Technical Field
[0001] The present invention relates to a heat exchanger used in, for example, an air conditioner,
a freezer, a freezer for transportation, and a water heater.
Background Art
[0002] A heat exchanger in which a refrigerant flows through each of a plurality of stacked
flat tubes is used in an apparatus such as an air conditioner and a freezer, and constitutes
a refrigerant circuit of the apparatus.
[0003] The heat exchanger has a configuration in which the plurality of flat tubes are assembled
to a plate-like or corrugated fin and a pair of headers. Both end parts of each of
the flat tubes are connected to the respective headers, and the refrigerant introduced
into the headers from a pipe of the refrigerant circuit is distributed to each of
the flat tubes. Heat is exchanged between the refrigerant flowing through the flat
tubes and air flowing into gaps among the fins and the flat tubes from a direction
orthogonal to flow of the refrigerant.
[0004] In a case where the heat exchanger functions as an evaporator, the refrigerant of
a gas-liquid two-phase flow flows into the headers. Inside the headers, distribution
of a gas-phase refrigerant and a liquid-phase refrigerant having density larger than
density of the gas-phase refrigerant is easily deviated in a stacking direction of
the flat tubes. Accordingly, a distribution state of the refrigerant to each of the
flat tubes is easily deviated.
[0005] To uniformize a heat transfer amount over the entire stacked body including the flat
tubes and the fins in addition to uniformization of such distribution state of the
refrigerant and to accordingly achieve necessary performance sufficiently, setting
of paths through which the refrigerant efficiently flows in the headers and the flat
tubes, a configuration of each of the headers, a shape of each of the fins, and the
like have been variously devised.
[0006] To secure a heat transfer area necessary for predetermined heat exchange performance,
a plurality of rows of heat exchange elements (assemblies each including flat tubes
and fins) are arranged in a direction connecting a windward side and a leeward side
in some cases (for example, Patent Literature 1).
[0007] In Patent Literature 1, an individual header is not provided on the windward side
(front row) and the leeward side (rear row), and the flat tubes in the front row and
the flat tubes in the rear row are connected to common headers. A large number of
horizontal partition plates are provided inside each of the headers. The flat tube
in the front row and the flat tube in the rear row on the same stage in the stacking
direction of the flat tubes communicate with the same section partitioned by the horizontal
partition plates. The refrigerant having flowed from the refrigerant pipe into each
of the sections inside each of the headers flows through the flat tubes in the front
row and the rear row on each stage.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0009] When the large number of partition plates are provided inside each of the headers,
heat transfer loss caused by deviation of the refrigerant distribution can be suppressed
but the number of parts is increased. Even in the case where the headers are shared
by the front row and the rear row as with Patent Literature 1, the partition plates
corresponding to the number of stages are still necessary, and the number of parts
is increased. Therefore, it is preferable to avoid the inside of each of the headers
from being finely partitioned by the partition plates.
[0010] Further, in the heat exchanger that functions as an evaporator in winter, frosting
progresses from the front row that is largely different in temperature from the air.
Therefore, deviation of the frosting state between the front row and the rear row
cannot be avoided. Thus, if an air passage is closed by frosting in the front row
and an air flow rate in the rear row is reduced, the rear row that can perform heat
exchange because a frosting amount is still small cannot function early.
[0011] Accordingly, an object of the present invention is to provide a heat exchanger that
can secure evaporation performance while suppressing heat transfer loss in a state
where deviation of frosting progressing from the front row and deviation of refrigerant
distribution from the headers to each of the flat tubes are present.
Solution to Problem
[0012] A first heat exchanger according to the present invention is a heat exchanger including
a plurality of stacked flat tubes, fins provided on the flat tubes, and headers that
are erected in a stacking direction in which the flat tubes are stacked, and connected
to the flat tubes. The heat exchanger functions as an evaporator that causes heat
exchange between air and a refrigerant flowing into the flat tubes through the headers,
to evaporate the refrigerant. Heat exchange elements each including the flat tubes,
the fins, and the headers are arranged in a front row located on an upstream side
of flow of the air and a rear row located on a downstream side of the flow of the
air. A flow path cross-sectional area of each of front-row headers that are the headers
in the front row is smaller than a flow path cross-sectional area of each of rear-row
headers that are the headers in the rear row such that a flow velocity of the refrigerant
flowing through each of the front-row headers is higher than a flow velocity of the
refrigerant flowing through each of the rear-row headers.
[0013] The first heat exchanger according to the present invention preferably further includes
a partition portion configured to partition an inside of at least any of the front-row
headers and the rear-row headers by extending in the stacking direction, and the flow
path cross-sectional area is preferably set by the partition portion.
[0014] In the first heat exchanger according to the present invention, a width of each
of the flat tubes in the rear row in a flowing direction of the air is preferably
wider than a width of each of the flat tubes in the front row in the flowing direction
of the air.
[0015] In the first heat exchanger according to the present invention, the heat exchange
elements preferably include two or more heat exchange elements connected in series,
and a heat exchange element of the heat exchange elements on a most downstream side
is preferably located in the front row.
[0016] In the first heat exchanger according to the present invention, the heat exchange
elements preferably include three or more heat exchange elements connected in series,
and a heat exchange element of the heat exchange elements on a most upstream side
is preferably located in the front row.
[0017] A second heat exchanger according to the present invention is a heat exchanger including
a plurality of stacked flat tubes, fins provided on the flat tubes, and headers that
are erected in a stacking direction in which the flat tubes are stacked, and connected
to the flat tubes. The heat exchanger functions as an evaporator that causes heat
exchange between air and a refrigerant flowing into the flat tubes through the headers,
to evaporate the refrigerant. Heat exchange elements each including the flat tubes,
the fins, and the headers are arranged in a front row located on an upstream side
of flow of the air and a rear row located on a downstream side of the flow of the
air. The heat exchanger further includes a flow rate adjusting unit configured to
adjust a flow rate of the refrigerant to be introduced to at least one of front-row
headers that are the headers in the front row and rear-row headers that are the headers
in the rear row such that a flow velocity of the refrigerant flowing through each
of the front-row headers is higher than a flow velocity of the refrigerant flowing
through each of the rear-row headers.
[0018] A third heat exchanger according to the present invention is a heat exchanger including
a plurality of stacked flat tubes, fins provided on the flat tubes, and headers that
are erected in a stacking direction in which the flat tubes are stacked, and connected
to the flat tubes. The heat exchanger functions as an evaporator that causes heat
exchange between air and a refrigerant flowing into the flat tubes through the headers,
to evaporate the refrigerant. Heat exchange elements each including the flat tubes,
the fins, and the headers are arranged in a front row located on an upstream side
of flow of the air and a rear row located on a downstream side of the flow of the
air. The heat exchange element in the front row and the heat exchange element in the
rear row are disposed while being shifted in the stacking direction such that a position
of an introduction portion introducing the refrigerant to a section inside the header
in the front row and a position of an introduction portion introducing the refrigerant
to a section inside the header in the rear row are different in the stacking direction.
[0019] In the third heat exchanger according to the present invention, the heat exchanger
preferably includes two heat exchange elements stacked in the stacking direction in
the front row, and two heat exchange elements stacked in the stacking direction in
the rear row.
Advantageous Effects of Invention
[0020] According to the present invention, as described below, a heat transfer amount in
the stacking direction (up-and-down direction) of the flat tubes as a whole of the
front row and the rear row can be balanced. Therefore, even when the partition plate
for uniformization of refrigerant distribution is not provided, deterioration of heat
exchange performance due to deviation of the refrigerant distribution can be avoided.
In addition, even in an operation state where frosting occurs, a time before operation
is switched to defrosting operation can be prolonged while the heat exchange capability
remains at least on a lower stage side in the rear row.
Brief Description of Drawings
[0021]
[FIG. 1] FIG. 1 is a perspective view schematically illustrating a heat exchanger
according to a first embodiment.
[FIG. 2] FIG. 2 is a schematic diagram to explain difference between flow velocity
of a refrigerant flowing through a front-row header and flow velocity of a refrigerant
flowing through a rear-row header illustrated in FIG. 1.
[FIGS. 3A to 3C] FIGS. 3A to 3C are graphs illustrating a distribution state of a
liquid-phase refrigerant to flat tubes in each of a front row and a rear row at respective
refrigerant flow rates.
[FIG. 4] FIG. 4 is a schematic diagram to explain action of the heat exchanger illustrated
in FIG. 1.
[FIG. 5] FIG. 5 is a schematic diagram illustrating a front-row header and a rear-row
header according to a modification of the first embodiment.
[FIG. 6] FIG. 6 is a schematic diagram illustrating a heat exchange element in a front
row and a heat exchange element in a rear row according to another modification of
the first embodiment.
[FIGS. 7A to 7D] FIG. 7A is a schematic diagram illustrating a heat exchanger according
to a second embodiment, FIG. 7B is a schematic diagram illustrating a heat exchanger
according to a modification of the second embodiment, and FIGS. 7C and 7D are diagrams
illustrating liquid-phase refrigerant distribution in a case where dryness is high.
[FIGS. 8A and 8B] FIG. 8A is a schematic diagram illustrating a heat exchanger according
to a third embodiment, and FIG. 8B is a schematic diagram illustrating a modification
of the third embodiment.
[FIGS. 9A and 9B] FIGS. 9A and 9B are schematic diagrams each illustrating a heat
exchanger according to a fourth embodiment without illustration of fins.
Description of Embodiments
[0022] Some embodiments of the present invention are described below with reference to accompanying
drawings.
[First Embodiment]
[0023] A heat exchanger 1 illustrated in FIG. 1 includes a front-row heat exchange element
10 and a rear-row heat exchange element 20. The heat exchanger 1 constitutes a refrigerant
circuit of an air conditioner, a freezer, a water heater, or the like. The refrigerant
circuit includes a compressor, a condenser, a decompression unit, and the heat exchanger
1 serving as an evaporator.
[0024] As described below, the heat exchanger 1 according to the present embodiment suppresses
deterioration of heat exchange performance while accepting deviation of refrigerant
distribution from headers 13 and 23 to each of flat tubes 11 and deviation of frosting.
(Heat Exchange Element)
[0025] The front-row heat exchange element 10 includes the plurality of stacked flat tubes
11 (tubes), a plurality of fins 12, and a pair of front-row headers 13 (13A and 13B)
connected to the flat tubes 11.
[0026] The front-row heat exchange element 10 exchanges heat between a refrigerant flowing
into each of the flat tubes 11 through one (13A) of the front-row headers 13 and air
flowing into gaps among the fins 12 and the flat tubes 11 from a direction orthogonal
to the flat tubes 11.
[0027] As with the front-row heat exchange element 10, the rear-row heat exchange element
20 includes the plurality of stacked flat tubes 11, the plurality of fins 12, and
the pair of rear-row headers 23 (23A and 23B) connected to the flat tubes 11. The
rear-row heat exchange element 20 exchanges heat between a refrigerant flowing into
each of the flat tubes 11 through one (23A) of the rear-row headers 23 and the air.
[0028] The flat tubes 11 and the fin 12 are components common to the front-row heat exchange
element 10 and the rear-row heat exchange element 20.
[0029] In this example, a direction in which the flat tubes 11 are stacked (stacking direction)
is referred to as an up-and-down direction D1.
[0030] Further, in flow of the air subjected to heat exchange with the refrigerant flowing
through the flat tubes 11, an upstream side is referred to as "front", and a downstream
side is referred to as "rear". The air sucked by an unillustrated fan or the like
is preferably supplied to an entire region of the heat exchanger 1.
[0031] The front-row heat exchange element 10 and the rear-row heat exchange element 20
are arranged in the air flowing direction (illustrated by void arrow). In each of
the drawings, the front row is denoted by "F", and the rear row is denoted by "R".
[0032] The front-row heat exchange element 10 and the rear-row heat exchange element 20
are connected to pipes of the refrigerant circuit in parallel. The refrigerant of
the same flow rate flows through the front-row heat exchange element 10 and the rear-row
heat exchange element 20.
[0033] The heat exchanger 1 includes the heat exchange elements 10 and 20 in at least a
part thereof. The heat exchanger 1 may include unillustrated another heat exchange
element in addition to the heat exchange elements 10 and 20.
(Flat Tube)
[0034] Each of the flat tubes 11 is a flat tube through which the refrigerant flows, has
a predetermined length, and extends linearly. Both end parts of each of the flat tubes
11 are connected to the respective headers 13 (or respective headers 23). Each of
the headers 13 and 23 includes insertion holes (not illustrated) each receiving the
corresponding end part of the flat tubes 11 to the inside of the headers 13 and 23.
[0035] The plurality of flat tubes 11 are stacked in parallel with one another with predetermined
intervals in the up-and-down direction D1. The end parts of each of the flat tubes
11 are opened inside the respective headers 13 (or respective headers 23).
(Fin)
[0036] The fins 12 according to the present embodiment each have a substantially rectangular
plate-like outer shape, and are provided on the flat tubes 11 in order to increase
a surface area coming into contact with the air. Each of the fins 12 includes a plurality
of notches 121 into which the respective flat tubes 11 are inserted. The fins 12 in
the front row F and the fins 12 in the rear row R may have different shapes.
[0037] FIG. 1 illustrates only a part of the fins 12 in each of the front row F and the
rear row R. The large number of fins 12 are actually provided on the stacked body
of the flat tubes 11 with intervals in a length direction of the flat tubes 11 in
each of the front row F and the rear row R.
[0038] In place of the plate-like fins 12, the other type of fins may be provided on the
flat tubes 11. For example, a corrugated fin may be provided between the flat tubes
11 adjacent in the up-and-down direction D1.
[0039] The members configuring the heat exchanger 1, such as the flat tubes 11, the fins
12, the front-row headers 13, and the rear-row headers 23 are made of a metal material
such as an aluminum alloy and a copper alloy. These members are integrated using a
joining material such as brazing filler metal to constitute the heat exchanger 1.
(Front-Row Header)
[0040] The pair of front-row headers 13 are both erected in the stacking direction (D1)
of the flat tubes 11 in the front row F. The flat tubes 11 in the front row F are
connected to these front-row headers 13.
[0041] Each of the pair of front-row headers 13 has a cylindrical shape, and has a closed
upper end and a closed lower end.
[0042] The refrigerant flows into each of the flat tubes 11 through one (13A) of the pair
of front-row headers 13, and the refrigerant flows out to the other (13B) of the pair
of front-row headers 13 from each of the flat tubes 11.
[0043] The front-row header 13A includes an introduction portion 131 that introduces the
refrigerant from an unillustrated refrigerant pipe or the like to the inside of the
front-row header 13. The inside of the front-row header 13A serves as a flow path
through which the refrigerant introduced through the introduction portion 131 flows
upward.
[0044] The introduction portion 131 is preferably located below the flat tube 11 that is
disposed at the lowest part inside the front-row header 13A because a gas-phase refrigerant
floating from the introduction portion 131 and a liquid refrigerant lifted together
with the gas-phase refrigerant can flow into all of the flat tubes 11 including the
flat tube 11 disposed at the lowest part in the front row F.
[0045] The refrigerant introduced into the front-row header 13A is distributed and flows
into each of the flat tubes 11 in the front row F. Further, heat is exchanged between
the air passing through the gaps (air passages) between the fins 12 and the flat tubes
11 and the refrigerant inside the flat tubes 11 while the refrigerant flows through
each of the flat tubes 11 (dashed arrows in FIG. 1). At this time, the refrigerant
flowing through the flat tubes 11 evaporates by absorbing heat from the air.
[0046] The refrigerant having flowed through each of the flat tubes 11 is merged inside
the front-row header 13B, and the merged refrigerant flows out from the front-row
header 13B to a refrigerant pipe or the like outside the heat exchanger 1. Alternatively,
in a case where the heat exchanger 1 includes the other heat exchange element connected
to the front-row header 13B, the refrigerant flows out from the front-row header 13B
to the other heat exchange element.
(Rear-Row Header)
[0047] The rear-row headers 23 are briefly described because the rear-row headers 23 have
a configuration similar to the configuration of the front-row headers 13 except that
each of the rear-row headers 23 has a flow path cross-sectional area different from
a flow path cross-sectional area of each of the front-row headers 13.
[0048] The refrigerant flows into each of the flat tubes 11 in the rear row R through one
(23A) of the pair of rear-row headers 23, and the refrigerant flows out to the other
(23B) of the pair of rear-row headers 23 from each of the flat tubes 11 in the rear
row R.
[0049] The rear-row header 23A includes an introduction portion 231 that introduces the
refrigerant from a refrigerant pipe or the like to the inside of the rear-row header
23.
[0050] The refrigerant introduced into the rear-row header 23A through the introduction
portion 231 is distributed and flows into each of the flat tubes 11 in the rear row
R. The refrigerant flowing through each of the flat tubes 11 in the rear row R is
subjected to heat exchange with the air passing through the front row F. Thereafter,
the refrigerant is merged inside the rear-row header 23B, and the merged refrigerant
flows out from the rear-row header 23B to a refrigerant pipe outside the heat exchanger
1 or to the other heat exchange element.
[0051] The heat exchanger 1 is basically used in a state where the front-row headers 13
and the rear-row headers 23 are disposed along the up-and-down direction D1 (vertical
direction). At this time, the flat tubes 11 extend in a horizontal direction and are
stacked in the up-and-down direction D1.
[0052] Note that the front-row headers 13 and the rear-row headers 23 may be slightly inclined
with respect to the up-and-down direction D1.
(Main Characteristics of Present Embodiment)
[0053] The present embodiment is mainly characterized in that a flow path cross-sectional
area Af (FIG. 2) of each of the front-row headers 13 is smaller than a flow path cross-sectional
area Ar (FIG. 2) of each of the rear-row headers 23 such that flow velocity of the
refrigerant flowing through each of the front-row headers 13 is higher than flow velocity
of the refrigerant flowing through each of the rear-row headers 23.
[0054] Each of the front-row headers 13 and the rear-row headers 23 according to the present
embodiment includes a flow path having a circular cross-section, and an inner diameter
of each of the front-row headers 13 is smaller than an inner diameter of each of the
rear-row headers 23.
[0055] Note that the cross-sectional shape of each of the front-row headers 13 and the rear-row
headers 23 may be an optional shape such as a rectangular shape and an elliptical
shape.
[0056] As illustrated in FIG. 5, the appropriate flow path cross-sectional areas Af and
Ar can be set by respectively installing vertical partition plates 14 and 24 inside
the front-row header 13 and the rear-row header 23. Only either one of the vertical
partition plates 14 and 24 may be installed.
[0057] The vertical partition plate 14 is erected along the up-and-down direction D1 orthogonal
to a paper surface of FIG. 5, and partitions the inside of the front-row header 13
into a section 141 on the introduction portion 131 side and a section 142 on the flat
tubes 11 side.
[0058] The refrigerant introduced from the introduction portion 131 into the section 141
flows into the section 142 through an opening 14A that penetrates a lower end part
of the vertical partition plate 14 in a thickness direction, and is distributed to
each of the flat tubes 11 while flowing upward inside the section 142.
[0059] The vertical partition plate 24 has a similar configuration to the above-described
vertical partition plate 14, and partitions the inside of the rear-row header 23 into
a section 241 on the introduction portion 231 side and a section 242 on the flat tubes
11 side. An opening 24A is provided at a lower end part of the vertical partition
plate 24.
[0060] When positions of the vertical partition plates 14 and 24 are set such that a dimension
G2 of a gap between the vertical partition plate 24 and the end part of each of the
flat tubes 11 is larger than a dimension G1 of a gap between the vertical partition
plate 14 and each of the flat tubes 11, the flow path cross-sectional area Ar that
is larger than the flow path cross-sectional area Af of the section 142 of the front-row
header 13 can be provided to the section 242 of the rear-row headers 23.
(Action by Present Embodiment)
[0061] As illustrated in FIG. 2, the refrigerant having flowed, at the predetermined flow
rate, from the pipe of the refrigerant circuit into the front-row header 13A through
the introduction portion 131 is distributed to each of the flat tubes 11 in the front
row while flowing upward inside the front-row header 13A at the flow velocity Vf corresponding
to the flow path cross-sectional area Af of the front-row header 13A.
[0062] In contrast, the refrigerant having flowed, at the flow rate same as the flow rate
of the refrigerant flowing into the introduction portion 131 of the front-row header
13A, from the pipe of the refrigerant circuit into the rear-row header 23A through
the introduction portion 231 is distributed to each of the flat tubes 11 in the rear
row while flowing upward inside the rear-row header 23A at the flow velocity Vr corresponding
to the flow path cross-sectional area Ar of the rear-row header 23A.
[0063] At this time, since the flow rate of the refrigerant flowing into the front-row header
13 through the introduction portion 131 and the flow rate of the refrigerant flowing
into the rear-row header 23 through the introduction portion 231 are equal to each
other and Af < Ar is satisfied for the flow path cross-sectional areas, Vf > Vr is
established for the flow velocities. In other words, the flow velocity Vf of the refrigerant
flowing through the front-row header 13A is higher than the flow velocity Vr of the
refrigerant flowing through the rear-row header 23A.
[0064] Lengths of arrows illustrated in grey in FIG. 2 schematically represent relative
magnitudes of the flow velocities Vf and Vr.
[0065] The refrigerant of a gas-liquid two-phase flow expanded by passing through the decompression
unit of the refrigerant circuit flows into the front-row header 13A and the rear-row
header 23A. A gas-phase component of the refrigerant is referred to as a gas-phase
refrigerant, and a liquid-phase component of the refrigerant is referred to as a liquid-phase
refrigerant. The liquid-phase refrigerant is carried upward by being caught in the
floating gas-phase refrigerant. Density of the liquid-phase refrigerant is larger
than density of the gas-phase refrigerant. Therefore, distribution of the gas-phase
refrigerant and the liquid-phase refrigerant in the up-and-down direction D1 is easily
deviated in each of the front-row header 13A and the rear-row header 23A.
[0066] Such a distribution state of the gas-phase refrigerant and the liquid-phase refrigerant
is different between the front-row header 13A and the rear-row header 23A based on
difference between the flow velocities Vf and Vr.
[0067] In the front-row header 13A having the higher flow velocity Vf, the liquid-phase
refrigerant is carried to an upper part as compared with the rear-row header 23A having
the relatively low flow velocity Vr. Accordingly, a percentage of the liquid-phase
refrigerant to the gas-phase refrigerant is relatively high in an upper part of the
flow path from an lower end to an upper end of the front-row header 13A, and the percentage
of the liquid-phase refrigerant to the gas-phase refrigerant is low in a lower part
of the flow path. The liquid-phase refrigerant that makes a phase transition to the
gas phase while flowing through the flat tubes 11 absorbs heat from the air based
on latent heat. When the flow percentage of the liquid-phase refrigerant is high,
a heat transfer amount between the air and the refrigerant is large.
[0068] A width of each of the grey arrows illustrated in FIG. 2 represents the percentage
of the liquid-phase refrigerant to the gas-phase refrigerant based on the flow rate.
In the front-row header 13A, the flow percentage of the liquid-phase refrigerant is
gradually increased as it goes upward from a lower side.
[0069] In contrast, in the rear-row header 23A having the low flow velocity Vr, the liquid-phase
refrigerant is difficult to be carried to an upper part as compared with the front-row
header 13A. Therefore, a range where the liquid-phase refrigerant is sufficiently
carried from the introduction portion 231 is limited to the lower part of the flow
path of the rear-row header 23A.
[0070] Accordingly, contrary to the above-described front-row header 13A, the percentage
of the liquid-phase refrigerant to the gas-phase refrigerant is high at the lower
part of the flow path of the rear-row header 23A, and the percentage of the liquid-phase
refrigerant to the gas-phase refrigerant is low at the upper part of the flow path.
[0071] Accordingly, in both of the distribution state of the liquid-phase refrigerant distributed
from the front-row header 13A to each of the flat tubes 11 in the front row F and
the distribution state of the liquid-phase refrigerant distributed from the rear-row
header 23A to each of the flat tubes 11 in the rear row R, deviation in the up-and-down
direction D1 is found in different forms.
[0072] FIGS. 3A to 3C respectively illustrate the flow percentage of the liquid-phase refrigerant
(flow ratio to gas-phase refrigerant) in the refrigerant having flowed into the flat
tubes 11 in each of the front row F and the rear row R based on experimental results
in a case FIG. 3A where the flow rate of the refrigerant introduced into the heat
exchanger 1 is small, in a case FIG. 3B where the flow rate is middle, and in a case
FIG. 3C where the flow rate is large. The numbers 1, 2, 3, ... are provided to the
flat tubes 11 in order from the flat tube 11 located at the uppermost part to the
flat tube 11 located at the lower part in each of the front-row header 13A and the
rear-row header 23A. Note that, in the experiment to obtain the data in FIGS. 3A to
3C, a front-row heat exchange element and a rear-row heat exchange element each including
seven flat tubes 11 were used.
[0073] FIGS. 3A to 3C all illustrate a tendency similar to the above description, namely,
a tendency that the percentage of the flowing-in liquid-phase refrigerant is high
in the flat tube 11 located at the upper part in the front row F whereas the percentage
of the flowing-in liquid-phase refrigerant is high in the flat tube 11 located at
the lower part in the rear row R.
[0074] As illustrated in FIGS. 3A to 3C, the deviation degree of the flow percentage of
the liquid-phase refrigerant in the up-and-down direction D1 in the front row F is
increased as the flow rate of the refrigerant is increased. In contrast, the deviation
degree of the flow percentage of the liquid-phase refrigerant in the up-and-down direction
D1 in the rear row R is decreased as the flow rate of the refrigerant is increased.
The tendency is qualitatively established because the flow path cross-sectional area
of each of the front-row headers 13 is smaller than the flow path cross-sectional
area of each of the rear-row headers 23.
[0075] As the flow rate relating to FIG. 3C, the flow rate of the heat exchanger 1 under
a situation where frosting easily occurs, for example, under a situation where the
air conditioner performs heating operation in winter is assumed. When the flow rate
is large as described above, uneven distribution of the liquid-phase refrigerant at
the upper part in the front row F becomes remarkable as illustrated in FIG. 3C. At
this time, in the heat exchange element 10 in the front row F, heat exchange is mainly
performed at an upper stage.
(Effects by Present Embodiment)
[0076] In the present embodiment, as described above, the flow path cross-sectional area
Af of each of the front-row headers 13 and the flow path cross-sectional area Ar of
each of the rear-row headers 23 are made different from each other to provide different
distribution to the liquid-phase refrigerants in the front row F and the rear row
R. This suppresses heat transfer loss and secures heat exchange performance as a whole
of the heat exchanger 1.
[0077] Action of the preset embodiment is described with reference to FIG. 4 and FIG. 2.
According to the present embodiment, even when deviation is present in the liquid-phase
flow percentage of the refrigerant distributed to each of the flat tubes 11 in each
of the front row F and the rear row R, the heat transfer amount is uniformized and
necessary heat exchange performance is secured even under restriction of the capacity
of the heat exchanger or the like, as a whole of the heat exchanger 1.
[0078] In the front-row header 13 (FIG. 2) having the high flow velocity, the liquid-phase
refrigerant is sufficiently carried to the upper part. Therefore, the heat transfer
amount between the air and the refrigerant flowing through the flat tube 11 on the
upper stage side having the large flow percentage of the liquid-phase refrigerant
among the flat tubes 11 in the front row F to which the refrigerant is distributed
from the front-row header 13 is large, whereas the heat transfer amount at the lower
part is small.
[0079] In contrast, in the rear-row header 23 (FIG. 2) having the flow velocity lower than
the flow velocity of the front-row header 13, the liquid-phase refrigerant is not
sufficiently carried to the upper part. Therefore, the heat transfer amount between
the air and the refrigerant flowing through the flat tube 11 on the lower stage side
having the large flow percentage of the liquid-phase refrigerant among the flat tubes
11 in the rear row R to which the refrigerant is distributed from the rear-row header
23 is large, whereas the heat transfer amount at the upper part is small.
[0080] The air flowing along an arrow 1 illustrated in FIG. 4 passes through the lower stage
side having the small heat transfer amount in the front row F and the lower stage
side having the large heat transfer amount in the rear row R. At this time, even if
heat of the air that has passed through the lower stage side having the low flow percentage
of the liquid-phase refrigerant in the front row F is not sufficiently dissipated
to the refrigerant, an amount of the liquid-phase refrigerant flowing through the
flat tubes 11 on the lower stage side in the rear row R into which the air flows subsequently
to the front row F is sufficient to dissipate heat of the air.
[0081] Further, the air flowing along an arrow 2 illustrated in FIG. 4 passes through the
upper stage side having the large heat transfer amount in the front row F and the
upper stage side having the small heat transfer amount in the rear row R. In this
case, the air, the heat of which has been already dissipated to the refrigerant that
has the high flow percentage of the liquid-phase refrigerant in the upper stage side
of the front row F, flows into the rear row R. Accordingly, it is sufficient that
the liquid-phase refrigerant of an amount enough to heat exchange with the air after
the heat dissipation in the front row F flows through the flat tubes 11 on the upper
stage side in the rear row R.
[0082] Accordingly, the heat transfer surface is effectively utilized while the heat transfer
loss is avoided over the whole of the heat exchanger 1 including the upper stage side
and the lower stage side of the front row F and the upper stage side and the lower
stage side of the rear row R. Therefore, even when the heat exchanger 1 is small,
it is possible to sufficiently secure the heat exchange performance. The flow velocity
is made different between the front-row header 13 and the rear-row header 23 as with
the present embodiment, which makes it possible to balance the heat transfer amount
in the up-and-down direction D1 as the whole of the front row F and the rear row R
as described above. This can avoid deterioration of the heat exchange performance
due to deviation of the refrigerant distribution. As a result, it is unnecessary to
provide the horizontal partition plate in each of the headers 13 and 23 for uniformization
of the refrigerant distribution. This makes it possible to avoid increase of the number
of parts, and to suppress a manufacturing cost of the heat exchanger 1.
[0083] Contrary to the present embodiment, even in a case where the flow path cross-sectional
areas are determined so as to establish Af > Ar, and the flow velocity Vf of the front-row
header 13 is made lower than the flow velocity Vr of the rear-row header 23, effects
similar to the effects by the present embodiment can be achieved in terms of avoidance
of performance deterioration due to deviation of the refrigerant distribution.
[0084] Further, the present embodiment cope with performance deterioration caused by frosting
in addition to performance deterioration caused by deviation of the refrigerant distribution.
When temperature of external air as a heat source is low during heating operation,
frosting progresses from the front row F that is largely different in temperature
with the contact air as compared with the rear row R in the heat exchanger 1 used
in an outdoor heat exchanger of the air conditioner. Alternatively, frosting may occur
in the heat exchanger 1 used to cool a heat load, for example, a heat exchanger inside
a refrigerator/freezer such as a refrigerating/freezing showcase. Also in this case,
frosting progresses from the front row F.
[0085] To avoid the performance deterioration caused by frosting, it is preferable that
relationship between the flow velocity Vf of the front-row header 13 and the flow
velocity Vr of the rear-row header 23 be specified such that the flow velocity Vf
of the front-row header 13 is larger than the flow velocity Vr of the rear-row header
23, as with the present embodiment. Further, in the present embodiment in which the
refrigerant at the same flow rate is introduced to each of the front row F and the
rear row R, the flow path cross-sectional areas are specified to Af < Ar.
[0086] In the upper stage side having the large flow percentage of the liquid-phase refrigerant
in the front row F where frosting easily occurs, frosting easily occurs because the
air is sufficiently cooled by the refrigerant having the large flow percentage of
the liquid-phase refrigerant. In contrast, frosting hardly occurs on the lower stage
side even in the front row F. In other words, deviation of frosting occurs in a manner
similar to deviation of the flow percentage of the liquid-phase refrigerant in the
up-and-down direction D1 in the front row (for example, FIG. 3C).
[0087] It is assumed that frosting on the upper stage side in the front row F having the
large flow percentage of the liquid-phase refrigerant progresses as illustrated in
FIG. 3C and an air flow rate on the upper stage side in the rear row R is reduced
due to closing of the air passage caused by the frost. At this time, however, frosting
does not much progress on the lower stage side in the front row F. Therefore, the
air flow rate can be maintained at least on the lower stage side in the rear row R
on the leeward of the lower stage side of the front row F.
[0088] In other words, after the heat exchange capability on the upper stage side including
the rear row R is lost due to frosting, the air is fed to the rear row R on the lower
stage side. Since the heat exchange capability remains on the heat transfer surface
on the lower stage side in the rear row R on which frost is not attached, a time before
operation is switched to defrosting operation is prolonged.
[0089] According to the present embodiment, suppressing heat transmission loss caused by
frosting makes it possible to avoid interruption of the heating operation or the like
by defrosting operation, and to continue the heating operation or the like.
[0090] FIG. 6 illustrates an example in which each of the flat tubes 11 inserted into the
rear-row headers 23 each having a diameter larger than the diameter of each of the
front-row headers 13 has a width Dr wider than a width Df of each of the flat tubes
11 in the front row F. To increase the heat transfer area, the large width Dr of each
of the flat tubes 11 in the air flowing direction substantially equal to the diameter
of each of the rear-row headers 23 is preferably secured. Widening the width Dr of
each of the flat tubes 11 in the rear row R makes it possible to improve capability
of the heat exchanger 1 without changing a space necessary for installation of the
heat exchanger 1.
[0091] Note that, instead of widening the width Dr of each of the flat tubes 11 in the rear
row R, two flat tubes 11 may be arranged in the width direction.
[Second Embodiment]
[0092] Next, a second embodiment of the present invention is described with reference to
FIGS. 7A to 7D.
[0093] In the second embodiment, an example of application to a heat exchanger including
a plurality of paths connected in serial is described.
[0094] A heat exchanger 2 illustrated in FIG. 7A includes the heat exchange elements 10
and 20 corresponding to the paths connected in series. This is different from the
heat exchange elements 10 and 20 that are connected to the pipe of the refrigerant
circuit in parallel, of the heat exchanger 1 according to the first embodiment.
[0095] FIG. 7A schematically illustrates the heat exchange elements 10 and 20. The heat
exchange elements 10 and 20 each have a similar configuration to the respective heat
exchange elements 10 and 20 in the first embodiment (FIG. 1) .
[0096] In other words, as illustrated in FIG. 1, the front-row heat exchange element 10
includes the flat tubes 11, the fins 12, and the front-row headers 13. The rear-row
heat exchange element 20 also includes the flat tubes 11, the fins 12, and the rear-row
headers 23. Since the flow path cross-sectional area Af of each of the front-row headers
13 is smaller than the flow path cross-sectional area Ar of each of the rear-row headers
23, the refrigerant flow velocity Vf of each of the front-row headers 13 is higher
than the refrigerant flow velocity Vr of each of the rear-row headers 23.
[0097] As with the first embodiment, the heat transfer amount in the up-and-down direction
D1 as the whole of the front row F and the rear row R can be balanced based on the
flow velocity difference, and the time before operation is switched to the defrosting
operation when frosting occurs can be prolonged.
[0098] The rear-row heat exchange element 20 corresponds to a first path P1 on the most
upstream side. The front-row heat exchange element 10 corresponds to a second path
P2 subsequent to the first path P1. In this example, the second path P2 is a path
on the most downstream side.
[0099] Dryness of the refrigerant is increased while the refrigerant flows from the most
upstream path P1 to the most downstream path P2.
[0100] When the refrigerant is introduced from an unillustrated refrigerant pipe to the
rear-row header 23A (FIG. 1) of the first path P1, the refrigerant is distributed
from the rear-row header 23A to each of the flat tubes 11 in the rear row R. The refrigerant
having flowed through each of the flat tubes 11 is merged inside the rear-row header
23B (FIG. 1), and the merged refrigerant flows into the second path P2 in the front
row F through a U-shaped pipe 17. Thereafter, the refrigerant is distributed from
the front-row header 13B (FIG. 1) in the second path P2 to each of the flat tubes
11 in the flat row F, and the refrigerant having flowed through each of the flat tubes
11 flows out from the front-row header 13A (FIG. 1) to the refrigerant pipe.
[0101] When the refrigerant absorbs heat from the air and dryness of the refrigerant is
increased, an absolute amount of the flow percentage of the liquid-phase refrigerant
is reduced. Therefore, it is particularly difficult to cause the liquid-phase refrigerant
to flow into the flat tube 11 on the upper stage side inside the header in the most
downstream path P2.
[0102] FIG. 7C and FIG. 7D both illustrate the liquid-phase refrigerant distribution in
a case where dryness of the refrigerant is high, based on the experiment; however,
the flow path cross-sectional area of a header is different in FIG. 7C and FIG. 7D.
FIG. 7C illustrates a case where the header has a typical flow path cross-sectional
area (for example, flow path cross-sectional area Am in FIG. 8), and FIG. 7D illustrates
a case where the flow path cross-sectional area of the header is smaller than the
typical area. Since the refrigerant flow rate is the same in FIGS. 7C and 7D, the
flow velocity inside the header is higher in the header having the small flow path
cross-sectional area (FIG. 7D). Accordingly, as compared with the header in which
the flow velocity is relatively low in FIG. 7C, the liquid-phase refrigerant reaches
up to the flat tube 11 located at the upper part in the header illustrated in FIG.
7D.
[0103] Based on the above description, the most downstream path P2 where dryness is the
highest is disposed in the front row F as illustrated in FIG. 7A. In the front-row
headers 13 where the flow velocity is high because of the small flow path cross-sectional
area, the liquid-phase refrigerant can be sufficiently lifted to the upper part so
as to flow into the flat tube 11 located at the upper part. As a result, the heat
transfer surface of the most downstream path P2 can be sufficiently used and can contribute
to performance.
[Modification of Second Embodiment]
[0104] In a case where a heat exchanger 2A includes three or more paths connected in series
as illustrated in FIG. 7B, a fourth path P4 on the most downstream side is preferably
disposed in the front row F and the first path P1 on the most upstream side is also
preferably disposed in the front row F as with illustration in FIG. 7A.
[0105] The second path P2 and a third path P3 are disposed in the rear row R.
[0106] The heat exchanger 2A includes the four paths P1 to P4. The first path P1 and the
second path P2 on the upstream side are located at the lower part in the heat exchanger
2A, and the third path P3 and the fourth path P4 on the downstream side are located
at the upper part in the heat exchanger 2A.
[0107] On the upstream side of a serial circuit in the heat exchanger 2A, pressure loss
at the same flow path cross-sectional area is lower than pressure loss on the downstream
side because the liquid-phase refrigerant is larger on the upstream side than on the
downstream side where dryness is increased. Accordingly, the flow path cross-sectional
area of each of the paths P1 and P2 on the upstream side is suppressed (number of
stages (number of flat tubes 11) is reduced) to a degree not causing excess pressure
loss as compared with the paths P3 and P4 on the downstream side, thereby suppressing
a height of the heat exchanger 2A.
[0108] FIG. 7B also schematically illustrates the heat exchange elements 10 and 20. The
heat exchange elements 10 and 20 each have a similar configuration to the respective
heat exchange elements 10 and 20 in the first embodiment (FIG. 1).
[0109] As with the first embodiment, the heat transfer amount as the whole of the front
row F and the rear row R can be balanced based on the flow velocity difference between
the front-row headers 13 and the rear-row headers 23, and the time before operation
is switched to the defrosting operation when frosting occurs can be prolonged.
[0110] When the refrigerant is introduced to the header 13A (FIG. 1) of the first path P1
in the configuration illustrated in FIG. 7B, the refrigerant is distributed from the
front-row header 13A to each of the flat tubes 11 in the front row F. The refrigerant
having flowed through each of the flat tubes 11 is merged inside the front-row header
13B (FIG. 1), and the merged refrigerant flows into the second path P2 in the rear
row R through a U-shaped pipe 181. Thereafter, the refrigerant is distributed from
the rear-row header 23B of the second path P2 to each of the flat tubes 11, and the
refrigerant having flowed through each of the flat tubes 11 flows from the rear-row
header 23A into the rear-row header 23A of the third path P3 on the upper stage side
through a U-shaped pipe 182. Furthermore, the refrigerant flows through the flat tubes
11 of the third path P3, and flows into the front-row header 13B of the fourth path
P4 through a U-shaped pipe 183. Thereafter, the refrigerant flows through the flat
tubes 11 of the fourth path P4 and then flows out to the refrigerant pipe.
[0111] According to the configuration illustrated in FIG. 7B, the most downstream path P4
where the dryness is the highest is disposed in the front row F as with the second
embodiment illustrated in FIG. 7A. This makes it possible to sufficiently use the
heat transfer surface of the most downstream path P4 and to contribute to performance.
[0112] In addition, the flow path cross-sectional area is small in the header 13 in the
most upstream path P1 where the refrigerant pressure loss is relatively small due
to the lowest dryness of the refrigerant flowing into the header 13, in particular,
in the header 13A as an inlet of the path P1. This makes it possible to suppress rise
of evaporation temperature caused by the refrigerant pressure loss. Suppressing rise
of the evaporation temperature makes it possible to avoid deterioration of evaporation
performance.
[Third Embodiment]
[0113] Next, a third embodiment of the present invention is described with reference to
FIGS. 8A and 8B.
[0114] A heat exchanger 3 according to the third embodiment illustrated in FIG. 8A includes
the front-row heat exchange element 10 and the rear-row heat exchange element 20 as
with the heat exchanger 1 (FIG. 2) according to the first embodiment.
[0115] In the first embodiment (FIG. 2), the flow path cross-sectional area Af smaller than
the flow path cross-sectional area Ar of the rear-row header 23 is provided to the
front-row header 13 such that the flow velocity Vf of the front-row header 13 is larger
than the flow velocity Vr of the rear-row header 23. In contrast, in the third embodiment,
a distributer 15 (flow rate adjusting unit) that can adjust the flow rate of the refrigerant
to be introduced to each of the front-row header 13 and the rear-row header 23 is
used.
[0116] The distributer 15 including a capillary tube and the like divides the refrigerant
flowing in from the unillustrated refrigerant pipe, at a predetermined flow ratio
such that a flow rate Rf of the refrigerant flowing into the front-row header 13 is
larger than a flow rate Rr of the refrigerant flowing into the rear-row header 23.
[0117] As a result, the flow velocity Vf corresponding to the flow rate Rf and the flow
path cross-sectional area Am is given to the front-row header 13, and the flow velocity
Vr corresponding to the flow rate Rr and the flow path cross-sectional area Am is
given to the rear-row header 23.
[0118] In the present embodiment, since the flow path cross-sectional area Am of the front-row
header 13 and the flow path cross-sectional area Am of the rear-row header 23 are
equivalent to each other, Rf/Rr = Vf/Vr is established.
[0119] According to the present embodiment, the distributer 15 is provided. Therefore, even
when the flow path cross-sectional area of the front-row header 13 and the flow path
cross-sectional area of the rear-row header 23 are equivalent to each other, the flow
velocity difference of the refrigerant is given to the front-row header 13 and the
rear-row header 23, and action and effects similar to the action and the effects according
to the first embodiment can be achieved based on the distribution of the flow percentage
of the liquid-phase refrigerant in the up-and-down direction D1 caused by the flow
velocity difference.
[0120] Further, using the same headers with the same diameter makes it possible to prevent
misassembly of the front-row heat exchange element 10 and the rear-row heat exchange
element 20 in manufacturing of the heat exchanger 3.
[0121] In place of the distributer 15, a throttle 16 (flow rate adjusting unit) may be used
as illustrated in FIG. 8B. The throttle 16 is provided on one conduit introduced to
the rear-row header 23 out of conduits divided at the equivalent flow rate from the
unillustrated refrigerant pipe. Pressure loss is given by the throttle 16 to the refrigerant
flowing to the rear-row header 23. As a result, the flow rate Rr of the refrigerant
introduced to the rear-row header 23 is smaller than the flow rate Rf of the refrigerant
introduced to the front-row header 13.
[Fourth Embodiment]
[0122] Next, a fourth embodiment of the present invention is described with reference to
FIGS. 9A and 9B.
[0123] FIGS. 9A and 9B each illustrate a heat exchanger 4 having the same configuration.
Illustration in FIGS. 9A and 9B is different only in an image of distribution of the
liquid-phase refrigerant. The heat exchanger 4 according to the fourth embodiment
includes two heat exchange elements 10 stacked in the up-and-down direction D1 in
the front row F, and two heat exchange elements 20 stacked in the up-and-down direction
D1 in the rear row R.
[0124] In the heat exchanger 4, the front-row heat exchange elements 10 and the rear-row
heat exchange elements 20 are disposed while being shifted in the up-and-down direction
D1. The front-row heat exchange elements 10 and the rear-row heat exchange elements
20 each have an equal height from a lower end to an upper end.
[0125] Further, the front-row heat exchange elements 10 and the rear-row heat exchange elements
20 are connected to the pipe of the refrigerant circuit in parallel or in series,
and the refrigerant of the same flow rate flows through the front-row heat exchange
elements 10 and the rear-row heat exchange elements 20.
[0126] The heat exchanger 4 includes the front-row heat exchange elements 10 and the rear-row
heat exchange elements 20 that each have a similar configuration to the front-row
heat exchange element 10 and the rear-row heat exchange element 20, respectively,
according to the first embodiment. Unlike the first embodiment, however, the flow
path cross-sectional area of each of the front-row headers 13 and the flow path cross-sectional
area of each of the rear-row headers 23 are equivalent to each other.
[0127] Since the front-row heat exchange elements 10 and the rear-row heat exchange elements
20 are shifted in the up-and-down direction D1, the positions of the introduction
portions 131 connected to the front-row headers 13 and the positions of the introduction
portions 231 connected to the rear-row headers 23 are different in the up-and-down
direction D1.
[0128] In a case where the flow rate of the refrigerant is small or in a case where dryness
is high, the flow velocity of the liquid-phase refrigerant having flowed into each
of the headers 13 and 23 is low as illustrated by grey arrows representing distribution
images of the liquid-phase refrigerant along the up-and-down direction D1 in FIG.
9A. Therefore, the liquid-phase refrigerant easily flows into the flat tubes 11 at
the lower part, namely, on the lower stage side of each of the headers 13 and 23.
[0129] In contrast, in a case where the flow rate of the refrigerant is large or in a case
where dryness is low, the flow velocity of the liquid refrigerant is high as illustrated
by grey arrows representing distribution images of the liquid-phase refrigerant along
the up-and-down direction in FIG. 9B. Therefore, the liquid-phase refrigerant easily
flows into the flat tubes 11 at the upper part, namely, on the upper stage side of
each of the headers 13 and 23.
[0130] As a result, as described with reference to FIG. 4, the heat transfer amount in the
up-and-down direction D1 as the whole of the front row F and the rear row R can be
balanced, and the time before operation is switched to the defrosting operation when
frosting occurs can be prolonged.
[0131] Further, using the same headers with the same diameter makes it possible to prevent
misassembly of the front-row heat exchange elements 10 and the rear-row heat exchange
elements 20 in manufacturing of the heat exchanger 4.
[0132] In the fourth embodiment, the inside of the front-row header 13 and the rear-row
header 23 may be partitioned into a plurality of sections, and introduction portions
that introduce the refrigerant to the respective sections may be prepared. Also in
this case, the introduction portions in the front row F and the introduction portions
in the rear row R can be made different in height position from each other by shifting
the front-row heat exchange elements 10 and the rear-row heat exchange elements 20
in the up-and-down direction D1. Therefore, similar action and effects can be achieved.
[0133] Other than the above description, the configurations described in the above-described
embodiments can be selected or appropriately modified without departing from the scope
of the present invention.
[0134] For example, any of the heat exchangers according to the present invention may include
one or more middle rows located between the front row F and the rear row R in addition
to the front row F and the rear row R.
[0135] In each of the above-described embodiments, each of the heat exchange elements 10
and 20 includes one line of flat tube element including the plurality of flat tubes
11 stacked in the up-and-down direction D1. The configuration is not limited thereto,
and each of the heat exchange elements according to the present invention may include
two lines, namely, two flat tube elements arranged side by side in the air flowing
direction, and these flat tube elements may be connected to the same headers.
Reference Signs List
[0136]
- 1 to 4
- Heat exchanger
- 10
- Front-row heat exchange element
- 11
- Flat tube
- 12
- Fin
- 13, 13A, 13B
- Front-row header
- 14
- Vertical partition plate (partition portion)
- 14A
- Opening
- 15
- Distributer (flow rate adjusting unit)
- 16
- Throttle (flow rate adjusting unit)
- 17
- U-shaped pipe
- 20
- Rear-row heat exchange element
- 23, 23A, 23B
- Rear-row header
- 24
- Vertical partition plate (partition portion)
- 24A
- Opening
- 121
- Notch
- 131
- Introduction portion
- 141
- Section
- 142
- Section
- 181, 182, 183
- U-shaped pipe
- 231
- Introduction portion
- 241
- Section
- 242
- Section
- Af, Ar, Am
- Flow path cross-sectional area
- D1
- Up-and-down direction
- Df, Dr
- Width
- F
- Front row
- G1
- Dimension
- G2
- Dimension
- P1 to P4
- Path
- R
- Rear row
- Rf, Rr
- Flow rate
- Vf, Vr
- Flow velocity