Heat exchange – Structural installation – Engine
Reexamination Certificate
2000-07-27
2001-06-19
Lazarus, Ira S. (Department: 3743)
Heat exchange
Structural installation
Engine
C165S153000, C165S166000
Reexamination Certificate
active
06247523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arrangement structure of segments of offset fins in an exhaust gas heat exchanger for performing a heat exchange between exhaust gas generated by a combustion and a cooling fluid such as cooling water. The present invention is suitably applied to an EGR cooler for cooling exhaust gas in an exhaust gas recirculation system (i.e., EGR system).
2. Description of Related Art
For effectively reducing nitrogen oxide contained in exhaust gas generated by a combustion, exhaust gas used for an exhaust gas recirculation (hereinafter, referred to as “EGR”) is cooled by an EGR cooler. However, when a heat exchanger having inner fins within a tube is simply applied to the EGR cooler, heat-exchanging capacity of the EGR cooler is difficult to be increased, because dust such as carbon is contained in the exhaust gas and is readily collected within tube, for example.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide an exhaust gas heat exchanger which prevents pressure loss within an exhaust gas tube from being increased and dust contained in exhaust gas from being collecting within the exhaust gas tube.
It is an another object of the present invention to provide an exhaust gas heat exchanger which improves heat-transmitting percentage of offset fins disposed within an exhaust gas tube, while it can prevent pressure loss within the exhaust gas tube from being increased and dust contained in exhaust gas from being collecting within the exhaust gas tube.
According to the present invention, an exhaust gas heat exchanger includes an exhaust gas tube through which exhaust gas generated by a combustion flows, a plurality of cooling fluid tubes through which cooling fluid for cooling exhaust gas flows, and an offset fin disposed within the exhaust gas tube. The cooling fluid tubes are disposed adjacent to both ends of the exhaust gas tube in a minor-diameter direction of the exhaust gas tube, and the offset fin has a plurality of plate-like segments which are approximately parallel to the minor-diameter direction and are arranged staggeringly in a longitudinal direction of the exhaust gas tube. In the exhaust gas heat exchanger, the segments are disposed to be tilted in a tilt direction relative to the longitudinal direction. Thus, it is possible to readily arrange the segments in accordance with a structure of the exhaust gas heat exchanger.
Preferably, cooling fluid communication passages through which the cooling fluid tubes communicate with each other are disposed on both end sides of the exhaust gas tube in the longitudinal direction at diagonal positions when being viewed from the minor-diameter direction, and the segments are disposed to be tilted relative to the longitudinal direction toward a side opposite to a diagonal line (L
1
) connecting the cooling fluid communication passages. Therefore, a cross angle between the tilt direction of the segments and a main flow of exhaust gas becomes smaller, and pressure loss, generated while exhaust gas flows through the exhaust gas tube, can be reduced. Accordingly, an exhaust gas amount flowing through the exhaust gas tube can be increased, and heat-exchanging capacity of the exhaust gas heat exchanger is increased. Further, even when the cross angle between the tilt direction of the segments and the main flow of exhaust gas becomes smaller, a flow of exhaust gas directly colliding with plate surfaces of the segments and a flow of exhaust gas crossing the segments at different tilt lines are generated. Therefore, dust adhered on the segments is removed, and flows forcedly at a downstream side. Thus, it can prevent dust from being collected in the offset fin within the exhaust gas tube.
Preferably, when an arrangement of the segments from one end to the other end of the exhaust gas tube in a major-diameter direction is indicated as a row, and when an arrangement of the segments from one end to the other end of the exhaust gas tube in the longitudinal direction is indicated as a line, a segment positioned at i-line and j-row is tilted toward a center of any one segment except for i-line segments, j-row segments and (i+n)-line and (j+n)-row positioned segments. Therefore, a distance between adjacent segments on the same tilt line in the tilt direction of the segments becomes larger, and it can prevent a temperature boundary layer from being generated over an entire area in the longitudinal direction of the exhaust gas tube. Thus, heat-transmitting percentage between the offset fins and exhaust gas can be improved, and heat-exchanging capacity of the exhaust gas heat exchanger is increased. In this case, when the segments are disposed to be tilted relative to the longitudinal direction toward the side opposite to the diagonal line (L
1
), the exhaust gas heat exchanger improves heat-transmitting percentage of the offset fin while preventing the pressure loss within the exhaust gas tube from being increased.
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Patent Abstracts of Japan, vol. 2000, No. 02, Feb. 29, 2000 & JP 11-303689.
Daidou Shigeki
Okochi Takaki
Shibagaki Kazuhiro
Uchimura Katsunori
Denso Corporation
Harness Dickey & Pierce PLC
Lazarus Ira S.
McKinnon Terrell
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