JP6690982B2 - Vacuum cooling device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a vacuum cooling device that cools an object to be cooled by utilizing heat of vaporization generated when the inside of the processing tank is evacuated and moisture is evaporated from the object to be cooled in the processing tank.

  BACKGROUND ART There is a vacuum cooling device in which an object to be cooled such as cooked food is stored in a processing tank and the object to be cooled is cooled by reducing the pressure in the processing tank. When the pressure inside the processing tank containing the object to be cooled is reduced, the saturated steam temperature in the processing tank decreases, and when the saturated steam temperature becomes lower than the temperature of the object to be cooled, the moisture in the object to be cooled evaporates. To do. At that time, since the heat of vaporization is taken from the object to be cooled, the object to be cooled can be cooled in a short time. As a vacuum generator used for the vacuum cooling device, an ejector using water or steam and a water-sealed or dry-type vacuum pump are used. When a dry-type vacuum pump is used, the supply of steam and the circulation of water are not required, so that the structure of the device can be simplified.

When the gas in the processing tank is sucked by the vacuum generator, the vapor generated from the object to be cooled is sucked together with the gas. However, since the volume of water increases significantly when it changes from liquid to gas, the amount of gas that must be discharged by the vacuum generator increases if the vapor is sucked into the vacuum generator as it is. In that case, the time required for depressurizing the inside of the processing tank becomes long, so that the cooling process time becomes long. Therefore, as described in JP-A-2014-159931, a heat exchanger for cooling the gas sucked by the vacuum generator is provided in the middle of the vacuum path for sending the gas in the processing tank to the vacuum generator. The gas is cooled in the middle of the vacuum path. When the gas is cooled by the heat exchanger, the volume of the gas is reduced. Particularly, when the vapor is cooled and returned to the liquid, the volume is significantly reduced, so that the volume of the gas that the vacuum generator has to suck is reduced, and the efficiency of vacuum cooling can be improved.

In the invention described in JP-A-2014-159931, the condensed water generated by cooling the steam is stored in a drain tank installed below the heat exchanger and discharged as a drain. In the case where the vacuum generator is a dry type vacuum pump, if the vacuum pump sucks in water droplets, the exhaust capability will be reduced. Therefore, water drops generated in the vacuum path are stored as drain in a drain tank so that they are not sent to the vacuum pump as much as possible. However, some of the water vapor is sent to the vacuum pump, and the drain generated in the vacuum pump may remain in the vacuum pump. Therefore, in the invention described in JP-A-2014-66384, the cooling operation is performed. After that, the vacuum pump is dried.

The vacuum pump conveys the air inside the pump by rotating the internal impeller, and lowers the internal pressure by pushing it out of the pump, and the air in the processing tank flows into the vacuum pump due to the decrease in pressure. This reduces the pressure inside the processing tank. Even if water enters the vacuum pump, there is no problem as long as it is discharged together with the exhaust, but when drainage is accumulated in the vacuum pump, the capacity of the vacuum pump is reduced. When the amount of air sucked from the vacuum passage portion decreases due to the accumulation of drain in the vacuum pump, the cooling time of the object to be cooled becomes longer. Therefore, in the invention described in Japanese Patent Laid-Open No. 2014-66384, the drying operation of the vacuum pump is performed. As also described here, the vacuum cooling operation cannot be performed during the drying operation of the vacuum pump. Therefore, the batch operation of vacuum cooling is continuously performed, and in the vacuum cooling device that performs the drying operation during the batch operation, if the time of the drying operation becomes long, the start of the vacuum cooling operation will be delayed. It was Therefore, it is necessary to dry the vacuum pump more efficiently and effectively.

JP, 2014-66384, A

  The problem to be solved by the present invention is to provide a vacuum cooling device capable of more efficiently and effectively performing a drying operation of a vacuum pump.

The invention according to claim 1 includes a processing tank for accommodating an object to be cooled, a vacuum pump connected to the processing tank by a vacuum path for sucking gas in the processing tank, and a vacuum path connecting the processing tank and the vacuum pump. Vacuum valve that shuts off the vacuum path on the way, vacuum pump air introduction valve for introducing outside air between the vacuum valve of the vacuum path and the vacuum pump, operation of the vacuum pump or vacuum valve, vacuum pump air introduction valve In the vacuum cooling device, which has an operation control device for controlling the cooling of the object to be cooled contained in the processing tank by evacuating the inside of the processing tank, the operation control device includes a vacuum cooling device. After the end, the vacuum pump drying operation is performed to operate the vacuum pump with the vacuum valve closed.In the vacuum pump drying operation, intermittent ventilation drying is performed by intermittently opening and closing the vacuum pump air introduction valve. rear Thereafter have line continuous throughdrying to remain open the vacuum pump air inlet valve, that is one that is to perform the drying under reduced pressure for reducing the pressure within the vacuum pump is stopped the air introduction into the vacuum pump Characterize.

According to the invention of claim 2 , in the vacuum cooling device, the shortest drying operation time for immediately performing the vacuum cooling operation of the next batch and the longest for the case where there is an interval before the vacuum cooling operation of the next batch. When the drying time is set and the vacuum cooling of the next batch is performed immediately, the drying operation is terminated when the drying operation of the shortest drying operation time is performed, and when there is an interval before the vacuum cooling operation of the next batch, It is characterized in that the drying operation is terminated when the drying operation for the longest drying time is performed.

  When the present invention is implemented, the drying operation of the vacuum pump can be performed more efficiently and effectively.

Flow chart of the vacuum cooling device in one embodiment of the present invention Time chart during vacuum cooling operation in one embodiment of the present invention Time chart during vacuum cooling operation in another embodiment of the present invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of a vacuum cooling device in one embodiment of the present invention, and FIGS. 2 and 3 are time charts during vacuum cooling operation in one embodiment of the present invention. The vacuum cooling device includes a processing tank 2, a vacuum pump 1, a heat exchanger 4, a cold water unit 3, a drain tank 6, an operation control device 5, and the like. The vacuum cooling device depressurizes the inside of the processing tank 2 to evaporate moisture from the object to be cooled housed in the processing tank 2 and cools it by the action of heat of vaporization generated at that time.

The processing tank 2 and the vacuum pump 1 are connected by a vacuum path 9, and the gas in the processing tank 2 is discharged by operating the vacuum pump 1. At this time, if the vacuum pump 1 sucks the vapor generated from the object to be cooled together with the gas in the processing tank 2, the volume of the gas that the vacuum pump 1 has to suck becomes large, and the inside of the processing tank 2 becomes large. Since it takes time to reduce the pressure, the cooling time becomes long. Therefore, the heat exchanger 4 is provided in the vacuum path 9 and the gas or vapor sucked by the vacuum pump 1 is cooled by the heat exchanger 4 to reduce the volume of gas to be sucked. ing.

The heat exchanger 4 is connected to the cold water unit 3 so that the cold water generated in the cold water unit 3 is stored in the tank of the heat exchanger 4. In the heat exchanger 4, a plurality of heat transfer tubes are installed so as to penetrate through a tank for storing cold water, and the gas sucked from the processing tank 2 is dispersed in the heat transfer tubes so that the sucked gas is cooled. I do. A drain collecting chamber 12 for collecting condensed water generated by cooling the suction gas as a drain is provided below the heat exchanger 4. The drain is collected in the drain collecting chamber 12 and then sent to the drain tank 6 connected to the lower side of the heat exchanger 4 through the drain discharge path, and is stored in the drain tank 6 in the drain discharge path.

The processing tank 2 is configured such that an object to be cooled can be housed and hermetically sealed therein. The processing tank 2 is housed in the processing tank 2 and a tank pressure detection device 7 for detecting the internal pressure. An article temperature detection device 8 for detecting the temperature of the object to be cooled is provided. A processing chamber vacuum release valve 10 for introducing air into the processing tank 2 after the completion of vacuum cooling is also installed in the processing tank 2. When the atmosphere in the processing tank vacuum release valve 10 is introduced, the door of the processing tank cannot be opened and the object to be cooled cannot be taken out from the processing tank when the inside of the processing tank is depressurized by vacuum cooling. When the cooling process is completed, the atmosphere is introduced into the process tank through the process tank vacuum release valve 10, and then the cooled object is taken out.

A vacuum valve 11 is installed between the heat exchanger 4 and the vacuum pump 1 in the vacuum path 9, and a vacuum pump intake air temperature sensor 15 and a vacuum pipe pressure sensor 13 are installed downstream of the vacuum valve 11 in the vacuum path 9. Further, a vacuum pump air introduction unit is provided for introducing the atmosphere between the vacuum valve 11 of the vacuum path 9, the vacuum pipe pressure sensor 13, and the vacuum pump intake air temperature sensor 15, and a vacuum provided in the vacuum pump air introduction unit. The open air is supplied to the suction side of the vacuum pump 1 by opening the pump air introduction valve 14. The respective detection devices and operation valves are connected to the operation control device 5 that controls the operation of each part. The operation control device 5 controls the operation of each device of the vacuum cooling device based on the operation control program and each measurement value detected by the sensors.

The vacuum cooling operation in the embodiment will be described based on FIGS. 2 and 3. As shown in FIGS. 2 and 3, the vacuum cooling process performed by the operation control device 5 includes a cooling preparation process for preparing cooling, a vacuum cooling process for depressurizing the inside of the processing tank 2, and a processing tank after completion of cooling. It is composed of a vacuum releasing step for returning the pressure inside 2. When the batch operation of vacuum cooling is continuously performed, the cooling preparation process for the next batch is started after the vacuum releasing process.

The operation control device 5 sets the shortest drying operation time for continuous cooling operation and the longest drying operation time for when there is an interval until the next batch cooling operation such as after one day of operation. If the cooling operation is continuously performed, the cooling operation of the next batch is enabled on the condition that the drying operation for the shortest drying operation time is performed, and if there is an interval until the next batch cooling operation, Perform the drying operation until the longest drying operation time has elapsed, and then finish the drying operation. 2 shows the case where the vacuum cooling operation of the next batch is carried out immediately after the completion of the vacuum cooling operation, and FIG. 3 shows the operation which is stopped after the completion of the vacuum cooling operation, and the drying operation for completely drying the vacuum pump is carried out. This is the case.

First, a batch operation of vacuum cooling will be described with reference to FIG. In the cooling preparation step, the object to be cooled is housed in the processing tank 2 and the processing tank 2 is closed by closing the door of the processing tank 2. Further, the cold water unit 3 is operated to store the cooling water in the cooling water tank of the heat exchanger 4.

In the cooling process, the vacuum valve 11 is open, and the processing tank vacuum release valve 10 and the vacuum pump air introduction valve 14 are closed. When the vacuum pump 1 is operated, the vacuum pump 1 sucks and discharges the gas in the processing tank 2 through the vacuum path 9, so that the pressure in the processing tank 2 decreases. When the pressure in the processing tank 2 decreases and the saturated vapor temperature in the processing tank 2 becomes lower than the temperature of the object to be cooled, water is evaporated from the object to be cooled contained in the processing tank 2. When water evaporates, the heat of vaporization is taken from the surroundings, so that the temperature of the object to be cooled rapidly drops. The heat of the object to be cooled in the processing tank 2 is sent through the vacuum path 9 together with the air sucked by the vacuum pump 1, passes through the vacuum pump 1, and is then discharged to the outside of the system.

The operation control device 5 performs the cooling operation so that the temperature of the object to be cooled in the processing tank 2 detected by the product temperature detection device 8 reaches the target temperature. At this time, when performing gradual cooling for adjusting the cooling rate, the opening degree of the processing tank vacuum release valve 10 is adjusted and the pressure is reduced while introducing air, thereby adjusting the pressure decrease rate in the processing tank 2. To do. When the object to be cooled is cooled to the target temperature and the cooling process is completed, the process of releasing the vacuum is performed in which the outside air is introduced into the processing tank 2 to restore the pressure in the processing tank to the atmospheric pressure. The operation control device 5 closes the vacuum valve 11 and opens the processing tank vacuum release valve 10 to increase the pressure in the processing tank. Also in this case, when performing the gradual return for adjusting the pressure-regaining speed, the opening rate of the processing tank vacuum release valve 10 is adjusted to adjust the pressure rising speed in the processing tank 2.

When the pressure in the processing bath 2 detected by the in-vessel pressure detection device 7 returns to atmospheric pressure, the vacuum releasing process is terminated. When the vacuum is released, the door of the processing tank 2 can be opened, and the object to be cooled is taken out of the processing tank 2. In addition, the vacuum pump is dried at the same time as the vacuum is released. If the subsequent batch is to be vacuum cooled, the vacuum pump must be dried during the vacuum releasing step. The vacuum pump is dried by closing the vacuum valve 11 and operating the vacuum pump. By closing the vacuum valve 11, the part of the vacuum pump 1 is separated from the processing tank 2, so that the vacuum release in the processing tank and the drying operation in the vacuum pump can be performed in parallel.

During the drying operation of the vacuum pump, the opening / closing of the vacuum pump air introduction valve 14 is controlled to adjust the amount of air introduced into the vacuum pump 1. The opening / closing control of the vacuum pump air introduction valve 14 is determined based on the amount of water in the vacuum pump 1. During the cooling operation of the vacuum cooling device, the vacuum pump 1 sucks air containing water vapor, so that water enters the vacuum pump 1 and water drops adhere to the surface of the vacuum pump. Therefore, the water droplets in the vacuum pump are removed by performing the drying operation. In the operation control device 5, as a step during the drying operation, intermittent ventilation drying for intermittently opening and closing the vacuum pump air introduction valve 14, continuous ventilation drying for maintaining the vacuum pump air introduction valve 14 in an open state, vacuum pump air introduction The reduced pressure drying for keeping the valve 14 closed is set, and the drying operation is performed by combining these steps.

The drying operation shown in FIG. 2 is performed in a batch operation of vacuum cooling continuously, and therefore is performed only in a short time of releasing the vacuum. The inside of the pump is being dried. When the vacuum pump air introduction valve 14 is opened while the vacuum pump is operating, a flow of air is created in the vacuum pump, and water drops adhering to the inner surface of the vacuum pump can be pushed away by the air flow. However, when the water droplets on the inner surface of the vacuum pump are small, the water droplets inside the vacuum pump 1 will be pressed against the wall surface of the vacuum pump by the air flow while a large amount of air is flowing, and the water droplets inside the vacuum pump will be suppressed. It spreads thinly on the wall. In this case, the action of the air flow pushing the water droplets is reduced, and the water droplets are less likely to be pushed out. In such a state, it is effective to open and close the vacuum pump air introduction valve 14 while continuing the operation of the vacuum pump 1. When the vacuum pump air introduction valve 14 is closed, the supply of air is stopped, so that the pressure in the vacuum pipe downstream of the vacuum valve 11 decreases. Then, the force that presses the water droplets against the wall surface by the air flow flowing in the vacuum pump becomes weaker, and the water droplets are gathered and aggregated by the surface tension, which increases the thickness. When the vacuum pump air introduction valve 14 is opened in this state and the air flow rate is increased, the area in which the water droplet receives the air flow is increased, so that the action of the air flow pushing the water drop is increased, and the water drop is directed toward the outlet. It can be pushed out greatly.

Intermittent aeration drying for opening and closing the vacuum pump air introduction valve 14 is effective when water droplets of a size that can be swept off are attached to the inner surface of the vacuum pump, but after running out of water drops that can be swept away. Even if the air is intermittently flown, it becomes impossible to push out the water drop having a thin film on the inner surface of the vacuum pump by the air flow. In that case, continuous aeration drying is performed in which air is continuously flowed and the force of the wind accelerates the evaporation of water droplets. The operation control device fixes the vacuum pump air introduction valve 14 in an open state after intermittently opening and closing the vacuum pump air introduction valve 14 for a predetermined time. When the vacuum pump air introduction valve 14 is opened, air always flows in the vacuum pump, and the moisture on the inner surface of the vacuum pump can be evaporated by the force of the wind.

If the batch operation of vacuum cooling is continuously performed and the next batch is to be performed immediately after the cooling is completed, in order to prevent the start of the next batch from being delayed by the vacuum pump drying operation, a predetermined time such as 30 seconds or vacuum release The drying operation is completed until the process is completed. The operation control device 5 vacuum-cools the next batch after the drying operation for the shortest drying operation time is completed. By performing the drying operation of the vacuum pump 1, the vacuum pump can exhibit the required capacity at the next vacuum cooling.

FIG. 3 is a time chart when the final vacuum cooling operation is performed for one day and then stopped. The process up to the end of the cooling process, the vacuum release process, and the drying operation of the vacuum pump in parallel with the vacuum release is the same as in the case of FIG. However, in the drying operation performed after the vacuum cooling step in FIG. 3, the inside of the vacuum pump is completely dried over a long time.

By performing intermittent aeration drying in which the vacuum pump air introduction valve 14 is intermittently opened and closed as described above, water droplets in the vacuum pump can be discharged from the vacuum pump by an air flow. Furthermore, after performing intermittent ventilation drying for a set time, continuous aeration drying with the vacuum pump air introduction valve 14 left open is performed. This continuous aeration drying creates an air flow in the vacuum pump 1 aiming at the effect of evaporating water droplets thinly attached to the surface inside the vacuum pump by the force of the wind.

In the longest drying operation, the vacuum pump air introduction valve 14 is closed and the vacuum pump is dried after the continuous aeration drying to dry the inside of the vacuum pump. When the vacuum pump air introduction valve 14 is closed, the inflow of outside air is stopped, so that the pressure inside the vacuum pump decreases. Since the vacuum valve 11 is closed during the drying operation of the vacuum pump, the range in which the vacuum pump depressurizes is narrow, and the pressure immediately drops in the vacuum pump. When the pressure inside the vacuum pump becomes lower than the saturated vapor pressure of the water droplets inside the vacuum pump, the water droplets inside the vacuum pump evaporate, so the inside of the vacuum pump can also be dried by reducing the pressure. For example, if water drops enter the groove, it is difficult to evaporate them only by the action of wind, but if the pressure inside the vacuum pump is made lower than the saturated vapor pressure, the water drops inside the vacuum pump will evaporate due to boiling. It is possible to evaporate water droplets that enter the groove, which is difficult to evaporate by the force of wind. When the drying operation time can be extended, the drying is performed for the longest drying operation time, and the vacuum pump is completely dried.

The present invention is not limited to the above-described embodiments, and many modifications can be made by a person having ordinary skill in the art within the technical idea of the present invention.

1 vacuum pump
2 processing tanks
3 Cold water unit
4 heat exchanger
5 Operation control device 6 Drain tank
7 Tank pressure detection device
8 Product temperature detector
9 Vacuum path
10 Processing tank vacuum release valve
11 Vacuum valve
12 drain meeting room
13 Vacuum piping pressure sensor 14 Vacuum pump air introduction valve 15 Vacuum pump intake air temperature sensor

Claims (2)

A processing tank that contains the object to be cooled, a vacuum pump that is connected to the processing tank by a vacuum path to suck gas in the processing tank, and a vacuum valve that shuts off the vacuum path in the middle of the vacuum path that connects the processing tank and the vacuum pump. A vacuum pump air introduction valve for introducing outside air between the vacuum valve and the vacuum pump of the vacuum path, an operation control device for controlling the operation of the vacuum pump and the vacuum valve, and the vacuum pump air introduction valve, In a vacuum cooling device configured to cool an object to be cooled contained in the processing tank by evacuating the inside of the processing tank, in the operation control device, a state in which a vacuum valve is closed after completion of vacuum cooling. The vacuum pump drying operation is performed by operating the vacuum pump with the vacuum pump drying operation.In the vacuum pump drying operation, the vacuum pump air introduction valve is opened after intermittent ventilation drying in which the vacuum pump air introduction valve is opened and closed intermittently. Thereafter have line continuous throughdrying maintaining gastric state, vacuum cooling apparatus, characterized in that the air inlet stop is one that is to perform the drying under reduced pressure for reducing the pressure within the vacuum pump to the vacuum pump.   The vacuum cooling device according to claim 1, wherein a minimum drying operation time for immediately performing a vacuum cooling operation of the next batch and a maximum drying time for an interval between vacuum cooling operations of the next batch are set. If vacuum cooling of the next batch is to be performed immediately, the drying operation will be terminated when the drying operation of the shortest drying operation time is performed, and if there is an interval before the vacuum cooling operation of the next batch, the drying of the longest drying time will be completed. The vacuum cooling device is characterized in that the drying operation is terminated when the operation is performed.

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