JP7167572B2 - vacuum cooling system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum cooling apparatus that cools food by decompressing the inside of a processing tank.

Conventionally, as disclosed in Patent Document 1 below, a refrigerator (2) that can store food, a vacuum exhaust means (3) that is connected to the refrigerator and can discharge the gas in the refrigerator, and the inside of the refrigerator There is known a vacuum cooling device provided with outside air introducing means (21) for releasing the vacuum state of the air. This device is provided with a temperature sensor (8) and a pressure sensor (9) in the refrigerator, and is configured to control the pressure in the refrigerator based on continuous detection signals from the temperature sensor. Specifically, the pressure in the cooler is adjusted so that the temperature (product temperature) of the food in the cooler becomes a temperature (T2) lower than the current product temperature (T1) by a predetermined amount or more. Further, the pressure may be adjusted so that the difference between the temperature inside the cooler and the temperature of the food placed in the cooler is within a set range.

Japanese Patent Application Laid-Open No. 2002-355020 (claim 1, paragraphs 0024 and 0027, FIG. 1)

When food is vacuum-cooled by a vacuum cooling device, as the pressure in the processing tank (cooling chamber) is lowered, the product temperature (food temperature in the processing tank) changes to the pressure conversion temperature in the tank (saturation temperature at the pressure in the processing tank ) will fall. However, when cooling progresses to a certain extent, particularly in the case of liquid foods, the product temperature cannot follow the pressure-converted temperature in the tank, and may deviate from the temperature to cause bumping. When bumping occurs, there is a risk that the yield will decrease due to scattering of food.

In the apparatus disclosed in Patent Document 1, the pressure in the tank is adjusted so as to gradually lower the product temperature. adjusted to However, the set temperature is fixed and remains constant from the start to the end of cooling. In this case, as the cooling progresses, the cooling becomes more difficult, and there is a risk that the cooling will not be completed or the cooling time will be too long.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vacuum cooling apparatus capable of rapidly cooling food while preventing bumping.

The present invention has been made to solve the above problems, and the invention according to claim 1 comprises a processing tank in which food is stored, a depressurizing means for sucking and discharging the gas in the processing tank to the outside, pressure restoring means for introducing outside air into the decompressed processing tank, a pressure sensor for detecting the pressure in the processing tank, a food temperature sensor for detecting the temperature of the food contained in the processing tank, and the and a control means for controlling each means, wherein the control means controls the temperature difference between the temperature detected by the product temperature sensor and the saturation temperature of the pressure detected by the pressure sensor to be a set temperature difference. The inside of the processing tank is decompressed while adjusting the pressure of , and the temperature detected by the product temperature sensor is monitored while the food is cooled by decompressing the inside of the processing tank. The vacuum cooling device is characterized in that the set temperature difference is increased when the temperature becomes less than the set value .

According to the first aspect of the invention, by suppressing the temperature difference between the product temperature and the tank internal pressure conversion temperature to the set temperature difference, the moisture evaporation from the food is controlled at a predetermined rate, and bumping is suppressed. Food can be cooled .

According to the first aspect of the invention, while the food is being cooled by decompressing the inside of the processing tank, the degree of decrease in the temperature of the food is monitored, and the set temperature difference is changed accordingly. Cooling can be achieved.

According to the vacuum cooling device of the present invention, food can be rapidly cooled while preventing bumping.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a vacuum cooling device according to one embodiment of the present invention, partly in cross section; It is a graph showing an example of the cooling operation by the vacuum cooling device of FIG. 1, showing the change in the product temperature TF and the tank internal pressure conversion temperature TS, the vertical axis is the temperature T, the horizontal axis is the elapsed time from the start of operation t.

Specific embodiments of the present invention will now be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a vacuum cooling device 1 according to one embodiment of the present invention, and shows a part thereof in cross section.

The vacuum cooling device 1 of the present embodiment includes a processing tank 2 containing food F, a decompression means 3 for decompressing the processing tank 2 by sucking and discharging the gas in the processing tank 2 to the outside, and A pressure restoring means 4 for introducing outside air into the processing tank 2 to restore the pressure inside the processing tank 2, and a control means (not shown) for controlling these means 3 and 4 to cool the food F in the processing tank 2. Prepare.

The processing tank 2 is a hollow container that can withstand the pressure reduction of the internal space, and can be opened and closed with a door. The processing tank 2 is typically formed in a substantially rectangular box shape, and the front opening can be opened and closed with a door. By opening the door, the food F can be taken in and out of the processing tank 2, and by closing the door, the opening of the processing tank 2 can be airtightly closed. Doors may be provided on both the front and back sides of the processing tank 2 . In the illustrated example, the food F is placed in a food container such as a hotel pan or a tray and stored in the treatment tank 2 .

The decompression means 3 is a means for decompressing the inside of the processing bath 2 by sucking and discharging the gas (air or steam) in the processing bath 2 to the outside. In this embodiment, the decompression means 3 includes a steam ejector 6, a heat exchanger 7 for steam condensation, a check valve 8, and a water-sealed vacuum pump 9 in the exhaust path 5 from the processing tank 2 in this order. .

The steam ejector 6 is provided with a suction port 6a connected to the processing tank 2, and steam from the ejector steam supply passage 10 can be ejected from the nozzle from the inlet 6b toward the outlet 6c. By jetting steam from the inlet 6b to the outlet 6c, the gas in the processing tank 2 is also sucked and discharged to the outlet 6c through the suction port 6a. By operating the opening/closing of the ejector steam supply valve 11 provided in the ejector steam supply path 10, the presence/absence of operation of the steam ejector 6 can be switched.

The heat exchanger 7 is an indirect heat exchanger that exchanges heat between the fluid in the exhaust path 5 and the cooling water without mixing. The heat exchanger 7 allows the steam in the exhaust line 5 to be cooled and condensed with cooling water. Cooling water is supplied to the heat exchanger 7 through a heat exchange water supply line 12 and discharged through a heat exchange water discharge line 13 . A heat exchange water supply valve 14 is provided in the heat exchange water supply path 12 . Although not shown, the heat exchange drainage path 13 is branched into a return path to the cold water tank (cold water supply source) and a drainage outlet path to the outside. is provided, and a heat exchanger drain valve (not shown) is provided in the drain outlet path to the outside. After passing through the heat exchanger 7, the chiller water valve and the heat exchanger drain valve either return the water to the cold water tank, discharge it to the drain outlet, or prevent the flow of water through the heat exchanger 7 without doing either. (that is, whether the cooling water outlet side of the heat exchanger 7 is closed) can be switched. When cold water is supplied to the heat exchanger 7, the cold water after passing through the heat exchanger 7 is returned to the cold water tank by closing the heat exchange drain valve and opening the chiller water valve. On the other hand, when normal temperature water is supplied to the heat exchanger 7, by closing the chiller water valve and opening the heat exchanger drain valve, the normal temperature water after passing through the heat exchanger 7 is discharged to the drainage outlet passage.

The vacuum pump 9 is of a water ring type in this embodiment, and as is well known, is operated while being supplied with water called seal water. Therefore, water is supplied to the water supply port 9 a of the vacuum pump 9 through the sealed water supply path 15 . A sealed water supply valve 16 is provided in the sealed water supply path 15 , and sealing water can be supplied to the vacuum pump 9 by opening the sealed water supply valve 16 . When the vacuum pump 9 is operated with the sealed water supply valve 16 open, the vacuum pump 9 sucks gas from the intake port 9b and exhausts and drains the gas from the exhaust port 9c. The vacuum pump 9 may be on/off controlled, or its output may be adjustable. In this embodiment, the vacuum pump 9 uses an inverter to change the driving frequency of the motor and thus the number of revolutions.

By the way, in the illustrated example, the sealing water supply line 15 and the heat exchange water supply line 12 are shared with the heat exchange water supply line 17 on the upstream side, and the heat exchange water supply valve 14 is provided in the common line 17 . In this case, when the heat exchange water supply valve 14 is opened, water is allowed to flow through the heat exchanger 7, and when the seal water supply valve 16 is opened, the vacuum pump 9 is supplied with water. In this embodiment, water supply to the heat exchanger 7 and the vacuum pump 9 can be switched between normal temperature water and cold water (water cooled by a chiller).

The pressure restoring means 4 is a means for introducing outside air into the decompressed processing tank 2 to restore the pressure inside the processing tank 2 . In this embodiment, the pressure recovery means 4 includes an air filter 19 and an air supply valve 20 in the air supply path 18 leading to the processing tank 2 . When the air supply valve 20 is opened while the inside of the processing tank 2 is depressurized, outside air is introduced into the processing tank 2 through the air filter 19, and the pressure inside the processing tank 2 can be restored. The air supply valve 20 preferably consists of a valve whose degree of opening is adjustable.

The processing tank 2 is further provided with a pressure sensor 21 for detecting the pressure inside the processing tank 2 and a product temperature sensor 22 for detecting the temperature (product temperature) of the food F contained in the processing tank 2 .

The control means is a controller (not shown) that controls the means 3 and 4 based on the detection signals of the sensors 21 and 22, the elapsed time, and the like. Specifically, the vacuum pump 9, ejector steam supply valve 11, heat exchange water supply valve 14, chiller water valve (not shown), heat exchange water discharge valve (not shown), sealing water supply valve 16, air supply valve 20, etc. , pressure sensor 21 and product temperature sensor 22 are connected to the controller. Then, the controller attempts to vacuum-cool the food F in the processing tank 2 according to a predetermined procedure (program), as described below.

A specific example of the operating method of the vacuum cooling device 1 of this embodiment will be described below.
FIG. 2 is a graph showing an example of the cooling operation by the vacuum cooling device 1 of the present embodiment, showing changes in the product temperature TF and the in-tank pressure conversion temperature TS, where the vertical axis is the temperature T and the horizontal axis is Elapsed time t from the start of operation is shown.

Before the start of operation, the air supply valve 20 is open, the ejector steam supply valve 11, the heat exchange water supply valve 14, and the seal water supply valve 16 are closed, and the vacuum pump 9 is stopped. . In this state, the food F is stored in the processing tank 2, and the door of the processing tank 2 is airtightly closed. When the start button is pushed or the like is instructed to start operation, the controller closes the air supply valve 20 and operates the decompression means 3 until the product temperature TF reaches the preset cooling target temperature. The inside of the processing tank 2 is decompressed to cool the food. At this time, in this embodiment, after the rapid cooling control S1, the constant temperature difference control S2 is performed to cool the food F to the cooling target temperature.

In the rapid cooling control S1, the tank internal pressure conversion temperature TS (saturation temperature at the internal pressure of the processing tank 2) is the product temperature TF (the temperature of the food in the processing tank 2). ), the inside of the processing tank 2 is depressurized. Under conditions where the pressure conversion temperature TS in the tank is higher than the product temperature TF, boiling and bumping of the food F do not occur. , the pressure in the treatment tank 2 should be quickly lowered.

The controller can obtain the tank internal pressure conversion temperature TS as the saturation temperature from the pressure detected by the pressure sensor 21 based on a predetermined arithmetic expression (or table) registered in advance. Then, after the rapid cooling control S1 is performed until the in-tank pressure conversion temperature TS falls below the product temperature TF, the temperature difference constant control S2 is performed.

In the temperature difference constant control S2, the pressure inside the processing bath 2 is adjusted so that the temperature difference ΔT between the product temperature TF and the inside pressure converted temperature TS becomes a set temperature difference (for example, 2° C.). is decompressed. That is, the pressure in the processing bath 2 is adjusted so that the temperature difference ΔT between the temperature TF detected by the product temperature sensor 22 and the saturation temperature TS at the pressure detected by the pressure sensor 21 becomes the set temperature difference. Reduce pressure. The pressure in the processing tank 2 is typically adjusted by adjusting the amount of air supplied by the pressure recovery means 4 while the decompression means 3 is in operation. In other words, the opening degree of the air supply valve 20 may be adjusted while the pressure reducing means 3 (at least the vacuum pump 9) is in operation. However, instead of or in addition to this, the decompression capability of the decompression means 3 may be adjusted.

In the temperature difference constant control S2, if the pressure in the processing tank 2 is adjusted so that the pressure conversion temperature TS in the tank is lower than the product temperature TF, the product temperature TF will decrease. The pressure in the tank (temperature TS converted to pressure in the tank) should be lowered in accordance with the decrease in . By suppressing the temperature difference ΔT between the product temperature TF and the pressure conversion temperature TS in the tank to the set temperature difference, the evaporation of water from the food F is controlled at a predetermined rate, and the food F is cooled while suppressing bumping. can be done. In other words, if the pressure is reduced without considering the temperature difference ΔT, the product temperature TF cannot follow the tank internal pressure conversion temperature TS, and when the temperature difference ΔT (pressure difference) increases, bumping occurs in which evaporation occurs suddenly. However, by suppressing the temperature difference ΔT to the set temperature difference, the occurrence of bumping can be suppressed.

It is preferable to lower the rotation speed of the vacuum pump 9 when shifting from the rapid cooling control S1 to the constant temperature difference control S2. For example, in the rapid cooling control S1, the power supply frequency of the vacuum pump 9 is set to the first frequency (for example, 60 Hz). do.

In a series of cooling operations including rapid cooling control S1 and constant temperature difference control S2, water supply to heat exchanger 7 and vacuum pump 9 and operation of steam ejector 6 are controlled as follows, for example. That is, at the start of the cooling operation, the inside of the processing tank 2 is decompressed by the vacuum pump 9 while the normal temperature water is being supplied to the vacuum pump 9 in a state where the water supply to the heat exchanger 7 is stopped. At this stage, the ejector steam valve 11 is closed and the steam ejector 6 is not operating. After that, when the temperature detected by the product temperature sensor 22 becomes equal to or lower than the water flow start temperature (for example, 60° C.), water flow through the heat exchanger 7 is started. At this time, cold water is supplied to the heat exchanger 7 and the vacuum pump 9 . After that, when the temperature detected by the product temperature sensor 22 is equal to or lower than the ejector operating temperature (eg, 30° C.) and the pressure detected by the pressure sensor 21 is equal to or lower than the ejector operating pressure (eg, 45 hPa), the ejector steam supply valve 11 is opened to open the steam ejector. 6 is activated. Then, when the temperature detected by the product temperature sensor 22 reaches the cooling target temperature (for example, 10° C.), the pressure reduction in the processing bath 2 is stopped. Specifically, the ejector steam supply valve 11, the heat exchange water supply valve 14, and the seal water supply valve 16 are closed, the steam ejector 6 and vacuum pump 9 are stopped, and water supply to the heat exchanger 7 is stopped. After that, the air supply valve 20 is opened to restore the pressure in the processing bath 2 to the atmospheric pressure.

During the temperature difference constant control S2, the temperature detected by the product temperature sensor 22 is monitored, and when the temperature drop of the product temperature within the set time Δt of the detected temperature becomes less than the set value, the set temperature difference is set to a predetermined temperature (for example, 0 .5-1°C) should be increased.

For example, during pressure control so that the temperature difference ΔT between the product temperature TF and the in-tank pressure conversion temperature TS becomes the first temperature difference ΔT1 (for example, 2°C), the rate of decrease in the product temperature TF slows down, and the set time Δt ( When the temperature drop width of the product temperature TF within 1 minute) becomes less than a set value (eg 1°C), the temperature difference ΔT becomes a second temperature difference ΔT2 (eg 3°C) larger than the first temperature difference ΔT1. A decrease in the product temperature TF can be promoted by controlling the pressure in such a manner. After that, the rate of decrease of the product temperature TF slows down again, and when the temperature drop width of the product temperature TF within the set time Δt becomes less than the set value, the temperature difference ΔT is set to a third temperature difference larger than the second temperature difference ΔT2. It suffices to repeat pressure control so as to achieve ΔT3 (for example, 4° C.) to promote a decrease in the product temperature TF.

In this way, even if the food is difficult to cool, the food F can be cooled while increasing the set temperature difference. Therefore, even if the food is hard to cool, there is no possibility that the cooling will not be completed or that the cooling time will be too long.

The vacuum cooling device 1 of the present invention is not limited to the configuration (including control) of the above embodiment, and can be modified as appropriate. In particular, a processing tank 2 containing food F, a depressurizing means 3 for sucking and discharging the gas in the processing tank 2 to the outside, a pressure restoring means 4 for introducing outside air into the decompressed processing tank 2, and a processing Equipped with a pressure sensor 21 for detecting the pressure in the tank 2, a product temperature sensor 22 for detecting the temperature of the food F contained in the processing tank 2, and a control means for controlling the means 3 and 4. The means adjusts the pressure in the processing tank 2 so that the temperature difference ΔT between the temperature TF detected by the product temperature sensor 22 and the saturation temperature TS at the pressure detected by the pressure sensor 21 becomes the set temperature difference. is reduced and the set temperature difference .DELTA.T is increased as the pressure in the processing tank 2 is reduced.

For example, in the above embodiment, the configuration of the decompression means 3 can be changed as appropriate. For example, in the above embodiment, the steam ejector 6 is provided as the decompression means 3, but installation of the steam ejector 6 may be omitted depending on the case.

Furthermore, in the above embodiment, the vacuum cooling device 1 has been described as a dedicated cooling machine, but it can be modified appropriately as long as it has a vacuum cooling function. For example, by providing heating means using steam, it may be configured like a steaming cooling device or a saturated steam cooking device. Alternatively, by providing cold air cooling means using a refrigerator or a fan, it may be configured like a cold air/vacuum combined cooling device.

REFERENCE SIGNS LIST 1 vacuum cooling device 2 treatment tank 3 decompression means 4 pressure recovery means 5 exhaust path 6 steam ejector (6a: suction port, 6b: inlet, 6c: outlet)
7 heat exchanger 8 check valve 9 vacuum pump (9a: water supply port, 9b: intake port, 9c: exhaust port)
10 Ejector Steam Supply Line 11 Ejector Steam Supply Valve 12 Heat Exchanger Water Supply Line 13 Heat Exchanger Drainage Line 14 Heat Exchanger Water Supply Valve 15 Sealed Water Supply Line 16 Sealed Water Supply Valve 17 Common Line 18 Air Supply Line 19 Air Filter 20 Air Supply Valve 21 Pressure sensor 22 Product temperature sensor F Food S1 Rapid cooling control S2 Constant temperature difference control

Claims (1)

A processing tank containing food, decompression means for sucking and discharging the gas in the processing tank to the outside, pressure recovery means for introducing outside air into the decompressed processing tank, and detecting the pressure in the processing tank. a pressure sensor, a temperature sensor for detecting the temperature of the food contained in the processing tank, and a control means for controlling each means,
The control means adjusts the pressure in the processing bath so that the temperature difference between the temperature detected by the product temperature sensor and the saturated temperature at the pressure detected by the pressure sensor becomes a set temperature difference. depressurize,
The temperature detected by the product temperature sensor is monitored while the food is cooled by decompressing the inside of the processing tank, and the set temperature difference is increased when the temperature drop range of the detected temperature within the set time is less than the set value.
A vacuum cooling device characterized by:

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