Heat exchange – Radiator core type – Deformed sheet forms passages between side-by-side tube means
Reexamination Certificate
2001-01-08
2003-02-18
Leo, Leonard (Department: 3743)
Heat exchange
Radiator core type
Deformed sheet forms passages between side-by-side tube means
C165S176000
Reexamination Certificate
active
06520251
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a plate for stack type heat exchangers and heat exchanger using such plates. In particular, the present invention relates to a plate for stack type heat exchangers and heat exchanger using such plates, which is capable of improving its performance of heat exchange by preventing the non-uniform flow distribution of refrigerant and increasing the turbulent flow effect of refrigerant, achieving its miniaturization and its optimal performance of heat exchange by designing the width of the plate and the arrangement of protrusions in accordance with an improved regularity, and improving its durability by enhancing the strength of attachment of its U-turn portion.
In general, a heat exchanger is a device in which an interior refrigerant passage is formed so that refrigerant exchanges heat with external air while being circulated through the refrigerant passage. The heat exchanger is employed in a variety of air conditioning apparatus. Particularly, in an air conditioning apparatus for automobiles, a stack type heat exchanger is mainly employed.
As depicted in
FIGS. 15
to
17
, a conventional stack type heat exchanger comprises of a plurality of flat tubes
90
, a plurality of fins
94
and two end plates
95
L,
95
R.
The flat tubes
90
are stacked side by side. Each of the flat tubes
90
is formed by attaching a pair of one-tank plates
91
to each other. Each of one-tank plates
91
includes a pair of cup portions
911
A
911
B, which are formed side by side on the upper portion of the one-tank plate
91
and the cup portions have slots
912
A,
912
B respectively. A heat exchange portion
913
is formed under the cup portions to communicate with the cup portions, is provided with a plurality of small, round protrusions
915
internally projected through an embossing process, and is divided into two sub-portions by a central, longitudinal partition protrusion
917
. A U-turn portion
919
is formed under the central, longitudinal partition protrusion
917
to connect the two sub-portions of the heat exchange portion
913
to each other, and is also provided with a plurality of small protrusions
915
. A flange
916
is formed along the edge of the plate to have the same height as that of the small, round protrusions
915
. When two one-tank plates
91
are attached to each other, a pair of pockets
93
A,
93
B and a U-shaped refrigerant passage are formed. The fins
94
are positioned between each pair of neighboring flat tubes
90
. The end plates
95
L,
95
R are respectively situated at the side ends of the heat exchanger to reinforce the structure of the heat exchanger. Two cylindrical manifold portions
96
L,
96
R are projected from the front pocket
93
A of the manifold tube
90
L,
90
R so as to be connected to a refrigerant inflow pipe(not shown) and a refrigerant outflow pipe (not shown), respectively.
In a conventional air conditioning apparatus employing the conventional heat exchanger as its evaporator, refrigerant enters one pocket(front pocket)
93
A of the manifold tube
90
L and flows into the neighboring both side front pockets
93
A of the neighboring flat tubes
90
through the slots
912
A of the front pockets
93
A of the inlet-side tubes
90
. Thereafter, the refrigerant flows to the rear pockets
93
B of the inlet-side tubes
90
through a first group of U-shaped refrigerant passages of the flat tubes
90
. While the refrigerant passes through the U-shaped refrigerant passages, the refrigerant exchanges heat with the exterior air. Subsequently, the refrigerant flows into the rear pocket
93
B, second group of U-turn passages and front pockets
93
A of the outlet-side tubes
90
through a process similar to the above-described inlet-side process. Next, the refrigerant in the pockets
93
A of the outlet-side tubes
90
is discharged to a compressor through the cylindrical manifold portion
96
R and the refrigerant outflow pipe. The refrigerant is evaporated in the process of heat exchange, and accordingly is supplied to the compressor in a gaseous state. A two-tank plate is similar to the one-tank plate in construction and operation except that two pairs of cup portions are respectively formed on the upper and lower end portions of the plate. Accordingly, for ease of explanation, only one-tank plate is described here.
The performance of an evaporator, which supplies cooled air into the interior of an automobile, depends upon the value of thermal conductivity by area. The performance is realized in a process in which the relatively cold refrigerant flowing through the flat tubes
90
exchanges heat with the relatively hot exterior air through the fins
94
stacked between the flat tubes
90
. A heat source having a relatively high temperature is required to evaporate refrigerant, and the enlargement of a heat exchange area in contact with the fins
94
and the increase of thermal conductivity are required to improve the effect of the evaporation of refrigerant. In the case of a heat exchanger used in an air conditioning apparatus for automobiles, the high performance of heat exchange and the miniaturization of the heat exchanger are required to satisfy the requirements of the reduction of weight and noise, the increase of the amount of wind and the convenience of mounting, thus the heat exchange area of a heat exchange plate cannot be excessively enlarged.
Although a reduction in the height of the fins
94
and an increase in the density of the fins
94
are proposed to solve the above-mentioned problem, these proposals may rather decrease the performance of heat exchange due to difficulty in the drainage of condensed water, a pressure drop of exterior air and a reduction in the amount of wind.
Of the principal factors affecting the performance of heat exchange, the area of a refrigerant passage is influenced by the number, size, shape and arrangement of protrusions
915
, and the intervals between protrusions. In the case of a heat exchanger having a relatively large capacity the influence of the arrangement of the protrusions
915
may be rather inconsiderable, but in the case of a compact heat exchanger comprised of flat plates each having a relatively small width the influence of the protrusions
915
is considerable. When the size of the protrusions is larger than the width of the plate by a certain ratio and the density of the protrusions is relatively small, flow resistance against the refrigerant is small but the performance of heat exchange is decreased due to the non-uniform flow distribution of refrigerant, the reduction of turbulent flow effect and the reduction of the amount of thermal contact with fins
94
. When the size of the protrusions is large in comparison with the width of the plate and the density of protrusions
915
is large, the effect of the evaporation of refrigerant is decreased due to an increase in flow resistance against the refrigerant. In such cases, although a decrease in the size of protrusions can be taken into account, the decrease in the size of the protrusions is difficult to employ due to difficulty in forming a protrusion to be smaller than a certain minimum and weakness in attaching two plates to each other.
The plate
91
is generally formed of a clad brazing sheet. The plate
91
is comprised of a pair of cup portions
911
A
911
B, a heat exchange portion
913
having a plurality of protrusions
915
, a longitudinal partition protrusion
917
and a U-turn portion
919
. Each flat tube
90
is formed by attaching two plates
91
to each other. The flat tube
90
has a pair of pockets
93
A,
93
B formed side by side by attaching a pair of cup portion
911
A,
911
B to another pair of cup portions
911
A,
911
B. While the refrigerant flows from the front pockets
93
A to the rear pockets
93
B, the refrigerant passes through the U-turn portion
919
and the flow direction of the refrigerant is reversed. In consequence, a relatively great flow pressure of the refrigerant is exerted on the U-turn portion
919
in comparison with the other portio
Kim Yong Ho
Shin Seung Hark
Halla Climate Control Corp.
Leo Leonard
LandOfFree
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