US1769963A - Gas-cooling apparatus - Google Patents

Description

J PRICE GAS COOLING APPARATUS July 8, 1930.

Filed April 14, 1927 INVENTOR Jdsep/I Fr/ce rim HIS AT ORNEYS Patented July 8 1930 UNITED STATES- OF STAPLE-TON, NEW YORK, ASSIGNOR To GRIS'COM-RUSSELL COMPANY, or NEW YORK, 1\T.-Y.,'A CORPORATION or DELAWARE JosErn PRICE,

iPAT NroFF cE" GAS-COOLING APIPABATUS' Application filed April 14 1927. Serial No. 1ss;es3.

The present invention relates to heat exchangers, and. more particularly to apparatus for cooling gases in which the gas to be cooled is passed over the exterior surfaces. of a banker bundle of-tubes through which a liquid,-such for example as water iscircu lated. 5

In. numerous installations of gas cooling apparatus, such for example as in the cooling of electric generators by the circulation of air, hydrogen, or other gas in closed circuit through thegenerator and gas .cooler, it is important that the gas be forced through the h cooling apparatus at relatively high velocity. This'relatively high velocity is important in a closed circuit generator air cooling-system because of the necessity of reducing the volume of air or other gas to a minimum, so as to reduce the possibility of explosion, and the damage resulting in case an explosion should occur.

ture. In order to suit the space requirements in certain installations, convenience demands that the exchangers be made of considerable length as compared to the lateral dimensions of the bank of tubes. Long tubes'also assist in reducing the cost. Hence relatively long, as Well as relatively flexible, tubes are desirable. Even in apparatus having comparatively rigid tubes, the passage ofgas over them at high velocity. tends to cause undesirable vibration of the tubes, and with long relatively flexible tubes the tendency to.vibrate is much increased. t

' In this type of heat exchanger, further I more, it is p'articularlydesirable to rovide a construction which will insure to t e .greatest possible degree against the leakage either of the gas from the shellpf the exchanger, or of the water from the tubes. To do this it is highly important to reduce to negligibility, if possible, the stresses tending to loosen the-tubes from the tube sheets which are set up'by the-forces of expansion and contraction. In the case ofa generator gas cooler for example, the tubes are'subj ected to relatively wide dilferences .in temperature, and the cooler may be operated for a considerable periodof timeat one temperature, and then comparatively suddenly, be operated for .another considerable period of time at asub- I stantially higher or a substantially lower This occurs for example when present invention is to provide an apparatus oflmproved construction for extracting the heat from the air or other gas which has been circulated through an electric generator for the purpose of cooling the same.

" Another object of the present invention is .taO provide a gas cooler in. which there will be j little, 'ifany, vibration of the tubes of the cooler 'evenwhen the gas is passed through the cooler at relatively high velocity.

"Another object of the invention is to provide a gas coolerin which the possibility of leakage'not only of cooling liquid, but also of gas, is reduced to the greatest possible extent. Y

"A further object of the invention is to so construct -a gas cooling apparatus. that the tendency of the tubes to become loosened at their connections with the tube sheet shall be negligible. 1

A still further object of the invention is toso improve the construction of apparatus for transferring heat between liquid and a gas as toreduce the cost of manufacture of such apparatus. 0 i i In the accompa illustrated by way of example. one embodiment of the invention. In these drawings Fig. 1 is a-longitudinal section taken vertiying drawings, I have the tube sheets i and are arranged in parallel horizontal rows (Figs. 1 and 3). The tubes cally and centrally cooler; i Fig. 2 is an end 'view looking from the left of Fig.1; J

Fig. 3 is a vertical section taken on the broken line '33 ofFigQl showing in its through a generator "gas upper portion the fins inposition on the tubes, and in its lower portion the spacingfor connecting with the air or gas duct of 'an electric enerator cooling system, the duct leading rom,'the generator and carrying the warm or hot air to the cooling apparatus being connected at the top, and the duct leading to the generator and ret rning the cooled I air thereto being connected to the cobling apparatus at its bottom. ,The" sides of the shell 1 are preferably provided, with vertical struts 2 for stifiness'. I F I I Flanges 3 are provided; at the ends of the shell towhich the tube sheets 4 are securely clamped by means of collar bolts 5 '(Fig. ,6). The tubesfi are expanded attheir ends into are provided with metal fins 7 which are threaded in closely spaced relation upon the tubes. The close relationship of the fins may be seen' in Fig. '5, and a'oonvenient meth odoi manufacture is to provide the fins Withcircumferentiail, or artially circumferential,

V "bases 7 (Fig. 5) w ich serve both to aid in 4 securing a good heat conductivity between 4 the surface of the tubes' and the fins, and in -.au tomatically spacing the finsfluniformly by the ,desired amount. u x The fins arerof relatively thin sheet metal and are of elongated shape so as to span two or more tubes in a horizontal row .as.is to" be seen in F ig, 3. The tubes themselves are also of relatively thin material. size tube is made from No. 18 B. W. G. copper.

'stock and is approximately 1" in outside diameter and about 12feet in length. A tube of these dimensions and material is relatively flexible-and sags under its own weight to a substantial extent] when the tubes are supported in the tube sheetsiwithoutlany intermediate' support. The extent of the natural sag or bow at the centers of tubes "of this length andcha-racter is approximately 3".

Eventhough both the tubes, and the fins are relatively flexiblev by themselves, when a. line e-c, f;

top and bottom edges with suitable flanges A convenient the elongated fins are assembled upon the tubesin closely spaced relation as indicated in Figs. 1 and 5, and with the fins-secured to two or more tubes, the tubes thus secured together'are rendered substantially rigid in the common plane passingthrough the axes of these tubes, but flexibility-in the plane at tially unimpaired. -"The water. is caused to pass through the 'righ-tangles 'to this common plane is substantubes by means of caps or heads 10 and 15 placed respectively on. the left and right tube sheets. Cap 10 is divided byhorizontal'pan titions 12 into four full width lateral compartments 14, and cap 15, subdivided by horizontal partitions 16 into threelateral chambers. -Hence in the example illustrated the water which enters at the inlet 11 in cap 10 makes six passes through the apparatus before leavingat the outlet 13. r i The caps-10 and 15 are clamped against their respective tube sheets by means of the collar bolts 5 (Fig. 6') These bolts, as shown in this figure, each have a collar rigidly secured to the bolt midway between .its' ends. By the use'of these collar bolts either or, both of the caps can be readilyremoved for the -purpose of inspectingor repairing the tube joints,without loosening the tube sheetswith respect to the flanges 3. This is an essential feature of construction whenxt within the interior of the shell is of an ex plosive, poisonous or obnoxious character, or

where the 'ga'sis valuable. The caps can be, removed without fearof permitting the gas to-leak from the shell at the tubesheet joints.

each. horizontal row are 're'strained against lateral or horizontal movement by means of the elon ated fins which are secured to a plurality oi tubes in each'horizontal row. The

he gas which is It will be remembered that the tubes in tubes are rendered substantially rigid inlthe plane ofthe major-dimension of the fins.

The fins are shown as being secured to only two adjacent tubes inasmuch as it is extremely.

convenient tomanufacture the heating elements in this way.

- Itis well know-n'that when aresilient attenuated body, such for-example as av reed, is'supported to permit freedom of motion or vibration in a given plane, the body can be set in vibration through the influence of even a relatively low velocity stream or current'of air which is'directed over thebody at right angles to the plane of its freedom of motion.

In accordance with the present invention the tubes in each row are restrained against lateral movement in the common planeipassing through these tlibS by meanspf the finned constructiomand'the air or gas is directed through the gas passage of the cooling apparatus over the surfaces of the tubes at right angles to this plane, as indicated by the arrows in Fi 1. The gas iscirculated over the tubes and t rough the generator windings by r'educedby employing this construction.

As was mentioned above, the tubes which are preferably used in the gas cooler of the present invention, have relatively thin walls and are of considerable length so that they are relatively flexible and have considerable natural sag. According to the invention, tubes of this character are mounted in the tube sheets in .such manner as to preserve the natural sag. That is, the tubes are not subjected to initial tension in order to.

straighten them. It will be understood from Fig. lof the accompanying drawings that the tubes are installed in this manner, the curvature indicated being that which is the result of the sagging of the tubes under-the influence of gravity. The tubes are provided with spacing members 8 which are arranged in a vertical tier midway between the tube sheets. The spacers 8 are of such vertical dimensions as to space the horizontal rows of tubes apart sufiiciently to prevent contact or interference betweenthe fins of adjacent rows.- A bar 9 extends transversely from side to side of the casing in contact with the spacing members of the lowermost horizontal row of tubes and serves as a rigid support for the entire tier. 7

Q r The details of construction of the spacing members 8 are shown in Figs. 4 and 5 which show these members as made in complementary upper and lower halves having partially circular recesses for clamping over a pair of horizontal tubes. These halves are held 1n clamped relation to the tubes by means of a rivet or bolt 8*. .The spacing blocks may be secured to individual tubes if desired, but it is more convenient to make themof sufficient length to spanat least two tubes because they can be readily clamped in place by the use of a single clamping rivet or bblt.

It will be understood that from the manufacturing standpoint it is preferable, when the apparatus is cold, to have the spacing members 8 in a given tier in contact, or substantially in contact, with one another sothat the centers of all of the tubes of the tube bundle or bank are firmly supported by the bar 9. Under these conditions when the apparatus is placed in operation, and the metal of the tubes is heated by the passage of the gas over them, the resulting expansion of the tubes causesthe tubes to bow downwardly between the tier of spacing blocks 8, and each of the tube sheets. Thusthe already sagging tubes bow or flex in a plurality of nodes throughout their length intermediate the tube sheets, and even though the tubes are held firmly at their centers againstdownward movement, and laterally throughout their entire length against lateral movement, nevertheless the stresses tending to loosen the tubes from the tube sheets are effectively re- 7 moved. For this reason leaks at the joints of the tubes with the tube sheets are not likely to occur.

, I should regard tubes arranged so that their spacing blocks 8 do not quite contact with one another when the tubes are cold, but;

which do come into contact when the tubes are heated, as bein the tubes bow in a plurality of nodes when the tubes are heated further.

With very long tubes, such for example as tubes over about 15' feet in length, it is de sirable to provide two or more tiers of spacing blocks 8 and transverse bars 9, and with this construction the tubes will bow in three or more nodes instead of two as in the example shown in the drawings. By passing the gas over the tubes gas tends to hold the spacing blocks firmly in contact with one another, and the lowermost blockagainst thebar 9. This relieves the tube sheet joints of a certain amount of stress which would be present if the air were forced through the apparatus in the opposite direction, and this stress would be largest 1n the upper tubes of the bank.

While I have illustrated my invention in connection with a heat exchanger in which the lateral rigidity is'imparted to the tubes by means of fins which span a plurality of tubes, it is to be understood that the lateral rigidity may be secured in other ways', and the tubes may be provided with fins which are mounted u on individual tubes only, or the tubes may ave no fins at all. Thus the lateral stiifness may be provided by the spacing blocks, particularly if the ends of the blocks, as shown in Fig. 3, are made to touch each other.

within my invention it If still greater lateral rigidity from top to bottom in the direction of the arrows the pressure of the is desired, means may be provided on the sides of the shell of the exchanger for engaging'the-outer ends of the outer supporting blocks in each row.. 7 v

It is also to b'e'unders'too d that, when relativelyflexible tubesareemployed, it is not necessary that they be given just the natural sag which they assume when supported .only at their ends, and 'no more or no less .v ,l/Vith flexible tubes the extent natural sag, manufacture,

of bowing may be increased or diminished above or below the depending upon convenience in;

bowing to relieve the stresses at the tube sheet joints under expansion and contraction.

. It will beunderstood'from the above that when the gas is forced over the tubes, which in many installations may be at relatively high veloeit the passage of this gas tends to set the tubes vibrating. This tendency to vibrate is by far the greatest in the horizontal or'lateral direction, and is effectively prevented by the lateral rigidity imparted'by the fins. The air passing the tubes at right angles to this plane of rigidity produces little,

if any, vibration in the tubes. The tendency to vibrate vertically which is produced by the passage of the air over the tubes is eliminated by causing the tubes to assume a natural'bow shape in the direction of movement oi the air, andby thesupport afforded by the one or more tiers of spacing blocks8. The provision of 'a natural bow of the tubes in the direction of movement ofthe air also assists in reducing the tendency of the tubes to vibrate laterall since a straight tube,

or a tube which isowed in the opposite direction to the movement of the airis in relatively unstable equilibrium as compared to a tube which is bowed in the direction of the air movement, and therefore vibrates more readily.

' I claim 1. In a heat exchanger comprising a bank of relatively flexible tubes secured at their opposite ends to a pair of tube sheets, means for restraining the tubes throughout their; length against lateral'movement in a' given plane, and means for restraining their later- J al movement in any direction at one or more points intermediate the ends of the tubes so [as to cause each tube to bow in. a predetermined direction 'in a plurality of nodes un-' der the influence of the forces of expansion and contraction.

. 2. In a-heat exchanger, a bankof relatively flexible tubes, tube sheets into which the tubes-are secured at their ends, said tubes being arranged in substantially parallel rows,

s mounted in closely adjacent relation throughout the length of said tubes, each fin spanning a plurality of tubes in 'a row and renderin the tubes substantially rigid in the 'planes-o .said rows, and means for restrainjlng he tubes against movement at rightr anglesto said planes at one or more points intermediate the ends of the tubes so as to cause the'tubes to bow in a plurality of nodes tube sheets into which the fins mounted in closely adjacentrelation substantially tubes, 05

throughout'the length of said each-fin spanning a; lurality of tubes in a row and rendering t e tubes substantially rigid in the planes of said rows, spac'-. .ing members secured to the tubes of each row and arranged in a tier substantially perpendicular to the axes of the tubes, and a sup port fixed at the bottom of the bank of tubes for engaging the spacing members of the bottom row of tubes, the said. spacing members engaging with one another and with said support to maintain the tubes in spaced parallel relationship and to cause each tube to bow in a plurality of nodes under the influence of the forces of expansion and contraction.

4. In a heat exchanger, a bank ofslender flexible tubes, tube sheets into which the tubes are secured at their ends, said tubes being arranged in parallel rows, fins secured to the tubes in closely spaced relation throughout the length thereof, each fin spanning a plurality of tubes in a row and restraining the tubes against lateral .movement throughout their length in the plane of said row, and means for passing a stream of gas over the surfaces. of said tubes in a direction substantially at right'angles-to the plane in which said tubes are restrained against lateral mpvement.

5. In a heat exchanger, a pair oftube sheets, a plurality-of slenderv flexible heat transfer tubes secured at their ends in said tube sheets, means for rendering said tubes substantially rigid in one direction throughout their length, said tubes being initiallybowed in a direction .at right angles thereto, means for engaging the tubes at a point intermediate their ends for maintaining said point in fixed position, and means for passing gas to be cooled over said tubes in the direc tion in which said tubes are bowed.

6. In a heat exchanger, a bank of slender flexible thin-walled tubes, tube sh'eets into which the tubes are secured at their ends, said tubes being arranged in substantially parallel rows, fins mounted in closely adjacent relation substantially throughout the length of said tubes, each fin spanning a plurallty of tubes ina row and rendering the tubes substantially rigid in the planes of said rows,

spacing members comprising pairs of complementary blocks laterally applied to the tubes and being arranged in a tier substantially perpendicular to the axes of the tubes,

and a support fixed at the bottom of the bank of tubes for engaging the spacing members of the bottom row of tubes, said spacing members engaging with one another. and with said support to maintain the tubes in spaced parallel'relationship and causing each tube to bow in a plurality of nodes under the influence of the forces of expansion and contraction.

7. A heat exchanger element comprising a pair of slender flexible thin-walled tubes having heat radiatin fins secured in closely adjacent relation su antially throughout the entire length of Said tubes' and rigidly holding the same in spaced parallel relationsh ip to one another, and a spacin member comprising a pair of blocks secure opposite one another uponsaid tubes intermedlate the ends thereof.

In testimony whereof I afiix my signature.

' JOSEPH PRICE.

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