Technical Field
[0001] The present invention relates to a fin-and-tube heat exchanger and a refrigeration
cycle apparatus including the fin-and-tube heat exchanger.
Background Art
[0002] A fin-and-tube heat exchanger known in the art includes a plurality of fins that
are plate-shaped and arranged at a predetermined fin pitch and a plurality of heat
transfer tubes extending through the fins in a direction in which the fins are arranged.
[0003] The plurality of fins each have a plurality of openings, such as through-holes and
cuts, and into which the heat transfer tubes penetrate. As a result, the heat transfer
tubes extend through the fins in the direction in which the fins are arranged. Each
heat transfer tube has an end connected to a distribution pipe or a header that forms
a refrigerant passage together with the heat transfer tubes. In the heat exchanger,
a heat exchange fluid, such as air, flowing through the spaces between the fins exchanges
heat with a heat-exchange target fluid, such as water and refrigerant, flowing inside
the heat transfer tubes.
[0004] A heat exchanger having raised cuts, called slits or louvers, that open to a direction
in which air mainly flows is known in the art. A heat exchanger including protrusions,
called scratches or a waffled pattern that protrude to the direction in which air
mainly flows is also known in the art. In such a heat exchanger, the raised cuts or
the protrusions increase the surface area on which heat is exchanged, thus improving
the performance of heat exchange.
[0005] Furthermore, for example, a heat exchanger including heat transfer tubes each having,
in the heat transfer tube, a plurality of passages and a heat exchanger including
heat transfer tubes each having an inner surface with grooves are known in the art.
In such a heat exchanger, the passages or the grooves increase the surface area on
which heat is exchanged, thus improving the heat exchange performance.
[0006] The types of heat transfer tubes included in the above-described heat exchangers
include flat heat transfer tubes having a substantially elliptical cross-section or
a substantially oblong cross-section. When a heat exchanger operates as an evaporator
in an environment in which an outdoor air temperature is at or below the freezing
point, frost tends to form on a region located upwind in an air passing direction
on the heat exchanger because this region serves as a thermal entrance region in which
the absolute humidity of air is high and the thermal boundary layer is thin. In particular,
on an outer surface of the heat exchanger, parts surrounding the heat transfer tubes
and closest to the refrigerant flowing inside the flat heat transfer tubes decrease
in temperature, leading to an increase in temperature difference between the air and
the parts of the heat exchanger. Thus, much frost forms on the parts. To solve this
problem, a heat exchanger has been proposed that includes fins each having an adequate
fin region for anti-blocking located upwind in the air passing direction to reduce
or eliminate the likelihood that the spaces between heat transfer tubes may be blocked
with frost (refer to Patent Literature 1, for example).
[0007] Frost is melted into water droplets by a defrosting operation. At completion of the
defrosting operation, an operation that can cause frost formation is resumed and the
air starts to pass through the heat exchanger. Consequently, the water droplets formed
in the defrosting operation move backward and accumulate on upper parts or lower parts
of the flat heat transfer tubes. Disadvantageously, the water droplets fail to appropriately
flow out of the heat exchanger. A heat exchanger has been proposed that includes fins
each having a fin region located downwind in the air passing direction to reduce or
eliminate the likelihood that water droplets may accumulate on the heat exchanger
after air starts to pass through the heat exchanger (refer to Patent Literature 2,
for example).
Patent Literature 3 discloses a heat exchanger comprising a flat plate fin, a flat
tube, and a notch part. The notch part is installed from the downstream side of the
flat plate fin where the flat tube is inserted in such a fashion that it may be inclined
upwardly against an air flow. Further, slits are installed on the downstream side
of the flat plate fin.
Patent Literature 4 discloses a heat exchanger comprising a first fin, a second fin,
and a drain part disposed between the first and second fins, wherein the first and
the second fins are horizontally arranged. The first fin has a plurality of first
tube couplers inclined in a predetermined direction, and the second fin coupled to
the first fin has a plurality of second tube couplers inclined in a predetermined
direction.
Patent Literature 5 discloses a heat exchanger utilizing a manifold formed with a
plurality of sheets and configured to intentionally redirect airflow therethrough,
wherein the manifold is generally perpendicular to the airflow while micro-channel
tubes installed on the manifold can be angled relative to the axis of the manifold
and the direction of the airflow.
Patent Literature 6 discloses a heat exchanger according to the preamble of claim
1.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0009] However, the heat exchanger disclosed in Patent Literature 1 has the following disadvantage.
As described above, after the start of the operation that can cause frost formation,
water droplets accumulate on upper parts or lower parts of the flat heat transfer
tubes and fail to appropriately flow out of the heat exchanger. This heat exchanger
thus has poor drainage performance. The heat exchanger disclosed in Patent Literature
2 has a configuration in which upwind parts of heat transfer tubes are exposed. Disadvantageously,
frost may form on and grow from the exposed upwind parts, so that air passages tend
to be blocked with the frost.
[0010] When a heating operation is started after the defrosting operation and water droplets
remain in a heat-transfer-tube region in which heat transfer tubes are arranged, the
water droplets will refreeze, resulting in growth of ice. In other words, the water
droplets remaining in the heat-transfer-tube region at the start of the heating operation
after the defrosting operation cause a reduction in reliability, which is due to,
for example, damage of the heat transfer tubes. Furthermore, the refreezing causes
the spaces between the heat transfer tubes to be blocked with frost, resulting in
an increase in resistance to air flow and a reduction in resistance to frost. The
resistance to frost is the retention of performance against frost. Furthermore, in
the next defrosting operation, it is necessary to melt not only frost that has formed
on a heat exchanger in the heating operation but also the frozen water droplets. Consequently,
an increase in duration of defrosting is caused, resulting in a reduction in comfort.
In addition, repeating the heating operation and the defrosting operation causes a
reduction in average heating capacity over a predetermined period of time. Additionally,
the blocking of the air passages with frost causes a reduction in air flow rate, resulting
in a reduction in capacity in the heating operation.
[0011] In other words, the heat exchangers including the flat heat transfer tubes disclosed
in Patent Literature 1 and Patent Literature 2 fail to have good drainage performance
and good resistance to frost, and have the above-described disadvantages.
[0012] The present invention has been made to overcome the above-described disadvantages
and aims to provide a heat exchanger that includes flat heat transfer tubes and has
improved drainage performance and improved resistance to frost as compared to those
in the art and a refrigeration cycle apparatus including the heat exchanger.
Solution to Problem
[0013] An embodiment of the present invention provides a heat exchanger that is supplied
with air by a fan. The heat exchanger according to the embodiment of the present invention
has a two-column structure and including an upwind heat exchanger element disposed
upwind in a passing direction in which the air passes and a downwind heat exchanger
element disposed downwind in the passing direction, each of the upwind heat exchanger
element and the downwind heat exchanger element. The heat exchanger includes a fin
that is plate-shaped, a first heat transfer tube extending through the fin and having
a flat cross-section, and a second heat transfer tube extending through the fin and
having a flat cross-section. The second heat transfer tube is disposed at a distance
from the first heat transfer tube in a gravity direction. The first heat transfer
tube has a first upwind end located upwind in a passing direction and a first downwind
end located downwind in the passing direction. The second heat transfer tube has a
second upwind end located upwind in the passing direction and a second downwind end
located downwind in the passing direction. The fin has an upwind fin end located upwind
in the passing direction and a downwind fin end located downwind in the passing direction.
Where the first upwind end and the second upwind end are connected by a first imaginary
line and the first downwind end and the second downwind end are connected by a second
imaginary line, the fin has an upwind fin region defined by the upwind fin end and
the first imaginary line, a heat-transfer-tube region defined by the first imaginary
line and the second imaginary line, and a downwind fin region defined by the second
imaginary line and the downwind fin end. In the upwind heat exchanger element, a dimension
of the upwind fin region is larger than a dimension of the downwind fin region in
the passing direction. A dimension of the upwind fin region in the downwind heat exchanger
element is equal in the passing direction to the dimension of the downwind fin region
in the upwind heat exchanger element. A dimension of the downwind fin region in the
downwind heat exchanger element is equal in the passing direction to the dimension
of the upwind fin region in the upwind heat exchanger element.
Advantageous Effects of Invention
[0014] When the heat exchanger is installed as an outdoor heat exchanger in a refrigeration
cycle and a heating operation is performed, moisture in outdoor air sent from the
air-sending fan deposits as frost on the heat exchanger. Subsequently, when a defrosting
operation is performed, the frost is melted. The heat exchanger according to an embodiment
of the present invention is configured in such a manner that a dimension of the upwind
fin region of the fin is larger than a dimension of the downwind fin region in the
passing direction of the air supplied from the fan. In other words, the fin has a
relatively long region located upwind and with which the air from the air-sending
fan first comes into contact. Such a configuration reduces or eliminates the likelihood
that frost may block the space between the heat transfer tubes on upwind part, on
which relatively much frost can form in the heating operation, of the fin, and allows
frost melted in the defrosting operation, or water droplets, to promptly flow downwardly
out of the upwind fin region. In addition, as the fin has the downwind fin region
in an embodiment of the present invention, air supply from the fan causes water droplets
formed by melting frost in the defrosting operation to move on upper and lower parts
of the heat transfer tubes and promptly flow downwardly out of the downwind fin region.
[0015] As described above, the heat exchanger according to an embodiment of the present
invention and a refrigeration cycle apparatus including the heat exchanger have improved
resistance to frost and improved drainage performance. In addition, as long as a facility
to manufacture the upwind heat exchanger elements is prepared, it is unnecessary to
prepare a facility to manufacture the downwind heat exchanger elements, thus reducing
an increase in manufacturing cost.
Brief Description of Drawings
[0016]
[Fig. 1] Fig. 1 is a refrigerant circuit diagram illustrating an example of a refrigeration
cycle apparatus according to Embodiment 1 not presented as an embodiment of the present
invention but as an example useful for understanding the present invention.
[Fig. 2] Fig. 2 is a perspective view of an example of an outdoor heat exchanger in
the refrigeration cycle apparatus according to Embodiment 1 not presented as an embodiment
of the present invention but as an example useful for understanding the present invention.
[Fig. 3] Fig. 3 is an enlarged view of essential part of the outdoor heat exchanger
of Fig. 2.
[Fig. 4] Fig. 4 is an enlarged view of essential part of the outdoor heat exchanger
of Fig. 2.
[Fig. 5] Fig. 5 is a perspective view illustrating a process of inserting heat transfer
tubes into fins.
[Fig. 6] Fig. 6 is an enlarged view of essential part of an outdoor heat exchanger
according to Comparative Example 1.
[Fig. 7] Fig. 7 is an enlarged view of essential part of an outdoor heat exchanger
according to Comparative Example 2.
[Fig. 8] Fig. 8 is an enlarged view of essential part of an outdoor heat exchanger
according to Comparative Example 3.
[Fig. 9] Fig. 9 is an enlarged view of essential part of an outdoor heat exchanger
according to Embodiment 2 not presented as an embodiment of the present invention
but as an example useful for understanding the present invention.
[Fig. 10] Fig. 10 is an enlarged view of essential part of an outdoor heat exchanger
according to Embodiment 3 not presented as an embodiment of the present invention
but as an example useful for understanding the present invention.
[Fig. 11] Fig. 11 is an enlarged view of essential part of an outdoor heat exchanger
according to Embodiment 4 of the present invention.
Description of Embodiments
[0017] Note that the relative sizes of components illustrated in Fig. 1 and subsequent figures
may differ from the actual relative sizes of the components. Furthermore, note that
components denoted by the same reference signs in Fig. 1 and the subsequent figures
are the same components or equivalents. The same applies to the entire description
herein. Furthermore, note that the forms of components described herein are intended
to be illustrative only and are not limited to the descriptions.
Embodiment 1
[0018] Embodiment 1 is not presented as an embodiment of the present invention but as an
example useful for understanding the present invention. A refrigeration cycle apparatus
501 according to Embodiment 1 will be described first. Fig. 1 is a refrigerant circuit
diagram illustrating an example of a refrigeration cycle apparatus according to Embodiment
1. In Fig. 1, the direction of refrigerant flow in a cooling operation is represented
by dotted-line arrows and that in a heating operation is represented by full-line
arrows. The refrigeration cycle apparatus 501 is an exemplary refrigeration cycle
apparatus.
[Configuration of Refrigeration Cycle Apparatus 501]
[0019] As illustrated in Fig. 1, the refrigeration cycle apparatus 501 includes a compressor
502, an indoor heat exchanger 503, an indoor fan 504, an expansion device 505, an
outdoor heat exchanger 10, an outdoor fan 506, and a four-way valve 507. The compressor
502, the indoor heat exchanger 503, the expansion device 505, the outdoor heat exchanger
10, and the four-way valve 507 are connected by refrigerant pipes, thus forming a
refrigerant circuit.
[0020] The compressor 502 compresses refrigerant. The refrigerant compressed by the compressor
502 is discharged from the compressor 502 and is sent to the four-way valve 507. The
compressor 502 can be, for example, a rotary compressor, a scroll compressor, a screw
compressor, or a reciprocating compressor.
[0021] The indoor heat exchanger 503 acts as a condenser in the heating operation, and acts
as an evaporator in the cooling operation. The indoor heat exchanger 503 can be, for
example, a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube
heat exchanger, a heat pipe heat exchanger, a double-pipe heat exchanger, or a plate
heat exchanger.
[0022] The expansion device 505 expands the refrigerant flowing through the indoor heat
exchanger 503 or the outdoor heat exchanger 10 to reduce the pressure of the refrigerant.
The expansion device 505 is preferably, for example, an electric expansion valve capable
of regulating the flow rate of refrigerant. Usable examples of the expansion device
505 include a mechanical expansion valve including a diaphragm, serving as pressure
receiving part, and a capillary tube in addition to the electric expansion valve.
[0023] The outdoor heat exchanger 10 acts as an evaporator in the heating operation, and
acts as a condenser in the cooling operation. The outdoor heat exchanger 10 may be
configured in such a manner that the heat exchanger is bent in a direction in which
heat transfer tubes extend to increase the efficiency of installation in an outdoor
unit. The outdoor heat exchanger 10 will be described in detail later.
[0024] The four-way valve 507 switches between a refrigerant flow direction for the heating
operation and a refrigerant flow direction for the cooling operation. Specifically,
the four-way valve 507 is switched to connect a discharge outlet of the compressor
502 to the indoor heat exchanger 503 and connect a suction inlet of the compressor
502 to the outdoor heat exchanger 10 in the heating operation. Furthermore, the four-way
valve 507 is switched to connect the discharge outlet of the compressor 502 to the
outdoor heat exchanger 10 and connect the suction inlet of the compressor 502 to the
indoor heat exchanger 503 in the cooling operation.
[0025] The indoor fan 504 is disposed adjacent to the indoor heat exchanger 503, and supplies
air, serving as a heat exchange fluid, to the indoor heat exchanger 503. The outdoor
fan 506 is disposed adjacent to the outdoor heat exchanger 10, and supplies air, serving
as a heat exchange fluid, to the outdoor heat exchanger 10.
[Operations of Refrigeration Cycle Apparatus 501]
[0026] Operations of the refrigeration cycle apparatus 501 will be described with the flow
of the refrigerant. The cooling operation performed by the refrigeration cycle apparatus
501 will be described first. In Fig. 1, the dotted-line arrows represent the refrigerant
flow direction in the cooling operation. As an example, in a case in which air is
a heat exchange fluid and the refrigerant is a heat-exchange target fluid, an operation
of the refrigeration cycle apparatus 501 will be described below.
[0027] As illustrated in Fig. 1, driving the compressor 502 causes the compressor 502 to
discharge high-temperature, high-pressure gas refrigerant. The refrigerant flows as
represented by the dotted-line arrows. The high-temperature, high-pressure, single-phase
gas refrigerant discharged from the compressor 502 passes through the four-way valve
507 and flows into the outdoor heat exchanger 10, serving as a condenser. In the outdoor
heat exchanger 10, the high-temperature, high-pressure gas refrigerant that has flowed
into the outdoor heat exchanger 10 exchanges heat with the air supplied by the outdoor
fan 506, so that the high-temperature, high-pressure gas refrigerant condenses into
high-pressure, single-phase liquid refrigerant.
[0028] The high-pressure liquid refrigerant sent from the outdoor heat exchanger 10 is
turned into low-pressure, two-phase gas-liquid refrigerant by the expansion device
505. The two-phase refrigerant flows into the indoor heat exchanger 503, serving as
an evaporator. In the indoor heat exchanger 503, the two-phase refrigerant that has
flowed into the indoor heat exchanger 503 exchanges heat with the air supplied by
the indoor fan 504, so that liquid refrigerant included in the two-phase refrigerant
evaporates. Thus, the refrigerant turns into low-pressure, single-phase gas refrigerant.
This heat exchange allows an indoor space to be cooled. The low-pressure gas refrigerant
sent from the indoor heat exchanger 503 passes through the four-way valve 507 and
flows into the compressor 502, in which the refrigerant is compressed into high-temperature,
high-pressure gas refrigerant. Then, the refrigerant is again discharged from the
compressor 502. Subsequently, such a cycle is repeated.
[0029] The heating operation performed by the refrigeration cycle apparatus 501 will be
described below. In Fig. 1, the full-line arrows represent the refrigerant flow direction
in the heating operation.
[0030] As illustrated in Fig. 1, driving the compressor 502 causes the compressor 502 to
discharge high-temperature, high-pressure gas refrigerant. The refrigerant flows as
represented by the full-line arrows. The high-temperature, high-pressure, single-phase
gas refrigerant discharged from the compressor 502 passes through the four-way valve
507 and flows into the indoor heat exchanger 503, serving as a condenser. In the indoor
heat exchanger 503, the high-temperature, high-pressure gas refrigerant that has flowed
into the indoor heat exchanger 503 exchanges heat with the air supplied by the indoor
fan 504, so that the high-temperature, high-pressure gas refrigerant condenses into
high-pressure, single-phase liquid refrigerant. This heat exchange allows the indoor
space to be heated.
[0031] The high-pressure liquid refrigerant sent from the indoor heat exchanger 503 is
turned into low-pressure, two-phase gas-liquid refrigerant by the expansion device
505. The two-phase refrigerant flows into the outdoor heat exchanger 10, serving as
an evaporator. In the outdoor heat exchanger 10, the two-phase refrigerant that has
flowed into the outdoor heat exchanger 10 exchanges heat with the air supplied by
the outdoor fan 506, so that liquid refrigerant included in the two-phase refrigerant
evaporates. Thus, the refrigerant turns into low-pressure, single-phase gas refrigerant.
[0032] The low-pressure gas refrigerant sent from the outdoor heat exchanger 10 passes through
the four-way valve 507 and flows into the compressor 502, in which the refrigerant
is compressed into high-temperature, high-pressure gas refrigerant. Then, the refrigerant
is again discharged from the compressor 502. Subsequently, such a cycle is repeated.
[0033] In the above-described cooling and heating operations, liquid refrigerant flowing
into the compressor 502 leads to liquid compression, causing a failure of the compressor
502. It is therefore preferred that the refrigerant flowing out of the evaporator
be single-phase gas refrigerant. The indoor heat exchanger 503 acts as an evaporator
in the cooling operation, and the outdoor heat exchanger 10 acts as an evaporator
in the heating operation.
[0034] In the evaporator, while the air supplied from the fan is exchanging heat with the
refrigerant flowing inside the heat transfer tubes included in the evaporator, moisture
in the air condenses into water droplets on the evaporator. The water droplets, formed
on the evaporator, downwardly move on the heat transfer tubes and fins and downwardly
flow, as drain water, out of the evaporator.
[0035] In the heating operation under low outdoor-air temperature conditions, the outdoor
heat exchanger 10 acts as an evaporator. In the heating operation, thus, moisture
included in the air may deposit as frost on the outdoor heat exchanger 10. For example,
a refrigeration cycle apparatus capable of performing the heating operation typically
performs a defrosting operation for removing frost when outdoor air is at or below
a predetermined temperature (for example, 0 degrees C).
[0036] The defrosting operation is an operation in which hot gas, which is high-temperature,
high-pressure gas refrigerant, is supplied from the compressor 502 to the outdoor
heat exchanger 10 to prevent frost from forming on the outdoor heat exchanger 10 acting
as an evaporator. The defrosting operation may be performed when the duration of the
heating operation reaches a predetermined value (e.g., 30 minutes). Furthermore, the
defrosting operation may be performed before the heating operation when the outdoor
heat exchanger 10 is at or below a predetermined temperature (e.g., -6 degrees C).
Frost or ice on the outdoor heat exchanger 10 is melted by hot gas supplied to the
outdoor heat exchanger 10 in the defrosting operation.
[0037] For example, the discharge outlet of the compressor 502 can be connected to the outdoor
heat exchanger 10 by a bypass refrigerant pipe (not illustrated) so that hot gas can
be supplied directly to the outdoor heat exchanger 10 from the compressor 502 in the
defrosting operation. Furthermore, the discharge outlet of the compressor 502 can
be connected to the outdoor heat exchanger 10 through a refrigerant flow switching
device, for example, the four-way valve 507, so that hot gas can be supplied to the
outdoor heat exchanger 10 from the compressor 502.
[Details of Outdoor Heat Exchanger 10]
[0038] Fig. 2 is a perspective view illustrating an example of an outdoor heat exchanger
in the refrigeration cycle apparatus according to Embodiment 1. Figs. 3 and 4 are
enlarged views of essential part of the outdoor heat exchanger of Fig. 2. Fig. 5 is
a perspective view illustrating a process of inserting heat transfer tubes into fins.
In Fig. 2 and subsequent figures, the X direction is a horizontal direction and corresponds
to the lateral direction, or width direction, of fins 30 of the outdoor heat exchanger
10. The Y direction is a horizontal direction and corresponds to a direction in which
the fins 30 included in a single heat exchanger element are arranged. The Z direction
is a vertical direction, or the direction of gravity, and corresponds to the longitudinal
direction of the fins 30. Outlined arrows represent the flow direction of air supplied
from the outdoor fan 506 to the outdoor heat exchanger 10. As seen from Fig. 2, the
outdoor heat exchanger 10 according to Embodiment 1 is supplied with air flowing in
the X direction from the outdoor fan 506 in Fig. 1. Fig. 3 illustrates the essential
part of the outdoor heat exchanger 10 viewed in the Y direction. Fig. 4 illustrates
the essential part of the outdoor heat exchanger 10 viewed in the X direction.
[0039] The outdoor heat exchanger 10 is, for example, a heat exchanger having a two-column
structure, and includes an upwind heat exchanger element 601 and a downwind heat exchanger
element 602. The upwind heat exchanger element 601 and the downwind heat exchanger
element 602 are each a fin-and-tube heat exchanger and are arranged in the X direction
corresponding to the flow direction, or passing direction, of the air supplied from
the outdoor fan 506 in Fig. 1. The upwind heat exchanger element 601 is disposed upwind
in the passing direction of the air supplied from the outdoor fan 506. The downwind
heat exchanger element 602 is disposed downwind in the passing direction of the air
supplied from the outdoor fan 506. First ends of heat transfer tubes included in the
upwind heat exchanger element 601 are connected to an upwind header collecting pipe
603. First ends of heat transfer tubes included in the downwind heat exchanger element
602 are connected to a downwind header collecting pipe 604. Second ends of the heat
transfer tubes of the upwind heat exchanger element 601 and those of the downwind
heat exchanger element 602 are connected to a column connecting part 605.
[0040] Specifically, in the outdoor heat exchanger 10 according to Embodiment 1, the refrigerant
is distributed from one of the upwind header collecting pipe 603 and the downwind
header collecting pipe 604 to the heat transfer tubes in the corresponding one of
the upwind heat exchanger element 601 and the downwind heat exchanger element 602.
Then, the refrigerant distributed to the heat transfer tubes in one of the upwind
heat exchanger element 601 and the downwind heat exchanger element 602 flows into
the heat transfer tubes in the other one of the upwind heat exchanger element 601
and the downwind heat exchanger element 602 through the column connecting part 605.
The refrigerant flowing into the heat transfer tubes in the other one of the upwind
heat exchanger element 601 and the downwind heat exchanger element 602 divides into
a plurality of streams flowing through the heat transfer tubes and then the plurality
of streams join together in the corresponding one of the upwind header collecting
pipe 603 and the downwind header collecting pipe 604. Subsequently, the refrigerant
flows to the suction inlet of the compressor 502 or the expansion device 505.
[0041] In Embodiment 1, the upwind heat exchanger element 601 and the downwind heat exchanger
element 602 have the same configuration. Consequently, the upwind heat exchanger element
601 will be described below as a representative of the two heat exchanger elements.
The upwind heat exchanger element 601 and the downwind heat exchanger element 602
correspond to a heat exchanger according to the present invention. As a matter of
course, when either one of the upwind heat exchanger element 601 and the downwind
heat exchanger element 602 can handle a heat exchange load of the outdoor heat exchanger
10, only one of the upwind heat exchanger element 601 and the downwind heat exchanger
element 602 may constitute the outdoor heat exchanger 10.
[0042] As illustrated in Figs. 3, 4, and 5, the outdoor heat exchanger 10 includes the plurality
of fins 30 and the plurality of heat transfer tubes. Specifically, each of the fins
30 is a plate-shaped part, which is long in the vertical direction. For example, the
fin has a vertically long rectangular shape. As illustrated in Fig. 4, the fins 30
are arranged at a predetermined fin pitch FP in each heat exchanger element.
[0043] As for the plurality of heat transfer tubes, two representative heat transfer tubes
are each illustrated in Figs. 3 to 5. In the following description, an upper one of
the heat transfer tubes in the Z direction will be referred to as a first heat transfer
tube 21 and a lower one of the heat transfer tubes in the Z direction will be referred
to as a second heat transfer tube 22. As illustrated in Figs. 3 and 4, the first heat
transfer tube 21 and the second heat transfer tube 22 are arranged at a predetermined
distance from each other in the vertical direction. As illustrated in Fig. 5, the
first heat transfer tube 21 and the second heat transfer tube 22 are each inserted
into the plurality of fins 30 in the Y direction, in which the plurality of fins 30
are arranged. The first heat transfer tube 21 and the second heat transfer tube 22
each extend through the fins 30. The first heat transfer tube 21 and the second heat
transfer tube 22 are each a flat tube having a flat cross-section taken along a plane
perpendicular to the longitudinal direction of the first heat transfer tube 21 and
the second heat transfer tube 22.
[0044] In Embodiment 1, each of the fins 30 of the outdoor heat exchanger 10 has an upwind
fin end 131 and a downwind fin end 132, serving as opposite ends in the X direction
corresponding to the lateral direction of the fin 30. For the heat transfer tubes
extending through the fins 30, the first heat transfer tube 21 has an upwind end 141
and a downwind end 142, serving as opposite ends in the X direction corresponding
to the lateral direction of the fins 30, and the second heat transfer tube 22 has
an upwind end 241 and a downwind end 242, serving as opposite ends in the X direction
corresponding to the lateral direction of the fins 30. The upwind end 141 of the first
heat transfer tube 21 and the upwind end 241 of the second heat transfer tube 22 are
located upwind in the passing direction of the air supplied from the outdoor fan 506.
The downwind end 142 of the first heat transfer tube 21 and the downwind end 242 of
the second heat transfer tube 22 are located downwind in the passing direction of
the air supplied from the outdoor fan 506.
[0045] The following terms are defined for description of the resistance to frost and the
drainage performance of the outdoor heat exchanger 10 according to Embodiment 1.
[0046] As used herein, the term "first imaginary line", denoted by 151, refers to a straight
line connecting the upwind ends of the heat transfer tubes located upwind in the passing
direction of the air supplied from the outdoor fan 506, and the term "second imaginary
line", denoted by 152, refers to a straight line connecting the downwind ends of the
heat transfer tubes located downwind in the passing direction of the air supplied
from the outdoor fan 506. These lines are represented by alternate long and short
dashed lines. In Fig. 3, the upwind end 141 of the first heat transfer tube 21 and
the upwind end 241 of the second heat transfer tube 22 are connected by the first
imaginary line 151, and the downwind end 142 of the first heat transfer tube 21 and
the downwind end 242 of the second heat transfer tube 22 are connected by the second
imaginary line 152. Furthermore, the term "upwind fin region", denoted by 161, refers
to a region defined by the upwind fin end 131 and the first imaginary line 151, the
term "downwind fin region", denoted by 162, refers to a region defined by the downwind
fin end 132 and the second imaginary line 152, and the term "heat-transfer-tube region",
denoted by 163, refers to a region defined by the first imaginary line 151 and the
second imaginary line 152. The heat-transfer-tube region 163 is a region in which
the heat transfer tubes are located in the Z direction. In Fig. 3, the first heat
transfer tube 21 and the second heat transfer tube 22 are located in the heat-transfer-tube
region 163. The dimension of the upwind fin region 161 in the X direction or the passing
direction is denoted by A, and the dimension of the downwind fin region 162 in the
X direction or the passing direction is denoted by B. The dimension A is larger than
the dimension B.
[Resistance to Frost and Drainage Performance of Outdoor Heat Exchanger 10]
[0047] The resistance to frost and the drainage performance of the outdoor heat exchanger
10 according to Embodiment 1 will be described below. For the sake of easy understanding
of advantages of the outdoor heat exchanger 10 according to Embodiment 1, the configurations
of outdoor heat exchangers according to Comparative Examples 1, 2, and 3 will be described
first. The resistance to frost and the drainage performance of the outdoor heat exchanger
10 according to Embodiment 1 will then be described.
[0048] In the configurations according to Comparative Examples 1 to 3, components in Comparative
Examples are denoted by reference signs obtained by adding 1000, 2000, and 3000 to
the reference signs of the corresponding components in Embodiment 1. For example,
an outdoor heat exchanger according to Comparative Example 1 is denoted by 1010, an
outdoor heat exchanger according to Comparative Example 2 is denoted by 2010, and
an outdoor heat exchanger according to Comparative Example 3 is denoted by 3010.
[Comparative Example 1]
[0049] Fig. 6 is an enlarged view of essential part of the outdoor heat exchanger according
to Comparative Example 1. Fig. 6 illustrates the essential part of the outdoor heat
exchanger 1010 according to Comparative Example 1 viewed in the Y direction. The outdoor
heat exchanger 1010 differs from the outdoor heat exchanger 10 according to Embodiment
1 in that the outdoor heat exchanger 1010 has no downwind fin region 162, which is
illustrated in Fig. 3. In the outdoor heat exchanger 1010 according to Comparative
Example 1, consequently, a downwind end 1142 of a first heat transfer tube 1021, a
downwind end 1242 of a second heat transfer tube 1022, and a downwind fin end 1132
are located at the same position in the X direction. A dimension A1 of an upwind fin
region 1161 in the X direction is larger than the dimension A, illustrated in Fig.
3, of the upwind fin region 161 in the X direction in Embodiment 1.
[0050] As the dimension of the upwind fin region 1161 in the X direction is large, the outdoor
heat exchanger 1010 according to Comparative Example 1 is highly resistant to frost.
However, the outdoor heat exchanger 1010 has no downwind fin region. When frost is
melted in the defrosting operation and the fan is again actuated to start an operation
that can cause frost formation, water droplets formed by melting the frost accumulate
on upper and lower parts of the first heat transfer tube 1021 and the second heat
transfer tube 2022 in proximity to the downwind fin end 1132 and fail to properly
flow out of the outdoor heat exchanger 1010. In other words, the outdoor heat exchanger
1010 according to Comparative Example 1 has poor drainage performance. Disadvantageously,
accumulating water droplets refreeze again and become an obstacle in air passages,
thus reducing the resistance to frost. An increase in amount of heat required for
defrosting is thus caused, resulting in an increase in duration of defrosting.
[Comparative Example 2]
[0051] Fig. 7 is an enlarged view of essential part of the outdoor heat exchanger according
to Comparative Example 2. Fig. 7 illustrates the essential part of the outdoor heat
exchanger 2010 according to Comparative Example 2 viewed in the Y direction. The outdoor
heat exchanger 2010 differs from the outdoor heat exchanger 10 according to Embodiment
1 in that the outdoor heat exchanger 2010 has no upwind fin region 161, which is illustrated
in Fig. 3. In the outdoor heat exchanger 2010 according to Comparative Example 2,
consequently, an upwind end 2141 of a first heat transfer tube 2021, an upwind end
2241 of a second heat transfer tube 2022, and an upwind fin end 2131 are located at
the same position in the X direction. A dimension B2 of a downwind fin region 2162
in the X direction is larger than the dimension B, illustrated in Fig. 3, of the downwind
fin region 162 in the X direction in Embodiment 1.
[0052] As the dimension of the downwind fin region 2162 in the X direction is large, the
outdoor heat exchanger 2010 according to Comparative Example 2 has relatively good
drainage performance because, even when frost is melted in the defrosting operation
and the fan is again actuated to start the operation that can cause frost formation,
air flow causes water droplets formed by melting the frost to flow to the rear of
fins and flow out of the outdoor heat exchanger 2010. However, upwind parts of the
first heat transfer tube 2021 and the second heat transfer tube 2022 are exposed.
Disadvantageously, frost may form on and grow from the exposed parts and thus tend
to block air passages. The outdoor heat exchanger 2010 has poor resistance to frost.
[Comparative Example 3]
[0053] Fig. 8 is an enlarged view of essential part of the outdoor heat exchanger according
to Comparative Example 3. Fig. 8 illustrates the essential part of the outdoor heat
exchanger 3010 according to Comparative Example 3 viewed in the Y direction. The outdoor
heat exchanger 3010 differs from the outdoor heat exchanger 10 according to Embodiment
1 in that a dimension A3 of an upwind fin region 3161 in the X direction is equal
to a dimension B3 of a downwind fin region 3162 in the X direction. Such a configuration
has relatively good drainage performance because, even when frost is melted in the
defrosting operation and the fan is again actuated to start the operation that can
cause frost formation, air flow causes water droplets formed by melting the frost
to flow to the rear of fins and flow out of the outdoor heat exchanger 3010. However,
upwind part of a first heat transfer tube 3021 and upwind part of a second heat transfer
tube 3022 are in close proximity to an upwind fin end 3131. Disadvantageously, the
outdoor heat exchanger 3010 has poor resistance to frost.
[0054] As illustrated in Fig. 3, the outdoor heat exchanger 10 according to Embodiment 1
has the downwind fin region 162 as in Comparative Example 3. Consequently, even when
frost is melted in the defrosting operation and the fan is again actuated to start
the operation that can cause frost formation, air flow causes water droplets formed
by melting the frost to flow to the rear of the fins and flow out of the outdoor heat
exchanger 10. The outdoor heat exchanger 10 has relatively good drainage performance.
In addition, as the dimension A of the upwind fin region 161 in the X direction is
larger than the dimension B of the downwind fin region 162 in the X direction, the
outdoor heat exchanger 10 has good resistance to frost in the operation that can cause
frost formation.
[0055] In other words, the upwind heat exchanger element 601 in Embodiment 1 has improved
drainage performance in the defrosting operation and has improved resistance to frost
in the operation that can cause frost formation. As described above, the downwind
heat exchanger element 602 has the same configuration as that of the upwind heat exchanger
element 601. Consequently, the downwind heat exchanger element 602 has the same advantages.
[0056] Furthermore, in the refrigeration cycle apparatus 501 including the outdoor heat
exchanger 10 having a two-column structure in which the upwind heat exchanger element
601 and the downwind heat exchanger element 602 are arranged adjacent to each other,
the time required for the defrosting operation is reduced, resulting in a reduction
in amount of heat required for the defrosting operation. Additionally, in the refrigeration
cycle apparatus 501 according to Embodiment 1, improved reliability, reduced resistance
to air flow, and improved resistance to frost are achieved by reducing water remaining
in the outdoor heat exchanger 10 in the operation that can cause frost formation and
retarding blocking of air passages in the outdoor heat exchanger 10 in the operation
that can cause frost formation. In other words, the refrigeration cycle apparatus
501 according to Embodiment 1 has increased average heating capacity in a defrosting
and frosting cycle.
Embodiment 2
[0057] Embodiment 2 is not presented as an embodiment of the present invention but as an
example useful for understanding the present invention. In Embodiment 1, the first
heat transfer tube 21 and the second heat transfer tube 22 are arranged parallel to
each other in the flow direction of the air supplied from the outdoor fan 506, and
extend perpendicular to the Z direction or the gravity direction. The angle of the
first heat transfer tube 21 and the second heat transfer tube 22 is not limited to
that in the configuration in Embodiment 1. For example, the first heat transfer tube
21 and the second heat transfer tube 22 may be arranged as will be described below
in Embodiment 2. Items not particularly mentioned in Embodiment 2 are similar to those
in Embodiment 1, and the same functions and components as those in Embodiment 1 are
denoted by the same reference signs in the following description.
[0058] Fig. 9 is an enlarged view of essential part of an outdoor heat exchanger according
to Embodiment 2. Similarly to Fig. 3, Fig. 9 illustrates the essential part of the
outdoor heat exchanger 10 viewed in the Y direction. Embodiment 2 differs from Embodiment
1 in that heat transfer tubes slope from the upwind ends downwardly in the gravity
direction to the downwind ends in fins 31. As illustrated in Fig. 9, the first heat
transfer tube 21 is inclined in such a manner that the downwind end 142 is located
at a lower level than the upwind end 141 in the gravity direction. Similarly, the
second heat transfer tube 22 is inclined in such a manner that the downwind end 242
is located at a lower level than the upwind end 241 in the gravity direction. In other
words, the first heat transfer tube 21 slopes from the upwind end 141 downwardly in
the gravity direction to the downwind end 142, and the second heat transfer tube 22
slopes from the upwind end 241 downwardly in the gravity direction to the downwind
end 242.
[0059] Consequently, in the outdoor heat exchanger 10 according to Embodiment 2 in a state
in which air is not supplied to the outdoor heat exchanger 10 from the outdoor fan
506 in Fig. 1, for example, even in the defrosting operation, water droplets formed
by melting frost on the heat-transfer-tube region 163 are directed downwind due to
the gravity and the slope of the first heat transfer tube 21 and the second heat transfer
tube 22, so that the water droplets are allowed to flow out of the outdoor heat exchanger
10 through the downwind fin region 162. Furthermore, in a state in which air is supplied
to the outdoor heat exchanger 10 from the outdoor fan 506, that is, in an operation
that can cause frost formation and that is performed after the defrosting operation,
the arrangement of the first heat transfer tube 21 and the second heat transfer tube
22 sloping downwardly in the gravity direction along the air flow allows water droplets
to be directed downwind and thus promotes drainage. As described above, the outdoor
heat exchanger 10 according to Embodiment 2 has further improved drainage performance.
Embodiment 3
[0060] Embodiment 3 is not presented as an embodiment of the present invention but as an
example useful for understanding the present invention. In Embodiments 1 and 2, the
outdoor heat exchanger 10 has a two-column structure, and the upwind heat exchanger
element 601 and the downwind heat exchanger element 602, which constitute the outdoor
heat exchanger 10, have the same configuration. The heat exchanger according to the
present invention may include heat exchanger elements, serving as columns, having
different configurations. Items not particularly mentioned in Embodiment 3 are similar
to those in Embodiment 1 or Embodiment 2, and the same functions and components as
those in Embodiment 1 or Embodiment 2 are denoted by the same reference signs in the
following description.
[0061] Fig. 10 is an enlarged view of essential part of an outdoor heat exchanger according
to Embodiment 3. Fig. 10 illustrates the essential part of the outdoor heat exchanger
10 when the upwind heat exchanger element 601 and the downwind heat exchanger element
602 constituting the outdoor heat exchanger 10 are viewed in the Y direction.
[0062] The fins 31 of the upwind heat exchanger element 601 of the outdoor heat exchanger
10 according to Embodiment 3 have the same configuration as that of the fins 31 in
Embodiment 2. The outdoor heat exchanger 10 according to Embodiment 3 differs from
that according to Embodiment 2 in that a dimension A_2 of an upwind fin region 161'
in the X direction in each fin 32 of the downwind heat exchanger element 602 is smaller
than a dimension A_1 of the upwind fin region 161 in the X direction in each fin 31
of the upwind heat exchanger element 601.
[0063] To increase the efficiency of installation in an outdoor unit, the outdoor heat exchanger
10 may have a bent configuration. The downwind fin region 162 of the fin 31 of the
upwind heat exchanger element 601 faces the upwind fin region 161' of the fin 32 of
the downwind heat exchanger element 602. When the outdoor heat exchanger 10 is bent,
consequently, the downwind fin region 162 and the upwind fin region 161' are each
likely to receive a load from the other one of the downwind fin region 162 and the
upwind fin region 161'. Disadvantageously, the fins 31 and the fins 32 may buckle.
[0064] As illustrated in Fig. 10, the outdoor heat exchanger 10 according to Embodiment
3 is configured in such a manner that the dimension A_2 of the upwind fin region 161'
in the X direction in the fin 32 of the downwind heat exchanger element 602 is smaller
than the dimension A_1 of the upwind fin region 161 in the X direction in the fin
31 of the upwind heat exchanger element 601. Such a configuration enhances the buckling
strength of the upwind fin region 161' in the fin 32 of the downwind heat exchanger
element 602. Furthermore, the downwind fin region 162 in the fin 31 of the upwind
heat exchanger element 601 has relatively high buckling strength as in Embodiment
2 because a dimension B_1 of the downwind fin region 162 in the X direction is smaller
than the dimension A_1 of the upwind fin region 161 in the X direction. The above-described
configuration enables the fins 31 and the fins 32 to be less likely to buckle when
the outdoor heat exchanger 10 is bent and installed in an outdoor unit.
[0065] The resistance to frost of the outdoor heat exchanger 10 according to Embodiment
3 will be described below. In the heating operation, air flowing through the outdoor
heat exchanger 10 first comes into contact with the upwind heat exchanger element
601. Moisture included in the air deposits as frost on the upwind heat exchanger element
601. The flowing air then comes into contact with the downwind heat exchanger element
602. At this time, the moisture in the air is reduced to some extent, and the amount
of frost on the downwind heat exchanger element 602 is smaller than that on the upwind
heat exchanger element 601. Consequently, the dimension A_2, which is small, of the
upwind fin region 161' in the X direction in the fin 32 of the downwind heat exchanger
element 602 has little influence on the resistance to frost of the outdoor heat exchanger
10.
[0066] As described above, as well as having the resistance to frost, the outdoor heat exchanger
10 according to Embodiment 3 has higher product quality, such as buckling strength,
than those in the art.
[0067] Although Fig. 10 illustrates an exemplary configuration in which the heat transfer
tubes slope, the configuration is not limited to this example. It is only required
that the dimension A_2 of the upwind fin region 161' in the X direction in the fin
32 of the downwind heat exchanger element 602 is smaller than the dimension A_1 of
the upwind fin region 161 in the X direction in the fin 31 of the upwind heat exchanger
element 601. The heat transfer tubes do not necessarily have to slope.
Embodiment 4
[0068] Fig. 11 is an enlarged view of essential part of an outdoor heat exchanger according
to Embodiment 4 of the present invention. As in Embodiments 1 to 3, the dimension
A_1 of the upwind fin region 161 in the X direction is larger than the dimension B_1
of the downwind fin region 162 in the X direction in each fin 31 of the upwind heat
exchanger element 601 according to Embodiment 4. Furthermore, a dimension B_2 of a
downwind fin region 162' in the X direction in each fin 33 of the downwind heat exchanger
element 602 is equal to the dimension A_1 of the upwind fin region 161 in the X direction
in the fin 31 of the upwind heat exchanger element 601, and the dimension A_2 of the
upwind fin region 161' in the X direction in the fin 33 of the downwind heat exchanger
element 602 is equal to the dimension B_1 of the downwind fin region 162 in the X
direction in the fin 31 of the upwind heat exchanger element 601. Specifically, the
downwind heat exchanger element 602 has a configuration obtained by flipping the upwind
heat exchanger element 601 horizontally and vertically. In other words, to manufacture
the outdoor heat exchanger 10 having a two-column structure, the upwind heat exchanger
element 601 can be flipped horizontally and vertically and be used as the downwind
heat exchanger element 602. Consequently, as long as a facility to manufacture the
upwind heat exchanger elements 601 is prepared, it is unnecessary to prepare a facility
to manufacture the downwind heat exchanger elements 602, thus reducing an increase
in manufacturing cost.
[0069] Although Fig. 11 illustrates an exemplary configuration in which the heat transfer
tubes slope, the configuration is not limited to this example. It is only required
that the dimension A_1 of the upwind fin region 161 in the X direction is larger than
the dimension B_1 of the downwind fin region 162 in the X direction in the fin 31
of the upwind heat exchanger element 601 and the downwind heat exchanger element 602
has a configuration obtained by flipping the upwind heat exchanger element 601 horizontally
and vertically. The heat transfer tubes do not necessarily have to slope.
[0070] Although the heat exchanger according to each of Embodiments 1 to 4 described above
is used as the outdoor heat exchanger 10, the use of the heat exchanger is not limited
to this example. The heat exchanger according to each of Embodiments 1 to 4 may be
used as the indoor heat exchanger 503 in Fig. 1. In such a case, reducing moisture
to accumulate on the indoor heat exchanger 503 can reduce power to be supplied to
the indoor fan 504, leading to a reduction in energy consumed by the refrigeration
cycle apparatus 501.
Reference Signs List
[0071] 10 outdoor heat exchanger 21 first heat transfer tube 22 second heat transfer tube
30 fin 31 fin 32 fin 33 fin 131 upwind fin end 132 downwind fin end 141 upwind end
142 downwind end 151 first imaginary line 152 second imaginary line 161 upwind fin
region 161' upwind fin region 162 downwind fin region 162' downwind fin region 163
heat-transfer-tube region 163' heat-transfer-tube region 241 upwind end 242 downwind
end 501 refrigeration cycle apparatus 502 compressor 503 indoor heat exchanger 504
indoor fan 505 expansion device 506 outdoor fan 507 four-way valve 601 upwind heat
exchanger element 602 downwind heat exchanger element 603 upwind header collecting
pipe 604 downwind header collecting pipe 605 column connecting part 1010 outdoor heat
exchanger 1021 first heat transfer tube 1022 second heat transfer tube 1132 downwind
fin end 1142 downwind end 1161 upwind fin region 1242 downwind end 2010 outdoor heat
exchanger 2021 first heat transfer tube 2022 second heat transfer tube 2131 upwind
fin end 2141 upwind end 2162 downwind fin region 2241 upwind end 3010 outdoor heat
exchanger 3021 first heat transfer tube 3022 second heat transfer tube 3131 upwind
fin end 3161 upwind fin region 3162 downwind fin region FP fin pitch