Heat exchange – Tubular structure – With discrete heat transfer means
Patent
1995-01-31
1997-04-08
Rivell, John
Heat exchange
Tubular structure
With discrete heat transfer means
F28F 114
Patent
active
056179162
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a finned tube formed by winding a serrated fin around a tube, a finned tube heat exchanger employing such finned tubes, and a heat recovery system having such a fin-tube heat exchanger disposed in an exhaust gas passage.
BACKGROUND ART
Conventional fin strips wound around tubes of, for example, heat exchangers for recovering heat from exhaust gas produced by combustion are those having an L-shaped cross section and fins formed by slitfing the edge thereof and those having a U-shaped cross section and fins formed by slitfing the edge thereof. Disclosed in U.S. Pat. No. 3,652,820 (Patent family: Japanese Utility Model Publication No. 55-42140) is a heat exchanger employing finned tubes each formed by winding a fin strip 4 having fins 3 separated by slits around a tube 1 and twisfing the fins 3 as shown in FIG. 12.
The inventors of the present invention proposed in Japanese Patent Laid-open Publication No. 4-126997 a heat exchanger employing finned tubes each having fins inclined at an inclination angle .theta. (FIG. 3) in the range of 2.degree. to 20.degree. to a straight line perpendicular to the axis of the tube, and having a fin slit ratio H/h, where h is the height of the base 2 of the fin strip 4 from which the fins 3 extend, i.e., a portion of the fin strip 4 not provided with any slits (FIG. 4), and H is the overall height of the fin strip 4 including the fins 3, not smaller than 1.5, preferably, in the range of 3 to 15. In the prior art fin strip having an L-shaped cross section and fins formed by slitfing the peripheral portion thereof, the fin strip is attached to a tube at a setfing angle, i.e., a fin inclination angle .theta., of zero degree, nothing is considered about the fin slit ratio (H/h) mentioned in the invention previously proposed by the inventors of the present invention, and any particulars about the twist angle of the fins of the fin strip are not taken into consideration. The inventors of the present invention had not taken particulars about the twist angle of the fins of the fin strip into consideration in making the invention previously proposed by the inventors.
Accordingly, it is an object of the present invention to provide a finned tube of a construction having an improved heat transfer coefficient. Another object of the present invention is to provide a heat exchanger having an improved heat transfer coefficient. A further object of the present invention is to provide a heat recovery system provided with a heat exchanger having an improved heat transfer coefficient.
DISCLOSURE OF THE INVENTION
The present invention provides a finned tube comprising: a tube; and a fin strip having fins formed by forming slits of a predetermined length in a fin portion of a strip perpendicularly to the length of the strip and at predetermined intervals, and a base portion in which no slit is formed, and wound around the tube so that the fins thereof extend substantially radially of the tube; characterized in that the fins are twisted at a twist angle in the range of 2.degree. to 40.degree. to a contact line along which the base portion of the fin strip is in contact with the tube, and inclined at an inclination angle in the range of 2.degree. to 20.degree. to a straight line perpendicular to the axis of the tube.
The present invention provides a heat exchanger provided with a plurality of the aforesaid finned tubes.
The present invention further provides a heat recovery system comprising a heat exchanger having a plurality of the aforesaid finned tubes, and disposed within a combustion gas passage with the finned tubes extending with their axes perpendicular to the longitudinal direction of the combustion gas passage and with the fins of the finned tubes declined to a straight line perpendicular to the axes of the tubes, or a heat recovery system comprising the heat exchanger having a plurality of the aforesaid finned tubes and disposed within a combustion gas passage with fins of the adjacent finned tubes inclined to a straight line perpe
REFERENCES:
patent: 1932610 (1932-10-01), Tilley
patent: 3752228 (1973-08-01), Bosse
patent: 4138997 (1979-02-01), LaPorte et al.
patent: 4258782 (1981-03-01), Kao
patent: 5195578 (1993-03-01), Le Goff et al.
patent: 5240070 (1993-08-01), Ryan
Kohtaka Ikuo
Machida Yukitaka
Marumoto Takahiro
Mimura Tetsuo
Shigenaka Toshinori
Atkinson Christopher
Babcock-Hitachi Kabushiki Kaisha
Rivell John
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