Note: Descriptions are shown in the official language in which they were submitted.
CONDENSE~S 13 3 4 6 2 7
BACKGROUND OF THE INVENTION
The present invention relates to a condenser
particularly adapted for use in automobile air
conditioning systems.
For such use, a ~serpentine" type of condenser is
well known and widely used, which is made up of a
multi-bored flat tube, commonly called ~harmonica~
tube, bent in zigzag form, and corrugated fins
sandwiched between the bent tube walls. In this way a
core is constituted.
The cooling medium-path in a condenser is roughly
classified into two sections, that is, an inlet side
section and an outlet side section. In the inlet side
section the cooling medium is still in a gaseous
state, and in the outlet side section it becomes
li~uid. In order to increase the efficiency of heat
exchange the area for heat exchange of the inlet side
paths should be as large as possible. On the other
hand, that of the outlet side paths can be relatively
small.
Since the "serpentinen type condenser consists of
a single cooling medium path provided by a single
pipe, an increase in the area for heat exchange in the
inlet side section increases that of the outlet ~ide
section. As a whole the size of the condenser become
1334627
large.
The inventors have made an invention relating to
a ~multi-flow" type condenser instead of the
serpentine type, which is disclosed in Japanese Patent
Publication (unexamined) No. 63-34466. The multi-flow
type condenser includes a plurality of tubes arranged
in parallel and corrugated fins sandwiched
therebetween, and headers connected to opposite ends
of the tubes. The headers have partitions which
divide their inner spaces into at least two sections
including an inlet side group of paths and an outlet
side group of paths, thereby causing the cooling
medium to flow in at least one zigzag pattern. The
total cross-sectional area of the inlet side group of
paths progressively diminishes toward the outlet side
group. In this way the inlet side section has an
optimum area for accommodating the cooling medium in a
gaseous state, and the outlet side section has an
optimum area for accommodating that in a liquid state.
Thus the multi-flow type condenser has succeeded in
reducing the size of condensers without trading off
the efficiency of heat exchange. However, one problem
arises in what proportion the whole path is divided
into the gaseous phase side (i.e. the inlet side
section) and the li~uid phase side (i.e. the outlet
side section) by partitions. The improper proportion
unfavorably affects the efficiency of heat exchange
and causes pressure 1088 on the flow of the cooling
1334627
medium.
If the area in the outlet side section is
insufficiently reduced as compared with that of the
inlet side section, it becomes difficult to secure a
sufficiently increased cross-sectional area of the
inlet side section. As a result the cooling medium
undergoes a larger pressure 1088, and the efficiency
of heat exchange decreases because.of the relatively
small area for heat exchange. If, however, the area
in the outlet side section is excessively reduced as
compared with that of the inlet side section, pressure
1088 is likely to increase on the flow of the cooling -
medium. The area for heat exchange of the inlet side
section becomes too large, thereby slowing down the
flow rate of the cooling medium.
Accordingly, it is an object of the present
invention is to provide a condenser having cooling
medium paths divided in an inlet side section and an
outlet side section in an optimum proportion, thereby
increasing the efficiency of heat exchange and
reducing the pressure 1088 of a cooling medium.
Other objects and advantages of the present
invention will become more apparent from the following
detailed description, when taken in conjunction with
the accompanying drawings which show, for the purpose
of illustration only, one embodiment in accordance
with the present invention.
133~627
SUMMARY OF THE INVENTION
According to the present invention, there is
provided a condenser particularly adapted for use in
automobile air conditioning systems, the condenser
comprising:
a plurality of flat tubes and corrugated fins
sandwiched between the flat tubes;
a pair of hollow headers connected to the ends of
the flat tubes;
an inlet and an outlet are provided in the
headers for introducing a cooling medium into the flat
tubes and discharging a used cooling medium;
wherein the headers have their inner spaces
divided by partitions 80 as to form a cooling medium
flow path in a zigzag pattern including an inlet side
group of paths and an outlet side group of paths,
wherein the entire cross-sectional area of the outlet
side group of paths is 30 to 60% of that of the inlet
8 ide group of paths.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view of a condenser according to
the present invention;
Fig. 2 is a cross-sectional view on an enlarged
scale taken along the line ~ ~ of Fig. l;
Fig. 3 is an exploded perspective view of the
1334627
condenser of Fig. l;
Fig. 4 is a fragmentary cross-sectional view on
an enlarged scale showing the flat tube and the
corrugated fin when observed in the same direction as
in Fig. 3;
Fig. 5 is a fragmentary front view showing a
relationship between the corrugated fins and the flat
tubes;
Fig. 6 is a diagrammatic view showing flow
patterns of a coolant medium;
Fig. 7 is a graph showing a relationship between
the ratios of cro~s-sectional area of the outlet side
section to the inlet side section and the rate of heat
exchange;
Fig. 8 is a graph showing a relationship between
the ratios of cross-~ectional area of the outlet side
section to the inlet side section and the pressure
1088 on the cooling medium;
Fig. 9 is a graph showing a relationship between
the number of cooling medium paths and the rate of
heat exchange;
Fig. 10 is a graph showing a relationship between
the number of cooling medium paths and the pressure
1088 on the cooling medium;
Fig. 11 is a graph showing a relationship between
the number of cooling medium paths, the rate of heat
exchange and the pressure 1088 on the cooling medium;
Fig. 12 is a graph showing a relationship between
133462~
the widths of flat tubes and the rate of heat transfer;
Fig. 13 is a graph showing a relationship between
the heights of flat tubes and the pneumatic pressure
1088,
Fig. 14 is a graph showing relationships between
the rate of heat exchange and the heights of
corrugated fins, and between the pneumatic pressure
1088 and the heights of corrugated fins; and
Fig. 15 is a graph showing relationships between
the rate of heat exchange and the pitches of
corrugated fins, and between the pneumatic pressure
1088 and the pitches of corrugated fins.
DETAILE~ DESCRIPTION OF THE PR~-~
EMBODIMENT
Referring to Figs. 1 to 6, the illustrated
condenser includes a plurality of flat tubes 1 stacked
in parallel and corrugated fins 2 sandwiched between
the flat tubes 1. The terminating ends of the flat
tubes 1 are connected to headers 3 and 4.
Each flat tube is made of extruded aluminum,
having a flat configuration as clearly shown in Figs.
2 to 4. Alternatively, the flat tubes can be multi-
bored flat tubes, commonly called ~harmonica tube" or
else, electrically seamed tubes can be used.
Each corrugated fin 2 has a width identical with
that of the flat tube 1. The fins 2 and the flat
1334627
tubes 1 are brazed to each other. Preferably the fins
2 are provided with louvers 2a on the surface.
The headers 3, 4 are made up of electrically
seamed pipes of aluminum, and each have holes 5 of the
same shape as the cross-section of the flat tubes 1 80
as to accept the tube ends la. The inserted tube ends
are brazed in the holes 5. As shown in Fig. 1, the
headers 3 and 4 are connected to an inlet pipe 6 and
an outlet pipe,~ respectively. The inlet pipe 6
allows a cooling medium to enter the header 3, and the
outlet pipe 8 allow~ the used cooling medium to
discharge. The headers 3 and 4 are closed with covers
7 and 9, respectively. The reference numerals 13 and
14 denote 8 ide places attached to the outermost
corrugated fins 2.
The header 3 has its inner space divided by a
partition 10 into two sections, and the header 4 also
has two sections divided by a partition 11. In this
way the whole cooling medium path 12 is divided into
an inlet side group (A), an intermediate group (B) and
an outlet side group (C) as shown Figs. l and 6. The
cooling medium flows in zigzag patterns throughout the
groups (A), (B) and (C). As shown in Fig. 6, it is
arranged that the intermediate group (B) has a smaller
number of flat tubes 1 (that is, paths) than the inlet
side group (A), which means that the cross-sectional
area of the intermediate group (C) of paths is smaller
than that of the group (A). It is also arranged that
1334627
the outlet side group (C~ has a smaller number of flat
tubes 1 (that i8, the number of cooling medium paths)
than the intermediate group (B), which means that the
cross-sectional area of the outlet side group (C) of
paths is smaller than that of the group (B).
In terms of percentage the entire cross-sectional
area of the outlet side group (C) is 30 to 60% of that
of the inlet side group (A). If the percentage is
less than 30~0, the cross-sectional area of the outlet
side group (C) becomes small to increase the pressure
1088 in the cooling medium. At the same time, the
cross-sectional area of the inlet side group becomes
large to slow down the flow rate of the cooling
medium, thereby reducing the efficiency of heat
exchange. If the percentage exceeds 60~o, the cross-
sectional area of the inlet side group (A) becomes
small to increase the pressure 1088 in the cooling
medium. In addition, the area for heat transfer is
reduced, thereby reducing the efficiency of heat
exchange. It is more preferred that the entire cross-
sectional area of the outlet side group (C) is 35 to
50% of that of the inlet side group (A). As shown in
Figs. 7 and 8, this more restricted range exhibits the
highest efficiency of heat exchange and the lowest
pressure 108~ in the cooling medium.
As shown in Fig. 6, the cooling medium is
introduced into the inlet ~ide group (A) through the
inlet pipe 6 and flows therethrough. Then the cooling
133~627
medium turns from the right-hand header 4 and enters
the intermediate group (B). Then it turns from the
left-hand header 3 and enters the outlet side group
(C). Finally the cooling medium i8 discharged through
the outlet pipe 8. In this way the cooling medium
flows in zigzag patterns. Air enters the zlir paths
constituted by the corrugated fins 2 in the direction
(W) in Fig. 2. Heat exchange is effected between the
air and the cooling medium flowing through the groups
(A), (B) and (C). While the cooling medium passes
through the inlet side group (A), it is still in a
gaseous state and has a relatively large volume, which
i8 effectively accommodated in the capacity provided
by the paths of the group (h) and keeps contact with
the flat tubes 1 in a wide range so that the gaseous
cooling medium smoothly condenses and reduces its
volume. When the cooling medium flows through the
outlet side group by way of the intermediate group
(B), it becomes completely liSluid, and has such a
reduced volume as to be accommodated in a relatively
small cross-sectional area of the outlet side group
(C). Thus the pressure 1088 is minimized, thereby
enhancing the efficiency of heat exchange.
The illustrated embodiment has three groups (A),
(B) and (C), but the number (N) of groups is not
limited to it. Preferably the number (N) is 2 to 5
groups for the reason explained below: -
Figs. 9 to 11 show the results obtained by
_ g _
1334627
experiments in which condensers having twenty-four
flat tubes are employed, each having a different
number of groups. A cooling medium is introduced into
each of the condensers at the same flow rate. Each
graph shows the resulting rate of heat exchange and
pressure 1088 in the cooling medium, and changes in
the rate of heat exchangè and pressure 1088 with
respect to the ratio of the outlet side group to the
inlet side group. Throughout the experiments the
inlet side group, the intermediate group and the
outlet side group have the same cross-sectional area.
Fig. 9 shows the rates of heat exchange achieved when
the speed of wind Vf i~ 2m/gec and when it is 3m/sec
each in front of the condenser. It will be understood
from Fig. 9 that when the number (N) of the group~ is
less than 2 the rate of heat exchange is low, whereas
when it exceeds five, the rate of heat exchange
gradually diminishes. It will be understood from Fig.
10 that as the number (N) of groups increases, the
pressure 1088 in the cooling medium increases,
especially when the number (N) exceeds five, it
abruptly increases. It will be understood from Fig.
11 that if the number (N) of the groups is less than
two, the pressure 10~8 is low but the rate of heat
exchange is also low. Therefore the ratio of the rate
of heat exchange to the pressure 1088 becomes low,
which indicates that there is an imbalance between the
pressure 1088 and the rate of heat exchange. If the
-- 10 --
1334627
number (N) of the groups exceeds five, the rate of
heat exchange becomes relatively high but the pressure
1088 becomes low. The ratio between them is low,
thereby causing an imbalance between the pressure 1088
and the rate of heat exchange.
As is evident from the results of the
experiments, when the number (N) of the groups is 2 to
5, the rate of heat exchange is high, and the pressure
1088 in the cooling medium is low. Thus the ratio
between them is well balanced. As described above, it
is arranged to ensure that the cross-sectional area of
the outlet side group (C) is arranged to have 30 to
60% of that of the inlet side group (A). In addition,
the number (N) of the group is arranged to be 2 to 5,
which enhances the efficiency of the heat exchange as
a result of the reduced pressure 1088.
It is preferred that the width (Wt) of each flat
tube 1 is in the range of 6.0 to 20mm, the height (Ht)
thereof is in the range of 1.5 to 7.Omm, the height
(Hp) of the cooling medium paths 12 in the flat tubes
1 is l.Omm or more. It is also arranged that the
height (Hf) of the corrugated fins 2 or a distance
between the adjacent flat tubes 1 i8 in the range of 6
to 16mm and that the fin pitch (Fp) is in the range of
1.6 to 4.Omm. The reasons why the above-mentioned
ranges are preferable will be described below:
As is evident from Fig. 12, if the width (Wt) of
the flat tubes 1 is less than 6.Omm, the corrugated
133~627
fins 2 sandwiched therebetween will be accordingly
narrow in width. The narrow width of the corrugated
fins 2 limit the size and number of the louvers 2a,
which decreases the efficiency of heat exchange. If
the flat tubes 1 are 20mm or more, the corrugated fins
2 sandwiched therebetween will accordingly become
large. The large fins increases a drag on the flowing
air. In addition, the large fins increases the weight
of the condenser. It i8 therefore preferred that the
width (Wt) of the flat tubes is in the range of 6.0 to
16mm, more preferably, 10 to 14mm.
The height (Ht) of each flat tube 1 is preferably
in the range of 1.5 to 7.Omm. If it exceeds 7.Omm,
the pressure loss in the air flow increases. If it is
less than 1.5mm, it is difficult to increase the
height (Hp) of the air paths by l.Omm or more because
of the limited thickness of the flat tubes. It is
preferred that it is in the range of 1.5 to 5.Omm;
more preferably, 2.5to 4.Omm.
The height (Hp) of the cooling medium flow paths
in the flat tubes 1 is preferably l.Omm or more. If
it is less than l.Omm, the pressure 1088 in the
cooling medium increases, thereby decreasing the rates
of heat transfer. It is preferred that it is in the
range of 1.5 to 2.Omm.
The height (Hf) of the corrugated fins 2 is in
the range of 6.0 to 16mm. If it is less than 6mm, the
pressure 1088 in the air will increase as shown in
- 12 -
1334627
Fig. 14. If it exceeds 16mm, the number of total fins
decreases, thereby reducing the efficiency of heat
exchange. The optimum range is 8.0 to 12mm.
As shown in Fig. 15, the fin pitches is
preferably in the range of 1.6 to ~.Omm. If they are
less than 1.6mm, the louvers 2a interfere with the
flow of the air, thereby-increasing the pressure 1088
in the air flow. If they exceed 4.Omm, the efficiency
of heat exchange decreases. It is therefore preferred
that the range is 1.6 to 3.2mm; more preferably, 2.0
to 3.2mm.
As is evident from the foregoing description,
the condensers of the present invention are
constructed with the flat tubes, the corrugated fins
and the headers in which the widths and heights of the
flat tubes, the heights of the cooling medium flow
paths, the heights and pitches of the fin are
determined at optimum values, thereby reducing the
pressure losses which the air and the cooling medium
undergo. As a result the efficiency of heat exchanger
is enhanced.
In the illustrated embodiment the cross-sectional
area of the cooling medium paths 12 progressively
diminishes from the inlet side group to the outlet
side group through the intermediate group. However it
is possible to modify it to an embodiment in which the
inlet side group and the intermediate group have the
same cross-sectional area which is larger than that of
- 13 -
1334627
the outlet side group. In the illustrated embodiment
the reduction in the cross-sectional area i8 effected
by reducing the number of the flat tubes, but it is
possible to reduce the cross-sectional areas of the
individual flat tubes without changing the number
thereof. The headers 3 and 4 are provided at their
erected postures between which the flat tubes 1 are
horizontally stacked one above another, but it is
possible to modify it to an embodiment in which the
headers 3 and 4 are positioned up and down between
which the flat tubes are vertically arranged in
parallel.
