JP2007192464A - Lumber artificial drying method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lumber artificial dehumidifying drying system capable of shortening a drying time and improving heat efficiency by reducing energy consumption. <P>SOLUTION: This lumber artificial drying method comprises an air heater 3 heating the air in a drying room 1, a humidifier 4 humidifying the air in the drying room, and a heat pump 2 cooling and dehumidifying the air in the drying room. In the lumber artificial drying method which dries the housed lumber in the drying room while adjusting a temperature and a relative humidity in the drying room, the heat pump 2 applies CO<SB>2</SB>as a refrigerant exchanging heat with the air in the drying room 1 to cool and dehumidify the air in an evaporation process of the heat pump, the CO<SB>2</SB>refrigerant after the evaporating process is compressed to a supercritical pressure, the heat of the CO<SB>2</SB>refrigerant of high temperature is supplied as a heat source of the air heater 3, then the heat is exchanged between the CO<SB>2</SB>refrigerant and the cooled and dehumidified air to reheat the air and to return the air into the drying room 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an artificial drying method for a wood which performs cooling and dehumidification of drying room air using a heat pump, which can supply a high heat source to the drying room, shorten the drying time, and improve the thermal efficiency. And the system.

Artificial drying of wood is performed by stacking wood in a drying chamber and using a heating source to raise the temperature in the drying chamber. In addition, it is important to adjust the humidity of the drying chamber in order to prevent cracking and warping of the wood in the drying process.
FIG. 10 shows an example of the moisture content of wood, the temperature in the drying chamber, and the relative humidity in the artificial drying of cedar wood. In the initial stage of the drying operation, the room temperature is raised to about 70 ° C. in several hours. At this time, in order to prevent cracking of the wood, it is necessary to raise the temperature so that the wet bulb temperature becomes equal to the dry bulb temperature (relative humidity 100%), and humidification is performed indoors using a humidifier simultaneously with the heating.

  Then, the relative humidity in the room is slowly lowered to evaporate moisture from the wood. In the drying process, the amount of water evaporation decreases as the moisture content of the wood decreases, so the drying chamber temperature is gradually raised and the relative humidity is reduced so that the number of drying days does not increase. In particular, in the process where the moisture content is 30% or less, the process of evaporating the bound water in the wood is performed, and therefore many days of drying are required unless high temperature and low humidity are maintained.

Conventional wood artificial drying systems include a steam heating type, a dehumidifying type, and a reduced pressure type. According to the 2002 data, the steam heating type is 74% and the dehumidifying type is 18%.
The steam heating method is a method in which steam generated by a boiler is sent to a heat radiating pipe in a drying chamber and dried by heated air. This method is often used because it is easy to raise the temperature of the room to a high temperature and the drying time is short. The humidity in the drying chamber is mainly adjusted by supplying and exhausting air from the outside to the inside of the room, and humidifying is performed by steam from the boiler at the initial stage of operation and when the humidity is reduced during operation.

However, such a method has a drawback that the heat loss due to the exhaust is large and the input energy of the heating source is increased.
An apparatus in which a heat pump is applied to drying wood or the like is proposed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2001-353398). This device is provided with an intake port and an exhaust port in a drying chamber for storing an object to be dried, a condenser for a heat pump is provided at the intake port, an evaporator is provided at the exhaust port, and air introduced from outside the drying chamber is supplied. Heated with a condenser and taken into the drying chamber from the intake port, and when the air that has become humid due to moisture from the object to be dried is exhausted from the drying port to the outside of the drying chamber, heat is recovered with the evaporator. The purpose is to reduce energy consumption and shorten the drying time.

However, the method disclosed in Patent Document 1 has a drawback in that the high-temperature air in the drying chamber is discharged outside and is not recirculated for use, so that there is still a lot of heat loss due to exhaust and the input energy of the heating source increases. ing.
Next, an example of a conventional dehumidifying drying system is shown in FIG. In FIG. 11, the apparatus includes a drying chamber 01 with good airtightness, a heat pump 02, a heater for heating (electric heater or steam radiating pipe) 03, a humidifier 04, and a blower 05.

  In FIG. 11, the heat pump 02 is placed indoors, but some are installed outside the room. The refrigerant of the heat pump 02 uses a chlorofluorocarbon refrigerant, and the air a which has been wet through the wood placed in the drying chamber 01 is cooled and dehumidified by an evaporator (not shown) of the heat pump 02, and the condenser The waste heat (not shown) is heated by the heater 03 and supplied to the wood.

JP 2001-353398 A

However, in the apparatus of FIG. 11, since the refrigerant is chlorofluorocarbon, the heat pump 02 has a limit of 70 ° C., and is usually used at about 40 ° C. in many cases. This method has the advantage that it is less distorted and changes in material color due to low temperature drying, but the drying time is 1.5 to 2 times longer than the steam heating type (especially in the late stage of drying), and the dehumidifying ability is long. If it is small, there is a problem that mold occurs on the material.
Further, in the latter stage of drying, it is necessary to maintain a high temperature and low humidity, and therefore it is necessary to increase the compression ratio of the compressor of the heat pump. For this reason, the evaporation temperature is lowered and the power consumption of the heat pump is increased. There is a problem that energy consumption increases (about 3 to 4 times the heat pump power consumption).

  In view of the problems of the conventional technology, the present invention solves the disadvantages of the conventional dehumidifying and drying system that the room temperature is low and the drying time is long, and that the energy consumption of the auxiliary heat source such as a heater is large in the late stage of drying. Therefore, an object of the present invention is to realize a dehumidifying and drying system for wood that can reduce energy consumption and improve thermal efficiency.

In order to achieve such an object, the wood drying method of the present invention comprises:
An air heater for heating the air in the drying chamber, a humidifier for humidifying the air in the drying chamber, and a heat pump for cooling and dehumidifying the air in the drying chamber, and adjusting the temperature and relative humidity in the drying chamber In the artificial drying method of wood for drying the wood housed in the room,
The heat pump is a CO ₂ as a refrigerant, the air dampening cooled dividing by exchange of heat with air drying cabinet at evaporation step of the heat pump,
Supplying the retained heat of the CO ₂ refrigerant, which has been heated to a supercritical pressure by compressing the CO ₂ refrigerant after the evaporation step, as a heat source of the air heater;
Then, heat is exchanged between the CO ₂ refrigerant and the cooled and dehumidified air to reheat the air.

The drying system of the present invention is a drying system for carrying out the method of the present invention.
An airtight drying chamber for drying wood, a heat pump that introduces air in the drying chamber, cools and dehumidifies the air, returns the drying chamber, an air heater that heats the air in the drying chamber, and humidifies the drying chamber In an artificial wood drying system equipped with a humidifier,
The heat pump uses CO ₂ as a refrigerant, exchanges heat with the air in the drying chamber to cool and dehumidify, a compressor that compresses the CO ₂ refrigerant and pressurizes it to a supercritical pressure, and expands the CO ₂ refrigerant An expander that is decompressed and introduced into the vaporizer; a means for supplying the retained heat of the CO ₂ refrigerant compressed to a supercritical pressure and heated to a high temperature as a heat source for the air heater; and the cooled and dehumidified air is reheated. Means for returning to the drying chamber.

In the present invention, since a heat pump with a supercritical cycle using CO ₂ as a refrigerant capable of high temperature heating is used, a heat source near 100 ° C. can be taken out.
A Ph diagram of the supercritical CO ₂ heat pump cycle is shown in FIG. In the supercritical cycle, the high pressure side becomes a supercritical gas above the critical pressure. Therefore, the temperature of the refrigerant does not change with the heat dissipation and the temperature decreases. This heat exchanger is generally called a gas cooler. In order to operate this cycle efficiently, it is important to reduce the gas cooler outlet temperature as much as possible. When the point A shown in FIG. 1 where the gas cooler outlet temperature is high is cooled to the low point B, the heating amount is Qha. From Qca to Qhb, the cooling heat quantity can be increased from Qca to Qcb.

Therefore, in this invention, the CO ₂ refrigerant after evaporation step the potential heat of the CO ₂ refrigerant that has a high temperature and compressed to a supercritical pressure supplied as a heat source of the air heater, further cooled dehumidified air reheated to for By providing the retained heat of the CO ₂ refrigerant as a heat source, the outlet temperature in the supercritical gas cooling step is reduced. In addition, since the cooled and dehumidified air is reheated and returned to the drying chamber, the drying chamber can be kept at a high temperature and low humidity.
When trying to dehumidify the circulating air in the drying chamber, it is necessary to cool a large amount of air, so the amount of cooling heat becomes very large. Therefore, it is preferable to take out a part of the circulated air using a fan for dehumidification and introduce it into a heat pump for cooling and dehumidification.

Also, if you want to dehumidify all the water evaporated from the wood in the drying chamber with a heat pump, you need to increase the refrigeration capacity of the heat pump. Therefore, increase the capacity of the compressor, or lower the evaporation temperature (evaporation pressure) to reduce the compression ratio. Although it is necessary to make it high, if it does so, the malfunction that initial cost becomes high or thermal efficiency falls will arise.
Therefore, in the present invention, preferably, a part of the air cooled and dehumidified in the evaporation step is exhausted, and the outside air is introduced by the amount of the exhaust, thereby reducing the load on the evaporator.

This also lowers the temperature of the cooled and dehumidified air, and then lowers the CO ₂ refrigerant temperature after heat exchange when exchanging heat with the CO ₂ refrigerant compressed to a supercritical pressure or higher. This will improve the refrigeration capacity of the heat pump. The supply / exhaust of the outside air is preferably controlled by a supply fan provided in the supply section by a humidity sensor provided in the drying chamber, and the exhaust amount is controlled by a damper according to the supply amount.
The air that has passed through the supply / exhaust section is heated by an air heater that exchanges heat with the high-pressure CO ₂ refrigerant, and then returned to the drying chamber.

In the present invention, the main heating amount necessary for evaporating the moisture of the wood in the drying chamber is performed by an air heater provided in the drying chamber. In the system of the present invention, as a means of supplying the retained heat of the CO ₂ refrigerant compressed to the supercritical pressure and heated to a high temperature as the heat source of the air heater, the heat source is supplied to the CO ₂ refrigerant compressed to the supercritical pressure and heated to the high temperature and the air heater A heater that exchanges heat with a secondary heat medium (for example, hot water) that performs heat exchange may be provided, or a region in which CO ₂ refrigerant that has been compressed to a supercritical pressure and heated to high temperature is exchanged with air in the drying chamber of the air heater. A pipe line may be provided to be returned to the air reheating means after being introduced into the air and exchanging heat with the air in the drying chamber.

  In the system of the present invention, preferably, a temperature sensor and a humidity sensor provided in the drying chamber, an air supply fan provided in the air supply unit, a dehumidifying fan for introducing the air in the drying chamber into the evaporator of the heat pump, The dehumidifying fan and a heat pump compressor driving device are controlled based on the temperature detected by the temperature sensor, and the air supply fan and the dehumidifying fan are controlled based on the humidity detected by the humidity sensor. And a controller.

  The wood drying process has a temperature and humidity suitable for the drying time (moisture content) as shown in FIG. 10, and the humidity sensor controls the rotational speed of the dehumidifying fan and the rotational speed of the compressor by the temperature sensor in the drying chamber. By controlling the rotational speed of the outside air supply fan and the dehumidifying fan, the drying chamber can be accurately controlled to the temperature and humidity set as shown in FIG.

As an embodiment in the initial operation of the present invention system, the air Tonetsu device to absorb latent heat of vaporization from the outside air in parallel with the evaporator arranged so that the CO ₂ refrigerant is introduced into the air Tonetsu device during the initial stage of drying operation And a humidifying heater for exchanging heat between the CO ₂ refrigerant compressed to a supercritical pressure and heated to a high temperature and the hot water sprayed by the humidifier, and supplying the hot water from the humidifier during the initial drying operation. Configure to spray.

  In the initial stage of operation, it is necessary to raise the temperature at a relative humidity of 100% from a state close to the outside air temperature / humidity to a drying temperature of about 70 ° C. In normal operation, as described above, air in the drying chamber is used as the heat collection source of the heat pump. However, since it is necessary to raise the temperature in a few hours, heat is collected from the outside air and the drying chamber is heated by the heat pump. .

  As another embodiment at the time of initial operation of the system of the present invention, an air flow path is provided in the air flow path on the upstream side of the evaporator, and passes from the air supply section through the evaporator to the air exhaust section at the time of initial operation. May be formed. In this way, it is not necessary to provide a separate air heat collector as in the above-described embodiment, and the evaporator for air dehumidification can also be used during initial operation.

The system of the present invention further includes a cooling water tank in which cooling water is stored and a conduit for circulating the cooling water between the cooling water tank and the evaporator, and is cooled by the evaporator and stored in the cooling water tank. You may comprise so that it cools and dehumidifies by introduce | transducing the air in the said drying chamber in cooling water.
If the air in the drying chamber is brought into direct contact with the cooling water in this way, the humidity control becomes easy and the heat transfer coefficient between the cooling water and the air is improved. Therefore, it is not necessary to increase the compression ratio so much.

According to the method of the present invention, since the heat pump is configured with a refrigeration cycle reaching the supercritical region using CO ₂ as a refrigerant, a high-temperature heat source can be supplied to the drying chamber, and compressed to a supercritical pressure to be heated to a high temperature. Drying of wood by dissipating the retained heat of the CO ₂ refrigerant as a heat source of the air heater for heating the drying chamber and as a heat source for reheating the drying chamber air cooled and dehumidified by the evaporator in at least two stages Therefore, the wood can be dried in a short time. Moreover, since the COP of the heat pump can be improved, the heat amount of the heat pump can be reduced, and the initial cost can be reduced.

According to the system of the present invention, the heat pump uses CO ₂ as a refrigerant, exchanges heat with the air in the drying chamber, cools and dehumidifies the evaporator, and compresses the CO ₂ refrigerant to compress it to a supercritical pressure or higher. An expander that expands and depressurizes the CO ₂ refrigerant and introduces it into the steamer; means for supplying the retained heat of the CO ₂ refrigerant that has been compressed to a supercritical pressure to a high temperature as a heat source for the air heater; and air that has been cooled and dehumidified Means for reheating and returning to the drying chamber, and a high temperature heat source can be supplied to the drying chamber by using a refrigeration cycle that reaches a supercritical region using CO ₂ as a refrigerant. Dissipate the retained heat of the CO ₂ refrigerant compressed to a high temperature to a heat source for the air heater that heats the drying chamber and as a heat source for reheating the drying chamber air that has been cooled and dehumidified by the evaporator in at least two stages. In Ri, it is possible to supply sufficient heat for drying the wood can be dried in a short time timber. At the same time, since the COP of the heat pump can be improved, the heat amount of the heat pump can be reduced, and the initial cost can be reduced.

Preferably, an exhaust unit that exhausts a part of the air after being cooled and dehumidified by the evaporator, and an air supply unit that supplies air by an amount corresponding to the exhaust amount, and is cooled and dehumidified from the exhaust unit by the evaporator. By exhausting a part of the air and introducing outside air from the air supply unit by the amount of the exhaust, the load on the evaporator can be reduced, and the capacity or compression ratio of the compressor can be reduced. it is possible to reduce the initial cost and further reducing the temperature of the cooling dehumidified air, then upon heat exchange with the CO ₂ refrigerant a supercritical pressure for thereby reducing the CO ₂ refrigerant temperature after the heat exchange, the heat pump It leads to improvement of freezing capacity.

  In the system of the present invention, preferably, a temperature sensor and a humidity sensor provided in the drying chamber, an air supply fan provided in the air supply unit, and a dehumidifying fan for introducing the air in the drying chamber into the evaporator of the heat pump; And controlling the dehumidifying fan and a heat pump compressor driving device based on the temperature detected by the temperature sensor, and controlling the air supply fan and the dehumidifying fan based on the humidity detected by the humidity sensor. By providing the controller, it is possible to accurately control the drying chamber to the temperature and humidity set as shown in FIG.

In the system of the present invention, preferably, an air heat collector that absorbs latent heat of vaporization from outside air is provided in parallel with the evaporator, and the CO ₂ refrigerant is introduced into the air heat collector during the initial drying operation. A humidifying heater for exchanging heat between the CO ₂ refrigerant compressed to a supercritical pressure and heated to the hot water sprayed by the humidifier, and spraying the hot water from the humidifier during the initial drying operation. If comprised, the rapid temperature rise required at the time of initial operation and the relative humidity of 100% can be achieved in a short time.

  Alternatively, as another embodiment at the time of initial operation, an exhaust part is provided in the air flow path on the upstream side of the evaporator, and at the time of initial operation, the air supply part on the evaporator flexible downstream side passes through the evaporator to the exhaust part. If the outside air flow path is formed, it is not necessary to provide a separate air heat collector, and the evaporator for air dehumidification can be used in the initial operation, so that the equipment cost can be reduced.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the present invention to that only, unless otherwise specified.
2 is a block diagram showing the first embodiment of the present invention, FIG. 3 is a block diagram showing the control system of the first embodiment, and FIG. 4 is a configuration diagram of an air damper 19a provided in the exhaust line 19. FIG. 5 is a block diagram showing the operation during the initial operation of the first embodiment, FIG. 6 is a block diagram showing the second embodiment of the present invention, and FIG. 7 is the third embodiment of the present invention. FIG. 8 is a block diagram showing a fourth embodiment of the present invention, and FIG. 9 is a block diagram showing a control system of the fourth embodiment.

  In FIG. 1 showing the first embodiment of the present invention, a wood W which is an object to be dried is placed in a drying chamber 1 having a sealing function so as to be spaced from each other so that air a flows therethrough. A partition 6 for forming a circulating air flow b is provided in the drying chamber 1. An air heater 3, a fan 5, a humidifier 4, a temperature sensor 8, and a humidity sensor 7 face the circulating flow path b. Has been placed.

On the other hand, the heat pump 2 uses CO ₂ as a refrigerant, a refrigerant dehumidifier (evaporator) 22, a compressor 23, a humidifier heater (condenser) 24, and hot water heating in a refrigerant line 21 through which the CO ₂ refrigerant circulates. A condenser (condenser) 25, an air heater (condenser) 26, and an expansion valve 27 are interposed.
Air in the drying chamber 1 is supplied to the cooling dehumidifier 22 by the dehumidifying fan 10 through the air line 9, and heat is exchanged with the CO ₂ refrigerant in the cooling dehumidifier 22 to cool and dehumidify, and then air is passed through the line 11. is sent to the heater 26, where CO ₂ refrigerant and by heat exchange to give the heat of condensation of the CO ₂ refrigerant is heated to the same temperature as the drying chamber vacant temperature, via a return line 12 back into the drying chamber 1 It is configured.

The air heater 3 is provided with a hot water circulation line 13 that is located in a region facing the air circulation flow b in the drying chamber 1 and that circulates hot water between the hot water heater 25 in the direction of the arrow by a pump 15. Yes. The buffer tank 14 interposed in the hot water circulation line 13 has a water supply part 14 b and also has a gas phase space 14 a inside, and has a buffering action when a sudden high pressure is generated inside the hot water circulation line 13. A branch line 16 branched from the hot water circulation line 13 is connected to a humidifier heater 24. The on-off valve 35 interposed in the branch line 16 during normal operation is closed, but is opened during initial operation, and the hot water introduced from the branch line 16 during initial operation into the humidifying heater 24 is CO ₂ refrigerant. The condensation heat is obtained and the temperature becomes high, and is sprayed to the air circulation flow b by the humidifier 4 in the drying chamber 1 through the hot water line 17.

The air line 11 is connected to an air supply line 18 provided with an air supply fan 18a and an exhaust line 19 provided with an air damper 19a. Further, the heat pump 2 is provided with an air heat collector (evaporator) 28 in parallel with the cooling dehumidifier 22, and the opening and closing valves 29 and 30 are opened and closed instead of the cooling dehumidifier 22 during the initial operation of the drying system. A CO ₂ refrigerant is introduced into the air heat collector 28 to obtain latent heat of vaporization from the outside air c.

FIG. 3 shows a control system of the first embodiment. In FIG. 3, the controller 31 includes a dehumidifying fan 10 and a drive motor 23a for a heat pump compressor based on the temperature in the drying chamber 1 detected by the temperature sensor 7. And the air supply fan 18 a and the dehumidifying fan 10 provided in the air supply line 18 are controlled based on the humidity detected by the humidity sensor 8.
The wood drying process has a temperature and humidity suitable for the drying time (moisture content) as shown in FIG. 10, and by performing the above control, the inside of the drying chamber 1 is set to the temperature and humidity set as shown in FIG. It can be controlled accurately.

FIG. 4 shows an air damper 19 a interposed in the exhaust line 19, and the exhaust line 19 is opened and closed by an opening / closing plate 33 provided rotatably by a shaft 32. The opening / closing plate 33 is urged by a weight 34 provided on the shaft 32 in a direction to close the opening 19 b of the exhaust line 19 by a preset urging force. With this configuration, when the air supply line 18 supplies air to the line 11 and the air pressure d in the exhaust line 19 exceeds the set pressure, the opening / closing plate 33 opens the opening 19b.
In FIG. 2, temperature indications shown in the respective parts indicate the temperature of the air, CO ₂ refrigerant, or hot water flowing through the line.

In the first embodiment having such a configuration, FIG. 5 shows an operating state during the initial operation. In FIG. 5, at the initial stage of operation, it is necessary to rapidly increase the air in the drying chamber 1 from a state close to the temperature and humidity of the outside air to a drying temperature of 70 ° C. and a relative humidity of 100% in several hours. Therefore, the on-off valve 29 is closed, the on-off valve 30 is opened, CO ₂ refrigerant is introduced into the air heat collector 28, and latent heat of evaporation is collected from the outside air c.
At the same time, the on-off valve 35 is opened, a part of the hot water circulating between the air heater 3 and the hot water heater 25 is taken out from the hot water circulation line 13 to the branch line 16, and the supercritical pressure is supplied by the compressor 23 in the humidifying heater 24. Heat is exchanged with the high-temperature CO ₂ refrigerant that has reached the temperature and heated, and then the heated warm water is sprayed onto the humidifier 4 in the drying chamber 1 to perform humidification.

After exchanging heat with warm water by the humidifying heater 24, the CO ₂ refrigerant exchanges heat with warm water flowing through the warm water circulation line 13 by the warm water heater 25 to heat the warm water with its condensation heat, and the heated warm water is converted into an air heater. 3 and supplied to the heat source of the air heater 3.
The initial operation is performed by such an operation, the inside of the drying chamber 1 is rapidly heated and humidified to make an atmosphere of 70 ° C. and a relative humidity of 100%, and then the normal operation shown in FIG. 2 is performed.

In the normal operation, as shown in FIG. 2, the on-off valve 29 is opened and the on-off valve 30 is closed so that the CO ₂ refrigerant flows through the cooling dehumidifier 22. At the same time, the on-off valve 35 is closed to stop the flow of warm water to the humidifying heater 24. As a result, the CO ₂ refrigerant that has been compressed to the supercritical pressure by the compressor 23 to a high temperature does not exchange heat in the humidifying heater 24, and the hot water that becomes the heat source of the air heater 3 is condensed in the hot water heater 25. Then, the air that has been cooled and dehumidified by the cooling dehumidifier 22 is heated by the air heater 26.

During normal operation, the air sent from the drying chamber 1 to the cooling dehumidifier 22 by the dehumidifying fan 10 is deprived of the latent heat of vaporization by the CO ₂ refrigerant, cooled and dehumidified to the air heater 26 via the line 11. At this point, it is heated by the condensation heat of the CO ₂ refrigerant, reheated to a temperature of 70 ° C., and returned to the drying chamber 1.
If all the air sent from the drying chamber 1 is cooled and dehumidified by the cooling dehumidifier 22, the refrigeration capacity of the heat pump 2 is burdened, and it is necessary to increase the capacity of the compressor or increase the compression ratio. When the compression ratio is increased, the COP is lowered. Therefore, a part of the air after cooling and dehumidification is exhausted from the exhaust line 19, and outside air at low humidity and room temperature is introduced from the air supply line 18 by the air supply fan 18a.

In addition, the air damper 19a provided in the exhaust line 19 can exhaust so that the air pressure in the line 11 may be hold | maintained to a setting value by having the structure shown in FIG. As a result, the exhaust air can be exhausted from the exhaust line 19 by the amount of the outside air introduced from the air supply line 18.
According to the first embodiment, a high-temperature heat source can be supplied to the drying chamber 1 by configuring the supercritical pressure refrigeration cycle in which the heat pump 2 uses CO ₂ as a refrigerant. Accordingly, a sufficient heat source can be supplied to the drying chamber 1 and the insertion time can be shortened. In particular, during the initial operation that requires rapid temperature increase and high humidity, the high-temperature retained heat of supercritical pressure is released, and the humidifier 8 The hot water heater 25 can release the heat of condensation to supply hot water for the heat source of the air heater 3, and the remaining condensation heat can be used to reheat the air returning to the drying chamber 1. .

Further, by releasing the condensation heat in two stages (three stages at the initial operation) as described above, the refrigeration capacity can be increased and the COP can be improved as shown in FIG.
Further, by replacing a part of the air cooled and dehumidified by the cooling dehumidifier 22 with the outside air in the line 11, it is possible to reduce the load of the heat pump, thereby improving the COP and reducing the initial cost. Can do.
Moreover, since the retained heat of the outside air can be used during the initial operation, rapid temperature increase is possible.
Moreover, by providing the control system shown in FIG. 3, the temperature and humidity in the drying chamber 1 can be accurately controlled to a desired state.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 6, this embodiment eliminates the air heat collector 28 of the first embodiment, and instead provides an exhaust line 41 in the air line 9 connected to the cooling dehumidifier 22, and provides an exhaust valve 42 in the exhaust line 41. It has a configuration. The other configurations are the same as those of the first embodiment shown in FIG. 2, and the same portions as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the second embodiment having such a configuration, during the initial operation, the exhaust valve 42 is opened, outside air is introduced from the air supply line 18, the retained heat of the outside air is collected as latent heat of evaporation by the cooling dehumidifier 22, and then the outside air is exhausted. Discharge from the line 41 to the outside.
Other operations during initial operation are the same as those in the first embodiment. The normal operation is the same as that in the first embodiment after the exhaust valve 42 is closed.
According to the second embodiment, since the air heat collector 28 that operates during the initial operation and the cooling dehumidifier 22 that operates during the normal operation can be used together in the first embodiment, the equipment cost can be reduced.

Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 7, this embodiment eliminates the hot water circulation line 13 and the branch line 16 that circulate hot water between the hot water heater 25 and the air heater 3 in the drying chamber 1 as compared with the first embodiment. A supply line 51 for supplying high-temperature and high-pressure CO ₂ refrigerant coming out of the humidifying heater 24 to the air heater 3 is provided, and a return line through which a pump 53 is provided to return the CO ₂ refrigerant from the air heater 3 to the air heater 26. 52 is provided.

Further, instead of eliminating the branch line 16, a water supply unit 24 a is provided in the humidification heater 24, and water supplied from the water supply unit 24 a during the initial operation is heated by the humidification heater 24 with CO ₂ refrigerant, and heated hot water Is supplied from the line 17 to the humidifier 4. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description of those same portions is omitted.
According to the third embodiment having such a configuration, the hot water heater 25 for exchanging heat between the CO ₂ refrigerant and the hot water, the buffer tank 15 interposed in the hot water circulation line 13 and the like are not necessary, and the facilities are reduced. Since the CO ₂ refrigerant directly exchanges heat with the vacant space in the drying chamber, there is an advantage that the thermal efficiency is improved.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 8, this embodiment is provided with a direct contact type dehumidifier 62 separately from the evaporator 61 constituting the heat pump 2 and the outside air supply line 18 and the exhaust line 19 are eliminated, as compared with the first embodiment. The point is different.
The dehumidifier 62 has a container shape and stores cooling water therein. The cooling water is circulated between the evaporator 61 by a pump 64 provided in a circulation line 63 and is absorbed by the evaporator 61 to be cooled. Is done. The air in the drying chamber 1 is discharged from the header 67 in the cooling water stored in the dehumidifier 62, and is cooled and dehumidified in direct contact with the cooling water.

  FIG. 9 shows a control system of this embodiment. In FIG. 9, the controller 31 controls the dehumidifying fan 10 and the drive motor 23 a of the compressor of the heat pump based on the temperature in the drying chamber 1 detected by the temperature sensor 7, and the humidity detected by the humidity sensor 8. Based on the above, the rotational speeds of the cooling water pump 64 and the dehumidifying fan 10 are controlled. By controlling the cooling water pump 64, the circulation amount of the cooling water can be controlled, and thereby the temperature of the cooling water can be adjusted. Therefore, the dehumidification amount of the dehumidifier 62 can be controlled.

Cooled dehumidified air is sent to the air heater 26 CO ₂ and refrigerant exchanges heat with the air heater 26, is identical to the first embodiment being heated by the heat of condensation of the CO ₂ refrigerant. Moisture dehumidified from the air accumulates in the dehumidifier 62, but if the water level of the cooling water becomes high, it is detected by the water level sensor 67, and the drain valve 66 is automatically opened and drained from the drain line 65. As a result, the water level of the cooling water is kept constant.

  According to the fourth embodiment, since the air is cooled and dehumidified by direct contact with the cooling water, the humidity control becomes easy, and the heat transfer coefficient between the air and the cooling water is good. Even if the air is cooled and dehumidified, it is not necessary to increase the capacity of the compressor 23 of the heat pump 2 or increase the compression ratio. Therefore, the air supply line 81 and the exhaust line 19 for replacing a part of the air with the outside air as in the first embodiment can be eliminated, the initial cost can be reduced, and the COP of the heat pump 2 can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the drying time of wood can be shortened, the COP of the heat pump used for a drying system is improved significantly, and the dehumidification drying system of wood which can reduce energy consumption and can improve thermal efficiency is realized. Can do.

It is a P-h diagram of supercritical CO ₂ heat pump cycle. It is a block diagram which shows 1st Example of this invention. It is a block diagram which shows the control system of the said 1st Example. It is a block diagram of the air damper 19a provided in the exhaust line 19 of the said 1st Example. It is a block diagram which shows the action | operation at the time of the initial stage driving | operation of the said 1st Example. It is a block diagram which shows 2nd Example of this invention. It is a block diagram which shows 3rd Example of this invention. It is a block diagram which shows 4th Example of this invention. It is a block diagram which shows the control system of the said 4th Example. It is a diagram which shows an example of the drying conditions in wood artificial drying. It is a block diagram which shows the conventional dehumidification wood artificial drying system.

Explanation of symbols

1 drying chamber 2 heat pump 3 the air heater 4 humidifier 7 temperature sensor 8 humidified sensor 9 air line 10 dehumidifying fan 12 return line 13 hot water circulation line 18 the air supply line 18a supply fan 19 exhaust line 19a air damper 21 CO ₂ refrigerant circulation line 22 Cooling dehumidifier 23 Compressor 23a Compressor drive motor 24 Humidification heater 25 Hot water heater 26 Air heater 28 Air heat collector 31 Controller 41 Exhaust line 51 CO ₂ refrigerant supply line 52 CO ₂ refrigerant return line 62 Direct contact type Dehumidifier 63 Cooling water circulation line W Wood

Claims (11)

An air heater for heating the air in the drying chamber, a humidifier for humidifying the air in the drying chamber, and a heat pump for cooling and dehumidifying the air in the drying chamber, and adjusting the temperature and relative humidity in the drying chamber In the artificial drying method of wood for drying the wood housed in the room,
The heat pump is a CO ₂ as a refrigerant, the air dampening cooled dividing by exchange of heat with air drying cabinet at evaporation step of the heat pump,
Supplying the retained heat of the CO ₂ refrigerant, which has been heated to a supercritical pressure by compressing the CO ₂ refrigerant after the evaporation step, as a heat source of the air heater;
A method for artificially drying wood, wherein the air is then reheated by exchanging heat between the CO ₂ refrigerant and the cooled and dehumidified air.   2. The method for artificially drying wood according to claim 1, wherein a part of the air cooled and dehumidified in the evaporation step is exhausted, and the outside air is introduced by an amount corresponding to the exhaust amount. In the evaporation process of the heat pump in the initial stage of the drying operation, heat is exchanged with the outside air instead of the air in the drying chamber to absorb the retained heat of the outside air,
The method for artificially drying wood according to claim 1, wherein the water sprayed by the humidifier is supplied with the heat retained by the CO ₂ refrigerant compressed to a supercritical pressure. An airtight drying chamber for drying wood, a heat pump that introduces air in the drying chamber, cools and dehumidifies the air, returns the drying chamber, an air heater that heats the air in the drying chamber, and humidifies the drying chamber In an artificial wood drying system equipped with a humidifier,
The heat pump uses CO ₂ as a refrigerant, exchanges heat with the air in the drying chamber to cool and dehumidify, a compressor that compresses the CO ₂ refrigerant and pressurizes it to a supercritical pressure, and expands the CO ₂ refrigerant and inflator to be introduced into the steam vessel by vacuum, and means for supplying a potential heat of CO ₂ refrigerant that has a high temperature and compressed to a supercritical pressure as a heat source of the air heater, and re-heating the cooled dehumidified air A wood artificial drying system comprising means for returning to the drying chamber.   5. The artificial wood according to claim 4, further comprising: an exhaust part that exhausts a part of the air after being cooled and dehumidified by the evaporator, and an air supply part that supplies air by an amount corresponding to the exhaust amount. Drying system. A heater that exchanges heat between the CO ₂ refrigerant compressed to a supercritical pressure and heated to a secondary heat medium that supplies a heat source to the air heater, and the CO ₂ refrigerant and the cooling dehumidifier after heat exchange with the heater 5. The artificial wood drying system according to claim 4, further comprising an air heater for exchanging heat with the air thus reheated. Claims, characterized in that supercritical pressure and compressed to a CO ₂ refrigerant that has a high temperature after introduction in the area in contact with air in the drying chamber of the air heater, is provided a conduit for returning to the air reheating device 4. Artificial drying system for wood according to 4. A temperature sensor and a humidity sensor provided in the drying chamber;
An air supply fan provided in the air supply unit;
A dehumidifying fan for introducing the air in the drying chamber into the evaporator of the heat pump;
A controller that controls a compressor driving device of the heat pump based on the temperature detected by the temperature sensor, and that controls the air supply fan and the dehumidifying fan based on the humidity detected by the humidity sensor. The artificial drying system for wood according to claim 5.   A cooling water tank in which cooling water is stored; and a conduit for circulating the cooling water between the cooling water tank and the evaporator, wherein the drying chamber is placed in the cooling water cooled by the evaporator and stored in the cooling water tank. The artificial drying system for wood according to claim 4, wherein the air is introduced to cool and dehumidify. An air heat collector that absorbs latent heat of vaporization from outside air is provided in parallel with the evaporator, and is configured such that CO ₂ refrigerant is introduced into the air heat collector during the initial drying operation.
A humidifier heater that exchanges heat between the CO ₂ refrigerant compressed to a supercritical pressure and heated to hot water sprayed by the humidifier is provided, and the warm water is sprayed from the humidifier during the initial drying operation. The artificial drying system for wood according to claim 4.   6. The exhaust passage is provided in an air flow path on the upstream side of the evaporator, and an outside air flow path is formed that passes from the air supply section through the evaporator to the exhaust section during initial operation. Artificial drying system for wood.

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