The present invention relates to a heat exchanger, and more specifically pertains to a heat exchanger designed to perform heat exchange by making a fluid flow between at least two opposed heat transfer members.
One proposed heat exchanger is an in-vehicle corrugated fin tube heat exchanger including multiple flat tubes arranged to make a coolant flow and corrugated fins attached between adjacent pairs of the multiple flat tubes (see, for example, Japanese Patent Laid-Open No. 2001-167782). One proposed structure of a cross fin tube heat exchanger uses multiple slit fins with thin slits formed therein (see, for example, Japanese Patent Laid-Open No. 2003-161588). Another proposed structure of the cross fin tube heat exchanger uses wavy fins with wave crests and wave troughs formed in a direction perpendicular to the direction of the air flow (see, for example, Japanese Patent Laid-Open No. 2000-193389). Still another proposed structure of the cross fin tube heat exchanger uses V-shaped wavy fins having wave crests and wave troughs arranged in a V shape at an angle of 30 degrees relative to the direction of the air flow (for example, Japanese Patent Laid-Open No. H01-219497). These proposed techniques adopt various shapes of fins with the purpose of accelerating heat transfer in the fin tube heat exchangers.
In the prior art heat exchanger with the slit fins or in the prior art heat exchanger with the wavy fins, however, while the slits or the wave crests and wave troughs improve the heat transfer coefficient, the resulting projections or the resulting partial cutting and folding may cause separation of the air flow or a local speed multiplication to increase the ventilation resistance rather than the heat transfer coefficient. In application of such a heat exchanger for an evaporator in refrigeration cycles, the water vapor content in the air may adhere in the form of dew or frost to the heat exchanger and clog the slits or the waveforms with condensed water or frost to interfere with the smooth air flow. In the prior art heat exchanger with the V-shaped wavy fins, there is no separation of the air flow or local speed multiplication caused by the projections or the partial cutting and folding. The V-shaped wave crests and wave troughs on the V-shaped wavy fins may, however, have the low heat transfer coefficient or the high ventilation resistance.
By taking into account the problems of the prior art techniques discussed above, there would thus be a demand for forming an appropriate shape of wave crests and wave troughs in the V-shaped wavy fins of the heat exchanger, so as to provide a high-performance, small-sized heat exchanger having high efficiency of heat exchange.
The present invention accomplishes at least part of the demand mentioned above and the other relevant demands by variety of configurations and arrangements discussed below.
According to one aspect, the invention is directed to a heat exchanger configured to perform heat exchange by making a fluid flow between at least two opposed heat transfer members. Each of the at least two opposed heat transfer members is structured to have a heat transfer plane located to make the fluid flow thereon and equipped with a wave crest line and an adjacent wave trough line formed thereon. The wave crest line and the wave trough line are arranged to have a preset angle in a specific angle range of 10 degrees to 60 degrees relative to a main stream of the fluid flow and are symmetrically folded back about folding lines arranged at a preset interval along the main stream of the fluid flow. The wave crest line and the adjacent wave trough line are arranged to satisfy an inequality of 1.3×Re−0.5<a/p<0.2. Here ‘a’ denote an amplitude of a waveform including one wave crest of the wave crest line and one wave trough of the adjacent wave trough line, ‘p’ denotes a pitch as an interval between adjacent heat transfer planes of the at least two opposed heat transfer members, and ‘Re’ denotes a Reynolds number defined by a bulk flow rate and the pitch ‘p’.
In the heat exchanger according to this aspect of the invention, the at least two opposed heat transfer members are structured to have the wave crest line and the wave trough line satisfying the inequality given above. The vortexes of the secondary flows generated in the course of the fluid flow can thus function as a secondary flow component effective for acceleration of heat transfer without being affected by the heat transfer planes of the opposed heat transfer members. This gives the high-performance, small-sized heat exchanger having the high efficiency of heat exchange.
In one preferable application of the heat exchanger according to the above aspect of the invention, each of the at least two opposed heat transfer members is structured to have the wave crest line and the wave trough line arranged to satisfy an inequality of 0.25<W/z<2.0. Here ‘W’ denotes the preset interval of the folding lines and ‘z’ denotes a wavelength of the waveform including the wave crest and the wave trough. This arrangement effectively controls an increase in ratio of a moving distance of the secondary flow component in a spanwise direction to a moving distance of the secondary flow component in a normal direction perpendicular to the heat transfer planes of the at least two opposed heat transfer members and keeps the large secondary flow component effective for acceleration of heat transfer. This gives the high-performance, small-sized heat exchanger having the higher efficiency of heat exchange.
In another preferable application of the heat exchanger according to the above aspect of the invention, each of the at least two opposed heat transfer members is structured to have the wave crest line and the wave trough line arranged to satisfy an inequality of 0.25<r/z. Here ‘r’ denotes a radius of curvature at a top of the wave crest and/or at a bottom of the wave trough in the waveform and ‘z’ denotes the wavelength of the waveform including the wave crest and the wave trough. This arrangement effectively controls a local speed multiplication of the flow climbing over the wave crests and thereby prevents an increase of the ventilation resistance. This gives the high-performance, small-sized heat exchanger having the higher efficiency of heat exchange.
In still another preferable application of the heat exchanger according to the above aspect of the invention, the wave crest line and the adjacent wave trough line formed on each of the at least two opposed heat transfer members are arranged to have an angle of inclination of not less than 25 degrees on a cross section of the waveform including the wave crest and the wave trough. This arrangement enhances the secondary flow component along the wave crests and the wave troughs. The enhanced secondary flow component leads to generation of effective secondary flows having contribution to the heat transfer and increases the area of an effective region for heat transfer of the inclined surface on the cross section of the waveform including the wave crest and the wave trough. This gives the high-performance, small-sized heat exchanger having the higher efficiency of heat exchange.
In another preferable application of the heat exchanger according to the above aspect of the invention, each of the at least two opposed heat transfer members includes multiple heat transfer sectional members parted at plural planes substantially perpendicular to the main stream of the fluid flow. This arrangement enhances the secondary flows effective for acceleration of the heat transfer and blocks development of a boundary layer at the plural planes of separation, so as to attain the high thermal conductivity. This gives the high-performance, small-sized heat exchanger having the higher efficiency of heat exchange.
In one preferable embodiment of the invention, the heat exchanger includes multiple heat transfer tubes arranged in parallel to one another as a pathway of a heat exchange medium. The at least two opposed heat transfer members are formed as multiple fin members attached to the multiple heat transfer tubes such as to be arranged perpendicular to the multiple heat transfer tubes in a heat exchangeable manner and to be overlapped in parallel to one another at a preset interval. This gives the high-performance, small-sized fin tube heat exchanger having the higher efficiency of heat exchange.
One mode of carrying out the invention is discussed below as a preferred embodiment with reference to the accompanied drawings.
The multiple heat exchange tubes 22a through 22c are arranged to be in parallel to one another and substantially perpendicular to the air flow for cooling to make bypass flows or split flows of the heat exchange medium, for example, a cooling liquid like cooling water or cooling oil or a coolant used for refrigeration cycles.
As shown in
Each of the fins 30 is designed to have the multiple continuous lines of the wave crests 34 and the multiple continuous lines of the wave troughs 36 (respectively shown by the one-dot chain lines and the two-dot chain lines), which are arranged to have a preset angle γ (for example, 30 degrees) in a specific angle range of 10 degrees to 60 degrees relative to the main stream of the air flow. The continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 are symmetrically folded back about folding lines (non-illustrated lines of connecting flexion points of the one-dot chain lines with the two-dot chain lines of
The angle γy is, however, not necessarily fixed but may be varied to draw curved continuous lines of the wave crests 34 and curved continuous lines of the wave troughs 36.
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have an amplitude-to-pitch ratio (a/p) satisfying Inequality (1) given below:
1.3×Re−0.5<a/p<0.2 (1)
The amplitude-to-pitch ratio (a/p) represents a ratio of an amplitude ‘a’ of a waveform including one wave crest 34 and one adjacent wave trough 36 (see
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have an interval-to-wavelength ratio (W/z) in a range of greater than 0.25 and less than 2.0 as shown by Inequality (2) given below:
0.25<W/z<2.0 (2)
The interval-to-wavelength ratio (W/z) represents a ratio of the folding interval W (see
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have a curvature radius-to-wavelength ratio (r/z) in a range of greater than 0.25 as shown by Inequality (3) given below:
0.25<r/z (3)
The curvature radius-to-wavelength ratio (r/z) represents a ratio of the radius of curvature ‘r’ at the top of the wave crest 34 or at the bottom of the wave trough 36 (see
In the corrugated fin tube heat exchanger 20 of the embodiment, the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 formed on each fin 30 are arranged to have an angle of inclination α of not less than 25 degrees on the cross section of the waveform including one wave crest 34 and one adjacent wave trough 36 (see
As described above, in the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 (respectively shown by the one-dot chain lines and the two-dot chain lines), which are arranged to have the preset angle γ (for example, 30 degrees) in the specific angle range of 10 degrees to 60 degrees relative to the main stream of the air flow and are folded back symmetrically about the folding lines of the preset interval (folding interval) W along the main stream of the air flow. This arrangement generates the effective secondary flows of the air and improves the heat transfer coefficient, thus enhancing the overall efficiency of heat exchange and allowing size reduction of the corrugated fin tube heat exchanger 20. Formation of the waveforms including the wave crests 34 and the wave troughs 36 on the fin 30 does not cause any partial cutting and folding of the fin 30 and does vary the interval between the adjacent fins 30. This arrangement effectively prevents separation of the air flow and a local speed multiplication of the air flow.
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have the amplitude-to-pitch ratio (a/p) satisfying Inequality (1) given above. The amplitude-to-pitch ratio (a/p) represents the ratio of the amplitude ‘a’ of the waveform including one wave crest 34 and one adjacent wave trough 36 to the fin pitch ‘p’ or the interval between the adjacent fins 30. This arrangement ensures the high heat transfer coefficient of the corrugated fin tube heat exchanger 20 and thereby allows further size reduction of the corrugated fin tube heat exchanger 20.
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have the interval-to-wavelength ratio (W/z) in the range of greater than 0.25 and less than 2.0 as shown by Inequality (2) given above. The interval-to-wavelength ratio (W/z) represents the ratio of the folding interval W of the folding lines arranged along the main stream of the air flow to symmetrically fold back the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 to the wavelength ‘z’ of the waveform including one wave crest 34 and one adjacent wave trough 36. This arrangement ensures the high heat transfer coefficient of the corrugated fin tube heat exchanger 20 and thereby allows further size reduction of the corrugated fin tube heat exchanger 20.
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is designed to have the curvature radius-to-wavelength ratio (r/z) in the range of greater than 0.25 as shown by Inequality (3) given above. The curvature radius-to-wavelength ratio (r/z) represents the ratio of the radius of curvature ‘r’ at the top of the wave crest 34 or at the bottom of the wave trough 36 (see
In the corrugated fin tube heat exchanger 20 of the embodiment, the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 formed on each fin 30 are arranged to have the angle of inclination α of not less than 25 degrees on the cross section of the waveform including one wave crest 34 and one adjacent wave trough 36. This arrangement ensures the high heat transfer coefficient of the corrugated fin tube heat exchanger 20 and thereby allows further size reduction of the corrugated fin tube heat exchanger 20.
In the corrugated fin tube heat exchanger 20 of the embodiment described above, each fin 30 is designed to have the interval-to-wavelength ratio (W/z), which is given as the ratio of the folding interval W of the folding lines arranged along the main stream of the air flow to symmetrically fold back the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 to the wavelength ‘z’ of the waveform including one wave crest 34 and one adjacent wave trough 36, in the range of greater than 0.25 and less than 2.0 as shown by Inequality (2) given above. In one modified structure, each fin 30 may be formed to have the interval-to-wavelength ratio
(W/z) in the range of not greater than 0.25 or in the range of not less than 2.0.
In the corrugated fin tube heat exchanger 20 of the embodiment described above, each fin 30 is designed to have the curvature radius-to-wavelength ratio (r/z), which is given as the ratio of the radius of curvature ‘r’ at the top of the wave crest 34 or at the bottom of the wave trough 36 to the wavelength ‘z’ of the waveform including one wave crest 34 and one adjacent wave trough 36, in the range of greater than 0.25 as shown by Inequality (3) given above. In one modified structure, each fin 30 may be formed to have the curvature radius-to-wavelength ratio (r/z) in the range of not greater than 0.25.
In the corrugated fin tube heat exchanger 20 of the embodiment described above, the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36 formed on each fin 30 are arranged to have the angle of inclination α of not less than 25 degrees on the cross section of the waveform including one wave crest 34 and one adjacent wave trough 36. In one modified structure, each fin 30 may be formed to have the angle of inclination α of less than 25 degrees.
In the corrugated fin tube heat exchanger 20 of the embodiment, each fin 30 is made of a single plate member and is designed to have the continuous lines of the wave crests 34 and the continuous lines of the wave troughs 36, which are arranged at 30 degrees relative to the main stream of the air flow and are folded back symmetrically about the folding lines of the preset interval (folding interval) W along the main stream of the air flow. In a corrugated fin tube heat exchanger 20B of one modified example shown in
The corrugated fin tube heat exchanger 20 of the embodiment performs heat exchange between the air flow and the heat exchange medium flowing through the multiple heat transfer tubes 22a to 22c. In one modification, heat exchange may be performed between a fluid flow other than the air (for example, a liquid flow or a gas flow) and the heat exchange medium flowing through the multiple heat transfer tubes 22a to 22c.
The embodiment describes the corrugated fin tube heat exchanger 20 as one preferable mode of carrying out the invention. The technique of the invention is, however, not restricted to the corrugated fin tube heat exchangers but may be applied to cross fin tube heat exchangers. The principle of the invention is also applicable to a heat exchanger of a modified structure with omission of all the fins 30 from the corrugated fin tube heat exchanger 20 of the embodiment. The heat exchanger of this modified structure has multiple heat transfer tubes opposed to one another and designed to include heat transfer planes. The heat transfer plane of each heat transfer tube arranged to face an adjacent heat transfer tube is designed to have continuous lines of wave crests and continuous lines of wave troughs, which are arranged to have a preset angle in the specific angle range of 10 degrees to 60 degrees relative to the main stream of the air flow and are folded back symmetrically about folding lines of a preset interval along the main stream of the air flow. Namely the technique of the invention is applicable to a heat transfer plane of any heat transfer member satisfying the following conditions in a heat exchanger that performs heat exchange by making a fluid flow between at least two opposed heat transfer members. The heat transfer plane of the heat transfer member is arranged to form the pathway of the fluid flow and is designed to have continuous lines of wave crests and continuous lines of wave troughs, which are arranged to have a preset angle in a specific angle range of 10 degrees to 60 degrees relative to a main stream of the fluid flow and are folded back symmetrically about folding lines of a preset interval along the main stream of the fluid flow. A ratio of an amplitude of a waveform including one wave crest of a wave crest line and one wave trough of an adjacent wave trough line to an interval between the heat transfer planes of adjacent heat transfer members satisfies Inequality (1) given above.
The embodiment and its applications discussed above are to be considered in all aspects as illustrative and not restrictive. There may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention.
The present invention is preferably applied to the manufacturing industries of heat exchangers.
Number | Date | Country | Kind |
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2007-015538 | Jan 2007 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2008/050778 | 1/22/2008 | WO | 00 | 7/21/2009 |