The present invention relates to a heat exchanger which is effective when applied to a radiator etc. for heat exchange between cooling water and air of an internal combustion engine.
The fins in a conventional heat exchanger have louvers. The edge effect of the louvers enables the heat conductivity of the fins to be improved. Further, by tilting the louvers with respect to the flat parts by a predetermined angle, the flow of the cooling air is changed to guide the cooling air to the louver passages between the adjoining louvers and thereby improve the heat conductivity of the fins (for example, see Japanese Patent Publication (A) No. 2003-83690).
However, in the above conventional heat exchanger, if the louver pitch is shortened to further improve the performance, there was the problem that the cooling air ended up no longer being guided to the louver passages, the edge effect was not improved, and as a result the heat conductivity of the fins could not be improved.
The present invention, in consideration of the above points, has as its object the improvement of the heat conductivity of the fins without shortening the louver pitch.
To achieve the above object, in the present invention, there is provided a heat exchanger provided with a plurality of tubes through the inside of which an inside fluid is circulated and arranged stacked over each other and fins arranged between the tubes and having flat parts substantially parallel to the direction of circulation of the outside fluid flowing between the tubes, a plurality of louvers twisted by a predetermined angle with respect to the flat parts being provided at the flat parts along the direction of circulation of the outside fluid and louver passages being formed between the adjoining louver, characterized in that when the direction along a predetermined angle is made the louver width direction, a step difference projecting out to the louver passage side is provided at an intermediate part of each louver in the louver width direction.
According to this, when the outside fluid flows through the louver passages, the flow of the outside fluid is disrupted by the step difference and the temperature boundary layer is destroyed, so at the location of the step differences, the local heat conductivity is again improved. Therefore, it is possible to improve the heat conductivity of the fins without shortening the louver pitch.
Further, in the present invention, the step difference is provided at the louver passage side positioned at the upstream side in the direction of circulation of the outside fluid in the louver passages positioned at the two sides of the louvers.
According to this, the flow of the outside fluid is strongly disrupted, so the heat conductivity of the fins can be further improved.
Further, in the present invention, there is provided a heat exchanger provided with a plurality of tubes through the inside of which an inside fluid is circulated and arranged stacked over each other and fins arranged between the tubes and having flat parts substantially parallel to the direction of circulation of the outside fluid flowing between the tubes, a plurality of louvers twisted by a predetermined angle with respect to the flat parts being provided at the flat parts along the direction of circulation of the outside fluid and louver passages being formed between the adjoining louver, characterized in that when the direction along a predetermined angle is made the louver width direction, a communicating passage for communicating the louver passages positioned at the two sides of each louver is provided at an intermediate part of the louver in the louver width direction.
According to this, when the outside fluid flows through the louver passages, the outside fluid passes through the communicating passages whereby the development of temperature boundary layers is suppressed. Therefore, it is possible to improve the heat conductivity of the fins without shortening the louver pitch.
Further, in the present invention, the communicating passages are long slits extending in the stacking direction of the tubes formed by making cuts along the stacking direction of the tubes, then deforming the two sides of the cuts.
According to this, it is possible to form communicating passages without generating waste material.
Further, in the present invention, the heat exchanger may use fins formed to corrugated shapes so as to have a plurality of flat parts arranged along the direction of circulation of the inside fluid and curved parts connecting the adjoining flat parts.
Below, the present invention will be able to be more sufficiently understood from the attached drawings and the preferred embodiments of the present invention.
The present embodiment applies the heat exchanger according to the present invention to a radiator 1 for heat exchange between cooling water of a running engine (internal combustion engine) and air so as to cool the cooling water.
As shown in
The tubes 2 are made of metal (in the present embodiment, aluminum alloy). Cooling water passages through which the cooling water flows are formed inside them and are formed as flat shapes. Further, a plurality of the tubes 2 are stacked over each other. The fins 3 are arranged between the adjoining tubes 2. Cooling air is designed to be able to flow between the adjoining tubes 2. Note that the cooling air corresponds to the outside fluid of the present invention.
The fins 3 promote the heat exchange between the cooling air and the cooling water and are comprised of a metal (in the present embodiment, aluminum alloy) and produced by press forming or rolling.
These fins 3, as shown in
Further, the flat parts 3a are formed integrally with louvers 3c by cutting and raising the flat parts 3a. The louvers 3c, when seen from the stacking direction X3 of the tubes 3 (hereinafter referred to as the “tube stacking direction X3”), are twisted from the flat parts 3a by a predetermined angle θ1 (hereinafter referred to as the “twist angle θ1”). A plurality are provided at the flat parts 3a along the air flow direction X2. Further, louver passages 5 are formed between the adjoining louvers 3c. The twist direction of the louvers 3c positioned at the upstream side in the air flow direction X2 and the twist direction of the louvers 3c positioned at the downstream side in the air flow direction X2 differ. Note that the twist angle θ1 is, in the present embodiment, made 23°.
Here, when the direction along the angle θ1 is made the louver width direction X4, the intermediate part of each louver 3c in louver width direction X4 is provided with a step difference 3d extending in the tube stacking direction X3 and projecting out to the louver passage 5 side.
One step difference 3d is provided at each louver 3c. The step difference 3d is provided at the louver passage 5 side positioned upstream in the air flow direction X2 among the louver passages 5 positioned at the two sides of each louver 3c. Further, the bending angle θ2 when viewing the step difference 3d from the tube stacking direction X3 is, in the present embodiment, made 90°.
Note that in the present embodiment, the fins 3 are made of aluminum alloy, the thickness t of the fins 3 is 0.05 mm, the length L of the louvers 3c in the louver width direction X4 (hereinafter referred to as the “louver width L”) is 0.8 mm, and the amount of projection S of the step differences 3d is made 0.05 mm.
Further, the amount of projection S of the step differences 3d is preferably at least the thickness t of the fins 3. Further, when the length of one period of the fins 3 formed in the corrugated shape is the fin pitch FP and the dimension of the cooling water circulation direction X1 in the louvers 3c is the louver pitch height HLP, it is preferable that FP/HLP be 10 or less.
Next, the actions and effects of the present embodiment will be explained.
As shown in
However, the radiator 1 of the present embodiment has step differences 3d projecting out to the louver passage 5 sides. By the cooling air striking these step differences 3d, the flow of the cooling air is disrupted by the step differences 3d and the temperature boundary layers are destroyed, so at the locations of the step differences 3d, the local heat conductivity again rises and the average heat conductivity is improved. Therefore, it is possible to improve the heat conductivity of the fins 3 without shortening the louver pitch.
Further, since the step differences 3d are provided at the louver passage 5 side positioned at the upstream side in the air flow direction X2, compared even with the case of providing the step differences 3d at the louver passage 5 side positioned at the downstream side of the air flow direction X2, the flow of the cooling air is strongly disrupted. Therefore, the heat conductivity of the fins 3 can be further improved.
Note that
A second embodiment of the present invention will be explained next.
The present embodiment is provided with, in place of the step differences 3d in the first embodiment, holes 3e in the louvers 3c. The other points are common with the first embodiment.
The holes 3e pass through the louvers 3c so as to communicate the louver passages 5 positioned at the two sides. Further, the holes 3e are oval in shape. A plurality are provided at the intermediate parts of the louvers 3c in the louver width direction X4 and at the louvers 3c along the tube stacking direction X3 (in this example, three). Note that the holes 3e correspond to the communicating passages of the present invention.
According to this, when the cooling air flows through the louver passages 5, part of the cooling air passes through the holes 3e and flow to the adjoining louver passages 5, whereby the development of temperature boundary layers is suppressed and therefore the average heat conductivity is improved. Therefore, it is possible to improve the heat conductivity of the fins 3 without shortening the louver pitch.
A third embodiment of the present invention will be explained next.
In the second embodiment, the holes 3e were formed by punching, but in the present embodiment, the holes 3e are formed by cutting and raising up parts of the louvers 3c. Due to this, it is possible to form holes 3e without generating waste material. Note that the 3f is a piece which is cut and raised up.
A fourth embodiment of the present invention will be explained next.
In the second embodiment, each louver 3c was provided with a plurality of holes 3e to communicate the louver passages 5 positioned at the two sides of the louver 3c, but the present embodiment each louver 3c is provided with one long slit 3g extending in the tube stacking direction X3 so as to communicate the louver passages 5 positioned at the two sides of the louver 3c. Note that the slits 3g correspond to the communicating passages of the present invention.
The slits 3g are formed as follows: That is, a cut is made in the intermediate part of each louver 3c in the louver width direction X4 along the tube stacking direction X3, then the two sides of the cut are deformed. Due to this, it is possible to form the slits 3g without generating any waste material.
In the above embodiments, the twist direction of the louvers 3c positioned at the upstream side in the air flow direction X2 and the twist direction of the louvers 3c positioned at the downstream side in the air flow direction X2 were made different, but it is also possible to make the twist directions of all of the louvers 3 the same.
Note that the present invention was explained in detail based on specific embodiments, but a person skilled in the art could make various changes, modifications, etc. without departing from the claims and idea of the present invention.
Number | Date | Country | Kind |
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2005-011466 | Jan 2005 | JP | national |