US2913009A - Internal and internal-external surface heat exchange tubing - Google Patents

Description

C. H. KUTHE Nov. 17, 1959 INTERNAL AND INTERNAL-EXTERNAL SURFACE HEAT EXCHANGE TUBING Filed July 16, 1956 FIGJ.

INVENTOR.

CHARLES H.KUTHE ATTORNEYS United States Patent INTERNAL AND INTERNAL-EXTERNAL SURFACE HEAT EXCHANGE TUBING Charles H. Kuthe, Highland Park, Mich., assignor t 0 Calumet.& Hecla, Inc., Calumet, Mich., a corporation of Michigan Application July 16, 1956, Serial No. 598,070

1 .Claim. .(Cl. 138-38) This invention relates :to .heat exchange tubing and refers more particularly tointernal andinternal-external surface heat exchange tubing.

The tubing in heat exchangeinstallations is often times provided with an external fin surface to increase the heat transfercharacteristics of the tubing. The construction of heat exchange tubing with an external fin surface is done primarily with prefabricated fins bonded mechanically or metallurgically to a :smooth surfaced tube. Other finned tubing -.-is produced with integral fins or corrugations on the external surface. It has been found, after much experimentation, that heat exchange tubing which is corrugated on the inside, either in addition to or in place of external fins, greatly increases the heat transfer between theroutside and inside fluids.

One object of this invention is to provide heat exchange tubing which is corrugated on the internal surface so as to produce turbulence of the fluid within the tube and promote better heat transfer between the inside and outside fluids.

Another object of the invention is to provide a tube assemblycomprising an outer tube and an inner tube positioned within the outer tube which is corrugated on the innersurface.

Another-object of the invention is to provide a tube assembly comprising an outer tube and an inner tube telescoped within theouter tube in heat exchange relation therewith, the inner tube being corrugated. to impart to the inner tube an undulating configuration in longitudinal section.

Still another object of the invention is to provide a heat exchange tube assembly, as described in the preceding paragraph, in which the outer tube has fins on its outer surface to cooperate with the inner tube in promoting better heat transfer between inside and outside fluids.

Other objects are to provide a tube assembly as described in which the inner tube has a helical corrugation extending over a portion of its length, and in which the inner tube has a plurality of longitudinally spaced circumferentially extending corrugations.

Other objects of the invention will become more apparent as the following description proceeds, especially when taken into consideration with the accompanying drawings, wherein:

Figure 1 is an elevational view, partly in section, of a heat exchange tube assembly embodying the invention.

Figure 2 is a view similar to Figure 1, illustrating a modification.

Figure 3 illustrates a further modification.

Referring now more particularly to the drawing and especially to Figure 1 thereof, the tube assembly there shown is generally indicated by the reference numeral and comprises anouter tube 12 and aninner tube 14 telescoped within the outer tube in coaxial relationship therewith, these tubes being formed of a suitable material having good heat transfer characteristics. The tube=assembly 10 is-adapted to be employed in .a heatexchange;

installation.

The outer tube '12 is .cylindrical, that is, the radially inner and outer surfaces thereof areof uniform. circular cross-section throughoutzthelengthof the tubeand, therefore, smooth.

outer surface of the tube to form a helical groove in the tube while at the same time feeding .the tube-axially However, as pointed out: above, the

and rotating it.inner tube 14 maybe formed by other means.

The corrugatedintermediate portion 20 has an un dulating configuration in longitudinal section as illustrated. The intermediate portion has a helical radiallyinwardly extendingcorrugation 22, each convolution of the corrugation being indicated at 24. The undulating configuration also provides, in effect, a helical radially outwardly extendingcorrugation 26, each convolution of which is indicated at 28.

The crests 30of the convolutions 28'are'of the sameoutside diameter and are of the same diameter as the outside diameter of the cylindrical plain end portions 16- and 18. Thecrests 32 of theconvolutions 24 are of the same inside diameter. It should also be pointed out that theinner tube 14 is of uniform wall thickness from one end to the other.

Thetubes 12 and 14 are :assembled together by inserting the -inner tube within the outer tube and then-sinking the outer tube on the inner tube. or metallurgical contact of the two tubes is thereby achieved with thecrests 30 of the convolutions 28-of'the' inner tube contacting the smoothinternal surface of the Preferably, thecrests 30 have a full and continuous contact with :the smooth internal surfaceof Outer tube.

the .outer tube throughout the full .extentof the corrugated portion. Theexternal surfaces of the plain end portions- 16 and 18 are also brought into full and continuous surface-to-surface contact with the smooth internal surface of the outer tube by the sinking operation.

As a result of this construction, a heat exchange tube assembly is provided having a substantial helical corrugation on the inside and producing turbulence in a fluid moving through the corrugated portion of the inner tube, and, hence, promoting better heat transfer with a fluid on the outer side of the tube assembly. The continuous and uninterrupted contact between thecrests 30 of the inner tube and the smooth inner surface of the outer tube also promotes heat transfer. The degree of turbulence may be controlled by varying the shape of the convolutions of the corrugation on the inner tube.

Figure 2 illustrates a modification in which corresponding parts are designated by the same reference numerals. Theinner tube 114 is exactly like theinner tube 14 described in the first embodiment. Theouter tube 112 differs from theouter tube 12 previously described in that it has anintegral fin 115 formed on the external surface, the fin extending helically and continuously about the outer surface of the tube. The crests of the corrugations on the inner tube have a continuous and uninterrupted contact with the smooth inner cylindrical surface of theouter tube 112, thus achieving a mechanical or metallurgical contact between the tubes which may be accomplished in any suitable manner.

Thefin 115 is shown as being formed integrally on Patented :Nov- 1 11. 59

A mechanical at the outer tube although it will be understood that the fin may be prefabricated and bonded mechanically or metallurgically to the outer surface of a smooth cylindrical tube such as thetube 12.

By varying height and linear spacing of the convolutions of the fin on the outer tube, and also by varying the shape of the corrugation on the inner tube, the desired inside-outside surface ratio may be obtained for optimum heat transfer.

.Figure 3 illustrates a further modification in which corresponding parts are designed by the same reference numerals. Theouter tube 212 is exactly like theouter tube 112. Theinner tube 214 differs from theinner tubes 14 and 114 only in the shape of thecorrugated portion 220. Thecorrugated portion 220 is formed of a plurality of circumferentially extending longitudinally spaced radiallyinward corrugations 224 which are disposed in a plane at right angles to the tube axis. Thecorrugations 224 are similar to theconvolutions 24 shown in the previous embodiments except that whereas the convolution-s 24 extend helically and connect end to end into adjacent convolutions to provide a continuous helical corrugation, thecorrugations 224 are separate and spaced from each other. The undulating configuration of thecorrugated portion 22!) also provides, in effect, radially outwardly extendingcorrugations 228 betweenadjacent corrugations 224, thecorrugations 228 being disposed in planes at right angles to the tube axis.

Thecrests 230 of thecorrugations 228 are of the same outside diameter and are of the same diameter as the outside diameter of the cylindrical plain end portions of the inner tube. Thecrests 232 of thecorrugations 224 are of the same inside diameter and thetube 214 is of uniform wall thickness from one end to the other.

Thetubes 212 and 214 are assembled together in any suitable manner so that "a mechanical or metallurgical contact of the two tubes is achieved with thecrests 230 of thecorrugations 228 contacting the smooth internal surface of the outer tube. Preferably, thecrests 230 have a full and continuous contact with the smooth internal surface of the outer tube. The external surfaces of the plane end portions of the tube also have a full and continuous surface-to-surface contact with the smooth internal surface of the outer tube.

It will be readily apparent that in the Figure 3 embodiment, theplain tube 12 might be substituted for the 4finned tube 212, in which event thecrests 230 and external surfaces of the ends of the inner tube would have a full continuous and uninterrupted surface-to-surface contact with the smooth inner surface of theouter tube 12.

The drawings and the foregoing specification constitute a description of the improved internal and internal-external surface heat exchange tubingin such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claim.

What I claim as my invention is:

A heat exchange tube assembly for use in a heat exchanger, said assembly comprising an outer tube having smooth cylindrical radially inner and outer surfaces, and an inner tube telescope coaxially within said outer tube in heat exchange relationship therewith, said inner tube being so corrugated as to have an undulating configurationin longitudinal section except at the ends thereof, the crests of the undulations being in full and continuous surface-to-surface contact with the radially inner surface of said outer tube, the interior of said inner tube, from the axis thereof radially outward, being in direct open communication with the undulating inner surface of said inner tube and the undulations being such that substantial turbulence is produced in fluid moving axially through said inner tube, each of the opposite ends of said inner tube having a smooth cylindrical radially outer surface which throughout its entire circumference is in full and continuous surface-to-surface contact with the radially inner surface of said outer tube to isolate the space between said tubes.

References Cited in the file of this patent UNITED STATES PATENTS 1,005,441 Lovekin Oct. 10, 1911 1,564,446 Rhoads Dec. 8, 1925 1,818,082 Mott Y Aug. 11, 1931 1,913,573 Turner June 13, 1933 2,118,060 Stone et al. May 24, 1938 2,271,131 Price Jan. 27, 1942 2,374,609 McCollum Apr. 24, 1945 2,456,775 Fausek et al. Dec. 21, 1948 2,820,615 Peters Jan. 21, 1958 FOREIGN PATENTS 684,602 Great Britain Dec. 24, 1952

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