Heat exchange – With first fluid holder or collector open to second fluid
Reexamination Certificate
2001-11-30
2003-04-15
Flanigan, Allen (Department: 3743)
Heat exchange
With first fluid holder or collector open to second fluid
C165S172000, C165S151000, C165S152000
Reexamination Certificate
active
06546998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro-multi channel heat exchanger. More particularly, the present invention relates to a tube structure of a micro-multi channel heat exchanger, in which a sectional area of a channel in a tube is changed for enhancing a heat transfer efficiency.
2. Background of the Related Art
The heat exchanger is applied to an air conditioner for heating or cooling a room temperature. A related art heat exchanger will be explained, with reference to
FIGS. 1-3
.
FIG. 1
illustrates a disassembled perspective view of a related art heat exchanger,
FIG. 2
illustrates a section across line I—I in
FIG. 1
, and
FIG. 3
illustrates a graph showing a temperature change of flowing air vs. a tube plate surface temperature along a length of the tube plate in an air flowing direction in the section in FIG.
1
.
Referring to
FIGS. 1 and 2
, the related art heat exchanger is provided with a lower hollow header
1
, an upper header
2
positioned to correspond to the lower header
1
, a plurality of tubes
4
between the upper header
2
and the lower header
1
, and fins
6
between adjacent tubes. The hollow cylindrical lower header
1
has a plurality of header holes
3
in an outer circumference at fixed intervals along a length of the lower header
1
each for inserting and fixing a first end of the tube
4
. The upper header
2
positioned opposite to the lower header
1
has the same shape, with the header holes
3
in the lower header
1
and the upper header
2
arranged to face each other. According to this, as the first end of the tube
4
is inserted in the header hole in the lower header
1
, and a second end of the tube
4
is inserted in the header hole in the upper header
2
, respective tubes
4
are arranged parallel along a length of the lower header
1
and upper header
2
.
The tube
4
is rectangular, and has a width and a small thickness enough to be fitted to the two headers. A plurality of channels
5
are provided inside of the tube. The tube
4
has rounded entrance and exit sides for smooth air flow. There are a plurality of channels
5
elongated along a length of the tube arranged perpendicular to a direction of air flow, each having a fine section. The tube
4
is fixed to the two headers
1
and
2
at both ends thereof such that the hollows in the headers
1
and
2
are in communication with the channels
5
. The fins
6
, fitted between adjacent tubes
4
, make heat exchange, while air passes therethrough. The fin
6
is a thin plate bent in a zigzag form. In the foregoing heat exchanger, a refrigerant, introduced into the hollow of the lower header
1
, makes heat exchange with the air, as the refrigerant passes through the channels
5
, and flows into the upper header
2
.
However, the foregoing heat exchanger has the following problems.
Referring to
FIG. 3
, the refrigerant in the channels
5
evaporates as the refrigerant makes heat exchange with the air. The heat exchanger has a tube plate surface temperature of approx. 8° C. maintained even if the air has a temperature relatively higher than the heat exchanger. Even if the tube surface temperature shows a little variation with an environment, since the tube surface temperature is substantially constant, the tube surface temperature is assumed to be constant. Of course, it is understandable that a temperature of the air making heat exchange with a surface of the heat exchanger varies with the seasons or an environment. For example, if a room air temperature is 27° C., the heat exchanger has an inlet air temperature of 27° C., and an outlet air temperature, after heat exchange with the refrigerant, of 14° C. Therefore, a temperature difference between the air and a surface of the first channel at the inlet side is 19° C., and the temperature difference between the air and a surface of the first channel at the outlet side is 6° C.
Heat transfer between two bodies is proportional to a temperature difference and a contact surface area. Therefore, there is approximately three times the heat transferred at the inlet side channel of the tube
4
, as compared to the heat transferred at the outlet side channel. Consequently, the refrigerant flowing through the inlet side channel vaporizes faster than the refrigerant flowing through the outlet side channel. In this instance, a refrigerant pressure in the upper header
2
is substantially uniform within the upper header
2
, and a refrigerant pressure in the lower header
1
is substantially uniform within the lower header
1
. As shown in
FIG. 3
, a curve showing the air temperature has a moderate slope at the air inlet side of the tube
4
and a steeper slope from a particular channel in the inlet side to the outlet channel, to form a convex curve overall.
As discussed, if refrigerant in the inlet side channel vaporizes faster than other channels, a flow resistance of the refrigerant is increased as a vapor phase region of the refrigerant in the inlet side channel increases. This reduces an amount of the refrigerant introduced into the inlet side channel from the lower header
1
. According to this, the amount of heat transfer from the inlet side of the tube is reduced, showing the reduced air temperature drop at the inlet side as shown in FIG.
3
. While the increase of vapor phase region caused by the vaporization of the refrigerant at the inlet side increases a pressure in the inlet side channel, the pressure in the outlet side channel decreases relatively, to cause a difference of pressure drops between the inlet side channel and the outlet side channel of the tube
4
. In the meantime, since flow of the refrigerant in the heat exchanger system is changed by a characteristic of maintaining identical pressure drop all over the heat exchanger system, refrigerant is supplied to the outlet side more than the inlet side of the tube
4
, making the pressure drops similar.
As discussed, since the amount of refrigerant in the inlet side channel is reduced due to the vapor phase region and the amount of refrigerant in the outlet side channel is increased, a width of the tube
4
in which an actual heat exchange occurs is reduced from an actual width of the tube
4
perpendicular to the air flow. Thus, formation of identical sectional areas of channels in the tube reduces an overall heat exchange efficiency of the heat exchanger.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a tube structure of a micro-multi channel heat exchanger that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a tube structure of a micro-multi channel heat exchanger, in which the whole heat exchanger is utilized more efficiently for enhancing a heat transfer efficiency.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the tube structure of a micro-multi channel heat exchanger includes a lower header having a hollow for receiving refrigerant, and an upper header having a shape the same as the lower header placed over, and opposite to the lower header. A plurality of tubes is arranged in a length direction of the upper and lower headers at fixed intervals each having opposite ends fixed to the upper header and the lower header. A plurality of channels are formed in the tubes and are elongated to be in communication with the hollows of the two headers each with an area of a section parallel to a length direction of the two headers reduced at a fixed ratio as it goes from an air inlet side to an
Jang Dong Yeon
Lee Wook Yong
Oh Sai Kee
Oh Se Yoon
Flanigan Allen
LG Electronics Inc.
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