US1884555A - Scale shedding heat transfer apparatus - Google Patents

Description

Oct. 25, 1932. 5. BROWN 1,884,555

SCALE SHEDDING HEAT TRANSFER APPARATUS Filed July 15, 1930 2 Sheets-Sheet 1 INVENTOR 5 ATTO R N EY5 Oct. 25, 1932. I 5. BROWN 1,384,555

I SCALE snnnnma HEAT TRANSFER APPARATUS Filed July 15. 1930 2 Sheets-Sheet 2 I\ W U 75a,

' INVENTOR Wan/g Brow/7 BY Mi/Zma f/s' ATTORNEYS Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE s'rAiIL-EY Brown, or GARDEN CITY, new yonzmnssmnon. To an omscou-nussm COMPANY, or new yonx, N. Y., A conronArron or DELAWARE SCALE SHEDDING HEAT TRANSFER APPARATUS Application filed July 15, 1930. Serial 1:10. 468,013.

The'present invention relates to heat exchangers such as evaporators, condensers and feed water heaters wherein tubes are employed as agencies of heat transmission from one fluid medium to another. The invention more especially relates to heat exchangers in which the tubes are partially or wholly covcred with liquid containing scale-forming rated. The raw water which is fed to the.

evaporator usually contains various solids or F other materials which tend-to form scale on the evaporator tubes. Moreover, in certain types of condensers, particularly those used in oil refining work, where very frequently the cooling water is contaminated with scaleforming impurities, the matter of scale removal is also a problem. In such condensers the oil is usually sent through the interiors of the tubes, and the cooling water over the exteriors of the tubes. The scale collects on the surfaces of the tubes and some provision has to be made for its removal. 7

Various expedients have been employed to provide for this scale removal, one of the most usual and most effective arrangements being the bowed tube construction in which the tubes are very nearly straight and the forces, of expansion and contraction caused by, temperature changes produce a warping movement or bowingof the tubes which removes the scaly deposits on the tubes. In the usual arrangement of the bowed tube construction, however, tube sheets are emsity of employing headers at both ends of the tube bundle..

Another object of the invention is to provide a heat exchanger having tubes of such construction that an effective self-scaling movement thereof is produced under variations in temperature and at the same time do away with the necessity for stress-carrying members extending throughout the length of the tube bundle.

A further objectof the invention is to provide a heat exchanger of improved construction' and having adequate scale-removing characteristics.

A still further object of the invention is to provide a heat exchanger having its tubes so constructed that changes in both temperature and pressure produce an effective scaleshedding movement thereof.

Having the above objects in view, the invention will now be described in connection with the accompanying drawings in which Fig. 1 is a sectional elevational view illustrating an apparatus embodying my invention.

Fig. 2 is a similar view of a'modified form of apparatus. r

Fig. 3 is a view looking toward the right hand end of Fig. 1 with the cover of the ap paratus removed. 7

Fig. 4 is a diagrammatic view of a single heat exchanger element of the kind shown in Figs. 1 and 2. 7

Fig. 5 is a diagrammatic view'of a modified form of heat exchanger element.

, Fig. 6 is adiagrammatic view showing another modification of the heat exchanger ele ment'; and

Fig. 7 is a view showing the cross-section of the curved portion of the element of Fig. 6.

The principle of operation of my invention by means of which the scale-shedding movement of the heat exchanger tubes is produced will be easily understood by referring first to Figs. 4. 5 and 6 of the drawings.

In Fig. at the heat exchanger tube 10 which is of copper, brass, steel or other suitable metal having a relatively high coefiicient of expansion, is made with two slender legs 11 and 12 of unequal length jointed together at straight portions one end by a curved portion 13. At their opposite ends the tubes are secured in manifolds 14 and or other mountings which are rigidly fixed in position in any suitable manner. The legs 11 and 12 may be perfectly straight, or nearg' straight, or they may be slightl bowed. ven if slightly bowed, however, t ey are straight in comparison to the curved portion 13.

Steam or other heating or cooling medium is delivered to and discharged from the tube means of these manifolds, the medium preferably entering through manifold 14 and leaving by manifold 15. The leg 11 is shorter than leg 12 as shown, and consequently when the temperature of the tube increases,

as for example when steam is sent through a cold tube, the expansion of the leg 12 is greater than that of leg 11. Consequently the tube moves upwardly and assumes a new position approximately as indicated by the dotted lines in Fig. 4.

Referring now to Fig. 5.0f the accompanying drawings, the heat exchanger tube 16 here illustrated is of serpentine form with a plurality of strai t portions joined together y return bends 1%, 18 and 19. The construction of the tube is suclnthat no two consecutive straight portions are of equal length, and the uppermost strai ht portion is connected to a supply manifo d 14a and the lowermost straight portion to a discharge manifold 15a.

This serpentine form of heat exchanger element, when heated by the passage of steam therethrough, behaves in a manner quite similar to the tube 10. Because of the compound formation of this tube, the movement is a compound movement and the tube 16 as a whole assumes e position about as shown in the dotted lines.

The heat exchanger elements reviousl referred to are constructed of tubing whic is circular in cross-section throu hout its length. In Figs; 6 and 7 there is i ustrated a form of heat exchanger element 10b which is similar in general proportions to tube 10.

In tube 10b thestraight portions 11b and 12b are of circular cross-section, but the curved portion or bend 13b, however, is of flattened cross-section.

With an increase in temperature and pressure there is a cooperative warping brought about by the ditference of elongation of the 11b and 12b and an efiort on the part of the curved portion 13b to increase its radius or straighten out. This cooperative action brings about a general deformation throughout the entire tube.

I make use of the motion imparted to tubes constructed in this manner and caused by the 7 normal variation in temperature which ordinarly takes place, or which can "readily be made to take place in the operation of many types of heat exchangers, such for example as evaporators,

the same after it has once formed.

In Fi 1, 2 and 3 I have shown the manner in which the tubular heat exchanging elements of the type illustrated in Figs. 3, l and 6 can be embodied in commerical forms of evaporators. In Fig. 1 a plurality of scaleshedding tubes 10 are arranged in the form of a tube bundle mounted within the containing shell 21. Steam is supplied to the tubes 10 through a suitable inlet opening 22 and after being condensed in its passage through the tubes 10 is discharged at the outlet 23 provided for this purpose.

The vapor generated in the evaporator shell rises into the dome 24 and leaves the evaporator through the opening 26. An inlet for raw water entering t e evaporator shell is provided at 28. The upper short legs of the tubes 10 are secured in a tube sheet 29 and the lower long legs in a tube sheet 30 and these tube sheets are disposed'in different vertical planes at a distance from one another, and are held in fixed position in a manner which will presently be described. The tubes in the tube bundle 20 are hence supported in the same way as described in connection with Fig. 4 so that the scale-shedding-movement takes lace when the tubes are subjected to change in tem erature.

Pre erabl the tube sections, an for this purpose sectional headers are employed in Fig. 3. Each of these headers 31 is a long narrow casting removably secured to the steam inlet manifold 32 by means of bolts 33 and 34 and to a drain manifold 35 by means bundle 20 is built in a plurality of of bolts 36.

Inlet manifold 32 extends horizontally across the upper portion of the evaporator shell and is placed in communication with the inlet 22 by means of a conduit 37 manifold 35 extends parallel to manifold 32 across the bottom part of the evaporator shell and is connected with the outlet 23 by a connection 38 which joins the drain manifold at its center.

Referring particularly to Fig. 1, each of the headers-31 has in its upper, part a distributing chamber 39 and in its lower part a collecting chamber 40, these chambers being separate by a partition wall 41. The distributin chamber 39 is relatively deep and extends or a considerable distance to the rear of the front face 42 of the header while collecting chamber is shallow. Tube sheet 29 forms the rear wall of distributing chamber 39 and tube sheet 30 forms the rear wall of collecting chamber 40.

The steam entering inlet 22 passes through conduit 37 and is delivered to each of the several headers 31 of manifold 32. Each of the as illustrated Drain 7 her 40 from which it headers 31 therefore receives its quota of steam from the manifold and the steam entering chamber 39 is distributed to the various tubes of the tube bundle. In passing through the tubes the steam is condensed and the hot condensate is discharged into collecting champasses to connection 38 and outlet 23. 1

The ends of the tubes 10 are preferably se cured in the tube sheets 29 and 30 by means of an expanding tool in the ordinary manner, and for the purpose of affording access to the tube ends, holes are made in the front face 42 of each header in register with the respective tube ends. A tool for aflixing the tubes to the tube sheet may be inserted through these.

holes and likewise accessibility is provided for cleaning the interior of the tubes. Each hole is tapped and provided with a suitable plug 43to render the chamber fluid-tight during the operation of the apparatus. Preferably each of the headers 31 supports two vertical rows of heating tubes arranged in staggered relation as shown in Fig. 3.

In the modified form of construction shown in Fig. 2, the arrangement of the various parts is identical with that just described in connection with Figs. 1 and 3, except that the staggering of the ends of the U-shaped heating tubes 10 is secured in a different Way.

Thus the evaporator shell, the raw water delivery, the vapor dome and vapor discharge are identical with the corresponding elements of Figs. 1 and 3, also the steam inlet and the outlet for the drains from the tube bundle.

'In order to provide for supporting the ends of the long legs of the heating tubes in staggered relation to the ends of the short legs, however, a somewhat different construction is employed. For this purpose the faces of the steam inlet manifold 32 and the drain discharge manifold 35' instead of being in a vertical plane, are arranged at an angle to the vertical, and the sectional headers 31 instead of being at right angles to the axes of the tubes 10' are oblique thereto. The headers 31' are, however, removably bolted in place as previously described in connection with Figs. 1 and 3.

The tubes 10 and 10' are preferably of small bore which not only gives them a large surface in proportion to their cross-sectional area, but at the same time provides a suitable degree of flexibility throughout their length.

Although it is preferable to mount the unequal length U-tube heating elements of Fig. 4- horizontally, this is not a necessary requirement and if desired they may be arranged vertically but in this event the headers should be placed at the bottom.

In the operation of the evaporators illustrated in Figs. 1 to 3 inclusive, the water level is preferably maintained 'as indicated by the dotted lines in Figs. 1 and 2 so as to just of the evaporator.

cover the tube bundles and also at about five-eighths to about two-thirds of the height of the shell so as to leave an adequate vapor space above the tube bundle.

The tubes are scaled by causing a quick expansion or contraction of the tubes. This may be accomplished by filling the evaporator shell with cold water and admitting steam to the tubes, or with hot water still in the shell the tubes may be flushed with cold water, also by successively introducing into the tubes a quantity of hot steam followed by a quantity of cold water, or vice versa. The elongation or shortening of the tubes thus produced will cause a distortion of the unequal length U-tubes and a distinct warping of the curved members as above described.

Because of the factthat the tube bundle 20 is constructed in sections, as previously described, it can be readily removed from the evaporator shell. Thus it is a simple matter to take off the shell cover and then take out the tube bundle sections one at a time.

By means of my present invention, the necessity of providing tube sheets at both ends of the tube bundle is eliminated, moreover the tube sheets 29 and 30 are both at the same end of the tube bundle and can be readily maintained in fixed relation one to another because of their proximity and because of the fact that they canbe readily made as a unitary structure, such, for example as the headers 31.

It will be understood that the legs of the tubes may be perfectly straight or that they may be slightly bowed, and the term straight as used in the appended claims is intended to include either construction.

The foregoing description of my invention in connection with the accompanying drawings, is to be considered as an exemplifying disclosure and the invention extends to'those forms of construction which come within the terms of the appended claims. for instance, the manifolds might be turned to the positions shown in the drawings, in which event all portions of each tube would lie in substantially the same horizontal plane. there may be a greater number of straight and curved portions than indicated and the longs and shorts need not be uniform, but may be varied if alternate lengths are 'different, so that the developed tube may conform to the contour of the containing shell I claim:

1. In a heat exchanger, a tube comprising a plurality of straight portions and at least one curved portion, each straight portion being serially joined through the medium of a curved portion of flattened cross section with at least one other straight portion of substantially different length, and means for Furthermore, referring to Fig. 5,

fixedly mountin whereby with c anges in temperature and measure a co-operative warping of the tube is bro ht about b the differences of elongation 0 the straig t portions and the effort of the curved portion to increase its radius resbilting in a general deformation of the to 2. In a heat exchanger, a U-shaped tube having legs of substantially difierent lengths and means for preventing relative displacement of the ends of the tube whereby variations in the lengths of said legs resulting from temperature chan es cause warping of the tube and thus facilitate the breaking up of scale-formations thereon.

3. In a heat exchanger, a plurality of U- shaped tubes having legs of unequal length, anda header having tube receiving surfaces displaced from one another in a direction longitudinally of the tubes and in relative}? fixed ositions, one end of each leg of said tubes ing secured in each of said tube receiving surfaces.

4. In a heat exchanger, a header having tube receiving surfaces in difierent planes and in relative fixed positions, and U-shaped tubes having legs of unequal length, one end of each leg being secured in each of said tube receiving surfaces.

5. In a heat exchanger, a tube of serpentine form comprising a plurality of substantially parallel straight portions joined together by return bends, and characterized by having no two consecutive straight portions of substantially the same length, wherebythe differences in lengthwise contraction and expansion of the consecutive straight ortions causes a deformationof the serpentlne tube and exerts a scale-shedding action upon the formations thereon.

6. In a heat exchanger, a.tube comprising a plurality of serially joined portions of different length with the ends of the tube contiguous with portions of substantially different length, and means for preventin relative displacement of the ends of said tu whereby the difference in deformation between ad- ]acent portions of difierent length resulting from temperature variations causes a flexing of the tube which aids in removing scale therefrom 7. In aheat exchanger, a tube comprising a plurality of serially joined straight portions with the ends of the tube contiguous with portions of substantially difl'erent length, and means for preventing relative displacement of the ends of the tube whereby the difference in lengthwise contraction and expansion between 'the adjoining straight portions of difierent le h causes said .stra ht portion to flex and t us exert ascaleshed mg action. upon scale formations thereon.

8. In a heat exchanger, abent tube comeach end of said tube, prising of di erent len a plurality of serially joined portions h with the ends of the tube contiguous wit ortions of substantially different length, said tube comprising at least one air 0 joined portions of difierent lengt constituting an assemblage in which the lon er portion has an over-change of length ue to temperature variations, greater than that of the other portion, and means for preventing relative displacement of the ends of said tube whereby the tubing of which said longer portion is composed is caused to warp in response to temperature variations, thus facilitating the breaking up of scale formations thereon.

9. In a heat exchanger, a tube comprising a plurality of substantially straight portions at least two of which are of different length, and at least one curved portion serially j oining at least two of the substantially straight portions, and means for securing the ends of the tube in relatively fixed relation to each other, the relative arrangement of the several portions of the tube being such that changes in temperature of the tube produce a general warping of the same.

10. A tube comprising a plurality of straight portions and at least one curved portion serially oining two of said straight portions, at least the curved portion of the tube having a flattened cross section, .and means for fixedly mounting each end of said tube, whereby a warping of the tube is produced at least in part by the effort of the curved portion to change its radius when changes in the temperature of the tube occur.

In testimony whereof I afiix my signature.

STANLEY BROWN.

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