U.S. patent application number 09/026040 was filed with the patent office on 2001-09-06 for heating apparatus.
Invention is credited to KONDOH, SHINJI, OBATA, TETSUO, OMORI, HIDEKI, SADAHIRA, MASAFUMI, UETANI, YOUJI, URATA, TAKAYUKI, YAMASHITA, HIDEKAZU.
Application Number | 20010019052 09/026040 |
Document ID | / |
Family ID | 26481996 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019052 |
Kind Code |
A1 |
SADAHIRA, MASAFUMI ; et
al. |
September 6, 2001 |
HEATING APPARATUS
Abstract
A heating apparatus includes a heating element having a
conductor, at least a part of which is an electrically closed
circuit along which an eddy current flows; a container for
accommodating the heating element; a magnetic field induction
section for induction-heating the heating element; and a high
frequency power supply device for supplying high frequency power to
the magnetic field induction section. The heating element is
induction-heated by an AC magnetic field generated by the magnetic
field induction section.
Inventors: |
SADAHIRA, MASAFUMI; (OSAKA,
JP) ; UETANI, YOUJI; (HYOGO, JP) ; KONDOH,
SHINJI; (OSAKA, JP) ; YAMASHITA, HIDEKAZU;
(OSAKA, JP) ; OMORI, HIDEKI; (HYOGO, JP) ;
OBATA, TETSUO; (OSAKA, JP) ; URATA, TAKAYUKI;
(HYOGO, JP) |
Correspondence
Address: |
PAUL F PRESTIA
RATNER & PRESTIA
SUITE 301 ONE WESTLAKES
BERWYN P O BOX 980
VALLEY FORGE
PA
194820980
|
Family ID: |
26481996 |
Appl. No.: |
09/026040 |
Filed: |
February 19, 1998 |
Current U.S.
Class: |
219/629 ;
219/672 |
Current CPC
Class: |
B01J 2208/00008
20130101; H05B 6/36 20130101; H05B 6/108 20130101 |
Class at
Publication: |
219/629 ;
219/672 |
International
Class: |
H05B 006/10; H05B
006/40 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 1997 |
JP |
9-153351 |
Nov 27, 1997 |
JP |
9-325742 |
Claims
What is claimed is:
1. A heating apparatus, comprising: a heating element having a
conductor, at least a part of which is an electrically closed
circuit along which an eddy current flows; a container for
accommodating the heating element; a magnetic field induction
section for induction-heating the heating element; and a high
frequency power supply device for supplying high frequency power to
the magnetic field induction section, wherein the heating element
is induction-heated by an AC magnetic field generated by the
magnetic field induction section.
2. A heating apparatus according to claim 1, wherein the conductor
of the heating element has a total thickness which is suitable for
generating an electromotive force to cause the eddy current to flow
along the closed circuit.
3. A heating apparatus according to claim 1, wherein the conductor
of the heating element is wound in one of a circumferential state
and a spiral state.
4. A heating apparatus according to claim 1, wherein the heating
element includes a plurality of non-magnetic metal bodies arranged
concentrically.
5. A heating apparatus according to claim 1, wherein the heating
element includes at least one non-magnetic metal body and at least
one magnetic metal body provided inside the at least one
non-magnetic metal body, the metal bodies being concentrically
provided.
6. A heating apparatus according to claim 1, comprising a plurality
of heating elements arranged in the container.
7. A heating apparatus according to claim 1, wherein the conductor
of the heating element is processed to be wavelike.
8. A heating apparatus according to claim 1, further comprising an
adsorbent provided in a gap between overlapping parts of the
conductor.
9. A heating apparatus according to claim 1, further comprising a
water-adsorbing material provided in a gap between overlapping
parts of the conductor.
10. A heating apparatus according to claim 1, further comprising a
material having a moisture maintenance capability provided in a gap
between overlapping parts of the conductor.
11. A heating apparatus according to claim 1, further comprising a
catalyst on the conductor.
12. A heating apparatus according to claim 1, wherein the conductor
has a hole.
13. A heating apparatus according to claim 12, wherein the
conductor has a wing in the vicinity of the hole for transferring a
fluid from one surface of the conductor to another surface of the
conductor.
14. A heating apparatus according to claim 1, wherein the conductor
is porous.
15. A heating apparatus according to claim 1, wherein the container
allows a fluid to pass through a part of the container involved in
heat exchange.
16. A heating apparatus according to claim 1, wherein the heating
element has a closed circuit which is disconnected when the heating
element reaches a prescribed temperature.
17. A heating apparatus according to claim 1, wherein the conductor
is formed of a material having a thermal dependent resistance.
18. A heating apparatus according to claim 1, wherein the conductor
is formed of a material memorizing a prescribed shape and
recoverable to the prescribed shape in accordance with a
temperature.
19. A heating apparatus according to claim 1, further comprising a
spring for restricting a shape change of the conductor.
20. A heating apparatus according to claim 1, wherein the magnetic
field induction section includes a coil provided on an outer
surface of the container, the coil having a greater number of
windings per unit length in an area in the vicinity of an end of
the coil than an area at a center of the coil.
21. A heating apparatus according to claim 1, wherein the magnetic
field induction section includes a coil having two ends provided on
an outer surface of the container, the coil having a greater number
of windings per unit length in an area in the vicinity of one end
of the coil than in an area in the vicinity of another end of the
coil.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heating apparatus for
heating a gas, a liquid, a solid and the like.
[0003] 2. Description of the Related Art
[0004] Conventionally, heating systems for heating by gas, such as
instantaneous water heaters, have been used in order to rapidly
raise the temperature of a liquid. In order to heat a solid, metal
sheathed tubular elements have been used, for example.
[0005] When water is rapidly heated by a conventional instantaneous
water heater, the temperature of a heat transfer surface to water
exceeds a boiling point due to an excessive calory density. Thus,
local boiling is easy to generate, which results in poor
safety.
[0006] In order to avoid local boiling, a heat exchange area needs
to be increased, but an increased heat exchange area enlarges the
heating apparatus because of the structure of the combustion
section.
[0007] Moreover, heating by gas, which is performed from outside a
pipe through which water flows, has a low thermal efficiency.
[0008] In the case of an electric water heater, a local abnormal
temperature rise is easily generated due to an excessive
electricity density. This type of water heater also has problems of
a low level of safety at the time of boiling and disconnection of
the heater. Accordingly, the electric water heater is not suitable
to boil water to a temperature close to a boiling point.
[0009] In the case where a solid having poor thermal transfer is
heated by metal sheathed tubular elements, the temperature is
excessively raised only in a portion opposed to the metal sheathed
tubular elements, which acts as a heat source.
[0010] In the case where the heat exchange surface is increased in
order to avoid generation of local heating, the heating apparatus
is enlarged and also the heat capacity of the heater is increased.
Thus, the temperature response is deteriorated.
[0011] In a heating apparatus for heating and thus recovering an
adsorbent such as active carbon or zeolite, it is necessary to
increase the heat exchange area so as to increase the surface to
contact the adsorbent. When a conventional electric heater is used,
the heating apparatus is enlarged and the recovering efficiency is
low due to the non-uniform temperature of the electric heater.
[0012] In a conventional heating apparatus for heating water to
generator vapor, the rise is slow and the energy efficiency is low
since the water in the reservoir is heated. In a structure in which
vapor is instantaneously generated, the heat exchange area needs to
be increased, and thus the heating apparatus is enlarged.
[0013] When a conventional electric heater is used in a heating
apparatus for purifying the air using a catalyst, the effective
reaction area cannot be increased due to a limit in the thermal
transfer in the carrier (catalyst). Accordingly, the purifying
capability is low.
[0014] Furthermore, a conventional heating apparatus requires a
thermostat and a temperature fuse to be installed in the vicinity
of the heat source, resulting in a complicated structure of the
heating apparatus.
[0015] A conventional electric water heater further has the problem
in that scale is accumulated on the surface of the heater and thus
abnormal heating disconnects a part of the electric heater to which
the scale adheres.
SUMMARY OF THE INVENTION
[0016] A heating apparatus according to the present invention
includes a heating element having a conductor, at least a part of
which is an electrically closed circuit along which an eddy current
flows; a container for accommodating the heating element; a
magnetic field induction section for induction-heating the heating
element; and a high frequency power supply device for supplying
high frequency power to the magnetic field induction section. The
heating element is induction-heated by an AC magnetic field
generated by the magnetic field induction section.
[0017] In one embodiment of the invention, the conductor of the
heating element has a total thickness which is suitable for
generating an electromotive force to cause the eddy current to flow
along the closed circuit. The total thickness will be defined
later.
[0018] In one embodiment of the invention, the conductor of the
heating element is wound in one of a circumferential state and a
spiral state.
[0019] In one embodiment of the invention, the heating element
includes a plurality of non-magnetic metal bodies arranged
concentrically.
[0020] In one embodiment of the invention, the heating element
includes at least one non-magnetic metal body and at least one
magnetic metal body provided inside the at least one non-magnetic
metal body, the metal bodies being concentrically provided.
[0021] In one embodiment of the invention, the heating apparatus
includes a plurality of heating elements arranged in the
container.
[0022] In one embodiment of the invention, the conductor of the
heating element is processed to be wave-like.
[0023] In one embodiment of the invention, the heating apparatus
further includes an adsorbent provided in a gap between overlapping
parts of the conductor.
[0024] In one embodiment of the invention, the heating apparatus
further includes a moisture-adsorbing material provided in a gap
between overlapping parts of the conductor.
[0025] In one embodiment of the invention, the heating apparatus
further includes a material having a moisture maintenance
capability provided in a gap between overlapping parts of the
conductor.
[0026] In one embodiment of the invention, the heating apparatus
further includes a catalyst on the conductor.
[0027] In one embodiment of the invention, the conductor has a
hole.
[0028] In one embodiment of the invention, the conductor has a wing
in the vicinity of the hole for transferring a fluid from one
surface of the conductor to another surface of the conductor.
[0029] In one embodiment of the invention, the conductor is
porous.
[0030] In one embodiment of the invention, the container allows a
fluid to pass through a part of the container involved in heat
exchange.
[0031] In one embodiment of the invention, the heating element has
a closed circuit which is disconnected when the heating element
reaches a prescribed temperature.
[0032] In one embodiment of the invention, the conductor is formed
of a material having a thermal dependent resistance.
[0033] In one embodiment of the invention, the conductor is formed
of a material memorizing a prescribed shape and recoverable to the
prescribed shape in accordance with a temperature.
[0034] In one embodiment of the invention, the heating apparatus
further includes a spring for restricting a shape change of the
conductor.
[0035] In one embodiment of the invention, the magnetic field
induction section includes a coil provided on an outer surface of
the container. The coil has a greater number of windings per unit
length in an area in the vicinity of an end of the coil than an
area at a center of the coil.
[0036] In one embodiment of the invention, the magnetic field
induction section includes a coil having two ends provided on an
outer surface of the container. The coil has a greater number of
windings per unit length in an area in the vicinity of one end of
the coil than in an area in the vicinity of another end of the
coil.
[0037] Thus, the invention described herein makes possible the
advantage of providing a heating apparatus having satisfactory
controllability and a sufficiently high thermal efficiency using a
heating element having a sufficiently large heat exchange area and
performing uniform heating.
[0038] This and other advantages of the present invention will
become apparent to those skilled in the art upon reading and
understanding the following detailed description with reference to
the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a schematic view of a heating apparatus in a first
example according to the present invention;
[0040] FIGS. 2A, 2B and 2C are respectively a top view, a side view
and a perspective view of a heating element usable in the heating
apparatus shown in FIG. 1;
[0041] FIG. 3 is a schematic view of another example of the heating
element usable in the heating apparatus shown in FIG. 1;
[0042] FIGS. 4A, 4B and 4C are top views of modifications of the
heating element in the heating apparatus shown in FIG. 1;
[0043] FIG. 5 is a schematic view of a modification of the heating
apparatus shown in FIG. 1;
[0044] FIGS. 6A and 6B are respectively a top view and a side view
of a heating element of a heating apparatus in a second example
according to the present invention;
[0045] FIGS. 7A and 7B are respectively a top view and a side view
of a heating element of a heating apparatus in a third example
according to the present invention;
[0046] FIG. 8 is a view illustrating a magnetic flux distribution
in the heating apparatus in the third example;
[0047] FIG. 9 is a plan view of a plurality of heating elements
included in a heating apparatus in a fourth example according to
the present invention;
[0048] FIG. 10 is a perspective view of a heating element of a
heating apparatus in a fifth example according to the present
invention;
[0049] FIG. 11 is a perspective view of a heating element of a
heating apparatus in a sixth example according to the present
invention;
[0050] FIG. 12 is a view showing the relationship between the
temperature increase and the distance of an active carbon from
metal sheathed tubular elements;
[0051] FIG. 13 is a perspective view of a heating element of a
heating apparatus in a seventh example according to the present
invention;
[0052] FIG. 14 is a perspective view of a heating element of a
heating apparatus in an eighth example according to the present
invention;
[0053] FIG. 15 is a perspective view of a heating element of a
heating apparatus in a ninth example according to the present
invention.
[0054] FIG. 16A is an enlarged view of a conductor of a heating
element of a heating apparatus in a tenth example according to the
present invention;
[0055] FIG. 16B is a schematic view of the heating element and an
induction coil of the heating element in the tenth example;
[0056] FIG. 16C is a partial enlarged view of the heating element
shown in FIG. 16B;
[0057] FIG. 17 is a perspective view of a heating element of a
heating apparatus in an eleventh example according to the present
invention;
[0058] FIG. 18A is a schematic view of a heating apparatus in a
twelfth example according to the present invention;
[0059] FIG. 18B is a schematic view of a heating apparatus in a
modification of the twelfth example according to the present
invention;
[0060] FIG. 19 is a perspective view of a heating element of a
heating apparatus in a thirteenth example according to the present
invention;
[0061] FIG. 20 is a perspective view of a heating element of a
heating apparatus in a fourteenth example according to the present
invention;
[0062] FIG. 21 is a graph illustrating the resistance
characteristic of a conductor of the heating element shown in FIG.
20;
[0063] FIG. 22 is a perspective view of a heating element of a
heating apparatus in a fifteenth example according to the present
invention;
[0064] FIGS. 23A and 23B are top views of the heating element shown
in FIG. 22 in two different states;
[0065] FIGS. 24A and 24B are partial schematic views of a heating
apparatus in a sixteenth example according to the present invention
in two different states;
[0066] FIG. 25 is a schematic view of a heating apparatus in a
seventeenth example according to the present invention; and
[0067] FIG. 26 is a schematic view of a heating apparatus in an
eighteenth example according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] Hereinafter, the present invention will be described by way
of illustrative examples with reference to the accompanying
drawings.
EXAMPLE 1
[0069] FIG. 1 is a schematic view of a heating apparatus 1 in a
first example according to the present invention.
[0070] As shown in FIG. 1, the heating apparatus 1 includes a
heating element 101 having a conductor formed of, for example, a
metal material. At least a part of the conductor forms an
electrically closed circuit, and an eddy current flows along the
closed circuit. The heating apparatus 1 further includes an
induction heating coil 102 for induction-heating the heating
element 101, a high frequency power supply device 103 for supplying
high frequency power to the induction heating coil 102, a fluid
transfer device 104 for transferring a fluid such as, for example,
gas, liquid or particles to the heating element 101, and a
container 105 for accommodating the heating element 101.
[0071] For example, the conductor in the heating element 101 is
formed of a stainless steel plate, the high frequency power supply
device 103 includes an inverter circuit, and the fluid transfer
device 104 includes a pump or a fan.
[0072] The heating apparatus 1 operates, for example, in the
following manner.
[0073] When heating starts by an instruction of a user, the fluid
transfer device 104 supplies a fluid to the container 105. The
fluid flows in the vicinity of the heating element 101 in the
container 105 and is discharged from the container 105. In
parallel, the high frequency power supply device 103 supplies high
frequency power to the induction heating coil 102, and thus causes
a high frequency AC magnetic field to be generated from the
induction heating coil 102. The high frequency AC magnetic field
generates an eddy current in the conductor in the heating element
101, and the eddy current and an electric resistance in the
conductor generate Joule heat in the heating element 101. The Joule
heat is transferred to the fluid in the container 105. Since the
heating element 101 is buried in the fluid at this point, the
thermal efficiency is as high as 100% in the steady state.
[0074] FIGS. 2A, 2B and 2C show an example of the heating element
101. The heating element 101 includes a stainless steel plate 201
which is circumferentially wound upon itself so as to have a
cylindrical shape and a connector 202 for connecting both of two
ends of the stainless steel plate 201 to each other. Since the
stainless steel plate 201 and the connector 202 form an
electrically closed circuit, a uniform eddy current flows in the
stainless steel plate 201 in a circumferential direction as
indicated by arrow E in FIG. 2C. As a result, the stainless steel
plate 201 generates heat uniformly. In the case where the distance
between overlapping parts of the stainless steel plate 201 is
reduced, the heating element 101 as a heat source has an increased
heat exchange area per unit volume and generates heat more
uniformly.
[0075] Next, the thickness of the conductor of the heating element
101 (the stainless steel 201 in this example) will be
described.
[0076] The magnetic flux generated by the induction heating
concentrates in a surface of the conductor in which the eddy
current flows due to a phenomenon referred to as the skin effect.
The skin depth .delta., at which the magnetic flux is (1-1/e) with
respect to the magnetic flux at the surface (e: natural logarithm)
is represented by the formula:
.delta.=(2.rho./(.omega..multidot..mu.)).sup.1/2
[0077] where .rho. represents the volumetric resistance, .omega.
represents the angular frequency, and .mu. represents the magnetic
permeability.
[0078] An electromotive force for starting the eddy current for
performing induction heating is not generated unless the magnetic
flux passes through the conductor. Therefore, the skin depth is a
criterion for performing induction heating.
[0079] Accordingly, by setting a total thickness of the overlapping
parts of the stainless steel 201 to be smaller than the skin depth,
the magnetic flux is efficiently utilized, so that an eddy current
is generated in each of the overlapping parts of the stainless
steel 201. In this specification, the expression "total thickness"
refers to a sum of thicknesses of the overlapping parts of a
conductor in a direction r in FIG. 2A.
[0080] For example, when a non-magnetic stainless steel plate
having a thickness of 0.3 mm is used for the conductor, the skin
depth is about 3 mm in the vicinity of the frequency of 20 kHz of
the high frequency AC magnetic field. Thus, the winding number of
the stainless steel plate is appropriately up to about 10.
[0081] In this example, the stainless steel plate 201, which is
circumferentially wound upon itself so as to have a cylindrical
shape, which has an appropriate thickness, and which has two ends
connected to each other by the connector 202, forms an electrically
closed circuit in the heating element 101. Thus, even when the
stainless steel plate 201 is formed of a non-magnetic stainless
steel plate, which is generally easily available, a sufficiently
large and uniform eddy current flows in the heating element
101.
[0082] FIG. 3 shows another example of the heating element 101. The
heating element 101 includes a stainless steel wire 301 which is
spirally wound and a connector 302 for connecting both of two ends
of the stainless steel wire 301 to each other. The stainless steel
wire 301 and the connector 302 form an electrically closed circuit.
In the case where the heating element 101 is enclosed by a
cylindrical solenoid having a limited length, the magnetic flux
density of the solenoid in an axial direction is low in the
vicinity of an opening of the solenoid and high in the vicinity of
a center of the solenoid. However, both ends of the stainless wire
301 are electrically connected to each other by the connector 302
in this example. Accordingly, even though the magnetic flux density
is not uniform in the axial direction of the heating element 101,
the amount of the electric current is uniform and the amount of
heat generated is the same throughout the heating element 101.
[0083] As described above, the heating apparatus 1 in the first
example according to the present invention has a sufficiently large
heat exchange area per unit volume and heats a fluid uniformly.
Even when the heating element 101 has a relatively small volume,
the liquid can be heated to a temperature close to the boiling
point, and the heat exchange efficiency is sufficiently high.
[0084] In the first example, the conductor of the heating element
101 is formed of stainless steel. The conductor can be formed of
any other material which generates an eddy current. Although the
conductor is circumferentially or spirally wound to have a
substantially circular cross section in the first example, the
conductor can also be circumferentially or spirally wound to have a
substantially rectangular (FIG. 4A), polygon (FIG. 4B) or
elliptical (FIG. 4C) cross section. The entirety of the heating
element 101 can have any shape as long as a part of the heating
element 101 forms a closed circuit.
[0085] In the first example, the induction heating coil 102 (FIG.
1) is located outside the heating element 101. Alternatively, the
induction heating coil 102 can be located inside the heating
element 101 or located above and below the heating element 101
(FIG. 5).
[0086] The fluid to be heated can be a liquid such as, for example,
water or oil, or a gas. This also applies to the following
examples.
EXAMPLE 2
[0087] FIGS. 6A and 6B are respectively a top view and a side view
of a heating element 601 of a heating apparatus in a second example
according to the present invention. The heating element 601
includes a plurality of cylindrical plates 601a formed of
non-magnetic stainless steel and located concentrically. The
plurality of cylindrical plates 601a are conductors forming closed
circuits.
[0088] The heating apparatus in the second example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 601 shown in FIGS. 6A and
6B.
[0089] The heating apparatus in the second example operates, for
example, in the following manner.
[0090] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in each cylindrical plate 601a in the heating
element 601, and the eddy current and an electric resistance in the
cylindrical plate 601a generate Joule heat in each cylindrical
plate 601a.
[0091] For the reason described in the first example, in the case
where the total thickness of the cylindrical plates 601a in a
direction r in FIG. 6A is sufficiently smaller than the skin depth
.delta., each cylindrical plate 601a efficiently generates heat and
thus uniform heat generation distribution in the heating element
601 is obtained. By increasing the number of the cylindrical plates
601a, the heat exchange area is increased.
[0092] In the second example, a simple shape and a simple structure
in which a plurality of cylindrical non-magnetic stainless steel
plates 601a are located concentrically increases the heat exchange
area per unit volume. In this example, a heating apparatus, which
can heat a liquid to a temperature close to a boiling point and has
a sufficiently high heat exchange efficiency, can be produced at a
relatively low cost.
[0093] The conductor can be formed of any other non-magnetic
material in lieu of stainless steel.
[0094] In the case where the thickness of the cylindrical plates
601a is gradually reduced from the outermost plate toward the
innermost plate, the cross-sectional areas of the inner plates are
smaller than those of the outer plates. Accordingly, the amount of
the heat generated by the inner plates is raised. This compensates
for the reduction in the heat generated by the inner plates which
is caused by the lower magnetic density in the inner plates. Thus,
the heat generation distribution becomes more uniform.
EXAMPLE 3
[0095] FIGS. 7A and 7B are respectively a top view and a side view
of a heating element 701 of a heating apparatus in a third example
according to the present invention. The heating element 701
includes a plurality of cylindrical plates 701a, 701b and 701c and
701d which are located concentrically. The plurality of cylindrical
plates 701a through 701d are conductors forming closed
circuits.
[0096] The innermost cylindrical plate 701a is formed of magnetic
stainless steel, and the other cylindrical plates 701b, 701c and
701d are formed of non-magnetic stainless steel.
[0097] The heating apparatus in the third example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 701 shown in FIGS. 7A and
7B.
[0098] The heating apparatus in the third example operates, for
example, in the following manner.
[0099] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in each of the cylindrical plates 701a through
701d in the heating element 701, and the eddy current and an
electric resistance in each of the plates 701a through 701d
generate Joule heat in each of the plates 701a through 701d.
[0100] For the reason described in the first example, in the case
where the total thickness of the cylindrical plates 701a through
701d is sufficiently smaller than the skin depth .delta., the
cylindrical plates 701a through 701d each efficiently generate heat
and thus uniform heat generation distribution in the heating
element 701 is obtained. By increasing the number of the
cylindrical plates 701a through 701d, the heat exchange area is
increased.
[0101] The eddy current caused to flow in the heating element 701
by the high frequency magnetic field generated from the induction
heating coil 102 flows in such a direction as to prevent a change
in the magnetic flux. Accordingly, a larger eddy current is
generated in a portion where more magnetic flux passes. The
magnetic permeability (which indicates how easy the magnetic flux
passes) of magnetic stainless steel is about 100 times that of
non-magnetic stainless steel. Thus, the innermost cylindrical plate
701a formed of magnetic stainless steel provides easier passage for
the magnetic flux and generates an eddy current more easily than
the other cylindrical plates.
[0102] The magnetic flux generated from the induction heating coil
102 is not parallel to the axial direction of the container 105. As
schematically shown in FIG. 8, the magnetic flux passes
elliptically or parabolically. Accordingly, the magnetic flux
crosses all the cylindrical plates 701a through 701d and thus
causes all the cylindrical plates 701a through 701d to generate
heat.
[0103] Since the innermost cylindrical plate 701a provides the
easiest passage for the magnetic flux and generates an eddy current
most easily as described above, the temperature of a central part
of the heating element 701 is higher than the rest thereof. Such a
temperature difference is specifically effective in the case where,
for example, the fluid to be heated has a high viscosity, such as,
for example, oil. Considering that the fluid passes through the
central part faster than the rest of the heating element 701, the
temperature distribution of the container 105 is uniformized by
setting the temperature of the central portion higher than the rest
of the heating element 701.
[0104] Although the heating element 701 includes four cylindrical
plates 701a through 701d, the number is not limited to this. The
cylindrical plates can be formed of any other material as long as
the inner plate or plates have a higher magnetic permeability than
that of the outer plates.
EXAMPLE 4
[0105] FIG. 9 is a plan view of a plurality of heating elements 901
included in a heating apparatus in a fourth example according to
the present invention. The heating elements 901 are arranged in
parallel in the container 105. Each of the heating elements 901 can
have any structure which at least partially contains an
electrically closed circuit along which an eddy current flows. Any
of the heating elements described in the first through third
examples is applicable to the heating element 901, as long as the
height thereof is reduced so that the plurality of heating elements
901 are accommodated in the container 105.
[0106] The heating apparatus in the fourth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating elements 901 shown in FIG. 9.
[0107] The heating apparatus in the fourth example operates, for
example, in the following manner.
[0108] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in each of the heating element 901, and the
eddy current and an electric resistance in each heating element 901
generate Joule heat in each heating element 901. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor in each heating
element is set to be smaller than the skin depth.
[0109] Although five heating elements 901 are provided in FIG. 9,
the number of heating elements 901 can be increased or decreased in
accordance with the purpose of use of the heating apparatus, so
that the heat exchange area and the amount of heat generated per
unit area are set appropriately.
[0110] For example, the heating apparatus can be used for heating
water to a temperature of up to 50.degree. C. so that the water is
used in contact with a human body such as, for example, in a
bathroom, for a shower, or in a toilet. In such a case, the number
of the heating elements 901 is decreased to reduce the volume of
the water passage, so that the temperature controllability is
raised. Thus, an easy-to-use heating apparatus is obtained.
[0111] In the case where the heating apparatus is used to heat
water to a temperature close to the boiling point, the number of
the heating elements 901 is increased to enlarge the heat exchange
area. Thus, the water is heated safely without boiling. In order to
realize a heating apparatus for receiving a higher level of input
power, the number of the heating elements 901 is further
increased.
[0112] The heating elements 901 can have any appropriate shape. The
plurality of heating elements 901 can generate different amounts of
heat.
EXAMPLE 5
[0113] FIG. 10 is a perspective view of a heating element 1001 of a
heating apparatus in a fifth example according to the present
invention. The heating element 1001 includes a conductor 1002
formed of, for example, a metal material treated to be wave-like
and circumferentially wound upon itself so as to have a cylindrical
shape, a connector 1004 for connecting both of two ends of the
conductor 1002, and an insulative sheet 1003 inserted between
overlapping parts of the conductor 1002. The conductor 1002 and the
connector 1004 form a closed circuit.
[0114] The heating apparatus in the fifth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 1001 shown in FIG. 10.
[0115] The heating apparatus in the fifth example operates, for
example, in the following manner.
[0116] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 1001, and the eddy
current and an electric resistance in the heating element 1001
generate Joule heat in the heating element 1001. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor 1002 is set to
be smaller than the skin depth.
[0117] The wave-like conductor 1002 used in the fifth example has a
larger heat exchange area per unit volume than a conductor formed
by rolling a flat plate. Thus, the heat exchange efficiency is
further enhanced. The wave-like conductor 1002 also allows a gap b
between overlapping parts of the conductor 1002 to be kept
appropriately simply by inserting the insulative sheet 1003
therebetween, without any other special device.
[0118] Alternatively, a plurality of wave-like conductors can be
arranged concentrically with an insulative sheet being inserted
therebetween.
EXAMPLE 6
[0119] FIG. 11 is a perspective view of a heating element 2001 of a
heating apparatus in a sixth example according to the present
invention. The heating element 2001 includes a stainless steel
plate 2002 which is circumferentially wound upon itself so as to
have a cylindrical shape, a connector 2003 for connecting both of
two ends of the stainless steel plate 2002, and an active carbon
1101 inserted between overlapping parts of the stainless steel
plate 2002. The stainless steel plate 2002 acts as a conductor,
which forms a closed circuit together with the connector 2003.
[0120] The heating apparatus in the sixth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 2001 shown in FIG. 11.
[0121] The heating apparatus in the sixth example operates, for
example, in the following manner.
[0122] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2001, and the eddy
current and an electric resistance in the heating element 2001
generate Joule heat in the heating element 2001. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor is set to be
smaller than the skin depth.
[0123] The heating apparatus in the sixth example can be used for
heating water. Water is caused to flow through the heating element
2001 and trihalomethane contained in the water is adsorbed by the
active carbon 1101. However, the adsorbing force (adsorbing
capability) of the active carbon 1101 rapidly decreases as the
total amount of water which has passed through the heating element
2001 increases. In order to recover the adsorbing force of the
active carbon 1101, the active carbon 1101 is heated when the total
amount of water which has passed through the heating element 2001
reaches a prescribed level. Thus, trihalomethane is released
together with vapor, and the adsorbing force of the active carbon
1101 is recovered. This is referred to as "heating recovery".
[0124] The heating recovery has the problem in that the active
carbon 1101 may undesirably heated to an excessively high
temperature and fire, when performed using conventional metal
sheathed tubular elements or the like. For example, as shown in
FIG. 12, when an active carbon piece 1202 is heated where metal
sheathed tubular elements heater 1201 exist closer to the active
carbon piece 1202, the inner temperature of the active carbon piece
1202 takes longer to increase as the distance between the active
carbon piece 1202 and the metal sheathed tubular elements 1201
increases. Thus, a large temperature gradient is generated in the
active carbon piece 1202 between a portion close to the metal
sheathed tubular elements 1201 and a portion farther from the metal
sheathed tubular elements 1201. When the input power to the metal
sheathed tubular elements 1201 is raised in order to perform the
heating recovery of the active carbon piece 1202 in a shorter time
period, only the portion of the active carbon piece 1202 in contact
with the metal sheathed tubular elements 1201 may be heated and the
temperature of such a portion may undesirably rise to the firing
point of the active carbon piece 1202.
[0125] However, in the heating apparatus in this example, the
heating area per unit volume for heating the active carbon 1101,
i.e., the contact area of the active carbon 1101 and the heating
element 2001 is sufficiently large to heat the entirety of the
active carbon 1101 substantially uniformly. Accordingly, the
entirety of the active carbon 1101 is efficiently heated to
recovery without raising the temperature of the active carbon 1101
to the firing point.
[0126] Using the heating apparatus in this example, a water
purifier by which trihalomethane can be continuously removed by the
active carbon 1101 is realized.
[0127] Although the stainless steel plate 2002 is circumferentially
wound upon itself so as to have a cylindrical shape in this
example, the stainless steel plate can also be spirally wound or
may have any shape described in the second through fifth example.
The heating procedure performing to recover the adsorbing force of
the active carbon 1101 also sterilizes the active carbon 1101.
EXAMPLE 7
[0128] FIG. 13 is a perspective view of a heating element 2201 of a
heating apparatus in a seventh example according to the present
invention. The heating element 2201 includes a stainless steel
plate 2202 which is circumferentially wound upon itself so as to
have a cylindrical shape, a connector 2203 for connecting both of
two ends of the stainless steel plate 2202, and a zeolite 1301
inserted between overlapping parts of the stainless steel plate
2202. The stainless steel plate 2202 acts as a conductor, which
forms a closed circuit together with the connector 2203.
[0129] The heating apparatus in the seventh example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 2201 shown in FIG. 13.
[0130] The heating apparatus in the seventh example operates, for
example, in the following manner.
[0131] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2201, and the eddy
current and an electric resistance in the heating element 2201
generate Joule heat in the heating element 2201. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor is set to be
smaller than the skin depth.
[0132] The heating apparatus in the seventh example can be used for
heating air. The fluid supply device 104 supplies air to the
container 105. Moisture contained in the air is adsorbed by the
zeolite 1301 and the air dried in this way is discharged from the
container 105. The heating apparatus in this example also acts as
an air dryer.
[0133] However, the adsorbing force of the zeolite 1301 is limited.
In order to recover the adsorbing force of the zeolite 1301, the
zeolite 1301 is heated to a temperature above a prescribed level by
periodically heating the heating element 2201. Thus, the adsorbed
moisture is released as a vapor. This is also referred to as
"heating recovery".
[0134] When the heating recovery is performed using conventional
metal sheathed tubular elements or the like, the following problem
occurs. When the input power to the metal sheathed tubular elements
is raised in order to perform the heating recovery of the zeolite
1301 in a shorter time period, only a portion of the zeolite in
contact with the metal sheathed tubular elements may heated to an
excessively high temperature as in the sixth example.
[0135] However, in the heating apparatus in this example, the
heating area per unit volume for heating the zeolite 1301, i.e.,
the contact area of the zeolite 1301 and the heating element 2201
is sufficiently large to heat the entirety of the zeolite 1301
substantially uniformly. Accordingly, the entirety of the zeolite
1301 is efficiently heated to recovery without raising the
temperature of the zeolite 1301 in contact with the heating element
2201 to an excessively high temperature. The zeolite 1301 is also
heated faster.
[0136] Although the stainless steel plate 2202 is circumferentially
wound upon itself so as to have a cylindrical shape in this
example, the stainless steel plate can also be spirally wound or
may have any shape described in the second through fifth
example.
EXAMPLE 8
[0137] FIG. 14 is a perspective view of a heating element 2301 of a
heating apparatus in an eighth example according to the present
invention. The heating element 2301 includes a stainless steel
plate 2302 which is circumferentially wound upon itself so as to
have a cylindrical shape, a connector 2303 for connecting both of
two ends of the stainless steel plate 2302, and a sponge 1401
having a relatively high moisture maintenance capability inserted
between overlapping parts of the stainless steel plate 2302. The
stainless steel plate 2302 acts as a conductor, which forms a
closed circuit together with the connector 2303.
[0138] The heating apparatus in the eighth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 2301 shown in FIG. 14.
[0139] The heating apparatus in the eighth example operates, for
example, in the following manner.
[0140] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2301, and the eddy
current and an electric resistance in the heating element 2301
generate Joule heat in the heating element 2301. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor is set to be
smaller than the skin depth.
[0141] The heating apparatus in the eighth example can be used for
water. The fluid supply device 104 supplies water to the container
105 in a unit of very small amount. The sponge 1401 absorbs the
water and guides the water with no directionality to the stainless
steel plate 2302. When the water touches the stainless steel plate
2302 which generates heat, the water is vaporized. Thus, the
heating apparatus in this example also acts as a vapor
generator.
[0142] In the case where the water is directly supplied to the
stainless steel plate 2302, the water becomes drops on a surface of
the stainless steel plate 2302, which reduces the contact area
between the water and the stainless steel plate 2302. The reduced
contact area deteriorates the vaporization efficiency.
[0143] However, in this example, water contacts the stainless steel
plate 2302 while being absorbed in the sponge 1401. Accordingly,
the water is put into contact with the entirety of the stainless
steel plate 2302, thus enhancing the vaporization efficiency. The
heating apparatus in this example can generate vapor in an
arbitrary direction without causing the water to drop and thus is
convenient when used as a handy vapor generator.
[0144] As described above, since a material having a relatively
high moisture maintenance capability is inserted into the gap
between overlapping parts of the conductor and the heating element
2302 is heated by the induction heating coil 102 (FIG. 1) while the
material contains water, vapor is generated in whichever direction
the heating element 2302 is directed.
[0145] By further heating the vapor, overheated vapor can be
generated. This is realized by, for example, providing a heating
element excluding a sponge in a subsequent stage of passage of
water to the heating element 2301 for further heating the
vapor.
EXAMPLE 9
[0146] FIG. 15 is a perspective view of a heating element 2401 of a
heating apparatus in a ninth example according to the present
invention. The heating element 2401 includes a stainless steel
plate 2402 which is circumferentially wound upon itself so as to
have a cylindrical shape, a connector 2403 for connecting both of
two ends of the stainless steel plate 2402, and a platinum catalyst
2404 carried on a surface of the stainless steel plate 2402. The
stainless steel plate 2402 acts as a conductor, which forms a
closed circuit together with the connector 2403.
[0147] The heating apparatus in the ninth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 2401 shown in FIG. 15.
[0148] The heating apparatus in the ninth example operates, for
example, in the following manner.
[0149] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2401, and the eddy
current and an electric resistance in the heating element 2401
generate Joule heat in the heating element 2401. In order to
utilize the magnetic flux as efficiently as possible, it is
desirable that the total thickness of the conductor is set to be
smaller than the skin depth.
[0150] The heating apparatus in the ninth example can be used in
the following manner. First, the heating element 2401 is heated to
raise the temperature of the platinum catalyst 2404 on the surface
of the stainless steel plate 2402 to the activation point thereof.
In this state, the fluid supply device 104 supplies air to the
container 105. In the container 105, an odor component such as
ammonium contained in the air is oxidized and thus decomposed by
the action of the platinum catalyst on the surface of the stainless
steel plate 2402.
[0151] When the action of catalyst 2404 is obtained using
conventional metal sheathed tubular elements or the like, the
following problem occurs. When the input power to the metal
sheathed tubular elements is raised in order to obtain the action
of the catalyst 2404 in a shorter time period, the temperature of
the contact area between the catalyst 2404 and the heater becomes
excessively high.
[0152] However, in the heating apparatus in this example, the
contact area of the platinum catalyst 2404 and air is sufficiently
large and the heat generation distribution is sufficiently uniform
to obtain deodorizing action efficiently without deteriorating the
performance of the catalyst 2404 due to a local excessive rise of
the temperature. Thus, the high deodorizing capability is
maintained.
[0153] As described above, due to the heating element 2401 carrying
the catalyst 2404, the catalyst 2404 is heated efficiently.
EXAMPLE 10
[0154] FIG. 16A is an enlarged view of a conductor 2502 of a
heating element 2501 of a heating apparatus in a tenth example
according to the present invention. FIG. 16B is a schematic view of
the heating element 2501 and the induction heating coil 102, and
FIG. 16C is a partial enlarge view of the heating element 2501
illustrating the passage of the fluid.
[0155] As shown in FIG. 16B, the heating element 2501 includes a
conductor 2502 formed of, for example, a metal material and is
circumferentially wound upon itself so as to have a cylindrical
shape and a connector 2503 for connecting both two ends of the
conductor 2502. The conductor 2502 forms a closed circuit together
with the connector 2503.
[0156] As shown in FIG. 16A, the conductor 2502 has a plurality of
wings 2502a and respective holes 2502b.
[0157] The heating apparatus in the tenth example has a structure
shown in FIG. 1 with the heating element 101 in the container 105
being replaced by the heating element 2501 shown in FIG. 16B.
[0158] The heating apparatus in the tenth example operates, for
example, in the following manner.
[0159] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2501, and the eddy
current and an electric resistance in the heating element 2501
generate Joule heat in the heating element 2501. In order to
utilize the magnetic flux as efficiently as possible, the total
thickness of the conductor 2502 is appropriately set.
[0160] Due to the holes 2502b and the wings 2502a, the fluid is
guided by the wings 2502a while passing through the vicinity of the
conductor 2502 and flows from one surface to the other surface of
the conductor 2502 through the holes 2502b.
[0161] As a result, the flow of the fluid is complicated and thus
contacts the heat exchange surface of the heating element 2501 in a
larger area. Accordingly, the heat exchange efficiency is enhanced.
Moreover, due to the flow disturbance, the fluid is sufficiently
mixed and the temperature of the entirety of the fluid is
uniformized.
[0162] The holes 2502b for disturbing the flow can be of any
structure. One of the wings 2502a and one of the holes 2502b can be
eliminated as long as the flow is disturbed.
EXAMPLE 11
[0163] FIG. 17 is a perspective view of a heating element 1701 of a
heating apparatus in an eleventh example according to the present
invention. The heating element 1701 includes a cylinder formed of a
porous foaming metal material. The porous foaming metal material
acts as a conductor, which forms a closed circuit.
[0164] The heating apparatus in the eleventh example has a
structure shown in FIG. 1 with the heating element 101 in the
container 105 being replaced by the heating element 1701 shown in
FIG. 17.
[0165] The heating apparatus in the eleventh example operates, for
example, in the following manner.
[0166] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 1701, and the eddy
current and an electric resistance in the heating element 1701
generate Joule heat in the heating element 1701. By setting a
thickness a of the heating element 1701 so that the total thickness
of the conductor portions of the heating element 1701 is
approximately the same as the skin depth, the eddy current flows
uniformly in the heating element 1701 and thus the magnetic flux
can be efficiently utilized.
[0167] Since the heating element 1701 is formed of a porous foaming
material, the heat exchange area for exchanging heat with the fluid
is enlarged. Due to the many pores in the heating element 1701, a
disturbance is generated in the flow of the fluid, which also
improves the heat exchange efficiency.
[0168] The heating element 1701 is formed by simply cutting the
foaming metal material.
[0169] In the case where water is heated by the heating apparatus
in this example, water is substantially prevented from becoming
large drops on a surface of the heating element 1701. Thus, the
contact area between the water and the heating element 1701 is
maintained sufficiently large. Accordingly, the heating apparatus
in this example can be used as a vapor generator providing a
satisfactory vaporization efficiency.
EXAMPLE 12
[0170] FIG. 18A is a schematic view of a heating apparatus 2 in a
twelfth example according to the present invention. As shown in
FIG. 18A, the heating apparatus 2 includes a cylindrical heating
element 1801, a cylindrical container 1805 or accommodating the
heating element 1801, and a water purifier 1806 located in a hollow
portion at a center of the container 1805. The heating apparatus 2
further includes an induction heating coil 102, a high frequency
power supply device 103, and a fluid transfer device 104 as shown
in FIG. 1.
[0171] As the heating element 1801, any of the heating elements
described in the previous examples can be applied as long as they
have a cylindrical shape. As the container 1805, any type of
container can be applied as long as it allows the water purifier
1806 therein. The water purifier 1806 is of a general type formed
of a hollow fiber membrane or active carbon.
[0172] The heating apparatus 2 operates, for example, in the
following manner.
[0173] Water is first purified by the water purifier 1806 and then
flows to the fluid transfer device 104. Then, the water is sent to
the container 1805, heated by the heating element 1801 and then
discharged from the container 1805.
[0174] In this structure, the water always passes through the
vicinity of the heating element 1801, not the center of the heating
element 1801. Thus, the heat exchange efficiency is improved. The
provision of the water purifier 1806 in the hollow portion in the
container 1805 saves space. The heating apparatus 2 in this example
can be used as a hot water supplier for supplying hot water
suitable for drinking.
[0175] FIG. 18B is a schematic view of a heating apparatus 3 in a
modification of the twelfth example. The heating apparatus 3
includes a ferromagnetic body 1807 formed of ferrite or the like in
the hollow portion in the container 1805 in lieu of the water
purifier 1806.
[0176] In such a structure, the ferromagnetic body 1807 located
inside the induction heating coil 102 raises the magnetic flux
density crossing the heating element 1801 and thus enhances the
induction electromotive force. Accordingly, the current flowing in
the induction heating coil 102 or the number of windings of the
induction heating coil 102 can be decreased. The reduction in the
current flowing in the induction heating coil 102 decreases a loss
of the high frequency power supply device 103. The reduction in the
number of windings of the induction heating coil 102 decreases a
loss caused by the Joule heat of the induction heating coil 102 per
se since the resistance of the induction heating coil 102
decreases.
[0177] As described above, in this example, a container having a
structure for preventing a fluid to flow in a portion which is not
used for heat exchange is used so as to improve the heat exchange
efficiency. Furthermore, the free space is utilized to water
purification or further improvement in the heat exchange
efficiency.
EXAMPLE 13
[0178] FIG. 19 is a perspective view of a heating element 2601 of a
heating apparatus in a thirteenth example according to the present
invention. The heating element 2601 includes a stainless steel
plate 2602 which is circumferentially wound upon itself so as to
have a cylindrical shape and a connector 2603 formed of a
temperature fuse for connecting both of two ends of the stainless
steel plate 2602. The stainless steel plate 2602 acts as a
conductor, which forms a closed circuit together with the connector
2603.
[0179] The heating apparatus in the thirteenth example has a
structure shown in FIG. 1 with the heating element 101 in the
container 105 being replaced by the heating element 2601 shown in
FIG. 19.
[0180] The heating apparatus in the thirteenth example operates,
for example, in the following manner.
[0181] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2601, and the eddy
current and an electric resistance in the heating element 2601
generate Joule heat in the heating element 2601. In order to
utilize the magnetic flux as efficiently as possible, the total
thickness of the conductor is set appropriately.
[0182] The heating apparatus in the thirteenth example can be used
in the following manner. First, water is supplied from the fluid
transfer device 104 to the container 105 and is heated by the
heating element 2601. In the case where the water is not supplied
to the container 105, the temperature of the heating element 2601
becomes excessively high. When the temperature to which the
container 105 is resistant is relatively low, the container 105
deteriorates. In order to avoid such deterioration, the melting
point of connector 2603 formed of a temperature fuse is set so that
the connector 2603 is disconnected by melting when the temperature
of the container 105 reaches a prescribed level which lower than
the melting point of the container 105. By such setting, the
connector 2603 is disconnected before the temperature of the
heating element 2601 becomes higher than the melting point of the
container 105, and thus the closed circuit formed of the stainless
steel 2601 and the connector 2603 is opened to stop the flow of an
eddy current in the heating element 2601. Thus, the heating element
2601 stops heating. This is effective to maintain safely against an
abnormal temperature rise caused by, for example, heating a
container with no fluid therein.
[0183] In such a structure, the connector 2603 formed of a
temperature fuse acts as a safety device for stopping the heating
of the heating element 2601 when the temperature of the heating
element 2601 is excessively high but does not resume heating.
[0184] Such a safety device can also be realized by a bimetal for
opening a closed circuit when the temperature is excessively
high.
EXAMPLE 14
[0185] FIG. 20 is a perspective view of a heating element 2701 of a
heating apparatus in a fourteenth example according to the present
invention. The heating element 2701 includes a stainless steel
plate 2702 which is circumferentially wound upon itself to have a
cylindrical shape and a connector 2703 for connecting both of two
ends of the stainless steel plate 2702. The stainless steel plate
2702 acts as a conductor, which forms a closed circuit together
with the connector 2703. The conductor is formed of a positive
characteristic resistance change metal plate (described below).
[0186] The heating apparatus in the fourteenth example has a
structure shown in FIG. 1 with the heating element 101 in the
container 105 being replaced by the heating element 2701 shown in
FIG. 20.
[0187] The heating apparatus in the fourteenth example operates,
for example, in the following manner.
[0188] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2701, and the eddy
current and an electric resistance in the heating element 2701
generate Joule heat in the heating element 2701. In order to
utilize the magnetic flux as efficiently as possible, the total
thickness of the conductor is set appropriately.
[0189] The positive characteristic resistance change metal plate
used as the conductor has a resistance which changes in accordance
with the temperature as shown in FIG. 21. The curie point at which
the resistance drastically changes can be set at a desirable
temperature (e.g., 95.degree. C.).
[0190] In such a state, when the temperature of the heating element
2701 reaches 95.degree. C., the resistance of the connector 2703
drastically rises so as to make difficult the flow of the eddy
current in the closed circuit formed of the stainless steel plate
2702 and the connector 2703. When the amount of the eddy current
reduces, the temperature of the heating element 2701 lowers. When
the temperature of the heating element 2701 lowers, the resistance
of the connector 2703 returns to the previous level, which
facilitates the flow of the eddy current in the closed circuit.
Thus, heating is resumed.
[0191] In this manner, the connector 2703 automatically adjusts the
temperature of the heating element 2701.
EXAMPLE 15
[0192] FIG. 22 is a perspective view of a heating element 2801 of a
heating apparatus in a fifteenth example according to the present
invention. The heating element 2801 includes a shape memory alloy
2802 which is circumferentially wound upon itself so as to have a
cylindrical shape and a flexible connector 2803 for connecting both
of two ends of the shape memory alloy plate 2802. The flexible
connector 2803 is freely deformable. The shape memory alloy plate
2802 acts as a conductor, which forms a closed circuit together
with the connector 2803.
[0193] The heating apparatus in the fifteenth example has a
structure shown in FIG. 1 with the heating element 101 in the
container 105 being replaced by the heating element 2801 shown in
FIG. 22.
[0194] The heating apparatus in the fifteenth example operates, for
example, in the following manner.
[0195] The fluid transfer device 104 supplies a fluid to the
container 105. In parallel, the high frequency power supply device
103 supplies high frequency power to the induction heating coil
102, and thus causes a high frequency AC magnetic field to be
generated from the induction heating coil 102. Then, an eddy
current is generated in the heating element 2801, and the eddy
current and an electric resistance in the heating element 2801
generate Joule heat in the heating element 2801. In order to
utilize the magnetic flux as efficiently as possible, the total
thickness of the conductor is set appropriately.
[0196] The shape memory alloy plate 2802 has a shape shown in FIG.
23A up to a prescribed temperature (e.g., 95.degree. C.); i.e., the
shape memory alloy plate 2802 is substantially fully extended only
to be limited by the container 105. At the temperature above the
prescribed level, the shape memory alloy plate 2802 contracts as
shown in FIG. 23B.
[0197] In the state shown in FIG. 23A, the shape memory alloy plate
2802 is sufficiently heated by the high frequency AC magnetic field
supplied by an induction heating coil 102. When the temperature of
the shape memory alloy plate 2802 reaches, for example, 95.degree.
C., the shape memory alloy plate 2802 is deformed to the shape
shown in FIG. 23B. In this state, the shape memory alloy plate 2802
becomes farther from the induction heating coil 102, which
deteriorates the magnetic coupling of the plate 2802 and the coil
102. Therefore, the amount of the eddy current flowing in the shape
memory alloy plate 2802 is reduced so as to substantially prevent
the heating of the shape memory alloy plate 2802. When the
temperature of the shape memory alloy plate 2802 is lowered to a
level below 95.degree. C. after a certain time period, the shape
memory alloy plate 2802 returns to the shape shown in FIG. 23A and
resumes heat generation. In this manner, the temperature is
automatically adjusted.
[0198] In the case where tap water or the like is heated by the
heating apparatus in the fifteenth example, calcium carbonate
contained in the tap water is possibly deposited on and adheres to
a surface of the conductor of the heating element 2801 since the
solubility of calcium carbonate is lowered as the temperature
rises. The calcium carbonate adhering in this manner is generally
referred to as scale. When the surface of the heating element is
covered with the scale, the heat exchange is prevented.
[0199] However, in this example, the shape memory alloy plate 2802
changes the shape repeatedly between the shape in FIG. 23A and the
shape in FIG. 23B. A mechanical force generated by such a shape
change prevents the adhesion of calcium carbonate and also peels
off calcium carbonate adhering to the conductor.
[0200] As described above, use of a shape memory alloy for the
heating element 2801 allows for automatic temperature adjustment,
prevention of scale adhesion, and scale removal realized without
using any special device.
EXAMPLE 16
[0201] FIGS. 24A and 24B are partial schematic views of a heating
apparatus 4 in a sixteenth example according to the present
invention in two different states. The heating apparatus 4 in the
sixteenth example includes a heating element 2901, a coil spring
2906, a container 105 for accommodating the heating element 2901
and the coil spring 2906, and a flat plate 2907 inserted between
the heating element 2901 and the coil spring 2906. The heating
apparatus 4 further includes an induction heating coil 102, a high
frequency power supply device (not shown) for supplying high
frequency power to the induction heating coil 102, and a fluid
transfer device (not shown) for transferring a fluid to the heating
element 2901. The coil spring 2906 constantly presses the heating
element 2901 through the flat plate 2907.
[0202] The heating element 2901 includes a shape memory alloy 2902
spirally wound and a connector 2903 for connecting both of two ends
of the shape memory alloy 2902. The shape memory alloy 2902 acts as
a conductor, which forms a closed circuit together with the
connector 2903.
[0203] The shape memory alloy 2902 is contracted as shown in FIG.
24A below a prescribed temperature (e.g., 95.degree. C.) and is
entirely located at a center inside the induction heating coil 102.
The shape memory alloy 2902 memorizes the shape shown in FIG. 24B
and is extended to such a shape when the temperature thereof
reaches, for example, 95.degree. C. At this point, the shape of the
shape memory alloy 2902 is stabilized since the elastic forces of
the shape memory alloy 2902 and the coil spring 2906 are balanced.
In this state, a part of the shape memory alloy 2902 is not covered
by the induction heating coil 102.
[0204] In the state of FIG. 24A, the shape memory alloy 2902 is
sufficiently heated by the high frequency AC magnetic field
supplied by the induction heating coil 102. When the temperature of
the shape memory alloy 2902 reaches, for example, 95.degree. C.,
the shape memory alloy 2902 is deformed to the shape shown in FIG.
24B. In this state, a part of the shape memory alloy 2902 is not
covered by the induction heating coil 102, and the induction
electromotive force is not generated in the uncovered part.
Therefore, the amount of the eddy current flowing in the shape
memory alloy 2902 is reduced so as to reduce the amount of heat
generated by the shape memory alloy 2902. Accordingly, the
temperature of the shape memory alloy 2902 is lowered. When the
temperature is lowered to a level below 95.degree. C., the shape
memory alloy 2902 returns to the shape shown in FIG. 24A and
increases the amount of heat generation. In this manner, the
temperature is automatically adjusted.
[0205] In the case where tap water or the like is heated by the
heating apparatus in the sixteenth example, heat exchange is
prevented by the scale for the reason described above. However, in
this example, the adhesion of calcium carbonate as the scale is
prevented and also the scale adhering to the conductor is peeled
off by the repetitive shape change of the shape memory alloy
2902.
[0206] As described above, use of a shape memory alloy for the
heating element 2901 allows for automatic temperature adjustment,
prevention of scale adhesion, and scale removal realized without
using any special device.
EXAMPLE 17
[0207] FIG. 25 is a schematic view of a heating apparatus 5 in a
seventeenth example according to the present invention. As shown in
FIG. 25, the heating apparatus 5 includes an induction heating coil
3001 having two outer areas 3001a and one inner area 3001b.
[0208] The number of windings of each outer area 3001a per unit
length is greater than that of the inner area 3001b per unit
length.
[0209] In the case where a cylindrical solenoid having a limited
length and wound uniformly between two ends thereof is used for the
induction heating coil 3001, the magnetic flux density generated
along the axis of the cylindrical solenoid is low in the vicinity
of an opening of the solenoid and high in the vicinity of a center
of the solenoid. Therefore, the magnetic flux density is low at
both of two ends of a heating element 101 and high at a center
thereof. In this case, the heat distribution is nonuniform.
[0210] In order to avoid such an inconvenience, the number of
windings of each outer area 3001a is greater than that of the inner
area 3001b. Accordingly, the magnetic flux density is uniform in
the entirety of the induction heating coil 3001. Therefore, the
magnetic flux density is also uniform in the entirety of the
heating element 101, and the uniform heat generation in the heating
element 101 is obtained.
EXAMPLE 18
[0211] FIG. 26 is a schematic view of a heating apparatus 6 in an
eighteenth example according to the present invention. As shown in
FIG. 26, the heating apparatus 6 includes an induction heating coil
3101 having a first area 3101a which is closest to a fluid intake
105a of the container 105, a second area 3101b slightly away from
the fluid intake 105a, and a third area 3101c farthest from the
fluid intake 105a.
[0212] The first area 3101a closest to the fluid intake 105a has
the greatest number of windings per unit length and the third area
3101c farthest from the fluid intake 105a has the smallest number
of windings per unit length.
[0213] The intensity of the high frequency AC magnetic field is
defined by the number of windings of the induction heating coil and
the amount of current. Since the number of windings of the coil
closer to the fluid intake 105a is greater per unit length in this
example, the magnetic flux density is also higher in an area closer
to the fluid intake 105a. Accordingly, the heating element 101
generates more heat in an area closer to the fluid intake 105a.
[0214] In the case where tap water or the like is heated by the
heating apparatus in the eighteenth example, the scale is more
easily generated as the temperature is higher since, as described
above, the solubility of calcium carbonate lowers as the
temperature rises. As the temperature difference between the water
and the heating element 101 increases, the difference in solubility
of calcium carbonate at two different temperatures increases, and
thus more scale is generated on a surface of the heating element
101.
[0215] In the case where heat exchange is performed between the
fluid and the heating element 101, the temperature difference
between the fluid and the heating element 101 is smaller as the
power density on the heat exchange surface decreases.
[0216] Accordingly, the scale generation is restricted where the
water temperature is relatively high by reducing the power density
of the heating element 101 and thus reducing the amount of heat
generation.
[0217] In the heating apparatus 6 in this example, the water
temperature is sufficiently low to substantially prevent the
generation of the scale in the vicinity of the fluid intake 105a of
the container 105. This permits an increase in the temperature
difference between the water and the heating element 101.
Accordingly, in the vicinity of the intake 105a of the container
105, the number of windings of the induction heating coil 3101 per
unit length is increased so as to increase the heat generation to
sufficiently heat the water.
[0218] In an area far from the intake 105a of the container 105,
the water temperature is relatively high. Therefore, the water
heating needs to be restricted to a low level to maintain the
temperature difference between the water and the heating element
101 small, so that the generation of scale is prevented. For this
purpose, in an area far from the intake 105a, the number of
windings of the induction heating coil 3101 per unit length is less
than the rest of the induction heating coil 3101.
[0219] It should be noted that the structures of the elements of
the heating apparatuses in the above-described examples can be
combined in any possible manner.
[0220] As described above, according to the present invention, high
frequency power is supplied from the high frequency power device to
the induction heating coil, and the heating element is heated by
the principle of induction heating. In the case where the heating
element includes a conductor which is circumferentially or spirally
wound, the heat exchange area per unit volume involved in heat
exchange is enlarged and heating is performed uniformly. When the
heating apparatus is used to heat a liquid, the temperature of the
liquid is raised to a level close to a boiling point with a
small-volume heating element and also the heat exchange efficiency
is improved.
[0221] In one embodiment of the invention, the heating element
includes a plurality of non-magnetic metal bodies arranged
concentrically. With such a shape, the heating apparatus can be
produced relatively easily and thus at low cost. Since the heat
exchange area per unit volume is enlarged, the liquid can be heated
to a temperature close to a boiling point. Thus, the heat exchange
efficiency is enhanced.
[0222] In one embodiment of the invention, the heating element
includes at least one non-magnetic metal body and at least one
magnetic metal body provided inside the at least one non-magnetic
metal body. The metal bodies are concentrically provided. In such a
case, the temperature of the liquid flowing in a central part of
the heating element is higher than the temperature of the fluid
flowing in the rest of the heating element, so that the temperature
distribution in the entirety of the heating element is uniform.
[0223] In one embodiment of the invention, a plurality of heating
elements which have a small height are arranged in a stacked
manner. Such an arrangement is easier to mass-produce than
producing different sizes of heating elements in accordance with
the use. In such a structure, the total length of the heating
elements can be changed relatively easily and at relatively low
cost by appropriately setting the input power to the heating
elements and the power density of the heating elements.
[0224] In one embodiment of the invention, the conductor of the
heating element is processed to be wave-like. By such processing,
the contact area between the heating element and the liquid is
enlarged, resulting in an enhanced heat exchange efficiency.
[0225] In one embodiment of the invention, an adsorbent such as,
for example, active carbon is provided in a gap between overlapping
parts of the conductor. By heating the heating element by the
induction heating coil, trihalomethane adsorbed by the adsorbent is
released together with a vapor. Thus, the trihalomethane adsorbing
force of the adsorbent is recovered.
[0226] In one embodiment of the invention, a water-adsorbing
material such as, for example, zeolite is provided in a gap between
overlapping parts of the conductor. By heating the heating element
by the induction heating coil, water is adsorbed by the adsorbent
and vaporized. Thus, the water adsorbing force of the sponge is
recovered.
[0227] In one embodiment of the invention, a material having a
moisture maintenance capability is provided in a gap between
overlapping parts of the conductor. By heating the heating element
containing moisture by the induction heating coil, vapor is
generated in whichever direction the heating element is
directed.
[0228] In one embodiment of the invention, a catalyst is carried on
the metal conductor included in the heating element uniformly
generating heat. In such a structure, the catalyst is uniformly
heated.
[0229] In one embodiment of the invention, the metal conductor of
the heating element has a hole. In such a structure, the flow of
the fluid is disturbed and thus the heat exchange efficiency is
improved.
[0230] In one embodiment of the invention, the metal conductor of
the heating element has a hole and also a wing in the vicinity of
the hole for transferring a fluid from one surface of the conductor
to another surface of the conductor. In such a structure, the heat
exchange efficiency is further improved.
[0231] In one embodiment of the invention, the conductor of the
heating element is formed of a porous material. Accordingly, the
heating element is produced relatively easily.
[0232] In one embodiment of the invention, a container which
prevents a fluid from passing through a part of the container not
involved in heat exchange is used. In such a structure, the heat
exchange efficiency is improved and the part not involved in heat
exchange can be used for water purification or improvement of the
heating characteristics.
[0233] In one embodiment of the invention, the heating element has
a closed circuit which is disconnected when the heating element
reaches a prescribed temperature. When the temperature of the
heating element becomes excessively high, a component of the
heating element acts as a safety device which does not allow the
heating element to be heated again.
[0234] In one embodiment of the invention, the conductor is formed
of a material having a resistance changing in accordance with a
temperature. Accordingly, automatic temperature adjustment is
performed by the conductor.
[0235] In one embodiment of the invention, the conductor is formed
of a shape memory alloy. Accordingly, automatic temperature
adjustment is performed. Moreover, adhesion of scale to the surface
of the shape memory alloy is prevented, and the scale adhering to
the surface can be removed without any specific device.
[0236] In one embodiment of the invention, the conductor of the
heating element is formed of a shape memory alloy, and the heating
element includes a spring for restricting a shape change of the
conductor. By such a structure, the automatic temperature
adjustment is performed. Moreover, adhesion of scale to the surface
of the shape memory alloy is prevented, and the scale adhering to
the surface can be removed without any specific device.
[0237] In one embodiment of the invention, a coil provided on an
outer surface of the container has a greater number of windings per
unit length in an area in the vicinity of an end of the coil than
an area at a center of the coil. Accordingly, the magnetic flux
density is uniformized so as to heat the heating element
uniformly.
[0238] In one embodiment of the invention, a coil has a greater
number of windings per unit length in an area in the vicinity of
one end of the coil than in an area in the vicinity of another end
of the coil. Accordingly, the power density of an area of the
heating element in contact with a high temperature water is reduced
so as to prevent deposition of scale.
[0239] Various other modifications will be apparent to and can be
readily made by those skilled in the art without departing from the
scope and spirit of this invention. Accordingly, it is not intended
that the scope of the claims appended hereto be limited to the
description as set forth herein, but rather that the claims be
broadly construed.
* * * * *