JP6138013B2 - Vacuum cooling device - Google Patents

Description

The present invention relates to a vacuum cooling device that evacuates the inside of a processing tank containing a processed product and uses heat of vaporization generated by evaporating moisture from the processed product to remove heat from the processed product and cool it. Is. More specifically, the present invention relates to a vacuum cooling device that can improve the cooling rate in vacuum cooling and perform cooling in a short time.

As described in Japanese Patent Application Laid-Open No. 2012-102956, there is a vacuum cooling device for storing a processed product such as food cooked in a processing tank and cooling the processed product by evacuating the processing tank. is there. When the inside of the treatment tank containing the treatment object is depressurized and the saturated vapor temperature in the treatment tank is lowered to the temperature of the treatment object, moisture in the treatment object evaporates, and at that time, the heat of vaporization is generated from the treatment object. Take away. In this case, heat can also be taken from the central portion of the processed material, and the cooling effect by the heat of vaporization is great, so that the processed material can be cooled in a short time. As a vacuum generator used for a vacuum cooling device, an ejector using water or steam or a water-sealed or dry vacuum pump is used. When the gas in the treatment tank is sucked by the vacuum generator, a large amount of moisture evaporates from the treatment object, so that the vapor generated from the treatment object is also sucked together with the gas in the treatment tank. However, since the volume of water greatly increases when water is changed to gas, if the vapor is sucked into the vacuum generator as it is, the amount of gas that must be discharged by the vacuum generator increases. In that case, since the time required for decompression in the treatment tank becomes longer, the cooling process time becomes longer.

Therefore, a heat exchanger that cools the gas sucked by the vacuum generator is provided in the middle of the vacuum pipe that sends the gas in the processing tank to the vacuum generator. When the suction gas is cooled in the middle of the vacuum pipe, the volume of the gas is reduced. In particular, when the vapor is returned to a liquid by cooling, the volume is significantly reduced. By reducing the volume of gas that the vacuum generator must suck, the efficiency of decompression can be increased. Drain generated by cooling the steam is accumulated in a drain tank installed below the heat exchanger. During the operation of vacuum cooling, the portion communicating with the treatment tank has a negative pressure. In this case, even if the drain valve for discharging the drain is opened, the drain cannot be discharged. Therefore, the drain is stored until the end of the vacuum cooling operation, and is discharged after the vacuum cooling operation is ended and the inside of the treatment tank is returned to the atmospheric pressure.

In the vacuum cooling device, in the early stage of the vacuum cooling process in which the pressure in the processing tank is high, the amount of gas that can be discharged by the vacuum generator increases, so the pressure in the processing tank decreases rapidly. In the early stage of cooling, since the temperature of the processed material is high, the amount of water evaporated from the processed material is increased, and the temperature of the processed material is rapidly decreased. As the vacuum cooling process progresses and the degree of vacuum in the processing tank increases, the amount of gas that can be discharged even when the vacuum generator is operating decreases, and the pressure reduction rate in the processing tank decreases. Go. Further, since the temperature of the processed product is lowered, the amount of evaporation is reduced, and the rate of decrease in the processed product temperature is reduced.

The vacuum cooling device lowers the saturated vapor temperature determined from the pressure in the treatment tank by lowering the pressure in the treatment tank, and evaporates moisture in the treatment object by lowering it to the temperature of the treatment object. It reduces the temperature of the object. Therefore, while the temperature of the processed material is high, the temperature of the processed material can be lowered even if the degree of vacuum is low, but in order to lower the processed material to a lower temperature, the pressure in the processing tank is further decreased. It will be necessary. In view of this, the low-temperature vacuum cooling apparatus can reduce the pressure until the inside of the processing tank becomes a high vacuum.

By the way, the drain stored in the drain tank is the one obtained by cooling and condensing the steam, but in the vacuum cooling device that depressurizes the inside of the processing tank to a high vacuum, when the drain tank is also in a high vacuum state, May evaporate again. When the steam generated in the drain tank is sent to the vacuum generator, the pressure reduction speed in the vacuum generator is reduced, so that the cooling time is extended. In addition, when the drain remains in the heat exchanger without flowing into the drain tank, the pressure in the heat exchanger becomes lower than the pressure in the drain tank, so that the evaporation of the drain occurs in the heat exchanger. . Even in this case, the cooling time becomes longer. Therefore, it has been desired that the drain tank can easily take in the drain from the heat exchanger, and that the drain tank does not easily re-evaporate in the drain tank.

JP 2012-102956 A

  The problem to be solved by the present invention is to provide a vacuum cooling device capable of improving the cooling rate and performing cooling in a short time in the vacuum cooling device.

  The invention described in claim 1 is a treatment tank that accommodates a processed material, a vacuum generator that is connected to the treatment tank by a vacuum pipe and sucks the gas in the treatment tank, and cools the gas sucked by the vacuum generator. In a vacuum cooling device that has a heat exchanger that condenses steam and a drain tank that accumulates drain generated in the heat exchanger, and that cools the processed material stored in the processing tank by evacuating the processing tank In addition, a drain transfer pipe and an air circulation pipe are connected between the heat exchanger and the drain tank, and a drain tank side tip of the drain transfer pipe is positioned to be submerged in the drain for the drain tank, and the air circulation pipe is It is provided at a position where the drain does not submerge.

According to a second aspect of the present invention, in the vacuum cooling apparatus, a vent valve is provided midway in the air circulation pipe, and the vent valve is opened at the beginning of the vacuum cooling process, A closing operation is performed at the end of the process.

In the present invention, the drain transfer pipe and the air circulation pipe are connected between the heat exchanger and the drain tank, and since the tip of the drain transfer pipe is close to the bottom of the drain tank, when the drain accumulates in the drain tank, The tip of the drain transfer pipe will be submerged in the drain. In the early stage of the vacuum cooling process, since the temperature of the processed product is high, a large amount of steam is generated from the processed product when the saturated vapor temperature in the processing bath becomes equal to or lower than the processed product temperature by reducing the pressure in the processing tank. This steam has a relatively high temperature and a large amount, and condenses by cooling with a heat exchanger and accumulates in the drain tank as drain.

When the pressure is reduced by the vacuum generator, the pressure in the heat exchanger is lower than the pressure in the drain tank because the heat exchanger is closer to the vacuum generator than the drain tank. Then, in the drain transfer pipe connecting the heat exchanger and the drain tank, the tip of the drain transfer pipe is submerged in the drain in the drain tank, so the outlet side of the drain transfer pipe has a covered shape, and the drain from the heat exchanger The drain flow toward the tank will be hindered. If the flow of drain from the heat exchanger to the drain tank stops, the drain stops in the heat exchanger, and drain re-evaporation occurs in the heat exchanger. At this time, if the heat exchanger and the drain tank are connected by the air circulation pipe, the pressure difference between the heat exchanger and the drain tank disappears, so the drain generated in the heat exchanger flows to the drain tank through the drain transfer pipe, Stopping in the heat exchanger can be prevented.

Further, when the vacuum cooling process proceeds and the inside of the vacuum line becomes a high vacuum, if the saturated vapor temperature becomes equal to or lower than the drain temperature, drain re-evaporation occurs. In this case, when the ventilation valve is closed, the heat exchanger and the drain tank are connected only by the drain transfer pipe, and the drain transfer pipe is submerged in the drain at the tip. There is no air flow to the vessel. As a result, the pressure in the drain tank becomes higher than the pressure in the heat exchanger, and by keeping the saturated vapor temperature in the drain tank higher than the temperature of the drain, it is possible to prevent the drain from re-evaporating in the drain tank. . If the amount of evaporation from the drain tank is reduced, the amount of steam that the vacuum generator must discharge is reduced, so that the pressure reduction speed in the vacuum generator is improved and the time required for vacuum cooling can be shortened.

By implementing this invention, a cooling rate can be improved and cooling can be performed in a short time.

Flow diagram of a vacuum cooling device implementing the present invention The graph which showed the change of the pressure in a tank and processed material temperature in one example of the present invention.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of a vacuum cooling apparatus embodying the present invention, and FIG. 2 is a graph showing changes in tank pressure and treatment object temperature in one embodiment of the present invention. The vacuum cooling device includes a processing tank 2, a vacuum generator 1, a heat exchanger 4, a cold water unit 3, a drain tank 6, and the like. The vacuum cooling device evacuates the inside of the processing tank 2 to evaporate moisture from the processed product (high-temperature food) stored in the processing tank 2, and performs cooling by the action of vaporization heat generated at that time.

The processing tank 2 and the vacuum generator 1 are connected by a vacuum pipe 5, and when the vacuum generator 1 is operated, the gas in the processing tank 2 is discharged through the vacuum pipe 5. At this time, in addition to the gas in the processing tank 2, if the vapor generated from the processed material is also sucked by the vacuum generator 1, the volume of the gas that the vacuum generator 1 must discharge increases. In the treatment tank 2 in particular, when the pressure reduction progresses, the water evaporates from the treated product, and when the water becomes vapor, the volume increases significantly. It gets worse. Therefore, the heat exchanger 4 is provided in the vacuum pipe 5 to cool the gas sucked by the vacuum generator 1 and the vapor in the gas. When the gas is cooled by the heat exchanger 4, the volume of the gas that must be discharged by the vacuum generator 1 is reduced, so that the pressure reduction efficiency in the vacuum generator 1 is improved.

The heat exchanger 4 is connected to the cold water unit 3 so that the cold water generated by the cold water unit 3 is stored in an internal tank. In the heat exchanger 4, a plurality of heat transfer tubes that pass through a tank storing cold water are installed, and the gas sucked from the treatment tank 2 is dispersed and flowed in the heat transfer tubes, thereby cooling the suction gas. I do. A drain collecting chamber 9 for collecting drains generated by cooling and condensing the steam is provided at the lower part of the heat exchanger 4, and the drain generated in the heat exchanger 4 is stored below the drain collecting chamber 9. A drain tank 6 is provided. A drain transfer pipe 7 connects between the bottom of the drain collecting chamber 9 and the inside of the drain tank 6, and the drain generated in the heat exchanger 4 collects in the drain collecting chamber 9 and then passes through the drain transferring pipe 7 to the lower side. It flows down to the drain tank 6 provided. The tip of the drain transfer pipe 7 on the side of the drain tank 6 is installed so as to be close to the bottom of the drain tank 6. When the drain is stored in the drain tank 6, the tip of the drain transfer pipe 7 is Keep it submerged in the drain.

The drain collecting chamber 9 and the drain tank 6 are also connected by an air circulation pipe 8. When the pressure in the drain collecting chamber 9 becomes lower than the pressure in the drain tank 6 and a pressure difference occurs, the air circulation pipe 8 allows the air to escape from the drain tank 6 to the drain collecting chamber 9. It is for eliminating. Therefore, the air circulation pipe 8 is connected to the side wall portion of the drain collecting chamber 9 and the upper surface of the drain tank 6 so that the drain which is liquid does not enter. A ventilation valve 10 is provided in the middle of the air circulation pipe 8, and the air circulation through the air circulation pipe 8 can be controlled by opening and closing the ventilation valve 10.

The operation in the vacuum cooling apparatus is started with the processed material stored in the processing tank 2 and the processing tank 2 sealed. When the vacuum generator 1 is operated, the vacuum generator 1 sucks the gas in the processing tank 2 through the vacuum pipe 5. In the early stage of the vacuum cooling process in which the pressure in the processing tank 2 is relatively high, if a vacuum is generated by the vacuum generator 1, a large amount of gas can be discharged in the vacuum generator 1. The pressure drops rapidly. When the pressure in the processing tank 2 decreases and the saturated vapor temperature in the processing tank determined from the pressure becomes lower than the temperature of the processing object stored in the processing tank, the moisture in the processing object evaporates. When the water evaporates, the heat of vaporization is taken away, so that the temperature of the processed material is lowered.

In the cold water unit 3, cold water is produced and supplied to the heat exchanger 4, and the gas sucked through the vacuum pipe 5 is cooled by the heat exchanger 4. When the gas is cooled by the heat exchanger 4, the volume of the gas is reduced, and particularly when the vapor is returned to the liquid by cooling the vapor, the volume is greatly reduced. When the volume of the gas is reduced, the amount of gas that must be exhausted by the vacuum generator 1 is reduced, so that the pressure in the treatment tank 2 can be reduced more quickly, and the time required for cooling can be reduced.

The drain generated by cooling the steam in the heat exchanger 4 is collected in the drain collecting chamber 9 provided in the lower part of the heat exchanger 4 and then sent to the drain tank 6 through the drain transfer pipe 7. The drain collected in the drain collecting chamber 9 flows downward in the drain transfer pipe 7 by the action of gravity, and enters a drain tank provided below the heat exchanger 4. In the early stage of the vacuum cooling process, the vent valve 10 is kept open, and the inside of the drain collecting chamber 9 and the inside of the drain tank 6 are also connected by the air circulation pipe 8.

As the vacuum cooling process proceeds, the pressure in the heat exchanger decreases, and the pressure also decreases in the drain tank. When the pressure of the drain tank is lowered and the saturated steam temperature in the drain tank is lowered to the drain temperature accumulated in the drain tank, the drain is re-evaporated in the drain tank. The drain tank 6 is closed before the drain re-evaporation occurs. For example, the vent valve 10 is set to be closed when the temperature of the processed product reaches a preset valve closing timing temperature. In FIG. 2, the ventilation valve 10 is closed when the temperature of the processed product reaches 10 ° C.

A large amount of air is discharged from the vacuum generator 1 in the early stage of the vacuum cooling process in which the pressure in the processing tank is high, and the amount of discharge decreases as the pressure in the processing tank decreases. Therefore, as shown in FIG. 2, the pressure in the processing tank at the time of the vacuum cooling process rapidly decreases in the early stage of vacuum cooling, and the pressure in the processing tank gradually decreases as the degree of vacuum increases. become. The temperature of the processed product does not decrease in the time zone in which the saturated vapor temperature in the processing tank immediately after the start of vacuum cooling is higher than the temperature of the processed product, and when the saturated steam temperature in the processing tank decreases to the processed product temperature, To drop. In this time zone, the temperature of the processed material is high, so that the water in the processed material evaporates actively, and when the water evaporates, the heat of vaporization is taken away from the surroundings, so that the temperature of the processed material decreases rapidly. Yes. As the vacuum cooling process proceeds, the pressure in the treatment tank gradually decreases, and the temperature of the processed product also decreases, so that the amount of water evaporation decreases and the temperature change of the processed product also moderates.

In the graph of FIG. 2, there is no description of the amount of steam generated, but in the portion where the temperature drop of the processed material is steep, the amount of steam generated increases, and if the amount of steam flowing in the vacuum pipe 5 increases, The amount of drain generated by cooling in the vessel 4 also increases. The drain generated in the heat exchanger 4 collects in a drain collecting chamber 9 provided in the lower part of the heat exchanger 4 and accumulates in the drain tank 6 through the drain transfer pipe 7. Since the tip of the drain transfer pipe 7 on the drain tank 6 side is installed so as to be close to the bottom in the drain tank 6, the drain transfer pipe 7 can be used during the time when the drain discharge amount is large in the early stage of the vacuum cooling process. The tip is submerged in the drain.

During the vacuum cooling process, the gas in the vacuum pipe is sucked by the operation of the vacuum generator 1, and the gas in the processing tank is sucked into the vacuum pipe due to the pressure drop in the vacuum pipe. The pressure is reduced from the side close to the device 1. In the heat exchanger 4 and the drain tank 6, the pressure of the heat exchanger 4 is lower than that of the drain tank 6 because the heat exchanger 4 close to the vacuum generator 1 is decompressed first. Therefore, if the pipe connecting the heat exchanger 4 and the drain tank 6 is only the drain transfer pipe 7 and the tip of the drain transfer pipe 7 is submerged in the drain, the outlet of the drain transfer pipe 7 closes the lid. As a result, the transfer of the drain to the drain tank 6 through the drain transfer pipe 7 is prevented. When this state is reached in the early stage of the vacuum cooling process with a large amount of drain generation, and drain cannot be sent to the drain tank 6 through the drain transfer pipe 7, the drain remains in the heat exchanger 4 in a large amount. End up.

When the vacuum cooling process proceeds in this state, the drain is re-evaporated in the heat exchanger. As the vacuum cooling process proceeds and the pressure in the heat exchanger decreases, the saturated steam temperature determined from the pressure decreases, and when the saturated steam temperature decreases to the temperature of the drain in the heat exchanger, the drain re-evaporates. . When drain re-evaporation occurs, the amount of gas that the vacuum generator 1 has to discharge increases, so the time required for vacuum cooling increases.

However, in the present invention, an air circulation pipe 8 is provided in addition to the drain transfer pipe 7, and if the pressure in the heat exchanger 4 becomes lower than the pressure in the drain tank 6, the drain tank is passed through the air circulation pipe 8. Since air flows from 6 to the heat exchanger 4, the pressure difference can be eliminated. Therefore, the drain of the heat exchanger 4 can continue to be sent to the drain tank 6 through the drain transfer pipe 7, and the drain does not accumulate in the heat exchanger 4. Thereby, delay of the vacuum cooling process due to re-evaporation of the drain in the heat exchanger 4 can be prevented.

Further, at the end of the vacuum cooling process, the amount of drain generated is small, so that it is difficult for the drain to accumulate in the heat exchanger 4, but when the pressure in the vacuum pipe 5 portion decreases, the drain tank 6 The pressure inside also decreases. In that case, when the saturated vapor temperature in the drain tank 6 is lowered to the temperature of the drain, re-evaporation also occurs from the drain in the drain tank. However, in the present invention, the vent valve 10 is closed at the end of the vacuum cooling process, and the air flow between the heat exchanger 4 and the drain tank 6 by the air flow pipe 8 is closed, and the drain transfer pipe Since the tip of 7 is submerged in the drain, the air in the drain tank 6 is not sent to the heat exchanger 4. Therefore, the pressure in the drain tank 6 does not decrease in the same manner as in the heat exchanger 4, and the pressure in the drain tank 6 becomes higher than the pressure in the vacuum pipe 5. Thereby, drain re-evaporation in the drain tank 6 can be prevented.

However, even in this case, since the drain transfer pipe 7 is connected to the heat exchanger 4 having a high degree of vacuum, steam is generated on the drain water surface in the drain transfer pipe 7, but the drain water surface formed in the drain transfer pipe Is a very small area. And since the drain water surface other than the inside of the drain transfer pipe is not in contact with the low pressure as in the vacuum pipe, the amount of reevaporation from the drain tank becomes a limited amount, and the vacuum cooling process can be prevented from being delayed.

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

1 Vacuum generator
2 Treatment tank 3 Cold water unit 4 Heat exchanger
5 Vacuum piping 6 Drain tank 7 Drain transfer pipe 8 Air flow pipe 9 Drain collecting chamber 10 Ventilation valve

Claims (2)

A treatment tank that contains the processed material, a vacuum generator connected to the treatment tank by a vacuum pipe and sucking the gas in the treatment tank, a heat exchange that cools the gas sucked by the vacuum generator and condenses the vapor In a vacuum cooling device that has a drain tank for accumulating drain generated in the heat exchanger, and cools the processed material stored in the processing tank by evacuating the processing tank,
Between the heat exchanger and the drain tank is connected by a drain transfer pipe and an air circulation pipe, the drain tank side tip of the drain transfer pipe is a position that is submerged in the drain for the drain tank,
The air cooling pipe is provided at a position where the drain does not submerge in the drain. 2. The vacuum cooling device according to claim 1, wherein a vent valve is provided in the air circulation pipe in the middle, and the vent valve is opened at the beginning of the vacuum cooling process and closed at the end of the vacuum cooling process. A vacuum cooling device characterized by being operated.

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