JP6537405B2 - Vacuum cooling system - Google Patents

Description

The present invention accommodates objects to be cooled such as cooked food in a treatment tank, decompresses the pressure in the treatment tank, evaporates water in the object, and rapidly heats the object by heat of vaporization. The present invention relates to a vacuum cooling device for cooling.

As described in JP-A-2008-249256, the gas in the processing tank containing the object to be cooled is exhausted to the outside, and the pressure in the processing tank is reduced to lower the saturation temperature in the processing tank. There is known a vacuum cooling device which cools an object to be cooled by utilizing the heat of vaporization by evaporating water from the object to be cooled. In feeding centers etc., it is required to pass through a temperature zone where bacteria easily propagates as quickly as possible when cooling cooked food, and if it is a vacuum cooling device, it will be cooled to the center of the object to be cooled in a short time. Is widely used because it is possible.

In the vacuum cooling apparatus, the object to be cooled is accommodated in the processing tank, and the processing tank is depressurized by the vacuum generator. A target cooling temperature is set in the vacuum cooling device, and pressure reduction is performed until the pressure in the processing tank reaches a pressure corresponding to the target cooling temperature. When the temperature of the object to be cooled reaches a desired target cooling temperature by vacuum cooling due to reduced pressure in the processing tank, the cooling is ended. Since the processing tank can not be opened if the inside of the processing tank is in a vacuum state, external air is introduced into the processing tank after cooling is completed, the pressure in the processing tank is reduced to atmospheric pressure, and then the object to be cooled is taken out.

Although the target temperature for cooling in the vacuum cooling device is often about 10 ° C. to 20 ° C., it may be desired to cool to a temperature as low as 5 ° C. or less. Since the vacuum cooling device reduces the temperature of the object to be cooled by evaporation of water generated when the temperature of the object to be cooled is higher than the saturation temperature of the pressure in the treatment tank, the pressure in the treatment tank is lowered. The temperature of the object to be cooled can be lowered. As a vacuum generator for depressurizing the inside of the treatment tank, a dry or water-sealed vacuum pump, an ejector using steam or water, or the like is used, and a vacuum generator capable of depressurizing to a lower pressure is used The product temperature can be reduced by doing this.

However, when the pressure in the processing tank and the vacuum piping is reduced, the liquid in the vacuum piping and the vacuum generator evaporates, which causes the pressure not to be reduced in the processing tank. The cooling capacity of the vacuum cooling device is limited to the temperature of the water supplied to the vacuum generating device + several degrees Celsius.

Therefore, the vacuum generator is supplied with cold water cooled by a chiller, and a heat exchanger is installed in the vacuum piping to supply cooling water to the heat exchanger, thereby performing cooling in the vacuum piping. ing. By supplying chilled water by the chiller, the inside of the treatment tank can be depressurized to a lower pressure, and the material temperature of the object to be treated can also be cooled to a lower temperature.

In the chiller, the water is cooled to near 0 ° C., but if the water is cooled too much and frozen, the chilled water can not be supplied, so it is necessary to control the operation so as not to freeze. In the chiller, the temperature of the supplied cold water is controlled by stopping the cooling operation when the supplied cold water temperature falls below the set thermo-off temperature and resuming the cooling operation when the cold water temperature rises. In this case, starting and stopping the cooling operation in a short time places a load on the chiller compressor. Therefore, the chiller sets a restart prohibition time of about 3 to 5 minutes to protect the compressor, and restarts the cooling operation after the restart prohibition time has elapsed when restarting the cooling operation. It is necessary to stop the chiller's cooling operation to prevent supercooling and set the restart prohibition time for chiller protection, but if the chilled water operation is stopped because the supplied cold water temperature falls below the thermo-off temperature Immediately after that, even if the temperature of the cooling water rises, the cooling operation can not be resumed until the restart prohibition time elapses, and the temperature of the cooling water may continue to be high. When the temperature of the cooling water rises, the pressure reduction capability of the vacuum generator decreases, and the progress of the vacuum cooling step is delayed.

Therefore, in the invention described in Japanese Patent No. 2624065, when the cold water temperature is detected and the cold water temperature decreases and approaches the thermo-off temperature, the output of the chiller is limited to a predetermined demand value before the temperature decreases to the thermo-off temperature. Load restriction control (chiller demand control) is performed. In chiller demand control, the chiller inlet temperature is measured, and restriction is started when the inlet temperature becomes lower than the lower limit temperature. For example, when the cooling water temperature is lowered by cooling at a capacity of 100% up to that point and the temperature is lowered to a set temperature before the thermo-off temperature, the cooling capacity is limited to a demand value, for example 30%. By limiting the cooling capacity to suppress the temperature drop of the cooling water, it is possible to continue the operation of the chiller and to prevent the chiller from being turned off. In addition, if the temperature of the cooling water rises by reducing the cooling capacity, it is possible to lower the cold water temperature by recovering the cooling capacity to 100%. In this way, the temperature of the cooling water can be maintained continuously in a predetermined range without stopping the compressor of the chiller.

However, even when the chiller demand control is performed, the cooling operation may not have to be stopped due to the temperature decrease of the cooling water. Therefore, it has been desired to perform more stable cooling operation control by reducing the temperature fluctuation of the supplied cold water.

Patent No. 2624065

The problem to be solved by the present invention is to increase the accuracy of chiller demand control in a vacuum cooling apparatus in which the temperature of the object is cooled to a lower temperature by supplying chilled water using a chiller, and the chiller It is an object of the present invention to provide a vacuum cooling system capable of cooling an object to be cooled stably by not stopping the cooling operation due to the decrease of the cold water temperature.

The invention according to claim 1 has a processing tank containing an object to be cooled, and a vacuum generator for discharging a gas in the processing tank, and the inside of the processing tank is decompressed to be contained in the processing tank. Vacuum cooling device for cooling objects, which is provided with a heat exchanger in the middle of the vacuum path connecting the treatment tank and the vacuum generator, and the heat exchanger is supplied with chilled water cooled by a chiller. In the device, the temperature was measured with a chiller inlet temperature measurement device that detects the temperature of cooling water returned from the heat exchanger to the chiller, the outside air temperature measurement device that detects the outside air temperature in the chiller installation part, the chiller inlet temperature measurement device and the outside air temperature measurement device may be provided a chiller operation controller for controlling the operation of the chiller based on the value, the chiller operation control device, the measurement value of the chiller inlet temperature measured by the chiller inlet temperature measuring device, chiller entry in "demand value change If it becomes lower than the demand operation start chiller inlet temperature calculated by the "decreased temperature + required chiller inlet temperature after completion of the demand transfer", the chiller demand control is performed to limit the chiller output to the demand value. It features.

The invention according to claim 2 is a cold water tank for storing cooling water returned to the chiller instead of the chiller inlet temperature measuring device for detecting the temperature of the cooling water returned from the heat exchanger to the chiller in the vacuum cooling device described above. The water tank temperature measurement device for detecting the temperature of the cooling water in the water supply system is provided, the water tank temperature measured by the water tank temperature measurement device is supplied to the chiller operation control device, and the chiller operation control device is the water tank temperature measurement device. If the measured value of the measured water tank temperature is lower than the demand operation start water tank temperature calculated by "water tank lowered temperature during change of demand value + required water tank temperature after completion of demand transition + adjustment value", the chiller output is requested It is characterized by performing chiller demand control limited to a value.

The invention according to claim 3 is characterized in that, in the vacuum cooling device described above, the chiller inlet drop temperature during change of demand value or the tank drop temperature during change of demand value prepares a table of chiller ability against the outside air temperature and circulates. It is characterized in that it is calculated by the chiller capacity for the amount of water and the predetermined amount of treatment.

By carrying out the present invention, even when the object to be cooled is cooled to a low temperature of 10 ° C. or less by the vacuum cooling device, the chiller will not stop cooling during the cooling operation of the vacuum cooling device. In the vacuum cooling device, stable cooling can be performed.

Flow diagram of a vacuum cooling system embodying the present invention Explanatory drawing of the chiller inlet temperature change condition in the vacuum cooling device which has implemented this invention Flow chart of vacuum cooling device in another embodiment of the present invention

One embodiment 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, FIG. 2 is an explanatory view of a temperature change of a chiller inlet in the vacuum cooling apparatus embodying the present invention, and FIG. 3 is another embodiment of the present invention. It is a flowchart of the vacuum cooling device in an example. The vacuum cooling apparatus has a processing tank 2 for containing the object to be cooled 7 and a vacuum generator 1 for discharging the gas in the processing tank 2. The vacuum cooling apparatus evaporates the water in the object to be cooled by reducing the pressure in the processing tank, and cools the object to be cooled 7 contained in the processing tank 2 by the heat of vaporization at the time of evaporation.

The vacuum generator 1 is connected to the processing tank 2 by a vacuum pipe 9, and the gas in the processing tank 2 is discharged through the vacuum pipe 9 by operating the vacuum generator 1. In the middle of the vacuum pipe 9, a heat exchanger 10 for cooling the gas drawn from the processing tank 2 is provided. The gas being drawn from the treatment tank contains steam, and the volume of the water is greatly increased when it becomes steam, so a large volume of steam will be sent to the vacuum generator 1 as it is. It becomes inefficient. For this purpose, the heat exchanger 10 is provided in the middle of the vacuum path, and the suction gas is cooled by the heat exchanger 10 to condense the vapor and reduce the volume of the gas that must be discharged by the vacuum generator 1 . The heat exchanger 10 has a structure in which a heat transfer pipe is installed in a cold water tank 5 for storing cold water, and the cold water tank 5 is supplied with cold water manufactured by the chiller 3. The chiller 3 producing cold water and the cold water tank 5 are connected by a cold water circulation pipe 6, the cold water produced by the chiller 3 is supplied to the cold water tank 5, and the cooling water cooled by the chiller 3 is the cold water of the cold water tank 5 The cold water is circulated between the chiller 3 and the cold water tank 5 through the cold water circulation pipe 6.

The chiller inlet temperature measuring device 8 for detecting the temperature of cooling water entering the chiller 3 is provided in the cold water circulation pipe 6, and the measured value of the chiller inlet temperature detected by the chiller inlet temperature measuring device 8 is the operation of the chiller 3 Output to the chiller operation control device 4 that controls the Further, an outside air temperature measuring device 12 for measuring the outside air temperature in the environment where the chiller 3 is installed is provided, and the outside air temperature measured by the outside air temperature measuring device 12 is also output to the chiller operation control device 4. The chiller operation control device 4 controls the operation of the chiller using a measured value of the chiller inlet temperature and the like.

The operation control in the chiller performs cooling at the maximum capacity of the chiller when the chiller inlet temperature is high, but when the chiller inlet temperature is low, it is necessary to perform control to prevent the cold water from freezing due to supercooling. Thermo-off control to stop the cooling operation and chiller demand control to limit the chiller output to the demand value are performed. In the thermo-off control, the thermo-off temperature for stopping the operation of the chiller is set, and when the chiller inlet temperature falls below the thermo-off temperature, the cooling operation in the chiller is stopped. When the operation of the chiller is stopped by the thermo-off control, a restart prohibition time of 3 to 5 minutes is set to protect the compressor, and the restart is not performed in a short time.

In chiller demand control, load limitation of the chiller is performed so that the cold water does not fall to the thermo-off temperature, and the measured value of chiller inlet temperature detected by the chiller inlet temperature measuring device 8 is up to demand operation start chiller inlet temperature Control to reduce the chiller's output when it falls. The demand operation start chiller inlet temperature is calculated by “the chiller inlet lowered temperature during change of demand value + the required chiller inlet temperature after completion of the demand shift + adjustment value”.

Even if the chiller inlet lowering temperature during demand value change starts operation to limit the chiller output, it takes some time until the chiller output is actually reduced to the demand value, It is for preventing that the cold-water temperature falls too much by the cooling done. For example, when changing from 100% output of the chiller to 30% output of the demand value, the time required to change from 100% output to 30% output is 3 minutes, and the output of the chiller is in time Assuming that it is changing in proportion, even if the chiller demand control is started, the output of the chiller is changing from 100% to 30%, and the output continues to be larger than the demand value for 3 minutes In this case, the same cooling as in the case where the output of 65% is continued for 3 minutes is performed.

The chiller inlet temperature drop during demand value change, which is the temperature that is considered to be a drop in temperature from the start of demand value change until chiller output becomes demand value, is affected by the outside temperature, so chiller operation The control device 4 calculates the ambient temperature in consideration. A program having a chiller capacity table corresponding to the outside air temperature is prepared in the chiller operation control device 4, and the chiller inlet temperature drop is calculated from the amount of circulating water and the chiller capacity for a predetermined processing amount. In addition, an adjustment value (setting value) is provided to cope with a change in the condition.

In the chiller operation control device 4, the value of the chiller inlet temperature measured by the chiller inlet temperature measuring device 8 is based on "the chiller inlet temperature under change of the demand value + the required chiller inlet temperature after adjustment of the demand transition + adjustment value" When the calculated demand operation start chiller inlet temperature or lower, the operation process of the chiller 3 is changed from the normal operation to the demand operation. However, as described above, even if the demand operation is started, the operation according to the demand value is not performed immediately, and the output is changed in a fixed time. Immediately after the start of the demand operation, the chiller operation control device 4 performs an operation of changing the output of the chiller 3 from the normal operation time to the output of the demand value, and performs the operation at the demand value when the output decreases to the demand value. . If the chiller inlet temperature rises after the start of demand operation and the measured chiller inlet temperature becomes higher than the demand operation start chiller inlet temperature, the demand operation is canceled and returned to normal operation, and the chiller output value is returned. The increase prevents the rise of cold water temperature.

FIG. 2 shows this situation, and the changes in the chiller inlet temperature and the chiller output value are described together with the chiller operation status. In FIG. 2, the thermo-off temperature at which the operation of the chiller 3 is stopped is 4 ° C., and the required chiller inlet temperature after completion of the demand shift to set the temperature higher than the thermo-off temperature is 5 ° C. And the demand transition completion time which is the time required to change the output of the chiller from 100% to 30% of the demand value is 3 minutes, and the temperature change of this demand transition completion time for 3 minutes at the current outside temperature The chiller inlet temperature drop during the demand value change, which is the width, is 4 ° C. In this case, assuming that the adjustment value is 1 ° C., the value of the demand operation start chiller inlet temperature is “the chiller inlet decrease temperature during the demand value change + the required chiller inlet temperature after the completion of the demand transition + the adjustment value”. ° C + 5 ° C + 1 ° C = 10 ° C.

When the measured value of the chiller inlet temperature decreases to 10 ° C. of the demand operation start chiller inlet temperature, the chiller operation control device 4 starts the demand operation. However, immediately after the start of the demand operation, the chiller output is still close to 100%, and it takes 3 minutes for the chiller output value to reach 30% of the demand value. When the demand operation is started at chiller inlet temperature 10 ° C and chiller power reduction is started, the chiller inlet temperature at the completion of the demand transition is 6 ° C which is lowered by 10 ° C to 4 ° C. It is possible to perform an operation limited to the demand value at a higher level.

The value of the demand operation start chiller inlet temperature is calculated from a table of chiller capacity with respect to the outside air temperature, and the chiller capacity with respect to the amount of circulating water and a predetermined processing amount. When the outside air temperature is high, when the circulation amount of the cooling water is large, and when the treated amount of the object to be cooled is large, the chiller inlet temperature is less likely to fall, and vice versa. When the chiller inlet temperature tends to decrease, the chiller inlet temperature decrease during the change of the demand value increases, so the demand operation start chiller inlet temperature increases. The demand operation can be started at an appropriate time by calculating an appropriate value of the demand operation start chiller inlet temperature according to the outside temperature and the like.

In the above embodiment, the demand operation control is performed based on the value of the chiller inlet temperature measured by the chiller inlet temperature measuring device 8 provided in the chilled water circulation pipe 6, but the temperature of the cold water tank 5 is Control based on may be performed. FIG. 3 is a diagram when performing control based on the cold water tank temperature. In this case, the cold water tank 5 is provided with the water tank temperature measurement device 11, and the water tank temperature measurement device 11 sends the measured water tank temperature value to the chiller operation control device 4. In the chiller operation control device 4, the value of the demand operation start water tank temperature is calculated by "water tank lowered temperature during change of demand value + necessary water tank temperature after completion of demand transition + adjustment value". Also in this case, a program having a chiller capacity table corresponding to the outside air temperature is prepared for the chiller operation control device 4, and the water tank reduction temperature during the change of demand value is calculated by the circulating water amount and the chiller capacity for a predetermined processing amount. calculate. By doing this, the demand operation control may be performed based on the temperature of the cold water tank 5.

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

1 Vacuum generator
2 treatment tank
3 chiller 4 chiller operation control device 5 cold water tank 6 cold water circulation piping 7 object to be cooled 8 chiller inlet temperature measurement device 9 vacuum piping 10 heat exchanger 11 water tank temperature measurement device 12 outside air temperature measurement device

Claims (3)

A vacuum cooling apparatus that has a processing tank that contains an object to be cooled, and a vacuum generator that discharges the gas in the processing tank, and that decompresses the inside of the processing tank to cool the object that is stored in the processing tank. In the vacuum cooling device, a heat exchanger is provided in the middle of a vacuum path connecting the treatment tank and the vacuum generator, and the heat exchanger is supplied with chilled water cooled by the chiller,
Based on the values measured by the chiller inlet temperature measurement device that detects the temperature of cooling water returned from the heat exchanger to the chiller, the outside air temperature measurement device that detects the outside air temperature at the chiller installation unit, the chiller inlet temperature measurement device and the outside air temperature measurement device Provided with a chiller operation control device to control the operation of the chiller,
The chiller operation control device is a demand that the measured value of the chiller inlet temperature measured by the chiller inlet temperature measurement device is calculated by "chiller inlet temperature drop during change of demand value + required chiller inlet temperature after completion of demand transition + adjustment value" A vacuum cooling apparatus characterized by performing chiller demand control which limits the output of a chiller to a demand value when it becomes lower than the operation start chiller inlet temperature. In the vacuum cooling device according to claim 1, instead of the chiller inlet temperature measuring device for detecting the temperature of the cooling water returned from the heat exchanger to the chiller, the cooling water in the cold water tank for storing the cooling water returned to the chiller A water tank temperature measuring device for detecting the temperature is provided, and the chiller operation control device is supplied with the water tank temperature measured by the water tank temperature measuring device,
The chiller operation control device calculates the measured value of the water tank temperature measured by the water tank temperature measuring device as "water tank decrease temperature during change of demand value + required water tank temperature after completion of demand transition + adjustment value" A vacuum cooling apparatus characterized by performing chiller demand control that limits the chiller output to a demand value when it becomes lower. In the vacuum cooling device according to claim 1 or 2, the chiller inlet lowering temperature during the demand value change or the water tank reduction temperature during the demand value change prepares a table of the chiller ability with respect to the outside air temperature A vacuum cooling device characterized by being calculated by a chiller capacity with respect to a processing amount.

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