KR20060051873A - Air-distribution unit for fast freezing - Google Patents

Abstract

The present invention provides an air distribution unit capable of providing high speed cold air to the surface of an object to be cooled while maintaining an acceptable pressure drop value.

According to an aspect of the present invention, there is provided an air distribution unit for rapidly freezing a liquid in a container, comprising: a supply flow path through which cold air is supplied and a return flow path through which the supplied cold air returns, wherein the supply flow path and the return flow path are formed periodically, And the return flow path are separated by crossbars separating the supply air flow and the return air flow.

In addition, at one end of the crossbar, a spacer for guiding the air supplied from the supply passage to return to the return passage at a high speed is installed at a constant distance from the container surface.

Description

Air distribution unit for quick freezing {AIR-DISTRIBUTION UNIT FOR FAST FREEZING}

1 shows a temperature distribution (° C.) for an air flow along a 10 mm opening of a surface.

2 shows temperature distribution (° C.) for a central inlet air flow (20 mm diameter) with a 2 mm spacing.

3 shows the pressure distribution Pa for periodic air supply into the gap.

4 shows the temperature distribution for the periodic air supply into the interval.

5 is a schematic view of an air distribution unit for periodic design with crossbars.

6 shows the pressure distribution Pa for the periodic design of an air distributor with crossbars.

FIG. 7 shows temperature distribution (° C.) for the periodic design of an air distributor with a crossbar. FIG.

8 shows the velocity distribution in m / sec for the periodic air supply into the gap with rungs.

9 is a perspective view of an air distribution unit providing periodic air supply into the gap with rungs;

Figure 10 is a perspective view showing a state in which a plurality of air distribution unit is installed on the surface of the cube-shaped container.

* Description of symbols on the main parts of the drawings *

10: air distribution unit 11: crossbar

12: spacer 15: rod

21: supply flow path 22: return flow path

23: connecting passage 25: supply slot

26: return slot 28: discharge port

29: cold air supply port 30: container

31: container surface 35: duct

The present invention relates to a system with periodic feeding for rapid freezing and super-fast freezing of a vessel to a temperature of -40 ° C. In particular, high speed cooling is carried out by increasing the air velocity in a special air distribution unit to increase the heat transfer at the surface of the vessel. To a quick refrigeration air distribution system.

In Russian Patent No. 2189750 is known a system for rapid freezing of dough, which comprises a preliminary cooling chamber, a quick freezing chamber, a coating chamber and a delivery sub-system commonly applied to all these chambers. These chambers are connected via an air duct in which an air blower for supplying and returning air is located, which improves product quality during quick freezing.

Apparatus for producing a frozen flat food and drink of the Russian Patent No. 2215248 is known in the food processing industry. The apparatus includes an adiabatic chamber, an air cooler, a net-belt transporter, and a product molding located at the inlet of the chamber. The top of the net-belt transporter is surrounded by an air inlet tube with nozzles, which direct the air flow perpendicularly to the net-belt from below and from above. This invention accelerates food freezing and reduces freezer traces.

Pages 1049 to 1061 of International Journal of Heat and Mass Transfer, No. 46 (2003), were studied with blowing air on a surface covered with naphthalene, with or without an air return tube. The results of studies on the heat and mass transfer characteristics of the air stream as it exits the guide channel are known. The air supply and return channels are periodically positioned alternately at different intervals.

U. S. Patent No. 5,551, 251 discloses a tunnel refrigerator with a moving conveyor for rapid freezing of meat products. For rapid freezing, cold air flows from below and above the product located on the moving conveyor are used. Air flow is formed through the orifice of the air duct.

All known systems do not have high levels of heat transfer to air because the product is located some distance from the nozzle or other air supply. However, the distance from the nozzle to the object to be cooled is very important for the heat transfer value.

The prototype system of an air distribution system invented for rapid freezing of US Pat. No. 6,557,367 is a chiller / freezer with multiple channels that forms an opening for returning air when air is supplied to a moving conveyor provided with the product. The air travels along the channel and exits in the vertical direction through the opening, with typical temperatures of cooling air being -48 to -49 ° C.

Most of the existing systems for rapid freezing are in the form of a conveyor for continuously supplying cooled products. At the same time, there are many application systems associated with ultra-fast refrigeration of containers containing liquids therein. The problem with these systems is that they only supply air to the five sides of the vessel at high speed. Expensive high efficiency air distribution systems are required to provide air at high speed to the surface of the vessel.

Also, using such a dispenser on six sides of the container is not efficient. This is because if the container is sealed with a lid, it can leak liquid or significantly reduce the heat transfer rate.

The present invention is to solve the above problems, an object of the present invention is to provide an air distribution unit that can provide high-speed cold air to the surface of the object to be cooled while maintaining an acceptable pressure drop value in the air distribution unit To provide.

In order to achieve the above object, the air distribution unit according to the present invention, in the air distribution unit for quick freezing the liquid in the container, includes a supply flow path for supplying cold air and a return flow path for returning the supplied cold air; The supply flow passage and the return flow passage are formed periodically.

In addition, the supply flow path and the return flow path are separated by a runway separating the supply air flow and the return air flow, one end of the cross to guide the air supplied from the supply flow path to return to the return flow path at a high speed Spacers are installed at regular intervals from the container surface.

The object of the invention is achieved by selecting the optimal design for cooling the object surface determined using the calculation method. It is necessary to rapidly freeze a vessel formed in a cuboid shape from a temperature of + 30 ° C to a temperature of -40 ° C. The cooling medium is air with a temperature of -100 ° C. The main task of the calculation is to select the optimal design that allows the air to flow so that the heat transfer rate is uniform over the entire cooling surface while still exceeding the value of 150 W / m ² Κ. The pressure drop in the vent should not be high enough to allow the use of a conventional air blower for air circulation.

To solve this task, it is necessary to calculate air flow conditions in different designs and compare the heat transfer rates on the cooling surface.

It is preferable to carry out the heat transfer analysis on the actual object by a numerical analysis method. These methods of interpretation are based on substituting the differential equation with the algebraic equation for a given net of nodes.

In order to carry out the optimal design, the Navier-Stoke equation system was calculated along with the energy equation. Velocity, pressure and temperature fields were also calculated as two-dimensional models. In some of the air distribution units, the velocity may be high and turbulence may occur, and the K-ε turbulence model was used to account for the effect of turbulence on this flow characteristic.

In numerical calculations, a 252 × 40 node net covering an area of 0,126 × 0.01 m ² was used. The software package PHOENICS was used to calculate these equations.

The heat transfer rate is α = q / (T _surf T _air ), where q is the heat flux at the surface of the object to be cooled, T _surf is the local surface temperature and T _air is the air temperature in the vent.

Several designs have been analyzed to determine their advantages and disadvantages.

Flat surface

For the first time, heat transfer was analyzed for the case of air flow along the flat plane. The temperature distribution is shown in FIG.

According to the calculations, the air velocity should be 28 m / sec to provide an average heat transfer rate of about 100 W / m ₂ Κ. In this case, the heat transfer rate values are relatively unevenly distributed along the surface and a maximum value (275 W / m ₂ K) is observed at the surface starting point, but the heat transfer rate (82 W / m ₂ K) at the end of the surface is much smaller.

The object of the invention can be achieved when the heat transfer rate values are distributed evenly along the surface or the maximum value is located at the center of the surface. At these flow rates, the air flow rate on all cooling surfaces is 7.4 CMM, with a pressure drop of 438 Pa at 10 mm flow intervals.

Conclusion-Flow / pressure drop characteristics are achievable but the heat transfer rate is lower than required.

Direct air flow towards surface center

Symmetric flow arrangements were considered to increase the heat transfer rate at the surface center. The design structure and the calculation results are shown in FIG. The angle between the cooling surface and the air distributor is 2 mm.

The figure shows the velocity vector and the temperature distribution. Calculations for the flow situation indicate that even at higher flow rates (about 2.7 CMM), it is necessary to operate at high pressure drop values (about 500 Pa) to provide a heat transfer rate of 128 W / m ₂ K. Increasing the heat transfer rate by decreasing the spacing causes the pressure drop to be severe.

Periodic design with crossbar

At these stages, a variant of the air distribution unit with a periodic supply / return flow pattern with crossbars separating supply and return flows was considered. In each case the calculation results for the pressure, velocity and temperature distributions are given in FIGS. 3 and 4.

As a result, this variant can be effectively used for cooling purposes.

At a flow rate of 3.3 CMM and a pressure drop of 170 Pa (2 mm angular), this design can provide a heat transfer rate of 156 W / m ₂ Κ. In the case of 1 mm small spacing, the pressure drop is increased to 400 Pa and the heat transfer rate gradually rises to 161 W / m ₂ K. Changes to the geometry of the air distribution unit (supply and return) also do not significantly change the heat transfer rate.

Crossbar Spacer  Periodic design

The final design of the air distribution unit is shown in FIG. 5, where heat transfer characteristics are determined.

In this design, supply and return flows are performed periodically, as before. The crossbar 11 separates the supply air flow and the return air flow, and a spacer 12 is formed at one end of the crossbar 11 to form a narrow connecting flow path 23 between the container surface 31 and the spacer 12. Air is supplied from the supply flow passage 21 to return to the return flow passage 22 at a high speed, and the air flowing from the supply flow passage 21 to the return flow passage 22 is relatively uniform on the container surface 31. The heat transfer rate is distributed.

Here, the distance W between the air distribution unit 10 and the container surface 30 is 0.8 to 2 mm and most preferably 1 mm.

The calculation results for the pressure, temperature and velocity distributions of the air distribution unit 10 with the crossbar 11 and the spacer 12 are given in FIGS. 6 to 8.

As can be seen from the various designs as described above, the best variant of the present invention is a periodic design having a crossbar 11 and a spacer 12.

The heat transfer characteristics in the periodic design with the crossbar 11 and the spacers 12 are better than the heat transfer characteristics in the previous design. At a flow rate of 1.67 CMM and a pressure drop of 140 Pa, the heat transfer rate is 151 W / m ₂ Κ. When the air flow rate doubles, the pressure drop increases up to 500 Pa and the heat transfer rate is 185 W / m ₂ Κ.

9 shows an air distribution unit 10 including a crossbar 11 and a spacer 12 to perform periodic air distribution in order to achieve the optimum efficiency among the various designs as described above.

5 and 9, an air distribution unit 10 according to an exemplary embodiment of the present invention will be described. The air distribution unit 10 has a hexahedral shape as a whole, and one surface of the air distribution unit 10 is disposed on the container surface 31. A supply slot 25 for supplying cold air and a return slot 26 for returning the supplied cold air are formed.

The supply slot 25 is connected to the supply flow passage 21 through which cold air is supplied, and the return slot 26 is connected to the return flow passage 22 through which cold air returns, and is returned to one end of the return flow passage 22. A discharge port 28 through which cold air is discharged is formed.

In addition, the supply flow passage 21 and the return flow passage 22 are alternately formed so that the cold air supplied from the supply flow passage 21 can return to the neighboring return flow passage 22. 25 and the return slot 26 are also formed alternately. In this embodiment, the supply passage 21 and the return passage 22 are alternately formed, but unlike the above embodiment, two supply passages 21 and one return passage 22 are periodically formed, such as repeated. It can be variously changed, such as formed.

The supply passage 21 and the return passage 22 are separated by the crossbar 11 of FIG. 5 which separates the supply air flow and the return air flow, and one end of the crosspiece 11 is provided with a spacer 12. The spacer 12 maintains a constant distance (W) from the container surface 31 and forms a connection flow path 23 so that the cool air supplied from the supply flow path 21 returns to the return flow path 22 at a high speed. The cold air flowing along the connection flow path 23 distributes the heat transfer rate on the container surface 31 relatively uniformly.

The width of the supply slot 25 and the return slot 26 formed between the spacer 12 is preferably 3 to 8mm and most preferably 5mm.

Also, at least three welds located across the feed slot 25 and the return slots 26 to provide a gap in the range 0.8 mm to 2 mm between the vessel surface 31 to be cooled and the air distribution unit 10. Bar 15 is installed in the air distribution unit 10.

On the opposite side of the surface on which the supply slot 25 and the return slot 26 are formed, a cold air supply port 29 to which the duct 35 shown in FIG. 10 is connected is formed, and the supply flow path 21 is the cold air supply port. Although it is in communication with (29), the return flow path 22 is not in communication with the cold air supply port (29).

When cold air is blown from the air distribution unit 10 configured as described above to the cold air supply port 29, the cold air is discharged to the supply slot 25 through the supply flow path 21. The cold air discharged into the supply slot 25 is sucked through the return slot 26 and discharged to the discharge port 28 through the return flow path 22.

FIG. 10 is a perspective view showing a state in which a plurality of air distribution units 10 are installed on a hexahedral container surface 31. In order to rapidly freeze the liquid in the container 30, the air distribution unit 10 is preferably provided on four or more of six surfaces of the hexahedral container 30 to supply the cold air.

As described above, the air distribution unit 10 is installed on a plurality of surfaces, and in the air distribution unit 10, the supply air flow and the return air flow are periodically formed, thereby supplying high-speed cold air, but reducing the pressure drop value. .

The air distribution unit according to the present invention can provide a high speed cold air on the surface of the object to be cooled while maintaining an acceptable pressure drop value, such an air distribution unit may be applied to objects and foods such as drugs, drugs, biology, etc. It can be effectively used in a variety of industrial or commercial systems for rapid and rapid refrigeration.

Claims (7)

An air distribution unit for quick freezing a liquid in a container, And a supply passage through which cold air is supplied, and a return passage through which the supplied cold air returns, wherein the supply passage and the return passage are formed periodically. The method of claim 1, And the container has a hexahedron shape, and the air distribution unit is installed on at least four of the six surfaces of the container to supply cold air. The method of claim 1, And the air distribution unit is installed at an interval of 0.8 to 2 mm from the container surface. The method of claim 3, wherein And a plurality of rods are installed in the air distribution unit to maintain a distance between the air distribution unit and the container surface. The method of claim 1, And the supply passage and the return passage are separated by crossbars separating the supply air flow and the return air flow. The method of claim 5, One end of the crosspiece is provided with a spacer for guiding the air supplied from the supply passage to return to the return passage at a high speed. The method of claim 6, And a width of the supply slot and the return slot formed between the spacers is 3 to 8 mm.

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