Vacuum cooling device

Abstract

To provide a vacuum cooling device capable of regulating an intra-tank pressure along with a target pressure for each time division even if the number of vacuum pumps to be operated is changed.SOLUTION: A vacuum cooling device 1 for cooling a cooled object F accommodated in a processing tank 2 comprises a plurality of vacuum pumps 5A-5C, a heat exchanger 4, slow cooling means 7, pressure detection means 14 and control means 10. The plurality of vacuum pumps are disposed in parallel, connected with the processing tank via the heat exchanger, and the heat exchanger is configured to condense steam exhausted from the processing tank. The slow cooling means is configured to reduce an exhaust speed of the processing tank by the plurality of vacuum pumps, and the pressure detection means is configured to detect a pressure inside of the processing tank. The control means includes a storage section, a slow cooling control section and a pump operation number determination section. The storage section stores a target pressure which is set for each of a plurality of predetermined time divisions, and the slow cooling control section controls the slow cooling means in such a manner that the intra-tank pressure of the processing tank detected by the pressure detection means becomes the target pressure stored in the storage section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum cooling device equipped with a plurality of vacuum pumps. [Background technology]

[0002] Conventionally, there are vacuum cooling devices that vacuum-cool objects such as cooked foods. For example, the vacuum cooling device disclosed in Patent Document 1 is equipped with a pressure detection means (pressure sensor) that detects the pressure inside the cooling tank and a slow cooling valve (pressure adjustment valve) that can introduce air into the cooling tank in order to increase productivity while reducing damage to the objects, and is capable of controlling the slow cooling valve so that the pressure inside the tank follows a characteristic line (slow cooling program) of preset pressure control conditions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-208478 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even in a vacuum cooling device that performs slow cooling control using a slow cooling means such as a slow cooling valve, in order to increase the exhaust speed (exhaust speed) and improve the cooling capacity, it is possible to provide multiple vacuum pumps and perform exhaust using the multiple vacuum pumps. When performing vacuum cooling using multiple vacuum pumps, it is preferable to reduce the number of operating vacuum pumps and slow down the exhaust speed at a stage when the pressure inside the cooling tank has been reduced, in order to suppress the occurrence of cavitation in the vacuum pumps and reduce power consumption.

[0005] However, increasing or decreasing the number of operating vacuum pumps results in a large increase or decrease in the pumping speed. Therefore, if the number of operating vacuum pumps is reduced based only on the chamber pressure, the chamber pressure control by the slow cooling valve may not be able to keep up with the change in the number of operating vacuum pumps, and the chamber pressure may not be adjusted in accordance with the slow cooling program.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and provides a vacuum cooling device equipped with multiple vacuum pumps, which is capable of adjusting the pressure inside the tank in accordance with target pressures set for multiple time intervals even if the number of vacuum pumps in operation is changed. [Means for solving the problem]

[0007] According to the present invention, there is provided a vacuum cooling device for cooling an object to be cooled contained in a treatment tank, the vacuum cooling device comprising a plurality of vacuum pumps, a heat exchanger, a slow-cooling means, a pressure detection means, and a control means, the plurality of vacuum pumps are arranged in parallel and connected to the treatment tank via the heat exchanger, the heat exchanger is configured to condense steam exhausted from the treatment tank, the slow-cooling means is configured to reduce the exhaust speed of the treatment tank by the plurality of vacuum pumps, the pressure detection means is configured to detect the pressure inside the treatment tank, the control means comprises a memory unit, a slow-cooling control unit, and a unit for determining the number of operating pumps, the memory unit stores target pressures set for a plurality of predetermined time intervals, the slow-cooling control unit controls the slow-cooling means so that the internal pressure of the treatment tank detected by the pressure detection means becomes the target pressure stored in the memory unit, and the unit for determining the number of operating pumps determines the number of operating vacuum pumps based on the following (1) or (2). (1) Required exhaust capacity for each of the multiple time periods (2) Reduction rate of exhaust speed by the slow cooling means

[0008] According to the present invention, the number of operating pumps can be reduced at an appropriate timing by the control means determining the number of operating vacuum pumps based on the above (1) or (2), and the slow cooling means can adjust the pressure inside the tank according to the target pressure for each of a plurality of predetermined time segments. Note that examples of the slow cooling means for reducing the exhaust speed of the treatment tank include the slow cooling valve described above, as well as a speed control unit for the vacuum pump provided in the control means and an aperture adjustment valve provided in the air supply line of the vacuum pump.

[0009] Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other.

[0010] Preferably, the unit for determining the number of operating pumps determines the number of operating pumps based on (1) above, and when the sum of the exhaust capacities of the remaining vacuum pumps exceeds the required exhaust capacity even after stopping operation of one or more of the plurality of vacuum pumps, the unit for determining the number of operating pumps stops operation of the one or more vacuum pumps.

[0011] Preferably, the unit for determining the number of operating pumps determines the number of operating pumps based on (2) above, and the unit for determining the number of operating pumps reduces the number of operating pumps if a rate of reduction in exhaust speed by the slow cooling means is equal to or greater than a predetermined rate, and does not reduce the number of operating pumps if a rate of reduction in exhaust speed by the slow cooling means is less than the predetermined rate.

[0012] Preferably, the slow cooling means includes a slow cooling valve capable of adjusting the air introduced into the treatment tank, and the pump operation number determination unit reduces the number of operating pumps if the opening degree of the slow cooling valve is equal to or greater than a predetermined opening degree, and does not reduce the number of operating pumps if the opening degree of the slow cooling valve is less than the predetermined opening degree.

[0013] Preferably, the vacuum pump is a water ring vacuum pump. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic diagram showing a vacuum cooling device 1 according to a first embodiment of the present invention. [Diagram 2] 2 is a block diagram showing a configuration of a control means 10 of the vacuum cooling device 1 of FIG. [Diagram 3] FIG. 3 is a graph showing an example of an annealing program stored in the storage unit 101 of the control means 10 in FIG. 2, in the form of a time-pressure graph. [Figure 4] 2 is a flowchart showing the operation of the vacuum cooling device 1 of FIG. [Diagram 5] 6 is a flowchart showing the operation of the vacuum cooling device 1 according to the second embodiment of the present invention. [Figure 6] FIG. 4 is a conceptual diagram showing a partial configuration of a vacuum cooling device 1 according to a modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described. Various features shown in the following embodiments can be combined with each other. Also, each feature can be an invention independently.

[0016] 1. First embodiment 1.1 Configuration of Vacuum Cooling Device 1 First, the configuration of a vacuum cooling device 1 according to an embodiment of the present invention will be described. The vacuum cooling device 1 vacuum-cools an object F to be cooled, such as a thermally cooked food, in a processing tank 2. As shown in FIG. 1, the vacuum cooling device 1 of this embodiment includes a processing tank 2, a heat exchanger 4, a plurality of vacuum pumps (three vacuum pumps, the first to third vacuum pumps 5A to 5C, in this embodiment), a water supply means 6, a slow cooling means 7, and a control means 10. The vacuum cooling device 1 also includes an exhaust path 11 for exhausting gas (air and steam) in the processing tank 2. The exhaust path 11 is connected to the heat exchanger 4, and the suction lines 9A to 9C of the first to third vacuum pumps 5A to 5C are connected in parallel downstream of the heat exchanger 4. In FIG. 1, the exhaust path 11 and the suction lines 9A to 9C connected thereto are shown by thick lines. Each configuration will be specifically described below.

[0017] The treatment tank 2 is a hollow container that can withstand reduced pressure in the internal space, and can be opened and closed with a door (not shown). The treatment tank 2 is typically formed in a substantially rectangular box shape, and the opening at the front can be opened and closed with a door. By opening the door, the object F to be cooled can be put in and taken out of the treatment tank 2, and by closing the door, the opening of the treatment tank 2 can be closed airtight. The door may be provided on both the front and back of the treatment tank 2. In the illustrated example, the object F to be cooled is placed in a food container such as a hotel pan or a food container and is contained in the treatment tank 2. In addition, the treatment tank 2 is provided with a pressure sensor 14 as a pressure detection means for detecting the pressure in the treatment tank 2. In addition, a product temperature sensor 15 is provided in the treatment tank 2 to detect the temperature (product temperature) of the object F to be cooled contained therein.

[0018] The heat exchanger 4 is an indirect heat exchanger that exchanges heat without mixing the fluid in the exhaust passage 11 with the cooling water. The heat exchanger 4 can cool and condense the steam in the exhaust passage 11 with the cooling water. The cooling water is supplied from a water supply means 6 described later through a heat exchange water supply passage 40 and discharged through a heat exchange drain passage 41. The heat exchange drain passage 41 is branched into a cold water return passage 42 to a cold water tank (a water supply source of the chiller) not shown and a drain outlet passage 43 to the outside, and a cold water return valve 44 is provided in the cold water return passage 42, and a drain outlet valve 45 is provided in the drain outlet passage 43. The cold water return valve 44 and the drain outlet valve 45 can switch between returning the water after passing through the heat exchanger 4 to the cold water tank, discharging it from the drain outlet passage 43, or not doing either and preventing water from passing through the heat exchanger 4 (i.e. closing the cooling water outlet side of the heat exchanger 4).

[0019] The first to third vacuum pumps 5A to 5C are each a water seal type vacuum pump, and are driven while being supplied with water called seal water. To supply the seal water, water is supplied to the water inlet 5x of each of the vacuum pumps 5A to 5C from a water supply means 6, which will be described later, via a seal water supply passage 50. Here, the seal water supply passage 50 branches into three seal water supply passages 50A to 50C corresponding to each of the vacuum pumps 5A to 5C. Each of the seal water supply passages 50A to 50C is provided with a seal water valve 51 and a constant flow valve 52. Here, the constant flow valve 52 is configured to allow water to pass at a constant flow rate, as is well known.

[0020] When the vacuum pumps 5A to 5C are operated while water is being supplied from the seal water supply passage 50, each of the vacuum pumps 5A to 5C draws in gas from the intake port 5y and exhausts and drains the gas to the exhaust port 5z.

[0021] Further, the suction lines 9A-9C of the first to third vacuum pumps 5A-5C are provided with corresponding check valves 13A-13C, respectively. The check valves 13A-13C serve to prevent gas from flowing back from the vacuum pumps 5A-5C to the suction lines 9A-9C. The check valves 13A-13C function as emergency cutoff valves to prevent gas from flowing back into the treatment tank 2 in the event of a malfunction or power outage of the vacuum pumps 5A-5C.

[0022] In addition, the first to third vacuum pumps 5A to 5C are each provided with a seal water temperature sensor 16. The seal water temperature sensor 16 is configured to be able to detect the temperature of the seal water (seal water temperature) present inside each of the vacuum pumps 5A to 5C. Specifically, the seal water temperature sensor 16 can be configured, for example, by a thermocouple inserted inside each of the vacuum pumps 5A to 5C.

[0023] The water supply means 6 is configured to be capable of supplying room temperature water or cold water to the heat exchanger 4 and the first to third vacuum pumps 5A to 5C. Here, cold water is water (chiller water) that has been cooled to a predetermined temperature by a chiller (not shown), and room temperature water is water that has not been cooled in this manner. Specifically, the water supply means 6 includes a room temperature water supply passage 60 connected to a water supply source, and a cold water supply passage 61 connected to the chiller. In addition, a room temperature water supply valve 62 is provided in the room temperature water supply passage 60, and a cold water supply valve 63 is provided in the cold water supply passage 61. In addition, a cold water temperature sensor 17 capable of detecting the temperature of the cold water is provided in the cold water supply passage 61.

[0024] The normal temperature water supply passage 60 and the cold water supply passage 61 join at positions downstream of the normal temperature water supply valve 62 and the cold water supply valve 63, respectively, to form a common water supply passage 64. This common water supply passage 64 branches into the heat exchanger supply passage 40 to the heat exchanger 4 and the seal water supply passage 50 to the first to third vacuum pumps 5A to 5C. The water supply means 6 supplies cooling water to the heat exchanger 4 by opening the normal temperature water supply valve 62 or the cold water supply valve 63, and further supplies water to the vacuum pumps 5A to 5C by opening the seal water valve 51.

[0025] The slow cooling means 7 is a means for reducing the exhaust speed of the treatment tank 2 by the first to third vacuum pumps 5A to 5C. In this embodiment, the slow cooling means 7 reduces the exhaust speed of the treatment tank 2 by introducing outside air into the treatment tank 2 during depressurization. Specifically, the slow cooling means 7 of this embodiment includes an air supply passage 70 connected to the treatment tank 2, an air filter 71, and a slow cooling valve 72. The air filter 71 and the slow cooling valve 72 are provided in the air supply passage 70 in this order from the upstream side. When the slow cooling valve 72 is opened while the treatment tank 2 is depressurized, outside air is introduced into the treatment tank 2 through the air filter 71, and the pressure in the treatment tank 2 can be restored.

[0026] Specifically, the slow cooling valve 72 is an electrically operated valve whose opening is adjustable, and by adjusting the opening, the amount of air introduced into the treatment tank 2 can be adjusted (the speed of pressure recovery can be adjusted). The vacuum cooling device 1 of this embodiment performs slow cooling control, which will be described later, by controlling the slow cooling valve 72 of the slow cooling means 7. After the cooling operation of the vacuum cooling device 1 is completed, the slow cooling valve 72 can be opened to restore the pressure inside the treatment tank 2 to atmospheric pressure.

[0027] The control means 10 controls each of the above-mentioned components based on the detection signals of each sensor, the elapsed time, etc. The control means 10 controls the cold water return valve 44, the drain outlet valve 45, the seal water valve 51, the normal temperature water supply valve 62, the cold water supply valve 63, and the slow cooling valve 72. The control means 10 also controls the driving of the first to third vacuum pumps 5A to 5C. In addition, the control means 10 is connected to a pressure sensor 14, a product temperature sensor 15, a seal water temperature sensor 16, a cold water temperature sensor 17, etc.

[0028] The control means 10 of this embodiment further includes a target pressure receiving unit 100, a storage unit 101, a slow cooling control unit 102, and a unit 103 for determining the number of operating pumps, as shown in FIG.

[0029] The target pressure receiving unit 100 receives a slow-cooling program configured by a table of target pressures set for multiple predefined time intervals, in other words, combinations of elapsed time from the start of operation and each target pressure, from a user via an input means (personal computer, touch panel, etc.) not shown. Here, each interval of the "multiple time intervals" may be a constant time or may be a non-constant time that changes with the passage of time. The target pressure receiving unit 100 also receives a correction to the slow-cooling program stored in the memory unit 101 and an addition of a slow-cooling program in response to an input from the user.

[0030] The storage unit 101 has a function of storing various data. In this embodiment, the storage unit 101 stores target pressures (slow cooling programs) for multiple time segments received by the target pressure receiving unit 100. It is preferable that multiple types of slow cooling programs are stored in the storage unit 101, and one of them can be selected and executed. It is also possible to configure the system without the target pressure receiving unit 100 by storing target pressures for multiple time segments in the storage unit 101 in advance. In addition, the storage unit 101 in this embodiment stores the required exhaust capacity for each of multiple time segments, which will be described later.

[0031] The slow cooling control unit 102 performs slow cooling control by controlling the slow cooling valve 72 of the slow cooling means 7. Specifically, the slow cooling control is a control for cooling the object F to be cooled while adjusting the exhaust speed by adjusting the opening of the slow cooling valve 72 so that the pressure inside the tank detected by the pressure sensor 14 becomes the target pressure for each of a plurality of time segments stored in the memory unit 101 (in accordance with the slow cooling program). Through the slow cooling control by the control unit 10, the inside of the processing tank 2 is depressurized along the line of the time-pressure graph as shown in Fig. 3, which is defined by the slow cooling program. In the graph of Fig. 3, the pressure is monotonically decreased as time progresses as an example, but it is also possible to use a slow cooling program that does not monotonically decrease the pressure depending on the type of the object F to be cooled, etc.

[0032] In this embodiment, the pump operation number determination unit 103 determines the number of the first to third vacuum pumps 5A to 5C to be operated based on the required exhaust capacity for each of a plurality of time segments stored in the memory unit 101. Here, the required exhaust capacity is the exhaust speed required to make the pressure inside the tank reach the target pressure within a predetermined time, and is calculated by setting a predetermined safety factor to the exhaust amount required from a certain time when the target pressure is set to a time when the next target pressure is set. However, the safety factor may be 0%. The required exhaust amount is calculated based on the volume of the processing tank 2 and an exhaust speed calculation formula for the vacuum pumps 5A to 5C. The required exhaust capacity may be calculated in advance and stored in the memory unit 101, or may be calculated in real time during the cooling operation of the vacuum cooling device 1.

[0033] The control means 10 configured as above performs control for cooling the object to be cooled F in accordance with a predetermined procedure (program), as will be described later.

[0034] Specifically, the control means 10 having the above configuration can be configured, for example, by an information processing device including a CPU, a memory (e.g., a flash memory), an input unit, and an output unit. The processing by each of the above-mentioned components of the control means 10 configured by the information processing device is performed by the CPU reading and executing a program stored in the memory. As the information processing device, for example, a personal computer, a PLC (Programmable Logic Controller), or a microcomputer is used. However, some functions of the control means 10 may be configured to be executed on a cloud connected by any communication means.

[0035] 1.2 Operation of Vacuum Cooling Device 1 Next, the operation of the vacuum cooling device 1 of this embodiment will be described with reference to the flowchart of Fig. 2. The vacuum cooling device 1 of this embodiment drives the vacuum pumps 5A-5C under the control of the control means 10 to reduce the pressure inside the treatment tank 2, thereby cooling the object to be cooled F contained in the treatment tank 2 while performing slow cooling control by the slow cooling means 7. The control means 10 of this embodiment also includes a unit 103 for determining the number of operating pumps, and is configured to stop driving some of the vacuum pumps (5A, 5B, 5C) based on the judgment of the unit 103 for determining the number of operating pumps as the pressure inside the treatment tank 2 decreases.

[0036] Hereinafter, a specific cooling control including the above-mentioned slow cooling control by the control means 10 will be described. Before the vacuum cooling device 1 starts operating, all valves of the slow cooling means 7 except for the slow cooling valve 72 are closed.

[0037] When an instruction to start operation is given, for example by pressing a start button (not shown) of the vacuum cooling device 1, the control means 10 first fully closes the slow cooling valve 72 in step S1, starts driving the first to third vacuum pumps 5A to 5C, and opens the room temperature water supply valve 62 and each seal water valve 51 of the water supply means 6. As a result, room temperature water is supplied as seal water to the vacuum pumps 5A to 5C, and the three vacuum pumps 5A to 5C start reducing the pressure inside the treatment tank 2. As a result, air containing steam generated from the high-temperature object to be cooled F is exhausted through the exhaust path 11.

[0038] At the same time, the control means 10 also opens the drain outlet valve 45 of the drain outlet passage 43. As a result, room temperature water is also supplied from the water supply means 6 to the heat exchanger 4, heat exchange occurs between the steam from the treatment tank 2 and the room temperature water, and the steam from the treatment tank 2 is condensed and sent to the vacuum pumps 5A to 5C. Meanwhile, the room temperature water that has absorbed heat in the heat exchanger 4 is discharged to the outside through the drain outlet passage 43. Note that in step S1, the pressure inside the tank is still high and no boiling or bumping of the cooled material F occurs, so the slow cooling valve 72 is fully closed and all the vacuum pumps 5A to 5C are driven to quickly reduce the pressure inside the treatment tank 2 (rapid cooling control).

[0039] Next, in step S2, the control means 10 judges whether a predetermined time has passed since the start of operation. Then, when the predetermined time has passed since the start of operation, in step S3, the control means 10 closes the normal temperature water supply valve 62 and opens the cold water supply valve 63 to supply cold water as sealing water to the first to third vacuum pumps 5A to 5C. At this time, the operation of each of the vacuum pumps 5A to 5C is continued. By using cold water as sealing water, the saturation pressure in each of the vacuum pumps 5A to 5C can be reduced, and the pressure in the treatment tank 2 can be further reduced.

[0040] Furthermore, in step S3, the control means 10 closes the drain outlet valve 45 and opens the cold water return valve 44 to supply cold water to the heat exchanger 4 as well, and returns the cold water that has absorbed heat in the heat exchanger 4 to a cold water tank (not shown). The water returned to the cold water tank is cooled in a chiller (not shown) and is supplied again to the cold water supply passage 61. By supplying cold water to the heat exchanger 4 as well, the gas passing through the exhaust passage 11 can be condensed.

[0041] Furthermore, in step S3, the control means 10 starts the slow-cooling control by the slow-cooling means 7. In the slow-cooling control, the slow-cooling control unit 102 of the control means 10 compares the tank pressure for each of the plurality of time segments detected by the pressure sensor 14 with the target pressure for that time stored in the memory unit 101. If the tank pressure is lower than the target pressure for that time, the slow-cooling control unit 102 increases the opening of the slow-cooling valve 72 to reduce the exhaust speed of the processing tank 2 by the vacuum pumps 5A to 5C.

[0042] On the other hand, if the internal tank pressure is higher than the target pressure at that time, the slow-cooling control unit 102 increases the exhaust speed of the vacuum pumps 5A-5C inside the processing tank 2 by reducing the opening of the slow-cooling valve 72. By such control, the slow-cooling control unit 102 of the control means 10 can quickly bring the internal tank pressure of the processing tank 2 close to the target pressure, and reduce the pressure inside the processing tank 2 in accordance with a preset slow-cooling program.

[0043] Next, in step S4, the unit 103 for determining the number of pumps in operation of the control means 10 judges whether the sum of the exhaust capacities of the second and third vacuum pumps 5B, 5C exceeds the required exhaust capacity for each of a plurality of time segments. If the sum of the exhaust capacities of the second and third vacuum pumps 5B, 5C exceeds the required exhaust capacity, the unit 103 for determining the number of pumps in operation judges that the first vacuum pump 5A does not need to be driven, and in the next step S5, stops the operation of the first vacuum pump 5A. At the same time, the water seal valve 51 corresponding to the first vacuum pump 5A is also closed.

[0044] After the third vacuum pump 5C is stopped, the second and third vacuum pumps 5B and 5C are driven to continue depressurizing the inside of the treatment tank 2. At this time, the unit 103 for determining the number of pumps to be operated of the control means 10 judges whether the exhaust capacity of the third vacuum pump 5C exceeds the above-mentioned required exhaust capacity for each of a plurality of time segments in step S6. If the exhaust capacity of the third vacuum pump 5C exceeds the required exhaust capacity, the unit 103 for determining the number of pumps to be operated judges that it is not necessary to drive the second vacuum pump 5B, and stops the operation of the second vacuum pump 5B in the next step S7. In addition, the water seal valve 51 corresponding to the second vacuum pump 5B is also closed.

[0045] After the second vacuum pump 5B is stopped, the third vacuum pump 5C is driven to continue decompressing the processing tank 2. At this time, the control means 10 judges in step S8 whether the tank pressure detected by the pressure sensor 14 has become equal to or lower than the final target pressure. When the tank pressure becomes equal to or lower than the final target pressure, the cooling of the object to be cooled F by the vacuum cooling device 1 is stopped. To stop the cooling, specifically, the control means 10 closes each of the cold water return valve 44, the sealing water valve 51, and the cold water supply valve 63, and stops the operation of the third vacuum pump 5C. Thereafter, the slow cooling valve 72 of the slow cooling means 7 is opened to restore the pressure in the processing tank 2 to atmospheric pressure. The stop of the cooling by the vacuum cooling device 1 can also be determined based on the elapsed time from the start of operation.

[0046] 1.3 Effects As described above, the vacuum cooling device 1 of this embodiment is capable of quickly reducing the pressure inside the tank immediately after cooling begins by using three vacuum pumps, the first to third vacuum pumps 5A to 5C, and when the pressure inside the processing tank 2 has progressed so that evacuation by all of the vacuum pumps 5A to 5C is no longer necessary, some of the vacuum pumps (5A, 5B, 5C) can be stopped, thereby reducing running costs.

[0047] In the vacuum cooling device 1 of the present embodiment, the control means 10 includes a pump operation number determination unit 103, which is configured to determine the number of the first to third vacuum pumps 5A to 5C to be operated based on the required exhaust capacity for each of a plurality of time segments stored in the storage unit 101, rather than based on the pressure inside the tank alone. More specifically, the pump operation number determination unit 103 stops the vacuum pump 5A when the sum of the exhaust capacities of the remaining vacuum pumps (5B, 5C) exceeds the required exhaust capacity at that time even if the operation of one vacuum pump (5A) of the vacuum pumps (5A, 5B, 5C) is stopped. In addition, when the exhaust capacity of the remaining vacuum pump (5C) exceeds the required exhaust capacity at that time even if the operation of one vacuum pump (5B) of the vacuum pumps (5B, 5C) is stopped, the unit 103 stops the operation of the one vacuum pump (5B).

[0048] Since the vacuum cooling device 1 of the present embodiment is configured as described above, it is possible to stop some of the vacuum pumps (for example, the first vacuum pump 5A) at an appropriate timing. In other words, if the sum of the exhaust capacities of the remaining vacuum pumps (5B, 5C) after the operation of some of the vacuum pumps (5A) is stopped falls below the required exhaust capacity, the exhaust speed does not catch up with the slow cooling program and the pressure reduction in the processing tank 2 is delayed, but it is possible to prevent such a delay in pressure reduction. Conversely, if the vacuum pump is not stopped even when the sum of the exhaust capacities of the vacuum pumps significantly exceeds the required exhaust capacity, the reduction in the exhaust speed by the slow cooling means 7 does not catch up even if the slow cooling valve 72 is fully opened, and the pressure is reduced earlier than the slow cooling program, but it is possible to prevent such an excessive pressure reduction that exceeds the slow cooling program. Furthermore, since it is possible to reduce the number of operating vacuum pumps (5A, 5B, 5C) at an appropriate timing, it is not necessary to perform slow cooling control using the large-capacity (large flow rate) slow cooling valve 72, and it is also possible to reduce the cost of parts.

[0049] 2. Second embodiment Next, a vacuum cooling apparatus 1 according to a second embodiment of the present invention will be described. The vacuum cooling apparatus 1 of this embodiment is similar to the vacuum cooling apparatus 1 according to the first embodiment, and differs only in the operation of the first to third vacuum pumps 5A to 5C under the control of the control means 10, specifically, in the method of determining the number of the first to third vacuum pumps 5A to 5C to be operated. Therefore, the following mainly describes the differences from the vacuum cooling apparatus 1 of the first embodiment, and a description of the same configuration will be omitted.

[0050] Specifically, the control means 10 of the vacuum cooling apparatus 1 according to this embodiment determines the number of pumps to be operated, the first to third vacuum pumps 5A to 5C, based on the reduction rate of the exhaust speed by the slow cooling means 7, by the pump operation number determination unit 103. In this embodiment, the reduction rate of the exhaust speed by the slow cooling means 7 is specifically determined by the opening degree of the slow cooling valve 72. That is, if the opening degree of the slow cooling valve 72 is large, a lot of outside air is introduced into the treatment tank 2 through the air supply passage 70, so the exhaust speed is significantly reduced and the reduction rate of the exhaust speed is high. On the other hand, if the opening degree of the slow cooling valve 72 is small, not much outside air is introduced into the treatment tank 2 through the air supply passage 70, so the exhaust speed is not reduced much and the reduction rate of the exhaust speed is low. Hereinafter, the cooling operation of the vacuum cooling apparatus 1 according to this embodiment will be described with reference to the flowchart of FIG. 5.

[0051] 2.1 Operation of Vacuum Cooling Device 1 When an instruction to start operation is given, for example by pressing a start button (not shown) of the vacuum cooling device 1, the control means 10 first fully closes the slow cooling valve 72 in step S1, starts driving the first to third vacuum pumps 5A to 5C, and opens the room temperature water supply valve 62 and each seal water valve 51 of the water supply means 6. As a result, room temperature water is supplied as seal water to the vacuum pumps 5A to 5C, and the three vacuum pumps 5A to 5C start reducing the pressure inside the treatment tank 2. As a result, air containing steam generated from the high-temperature object to be cooled F is exhausted through the exhaust path 11.

[0052] At the same time, the control means 10 also opens the drain outlet valve 45 of the drain outlet passage 43. As a result, room temperature water is also supplied from the water supply means 6 to the heat exchanger 4, heat exchange occurs between the steam from the treatment tank 2 and the room temperature water, and the steam from the treatment tank 2 is condensed and sent to the vacuum pumps 5A to 5C. Meanwhile, the room temperature water that has absorbed heat in the heat exchanger 4 is discharged to the outside through the drain outlet passage 43. Note that in step S1, the pressure inside the tank is still high and no boiling or bumping of the cooled material F occurs, so the slow cooling valve 72 is fully closed and all the vacuum pumps 5A to 5C are driven to quickly reduce the pressure inside the treatment tank 2 (rapid cooling control).

[0053] Next, in step S2, the control means 10 judges whether a predetermined time has passed since the start of operation. Then, when the predetermined time has passed since the start of operation, in step S3, the control means 10 closes the normal temperature water supply valve 62 and opens the cold water supply valve 63 to supply cold water as sealing water to the first to third vacuum pumps 5A to 5C. At this time, the operation of each of the vacuum pumps 5A to 5C is continued. By using cold water as sealing water, the saturation pressure in each of the vacuum pumps 5A to 5C can be reduced, and the pressure in the treatment tank 2 can be further reduced.

[0054] Furthermore, in step S3, the control means 10 closes the drain outlet valve 45 and opens the cold water return valve 44 to supply cold water to the heat exchanger 4 as well, and returns the cold water that has absorbed heat in the heat exchanger 4 to a cold water tank (not shown). The water returned to the cold water tank is cooled in a chiller (not shown) and is supplied again to the cold water supply passage 61. By supplying cold water to the heat exchanger 4 as well, the gas passing through the exhaust passage 11 can be condensed.

[0055] Furthermore, in step S3, the control means 10 starts a slow cooling control for adjusting the pressure in the processing tank 2 by adjusting the opening degree of the slow cooling valve 72 of the slow cooling means 7. In the slow cooling control, the slow cooling control unit 102 of the control means 10 compares the tank pressure for each of a plurality of time segments detected by the pressure sensor 14 with the target pressure at that time stored in the memory unit 101. If the tank pressure is lower than the target pressure, the slow cooling control unit 102 increases the opening degree of the slow cooling valve 72 to reduce the exhaust speed of the processing tank 2 by the vacuum pumps 5A to 5C. On the other hand, if the tank pressure is higher than the target pressure, the slow cooling control unit 102 decreases the opening degree of the slow cooling valve 72 to increase the exhaust speed of the processing tank 2 by the vacuum pumps 5A to 5C. By such control, the slow cooling control unit 102 of the control means 10 brings the tank pressure of the processing tank 2 closer to the target pressure, and can reduce the pressure in the processing tank 2 in accordance with a preset slow cooling program.

[0056] Next, in step S4, the unit 103 for determining the number of operating pumps of the control means 10 judges whether the rate of reduction in the exhaust speed of the treatment tank 2 by the slow cooling means 7 is equal to or greater than a predetermined rate, i.e., whether the opening degree of the slow cooling valve 72 is equal to or greater than a first predetermined opening degree. If the opening degree of the slow cooling valve 72 is equal to or greater than the first predetermined opening degree (the rate of reduction in the exhaust speed is equal to or greater than a predetermined rate), the unit 103 for determining the number of operating pumps judges that the exhaust by the three vacuum pumps 5A to 5C is excessive, and in the next step S5, stops the operation of the first vacuum pump 5A. On the other hand, if the opening degree of the slow cooling valve 72 is less than the first predetermined opening degree (the rate of reduction in the exhaust speed is less than a predetermined rate), the unit 103 for determining the number of operating pumps 5A to 5C judges that the number of operating vacuum pumps 5A to 5C is appropriate, and continues exhaust by the three vacuum pumps 5A to 5C. The first predetermined opening degree is specifically set to, for example, 30 to 40%. However, the first predetermined opening degree is set appropriately depending on the flow rate characteristics of the slow cooling valve 72 and other conditions, and can be changed depending on the operating conditions.

[0057] After the operation of the first vacuum pump 5A is stopped, the second and third vacuum pumps 5B and 5C are driven to continue depressurizing the inside of the treatment tank 2. At this time, the unit 103 for determining the number of operating pumps of the control means 10 judges in step S6 whether the rate of reduction in the exhaust speed of the treatment tank 2 by the slow cooling means 7 is equal to or greater than a predetermined rate, i.e., whether the opening degree of the slow cooling valve 72 is equal to or greater than a second predetermined opening degree (the rate of reduction in the exhaust speed is equal to or greater than a predetermined rate). If the opening degree of the slow cooling valve 72 is equal to or greater than the second predetermined opening degree, the unit 103 for determining the number of operating pumps judges that the exhaust by the two vacuum pumps 5B and 5C is excessive, and in the next step S7, stops the operation of the second vacuum pump 5B.

[0058] On the other hand, if the opening degree of the slow cooling valve 72 is less than the second predetermined opening degree (the reduction rate of the exhaust speed is less than a predetermined rate), the unit 103 for determining the number of operating pumps determines that the number of operating vacuum pumps 5B, 5C is appropriate, and continues exhausting by the two vacuum pumps 5B, 5C. The second predetermined opening degree may be the same as the first predetermined opening degree, or may be set to a value different from the first predetermined opening degree. Specifically, the second predetermined opening degree is set to, for example, 30 to 40%. However, the second predetermined opening degree is also set appropriately depending on the flow characteristics of the slow cooling valve 72 and other conditions, and can also be changed depending on the operating situation.

[0059] After the second vacuum pump 5B is stopped, the third vacuum pump 5C is driven to continue decompressing the processing tank 2. At this time, the control means 10 judges in step S8 whether the tank pressure detected by the pressure sensor 14 has become equal to or lower than the final target pressure. When the tank pressure becomes equal to or lower than the final target pressure, the cooling of the object to be cooled F by the vacuum cooling device 1 is stopped. To stop the cooling, specifically, the control means 10 closes the cold water return valve 44, the sealing water valve 51, and the cold water supply valve 63, and stops the operation of the third vacuum pump 5C. Thereafter, the slow cooling valve 72 of the slow cooling means 7 is opened to restore the pressure in the processing tank 2 to atmospheric pressure. It is also possible to decide the stop of the cooling by the vacuum cooling device 1 depending on the elapsed time from the start of operation.

[0060] 2.2 Effects As described above, the unit 103 for determining the number of pumps in operation of the control means 10 in this embodiment reduces the number of the first to third vacuum pumps 5A to 5C in operation if the opening degree of the slow cooling valve 72 is equal to or greater than the predetermined opening degree, and does not reduce the number of the first to third vacuum pumps 5A to 5C in operation if the opening degree of the slow cooling valve 72 is less than the predetermined opening degree. The vacuum cooling device 1 in this embodiment is also configured in this way, so that it is possible to stop some of the vacuum pumps (for example, the first vacuum pump 5A) at an appropriate timing. In other words, by acquiring the opening degree of the slow cooling valve 72 of the slow cooling means 7 that opens and closes for slow cooling control, it is possible to estimate whether or not there is a margin in the exhaust capacity of the vacuum pumps (5A, 5B, 5C) in operation. Then, the unit 103 for determining the number of pumps in operation reduces the number of vacuum pumps (5A, 5B, 5C) in operation when there is a margin in the exhaust capacity, so that the pressure inside the tank can be adjusted to the target pressure for each of the multiple time segments stored in the storage unit 101 (to follow the slow cooling program). Furthermore, by reducing the number of operating first to third vacuum pumps 5A to 5C based on the opening degree of the slow cooling valve 72, it is possible to maintain the pumping speed even when a slow cooling program is added or updated (for example, when the cooling speed is increased).

[0061] 4. Variations The present invention can also be implemented in the following aspects.

[0062] In each of the above embodiments, the unit 103 for determining the number of operating pumps of the control means 10 determines to gradually reduce the number of vacuum pumps (5A, 5B, 5C) to be driven, from 3, to 2, to 1. However, the unit 103 for determining the number of operating pumps may determine to increase again the number of vacuum pumps (5A, 5B, 5C) to be driven, which was once reduced, depending on the slow cooling program or the cooling state of the object to be cooled F, etc.

[0063] In each of the above embodiments, in the cooling operation, first the first vacuum pump 5A is stopped, and then the operation of the second vacuum pump 5B is stopped. However, it is not necessary that the same vacuum pump among the first to third vacuum pumps 5A to 5C is stopped every time.

[0064] In the above embodiments, the vacuum pumps 5A to 5C are water-sealed vacuum pumps. However, the vacuum pumps 5A to 5C may be of other types, such as a dry pump with adjustable rotation speed (displacement), or an oil-sealed rotary pump.

[0065] In each of the above-mentioned embodiments, the slow cooling means 7 for reducing the exhaust speed of the processing tank 2 by the first to third vacuum pumps 5A to 5C includes an air supply passage 70 and a slow cooling valve 72, and adjusts the pressure in the processing tank 2 by introducing outside air into the processing tank 2 during decompression. However, the slow cooling means 7 for reducing the exhaust speed of the processing tank 2 is not limited to such a configuration. For example, when the first to third vacuum pumps 5A to 5C are vacuum pumps (e.g., dry pumps) whose rotation speeds can be adjusted and the control means 10 includes a rotation speed control unit (not shown) for controlling the rotation speeds of the vacuum pumps 5A to 5C, the rotation speed control unit can be the slow cooling means 7. In this case, the rotation speed control unit as the slow cooling means 7 can reduce the exhaust speed of the processing tank 2 by reducing the rotation speeds of the vacuum pumps (5A, 5B, 5C) during operation.

[0066] In this configuration, the unit 103 for determining the number of operating pumps can determine the number of operating vacuum pumps, the first to third vacuum pumps 5A to 5C, based on the rotation speeds of the vacuum pumps (5A, 5B, 5C) in operation. That is, in this configuration, the unit 103 for determining the number of operating pumps obtains the rotation speeds of the vacuum pumps 5A to 5C from the rotation speed control unit as the slow cooling means 7, and defines the ratio of the rotation speed to the rated rotation speed as the reduction rate of the pumping speed. Then, by estimating whether the vacuum pumps (5A, 5B, 5C) in operation have a margin in their exhaust capacity based on the reduction rate of the exhaust speed, it becomes possible to stop some of the vacuum pumps at an appropriate timing, similar to the control means 10 of the second embodiment.

[0067] In addition, when an automatic valve (not shown) capable of adjusting the opening degree is provided in the exhaust passage 11 or the air supply line of the vacuum pumps 5A to 5C, the opening degree adjustment valve can be used as the slow cooling means 7 for reducing the exhaust speed of the processing tank 2. In this case, the opening degree adjustment valve as the slow cooling means 7 can reduce the exhaust speed of the processing tank 2 by reducing the opening degree. In this case, the pump operation number determination unit 103 can determine the number of operating first to third vacuum pumps 5A to 5C based on the opening degree of the opening degree adjustment valve. That is, in this case, the pump operation number determination unit 103 specifies the value obtained by subtracting the opening degree (%) of the opening degree adjustment valve as the slow cooling means 7 from 100% as the reduction rate of the exhaust speed. Then, by estimating whether or not there is a margin in the exhaust capacity of the vacuum pumps (5A, 5B, 5C) in operation based on the reduction rate of the exhaust speed, it becomes possible to stop some of the vacuum pumps at an appropriate timing, similar to the control means 10 of the second embodiment.

[0068] In each of the above embodiments, the vacuum cooling device 1 is configured to include three vacuum pumps 5A to 5C. However, the number of vacuum pumps included in the vacuum cooling device 1 may be two, or may be four or more. Also, in the above first embodiment, the vacuum pumps 5A to 5C are stopped one by one in steps S4 and S6. However, two or more vacuum pumps may be stopped at once depending on the difference between the sum of the exhaust capacities of the remaining vacuum pumps and the required exhaust capacity.

[0069] The vacuum cooling device 1 in each of the above embodiments is configured to exhaust gas (air and steam) from within the processing tank 2 using the first to third vacuum pumps 5A to 5C. However, in addition to the first to third vacuum pumps 5A to 5C, an ejector (not shown) may be provided between the processing tank 2 and the heat exchanger 4, and after the pressure inside the processing tank 2 has been reduced, the gas (air and steam) inside the processing tank 2 may be exhausted using the ejector and the first to third vacuum pumps 5A to 5C. Here, the ejector creates a reduced pressure area by passing a fluid (e.g., steam) through it at high speed, and sucks the fluid from a suction port provided around the reduced pressure area.

[0070] In each of the above embodiments, the seal water supply passage 50 includes three seal water supply passages 50A-50C corresponding to the first to third vacuum pumps 5A-5C. However, as shown in FIG. 6, it is also preferable to branch the seal water supply passage 50A to the first vacuum pump 5A into two seal water supply passages 50AX, 50AY, and provide seal water valves 51X, 51Y and constant flow valves 52X, 52Y in each of the seal water supply passages 50AX, 50AY (although not shown, the seal water supply passages 50B, 50C are similarly branched for the second and third vacuum pumps 5B, 5C). With this configuration, it is possible to adjust the amount of seal water supplied to each vacuum pump 5A-5C via the seal water supply passage 50. That is, for example, the seal water supplied to the first vacuum pump 5A is reduced in flow rate by opening either the seal water valve 51X or the seal water valve 51Y (for example, the seal water valve 51X) and closing the other (for example, the seal water valve 51Y), and is increased in flow rate by opening both the seal water valve 51X and the seal water valve 51Y. As a specific control, the control means 10 opens only one of the seal water valves 51X until the pressure reduction progresses after the start of vacuum cooling, and supplies a small flow rate of seal water (room temperature water or cold water) to the vacuum pumps 5A to 5C being driven. Then, when the pressure reduction progresses, the control means 10 opens both seal water valves 51X and 51Y to supply a large flow rate of seal water (cold water) to the vacuum pumps being driven (for example, the second and third vacuum pumps 5B and 5C). With such control, it is possible to conserve the amount of water supply while supplying a large flow rate of cold water in a high vacuum state, thereby increasing the exhaust capacity of the vacuum pump being driven.

[0071] Furthermore, in the above embodiment, the vacuum cooling device 1 has been described as a dedicated cooling device, but as long as it has at least a vacuum cooling function, it can be modified as appropriate. For example, it may be configured as a steam cooling device or a saturated steam cooking device by providing a heating means using steam. Alternatively, it may be configured as a cold air vacuum combined cooling device by providing a cold air cooling means using a refrigerator or a fan. [Explanation of symbols]

[0072] 1:Vacuum cooling device 2: Treatment tank 4: Heat exchanger 5A: First vacuum pump 5B: Second vacuum pump 5C: 3rd vacuum pump 5x: Water inlet 5y: Air intake 5z: Exhaust port 6: Water supply means 7: Slow cooling method 9A~9C: Intake lines 10: Control means 11: Exhaust duct 13A~13C: Check valve 14: Pressure sensor (pressure detection means) 15: Product temperature sensor 16: Sealing water temperature sensor 17: Cold water temperature sensor 40: Heat exchange waterway 41:Heat exchange drainage channel 42: Cold water return passage 43: Drainage outlet channel 44: Cold water return valve 45: Drain outlet valve 50: Sealed water supply channel 50A~50C: Sealed water supply channel 51: Water seal valve 52: Constant flow valve 60: Room temperature water supply channel 61: Cold water supply channel 62: Normal temperature water supply valve 63: Cold water supply valve 64: Common water supply channel 70:Air supply path 71: Air filter 72: Slow cooling valve 100: Target pressure reception section 101: Storage section 102: Slow cooling control section 103: Pump operation number determination unit F: Object to be cooled S1~S8: Step

Claims

1. A vacuum cooling device for cooling an object to be cooled contained in a treatment tank, The apparatus includes a plurality of vacuum pumps, a heat exchanger, a slow cooling means, a pressure detection means, and a control means, the plurality of vacuum pumps are arranged in parallel and connected to the treatment tank via the heat exchanger; The heat exchanger is configured to condense steam exhausted from the treatment tank, the slow cooling means is configured to be capable of reducing an exhaust speed of the treatment tank by the plurality of vacuum pumps, The pressure detection means is configured to detect the pressure in the treatment tank, The control means includes a storage unit, a slow-cooling control unit, and a unit for determining the number of pumps to be operated, The storage unit stores target pressures set for a plurality of predetermined time segments, the slow-cooling control unit executes slow-cooling control for controlling the slow-cooling means so that the internal pressure of the treatment tank detected by the pressure detection means becomes the target pressure stored in the memory unit; The vacuum cooling device, wherein the pump operating number determination unit stops operation of one or more of the plurality of vacuum pumps when the sum of the exhaust capacities of the remaining vacuum pumps exceeds the required exhaust capacities for each of the plurality of time segments even if the operation of the one or more vacuum pumps is stopped during execution of the slow cooling control.

2. A vacuum cooling device for cooling an object to be cooled contained in a treatment tank, The apparatus includes a plurality of vacuum pumps, a heat exchanger, a slow cooling means, a pressure detection means, and a control means, the plurality of vacuum pumps are arranged in parallel and connected to the treatment tank via the heat exchanger; The heat exchanger is configured to condense steam exhausted from the treatment tank, the slow cooling means is configured to be capable of reducing an exhaust speed of the treatment tank by the plurality of vacuum pumps, The pressure detection means is configured to detect the pressure in the treatment tank, The control means includes a storage unit, a slow-cooling control unit, and a unit for determining the number of pumps to be operated, The storage unit stores target pressures set for a plurality of predetermined time segments, the slow-cooling control unit performs slow-cooling control to control the slow-cooling means so that the internal pressure of the treatment tank detected by the pressure detection means becomes the target pressure stored in the memory unit, The unit for determining the number of operating pumps determines the number of operating vacuum pumps based on a reduction rate of an exhaust speed by the slow cooling means.

3. A vacuum cooling device as described in claim 2, The unit for determining the number of operating pumps reduces the number of operating pumps if the rate of reduction in exhaust speed by the slow cooling means is equal to or greater than a predetermined rate, and does not reduce the number of operating pumps if the rate of reduction in exhaust speed by the slow cooling means is less than the predetermined rate.

4. 4. The vacuum cooling device according to claim 3, the slow-cooling means includes a slow-cooling valve capable of adjusting the amount of air introduced into the treatment tank; The unit for determining the number of operating pumps reduces the number of operating pumps when the opening degree of the slow cooling valve is equal to or greater than a predetermined opening degree, and does not reduce the number of operating pumps when the opening degree of the slow cooling valve is less than the predetermined opening degree.

5. A vacuum cooling device according to any one of claims 1 to 4, A vacuum cooling device, wherein the vacuum pump is a water-sealed vacuum pump.

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