Quick freezing device based on refrigerating fluid and temperature adjusting method

Abstract

The invention discloses a quick-freezing device based on refrigerating fluid and a temperature adjusting method, and belongs to the technical field of quick-freezing devices.The quick-freezing device comprises a freezing tank used for freezing food, and a refrigerating unit, a layered refrigerator and a temperature adjusting tank are arranged below the freezing tank; a refrigerating pipe is arranged at the refrigerating end of the refrigerating unit, the refrigerating pipe is located in the layered refrigerator, the layered refrigerator is filled with partial freezing liquid, and during working, the partial freezing liquid is refrigerated in the layered refrigerator, then conveyed to the temperature adjusting tank, conveyed to the freezing groove, contacted with food and then flows back to the layered refrigerator; three layers of refrigeration cavities are sequentially arranged in the layered refrigerator from top to bottom, a one-way valve is arranged between every two adjacent layers of refrigeration cavities, each layer of refrigeration cavity is provided with a liquid mixing pipe connected with the temperature adjusting tank, and each liquid mixing pipe is provided with a control valve. And the opening degree and the opening time of the three control valves are controlled according to different temperature requirements during working. Accurate and dynamic temperature control in the freezing process is achieved.

Description

Technical Field

[0001] This invention relates to the field of quick-freezing equipment technology, and in particular to a quick-freezing device and temperature control method based on a refrigerant. Background Technology

[0002] Food freezing and preservation is one of the core technologies of modern food industry. Its principle is to extend the shelf life of food by inhibiting microbial activity and enzymatic reactions through low temperatures. However, ice crystals formed during traditional freezing, especially large ones, can puncture the cell structure of food, leading to juice loss, soft texture, and a significant decline in flavor and nutritional quality upon thawing. Therefore, the core challenge of freezing technology has shifted from simply "rapid cooling" to "how to effectively control the morphology, size, and distribution of ice crystals during rapid cooling." To address the shortcomings of traditional freezing technology, microfreezing liquid technology has emerged. This technology uses high-tech biotechnology to study the ice crystallization state of biological cells at low temperatures. It applies low-temperature and ultra-low-temperature technologies and microfreezing liquids made from natural ingredients to directly freeze and preserve food using innovative freezing curves. Microfreezing liquid is a special solution derived from natural substances that remains liquid at temperatures ranging from -40°C to -30°C. Its density is 1300 times that of air, and its thermal conductivity is as high as 4 calories per (m·h·°C). This physical property enables microfreezing liquids to achieve extremely rapid heat conduction, greatly shortening the freezing time of food. Depending on the type of food and the size of the object, microfreezing liquid technology can complete the freezing and preservation of food within 6-30 minutes, resulting in the cell membranes within the frozen food remaining intact and in a micro-frozen state.

[0003] Existing freezing devices experience significant temperature fluctuations at different freezing times, leading to larger ice crystals. Furthermore, when changing to different frozen foods, the temperature cannot be quickly adjusted to the appropriate level. They also cannot adjust the osmotic pressure, freezing point, or nucleation characteristics of the freezing liquid in real time based on the differences in cell structure between different types of foods, such as high-moisture fruits and vegetables versus high-fat meats. Summary of the Invention

[0004] To address the aforementioned problems, this invention aims to solve the problems described above. One objective of this invention is to provide a quick-freezing device and temperature control method based on a cryogenic fluid, which achieves precise and dynamic temperature control during the freezing process and effectively suppresses the formation of destructive ice crystals.

[0005] The present invention adopts the following solution: a quick-freezing device based on a freezing liquid, comprising a freezing tank for freezing food, a refrigeration unit, a layered refrigeration unit, and a temperature-regulating tank arranged below the freezing tank; the refrigeration unit is provided with a refrigeration pipe at its refrigeration end, the refrigeration pipe being located inside the layered refrigeration unit, the layered refrigeration unit being filled with a micro-freezing liquid, during operation, the micro-freezing liquid is cooled in the layered refrigeration unit and then transported to the temperature-regulating tank and then to the freezing tank, and after contacting the food, it flows back to the layered refrigeration unit; The stratified refrigerator has three layers of refrigeration chambers arranged from top to bottom. A one-way valve is installed between two adjacent layers of refrigeration chambers. Each layer of refrigeration chamber is equipped with a mixing pipe connected to the temperature control tank. Each mixing pipe is equipped with a control valve. During operation, the opening degree and opening time of the three control valves are controlled according to different temperature requirements.

[0006] The preferred technical solution is that the refrigeration pipe has a serpentine bend structure, the refrigeration pipe enters from the bottommost refrigeration chamber, passes through each refrigeration chamber in sequence, and exits from the top; the top of the layered refrigeration unit is provided with a return pipe, the return pipe is connected to the freezing tank, and a return flow shut-off valve is provided on the return pipe.

[0007] The preferred technical solution is that the space of the refrigeration chamber gradually decreases along the top-to-bottom direction, and a temperature sensor is provided in each refrigeration chamber; the one-way valve is located on one side of the mixing tube.

[0008] A preferred technical solution is that a circulation pump is provided at the top of the temperature-regulating tank, the circulation pump is fixed to the lower side of the freezing tank, the inlet pipe of the circulation pump extends to the bottom of the temperature-regulating tank, and the outlet pipe of the circulation pump extends into the freezing tank.

[0009] A preferred technical solution is that an installation platform is provided on one side of the temperature regulating tank, and the three control valves are all fixedly installed on the installation platform. The three mixing pipes are connected to the three control valves in sequence according to their height.

[0010] A preferred technical solution is that the refrigeration unit includes a compressor, a radiator, and a controller. The controller is electrically connected to both the compressor and the radiator. The hot end of the compressor is connected to the radiator. The radiator includes a cooling fan, cooling fins, and a heat pipe. The heat pipe is connected to the hot end of the compressor and extends into the cooling fins. The cooling fan is fixed to one side of the cooling fins.

[0011] A preferred technical solution is that the temperature regulating tank is also equipped with a temperature sensor, the controller is electrically connected to all the temperature sensors, and the controller is electrically connected to the control valve and the return flow cut-off valve. The controller adjusts the opening of the control valve and the return flow cut-off valve according to the temperature signal from the temperature sensor.

[0012] A preferred technical solution is that the freezing tank is provided with a liquid outlet buffer and a reflux filter at both ends, the liquid outlet buffer is connected to the liquid outlet pipe of the circulation pump, the liquid outlet buffer is provided with a plurality of liquid outlet holes, the reflux filter is provided with a filter screen, and the reflux filter is connected to the reflux pipe.

[0013] The preferred technical solution is that the freezing tank, the stratified refrigerator, and the temperature regulating tank are all provided with an insulation layer, and the top of the freezing tank is provided with a sealing cover.

[0014] This invention also provides a temperature control method for a quick-freezing device based on cryogenic fluid, comprising the following steps: S1: System initialization and temperature gradient establishment: The refrigeration unit is started, and the compressor drives the refrigerant to circulate in the refrigeration pipe; the controller turns on the cooling fan to dissipate heat from the hot end of the compressor; the refrigeration pipe flows sequentially through the lower, middle, and upper three layers of the stratified refrigeration chamber, cooling the micro-cryogenic fluid therein; three different stable low-temperature zones of high, medium, and low are formed in the three refrigeration chambers respectively, establishing a vertical temperature gradient; the temperature sensors of each chamber monitor the temperature data in real time and feed it back to the controller; S2: Set target freezing curve: Based on the type of food to be quick-frozen and the optimal preservation process requirements, select or customize a target freezing temperature-time curve on the human-machine interface of the controller; this curve clarifies the real-time target temperature that the micro-freezing liquid in the freezing tank needs to reach during the entire freezing cycle. S3: Dynamic mixing and temperature control: Based on the target temperature set in S2, the controller, combined with the feedback from the temperature sensor inside the temperature control tank, calculates the mixing ratio of high, medium, and low temperature micro-freezing liquids required to reach the target temperature using a built-in algorithm. Subsequently, the controller sends instructions to the three corresponding control valves to dynamically adjust their opening degree and opening time, so that the micro-freezing liquid at the corresponding temperature flows into the temperature control tank through the mixing pipe according to the calculated ratio. S4: Homogenization and quick freezing: The micro-freezing liquid in the temperature control tank is pumped to the liquid outlet buffer of the freezing tank by the circulation pump, and is evenly added to the freezing tank through the liquid outlet hole on it, which acts on the food surface for rapid heat exchange; after the micro-freezing liquid is used, it is filtered to remove impurities by the return filter and returned to the interior of the stratified refrigerator through the return pipe to complete the circulation. S5: Real-time feedback and closed-loop control: During the quick-freezing process, the temperature sensors of each layer of the freezing tank and the layered refrigerator continuously transmit temperature signals to the controller; the controller compares these real-time data with the target curve in S2. If there is a deviation, it immediately returns to step S3, recalculates and adjusts the opening of each control valve to form a closed-loop control, ensuring that the freezing process accurately follows the preset curve. S6: Process End and Reset: When the controller determines that the quick-freezing process has reached the set time and final temperature, or is manually terminated by the operator, the controller first shuts down the circulating pump and refrigeration unit, and then gradually closes all control valves and return flow shut-off valves. The system enters standby mode, completing this temperature-adjusting quick-freezing operation.

[0015] Compared with the prior art, the quick-freezing device and temperature control method based on cryogenic liquid of the present invention have the following technical effects: 1. This application relates to a quick-freezing device and temperature control method based on cryogenic liquid. Through an intelligent closed-loop control system consisting of a controller, multi-layered refrigeration chambers, temperature sensors, and control valves, the temperature of the micro-freezing liquid in the freezing tank can strictly follow the preset optimal freezing curve. This system can sense temperature deviations in real time and dynamically adjust the mixing ratio of high, medium, and low-temperature micro-freezing liquids, thereby controlling temperature fluctuations during the freezing process within a very small range. This stable cooling environment allows food to quickly and evenly pass through the maximum ice crystal formation zone, promoting the formation of numerous small-sized micro-ice crystals, greatly reducing mechanical damage to the food's cellular structure, and laying a solid foundation for high-quality preservation after thawing.

[0016] 2. To address the need to adjust operating conditions when changing to different types of frozen foods, users only need to select or set the freezing program corresponding to the new food in the controller. The intelligent system can then rapidly synthesize the micro-freezing liquid at the new temperature target in the temperature-controlled tank by quickly adjusting the opening and closing strategies of the control valves at each layer according to the preset curve. This temperature control method based on active mixing has a significantly faster response speed compared to the traditional method that relies on the thermal inertia of the entire system for heating or cooling, shortening the changeover time between batch operations. This allows a single unit to efficiently handle various types of small-batch differentiated quick-freezing tasks, offering high flexibility.

[0017] Other features and advantages of the invention will become clear when reading the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the invention, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without any inventive effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the quick-freezing device based on cryogenic liquid provided in a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of a quick-freezing device based on cryogenic liquid provided in a specific embodiment of the present invention. Figure 3 This is a detailed enlarged structural diagram of the internal structure of the quick-freezing device based on cryogenic liquid provided in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of the internal structure of the layered cooler provided in a specific embodiment of the present invention.

[0020] In the picture: 1. Freezing tank; 11. Sealing cover; 12. Liquid outlet buffer; 121. Liquid outlet hole; 13. Refrigeration filter; 2. Refrigeration unit; 21. Radiator; 22. Compressor; 23. Controller; 211. Heat dissipation fins; 212. Heat pipe; 213. Cooling fan; 3. Temperature control tank; 4. Stratified refrigerator; 41. Refrigeration shut-off valve; 411. Refrigeration pipe; 42. Refrigeration chamber; 43. Check valve; 5. Circulation pump; 51. Liquid outlet pipe; 52. Control valve; 53. Liquid inlet pipe. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other. Example 1

[0022] The following description, in conjunction with the accompanying drawings and embodiments, shows... Figure 1-4 The diagram illustrates in detail the quick-freezing device and temperature control method based on cryogenic fluid.

[0023] In the continuous industrial production of food micro-freezing and preservation, maintaining absolute temperature stability on the production line is a core challenge to ensure consistent product quality and extend shelf life for each batch. Existing continuous micro-freezing equipment faces periodic and drastic temperature fluctuations when one batch is completed and the next is added. When the previous batch of food is removed after micro-freezing, the micro-freezing liquid in the freezing tank is at a stable low temperature, such as -3 degrees Celsius. When the next batch of room-temperature food, such as fish fillets at 20 degrees Celsius, is added, the huge temperature difference causes the tank liquid temperature to rapidly rise to zero or even higher within tens of seconds, forming a sharp temperature pulse. Current technologies rely on slow cooling by refrigeration units or simple full liquid replacement to correct this, resulting in a delayed response and a period of temperature runaway after each batch is added. During this period, the previously added food experiences repeated temperature fluctuations, leading to uncontrolled ice crystal growth; and the overall line temperature takes several minutes or even longer to stabilize, severely restricting production cycle time and product quality consistency. How to respond instantly and counteract such periodic thermal shocks to achieve truly smooth continuous production is a pain point that existing technologies have failed to address.

[0024] This embodiment adopts the following scheme: a micro-freezing preservation device based on cryogenic liquid, including a freezing tank for freezing food, with a refrigeration unit, a layered refrigeration unit, and a temperature-regulating tank arranged below the freezing tank; the refrigeration end of the refrigeration unit is provided with a refrigeration pipe, which is located inside the layered refrigeration unit, which is filled with micro-freezing liquid. During operation, the micro-freezing liquid is cooled in the layered refrigeration unit and then transported to the temperature-regulating tank and then to the freezing tank. After contacting the food, it flows back to the layered refrigeration unit; the layered refrigeration unit has three layers of refrigeration chambers arranged sequentially from top to bottom, with a one-way valve between adjacent layers of refrigeration chambers. Each layer of refrigeration chamber is provided with a mixing pipe connected to the temperature-regulating tank, and each mixing pipe is provided with a control valve. During operation, the opening degree and opening time of the three control valves are controlled according to different temperature requirements.

[0025] The core of this solution lies in constructing a gradient energy system with dynamic cold buffering and instantaneous release capabilities. The system's layered chiller is not a uniformly heated cold source, but rather a precisely designed energy storage system with a specific temperature architecture. By controlling the operating parameters of the chiller unit, the three refrigeration chambers are established and maintained at three stable temperature reference points: -2°C, -4°C, and -6°C. One-way valves between each layer ensure that these three temperature layers do not interfere with each other in a static state. In the steady-state phase of continuous production, such as when maintaining a tank temperature of -3°C, the control system uses an algorithm to primarily maintain this temperature by mixing micro-freezing liquids of -2°C and -4°C in a specific ratio. At this time, the bottom chamber at -6°C serves as a reserve, in a state of cold storage standby. When the sensor detects a sharp temperature rise caused by material feeding, the system immediately identifies it as a thermal shock event during batch switching. The controller instantly changes its mixing strategy, significantly increasing the opening of the -6°C control valve. This rapidly injects a large amount of stored deep cooling energy into the temperature-regulating tank, mixing it with the existing micro-freezing liquid to form a powerful cold stream with a temperature significantly lower than the set target, such as instantly reaching -5°C, which is then pumped into the freezing tank. This pre-prepared powerful cold stream has a much higher cooling density than the steady-state micro-freezing liquid, and can absorb the sensible heat from newly added food with extremely high efficiency, thereby minimizing the rise in tank temperature and causing it to drop back to the set point in a very short time. Subsequently, the system smoothly transitions back to the steady-state mixing mode. This design ensures that the cooling capacity to cope with shocks comes from pre-prepared reserves, rather than requiring the refrigeration unit to work under temporary overload. Therefore, the response is immediate and powerful, without impacting the main refrigeration system.

[0026] Taking a continuous micro-freezing production line for crucian carp fillets as an example, the target process temperature is a constant -3 degrees Celsius, and the production cycle is one batch every five minutes. The moment the third batch of fillets is removed and the fourth batch of room-temperature fillets is added, the temperature of the freezing tank begins to surge from -3 degrees Celsius. The built-in algorithm immediately triggers an anti-shock mode when the temperature change rate exceeds 0.5 degrees Celsius per second. The -6 degrees Celsius control valve on the mounting platform switches from closed to 80% open within 0.3 seconds and remains open for 20 seconds. Simultaneously, the -4 degrees Celsius valve's opening is reduced from 50% to 20%, and the -2 degrees Celsius valve is temporarily closed. Within these 20 seconds, the system injects approximately -5 degrees Celsius micro-freezing liquid into the freezing tank, the total cooling capacity of which is sufficient to completely offset the heat released by the 200 kilograms of fillets as they drop from 20 degrees Celsius to 0 degrees Celsius. Actual monitoring shows that under this mode, the highest temperature of the bath only rises to -1.5 degrees Celsius and fully recovers to -3 degrees Celsius within 35 seconds. The temperature fluctuation range is smaller and the recovery time is shorter than that of the traditional system. This ensures that each batch of fish fillets is in a strictly controlled low-temperature environment from the moment it is added, with a consistent freezing process, resulting in highly uniform product quality and laying a solid foundation for a subsequent shelf life of up to 21 days.

[0027] After achieving the aforementioned dynamic cold energy allocation, ensuring the efficient, continuous, and stable regeneration of this gradient cold source is crucial for uninterrupted continuous production. In traditional systems, the cryogenic cold energy used to cope with shocks often requires the refrigeration unit to operate at full capacity after the event to regenerate it. This leads to low system efficiency for a period after the shock and may affect the stability of the main temperature zone. Simultaneously, improperly handled heat returning from the freezing tank can directly enter the cryogenic zone, disrupting valuable cold energy reserves. The refrigeration pipe has a serpentine, curved structure, entering from the bottommost refrigeration chamber, passing through each chamber sequentially, and exiting from the top. A return pipe is installed at the top of the stratified refrigeration unit, connecting to the freezing tank, and equipped with a return flow shut-off valve. The serpentine, curved refrigeration pipe significantly increases the heat transfer area. The refrigerant flow first enters the bottommost -6°C chamber, where the most intense heat exchange occurs, ensuring the energy supply of the strategic cold source. The refrigerant, having absorbed cold energy and increased in temperature, is not directly discharged but continues to flow through chambers at -4°C and -2°C. Since the refrigerant temperature is still below the set temperatures of these two chambers, it can continue to provide effective cooling, thus extracting the cold energy of a single unit of refrigerant three times sequentially, achieving tiered utilization of cold energy and significantly improving the overall system energy efficiency ratio. The placement of the reflux pipe is crucial for energy recovery. The relatively high-temperature reflux micro-freeze, after heat exchange, is guided to the inlet of the highest-temperature top-level chamber. This constitutes a counter-current heat exchange system, where the highest-temperature reflux liquid meets the relatively highest-temperature refrigerant, and the next-highest-temperature reflux liquid meets the next-lowest-temperature refrigerant. This matching keeps the global average temperature difference in the heat exchange process at an optimal value, maximizing heat exchange efficiency. As a result, the heat carried by the reflux liquid is rapidly and systematically stripped away, its temperature is gradually cooled to near the set points of each layer, and then smoothly integrated into the corresponding chambers as makeup liquid. This mechanism can not only quickly replenish the underlying cold energy consumed in response to thermal shock, but also ensure that the recycling process itself is smooth and will not cause disturbance to the stable temperature field of each layer due to violent mixing.

[0028] Continuing with the crucian carp production line case above, after the fourth batch of feed was completed, the system utilized its -6°C reserve for strong cooling compensation, resulting in a decrease in both the liquid level and cooling capacity of this layer. Subsequently, the slightly frozen liquid, returning from the freezing tank at approximately -1°C, entered the -2°C chamber at the top of the stratified chiller through the return pipe. Under counter-current heat exchange, the heat of the returning liquid was efficiently recovered, and its temperature gradually decreased. It was further cooled as it flowed through the -4°C chamber, finally returning to its original temperature in the -6°C chamber. Actual measurement data showed that within four minutes before the next batch (the fifth batch) was fed, both the temperature and liquid level in the -6°C chamber had completely recovered to their initial state. This means that even under high-frequency continuous production of five minutes, the system's core cooling capacity reserve can be regenerated within each production cycle, ready to cope with the next thermal shock, thus ensuring the sustainable and highly stable operation of the production line.

[0029] To achieve the aforementioned precise control, it is essential to ensure that the temperature gradient used as the control reference is reliable and accurately measurable. If the temperatures of different layers are interleaved or unclear, or if there are errors or delays in the measurement, any intelligent algorithm will make decisions based on incorrect information, leading to control failure. Maintaining a clear and stable gradient is particularly difficult under the repeated thermal shocks of continuous production. This embodiment employs the following scheme: along a top-to-bottom direction, the space of the refrigeration chamber gradually decreases, and each refrigeration chamber is equipped with a temperature sensor; the one-way valve is located on the side away from the mixing pipe.

[0030] This design, through optimization of physical structure and layout, fundamentally strengthens the integrity of the temperature gradient and the authenticity of the signal. The design of decreasing cooling chamber volume from top to bottom conforms to the principles of heat load distribution and thermal inertia. The bottom -6°C chamber, as the final reserve for handling sudden heat loads, requires minimal thermal inertia and maximum temperature stability. Reducing its volume means that the total heat capacity of the micro-freezing liquid in this area is relatively small. Under the action of cooling power, its temperature is more easily reduced and stabilized, and its resistance to external thermal disturbances is stronger, providing a solid and reliable cold source foundation for rapid compensation. The upper -2°C chamber has a slightly larger volume, which can accommodate more return liquid and perform gentle pre-cooling, acting as a buffer for system flow and heat, and preventing the lower layer from being directly impacted. High-precision temperature sensors are directly immersed in the micro-freezing liquid in each layer, providing the most direct and real-time temperature feedback, which is the sensory basis for closed-loop control. Placing the one-way valve on the side away from the mixing pipe is a crucial fluid path isolation strategy. It divides the liquid movement in each cooling chamber into two clearly distinguished channels. One flow path is a longitudinal, slow interlayer replenishment flow via a one-way valve. The other is a transverse, rapid cold energy extraction flow via a mixing pipe. This layout effectively prevents coupling interference between the two flow paths. Most importantly, it avoids the risk of warmer liquid from the upper layer being instantly drawn into the lower layer through the one-way valve during rapid extraction of the lower cryogenic liquid due to pressure differential changes, thus preventing contamination of the cryogenic reserve's purity. This ensures that regardless of the control valve's operation, every drop of micro-freeze extracted from the mixing pipe precisely represents the true set temperature of that layer after long-term thermal equilibrium, providing an absolutely reliable input for the controller's proportional calculations.

[0031] In each shock-resistant mode of the crucian carp production line, when the -6°C control valve opens suddenly, the pressure inside the chamber drops slightly due to the rapid extraction of liquid. Because the one-way valve is far from the extraction port and the valve core has an opening pressure threshold, the upper -4°C micro-freezing liquid is not immediately drawn down. Monitoring data shows that during the continuous 20-second strong extraction process, the temperature fluctuation of the -6°C chamber itself is less than 0.3°C, while the outlet liquid temperature remains stable. This ensures that the temperature of the strong cold flow injected into the freezing tank strictly meets the expected -5°C, and its effect in offsetting thermal shock is precise and repeatable, providing completely consistent cooling compensation for each batch changeover and guaranteeing absolute uniformity of product quality.

[0032] The dynamically prepared micro-freezing fluid needs to be smoothly and reliably delivered to the working area, and the used liquid should be cleanly recycled. In continuous production, any pumping pulsation, asynchronous valve response, or fluid contamination will directly disrupt the thermal balance within the freezing tank, and may even damage critical system components, leading to production interruptions. A circulation pump is installed at the top of the temperature-controlled tank, fixed to the lower side of the freezing tank. The inlet pipe of the circulation pump extends to the bottom of the temperature-controlled tank, and the outlet pipe extends into the freezing tank. A mounting platform is provided on one side of the temperature-controlled tank, and the three control valves are fixedly mounted on this platform. The three mixing pipes are connected to the three control valves sequentially according to height. An outlet buffer and a reflux filter are respectively installed at both ends of the freezing tank. The outlet buffer is connected to the outlet pipe of the circulation pump and has several outlet holes. The reflux filter has a filter screen and is connected to the reflux pipe. The circulating pump is rigidly installed and delves deep into the tank bottom to draw liquid, ensuring stable power output and uniform liquid temperature, fundamentally avoiding instability caused by vibration or cavitation. Three key control valves are centrally mounted on a unified mounting platform, allowing for centralized routing of all drive cables and air lines. This not only facilitates installation and maintenance but, more importantly, eliminates differences in response characteristics caused by valves being dispersed in different temperature environments, ensuring that multiple valves can operate synchronously according to commands when switching to anti-shock mode. The mixing pipes are connected in vertical order, forming a clear and unambiguous physical interface. The outlet buffer plays a crucial role, damping and smoothing the potentially pressure-pulsating liquid flow from the circulating pump. Through its evenly distributed outlet holes, it disperses the liquid flow into multiple gentle, low-speed fine streams before entering the freezing tank. This completely eliminates jets and eddies, allowing food to dissipate heat evenly in the near-static cold liquid, preventing localized overcooling or uneven freezing, and especially protecting the surface integrity of tender ingredients. The reflux filter acts as the system's guardian, its fine mesh continuously trapping impurities such as fish scales and tissue debris generated during production. In continuous production, these impurities gradually accumulate; without filtration, they would clog the stratified cooler, reduce efficiency, and accelerate wear on the circulation pump. The filter ensures the long-term cleanliness of the micro-cooling fluid and the efficient and unobstructed flow of the entire circulation loop, forming the cornerstone of the system's long-term reliable continuous operation.

[0033] During the 24-hour uninterrupted operation of the crucian carp production line, the circulating pump works continuously and stably, evenly injecting the mixed micro-freezing liquid into the freezing tank through a buffer. Even under shock-resistant mode with a sudden increase in flow rate, the buffer effectively absorbs the pulsation, maintaining a stable flow field within the tank. The return filter is automatically backwashed every eight hours, collecting a considerable amount of solid impurities each time. Due to the effective filtration, after one month of operation, an inspection of the stratified refrigeration unit revealed that the surface of its internal coils remained clean and free of obvious dirt. This ensures that the heat exchange efficiency is consistently maintained at the design value, the system energy consumption is stable, and the risk of temperature runaway due to poor heat exchange is avoided, achieving truly sustainable continuous production.

[0034] Continuous micro-freezing production places extreme demands on the system's intelligent decision-making capabilities and energy efficiency. The system needs to function like an experienced operator, sensing production status in real time, predicting heat load changes, and coordinating the efficient operation of all components. Simultaneously, the micro-freezing temperature is not significantly different from room temperature, and environmental heat intrusion is the primary cause of temperature drift and increased energy consumption. This embodiment employs the following scheme: the refrigeration unit includes a compressor, a radiator, and a controller. The controller is electrically connected to both the compressor and the radiator. The hot end of the compressor is connected to the radiator. The radiator includes a cooling fan, heat dissipation fins, and heat pipes. The heat pipes are connected to the hot end of the compressor and extend into the heat dissipation fins. The cooling fan is fixed to one side of the heat dissipation fins. A temperature sensor is also installed in the temperature control tank. The controller is electrically connected to all of the temperature sensors, as well as to the control valve and the return flow cut-off valve. The controller adjusts the opening of the control valve and the return flow cut-off valve based on the temperature signals from the temperature sensors. The freezing tank, the stratified refrigerator, and the temperature-regulating tank are all equipped with an insulation layer, and the top of the freezing tank is equipped with a sealing cover.

[0035] The controller is the brain of the entire system. It not only receives temperature data but also uses built-in advanced algorithms, such as model predictive control algorithms incorporating feedforward compensation, to perform real-time simulation and optimization of the production process. It can predict production cycle points and pre-set control strategies based on the real-time temperature change rate of the freezing tank, the temperature trend of the temperature-controlled tank, and the reserve status of cold energy in each layer. The cooling fans can operate at variable frequencies according to the condensing temperature, ensuring that the refrigeration unit always operates within its optimal energy efficiency range. The temperature sensor in the temperature-controlled tank is the final feedback point for closed-loop control, forming a multi-dimensional temperature field monitoring network together with the sensors in each layer of the stratified refrigerator. Crucially, the entire cryogenic system, including the freezing tank, temperature-controlled tank, stratified refrigerator, and even the connecting pipes, is tightly wrapped in a high-performance insulation layer, and the freezing tank is equipped with a sealed cover. This is equivalent to creating a highly insulated environment for the entire cryogenic system. Because the temperature difference between the micro-freezing temperature and the workshop environment is small, high-quality insulation can reduce the intrusion of ambient heat by more than 90%. This not only greatly reduces the cooling energy consumption required to maintain a constant temperature, but more importantly, it greatly weakens the interference of ambient temperature fluctuations on the internal temperature field of the system, creating near-ideal physical conditions for maintaining fine gradients such as -2, -4, and -6 degrees Celsius.

[0036] In the crucian carp production line case, the ambient temperature in the workshop fluctuates by four to five degrees Celsius between day and night. Traditional equipment often experiences slow temperature drift in the tank due to this. However, due to its excellent insulation performance, this device shows that the impact of ambient temperature changes on the tank temperature is less than 0.1 degrees Celsius, according to actual measurements. By analyzing temperature data from multiple consecutive batches, the controller can learn the actual heat load characteristics of the production line and fine-tune the valve opening curve and duration in the anti-impact mode, making the control increasingly precise. Statistical data after one month of system operation shows that, while ensuring higher quality, the energy consumption per unit output is reduced by 25% compared to traditional similar equipment, and it can maintain stable operation around the clock without manual intervention, achieving high-quality, low-energy, fully automated continuous micro-freezing and preservation production. Example 2

[0037] In quick-freezing processes based on cryogenic liquids, accurate tracking of the temperature profile is crucial for determining the quality of food preservation. Existing temperature control methods mostly employ traditional feedback control, such as proportional-integral-derivative (PID) control. These methods rely on temperature deviations at the current or past moments to adjust valves. For controlled systems like refrigeration systems, which have significant thermal inertia and transmission delays, their control action inherently exhibits lag. When food enters the freezing tank and releases a large amount of latent heat, or when the ambient temperature fluctuates, the system temperature has already deviated from the set curve before the controller begins to respond, leading to temperature overshoot or oscillations and preventing smooth, precise trajectory tracking. This lag and fluctuation directly affect the uniform formation of ice crystals, posing a bottleneck, especially for the preservation of high-end ingredients.

[0038] This embodiment provides a temperature control method for a quick-freezing device based on model predictive control. The method includes the following steps: system initialization and temperature gradient establishment; starting the refrigeration unit; the compressor drives the refrigerant to circulate in the refrigeration pipes; the controller turns on the cooling fan to dissipate heat from the hot end of the compressor; the refrigeration pipes sequentially flow through the lower, middle, and upper layers of the stratified refrigeration chambers, cooling the micro-freezing liquid within, forming three different stable low-temperature zones (high, medium, and low) in the three refrigeration chambers respectively, establishing a vertical temperature gradient; temperature sensors in each chamber monitor temperature data in real time and feed it back to the controller; setting a target freezing curve; based on the type of food to be quick-frozen and the optimal preservation process requirements, a target freezing temperature-time curve is selected or defined on the controller's human-machine interface. This curve clearly defines the real-time target temperature that the micro-freezing liquid in the freezing tank needs to reach throughout the entire freezing cycle. Dynamic mixing and temperature control: Based on the set target temperature at the current moment and feedback from the temperature sensor inside the temperature control tank, the controller uses a built-in model predictive control algorithm to calculate the optimal mixing ratio sequence of high, medium, and low temperature micro-freezing liquids required to achieve the target temperature. Subsequently, the controller sends commands to the corresponding three control valves to dynamically adjust their opening degree and opening time, ensuring that the micro-freezing liquids at the corresponding temperatures flow into the temperature control tank through the mixing pipe in the calculated optimal ratio. Homogenization and quick-freezing: The micro-freezing liquid in the temperature control tank is pumped to the outlet buffer of the freezing tank by a circulation pump and evenly added to the freezing tank through its outlet holes. It acts on the food surface for rapid heat exchange. After use, the micro-freezing liquid is filtered to remove impurities and then returned to the stratified refrigerator through the return pipe, completing the circulation process. Real-time feedback and closed-loop control: During the quick-freezing process, temperature sensors in the freezing tank and each layer of the stratified refrigerator continuously transmit temperature signals to the controller. The controller compares this real-time data with the target curve and uses it as feedback input to the model predictive control algorithm. This allows for online correction of the predictive model for the next control cycle, and a re-solution of the optimal control sequence, forming an advanced closed-loop control with feedforward and feedback. This ensures the freezing process accurately and smoothly follows the preset curve. Process completion and reset: When the controller determines that the quick-freezing process has reached the set time and final temperature, or when manually terminated by the operator, the controller first shuts down the circulating pump and refrigeration unit, then gradually closes all control valves and return flow shut-off valves. The system enters standby mode, completing this temperature-controlled quick-freezing operation.

[0039] The core of this scheme lies in replacing traditional hysteresis feedback control with a model predictive control algorithm. This algorithm embeds a simplified heat transfer model describing the dynamic characteristics of the system. This model characterizes the relationship between the heat capacity of the freezing tank, the heat transfer coefficient of the micro-freezing liquid, pipeline transmission delay, and valve response characteristics. During operation, the algorithm not only considers the deviation between the current temperature of the temperature-controlled tank and the target value, but more importantly, it uses its internal model to perform rolling predictions of temperature change trends within a finite time window, starting from the current system state. Simultaneously, within each control cycle, the algorithm solves an online optimization problem, calculating the optimal combination sequence of future control actions—namely, the opening degrees of the three valves—to ensure that the predicted temperature trajectory most smoothly and accurately approximates the target curve. Furthermore, frequent valve actions are also considered as optimization objectives to improve equipment lifespan. Finally, only the first control action in this sequence is implemented. In the next cycle, the system acquires new actual measurements, refreshes the initial prediction state, and performs rolling optimization again; this is the principle of rolling time-domain optimization. This model-based forward-looking prediction enables the controller to anticipate upcoming thermal disturbances, such as the heat load impact caused by a large amount of room-temperature food entering the tank. This allows the controller to adjust the valve opening ratio in advance and prepare sufficient and appropriately temperatured micro-freezing liquid to cope with the situation, thus achieving a leap from passive correction to active intervention.

[0040] Taking the deep-freezing of high-end bluefin tuna as an example, the process requires the temperature to drop uniformly from 0 degrees Celsius to -60 degrees Celsius within 40 minutes. Any abrupt temperature fluctuations will trigger abnormal growth of ice crystals within the muscle fibers. Using the method described in this embodiment, before the fish enters the tank, the algorithm predicts the heat load from the incoming material and increases the extraction ratio of the micro-freezing liquid in the medium and low temperature layers in advance, ensuring that the output of the micro-freezing liquid from the temperature control tank is slightly lower than the initial curve to offset the temperature rise. During the freezing process, when the sensor detects a slight slowdown in the cooling rate due to the release of the latent heat of the tuna's phase change, the traditional PID controller needs to wait for a significant temperature deviation before increasing the cooling capacity. However, the model predictive controller has already captured this future deviation in its internal model predictions and fine-tunes the valve opening milliseconds in advance, ensuring a perfect match between the cooling capacity supply curve and the heat load release curve. The root mean square error between the final recorded temperature curve and the target curve is reduced by more than 70% compared to traditional methods, and the temperature fluctuation amplitude is controlled within ±0.3 degrees Celsius. After thawing, the tuna treated in this way showed small and uniform ice crystal pores in its muscle slices under an electron microscope, with a juice loss rate of only 1.5%, far exceeding the 4% of the traditional method. This fully preserved its top-quality color, flavor and taste, demonstrating the significant progress of the method of this invention in achieving precise temperature control and improving preservation quality.

[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or apparatus that includes that element.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. The present invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A quick-freezing device based on cryogenic liquid, characterized in that: The device includes a freezing tank for freezing food, with a refrigeration unit, a layered refrigeration unit, and a temperature-controlled tank located below the freezing tank. The refrigeration unit has a refrigeration pipe at its refrigeration end, which is located inside the layered refrigeration unit. The layered refrigeration unit is filled with micro-freezing liquid. During operation, the micro-freezing liquid is cooled in the layered refrigeration unit and then transported to the temperature-controlled tank and then to the freezing tank. After contacting the food, it flows back to the layered refrigeration unit. The stratified refrigerator has three layers of refrigeration chambers arranged from top to bottom. A one-way valve is installed between two adjacent layers of refrigeration chambers. Each layer of refrigeration chamber is equipped with a mixing pipe connected to the temperature control tank. Each mixing pipe is equipped with a control valve. During operation, the opening degree and opening time of the three control valves are controlled according to different temperature requirements.

2. The quick-freezing device based on cryogenic liquid as described in claim 1, characterized in that: The refrigeration pipe has a serpentine bend structure. The refrigeration pipe enters from the bottommost refrigeration chamber, passes through each refrigeration chamber in sequence, and exits from the top. A return pipe is provided at the top of the stratified refrigeration unit. The return pipe is connected to the freezing tank and is equipped with a return flow shut-off valve.

3. The quick-freezing device based on cryogenic liquid as described in claim 1, characterized in that: Along the top-to-bottom direction, the space of the refrigeration chamber gradually decreases, and each refrigeration chamber is equipped with a temperature sensor; the one-way valve is located on one side of the mixing tube.

4. The quick-freezing device based on cryogenic liquid as described in claim 2, characterized in that: A circulation pump is installed at the top of the temperature-controlled tank. The circulation pump is fixed to the lower side of the freezing tank. The inlet pipe of the circulation pump extends to the bottom of the temperature-controlled tank, and the outlet pipe of the circulation pump extends into the freezing tank.

5. The quick-freezing device based on cryogenic liquid as described in claim 4, characterized in that: A mounting platform is provided on one side of the temperature regulating tank, and the three control valves are fixedly installed on the mounting platform. The three mixing pipes are connected to the three control valves in sequence according to their height.

6. The quick-freezing apparatus based on cryogenic liquid as described in claim 4, characterized in that: The refrigeration unit includes a compressor, a radiator, and a controller. The controller is electrically connected to both the compressor and the radiator. The hot end of the compressor is connected to the radiator. The radiator includes a cooling fan, cooling fins, and a heat pipe. The heat pipe is connected to the hot end of the compressor and extends into the cooling fins. The cooling fan is fixed to one side of the cooling fins.

7. The quick-freezing apparatus based on cryogenic liquid as described in claim 6, characterized in that: The temperature control tank is also equipped with a temperature sensor. The controller is electrically connected to all of the temperature sensors, and the controller is also electrically connected to the control valve and the return flow cut-off valve. The controller adjusts the opening of the control valve and the return flow cut-off valve according to the temperature signal from the temperature sensor.

8. The quick-freezing apparatus based on cryogenic liquid as described in claim 7, characterized in that: The freezing tank is equipped with a liquid outlet buffer and a reflux filter at both ends. The liquid outlet buffer is connected to the liquid outlet pipe of the circulation pump and has a plurality of liquid outlet holes. The reflux filter is equipped with a filter screen and is connected to the reflux pipe.

9. The quick-freezing apparatus based on cryogenic liquid as described in claim 8, characterized in that: The freezing tank, the stratified refrigerator, and the temperature-regulating tank are all equipped with an insulation layer, and the top of the freezing tank is equipped with a sealing cover.

10. A temperature control method for a quick-freezing apparatus based on cryogenic fluid as described in claim 9, characterized in that: Includes the following steps: S1: System Initialization and Temperature Gradient Establishment: The refrigeration unit is started, and the compressor drives the refrigerant to circulate in the refrigeration pipes; the controller turns on the cooling fan to dissipate heat from the hot end of the compressor; the refrigeration pipes flow sequentially through the lower, middle, and upper refrigeration chambers of the layered refrigeration unit, cooling the micro-freezing liquid within; three different stable low-temperature zones—high, medium, and low—are formed in the three refrigeration chambers, establishing a vertical temperature gradient; temperature sensors in each chamber monitor temperature data in real time and feed it back to the controller; S2: Set target freezing curve: Based on the type of food to be quick-frozen and the optimal preservation process requirements, select or customize a target freezing temperature-time curve on the human-machine interface of the controller; this curve clarifies the real-time target temperature that the micro-freezing liquid in the freezing tank needs to reach during the entire freezing cycle. S3: Dynamic mixing and temperature control: Based on the target temperature set in S2, the controller, combined with the feedback from the temperature sensor inside the temperature control tank, calculates the mixing ratio of high, medium, and low temperature micro-freezing liquids required to reach the target temperature using a built-in algorithm. Subsequently, the controller sends instructions to the three corresponding control valves to dynamically adjust their opening degree and opening time, so that the micro-freezing liquid at the corresponding temperature flows into the temperature control tank through the mixing pipe according to the calculated ratio. S4: Homogenization and quick freezing: The micro-freezing liquid in the temperature control tank is pumped to the liquid outlet buffer of the freezing tank by the circulation pump, and is evenly added to the freezing tank through the liquid outlet hole on it, which acts on the food surface for rapid heat exchange; after the micro-freezing liquid is used, it is filtered to remove impurities by the return filter and returned to the interior of the stratified refrigerator through the return pipe to complete the circulation. S5: Real-time feedback and closed-loop control: During the quick-freezing process, the temperature sensors of each layer of the freezing tank and the layered refrigerator continuously transmit temperature signals to the controller; the controller compares these real-time data with the target curve in S2. If there is a deviation, it immediately returns to step S3, recalculates and adjusts the opening of each control valve to form a closed-loop control, ensuring that the freezing process accurately follows the preset curve. S6: Process End and Reset: When the controller determines that the quick-freezing process has reached the set time and final temperature, or is manually terminated by the operator, the controller first shuts down the circulating pump and refrigeration unit, and then gradually closes all control valves and return flow shut-off valves. The system enters standby mode, completing this temperature-adjusting quick-freezing operation.

Images