1 to 11, a compressor, a drying box, a vacuum device, and a heating device; the micro-channel refrigeration evaporator is surrounded by On the side wall of the drying box; the vacuum device and the bottom of the drying box are connected to each other; the heating device is located inside the drying box, and the compressor is connected to the micro-channel refrigeration evaporator.
A freeze-drying system according to claim 14, characterized in that the compressor is an air-cooled compressor and is connected to the other side of the micro-channel refrigeration evaporator away from the drying box, Make the device layout of the entire freeze-drying system a regular polygon.
A freeze-drying system according to claim 14, characterized in that the drying box adopts a cylindrical shape, and the flat tube structure is made of aluminum material.