U.S. patent application number 13/141827 was filed with the patent office on 2011-10-20 for solar heat exchanger.
This patent application is currently assigned to MITAKA KOHKI CO., LTD.. Invention is credited to Katsushige Nakamura.
Application Number | 20110253128 13/141827 |
Document ID | / |
Family ID | 42287748 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110253128 |
Kind Code |
A1 |
Nakamura; Katsushige |
October 20, 2011 |
SOLAR HEAT EXCHANGER
Abstract
A light receiving plate floating on the surface of tin, i.e., a
low-melting-point heating medium and receiving solar beams is made
of solid carbon material entirely coated with a silicon carbide
film. Due to the silicon carbide film, the surface of the light
receiving plate is black to realize a high absorption ratio of the
solar beams. In addition, the light receiving plate is made of the
silicon carbide film at least at the surface thereof, to
demonstrate excellent heat resistance.
Inventors: |
Nakamura; Katsushige;
(Tokyo, JP) |
Assignee: |
MITAKA KOHKI CO., LTD.
Tokyo
JP
|
Family ID: |
42287748 |
Appl. No.: |
13/141827 |
Filed: |
December 24, 2009 |
PCT Filed: |
December 24, 2009 |
PCT NO: |
PCT/JP2009/071427 |
371 Date: |
June 23, 2011 |
Current U.S.
Class: |
126/645 ;
126/610; 126/679 |
Current CPC
Class: |
F24S 10/70 20180501;
Y02E 10/40 20130101; F24S 10/30 20180501; F24S 60/10 20180501; F24S
70/10 20180501; F24S 20/20 20180501; F24S 70/20 20180501; Y02E
10/44 20130101; F24S 23/79 20180501 |
Class at
Publication: |
126/645 ;
126/679; 126/610 |
International
Class: |
F24J 2/30 20060101
F24J002/30; F24J 2/48 20060101 F24J002/48; F24J 2/04 20060101
F24J002/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2008 |
JP |
2008-327647 |
Claims
1. A solar heat exchanger having a structure including a top-open,
heat-resistant container holding a low-melting-point heating medium
and a light receiving plate being supported on and in contact with
the surface of the low-melting-point heating medium, wherein the
light receiving plate is made of solid silicon carbide, or solid
carbon material being entirely coated with a silicon carbide
film.
2. The solar heat exchanger according to claim 1, wherein the
low-melting-point heating medium is low-melting-point metal
selected from any one of tin, lead, and solder.
3. The solar heat exchanger according to claim 1, wherein the
low-melting-point heating medium is molten salt.
4. The solar heat exchanger according to claim 1, wherein the
heat-resistant container has an upwardly widening tapered
shape.
5. The solar heat exchanger according to claim 4, wherein the
heat-resistant container is made of solid silicon carbide, or solid
carbon material being entirely coated with a silicon carbide
film.
6. The solar heat exchanger according to claim 1, wherein the light
receiving plate has an open top container shape.
Description
TECHNICAL FIELD
[0001] The present invention relates to a solar heat exchanger.
BACKGROUND TECHNOLOGY
[0002] There is known a beam-down solar concentration apparatus
that reflects, with a plurality of reflection mirrors called
heliostats, solar beams toward a center mirror supported at the top
of a high tower and concentrates downwardly reflected solar beams
from the center mirror on a point to obtain heat (for example,
Japanese Unexamined Patent Application Publication No.
H11-119105).
[0003] In the case of the beam-down structure of this sort, the
downwardly reflected solar beams directly heat, for example, a
metallic coil to change water circulated inside the coil into
vapor.
OUTLINE OF INVENTION
[0004] According to the structure of the related art of directly
heating the metallic coil with solar beams, however, a metallic
color of the surface of the metallic coil reflects solar beams to
hinder efficient heat exchange. The surface of the metallic coil is
heated with solar beams to very high temperatures, and therefore, a
black coating, should it be applied to the surface, will easily
peel off.
MEANS TO SOLVE THE PROBLEMS
[0005] In consideration of the related art, the present invention
provides a solar heat exchanger capable of efficiently converting
solar beams into heat.
[0006] According to a technical aspect of the present invention, a
structure includes a top-open, heat-resistant container that holds
a low-melting-point heating medium and a light receiving plate that
is supported on and is in contact with the surface of the
low-melting-point heating medium. It is characterized in that the
light receiving plate is made of solid silicon carbide, or solid
carbon material entirely coated with a silicon carbide film.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a general view illustrating a solar concentration
apparatus according to a first embodiment of the present
invention.
[0008] FIG. 2 is a sectional view illustrating a heat
exchanger.
[0009] FIG. 3 is a perspective view illustrating a light receiving
plate and heat-resistant container.
[0010] FIG. 4 is an enlarged sectional view illustrating a silicon
carbide film on the surface of the light receiving plate and
heat-resistant container.
[0011] FIG. 5 is a sectional view illustrating a heat exchanger
according to a second embodiment of the present invention.
MODE OF IMPLEMENTING INVENTION
First Embodiment
[0012] FIGS. 1 to 4 are views illustrating a first embodiment of
the present invention. Numeral 1 represents an elliptic mirror
serving as a center mirror that is supported with a support tower
(not illustrated) at a predetermined height in a downwardly
oriented state. A circular opening 1a is formed at the center of
the elliptic mirror 1. The elliptic mirror 1 has a mirror surface
that is defined as a part of an ellipsoid, and under the same,
there are a first focus A and a second focus B. Under the elliptic
mirror 1, a heat exchanger 2 is arranged to convert solar beams L
into heat energy. At an upper part of the heat exchanger 2, there
is a collector mirror 3 substantially having a tapered cylindrical
shape. On the ground around the heat exchanger 2, many heliostats 4
are arranged to surround the elliptic mirror 1.
[0013] Each of the heliostats 4 is controlled by a sensor system
(not illustrated) so that solar beams L reflected by the heliostat
4 may pass through the first focus A. Once the solar beams L
reflected by the heliostats 4 pass through the first focus A, the
solar beams are downwardly reflected by the elliptic mirror 1, are
always collected at the second focus B, and reach the heat
exchanger 2 through the collector mirror 3.
[0014] The heat exchanger 2 has a box 6 that has an opening 5 at
the top thereof and is made of autoclaved lightweight concrete
(ALC). The collector mirror 3 is arranged at the opening 5. In the
box 6, there is a heat-resistant container 7 made of black carbon
material. Inside the heat-resistant container 7, there is held tin
8 serving as a low-melting-point heating medium. On the surface of
the tin 8, a light receiving plate 9 made of black carbon material
floats. In the tin 8, a heat exchanging pipe 10 meanders. In the
pipe 10, water W serving as a heat conducting medium is supplied
from one side and vapor S is discharged from the other side.
[0015] The heat-resistant container 7 has an open top shape having
a tapered side face that upwardly widens from a circular bottom.
The black carbon material that forms the heat-resistant container 7
is entirely coated with a silicon carbide (SiC) film 11.
[0016] The light receiving plate 9 floating on the surface of the
tin 8 has a disk shape and is made of black carbon material
entirely coated with a silicon carbide film 11. The silicon carbide
film 11 itself is black, and therefore, the solar beams L collected
by the collector mirror 3 and received by the light receiving plate
9 are absorbed at a high absorption ratio (about 95%) and are
changed into heat.
[0017] The heat changed by the light receiving plate 9 is conducted
to the tin 8 that becomes molten when the temperature thereof
reaches a melting point (232.degree. C.). The molten tin 8 in a wet
state contacts the light receiving plate 9 and pipe 10, to increase
heat conduction efficiency to surely convert the water W passing
through the pipe 10 into vapor S.
[0018] The black carbon material that forms the light receiving
plate 9 is smaller in specific gravity than the tin 8, and
therefore, the light receiving plate 9 floats on the surface of the
tin 8 and never sinks into the tin 8 even if the tin 8 becomes
molten. The light receiving plate 9 is entirely coated with the
silicon carbide film 11. The silicon carbide film 11 itself is
highly heat resistive and prevents the inside black carbon material
from contacting air, and therefore, the black carbon material never
burn even if the light receiving plate 9 is heated to high
temperatures.
[0019] The heat-resistant container 7 is also coated with the
silicon carbide film 11, and when an exposed part thereof receives
solar beams L, the part absorbs the solar beams L and converts the
same into heat to heat the tin 8.
[0020] In a first stage of the tin 8 receiving heat from the light
receiving plate 9, the tin 8 is solid and expands due to the heat.
At this time, if the tin 8 and an inner face of the heat-resistant
container 7 are tightly attached to each other, stress may
concentrate on part of the tin 8 and heat-resistant container 7, to
partly distort or break the container.
[0021] For this, the embodiment forms the heat-resistant container
7 with black carbon material coated with the silicon carbide film
11. Compared with making the heat-resistant container 7 from metal,
contact force between the tin and the container is weaker so that
the tin 8 may easily slide on the inner face of the heat-resistant
container 7. In addition, the heat-resistant container 7 has an
upwardly widening tapered shape to allow the solid tin 8 to slide
upwardly. As a result, the tin 8 and heat-resistant container 7
will have no part where stress concentration occurs to cause
partial distortion or breakage.
[0022] According to the present embodiment, the light receiving
plate 9 and heat-resistant container 7 are made of black carbon
material coated with the silicon carbide film 11. Instead, they may
entirely be made of silicon carbide. Although one piece of the
light receiving plate 9 is floated on the surface of the tin 8, a
plurality of small light receiving plates 9 may be floated
thereon.
[0023] According to the present embodiment, water W passes through
the pipe 10 and is converted into vapor S. Instead, the pipe 10 may
pass air as the heat conducting fluid. The air passing through the
pipe 10 is heated to high temperatures and is circulated through
another apparatus to conduct the heat from the tin 8 to the
apparatus.
[0024] Instead of the tin 8, low-melting-point metal such as lead
and solder may be used as the low-melting-point heating medium.
Second Embodiment
[0025] FIG. 5 is a view illustrating a second embodiment of the
present invention. This embodiment and embodiments that follow
employ structural elements that are similar to those of the first
embodiment. Accordingly, similar structural elements are
represented with common marks to omit overlapping explanations.
[0026] A heat exchanger 12 according to the present embodiment has
a heat-resistant container 13 that is made of stainless steel. A
light receiving plate 14 is of an open-top type having a tapered
side face that upwardly widens from a circular bottom. Between the
light receiving plate 14 and the heat-resistant container 13, there
is molten salt 15 serving as a low-melting-point heating medium.
The molten salt 15 is a mixture of potassium nitrate and sodium
nitrate and becomes liquid at a melting point of about 140.degree.
C. At an upper end of the heat-resistant container 13, a flange 16
is fixed to press from above the light receiving plate 14 that may
rise due to buoyancy. In the molten salt 15, there is a pipe
17.
[0027] According to the present embodiment, the light receiving
plate 14 has an open top shape to realize a large area to receive
solar beams L. In addition, a contact area thereof to the molten
salt 15 is also large. Accordingly, the molten salt 15 can quickly
be put in a molten state. Side faces of the light receiving plate
14 and heat-resistant container 13 are inclined into a tapered
shape and the molten salt 15 is heated even around the bottom of
the heat-resistant container 13. Due to this, the molten salt 15 in
a molten state easily circulates due to convection, to relax
temperature variations and further improve heat exchanging
efficiency. In addition, the molten salt 15 is inexpensive compared
with, for example, tin, to provide an advantage in terms of cost.
The molten salt 15 may be used alone, or may be mixed with solid
heat storage material that does not melt when heated.
EFFECT OF INVENTION
[0028] According to the present invention, the light receiving
plate floating on the surface of a low-melting-point heating medium
and receiving solar beams is made of solid silicon carbide, or
solid carbon material entirely coated with a silicon carbide film.
Due to the silicon carbide film, the surface of the light receiving
plate is black to improve an absorption ratio of solar beams. The
light receiving plate is formed with the silicon carbide film at
least at the surface thereof, and therefore, demonstrates excellent
heat resistance. The low-melting-point heating medium melts to
become a liquid heat source that may take any shape depending on
the shape of the heat-resistant container. This increases a contact
area and improves heat exchange efficiency.
[0029] The low-melting-point heating medium may be
low-melting-point metal selected from any one of tin, lead, and
solder, to serve as a high-temperature liquid heat source.
[0030] The low-melting-point heating medium may be molten salt that
is advantageous in terms of cost.
[0031] The heat-resistant container has a tapered shape that
upwardly widens. Even if the low-melting-point heating medium
causes in a solid state a volume change due to thermal expansion
during heating or cooling, the low-melting-point heating medium
easily slides on the inner face of the heat-resistant container, to
cause no stress concentration at any part of the low-melting-point
heating medium and heat-resistant container. Accordingly, the
low-melting-point heating medium and heat-resistant container never
cause partial distortion or breakage.
[0032] Further, the heat-resistant container is made of solid
silicon carbide, or solid carbon material entirely coated with a
silicon carbide film, and therefore, even the heat-resistant
container can absorb, at its exposed part, solar beams and can
change them into heat. Compared with the case of making the
heat-resistant container from metal, contact force (a mutual action
at an interface) between the solid low-melting-point heating medium
and the container is weaker so that the low-melting-point heating
medium may easily slide when thermal expansion occurs, thereby
reducing stress on the heat-resistant container.
[0033] Moreover, the light receiving plate has an open top
container shape, to increase a light receiving area and an area in
contact with the low-melting-point heating medium, so that the
low-melting-point heating medium may quickly be put in a molten
state.
UNITED STATES DESIGNATION
[0034] In connection with United States designation, this
international patent application claims the benefit of priority
under Article No. 119(a) of United States patent Law to Japanese
Patent Application No. 2008-327647 filed on Dec. 24, 2008 whose
disclosed contents are cited herein.
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