JP2001263950A - Open type air cycle drying system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an open type air cycle drying system having a high energy efficiency by increasing the recovering amount of heat from discharging air. SOLUTION: The drying system is equipped with a heat exchanger 5 effecting heat exchange between high-temperature discharging air 9 discharged out of a drying chamber 1 through an air discharging passage 17, and air 8 for drying which is introduced into the drying chamber 1 through an air introducing passage 16. In such a drying system, an expander 3 for reducing the temperature of the air 8 for drying by the expansion thereof is provided at the upstream side of the heat exchanger 5 in the air introducing passage 18. The amount of heat which can be received by the air 8 for heating as a sensitive heat is increased and the energy efficiency of the whole drying system is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying system which recovers a part of heat from high-temperature and high-humidity air discharged from a drying space to improve energy efficiency, and is particularly excellent as a clothes drying system. It is effective.

[0002]

2. Description of the Related Art A clothes drying cycle disclosed in Japanese Patent Application Laid-Open No. 3-218800 is known as a clothes drying cycle in which latent heat is recovered mainly from air discharged from a drying drum to improve energy efficiency.

[0003] This clothes dryer will be described with reference to Fig. 6. In the figure, 1 is a drying drum, 10 is a heat recovery heat exchanger, 11 is a cooling heat exchanger, 12 is a heater, 13
Is a blower for drying, 14 is a blower for cooling, 8 is drying air taken in from the room, 9 is exhaust air from the drying drum, and 15 is cooling air.

The drying air 8 taken in from the room exchanges heat with the air 9 discharged from the drying drum 1 in a heat recovery heat exchanger 10 and passes through a drying blower 13 to a heater 12.
Becomes high temperature air with low relative humidity,
Is introduced to Inside the drum, the drying air 8 that promotes the evaporation of moisture from the clothes to be dried is discharged from the drying drum 1 as high-temperature, high-humidity exhaust air 9 whose temperature has dropped due to the latent heat of evaporation and the humidity has increased to near saturation. Is done.

The discharged air 9 is cooled by the drying air 8 taken in from the room in the heat exchanger 10 and condenses a part of the water vapor evaporated by the drying drum 1.
Further, the discharged air 9 is cooled to near room temperature by the cooler 11 introduced from the room in the heat exchanger 10, and after condensing remaining moisture, is discharged to the room.

In the above cycle, in the heat recovery heat exchanger 10, the discharged air 9 condenses a part of the water vapor evaporated in the drying drum 1, so that the drying air 8 recovers the sensible heat and the latent heat of condensation. It becomes possible to increase the energy efficiency of drying.

[0007]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 3-218 is disclosed.
The specification of the clothes dryer according to the method disclosed in Japanese Patent Publication No. 800 is as follows, for example. Temperature and humidity conditions of outside air: 25 ° C., 50% RH (relative humidity) Drying drum inlet temperature: 120 ° C. Drying rate in a constant-rate drying state: 70 g / min (evaporation rate of water) Under the above conditions, outdoor Air temperature and humidity to the
When the operating state of the clothes dryer is analyzed when 0 ° C. and 100% RH are determined, the following results are obtained as shown in FIG.

The drying air 8 taken in at 25 ° C. is heated to 35 ° C. by heat exchange with the discharged air 9 in a heat recovery heat exchanger 10, passed through a blower 13 and then heated by a heater 12. Raise the temperature to 120 ° C, 0.8% RH as shown in the specifications,
It is sent to the drying drum 1. The air that has promoted the evaporation of water from the material to be dried inside the drying drum 1 is discharged from the drying drum as discharged air 39 of 39 ° C. and 100% RH due to its latent heat of vaporization.

Thereafter, the latent heat is released by the heat recovery heat exchanger 10 described above, and after cooling to 38 ° C. and 100% RH, the heat is exchanged with the cooling air 15 in the cooling heat exchanger 11 to 30 ° C. The temperature is lowered until it is released to the outside air. Here, the inlet temperature of the cooling air is 25 ° C., and the outlet temperature is 34 ° C.

When the clothes are dried in the above operating condition, the air volume of the drying air 8 required to satisfy the specification of the drying speed of 70 g / min is 1.54 m ³ / min. The total amount of heat required to heat to 120 ° C. is 3195 W. Among them, heat recovery heat exchanger 10
In this case, 334 W is recovered from the exhaust air, and the remaining heat must be supplied from the heater 12. This indicates that the amount of heat recovered from the exhaust air is only about 10% of the amount of heat required to heat the drying air.

Accordingly, it is an object of the present invention to provide a drying system having high energy efficiency by increasing the amount of heat recovered from exhaust air.

[0012]

As a result of various studies conducted by the present inventor to achieve the above object, the cause of the low heat recovery amount in the drying system is that the heat recovery heat exchanger 10
The method of recovering heat at room temperature uses heat discharged from the exhaust air 9 at 39 ° C. as latent heat and drying air 8 at 25 ° C. introduced from the room.
To receive the heat as sensible heat, and found that the temperature difference between the two fluids that exchange heat was as small as 14 ° C., and that the heat recovery amount itself could not be received so much that the present invention was completed. It is.

That is, the open-type air cycle drying system according to the present invention uses air as a working medium, obtains a heat source at a temperature lower than room temperature to improve the energy efficiency of drying, recovers heat from exhaust air, and recovers the recovered heat. Is installed in a drying chamber, an air introduction path that takes in outside air as drying air and introduces it into the drying chamber, and an air introduction path. A heat source for heating the dried air, an air discharge path for discharging air from the drying chamber, and a heat exchanger for exchanging heat between the discharged air discharged from the drying chamber and the drying air. On the upstream side of the heat exchanger in the introduction path, there is provided an expander for expanding the drying air to lower the temperature.

According to the above configuration, after the heating air flowing through the air introduction path is adiabatically expanded by the expander to lower the temperature,
Since heat is exchanged with the exhaust air in the heat exchanger, the amount of heat that can be received by the heating air as sensible heat can be increased by an amount corresponding to a temperature decrease from room temperature. Therefore, a large amount of heat released from the discharged air as latent heat can be efficiently recovered.

In order to enhance the thermal efficiency of the drying system, as described above, in addition to increasing the amount of heat recovered from the exhaust air, a gas-liquid connection between the expander and the heat exchanger in the air introduction passage is made. A configuration in which a separator is provided may be employed.

That is, the air discharged from the expander is
Since the temperature drops below the dew point or freezing point due to the temperature drop, water vapor in the air is condensed. When the freezing point is reached, saturated moist air containing partially frozen sherbet-like water is formed.

Therefore, if a gas-liquid separator is installed between the expander and the heat exchanger, it is possible to remove moisture condensed in the drying air or solidified ice by the gas-liquid separator, and It has the effect of reducing the absolute humidity of the air introduced into the room and increasing the drying speed, and at the same time, reducing the heat loss of the heat transfer surface in the air introduction path in the heat recovery heat exchanger, so that the overall thermal efficiency of the drying system Can be increased.

The structure of the expander is not particularly limited as long as it reduces the temperature by adiabatically expanding the heating air, and examples thereof include an expansion valve, an ejector, and an expansion turbine. Further, in the process of expanding the air by the expander, expansion energy is generated. Therefore, if a configuration for recovering the expansion energy as power is employed, it is possible to provide a drying system having excellent operation efficiency.

As a specific configuration for recovering power, for example, when an expansion turbine that is rotationally driven by a motor is used as an expander, the expansion turbine is driven by a motor so that a turbine impeller rotates, and The motor is configured so that the air becomes an adiabatic jet through the nozzle and flows into the turbine impeller. Power consumption can be reduced.

It is also possible to recover the power in another way. For example, a power recovery rotor is provided on a rotating shaft of a motor that drives an expansion turbine, and the power recovery rotor can be used as a generator rotor and a compressor rotor.

Any heat source may be used as long as it heats the drying air. Specifically, a heater or the like can be used. However, if a compressor is used, the air which has been reduced in temperature and pressure by the expander can be used. The pressure can be returned to the atmospheric pressure, and the temperature can be raised by adiabatic compression to be introduced into the drying chamber.

Further, when the compressor is used, it can be driven by the same motor as the expander, as described above.
By adjusting the rotation speed of the motor so that both the compressor and the expander have high efficiency, the power consumption of the motor can be reduced.

Further, if a configuration is employed in which the second heat exchanger is provided on the air introduction path on the upstream side of the expander, the relative humidity is reduced by increasing the temperature of the air introduced into the expander. Water can be prevented from condensing in the air, and the water condenses inside the expander, causing a reduction in the efficiency of power recovery, and further causing erosion damage to the stationary blades and the rotor blades due to the condensed water. There is no fear.

[0024] Further, an expander arranged upstream of the heat exchanger in the air introduction path is constituted in two or more stages, and a heat exchanger different from the heat exchanger is arranged between each stage. If the expander is adopted, the heat recovery efficiency is higher than that of a single-stage expander, and the expansion ratio is adjusted so that the air introduced in each expander does not condense the moisture in the air by adiabatic expansion. By reducing the efficiency of power recovery due to condensation of water vapor inside the expander,
Erosion damage of the rotor can be prevented.

In the open-type air cycle drying system described above, the rate of heat recovery from the air discharged from the drying chamber can be increased to 49% of the amount of heat required for drying. It is suitable as a drying system for clothes such as a drying drum, but it is also applicable as a drying system for a living room, bathroom, washroom, kitchen or living room. In addition, since an expander is used, a blower such as a conventional clothes dryer is not required, and the structure of the system can be simplified.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing a first embodiment of the open air cycle drying system. The drying system in the present embodiment is a system for drying clothes, a drying drum 1 that stores clothes as a drying chamber, an air introduction path 16 that takes in outside air as drying air 8 and introduces the drying air into the drying drum 1. An air discharge passage 17 for discharging the air 9 discharged from the drying drum 1 to the outside of the system; an air introduction passage 16 and an air discharge passage 1;
7 and a heat exchanger 5 for heat recovery is arranged.
Heat is exchanged between the high-temperature exhaust air 9 discharged from the drying drum 1 and the low-temperature drying air 8. The air filter 16, the expander 3, the heat exchanger 5, and the compressor 2 are installed in this order from the upstream side in the air introduction path 16. The expander 3 and the compressor 2 are the same motor 4. It is arranged to be driven by.

In the above configuration, the drying air 8 taken in from the room is adiabatically expanded by the expander 3 to become low-pressure low-temperature air at a pressure lower than the atmospheric pressure, introduced into the heat exchanger 5, and supplied from the drying drum 1. After exchanging heat with the discharged air 9, the pressure is returned to the atmospheric pressure in the compressor 2, and the compressed air is introduced into the drying drum 1 at high temperature and normal pressure.

Here, part of the power required for the compression work to the atmospheric pressure utilizes the power recovered in the expansion process in the expander 3 described above, and the remaining power is supplied from the motor 4.

The drying air 8 introduced into the drum 1 promotes the evaporation of water from clothes to be dried, and then the temperature of the air is reduced due to latent heat of evaporation and the humidity is increased to near saturation. 9 and is discharged from the drying drum 1 and cooled by the low-temperature and low-pressure drying air 8 in the above-described heat exchanger 5, whereby the drying drum 1
A part of the water vapor evaporated in is condensed and discharged into the room.

In the above-mentioned drying system, the heat recovery heat exchanger 5 condenses a part of the water vapor evaporated by the drying drum 1 in the exhaust air 9, so that the sensible heat and the latent heat of condensation are recovered in the drying air 8. Increase energy efficiency of drying.

The drying drum 1 has a diameter of, for example, 500 to 60.
It is composed of a stationary drum having a cylindrical shape of about 0 mm, a rotating drum inside the stationary drum having a number of small holes for air circulation, and a drum motor for driving the rotating drum. Inside the rotary drum, three to six baffles having a function of loosening clothes during drying are provided, and a motor for the drum is driven based on a control signal, for example, every one minute, the normal rotation of the rotary drum,
The operation is performed so that the reverse rotation is repeated.

The compressor 2 and the expander 3 are driven by one motor 4 as described above, and a part of the power required for compression is recovered in the expander 3. Both the compressor 2 and the expander 3 are of a centrifugal type that facilitates power recovery.

More specifically, an expansion turbine is used as the expander 3, and as shown in FIG.
The nozzle 19 and the turbine impeller 20 are housed therein. The turbine impeller 20 is a rotating shaft 4 a of the motor 4.
Is connected to one end side of the camera and is driven.

The air for drying 8 is supplied to the expander 3 having such a configuration.
Is introduced, the static pressure is first converted to dynamic pressure by the nozzle 19 and expanded. The air that has flowed into the turbine impeller 20 from the nozzle 19 gives rotational energy to the turbine impeller 20 and flows out of the expander 3.
The compressor 2 is connected to the other end of the rotating shaft 4 a of the motor 4, and the rotational energy given to the turbine impeller 20 is directly used for compression work.

The rotation speed of the motor 4 is adjusted so that both the compressor 2 and the expander 3 operate efficiently. Therefore, the ratio of the recovered power in the expander 3 to the required power in the compressor 2 Therefore, the power consumption required for the motor 4 can be reduced. In addition, a gas bearing is used as a bearing for supporting the rotary shaft 4a for the purpose of preventing oil from being mixed into the airflow and for coping with high-speed rotation.

As the heat recovery heat exchanger 5, for example, an air-to-air counter-flow heat exchanger is used. Heat is exchanged between the two fluids by alternately flowing high-pressure air at normal pressure and low-temperature air at low pressure in a gap partitioned by an aluminum plate, so that the two fluids are opposed to each other. Therefore, the heat exchange efficiency can be improved. Further, fins are inserted into the respective gaps to increase the heat transfer area, thereby increasing the efficiency of heat exchange and reducing the size of the heat exchanger itself.

The air filter 6 can protect the compressor 2 and the expander 3 from dust contained in the air and can remove 100% of dust having a particle diameter of 10 μm or more for the purpose of preventing contamination loss of the heat exchanger. Therefore, a cyclone dust collector is used. That is, since the taken-in air forms a swirling flow along the wall surface, dust heavier than the air is separated from the air flowing upward by centrifugal force and settles to the lower part of the dust collector. The settled dust is stored in the collecting section, and the collecting section is configured to be detachable from the dust collector main body, thereby improving maintainability.

Further, since the cyclone dust collector has a lower pressure loss than a dust collecting method using a filter having the same level of dust collecting capability, the load on the motor 4 for driving the drying cycle is reduced, and the power consumption is reduced. It becomes possible.

As the gas-liquid separator 7, a centrifugal gas-liquid separator based on the same principle as the above-mentioned cyclone dust collector is used. In other words, the entrapped air forms a flow that swirls along the wall surface, so water heavier than the air collides with the wall surface due to centrifugal force and stalls, so it is separated from the air flow and provided near the air discharge section. The liquid is temporarily fed into the receiver tank from the liquid discharge groove and then discharged from the drain discharge flow path.

When the clothes dryer is constructed by the above-described method, for example, if the specifications are the same as before, it is as follows. Temperature and humidity conditions of outside air: 25 ° C., 50% RH Drying drum inlet temperature: 120 ° C. Drying rate in a constant rate drying state: 70 g / min (moisture evaporation rate) Under the above conditions, the heat insulating efficiency of the compressor is 77. %, And when the heat insulating efficiency of the expander is 75%, the operating state of the clothes dryer is analyzed as shown in FIG.

When the drying air 8 taken in from outside air at 25 ° C. is reduced to 48 kPa (abs) in the expander 3, it becomes air at −4 ° C. at the outlet due to adiabatic expansion.
Since this air reaches a temperature below the freezing point, water vapor in the air is condensed and becomes saturated humid air containing partially frozen sherbet-like water.

This air exchanges heat with the exhaust air 9 at 39 ° C. in the subsequent heat recovery heat exchanger 5, and the heat released by the exhaust air 8 as latent heat is transferred to the upstream part of the heat exchanger such as heat of fusion and heat of evaporation. Latent heat, other parts receive as sensible heat,
After the temperature was raised to 33 ° C., the pressure was restored to the atmospheric pressure in the compressor 2, and the compression work there caused the work to reach the specified 120 ° C.
The temperature is raised to 0.8 ° C. and 0.8% RH, and flows into the drying drum 1.

Inside the drying drum 1, the air which has promoted the evaporation of water from the material to be dried is lowered in temperature by the latent heat of evaporation, and is discharged from the drying drum 1 as discharged air 9 at 39 ° C. and 100% RH. You. Thereafter, the heat is exchanged with low-pressure air at -4 ° C. in the heat recovery heat exchanger 5 described above.
The discharged air 9 whose temperature has dropped to 0 ° C. is discharged to the outside air after the water condensed by the temperature drop is removed in the gas-liquid separator 7.

When the clothes are dried in the above-described operation state, the amount of the drying air 8 required to satisfy the specification of the drying speed of 70 g / min is 1.54 m ³ / mi.
n, and the energy required to raise the temperature of the outside air at 25 ° C. to 120 ° C. at this time is 3195 W, of which 1574 W is recovered in the heat exchanger 5. Thus, the amount of heat recovered from the exhaust gas reaches up to 49% of the required amount of heat.

This indicates that a heat recovery capacity approximately five times that of the conventional heat recovery method having the same specifications can be obtained.

The power required by the expander 3 and the compressor 2 for reducing the pressure to 48 kPa (abs) and then returning to normal pressure is 2825 W, whereas the power required by the expander 3 in the flow path immediately before the pressure is 2825 W. Since the power of 1642 W is recovered as expansion work, the power required for the motor connecting the compressor 2 and the expander 3 is 1 by subtracting the latter from the former.
183 W, for example, if the efficiency of the motor is 70%, the power consumption required to operate the clothes dryer is 1690
W, which is required for the operation of the above-mentioned conventional clothes dryer 2
With respect to the power consumption of 861 W, the energy can be reduced by 41%.

Since the compressor 2 and the expander 3 used in the above numerical analysis are required to have high efficiency, for example, a blade having an impeller diameter of 60 to 64 mm for the compressor and 39 to 43 mm for the expander is used. , It is desirable to drive with a motor rotating at a speed of 100,000 to 120,000 rpm.

[Second Embodiment] FIG. 2 is a system diagram showing an open-type air cycle drying system according to a second embodiment. The present embodiment is characterized in that, in addition to the configuration of the first embodiment, a gas-liquid separator 7 is further provided in an air introduction passage 16 that leads from the outlet of the expander 3 to the heat recovery heat exchanger 5. Thus, a structure is provided in which moisture condensed from the drying air 8 or solidified ice is removed.

That is, from the upstream side of the air introduction passage 16,
The expander 3, the gas-liquid separator 7, and the heat exchanger 5 are arranged in this order, and the drying air 8 whose temperature has been reduced by the expander 3 removes moisture condensed in the gas-liquid separator 7 or solidified ice. Is removed, the absolute humidity of the air is reduced and the drying speed is increased, and at the same time, the wet loss of the heat transfer surface in the air introduction path in the heat exchanger 5 is reduced, so that the thermal efficiency of the entire drying system can be increased Becomes

[Third Embodiment] FIG. 3 is a system diagram showing an open type air cycle drying system according to a third embodiment. In the present embodiment, in addition to the configuration of the first embodiment, a second heat exchanger 5a for recovering heat from the exhaust air 9 is further provided upstream of the expander 3 in the air introduction path 16. Is characterized by the fact that the expander 3
The structure is such that the relative humidity is reduced by increasing the temperature of the drying air 8 introduced into the expansion device 3 in advance, and condensation of water vapor inside the expander 3 is prevented.

Therefore, it is possible to prevent the efficiency of power recovery from being reduced due to the condensation of water vapor, and to prevent erosion damage of the stationary blade and the rotary blade due to the condensed water.

[Fourth Embodiment] FIG. 4 is a system diagram showing an open-type air cycle drying system according to a fourth embodiment. In this embodiment, the expander 3 in the first embodiment is configured in multiple stages to gradually expand the drying air 8, and heat is recovered from the exhaust air 9 separately from the heat exchanger 5 between each stage. And a heat exchanger 5b for each.

The expansion ratio of each stage of the expander 3 is designed so that the introduced air does not condense water in the air due to adiabatic expansion.

Since the relative humidity of the air expanded by the expanders 3 of each stage approaches saturation, the air is regenerated into low relative humidity air by increasing the temperature in the heat recovery heat exchanger 5b. By repeating this process, while efficiently recovering heat from the exhaust air 9, the efficiency of power recovery due to the condensation of water vapor inside the expander 3 is prevented, and the erosion damage of the stationary blades and the rotor blades due to the condensed water is prevented. It becomes possible.

[0055]

As is apparent from the above description, according to the present invention, heat is exchanged between high-temperature exhaust air discharged from the drying chamber and drying air reduced in temperature and pressure by the expander. The amount of heat that can be received by the heating air as sensible heat can be increased by an amount corresponding to a temperature decrease from room temperature, and the energy efficiency of the entire drying system can be increased.

Further, by providing a gas-liquid separator between the expander and the heat exchanger in the air introduction passage, the absolute humidity of the air introduced into the drying chamber is reduced, the drying speed is increased, and the entire drying system is increased. It is possible to increase the thermal efficiency.

Further, by using an expansion turbine as an expander and a compressor as a heat source and connecting them to the same motor and driving them, it is possible to operate both of them efficiently, and further, the generation of the expander Since the expansion energy of the generated air can be used as it is for the compression work, the power consumption of the motor can be reduced.

Further, by adjusting the temperature or expansion ratio of the drying air introduced into the expander, the efficiency of power recovery due to the condensation of water vapor inside the expander is prevented, and the stationary blades and the rotary blades are further prevented from being condensed. Erosion damage can be prevented.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an open type air cycle drying system according to a first embodiment;

FIG. 2 is a system diagram showing an open air cycle drying system according to a second embodiment.

FIG. 3 is a system diagram showing an open type air cycle drying system according to a third embodiment;

FIG. 4 is a system diagram showing an open-type air cycle drying system according to a fourth embodiment;

FIG. 5 is a sectional view of an expansion turbine.

FIG. 6 is a system diagram showing a conventional clothes dryer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drying drum 2 compressor 3 expander 4 motor 5 heat exchanger 7 gas-liquid separator 8 drying air 9 discharge air 16 air introduction path 17 air discharge path

Claims (8)

[Claims] 1. A drying chamber, an air introduction path for taking in outside air as drying air and introducing the drying air into the drying chamber, a heat source installed in the air introduction path to heat the drying air, and In a drying system comprising: an air discharge path for discharging air; and a heat exchanger for exchanging heat between the discharge air discharged from the drying chamber and the drying air, the heat exchanger in the air introduction path. An open type air cycle drying system, characterized in that an expander for expanding the drying air to lower the temperature is provided upstream of the air drying system. 2. The open air cycle drying system according to claim 1, wherein a gas-liquid separator is provided between the expander and the heat exchanger in the air introduction path. 3. The open air cycle drying system according to claim 1, wherein the heat source is a compressor. 4. The open-type air cycle drying system according to claim 1, wherein a part of the air is recovered as power by using expansion energy of drying air expanded in the expander. 5. The expansion machine is an expansion turbine, a power recovery rotor is formed on a rotating shaft of a motor for driving the expansion turbine, and expansion of drying air generated in the expansion turbine by driving the motor. 4. The open-type air cycle drying system according to claim 1, wherein energy is converted into rotational energy of the expansion turbine and used as rotational power of the rotor. 6. A heat exchanger according to claim 1, wherein a second heat exchanger for recovering heat from the exhaust air is provided upstream of the expander in the air introduction path. An open air cycle drying system as described. 7. The expander has two or more stages, and a heat exchanger for recovering heat from the discharged air is provided between each stage separately from the heat exchanger. 7. The open-type air cycle drying system according to any one of 6. 8. The open-type air cycle drying system according to claim 1, wherein the drying chamber is for drying clothes.