Circulating air freeze-drying method and system
By using a circulating air freeze-drying method, which combines a circulating fan and a heating element, the problems of low heat transfer efficiency and automated defrosting in vacuum freeze dryers are solved, achieving efficient freezing and automated defrosting while reducing energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG LIJU REFRIGERATION CO LTD
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-12
AI Technical Summary
Existing vacuum freeze dryers suffer from problems such as low heat transfer efficiency, poor freezing effect, inconvenience in melting frost, and difficulty in forced convection heat exchange, resulting in long freezing time, high energy consumption, and inability to achieve automated defrosting.
The circulating air freeze-drying method uses a circulating fan to drive airflow to form a forced circulation between the cold trap and the ventilation duct. Combined with heating and detection components, it achieves closed-loop automated defrosting, improving heat exchange efficiency and reducing energy consumption.
It improves the heat exchange efficiency of the cold trap inner wall, shortens the freezing time, enhances the efficiency of the drying process, and enables automated defrosting, thereby reducing energy consumption.
Smart Images
Figure CN122015432A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of freeze-drying technology, and in particular to a circulating air freeze-drying method and system. Background Technology
[0002] Vacuum freeze-drying technology, with its advantage of preserving the morphology and nutritional components of dried materials, is widely used in food, pharmaceuticals, and biological products. Vacuum freeze dryers are crucial equipment for this technology. The cooler and cold trap dryer of a vacuum freeze dryer are integrated to form a cold trap. The cold trap has two core functions: first, to cool the material to be dried from room temperature to a set low temperature below the eutectic point, thus freezing the material; second, to cause the ice frozen inside the material to sublimate under vacuum conditions, achieving sublimation drying; and third, to ensure the continuous drying process through the condensation of water vapor generated by sublimation at low temperature.
[0003] During the cooling and freezing process of the object being dried, heat transfer occurs sequentially through the following paths: the low-temperature evaporator coil on the outer wall of the cold trap transfers cold energy to the outer wall surface of the cold trap; the outer wall surface of the cold trap transfers cold energy to the inner wall surface of the cold trap through heat conduction; the inner wall surface of the cold trap transfers cold energy to the air inside the trap through heat release; and the air inside the trap then transfers cold energy to the object being dried through heat release.
[0004] Existing vacuum freeze dryers have many technical problems in practical applications, as follows: (1) Low heat transfer efficiency and poor freezing effect: The inner wall of the cold trap is a natural convection heat transfer method. Analyzing from the heat transfer formula... air convection heat transfer coefficient Only about 8W / m 2 .K, corresponding to a thermal resistance of 1 / =0.125mK / W, which is much greater than the thermal resistance of the cold trap wall. =0.002 / 12.1=0.000165mK / W), resulting in a low overall heat transfer coefficient, limited heat transfer capacity, and the inability of the refrigeration unit to fully utilize its cooling efficiency. This leads to a slow cooling rate of the frozen items, a significant increase in freezing time, and consequently affects the quality of the dried items. (2) The defrosting method has significant drawbacks: After freeze-drying, the inner wall of the cold trap will be covered with a certain thickness of frost. If the refrigeration system is used to defrost the hot air in reverse, the frost will melt from the contact surface with the wall and then peel off the wall in one piece. This not only makes it impossible for the frost to melt quickly, but the melted frost water is also easily cooled back into ice, clogging the drain of the cold trap. At present, the industry generally adopts the manual operation method, which is to open the cold trap door and use an external hot air blower to blow hot air into the cold trap to defrost. In this method, the hot air has no circulation, the heat loss is large, the energy consumption is high and it is not energy-saving. At the same time, it relies on manual operation and cannot achieve automated defrosting. (3) Forced convection heat transfer is difficult to achieve: The best measure to improve the heat transfer capacity of natural convection air on the inner wall of the cold trap is to change natural convection heat transfer to forced convection heat transfer. However, the internal space of the cold trap is limited, and there are strict requirements for vacuum sealing. At the same time, the cold trap is an extreme working environment with alternating high and low temperatures, and there is no condition to install a fan inside the cold trap to achieve forced convection heat transfer. Summary of the Invention
[0005] One objective of this invention is to propose a circulating air freeze-drying method that achieves forced circulation of airflow within the cold trap, improves the heat exchange efficiency of the inner wall of the cold trap, and simultaneously enables closed-loop automated defrosting, reducing defrosting energy consumption. Furthermore, the system structure is adapted to the vacuum sealing and high / low temperature operating environment requirements of the cold trap.
[0006] Another objective of this invention is to provide a circulating air freeze-drying system to achieve the circulating air freeze-drying method described above.
[0007] To achieve this objective, the present invention adopts the following technical solution: A circulating air freeze-drying method is applied to a circulating air freeze-drying system, comprising a freezing process, a vacuum sublimation drying process, and a defrosting process, wherein the three processes are performed sequentially. The freezing process includes: starting the refrigeration components to cool the cold trap, simultaneously starting the circulating fan, and driving the airflow through the circulating fan to form a circulating airflow between the ventilation duct and the cold trap. The circulating airflow blows along the inner wall of the cold trap and exchanges heat with the material to be dried in the cold trap. The vacuum sublimation drying process includes: keeping the refrigeration components working continuously, stopping the circulating fan, starting the vacuum components to evacuate the inside of the cold trap to a preset vacuum level, causing the ice frozen inside the object to be dried to sublimate, and the water vapor generated by sublimation to form a frost layer on the inner wall of the cold trap. The defrosting process includes: after the vacuum sublimation drying process is completed, the refrigeration component and the vacuum component are turned off, and the circulating fan and the heating component are started simultaneously. The heating component heats the airflow in the ventilation duct, and the heated airflow is driven by the circulating fan to form a closed circulating airflow between the ventilation duct and the cold trap. The heated airflow blows away the frost layer on the inner wall of the cold trap along the inner wall. The temperature of the inner wall of the cold trap is detected by the detection component. When the detected temperature value reaches the preset value, the heating component and the circulating fan are turned off.
[0008] Preferably, in the defrosting process, the heating component heats the airflow in the ventilation duct to a temperature of 60-80°C.
[0009] Preferably, during the operation of the circulating fan, the heat generated by the motor of the circulating fan is discharged to the external environment through the heat dissipation component.
[0010] A circulating air freeze-drying system for implementing the above-mentioned circulating air freeze-drying method includes a freeze-drying body, a refrigeration component, a circulating air component, a heating component, a detection component, a heat dissipation component, a vacuum component, and a control component; The interior of the freeze-drying body forms a cold trap, and the two ends of the cold trap are respectively provided with an air inlet and an air return outlet; The cooling component cooperates with the outer wall of the cold trap to provide cooling to the cold trap; The circulating air assembly includes a circulating fan, a ventilation duct, and a sealing shell. The circulating fan includes a motor and an impeller. The impeller is disposed inside the ventilation duct, and the motor is disposed inside the sealing shell. The ventilation duct has a through hole, and the sealing shell covers the outside of the through hole of the ventilation duct. The output shaft of the motor passes through the through hole and is drivenly connected to the impeller. The two ends of the ventilation duct are respectively connected to the air inlet and air outlet of the cold trap. The heating component is disposed inside the ventilation duct and is used to heat the airflow inside the ventilation duct; The detection component includes a first temperature sensor, a second temperature sensor, and a third temperature sensor. The first temperature sensor is located at the heating component, the second temperature sensor is located at the cold trap, and the third temperature sensor is located at the motor. The heat dissipation component is disposed outside the sealed housing and is used to dissipate the heat generated by the motor during operation; The vacuum assembly is connected to the interior of the cold trap and is used to evacuate the interior of the cold trap. The vacuum assembly includes a vacuum pump, a vacuum pipeline, and a vacuum valve. The vacuum pump is connected to the cold trap through the vacuum pipeline, and the vacuum valve is located on the vacuum pipeline. The control component is electrically connected to the refrigeration component, the circulating fan, the heating component, the detection component, and the heat dissipation component, respectively, and the control component is used to control the working status of each component.
[0011] Preferably, the freeze-drying body is formed by two opposing walls and a connecting wall connecting the two opposing walls, and the two opposing walls and the connecting wall form the cold trap, wherein one of the opposing walls is detachably connected to the freeze-drying body. The opposing wall, which is fixedly connected to the freeze-drying body, has a plurality of air inlets radially arranged around its center. An air inlet ring pipe is arranged around the plurality of air inlets on the outer wall of the opposing wall. The plurality of air inlets are all connected to the air inlet ring pipe, and the air inlet ring pipe is connected to the ventilation duct. The connecting wall has several return air inlets on its surface around the axial direction of the cold trap. The outer wall of the connecting wall is provided with a return air ring pipe around the several return air inlets. The several return air inlets are all connected to the return air ring pipe, and the return air ring pipe is connected to the ventilation duct.
[0012] Preferably, the refrigeration assembly includes a refrigeration compressor, a condenser, a dryer filter, a solenoid valve, a thermostatic expansion valve, and an evaporator coil connected in sequence by pipelines. The evaporator coil is spirally wound and attached to the outer wall of the freeze-drying body.
[0013] Preferably, the circulating fan is a vortex centrifugal fan, and a heat insulation plate is provided between the sealing shell and the ventilation duct where the impeller is located. The heat insulation plate is provided with mounting holes, and the mounting holes and through holes are correspondingly arranged. The output shaft of the motor passes through the mounting holes and through holes in sequence and is connected to the impeller for transmission. The output shaft of the motor and the mounting holes and through holes are all in a small clearance fit, and the distance of the small clearance is 0.1-0.2mm.
[0014] Preferably, the heating component is a tubular electric heater.
[0015] Preferably, the heat dissipation assembly includes a heat pipe evaporator, a heat pipe condenser, and a connecting pipe. The heat pipe condenser is located above the heat pipe evaporator. The heat pipe evaporator is spirally wound and attached to the motor. The two ends of the connecting pipe are respectively connected to the heat pipe evaporator and the heat pipe condenser for circulating the working medium between the heat pipe evaporator and the heat pipe condenser.
[0016] Preferably, the control component includes a programmable controller and a relay, wherein the programmable controller is electrically connected to the refrigeration component, the circulating fan, the heating component, the detection component, and the heat dissipation component through the relay.
[0017] One of the above technical solutions has the following beneficial effects: (1) By driving the airflow through the circulating air assembly to form a forced circulation between the cold trap and the ventilation duct, the heat exchange efficiency of the inner wall of the cold trap is greatly improved during the freezing stage, the freezing speed of the material is accelerated, and the freezing cycle is shortened. During the sublimation drying stage, the water vapor generated by sublimation is quickly carried to the inner wall of the cold trap to achieve condensation, which improves the water vapor condensation rate and avoids the water vapor from recondensing on the surface of the material, ensuring that the drying process is carried out continuously and efficiently, and solving the problem of low heat exchange and drying efficiency caused by natural convection in traditional freeze dryers. During the defrosting process, the frost layer gradually melts from the surface, and the frost water is smoothly discharged through the drain outlet at the bottom of the cold trap, avoiding the problem of frost blocks falling off and clogging the drain outlet.
[0018] (2) The circulating air assembly places the motor inside the sealed housing, isolating it from the high and low temperature airflow in the ventilation duct. With the small gap shaft hole fit structure, it not only meets the vacuum sealing requirements of the cold trap, but also avoids the influence of high and low temperature environment on the motor. The heat dissipation assembly discharges the heat generated by the motor in real time, ensuring that the motor works stably within the appropriate temperature range. (3) The air inlet and return air outlet of the freeze dryer are arranged in a radial and axially uniform manner, and are combined with air inlet and return air ring pipes to make the airflow uniformly enter and exit the cold trap. The airflow blows along the inner wall of the cold trap, which improves the heat exchange efficiency between the airflow and the inner wall of the cold trap and the dried material, shortens the freezing time of the material, and improves the working efficiency of the freeze dryer. (4) The components of the system are closely coordinated, the control components realize the automated control of each process, the overall structure is reasonably designed, it is suitable for the cold trap working condition of the vacuum freeze dryer, it is easy to process, manufacture and install and debug, and has good practical application value. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of a circulating air freeze-drying method; Figure 2 This is a schematic diagram of a circulating air freeze-drying system. Figure 3 This is a cross-sectional schematic diagram of the freeze-drying body in a circulating air freeze-drying system; Figure 4 This is an assembly diagram of the circulating air component in a circulating air freeze-drying system; In the attached diagram: 1. Freeze-drying main body; 11. Opposing wall; 111. Air inlet; 112. Air inlet loop pipe; 12. Connecting wall; 121. Return air inlet; 122. Return air loop pipe; 13. Cold trap; 2. Refrigeration assembly; 21. Refrigeration compressor; 211. Return air pipe; 22. Condenser; 23. Dryer filter; 24. Thermal expansion valve; 25. Evaporator coil; 3. Circulating air assembly; 31. Circulating fan; 311. Motor; 312. Impeller; 313, Output shaft; 32, Ventilation duct; 321, Through hole; 33, Sealing shell; 34, Heat insulation plate; 341, Mounting hole; 4, Heating assembly; 5, Detection assembly; 51, First temperature sensor; 52, Second temperature sensor; 53, Third temperature sensor; 6, Heat dissipation assembly; 61, Heat pipe evaporator; 62, Heat pipe condenser; 63, Connecting pipe; 7, Control assembly; 71, Programmable controller; 72, Relay. Detailed Implementation
[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "left," "right," "vertical," "level," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0024] A circulating air freeze-drying method is applied to a circulating air freeze-drying system, comprising a freezing process, a vacuum sublimation drying process, and a defrosting process, wherein the three processes are performed sequentially. The freezing process includes: starting the refrigeration component 2 to supply cooling to the cold trap 13, and simultaneously starting the circulating fan 31. The circulating fan 31 drives the airflow to form a circulating airflow between the ventilation duct 32 and the cold trap 13. The circulating airflow blows along the inner wall of the cold trap 13 and exchanges heat with the dried material in the cold trap 13. The vacuum sublimation drying process includes: keeping the refrigeration component 2 working continuously, stopping the circulation fan 31, starting the vacuum component to evacuate the inside of the cold trap 13 to a preset vacuum level, so that the ice frozen inside the dried object sublimates, and the water vapor generated by sublimation forms a frost layer on the inner wall of the cold trap 13. The defrosting process includes: after the vacuum sublimation drying process is completed, the refrigeration component 2 and the vacuum component are turned off, and the circulating fan 31 and the heating component 4 are started simultaneously. The heating component 4 heats the airflow in the ventilation duct 32. The heated airflow is driven by the circulating fan 31 to form a closed circulating airflow between the ventilation duct 32 and the cold trap 13. The heated airflow blows away the frost layer on the inner wall of the cold trap 13. The temperature of the inner wall of the cold trap 13 is detected by the detection component 5. When the detected temperature value reaches the preset value, the heating component 4 and the circulating fan 31 are turned off.
[0025] To further explain, in the defrosting process, the heating component 4 heats the airflow in the ventilation duct 32 to a temperature of 60-80°C.
[0026] To further explain, during the operation of the circulating fan 31, the heat generated by the motor 311 of the circulating fan 31 is discharged to the external environment through the heat dissipation component 6.
[0027] like Figure 1 As shown, this method is applied to a circulating air freeze-drying system, and includes a freezing process and a defrosting process. The specific steps are as follows: Freezing process: The refrigeration component 2 is started, which provides cooling to the cold trap 13, lowering the temperature inside the cold trap 13 to a set low temperature below the eutectic point temperature of the material to be dried; the circulating fan 31 is started simultaneously, driving the airflow to form a circulating airflow between the ventilation duct 32 and the cold trap 13. This circulating airflow blows along the inner wall of the cold trap 13 and exchanges heat with the material to be dried inside the cold trap 13, thus freezing the material; during the operation of the circulating fan 31, the heat generated by the motor 311 of the circulating fan 31 is discharged through the heat dissipation component 6, ensuring that the motor 311 operates within a suitable temperature range.
[0028] Vacuum sublimation drying process: Keep the refrigeration component 2 working continuously, stop the circulating fan 31, and maintain the set low temperature in the cold trap 13; start the vacuum component to evacuate the inside of the cold trap 13, so that the cold trap reaches the preset vacuum degree, causing the ice frozen inside the dried object to sublimate. The water vapor generated by sublimation is quickly carried to the inner wall of the cold trap 13 to achieve low-temperature condensation, ensuring that the sublimation drying process continues.
[0029] Defrosting process: After vacuum sublimation drying is completed, the refrigeration component 2 and vacuum component are turned off, the cooling supply to the cold trap 13 is stopped, and the vacuum state inside the cold trap 13 is released; the circulating fan 31 and heat dissipation component 6 are started simultaneously, and the heating component 4 heats the airflow in the ventilation duct 32 to the set temperature, such as 60-80℃; the circulating fan 31 drives the heated airflow to form a closed circulating airflow between the ventilation duct 32 and the cold trap 13. The heated airflow blows along the inner wall of the cold trap 13, melting the frost layer on the inner wall of the cold trap 13; the temperature of the inner wall of the cold trap 13 is detected in real time by the detection component 5. When the detected temperature value reaches the preset value, the heating component 4 and the circulating fan 31 are turned off, and the defrosting is completed.
[0030] A circulating air freeze-drying system for implementing the above-described circulating air freeze-drying method includes a freeze-drying body 1, a refrigeration component 2, a circulating air component 3, a heating component 4, a detection component 5, a heat dissipation component 6, a vacuum component, and a control component 7. The freeze-drying body 1 has a cold trap 13 inside, and the cold trap 13 has an air inlet 111 and an air return outlet 121 at its two ends respectively. The refrigeration component 2 cooperates with the outer wall of the freeze-drying body 1 to provide cooling capacity to the cold trap 13; The circulating air assembly 3 includes a circulating fan 31, a ventilation duct 32, and a sealing shell 33. The circulating fan 31 includes a motor 311 and an impeller 312. The impeller 312 is disposed inside the ventilation duct 32, and the motor 311 is disposed inside the sealing shell 33. The ventilation duct 32 has a through hole 321. The sealing shell 33 covers the outside of the through hole 321 of the ventilation duct 32. The output shaft 313 of the motor 311 passes through the through hole 321 and is connected to the impeller 312 for transmission. The two ends of the ventilation duct 32 are respectively connected to the air inlet 111 and the air return outlet 121 of the cold trap 13. The heating component 4 is disposed inside the ventilation duct 32 and is used to heat the airflow inside the ventilation duct 32. The detection component 5 includes a first temperature sensor 51, a second temperature sensor 52 and a third temperature sensor 53. The first temperature sensor 51 is disposed at the heating component 4, the second temperature sensor 52 is disposed at the cold trap 13, and the third temperature sensor 53 is disposed at the motor 311. The heat dissipation component 6 is disposed outside the sealing shell 33 and is used to dissipate the heat generated by the motor 311 during operation; The vacuum assembly is connected to the interior of the cold trap and is used to evacuate the interior of the cold trap. The vacuum assembly includes a vacuum pump, a vacuum pipeline and a vacuum valve. The vacuum pump is connected to the cold trap 13 through the vacuum pipeline and the vacuum valve is located on the vacuum pipeline. The control component 7 is electrically connected to the cooling component 2, the circulating fan 31, the heating component 4, the detection component 5, and the heat dissipation component 6, respectively. The control component 7 is used to control the working status of each component.
[0031] To achieve the aforementioned circulating air freeze-drying method, a circulating air freeze-drying system is proposed, comprising a freeze-drying main body 1, a refrigeration component 2, a circulating air component 3, a heating component 4, a detection component 5, a heat dissipation component 6, and a control component 7. The structure and connection relationship of each component are as follows: Freeze-drying body 1: A cold trap 13 is formed inside it, which provides a working space for freezing and drying the object to be dried; an air inlet 111 and an air return 121 are respectively provided at both ends of the cold trap 13 to realize the entry, exit and circulation of airflow.
[0032] Refrigeration component 2: It cooperates with the outer wall of the freeze-drying body 1. Its core function is to provide cooling to the cold trap 13 so that the material inside the cold trap 13 reaches the low temperature required for freezing.
[0033] The circulating air assembly 3 includes a circulating fan 31, a ventilation duct 32, and a sealing shell 33. The circulating fan 31 includes a motor 311 and an impeller 312. The impeller 312 is disposed within the ventilation duct 32, providing power for airflow circulation. The motor 311 is disposed within the sealing shell 33, which protects the motor 311. The ventilation duct 32 has a through hole 321, and the sealing shell 33 covers the outside of the through hole 321 to seal it. The output shaft 313 of the motor 311 passes through the through hole 321 and is connected to the impeller 312 for power transmission. The two ends of the ventilation duct 32 are connected to the air inlet 111 and the air return outlet 121 of the cold trap 13, respectively, forming a complete airflow circulation channel. Figure 2 As indicated by the middle arrow.
[0034] Heating component 4: It is installed inside the ventilation duct 32. Its core function is to heat the airflow inside the ventilation duct 32 to provide hot airflow for the defrosting process.
[0035] Detection component 5 includes a first temperature sensor 51, a second temperature sensor 52, and a third temperature sensor 53. The first temperature sensor 51 is located at the heating component 4 and is used to detect the airflow temperature at the heating component 4 and monitor the working status of the heating component 4. The second temperature sensor 52 is located on the inner wall of the cold trap 13 and is used to detect the temperature of the inner wall of the cold trap 13, providing a signal basis for starting and stopping the defrosting process. The third temperature sensor 53 is located at the motor 311 and is used to detect the working temperature of the motor 311 and monitor the working status of the motor 311.
[0036] Heat dissipation component 6: Located outside the sealed housing 33, its core function is to dissipate the heat generated by the motor 311 during operation, ensuring that the motor 311 operates within a suitable temperature range.
[0037] Vacuum assembly (not shown in the attached figure): It is connected to the inside of the cold trap 13 and is used to evacuate the cold trap 13 so that the cold trap 13 reaches the preset vacuum level required for sublimation drying; The vacuum assembly includes a vacuum pump and a vacuum pipeline. The vacuum pump is connected to the cold trap through the vacuum pipeline, and a vacuum valve can be added to the vacuum pipeline to control the gas flow.
[0038] Control component 7: Electrically connected to the cooling component 2, circulating fan 31, heating component 4, detection component 5, and heat dissipation component 6 respectively, such as... Figure 2 As shown by the dashed line, its core function is to receive the detection signal from the detection component 5 and control the start-up, shutdown and working status of each component according to the preset program, so as to realize the automated control of the freeze-drying process.
[0039] To further explain, the freeze-drying body 1 is formed by two opposing walls 11 and a connecting wall 12 connecting the two opposing walls 11. The two opposing walls 11 and the connecting wall 12 form the cold trap 13, and one of the opposing walls 11 can be opened and closed to the freeze-drying body 1. The opposing wall 11, which is fixedly connected to the freeze-drying body 1, has a plurality of air inlets 111 radially arranged around its center. An air inlet ring pipe 112 is arranged around the plurality of air inlets 111 on the outer wall of the opposing wall 11. The plurality of air inlets 111 are all connected to the air inlet ring pipe 112. The air inlet ring pipe 112 is connected to the ventilation duct 32. The connecting wall 12 has a plurality of return air inlets 121 on its surface around the axial direction of the cold trap 13. The outer wall of the connecting wall 12 is provided with a return air ring pipe 122 around the plurality of return air inlets 121. The plurality of return air inlets 121 are all connected to the return air ring pipe 122. The return air ring pipe 122 is connected to the ventilation duct 32.
[0040] Specifically, the freeze-drying body 1 includes two opposing walls 11 and a connecting wall 12 connecting the two opposing walls 11. The two opposing walls 11 and the connecting wall 12 enclose the cold trap 13. One of the opposing walls 11 is closable to the freeze-drying body 1 for easy handling of the object to be dried. The opposing wall 11, which is fixedly connected to the freeze-drying body 1, has a plurality of air inlets 111 radially arranged around its center. The outer wall of the opposing wall 11 is provided with an air inlet ring pipe 112 around the plurality of air inlets 111. The plurality of air inlets 111 are all connected to the air inlet ring pipe 112, so that the airflow passes through the air inlet ring pipe 112 and the air inlets 111. 11. Air enters the cold trap 13 evenly and blows through the inner wall of the cold trap 13, and exchanges heat with the dried material in the cold trap 13 to achieve freezing of the dried material; the air inlet ring pipe 112 is connected to the ventilation duct 32, and the wall surface of the connecting wall 12 is provided with a plurality of return air inlets 121 around the axial direction of the cold trap 13. The outer wall of the connecting wall 12 is provided with a return air ring pipe 122 around the plurality of return air inlets 121. The plurality of return air inlets 121 are all connected to the return air ring pipe 122, and the return air ring pipe 122 is connected to the ventilation duct 32, so that the airflow in the cold trap 13 flows back to the ventilation duct 32 evenly through the return air inlets and the return air ring pipe 122.
[0041] To further explain, the refrigeration assembly 2 includes a refrigeration compressor 21, a condenser 22, a dryer filter 23, a solenoid valve 24, a thermal expansion valve 25, and an evaporator coil 26 connected in sequence by pipelines. The evaporator coil 26 is spirally wound and attached to the outer wall of the freeze-drying body 1.
[0042] Specifically, the components of the refrigeration assembly 2 are connected in sequence through pipes to form a complete refrigeration cycle, which can stably generate cold energy. The evaporator coil 26, which is spirally wound and attached to the outer wall of the freeze-drying body 1, can increase the cold energy transfer area, so that the cold energy can be quickly and evenly transferred to the interior of the cold trap 13, ensuring that the temperature inside the cold trap 13 quickly reaches the low temperature required by the freeze-drying process and improves the freezing efficiency of the material. At the same time, without making any structural modifications to the aforementioned freeze-drying body 1 and the circulating air assembly 3, the coordinated operation of cold energy supply and airflow circulation can be achieved.
[0043] To further explain, the circulating fan 31 is a vortex centrifugal fan. A heat insulation plate 34 is provided between the sealing shell 33 and the ventilation duct 32 where the impeller 312 is located. The heat insulation plate 34 is provided with mounting holes 341. The mounting holes 341 and through holes 321 are correspondingly arranged. The output shaft 313 of the motor 311 passes through the mounting holes 341 and through holes 321 in sequence and is connected to the impeller 312 for transmission. The output shaft 313 of the motor 311 and the mounting holes 341 and through holes 321 are all in small clearance fit. The distance of the small clearance is 0.1-0.2mm.
[0044] Specifically, the vortex centrifugal fan is suitable for the high and low temperature and vacuum working environment of the cold trap, and has the advantages of stable air volume, low noise, low energy consumption, and strong anti-interference ability, and can operate stably for a long time. The heat insulation plate 34 plays a role in heat insulation and protection, in order to further reduce the influence of the temperature of the ventilation duct 32 on the space inside the motor 311 and the sealing shell 33. The output shaft 313 of the motor 311 is fitted with the mounting hole 341 and the through hole 321 with a small clearance of 0.1-0.2mm. Figure 3 As shown in d, it ensures smooth rotation of the output shaft 313, avoids jamming that affects power transmission, and minimizes airflow leakage in the ventilation duct 32, further improving the sealing performance of the ventilation duct 32 and the cold trap 13, maintaining a stable vacuum environment in the cold trap 13. At the same time, the small clearance fit structure is simple, requiring no additional seals, reducing manufacturing costs and facilitating assembly and maintenance.
[0045] To further explain, the heating component 4 is a tubular electric heater.
[0046] Specifically, the heating component 4 is a tubular electric heater installed inside the ventilation duct 32. It has high heating efficiency, small size, and fits the installation space of the ventilation duct 32, making it easy to fix and install. The heating component 4 is installed inside the ventilation duct 32 and can directly heat the circulating airflow, providing a stable hot airflow for the defrosting process of the freeze dryer, avoiding hot airflow loss and improving defrosting efficiency. At the same time, the structural characteristics of the tubular electric heater make it easy to cooperate with the control component 7 to achieve precise temperature control and adapt to the needs of different defrosting conditions.
[0047] To further explain, the heat dissipation assembly 6 includes a heat pipe evaporator 61, a heat pipe condenser 62, and a connecting pipe 63. The heat pipe condenser 62 is located above the heat pipe evaporator 61. The heat pipe evaporator 61 is spirally wound and attached to the motor 311. The two ends of the connecting pipe 63 are respectively connected to the heat pipe evaporator 61 and the heat pipe condenser 62, and are used to circulate the working medium between the heat pipe evaporator 61 and the heat pipe condenser 62.
[0048] Specifically, when the heat dissipation component 6 is working, the working medium absorbs heat through heat exchange in the heat pipe evaporator 61, at which point the working medium transforms into a gaseous working medium. This gaseous working medium flows from the heat pipe evaporator 61 through the connecting pipe 63 to the heat pipe condenser 62. In the heat pipe condenser 62, the gaseous working medium releases heat through heat exchange, transforming into a liquid working medium. Under the influence of gravity, the liquid working medium flows back from the heat pipe condenser 62 to the heat pipe evaporator 61 through the connecting pipe 63, thus recycling the medium. In this embodiment, the working medium is a low-boiling-point organic liquid.
[0049] To further explain, the control component 7 includes a program controller 71 and a relay 72. The program controller 71 is electrically connected to the cooling component 2, the circulating fan 31, the heating component 4, the detection component 5, and the heat dissipation component 6 through the relay 72.
[0050] Specifically, the programmable controller 71 uses relays 72 to control the power supply to all actuators, such as the refrigeration component 2, the circulating fan 31, and the heating component 4, thereby improving the stability and reliability of the control and preventing abnormal operation of the components due to control signal interference. The programmable controller 71 can preset the freeze-drying process program and automatically adjust the working status of each component according to the monitoring signals of the detection components, thereby realizing the automated switching of freezing, drying, and defrosting processes, reducing the difficulty of manual operation, and improving the accuracy and consistency of the freeze-drying process.
[0051] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the following embodiments.
[0052] Example This embodiment provides a circulating air freeze-drying method, applied to the circulating air freeze-drying system of the present invention, which sequentially completes three processes: freezing, vacuum sublimation drying, and defrosting. The specific steps are as follows: Freezing Process: The refrigeration unit 2 is activated via control component 7. The refrigerant discharged from the refrigeration compressor 21 flows sequentially through the condenser 22, the dryer filter 23, and the thermal expansion valve 24 before entering the evaporator coil 25, which is spirally wound around the outer wall of the cold trap 13. The refrigerant evaporates and cools within the evaporator coil 25, providing cooling to the cold trap 13 and lowering the temperature inside the cold trap 13 to -45℃ (the low temperature is set below the eutectic point of the dried material). Simultaneously, the circulating fan 31, a centrifugal fan in the form of a vortex type, is activated. The motor 311 drives the impeller 312 to rotate, and the impeller 312 drives the airflow to form a circulating airflow between the ventilation duct 32 and the cold trap 13. The airflow enters the cold trap 13 through the inlet ring pipe 112 and the inlet 111, blowing against the inner wall of the cold trap 13. After completing heat exchange with the dried material inside the cold trap 13, the airflow returns to the ventilation duct 32 through the return air ring pipe 122 and the return air inlet 121. The material being dried is rapidly frozen; the heat generated by the motor 311 is absorbed by the heat pipe evaporator 61, which is installed in close contact with the motor. The working medium in the heat pipe evaporator 61 undergoes heat exchange and absorbs heat, at which point the working medium is converted into a gaseous working medium. The gaseous working medium flows from the heat pipe evaporator 61 through the connecting pipe 63 to the heat pipe condenser 62. The gaseous working medium releases heat through heat exchange in the heat pipe condenser 62, and is converted into a liquid working medium. Under the action of gravity, the liquid working medium flows back from the heat pipe condenser 62 through the connecting pipe 63 to the heat pipe evaporator 61, thus recycling the process. The third temperature sensor 53 detects the temperature of the motor 311 in real time, and the heat insulation plate 34 between the sealing shell 33 and the ventilation duct 32 effectively blocks the low-temperature airflow in the ventilation duct 32 from being conducted to the motor 311, thus achieving heat insulation protection for the motor 311.
[0053] Vacuum sublimation drying process: Keep the refrigeration component 2 working continuously to maintain the set low temperature of -45°C inside the cold trap 13; stop the circulating fan 31, start the vacuum component (not shown in the attached figure) in the control component 7, open the vacuum valve, and the vacuum pump draws a vacuum inside the cold trap 13 through the vacuum pipeline to achieve a preset vacuum degree of 30Pa inside the cold trap 13, causing the ice frozen inside the dried object to sublimate, and the water vapor generated by sublimation is quickly carried to the inner wall of the cold trap 13 to achieve low-temperature condensation; the vacuum sensor monitors the vacuum degree inside the cold trap 13 in real time, and this process continues until the dried object reaches the preset dryness degree.
[0054] Defrosting Process: After the vacuum sublimation drying process is completed, the control component 7 sequentially shuts down the refrigeration component 2 and the vacuum component, closes the vacuum valve, stops supplying cooling to the cold trap 13, and releases the vacuum state inside the cold trap 13; the heating component 4, in the form of a tubular electric heater, is activated to heat the airflow in the ventilation duct 32 to 70°C. The first temperature sensor 51 monitors the temperature of the heated airflow in real time to ensure the defrosting temperature requirements; simultaneously, the circulating fan 31 is activated, and the impeller 312 drives the 70°C hot airflow to form a closed loop between the ventilation duct 32 and the cold trap 13, with the hot airflow adhering to the cold trap 13. The inner wall of the cold trap 13 is purged to gradually melt the frost layer formed by water vapor condensation on the inner wall of the cold trap 13. The frost water produced by melting is discharged through the drain port at the bottom of the cold trap 13 (not shown in the attached figure). The heat insulation plate 34 blocks the heat flow from being conducted to the motor 311. The heat dissipation component 6 operates as needed according to the motor temperature detected by the third temperature sensor 53 to ensure the normal operation of the motor 311. The second temperature sensor 52 detects the temperature of the inner wall of the cold trap 13 in real time. When the detected temperature reaches 25°C (preset value), the control component 7 automatically shuts down the heating component 4 and the circulating fan 31 to complete the defrosting.
[0055] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.
Claims
1. A circulating air freeze-drying method, characterized in that, It is applied to a circulating air freeze-drying system, which includes a freezing process, a vacuum sublimation drying process, and a defrosting process, and the three processes are performed sequentially; The freezing process includes: starting the refrigeration component (2) to cool the cold trap (13), and simultaneously starting the circulating fan (31). The circulating fan (31) drives the airflow to form a circulating airflow between the ventilation duct (32) and the cold trap (13). The circulating airflow blows along the inner wall of the cold trap (13) and exchanges heat with the dried material in the cold trap (13). The vacuum sublimation drying process includes: keeping the refrigeration component (2) working continuously, stopping the circulation fan (31) from working, starting the vacuum component to evacuate the inside of the cold trap (13) to a preset vacuum level, so that the ice frozen inside the dried object sublimates, and the water vapor generated by sublimation forms a frost layer on the inner wall of the cold trap (13). The defrosting process includes: after the vacuum sublimation drying process is completed, the refrigeration component (2) and the vacuum component are turned off, and the circulating fan (31) and the heating component (4) are started simultaneously. The heating component (4) heats the airflow in the ventilation duct (32). The heated airflow is driven by the circulating fan (31) to form a closed circulating airflow between the ventilation duct (32) and the cold trap (13). The heated airflow blows the frost layer on the inner wall of the cold trap (13) along the inner wall. The temperature of the inner wall of the cold trap (13) is detected by the detection component (5). When the detected temperature value reaches the preset value, the heating component (4) and the circulating fan (31) are turned off.
2. The circulating air freeze-drying method according to claim 1, characterized in that, In the defrosting process, the heating component (4) heats the airflow in the ventilation duct (32) to a temperature of 60-80°C.
3. The circulating air freeze-drying method according to claim 1, characterized in that, During operation, the circulating fan (31) discharges the heat generated by the motor (311) of the circulating fan (31) to the external environment through the heat dissipation component (6).
4. A circulating air freeze-drying system for implementing the circulating air freeze-drying method according to any one of claims 1-3, characterized in that, It includes a freeze-drying body (1), a refrigeration component (2), a circulating air component (3), a heating component (4), a detection component (5), a heat dissipation component (6), a vacuum component, and a control component (7); The freeze-drying body (1) forms a cold trap (13) inside, and the cold trap (13) is provided with an air inlet (111) and an air return outlet (121) at its two ends respectively. The refrigeration component (2) cooperates with the outer wall of the cold trap (13) to provide cooling to the cold trap (13); The circulating air assembly (3) includes a circulating fan (31), a ventilation duct (32), and a sealing shell (33). The circulating fan (31) includes a motor (311) and an impeller (312). The impeller (312) is disposed inside the ventilation duct (32). The motor (311) is disposed inside the sealing shell (33). The ventilation duct (32) has a through hole (321). The sealing shell (33) covers the outside of the through hole (321) of the ventilation duct (32). The output shaft (313) of the motor (311) passes through the through hole (321) and is connected to the impeller (312) in a driving connection. The two ends of the ventilation duct (32) are respectively connected to the air inlet (111) and the air return outlet (121) of the cold trap (13). The heating component (4) is disposed inside the ventilation duct (32) and is used to heat the airflow inside the ventilation duct (32); The detection component (5) includes a first temperature sensor (51), a second temperature sensor (52) and a third temperature sensor (53). The first temperature sensor (51) is located at the heating component (4), the second temperature sensor (52) is located at the cold trap (13), and the third temperature sensor (53) is located at the motor (311). The heat dissipation component (6) is disposed outside the sealing shell (33) to dissipate the heat generated by the motor (311) during operation; The vacuum assembly is connected to the interior of the cold trap and is used to evacuate the interior of the cold trap. The vacuum assembly includes a vacuum pump, a vacuum pipeline and a vacuum valve. The vacuum pump is connected to the cold trap (13) through the vacuum pipeline and the vacuum valve is located on the vacuum pipeline. The control component (7) is electrically connected to the refrigeration component (2), the circulating fan (31), the heating component (4), the detection component (5), and the heat dissipation component (6), respectively. The control component (7) is used to control the working status of each component.
5. The circulating air freeze-drying system according to claim 4, characterized in that, The freeze-drying body (1) is formed by two opposing walls (11) and a connecting wall (12) connecting the two opposing walls (11). The two opposing walls (11) and the connecting wall (12) form the cold trap (13). One of the opposing walls (11) can be opened and closed to the freeze-drying body (1). The opposing wall (11) fixedly connected to the freeze-drying body (1) has a plurality of air inlets (111) radially arranged around its center. The outer wall of the opposing wall (11) is provided with an air inlet ring pipe (112) around the plurality of air inlets (111). The plurality of air inlets (111) are all connected to the air inlet ring pipe (112), and the air inlet ring pipe (112) is connected to the ventilation duct (32). The connecting wall (12) has a plurality of return air inlets (121) on its wall surface around the axial direction of the cold trap (13). The outer wall of the connecting wall (12) is provided with a return air ring pipe (122) around the plurality of return air inlets (121). The plurality of return air inlets (121) are all connected to the return air ring pipe (122). The return air ring pipe (122) is connected to the ventilation duct (32).
6. The circulating air freeze-drying system according to claim 4, characterized in that, The refrigeration assembly (2) includes a refrigeration compressor (21), a condenser (22), a dryer filter (23), a solenoid valve (24), a thermal expansion valve (25), and an evaporator coil (26) connected in sequence by pipelines. The evaporator coil (26) is spirally wound and attached to the outer wall of the freeze-drying body (1).
7. The circulating air freeze-drying system according to claim 4, characterized in that, The circulating fan (31) is a vortex centrifugal fan. A heat insulation plate (34) is provided between the sealing shell (33) and the ventilation duct (32) where the impeller (312) is located. The heat insulation plate (34) is provided with mounting holes (341). The mounting holes (341) and through holes (321) are provided in correspondence. The output shaft (313) of the motor (311) passes through the mounting holes (341) and through holes (321) in sequence and is connected to the impeller (312) for transmission. The output shaft (313) of the motor (311) and the mounting holes (341) and through holes (321) are all in small clearance fit. The distance of the small clearance is 0.1-0.2mm.
8. The circulating air freeze-drying system according to claim 4, characterized in that, The heating component (4) is a tubular electric heater.
9. The circulating air freeze-drying system according to claim 6, characterized in that, The heat dissipation assembly (6) includes a heat pipe evaporator (61), a heat pipe condenser (62), and a connecting pipe (63). The heat pipe condenser (62) is located above the heat pipe evaporator (61). The heat pipe evaporator (61) is spirally wound and attached to the motor (311). The two ends of the connecting pipe (63) are respectively connected to the heat pipe evaporator (61) and the heat pipe condenser (62) for circulating the working medium between the heat pipe evaporator (61) and the heat pipe condenser (62).
10. The circulating air freeze-drying system according to claim 4, characterized in that, The control component (7) includes a program controller (71) and a relay (72). The program controller (71) is electrically connected to the refrigeration component (2), the circulating fan (31), the heating component (4), the detection component (5), and the heat dissipation component (6) through the relay (72).