Heat exchange – Gradated heat transfer structure
Reexamination Certificate
1999-05-17
2002-05-21
Bennett, Henry (Department: 3743)
Heat exchange
Gradated heat transfer structure
C165S147000, C165S109100
Reexamination Certificate
active
06390183
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat exchanger such as a heat exchanger having fins or a double tube heat exchanger mainly used in an air conditioner.
BACKGROUND TECHNIQUE
As shown in
FIG. 8
, a conventional heat exchanger having fins comprises fins
201
arranged at a predetermined distance from one another, and heat exchanger tubes
202
inserted through fin surfaces of the fins
201
perpendicularly to the latter. A current
203
of air flows in the direction of the arrow between the fins, and exchanges heat with fluid flowing the passages of the heat exchanger tubes
202
. When such a heat exchanger having fins is used, it is common that an end portion thereof is bent at a predetermined radius of curvature R, and the heat exchanger is accommodated in an outdoor unit of an air conditioner.
First prior art (Japanese Patent Application Laid-open No.S61-15089) is shown in
FIGS. 9
a
and
9
b.
FIG. 9
a
is a vertical sectional view showing a portion of a heat exchanger tube, and
FIG. 9
b
is an enlarged sectional view of an essential portion showing an inner wall surface of the heat exchanger tube.
According to the first prior art of the heat exchanger, a coil
204
comprising spirally wound metal fine wire is inserted into a heat exchanger tube
202
, an outer periphery of this coil
204
is tightly fixed to an inner surface of the heat exchanger tube
202
, and a large number of powdery members
205
are jointed to the inner surface of the heat exchanger tube
202
to form a porous material layer.
According to this structure, heat transfer area of the inner surface of the heat exchanger tube
202
is increased, a turbulent flow effect, a capillary action effect and a nucleate boiling effect are exhibited to enhance the heat transfer performance.
Second prior art (Japanese Utility Model Registration Application Laid-open No.S58-52491) is shown in FIG.
10
.
FIG. 10
is a sectional view of a heat exchanger having fins taken along the surface passing through the center of a heat exchanger tube thereof.
According to the second prior art, a spacer
206
which can be deformed by heat is inserted into a heat exchanger tube
202
, and after the insertion, the spacer
206
is heated so that the spacer
206
is tightly adhered to an inner wall of the tube. A fin group
201
is jointed to an outer peripheral surface of the heat exchanger tube
202
.
With this structure, the heat transfer area of the inner surface of the heat exchanger tube
202
is increased, and a turbulent flow effect is exhibited to enhance the heat transfer performance.
Third prior art (Japanese Patent Application No.H10-2638) is shown in FIG.
11
.
FIG. 11
is a perspective view showing a structure of a heat exchanger having fins.
According to the third prior art, in the heat exchanger having fins functioning as a condenser, the number of paths of an outlet tube
207
for refrigerant is reduced, the outlet tube
207
is disposed in the windward side with respect to the direction
203
of air flow, and a fin
201
between the adjacent tubes
202
at the downwind side is provided with a slit
208
in the longitudinal direction of the fin
201
.
With this structure, it is regarded that when the heat exchanger is used as a condenser, since it is possible to increase the speed in the tube mainly by the outlet tube
207
which is excessively cooled region, the heat transfer performance is enhanced, and by disposing the excessively cooled region having low temperature in the windward side, it is possible to increase the temperature difference between the air and the excessively cooled region, and the condense performance can be enhanced.
Forth prior art (Japanese Patent Application No.S57-127732) is shown in FIG.
12
.
FIG. 12
is a perspective view showing a structure of a heat exchanger having fins.
According to the fourth prior art, in the heat exchanger having fins functioning as a condenser, the diameter of an outlet tube
209
of refrigerant is made thinner than those of other portions.
According to this structure, it is regarded that when the heat exchanger is used as a condenser, since it is possible to increase the speed in the tube by the outlet tube
209
which is excessively cooled region, the heat transfer performance is enhanced, and by disposing the excessively cooled region having low temperature in the windward side, it is possible to increase the temperature difference between the air and the excessively cooled region, and the condense performance can be enhanced.
Fifth prior art (Japanese Patent Application No.H2-103355) is shown in
FIGS. 13
a
and
13
b.
FIG. 13
a
is a perspective view showing a structure of a heat exchanger having fins, and
FIG. 13
b
is a sectional view of a heat exchanger tube constituting the heat exchanger.
According to the fifth prior art, in the heat exchanger having fins functioning as a condenser, inner rods
211
are inserted in the heat exchanger tube
210
in the vicinity of the refrigerant outlet.
With this structure, it is regarded that the heat exchanger having fins used as the condenser can reduce the amount of refrigerant charged by the inner rods
211
inserted in the excessive cooled regions.
However, according to the structure of the first prior art, since a wire of very small diameter is used as the coil, the volume of the tube can not be remarkably reduced by inserting the coil. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the second prior art, since this prior art mainly aims at increasing the heat transfer area of the inner surface of the heat transfer tube and at the turbulent flow effect, and the thickness of the spacer is not specified, it is judged that the thickness of the spacer is equal to that of the heat exchanger tube, and the volume of the tube can not be remarkably reduced by inserting the coil. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the third prior art, the current speed can be increased by minimizing the number of paths, but the current speed of the minimum paths is the highest, and it is not possible to further enhance the speed. Further, the speed can only be changed at least for one heat exchanger tube by on heat exchanger tube. It is not possible to reduce the volume in the tube. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the fourth prior art, the current speed in the thin tube can be increased, and the current speed can be arbitrarily determined by selecting the diameter of the thin tube, but in order to change the diameter of the thin tube, it is necessary to change the molding dies of the fin having a hole in which the thin tube is inserted. Therefore, it is necessary to make a significant investment in the molding dies, and it is not easy to change the diameter. It is not possible to reduce the volume in the tube. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the fifth prior art, this is only effective to reduce the amount of refrigerant when the heat exchanger is used as a condenser. When the heat exchanger is used as an evaporator, since it is described that a member which satisfies the pressure of 4 kg/cm
2
is inserted to the outlet of the condenser, this will bring ab
Ando Toshiaki
Aoyagi Osamu
Yokoyama Shoichi
Armstrong Westerman & Hattori, LLP
Bennett Henry
Duong Tho V
Matsushita Electric - Industrial Co., Ltd.
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