JPS61250479A - Continuous cooling method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The method of the present invention is suitable for continuous freezing of continuum or solid objects, pre-cooling for low-temperature treatment, aging treatment within a short period of time, and product inspection. It relates to a continuous cooling method for continuous cooling on a line.

[Conventional technology]

Continuums and solids are cooled continuously by passing them through a cooling tank having an inlet and an outlet. Any cooling method may be used as long as it can obtain cold energy, but from an industrial perspective, refrigeration is recommended because it cannot be used depending on the object to be cooled, requires post-processing, and costs. It is common to use a cold gas (usually air) obtained by a machine. The cooling tank has a built-in evaporator for a refrigerator, or a chamber containing a built-in evaporator is connected to the system through a duct, etc., and while the atmosphere inside the tank is circulated, cold air is continuously delivered to the object to be cooled as it passes through. It cools down by exposing it to water.

However, due to the entry of these objects into the cooling tank,
Near the inlet of the cooling tank, surrounding outside air enters. Then, this moisture in the outside air becomes low temperature in the cooling tank,
A large amount of very small frost occurs.

FIG. 1 shows the relationship between the amount of water per INryr in the standard state of air, obtained from the saturated vapor pressure table.

For example, when the atmospheric temperature is 25°C, approximately 26 g/Nn? It becomes saturated with water vapor of about 17 g/Nr at 65% relative humidity.
rr of water vapor is present. The saturated vapor pressure at low temperatures and extremely low temperatures is extremely low, and when this outside air is cooled to a low temperature of -20° C. or lower, for example, most of the moisture contained in the outside air condenses and becomes frost.

These frosts then ride on the flow of the atmosphere circulating within the cooling tank and adhere to various parts within the cooling tank. In particular, when frost adheres to the evaporator, which is the heat exchanger of the refrigerator, and its thickness increases, the heat exchange efficiency deteriorates and the refrigeration capacity decreases significantly. In addition, when cooling the solids in the cooling tank, if a conveyor or the like is provided to transport the solids, and if each part has rotating parts, the rolls, bearings, and other parts of these rotating bodies are also cooled to low temperatures. ing. When the surrounding outside air enters, dew condensation and frost forms on the rolls and bearings of these rotating bodies, and the resulting rotational defects can cause transportation problems and malfunctions. .

[Problem that the invention seeks to solve]

The present invention aims to solve the problems of the conventional technology as described above, and aims to obtain a stable cooling temperature without reducing the refrigerating capacity, and to achieve a continuous cooling temperature without causing rotation failure of the rotating body. Alternatively, it is an object of the present invention to provide a method that can stably, efficiently and continuously cool an individual.

[Means for solving problems]

According to the present invention, a continuous cooling method is provided, in which the object to be cooled is continuously cooled to below -20°C by passing it through a cooling tank using refrigerator equipment. The cooling process is characterized by continuous cooling while removing frost generated in the cooling tank.

The object to be cooled in the present invention is a long object that is continuously connected in the length direction or an individual placed on a conveyor sheet such as a conveyor for continuous processing. The purpose of this is to perform cooling treatment.

Continuous materials include thick sheets, films, and bundles of continuous fibers, which are cooled or frozen for low-temperature treatment and pre-cooling. In addition, in solid products, it is used to quickly freeze fresh and frozen foods to storage temperatures, to continuously cool them for on-line product inspection, and to perform aging treatments within a short period of time. Rapid freezing is necessary for perishable products in order to quickly pass through the maximum ice crystal formation zone of around 0 to -15℃ and freeze with many small ice crystals to prevent quality changes. Reduce cooling time. After that, storage can be done in a regular refrigerator, because when trying to obtain a low temperature with a refrigerator, the lower the temperature, the lower the efficiency of the refrigerator, and it is difficult to obtain a large freezing capacity. This is because the device needs to be larger and energy consumption increases. Therefore, continuous cooling is used only for rapid freezing at a low cooling temperature level to increase efficiency.

These objects to be cooled enter the cooling tank through the inlet, pass through the cooling tank, and are carried out through the exit, where they are continuously cooled. The cooling tank has a built-in evaporator for a refrigerator, or a chamber containing a built-in evaporator is connected to the system through a duct, etc., and while the atmosphere inside the cooling tank is circulated, cold air is delivered to the object to be cooled as it passes through. Cool by applying

As the refrigerator, equipment shown in Table 1 below is generally used depending on the required cooling temperature.

Table 1 Cooling temperature and refrigerator equipment When moist air is exposed to low temperatures, it is cooled in a very short time, but the formation and properties of frost differ depending on the temperature. In Figure 2, consider the case where the insulation is shielded from the atmosphere (25°C here) and the low temperature inside the cooling tank. Simply thinking, the temperature gradient when the temperature in the cooling tank is 0°C, -20°C, and -70°C is (at, (bl
, (cl.
When air is about to enter the cooling tank,
This atmosphere is cooled over time and reaches 0° C. within a very short time after entering the cooling tank. During this process, as shown in Figure 1, the moisture in the atmosphere is condensed into small water particles, which dew, condense, become water, and accumulate in various parts of the interior of the artificial body and the inner wall of the cooling tank. Next, in the case of (bl), as in case (a), it is exposed and condenses to become water, but it is further cooled and a portion of it becomes a tank of ice. , the amount of atmospheric moisture that becomes minute frost particles and floats in the atmosphere inside the cooling tank also increases.Furthermore, if the temperature inside the cooling tank is extremely low, as in case (C),
Coupled with the fact that the cooling time for atmospheric moisture is extremely short, most of the moisture in the atmosphere becomes microscopic frost particles that float in the cooling tank. In addition, snow formed by frost gathering is relatively moist at temperatures above -20℃, but at temperatures below -20℃, it has very little moisture and is smooth. It shows a powder-like state.

Here, a schematic diagram of a cooling tank that can be used in the present invention is shown in FIG. Entrance 4
and an outlet 5. Inside the cooling tank 1, an evaporator 6 of a refrigerator and a heater 7 for temperature control are provided, and a partition plate 9 is provided so that the atmosphere inside the cooling tank is circulated in the direction of arrow a by a fan 8.
It is separated by. The object to be cooled is cooled by applying cold air cooled by the evaporator 6 to the object to be cooled.

The atmosphere sent into the tank is cooled again by the evaporator 6 and circulated through the filter 10 provided at the bottom of the tank.

Here, in the cooling tank cooled to -20° C. or lower, a large amount of minute frost that has settled due to passage of the object to be cooled floats inside the cooling tank by riding on the flow of the atmosphere. In order to remove this frost, a filter 10 such as a mesh is provided in the middle of the circulating atmosphere in the cooling tank. It goes without saying that the finer the mesh is, the better it is for removing frost, but on the other hand, it is necessary to ensure that it does not impede the flow of the atmosphere within the cooling tank. In other words, it is necessary to prevent the flow velocity from decreasing, and if the cold air hits the object to be cooled at right angles, a cooling time of about A is sufficient at a wind velocity of 1 m/1 II inch, and the cooling time is sufficient for the evaporator of the refrigerator and the inside of the tank. Even when considering heat exchange with the atmosphere, it can be seen that lowering the wind speed reduces efficiency.

Moreover, FIG. 4 shows the refrigerating capacity of the refrigerator with respect to the roughness of the mesh. (A) is 10 mesh/1nch, (B)
is 18 mesh/1nch-(c) is 30 mesh/1
This is a case where each mesh of nch is attached. These differences are due to the fact that the flow rate of the atmosphere in the cooling tank to the evaporator is different, and the heat exchange between the evaporator and the atmosphere is different. In this way, it is necessary to select a mesh roughness that does not create resistance to the circulation of the atmosphere within the cooling tank. Further, it is possible that a small amount of fine dust may be generated from the object to be cooled that is passed through the cooling tank, and it is preferable to remove this as well as frost.

Next, for example, Figure 5 shows the refrigerating capacity of the refrigerator when the mesh shown in (b) is attached and air is actively introduced into the cooling tank to generate a large amount of frost inside the cooling tank. . Here, (i) is before introducing the atmosphere, and (ii) is the atmosphere (25℃, 65℃).
After introducing 5rd %R) (), (iii) similarly changes the same atmosphere to Ion? As shown in the figure below, the refrigeration capacity decreases depending on the amount and amount of air supplied. Here, these (ii)
When the filter mesh is removed from the state of (iii), the refrigerating capacity is shown as (iv). This refrigerating capacity almost matches (i), and is recovered to almost the same level as before introducing the atmosphere. On the other hand, the removed
There is a lot of frost on Nosh, and each grid is clogged. The appearance of the adhesion is that frost gathers around the grid lines and grows, creating a snow-like condition.

There is no need for the size of one grid to be smaller than a grain of frost. In this way, the filter mesh collects frost generated in the cooling tank and prevents frost from forming on the surface of the evaporator of the refrigerator.

By periodically replacing this filter mesh, frost can be removed.

On the other hand, if dehumidification or atmosphere replacement is performed before the cooling tank to minimize the intrusion of atmospheric air, the replacement period can be greatly extended.

Further, the frost can also be removed using static electricity. The frost particles that are generated in the cooling tank and carried by the circulating atmosphere in the cooling tank repeatedly collide with and repel various parts such as the walls and objects to be cooled in the cooling tank. At the moment of collision, frost or local deformation of each part occurs, and electric charges are transferred through the contact surfaces. Then, they instantly repel and separate at a very high speed. The frost becomes electrically charged due to the charge movement caused by this collision and repulsion. By repeating this process many times, the amount of charge on the frost reaches saturation. This charged frost may be collected using the principle of electrostatic precipitation. In this case, of the two electrodes,
Apply a negative DC high voltage to one wire electrode. By generating a corona current between these electrodes, the other electrode receives the action of a strong Ronca, causing frost to accumulate.

A charging section may be provided on this upstream side to promote charging of the frost.

On the other hand, the material of the mesh filter is not particularly limited, such as metal or polymeric material, but it is also possible to utilize the electrification caused by the collision of the atmosphere in the cooling tank with the filter mesh. For example, nylon 6, nylon 66, etc. are easily charged positively, and Teflon, polyethylene, etc. are easily charged negatively. By utilizing this property, the present invention prevents frost generated in the cooling tank from adhering to the surface of the evaporator of the refrigerator, prevents a decrease in the refrigerating capacity, and stabilizes the static electricity of the mesh filter. Continuous cooling can be performed over a long period of time. Furthermore, frost is prevented from adhering to various parts within the cooling tank, and there is no rotational failure of the rotating body, and there is no possibility of defects in transportation or malfunctions.

〔Example〕

The present invention will be further explained below with reference to Examples.

Embodiment 1 As shown in FIG. 3, a mesh filter 10 provided at the bottom of the cooling tank is provided so as to be pulled out from the outside of the cooling tank in the direction of the arrow (b1) using a handle 11.

■ Body to be cooled Niacrylic synthetic fiber (product name: Cashmilon ■) A tow-like continuous fiber bundle with a single yarn denier of 3 d and a total denier of 500,000 d.

■ Temperature inside the cooling tank: -70°C (using a two-way refrigerator using R-12 and R-13 fluorocarbon gases).

■ Tow passing speed in the cooling tank: 8 m/l 1 lin ■ Cooling tank opening and exit section: Width 200 m, slit-shaped opening with a smooth inner surface and a gap of 8.

■ Circulating air volume in the cooling tank: Approx. 40 rrr/win ■ Filter mesh: Area: 10100 x 100.
Phase: When the tow was continuously cooled under conditions of 18 mesh/1 nch or more, continuous operation for about 4 hours was possible. This is due to the heat load Qkcal of the tow being cooled from 25°C to -70°C.
/h is =810 (kcal/h) (assuming that the specific heat of the tow is approximately 0.32 cal/g・℃), and the net refrigerating capacity that the refrigerator contributes to cooling the tow is This is the time required for the temperature to drop to 810 kcal/h or less at 70°C.

When the frame forming the filter was replaced with the same one, continuous operation for an additional 4 hours was possible.
This repetition made it possible to maintain continuous operation for a long time.

Embodiment 2 As shown in FIG. 6, the mesh filter 0 is a rotating mensch 11. The frost generated in the cooling tank forms a frost-resistant laminated layer 12 on the outer periphery of the mesh due to the circulation of the atmosphere in the cooling tank. Then, the rotating shaft 1 of the rotating mesh 11
3 by 90° in the direction of arrow (C), and
Bring 2 downward.

Then, from the nozzle 15i provided in the nozzle pipe 14 disposed at the axial center of the rotating mesh 11, the dry air supply port 16 of the nozzle pipe 14 is
The dry air supplied by the mesh is blown out to blow away the frost attached to the outer periphery of the mesh. This frost is in chamber 1
It falls on the inner wall of No. 7 and accumulates from below. This chamber 1
A wire heater 18 is wound around the outside of the pipe 7, and frost melted by the heat becomes water and is discharged from a drain port 19.

Further, the frost cake that cannot be removed by the dry air jetted from the nozzle 32 is also removed by a frost stripping plate 20 provided at the rear upper end of the chamber 34 when the rotating mesh 11 rotates.

By repeating this operation, frost generated in the cooling tank can be constantly removed.

When cooling was carried out in the same manner as in Example 1 using this defrosting method, continuous operation for a long period of time was possible without decreasing the capacity of the refrigerator. In addition, at this time, the water in the drainage water contained minute short fiber waste (fly) produced from the tow, which could be discharged at the same time.

Embodiment 3 As shown in FIG. 7, a conveyor 21 is placed in a cooling tank,
Convey in the direction of arrow (e). Fish are placed on the conveyor for rapid freezing, and are carried in through an inlet 4 at a constant speed, and the frozen fish are carried out through an outlet 5 and sent into a freezer for storage. The temperature inside the cooling tank is maintained at -70° C. using a binary refrigerator, and the atmosphere inside the cooling tank is circulated at a wind speed of about 4 m/sec. Fish is O~-1
It passes through the zone of maximum ice crystal formation at 5°C in an extremely short time. The inlet 5 and outlet 6 are open to the extent that fish can pass through, and a curtain-like plate 22 is attached to prevent a large amount of outside air from flowing in. At the bottom of this cooling tank,
The rotating mesh 11 shown in FIG. 6 is arranged and is famous for being able to continuously remove the frost 12 accumulated on the outer periphery of the rotating mesh 11.

When fish were rapidly frozen using this defrosting method, the freezing capacity of the refrigerator was stably maintained, and rapid freezing could be performed continuously over a long period of time without deteriorating the quality of the fish.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the amount of moisture per INrrr in the standard state of air, determined from the saturated vapor pressure table. FIG. 2 is a model diagram showing the temperature gradient of the heat insulating section between the outside air and the inside of the cooling tank. FIG. 3 is a schematic view of the interior of the cooling tank, with (A) being a longitudinal sectional view and (B) being a side sectional view. FIG. 4 shows the refrigerating capacity that can be cooled in the cooling tank with respect to the roughness of the mesh provided in the middle of the circulation path of the atmosphere in the cooling tank. FIG. 5 shows how the refrigerating capacity decreases when air is supplied into the cooling tank. FIG. 6 is a schematic diagram of an apparatus in which a mesh filter placed in the lower part of the cooling tank is rotatable, with (A) being a longitudinal cross-sectional view and (B) being a side cross-sectional view. FIG. 7 is a schematic diagram of a device equipped with an electric defrost at the bottom of the cooling tank, with (A) being a longitudinal cross-sectional view and (B) being a side cross-sectional view. DESCRIPTION OF SYMBOLS 1... Cooling tank, 2... Freezer, 3... Heat insulation layer, 4... Inlet, 5... Outlet, 6... Evaporator, 7... Heater, 8... Fan, 10...
Filter, 11...Rotating mesh, 13...
・Rotating shaft, 15... Nozzle, 17... Chamber, 19... Drain port.

Claims (1)

[Claims] 1. The object to be cooled is passed through a cooling tank equipped with refrigerator equipment to continuously cool it down to -20°C or lower, while removing frost generated in the cooling tank. Continuous cooling method.