U.S. patent application number 12/808454 was filed with the patent office on 2011-05-19 for heat exchanger of upward combustion type condensing boiler.
This patent application is currently assigned to KYUNGDONG NAVIEN CO., LTD.. Invention is credited to Yong-bum Kim, Myoung-gee Min.
Application Number | 20110114300 12/808454 |
Document ID | / |
Family ID | 40801356 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110114300 |
Kind Code |
A1 |
Kim; Yong-bum ; et
al. |
May 19, 2011 |
HEAT EXCHANGER OF UPWARD COMBUSTION TYPE CONDENSING BOILER
Abstract
A heat exchanger of an upward combustion condensing boiler
maximizes latent-heat recovery efficiency by causing the flow
direction of exhaust gas to coincide with the flow direction of
condensed water in a latent heat exchange unit. The heat exchanger
includes a sensible heat exchange unit that absorbs sensible heat
generated from an upward combustion burner; a latent heat exchange
unit that absorbs latent heat of vapor included in exhaust gas
which has been heat-exchanged in the sensible heat exchange unit;
and a condensed-water tray that discharges condensed water
generated from the latent heat exchange unit. An upward flow of
exhaust gas passed through the sensible heat exchange unit is
converted into a downward flow that passes through the latent heat
exchange unit, and the latent heat exchange unit is installed so
that the flow direction of the exhaust gas passing through the
latent heat exchange unit vertically coincides with the falling
direction of condensed water generated by the latent heat exchange
unit.
Inventors: |
Kim; Yong-bum; (Incheon,
KR) ; Min; Myoung-gee; (Seoul, KR) |
Assignee: |
KYUNGDONG NAVIEN CO., LTD.
Gyeonggi-do
KR
|
Family ID: |
40801356 |
Appl. No.: |
12/808454 |
Filed: |
November 18, 2008 |
PCT Filed: |
November 18, 2008 |
PCT NO: |
PCT/KR08/06788 |
371 Date: |
June 16, 2010 |
Current U.S.
Class: |
165/181 |
Current CPC
Class: |
F24H 8/006 20130101;
F24H 1/40 20130101; Y02B 30/00 20130101; F24H 8/00 20130101 |
Class at
Publication: |
165/181 |
International
Class: |
F28F 1/12 20060101
F28F001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2007 |
KR |
2007-0135520 |
Claims
1. A heat exchanger of an upward combustion condensing boiler,
comprising: a sensible heat exchange unit that absorbs sensible
heat generated from an upward combustion burner; a latent heat
exchange unit that absorbs latent heat of vapor included in an
exhaust gas which has been heat-exchanged in the sensible heat
exchange unit; and a condensed-water tray that discharges condensed
water generated from the latent heat exchange unit, wherein an
upward flow of exhaust gas passed through the sensible heat
exchange unit is converted into a downward flow to pass through the
latent heat exchange unit, and the latent heat exchange unit is
installed so that flow direction of the exhaust gas passing through
the latent heat exchange unit vertically coincides with direction
of falling of condensed water generated by the latent heat exchange
unit.
2. The heat exchanger according to claim 1, wherein the latent heat
exchange unit includes a box-shaped body having top and bottom
surfaces that are open and side surfaces that are closed, and a
plurality of heat exchange tubes which are installed inside the
body and spaced a predetermined distance from each other in a
horizontal direction.
3. The heat exchanger according to claim 1, wherein the sensible
heat exchange unit and the latent heat exchange unit, respectively,
include fin-tube heat exchange tubes, each of the fin heat exchange
tubes including a tube coupled to heat transfer fins.
4. The heat exchanger according to claim 1, wherein height of an
upper end portion of the condensed-water tray is at least equal to
height of an exhaust-flue entrance portion through which exhaust
gas is discharged.
5. The heat exchanger according to claim 2, wherein height of an
upper end portion of the condensed-water tray is at least equal to
height of an exhaust-flue entrance portion through which exhaust
gas is discharged.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger of an
upward combustion type condensing boiler, and more specifically, to
an upward combustion type condensing boiler in which a sensible
heat exchanger and a latent heat exchanger are sequentially
disposed above an upward combustion type burner.
BACKGROUND ART
[0002] Boilers currently produced are boilers including a heat
exchanger to increase heat efficiency. Such a heat exchanger is
composed of a sensible heat exchange unit and a latent heat
exchange unit. The sensible heat exchange unit absorbs sensible
heat of exhaust gas generated from a combustion chamber, and the
latent heat exchange unit absorbs residual heat and latent heat
from the exhaust gas which has been heat-exchanged in the sensible
heat exchange unit. Such a type of boiler is referred to as a
condensing boiler.
[0003] Such condensing boilers have been put to practical use as
oil boilers which use oil fuel as well as gas boilers which use gas
fuel such as LNG or LPG, thereby contributing to an increase in
boiler efficiency and a reduction in fuel cost.
[0004] FIG. 1 is a schematic view of a conventional downward
combustion type condensing boiler.
[0005] Referring to FIG. 1, exhaust gas generated from a downward
combustion type burner 12 is cooled down to about 200.degree. C.
while passing through a sensible heat exchanger 13. Then, the
exhaust gas is further cooled down to about 40-70.degree. C. while
passing through the latent heat exchange unit 14.
[0006] Heating water, which is heated while passing through the
heat exchange units 13 and 14, is transferred to the interior of a
room through a supply pipe 15 so as to deliver thermal energy, and
is then cooled down so as to return to a recovery pipe 16. The
heating water returning to the recovery pipe 16 must be introduced
into the latent heat exchange unit 14 such that the latent heat
exchange unit 14 can effectively absorb latent heat. This is
because when the exhaust gas passing through the sensible heat
exchange unit 13 is set to be equal to or less than a dew point
temperature, vapor (H.sub.2O) included in the exhaust gas can be
condensed so as to deliver latent heat to the heating circulation
water.
[0007] In the downward combustion type condensing boiler, a
direction where the condensed water falls due to gravity (i.e. a
downward direction) naturally coincides with the flow direction of
the exhaust gas passing through the sensible and latent heat
exchange units. This is a very important factor for increasing the
efficiency of the condensing boiler.
[0008] That is, while the exhaust gas passes through the latent
heat exchange unit, vapor in the exhaust gas is condensed so as to
deliver latent heat to the heating circulation water, and the
exhaust gas is significantly cooled down. Therefore, since the
internal temperature of a condensed-water tray 17 considerably
decreases, it is possible to minimize a heat loss caused by
regasification of the vapor liquefied into the condensed water.
[0009] The downward combustion type condensing boiler is considered
to have an optimal condensing-boiler structure in that the recovery
of latent heat can be maximized. However, the downward combustion
type condensing boiler must be equipped with a downward combustion
type burner.
[0010] In general, burners which are applied to boilers can be
divided into a Bunsen burner and a premixed burner. In the Bunsen
burner, a nozzle unit for jetting gas supplies the minimum primary
air required for combustion, and supplies excess secondary air to a
portion where flames are formed, thereby implementing perfect
combustion. The Bunsen burner has high combustion stability.
However, since the flames are formed by the secondary air, the
flames lengthen, and downward combustion is impossible. That is,
since the length of the flames (outer flames) reacting with the
secondary air is large and the flame density is low, the flames
tend to face upward. Therefore, the Bunsen burner can be applied
only to an upward combustion type condensing boiler.
[0011] The premixed burner burns premixed gas which is obtained by
premixing combustion gas and air in a mixing chamber. In the
premixed burner, excess air does not exist in a portion where
flames are formed. Further, the length of the flames is very small,
and the flame density is high. Therefore, the burner can be
installed regardless of combustion directions (upward, downward,
and sideward). However, since a predetermined amount of air
required for combustion should be premixed, combustion control is
very complicated. Further, since the premixed burner is easily
affected by disturbance, its combustion stability is low.
[0012] As described above, it is important to cause the falling
direction of condensed water and the flow direction of exhaust gas
to coincide with the direction of gravity, in order to maximize the
efficiency of the condensing boiler. Therefore, the premixed burner
which can perform the downward combustion is generally used.
[0013] However, the premixed burner has low combustion stability,
and an expensive control system should be used to implement
complicated combustion control.
[0014] To overcome such a problem, a variety of methods for
constructing a heat exchanger of a condensing boiler by using the
upward combustion type Bunsen burner have been proposed. An example
of one such heat exchanger is illustrated in FIG. 2.
[0015] FIG. 2 is a schematic view of a conventional upward
combustion type condensing boiler.
[0016] Referring to FIG. 2, a latent heat exchange unit 24 is
disposed above a sensible heat exchange unit 23 so as to be
inclined, and exhaust gas passed through the sensible heat exchange
unit 23 passes through the latent heat exchange unit 24 via a side
portion of a condensed-water tray 27. For the latent heat exchange
unit 24, an aluminum rolled pipe or stainless flexible tube have
been proposed.
[0017] In FIG. 2, as the latent heat exchange unit 24 is disposed
above the sensible heat exchange unit 23, the condensing boiler can
be constructed relatively easily and can be reduced in size.
[0018] However, the condensation efficiency of the upward
combustion type condensing boiler is reduced by as much as 3-5%,
compared with that of a traditional downward combustion type
condensing boiler. The reduction in condensation efficiency happens
for the following two reasons.
[0019] (1) As the condensed-water tray 27 is positioned right above
the sensible heat exchange unit 23, the condensed-water tray 27 is
heated to a high temperature. Therefore, although condensed water
which is generated while the exhaust gas passes through the latent
heat exchange unit 23 falls to the condensed-water tray 27, a
considerable amount of condensed water is evaporated by the heated
condensed-water tray 27. Therefore, since latent heat recovered by
the condensation is discharged in the form of evaporation heat, it
is impossible to obtain the maximum condensation efficiency. To
overcome such a problem, a heat insulating plate 25 may be used in
the condensed-water tray 27. However, it has only a limited
effect.
[0020] (2) The fundamental reason for the reduction of the
condensation efficiency is that high-temperature wet exhaust gas
(exhaust gas including vapor) passed through the sensible heat
exchange unit 23 comes in contact with the condensed water. This
inevitably occurs, because the falling direction of the condensed
water is set perpendicular to the flow direction of the exhaust
gas. Therefore, the condensation hardly occurs in a portion that
comes in contact with high-temperature wet exhaust gas. As a
result, a great part of the latent heat exchange unit 24 does not
reliably carry out its primary function of condensation recovery.
Accordingly, as the size of the latent heat exchange unit 24
considerably increases in comparison with that of the sensible heat
exchange unit 23, the economic efficiency of the condensing boiler
decreases.
[0021] FIG. 3 is a schematic view of a general fin-tube type heat
exchanger.
[0022] There are difficulties in applying a fin-tube type heat
exchanger (refer to FIG. 3), which is generally used as a sensible
heat exchange unit, to the conventional upward combustion type
condensing boiler.
[0023] The fin-tube heat exchanger is composed of a heat exchange
tube 31 and heat transfer fins 32. The fin-tube heat exchanger is
typically formed of copper (Cu) or stainless steel and is bonded by
brazing. Since the fin-tube heat exchanger has a small size and can
secure a large heat-transfer area, the fin-tube heat exchanger is
widely used as a heat exchanger for boilers. When the fin-tube heat
exchanger is used, it is natural for the flow direction of exhaust
gas to be set perpendicular to the paper surface of FIG. 3.
[0024] However, when the fin-tube heat exchanger is applied to the
latent heat exchange unit of the conventional upward combustion
condensing boiler, the flow direction of exhaust gas is set to the
horizontal direction (direction A of FIG. 3) or the vertical
direction (direction B of FIG. 3) where the exhaust gas serially
flows in several tubes. Then, since a pressure loss of the exhaust
gas excessively increases, the application is impossible in
practice. Therefore, since a heat exchanger having a different
structure from the heat exchanger used in the sensible heat
exchange unit should be separately manufactured, the economic
efficiency of the condensing boiler decreases.
[0025] The condensed water of the condensing boiler is discharged
to the outside through a condensed-water discharge port 28 and a
separate hose connected to the condensed-water discharge port 28.
However, when the condensed-water discharge hose is bent or frozen
such as in the winter, the condensed water is not discharged
smoothly.
[0026] In this case, as shown in FIG. 2, the condensed water is
filled up to more than the height of the surface A of the condensed
water, which corresponds to the upper end 27a of the
condensed-water tray 27, so as to overflow the condensed-water tray
27. The condensed water overflowing the condensed-water tray 27
falls to the combustion unit of the burner 22 through the sensible
heat exchange unit 23. Since the sensible heat exchange unit 23 is
typically formed of a material having no corrosion resistance to
the condensed water, the sensible heat exchange unit 23 may
corrode, so that its lifespan is reduced.
[0027] In a typical boiler, a safety device such as a wind pressure
switch or sensor is mounted, which detects whether an exhaust flue
29 is closed or not and then gives an instruction to stop the
boiler. As shown in FIG. 2, however, since the upper end 27a of the
condensed-water tray 27 is positioned at a lower position than an
entrance portion 29a of the exhaust flue 29, a path communicating
with the exhaust flue 29 is not closed, even when the condensed
water is filled up to the surface A. Therefore, the wind pressure
switch or sensor does not generate a signal indicating that the
exhaust flue 29 is closed.
[0028] To solve such a problem, the conventional upward combustion
type condensing boiler should include a separate safety device
which detects whether the condensed water discharge portion is
closed or not, for example, a level sensor which detects the level
of condensed water staying in the upper portion of the
condensed-water tray and stops the operation of the boiler when the
level of the condensed water exceeds a predetermined value.
Therefore, the structure of the condensing boiler becomes complex,
and the manufacturing cost increases.
[0029] Reference numerals 11 and 21 represent a blower, reference
numeral 18 represents a condensed-water discharge port, reference
numeral 19 represents an exhaust flue, and reference numeral 22
represents a burner.
Technical Problem
[0030] The present invention is directed to a heat exchanger of an
upward combustion type condensing boiler, which can maximize
latent-heat recovery efficiency by causing the flow direction of
exhaust gas to coincide with the flow direction of condensed water
in a latent heat exchange unit.
[0031] The present invention is also directed to a heat exchanger
of an upward combustion type condensing boiler, in which the same
fin-tube type heat exchanger is applied to both a sensible heat
exchange unit and a latent heat exchange unit, so that the sensible
heat exchange unit does not need to be separately manufactured.
[0032] The present invention is also directed to a heat exchanger
of an upward combustion type condensing boiler, which can safely
stop an operation without a separate device, even when the boiler
is clogged with condensed water.
Technical Solution
[0033] According to an aspect of the present invention, a heat
exchanger of an upward combustion type condensing boiler comprises
a sensible heat exchange unit that absorbs sensible heat generated
from an upward combustion type burner; a latent heat exchange unit
that absorbs latent heat of vapor included in exhaust gas which has
been heat-exchanged in the sensible heat exchange unit; and a
condensed-water tray that discharges condensed water generated from
the latent heat exchange unit. An upward flow of exhaust gas passed
through the sensible heat exchange unit is converted into a
downward flow so as to pass through the latent heat exchange unit,
and the latent heat exchange unit is installed in such a manner
that the flow direction of the exhaust gas passing through the
latent heat exchange unit vertically coincides with the falling
direction of condensed water generated from the latent heat
exchange unit.
[0034] The latent heat exchange unit may include a box-shaped body,
of which the top and bottom surfaces are opened and the side
surfaces are closed, and a plurality of heat exchange tubes which
are installed inside the body so as to be spaced a predetermined
distance from each other in a horizontal direction.
[0035] The sensible heat exchange unit and the latent heat exchange
unit may respectively have fin-tube type heat exchange tubes
installed therein, the fin-tube type heat exchange tube being
coupled to heat transfer fins.
[0036] The height of an upper end portion of the condensed-water
tray may be set to be equal to or more than that of an exhaust-flue
entrance portion through which exhaust gas is discharged.
Advantageous Effects
[0037] According to the present invention, as the flow direction of
exhaust gas in the latent heat exchange unit is caused to coincide
with the falling direction of condensed water, it is possible to
maximize latent heat recovery efficiency. Further, as the same
fin-tube type heat exchanger is applied to the sensible heat
exchange unit and the latent heat exchange unit, the sensible heat
exchange unit does not need to be separately manufactured. Further,
since the size of the latent heat exchange unit can be reduced, the
size of the entire boiler can be reduced. Furthermore, although the
condensed-water discharge port is clogged with condensed water, the
condensed water can be prevented from falling to the sensible heat
exchange unit, which makes it possible to safely stop an operation
without a separate device.
DESCRIPTION OF DRAWINGS
[0038] FIG. 1 is a schematic view of a conventional downward
combustion type condensing boiler.
[0039] FIG. 2 is a schematic view of a conventional upward
combustion type condensing boiler.
[0040] FIG. 3 is a schematic view of a general fin-tube type heat
exchanger.
[0041] FIG. 4 is a schematic view of an upward combustion type
condensing boiler according to an example embodiment of the present
invention.
BEST MODE FOR INVENTION
[0042] Hereinafter, example embodiments of the present invention
will be described in detail with reference to the accompanying
drawings.
[0043] FIG. 4 is a schematic view of an upward combustion type
condensing boiler according to an example embodiment of the present
invention.
[0044] The condensing boiler according to the present invention
includes an upward combustion type burner 120 which is installed
directly above a blower 110 so as to form flames upward, a sensible
heat exchange unit 130 which absorbs sensible heat generated from
the burner 120, and a latent heat exchange unit 150 which absorbs
latent heat of vapor included in exhaust gas which has been
heat-exchanged in the sensible heat exchange unit 130.
[0045] For the burner 120, any one of a Bunsen burner and a
premixed burner may be used. The Bunsen burner supplies the minimum
primary air, which is required for combustion, to a nozzle unit,
and supplies secondary air to a portion where flames are formed.
The premixed burner premixes gas and air and then burns the gas and
air.
[0046] The sensible heat exchange unit 130, which is installed
directly above the burner 120, has a plurality of heat-exchange
tubes 131 which are arranged in parallel so as to be spaced a
predetermined distance from each other in a horizontal direction.
FIG. 4 shows a state in which the heat-exchange tubes 131 are
installed in one line. However, the heat-exchange tubes 131 may be
installed in two or more lines. The sensible heat exchange unit 130
is a fin-tube type heat exchanger in which heat-transfer fins as
shown in FIG. 3 are coupled to the outer circumferential surfaces
of the heat-exchange tubes 131.
[0047] The exhaust gas passed through the sensible heat exchange
unit 130 is introduced into the latent heat exchange unit 150
through a gas flow path unit 140 of which the width is
narrowed.
[0048] A housing 141 composing the gas flow path unit 140 is formed
in a shape of which the lower side is wide and the width is
narrowed toward the upper side. Therefore, a flow of the exhaust
gas is inclined to the right side by the housing 141.
[0049] The flow direction of the exhaust gas flowing upward along
the inside of the housing 141 is switched to the left direction at
an upper end portion of the housing 141, and is then switched to
the vertical direction such that the exhaust gas is introduced into
the latent heat exchange unit 150.
[0050] The latent heat exchange unit 150 includes a box-shaped body
152, of which the top and bottom surfaces are opened, and a
plurality of heat-exchange tubes 151 which are installed inside the
body 152 so as to be spaced a predetermined distance from each
other in the horizontal direction. The heat-exchange tubes 151 may
be installed in one or more lines.
[0051] The latent heat exchange unit 150 is a fin-tube type heat
exchanger in which heat-transfer fins as shown in FIG. 3 are
coupled to the outer circumferential surfaces of the heat-exchange
tubes 151. The fin-tube type heat exchanger can be applied, because
since the heat-exchange tubes 151 are installed so as to be spaced
a predetermined distance from each other in the horizontal
direction as shown in FIG. 3, the flow of the exhaust gas flowing
in the latent heat exchange unit 150 is not affected by the
heat-transfer fins.
[0052] Therefore, since the heat-exchange tubes 141 and 151 of the
sensible heat exchange unit 140 and the latent heat exchange unit
150 are constructed in a fin-tube type, the latent heat exchange
unit 150 does not need to be separately manufactured, which makes
it possible to reduce inconvenience. Further, since the size of the
latent heat exchange unit 150 can be reduced, it is possible to
reduce the total size of a product.
[0053] The top and bottom surfaces of the body 152 are opened, but
the side surfaces thereof are closed. Therefore, the flow of the
exhaust gas is not inclined in the right and left direction, but is
induced so as to be directed to the vertical direction.
[0054] Therefore, a flow of condensed water, which is generated
from the heat exchange tubes 151 so as to fall in the vertical
direction, coincides with the flow of the exhaust gas.
[0055] To obtain the maximum condensation efficiency in the latent
heat exchange unit 150, a possibility of wet exhaust gas coming in
contact with condensed water needs to be minimized, and only
low-temperature dry exhaust gas should come in contact with the
condensed water. That is, when the number of contacts between the
exhaust gas and the condensed water generated from the surfaces of
the heat exchange tubes 151 increases, an amount of heat
transferred between the exhaust gas and the heat exchange tubes 151
decreases, and the regasification of the condensed water occurs due
to the heat exchange between the high-temperature exhaust gas and
the condensed water. Therefore, the condensation does not reliably
occur.
[0056] Therefore, as the flow direction of the exhaust gas is
caused to coincide with the falling direction of the condensed
water so as to reduce the possibility of the exhaust gas coming in
contact with the condensed water, the condensation reliably occurs,
and the latent recovery efficiency can be maximized.
[0057] The exhaust gas passing through the latent heat exchange
unit 150 from the upper side to the lower side thereof is
sufficiently cooled, and vapor included in the exhaust gas is
condensed in the heat exchange tubes 151 of the latent heat
exchange unit 150 so as to transfer latent heat to heating
circulation water.
[0058] The condensed water generated from the latent heat exchange
unit 150 falls so as to be collected by an inclined condensed-water
tray 160, and is then discharged to the outside.
[0059] The flow direction of the exhaust gas passed through the
latent heat exchange unit 150 is switched to the upward direction
such that the exhaust gas is discharged to the outside through an
exhaust flue 170.
[0060] To maximize the recovery of condensation latent heat, the
condensed-water tray 160 forming the boundary between the latent
heat exchange unit 150 and the sensible heat exchange unit 140 may
be formed of stainless steel of which the inside is filled with a
heat insulator 180. Therefore, although the boundary surface is
heated by the high-temperature exhaust heat passing through the
sensible heat exchange unit 140, some of the condensed water
falling on the condensed-water tray 160 can be prevented from being
regasified.
[0061] Meanwhile, the height of the upper end portion 160a of the
condensed-water tray 160 is set to be equal to or more than that of
an exhaust-flue entrance portion 171 through which the exhaust gas
is discharged.
[0062] Therefore, even when a hose through which condensed water is
discharged is closed so that condensed water is filled up to the
height of the exhaust-flue entrance portion 171, the condensed
water is prevented from falling onto the sensible heat exchange
unit 130, which makes it possible to prevent the durability of the
sensible heat exchange unit 130 from being degraded.
[0063] Further, when the condensed water is filled up to the height
of the exhaust-flue entrance portion 171, it has the same effect as
when the exhaust flue 170 is closed. In this case, a typical
exhaust safety device such as a wind pressure switch or sensor may
be used to detect whether the condensed-water discharge portion is
closed or not. Therefore, a separate safety device such as a level
sensor does not need to be used.
[0064] In this case, as shown in FIG. 4, the body 152 of the latent
heat exchange unit 150 may be fixed and coupled to the exhaust-flue
entrance portion 171 and the upper end portion 160a of the
condensed-water tray 160.
INDUSTRIAL APPLICABILITY
[0065] The heat exchanger of the upward combustion type condensing
boiler according to the present invention can maximize latent-heat
recovery efficiency by coinciding a direction where the condensed
water falls with the flow direction of the exhaust gas in the
latent heat exchange unit, and thus has industrial
applicability.
* * * * *