Fluid vacuum cooling method and system based on critical shear rate control

Abstract

The invention discloses a fluid vacuum cooling method based on critical shear rate control. The fluid vacuum cooling method comprises the following steps: placing a fluid material in a rotationally symmetrical vacuum cavity with a material container; establishing a vacuum environment, and enabling the ultimate vacuum pressure in the vacuum cavity to be lower than the saturated vapor pressure corresponding to the target cooling temperature; stirring the fluid material to form a water directional migration channel pointing to the surface from the interior of the material; the stirring shear rate gamma is controlled to be larger than or equal to the critical shear rate gamma crit, a pressure shell layer in fluid is destroyed, an evaporation area is transferred to the surface from the interior of a material, and splashing is fundamentally restrained; and meanwhile, centrifugal backflow of splashing liquid drops is realized by adopting a rotary symmetrical vacuum cavity. Therefore, the splashing of fluid vacuum cooling is greatly reduced, the vacuum cooling time is shortened, and the cooling efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum cooling of fluid materials, and is particularly suitable for rapid cooling of high-viscosity fluids in the fields of food, chemical industry, biomedicine, etc. Background Art

[0002] Traditional vacuum cooling equipment places a container containing the material to be cooled in a vacuum chamber, reducing the pressure within the chamber, lowering the boiling point of water vapor. The evaporation of a small amount of water vapor from the material absorbs a large amount of evaporation heat, rapidly cooling the material. This technology offers advantages such as rapid cooling, uniform cooling inside and outside the material, and controllable temperature. However, traditional vacuum cooling technology can cause severe flash and splashing during the cooling process, resulting in significant loss of the material being cooled and severe contamination of the vacuum chamber and system. Furthermore, cooling uniformity is poor.

[0003] Traditional methods for suppressing splash typically involve covering the material container to prevent splashing or controlling the pressure drop to slow evaporation and reduce splashing. However, these methods fail to address the underlying cause of splashing, resulting in poor results. This has made fluid vacuum cooling a forbidden area for traditional vacuum cooling. Fluid vacuum cooling differs significantly from general solid vacuum cooling. General solids, especially cooked foods, form internal-to-external vapor escape channels during the cooking process. Therefore, during vacuum cooling, vapor can rapidly escape from the inside out, removing significant heat of evaporation and rapidly cooling the material. However, during fluid vacuum cooling, the surface of the fluid can rapidly evaporate, leading to rapid cooling. Some fluids even form a hardened layer after cooling. However, vapor deep within the fluid has no escape channel and can only escape through the accumulation of pressure, ultimately breaking through the surface in a flash explosion, resulting in splashing. Therefore, the fundamental problem with traditional vacuum cooling anti-splash methods lies in their failure to address the shortcomings of flash evaporation dynamics control and structural design. Addressing the splash problem in fluid vacuum cooling requires a completely new approach. Summary of the Invention

[0004] The present invention provides a fluid vacuum cooling method and system based on critical shear rate control, which greatly reduces splashing of fluid vacuum cooling, shortens vacuum cooling time, and greatly improves cooling efficiency.

[0005] The fluid vacuum cooling method based on critical shear rate control comprises the following steps: S1: placing the fluid material in a rotationally symmetrical vacuum chamber; S2: Establish a vacuum environment so that the ultimate vacuum pressure in the vacuum chamber is lower than the saturated vapor pressure corresponding to the target cooling temperature; S3: Stirring the fluid material to form a directional water migration channel from the interior of the material to the surface; S4: Control the stirring process so that the shear rate γ is always not lower than the critical shear rate γ of the fluid material crit , critical shear rate γ crit Determined by rheological testing and meeting the following requirements: Newtonian fluid: γ crit The minimum shear rate that causes the surface vapor film to rupture; Non-Newtonian fluid: γ crit is the critical shear rate at which the apparent viscosity changes suddenly; S5: The splashing droplets centrifugally flow back to the main body of the material along the wall of the vacuum chamber; S6: Remove boil-off gas.

[0006] Preferably, the inner surface of the vacuum cavity serves as both a material holding surface and a splash recovery surface.

[0007] Preferably, a vacuum environment is established by using a vacuum generating device; and the evaporated gas is removed by the vapor removal unit and the vacuum generating device.

[0008] A system for implementing the above-mentioned fluid vacuum cooling method based on critical shear rate control comprises: The rotationally symmetrical vacuum chamber has an inner surface structure that is used for both containing materials and centrifugally recovering splashing droplets. Fluid dynamics perturbator, generating γ≥γ in the vacuum chamber crit Shear force; A vacuum generating device is used to make the ultimate vacuum pressure of the vacuum chamber lower than the saturated vapor pressure corresponding to the target cooling temperature; Control module, dynamically adjusts the speed of the fluid dynamics perturbator and maintains γ≥γ crit ; Vapor removal unit, removes boil-off gases.

[0009] Preferably, one end of the vapor removal unit is connected to the vacuum cavity, and the other end is connected to the vacuum generating device.

[0010] Preferably, the control module controls the opening and closing of the vacuum generating device and the steam removing unit.

[0011] The present invention has the following beneficial effects: 1) It fundamentally solves the cause of fluid vacuum cooling splashing and significantly reduces fluid vacuum cooling splashing.

[0012] Establishing a phase change zone transfer mechanism: By disrupting the pressure shell through agitation, a directional channel for steam to flow to the surface is established, converting the evaporated and cooled material on the surface with the high-temperature material at depth, shifting evaporation from the depths of the material to surface evaporation. This transforms the previously uncontrollable phase change zone into stable evaporation at the surface, converting internal evaporation pressure energy into surface evaporation kinetic energy, and fundamentally resolving the causes of flashover and splashing.

[0013] The shear rate is critically controlled and dynamically adjusted according to the fluid state to effectively break through the transportation obstacles.

[0014] The rotationally symmetrical structural design that combines the material container and the vacuum chamber ensures that a small amount of splashed material can still be centrifugally recovered by flowing back through the inner surface of the chamber, completely solving the problem of splash loss.

[0015] 2) The temperature inside and outside the fluid is more uniform, which greatly shortens the cooling time.

[0016] 3) Eliminates the pollution problem caused by splashing.

[0017] The vacuum chamber is designed to have a rotationally symmetrical structure, and the vacuum chamber also serves as a material container. The vacuum chamber and the material container are combined into one. Even if there is still a small amount of splashing during the cooling process, the small amount of splashing material can still be centrifugally recovered by flowing back through the inner surface of the chamber. This structural design also completely solves the problem of splashing escape loss and pollution caused by the separation of the vacuum chamber and the material container in traditional vacuum cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a fluid vacuum cooling method based on critical shear rate control of the present invention; Figure 2 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] See also Figure 1 The fluid vacuum cooling method based on critical shear rate control of the present invention comprises the following steps: S1: Place the fluid material in a rotationally symmetrical vacuum cavity 1; the vacuum cavity 1 combines the material container and the vacuum cavity into one, and the inner surface of the cavity serves as both the material holding surface and the splash recovery surface.

[0021] S2: A vacuum environment is established by the vacuum generating device 3 so that the ultimate vacuum pressure in the vacuum chamber 1 is lower than the saturated vapor pressure corresponding to the target cooling temperature, so as to ensure that the final target cooling temperature is achieved.

[0022] S3: Using the fluid dynamics disturber 2 to stir the fluid material, so that the internal high-temperature material and the surface low-temperature material are mixed, forming a directional moisture migration channel from the interior of the material to the surface.

[0023] S4: Control the stirring process so that the shear rate γ is always not lower than the critical shear rate γ of the fluid material crit , critical shear rate γ crit Determined by rheological testing and meeting the following requirements: Newtonian fluid: γ crit The minimum shear rate that causes the surface vapor film to rupture; Non-Newtonian fluid: γ crit is the critical shear rate at which the apparent viscosity changes suddenly.

[0024] γ crit Determined through experimental rheological testing. As the temperature of the vacuum cooling fluid decreases, the fluid viscosity will change. In the experiment, rheological testing is used to establish a fluid temperature-viscosity curve and determine the viscosity mutation point.

[0025] S5: The splashing droplets centrifugally flow back to the main body of the material along the wall of the vacuum chamber 1.

[0026] S6: Removing evaporated gas. Most of the evaporated steam is condensed and removed by the steam removal unit 5 , and the remaining gas is removed by the vacuum generating device 3 .

[0027] In summary, the present invention fundamentally solves the cause of fluid vacuum cooling splashing, greatly reduces fluid vacuum cooling splashing, makes the temperature inside and outside the fluid more uniform, greatly shortens the cooling time, and eliminates the pollution problem caused by splashing.

[0028] See also Figure 2 , a system for implementing a fluid vacuum cooling method based on critical shear rate control, comprising: a rotationally symmetric vacuum chamber 1, a fluid dynamics disturber 2, a vacuum generating device 3, a control module 4 and a vapor removal unit 5.

[0029] The inner surface of the vacuum chamber 1 is used for both holding materials and centrifugation to recover splashed droplets. The fluid dynamics disturber 2 generates γ≥γ in the vacuum chamber. crit The fluid dynamics disturber 2 is partially arranged in the vacuum chamber 1 for stirring, and partially arranged outside the vacuum chamber 1 for providing power for stirring.

[0030] The vacuum generating device 3 makes the ultimate vacuum pressure of the vacuum chamber 1 lower than the saturated vapor pressure corresponding to the target cooling temperature.

[0031] The control module 4 dynamically adjusts the speed of the fluid dynamics disturber 2 and maintains γ≥γ crit In addition, the opening and closing of the vacuum generating device 3 and the steam removal unit 5 are controlled simultaneously.

[0032] The vapor removal unit 5 removes most of the evaporated gas. The remaining gas is removed by the vacuum generating device 3. One end of the vapor removal unit 5 is connected to the interior of the vacuum chamber 1, and the other end is connected to the vacuum generating device 3.

[0033] The following are applications of the fluid vacuum cooling method of the present invention: 1) Cooling the ketchup: 90℃→10℃ dynamic control: Initial γ = 8s -1 → Final temperature γ=35s -1 ; Result: Cooling time 28 minutes, splash rate 2.1%.

[0034] 2) Compensation for excess black sesame paste: 70℃→10℃ control: Initial γ = 28s -1 At 15℃, the measured γ_y=55s -1 → Enable γ≥44s -1 ; Result: Spatter rate 2.8%.

[0035] 3) Syrup cooling: 90℃→10℃ control: Initial γ = 85s -1 (Newtonian fluid) → Final temperature γ = 42s -1 ; Result: Spatter rate 3.2%.

[0036] See Table 1 below for a comparison of splash rates. It can be seen that the splash rate is significantly reduced by applying the fluid vacuum cooling method of the present invention.

[0037] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0038] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A fluid vacuum cooling method based on critical shear rate control, characterized in that: The following steps are involved: S1: placing the fluid material in a rotationally symmetrical vacuum chamber; S2: Establish a vacuum environment so that the ultimate vacuum pressure in the vacuum chamber is lower than the saturated vapor pressure corresponding to the target cooling temperature; S3: Stirring the fluid material to form a directional water migration channel from the interior of the material to the surface; S4: Control the stirring process so that the shear rate γ is always not lower than the critical shear rate γ of the fluid material crit , critical shear rate γ crit Determined by rheological testing and meeting the following requirements: Newtonian fluid: γ crit The minimum shear rate that causes the surface vapor film to rupture; Non-Newtonian fluid: γ crit is the critical shear rate at which the apparent viscosity changes suddenly; S5: The splashing droplets centrifugally flow back to the main body of the material along the wall of the vacuum chamber; S6: Remove boil-off gas.

2. The fluid vacuum cooling method based on critical shear rate control according to claim 1, characterized in that: The inner surface of the vacuum chamber serves as both a material holding surface and a splash recovery surface.

3. The fluid vacuum cooling method based on critical shear rate control according to claim 1, characterized in that: A vacuum environment is established using a vacuum generating device; and evaporated gas is removed by a vapor removal unit and the vacuum generating device.

4. A system for implementing the fluid vacuum cooling method based on critical shear rate control according to claim 1, characterized in that: include: The rotationally symmetrical vacuum chamber has an inner surface structure that is used for both containing materials and centrifugally recovering splashing droplets. Fluid dynamics perturbator, generating γ≥γ in the vacuum chamber crit Shear force; A vacuum generating device is used to make the ultimate vacuum pressure of the vacuum chamber lower than the saturated vapor pressure corresponding to the target cooling temperature; Control module, dynamically adjusts the speed of the fluid dynamics perturbator and maintains γ≥γ crit ; Vapor removal unit, removes boil-off gases.

5. The system according to claim 4, characterized in that One end of the vapor removal unit is connected to the vacuum chamber, and the other end is connected to the vacuum generating device.

6. The system according to claim 4, characterized in that The control module controls the opening and closing of the vacuum generating device and the vapor removing unit.

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