Field of the Invention
[0001] The invention relates to a heat exchanger, especially a heat exchanger in which heat
is transferred from a flue gas to a flowing liquid.
Background
[0002] Such a heat exchanger is known from
WO 2009/053248. This heat exchanger is provided with a front wall and a back wall. A combustion
space is formed in the upper part of the space between the front wall and the back
wall. Flammable gas is injected and combusted by a burner mounted on a top of the
heat exchanger. Channels in which water flows are respectively formed in the front
wall and the back wall. Heat generated by gas combustion is transferred to water flowing
in the channels. The walls are arranged symmetrically with respect to the center line
in side view. In the heat exchanger, since the walls are arranged symmetrically, the
fluid flowing both of the channels is heated almost equally when the channels are
equally designed.
[0003] The known heat exchanger mentioned above has certain efficiency in heat exchange,
although further improvement is required in aspect of downsizing a system equipped
with the heat exchanger. However, if the arrangement of the walls is changed for downsizing
the system equipped with the heat exchanger, there is a possibility that the fluid
flowing through both of the channels is heated unequally even though the channels
are symmetrically designed. The heat exchange efficiency is thereby deteriorated.
[0004] It is the object of the present invention to provide a heat exchanger which contributes
to the miniaturization of the system equipped with the heat exchanger while maintaining
heat exchange efficiency.
Summary
[0005] A first aspect of the present invention provides a heat exchanger comprising a front
wall and a back wall to form a space for a flue gas, and a front channel and a back
channel formed in the front wall and the back wall, respectively, in which a fluid
is to flow. The heat exchanger is configured such that the fluid in the front and
back channels can exchange heat with the flue gas, in use. The entire back wall extends
along a first plane. The front wall includes a lower portion and an upper portion.
The lower portion extends upwardly along the back wall. The upper portion extends
upwardly from the upper end of the lower portion and extends outwardly away from the
back wall so as to form a combustion space of a flammable gas between the upper portion
and the back wall. The heat exchanger is further configured such that the volume flow
rate and/or mass flow rate of the fluid in the front channel is greater than the back
channel, in use.
[0006] Volume flow rate means the volume of fluid which passes per unit time. Mass flow
rate means mass of a fluid which passes per unit of time.
[0007] "The volume flow rate and/or mass flow rate of the fluid in the front channel is
greater than the back channel" means that the average volume flow rate and/or average
mass flow rate of the fluid in the front channel is greater than the back channel.
Average volume/mass flow rate means volume/mass flow over the entire front or back
channel.
[0008] Volume/mass flow rate is generally measured at the inlet/outlet of each channel.
[0009] With this configuration mentioned above, the heat exchanger can contribute the downsizing
of a heat exchanging system accommodated in a housing and equipped with the heat exchanger.
This is because the back wall extending along the first plane without extending outwardly
can minimize a useless space between the heat exchanger and the housing.
[0010] The heat transfers on the front wall side and back wall side have different characteristic
because of the unsymmetrical design of the walls. Specifically, the fluid in the front
channel of the front wall can obtain more heat from the flue gas than the fluid in
the back channel of the back wall. The volume flow rate or mass flow rate of the fluid
is adjusted to be different on each side. Thereby the temperature of the fluid at
the outlet of each channel can reach to substantially the same temperature.
[0011] In this way, high space efficiency and high heat exchange efficiency can be achieved.
[0012] According to a preferred embodiment of the heat exchanger mentioned above, the back
channel is configured to have a higher fluid resistance than the front channel.
[0013] With the above configuration, it is possible to adjust the volume flow rate and/or
mass flow rate of the fluid in the front channel greater than the back channel.
[0014] According to another preferred embodiment of any one of the heat exchangers mentioned
above, a minimum cross section in the back channel is smaller than the minimum cross
section in the front channel with respect to cross sections intersecting with the
direction of the fluid flow.
[0015] With the above configuration, the heat exchanger is configured so that the back channel
has a higher fluid resistance than the front channel. It is therefore possible to
adjust the volume flow rate and/or mass flow rate of the fluid in the front channel
greater than the back channel.
[0016] According to a preferred embodiment of any one of the heat exchangers mentioned above,
an average cross-sectional area of the back channel is smaller than the an average
cross-sectional area of the front channel with respect to cross sections intersecting
with the direction of the fluid flow.
[0017] With the above configuration, the higher fluid resistances in the front and back
channels are controlled by adjusting the average cross-sectional areas of the front
and back channels. It is therefore possible to adjust the volume flow rate and/or
mass flow rate of the fluid in the front channel greater than the back channel in
a more accurate manner.
[0018] According to a preferred embodiment of any one of the heat exchangers mentioned above,
the front channel includes a plurality of front sub channels which are arranged in
substantially parallel to each other and are connected in series. The back channel
includes a plurality of back sub channels which are arranged in substantially parallel
to each other. The back sub channels are connected in series, and each of which faces
to one of the first sub channels. With respect to cross sections intersecting with
the direction of the fluid flow, at least one of the back sub channel has the minimum
cross section smaller than the minimum cross section of the corresponding front sub
channel, and/or an average cross-sectional area smaller than an average cross-sectional
area of the corresponding front sub channel.
[0019] With the above configuration, it is therefore possible to adjust the volume flow
rate and/or mass flow rate of the fluid in the front channel greater than the back
channel in a more accurate manner.
[0020] According to a preferred embodiment of any one of the heat exchangers with the front
channel including a plurality of the front sub channels and the back channel including
a plurality of the back sub channels mentioned above, with respect to cross sections
intersecting with the direction of the fluid flow, each of the back sub channels has
the minimum cross section smaller than the minimum cross section of the corresponding
front sub channel, and/or an average cross-sectional area smaller than an average
cross-sectional area of the corresponding front sub channel.
[0021] With the above configuration, it is therefore possible to adjust the volume flow
rate and/or mass flow rate of the fluid in the front channel greater than the back
channel in a more accurate manner.
[0022] According to a preferred embodiment of any one of the heat exchangers mentioned above,
the volume of the entire back channel is smaller than the volume of the entire front
channel.
[0023] With the above configuration, it is therefore possible to adjust the volume flow
rate and/or mass flow rate of the fluid in the front channel greater than the back
channel in a more accurate manner.
[0024] According to a preferred embodiment of any one of the heat exchangers mentioned above,
a flow suppression means is arranged in the back channel.
[0025] In general, it is preferable to reduce the fluid resistance of the channel in view
of reducing the energy necessary for flowing the fluid. However, in this configuration,
a flow suppression mean is provided in the back channel to adjust the volume flow
rate and/or mass flow rate of the fluid in the front channel greater than the back
channel so as to maintain the high heat exchange efficiency.
[0026] Examples of such a flow suppression means are obstacles arranged in the back channel
such as protrusions extending from the walls forming the back channel.
[0027] According to a preferred embodiment of any one of the heat exchangers mentioned above,
the heat exchanger further comprises a distribution mechanism connected to the inlets
of each of the front channel and the back channel. The distribution mechanism is configured
to distribute the fluid to the front channel and the back channel, in use. The distribution
mechanism is further configured to distribute more fluid to the front channel than
to the back channel.
[0028] With the above configuration, it is possible to adjust the volume flow rate and/or
mass flow rate of the fluid in the front channel greater than the back channel by
providing more fluid to the front channel.
[0029] According to a preferred embodiment of any one of the heat exchangers mentioned above,
the heat exchanger further comprises a converging mechanism connected to the outlets
of each of the front channel and the back channel. The converging mechanism is configured
to converge the fluid from the front channel and the back channel and output therefrom,
in use. The converging mechanism is configured to control the fluid resistance of
the fluid flowing from the back channel higher than the fluid resistance of the fluid
flowing from the front channel, in use.
[0030] With the above configuration, it is possible to adjust the volume flow rate and/or
mass flow rate of the fluid in the front channel greater than the back channel in
an easier manner.
[0031] According to a preferred embodiment any one of the heat exchangers mentioned above,
the heat exchanger is configured such that the temperature of the fluid at each outlet
of each channel is substantially the same, in use.
[0032] With the above configuration, the volume flow rate and/or mass flow rate of the fluid
in the front channel is controlled so that the temperature of the fluid at each outlet
of each channel is adjusted substantially the same. As a result, high heat exchange
efficiency can be achieved.
Brief Description of the Drawings
[0033]
FIG. 1 is a schematic diagram of the heat exchange system equipped with the heat exchanger
according to an embodiment of the present invention;
FIG. 2 is a perspective view of the heat exchanger according to FIG. 1;
FIG. 3 is a side view of the heat exchanger on which the burner is mounted according
to FIG. 1;
FIG. 4 is a front view of the heat exchanger according to FIG. 1;
FIG. 5 is a cross section view of the heat exchanger viewing from the arrow direction
of the V-V line of FIG.4;
FIG. 6 is a cross section view of the heat exchanger viewing from the arrow direction
of the VI-VI line of FIG.4;
FIG. 7 is a cross section view of the heat exchanger viewing from the arrow direction
of the VII-VII line of FIG.3;
FIG. 8 is a cross section view of the heat exchanger viewing from the arrow direction
of the VIII-VIII line of FIG.3;
FIG. 9 is a partial enlarged view of FIG. 8;
Fig. 10 is a schematic diagram of the heat exchanger according to another embodiment
of the present invention;
Fig. 11 is a schematic diagram of the heat exchanger according to another embodiment
of the present invention; and
Fig. 12 is a schematic diagram of the heat exchanger according to another embodiment
of the present invention.
Detailed Description of Preferred Embodiments
[0034] Preferred embodiments of the heat exchanger according to the present invention will
be described with reference to the drawings.
[0035] It should be understood that the detailed explanation are provided merely for the
purpose of explanation, and are in no way to be construed as limiting of the present
invention. While the present invention will be described with reference to exemplary
preferred embodiments, it is understood that the words which have been used herein
are words of description and illustration, rather than words of limitation. Changes
may be made, within the purview of the appended claims, as presently stated and as
amended, without departing from the scope and spirit of the present invention in its
aspects. Although the present invention will be described herein with reference to
preferred structures, materials and embodiments, the present invention is not intended
to be limited to the particulars disclosed herein; rather, the present invention extends
to all functionally equivalent structures, methods and uses, such as are within the
scope of the appended claims.
[0036] FIG. 1 shows a schematic diagram of a heat exchange system 1 equipped with a heat
exchanger 10 according to a preferred embodiment of the present invention.
[0037] The heat exchange system 1 is used for heating medium fluid which is used for space
heating and heating domestic water, while the heat exchange system 1 may be used only
for heating the medium fluid for space heating or only for heating the domestic water.
[0038] As shown in FIG. 1, the heat exchange system 1 is mainly provided with the heat exchanger
10, a fan 2a, a burner 3, a siphon 4b, a pump 5a, a heat exchanger 6, and a housing
9. As shown in FIG. 1, the heat exchange system 1 has a gas inlet connector 9a to
which a fuel gas supply pipe (not shown) is connected, a condensate outlet connector
9b to which a drain outlet pipe (not shown) is connected, medium fluid water inlet/outlet
connectors 9c, 9d to which medium fluid inlet/outlet pipes (not shown) are respectively
connected, and DHW (domestic heat water) inlet/outlet connectors 9e, 9f to which DHW
inlet/outlet pipes (not shown) are respectively connected.
[0039] The housing 9 shown in FIG. 1 has a box-like-shape such as a cuboid shape. The housing
9 accommodates the heat exchanger 10, the fan 2a, the burner 3, the siphon 4b, the
pump 5a, and the heat exchanger 6 as shown in FIG. 1.
[0040] The fan 2a intakes a fuel gas, such as natural gas, supplied from the fuel gas supply
pipe (not shown) via the gas inlet connector 9a and a gas pipe 2 as shown in FIG.
1. The fan 2a also intakes air from the outside of the housing 9. The fan 2a then
supplies the mixture gas with the fuel gas and the air to the burner 3.
[0041] The burner 3 is mounted on the heat exchanger 10 as shown in FIG. 3. Specifically,
the burner 3 is mounted on the top of the heat exchanger 10. A burner port 3a of the
burner 3, from which flammable gas is injected, is arranged in a combustion space
42 formed in the heat exchanger 10 as shown in FIG. 6. The burner 3 injects the flammable
gas (mixture gas with the fuel gas and the air) into the combustion space 42 and combusts
the flammable gas in the combustion space 42.
[0042] The heat exchanger 10 has a flue gas space 40 including the combustion space 42 and
two channels 60, 70 as shown in FIG. 5. The heat exchanger 10 is configured such that
the medium fluid in the two channels 60, 70 can exchange heat with the flue gas flowing
in the flue gas space 40, in use.
[0043] As mentioned above, the burner port 3a of the burner 3 is arranged over the combustion
space 42 and the flammable gas is combusted in the combustion space 42. Flue gas generated
by the combustion of the flammable gas flows downward in the flue gas space 40.
[0044] The channels 60, 70 constitute a part of a medium fluid circuit 5 in which a medium
fluid circulates. The medium fluid circuit 5 further includes an inlet pipe 5b, an
outlet pipe 5c, and the medium fluid inlet/outlet pipes (not shown) which are arranged
outside the heat exchange system 1 and are connected to the medium fluid water inlet/outlet
connectors 9c, 9d. The medium fluid circuit 5 also includes space heating devices
(not shown), such as floor heating devices and radiators, which are arranged outside
the heat exchange system 1 and which are connected to the medium fluid outlet pipe
and the medium fluid inlet pipe. For example, the medium fluid circulating in the
medium fluid circuit 5 is an aqueous medium.
[0045] In the medium fluid circuit 5, the medium fluid is supplied to the medium fluid inlet
connector 9c from the medium fluid inlet pipe (not shown). The medium fluid then flows
in each of the channels 60, 70 from the inlet of each of the channels 60, 70 through
the inlet pipe 5b. On the inlet pipe 5b, the pump 5a is arranged to circulate the
medium fluid in the medium fluid circuit 5. In the heat exchanger 10, the medium fluid
flows in the channels 60, 70 and exchanges heat with the flue gas flowing in the flue
gas space 40. After passing through the channels 60, 70, the medium fluid in each
of the channels 60, 70 flows out from an outlet of each of the channels 60, 70. The
medium fluid then flows out to the medium fluid outlet pipe (not shown) through the
outlet pipe 5c and the medium fluid outlet connector 9d and is sent to space heating
devices (not shown) through the medium fluid outlet pipe.
[0046] The configuration of the heat exchanger 10 will be explained in detail later.
[0047] After the flue gas has passed through the flue gas space 40, the flue gas is exhausted
out of the housing 9 though a gas duct 8. Condensate from the flue gas is corrected
at a drain collecting part 4 located below the heat exchanger 10. The drain collecting
part 4 includes a drain pipe 4a. The end portion of the drain pipe 4a is connected
to the siphon 4b. The siphon 4b allows the condensate from the flue gas to drain to
the drain outlet pipe (not shown) which is connected to the condensate outlet connector
9b while preventing the release of the flue gas.
[0048] The medium fluid circuit 5 includes a connecting pipe 5d which connects the inlet
pipe 5b and the outlet pipe 5c of the medium fluid circuit 5 via a medium fluid channel
6a formed in the heat exchanger 6. The connecting pipe 5d is configured so that the
medium fluid can flow from the outlet pipe 5c to the inlet pipe 5b through the medium
fluid channel 6a.
[0049] The heat exchanger 6 also has a domestic water channel 6b formed therein. An inlet
pipe 7a of the domestic water is connected to an inlet of the domestic water channel
6b. An outlet pipe 7b of the domestic water is connected to an outlet of the domestic
water channel 6b. The inlet pipe 7a of the domestic water is connected to DHW inlet
connector 9e. The outlet pipe 7b of the domestic water is connected to DHW outlet
connector 9f. The inlet/outlet pipes 7a, 7b of the domestic water are configured so
that domestic water flows in the domestic water channel 6b from the inlet of the domestic
water channel 6b, and flows out to the outlet pipe 7b from the outlet of the domestic
water channel 6b after the domestic heat water passes through the domestic water channel
6b. In the heat exchanger 6, domestic heat water flowing in domestic water channel
6b exchanges heat with the medium fluid flowing the medium fluid channel 6a, in use.
[0050] The operation of the heat exchange system 1 is briefly explained.
[0051] Fuel gas is supplied via the gas inlet connector 9a. Fuel gas and air taken from
the outside of the housing 9 are mixed. The mixture gas is supplied to the burner
3. The flammable gas (mixture gas) is injected into the combustion space 42 from the
burner 3 and is combusted in the combustion space 42. Flue gas then flows downwardly
in the flue gas space 40.
[0052] Medium fluid is circulated in the medium fluid circuit 5. During circulation, relatively
low temperature medium fluid flows into the channels 60, 70 via medium fluid inlet
connector 9c and the inlet pipe 5b. Medium fluid flowing in the channels 60, 70 exchanges
heat with the flue gas in the flue gas space 40 in use. The medium fluid heated at
the heat exchanger 10 flows out from the medium fluid outlet connector 9d through
the outlet pipe 5c and is sent to the space heating devices (not shown). The heat
of the medium fluid is used for the space heating devices and cooled medium fluid
(the medium fluid taken its heat by the space heating devices) then returns to the
heat exchange system 1. By changing the direction of the flowing direction of the
medium fluid, the medium fluid heated at the heat exchanger 10 is sent to the heat
exchanger 6 to heat the domestic water. The heated domestic water is sent to the usage
point such as bath room and kitchen.
[0053] The flue gas flowing out of the flue gas space 40 is exhausted through the gas duct
8. The condensate from the flue gas is drained to the drain outlet pipe through the
siphon 4b.
[0054] A heat exchanger 10 according to a preferred embodiment of the present invention
will be described in detail.
[0055] FIG. 2 shows a perspective view of the heat exchanger 10. FIG. 3 shows a side view
of the heat exchanger 10 on which the burner is mounted. FIG. 4 shows a front view
of the heat exchanger 10.
[0056] The heat exchanger 10 is preferably manufactured by corrosion resistant metal such
as aluminum alloy. For example, heat exchanger 10 is manufactured as monoblock sand-cast,
although manufacturing method is not limited to this. The heat exchanger 10 is designed
so that the burner 3 is mounted on the top of the heat exchanger 10 as shown in FIG.
3.
[0057] The heat exchanger 10 mainly includes a front wall 20, a back wall 30, side walls
50, an inlet distribution pipe 52, and an outlet converging pipe 54 as shown in FIG.2.
[0058] The front wall 20 and the back wall 30 form a flue gas space 40 for a flue gas. The
flue gas space 40 is formed by a space defined by the front wall 20, the back wall
30 and the side walls 50 which are attached to lateral ends of the front wall 20 and
the back wall 30. The flue gas space 40 includes the combustion space 42 of the flammable
gas. The combustion space 42, in which the burner port 3a of the burner 3 is installed,
is arranged at the upper part of the flue gas space 40 as shown in FIG. 5. The flue
gas flows downwardly in the flue gas space 40 from the combustion space 42 and flows
out from an opening 44 arranged at the bottom of the heat exchanger 10, in use.
[0059] A front channel 60 is formed in the front wall 20 and a back channel 70 is formed
in the back wall 30 as shown in FIG.5. The medium fluid flows in the front channel
60 and back channel 70, in use.
[0060] The inlet distribution pipe 52 has a tube-shape which has an inlet opening 52a in
the front side as shown in FIG. 4. The inlet pipe 5b of the medium fluid circuit 5
is connected at the inlet opening 52a. The inlet distribution pipe 52 is also connected
to the inlets of each of the front channel 60 and the back channel 70. The inlet distribution
pipe 52 is configured to distribute the fluid to the front channel 60 and the back
channel 70, in use. The medium fluid flows into the front channel 60 and the back
channel 70 through the inlet distribution pipe 52, in use.
[0061] The outlet converging pipe 54 has a tube-shape which has an outlet opening 54a in
the front side as shown in FIG. 4. The outlet pipe 5c of the medium fluid circuit
5 is connected at the outlet opening 54a. The outlet converging pipe 54 is also connected
to the outlets of each of the front channel 60 and the back channel 70. The outlet
converging pipe 54 is configured to converge the fluid from the front channel 60 and
the back channel 70, and output therefrom, in use. The converged medium fluid flows
in the outlet pipe 5c of the medium fluid circuit 5, in use.
[0062] Now, the back wall 30 and the front wall 20 will be described in more detail.
[0063] The back wall 30 has a tabular shape. The back wall 30 extends along a first plane
P1 as shown in FIG. 5. The heat exchanger 10 is arranged on a horizontal plane and
the first plane P1 is a vertical plane in this embodiment, although the arrangement
of the heat exchanger 10 is not limited to this. In the heat exchange system 1, the
heat exchanger 10 is preferably accommodated such that the back wall 30 extends along
one of the walls of the housing 9. Due to the shape of the back wall 30, a dead space
between the back surface of the heat exchanger 10 and the inner surface of the wall
of the housing 9 can be minimized.
[0064] The front wall 20 includes a lower portion 22 and an upper portion 24 as shown in
FIG. 2. The lower portion 22 extends upwardly along the back wall 30 as shown in FIG.
3. In other word, the lower portion 22 of the frond wall extends in parallel with
the back wall 30. The lower portion 22 preferably has a plane-like shape. The upper
portion 24 extends upwardly from the upper end of the lower portion 22 as shown in
FIG. 3. More specifically, the upper portion 24 extends upwardly from the upper end
of the lower portion 22 in a planar fashion. The upper portion 24 of the front wall
20 has a plane-like shape. Furthermore, the upper portion 24 extends outwardly away
from the back wall 30 so as to form a combustion space 42 of a flammable gas between
the upper portion 24 of the front wall 20 and the back wall 30. The length L2 of the
upper portion 24 along the longitudinal direction thereof is preferably longer than
the length L1 of the lower portion 22 along the longitudinal direction thereof as
shown in FIG. 3. Each of the longitudinal direction of the upper portion 24 and the
lower portion 22 is a direction along which each of the upper portion 24 and the lower
portion 22 extends in side view.
[0065] The space formed under the upper portion 24 is effectively used for arranging elements
of the heat exchange system 1 such as the fan 2a to achieve the downsizing of the
housing 9 of the heat exchange system 1 as shown in FIG. 3. The space formed under
the upper portion 24 may also be used for arranging the other elements of the heat
exchange system 1 such as valve, pipe, and venturi device.
[0066] Next, the structures which are arranged on the inner surface of the front wall 20
and the inner surface of the back wall 30 will be described with reference to FIG.
5 to FIG. 7. The inner surface of the upper portion 24 is a surface which faces the
back wall 30. The inner surface of the back wall 30 is a surface which faces the front
wall 20.
[0067] FIG. 5 is a cross section view of the heat exchanger viewing from the arrow direction
of the V-V line of FIG.4. FIG. 6 is a cross section view of the heat exchanger viewing
from the arrow direction of the VI-VI line of FIG.4. FIG. 7 is a cross section view
of the heat exchanger viewing from the arrow direction of the VII-VII line of FIG.3.
[0068] The upper portion 24 of the front wall 20 is provided with front fins 110 as shown
in FIG. 5. The front fins 110 are formed to protrude from the inner surface of the
front wall 20. A plurality of the front fins 110 is arranged along the lateral direction
(left-right direction) of the front wall 20 on the inner surface of the upper portion
24 at a predetermined interval. The number of the front fins 110 and the interval
between the front fins 110 depend on the various factors such as the amount of heat
transferred from the flue gas to the medium fluid, materials of the walls, and the
power of the burner to be installed.
[0069] In addition to the front fins 110, the front wall 20 is provided with front pins
130, 150 as shown in FIG. 5. The front pins 130, 150 are arranged on the downstream
side of the front fins 110 with respect to the flue gas flow direction. In other words,
the front pins 130, 150 are arranged below the front fins 110. The cross-sectional
of the front pins 130, 150 with respect to its main axis has a circular shape, or
preferably an elliptic shape which is longer in the longitudinal direction than the
lateral direction of the front wall. Each of the pins 130, 150 has larger surface
area per unit volume than the front fins 110. The front pins 130, 150 extend backwardly
from the inner surface of the front wall 20. A part of the front pins (pins 130) is
arranged at the upper portion 24 of the front wall 20 below the front fins 110. A
plurality of the front pins 130 is preferably arranged along the lateral direction
(left-right direction) of the front wall 20 on the inner surface of the upper portion
24 at a predetermined interval. Several lines of the front pins 130 are preferably
arranged at the upper portion 24 along the longitudinal direction at a predetermined
interval. The rest of the front pins 150 are arranged at the lower portion 22 of the
front wall. A plurality of the front pins 150 is arranged along the lateral direction
(left-right direction) of the front wall 20 on the inner surface of the lower portion
22 at a predetermined interval. Several lines of the front pins 150 are arranged at
the lower portion 22 along the longitudinal direction at a predetermined interval.
The number of the front pins 130, 150, and the interval between the front pins 130,
150 depend on the various factors such as the amount of heat transferred from the
flue gas to the medium fluid, materials of the walls, and the power of the burner
to be installed.
[0070] The back wall 30 is provided with back fins 120 as shown in FIG. 5. The back fins
120 are formed to protrude from the inner surface of the back wall 30. A plurality
of the back fins 120 is arranged along the lateral direction (left-right direction)
of the back wall 30 on the inner surface of the back wall 30 at a predetermined interval
as shown in FIG. 7. The number of the back fins 120 and the interval between the back
fins 120 depend on the various factors such as the amount of heat transferred from
the flue gas to the medium fluid, materials of the walls, and the power of the burner
to be installed.
[0071] The number of the back fins 120 and the interval between the back fins 120 are preferably
the same as those of the front fins 110. Each of the back fins 120 preferably corresponds
to one of the front fins 110 such that the corresponding front and back fins face
to each other. The front fin 110 and the corresponding back fin 120 are arranged symmetrically
with respect to a virtual line C2 along which the flammable gas is to be injected
into the combustion space 42 as shown in FIG. 5.
[0072] The shapes of the front fins 110 and the back fins 120 are described in detail with
reference to FIG. 6.
[0073] Most of the front fins 110 and the corresponding back fins 120, except for fins 110,
120 arrange under the outlet converging pipe 54 (refer to FIG. 7), include respectively
a first portion 112, 122 and a second portion 114, 124 arranged below the first portion
112, 122 as shown in FIG. 6. The height H1 of the first portion 112, 122 from the
inner surface of the corresponding wall 20, 30 is smaller than the height H2 of the
second portion 114, 124 from the inner surface of the corresponding wall 20, 30 as
shown in FIG.6.
[0074] Preferably, each of the fins 110, 120 includes the first portion 112, 122 and the
second portion 114, 124.
[0075] Most of the front fins 110 and the corresponding back fins 120, except for fins 110,
120 arrange under the outlet converging pipe 54 (refer to FIG. 7), include an inwardly
bulged portion 112a, 122a which bulges toward the virtual line C2 and an outwardly
curved portion 112b, 122b which curves away from the virtual line C2 as shown in FIG.
6. The outwardly curved portion 112b, 122b is arranged below the inwardly bulged portion
112a, 122a as shown in FIG.6.
[0076] The inwardly bulged portion 112a, 122a and the outwardly curved portion 112b, 122b
are formed so as to keep a predetermined distance between the burner 3, more specifically
the burner port 3a of the burner 3, to be installed on the heat exchanger 10 and the
fin 110, 120. The predetermined distance depends on various factors such as the desired
power of the burner 3 and the material of the fins 110, 120.
[0077] Preferably, each of the fins 110, 120 includes the inwardly bulged portion 112a,
122a and the outwardly curved portion 112b, 122b.
[0078] Each of the most of the front fins 110 and the corresponding back fins 120, except
for fins 110, 120 arranged under the converging pipe 54 (refer to FIG. 7), has a tapered
portion 112c, 122c where the height of the fin 110, 120 from the inner surface of
the corresponding wall 20, 30 gradually decreases towards an upper end of the fin
110, 120 as shown in FIG. 6.
[0079] The tapered portion 112c, 122c is formed so as to keep a predetermined distance between
the burner 3, more specifically the burner port 3a of the burner 3, to be installed
in the heat exchanger 10 and the fin 110, 120. The predetermined distance depends
on various factors such as the desired power of the burner 3 and the material of the
fins 110, 120.
[0080] Preferably, each of the fins 110, 120 has the tapered portion 112c, 122c.
[0081] In addition to the back fins 120, the back wall 30 is provided with back pins 140,
150 as shown in FIG. 5. The cross-sectional of the back pins 140, 150 with respect
to its main axis has a circular shape, or preferably an elliptic shape which is longer
in the longitudinal direction than the lateral direction of the back wall 30. Each
of the pins 140, 150 has larger surface area per unit volume than the back fins 120.
The back pins 140, 150 extends forwardly from the inner surface of the back wall 30.
A plurality of the back pins 140, 150 is arranged in the lateral direction (left-right
direction) of the back wall 30 on the inner surface of the back wall 30 at a predetermined
interval. Several lines of the back pins 140, 150 are arranged on the back wall 30
along the longitudinal direction at a predetermined interval. The number of the back
pins 140, 150 and the interval between the back pins 140, 150 depend on the various
factors such as the amount of heat transferred from the flue gas to the medium fluid,
materials of the walls, and the power of the burner to be installed.
[0082] The front pins 150 arranged at the lower portion 22 of the front wall 20 are preferably
connected to the corresponding back pins 150. In this embodiment, each of the pins
150 extends from the front wall 20 to the back wall 30. In other words, front pins
150 arranged at the lower portion 22 of the front wall 20 are integrated with the
back pins 150.
[0083] The front pins 130 arranged at the upper portion 24 of the front wall 20 so as to
face to the corresponding back pins 140. In other words the front pins 130 are arranged
at the upper portion 24 of the front wall 20 is not connected to the corresponding
the back pins 140 so as to make a space between them.
[0084] As explained above, the upper portion of the front wall 20 and the corresponding
part of the back wall 30, which forms the combustion space 42 of heat exchanger 10
therebetween, is designed symmetrically with respect to the virtual line C2 which
tilts against a virtual line C1. The lower portion 22 of the front wall 20 and the
back wall 30 is arranged symmetrical with respect to the virtual line C1. With this
configuration, flammable gas can be combusted under proper condition and the concentration
of CO and NOx contained in the emission gas can be lowered.
[0085] Next, the front channel 60 formed in the front wall 20 and the back channel 70 formed
in the back wall 30 will be described in detail with reference to FIG. 5 and FIG.
8. FIG. 8 is a cross section view of the heat exchanger viewing from the arrow direction
of the VIII-VIII line of FIG.3.
[0086] The front wall 20 has an inside wall 602 and an outside wall 604 which face to each
other and form the front channel 60 therebetween. The front wall 20 also has wall
elements 606 which connect the inside wall 602 and the outside wall 604 and define
the front channel 60. The back wall 30 has an inside wall 702 and an outside wall
704 which face to each other and form the back channel 70 therebetween. The back wall
30 has wall elements 706 which connect the inside wall 702 and outside wall 704 and
define the back channel 70.
[0087] The front channel 60 includes straight portions 60a, 60b, 60c, 60d, 60e, 60f, 60g,
60h, and 60i which are arranged in substantially parallel to each other and are connected
in series as shown in FIG. 8. The medium fluid supplied from the inlet of the front
channel 60 flows the straight portions 60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, and
60i in this order and flows out from the outlet of the front channel 60. In this paragraph,
parallel means that the two straight portions are connected with an angle such that
the speed of the turning fluid in the channel drops to nearly zero on the inner side
in the connecting area 61 a, 61 b, 61 c, 61 d, 61 e, 61 f, 61 g, and 61 h. For example,
in the vicinity of an inner part T1 of a joint 60ab in the connected area 61 a of
the straight portions 60a and the straight portions 60b, the fluid nearly stops upon
turning.
[0088] A plurality of pins 62 extending from the inside wall 602 is arranged in the straight
portions 60a, 60b so as to improve the heat transfer efficiency between the medium
fluid flowing in the straight portions 60a, 60b and the flue gas which flows along
the inside wall 602. The straight portions 60a, 60b require higher strength against
burst than the straight portions 60c-60i since the straight portions 60a, 60b has
the larger surface area compared with the straight portions 60c-60i. A plurality of
pins 62 can also improve the strength against burst of the straight portions 60a,
60b. In the straight portions 60c-60i, a plurality of grooves 68 extending along the
longitudinal direction of the straight portions 60c-60i is formed on the inside wall
602. Thereby the heat transfer area is increased between the medium fluid flowing
in the straight portions 60c-60i and the flue gas which flows along the inside wall
602.
[0089] Preferably, the cross-sectional area of the straight portion 60a arranged on the
most upstream side is larger than the cross-sectional area of the other straight portions
60b-60i arranged on downstream side with respect to the fluid flow as shown in FIG.
5.
[0090] The back channel 70 also includes straight portions 70a, 70b, 70c, 70d, 70e, 70f,
70g, 70h, and 70i as shown in FIG. 5. The straight portions 70a-70i are arranged in
substantially parallel to each other and are connected in series. The medium fluid
flowing from the inlet of the back channel 70 flows the straight portions 70a, 70b,
70c, 70d, 70e, 70f, 70g, 70h, and 70i in this order and flows out from the outlet
of the back channel 70. In this paragraph, parallel has the same meaning with the
previous paragraph for the front channel 60. In a manner similar to the above, a plurality
of pins (not shown) extending from the inside wall 702 is arranged in the straight
portions 70a, 70b and a plurality of grooves 78 extending along the longitudinal direction
of the straight portions 70c-70i are formed on the inside wall 702 in the straight
portions 70c-70i. The cross-sectional area of the straight portion 70a arranged on
the most upstream side is larger than the cross-sectional area of the other straight
portions 70b-70i arranged on downstream side with respect to the fluid flow.
[0091] The front channel 60 is further explained with reference to FIG. 8.
[0092] In the front channel 60, stagnation prevention means 64, 66 are preferably arranged
in each of the connecting area 61 a-61 h of the straight portions 60a-60i as shown
in FIG. 8. The stagnation prevention means 64, 66 connects the inside wall 602 and
the outside wall 604 of the front wall 20.
[0093] In this embodiment, stagnation prevention means 64, 66 are arranged in each of the
connecting area 61 a-61 h of the straight portions 60a-60i, but it is not limited
to this configuration. It is preferable that at least the first stagnation prevention
means 64 is arranged in the connecting area 61 a of the straight portions 60a and
the straight portion 60b which locates on the most upstream side in the channel 60
with respect to a fluid flow.
[0094] The first stagnation prevention means 64 is arranged in the connecting area 61 a
of the straight portions 60a and the straight portion 60b which locates on the most
upstream side in the channel 60 with respect to the fluid flow. The first stagnation
prevention means 64 is arranged in the vicinity of the inner part T1 of the joint
60ab of the straight portions 60a, 60b around which the fluid is to turn as shown
in FIG. 8. The first stagnation prevention means 64 is formed in a hook-like shape
when seen from the direction perpendicular to the front wall 20 as shown in FIG. 8.
[0095] At least one or more second stagnation prevention means 66 are preferably arranged
in the connecting area 61b-61h of the straight portions 60b-60i in the channel 60.
In other words, the second stagnation prevention means 66 are arranged in the connecting
areas other than the connecting area 61 a which locates on the most upstream side
in the channel 60 with respect to the fluid flow. The second stagnation prevention
means 66 are formed in an arc-like shape when seen from the direction perpendicular
to the front wall 20 as shown in FIG. 8. The arc-like shaped second stagnation prevention
means 66 are arranged in the front channel 60 such that the arc-like shaped surface
is substantially along the fluid flow.
[0096] Each of the second stagnation prevention means 66 is arranged in the vicinity of
an inner part of a joint of the straight portions 60b-60i around which the fluid is
to turn. For example, one of the second stagnation prevention means 66 is arranged
in the vicinity of an inner part T2 of a joint 60bc of the straight portions 60b,
60c around which the fluid is to turn as shown in FIG. 8.
[0097] The first stagnation prevention means 64 is arranged so as to partially surround
the inner part T1 of the joint 60ab of the straight portions 60a, 60b around which
the fluid is to turn when seen from the direction perpendicular to the wall 20 as
shown in FIG. 8. Specifically the first stagnation prevention means 64 is preferably
arranged so as to surround the inner part T1 of the joint 60ab of the straight portions
60a, 60b over an angle range of more than 90 degrees, and more preferably over an
angle range of more than 180 degrees when seen from the direction perpendicular to
the wall 20 as shown in FIG. 8.
[0098] The one or more second stagnation prevention means 66 are also arranged so as to
partially surround the inner part of the joint of the straight portions around which
the fluid is to turn when seen from the direction perpendicular to the wall 20 as
shown in FIG. 8. For example, the second stagnation prevention means 66 are arranged
so as to partially surround the inner part T2 of the joint 60bc of the straight portions
60b, 60c around which the fluid is to turn when seen from the direction perpendicular
to the wall 20 as shown in FIG. 8. The second stagnation prevention means 66 are arranged
so as to surround the inner part T2 of the joint 60bc of the straight portions 60b,
60c over an angle range of more than 90 degrees when seen from the direction perpendicular
to the wall 20.
[0099] The wall elements 606 which connects the inside wall 602 and the outside wall 604
include extending wall elements W1, W2 which respectively extend along the main axis
A1, A2 of the straight portion 60a, 60b. The wall elements W1, W2 extend from the
inner part T1 of the joint 60ab of the straight portions 60a, 60b around which the
fluid is to turn as shown in FIG. 9. The main axes A1, A2 are axes along which the
straight area of the straight portion 60a, 60b extends. The first stagnation prevention
means 64 includes a first portion 64a which is arranged on the upstream side and a
second portion 64b which is arranged on the downstream side with respect to the fluid
flow as shown in FIG. 9. A maximum distance D1 between the second portion 64b and
the extending wall element W2 is shorter than a maximum distance D2 between the first
portion 64a and the extending wall element W2. The distance between the second portion
64b and the extending wall element W2 may be almost equal at any points.
[0100] The first stagnation prevention means 64 is arranged in the connecting area 61 a
in the straight portion 60b which is located on the downstream side among the two
straight portions 60a, 60b connected. Each of the straight portions 60a, 60b has a
straight area which has a straight tube-like shape. The first stagnation prevention
means 64 is arranged to extend from the connecting area 61 a into part of the straight
area in the straight portion 60b. The first stagnation prevention means 64 may extend
into the connecting area 61 a located in the straight portion 60a at the upstream
side with respect to the fluid flow.
[0101] The second stagnation prevention means 66 are arranged in the straight portion which
is located at the downstream side with respect to the fluid flow among the straight
portions connected. More specifically, the second stagnation prevention means 66 are
arranged in the connecting area in the straight portion which is located on the downstream
side among the two straight portions connected. Each of the straight portions 60c-60i
has a straight area which has a straight tube-like shape. The second stagnation prevention
means 66 may be arranged to extend from a connecting area into the straight area of
the straight portion located on the downstream side.
[0102] The front channel 60 is explained above in detail with reference to FIG. 8. To avoid
the redundancy of the explanation, the explanation of the back channel 70 is omitted
regarding the common feature between the front channel 60 and the back channel 70.
Only the difference between the front channel 60 and the back channel 70 will be explained
below.
[0103] The heat transfers on the side of the front wall 20 and the side of the back wall
30 have different characteristic because of the unsymmetrical design of the walls.
Specifically, the medium fluid in the front channel 60 of the front wall 20 can obtain
more heat from the flue gas than the medium fluid in the back channel 70 of the back
wall 30. However, the heat exchanger 10 is configured such that the temperature of
the medium fluid at each outlet of each channel 60, 70 is substantially the same,
in use.
[0104] The heat exchanger 10 is therefore configured such that the volume flow rate and/or
mass flow rate of the fluid in the front channel 60 is greater than the back channel
70, in use. It is preferable that the heat exchanger 10 is configured such that at
least the mass flow rate of the fluid in the front channel 60 is greater than the
back channel 70, in use. Volume flow rate means the volume of fluid which passes per
unit time. Mass flow rate means mass of a fluid which passes per unit of time. The
volume flow rate and mass flow rate of the fluid in the front channel 60 is greater
than the back channel 70 means that the average volume flow rate and average mass
flow rate of the fluid in the front channel 60 is greater than the back channel 70.
Average volume/mass flow rate means volume/mass flow over the entire front or back
channel 60, 70. Volume/mass flow rate is generally measured at the inlet/outlet of
each channel 60, 70.
[0105] To achieve this, the back channel 70 is configured to have a higher fluid resistance
than the front channel 60.
[0106] Preferably, the minimum cross section in the back channel 70 is smaller than the
minimum cross section in the front channel 60 with respect to cross sections intersecting
with the direction of the fluid flow.
[0107] Preferably, an average cross-sectional area of the back channel 70 is smaller than
the an average cross-sectional area of the front channel 60 with respect to cross
sections intersecting with the direction of the fluid flow.
[0108] The front channel 60 includes a plurality of the straight portions 60a-60i as front
sub channels which are arranged in substantially parallel to each other and are connected
in series. The back channel 70 includes a plurality of the straight portions 70a-70i
as back sub channels which are arranged in substantially parallel to each other. The
straight portions 70a-70i are connected in series, and each of which faces to one
of the straight portions 60a-60i. With respect to cross sections intersecting with
the direction of the fluid flow, at least one of the straight portions 70a-70i has
a minimum cross section smaller than a minimum cross section of the corresponding
straight portions 60a-60i and/or an average cross-sectional area smaller than an average
cross-sectional area of the corresponding straight portions 60a-60i.
[0109] Preferably, each of the straight portions 70a-70i has a minimum cross section smaller
than a minimum cross section of the corresponding straight portions 60a-60i and/or
an average cross-sectional area smaller than an average cross-sectional area of the
corresponding straight portions 60a-60i.
[0110] The volume of the entire back channel 70 is smaller than the volume of the entire
front channel 60.
Other embodiments
[0111] Other embodiments will be described below. Some or all of the embodiments can be
combined except they are not contrary to each other.
- (1) In the above embodiment, the cross section of the back channel 70 is different
from that of the front channel 60 at least partially with respect to cross sections
intersecting with the direction of the fluid flow. With this configuration, the heat
exchanger 10 is configured such that the volume flow rate and/or mass flow rate of
the fluid in the front channel 60 is greater than the back channel 70, in use,
In another preferable embodiment, in addition to the above mentioned configuration
or instead of the above mentioned configuration, a flow suppression means 75 is arranged
in the back channel 70 as shown in FIG. 10. An example of such a flow suppression
means 75 is obstacles arranged in the back channel such as protrusions extending from
the inside wall 702, and/or outside wall 704, and/or wall elements in the back channel
70.
- (2) In the above embodiment, the cross section of the back channel 70 is different
from that of the front channel 60 at least partially with respect to cross sections
intersecting with the direction of the fluid flow. With this configuration, the heat
exchanger 10 is configured such that the volume flow rate and/or mass flow rate of
the fluid in the front channel 60 is greater than the back channel 70, in use,
In another preferable embodiment, in addition to the above mentioned configuration
or instead of the above mentioned configuration, the distribution pipe 52 as an example
of the distribution mechanism is arranged to distribute more fluid to the front channel
60 than to the back channel 70. For example, the distribution pipe 52 branches off
into a passage 52f and another passage 52b connected to the front channel 60 and the
back channel 70, respectively. Specifically the distribution pipe 52 may be formed
so that the passage 52b to the back channel 70 has the minimum and/or an average cross
section smaller than that of the passage 52 to the front channel 60 with respect to
cross sections intersecting with the direction of the fluid flow. In addition, or
alternatively, the distribution pipe 52 may have a flow suppression means 52a such
as obstacles which is arranged in the passage 52b to the back channel 70 as shown
in FIG. 11.
- (3) In the above embodiment, the cross section of the back channel 70 is different
from that of the front channel 60 at least partially with respect to cross sections
intersecting with the direction of the fluid flow. With this configuration, the heat
exchanger 10 is configured such that the volume flow rate and/or mass flow rate of
the fluid in the front channel 60 is greater than the back channel 70, in use,
In another preferable embodiment, in addition to the above mentioned configuration
or instead of the above mentioned configuration, the converging pipe 54 as an example
of the converging mechanism is arranged to control the fluid resistance of the fluid
flowing from the back channel 70 higher than the fluid resistance of the fluid flowing
from the front channel 60, in use. For example, the converging pipe 54 branches off
into a passage 54f and another passage 54b connected to the front channel 60 and back
channel 70, respectively. Specifically the converging pipe 54 may be formed so that
the passage 54b from the back channel 70 has the minimum and/or an average cross section
smaller than that of the passage 54f from the front channel 60 with respect to cross
sections intersecting with the direction of the fluid flow. In addition, or alternatively,
the converging pipe 54 may have a flow suppression means 54a such as an obstacle arranged
in the passage 54b from the back channel 70 as shown in FIG. 12.
[0112] The present invention is not limited to the above described embodiments, and various
variations and modifications may be possible without departing from the scope of the
present invention.
1. A heat exchanger (10) comprising
a front wall (20) and a back wall (30) to form a space (40) for a flue gas, and
a front channel (60) and a back channel (70) formed in the front wall (20) and the
back wall (30), respectively, in which a fluid is to flow,
wherein
the heat exchanger (10) is configured such that the fluid in the front and back channels
(60, 70) can exchange heat with the flue gas, in use,
the entire back wall (30) extends along a first plane (P1),
the front wall (20) includes
a lower portion (22) extending upwardly along the back wall (30), and
an upper portion (24) extending upwardly from the upper end of the lower portion (22),
extending outwardly away from the back wall (30) so as to form a combustion space
(42) of a flammable gas between the upper portion (24) and the back wall (30), and
the heat exchanger (10) is further configured such that the volume flow rate and/or
mass flow rate of the fluid in the front channel (60) is greater than the back channel
(70), in use.
2. The heat exchanger (10) according to the claim 1, wherein
the back channel (70) is configured to have a higher fluid resistance than the front
channel (60).
3. The heat exchanger (10) according to the claim 1 or 2, wherein
a minimum cross section in the back channel (70) is smaller than the minimum cross
section in the front channel (60) with respect to cross sections intersecting with
the direction of the fluid flow.
4. The heat exchanger (10) according to the claim 1, 2 or 3, wherein
an average cross-sectional area of the back channel (70) is smaller than an average
cross-sectional area of the front channel (60) with respect to cross sections intersecting
with the direction of the fluid flow.
5. The heat exchanger (10) according to any one of the claims 1 to 4, wherein
the front channel (60) includes a plurality of front sub channels (60a, 60b, 60c,
60d, 60e, 60f, 60g, 60h, 60i) which are arranged in substantially parallel to each
other and are connected in series,
the back channel (70) includes a plurality of back sub channels (70a, 70b, 70c, 70d,
70e, 70f, 70g, 70h, 70i) which are arranged in substantially parallel to each other
and are connected in series, and each of which faces to one of the first sub channels
(60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i), and
with respect to cross sections intersecting with the direction of the fluid flow,
at least one of the back sub channel (70a, 70b, 70c, 70d, 70e, 70f, 70g, 70h, 70i)
has
a minimum cross section smaller than a minimum cross section of the corresponding
front sub channel (60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i), and/or
an average cross-sectional area smaller than an average cross-sectional area of the
corresponding front sub channel (60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i).
6. The heat exchanger (10) according to claim 5, wherein, with respect to cross sections
intersecting with the direction of the fluid flow, each of the back sub channels (70a,
70b, 70c, 70d, 70e, 70f, 70g, 70h, 70i) has
a minimum cross section smaller than a minimum cross section of the corresponding
front sub channel (60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i), and/or
an average cross-sectional area smaller than an average cross-sectional area of the
corresponding front sub channel (60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i).
7. The heat exchanger (10) according to any one of the claims 1 to 6, wherein
the volume of the entire back channel (70) is smaller than the volume of the entire
front channel (60).
8. The heat exchanger (10) according to any of the claims 1 to 7, wherein
a flow suppression means (75) is arranged in the back channel (70).
9. The heat exchanger (10) according to any of the claims 1 to 8, further comprising,
a distribution mechanism (5c) connected to the inlets of each of the front channel
(60) and the back channel (70), the distribution mechanism (52) being configured to
distribute the fluid to the front channel (60) and the back channel (70), in use,
wherein the distribution mechanism (52) is further configured to distribute more fluid
to the front channel (60) than to the back channel (70).
10. The heat exchanger (10) according to any of the claims 1 to 9, further comprising,
a converging mechanism (54) connected to the outlets of each of the front channel
and the back channel, the converging mechanism (54) being configured to converge the
fluid from the front channel (60) and the back channel (70) and output therefrom,
in use,
wherein the converging mechanism (54) is configured to control the fluid resistance
of the fluid flowing from the back channel (70) higher than the fluid resistance of
the fluid flowing from the front channel (60), in use.
11. The heat exchanger (10) according to any of the claims 1 to 10, wherein,
the heat exchanger (10) is configured such that the temperature of the fluid at each
outlet of each channel is substantially the same, in use.