Vacuum cooling and freezing integrated device and method based on over-vacuum degree

Abstract

The invention discloses a vacuum cooling and freezing integrated device and method based on the over-vacuum degree, the device comprises a vacuum chamber, a vacuum pump set, a cooling system and a freezing system, the cooling system adopts a compression type refrigerating unit, and an evaporator of the cooling system is arranged at the bottom of the vacuum chamber; the refrigeration system adopts a liquid nitrogen injection module, and a liquid nitrogen nozzle is arranged at the top of the vacuum chamber; the carrier is located between the two parts, has a hollow structure and is integrated with an ultrasonic vibration module. The vacuum pump set comprises a vortex pump and a roots pump, and a pressure adjusting range of 0.1 kPa to 5 kPa is formed. The invention further discloses a cooling and freezing method combining the over-vacuum phase change characteristic, multi-stage temperature control and vacuum degree control are achieved, and the method is suitable for the efficient, rapid and low-loss food cold chain treatment process. The device has the advantages of precise temperature control, simple structure, high freezing speed, high product quality retention and the like.

Description

Technical Field

[0001] The present invention relates to a vacuum cooling and freezing integrated device and method based on over-vacuum degree. Background Art

[0002] With the increasing circulation of fresh food, quick-frozen food and high-end agricultural products, the demand for "rapid cooling" and "low-temperature preservation" in the cold chain processing link is becoming increasingly prominent. Traditional cooling methods usually use forced air convection, water cooling or ice-water bath cooling methods. These methods are limited by heat conduction efficiency and phase change hysteresis. When processing high-moisture foods, it is difficult to achieve uniform cooling in a short time. Vacuum cooling technology is widely used in the field of food pre-cooling because it can induce rapid vaporization of water and absorb heat through low pressure. However, deep freezing after vacuum cooling still needs to rely on other freezing equipment, resulting in complex process flow, high energy consumption, and inaccurate temperature control. In addition, existing vacuum cooling equipment generally lacks optimization of ultra-low temperature phase change control and freezing uniformity, and cannot meet the high requirements for the internal structure and taste of the product. Therefore, there is an urgent need for a device and method that can integrate efficient cooling and deep freezing, and has multi-stage vacuum control, rapid heat exchange and uniform freezing effects. Summary of the Invention

[0003] The purpose of the present invention is to solve the above deficiencies in the prior art and to provide a vacuum cooling and freezing integrated device and method based on super vacuum.

[0004] A vacuum cooling and freezing integrated device and method based on over-vacuum degree, including a vacuum chamber, which is connected to an external vacuum pump group. A cooling system and a freezing system are provided in the vacuum chamber. The cooling system includes a compression refrigeration unit, and the evaporator in the compression refrigeration unit is arranged at the bottom of the vacuum chamber. The freezing system includes a liquid nitrogen injection module, and the liquid nitrogen nozzle in the liquid nitrogen injection module is arranged at the top of the vacuum chamber. A suspended carrier is provided between the evaporator and the liquid nitrogen nozzle. The carrier is a hollow structure and an ultrasonic vibration module is integrated in the carrier. A water trap is provided in the vacuum chamber.

[0005] This device can achieve seamless switching between cooling and freezing, and uses ultrasound to suppress ice crystals and reduce cell damage. The bottom layout of the evaporator utilizes cold air to sink, and liquid nitrogen is sprayed from the top to cover the entire cavity.

[0006] As a further improvement, the vacuum pump group includes a first-stage vortex pump and a second-stage Roots pump, with a pressure adjustment range of 0.1 kPa to 5 kPa. The high pumping speed of the Roots pump can cope with steam explosion during the phase change stage.

[0007] As a further improvement, the outer wall of the vacuum chamber adopts a double-layer stainless steel shell, and a polyurethane insulation layer is filled between the double-layer stainless steel shell. A self-starting emergency pressure relief valve is provided on the outside of the vacuum chamber. The thermal conductivity of the insulation layer is low, which reduces cold loss. The pressure relief valve has a short response time to prevent the risk of overpressure explosion.

[0008] As a further improvement, the liquid nitrogen nozzle is an annular atomizing nozzle, on which a number of injection ports are evenly distributed, providing 360° uniform coverage, eliminating freezing dead corners, and having a small droplet size, which can improve heat exchange efficiency.

[0009] As a further improvement, the carrier is a rotatable structure, which includes a circular carrier plate, which is mounted on a cylindrical mounting frame. A ring-shaped slide is provided at the bottom of the cylindrical mounting frame, which is connected to the ring-shaped slide on the inner wall of the vacuum chamber. A gear ring is provided on the inner side of the cylindrical mounting frame, and a matching gear is provided on the inner side of the gear ring. The gear is connected to the drive motor through a transmission mechanism, with high rotation accuracy. The slide rail is resistant to low temperatures and is more resistant to cold brittleness than bearings.

[0010] As a further improvement, the compression refrigeration unit includes a compressor, a condenser, an expansion valve and an evaporator. The evaporator is a copper coil distributed in a serpentine array, which can increase the heat exchange area. The copper tube is resistant to vacuum corrosion and extends its service life.

[0011] As a further improvement, the liquid nitrogen injection module includes a storage tank, a delivery pipeline, a liquid nitrogen nozzle and a flow control component, so that the liquid nitrogen flow rate can be controlled with high precision to match the needs of different ingredients.

[0012] A vacuum cooling and freezing method based on over-vacuum degree comprises the following steps; Step 1: Pre-cooling stage; Place the food in a vacuum chamber and start the first-stage vacuum pump to gradually reduce the pressure, causing water to evaporate and absorb heat; The vacuum pump speed is adjusted through feedback from the humidity sensor to maintain a stable evaporation rate, and the water trap is activated to capture the evaporated water vapor in the device; Step 2: Phase change transition stage; Start the secondary Roots pump to drop the pressure to 0.5kPa, and reduce the core temperature of the food to 0℃; The liquid nitrogen spray was turned on synchronously to reduce the chamber temperature from 15°C to -30°C within 120 seconds; Step 3: Deep freezing stage; Switch to compressor cooling mode to maintain an ambient temperature of -35°C; Through intermittent vacuum fluctuations, oscillations within the range of 0.2kPa±0.05kPa promote uniform distribution of ice crystals; Step 4: Termination condition; When the infrared temperature measurement shows that the center temperature of the food reaches -18℃ and the humidity sensor reading is stable, the pressure is automatically released and the material is discharged. Beneficial effects

[0013] 1. Integrated cooling and freezing design: By integrating the compressor refrigeration system and liquid nitrogen injection system in the same vacuum chamber, the equipment structure and control process are simplified, and the cold chain processing efficiency is improved.

[0014] 2. Over-vacuum phase change control: By setting up the joint operation of the first and second vacuum pumps, the system can be flexibly adjusted between 0.1kPa and 5kPa, optimizing the water vaporization and ice crystal formation process, and improving the cooling rate and freezing quality.

[0015] 3. Multi-point rapid cooling: A liquid nitrogen atomization nozzle is installed on the top, which can reduce the cavity temperature to below -30°C in a short time, so that the core temperature of the food can quickly pass the critical point.

[0016] 4. Uniform freezing structure design: A rotatable hollow loading rack is set up, and it is equipped with an ultrasonic vibration module and an intermittent vacuum fluctuation mechanism to promote the uniform distribution of the freezing medium and the formation of ice crystals inside the food.

[0017] 5. Energy saving and thermal insulation: The vacuum chamber adopts a double-layer stainless steel + polyurethane insulation structure, combined with an emergency pressure relief design to ensure safe operation of the device while reducing energy loss.

[0018] 6. Automation and intelligent control: Based on infrared temperature measurement and humidity feedback control system, closed-loop control of temperature and vacuum degree of the whole process is achieved, improving product consistency and operation convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the internal structure of a vacuum cooling and freezing integrated device based on over-vacuum degree; 1. Vacuum chamber 2. Vacuum pump unit 3. Compression refrigeration unit 4. Evaporator 5. Liquid nitrogen injection module 6. Liquid nitrogen nozzle 7. Carrier 8. Cylindrical mounting frame 9. Slide rail 10. Drive motor DETAILED DESCRIPTION

[0020] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0021] like Figure 1 As shown, a vacuum cooling and freezing integrated device based on over-vacuum degree includes a vacuum chamber 1, a vacuum pump group 2, a compression refrigeration unit 3, an evaporator 4, a liquid nitrogen injection module 5, a liquid nitrogen nozzle 6, a carrier 7, a cylindrical mounting frame 8, a slide rail 9, and a drive motor 10.

[0022] A vacuum cooling and freezing integrated device and method based on over-vacuum degree, including a vacuum chamber 1, the vacuum chamber 1 is connected to an external vacuum pump group 2, and a cooling system and a freezing system are provided in the vacuum chamber 1. The cooling system includes a compression refrigeration unit 3, and the evaporator 4 in the compression refrigeration unit 3 is arranged at the bottom of the vacuum chamber 1. The freezing system includes a liquid nitrogen injection module 5, and the liquid nitrogen nozzle 6 in the liquid nitrogen injection module 5 is arranged at the top of the vacuum chamber 1. A suspended carrier 7 is provided between the evaporator 4 and the liquid nitrogen nozzle 6. The carrier 7 is a hollow structure, and an ultrasonic vibration module is integrated in the carrier 7.

[0023] This device can achieve seamless switching between cooling and freezing, and uses ultrasound to suppress ice crystals and reduce cell damage. The bottom layout of the evaporator 4 utilizes cold air to sink, and liquid nitrogen is sprayed from the top to cover the entire cavity.

[0024] The vacuum pump group 2 includes a first-stage vortex pump and a second-stage Roots pump. The pressure adjustment range is 0.1 kPa to 5 kPa. The high pumping speed of the Roots pump can cope with the steam explosion in the phase change stage.

[0025] The outer wall of the vacuum chamber 1 adopts a double-layer stainless steel shell, and a polyurethane insulation layer is filled between the double-layer stainless steel shell. A self-starting emergency pressure relief valve is provided on the outside of the vacuum chamber 1. The thermal conductivity of the insulation layer is low, which reduces cold loss. The pressure relief valve has a short response time to prevent the risk of overpressure explosion.

[0026] The liquid nitrogen nozzle 6 is an annular atomizing nozzle, on which a number of injection ports are evenly distributed, providing 360° uniform coverage, eliminating freezing dead corners, and having a small droplet size, which can improve heat exchange efficiency.

[0027] The carrier 7 is a rotatable structure. The carrier 7 includes a circular carrier plate, which is mounted on a cylindrical mounting frame 8. A ring-shaped slide rail 9 is provided at the bottom of the cylindrical mounting frame 8. The slide rail 9 is connected to the ring-shaped slide rail on the inner wall of the vacuum chamber 1. A gear ring is provided on the inner side of the cylindrical mounting frame 8. A matching gear is provided on the inner side of the gear ring. The gear is connected to the drive motor 10 through a transmission mechanism. The rotation accuracy is high. The slide rail 9 is resistant to low temperatures and is more resistant to cold brittleness than bearings.

[0028] The compression refrigeration unit 3 includes a compressor, a condenser, an expansion valve and an evaporator 4. The evaporator 4 is a copper coil distributed in a serpentine array, which can increase the heat exchange area. The copper tube is resistant to vacuum corrosion and has a longer service life.

[0029] The liquid nitrogen injection module 5 includes a storage tank, a delivery pipeline, a liquid nitrogen nozzle 6 and a flow control component, so that the liquid nitrogen flow rate can be controlled with high precision to meet the needs of different food ingredients.

[0030] A vacuum cooling and freezing method based on over-vacuum degree comprises the following steps; Step 1: Pre-cooling stage; Place the food in vacuum chamber 1, start the first-stage vacuum pump to gradually reduce the pressure, causing water to evaporate and absorb heat; The vacuum pump speed is adjusted through feedback from the humidity sensor to maintain a stable evaporation rate, and the water trap is activated to capture the evaporated water vapor in the device. Step 2: Phase change transition stage; Start the secondary Roots pump to drop the pressure to 0.5kPa, and reduce the core temperature of the food to 0℃; The liquid nitrogen spray was turned on synchronously to reduce the chamber temperature from 15°C to -30°C within 120 seconds; Step 3: Deep freezing stage; Switch to compressor cooling mode to maintain an ambient temperature of -35°C; Through intermittent vacuum fluctuations, oscillations within the range of 0.2kPa±0.05kPa promote uniform distribution of ice crystals; Step 4: Termination condition; When the infrared temperature measurement shows that the center temperature of the food reaches -18℃ and the humidity sensor reading is stable, the pressure is automatically released and the material is discharged.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vacuum cooling and freezing integrated device based on super vacuum degree, characterized in that: The vacuum chamber includes a vacuum chamber connected to an external vacuum pump group. A cooling system and a freezing system are provided in the vacuum chamber. The cooling system includes a compression refrigeration unit. The evaporator in the compression refrigeration unit is arranged at the bottom of the vacuum chamber. The freezing system includes a liquid nitrogen injection module. The liquid nitrogen nozzle in the liquid nitrogen injection module is arranged at the top of the vacuum chamber. A suspended carrier is provided between the evaporator and the liquid nitrogen nozzle. The carrier is a hollow structure. An ultrasonic vibration module is integrated in the carrier. A water trap is provided in the vacuum chamber.

2. The vacuum cooling and freezing integrated device based on super vacuum according to claim 1, characterized in that: The vacuum pump group includes a first-stage vortex pump and a second-stage Roots pump, and the pressure adjustment range is 0.1kPa to 5kPa.

3. The vacuum cooling and freezing integrated device based on super vacuum degree according to claim 1, characterized in that: The outer wall of the vacuum chamber adopts a double-layer stainless steel shell, and a polyurethane insulation layer is filled between the double-layer stainless steel shells. A self-starting emergency pressure relief valve is provided outside the vacuum chamber.

4. The vacuum cooling and freezing integrated device based on super vacuum degree according to claim 1, characterized in that: The liquid nitrogen nozzle is an annular atomizing nozzle, and a plurality of injection ports are evenly distributed on the annular atomizing nozzle.

5. The vacuum cooling and freezing integrated device based on super vacuum according to claim 4, characterized in that: The carrier is a rotatable structure, and the carrier includes a circular carrier plate, which is mounted on a cylindrical mounting frame. A ring-shaped slide rail is provided at the bottom of the cylindrical mounting frame, and the slide rail is connected to the ring-shaped slide rail on the inner wall of the vacuum chamber. A gear ring is provided on the inner side of the cylindrical mounting frame, and a matching gear is provided on the inner side of the gear ring. The gear is connected to the drive motor through a transmission mechanism.

6. The vacuum cooling and freezing integrated device based on super vacuum degree according to claim 1, characterized in that: The compression refrigeration unit comprises a compressor, a condenser, an expansion valve and an evaporator, wherein the evaporator is a copper coil distributed in a serpentine array.

7. The vacuum cooling and freezing integrated device based on super vacuum according to claim 1, characterized in that: The liquid nitrogen injection module includes a storage tank, a delivery pipeline, a liquid nitrogen nozzle and a flow control component.

8. A vacuum cooling and freezing method based on super vacuum, characterized in that: The following steps are included: Step 1: Pre-cooling stage; Place the food in a vacuum chamber and start the first-stage vacuum pump to gradually reduce the pressure, causing water to evaporate and absorb heat; The vacuum pump speed is adjusted through feedback from the humidity sensor to maintain a stable evaporation rate, and the water trap is activated to capture the evaporated water vapor in the device; Step 2: Phase change transition stage; Start the secondary Roots pump to drop the pressure to 0.5kPa, and reduce the core temperature of the food to 0℃; The liquid nitrogen spray was turned on synchronously to reduce the chamber temperature from 15°C to -30°C within 120 seconds; Step 3: Deep freezing stage; Switch to compressor cooling mode to maintain an ambient temperature of -35°C; Through intermittent vacuum fluctuations, oscillations within the range of 0.2kPa±0.05kPa promote uniform distribution of ice crystals; Step 4: Termination condition; When the infrared temperature measurement shows that the center temperature of the food reaches -18℃ and the humidity sensor reading is stable, the pressure is automatically released and the material is discharged.

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