U.S. patent application number 15/897244 was filed with the patent office on 2018-08-16 for heat exchanger and water heater.
The applicant listed for this patent is Rinnai Corporation. Invention is credited to Takuya Miura, Takaaki Nakagoshi.
Application Number | 20180231333 15/897244 |
Document ID | / |
Family ID | 63105024 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180231333 |
Kind Code |
A1 |
Miura; Takuya ; et
al. |
August 16, 2018 |
HEAT EXCHANGER AND WATER HEATER
Abstract
The heat exchanger including a plurality of fluid flow paths
(401), (402), (403) arranged in a plurality of stages in a height
direction, wherein a fluid inlet port (13a) and a fluid outlet port
(13b) of the fluid flow path (403) located at a lowermost stage
among the plurality of fluid flow paths (401), (402), (403) have
larger flow path cross-sectional areas than a fluid inlet port
(11a) and a fluid outlet port (11b) of the fluid flow path (401)
located at an uppermost stage.
Inventors: |
Miura; Takuya; (Nagoya-shi,
JP) ; Nakagoshi; Takaaki; (Nagoya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rinnai Corporation |
Nagoya-shi |
|
JP |
|
|
Family ID: |
63105024 |
Appl. No.: |
15/897244 |
Filed: |
February 15, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 1/02 20130101; F24H
1/14 20130101; F28D 1/04 20130101; F28F 21/083 20130101 |
International
Class: |
F28F 1/02 20060101
F28F001/02; F28F 21/08 20060101 F28F021/08; F24H 1/14 20060101
F24H001/14; F28D 1/04 20060101 F28D001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2017 |
JP |
2017-026634 |
Claims
1. A heat exchanger comprising: a case body including a flow
passage of combustion exhaust gas therein; a plurality of fluid
flow paths arranged in a plurality of stages in a height direction
along a side wall of the case body; a distribution header
communicating with fluid inlet ports of the plurality of fluid flow
paths and distributing a fluid to be heated to the plurality of
fluid flow paths; and a collection header communicating with fluid
outlet ports of the plurality of fluid flow paths and collecting
the fluid to be heated from the plurality of fluid flow paths,
wherein the fluid inlet port and the fluid outlet port of the fluid
flow path located at a lowermost stage among the plurality of fluid
flow paths have larger flow path cross-sectional areas than the
fluid inlet port and the fluid outlet port of the fluid flow path
located at an uppermost stage among the plurality of fluid flow
paths, respectively.
2. The heat exchanger according to claim 1, wherein the fluid inlet
port and the fluid outlet port of a lower-stage fluid flow path
located at a lower stage than the fluid flow path located at the
uppermost stage among the plurality of fluid flow paths have larger
flow path cross-sectional areas than the fluid inlet port and the
fluid outlet port of the fluid flow path located at the uppermost
stage, respectively.
3. The heat exchanger according to claim 1, wherein the fluid inlet
port and the fluid outlet port of the fluid flow path located at
the lowermost stage among the plurality of fluid flow paths have
larger flow path cross-sectional areas than the fluid inlet port
and the fluid outlet port of an upper-stage fluid flow path located
at a upper stage than the fluid flow path located at the lowermost
stage, respectively.
4. The heat exchanger according to claim 1, wherein the fluid flow
path located at the lowermost stage among the plurality of fluid
flow paths is disposed so as to protrude more inwardly of the case
body than an upper-stage fluid flow path located at an upper stage
than the fluid flow path located at the lowermost stage as viewed
from an upstream side of the flow passage of the combustion exhaust
gas.
5. A water heater comprising the heat exchanger according to claim
1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims a priority based on a
Japanese Patent Application No. 2017-26634 filed on Feb. 16, 2017,
the content of which is hereby incorporated by reference in its
entirely.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a heat exchanger configured
to heat a fluid to be heated flowing through a plurality of fluid
flow paths arranged in a plurality of stages in a height direction
by heat exchange with combustion exhaust gas and a water heater
including the heat exchanger.
Description of the Related Art
[0003] Conventionally, there has been known a water heater having a
can body in which a sub heat exchanger as a latent heat exchanger,
a main heat exchanger as a sensitive heat exchanger, and a gas
burner are disposed in this order from above (For example, Japanese
Unexamined Patent Publication No. 2002-327960 A). In this type of
water heater, as a part of a fluid flow path through which a fluid
to be heated flows, a coiled water pipe is provided along side
walls of the can body between a main heat transfer pipe of the main
heat exchanger and the gas burner.
[0004] The fluid to be heated such as water supplied from a water
supply pipe flows from a sub heat transfer pipe of the sub heat
exchanger to the main heat transfer pipe of the main heat exchanger
through the coiled water pipe. During the fluid to be heated flows
through the fluid flow path, the fluid to be heated is heated by
heat exchange with combustion exhaust gas ejected from the gas
burner, and a heated fluid is supplied to a supply terminal through
a hot-water supplying pipe connected to the main heat transfer
pipe.
[0005] In the water heater described above, a single coiled water
pipe is wound along the side walls of the can body, whereby
abnormal overheating of the side walls is prevented. Further, in
order to smoothly discharge the fluid to be heated from the fluid
flow path in drainage work for preventing freezing, when the water
heater can use a can body having a sufficient height, the coiled
water pipe inclined at a predetermined degree is wound around the
side walls of the can body (for example, at about 5 degrees with
respect to the horizontal).
[0006] On the other hand, there has also been proposed a so-called
downward combustion-type water heater in which a heat exchanger is
provided below a gas burner having a downward combustion surface on
the contrary to such disposition of the heat exchanger and the gas
burner as described above (For example, Japanese Unexamined Patent
Publication No. 2016-169934 A).
[0007] In order to reduce flow resistance by the coiled water pipe,
the above-described downward combustion-type water heater includes
a main heat exchanger having a single distribution header
connecting with a plurality of fluid flow paths and a single
collection header connecting with the plurality of fluid flow
paths.
[0008] The plurality of fluid flow paths have straight heat
transfer pipes arranged in a plurality of stages in a height
direction along two opposite side walls of a case body. Moreover,
fluid inlet ports and fluid outlet ports of the plurality of fluid
flow paths are connected to the single distribution header and the
single collection header, respectively.
[0009] In order to reduce a height of the main heat exchanger
having such a configuration, each of the fluid flow paths is needed
to be arranged in a substantially horizontal posture. However, in a
case where the respective fluid flow paths are provided
substantially horizontally, the fluid inlet port and the fluid
outlet port of each of the fluid flow paths are located at
substantially the same height. Therefore, drainage performance for
water from the fluid flow path deteriorates.
[0010] In particular, the water is hardly discharged from the fluid
flow path located at a lowermost stage among the fluid flow paths
arranged in the plurality of stages, whereby the water tends to
remain in the fluid flow path located at the lowermost stage. As a
result, when an outside air temperature drops to 0 degrees Celsius
or less in winter in a state in which the water remains in the
fluid flow paths, residual water freezes and a volume of the
residual water expands, which may result in damaging the fluid flow
paths.
SUMMARY OF THE INVENTION
[0011] The present invention has been made in view of the foregoing
problems, and an object of the present invention is to provide a
heat exchanger capable of smoothly and reliably discharging a fluid
to be heated from a plurality of fluid flow paths even when the
plurality of fluid flow paths are arranged in a plurality of stages
in a height direction along a side wall of a case body, and fluid
inlet ports and fluid outlet ports of the plurality of fluid flow
paths are connected to a single distribution header and a single
collection header, respectively, and to provide a water heater
using the heat exchanger.
[0012] According to one aspect of the present invention, there is
provided a case body including a flow passage of combustion exhaust
gas therein;
[0013] a plurality of fluid flow paths arranged in a plurality of
stages in a height direction along a side wall of the case
body;
[0014] a distribution header communicating with fluid inlet ports
of the plurality of fluid flow paths and distributing a fluid to be
heated to the plurality of fluid flow paths; and
[0015] a collection header communicating with fluid outlet ports of
the plurality of fluid flow paths and collecting the fluid to be
heated from the plurality of fluid flow paths, wherein
[0016] the fluid inlet port and the fluid outlet port of the fluid
flow path located at a lowermost stage among the plurality of fluid
flow paths have larger flow path cross-sectional areas than the
fluid inlet port and the fluid outlet port of the fluid flow path
located at an uppermost stage among the plurality of fluid flow
paths, respectively.
[0017] According to another aspect of the present invention, there
is provided a water heater having the heat exchanger described
above.
[0018] In accordance with the present invention, the fluid to be
heated can be discharged smoothly and reliably even in the heat
exchanger in which the plurality of fluid flow paths are arranged
in the plurality of stages in the height direction along the side
wall of the case body, and the fluid inlet ports and the fluid
outlet ports of the plurality of fluid flow paths are connected to
the single distribution header and the single collection header,
respectively. Therefore, a height of the case body can be reduced
as compared with a heat exchanger in which a heat transfer pipe is
inclinedly wound around the side walls of the case body. Hence, the
heat exchanger suitably used for a downward combustion-type water
heater can be provided.
[0019] Moreover, since the water heater having the above-described
heat exchanger is excellent in drainage performance for water, even
in winter when an outside air temperature drops, freezing and
expansion of the fluid remaining in the fluid flow path hardly
occur. Therefore, rupture or damage of a heat transfer pipe
constituting the fluid flow path hardly occurs. Hence, the water
heater having excellent durability can be provided.
[0020] Other objects, features and advantages of the present
invention will become more fully understood from the detailed
description given hereinbelow and the accompanying drawings which
are given by way of illustration only, and thus are not to be
considered as limiting the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic configuration diagram showing one
example of a water heater including a heat exchanger according to
an embodiment of the present invention;
[0022] FIG. 2 is a schematic partial exploded perspective view
showing one example of the heat exchanger according to the
embodiment of the present invention;
[0023] FIG. 3 is a schematic partial enlarged cross-sectional view
showing one example of the heat exchanger according to the
embodiment of the present invention; and
[0024] FIG. 4 is schematic partial enlarged front views showing
heat exchangers according to other embodiments of the present
invention, wherein FIG. 4A shows a heat exchanger in which a
plurality of fluid flow paths are arranged in such a manner that
flow path cross-sectional areas of a fluid inlet port and a fluid
outlet port become larger in order from above, respectively, FIG.
4B shows a heat exchanger in which a plurality of fluid flow paths
are arranged in such a manner that fluid inlet ports and fluid
outlet ports of the fluid flow paths located at middle and
lowermost stages have the same flow path cross-sectional areas,
respectively, and that the fluid inlet ports and the fluid outlet
ports of the fluid flow paths located at the middle and lowermost
stages have larger flow path cross-sectional areas than a fluid
inlet port and a fluid outlet port of the fluid flow path located
at an uppermost stage, respectively, and FIG. 4C shows a heat
exchanger in which a plurality of fluid flow paths are arranged in
such a manner that flow path cross-sectional areas of the plurality
of fluid flow paths become larger in order of an uppermost, a
lowermost, and middle stages.
DESCRIPTION OF THE EMBODIMENTS
[0025] Hereinafter, referring to drawings, a heat exchanger
according to an embodiment of the present invention will be
described in detail.
[0026] The heat exchanger (3) according to the present embodiment
is incorporated in a water heater (4). As shown in FIG. 1, in the
water heater (4), a gas burner (50) having a downward combustion
surface is disposed in an upper region of the water heater (4).
Moreover, a lower portion of the gas burner (50) is continuously
connected to a substantially rectangular box-shaped case body (30)
of a heat exchanger (3). Furthermore, a lower portion of the case
body (30) is continuously connected to an exhaust passage (31)
guiding combustion exhaust gas supplied from the gas burner (50) to
an outside of the water heater (4).
[0027] An upper portion of the gas burner (50) is connected to a
fan unit (5) supplying air outside the water heater (4) as
combustion air for the gas burner (50). The combustion exhaust gas
ejected from the gas burner (50) is fed into the heat exchanger (3)
by the fan unit 5. Then, the combustion exhaust gas is discharged
to the outside of the water heater (4) through the exhaust passage
(31).
[0028] Water, as a fluid to be heated, supplied from a water supply
pipe (41) flows into second heat transfer pipes (2) located in a
lower half region of the case body (30) of the heat exchanger (3),
and subsequently, flows into first heat transfer pipes (1) as
coiled water pipes located in an upper half region of the case body
(30). When the water sequentially flows through the second heat
transfer pipes (2) and the first heat transfer pipes (1), the water
is heated by heat exchange with the combustion exhaust gas ejected
from the gas burner (50), and hot water as a heated fluid is
supplied to a hot water supply terminal through a hot-water supply
pipe (42).
[0029] Acid drain generated on surfaces of heat transfer fins (33)
is collected by a drain receiver (40) to discharge to the outside
of the water heater (4) through a drain neutralizer (not shown)
from a drain pipe (43).
[0030] As shown in FIG. 2, between front and back facing side walls
(301), (302) of the case body (30), a plurality of plate-shaped
heat-transfer fins (33) made of stainless steel-based metal are
provided vertically, and arranged side horizontally by side at
predetermined intervals in substantially parallel with the front
and back side walls (301), (302). Only some heat-transfer fins (33)
are shown in FIG. 2 to avoid over-crowding the drawing.
[0031] Furthermore, a plurality of first heat transfer pipes (1)
made of stainless steel-based metal and a plurality of second heat
transfer pipes (2) made of stainless steel-based metal are
individually extended so as to bridge between the front and back
facing side walls (301), (302) of the case body (30). The second
heat transfer pipes (2) are disposed so as to penetrate the
heat-transfer fins (33).
[0032] In the following description of the present specification,
an outer surface of the front side wall (301) corresponds to a
front of the heat exchanger (3), a depth direction as viewed from a
front side of the case body (30) corresponds to a front-and-back
direction, and a width direction and a height direction as
similarly viewed correspond to a left-and-right direction and an
up-and-down direction, respectively.
[0033] The plurality of second heat transfer pipes (2) (here,
eight) are arranged substantially in the lower half region of the
case body (30). Each of the second heat-transfer pipes 33 is made
of a straight pipe having a substantially elliptical
cross-sectional shape. The number of second heat transfer pipes (2)
can be selected as appropriate depending on a configuration of the
heat exchanger (3).
[0034] In FIG. 2, two upstream open ends (2a) disposed adjacent in
the left-and-right direction open at a left end of the front side
wall (301), two downstream open ends (2b) disposed adjacent in the
left-and-right direction open at a right end of the front side wall
(301), and four open ends (not shown) open at a middle portion of
the front side wall (301). The two upstream open ends (2a), the two
downstream open ends (2b), and the four open ends are configured to
communicate with one another via an inflow header (21) connected to
the water supply pipe (41), via a distribution header (22)
connected to the first heat transfer pipes (1), and via an
intermediate header (23), respectively. Although not shown, on the
back side wall (302), two left and right connection headers are
provided in such a manner that eight open ends of the second heat
transfer pipes (2) on a back side wall (302) side communicate four
by four with one another. Thereby, a lower fluid flow path (410) is
formed in the case body (30).
[0035] Along substantially upper halves of left and right side
walls (303), (304) in the case body (30), the plurality of first
heat transfer pipes (1) (here, six) are arranged substantially
horizontally. Each of the first heat-transfer pipes (1) is made of
a straight pipe having a substantially circular cross-sectional
shape. The number of first heat transfer pipes (1) can be selected
as appropriate depending on the configuration of the heat exchanger
(3).
[0036] In FIG. 2, three heat transfer pipes (11), (12), (13)
located at uppermost, middle, and lowermost stages are arranged
along the right side wall (304), and upstream open ends (11a),
(12a), (13a) thereof open at the right end of the front side wall
(301) and communicate with the downstream open ends (2b) of the
second heat transfer pipes (2) via the distribution header (22).
Moreover, another three heat transfer pipes (11), (12), (13)
located at uppermost, middle, and lowermost stages are arranged
along the left side wall (303), and downstream open ends (11b),
(12b), (13b) thereof open at the left end of the front side wall
(301) and communicate with the collection header (22) connected to
the hot-water supply pipe (42).
[0037] Although not shown, on the back side wall (302), there is
provided one back-side connection header configured to connect the
open ends of the left and right heat transfer pipes (11) located at
the uppermost stage. Further, on the back side wall (302), there is
provided another back-side connection header configured to connect
the open ends of the left and right heat transfer pipes (12), (13)
located at the middle and lowermost stages.
[0038] Thereby, upper fluid flow paths (401), (402), (403) are
formed at three stages in the up-and-down direction in such a
manner that the water supplied from the lower fluid flow path (410)
flows in parallel in a substantially U-shape along substantially
the upper halves of the back, left, and right side walls (302),
(303), (304) in the case body (30). Accordingly, the three upstream
open ends (11a), (12a), (13a) of the first heat transfer pipes (1)
disposed along the right side wall (304) and connected to the
distribution header (22) constitute fluid inlet ports of the
respective upper fluid flow paths (401), (402), (403). Moreover,
the three downstream open ends (11b), (12b), (13b) of the first
heat transfer pipes (1) disposed along the left side wall (303) and
connected to the collection header (24) constitute fluid outlet
ports of the respective upper fluid flow paths (401), (402),
(403).
[0039] In the present embodiment, the left and right first heat
transfer pipes (11), (12), (13) are arranged in such a manner that
opening areas (for example, inner diameter: 14 mm) of the upstream
open ends (13a) and downstream open ends (13b) of the heat transfer
pipes (13) located at the lowermost stage are larger than opening
areas (for example, inner diameter: 11 mm) of the upstream open
ends (11a), (12a) and downstream open ends (11b), (12b) of the heat
transfer pipes (upper-stage heat transfer pipes) (11), (12) located
at the uppermost and middle stages (an upper stage as viewed from
the lowermost stage), respectively.
[0040] Moreover, the heat transfer pipes (13) located at the
lowermost stage are disposed so as to protrude more inwardly of the
case body (30) in the left-and-right direction than the upper-stage
heat transfer pipes (11), (12) located at the upper stage.
[0041] The respective headers (21) to (24) include header bodies
(21a) to (24a) and header covers (21b) to (24b). Each of the header
bodies (21a) to (24a) is formed by depressing a part of the front
side wall (301) inward by subjecting drawing to a predetermined
portion of the front side wall (301) of the case body (30), and
each of the header covers (21b) to (24b) is connected in a
watertight state to a peripheral edge of each of the header bodies
(21a) to (24a). This allows an internal space in a predetermined
volume to be formed between a depressed bottom surface of each of
the header bodies (21a) to (24a) and a back surface of each of the
header cover (21b) to (24b).
[0042] The upstream open ends (2a) of the second heat transfer
pipes (2), the downstream open ends (2b) of the second heat
transfer pipes (2) and the upstream open ends (11a) to (13a) of the
first heat transfer pipe (1), and the downstream open ends (11b) to
(13b) of the first heat transfer pipe (1) are open to internal
spaces of the headers (21), (22), (24), respectively. Namely, the
respective headers (21), (22), (24) communicate with the upstream
open ends (2a), the downstream open ends (2b) and the upstream open
ends (11a) to (13a), the downstream open ends (11b) to (13b).
[0043] In the heat exchanger (3) of the present embodiment, the
plurality of first heat transfer pipes (1) are arranged in the case
body (30). Since these first heat transfer pipes (1) are arranged
in a plurality of stages (here, three stages) in the up-and-down
direction (the height direction) along the left and right side
walls (303), (304), heat of the combustion exhaust gas at a high
temperature introduced into the case body (30) from the gas burner
(50) located above is efficiently absorbed by the plurality of
first heat transfer pipes (1). Therefore, abnormal overheating of
the left and right side walls (303), (304) is suppressed.
[0044] Moreover, while the first heat transfer pipes (1) are
arranged in three stages in the up-and-down direction, the heat
transfer pipes (13)located at the lowermost stage are arranged so
as to protrude more inwardly of the case body (30) than the
upper-stage heat transfer pipes (11), (12). Therefore, it is
possible not only to efficiently heat the heat transfer pipes (13)
located at the lowermost stage by the combustion exhaust gas
flowing in the case body (30) but also to flow the combustion
exhaust gas inwardly of the case body (30). As a result, even in a
case where no first heat transfer pipe (1) is disposed along the
lower halves of the left and right side walls (303), (304) of the
case body (30), the abnormal overheating of the left and right side
walls (303), (304) can be prevented reliably. Further, the water
flowing through the respective upper fluid flow paths (401), (402),
(403), is efficiently heated by heat exchange with the combustion
exhaust gas.
[0045] When combustion operation is performed by the water heater
(4) of the present embodiment, the water supplied from the water
supply pipe (41) into the heat exchanger (3) flows into the second
heat transfer pipes (2) from a water supply port (20) provided on
the inflow header (21) located at a left front lower end of the
case body (30).
[0046] Subsequently, the water flowing through the second heat
transfer pipes (2) is supplied into the internal space of the
distribution header (22) from the downstream open ends (2b) located
at a right front lower end of the case body (30). Then, the water
flows from the upstream open ends (11a), (12a), (13a) to the first
heat transfer pipes (1) arranged along the right side wall (304).
Moreover, the water flowing through the respective upper fluid flow
paths (401), (402), (403) flows out from the respective downstream
open ends (11b), (12b), (13b), which open at a left-end upper
region of the front side wall (301) of the case body (30), to the
internal space of the collection header (24) provided from the
left-end upper region of the front side wall (301) of the case body
(30) to a central region thereof. The water that has flown out to
the collection header (24) is discharged to the hot-water supply
pipe (42) via a hot-water supply port (25) provided in the
collection header (24).
[0047] On the other hand, when drainage work is performed in the
water heater (4) of the present embodiment, the water is discharged
from the lower water supply port (20). Then, following discharging
of the water from the water supply port (20), the water remaining
in the first and second heat transfer pipes (1), (2) flows
reversely through the first and second heat transfer pipes (1), (2)
toward the upstream open ends (2a) of the second heat transfer
pipes (2).
[0048] Moreover, following discharging of the water, the water
filling the internal spaces of the distribution header (22) and the
collection header (24) decreases, and water levels in the internal
spaces thereof drop. When the water level drops below the hot-water
supply port (25) of the collection header (24), air enters the
collection header (24) from the hot-water supply port (25), and a
volume of the discharged water is replaced with air.
[0049] As shown in FIG. 3, among the plurality of first heat
transfer pipes (1), the downstream open end (11b) of the heat
transfer pipe (11) located at the uppermost stage is first opened
to an air layer in the collection header (24). Then, as shown by an
arrow 1, as the water is discharged from the upstream open end
(11a) (see FIG. 2), the air flows into the heat transfer pipe (11)
located at the uppermost stage. As described above, since the water
in the heat transfer pipe (11) located at the uppermost stage is
preferentially discharged, the water hardly remains in the heat
transfer pipe (11) located at the uppermost stage.
[0050] Subsequently, as the water level in the distribution header
(22) further drops, the water in the heat transfer pipe (12)
located at the middle stage is also discharged from the upstream
open end (12a) (see FIG. 2). Then, as shown by an arrow 2, the air
flows into the heat transfer pipe (12) located at the middle stage
from the downstream open ends (12b).
[0051] Finally, the water is discharged from the upstream open end
(13a) of the heat transfer pipe (13) located at the lowermost stage
(see FIG. 2). Although the heat transfer pipe (13) is communicated
with the internal space of the collection header (24), the
downstream open end (13b) is open to a lower region in the
collection header (24). Therefore, all the water in the heat
transfer pipe (13) located at the lowermost stage is hardly
replaced with air, and the water tends to remain in the heat
transfer pipe (13).
[0052] In particular, as compared with the heat transfer pipes
(11), (12) located at the uppermost and middle stages, in the heat
transfer pipe (13) located at the lowermost stage, a water head
pressure is lowered by discharging of the water up to that time.
Therefore, the water is hardly discharged by surface tension acting
on the upstream open end (13a).
[0053] However, since a flow path cross-sectional area of the
upstream open end (13a) of the heat transfer pipe (13) located at
the lowermost stage is set larger than those of the upstream open
ends (11a), (12a) of the heat transfer pipes (11), (12) located at
the uppermost and middle stages, an amount of the water in the heat
transfer pipes (13) located at the lowermost stage is larger than
those of the heat transfer pipes (11), (12) located at the
uppermost and middle stages. Therefore, during the drainage work,
the water head pressure in the heat transfer pipes (13) can be
increased to such an extent of overcoming the surface tension
acting on the upstream open end (13a). As a result, as indicated by
an arrow 3, the air flows into the heat transfer pipes (13), and
the water remaining in the heat transfer pipes (13) located at the
lowermost stage can be discharged smoothly. Further, since the
second heat-transfer pipes (2) are made of a straight pipe having
the substantially elliptical cross-sectional shape excellent in
drainage performance, the water in the second heat-transfer pipes
(2) can be also discharged smoothly.
[0054] In accordance with the above-described embodiment, even in a
case where the three heat transfer pipes (11) to (13) located at
the uppermost, middle, and lowermost stages are arranged
substantially horizontally along each of the left and right side
walls (303), (304) of the case body (30), it is possible to
promptly discharge the water from all of the heat transfer pipes
(11) to (13). Therefore, even in winter when an outside air
temperature drops to 0 degrees Celsius or less, it is possible to
prevent damage of the first and second heat transfer pipes (1), (2)
due to freezing and expansion of the water remaining in the first
and second heat transfer pipes (1), (2) of the heat exchanger
(3).
[0055] Moreover, in accordance with the above-described embodiment,
the water can be discharged smoothly even if the heat transfer
pipes (11) to (13) are arranged substantially horizontally in the
heat exchanger (3). Therefore, the height of the case body (30) can
be reduced as compared with such a heat exchanger in which an
inclined coiled water pipe is wound around the side walls of the
case body (30). Hence, the heat exchanger (3) can be suitably
incorporated in the water heater (4) as shown in FIG. 1.
[0056] In the above-described embodiment, as shown in FIGS. 2 and
3, the straight pipes having the upstream open ends (11a), (12a)
and downstream open ends (11b), (12b) with the same small flow path
cross-sectional area are used as the heat transfer pipes (11), (12)
located at the uppermost and middle stages, and the straight pipes
having the upstream open ends (13a) and downstream open ends (13b)
with the larger flow path cross-sectional areas than the upstream
open ends (11a), (12a) and downstream open ends (11b), (12b) of the
heat transfer pipes (11), (12) are used as the heat transfer pipes
(13) located at the lowermost stage.
[0057] However, the present invention is not limited to such an
arrangement form of the heat transfer pipes (11), (12), (13). As
long as the upstream open end (13a) and downstream open end (13b)
of the heat transfer pipe (13) located at the lowermost stage have
larger flow path cross-sectional areas than the upstream open end
(11a) and downstream open end (11b) of the heat transfer pipes (11)
located at the uppermost stage, respectively, the present invention
can also be applied to other arrangement form of the heat transfer
pipes (11), (12), (13) as described below.
[0058] For example, as shown in FIG. 4A, the plurality of first
heat transfer pipes (11), (12), (13) may be arranged in such a
manner that the flow path cross-sectional areas of the upstream
open ends (11a), (12a), (13a) and the downstream open ends (11b),
(12b), (13b) become larger in order from the top, respectively.
[0059] Moreover, for example, as shown in FIG. 4B, the plurality of
heat transfer pipes (11), (12), (13) may be arranged in such a
manner that the upstream open ends (12a), (13a) and downstream open
ends (12b), (13b) of the heat transfer pipes (12), (13) located at
the middle and lowermost stages (a lower stage as viewed from the
uppermost stage) have the same flow path cross-sectional area, and
that the above-described flow path cross-sectional area of the
upstream open ends (12a), (13a) and downstream open ends (12b),
(13b) of the lower-stage heat transfer pipes (12), (13) becomes
larger than that of the upstream open end (11a) and downstream open
end (11b) of the heat transfer pipe (11) located at the uppermost
stage.
[0060] Furthermore, for example, as shown in FIG. 4C, the plurality
of heat transfer pipes (11), (12), (13) may be arranged in such a
manner that the upstream open end (12a) and downstream open ends
(12b) of the heat transfer pipes (12) located at the middle stage
have the largest flow path cross-sectional areas as long as the
flow path cross-sectional areas of the upstream open end (13a) and
downstream open end (13b) of the heat transfer pipe (13) located at
the lowermost stage are larger than those of the heat transfer pipe
(11) located at the uppermost stage, respectively.
[0061] In the above-described embodiment, straight pipes having the
upstream open end (13a) and the downstream open end (13b) with the
same flow path cross-sectional area are used as the heat transfer
pipes (13) located at the lowermost stage. However, only openings
of the upstream open end (13a) and the downstream open end (13b)
just need to be largely expanded in diameter, and a pipe diameter
of an intermediate portion of the fluid flow path (403) other than
both of the open ends (13a), (13b) may be the same as that of the
heat transfer pipes (11) located at the uppermost stage or the heat
transfer pipes (12) located at the middle stage. Even if the heat
transfer pipes (13) located at the lowermost stage have such a
shape, the surface tension acting on the upstream open end (13a)
and the downstream open end (13b) decreases by using the heat
transfer pipes (13) having the upstream open end (13a) and the
downstream open end (13b), each having a large flow path
cross-sectional area. In this way, the water in the heat transfer
pipes (13) located at the lowermost stage can be discharged
smoothly.
[0062] Moreover, the first heat transfer pipes (1) constituting the
upper fluid flow paths (401), (402), (403) are not limited to
straight pipes. For example, substantially U-shaped continuous
pipes in which the upstream open ends (11a), (12a), (13a) and the
downstream open ends (11b), (12b), (13b) only open at the front
side wall (301) may be used. Further, the upper fluid flow paths
(401), (402), (403) may be arranged along only either one of the
left and right side walls (303), (304). Furthermore, the number of
stages is not limited to three stages. The plurality of fluid flow
paths may be arranged in two stages or arranged in four or more
stages.
[0063] Meanwhile, the water heater may have a sub heat exchanger
below the heat exchanger (3).
[0064] As described above in detail, the present invention is
summarized as follows.
[0065] According to one aspect of the present invention, there is
provided a heat exchanger comprising:
[0066] a case body including a flow passage of combustion exhaust
gas therein;
[0067] a plurality of fluid flow paths arranged in a plurality of
stages in a height direction along a side wall of the case
body;
[0068] a distribution header communicating with fluid inlet ports
of the plurality of fluid flow paths and distributing a fluid to be
heated to the plurality of fluid flow paths; and
[0069] a collection header communicating with fluid outlet ports of
the plurality of fluid flow paths and collecting the fluid to be
heated from the plurality of fluid flow paths, wherein
[0070] the fluid inlet port and the fluid outlet port of the fluid
flow path located at a lowermost stage among the plurality of fluid
flow paths have larger flow path cross-sectional areas than the
fluid inlet port and the fluid outlet port of the fluid flow path
located at an uppermost stage among the plurality of fluid flow
paths, respectively.
[0071] According to the heat exchanger described above, the fluid
to be heated flows into the plurality of fluid flow paths from the
fluid inlet ports of the plurality of fluid flow paths arranged in
the plurality of stages in the height direction along the side wall
of the case body, flows through the plurality of fluid flow paths,
and then flows out from the fluid outlet ports into the collection
header. The plurality of fluid flow paths are arranged in the
plurality of stages along the side wall of the case body through
which the combustion exhaust gas flows. Therefore, heat of the
combustion exhaust gas is efficiently absorbed by the plurality of
fluid flow paths and abnormal overheating of the side wall is
suppressed.
[0072] Moreover, for example, when drainage work is performed in
the heat exchanger in which a water supply port is disposed below a
hot-water supply port, the fluid flowing reversely toward an
upstream side through the fluid flow paths is discharged from the
water supply port at a lower position.
[0073] At the same time, air flows into the fluid flow paths from
the hot-water supply port at an upper position. Following
discharging of the fluid to be heated, the fluid to be heated
filling the internal spaces of the distribution header and the
collection header decreases, so that the air flows into the fluid
flow paths from the fluid outlet ports being open to the collection
header and a volume of the discharged fluid is replaced with air.
At this time, since a plurality of fluid outlet ports are arranged
in the plurality of stages in the height direction in the
connection header, the air preferentially flows into the fluid
outlet port of the fluid flow path located at the uppermost stage,
which is open to the collection header. Therefore, the fluid to be
heated in the fluid flow path located at the uppermost stage is
relatively easily discharged.
[0074] On the other hand, a water head pressure in the fluid flow
path located at the lowermost stage is lowered by discharging the
fluid up to that time. Therefore, the fluid to be heated is held by
surface tension acting on the fluid inlet port of the fluid flow
path located at the lowermost stage, whereby the fluid to be heated
is extremely hardly discharged.
[0075] However, according to the heat exchanger described above,
since the flow path cross-sectional areas of the fluid inlet port
and the fluid outlet port of the fluid flow path located at the
lowermost stage are set larger than those of the fluid inlet port
and the fluid outlet port of the fluid flow path located at the
uppermost stage, respectively, an amount of the fluid to be heated
in the fluid flow path located at the lowermost stage is larger
than that of fluid flow path located at the uppermost stage. As a
result, the water head pressure in the fluid flow path located at
the lowermost stage can be increased to such an extent of
overcoming the surface tension acting on the fluid inlet port of
the fluid flow path located at the lowermost stage, whereby the
fluid to be heated remaining in the fluid flow path located at the
lowermost stage can be discharged smoothly.
[0076] Preferably, in the heat exchanger described above,
[0077] the fluid inlet port and the fluid outlet port of a
lower-stage fluid flow path located at a lower stage than the fluid
flow path located at the uppermost stage among the plurality of
fluid flow paths have larger flow path cross-sectional areas than
the fluid inlet port and the fluid outlet port of the fluid flow
path located at the uppermost stage, respectively.
[0078] According to the heat exchanger described above, since the
fluid inlet port and the fluid outlet port of the lower-stage fluid
flow path located at the lower stage than the fluid flow path
located at the uppermost stage have larger flow path
cross-sectional areas than the fluid inlet port and the fluid
outlet port of the fluid flow path located at the uppermost stage,
respectively, the amount of the fluid to be heated in the
lower-stage fluid flow path becomes larger than that in the
uppermost fluid flow path. Therefore, the water remaining in the
lower-stage fluid flow path including the fluid flow path located
at the lowermost stage can be discharged smoothly.
[0079] Preferably, in the heat exchanger described above,
[0080] the fluid inlet port and the fluid outlet port of the fluid
flow path located at the lowermost stage among the plurality of
fluid flow paths have larger flow path cross-sectional areas than
the fluid inlet port and the fluid outlet port of an upper-stage
fluid flow path located at a upper stage than the fluid flow path
located at the lowermost stage, respectively.
[0081] As described above, the fluid to be heated in the fluid flow
path located at the lowermost stage is extremely hardly
discharged.
[0082] However, according to the heat exchanger described above,
since the fluid inlet port and the fluid outlet port of the fluid
flow path located at the lowermost stage have larger flow path
cross-sectional areas than the fluid inlet port and the fluid
outlet port of the upper-stage fluid flow path located at the upper
stage than the fluid flow path located at the lowermost stage,
respectively, the amount of the fluid to be heated in the fluid
flow path located at the lowest stage becomes larger than that in
the upper-stage fluid flow path. Therefore, the water remaining in
the fluid flow path located at the lowermost stage can be
discharged smoothly.
[0083] Preferably, in the heat exchanger described above,
[0084] the fluid flow path located at the lowermost stage among the
plurality of fluid flow paths is disposed so as to protrude more
inwardly of the case body than an upper-stage fluid flow path
located at a upper stage than the fluid flow path located at the
lowermost stage as viewed from an upstream side of the flow passage
of the combustion exhaust gas.
[0085] According to the heat exchanger described above, it is
possible not only to efficiently heat the fluid flow path located
at the lowermost stage by the combustion exhaust gas flowing in the
case body but also to flow the combustion exhaust gas inwardly of
the case body. Therefore, the abnormal overheating of the side wall
of the case body can be prevented reliably. Moreover, the fluid to
be heated flowing through the fluid flow paths is efficiently
heated by heat exchange with the combustion exhaust gas.
[0086] According to another aspect of the present invention, there
is provided a water heater having the heat exchanger described
above.
[0087] By use of the heat exchanger described above, it makes
possible to enhance the drainage performance for water. Therefore,
damage of the heat exchanger caused by freezing and expansion of
the fluid to be heated remaining in the fluid flow path can be
prevented reliably. Hence, the water heater having excellent
durability can be provided.
[0088] Although the present invention has been described in detail,
the foregoing descriptions are merely exemplary at all aspects, and
do not limit the present invention thereto. It should be understood
that an enormous number of unillustrated modifications may be
assumed without departing from the scope of the present
invention.
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