JP3440157B2 - Tunnel freezer for food freezing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel freezer for freezing foods, and more particularly to a tunnel freezer for freezing foods by colliding them with a low temperature cold air flow.

[0002]

2. Description of the Related Art A conventional tunnel freezer used for cooling and freezing foods or the like places an object to be cooled (food) on a belt conveyor or a net conveyor and continuously introduces it into a cooling zone in the tunnel. It is transferred and forced convection is caused in the cold gas gasified cold gas in the cooling zone to cause a stirring gas flow around the object to be cooled, or countercurrent or parallel to the transfer direction of the object to be cooled. It adopts a freezing system that cools a flowing cold gas flow.

In the case of the above method, heat transfer can be considered as being divided into heat transfer due to contact between the surface of the object to be cooled and the cold gas and heat transfer between the cold gases, but the contact heat transfer is the gas transfer. The faster the flow, the more effective. In the latter case, the heat transfer between the cold gases is not expected to improve the heat transfer coefficient when the gas flow is laminar. That is, in the case of the uniform flow cooling or refrigerating system, the heat transfer coefficient between the cold gases cannot be improved, and as a result, the heat transfer performance is poor and a cooler having a large air volume and a large heat transfer area is required. Came.

Therefore, in order to obtain the best cooling effect, the cold gas mass is made into a finely divided and scattered flow state, and the gas mass is not brought into contact with the surface of the object to be cooled but the gas mass is dispersed particles. It was found that it is necessary to bring the dispersed particles into close contact with each other in a fine state, and therefore, the gas flow is dispersed in a large number of low-temperature, high-speed slit-like jet streams and made to collide at right angles with the surface of the object to be cooled. A so-called impinging jet theory, in which the surface is placed in a low-temperature high-speed turbulent gas flow to increase cooling efficiency, a so-called impinging jet theory has been proposed, and a food tunnel freezer applying this theory has been developed to greatly improve the heat transfer coefficient of the surface to be cooled. Is seen. However, in this freezer, a conventional plate fin type heat exchanger is used for the air cooler, which is the impinging jet source, and further, a straightening plate, a slit, and a nozzle for forming the impinging jet are required, and the original The situation is not sufficient to reduce the size and increase the capacity of the freezer, which is the objective.

On the other hand, in the case of cooling and freezing foods, in the initial stage of cooling, water vapor mainly generated from warm unfrozen foods concentrates at the inlet of the coil row of the cooling coil in the cooler to form frost. However, it becomes an obstacle to the cooling coil array, obstructs the flow of cold gas, lowers the function of the refrigerator, and the frozen state of the frozen product becomes unstable, making continuous operation difficult and having to stop production. There is a problem that it is caused and the operation efficiency is reduced.

Therefore, in order to solve this problem, Japanese Patent Publication No. 6
The invention described in JP-A 1-38789 discloses a refrigeration system with a pre-cooling unit. As shown in FIG. 7, the schematic configuration of the invention described above includes a tunnel freezer 52 provided with a net conveyor, a pre-cooling unit 53, a cooler coil array 54, and an upper portion near the exit of the tunnel freezer 52. It is composed of an inflow pipe 55 for sending the cooling air of the tunnel freezer 52 to the outlet of the cooling unit 53, and an outflow pipe 56 for connecting from the inlet of the precooling unit 53 to the intake side of the cooling coil array of the tunnel freezer 52. There is. Then, the cooling air enters the unit from the outlet of the pre-cooling unit through the inflow pipe 55 from the upper part of the tunnel freezer, goes counter to the flow of the food and reaches the inlet of the unit, and passes through the outflow pipe 56 of the coil array 57. The configuration is such that it returns to the intake side, and the air in the refrigeration system is maintained in an equilibrium state so that frost is evenly distributed over all coil rows.

However, in this case, there is no consideration on the temperature of the cooling air of the pre-cooling unit, which is necessary for freezing the food, and on the removal of water vapor which causes frost,
However, the frost is generated evenly over the entire coil array, and the interval between operation suspensions for defrosting is lengthened.

Further, as food cooling or freezing is put into practical use, the cooling and freezing process is divided in terms of temperature and time, for example, a precooling process, a quick freezing process, and a cold storage process to crystallize free water in food. It is strongly desired to prevent cells from flowing out of the drip cells by compressing the cells in the unfrozen part due to the above.For this reason, it is essential for the plan of the food tunnel freezer to zone the cooling temperature in the continuous tunnel flow direction. It is considered to be a matter. For example, as disclosed in the invention described in Japanese Examined Patent Publication No. Sho 55-9623, as shown in the sectional view of the main part of FIG. 8, the inside of the cooling zone 60 is divided into a plurality of compartments 61 in the transfer direction of the object to be cooled, 62, 63, 64
And the air blowers 65, 65, 6 in the compartment, respectively.
5, 65 are provided, a conveyor 66 for transferring an object to be cooled is provided at the center, and the sections 61, 6 are provided on the conveyor.
A partition member 67 corresponding to 2, 63, 64 is provided,
The object to be cooled is intermittently transferred at a constant pitch in the direction of arrow A. Reference numeral 68 is an inlet for the object to be cooled.

In the above-mentioned construction, the present prior art provides nozzles 69, 7 with cold gas corresponding to the final desired cooling temperature of the object to be cooled in the sections 63, 64 on the lower side in the transfer direction.
Section 6 on the upper side in the transfer direction, filled from 0
For the compartments 1 and 62 in which the object to be cooled only needs to be cooled in a precooling manner, the low temperature liquefied gas is not jetted and the atmosphere in the compartment is cooled by the ordinary heat exchanger 71. Is. However, in this case, cold gas or cooling air is circulated in each section as indicated by a dotted arrow crossing the transfer direction, and a part of the cold gas or cooling air is discharged to the outside.

[0010]

However, the above-mentioned prior art is not specially proposed for cooling and freezing food, but it is intended to provide an efficient cooling device. Therefore, since the inside of the tunnel freezer is divided into a plurality of temperature regions and is designed to have a plurality of zones, the present invention is similar to the present invention in that it does not consider the freezing of foods, and therefore the following problems occur. . That is, in the above-mentioned conventional technique, the precooling region is set to a temperature zone by vaporization of the low-temperature liquefied gas used for the main freezing, and therefore the precooling region is necessarily 0
Since it becomes a temperature zone of ℃ or less, when used for cooling and freezing food in such a refrigerating device, there is a problem that it is forced to take a long time to rest due to removal of frost on the cooling coil due to water vapor generated from food. is there.

Further, since the refrigerating device is partitioned by the partition plate for each temperature zone, it is unavoidable to intermittently drive even if a conveyor is used, and there is a problem in productivity.
In addition, since it is generally necessary for food to pass through the maximum ice crystal production zone in a short time in a short time, the collision jet type is suitable, but in any of the above technologies, the jet stream jetted from the narrow gap of the collision jet type. If there is no appropriate heat exchanger with a straightening plate, nozzles and slits for the above, and if a collision jet type is adopted in the conventional plate fin type heat exchanger, the plate fin type heat exchanger is arranged above the jet jet generation means. Must be done, and inevitably increases in size.

The present invention has been made in view of the above-mentioned problems, and in cooling and refrigerating food, it is possible to perform collision jet cooling with good heat transfer efficiency without relying on a conventional plate fin type heat exchanger, An object of the present invention is to provide a food collision jet type tunnel freezer which is free from frost on the evaporator which is a cooling coil and which is composed of a plurality of zones most suitable for cooling and freezing food.

[0013]

In order to achieve the above-mentioned technical object, the first invention of the present invention provides a food by means of a food transferring means,
In a tunnel freezer that freezes to a predetermined temperature while sequentially transferring to a predetermined temperature zone in the tunnel, divides the temperature zone into a plurality of temperature zones along the food transfer direction, and introduces food into the tunnel. The first temperature range zone to be set is set to a non-freezing temperature range zone of a temperature range of about 0 to 5 ° C., and water vapor evaporated in the non-freezing temperature range zone (hereinafter referred to as the first zone) is removed as droplets. It is characterized in that a removing means is provided, and after removing unnecessary steam of the food in the non-freezing temperature range by the removing means, the food can enter the freezing temperature range zone. As the removing means for removing the water vapor as liquid droplets, as shown in the examples below, it may be supercooled by a heat exchange coil at 0 to 1 ° C. to form liquid droplets, or may be removed by a filter or the like.

In this case, the temperature range zone after passing through the non-freezing temperature range zone is, for example, the second zone for quick freezing which completes the passage of the maximum ice crystal production zone in a short time and the third zone for cold storage for cooling and preservation. It is preferable that a partition for shielding cold gas is provided in the upper area of the conveyor between the first zone and the second zone. The temperature cutoff between the adjacent zones may be performed by a slit-shaped cool air curtain or a partition wall, but in any case, the food transfer means is constituted by a belt or a net conveyor, and the tunnel is used. It is possible to improve the productivity by constructing a food product in which the food can be continuously transferred.

The refrigeration system of the tunnel freezer is composed of a two-stage compressor, and the refrigerant gas after the non-freezing temperature zone is generated can be directly introduced into the high-stage side of the two-stage compressor. Good.

In the second aspect of the invention, in the tunnel freezer for freezing the food while colliding the low temperature cold air flow with the food introduced into the tunnel through the food transferring means, a direction substantially orthogonal to the transferring direction. A large number of refrigerant passages having a substantially rectangular cross-section extending in parallel along the slit gaps are arranged, and the cooling airflow passing through the slit gaps is accelerated while exchanging heat with the refrigerant in the passages. It is characterized that it can collide with food. In this case, the temperature of the refrigerant gas circulating in the heat exchange passage is made different for each predetermined zone, and the temperature zone of the cold airflow passing through the slit gap is divided into a plurality of temperature zones along the food transfer direction. As a result, the first invention can be easily achieved.

Also in this case, the refrigeration system of the tunnel freezer is constituted by a two-stage compressor, and the refrigerant gas after passing through the temperature zone located on the food introduction side is directly introduced to the high stage side of the two-stage compressor. It should be configured as possible.

[0018]

With the above technical configuration, the tunnel freezer is
Since the first zone with a cooling temperature of 0 to 5 ° C is provided, unnecessary water vapor generated from food is removed as droplets in the first zone, so that the water vapor that evaporates in the subsequent freezing temperature zone is greatly reduced. Further, since the first zone is in the temperature range of 0 ° C. or higher, the steam supercooled in the first zone is easily removed as droplets and does not adhere as frost even in the first zone. As a result, it is possible to significantly increase the interval between defrosting operations for removing frost and improve operating efficiency. Further, since the food is cooled to around 0 to 5 ° C. in the first zone, the food can pass through the maximum ice crystal formation zone in a short time in the second zone for rapid freezing in the next stage. By compressing the cells in the unfrozen part due to the crystallization of free water in the inside, it is possible to effectively prevent drip etc. caused by
Good food freezing can be performed.

Now, like tuna, -30 to -40 ° C
In the case of foods that are frozen at low temperature, it is preferable to use a two-stage compressor as the refrigeration system in order to reduce the shaft power. At this time, the refrigerant gas temperature after passing through the first zone is about 0. ℃
On the other hand, the temperature of the refrigerant gas after passing through the freezing zone in the subsequent stages is around -30 to -40 ° C.

Therefore, the refrigerant gas around 0 ° C. after passing through the first zone is directly introduced into the high-stage side of the two-stage compressor, while the refrigerant gas around -40 ° C. after passing through the freezing zone after the next stage. It is better to put the temperature on the lower stage side.

According to the second aspect of the present invention, by arranging a plurality of refrigerant passages each having a substantially rectangular cross section through the slit gaps, jet cold air gas can be generated through the slit gaps, and the cold air gas passes through the passages. It is preferable because heat can be directly exchanged with the refrigerant in the passage via the above. As a result, the passage and the arrangement structure thereof can be used also as a plate fin type heat exchanger, a rectifying plate, a nozzle, etc., so that the device can be downsized or the capacity can be increased.

Further, the heat removal efficiency is improved by the above configuration, the food transfer means can be configured by a belt or a net conveyor, and the food can be continuously transferred in the tunnel, which leads to improvement in productivity.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Absent.
FIG. 1 is a vertical cross-sectional view showing a schematic structure of a food collision jet type tunnel freezer of the present invention, FIG. 2 is a horizontal cross-sectional view, FIG. 3 shows an arrangement structure of a refrigerant passage, and FIG. 4 shows a precooling zone. It is a figure which shows the condition which the droplet generate | occur | produced in the cold gas drips along the evaporator surface, FIG. 5 is a typical sectional view which shows the relationship between a refrigerant passage and a slit, and FIG. 6 is an overall plan view of a refrigerant passage. .

As shown in FIG. 1, in the food impact jet type tunnel freezer of the present invention, a tunnel type cooler 31 provided with a net conveyor 14 for transferring food in the direction of an arrow is divided into three zones, and a food introducing direction is provided. Along with, a first zone 10 for evaporating food from upstream to downstream and removing the water vapor as droplets, and a second zone 11 for quick freezing capable of completing passage through the maximum ice crystal formation zone in a short time And, the third zone 12 for cold storage for freezing and storing is sequentially arranged, and unnecessary steam on the surface of the food is removed by colliding high-speed cold air gas of 3 to 5 ° C. with the food in the first zone 10. In the second zone 11, the high-speed cold air gas of −30 to −40 ° C. collides with the food to quickly freeze it while preventing drip, and in the third zone, the high-speed cold air gas of around −40 ° C. collides with the food. Constituting the zone type tunnel freezer to stabilize the freeze. Since there is a temperature difference between the first zone 10 and the second zone 11, the partition wall 24 for blocking the cold gas is provided.

Next, the structure of the refrigeration system will be described. Reference numeral 15 is a two-stage compressor for refrigeration which is connected to the motor 33 via the coupling 32 and is arranged in the second and third zones. Refrigerant gas after passing through the refrigerant passages 20B and 20C (around -30 ° C)
Is introduced to the lower stage side 15A and low stage compression is performed (about 5 ° C.
The temperature of the refrigerant gas compressed in the low stage is mixed with the refrigerant gas (about 5 ° C.) after passing through the refrigerant passage 20A arranged in the first zone 10 and introduced into the high stage side 15B, High-stage compression.

The compressed gas discharged from the high-stage compression side 15B is liquefied in the condenser 16, and the liquefied refrigerant is expanded by the respective expansion valves 22A to 20B whose opening degrees are adjusted to a predetermined level. In the zone 10, the refrigerant gas of 0 to 1 ° C. is set, and in the second and third zones, it is set to −40 ° C., respectively. The heat exchangers 17, 18, and 19 are shown in FIGS.
And, as shown in FIG. 6, a plurality of refrigerant passages 20A to 20C formed in a horizontally-long U-shape having a thin rectangular cross section are arranged in parallel so as to traverse the upper part of the conveyor 14, and between adjacent passages and passages. A slit space 29 to be sandwiched is provided, and a refrigerant gas 39 is formed in a hollow shape so that the refrigerant gas 39 can circulate in the passages 20A to 20C.

The adjacent passages 20A for each zone,
The passages of 20B and 20C are connected by a coil-shaped heat exchange coil 38 as shown in FIG. 6, and the circulation of the refrigerant gas is secured by a closed circuit for each zone. The heat exchange coil 38 is housed in the precooling cooler 17 arranged on the side of the conveyor 14 for each zone.

The precooling cooler 17 is provided with reflux fans 21A and 21C on the lower side for each zone, and the conveyor 1
The cold air gas that has absorbed heat by colliding with the heat exchanger 4 is heat-exchanged with the heat exchange coil 38, is cooled again, and is circulated above the refrigerant passage 20, and the recooled cold air gas is passed through the slit gap 29 between the passages. By passing through the conveyor 1, the high-speed jet cold air gas flow 30 can be speeded up and exchanged heat with the refrigerant gas in the passage.
Collide with the food on 4. In addition, as shown in FIG. 5, the gap of the slit (cooling plate gap) 28 is set to L = 1 mm to 8 mm.
mm, and the speed of the jet cold air gas flow 30 is 10 to 10.
When set to 25 m / s, the heat transfer coefficient is 100 to 20
0 Kcal / m2 × h × ° C. was obtained. The refrigerant passage 20 may be composed of a plurality of parallel refrigerant passages 20 that cross the upper portion of the conveyor 14.

Now, the precooling cooler 1 of the first precooling zone
As shown in FIG. 3, the drain receiver 26
Is arranged so that the water vapor is supercooled by contact with the heat exchange coil 38 at 0 to 1 ° C., and the droplets adhering to the coil 30 drop onto the drain receiver 26. In addition, the partition wall 24 for blocking the cold gas is provided between the first zone 10 and the second zone 11 as described above, and the cold gas in the first zone 10 containing a large amount of water vapor is transferred to the second zone 11. Without this, frost is prevented from being generated on the surface of the evaporator 18 in the second zone 11.

Next, the operation of this embodiment will be described. The food placed on the net conveyor enters the first zone 10 as the net conveyor 14 moves. In the first zone 10, the air located above the tunnel freezer is accelerated by the suction of the reflux fan arranged below the net conveyor, passes through the slit gap 29 of the refrigerant passage 20 and is accelerated, and the refrigerant gas and heat in the passage are heated. Exchange it 0-5
C., preferably 3-5.degree. C., produces a high velocity jet cold air stream 30 which impinges on the food on the conveyor 14. As a result, unnecessary steam is evaporated from the food, and the steam is introduced into the pre-cooling cooler 17 by the reflux fan 21 together with the cold air gas flow after the heat is removed, and in the pre-cooling cooler 17, a heat exchange coil of 0 to 1 ° C. Of water vapor supercools and adheres to the coil. Then, the droplets attached to the coil drop onto the drain receiver 26.

On the other hand, the cold air gas from which the water vapor has been removed is heat-exchanged with the heat exchange coil 38 and cooled again to cool the refrigerant passage 2
It circulates upward by 0 and repeats the above operation. Since the heat exchange coil 38 is in a temperature range of 0 ° C. or higher, the water vapor adhering to the coil 38 is easily dropped and removed downward as a droplet, and adheres as frost to the slit void 29 of the refrigerant passage 20. There is nothing to do. Then, the food product from which unnecessary steam has been removed enters the second zone 11 for quick freezing in the next stage, and in this zone, the low-temperature high-speed jet cold airflow 30 of about -40 ° C passes through the slit void 29 of the refrigerant passage 20. Contact with food, which allows the food to pass through the maximum ice crystal formation zone in a short time, and drip caused by pressing cells in the unfrozen portion of the food due to crystallization of free water Can be effectively prevented, and good food freezing can be performed. Then, the freezing temperature is further stabilized in the third zone 12, and the conveyor 14 discharges the food to the outside of the freezer 25.

[0032]

According to the present invention, the cooling temperature is 3 to 5 ° C.
Since the first zone for removing droplets for controlling the positive temperature is provided, the water vapor generated from the food is mixed in the cold gas after the heat is removed in the first zone to remove the droplets provided at a predetermined location. Since it is removed as droplets by the means, it does not adhere to the first zone and the freezing zone in the next step as frost,
Further, even if it slightly adheres to the slit wall in the next step, it can be blown off due to the jet stream. As a result, it is possible to increase the operation interval by increasing the period of rest for frost removal, and to enable non-defrost long-time continuous operation.

Further, according to the second aspect of the invention, the formation and cooling of the jet airflow, which is the impinging jet flow, are made up of the refrigerant passage 20 having the slit-shaped passage wall structure and the recirculation fan and other suction means. Since the plate fin type heat exchanger, the straightening plate, the nozzle, etc. are not required, the size of the apparatus can be dramatically reduced or the capacity can be increased. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a food impact jet type tunnel freezer of the present invention.

2 is a cross-sectional view of FIG.

FIG. 3 is a diagram showing a situation in which steam generated in cold gas in the first zone of FIG. 1 is dropped as droplets.

FIG. 4 is a perspective view showing a schematic configuration of a refrigerant passage of FIG.

5 is a schematic cross-sectional view showing the relationship between the refrigerant passage and the slit shown in FIG.

6 is a plan view showing the overall configuration of the refrigerant passage of FIG. 4. FIG.

FIG. 7 is a schematic cross-sectional view of a conventional technique in which defrosting is performed by precooling.

FIG. 8 is a schematic cross-sectional view of a main part showing a conventional technique for cooling compartments with a temperature difference.

[Explanation of symbols]

10 Non-freezing temperature zone 14 Belt or net conveyor 15 Two-stage compressor 20 Droplet removing means 29 slit void 52 Tunnel Freezer

Continuation of the front page (56) References JP-A-60-152876 (JP, A) JP-A-5-223368 (JP, A) Actual Kaihei 5-42980 (JP, U) Actual Kaihei 3-115375 (JP , U) Actual Kaihei 3-57378 (JP, U) Actual Kaihei 6-13495 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F25D 13/06

Claims (6)

(57) [Claims] 1. A tunnel freezer for freezing a food to a predetermined temperature while sequentially transferring the food to a predetermined temperature zone in a tunnel through a food transfer means, wherein a plurality of temperature zones are provided along the food transfer direction. In addition to dividing into temperature zones, the first temperature zone in which food is introduced into the tunnel is set to a non-freezing temperature zone of a temperature range of about 0 to 5 ° C, and evaporation is performed in the non-freezing temperature zone. A tunnel characterized in that a removing means for removing water vapor as droplets is provided, and after removing unnecessary water vapor of food in the non-freezing temperature range by the removing means, the food can enter the freezing temperature range zone. Freeza 2. The tunnel freezer according to claim 1, wherein the food transfer means is constituted by a belt or a net conveyor, and the food can be continuously transferred in the tunnel. 3. The refrigeration system of the tunnel freezer is configured by a two-stage compressor, and the refrigerant gas after generation of the non-freezing temperature zone can be directly introduced into the high-stage side of the two-stage compressor. Tunnel freezer described in 1. 4. In a tunnel freezer for freezing food while colliding a low temperature cold air flow with the food introduced into the tunnel through the food transfer means, the freezer extends parallel to a direction substantially orthogonal to the transfer direction. A large number of existing refrigerant passages having a substantially rectangular cross section are arranged through slit gaps, and the cold airflow passing through the slit gaps accelerates while exchanging heat with the refrigerant in the passages and collides with food. Tunnel freezer characterized by being configured as possible 5. The temperature of the refrigerant gas circulating in the heat exchange passage is varied for each predetermined zone, and the temperature zone of the cold air flow passing through the slit gap is divided into a plurality of temperature zones along the food transfer direction. The tunnel freezer according to claim 1, which is divided. 6. The refrigeration system of the tunnel freezer is configured by a two-stage compressor, and the refrigerant gas after passing through the temperature zone located on the food introduction side can be directly introduced to the high stage side of the two-stage compressor. The constructed tunnel freezer according to claim 1.