JP2007248042A - Steam generator and steam generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a generator of superheated steam capable of generating superheated steam without employing a complicated device configuration, and excelling in controllability and responsiveness; and to provide a generation method thereof. <P>SOLUTION: This steam generator 1 is provided with a porous body 6 partially immersed in a liquid bath W, and heating elements 8 for generating superheated steam S by heating water in the liquid bath supplied by a capillary phenomenon of the porous body. A hollow part 7 is formed in the porous body, and the superheated steam S is delivered to the outside of the porous body from the hollow part through steam delivery means 7a and 3. Exit parts 31 of pores 30 of the porous body are located on the inside wall surface 6a of the hollow part, and the heating elements contact or in proximity to the inside wall surface, and extend along the inside wall surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water vapor generation apparatus and a water vapor generation method, and more specifically, superheated water vapor can be generated in a very short time using a capillary water supply action of a porous body and a heating action of a heating element. The present invention relates to an apparatus and a method for generating superheated steam.

  Superheated steam heated to a saturated steam temperature or higher is industrially used in various plant processes, or is used for drying, processing, sterilization and the like of wood and food. In recent years, household cooking appliances and the like using such superheated steam are spreading in the market, and the use of superheated steam has been especially expanded in recent years. In this kind of household cooking appliances, the superheated steam is generated by immersing an electric heater in the water in the water tank to heat the water in the water tank, and reheating the water vapor generated by the vaporization of the water. For example, Japanese Patent Application Laid-Open No. 2004-186103 (Patent Document 1) discloses a steam generator for a cooker provided with a steam generating heater and a steam heater. In this type of apparatus, a relatively complicated apparatus configuration is adopted in which a two-stage process consisting of a water vapor generation process for vaporizing water to generate water vapor and a water vapor heating process for heating the water vapor is executed in stages. . However, when superheated steam is generated by such a method, the structure of the apparatus increases in size, and a considerable time is required for the pre-process from the start of the apparatus to the generation of water vapor. For this reason, development of the apparatus which can generate superheated steam quickly with a simple apparatus or method is desired.

  In JP-A-9-273755 (Patent Document 2), a porous body having microwave permeability and water absorption is heated by microwave heating means, and water supplied to the porous body is heated to superheated steam. A steam generator configured to generate water is described. Similarly, Japanese Patent Application Laid-Open No. 2001-267061 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2001-254952 (Patent Document 4) disclose a steam generator using a microwave heating means and a porous body. . This type of apparatus requires a relatively complicated apparatus configuration including a microwave heating apparatus.

  As a steam generator using a porous body and a heating element, there is known a steam generating apparatus in which a porous body in which a heating element such as an electric heater is embedded is partially immersed in a liquid bath (Japanese Patent Laid-Open No. 50). No. 14901 (Patent Document 5)). The structure of this type of steam generator is schematically shown in FIG. As shown in FIG. 13, the water in the liquid bath W is sucked into the pores of the porous body 101, heated by the heating element 102, and flows out from the outer surface of the porous body 101. As a water vapor generator having another structure, a water vapor generator configured to efficiently generate water vapor by forming a porous spray coating layer to improve heat transfer efficiency on the inner surface of the vaporizer and the surface of the heating element 56-49163 (Patent Document 6)), or configured to supply water to a porous body disposed between electrodes and vaporize water by conductivity or Joule effect of water in the porous body. A steam generator (Japanese Patent Laid-Open No. 53-109001 (Patent Document 7)) is known.

As a water vapor generator with a similar structure using a porous body, a liquid is supplied to the porous body using a metering pump in order to prevent the generation of non-evaporated mist in a zero-gravity space such as the universe. Japanese Patent Application Laid-Open No. 61-243201 (Patent Document 8) describes a configuration in which liquid leaking to the inner wall surface of the tube is evaporated by the heat generated by the heat transfer tube.
JP 2004-186103 A JP-A-9-273755 JP 2001-267061 A Japanese Patent Laid-Open No. 2001-254952 JP 50-14901 A JP 56-49163 A JP-A-53-109001 JP-A 61-243201

  However, in the conventional water vapor generating apparatus (Patent Documents 5 and 6) configured to generate water vapor from the outer surface of the porous body that covers the heat generating element or has the heat generating element embedded therein, The whole must be heated. Since the water-retained porous body has a large heat capacity, a considerable time is required from the start of heating of the heating element to the generation of water vapor. Temporarily, in order to generate water vapor in a short time, it can be considered to reduce the volume of the porous body and to cover the heating element with a thin porous body, but when such a design is adopted, Since the function of the porous body that sucks water from the liquid bath (that is, the amount of liquid supplied to the heating element) is extremely reduced, the amount of water vapor generated is greatly reduced.

  The water to be vaporized flows in the porous body radially inward toward the heating element by capillary action, whereas the water vapor generated on the heating surface is accompanied by a rapid volume increase due to vaporization. It flows in the opposite direction, that is, radially outward from the heating surface. That is, the water vapor goes backwards with the water and the supply of water to the heating surface is hindered. As a result, if the heat generation amount of the heating element is increased due to an increase in the amount of water vapor generated or a rise in the water vapor temperature, the porous body portion around the heating element is overdried or the electric heater constituting the heating element is overheated. The problem that it burns out or burns out arises.

  On the other hand, in the conventional water vapor generating device (Patent Document 7) configured to directly energize the water in the porous body and vaporize the water by heat generation of the water (Patent Document 7), the water is fed into the porous body by a pumping device such as a pump. It is necessary to press fit. Further, in the apparatus having this configuration, it is necessary to evaporate a large amount of water in the porous body as a whole or uniformly, and therefore, a high voltage must be applied to the water in the porous body. For this reason, a high-voltage power supply is required, which is not desirable from the viewpoint of safety in use of the apparatus.

On the other hand, although the water vapor generating device of the above-mentioned Patent Document 8 has a configuration for supplying water with a metering pump, according to this water vapor generating device, the flow of water is not hindered by the behavior of water vapor, and the porous body. Therefore, it is considered that the problem of overdrying can be avoided. Therefore, the water vapor generator of Patent Document 8 has an excellent structure in this sense. However, in the water vapor generating device of Patent Document 8, the porous body is merely used mainly as a means for holding the liquid in the porous body and preventing the non-evaporated mist from scattering into the hollow portion. The liquid leaks to the inner wall surface of the hollow portion of the porous body and then comes into heat transfer contact with the outer surface of the heater and evaporates. For this reason, in the apparatus of Patent Document 8, a sheath heater having a double tube structure with a large surface area is used. However, the surface average heat flux of the sheath heater is only about 40 to 90 kW / m ² , and the heat flux on the heat transfer surface is small. In such a configuration, even if saturated steam can be generated, superheated steam cannot be generated.

  Even if the heater heat generation amount is increased in the apparatus of Patent Document 8, much of the supplied heat is consumed to increase the amount of water vapor generated, and only the amount of water vapor generated increases. The heat of the heating element is unlikely to contribute as desired to the increase in water vapor temperature. That is, the steam generator of Patent Document 8 is not intended to generate superheated steam, and does not disclose or suggest the possibility of generating superheated steam.

  The present invention has been made in view of such problems, and the object of the present invention is to quickly generate superheated steam without adopting a complicated apparatus configuration, and to achieve controllability and An object of the present invention is to provide an apparatus and a method for generating superheated steam having excellent responsiveness.

  The present invention can also shorten the time from the start of heating to the generation of superheated steam without impairing the function of the porous body that sucks up water from the liquid bath, and can prevent overdrying or overheating of the porous body and the heating element. An object of the present invention is to provide a superheated steam generator and method.

  The present invention further generates superheated steam that can smoothly generate superheated steam by supplying water to the steam generation surface smoothly without supplying a pumping device, and by supplying relatively low voltage power. An object is to provide an apparatus and a generation method.

In order to achieve the above object, the present invention provides a porous body partially immersed in a liquid bath, and a heating element that generates water vapor by heating the water in the liquid bath supplied by the capillary phenomenon of the porous body. In the steam generator with
A hollow portion formed in the porous body;
Water vapor delivery means for delivering the water vapor generated in the hollow part out of the porous body from the hollow part,
The outlet portion of the pore of the porous body is located on the inner wall surface of the hollow portion,
The heating element is in contact with or close to the inner wall surface of the hollow portion so as to vaporize the water in the outlet portion and superheat the water vapor generated in the pore. A water vapor generating device is provided.

The present invention also provides a water vapor generation method in which water is supplied to a heating element by capillary action of a porous body partially immersed in a liquid bath, and water vapor is generated by the heat of the heating element.
The heating element that contacts or is close to the inner wall surface of the hollow portion formed in the porous body and extends along the inner wall surface of the pore outlet portion of the porous body located on the inner wall surface of the hollow portion. Heat the water,
The water of the meniscus part of the outlet part is evaporated by the heat of the heating element to generate water vapor at the outlet part of the pores and superheat the water vapor generated in the pores,
Provided is a method for generating water vapor, characterized in that superheated water vapor is sent out of the porous body from the hollow portion.

  According to the said structure of this invention, the water of a liquid bath is supplied to the exit part of a hollow part inner wall surface by a capillary phenomenon. The water vapor generated from the outlet portion is sent out of the apparatus from the region in the hollow portion by the water vapor delivery means. The water vapor flow region and the feed water flow region are separated, and the water vapor does not hinder the water supply.

  Further, the heat of the heating element acts on the water in the meniscus portion formed at the outlet portion. Since the thin water film of the meniscus portion is a minute amount of water having a small heat capacity, water can be rapidly evaporated by the heat of the heating element by supplying relatively low voltage power to the heating element. Moreover, since water vaporizes in the pores, the water vapor is immediately heated by the heating element close to the pore outlet. The superheated steam is generated in the hollow portion within several tens of seconds to several minutes after the start of heat generation, and disappears rapidly after the heat generation is stopped.

  Furthermore, since the water in the liquid bath is supplied according to the evaporation rate due to the capillary action of the porous body, water vapor is continuously generated from the inner wall surface of the hollow portion. Since water is always supplied to the contact portion of the porous body and the heating element or in the vicinity thereof, overdrying or overheating of the porous body and the heating element can be prevented. In addition, since the heat of the heating element that conducts heat to the porous body is effectively used for preheating water flowing toward the outlet, the amount of heat dissipated out of the system from the outer surface of the porous body is reduced.

Preferably, a drying zone is formed on the inner wall surface in the vicinity of the heating element by the heat of the heating element, and a wet inner wall zone is formed between the drying zones. More preferably, the heat flux at the contact portion between the inner wall surface of the hollow part and the heating element is set to 1 MW / m ² or more, or the average heat flux value of the entire surface of the heating element is set to 200 kW / m ² or more. . Thereby, water in the pores can be instantly vaporized, and superheated steam at 200 ° C. or higher can be reliably generated in the hollow portion within 1 minute after the start of heat generation. If desired, it is possible to generate superheated steam at 300 ° C. or higher in the hollow portion within 30 seconds after the start of heat generation.

From another viewpoint, the present invention provides a porous body partially immersed in a liquid bath,
A heating element for heating the liquid in the liquid bath supplied by the capillary action of the porous body to generate steam;
A hollow portion formed in the porous body;
Vapor delivery means for delivering the vapor generated in the hollow part out of the porous body from the hollow part,
The outlet portion of the pore of the porous body is located on the inner wall surface of the hollow portion,
The heating element is in contact with or close to the inner wall surface of the hollow portion and along the inner wall surface so as to vaporize the liquid in the outlet portion in the pores and superheat water vapor generated in the pores. A steam generator is provided that extends.

The present invention also supplies the liquid in the liquid bath to the heating element by capillary action of a porous body partially immersed in the liquid bath,
The heating element that contacts or is close to the inner wall surface of the hollow portion formed in the porous body and extends along the inner wall surface of the pore outlet portion of the porous body located on the inner wall surface of the hollow portion. Heating the liquid,
Vaporizing the liquid in the meniscus portion of the outlet portion by the heat of the heating element to generate steam at the outlet portion of the pores and superheating the steam generated in the pores;
Provided is a steam generation method characterized in that superheated steam is sent out of the porous body from the hollow portion.

  The present invention can be applied not only to the generation of water vapor but also to the evaporation of liquid that can be sucked up by the capillary action of a porous body. Examples of usable liquids include various liquid fuels. According to the steam generating apparatus or the steam generating method of the present invention, the liquid in the liquid bath is supplied to the outlet portion of the inner wall surface of the hollow portion by capillary action, and the vapor of the fuel vaporized at the outlet portion is contained in the hollow portion by the steam delivery means. It is sent out of the device from the area. Since the flow region of the steam and the flow region of the supply liquid are separated, the steam does not hinder the supply of the liquid. Further, since the liquid is vaporized in the pores, the vapor is superheated by a heating element close to the outlet portion of the pores.

  The present invention provides a superheated steam generator and a method for generating superheated steam that can quickly generate superheated steam without adopting a complicated apparatus configuration, and that are excellent in controllability and responsiveness.

  According to the steam generator and the steam generating method of the present invention, the time from the start of heating to the generation of superheated steam is shortened without impairing the function of the porous body that sucks up water from the liquid bath, and the excess of the porous body and the heating element is reduced. Drying or overheating can be prevented.

  Moreover, according to the water vapor generation apparatus and the water vapor generation method of the present invention, it is possible to smoothly supply water to the water vapor generation surface without requiring a pumping apparatus and to generate superheated water vapor by supplying a relatively low voltage. .

  Furthermore, the present invention provides a steam generating apparatus and a steam generating method capable of effectively generating superheated steam with the heat of the heating element without impairing the function of the porous body that sucks the liquid from the liquid bath.

  In a preferred embodiment of the present invention, the steam generator further includes a steam heating device that further heats the superheated steam generated in the hollow portion, and the steam heating device is a porous body through a steam delivery means. It communicates with the hollow part. The superheated steam generated in the hollow portion is further heated to a high temperature by the heating device. The steam heated by the heating device is supplied to a device outside the system as high-temperature superheated steam. Preferably, a water purification device is interposed in a water supply system for supplying water to the liquid bath. The water purification apparatus incorporates, for example, an ion exchange resin filter that adsorbs hardness components such as calcium contained in the water supply.

  The heating element is made of, for example, a nichrome wire or a Kanthal wire that is in close contact with the inner wall surface of the hollow portion. The heating element is heated to the extent that it is red hot as desired. Even in the case of heating in this way, the radiant heat of the heating element is absorbed by the porous body in a water-containing state, so that heat loss due to heat dissipation is extremely small, and thus the desired thermal efficiency can be obtained.

  Preferably, the hollow portion has a circular cross section, and the heating element is formed of a coiled electric heating body that is in contact with or close to the inner peripheral surface of the hollow portion and whose axis is oriented in the axial direction of the hollow portion. The coiled electric heating body thermally expands in the radial direction during heating and presses the inner peripheral surface of the hollow portion, so that the contact thermal resistance is reduced, and moreover superheated steam or superheated steam is efficiently generated in the hollow portion. Such a device structure is compared to a structure in which the porous body and the electric heating element are separated by thermal expansion of the electric heating element and the contact thermal resistance is increased (for example, a structure in which the electric heating element is disposed on the outer periphery of the porous body) This is extremely advantageous from the viewpoint of thermal efficiency. If desired, a plurality of hollow portions may be formed in a porous body, and a heating element may be provided in each hollow portion.

  The pore diameter, effective thermal conductivity, material, cross-sectional dimension of the hollow portion, etc. of the porous body are appropriately set according to the purpose of use of the steam heating device or the steam heating device, the physical properties of the liquid, the physical properties of the steam or steam, etc. . For example, when the pore diameter of the porous body is set to a small diameter, the capillary force and the evaporation interface area can be increased, but the flow resistance of the liquid is increased. Therefore, it is considered that there is an optimum value corresponding to the purpose of use and the like in the pore diameter of the porous body. In addition, when a porous body having a small effective thermal conductivity is used, the temperature gradient in the porous body increases and the surface temperature of the inner wall surface of the hollow portion increases, so that water vapor or steam is efficiently generated from the evaporation interface. . However, in fact, it is necessary to consider factors such as heat resistance and thermal deformation of the porous material, so select a porous material with the optimum effective thermal conductivity in consideration of various factors. It is considered necessary.

  In addition, the dimensions of the porous body, in particular, the height of the porous body, is preferably set so that the liquid in the liquid bath can be supplied to the entire inner peripheral wall surface of the hollow portion by the capillary force inherent to the porous body. .

  According to a preferred embodiment of the present invention, the steam generator or the steam generator further includes a power supply device for energizing the heating element. More preferably, the power supply device includes a heating element control unit that controls a voltage value or a current value of power to be supplied to the heating element to control a heat generation amount of the heating element. In the steam generator or the steam generator of the present invention, since the evaporation rate of water or liquid can be changed by controlling the heat generation amount of the heating element, the heating element control means controls the evaporation rate of water or liquid. Variable control is possible. Therefore, according to such a configuration, the evaporation rate of water or steam can be arbitrarily set according to the calorific value of the heating element, and thus, for example, the superheated steam or superheated steam supplied to the next process can be set. It becomes possible to execute flow rate control and the like.

  FIG. 1 is a perspective view schematically showing an embodiment of a steam generator to which the present invention is applied, and FIGS. 2 and 3 are a longitudinal sectional view and a transverse sectional view of the steam generator shown in FIG.

  The steam generator 1 includes a vaporizer 2 that generates superheated steam and an auxiliary heating device 4 that is connected to the vaporizer 2 via a steam delivery pipe 3. The vaporizer 2 includes a liquid tank 5 that contains a liquid bath W, a porous body 6 that has a lower part immersed in the liquid bath W in the liquid tank 5, and a coiled heating element that is housed in a hollow part 7 of the porous body 6. 8. The downstream end (steam outlet) 7 a of the hollow portion 7 is positioned on the end surface of the porous body 6. On the other hand, the upstream side of the hollow portion 7 terminates at a closed end 7 b in the porous body 6.

  The upstream end of the water vapor delivery pipe 3 is connected to the downstream end 7 a of the hollow portion 7. The auxiliary heating device 4 includes a main body 9 made of a heat-resistant heat insulating material, a water vapor channel 10 penetrating the main body 9, and a heating element 11 for auxiliary heating accommodated in the water vapor channel 10. The downstream end (steam outlet) of the steam channel 10 is connected to the upstream end of the steam feed pipe 12, and the downstream end (not shown) of the steam feed pipe 12 is a device outside the system (not shown). Or superheated steam is discharged into a device outside the system.

  The hollow portion 7 of the vaporizer 2 forms a circular cross-section water vapor channel having a uniform diameter over the entire length in the porous body 6. The heating element 8 of the vaporizer 2 is formed of a coiled nichrome wire or a Kanthal wire having a circular cross section that is in contact with or in close contact with the inner peripheral surface of the hollow portion 7 over the entire circumference, and generates heat when energized. The steam channel 10 of the auxiliary heating device 4 forms a fluid channel with a circular cross section having a uniform diameter over the entire length in the main body 9. The heating element 11 of the auxiliary heating device 4 has a gap through which water vapor can flow. The heating element 11 also generates heat when energized. In this example, an irregularly bent and rounded metal wire rod (stainless steel wire or the like) is filled into the water vapor channel 10 as a heating element 11. Such a heating element 11 has a large surface area, and therefore ensures a sufficient heat transfer contact area between the heating element 11 and water vapor, so that the water vapor can be efficiently heated.

  Lead wires 15 are connected to the heating elements 8 and 11 of the vaporizer 2 and the auxiliary heating device 4, respectively. An energization wiring 21 of the current supply device 20 is connected to the terminal 16 of each lead wire 15. The current supply device 20 is connected to the AC power source 23 via the feeder line 22. The current supply device 20 of this example includes a voltage regulator that drops the voltage of the AC power supply (AC 100 V) 23 and supplies relatively low voltage power to the heating element 10. The current supply device 20 applies an AC voltage to the heating elements 8 and 11 via the terminal 16 to cause the heating elements 8 and 11 to generate heat.

  A water supply device 25 is provided in the water vapor generator 1 in association with the liquid tank 5 of the vaporizer 2. The water supply device 25 includes a water supply pipe 26 connected to a water supply facility (not shown) outside the system, a water quality purification device 27 that purifies the water supply, and a supply pipe 28 that supplies water into the liquid tank 5. The The purification device 27 incorporates an ion exchange resin filter that adsorbs hardness components such as calcium contained in the water supply, and purifies the water to be supplied to the liquid tank 5. Accordingly, the purified water is stored in the liquid tank 5 as the liquid bath W and is appropriately replenished to the liquid bath W in connection with the liquid level lowering of the liquid bath W.

  As shown by the arrows in FIG. 3, the porous body 6 sucks up the water in the liquid bath W. The sucked water flows toward the hollow portion 7 and receives heat from the heating element 8 on the inner peripheral surface of the hollow portion 7. Water is heated by the heat of the heating element 8 and vaporizes rapidly. The water vapor S generated from the inner peripheral surface of the hollow portion 7 is further heated by heat transfer contact with the heating element 8. The water vapor S in the hollow portion 7 has a temperature of 100 ° C. or higher.

  In general, when a hot object is brought close to a hydrous porous body, rapid vaporization of water occurs on the surface of the porous body, and when the water on the surface of the porous body is reduced by evaporation, the capillary force of the porous body It is known that water is automatically supplied to the surface of the porous body due to the above, and that the surface of the porous body does not easily drain. The vaporizer 2 applies such a principle and intends to enable rapid start-up of the apparatus, instantaneous saturated steam (or superheated steam) generation, and rapid supply of superheated steam. The vaporizer 2 generates saturated water vapor in about 7 seconds after the start of the device, as is apparent from the operation test results described later. This time can be further shortened by optimizing the structure and setting the power supply amount.

  As shown in FIG. 2, the water vapor S in the hollow portion 7 flows into the water vapor flow path 10 of the auxiliary heating device 4 through the water vapor delivery pipe 3 and is in heat transfer contact with the heat generating body 11 for auxiliary heating. 11 heat is received and further heated. The steam S after heating is sent to the steam feed pipe 12 from the steam channel 10 as superheated steam having a temperature of about 300 ° C.

  4A is a cross-sectional view taken along the line II of FIG. 3, and FIG. 4B is a partially enlarged cross-sectional view of FIG. 4A.

  The porous body 6 is made of a ceramic molded body having a large number of communicating voids, and has heat resistance and electrical insulation. A large number of pores 30 formed in the porous body 6 by the communicating voids are schematically shown in FIG. The pores 30 are in contact with the water (liquid bath W) in the liquid tank 5 at the lower part of the porous body 6, and the water is sucked into the pores 30 by capillary action. The pore 30 opens at the inner wall surface 6 a of the hollow portion 7, and the opening 31 of the pore 30 is close to the surface of the heating element 8.

  FIG. 5 is an enlarged view of a portion “a” shown in FIG.

  The water in the pores 30 is bent by the surface tension at the opening 31 to form a meniscus M. The meniscus M is formed as a thin water film all around the opening 31. The heat H of the heating element 8 conducted from the heating element 8 to the porous body 6 is transferred to the water of the meniscus M and heats the water of the meniscus M. The water of the meniscus M is also heated by the radiant heat of the heating element 8. Since the meniscus M is a minute mass of water or a thin water film located at the edge of the outlet of the pore 30, the heat capacity is extremely small, and the water of the meniscus M is instantly vaporized by the heat of the heating element 8. The water vapor S generated by the vaporization of the water of the meniscus M flows along the surface of the heating element 8, exchanges heat with the surface of the heating element 8, and further receives the heat of the heating element 8.

  The steam S generated in the hollow part 7 flows in the hollow part 7 and flows out to the steam delivery pipe 3 (FIG. 1) as described above. On the other hand, the water sucked up by the pores 30 from the liquid bath W as shown by arrows in FIG. 4B is supplied from the outer surface (outer side surface) of the porous body 6 to the openings of the pores 30. Therefore, the water vapor S generated from the inner wall surface 6 a does not hinder the flow of water supplied toward the opening 31. That is, the inner wall surface 6a of the porous body 6 constituting the water vapor generating surface and the liquid bath W for supplying water to the inner wall surface 6a are located on the opposite side with respect to the porous body 6 (that is, separated from each other). ), Since the flow directions of water and water vapor are set to be substantially the same direction, the water in the liquid bath W is smoothly supplied to the opening 31, and the meniscus M is always formed in the opening 31. Thus, the water vapor S is continuously generated in the hollow portion 7 under the capillary water supply action of the porous body 6.

  Moreover, the heat H transmitted to the porous body 6 is thermally conducted outward in the radial direction of the inner wall surface 6 a and is transferred to the water sucked up by the pores 30. Therefore, the water supply is preheated before being supplied to the opening 31, and the temperature rise of the porous body 6 is suppressed.

  FIG. 6 is a diagram showing an operation test result of the steam generator 1 shown in FIG.

  The inventor opened the end of the water vapor feed pipe 12 to the atmosphere, inserted a thermocouple 40 into the water vapor feed pipe 12 as shown in FIG. 2, and measured the temperature of the water vapor S by the measuring instrument 41. The porous body 6 and the main body 9 used in the operation test are each formed with a circular hollow portion 7 having a diameter of 9 mm and a water vapor channel 10, and the lower portion of the porous body 6 has a water bath W of about 1 mm. Soaked in

  Further, in the operation test, a rectangular parallelepiped ceramic porous body having a height of about 3 cm was adopted as the porous body 6. In such a porous body 6, it was observed that the upper surface of the porous body 6 located at a height of about 3 cm from the water surface was naturally wetted or wetted by water. This means that the water sucked up by the capillary force of the porous body 6 rises beyond the height of the hollow portion 7 and reaches the entire inner peripheral wall surface (inner wall surface 6a) of the hollow portion 7. That is, the dimensions (in particular, the height) of the porous body 6 are set in relation to the capillary force unique to the porous body so that the water of the liquid bath W can be supplied to the entire inner peripheral wall surface of the hollow portion 7. It is desirable.

  The temperature measurement result of the measuring instrument 41 is shown in FIG. The horizontal axis in FIG. 6 indicates the elapsed time after the activation of the water vapor generator 1, and the vertical axis in FIG. 6 indicates the water vapor temperature measured by the measuring instrument 41.

  In the operation test, 350 W of electric power was supplied from the current supply device 20 to the heating element 8, and the heating element 11 was energized by the current supply device 20 to heat the heating element 11. As shown in FIG. 6, the steam generator 1 generated saturated steam at 100 ° C. after about 7 seconds from startup, and generated superheated steam at about 300 ° C. after about 20 seconds from startup. When about 60 seconds passed after the start-up, power supply from the power supply device 20 to the heating elements 8 and 11 was stopped, and when the heating of the heating elements 8 and 11 was stopped, the water vapor temperature rapidly decreased.

  As is apparent from the operation test results, the steam generator 1 generates superheated steam in a short time after startup under a steep steam generating action, and immediately after the heating elements 8 and 11 stop heating, saturated steam and superheat. Stop the generation of water vapor. That is, the steam generator 1 is extremely excellent in responsiveness and controllability.

  As described above, according to the steam generator 1 having the above-described configuration, the time from the start of heating to the generation of steam can be shortened without impairing the function of the porous body 6 that sucks water from the liquid bath W. In addition, due to the capillary water supply action of the porous body 6, overdrying or overheating of the porous body 6 and the heating element 8 can be prevented.

  Therefore, according to the steam generator 1, it is possible to generate saturated steam or superheated steam almost instantaneously and to stop the supply of saturated steam or superheated steam almost instantaneously.

  Moreover, since the water vapor generating device 1 supplies water to the water vapor generating surface by the capillary force of the porous body, a pumping device such as a water supply pump is not required.

  Furthermore, since the water vapor generating device 1 is configured to generate water vapor by vaporizing water on the surface of the porous body, noise during boiling (water boiling action is used by appropriately setting the pore diameter and the like. The noise at the time of boiling as occurs in the case of a steam generator is considerably reduced.

  Moreover, the water vapor generator 1 has a structure that can be designed extremely simply and in a small size. This also makes it possible to reduce the cost of the apparatus, which is extremely advantageous from a practical viewpoint.

  FIG. 7 is a perspective view schematically showing the configuration of the steam generator according to the second embodiment of the present invention, and FIG. 8 is a longitudinal sectional view of the steam generator shown in FIG. 7 and 8, substantially the same components as those of the first embodiment are given the same reference numerals.

  The steam generator 1 of the present embodiment is a further development of the steam generator of the first embodiment, and the steam generator of the first embodiment provides additional heating means (auxiliary heating device 4). On the other hand, the steam generator 1 of the present embodiment does not include such additional heating means, and has a configuration in which superheated steam is generated directly by the vaporizer 2. That is, the water vapor generator 1 has a vaporizer 2, a water vapor delivery pipe 3, a liquid tank 5, a porous body 6, and a coiled heating element 8, and a downstream end (not shown) of the water vapor delivery pipe 3 is connected to the system. Connected to an external device (not shown) to supply superheated steam to the device, or discharge superheated steam into the external device. A lead wire 15 is connected to the heating element 8, an energization wiring 21 of a current supply device 20 is connected to a terminal 16 of the lead wire 15, and the current supply device 20 is connected to an AC power supply 23 via a feeder line 22. Connected. A water supply device 25 is provided in the water vapor generator 1 in association with the liquid tank 5 of the vaporizer 2. A water supply device 25 including a water supply pipe 26, a water purification device 27, and a supply pipe 28 supplies water that has undergone water purification into the liquid tank 5. The lower part of the porous body 6 is immersed in the liquid bath W of the liquid tank 5.

  The hollow part 7 of the vaporizer 2 forms a circular cross-section water vapor channel having a uniform diameter over the entire length in the porous body 6 as in the first embodiment. According to the inventor's experiment, by configuring the heating element so that the heat capacity of the heating element 8 in contact with the porous body 6 is reduced as much as possible and a high heat flux can be obtained with a small electric power, It has been found that superheated steam can be generated from water at room temperature in a short time and efficiently.

  9 is a transverse sectional view of the porous body 6 used in the experiment, and FIG. 10 is a partially enlarged sectional view of the hollow portion 7 shown in FIG. FIG. 11 is a diagram showing experimental results regarding the temperature and generation time of superheated steam, and FIG. 12 is a diagram showing the relationship between the heating amount of the heating element 8 and the energy conversion efficiency.

The porous body 6 shown in FIG. 9 is a commercially available heat-resistant insulating brick having dimensions of 50 mm width × 50 mm height × 120 mm length (model B5, product of Isolite, main component: SiO ₂ 55%, Al ₂ O ₃ 41 %, Effective thermal conductivity: 0.33 [W / (m · K)]), and has physical properties of average pore diameter = 9 μm, mode diameter = 90.6 μm, porosity = 62.3%. A hollow portion 7 having a diameter D = 8 mm was formed in the porous body 6 as a through hole at the center of the cross section (50 mm × 50 mm) shown in FIG. A Kanthal wire having a diameter d (L1) = 0.35 mm and a length of 1.1 m was spirally disposed in the hollow portion 7 as a heating element 8. As shown in FIG. 10 (A), the Kanthal line was disposed so as to be in close contact with the inner wall surface 6a. The pitch interval L2 of the Kanthal line was set to about 2.5 mm, and the number of turns of the Kanthal line was set to about 40 turns. One end of the hollow portion 7 was closed with a silicon rubber stopper, and distilled water was supplied to the liquid tank 5 to prepare a room temperature liquid bath W in which the porous body 6 can be immersed. The lower part of the porous body 6 was immersed in the liquid bath W. The water depth of the lower surface of the porous body 6 was set to about 3 mm. An alternating current was applied to the cantal wire (heating element 8), and the heating element 8 generated heat.

  The surface temperature of the heating element 8 reached 100 ° C. or higher in a short time after heating was started. When 300 W (100 V × 3 A) was supplied, the surface temperature of the heating element 8 rose from 25 ° C. (room temperature) to 100 ° C. in about 0.1 seconds. 100 W, 200 W, and 300 W of electric power were gradually supplied to the heating element 8, and the temperature and amount of water vapor flowing out of the hollow portion 7 were measured. In the measurement, a thermocouple (not shown) is arranged in a measurement pipe line (not shown) connected to the outlet of the hollow portion 7, a condenser or a cooler (not shown), and a graduated cylinder (not shown). Was placed downstream of the thermocouple. Note that the position of the thermocouple is set in a measurement pipe line separated by a distance of 30 mm from the outlet of the hollow part 7 to the downstream side, and the amount of water vapor generated is the condensed water obtained by continuous operation for 20 minutes. Was measured by measuring with a graduated cylinder.

  As shown in FIG. 11, when power of 100 W (J / s) is supplied to the heating element 8, saturated water vapor is generated in the hollow portion 7 after about 20 seconds, and the saturated water vapor is continuously generated in the hollow portion 7. Generated. When power of 200 W was supplied to the heating element 8, superheated steam at 300 ° C. or higher was generated in the hollow portion 7 after about 40 seconds had elapsed. When 300 W of electric power was supplied to the heating element 8, superheated steam at 300 ° C. or higher was generated in the hollow portion 7 after about 19 seconds had elapsed. In addition, when power of 200 W or 300 W is supplied to the heating element 8, the temperature in the pipe line reaches 100 ° C. in a few seconds, and after the temperature of 100 ° C. is temporarily maintained, the temperature rapidly rises. It was.

  In consideration of the fact that the temperature of the measurement pipe is initially room temperature and the water vapor generated in the hollow portion 7 is initially condensed in the measurement pipe, the measured value of the thermocouple is slightly delayed. It is considered that the water vapor temperature of the hollow portion 7 actually reaches a high temperature earlier than the measured value.

  In addition, when power of 200 W or 300 W was supplied to the heating element 8, when the power supply was stopped, the temperature of the water vapor dropped rapidly. However, in the measurement result shown in FIG. 11, the water vapor temperature has not dropped to room temperature after the heating of the heating element 8 is stopped. This is considered to be due to the fact that the measurement pipeline is heated by the superheated steam, and that the steam in the measurement pipeline is affected.

  Thus, the steam generator 1 of this embodiment generates superheated steam quickly and efficiently only by the porous body 6 and the heating element 8 without using an auxiliary heating means. Moreover, the steam generator 1 can generate superheated steam very quickly after the heating element 8 generates heat, and the temperature drops very quickly after the heating element 8 stops generating heat. That is, the steam generator 1 is extremely excellent in controllability and responsiveness.

  FIG. 12 shows the relationship between the energy conversion efficiency η and the bottom surface temperature of the porous body 6. The energy conversion efficiency η was obtained by the following equation.

Energy conversion efficiency η = Q / P
Q = m ・ C _pl (T _sat -T _in ) + m ・ h _fg + m ・ C _pv (T _v -T _sat )
P = V × I
here,
m: Steam generation rate [kg / s]
T _sat : Saturation temperature [K]
T _in : Temperature of the lower surface of the porous body [K]
T _v : Water vapor temperature [K] 30mm downstream from the porous hollow section outlet
C _pl : Constant-pressure specific heat of water at (T _sat + T _in ) / 2 [J / (kg ・ K)]
C _pv : Specific pressure specific heat of water vapor at (T _sat + T _v ) / 2 [J / (kg · K)]
h _fg : latent heat of vaporization [J / kg]
I: Current [A]
V: Voltage [V]

When the power supplied to the heating element 8 was increased stepwise from 100 W to 300 W, the energy conversion efficiency η increased as shown in FIG. 12, and the maximum value of the energy conversion efficiency η reached 0.89. On the other hand, the bottom surface temperature T _in of the porous body 6, showed a tendency to decrease with an increase of power feeding to the heating element 8. This is because the direction of heat release by heat conduction (direction indicated by solid line arrows in FIG. 9) and the direction of liquid (water) supply to the evaporation surface by capillary force of the porous body 6 (direction indicated by broken line arrows in FIG. 9). Is the reverse direction, and is caused by the fact that a part of the heat transferred to the inside of the porous body 6 by heat conduction is consumed for preheating water toward the evaporation surface. That is, as the amount of heat generated by the heating element 8 increases, the flow rate of water that flows into the evaporation surface increases, so that the capillary force is greater than the heat conduction effect of the heat directed radially outward of the hollow portion 7. outperform the sensible heat transport effect of the water supplied to the evaporation surface by this result, it is considered that the energy conversion efficiency η bottom temperature T _in of the porous body 6 is relatively lowered is increased.

  Therefore, the steam generator 1 of the present embodiment generates the superheated steam in the hollow portion 7 by using the heat generated by the heating element 8 very efficiently and rationally.

  FIGS. 9B and 9C schematically show the principle of superheated steam generation in the steam generator 1.

  When the heating element 8 is energized, the surface temperature of the heating element 8 reaches 500 ° C. or higher, for example, 700 ° C. The heat generated by the heating element 8 is transferred mainly from the contact portion between the heating element 8 and the inner wall surface 6a to the porous body 6, and as a result, as shown in FIG. Steep evaporation of water W occurs in the liquid film portion of the meniscus formed. When a material having a relatively low thermal conductivity is adopted as the porous body 6, the heat transfer action to the inside of the porous body is suppressed, and therefore the time until the vaporization of the water W can be shortened. Conceivable.

  When the total heat generated by the heating element 8 is transferred to the water W and consumed as the heat of vaporization of the water W, the amount of water vapor generated increases, but the heat generated by the heating element 8 is unlikely to contribute as desired to the increase in water vapor temperature. . However, in the water vapor generator 1, when the vaporization of the water W starts, a vapor layer is formed in the pores 30 in the inner wall surface 6a in contact with the heating element 8 and in the vicinity thereof, and the inner wall surface 6a is locally localized. Dry. In the pores 30 in the vicinity of the heating element 8, the liquid level of the water W recedes from the outlet opening of the pores 30 into the pores 30 as shown in FIG. As a result, the heat generation of the heating element 8 acts to superheat the water vapor S generated in the pores 30. That is, when the water vapor S generated in the pores 30 flows out of the pores 30 and flows in the hollow portion 7, the water vapor S flows in the vicinity of the heating element 8, Due to the convective heat transfer action in the region near the surface of the heating element 8, it is rapidly heated. Thus, superheated steam is generated in the hollow portion 7 and supplied from the hollow portion 7 to a device outside the system.

Thus, in order to locally heat the inner wall surface 6a and superheat the water vapor S generated in the pores 30, it is considered that the heating element 8 needs to generate a very high heat flux locally. Assuming that the contact area between the inner wall surface 6a and the heating element 8 is 1/5 of the surface area of the heating element, it is assumed that all the heat is transferred to the porous body 6 through the contact portion between the inner wall surface 6a and the heating element 8. Then, when 300 W of electric power is supplied to the heating element 8, the heat flux at the contact portion is about 1.3 MW / m ² in calculation. Preferably, the heating element 8 is configured such that a heat flux of 1 MW / m ² or more is obtained at the contact portion between the inner wall surface 6a and the heating element 8, or the average heat flux value of the entire surface of the heating element 8 is 200 kW. Set to / m ² or higher.

  Further, since the heating element 8 is arranged not to uniformly heat the entire inner wall surface 6a but to locally heat the inner wall surface 6a at an interval, vaporization of the water W and overheating of the steam S Are appropriately balanced, and superheated steam is constantly generated in the hollow portion 7. The ratio between the wire diameter L1 of the heating element 8 (FIG. 9A) and the interval L2 between the heating elements 8 (FIG. 9A) is set in the range of 1/3 to 1/10, for example.

  On the inner wall surface 6a, an inner wall surface zone near the dried heating element 8 and an inner wall surface zone between the wet heating elements 8 are formed by local heating of the inner wall surface 6a. By forming the drying zone at an interval, three-dimensional movement of the water W to the vicinity of the heating element 8 occurs, and the entire porous body 6 is prevented from being dried, so that the water W is smooth by capillary action. In the vicinity of the heating element 8 is replenished.

  As described above, according to the steam generator 1 having the above-described configuration, the superheated steam can be constantly generated by the simple configuration including the porous body 6 and the heating element 8. Moreover, the generation of superheated steam starts almost simultaneously with the start of heat generation of the heating element 8 and ends almost simultaneously with the stop of heat generation of the heating element 8. That is, in the conventional cooker using superheated steam, the preheating time or preparation time for generating superheated steam required a long time more than enough, whereas according to the steam generator of the present invention, It is possible to start supplying superheated steam in a short time of several seconds to several tens of seconds. Moreover, since the generation of superheated steam quickly responds to the start and stop of heat generation of the heating element 8, the water vapor generating device 1 exhibits extremely excellent controllability and responsiveness. Therefore, the water vapor generating apparatus of the present invention is extremely advantageous practically from the viewpoint of controllability and responsiveness.

  Moreover, since the steam generator 1 exhibits extremely high energy conversion efficiency, input energy such as heating element operating power can be used very effectively.

  Furthermore, since the water vapor generator 1 supplies water to the water vapor generation surface by the capillary force of the porous body, a pressure feed device such as a water feed pump is not required, and the problem of boiling noise is solved.

  In addition, since the steam generator 1 of the present embodiment does not include auxiliary heating means (heating device 4) unlike the steam generator of the first embodiment, it is simpler and more compact than the steam generator of the first embodiment. Can be designed to

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

  For example, the pore diameter of the porous body, the cross-sectional dimension of the hollow portion, the number of locations of the hollow portion, and the like can be appropriately changed. Further, as the porous body, a material having heat resistance and electrical insulation and which is not deteriorated or decomposed by the heat of the heating element can be appropriately employed.

  ADVANTAGE OF THE INVENTION According to this invention, it has the small and cheap structure which can be employ | adopted in the various apparatuses using water vapor | steam, Furthermore, the water vapor | steam generator and the water vapor | steam generation method which generate superheated water vapor | steam very rapidly are provided. In particular, the water vapor generating apparatus and water vapor generating method of the present invention can be suitably used in household or industrial equipment using superheated water vapor, such as household cooking appliances, steamers, sterilizers, and dryers. . When the present invention is applied to such a device, the present invention is very advantageous because it allows a water vapor generating mechanism to be reduced in size and price. Further, since the configuration of the present invention can be applied to a steam generating means for vaporizing liquid fuel or the like, its practical effect is remarkable.

It is a perspective view showing roughly an example of a steam generator to which the present invention is applied. It is a longitudinal cross-sectional view of the water vapor generator shown in FIG. It is a cross-sectional view of the water vapor generator shown in FIG. 4A is a cross-sectional view taken along the line II of FIG. 3, and FIG. 4B is a partially enlarged cross-sectional view of FIG. 4A. FIG. 5 is an enlarged view of a “a” portion shown in FIG. It is a diagram which shows the operation test result of the water vapor generator shown in FIGS. It is a perspective view which shows roughly the structure of the water vapor generating apparatus which concerns on 2nd Example of this invention. It is a longitudinal cross-sectional view of the water vapor generator shown in FIG. It is a cross-sectional view of the porous body and heating element used for the superheated steam generation test. It is a partial expanded sectional view of the hollow part shown in FIG. It is a diagram which shows the experimental result regarding the temperature and generation | occurrence | production time of superheated steam. It is a diagram which shows the relationship between the heating amount of a heat generating body, and energy conversion efficiency. It is sectional drawing which shows roughly the structure of the conventional water vapor generating apparatus using a porous body and a heat generating body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steam generator 2 Vaporizer 3 Steam delivery pipe 5 Liquid tank 6 Porous body 6a Inner wall surface 7 Hollow part 7a Downstream end (steam delivery port)
8 Heating element 20 Current supply device 30 Fine pore 31 Opening portion W Liquid bath M Meniscus

Claims (12)

In a water vapor generating apparatus comprising: a porous body partially immersed in a liquid bath; and a heating element that generates water vapor by heating water in the liquid bath supplied by capillary action of the porous body,
A hollow portion formed in the porous body;
Water vapor delivery means for delivering the water vapor generated in the hollow part out of the porous body from the hollow part,
The outlet portion of the pore of the porous body is located on the inner wall surface of the hollow portion,
The heating element is in contact with or close to the inner wall surface of the hollow portion so as to vaporize the water in the outlet portion and superheat the water vapor generated in the pore. A steam generator characterized by extending.   The steam generator according to claim 1, further comprising a steam heater for further heating the superheated steam, wherein the steam heater is communicated with the hollow portion via the steam delivery means.   2. The inner wall surface in the vicinity of the heating element is formed with a dry zone whose surface is dried by the heat of the heating element, and a wet inner wall surface zone is formed between the drying zones. Or the water vapor generator according to 2. The steam generator according to claim 3, wherein a heat flux at a contact portion between the inner wall surface and the heating element is set to 1 MW / m ² or more.   The hollow portion has a circular cross section, and the heating element is formed of a coil-shaped electric heating element in contact with or close to the inner peripheral surface of the hollow portion and having an axial core oriented in the axial direction of the hollow portion. The water vapor generator according to any one of claims 1 to 4. In a water vapor generating method of supplying water to a heating element by capillary action of a porous body partially immersed in a liquid bath, and generating water vapor by the heat of the heating element,
The heating element that contacts or is close to the inner wall surface of the hollow portion formed in the porous body and extends along the inner wall surface of the pore outlet portion of the porous body located on the inner wall surface of the hollow portion. Heat the water,
The water of the meniscus part of the outlet part is evaporated by the heat of the heating element to generate water vapor at the outlet part of the pores and superheat the water vapor generated in the pores,
A method for generating water vapor, characterized in that superheated water vapor is sent out from the hollow portion to the outside of the porous body.   The steam generation method according to claim 6, wherein the superheated steam generated in the hollow portion is further heated to generate high-temperature superheated steam.   The method for generating water vapor according to claim 6, wherein a drying zone is formed on an inner wall surface in the vicinity of the heating element by heat of the heating element, and a wet inner wall zone is formed between the drying zones. The water vapor generation method according to claim 8, wherein a heat flux at a contact portion between the inner wall surface and the heating element is set to 1 MW / m ² or more.   The steam generation method according to claim 8 or 9, wherein superheated steam having a temperature of 200 ° C or higher is generated in the hollow portion within 1 minute after the heat generation of the heating element is started. A porous body partially immersed in a liquid bath;
A heating element for heating the liquid in the liquid bath supplied by the capillary action of the porous body to generate steam;
A hollow portion formed in the porous body;
Vapor delivery means for delivering the vapor generated in the hollow part out of the porous body from the hollow part,
The outlet portion of the pore of the porous body is located on the inner wall surface of the hollow portion,
The heating element is in contact with or close to the inner wall surface of the hollow portion and along the inner wall surface so as to vaporize the liquid in the outlet portion in the pores and superheat the vapor generated in the pores. The steam generator characterized by extending. Supplying the liquid bath liquid to the heating element by capillary action of the porous body partially immersed in the liquid bath;
The heating element that contacts or is close to the inner wall surface of the hollow portion formed in the porous body and extends along the inner wall surface of the pore outlet portion of the porous body located on the inner wall surface of the hollow portion. Heating the liquid,
Vaporizing the liquid in the meniscus portion of the outlet portion by the heat of the heating element to generate steam at the outlet portion of the pores and superheating the steam generated in the pores;
A method for generating steam, characterized in that superheated steam is sent out of the porous body from the hollow portion.

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