U.S. patent application number 12/742589 was filed with the patent office on 2011-02-24 for chemical heat-storage apparatus.
This patent application is currently assigned to Panasonic Corporation. Invention is credited to Mio Furui, Atsushi Kakimoto, Toru Sukawa, Motohiro Suzuki.
Application Number | 20110042036 12/742589 |
Document ID | / |
Family ID | 40638495 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110042036 |
Kind Code |
A1 |
Suzuki; Motohiro ; et
al. |
February 24, 2011 |
CHEMICAL HEAT-STORAGE APPARATUS
Abstract
A chemical heat-storage apparatus 100 is provided with: a
container 202 accommodating a heat storage material 210 that has a
higher specific gravity than water and exothermically reacts with
water; a heat exchanger 209 that is provided inside the container
202 and that gives heat to the heat storage material 210 in a heat
storage process as well as absorbing heat from the heat storage
material 210 in a heat release process; a water flow path 204 that
has openings 203 opening downwardly and that is provided below the
heat exchanger 209 inside the container 202 so as to supply, to the
inside of the container 202, the water to react with the heat
storage material 210; and a distribution plate 206 that is provided
below the heat exchanger 209 inside the container 202 and above the
opening 203 and that has a plurality of through holes 205 for
introducing the water supplied to the inside of the container 202
from a lower part to an upper part.
Inventors: |
Suzuki; Motohiro; (Osaka,
JP) ; Kakimoto; Atsushi; (Hyogo, JP) ; Sukawa;
Toru; (Osaka, JP) ; Furui; Mio; (Osaka,
JP) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON P.C.
P.O. BOX 2902
MINNEAPOLIS
MN
55402-0902
US
|
Assignee: |
Panasonic Corporation
Kadoma-shi, Osaka
JP
|
Family ID: |
40638495 |
Appl. No.: |
12/742589 |
Filed: |
November 13, 2008 |
PCT Filed: |
November 13, 2008 |
PCT NO: |
PCT/JP2008/003312 |
371 Date: |
August 24, 2010 |
Current U.S.
Class: |
165/10 |
Current CPC
Class: |
F28D 2020/0078 20130101;
Y02E 60/14 20130101; F28D 20/003 20130101; Y02E 60/145 20130101;
F28D 2020/0069 20130101; Y02E 60/142 20130101; C09K 5/063 20130101;
F28D 20/025 20130101; F28D 20/021 20130101 |
Class at
Publication: |
165/10 |
International
Class: |
F28D 20/00 20060101
F28D020/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2007 |
JP |
2007-293925 |
Claims
1. A chemical heat-storage apparatus comprising: a container
accommodating a heat storage material with a higher specific
gravity than water, the heat storage material being capable of
exothermically reacting with water; a heat exchanger provided in
the container, the heat exchanger capable of giving heat to the
heat storage material in a heat storage process as well as
absorbing heat from the heat storage material in a heat release
process; a water flow path having an opening downwardly, the water
flow path being provided below the heat exchanger inside the
container so as to supply, to the inside of the container, water to
react with the heat storage material; and a distribution plate
provided below the heat exchanger and above the opening inside the
container, the distribution plate having a plurality of through
holes for introducing water supplied to the container from a lower
part to an upper part.
2. The chemical heat-storage apparatus according to claim 1,
wherein the heat storage material is in a solid-liquid coexistence
state or in a liquid phase at the time of the start of the heat
release process, and the heat storage material is in a solid phase
at the time of the start of the heat storage process.
3. The chemical heat-storage apparatus according to claim 1,
wherein the water flow path extends in a horizontal direction
inside the container, and the distribution plate is arranged above
the opening and below a top of the water flow path.
4. The chemical heat-storage apparatus according to claim 1,
wherein the water weight W.sub.1 inside the water flow path and the
total area S.sub.1 of the opening satisfy the following formula
(1): 500.ltoreq.(W.sub.1/S.sub.1)(unit: kg/m.sup.2) (1).
5. The chemical heat-storage apparatus according to claim 4,
wherein the water flow path has an internal diameter of 3 to 30
mm.
6. The chemical heat-storage apparatus according to claim 1,
wherein the water flow path has a plurality of the openings, and a
horizontal distance between one through hole selected from the
plurality of the through holes and the opening located closest to
the selected through hole is constant for every one of the
plurality of through holes
7. The chemical heat-storage apparatus according to claim 6,
wherein the number of the through holes formed in the distribution
plate is at least twice the number of the openings.
8. The chemical heat-storage apparatus according to claim 6,
wherein the heat exchanger is a fin-tube heat exchanger having a
plurality of fins and a heat transfer tube passing through the
plurality of the fins, the plurality of the fins each are arranged
perpendicular to a longitudinal direction of the water flow path,
and the distribution plate is formed with the plurality of the
through holes at equal intervals to a fin pitch of the plurality of
the fins in a direction parallel to the longitudinal direction of
the water flow path.
9. The chemical heat-storage apparatus according to claim 1,
wherein the heat exchanger is in contact directly with the
distribution plate.
10. The chemical heat-storage apparatus according to claim 1,
wherein the distribution plate has a lower plate portion located so
that water is introduced through the water flow path into a gap
between a bottom surface of the container and the lower surface of
the lower plate portion, an upper plate portion located between the
lower plate portion and a top of the water flow path, and an
internal space formed between the lower plate portion and the upper
plate portion, and the plurality of the through holes include a
plurality of lower through holes formed in the lower plate portion
for the purpose of introducing, into the internal space, the water
supplied through the water flow path to the inside of the
container, and a plurality of upper through holes formed in the
upper plate portion for the purpose of introducing the water
present in the internal space upwardly.
11. The chemical heat-storage apparatus according to claim 1,
wherein the heat storage material is at least one selected from
calcium chloride hydrate, calcium bromide hydrate and magnesium
sulfate hydrate.
12. A heat storage system comprising: a heat storage circuit having
the heat storage apparatus according to claim 1, a condenser for
condensing water vapor, a reflux path for introducing water vapor
generated from the heat storage material of the heat storage
apparatus into the condenser in a heat storage process, a tank for
storing the condensed water, a supply path for introducing the
water of the tank into the heat storage apparatus in a heat release
process; a heating apparatus for giving heat to the heat storage
material of the heat storage apparatus in the heat storage process;
and a heating medium circuit for extracting heat from the heat
storage material of the heat storage apparatus.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat storage apparatus
using a chemical reaction of a heat storage material.
BACKGROUND ART
[0002] Heat storage technology for storing energy is useful as one
of energy-saving technologies. In recent years, water heaters or
heaters using a CO.sub.2 heat pump or a fuel cell cogeneration
system have attracted attention. High-density heat-storage
technology is under development aiming to average the electricity
demand throughout a day by heat storage using midnight power as
well as to improve the installation convenience by downsizing these
devices.
[0003] For example, JP 2005-188916 A and JP 2007-132534 A each
describe a latent heat storage apparatus in which heat is stored by
direct heat exchange between a heat storage material (latent heat
storage material) and a heat exchange medium (oil). In the latent
heat storage apparatus of JP 2005-188916 A, oil 2 and a heat
storage material 3 are accommodated separately in a container 1a,
as indicated in FIG. 12. Two pipes 4 and 6 are connected to a heat
exchanger 5a. The pipe 4 is formed with a plurality of openings 4a
for discharging the oil 2. The oil 2 is introduced through the pipe
6 into the heat exchanger 5a, and the oil 2 is supplied through the
pipe 4 to the heat storage material 3. The oil 2 discharged through
the pipe 4 moves upward through the layers of the heat storage
material 3 based on the difference in specific gravity between the
oil 2 and the heat storage material 3. At this time, heat is
exchanged between the oil 2 and the heat storage material 3, so
that the heat is stored.
[0004] The heat storage material 3 such as sodium acetate is in a
solid state at the time of the start of the heat storage process.
Therefore, there is a possibility that the openings 4a of the pipe
4 are closed by the heat storage material 3. For such a case, an
end 4B of the pipe 4 opens into the upper space where the oil 2 is
stored so that the oil 2 could flow through the pipe 4 even in the
case where the openings 4a are closed. The oil 2 flows through the
pipe 4, and thereby the pipe 4 acts as a heat exchanger. Thus, heat
exchange occurs between the oil 2 and the heat storage material 3.
The heat storage material 3 gradually is liquefied, and thereby the
closure of the openings 4a naturally is released.
[0005] JP 2004-3832 A describes an example of a chemical
heat-storage apparatus using a chemical reaction of a heat storage
material. FIG. 13 indicates the chemical heat-storage apparatus of
JP 2004-3832 A in which a heat storage material 9 is heated by a
heating medium flowing through a heat exchanger 11, and heat is
stored while water vapor generated from the heat storage material 9
is discharged outside a container 10. Thus, heat can be stored
efficiently in a short time. In the heat release process, water is
supplied to the heat storage material 9 in a solid state, and the
heat of the heat storage material 9 is extracted using the heat
exchanger 11. Water droplets W each having a diameter of at least
0.2 mm are spread on the heat storage material 9 from above in
order to increase the conversion speed of the heat storage material
9 into a hydrate.
[0006] However, according to such a configuration in which water is
spread on the heat storage material from above, in the case where
the heat storage material at the time of heat storage is, for
example, in a liquid state or in a solid-liquid coexistence state,
and the heat storage material has a higher specific gravity than
water, a uniform water supply to the heat storage material is
difficult because water stays in an upper part of the heat storage
material due to the difference in specific gravity.
[0007] In view of the above-mentioned circumstances, it is an
object of the present invention to provide a chemical heat-storage
apparatus capable of supplying water uniformly to a heat storage
material in the heat release process.
DISCLOSURE OF THE INVENTION
[0008] That is, the present invention provides a chemical
heat-storage apparatus provided with: a container accommodating a
heat storage material that has a higher specific gravity than water
and that is capable of exothermically reacting with water; a heat
exchanger that is provided in the container and that is capable of
giving heat to the heat storage material in a heat storage process
as well as absorbing heat from the heat storage material in a heat
release process; a water flow path that has an opening downwardly
and that is provided below the heat exchanger inside the container
so as to supply, to the inside of the container, water to react
with the heat storage material; and a distribution plate that is
provided below the heat exchanger and above the opening inside the
container and that has a plurality of through holes for introducing
water supplied to the container from a lower part to an upper
part.
[0009] In the above-mentioned chemical heat-storage apparatus of
the present invention, the water supplied through the water flow
path to the inside of the container reacts with the heat storage
material while moving upward in the container. Since the water flow
path is provided below the heat exchanger, the heat storage
material present around the heat exchanger can react with water
efficiently in the heat release process. Further, since the
distribution plate is provided between the opening in the water
flow path and the heat exchanger, the water supplied through the
opening to the inside of the container moves upward while being
distributed by the distribution plate in the horizontal direction.
Thus, it is possible to supply the water uniformly to the heat
storage material, that is, a uniform mixture of the heat storage
material and the water can be achieved, and efficient and rapid
heat extraction is rendered possible. Furthermore, according to the
present invention, the opening of the water flow path opens
downwardly, and therefore the heat storage material is unlikely to
enter the water flow path. That is, it is possible to prevent
unintended reactions during heat storage from occurring due to the
entering of the heat storage material into the water flow path.
[0010] According to another aspect of the present invention, there
is provided a heat storage system provided with: a heat storage
circuit having the above-mentioned heat storage apparatus of the
present invention, a condenser for condensing water vapor, a reflux
path for introducing water vapor generated from the heat storage
material of the heat storage apparatus to the condenser in a heat
storage process, a tank for storing the condensed water, and a
supply path for introducing the water of the tank into the heat
storage apparatus in a heat release process; a heating apparatus
for giving heat to the heat storage material of the heat storage
apparatus in the heat storage process; and a heating medium circuit
for extracting heat from the heat storage material of the heat
storage apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram illustrating a heat storage
system according to one embodiment of the present invention.
[0012] FIG. 2 is a top view of a heat storage apparatus used in the
heat storage system of FIG. 1.
[0013] FIG. 3 is a sectional view of the heat storage apparatus
taken along the line III-III.
[0014] FIG. 4 is an enlarged partial view of FIG. 2.
[0015] FIG. 5 is a sectional view illustrating a distribution plate
according to a modified embodiment.
[0016] FIG. 6 A is an enlarged partial view of FIG. 5.
[0017] FIG. 6 B is an enlarged partial view illustrating a
distribution plate according to another modified embodiment.
[0018] FIG. 7 is an explanatory diagram of a model used for the
calculation of the preliminary reaction rate.
[0019] FIG. 8 A is a graph indicating the calculation results
(CaCl.sub.2) of the preliminary reaction rate.
[0020] FIG. 8 B is a graph indicating the calculation results
(MgSO.sub.4) of the preliminary reaction rate.
[0021] FIG. 9 is an operational diagram illustrating the heat
storage process in the heat storage system illustrated in FIG.
1.
[0022] FIG. 10 is an operational diagram illustrating the heat
release process in the heat storage system illustrated in FIG.
1.
[0023] FIG. 11 is a phase diagram indicating the transformation of
the heat storage material (calcium chloride hydrate).
[0024] FIG. 12 is a schematic diagram illustrating a conventional
latent heat storage apparatus.
[0025] FIG. 13 is a schematic diagram illustrating a conventional
chemical heat-storage apparatus.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026] FIG. 1 is a schematic diagram illustrating a heat storage
system according to one embodiment of the present invention. A heat
storage system 100 is equipped with a heat pump 116, a heat storage
circuit 121 and a heating medium circuit 122.
[0027] The heat pump 116 is equipped with a compressor 111, a heat
radiator 112, an expander 113, a first evaporator 114 and a second
evaporator 115. These equipments are connected by refrigerant
pipes, thereby forming a refrigerant circuit. The second evaporator
115 is used as a condenser 115 for the heat storage circuit 121.
The refrigerant circuit is filled with refrigerant such as carbon
dioxide and hydrofluorocarbon. The refrigerant that has been
compressed in the compressor 111 is cooled in the heat radiator
112. Thereafter, it is expanded in the expander 113, then
evaporated in the first evaporator 114 and the second evaporator
115, and returned to the compressor 111 again.
[0028] As a heating apparatus other than the heat pump 116,
resistance heating apparatuses, combustion heating apparatuses,
heating apparatuses using natural energy such as sunlight and
geothermal heat, and heating apparatuses using heat discharged from
plants or buildings can be employed.
[0029] The heat storage circuit 121 has a heat storage apparatus
101, a condenser 115, a recovery tank 123, a vacuum pump 119, an
on-off valve 120, a reflux path 124 and a supply path 125. The
reflux path 124 is a circuit for collecting, into the recovery tank
123, the water vapor that has been extracted from the heat storage
apparatus 101 in the heat storage process. The reflux path 124
connects the upper part of the heat storage apparatus 101, the
condenser 115 and the upper part of the recovery tank 123 in this
order. The water vapor that has been extracted from the heat
storage apparatus 101 is condensed in the condenser 115, and the
condensed water is stored in the recovery tank 123. The supply path
125 is a circuit for supplying water in the recovery tank 123
(dilution water) to the heat storage apparatus 101 in the heat
release process. The supply path 125 connects the lower part of the
recovery tank 123 to the water flow path of the heat storage
apparatus 101. The supply path 125 is provided with a water supply
pump 132.
[0030] The heating medium circuit 122 is a circuit for supplying
heat of the heat pump 116 to the heat storage apparatus 101 in the
heat storage process and extracting heat from the heat storage
apparatus 101 in the heat release process. A heating medium to flow
through the heating medium circuit 122 typically is water.
Specifically, the heating medium circuit 122 is constituted by an
introduction circuit 127, a hot water supply circuit 128 and a main
circuit 129. The heat radiator 112, a second three-way valve 118,
the heat storage apparatus 101, a first three-way valve 117 and a
circulation pump 126 are connected in this order by pipes, thereby
forming the main circuit 129.
[0031] In the heat storage process, the heating medium is
circulated in the main circuit 129 and the heat of the heating
medium that has been heated by the heat pump 116 is stored in the
heat storage apparatus 101. The introduction circuit 127 is
connected to the first three-way valve 117, and city water can be
supplied to the main circuit 129 through the introduction circuit
127. The hot water supply circuit 128 is connected to the second
three-way valve 118, and the hot water of the main circuit 129 can
be supplied to a tap 130 through the hot water supply circuit 128.
In the heat release process, the city water from the introduction
circuit 127 is heated in the heat storage apparatus 101, which then
is introduced into the hot water supply circuit 128.
[0032] Next, the heat storage apparatus 101 is described in detail.
FIG. 2 is a top view of the heat storage apparatus used in the heat
storage system of FIG. 1. FIG. 3 is a sectional view of the heat
storage apparatus taken along the line III-III. The heat storage
apparatus 101 is classified as a chemical heat-storage apparatus,
and specifically, a hybrid type of sensible heat storage, latent
heat storage and chemical heat storage is employed therefor. As
indicated in FIG. 2 and FIG. 3, the heat storage apparatus 101 is
provided with a container 202 (heat storage container), water flow
paths 204, a heat exchanger 209 and a distribution plate 206.
[0033] In view of preventing radiation loss, the container 202
preferably has excellent thermal insulation properties. The upper
part of the container 202 is connected with the reflux path 124 for
introducing water vapor into the condenser 115 (FIG. 1).
[0034] As indicated in FIG. 3, the container 202 accommodates a
heat storage material 210 having a higher specific gravity than
water. The heat storage material 210 exothermically reacts with
water, and endothermically reacts by dehydration. The heat storage
material 210 has a higher specific gravity than water at any time
of heat storage and heat release, and during the period of
performing the heat storage process and the period of performing
the heat release process. As the heat storage material 210, at
least one selected from calcium chloride hydrate, calcium bromide
hydrate and magnesium sulfate hydrate can be used. Among these,
calcium chloride hydrate is used suitably because of its high
storage capacity, the ease of heat extraction, and the like.
Calcium chloride hydrate is capable of reversibly adsorbing and
desorbing water. It absorbs heat due to water elimination and
generates heat due to bonding with water. Particularly, calcium
chloride hexahydrate that transforms, due to water elimination,
into calcium chloride tetrahydrate, further into calcium chloride
dihydrate, can be used suitably.
[0035] FIG. 11 is a phase diagram indicating the transformation of
calcium chloride hydrate as one example of the heat storage
material. The horizontal axis indicates the weight concentration of
calcium chloride with respect to the total weight of the heat
storage material, and the vertical axis indicates the temperature
thereof. In FIG. 11, the phases of the heat storage material are
indicated. For example, calcium chloride hydrate (hexahydrate)
having a weight concentration of 50% is in a solid state at a
temperature of less than 30.degree. C. If the temperature exceeds
30.degree. C., a calcium chloride solution is generated.
[0036] In this embodiment, the heat storage material 210 is in a
solid-liquid coexistence state or in a liquid phase at the time of
the start of the heat release process. Specifically, a controller
136 controls the amount of water vapor to be introduced from the
container 202 into the condenser 115 in the heat storage process so
that the heat storage material 210 is maintained in a solid-liquid
coexistence state or in a liquid phase. For example, it controls
the amount of water vapor to be drawn from the container 202 so
that the weight concentration of calcium chloride falls within the
range of 60% to 75% at 80.degree. C. Specifically, the controller
136 controls the period of performing the heat storage process (the
operation period of the heat pump 116) by monitoring the amount of
water of the recovery tank 123 using a detector 134 such as a float
sensor so that the amount of water of the recovery tank 123 falls
within a predetermined range. Thus, heat is stored while the heat
storage material 210 is in a solid-liquid coexistence state. In the
case of the heat storage material 210 in a solid-liquid coexistence
state, uniform water supply to the heat storage material 210 is
possible in the heat release process. Accordingly, the heat storage
apparatus 101 of this embodiment makes it feasible to extract heat
efficiently and rapidly.
[0037] On the other hand, the heat storage material 210 at the time
of the start of the heat storage process may be in a solid phase.
For example, the controller 136 controls the amount of water supply
to the container 202 in the heat release process so that the weight
concentration of calcium chloride is about 50%. Specifically, it
controls the operation of the water supply pump 132 so that the
amount of water of the recovery tank 123 falls within a
predetermined range. The temperature inside the container 202 after
the sufficient extraction of heat is, for example, less than
30.degree. C., and calcium chloride hexahydrate in a solid state
precipitates therein. Of course, it is possible that the weight
concentration of calcium chloride is set in the range of 50 to 60%
and a mixture of the tetrahydrate and hexahydrate is formed.
[0038] Further, it also is possible to reduce the discharge amount
(condensation amount) of water vapor so that the heat storage
material 210 at the time of the completion of the heat storage
process is in a liquid phase. Furthermore, a valve may be provided
on the reflux path 124. A configuration in which the valve is
opened during the period of performing the heat storage process and
closed during periods other than the above period also is possible.
Such a configuration can prevent the water vapor from escaping from
the container 202 until the heat storage material 210 transforms
into a solid phase as well as reducing radiation loss.
[0039] It should be noted that although a control line is omitted
in FIG. 1, the controller 136 may be configured to control the heat
pump 116, the first three-way valve 117, the second three-way valve
118, the vacuum pump 119, the on-off valve 120 and the circulation
pump 126.
[0040] As indicated in FIG. 2 and FIG. 3, the heat exchanger 209 in
this embodiment is a fin-tube heat exchanger having a plurality of
fins 207 aligned parallel to each other, and a heat transfer tube
208 passing through the plurality of the fins 207. Use of the
fin-tube heat exchanger enables rapid heat storage/heat release. In
the heat storage process, the heating medium heated in the heat
pump 116 flows through the heat transfer tube 208. In the heat
release process, city water from the introduction circuit 127 flows
through the heat transfer tube 208.
[0041] The water flow paths 204 are provided in a lower part of the
container 202. The water flow paths 204 are located below the heat
exchanger 209 inside the container 202. Openings 203 opening
downwardly are formed on the water flow paths 204, as apertures for
water supply. Water in the water flow paths 204 is supplied to the
inside of the container 202 through the openings 203. The openings
203 face a bottom surface 202b of the container 202, and a gap
having an appropriate width is ensured between the openings 203 and
the bottom surface 202b of the container 202. The gap enables a
smooth water supply to the container 202 through the openings 203.
Further, since the heat storage material 210 at the time of the
completion of the heat storage process is in a solid-liquid
coexistence state or in a liquid phase in this embodiment, water
can be supplied uniformly to the heat storage material 210 through
the water flow paths 204 provided in the lower part of the
container 202.
[0042] The water flow paths 204 each may have an internal diameter
in the range of 3 to 30 mm (more preferably 3 to 8 mm) in view of
the reduction of dead space not contributing to heat storage as
well as the prevention of the increase in pressure loss due to
scale deposition. In this embodiment, a plurality of pipes
horizontally aligned parallel to each other are laterally inserted
straight into the container 202 for constituting the water flow
paths 204. That is, the water flow paths 204 each extend in the
horizontal direction inside the container 202. A plurality of the
openings 203 are formed on each of the water flow paths 204 along
the longitudinal direction at equal intervals. The water flow paths
204 are merged into one outside the container 202, which is
connected to the supply path 125. The total area of the plurality
of the openings 203 formed on each water flow path 204 may be in
the range of 30 to 50% with respect to the cross-sectional area of
the water flow path 204. This makes it possible to supply an equal
amount of water to the inside of the container 202 through each
opening 203.
[0043] The distribution plate 206 is provided below the heat
exchanger 209 inside the container 202 as well as above the
openings 203 of the water flow paths 204. In other words, the
thickness of the distribution plate 206 used in this embodiment is
smaller than the outer diameter of the water flow path 204.
Although the material of the distribution plate 206 is not
specifically limited, the distribution plate 206 may be made of a
metal or a resin having an excellent corrosion resistance. In the
distribution plate 206, a plurality of through holes 205 are formed
so that the water supplied through the water flow paths 204 to the
inside of the container 202 is introduced from the bottom to the
top. The through holes 205 are formed along the longitudinal
direction of the water flow path 204 so that each through hole 205
is located between adjacent two of the fins 207.
[0044] In this embodiment, the upper parts of the water flow paths
204 are exposed above the distribution plate 206, and the lower
parts of the water flow paths 204 are exposed below the
distribution plate 206. In other words, the distribution plate 206
is arranged above the openings 203 of the water flow paths 204 and
below the tops of the water flow paths 204. That is, the
distribution plate 206 is provided, extending over one of the water
flow paths 204 and another of the water flow paths 204 that are
adjacent to each other. In this way, it is possible to ensure an
effect on the distribution in the horizontal direction of the water
supplied to the inside of the container 202, while suppressing the
reduction of the filling amount of the heat storage material 210
due to the providing of the distribution plate 206.
[0045] As indicated in FIG. 3, a gap G having a height exceeding
the projecting height of the water flow paths 204 from a lower
surface 206p is formed between the lower surface 206p of the
distribution plate 206 and the bottom surface 202b (inside bottom
surface) of the container 202. This gap G also is filled with the
heat storage material 210. The gap G may have a height that allows
water to flow smoothly through the horizontal direction, such as a
height of 1 to 3 mm, for example.
[0046] The mutual relationship of the heat exchanger 209, the water
flow paths 204 and the distribution plate 206 is described further
in detail.
[0047] As indicated in FIG. 2, the plurality of the fins 207
aligned in parallel are accommodated in the container 202 while
standing upright. In the container 202, the longitudinal direction
of the heat transfer tube 208 is consistent with the longitudinal
direction of the water flow path 204. Further, the heat transfer
tube 208 and the water flow paths 204 are aligned alternately in
the direction (direction WL indicated in FIG. 2) parallel to both
of the horizontal direction and the in-plane direction of the fin
207. That is, the heat transfer tube 208 and the water flow paths
204 have a staggered arrangement in the cross section (FIG. 3)
perpendicular to the longitudinal direction of the water flow path
204. With such an arrangement, the water that has been supplied to
the inside of the container 202 can move upward smoothly along the
fins 207, so that the water spreads uniformly all over the inside
of the container 202. As a result, efficient and rapid heat release
is rendered possible.
[0048] Further, the horizontal distance H.sub.1 between one
selected from the plurality of the through holes 205 and the
opening 203 located closest to the selected through hole 205 is
constant for every one of the plurality of through holes 205, as
indicated in the enlarged plan view of FIG. 4. With such a
positional relationship, the water that has been supplied through
the water flow paths 204 to the inside of the container 202 flows
into each of the plurality of the through holes 205 in an equal
amount. Therefore, the water can be supplied, without unevenness,
to the heat storage material 210 present above the distribution
plate 206, so that concentration distribution is unlikely to occur
in the heat storage material 210. As a result, efficient and rapid
heat release is rendered possible.
[0049] Further, the number of the through holes 205 formed in the
distribution plate 206 is at least twice the number of the openings
203 formed in the water flow paths 204. Thus, the effect on the
distribution in the horizontal direction of the water supplied
through the water flow paths 204 to the inside of the container 202
is enhanced.
[0050] As indicated in FIG. 4, the plurality of the fins 207 are
arranged perpendicularly to the longitudinal direction of the water
flow path 204. The plurality of the openings 203 are formed in the
water flow path 204 at the interval D.sub.1 equal to the fin pitch
FP for the plurality of the fins 207. The fin pitch FP means the
interval between the arrays of the fins 207 when the thickness of
the fins 207 is assumed to be zero. Furthermore, the through holes
205 are formed in the distribution plate 206 at the interval
D.sub.1 equal to the fin pitch FP in a direction parallel to the
longitudinal direction of the water flow path 204. Such a
configuration allows water to be introduced in equal amounts to
each fin 207, which therefore is effective for more efficient and
rapid heat release. This configuration is particularly effective in
the case where the inside of the container 202 is partitioned by
the fins 207 in a direction orthogonal to the longitudinal
direction of the water flow path 204.
[0051] Further, the interval between two of the through holes 205
adjacent to each other in the direction (direction WL indicated in
FIG. 2) parallel to both of the horizontal direction and the
in-plane direction of the fin 207 is larger than the interval
D.sub.1 of the openings 203. The formation of the through holes 205
in the above-mentioned direction at an appropriately large interval
makes it possible to deal with the reduction of the number of the
water flow paths 204. The reduction in the number of the water flow
paths 204 leads to a decrease in dead space and therefore is
preferable.
[0052] Further, the heat exchanger 209 (specifically, the fins 207)
is in contact directly with the distribution plate 206 in this
embodiment. The heat exchanger 209 (specifically, the fins 207)
also is in contact directly with the water flow paths 204. In this
way, it is possible to heat the water flow paths 204 and the
distribution plate 206 efficiently at the time of heat storage.
Then, it also is possible to heat the heat storage material 210
present in the periphery of the water flow paths 204 and the
distribution plate 206 without fail, therefore preventing the
openings 203 and the through holes 205 from being closed by the
heat storage material 210 in a solid state.
[0053] For example, if the fins 207 are distant from the water flow
paths 204 and the distribution plate 206, heat is not conducted
sufficiently from the heat exchanger 209 to the heat storage
material 210 present in the lower part of the container 202. Thus,
there is a possibility that the heat storage process ends with the
openings 203 and the through holes 205 being closed by the heat
storage material 210 in a solid state. In contrast, according to
this embodiment, the heat of the heat exchanger 209 (to be precise,
the heat of the heating medium) is conducted directly to the water
flow paths 204 and the distribution plate 206, so that the heat
storage material 210 present in the lower part of the container 202
can be melted without fail, thereby avoiding the closure of the
openings 203 and the through holes 205.
[0054] Further, the water flow paths 204 are in contact directly
with the distribution plate 206. Specifically, the pipes (the water
flow paths 204) are fitted tightly into the distribution plate 206
so as to inhibit water from moving upward along the surface of the
pipes constituting the water flow paths 204. In this way, the
entire amount of the water supplied to the inside of the container
202 through the openings 203 of the water flow paths 204 hits the
lower surface 206p of the distribution plate 206, thereby being
distributed in the horizontal direction so as to move upward
through the through holes 205. As a result, it is possible to
supply the water uniformly to the heat storage material 210 present
above the distribution plate 206. Further, the heat of the water
flow paths 204 is conducted directly to the distribution plate 206.
Therefore, it is possible to prevent the through holes 205 from
being closed by the heat storage material 210 more reliably.
[0055] The distribution plate for distributing water flow is not
limited to those having the structure indicated in FIG. 3. For
example, as indicated in FIG. 5, a distribution plate 217 having a
double layer structure can be used suitably.
[0056] As indicated in FIG. 5, the distribution plate 217 of this
modified embodiment is constituted by an upper plate portion 211, a
lower plate portion 213 and internal spaces 215 formed between the
upper plate portion 211 and the lower plate portion 213. The lower
plate portion 213 is located so that water is introduced through
the water flow paths 204 into the gap G between the bottom surface
202b of the container 202 and the lower surface 213p of the lower
plate portion 213 itself. In the lower plate portion 213, a
plurality of lower through holes 214 are formed for introducing,
into the internal spaces 215, the water supplied to the inside of
the container 202 through the water flow paths 204. The upper plate
portion 211 is located between the lower plate portion 213 and the
tops of the water flow paths 204. The upper plate portion 211 is
formed with a plurality of upper through holes 212 for introducing
the water present in the internal spaces 215 upwardly. The water
supplied to the inside of the container 202 through the water flow
paths 204 flows through the lower through holes 214, the internal
spaces 215 and the upper through holes 212 in this order, so that
it moves from the space (gap G) below the distribution plate 217 to
the space above the distribution plate 217. The distribution plate
217 has an excellent function of distributing water in the
horizontal direction because a plurality of the upper through holes
212 are provided with respect to one of the lower through holes
214.
[0057] As indicated in FIG. 6 A, the horizontal distance H.sub.2
from one of the openings 203 of the water flow paths 204 to the
closest one of the lower through holes 214 is constant. The lower
through holes 214 formed in the distribution plate 217 of this
modified embodiment each have a wide mouth, and therefore the
center position of each of the lower through holes 214 is adjusted
(offset) so that the water flows equally into the two upper through
holes 212. As indicated in FIG. 6 B, the horizontal distance
H.sub.3 between the one of the lower through holes 214' and the
closest one of the upper through holes 212 may be constant with
respect to all the upper through holes 212.
[0058] As indicated in FIG. 3 etc., since the openings 203 of the
water flow paths 204 open downwardly, it is possible to prevent the
heat storage material 210 from entering the water flow paths 204
through the openings 203 in this embodiment. However, since the
heat storage material 210 is in a solid-liquid coexistence state or
in a liquid phase at the time of the completion of the heat storage
process, the heat storage material 210 can be diffused to some
extent inside the water flow paths 204 through the openings 203,
thus causing unintended reactions. Hereinafter, such a phenomenon
is referred to as "preliminary reactions".
[0059] There is a limitation on the size of the openings 203 of the
water flow paths 204 in this embodiment, in order to minimize
preliminary reactions. Specifically, the total area S.sub.1 of the
openings 203 is defined so that the water weight W.sub.1 in each
water flow path 204 and the total area S.sub.1 of the openings 203
formed in the water flow path 204 satisfy the relationship
expressed by the following formula (1).
500.ltoreq.(W.sub.1/S.sub.1)(unit: kg/m.sup.2) (1)
[0060] The above-described formula (1) has been found as a result
of the following study. Specifically, the preliminary reaction rate
after 8 hours was calculated for the model indicated in FIG. 7
based on the following diffusion equation in order to predict the
degree of the diffusion of the heat storage material. Here, the
"preliminary reaction rate" means a value indicating the ratio of
the heat storage material diffused into water present inside the
pipe (water flow path 204). For example, the state of the
"preliminary reaction rate=100%" means that the heat storage
material concentration in the solution inside the pipe and the heat
storage material concentration in the solution outside the pipe are
equalized. Assuming that the heat storage process was performed
during the night and the heat release process was performed during
the daytime, the preliminary reaction rate after 8 hours was
calculated.
[0061] Calculation formula:
.differential.C/.differential.t=D(.differential..sup.2C/.differential.x.-
sup.2+.differential..sup.2C/.differential.y.sup.2+.differential..sup.2C/.d-
ifferential.z.sup.2)
C: molar concentration (mol/liter) t: time (sec) x, y, z:
coordinates Diffusion coefficient (CaCl.sub.2) D=1.11*10
.sup.9m.sup.2/sec Diffusion coefficient (MgSO.sub.4) D=0.849*10
.sup.9m.sup.2/sec
[0062] In the model indicated in FIG. 7, one opening 203 is
provided in each pipe 204. The preliminary reaction rate was
calculated for each of 4 types of pipes respectively having an
internal diameter of 3 mm, 8 mm, 16 mm and 30 mm while varying the
amount of the water present therein by varying the length of the
pipe. The diameter of the opening 203 was fixed to 0.3 mm. A
calcium chloride aqueous solution and a magnesium sulfate aqueous
solution each having an initial concentration indicated in FIG. 7
were used as a heat storage material in the calculation model.
[0063] FIG. 8 A and FIG. 8 B indicate the calculation results. FIG.
8 A indicates the calculation results for sodium chloride, and FIG.
8 B indicates the calculation results for magnesium sulfate. The
vertical axis in the graph indicates the preliminary reaction rate
(%). The horizontal axis indicates the value of (W.sub.1/S.sub.1)
(unit: kg/m.sup.2), when the water weight in the pipe is referred
to as W.sub.1 and the area of the opening (opening area) is
referred to as S.sub.1. As indicated in FIG. 8 A and FIG. 8 B, the
thicker the pipe is, the lower the preliminary reaction rate should
be. The preliminary reaction rate after about 8 hours was less than
10% in the pipe having an internal diameter of 8 mm or more.
[0064] However, since there are problems such as an increase in
dead space and a reduction in the amount of heat to be stored,
there also is a limitation on the thickness of pipes to be used.
Further, the pipe should not be too thin because of the problem of
scale deposition. Specifically, a pipe having an internal diameter
of 3 to 8 mm is used suitably for the water flow path 204.
Therefore, it is fairly reasonable to find a suitable range of
(W.sub.1/S.sub.1) from the calculation results for the pipe having
an internal diameter of 3 mm. Further, according to the calculation
results for the pipe of .phi.3 mm, there is a sudden inclination
variation in the curve of the preliminary reaction rate at the
border of (W.sub.1/S.sub.1)=500. Accordingly, the design of the
water flow path 204 satisfying 500.ltoreq.(W.sub.1/S.sub.1) makes
it possible to achieve the preliminary reaction rate of less than
10%.
[0065] There is no particular limitation on the upper limit of the
value of (W.sub.1/S.sub.1), but a measure of the upper limit of the
value can be determined in view of the following. For example, in
the case of using a 0.1 mm thick fin for the heat exchanger, it is
conceivable that the fin pitch is set to at least 1 mm as well as
the interval of the openings 203 is set to at least 1 mm, in order
to achieve the filling rate of the heat storage material inside the
container to at least 90%. On the other hand, each pipe (water flow
path 204) preferably has an internal diameter of 1 inch (25.4 mm)
or less in view of processability. Considering the openings 203 of
.phi.0.3 mm in the context of these conditions, the water flow path
204 may be designed so that (W.sub.1/S.sub.1).ltoreq.7000 is
satisfied approximately.
[0066] <<Heat Storage Operation>>
[0067] Next, heat storage operation is described with reference to
FIG. 9.
[0068] First, the on-off valve 120 is opened, so that the vacuum
pump 119 is started, and the pressure inside the container 202 of
the heat storage apparatus 101, the reflux path 124 and the
condenser 115 is reduced. After the pressure is reduced to a
predetermined level, the on-off valve 120 is closed, so that the
vacuum pump 119 is stopped.
[0069] Next, the first three-way valve 117 and the second three-way
valve 118 are set so that water is circulated in the main circuit
129 of the hot water supply circuit 122 in the direction of the
arrow a. Thereafter, the operation of the heat pump 116 is started.
The water circulating in the main circuit 129 is heated by the heat
radiator 112 of the heat pump 116. The water heated to a
temperature of about 80.degree. C. flows into the heat exchanger
209 of the heat storage apparatus 101 (to be precise, the heat
transfer tube 208) to heat the heat storage material 210. Since the
fins 207 of the heat exchanger 209 are in contact directly with the
water flow paths 204 and the distribution plate 206, the water flow
paths 204 and the distribution plate 206 also are heated
efficiently and the heat is delivered sufficiently to the heat
storage material 210 present in the lower part of the container
202.
[0070] As indicated in FIG. 11, the heat storage material 210 is in
a solid state at the time of the start of the heat storage process
(point A). The heating proceeds, and when the temperature is
increased to 30.degree. C. or more (point B), the heat storage
material 210 transforms into a liquid. Since the pressure of each
of the container 202, the reflux path 124 and the condenser 115 is
reduced, dehydration starts after the heat storage material 210 is
transformed into a liquid. The condenser 115 is cooled by
refrigerant at low temperature (e.g. 0.degree. C.) circulating in
the heat pump 116. Accordingly, the water vapor generated from the
heat storage material 210 is condensed due to heat exchange with
the refrigerant in the condenser 115. The condensation heat is
recovered by the heat pump 116.
[0071] The heating proceeds further, and the heat storage material
210 is concentrated with the temperature increase. When the
concentration exceeds the solubility curve (point C), the heat
storage material 210 in a solid state precipitates again so as to
be transformed into a solid-liquid solution. At the time when the
heat storage material 210 has a temperature of 80.degree. C. and a
weight concentration of 61% (point D), the heat storage process is
completed.
[0072] <<Heat Release Operation>>
[0073] Next, heat release operation is described with reference to
FIG. 10.
[0074] First, the first three-way valve 117 and the second
three-way valve 118 are set so that water flows through the hot
water supply circuit 122 in the direction of the arrow b, and city
water is supplied through the introduction circuit 127 to the heat
storage apparatus 101.
[0075] Next, water is supplied from the recovery tank 123 through
the supply path 125 to the heat storage apparatus 101. The water
for dilution supplied through the supply path 125 flows through the
water flow paths 204 to be jetted downwardly through the openings
203 into the inside of the container 202. The water supplied to the
inside of the container 202 immediately forms an upward flow based
on the difference in specific gravity. For example, the specific
gravity of the heat storage material 210 having a weight
concentration of calcium chloride of 60 to 75% is about 1.5 kg/L at
80.degree. C., and the specific gravity of the water supplied to
the inside of the container 202 is about 1 kg/L.
[0076] In this embodiment, since the distribution plate 206 is
provided above the openings 203, the water hits the distribution
plate 206 to be distributed in the horizontal direction.
Thereafter, the water in an equal amount is supplied through each
through hole 205 to the heat storage material 210 in the upper part
of the container 202. Then, the heat storage material 210 is
diluted to a weight concentration of about 50%. The temperature of
the heat storage material 210 rises up to 95.degree. C. due to the
exothermic reaction (point E in FIG. 11). The heat storage material
210 is in a liquid phase at this time.
[0077] The action of the heat exchanger 209 causes the heat
exchange between the city water flowing through the heat transfer
tube 208 and the heat storage material 210. The city water absorbs
heat from the heat storage material 210 and is introduced into the
tap 130 through the hot water supply circuit 122. The temperature
of the heat storage material 210 decreases, and when the
temperature decreases to 30.degree. C. (point B) or less, the heat
storage material 210 transforms into a solid. The heat release
process is continued until the temperature of the city water at the
outlet of the heat storage apparatus 101 decreases to a
predetermined temperature (e.g. 42.degree. C. or less).
INDUSTRIAL APPLICABILITY
[0078] The heat storage apparatus of the present invention can be
used suitably for domestic water heaters and heating apparatuses.
However, the present invention is not limited thereto, and it can
be used widely for various systems for storing waste heat.
* * * * *