JP7421798B2 - vacuum cooling device - Google Patents

Description

The present invention stores an object to be cooled, such as cooked food, in a processing tank, evaporates the moisture in the object by reducing the pressure inside the processing tank, and rapidly cools the object using the heat of vaporization caused by the evaporation. The present invention relates to a vacuum cooling device that cools the air.

As described in Japanese Unexamined Patent Publication No. 2018-204860, the pressure inside the processing tank is reduced by exhausting the gas inside the processing tank containing the object to be cooled to the outside and reducing the pressure inside the processing tank. Vacuum cooling equipment is known in which the vapor pressure of the object to be cooled is lowered below the saturated vapor pressure of the object to be cooled, and water is evaporated from the object to be cooled, thereby utilizing the heat of vaporization to cool the object. ing. When the pressure inside the processing tank containing the object to be cooled is reduced and the boiling point within the processing tank is lowered than the temperature of the object to be cooled, the moisture in the object to be cooled evaporates, and at that time, water is removed from the object to be cooled. Since the heat of vaporization is taken away, the object to be cooled can be cooled in a short time. In places such as school lunch centers, when cooling cooked food, there is a need to allow the food to pass through the temperature range where bacteria are likely to grow as quickly as possible, and with vacuum cooling equipment, it is possible to cool down the center of the object in a short period of time. It is widely used because it is possible.

A target cooling temperature of the object to be cooled is set in the vacuum cooling device, and vacuum cooling is performed by reducing the pressure inside the processing tank until the temperature of the object stored in the processing tank reaches the target temperature. . To detect the temperature of the object to be cooled, a temperature measurement device that detects the temperature of the object to be cooled is installed in the processing tank, and the temperature of the object to be cooled can be directly detected by inserting the temperature measuring part of the temperature measurement device into the object to be cooled. To detect. In the cooling step, the pressure inside the processing tank is reduced until the temperature of the object to be cooled reaches the cooling end temperature, and when the temperature of the object to be cooled becomes equal to or lower than the cooling end temperature, cooling is ended. After the cooling process is completed, outside air is introduced into the processing tank, the pressure inside the processing tank is restored to atmospheric pressure, and then the object to be cooled is taken out.

Vacuum cooling equipment lowers the pressure inside the processing tank by operating a vacuum generator such as a vacuum pump that exhausts the air inside the processing tank, and cools the object as quickly as possible. If the pressure is reduced at 100% capacity of the device, the speed of pressure reduction may become too fast. If the decompression rate is too fast, the water in the object to be cooled may boil violently, causing the object to boil over from the container if it is liquid, or destroy its shape if it is solid. Therefore, it is desired to cool as quickly as possible without causing bumping or boiling over, and in the cooling process, cooling is performed while adjusting the pressure inside the processing tank.

In the vacuum cooling system, a target temperature is set based on the detected current temperature of the object to be cooled, and processing is performed so that the actual pressure in the processing tank becomes the target pressure using the saturation pressure corresponding to the target temperature as the target pressure. Adjust the pressure inside the tank. The rate of pressure reduction within the processing tank is adjusted by installing an outside air intake valve for taking outside air into the processing tank and adjusting the amount of outside air taken into the processing tank. In the vacuum generator, the rate of pressure reduction in the processing tank is adjusted by adjusting the amount of outside air taken into the processing tank by the outside air intake valve while exhausting air at a constant operating rate.

If the amount of outside air taken in by the outside air intake valve is reduced, the rate of pressure drop in the processing tank will increase, and if the amount of outside air taken in is increased, the rate of pressure drop will be decreased. The pressure will also increase slightly. Since pressure control is performed while adjusting the amount of outside air taken in with respect to the target pressure, which decreases over time, the actual pressure in the treatment tank decreases with a certain control range relative to the target pressure. I'm going to go to the middle of the day. At this time, in areas where the actual pressure is high and the product temperature is high, a 1°C change in product temperature will cause a large change in saturation pressure, so the target pressure will change greatly in response to a change in the current product temperature, and the actual pressure will increase or decrease significantly. However, it continues to decline. However, in a region where the actual pressure is low and the product temperature is low, the change in saturation pressure due to a 1°C change in the product temperature is small, so the actual pressure decreases with a small increase or decrease.

The temperature of the object to be cooled in the processing tank decreases as the actual pressure in the processing tank decreases, but there is a time lag in the decrease in the temperature. When the actual pressure is decreasing with large fluctuations, the interval between increases and decreases in the actual pressure is long, so even if there is a time lag in the decrease in the product temperature, the product temperature will continue to decrease steadily. However, when decreasing the pressure while the range of change in the actual pressure is small, the actual pressure may rise before the product temperature drops due to the time lag of the product temperature drop because the interval between increases and decreases in the actual pressure is small. . In this case, a stagnation occurs in which the product temperature does not decrease, so the cooling time becomes longer.

JP2018-204860A

The problem to be solved by the present invention is a vacuum cooling device that cools objects to be cooled in a processing tank by reducing the pressure inside the processing tank, and the problem is to provide a vacuum cooling device that cools objects to be cooled in a processing tank by reducing the pressure inside the processing tank. It is an object of the present invention to provide a vacuum cooling device which can reduce the cooling time compared to the conventional one.

The invention according to claim 1 provides a processing tank that accommodates an object to be cooled, a vacuum generator that sucks gas in the processing tank, a temperature measuring device that measures the temperature of the object to be cooled in the processing tank, and a processing tank. A pressure measuring device to detect the internal pressure and an outside air intake valve to adjust the pressure inside the processing tank are installed, and by reducing the pressure inside the processing tank, a vacuum is created to cool the objects to be cooled stored in the processing tank. The cooling device is equipped with a temperature measuring device that measures the temperature of the object to be cooled in the processing tank, a pressure measuring device that detects the pressure inside the processing tank, and an outside air intake valve to adjust the pressure inside the processing tank. This is a vacuum cooling device that cools objects to be cooled stored in a processing tank by lowering the pressure inside the processing tank, and during the cooling process, a target product temperature is determined based on the current product temperature measured by the temperature measuring device. The saturation pressure of the target product temperature is set as the target pressure, and the vacuum generator and the outside air intake valve are used to control the pressure so that the pressure inside the processing tank reaches the target pressure. In a vacuum cooling system that performs cooling while updating the target pressure from time to time, when the outside air intake valve is fully closed to adjust the pressure inside the processing tank during the cooling process, the target pressure that is updated from time to time is From pressure control aiming at the desired pressure, the valve adjustment end product temperature is determined based on the current product temperature at that point, and the outside air intake valve is kept fully closed until the measured current product temperature reaches the valve adjustment end product temperature. The vacuum cooling apparatus is characterized in that when the current product temperature becomes equal to or lower than the preset valve adjustment end product temperature, the vacuum cooling device switches back to the pressure control aiming at the target pressure that is updated from time to time.

The invention according to claim 2 provides that in the vacuum cooling apparatus, when the pressure in the processing tank is high at the beginning of the cooling process, the target product temperature determined relative to the detected current product temperature is set to be relatively low. A rapid cooling operation is performed, and when the product temperature drops to a set temperature, a slow cooling operation is performed in which a target product temperature determined relative to the current product temperature is made relatively high.

The invention according to claim 3 provides that in the vacuum cooling apparatus, when the current product temperature becomes lower than the target product temperature near the end of the cooling process and the outside air intake valve is opened, the outside air intake valve is opened. 1. A vacuum cooling device that performs supercooling suppression operation that increases the opening speed of an outside air intake valve per unit time when the valve is operated in the opening direction.

By implementing the present invention, food can be cooled more quickly while preventing the occurrence of bumping and boiling over, and suppressing overcooling.

Flow diagram of a vacuum cooling device implementing the present invention Flowchart of pressure control of a vacuum cooling device implementing the present invention

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of a vacuum cooling device implementing the present invention, and FIG. 2 is a flowchart of pressure control of the vacuum cooling device implementing the present invention.

The vacuum cooling device includes a processing tank 2, a device for generating vacuum, and the like. The vacuum pump 1 is connected to the processing tank 2 through a vacuum pipe 9, and the gas in the processing tank 2 is discharged through the vacuum pipe 9 by operating the vacuum pump 1. A heat exchanger 8 for cooling the gas sucked from the processing tank 2 is provided in the middle of the vacuum piping 9. The gas sucked from the processing tank contains steam evaporated from the object to be cooled, and when water turns into steam, its volume increases significantly. If the steam is sent to the vacuum pump 1 as it is, a large volume of steam must be processed by the vacuum pump 1, which deteriorates the efficiency of the vacuum pump 1. For this purpose, a heat exchanger 8 is provided in the middle of the vacuum piping 9, and the heat exchanger 8 cools the suction gas to condense the steam and reduce the volume of gas that must be exhausted by the vacuum pump 1. ing. A cold water unit 3 that supplies cold water for cooling is connected to the heat exchanger 8, and the cold water is circulated between the cold water unit 3 and the heat exchanger 8. The condensed water separated by the heat exchanger 8 is stored in a condensed water tank installed below the heat exchanger 8, and is discharged from the condensed water tank after the cooling operation is completed.

The processing tank 2 is provided with a pressure measuring device 5 for measuring the pressure inside the processing tank and a temperature measuring device 4 for measuring the temperature of the object 7 to be cooled. The pressure within the processing tank measured by the pressure measuring device 5 and the temperature of the object to be cooled measured by the temperature measuring device 4 are output to an operation control device 6 that controls the operation of the vacuum cooling device. The operation control device 6 controls the operation of the vacuum cooling device by controlling each device of the vacuum cooling device, such as the vacuum pump 1 and the outside air intake valve 10. The operation control device 6 controls each device based on the elapsed time, the temperature of the object to be cooled 7 measured by the temperature measuring device 5, the internal pressure of the processing tank measured by the pressure measuring device 5, and the like.

When performing vacuum cooling, the cold water unit 3 is activated first, and cold water is prepared in the tank of the heat exchanger 8. Then, the object to be cooled 7 is placed in the processing tank 2, and the vacuum pump 1 is operated with the door of the processing tank 2 closed and the inside of the processing tank 2 hermetically sealed. When the vacuum pump 1 is operated, the air in the processing tank 2 is sent to the vacuum pump 1 through the vacuum piping 9, and the air is discharged from the vacuum pump 1 to the outside of the system. The air sent through the vacuum pipe 9 is cooled and reduced in volume as it passes through the heat exchanger 8. In particular, if the air contains steam, the volume can be significantly reduced by cooling the gas and condensing it.

In the cooling process, a target product temperature is calculated based on the current product temperature of the object to be cooled 7 detected by the temperature measuring device 4. To calculate the target product temperature, setting 1, which is a value for calculating the target product temperature from the current product temperature, is determined, and the calculation is performed as target product temperature=current product temperature+setting 1. The appropriate target product temperature is a temperature that is equal to the current product temperature or about 2° C. lower than the current product temperature, but the appropriate difference from the current product temperature varies depending on the shape of the object to be cooled. For example, if the product contains a lot of oil and water is difficult to evaporate, it is better to set the target temperature to a value that is lower than the current temperature. Check the value.

When cooling a material to be cooled, the temperature is controlled so that it reaches the calculated target temperature, but since the vacuum cooling system is operated by controlling the pressure inside the processing tank, I try to set a target pressure. The target pressure is set to the saturation pressure of the target product temperature. Once the target product temperature is determined, the saturation pressure at that temperature is uniquely determined, so the target pressure can be calculated from the target product temperature. The temperature measuring device measures the current product temperature as needed, and the target product temperature is updated as needed. When the target product temperature is updated, the target pressure is also updated, and the pressure in the processing tank is adjusted to reach the updated target pressure. The target product temperature is repeatedly updated until it reaches a preset cooling end temperature, and when the current product temperature reaches the cooling end temperature, the cooling process is ended.

When the target pressure is given, the actual pressure, which is the measured value of the pressure inside the processing tank at the moment, is compared with the target pressure, and if the actual pressure is higher than the target pressure, an operation is performed to lower the pressure inside the processing tank, and vice versa. If the actual pressure is lower than the target pressure, the pressure is adjusted by returning the pressure inside the processing tank. The pressure is adjusted by adjusting the opening degree of the outside air intake valve 10 while the vacuum pump 1 is operating at a constant capacity. If the amount of outside air entering the processing tank 2 is reduced by reducing the opening of the outside air intake valve, the rate of decrease in the pressure inside the processing tank 2 will increase, and the opening of the outside air intake valve will be increased to reduce the amount of outside air entering the processing tank 2. When the amount of outside air entering the tank 2 is increased, the rate of pressure drop in the processing tank 2 becomes smaller. Further, if the amount of outside air taken in by the outside air intake valve is larger than the amount of exhaust air sucked by the vacuum pump 1, the pressure inside the processing tank 2 will increase. When the actual pressure is equal to the target pressure, the opening degree of the outside air intake valve 10 is not changed.

If setting 1 is set to -2℃, the operation will always aim at a target product temperature that is 2℃ lower than the current product temperature, and if the current product temperature decreases, the target product temperature and target pressure will also decrease. , the current product temperature will continue to fall. However, in this case, after cooling progresses to a certain extent, the product temperature may stop decreasing. When a stagnation in the decline in product temperature occurs, the time required for the product temperature to drop to the cooling end temperature increases.

Therefore, as a control to prevent the stagnation of product temperature drop, when the outside air intake valve 10 is fully closed, control is performed to extend the time during which the actual pressure is lower than the target pressure by keeping it fully closed for a longer period of time. I do. Specifically, when the outside air intake valve 10 is fully closed, the outside air intake is continued until the current product temperature reaches a temperature lower by the setting 2 than the temperature at the time when the valve is fully closed (valve adjustment completed product temperature). Keep valve 10 fully closed. The outside air intake valve 10 is kept fully closed until the current product temperature reaches the product temperature at which valve adjustment has been completed, and when the product temperature reaches the product temperature at which valve adjustment has been completed, the original current product temperature + setting 1 is set as the target product temperature and the pressure is adjusted. to return to control.

FIG. 2 is a flowchart of the above control, and will be explained based on the flowchart of FIG. In the flowchart, in ST1, the target product temperature is set from the current product temperature and the value of setting 1, and in ST2, the target pressure is set from the saturation pressure of the target product temperature. A in ST3 is the opening degree of the outside air intake valve 10, and the previous opening degree of the outside air intake valve is used as a reference. In the next ST4, the target pressure determined in ST2 and the actual pressure in the processing tank measured by the pressure measuring device 5 are compared, and if the actual pressure is higher than the target pressure, the process goes to ST6, otherwise the process branches to ST5. In ST5, it is further confirmed whether the actual pressure is equal to the target pressure, and if the actual pressure is equal to the target pressure, the process moves to ST8; otherwise, if the actual pressure is lower than the target pressure, the process moves to ST7.

If ST6 is to be executed because the actual pressure is higher than the target pressure, it is necessary to reduce the pressure inside the processing tank, so the opening degree of the outside air intake valve 10 is adjusted in the closing direction, and the processing tank 2 An operation is performed to lower the pressure inside the processing tank 2 by reducing the amount of outside air taken into the tank. On the other hand, if ST7 occurs because the actual pressure is lower than the target pressure, the pressure in the processing tank has dropped too much, so adjust the opening of the outside air intake valve 10 in the opening direction. By increasing the amount of outside air taken into the processing tank 2, the depressurization speed is reduced, and furthermore, the pressure inside the processing tank 2, which has fallen too low, is increased. When the actual pressure is equal to the target pressure, the opening degree of the outside air intake valve 10 is not changed.

In the next step ST8, the process branches depending on the opening degree of the outside air intake valve 10. If the outside air intake valve 10 is fully closed, the process moves to ST9, and in ST9, the valve adjustment finished product temperature is set to a value that is two settings lower than the current product temperature.

In the next ST10, the product temperature for which valve adjustment has been completed and the current product temperature are compared, and if the current product temperature is higher than the product temperature for which valve adjustment has been completed, the outside air intake valve is Continue with fully closed. When the current product temperature is equal to or lower than the valve adjustment end product temperature, the valve adjustment control is ended in ST11, and the opening degree of the outside air intake valve 10 is returned to a state where it can be changed.

In this valve adjustment control, the outside air intake valve 10 is fully closed until the current product temperature becomes equal to or lower than the valve adjustment end product temperature. The pressure will decrease, and the product temperature will decrease. Therefore, it is possible to prevent the decline in product temperature from stagnation.

The reason why the outside air intake valve 10 is fully closed is when the pressure inside the processing tank is low, making it difficult for the pressure to drop, and this period coincides with the period when a stagnation in the drop in product temperature is likely to occur. At the timing when the outside air intake valve 10 is fully closed, valve adjustment control is performed to keep the outside air intake valve 10 fully closed, and the outside air intake valve is kept fully closed until the product temperature drops by the amount set by setting 2. By continuing to do this, it is possible to prevent a stagnation in the drop in product temperature and to steadily lower the product temperature.

In addition, at the beginning of the cooling process, when the pressure inside the processing tank is high, rapid cooling operation is performed to relatively lower the target product temperature determined based on the detected current product temperature, and when the product temperature drops to the set temperature, the current By performing a slow cooling operation in which the target product temperature determined relative to the product temperature is relatively high, the time required for the cooling operation can be shortened while suppressing bumping. If the time is before boiling occurs due to moisture in the object to be cooled, rapid depressurization will not affect the shape of the object to be cooled, so the cooling process time can be shortened by performing rapid cooling operation during that time. be able to.

In the pressure control in the cooling process, the outside air intake valve 10 is operated in the opening direction to lower the pressure reducing ability and increase the pressure in the processing tank, and the outside air intake valve 10 is operated in the closing direction. The pressure inside the processing tank is reduced by increasing the decompression capacity. At this time, it is also preferable that the amount of operation performed in the direction of closing the outside air intake valve 10 and the amount of operation performed in the direction of opening the outside air intake valve 10 are made different. In a high vacuum state, the pressure inside the processing tank will immediately rise even if the opening degree of the outside air intake valve 10 is slightly increased; however, if you try to reduce the pressure inside the processing tank, Even if the open air intake valve 10 is slightly closed, the pressure inside the processing tank does not decrease easily. Therefore, if weighting is performed so that the amount of operation when opening the outside air intake valve 10 is small and the amount of operation when closing the outside air intake valve 10 is weighted to be large, more appropriate pressure control can be performed.

Regarding the opening degree (opening speed) of the outside air intake valve 10 per unit time, near the end of the cooling process, the opening degree per unit time when the outside air intake valve 10 is operated in the opening direction is By increasing the size, the pressure inside the processing tank increases faster. At the end of the cooling process, when the difference between the current product temperature and the cooling end temperature becomes less than a predetermined temperature, supercooling becomes a problem. Even if the internal pressure of the processing tank increases, the product temperature does not rise, and by speeding up the pressure rise time, it is possible to prevent the product temperature from falling too much from the target product temperature, and it is possible to suppress overcooling.

It should be noted that the present invention is not limited to the embodiments described above, and many modifications can be made within the technical idea of the present invention by those having ordinary knowledge in this field.

1 Vacuum pump
2 Processing tank
3 Chilled water unit 4 Temperature measurement device 5 Pressure measurement device 6 Operation control device 7 Object to be cooled 8 Heat exchanger 9 Vacuum piping 10 Outside air intake valve

Claims (3)

A processing tank that accommodates objects to be cooled, a vacuum generator that sucks gas in the processing tank, a temperature measurement device that measures the temperature of the objects to be cooled in the processing tank, and a pressure measurement device that detects the pressure inside the processing tank. A vacuum cooling device is provided with an outside air intake valve for adjusting the pressure inside the processing tank, and cools objects to be cooled stored in the processing tank by reducing the pressure inside the processing tank,
During the cooling process, a target product temperature is determined based on the current product temperature measured by the temperature measuring device, the saturation pressure of the target product temperature is set as the target pressure, and a vacuum generator and outside air are used to bring the pressure inside the processing tank to the target pressure. In the vacuum cooling system, the pressure is controlled by the intake valve, and the detection of the current product temperature is updated as needed to perform cooling while updating the target pressure as needed.
When the outside air intake valve is fully closed to adjust the pressure inside the processing tank during the cooling process, the valve adjustment is completed based on the current product temperature at that point, starting from pressure control aiming at the target pressure that is updated from time to time. The product temperature is determined, and the control is switched to keep the outside air intake valve fully closed until the measured current product temperature reaches the product temperature at which valve adjustment has been completed, and the current product temperature is below the preset product temperature at which valve adjustment has been completed. In this case, the vacuum cooling device returns to pressure control aiming at the target pressure that is updated from time to time. In the vacuum cooling apparatus according to claim 1, at the beginning of the cooling process and when the pressure in the processing tank is high, a rapid cooling operation is performed in which a target product temperature determined with respect to the detected current product temperature is relatively low; A vacuum cooling device characterized in that, when a product temperature falls to a set temperature, a gradual cooling operation is performed in which a target product temperature set relative to the current product temperature is made relatively high. In the vacuum cooling device according to claim 1 or 2, when the current product temperature becomes lower than the target product temperature near the end of the cooling process and the outside air intake valve is opened, the outside air intake valve is moved in the opening direction. 1. A vacuum cooling device that performs supercooling suppression operation that increases the opening speed of an outside air intake valve per unit time when operated.

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