US2350976A - Heat exchanger - Google Patents

Description

June 6, 1944. WORN 2,350,976

HEAT EXCHANGER Filed Jan. 16, 1945 11 10 18 /L V w 21.

l i J INVENTOR BY x 42w ATTORNEY Patented June 6, 1944 UNITED STATES m OFFICE @3133... George A. Worn, Greenwich, Conn. Application January 16, 194:, sci-a1 No. 472,571 1 Claims. (01. 251-202) This invention relates to heat exchangers and particularly to improvements in heat-exchanger tubing of the type provided with an extended heat-conducting surface in the form of external fins extending along the tubingto increase the heat conduction between ajfluicl within the tubing and a fluid surrounding the tubing.

Heretofdre, the employment of such flns upon tubes arranged in a group or bundle has presented a serious difficulty in the way of cleaning the tube, surfaces and the fin surfaces located within the bundle. Generally, the fluid circulating around the tubes leaves upon the surfaces of the tubes and the flnsa deposit which materially impairs their heat transfer elflciency and which it is highly desirable to remove. jrhe fins, however, obstruct-lateral insertion of a scrapin tool into-the tube bundle for removal of such deposit so that it is possible, if, at all, to scrape the tube surfaces and the extended surfaces located within thebundle only by insertion of a tool into one end of the bundle and operation of such tool lengthwise of the tubing. Even in such case, however,'the tubing isoften quite long, and the intertube and interfln spaces are quite narrow so that a very long, slender tool is required to reach the entire...area of-the'surfaces to be cleaned. Itis dlfllcult and sometimes impossible to remove the deposit in such a manner particularly where the tubing is relatively long.

An important object of my present invention is to provide improved flnned heat-exchanger tublug-designed to facilitate cleaning of the surfaces thereof located within a tube group or bundle.

Another important object of my invention is to provide, in a heat-exchanger tubebundle, an improved arrangement of tubes and heat-conducting flns in a correlation such as to provide suflicient clearances around and within the bundle for convenient insertion of a scraping tool transversely or laterally of the bundle and for eflicient operation of the tool to clean all of the tube surfaces and the extended surfaces exposed within the bundle.

A further object of my invention is to provide finned tubing having the aforesaid advantages and devised particularly for satisfactory embodiment in a heat exchanger such as that disclosed in the copending application of George A. Worn and Edward A. Bertram, Serial No. 453.234, flied August 1', 1942. I

Other objects and advantages of my invention will appear hereinafter.

In the drawing.

Fig. l is a vertical longitudinal sectional view of a'heat exchanger embodying my invention;

Fig. 2 is a horizontal longitudinal sectional view of the heat exchanger shown in Fig. 1;

Fig. 3 is an enlarged transverse section taken along the line 3-8 of Fig. 1;

Fig. 4 is a further enlarged transverse section of the inner tubing unit or bundle removed from the outer tube or shell of the heat exchanger wherein the manner of laterally inserting the scraping tool into the interior of the unit is indicated; and

Fig. 5 is a view similar to Fig. 4 and illustrates is modified arrangement of the fins upon the tub- My invention is illustrated and described as embodied in a heat exchanger such as that disclosed in the aforesaid copending application, although it is not necessarily limited thereto. This invention was particularly devised to provide for convenient and thorough cleaning of the heat-conducting surfaces of such a heat exchanger.

In general, the heat exchanger unit disclosed in such copending application is one of a doublepipe type. This unit comprises an elongated outer tube ill of welded construction formed in three sections including a long main tube section ll, a cover I! welded, as at It, to one end of said main section, and an annular flange section It welded as at" to the opposite end of the main section. The flange section is formed with a thick peripheral flange l8 and a tapering tubular neck ll. The bore of the flange section is flared at its outer end, as at l8, and the section is formed with a relieved face around the mouth of the bore and with "a gasket-receiving groove 20 in the face. A thick cover plate or disk 2| has a similar face and a similar groove 22 in opposition to the groove 20. A metal gasket rin 23 of a depth exceeding the combined depth of the grooves has its edges seated in the grooves. The grooves have flat bottoms and inwardly 'converging side walls; and the edges of the gasket are beveled to wedge in the grooves. Bolts 24 extend through holes in flange l6 and the cover plate 2| and have nuts 25 screwed upon their opposite ends to secure the plate to the flange and to hold the gasket under compression.

Cover plate 2! has a fluid inlet passage 28 and a fluid outlet passage 21 extending between its faces. Through most of the thickness of the plate, these passages are parallel; but, adjacent the inner face of the plate, they converge and open through flat abutments 20 at the bottom of flared counterbores 28 at the inner face of the plate. These abutments are at right angles to the converging ends of the passages. At the outer face of the plate, the passages are counterbored to provide them with a flared or beveled seat 30.

Within the outer tube "I there is an inner tube unit forming a small tube bundle defined by a single bifurcated U-tube. Tubular stems II and 82, at the forward end of the outer tube, form the end portions of this U-tube. Stem 3| is the inlet stem and opens into a tubular fork fins, at least all the fins on each tube, have the same radial dimension.

In the arrangement of the fins shown in Figs. 1 to 4, inclusive, each tube 34 is provided with only two of the fins 42 within a semiclrcumference of the tube. One of these fins projects into the space II. From this fork, parallel branched tubing 34 extends forwardly for the major portion of the length of the outer tube, forms return bends 35, and, from these bends, extends in a reverse direction to a tubular fork 36 opposite the first fork and connected to the outlet stem 32. In the present instance, there are two of the branch tubes in each leg of the U-tube, and they provide for divided flow from the stem 3! to the stem I2. Their caliber is desirably smaller than that of the stems. At their outer ends, the stems SI and 32 are secured and sealed in communication with the passages 28 and 21, respectively,

- in the cover plate. The outer end portions of 'the stems diverge in order to reach the passages, 'and the ends of the stems contact squarely with structed in the manner described in the above,

copending application.

Inlet and outlet connections such as those disclosed in the aforesaid copending application, for example, may be sealed to the cover plate 2| in communication with the passages 26 and 21, respectively, to provide for circulation of a fluid through the inner tubing. The outer tube is provided, at points near its opposite ends, with an inlet nipple l0 and outlet nipple 4| to provide for circulation of another fluid through the outer;

tube and around the inner tubing.

The four parallel longitudinal sections of the tubing 34 are desirably provided with radially projecting heat-conducting fins 42 extending along most of the length of the sections. In order to. accommodate the improved fin arrangement of my invention, these four tube sections, which, in effect, form a bundle of four tubes, are preferably equally spaced around a central space within the bundle and substantially entirely around such space and are desirably located equidistantly from the central longitudinal axis of the bundle. In the present instance, the tubes are spaced apart aroimd said space a distance approximately equal to the outside diameter of the tubes. Each fln de-i sirably has an approximately triangular crosssectional shape and is desirably formed of a strip oi sheet metal bent along longitudinal lines into a triangular form with its opposite longitudinal edges meeting at the apex of the triangle and!" there welded together. The portion of the fin forming the base of the triangle is made concave to fit the tubing and is welded thereto so that the fin projects radially from each tube. For the purposes of my invention, it is desirable that all the lo surrounded by the tubes, and the other fin projects away from said space. The inwardly projecting fins oi' the four tubes are arranged ap proximately tangentially to an imaginary circle concentrically positioned with respect to the tube bundle and having a diameter approximately equal to that of the tubes. These fins also terminate at such circle. Therefore, the crests or inner edges of the successive fins are spaced ninety degrees apart armmd the circle to provide liberal clearance between the fins. The outwardly projecting fins are preferably arranged an proportioned so that their crests or outer edges lie approximately upon an imaginary circle surrounding the tube bundle and approximately tangential to the peripheries of the four tubes 34.

The arrangement of the fins just described provides clearances around and within the tube bundle so as to enable a straight scraping tool T to be inserted transversely oi the bundle and operated conveniently at various angles, as indicated in Fig. 4, to clean all of the surfaces of the tubes and the fins upon which any deposit accumulates. At the same time, this arrangement provides a good distribution of the fins within the outer tube II for efficient heat exchange between the fluid wthin the inner tubing and the fluid within the outer tube. I

In the form of my invention shown in- Fig. 5, the arrangement of the tubes 34 is identical with that just described, but each tube is provided with three fins 4211. One of these fins upon each tube projects radially of the latter straight toward the center of the bundle, and the inwardly projecting fins of all the tubes have their crests or inner edges arranged approximately equidistantly from the center of the tube bundle and terminating radially upon an imaginary circle centrally located with respect to the tubes as indicated. The other two fins of each tube are desirably arranged at least ninety degrees outwardly around the tube from the inwardly projecting fin and project radially in opposite directions from the tube. These outer fins are arranged an proportioned to provide liberal clearance for insertion of the scraping tool between the crests of the fins upon adjacent tubes and for convenient operation of the tool to clean all of the exposed tube and fin surfaces within the tube bundle. This modifled arrangement of the fins provides additional extended surface and also provides a good distribution of the fins in the bundle for efi'ective heat conduction.

Although I have shown a four-tube arrange- 0 ment, my invention is susceptible of embodiment in a tube bundle having a different number of tubes. In addition, my invention is not necessarily limited to the use or the triangular type of fin shown. while I have disclosed a preferred form of embodiment of my' invention, it will be understood that it is possible to modify details of the structure disclosed without departing from the invention as defined in the appended claims.

I claim:

1. A heat-exchanger tube bundle comprising a group of four parallel tubes of approximately the same diameter spaced apart a distance approximately equal to said diameter around a central space and approximately equidistantly from the center of said space, a pair of external radial heat-conducting fins borne by each of said tubes and extending longitudinally thereof. one of said fins upon each tube projecting into said space, all of said inwardly projecting fins terminating upon and being tangential to a circle centrally located within the said space and having approximately the same diameter as the tubes, the other fin upon each tube diverging outwardly from the inwardly projecting fin relatively widely but at an angle thereto less than 180 and being materially spaced from the next adjacent tube, to thereby provide intertube and interfin clearances around and within the bundle for straight insertion of a scraping tool transversely of the bundle and into contact with all of the exposed tube surfaces and the fin surfaces and for operation of the inserted tool for complete scraping of said surfaces.

2. A'heat-exchanger tube bundle comprising a group of parallel tubes spaced apart around a central space and approximately equidistantly from the center of said space, three external radial heat-conducting fins borne by each of said tubes and extending longitudinally thereof, one of said fins upon each tube projecting into said space, all of said inwardly projecting fins terminating upon and being radial to a circle centrally located within said space, the other two fins of each tube diverging outwardly from the inwardly projecting fin relatively widely but at an angle thereto of less than 180 and being spaced materially from the fins of adjacent tubes of the group, to thereby provide intertube and interfin clearances around and within the bundle for straight insertion of a scraping tool transversely of the bundle and into contact with all of the exposed tube surfaces and the fin surfaces and for operation of the inserted tool for complete scraping of said surfaces.

3. The heat-exchanger tube bundle as claimed in claim 2, wherein each of the outwardly extending fins on each tube is spaced at least ninety degrees around the tube from the inwardly projecting fin, one on each side of the latter, andall of said fins have substantially the same radial dimension.

4. A heat-exchanger tube bundle comprising a group of four parallel tubes of approximately the same diameter spaced apart a distance approximately equal to said diameter around a central space and approximately equidlstantly from the center of said space, a pair of external radial heat-conducting fins borne by ach of said tubes and extending longitudinally thereof, one of said fins upon each tube projecting into said space, all of said inwardly projecting fins terminating upon and being tangential to a circle centrally located within the said space and having approximately the same diameter as the tubes, the other fin upon each tube diverging outwardly, with respect to said space, from the inwardly projectbundle and into contact with all of the exposed tube surfaces and the fin surfaces for complete scraping of said surfaces.

5. In a heat-exchanger tube bundle comprising a circular series of parallel tubes spaced around a central space within the bundle, heatconducting fins including a pair of external radial fins borne by each of said tubes and extending longitudinally thereof and diverging from each other relatively widely but at an angle of less than 180 and in a direction toward the next succeeding tube around the series, one of said fins of each pair projecting into said space, the crests of said fins upon each tube lying upon a plane intermediate the tube and the next succeeding tube and the said fins upon the latter tube being circumferentially positioned thereon to space their crests from said plane, to provide intertube and interfin clearances around and within the bundle for straight insertion of a scraping tool transversely of the bundle and into contact with all of the tube surfaces and the fin surfaces exposed within the bundle and for operation of the inserted tool for complete scraping of said surfaces.

6. In a heat-exchanger tube bundle comprising a group of parallel tubes spaced around a central space within the bundle, heat-conducting fins including a pair of external fins borne by each of said tubes and extending longitudinally thereof and diverging outwardly from each other relatively widely but at an angle of less than 180, one of said fins projecting inwardly into said space and the other fin projecting outwardly of said space and the pairs of fins of the successive tubes around said space being in positions progressively displaced circumferentially of the tubes, to provide intertube and interfin clearances around and within the bundle for straight insertion of a scraping tool transversely of the bundle and into contact with all of the tub surfaces and the fin surfaces exposed within the bundle and for operation of the inserted tool for complete scraping of said surfaces.

7. In a heat-exchanger tube bundle comprising a group of parallel tubes spaced around a central space within the bundle, heat-conducting fins including a pair of external fins borne by each of said tubes and extending longitudinally thereof and diverging outwardly from each other relatively widely but at an angle of less than 180', each of said fins being approximately triangular in cross-section and tapering outwardly from its respective tube, one of said fins projecting inwardly into said space and the other fin projecting outwardly of said space and the pairs of fins of the successive tubes around said space being in positions progressively displaced circumferentially of the tubes to provide intertube and interfin clearances around and within the bundle serted tool for complete scraping of said surfaces.

onoaon A. WORN.

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