JP2005229959A - Thawing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thawing method intended for performing short time thawing and high quality thawing at the same time. <P>SOLUTION: A thawing apparatus has a pressure reducing means 4 of reducing pressure in a thawing area 2 holding an object 1 to be thawed, a steam supplying means 3 of supplying steam to the thawing area 2, and a control means 8 of controlling the pressure reducing means 4 and the steam supplying means 3 to thaw the object 1 to be thawed with low-pressure steam. The control means 8 comprises a thawing process of controlling temperature or pressure in the thawing area 2 to a first set value, and an adjusting process of controlling temperature or pressure in the thawing area 2 to a second set value lower than the first set value following on the thawing process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a so-called vacuum steam thawing method and apparatus for thawing an object to be thawed by low-pressure steam in a thawing zone.

  In general, in thawing the material 1 to be thawed, short-time thawing and high-quality thawing are major technical problems. There is vacuum vapor thawing as a high-quality thawing method in a short time. In this vacuum vapor thawing, when the material to be thawed is placed in a container filled with saturated steam at a pressure lower than atmospheric pressure, the vapor condenses on the surface of the material to be thawed, and a large amount of latent heat of condensation generated at that time is defrosted. This is a thawing method for thawing an object to be thawed and is known from Patent Document 1 or the like.

JP-A-10-179019

  In recent years, in the convenience store industry and the like, the demand for frozen foods is increasing, and further shortening of the thawing time is desired.

  In the vacuum vapor thawing method as in Patent Document 1, the thawing time can be further shortened by setting the thawing temperature high. However, when the thawing temperature is set high, there is a problem that the internal temperature after thawing becomes non-uniform.

  It is an object of the present invention to provide a thawing method and apparatus for realizing thawing for a short time and equalizing the temperature of the material to be thawed after thawing.

  The present invention has been made to solve the above-mentioned problems. The invention according to claim 1 is a thawing method for thawing an object to be thawed with low-pressure steam in a thawing zone, and a temperature in the thawing zone. Or a thawing step for controlling the pressure to a first set value, and an adjustment step for controlling the temperature or pressure in the thawing zone to a second set value lower than the first set value following the thawing step. It is characterized by.

  The invention according to claim 2 is characterized in that, in claim 1, the adjusting step makes the difference between the surface temperature of the object to be thawed and the core temperature smaller than that of the thawing step, and uniformizes the temperature of the entire object to be thawed. It is a process.

  Furthermore, the invention according to claim 3 controls the steam supply means into the thawing area, the pressure reducing means in the thawing area 2 for storing the material to be thawed, the steam supply means and the pressure reducing means to control the low pressure. In a thawing apparatus comprising control means for thawing the material to be thawed with steam, the control means controls the temperature or pressure in the thawing zone to a first set value, and the thawing process is followed by the thawing process. And adjusting the temperature or pressure in the thawing zone to a second set value lower than the first set value.

  According to this invention, after performing thawing with the thawing process as a relatively high thawing temperature, the difference between the surface temperature and the core temperature of the object to be thawed is made smaller in the adjustment process than in the thawing process. And the temperature of the entire object to be thawed is made uniform.

(Embodiment)
Next, an embodiment of the present invention will be described. This embodiment is implemented in a thawing apparatus that performs thawing of a material to be thawed by low-pressure steam in a thawing zone. This thawing device includes a thawing device for home use as well as for business use.

  First, an outline of the embodiment will be described. In this embodiment, the decompression means for decompressing the inside of the thawing area for containing the material to be thawed, the steam supply means for supplying steam into the thawing area, the decompression means and the steam supply means are controlled to control the low pressure steam. And a control means for thawing the object to be thawed, wherein the control means includes a step of controlling the temperature or pressure in the thawing zone high and a step of controlling the temperature or pressure thereafter. A thawing device.

  More specifically, this embodiment includes a decompression unit that depressurizes the inside of a thawing area that accommodates an object to be thawed, a steam supply unit that supplies steam into the thawing region, the decompression unit, and the steaming unit. A thawing device comprising: a control means for controlling the temperature and pressure in the thawing zone to a first set value, and a thawing step comprising: And a regulating step of controlling the temperature or pressure in the thawing zone to a second set value lower than the first set value following the step.

  According to this embodiment, the control means controls the temperature or pressure in the thawing zone to the first set value in the thawing step to defrost the material to be thawed at a relatively high thawing temperature. Thereby, the thawing of the material to be thawed proceeds rapidly. In the adjustment step subsequent to the thawing step, the temperature or pressure in the thawing zone is controlled to the second set value. Thereby, the temperature of the whole to-be-thawed object is equalized. Moreover, since the temperature of the to-be-thawed object is lowered, propagation of miscellaneous bacteria after thawing can be suppressed.

  Here, the low-pressure steam means steam having a pressure equal to or lower than atmospheric pressure, but the pressure of steam used for thawing can be about 6 hPa to 40 hPa. The temperature in the thawing zone has a predetermined correspondence with the pressure in the thawing chamber in a state where saturated steam is filled in the thawing zone, and can be controlled by the pressure in the thawing chamber. is there. Thus, in the present invention, the temperature in the thawing zone is equivalent to the pressure in the thawing zone, and the temperature control in the thawing zone is equivalent to the pressure control.

  The first set value of the thawing step can also be called a thawing temperature. The first set value is also a value set in the conventional thawing method, and is a set temperature in the thawing zone as a control target.

  Next, each component of this embodiment will be described. First, the thawing area is an area used for thawing the material to be thawed, and means a room, room, container, or tank in which the material to be thawed can be stored and taken in and can also be called a thawing area or a thawing space.

  The thawing of the material to be thawed with low-pressure steam in this embodiment may be performed by a method of thawing with steam having a pressure lower than atmospheric pressure (hereinafter referred to as low pressure). That is, the low-pressure steam thawing (also referred to as vacuum steam thawing) supplies (steams) steam into the thawing area while reducing the pressure in the thawing area by operating a decompression means such as a vacuum pump. A method, a method of depressurizing the inside of the thawing zone and then stopping the operation of the pressure-reducing means, and steaming, and a method combining these two methods.

The steam supply means is means for supplying steam to the thawing zone, and includes a steam generating device and the like. This steam generator is preferably a reboiler that generates clean steam.

  The decompression means is not limited to a specific one, but preferably a combination of an ejector, a heat exchanger, and a vacuum pump. By doing so, the temperature in the thawing zone can be controlled low. The ejector may be a steam ejector, and the vacuum pump may be a water ring vacuum pump.

  The control means controls the temperature or pressure in the thawing zone to the first set value in the thawing step, and controls the temperature or pressure in the thawing zone in the adjustment step following the thawing step. Control to two setting values.

  In the thawing step, the steam supply means and the decompression means are controlled to obtain the first set value. The first set value is about 12.3 hPa to 23.4 hPa (about 10 ° C. to 20 ° C. in terms of temperature), and can be configured to be variable, that is, the set value can be changed. This thawing process can be configured to be executed only for the first set time by timer control. This first set time can be made variable by the user. The first set time can be set according to the amount and type of the material to be thawed, referring to data obtained through experiments in advance or based on user experience.

  In this thawing step, the higher the value of the first set value, the shorter the thawing can be performed, but the difference between the surface temperature of the material to be thawed and the center temperature tends to increase. However, the subsequent adjustment process can reduce variations in the decompression quality due to the difference in the first setting value and the difference in the first setting time.

  In the adjustment step, the operation of the steam supply unit is stopped, and the second set value is controlled only by the control of the decompression unit. In this adjustment step, the pressure reducing means is preferably operated intermittently. This intermittent operation can be configured to operate when the pressure in the thawing zone becomes higher than the second set value, and to stop when the pressure reaches the second set value.

  The second set value is preferably a fixed value, but can be variable. Moreover, this adjustment process can be comprised so that it may perform only 2nd setting time by timer control. This second set time is preferably fixed, but can be variable.

  In the adjusting step, the vacuum cooling operation is performed by the pressure reduction by the pressure reducing means. By this vacuum cooling operation, the temperature difference between the surface of the object to be thawed and the core portion is made uniform.

  The adjustment step can be configured to end the thawing operation without performing the adjustment step when the first preset temperature of the thawing step is low.

  The present invention is not limited to the first embodiment, but includes the following second embodiment.

(Embodiment 2)
In this second embodiment, the decompression means for decompressing the inside of the thawing area for storing the material to be thawed, the steam supply means for supplying the steam into the thawing area, the decompression means and the steam supply means are controlled, and the pressure is reduced. A first thawing mode including a step of controlling a temperature or a pressure in the thawing zone to be high and then a step of controlling the temperature or pressure in the thawing zone. A thawing apparatus that selectively performs a second thawing mode including a step of controlling the temperature or pressure in the thawing zone low and a step of controlling the pressure or pressure thereafter.

  According to the second embodiment, when the first thawing mode is selected, thawing is performed with emphasis on shortening the thawing time. In addition, when the second thawing mode is selected, the time of exposure to high-temperature steam in the initial stage of thawing can be reduced, and thawing is performed without raising the surface temperature of the object to be thawed. The thawing is performed with emphasis on thawing quality.

  Hereinafter, specific examples of the decompression apparatus embodying the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the embodiment, FIG. 2 is a flowchart showing an outline of the control procedure of the embodiment, and FIG. 4 is a time for explaining the thawing in the first thawing mode according to the embodiment. FIG. 5 is a time chart for explaining the thawing in the second thawing mode according to the embodiment. 4 and 5, the solid line portion below the pressure characteristic diagram indicates the operation of each device.

  The thawing device of this embodiment is applied to a business thawing device. This thawing device is provided with a thawing chamber 2 serving as a thawing area for storing the material 1 to be thawed, a steam supply (steaming) means 3 for supplying steam into the thawing chamber 2, and the thawing chamber 2 with suction and exhaust. Depressurization means 4 that maintains a low pressure, decompression means 5 that restores pressure by introducing outside air into the decompressed thawing chamber 2, and a cart on which the object 1 to be thawed 1 is placed and can be taken in and out of the thawing chamber 2 (Transport vehicle) 6, a pressure detector 7 for detecting the pressure in the thawing chamber 2, and a low pressure steam in the thawing chamber 2 based on a control procedure in which a signal of the pressure detector 7 is inputted and stored in a memory A controller 8 that controls the thawing of the object 1 is provided as a main part.

  The to-be-thawed material is meat or the like that is vacuum-packed, and includes those that are not vacuum-packed. The object to be thawed that has been vacuum packaged is desirably formed with a cut hole or a ventilation hole (not shown) formed of a hole in the package with a blade or the like before thawing. By forming such vents, it is possible to prevent the heat transfer from being hindered due to the expansion of the package when the low-pressure steam is thawed, and it is possible to shorten the thawing time by directly contacting the food with the steam.

  The thawing chamber 2 includes a door (not shown) for taking in and out the material 1 to be thawed, and is configured so that the cart 6 can be easily taken in and out by forming a lower floor surface. In this embodiment, thawing with low-pressure steam is performed and the inside of the thawing chamber 2 is not set to atmospheric pressure or higher, so that it is not formed as a pressure-resistant pressure vessel. However, in the case of providing the function of steam heating of food with high-pressure steam, a pressure-resistant pressure vessel can be obtained.

  The steam supply means 3 includes a first steam supply path 9 for connecting one end to the thawing chamber 2 and supplying clean steam into the thawing chamber 2. 10. A reboiler 11 as a steam generation source for generating clean steam using soft water supplied from the water softener 10, a first steam supply valve 12 for controlling supply of steam, and a tip of the first steam supply path 9 A nozzle 13 is provided for ejecting steam into the thawing chamber 2. The first steam supply valve 12 uses a valve such as a proportional valve capable of adjusting the steam supply amount by adjusting the opening.

  The reboiler 11 is made of stainless steel, uses a water softener 10 and is non-chemically poured. Thereby, since the supply steam to the thawing chamber 2 does not contain chemicals or iron, thawing by safe low-pressure steam is realized. The heating source of the reboiler 11 is a steam boiler (not shown) that normally generates steam.

The decompression means 4 includes a decompression path 14 that decompresses the inside of the thawing chamber 2. The decompression path 14 is provided with a steam ejector 15, a heat exchanger 16, a check valve 17 for blocking the flow in the direction of the thawing chamber 2, and a water-sealed vacuum pump 18. The steam ejector 15 is connected to a second steam supply passage 19 for supplying steam from the steam boiler, and a second steam supply valve 20 is connected to the second steam supply passage 19.
Is provided. A cooling water supply passage 21 is connected to the heat exchanger 16, and a water supply valve 22 is provided in the cooling water supply passage 21.

  The return pressure means 5 includes an outside air introduction path 23 having one end connected to the thawing chamber 2. The outside air introduction path 23 includes a return pressure valve 24 for controlling the introduction of outside air and a filter 25 for sterilization. The return pressure valve 24 uses a valve such as a motor valve capable of adjusting the amount of introduced air by adjusting the opening degree.

  The thawing chamber 2 performs various settings such as a thawing mode, and is provided with a display 26 for displaying the operating state on the front door of the thawing chamber 2 and a notification of the end of thawing at a position away from the thawing device installation location such as the upper surface. An alarm 27 such as a rotating lamp is provided.

  The cart 6 is provided with a plurality of stages of shelves 28, 28,.

  The controller 8 receives a signal from the pressure detector 7 and, according to a predetermined processing procedure (program), the first steam supply valve 12, the vacuum pump 18, the second steam supply valve 20, and the water supply The valve 22, the return pressure valve 24, the indicator 26, the indicator 27, and the like are configured to be controlled.

  In this embodiment, the processing procedure includes a first thawing mode M1 that is a short-time thawing mode and a second thawing mode M2 that is a high-quality thawing mode, and both thawing modes M1 and M2 can be selected. The first thawing mode includes a thawing method according to the present invention, a control for thawing the material to be thawed by low-pressure steam in the thawing zone, and increasing or lowering the temperature or pressure in the thawing zone at the initial stage of thawing. Yes. The main part of the processing procedure is shown in FIG.

  As shown in FIG. 3, the first thawing mode M1 includes a first thawing step A in which thawing is performed with the set pressure in the thawing chamber 2 as the first set pressure P1 in the initial and subsequent thawing, and the thawing step A. And an adjustment step B that is performed subsequently. The adjustment step B is a step of equalizing the entire temperature of the object 1 to be thawed, with the set pressure in the thawing chamber 2 set to a second set pressure P2 lower than the first set pressure P1. . The second set pressure P2 is a fixed value in this embodiment.

  In the second thawing mode M2, as shown in FIG. 4, following the second thawing step C and the second thawing step C in which the set pressure in the thawing chamber 2 is thawed at the initial stage of thawing as the third set pressure P3. A transition step D in which the set pressure in the thawing chamber 2 is increased stepwise from the third set pressure P3 and thawed, and following the transition step D, the third set pressure is set in the thawing chamber 2 And a third thawing step E for thawing as a fourth set pressure P4 higher than P3. Eventually, the third set pressure P3 is set lower than the first set pressure P1, and in the transition process D, the set pressure is controlled to be gradually increased from P3 to P4.

  Here, the initial stage of thawing means before melting of the core of the material to be thawed, and before melting of the core of the material to be thawed 1 means that the core temperature (temperature of the core) of the material to be thawed is near the melting point. Means before. Here, although the melting point of the core part of the to-be-thawed object 1 changes with kinds of to-be-thawed object, it is about -3 to -0.5 degreeC.

The set pressures P1 and P4 in the first thawing step A and the third thawing step E can also be referred to as thawing set values or thawing temperatures. The thawing temperature is also a value set in the conventional thawing method, and is a set temperature in the thawing chamber 2 in the latter thawing period which is a control target. Accordingly, the temperature of the material to be thawed 1 eventually reaches the above-mentioned thawing temperature if it takes a long time, but it is not necessary that the temperature of the whole material to be thawed is the thawing temperature at the end of thawing.

  Here, the effect | action of the Example of the said structure is demonstrated based on FIGS. 1-4. 3 and 4, the solid line portion shown below the pressure characteristic diagram indicates the operation of the vacuum pump 18, the steam ejector 15, and the first steam supply valve 12. First, referring to FIG. 1, in a state where the cart 6 is pulled out from the thawing chamber 2, the material 1 to be thawed is placed, and thereafter the cart 6 is accommodated in the thawing chamber 2, and the thawing chamber 2 is placed. To seal.

<Settings such as decompression mode selection>
In FIG. 2, the decompression mode is selected in processing step S1 (hereinafter, processing step SN is simply referred to as SN). When this mode selection is confirmed, the selected decompression mode is stored, and the process proceeds to S2.

  In S2, a time setting such as a thawing time is performed. Here, a thawing time is set for each selected thawing mode. This thawing time is the first thawing time T1 of the first thawing step A when the first thawing mode M1 is selected. When the second thawing mode M2 is selected, the second thawing time T2, which is the total time of the second thawing step C, the transition step D, and the third thawing step E, is set. These thawing times T1 and T2 are set by the user based on the type and amount of the object 1 to be thawed. When this setting is confirmed, the set value is stored, and the process proceeds to S3.

  In S3, the thawing temperature for each thawing mode is set. The thawing temperature is the first set pressure P1 and the fourth set pressure P4, and the user sets the temperature based on the temperature, but the controller 8 converts this into a pressure and stores it. The set pressures of the adjustment process B, the second thawing process C, and the transition process B are set to preset values in this embodiment. When the setting of the thawing temperature is confirmed, the set value is stored and the process proceeds to S4.

  In S4, the low pressure holding is set. As shown in FIG. 3, the low-pressure holding step F is performed by operating the pressure-reducing means 4 after the thawing step, so that the inside of the thawing chamber 2 is set to the second set pressure P2 in the first thawing mode M1. In the second thawing mode M2, the temperature of the object to be thawed is kept low by keeping the fifth set pressure P5. Thereby, after completion | finish of thawing | decompression, increase of the germs of the to-be-thawed object 1 is prevented, and quality is maintained. In this low pressure holding process F, “Yes” or “No” can be selected. When the low pressure holding setting is confirmed, the setting is stored and the process proceeds to S5.

  In S5, the gradual pressure is set. As shown in FIG. 4, this gradual pressure means that after the third thawing step E of the second thawing mode M2, that is, after the thawing step is completed, in the pressure-reducing step G in which the pressure-reducing valve 24 is opened to return pressure. In this step, the return pressure valve 24 is gradually opened. Due to this gradual pressure, the pressure in the thawing chamber 2 gradually increases, and it is possible to prevent the occurrence of drip from the material 1 to be thawed due to a rapid re-pressure. This gradual pressure is set to “Yes” or “No”, and when the setting is confirmed, the process proceeds to S6. This slow pressure setting cannot be selected in the first thawing mode M1, and is set to “none”.

<Extract thawing operation>
In S6, after determining whether or not an operation switch (not shown) is pressed, the thawing operation is executed based on the contents stored in S1 to S5. Hereinafter, the first thawing mode M1 and the second thawing mode M2 will be sequentially described.

<First thawing mode M1>
First, the first thawing mode M1 will be described with reference to FIG. Now, assuming that low pressure holding: “Yes” is set, the process is performed in the order of the air exclusion process F → the first thawing process A → the adjustment process B → the low pressure holding process G → the return pressure process H. Executed. In the example of FIG. 3, the first set pressure P1 is set to about 23.4 hPa (20 ° C.), and the second set pressure P2 is set to about 8.7 hPa (5 ° C.).

(Air exclusion process F)
The air exclusion process E, which is a thawing preliminary process, includes a process of supplying steam while continuously reducing the pressure. With the return pressure valve 24 closed, the pressure reducing means 4 is continuously operated to perform continuous pressure reduction. That is, at the time t0 (hereinafter, the time tn is simply referred to as tn), the vacuum pump 18 is operated, the pressure is reduced to a set pressure, the second steam supply valve 20 is opened at the time t1, and the steam ejector is opened. 15 is activated. The water supply valve 22 opens in conjunction with the operation of the vacuum pump 18 and the steam ejector 15. However, when the heat exchanger 16 has a cooling capacity, the water supply valve 22 may be configured to stop water supply and save water. it can.

  Due to the continuous operation of the decompression means 4, the pressure in the thawing chamber 2 rapidly decreases. When the pressure in the thawing chamber 2 reaches the set pressure P6, the first steam supply valve 9 is fully opened at t2, and supply of steam into the thawing chamber 2 is started. The controller 8 controls the steaming means 3 so that the pressure in the thawing chamber 2 becomes the first set pressure P1 during the steaming. Thus, in the air evacuation step F, only the pressure reducing means 4 is exhausted first, and then the air in the thawing chamber 2 is exhausted by exhausting by steaming while reducing the pressure.

(First thawing step A)
In the first thawing step A performed following the air exclusion step E, the controller 8 performs a combination of intermittent operation and continuous operation of the decompression unit 4 while continuously operating the steam supply unit 3. Thus, the pressure P in the thawing chamber 2 detected by the pressure detector 7 is controlled to be the first set pressure P1.

  That is, the decompression means 4 is operated intermittently in the base mode. Then, the operation and stop of the decompression means 4 are repeated. The operation of the pressure reducing means 4 is to open the second steam supply valve 20 to operate the steam ejector 15, open the water supply valve 22 to operate the cooling by the heat exchanger 16, and The stop of the decompression means 4 means an operation opposite to the operation. This intermittent operation is controlled by the timer of the controller 8.

  The intermittent operation and continuous operation of the decompression means 4 will be described with reference to FIG. The pressure in the thawing chamber 2 starts to rise after passing through the lowest point P7 as the steaming proceeds, and reaches the first set pressure P1 at t3. Then, the counting of the first thawing time T1 is started, and the first thawing step A is started. The pressure reducing means 4 is operated for a short time after t3, but then shifts to an intermittent operation in which the pressure reducing means 4 is operated intermittently.

  Then, when the pressure in the thawing chamber 2 becomes the switching set pressure P1 + ΔP due to an increase in the amount of gas generated from the material 1 to be thawed, the decompression means 4 is continuously operated, that is, continuously decompressed. The determination of switching to the continuous operation is preferably performed when the pressure in the thawing chamber 2 becomes the switching set pressure P1 + ΔP and this continues for a predetermined time.

  This continuous operation is not a timer control but a control by pressure. This continuous operation is continued until t6 when the pressure in the thawing chamber 2 returns to the first set pressure P1 and the thawing set pressure in the thawing chamber 2 is changed. The switching from the intermittent operation to the continuous operation can be performed at the time of returning to the first set pressure P1.

  By this continuous decompression, the pressure in the thawing chamber 2 quickly returns to the first set pressure P1. In this way, the inside of the thawing chamber 2 can be quickly controlled to an intended pressure regardless of an increase in the amount of outflow gas from the object 1 to be thawed, and the pressure fluctuation in the thawing chamber 2, that is, the temperature fluctuation is minimized. be able to.

  In the intermittent operation, when the decompression means 4 is stopped, the steam is supplied into the thawing chamber 2 and condensed to the material 1 to be thawed, so that thawing proceeds. The pressure in the thawing chamber 2 is maintained substantially at the first set pressure P1 even when the decompression means 4 is stopped due to the pressure drop caused by the condensation of the steam and the continuous supply of the steam.

  And when this decompression means 4 stops, it is economical because steam does not contribute to thawing and is not exhausted unnecessarily. Further, the amount of steam used can be reduced by stopping the steam ejector 15. Moreover, since supply of the cooling water to the said heat exchanger 16 is stopped, while being able to reduce the usage-amount of cooling water, the power usage-amount for cooling a cooling water can be reduced. Furthermore, since the vacuum pump 18 is stopped, the amount of energy used for the operation can be reduced, and the amount of sealed water used can be reduced. As a result, significant energy saving is realized by power saving and water saving. Furthermore, the amount of noise can be reduced by stopping the vacuum pump 18.

  Further, in the intermittent operation, when the decompression means 4 is operated, the inside of the thawing chamber 2 is evacuated, so that gas generated from the thawing object 1 during thawing is discharged out of the thawing chamber 2, Inhibition of heat conduction due to gas staying around 1 and inhibition of heat conduction due to an increase in air partial pressure in the thawing chamber 2 can be reduced. As a result, the time required for thawing can be shortened and uniform thawing can be realized.

  Further, the steam supply from the steam supply means 4 is continued during the operation of the decompression means 4, and the inside of the thawing chamber 2 is controlled to the first set pressure P1, so that the material 1 to be thawed is the first set pressure P1. Thawing is performed at a temperature corresponding to. The pressure fluctuation from the first set pressure P1 can be minimized by adjusting the steam supply amount by controlling the first steam supply valve 12 regardless of whether the decompression means 4 is stopped or activated. .

  The intermittent operation and the continuous operation of the decompression means 4 are also performed in the second thawing step C, the transition step D, and the third thawing step E of the second thawing mode M2, but the description thereof is omitted in the following description. doing.

(Adjustment process B)
When the first thawing process A is performed for the set time T21, the process proceeds to the next adjustment process B. This adjustment process B is performed for the fourth time T4 from t6 to t7. The pressure control in the adjustment process B is not a timer control but a pressure control for controlling the target set value.

  In this adjustment step B, the temperature difference between the surface of the object to be thawed and the core is made uniform by vacuum cooling by the decompression by the decompression means 4. Thereby, control of the surface temperature of the to-be-thawed object 1 after completion | finish of thawing | decompression operation is attained.

(End of thawing process)
When the first thawing time T1 elapses, the notification device 27 is turned on in S7 to notify the end of the thawing process. The notification of the end of the thawing process is useful for an operator who works away from the thawing apparatus because thawing may take several hours. This notification can be made after the adjustment step B is completed.

  At the same time, when the thawing process ends, in S8, when the low pressure holding: “Yes” is set, the low pressure holding process F is executed.

(Low pressure holding process G)
In the low pressure holding process G, as shown in FIG. 3, first, the pressure reducing means 4 is intermittently operated and stopped so as to hold the pressure in the thawing chamber 2 at the second set pressure P2. This intermittent operation is not based on timer control but pressure control for controlling the pressure to a set value. Due to the vacuum cooling effect associated with this low pressure holding, the object 1 to be thawed can be held at a temperature lower than the thawing temperature, and can be prepared for the next step such as the impregnation step. The low pressure holding process G is executed for the third time T3, and when completed, the process proceeds to S9. If the pressure is maintained: “None”, the low pressure holding step F is omitted, and the process proceeds to S9.

(Return pressure process)
In S9, the return pressure process H is performed. In the return pressure step H of the first thawing mode M1, since the gradual pressure is “none”, the return pressure valve 24 is fully opened to perform the return pressure. The pressure change in this case is indicated by a solid line X in FIG. When this decompression process H is completed, the entire operation of the thawing device is completed. In FIG. 3, an alternate long and short dash line X indicates a case where pressure is maintained: “none”.

<Second thawing mode M2>
Next, the second thawing mode M2 will be described with reference to FIG. Now, assuming that low pressure holding: “present” and gradual pressure: “present” are set, the process is the air evacuation process F → the second thawing process C → the transition process D → the third thawing process E. → The low pressure holding process G → the return pressure process H is performed in this order. In the example of FIG. 4, the second set pressure P2 is set to about 12.3 hPa (10 ° C.), and the first set pressure P1 is set to about 8.7 hPa (5 ° C.).

  The second thawing mode M2 differs from the first thawing mode M1 in that the thawing process is composed of the second thawing process C, the transition process D, and the third thawing process E, and the decompression process. In the pressure step H, “Yes” and “No” of the slow pressure can be selected, and the description of the common steps is omitted.

(Air exclusion process F)
Same as the first thawing mode.

(Second thawing step C)
Basically, it is the same as the first thawing step, except that the thawing temperature is low. Only the operation related to this will be described.

  In the second thawing step C, the third set pressure P3 is set to a pressure lower than the first set pressure P1 of the first thawing step A, so that the residence time of the thawing object 1 at a high temperature can be reduced. The material to be thawed 1 is thawed without raising its surface temperature too much. As a result, thawing can be performed while maintaining high thawing quality. In addition, the material 1 to be thawed is in a frozen state in the second thawing step C, and has high thermal conductivity and low specific heat, so that it is thawed in a relatively short time despite the low steam temperature.

  Next, the transition process B and the second thawing process C are also controlled by the processing procedure of FIG. The difference from the thawing step A is that the thawing set value is changed. The outline of the processing will be described below with reference to FIG.

(Transition process B)
Referring to FIG. 4, when the second thawing process C is completed by performing the set time T21 by timer control, the transition process D is started at t4. In this transition process D, the steam supply means 3 and the pressure reducing means 4 are controlled so that the set pressure increases stepwise as shown and the detected pressure P becomes a set pressure that changes stepwise. This transition process D is also executed for a set time T22 by timer control.

  In the transition process D, the temperature in the thawing chamber 2 rises stepwise. Along with this, the surface temperature of the object 1 to be thawed gradually increases, so that the time during which the surface of the object 1 to be thawed is exposed to a high temperature is shortened, and drip outflow can be suppressed.

(Third thawing step E)
At t5, the transition process D ends, and the third thawing process E is started. In the third thawing step E, the steam supply means 3 and the pressure reducing means 4 are controlled so that the detected pressure P becomes the fourth set pressure P4. This third thawing step E is also executed for a set time T23 by timer control.

  Thus, the second thawing process C, the transition process D, and the third thawing process D are executed only for the second thawing time T2. The second thawing time T2 is not counted from the start of the air evacuation process E, but is counted after the air evacuation process E is completed.

(Return pressure process)
The decompression process H in S9 of the second thawing mode M2 will be described. In the return pressure step H, when the gradual pressure is “Yes”, the gradual pressure is executed. The pressure change in the thawing chamber 2 in this case is indicated by a solid line Y. In FIG. 4, an alternate long and short dash line Y indicates a case where pressure is maintained: “none”. Further, when the setting of slow pressure: “none” is made, the same as in the first thawing mode M1.

  As described above, in this embodiment, since the user can select the first thawing mode M1 and the second thawing mode M2, if the user wants to perform thawing for a short time, he selects the first thawing mode M2, When it is desired to perform decompression with emphasis on decompression quality, the first decompression mode M1 can be selected to perform decompression, and decompression can be performed as desired.

It is explanatory drawing which shows schematic structure of the Example of this invention. It is a flowchart figure which shows the outline | summary of the process sequence of the Example. It is a time chart explaining the decompression | decompression by the 1st decompression | decompression mode of the Example. It is a time chart explaining the decompression | decompression by the 2nd decompression | decompression mode of the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thawed object 2 Thawing chamber 3 Steaming means 4 Depressurizing means 5 Restoring means 7 Pressure detector

Claims (3)

  In the thawing method for thawing the material 1 to be thawed by the low-pressure steam in the thawing zone 2, a thawing step for controlling the temperature or pressure in the thawing zone 2 to a first set value, and following the thawing step, the thawing zone And a regulating step for controlling the temperature or pressure in 2 to a second set value lower than the first set value.   The adjusting step is a step of making the difference between the surface temperature and the core temperature of the object to be thawed 1 smaller than that of the thawing step and making the temperature in the object to be thawed 1 uniform. The thawing method described. Steaming means 3 into the thawing zone 2, decompressing means 4 in the thawing zone 2 containing the material 1 to be thawed, the steaming means 3 and the decompressing means 4 are controlled, and the material to be thawed by low-pressure steam. In the thawing apparatus comprising the control means 8 for performing thawing of 2, the control means 8 controls the temperature or pressure in the thawing zone 2 to a first set value, and the thawing following this thawing process. A thawing device that performs an adjustment step of controlling the temperature or pressure in the zone 2 to a second set value lower than the first set value.

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