US1826747A - Heat exchanger - Google Patents

Description

Oct. 13, 1931. H. c. DAvls ET AL HEAT EXGHANGER v Filed June 29, 1929 Patented Oc't. 13, 1931 UNITED STAT Es PATENT OFFICE HOWARD C. DAVIS, OF ELIZABETH, AND WILLIAM H. vTHOlMPSON, OF CHATH'AM,

JERSEY, ASSIGNORS TO DAVIS ENGINEERING CORPORATION, CORPORATION OF pELAw-ABE Application led June 29,-

In straight tube heat exchangers, the elements are subjected to frequent changes in temperature which cause them to expand and contract. This expansion and contraction vof the elements of the heat exchanger, unless r to compensate for the expansion and contraction lof the tubes bysome form of floating joint between the tube sheet and the casing. The floating joint, however, after use, com-v monly becomes worn and leakage occurs between the tube sheet and the casing.

In accordance with our invention, we construct a heat exchanger in which the elements are free to expand and contract with changes in the temperature without setting up strains that produce leakage. We employ a construction in which the tube'sheets may be rigidly secured to the casing, the arrangement of tubestbeing such that one end of the tubes is free to move longitudinally.

Among the characteristics of our invention is the fact that the arrangement of the tubes and the proportioning of the area thereof produces a high velocity in the heat conducting medium for sweeping the condensate off of the heating surface, thereby maintaining its heat transfer efficiency.

Another feature of our invention is. an arrangement of bales that insures a cross flow,

and maintains a uniform pressure dro throughout the length of travel of the liqui Specifically,- we employ a casing made up of two parts, separable near one end thereof, each part being closed at its outerv end with a suitable head. Near one end of the casing, a tube sheet is rigidly secured to the inner; surface thereof. A second tube sheet, spaced a short distance from the first tube sheet, is secured between the twoparts of the casing and forms with the first tube sheet a condensate chamber. A set of strategically located nism.

HEAT EXCHANGE-:n

1929. seriaiiwo. 374,625.

I tubes are secured at one end in the second tube sheet and extend longitudinally of the casing, the end opposite the tube sheet being closed or plugged. Tubes of aisecond set o f a lesser diameter are secured in the rst tube sheet and extend into and along the tubes secured in the second tube sheet, the inner tubes ending at a point adjacent the plugs in the ends of the I outer tubes. The Aheat conductin medium is lintroduced into the chamber in ront of the first tube sheet, enters the tubes of lesser diameter, flows along the tubes to the end thereof, and is returned through the outer tubes to the condensate chamber formed between the tube sheets .from which it has an outlet. The area of the inner and outer tubes is so proportioned that the fluid in returning through the outer tube is given a high velocity and sweeps the condensate off ofthe inner surface of the tubes and thereby maintains their heat transfer efficiency. The Huidto be heated is admitted to` the casing just '/beyond the second tubesheet and by a series of baffles is forced to take a cross flow back and forth transversely of the casing to the let.

The inner tubes are desirably centered in the` outer tubes. We accomplish this centering of the inner tubes by providing a tapering strap which is secured over the remote end of the inner tube. This strap also serves to guide the inner tubeslinto and along the outertubes inthe assembly of the mecha- The baffles arespaced in accordance with the change in the viscosity of the fluid to be heated so that there will be a uniform 'pressure drop in the heated Huid throughout its travel through the exchanger.

Our invention comprehends other features l iand advantages which will hereinafter more particularly appear. y

We shall now describe one embodimentof end thereof in which there is a suitable out` our invention -in connection with the accomc panyng drawings in which: f y

Fig. 1 is a longitudinal sectional elevation taken along tlievcenter line of a heat exchanger embodying our invention;

taken on the line 3 3 of Fig. 1, and

Fig. 4 is a longitudinal and end elevation of the end of an inner tube showing the centering strap thereon.l

For the purpose of illustrating our inven tion, we have shown it as embodied in an oil preheater.- lt is to be understood, however, that it is by no means limited to such use.

. The exchanger comprises acasing made up of ing assernb'l r"two parts-1 and 2-separable near one end thereof. A. tube sheet 3 having suitable acking 4, on either side thereof, is secured etween anges 5 and 6 by means of which the two parts of the casing 1 and 2 are secured together. Adjacent the head 7 of the part 1, a second tube sheet 8 is secured to the inner surfaces of the casing in sealing relation therewith. vTubes 9 are secured in the tube sheet 3 and extend along inside of the casing -parallel to the longitudinal axes thereof, to a point adjacent the headlO of the part 2. The ends of the tubes adjacent the head 10 are effectively sealed by plugs 11 which are desirably welded therein. Tubes 12, of lesser diameter than the tubes 9. are secured at one end in the tube sheet 8 and extend into the tubes 9 to a point adjacent the plugs 11.

The tubes 12 are provided at the end adj acent the plugs 11 of the outer tubes 9 with rods 13 formingtapered straps adapted to centerV the tubes 12 within the tubes 9. These straps 13 project beyond the ends of the tubes 12 in substantially the shape of a V, the sides of th1s V havlng end portions extending along the sides of the end portion of the tube 12"and secured thereto, so that thereby the inner tube 12 will be guided into and along the inside of the outer tube 9 in effectas Well as also servingto center these tu es.

Strategically located spacers. 14 serve to keep the bames in spaced relation so as to reduce the frictional resistance to the cross flow of the heated medium. The spacers 14 to which the baiies are secured are secured at one end to the tube sheet 3 and at the opposlte end to a plate 15 adjacent the ends of the outer tubes 9. The plate 15 is secured to the ends ofthe tubes by bolts lyengaging threaded openings in the plugs in the end of the spacing tubes 14, the .fluid carrying tubes 9 not being secured to this plate 15.

A series of baiiles 17 are located within the casing and produce a back and forth transverse flow of the. heated fluid through the casing. lSuccessive baiiies have a short segmental portion cut away near diametrically opposite sides of the casing; The' bales are spaced in accordance with the change'in viscosity ofthe heated fluid as it Hows through Ltheexchanger. In the exchanger readme' illustrated, which is adapted for preheating oil, the distance between the bames near the oil inlet is greatest, and decreases as the oil is heated and the viscosity lessened.

In the periphery of the casing, near the flange 6 of the section 2 thereof, an oil inlet 18 is provided. The first of the series of bames 17 is placed adjacent the inlet so that as the'oil enters, it flows across the tubes to the diametrically opposite sideof the casing, through the cut-away segmental portion of the bae, back across the tubes, and so on to the end of the casing where there is a suitable outlet 19 provided in the head 10. A. steam inlet 20 is provided in the head 7 of the section 1. rlhe steam entering the the tube sheet 8, proceeds along the tubes 12 to the end thereof, and is dischar ed into the outer tubes 9 returning along t e outer tubes to be discharged into the condensate chamberformed between the tube sheets 3 and 8. Adjacent the tube sheet 3 there' is a condensate outlet 21 provided in the wall of the casing.V L

By virture of the fact that the tubes are free at one end they may expand and contract with the changes in temperature without setting up strains that would cause leakage either' between the tubes and the tube sheet or between the tube sheet and the casing. Thev tubes 12 expand within the tubes 9, and the tubes 9 and the spacers 14 which carry the plate 15 expand independently. By this arrangement the possibilities ofy leakage caused by strains setup from the expansion and contraction of the elements of the exchanger, or duev to fatigue of material, by alternately setting up stresses and strains thereln, 1s avoided.

It is obvious that various changes may be made in the embodiment shown in the drawings and above particularly described within the principleand scope of our invention as expressed in the appended claims.

Claims:

1. A heat exchanger comprising-a casing having inlet and outlet openings therein, a tube sheet adjacent one end of said casing having openings therethrough, a second tube inlet 20, enters the tubes 12 extending through y sheet inthe rear of said first mentioned tube centering the tubes secured in the first men tioned tube sheet in the tubes secured in said second mentioned tube sheet, said means including tapering guides projecting beyond the ends of the inner tubes.

2. A heat exchanger comprising a casing.`

. tube sheet having openings having inlet and outlet openings therein, a ltube sheet adjacent one end thereof having openings therethrough, a second tube sheet in the rear of said first mentioned tube sheet having openings therethrough in alignment with and of greater diameter than the openings in said first tube sheet, and tubes extending longitudinally of said casing secured in said openings, the tubes secured in the openings in said first mentioned tube sheet extending within the tubes secured in said second mentioned tube sheet and having tapered guide straps von the end thereof remote from the tube sheet, said guide straps being substantially V-shape with their end portions extending over andl their tapered middle portions projecting beyond the ends of the tubes so as to form both guiding andcentering means, the ends remote from the tube sheet of the tubes secured in said second tube sheet being sealed. said casing havin an inlet in advance of said first mentioned tu e sheet and an outlet between said tube sheets, said casing also having another inlet 'ust beyond said second tube sheet and another outlet from the remote end of the casg- 3. A heat exchanger comprising a two part casing separable nearv one end thereof, a tube sheet having openings therethrough se cured between the parts of said casing, a second tube sheet secured to the inner wall of said casing in advance o f said first'mentioned i therethrough of lesser diameter than and in alignment with the openings in said first tube sheet. tubes extending longitudinally of said casing secured at one end in the openings in said tube sheets, the tubes secured in said second: tube sheet extending Within the tubes secured in said first mentioned tube-sheet; a series of baffles transverse to said casing to create a cross flow of the fluid to be heated, and spacers to which the baffles are secured extending longitudinally of the casing for maintaining the baiiies in spaced relation., said spacers being secured at one end to said first mentioned tube sheet.

4. A heat exchanger comprising'a two part casing separable near one end'thereof, a tube therethrough secured betweenthe parts of said casing, a second tube sheet secured to the inner wall of said casing in advance of sheet having openings therethrough of lesser ydiameter than and in alignment` with the openings in said first tube sheet, tubes extending longitudinally of said casing secured at one end 1n the openings` in said tube sheets,

the tubes secured in said second tube/sheet extending within the tubes secured in said first mentioned tube sheet and having tapered straps on the ends thereof remote from the tube sheet, a series of baflies transverse to sald casing to create a cross flow ofthe fluid said first mentioned tube to be heated, and spacers extending longitudinally of the casing for maintaining the baffles in spaced relation, said spacers being secured at one end to said first mentioned tube sheet and at the other end to a plate adjacent against the ends' remote fromv the tube sheet of the tubes secured in said first mentioned tube sheet.

5. A heat exchanger comprising an enclosing casing, a tube sheet extending across the casing to form an end chamber adjacent one end thereof, a second tube sheet extending across the casing in spaced relation with the first tube sheet to form a. second end chamber in the other end portion of the castudinally into and along the tubes of the first set into-which they open at their remote ends, a series of transverse longitudinally spaced baffles in the second end chamber, and longitudinally extending spacers for said baffies secured at one end to the second tube sheet for thereby supporting the-baliies, an inlet and an outlet being provided for passing through the second end chamber, and another inlet and another outlet being provided for independently passing another fluid through the other two said chambers and to include the passage of this latter fluid through the saidtwo sets of tubes from one of these latter chambers to the other.

Inuwitness whereof, we hereunto subscribe our signatures.

HOWARD C. DAVIS.

WILLIAM H. THOMPSON.

a fluid from one end to the other

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