Food drying apparatus and food drying method

Abstract

To provide a food drying apparatus and method that can dry food at high speed while saving power by recovering heat when exhausting humidity, even with a compact configuration. [Solution] The food drying device 10 comprises a drying chamber 11 in which food ingredients F are placed inside, an indoor heater 12 that raises the temperature inside the drying chamber 11, a circulator 13 that moves the air inside the drying chamber 11, a heat exchanger that exchanges heat between the air inside the drying chamber 11 and the outside air, and a control unit that controls the temperature inside the drying chamber 11. The heat exchanger comprises an exhauster that discharges the air inside the drying chamber 11 to the outside of the drying chamber 11, an intakeer that introduces outside air into the drying chamber 11, a first heat exchanger body through which the air inside the drying chamber 11 is circulated to the outside of the drying chamber 11 by the exhauster, and a second heat exchanger body through which outside air is circulated to the drying chamber 11 by the intakeer.

Description

Technical Field

[0001] The present invention relates to a food drying device and a food drying method.

Background Art

[0002] As a food drying device for drying and eating foods such as shiitake mushrooms and fish, a device has been proposed in which a fan and a heat source are arranged in a heating chamber, and a heat exchanger is provided in an air supply and exhaust passage (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above conventional food drying device becomes large-sized due to the laying of the air supply and exhaust passage, and the structure of the heat exchanger also becomes complicated.

[0005] In view of the above circumstances, the present invention has been made, and an object thereof is to provide a food drying device and a food drying method that can recover heat when exhausting humidity to achieve power saving and dry at high speed even with a compact configuration.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention employs the following means. The food drying apparatus according to the present invention comprises a drying chamber in which food is placed, an indoor heater for raising the temperature inside the drying chamber, a circulator for moving air inside the drying chamber, a heat exchanger for exchanging heat between the air inside the drying chamber and outside air, and a control unit for controlling the temperature inside the drying chamber. The heat exchanger comprises an exhaust fan for discharging air from the drying chamber to the outside, an intake fan for introducing outside air into the drying chamber, a first heat exchanger body through which the air inside the drying chamber is circulated to the outside by the exhaust fan, and a second heat exchanger body through which the outside air is circulated to the drying chamber by the intake fan.

[0007] Furthermore, in the food drying apparatus according to the present invention, the indoor heater is continuously powered.

[0008] Furthermore, the food drying apparatus according to the present invention further includes an outdoor intake air heater that heats the outside air being drawn into the heat exchanger.

[0009] Furthermore, the food drying apparatus according to the present invention further comprises Japanese paper and carbon in the indoor heater and / or the outdoor intake air heater.

[0010] Furthermore, the food drying apparatus according to the present invention further comprises a first temperature detector for detecting the temperature of the indoor heater, a second temperature detector for detecting the temperature of the drying chamber, and a humidity detector for detecting the humidity of the drying chamber, and the control unit comprises an indoor heating unit for driving and controlling the indoor heater, a circulation unit for driving and controlling the circulator, a heat exchange drive unit for driving and controlling the exhaust and intake, and a heating determination unit for suppressing condensation in the heat exchanger.

[0011] Furthermore, the food drying apparatus according to the present invention further includes an outdoor intake air heating unit in which the control unit drives and controls the outdoor intake air heater, and the heating temperature by the outdoor intake air heater is suppressed compared to the heating temperature by the indoor heater.

[0012] Furthermore, the food drying method according to the present invention is a food drying method that uses a computer to raise the temperature of a drying chamber in which food is placed, and comprises an initial heating step of raising the temperature inside the drying chamber to an initial temperature, and a drying step of raising the temperature inside the drying chamber to a temperature target value while lowering the humidity to a humidity target value, wherein at least in the drying step, a portion of the heated and humidified air inside the drying chamber is exhausted to the outside of the drying chamber while outside air is drawn into the drying chamber, thereby suppressing condensation and allowing heat exchange between them.

[0013] Furthermore, the food drying method according to the present invention further includes a follow-up drying step in which the state in which the humidity inside the drying chamber has been reduced to a humidity target value is continued for a predetermined time while maintaining the temperature target value and the humidity target value.

[0014] Furthermore, the food drying method according to the present invention further sets the target humidity value in the drying chamber based on the time period between heat exchange and non-heat exchange between the air in the drying chamber and the outside air, and the cumulative time ratio between the heat exchange and non-heat exchange periods.

[0015] Furthermore, the food drying method according to the present invention further involves exhausting a portion of the heated and humidified air in the drying chamber to the outside of the drying chamber while drawing in outside air into the drying chamber, wherein the outside air is heated for a predetermined time before being drawn in. [Effects of the Invention]

[0016] According to the present invention, even with a compact configuration, food drying can be achieved at high speed while saving power by recovering heat when exhausting humidity. [Brief explanation of the drawing]

[0017] [Figure 1] This is a diagram showing an overview of a food drying apparatus according to one embodiment of the present invention. [Figure 2] This is a diagram showing the indoor heater of a food drying apparatus according to one embodiment of the present invention. [Figure 3]It is a structural diagram showing a part of the heat exchanger of the food drying device according to an embodiment of the present invention. [Figure 4] It is a functional diagram showing the control unit of the food drying device according to an embodiment of the present invention. [Figure 5] It is a diagram showing the temperature and humidity profile of the food drying device according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0018] An embodiment according to the present invention will be described with reference to FIGS. 1 to 5. The food drying device 10 according to this embodiment includes a drying chamber 11 in which the food F to be dried is arranged inside, an air circulation machine 12 that moves the air in the drying chamber 11, an indoor heater 13 that raises the temperature in the drying chamber 11, a heat exchanger 15 that performs heat exchange between the air in the drying chamber 11 and the outside air, and a control device (control unit) 16.

[0019] The drying chamber 11 includes a ceiling surface 11A, a floor surface 11B, side surfaces 11C and a back surface 11D that connect the ceiling surface 11A and the floor surface 11B. It also includes a first thermometer (first temperature detector) 17 that measures the temperature of the indoor heater 13, a second thermometer (second temperature detector) 18 that measures the temperature in the drying chamber 11, a hygrometer (humidity detector) 20 that measures the humidity in the drying chamber 11, and a third thermometer 21 that measures the outside air temperature. The second thermometer 18 and the hygrometer 20 are arranged at least on the ceiling surface 11A side in the drying chamber 11.

[0020] The air circulation machine 12 includes an air circulation machine main body 22 that extends in the vertical direction with respect to the back surface 11D and has a suction port 22A on the upper side and an exhaust port 22B on the lower side opening into the drying chamber 11, and a circulation fan (circulator) 23 arranged at the suction port 22A of the air circulation machine main body 22. The suction port 22A and the exhaust port 22B of the air circulation machine main body 22 are communicated inside the air circulation machine main body 22.

[0021] The indoor heater 13 includes a heater body 25 made of Japanese paper containing carbon, which is formed in a strip shape and has electrodes 25A and B arranged at both ends, a wiring part 26 that supplies power to the heater body 25, and a sealing body 27 that seals the connection part between the heater body 25 and the wiring part 26. The first thermometer 17 is arranged on the surface of the heater body 25. The wiring part 26 includes a thermostat or a thermal fuse (not shown) for preventing overheating.

[0022] The heat exchanger 15 includes a first duct (first heat exchanger body) 28 through which the first suction port 28A and the first discharge port 28B are inserted and through which the air inside the drying chamber 11 passes to the outside of the drying chamber 11, a second duct (second heat exchanger body) 30 through which the second suction port 30A and the second discharge port 30B are inserted and through which the outside air passes into the drying chamber 11, an exhaust fan (exhauster) 31 that discharges the air inside the drying chamber 11 to the outside of the drying chamber 11, a suction fan (suction device) 32 that introduces the air outside the drying chamber 11 into the drying chamber 11, and an outdoor intake air heater 33 that is formed so that air can pass through and heats the air outside the drying chamber 11.

[0023] The intersection part of the first duct 28 and the second duct 30 is configured such that the air passing through them does not mix with each other, but can exchange heat with each other during passage. A through plate 34 with passages 34A formed in parallel in one direction is laminated so as to intersect each other at 90-degree intervals. The exhaust fan 31 is arranged near the first suction port 28A. The suction fan 32 is arranged near the second suction port 30A. During heat exchange, the exhaust fan 31 and the suction fan 32 are driven. During non-heat exchange, the exhaust fan 31 and the suction fan 32 are stopped. The outdoor intake air heater 33 has the same configuration as the indoor heater 13 and is configured such that air can pass through.

[0024] The control device 16 comprises a control unit 35 implemented by an integrated circuit such as an MCU (Micro Controller Unit) or FPGA (Field Programmable Gate Array) (not shown), and a storage unit 36 ​​implemented by semiconductor memory elements such as RAM (Random Access Memory) or flash memory built into the MCU (Micro Controller Unit) (not shown), and realizes or executes functions and operations related to temperature and humidity control in the drying chamber 11.

[0025] The control unit 35 is a controller, and for example, it executes the program stored in the memory unit 36 ​​using RAM as the working area, via an MCU (Micro Controller Unit), etc. Note that the internal configuration of the control unit 35 may be any other configuration as long as it performs the information processing described later.

[0026] The control unit 35 comprises a time counting unit 37, an indoor temperature detection unit 38, an outdoor temperature detection unit 40, a humidity detection unit 41, an indoor heating unit 42, a circulation unit 43, a heat exchange drive unit 45, an outdoor intake air heating unit 46, a dew point calculation unit 47, and a heating determination unit 48, and realizes or executes the information processing functions and operations described below. Note that the connection relationships of the various parts of the control unit 35 are not limited to those shown in Figure 4, and other connection relationships are also possible.

[0027] The time counting unit 37 calculates the cumulative drying time and the cumulative operating or stopped time of the exhaust fan 31 and intake fan 32. The indoor temperature detection unit 38 detects the temperature data detected by the first thermometer 17 and the second thermometer 18. The outdoor temperature detection unit 40 detects the temperature data detected by the third thermometer 21. The humidity detection unit 41 detects the humidity data detected by the hygrometer 20. The indoor heating unit 42 drives and controls the indoor heater 13. The circulation unit 43 drives and controls the circulation fan 23 of the air circulator 12.

[0028] The heat exchange drive unit 45 drives the exhaust fan 31 and the intake fan 32 based on a preset target humidity. The outdoor intake air heating unit 46 drives and controls the outdoor intake air heater 33.

[0029] The dew point calculation unit 47 calculates the dew point temperature inside the drying chamber 11, which is necessary for controlling the operation of the outdoor intake air heater 33 to prevent condensation on the heat exchanger 15, based on the temperature data and humidity data detected by the indoor temperature detection unit 38 and the humidity detection unit 41. The heating determination unit 48 compares the calculated dew point temperature with the temperature outside the drying chamber 11 to determine whether condensation will occur, and if it determines that condensation will occur, it instructs the outdoor intake air heating unit 46 to drive the outdoor intake air heater 33.

[0030] The memory unit 36 ​​stores a program for executing the temperature and humidity profile P during drying, as shown in Figure 5, as well as various information that defines the final temperature and humidity in the drying chamber 11 according to the food ingredient F, the reduction value of the target humidity as drying progresses, and the additional drying time after the target humidity is achieved. The temperature and humidity profile P according to this embodiment is realized by a combination of an initial heating step PH, a drying step DR, and an additional drying step ADR, and the temperature and humidity can be set for each step.

[0031] Next, the information processing and operation of the food drying apparatus 10 according to this embodiment will be explained along with the food drying method.

[0032] After inserting the food ingredients F into the drying chamber 11, the food drying device 10 is started to perform the initial heating step PH. In the initial heating step PH, the temperature inside the drying chamber 11 is raised to the temperature set by the temperature and humidity profile P. When the humidity exceeds a certain value (for example, 80%), the outdoor intake air heater 33, exhaust fan 31, and intake fan 32 are driven.

[0033] First, the time counting unit 37 starts measuring the drying time and the time during and without heat exchange. The indoor temperature detection unit 38 starts detecting the temperature data detected by the first thermometer 17 and the second thermometer 18, the outdoor temperature detection unit 40 starts detecting the temperature data detected by the third thermometer 21, and the humidity detection unit 41 starts detecting the humidity detected by the hygrometer 20. The indoor heating unit 42 drives the indoor heater 13 to start heating the drying chamber 11. The circulation unit 43 drives the circulation fan 23 to agitate the air inside the drying chamber 11. The dew point calculation unit 47 starts calculating the dew point temperature inside the drying chamber 11.

[0034] At this time, the relatively hot air heated by the indoor heater 13 and moved to the upper side of the drying chamber 11 is drawn into the air circulator body 22 from the suction port 22A by the drive of the circulation fan 23, and discharged to the lower side of the drying chamber 11 from the exhaust port 22B via the air circulator body 22, thereby equalizing the temperature at the top and bottom of the drying chamber 11.

[0035] When the humidity exceeds a certain value, the heat exchange drive unit 45 drives the exhaust fan 31 and the intake fan 32 to start heat exchange between the outside air and the air inside the drying chamber 11. In this process, the humid air in the drying chamber 11 is drawn in through the first intake port 28A into the first duct 28 and discharged outside the drying chamber 11 through the first exhaust port 28B. Meanwhile, outside air is drawn in through the second intake port 30A into the second duct 30 and discharged into the drying chamber 11 through the second exhaust port 30B. At this time, the heat from the warm air in the drying chamber 11 is cooled by the outside air as it passes through the passages 34A of the multiple through plates 34 stacked alternately in vertical and horizontal directions, while the outside air is heated by the warm air in the drying chamber 11; in other words, heat exchange takes place.

[0036] When calculating the dew point temperature, the dew point calculation unit 47 calculates the saturated vapor pressure inside the drying chamber 11 using a known method based on the detected temperature and humidity data inside the drying chamber 11, and then calculates the dew point temperature. The heating determination unit 48 compares the calculated dew point temperature with the outside air temperature, and if the dew point temperature is lower, it determines that condensation will occur on the heat exchanger 15 and instructs the outdoor intake air heating unit 46 to drive the outdoor intake air heater 33. In this case, it instructs the heat exchange drive unit 45 to drive the exhaust fan 31 and the intake fan 32 after a predetermined time has elapsed since heating by the outdoor intake air heating unit 46. On the other hand, if the dew point temperature is higher, it determines that condensation will not occur and instructs the heat exchange drive unit 45 to drive the exhaust fan 31 and the intake fan 32 without driving the outdoor intake air heater 33.

[0037] When the temperature inside the drying chamber 11 reaches a predetermined first temperature T1, the process moves to drying step DR. The humidity inside the drying chamber 11 at this time is defined as the first humidity H1. In drying step DR, the temperature inside the drying chamber 11 is raised from the first temperature T1 to the final target temperature TF, while the humidity is reduced from the first humidity H1 to a preset final target humidity HF. Here, multiple target temperatures may be set from the first temperature T1 to the final target temperature TF, and the temperature may be raised in stages. Here, the target temperature is determined by humidity control. That is, the temperature rises by dividing the change in temperature from the final target temperature TF to the first temperature T1 by the interval between the first humidity H1 and the final target humidity HF. If the final target temperature TF and the first temperature T1 are equal, the temperature does not change.

[0038] First, when raising the temperature inside the drying chamber 11 from the first temperature T1 to the second temperature T2, the indoor heating unit 42 drives the indoor heater 13 to raise the temperature inside the drying chamber 11 from the first temperature T1 to the second temperature T2. At this time, in order to keep the temperature inside the drying chamber 11 constant, the indoor heating unit 42 controls the indoor heater 13 so as not to exceed the target temperature.

[0039] The indoor heater 13 is driven by known methods such as ON-OFF control, PWM (Pulse Width Modulation) control, or variable control of the applied voltage. In the case of ON-OFF control, the output voltage from the power supply (not shown) is kept constant, and the indoor heating unit 42 outputs a high-level signal when heating the indoor heater 13 and a low-level signal when not heating. In the case of PWM control, the output voltage from the power supply (not shown) is kept constant, and the indoor heating unit 42 adjusts the output level to the indoor heater 13 by changing the PWM duty cycle. On the other hand, in the case of applied voltage control, the indoor heating unit 42 adjusts the temperature by varying the output voltage to the indoor heater 13 itself.

[0040] In this case, with ON-OFF control or PWM control, the far-infrared radiation from the indoor heater 13 stops when the applied voltage becomes 0V. On the other hand, with the variable applied voltage method, the applied voltage never becomes 0V, so the indoor heater 13 can be driven continuously and far-infrared radiation can be continuously emitted.

[0041] The heat exchange drive unit 45 operates the exhaust fan 31 and intake fan 32 when the humidity in the drying chamber 11 is higher than the target humidity, and stops the exhaust fan 31 and intake fan 32 when the humidity is below the target humidity, in order to reduce the humidity in the drying chamber 11 by a predetermined value.

[0042] Here, when the duty cycle, which is set from the operating time of the exhaust fan 31 and the intake fan 32 and their stopping time, falls below a preset operating duty cycle, it is determined that drying has progressed in the drying chamber 11, and the set target humidity is lowered by a preset value.

[0043] The dew point calculation unit 47 calculates the dew point temperature in the same manner as in the initial heating step. The heating determination unit 48 compares the calculated dew point temperature with the temperature outside the drying chamber 11 to determine the timing for driving the outdoor intake air heater 33 and the exhaust fan 31 and intake fan 32, in order to prevent condensation on the heat exchanger 15, in the same manner as in the initial heating step.

[0044] When the humidity inside the drying chamber 11 reaches the final target humidity HF, the process moves to the additional drying step ADR. In the additional drying step ADR, the same control as in the drying step DR is continued while maintaining the final achieved temperature TF and final achieved humidity HF until the additional drying time after the predetermined drying target is achieved. In this way, the drying of the food ingredients F in the drying chamber 11 is completed.

[0045] According to this food drying apparatus 10 and food drying method, when the moisture generated by heating the food F is discharged to the outside of the drying chamber 11 along with the air, it is passed through the heat exchanger 15 to recover some of the heat contained in the air, thereby reducing the amount of heat discharged and enabling high-speed drying of the food F while saving power. At this time, the humid air in the drying chamber 11 can be exhausted to the outside via the drive of the outdoor intake air heater 33 to prevent condensation inside the heat exchanger 15, thereby suppressing the growth of mold and other contaminants. Furthermore, since the indoor heater 13 is made of Japanese paper containing carbon, far-infrared rays with wavelengths of 4 to 14 microns are generated when electricity is applied. These wavelengths can vibrate only the water molecules in the food F, allowing it to be dried without damaging the cells of the food F. In addition, odors generated in the drying chamber 11 can be released to the outside via the first duct 28.

[0046] Furthermore, by periodically driving the exhaust fan 31 and the intake fan 32 based on the duty cycle, the humidity can be reduced without constantly driving the fans, even when the temperature inside the drying chamber 11 is constant. In addition, by continuing to operate for a certain period of time after the target humidity is reached, the drying depth can be increased.

[0047] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, a filter (not shown) may be placed near the second intake port 30A to prevent dust and other particles from entering from outside the drying chamber 11. [Explanation of Symbols]

[0048] 10 Food drying equipment 11 Drying room 13 Indoor heater 15 Heat exchanger 16 Control device (control unit) 17. First thermometer (first temperature detector) 18. Second thermometer (second temperature detector) 20. Hygrometer (Humidity Detector) 23. Circulatory fan (circulatory system) 28. First duct (first heat exchanger body) 30. Second duct (second heat exchanger body) 31. Exhaust fan (exhaust device) 32. Inhalation fan (inhaler) 34 Outdoor intake air heater 42 Indoor heating section 43 Circulation section 45 Heat exchange drive unit 46 Outdoor intake air heating unit 48 Heating judgment section F Ingredients

Claims

1. A drying chamber where the ingredients are placed inside, An indoor heater that raises the temperature inside the drying chamber, A circulator for moving the air in the drying chamber, A heat exchanger that exchanges heat between the air inside the drying chamber and the outside air, A control unit that controls the temperature inside the drying chamber, Equipped with, The heat exchanger includes an exhaust fan that discharges the air inside the drying chamber to the outside of the drying chamber, An inhaler for introducing the outside air into the drying chamber, The first heat exchanger body, through which the air inside the drying chamber is circulated to the outside of the drying chamber by the exhaust fan, The second heat exchanger body through which the outside air is circulated into the drying chamber by the aforementioned inhaler, A food drying device equipped with the following features.

2. The food drying machine according to claim 1, wherein the indoor heater is constantly powered.

3. The food drying apparatus according to claim 1, wherein the heat exchanger comprises an outdoor intake air heater that heats the outside air being drawn in.

4. The food drying apparatus according to claim 3, wherein the indoor heater and / or the outdoor intake air heater comprises Japanese paper and carbon.

5. A first temperature detector for detecting the temperature of the indoor heater, A second temperature detector for detecting the temperature inside the drying chamber, A humidity detector for detecting the humidity inside the drying chamber, Equipped with, The control unit includes an indoor heating unit that drives and controls the indoor heater, A circulation unit that drives and controls the aforementioned circulator, A heat exchange drive unit that drives and controls the exhaust and the inhaler, A heating determination unit that suppresses condensation inside the heat exchanger, A food drying machine according to claim 1, comprising:

6. The control unit includes an outdoor intake air heating unit that drives and controls the outdoor intake air heater, The food drying machine according to claim 3, wherein the heating temperature by the outdoor intake air heater is lower than the heating temperature by the indoor heater.

7. A method for drying food ingredients in which a computer raises the temperature of a drying chamber in which the food ingredients are placed, An initial heating step to raise the temperature inside the drying chamber to the initial temperature, A drying step in which the temperature inside the drying chamber is raised to a temperature target value while the humidity is lowered to a humidity target value, Equipped with, A method for drying food ingredients, in which, at least in the drying step, a portion of the heated and humidified air in the drying chamber is exhausted to the outside of the drying chamber while outside air is drawn into the drying chamber, thereby suppressing condensation and allowing heat exchange between them.

8. The food drying method according to claim 7, further comprising a follow-up drying step of maintaining the state in the drying chamber, when the humidity has been reduced to a humidity target value, for a predetermined time while maintaining the temperature target value and the humidity target value.

9. The method for drying food ingredients according to claim 7, wherein the target humidity value in the drying chamber is set based on the time period between heat exchange and non-heat exchange between the air in the drying chamber and the outside air, and the cumulative time ratio between the heat exchange and non-heat exchange periods.

10. The food drying method according to claim 7, wherein when exhausting a portion of the heated and humidified air in the drying chamber to the outside of the drying chamber and drawing in outside air into the drying chamber, the outside air is heated for a predetermined time before being drawn in.

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