JP3077602B2 - Vacuum cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum cooling device for evaporating the water content of an object to be cooled under reduced pressure and using the latent heat of vaporization for cooling.

[0002]

2. Description of the Related Art As is well known, a vacuum cooling device is designed to reduce a saturated steam temperature and evaporate water in a cooling object by vacuum-suctioning and depressurizing a cooling tank containing the object to be cooled. Thus, the object to be cooled is cooled using the latent heat of vaporization at that time. This vacuum cooling device is used, for example, in the food industry in a process of packing and shipping cooked food. That is, from the viewpoint of food hygiene, it is necessary to rapidly cool to the center of the food, instead of cooling the food from the surface over a long period of time with cold air or a fan.

[0003] Since the cooling capacity of such a vacuum cooling device is determined by how quickly the pressure in the cooling tank is reduced, various devices for performing this pressure reduction (vacuum suction) have been proposed and put into practical use. It has been. For example, a vacuum pump sucks air and evaporated water vapor in a cooling tank (for normal temperature), or a heat exchanger and a vacuum pump are used in combination to condense most of the water vapor, and a vacuum pump is used to condense air and steam. The part is for suctioning (for low temperature). Also, in the case of using a steam ejector, this steam ejector and condenser are used in multiple stages, or a water ejector is installed downstream of the steam ejector, and the water ejector doubles as a condenser and steam ejector. And rarely used alone.

A vacuum cooling apparatus having a large scale and a high cooling capacity (cooling to a low temperature) generally has a structure in which a steam ejector is connected to a cooling tank and a water ejector is further connected downstream of the steam ejector. I have. According to this configuration, an enormous amount of steam and water are required to be supplied to each of the steam ejector and the water ejector. Furthermore, in the case of using the water ejector, water as a working fluid is circulated through a water tank to reduce the amount of water used, but water and gas discharged from the water ejector are stored in the water tank. Since the water flows in at high speed, the capacity of the water tank needs to be large,
In addition, the noise is loud. In the case of a system in which water is circulated using a water ejector, food fragments and fine particles sucked from the cooling tank at the time of vacuum suction enter the water circulation line, and these stay in the water tank. And become more polluted. The water temperature in the tank is in a temperature range in which various germs can easily propagate, and thus the soil is suitable for germ propagation. Since such a water circulation line and a water tank are arranged close to a cooling tank for cooling food, in a work environment which should be originally clean, odor problems and hygiene problems due to the sewage occur. . In order to solve this problem, it is necessary to frequently clean the circulation line including such a water tank. However, since the water tank has a large capacity, the cleaning operation requires much labor. Further, since the pump efficiency of both the water ejector and the steam ejector is low, in order to obtain a predetermined exhaust capacity, it must be large, and in this respect, as in the case of the water tank, compared with the cooling tank itself. However, the installation space becomes large, which is an obstacle to downsizing the vacuum cooling device.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vacuum cooling device having a high cooling capacity and capable of being miniaturized.

[0006]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 has a structure in which a steam ejector is connected to a cooling tank for containing an object to be cooled. , Characterized in that a positive displacement vacuum pump is connected to the discharge side of this steam ejector via a heat exchanger.
The invention according to claim 2 is characterized in that a control means for adjusting the amount of steam supplied to the steam ejector is provided, and the invention according to claim 3 is further characterized in that the displacement type vacuum pump is a liquid ring type vacuum pump. It is characterized by being a pump.

[0007]

According to the present invention, a suction end of a steam ejector is connected to an exhaust line of a cooling tank of a vacuum cooling device, and a positive displacement vacuum pump is connected to a discharge side of the steam ejector via a heat exchanger. This is realized by the configuration described above. The steam ejector receives the supply of steam, draws in the air in the cooling tank by the kinetic energy of the expanding steam, compresses and discharges the air. The fluid discharged from the steam ejector is a fluid in which the air in the cooling tank and the steam evaporated from the object to be cooled in the cooling tank and the steam introduced into the steam ejector are mixed and pressurized. Later, the mixed fluid flows into the heat exchanger. This heat exchanger condenses the pressurized steam in the flowing fluid, and its saturated steam temperature is considerably higher than that of the cooling water, so that the partial pressure of the steam in the fluid is reduced, and The partial pressure of air increases. The mixed fluid whose main part is occupied by air by the heat exchanger is sucked and exhausted by the positive displacement vacuum pump.
Therefore, even if the temperature inside the cooling tank is low and the pressure is very low, the inside of the cooling tank can be suctioned in vacuum by the steam ejector, and the steam of the mixed fluid compressed and pressurized by the steam ejector is condensed by the heat exchanger. Then, since the remaining air is suctioned and exhausted by the positive displacement vacuum pump, the ultimate pressure of the vacuum in the cooling tank is reduced, and the time required to reach the ultimate vacuum is greatly reduced.

Further, a control means for adjusting the amount of steam supplied to the steam ejector is provided, and the amount of steam supplied is adjusted based on the temperature or pressure in the cooling bath. Further, by using a liquid ring type vacuum pump as the positive displacement vacuum pump, it is possible to collectively process a mixed fluid of the air in the cooling tank, the object to be cooled, the steam from the steam ejector and the condensed water thereof. it can.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a drawing for explaining a schematic configuration of a first embodiment of a vacuum cooling device according to the present invention.

Referring to FIG. 1, the basic structure of a vacuum cooling device will be described first. This vacuum cooling device includes a cooling tank 1 for hermetically containing an object to be cooled, a vacuum suction line 2 for reducing the pressure of the cooling tank 1, and a vacuum suction line 2. And an outside air introduction line 3 for returning the pressure in the cooling tank 1 to atmospheric pressure after vacuum cooling. The cooling tank 1 is provided with an opening / closing door (not shown) for operations such as taking in and out of an object to be cooled, and this opening / closing door has a sealable configuration. The cooling tank 1 is provided in the vacuum suction line 2.
A steam ejector 4, a heat exchanger 5, and a positive displacement vacuum pump 6 are connected from the side. A check valve 7 for maintaining a reduced pressure state is connected between the cooling tank 1 and the steam ejector 4. A filter 8 is connected to the upstream end of the outside air introduction line 3, and an outside air introduction valve 9 is connected between the filter 8 and the cooling tank 1.

The steam ejector 4 has a suction side end 4.
a is connected to the cooling tank 1, the exhaust side end 4b is connected to the heat exchanger 5, and the steam introduction section 4c is connected to a steam supply line 10 extending from a steam supply device (not shown). . The steam ejector 4 is connected to the steam supply line 1
The supply of the steam from 0, the fluid on the suction side end 4a side is sucked by the kinetic energy due to the expansion of the steam, compressed, and discharged to the exhaust side end 4b. The fluid on the suction side end 4a side is the air in the cooling tank 1 and the vapor evaporated from the object to be cooled stored in the cooling tank 1. The steam ejector 4 controls the pressure of the fluid flowing from the suction side end 4a side by 2 to 20.
It is compressed to about 2 times, preferably about 4 to 10 times, and discharged to the exhaust side end 4b. This value is determined based on the suction pressure at which the positive displacement vacuum pump 6 can suction and the evacuation speed at that time. In a general commercially available vacuum pump, the value is selected from the above range. The steam supply line 10 is connected to a steam control valve 11 for interrupting the supply of steam to the steam ejector 4.

The heat exchanger 5 cools the fluid from the steam ejector 4 and condenses the vapor in the fluid. The cooling liquid for this condensation is sent to the heat exchanger 5 after being cooled in a cooler 13 connected to the heat exchanger 5 via a cooling liquid circulation line 12. A circulation pump 14 for circulating the coolant is connected to the coolant circulation line 12.

The positive displacement vacuum pump 6 sucks and removes the fluid that has passed through the heat exchanger 5. The positive displacement vacuum pump 6 eliminates air in the cooling tank 1 by suction under a negative pressure and condenses the fluid in the heat exchanger 5. In this embodiment, a liquid ring vacuum pump is used as the positive displacement vacuum pump 6. For this reason, a water sealing line 15 for supplying water is connected to the liquid ring vacuum pump 6 (hereinafter, referred to as “vacuum pump 6”).

The filter 8 in the outside air introduction line 3
Is for removing dust, various germs and the like in the outside air introduced into the cooling tank 1 and preventing the dust from adhering to the object to be cooled. Further, the outside air introduction valve 9 adjusts the speed of the decompression by adjusting the flow rate of the air flowing into the cooling tank 1 through the outside air introduction line 3. In this embodiment, the outside air introduction valve 9 has an air introduction amount (airflow resistance).
The motorized valve which can be changed continuously or in several steps is used.

Further, this vacuum cooling device includes a control device 2
The control device 20 includes a steam control valve 11 for interrupting the supply of steam to the steam ejector 4, the vacuum pump 6, and the outside air introduction valve 9.
Connected to each other. The cooling tank 1 is provided with a temperature detector 21 and a pressure detector 22, which are also connected to the control device 20 via signal lines 17, respectively. Therefore, the following description explains the operation of the vacuum cooling device of the present invention, including the functional description of the control device 20.

In the above configuration, first, an object to be cooled is accommodated in the cooling tank 1, and a work opening / closing door (not shown) is closed. At this time, the control device 20 keeps the outside air introduction valve 9 and the steam control valve 11 closed. Next, the circulation pump 14 is activated to activate the heat exchanger 5 and the vacuum pump 6 is activated. By starting the vacuum pump 6, the air in the cooling bath 1 is vacuum-suctioned through the vacuum suction line 2. Then, as the pressure in the cooling tank 1 decreases, the saturated steam temperature decreases, so that the moisture of the object to be cooled in the cooling tank 1 evaporates actively, and this steam is sucked by the vacuum suction line 2 together with the air. Is done. And
The object to be cooled is cooled by latent heat of vaporization accompanying the evaporation of water in the object to be cooled. At this time, paying attention to the gas flowing from the cooling tank 1 to the vacuum suction line 2, compared with the air amount,
The amount of vapor evaporating from the object to be cooled is significantly increased.
In the case where the object to be cooled is food after cooking,
The water in the object to be cooled is vaporized as steam, and the amount of steam generated at this point is enormous.

When the mixed fluid of air and steam from the cooling tank 1 flows into the heat exchanger 5, the mixed fluid is cooled by the heat exchanger 5 and the steam is condensed. Therefore, the partial pressure of air sharply increases, and most of the gas that needs to be evacuated by the vacuum pump 6 is air, so that vacuum suction by the vacuum pump 6 is performed in a short time. The vacuum pump 6
Is a constant volume per unit time. Therefore, when the pressure in the cooling bath 1 becomes extremely low, the flow of the discharged mass becomes small and the pressure does not easily decrease. . Therefore, when the inside of the cooling tank 1 reaches a predetermined pressure (or a predetermined temperature), the steam ejector 4
Activate Specifically, the temperature inside the cooling bath 1 is monitored by a temperature detector 21 or a pressure detector 22 attached to the cooling bath 1, and when a predetermined pressure (or a predetermined temperature) is reached. , The control device 20 controls the steam supply line 1
Then, the steam control valve 11 is opened, and the steam ejector 4 is operated. The pressure at which the operation of the steam ejector 4 is started is, for example, about 30 torr, and the saturated steam temperature at this pressure is 29 ° C. However, in practice, a slight cooling delay occurs, so is there.

When the steam control valve 11 is opened, steam from the steam supply line 10 flows into the steam introduction section 4c of the steam ejector 4, and the air and the air in the cooling tank 1 are blocked by the fluid force of the steam. Steam from the cooling material is sucked from the suction side end 4a, and is discharged from the exhaust side end 4b together with the steam from the steam supply line 10. Since the steam ejector 4 performs vacuum suction by the fluid force of the steam as described above, it functions as a low-pressure compressor close to a vacuum, and removes air and steam from the low-pressure cooling tank 1. Can be discharged.

The mixed fluid of air and steam discharged from the exhaust end 4b by the steam ejector 4 is cooled in the heat exchanger 5 as described above, and the steam is rapidly condensed. In the heat exchanger 5, since the pressure of the mixed fluid at the inlet and the outlet is substantially the same, the partial pressure of the vapor of the mixed fluid at the outlet is sharply reduced, while the partial pressure of the air is Increase rapidly. Therefore, most of the mixed fluid that has passed through the heat exchanger 5 is air, and the pressure inside the cooling tank 1 is extremely low, but the upstream side of the vacuum pump 6 (of the steam ejector 4). On the downstream side), since the pressure of the mixed fluid increases and the saturated steam temperature increases, the capacity of the heat exchanger 5 increases, the partial pressure of air at the outlet increases, and the vacuum suction by the vacuum pump 6 is performed for a short time. Is performed efficiently.
As described above, the ultimate pressure in the cooling bath 1 decreases, and the cooling temperature accordingly decreases. That is, since the steam ejector 4 pressurizes the air and steam sucked from the cooling tank 1, the saturated steam temperature of the mixed fluid flowing into the heat exchanger 5 increases, so that the heat exchanger Even if the temperature of the cooling liquid supplied to 5 is high, the vapor can be effectively condensed.

As described above, when the temperature detector 21 or the pressure detector 22 detects that the pressure in the cooling bath 1 has decreased and has decreased to a predetermined temperature, the control device 20 The steam control valve 11 is closed to stop the supply of steam to the steam ejector 4 and the vacuum pump 6 is stopped. And the control device 20
Opens the outside air introduction valve 9, and opens the outside air introduction line 3.
Then, air is introduced into the cooling tank 1 to return to the atmospheric pressure. Here, when the cooling bath 1 is returned to the original pressure after cooling, the quality of the object to be cooled is deteriorated by setting the speed of gradually returning the pressure in the cooling bath 1 and returning the pressure. To prevent

Although the outside air introduction valve 9 is opened after cooling, it can be controlled so as to adjust the decompression speed by opening it appropriately during vacuum suction. That is, the control device 20 controls the outside air introduction valve 9.
By controlling the flow rate at
The amount of outside air introduced is larger than the amount of vacuum exhaustion by the vacuum suction line 2, and the rate of pressure reduction in the cooling bath 1 is reduced, so that the cooling rate can be reduced.

Next, a vacuum cooling apparatus according to another embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.

The second embodiment shown in FIG. 2 is provided with control means 16 for adjusting the amount of steam supplied to the steam ejector 4. That is, parallel circuits 10a and 10b as the control means 16 are provided in the middle of the steam supply line 10 described in the first embodiment.
The steam control valves 11a and 11b are inserted into the control valves 20a and 10b, respectively, and the steam control valves 11a and 11b are connected to the control device 20 via signal lines 17. The configuration other than the above is the same as that of the first embodiment, and the description is omitted.

According to the second embodiment having the above structure, first, the object to be cooled is accommodated in the cooling tank 1, and the opening / closing door (not shown) is closed. At this time, the control device 20 keeps the outside air introduction valve 9 and the steam control valves 11a and 11b in a closed state. Next, the circulation pump 14 is activated to activate the heat exchanger 5 and the vacuum pump 6 is activated. By the activation of the vacuum pump 6, the temperature in the cooling bath 1 drops rapidly. That is, as shown in FIG. 3, for example, when cooling cooked rice, the rice temperature when stored in the cooling tank 1 is about 8
0 ° C., and the cooked rice is cooled to about 10 ° C. in about 15 minutes (about 15 ° C. in a conventional vacuum cooling apparatus) and one batch is completed. In a minute, the temperature of the cooked rice drops to about 30 ° C.
In the second embodiment of the present invention, the steam ejector 4
Activate That is, when the temperature detector 21 detects the predetermined temperature (30
° C) and notifies the controller 20 via the signal line 17. The control device 20 that has received the notification opens the steam control valve 11a and supplies the steam ejector 4 with approximately 50% of the total supply amount of steam. Then, after a further lapse of 4 minutes (the temperature of the cooked rice drops to about 15 ° C.), the steam control valve 11 b is opened to supply the entire supply amount of steam to the steam ejector 4. After a further 4 minutes, the temperature of the cooked rice is about 10 ° C.
(The temperature detector 21 attached to the cooling tank 1 detects the temperature), and the cooling is completed. The operation after the end is the same as that of the first embodiment, and the description is omitted.

As described above, according to the second embodiment,
The amount of steam supplied to the steam ejector 4 is
Since the supply is adjusted based on the internal temperature or pressure, the steam supply amount can be saved and the load on the cooler 13 connected to the heat exchanger 5 can be reduced. Therefore, the capacity of the cooler 13 can be reduced.

[0026]

As described above, according to the vacuum cooling apparatus of the present invention, even if the pressure inside the cooling tank becomes extremely low, the inside of the cooling tank can be vacuum-evacuated by the steam ejector. Of the mixed fluid compressed and pressurized by the ejector, the remaining air is compressed by condensing the vapor with the heat exchanger, and it is sucked and evacuated by the positive displacement vacuum pump. In addition, the time required to reach the vacuum pressure can be significantly reduced. Furthermore, unlike a conventional device using a water ejector, a water circulation line and a water tank for operating the water ejector are not required, and a circulation pump for circulating water at a high pressure is also unnecessary, so that space is saved and power is reduced. Savings can be achieved.
Further, in the present invention, since a water circulation line and a water tank for a water ejector are not required, a water circulation line in which food fragments or fine particles sucked from the cooling tank during vacuum suction are mixed. Since there is no water tank, the problem of odor due to the contamination of circulating water and the problem of hygiene, which have conventionally been problems, can be prevented, and the effects of cleaning can be saved. Further, according to the vacuum cooling device of the present invention, since the steam ejector, the heat exchanger, and the positive displacement vacuum pump are configured for vacuum suction, the noise is lower than that of a conventional water ejector. . Further, according to the vacuum cooling device of the present invention, the steam ejector is used in a low pressure region, and most of the pressure rise is efficiently exhausted by a positive displacement vacuum pump, so that a plurality of steam ejectors are connected in series. Significantly less steam consumption compared to the method used. In addition, since the steam ejector pressurizes the steam from the cooling tank, the temperature of the saturated steam flowing into the heat exchanger is increased, so that the steam is effectively condensed even when the coolant temperature of the heat exchanger is high. This has the effect of relatively improving the performance of the heat exchanger.

[Brief description of the drawings]

FIG. 1 is an explanatory drawing showing a schematic configuration of a first embodiment of a vacuum cooling device according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of a second embodiment of the present invention.

FIG. 3 is an explanatory view when rice is cooled in a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling tank 2 Vacuum suction line 4 Steam ejector 4a Suction side end 4b Exhaust side end 4c Steam introduction part 5 Heat exchanger 6 Positive displacement vacuum pump (liquid ring vacuum pump) 16 Control means 20 Control device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kumi Matsuya, Inventor 7th Horie-cho, Matsuyama-shi, Ehime Miura Kogyo Co., Ltd. (72) Inventor Akiyoshi Itabashi 7 Horie-cho, Matsuyama-shi, Ehime Miura Research Institute Co., Ltd.Examiner Toru Uehara (56) References JP-A-53-71359 (JP, A) JP-A-4-338232 ( JP, A) JP-A-7-139860 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25D 7/00 A23L 3/36 B01J 19/00 301

Claims (3)

(57) [Claims] 1. A steam ejector (4) is connected to a cooling tank (1) for accommodating an object to be cooled, and a positive displacement vacuum pump (6) is connected to an exhaust side of the steam ejector (4) via a heat exchanger (5). Vacuum cooling device. 2. The vacuum cooling device according to claim 1, further comprising control means for adjusting an amount of steam supplied to the steam ejector. 3. The vacuum cooling device according to claim 1, wherein the positive displacement vacuum pump is a liquid ring vacuum pump.