US2612350A - Expansion compensated countercurrent heat exchanger - Google Patents

Description

Sept. 30, 1952 w S'TADLER 2,612,350

EXPANSION COMPENSATED COUNTERCURRENT HEAT EXCHANGER Filed Sept. 17, 1948 win-l INVENTOR Man; I. BY QM-L, (Junk, hunch ATTORNEYS Patented Sept. 30, 1952 EXPANSION COMPENSATED COUNTER- CURRENT HEAT EXCHANGER Walter L. Stadler, Bayside, -N.=Y.,.assignor to The Griscom-Russell Company, New corporation of Delaware York, N.-- Y., a

I Application'September 17, 1948, Serialhlo. 49,695

This invention relates to heat exchangers of the shell and tube bundle type, and theprincipal object of the invention-is to provide a heat exchanger of this type having generally improved characteristics, and particularly alleviating the difliculties encountered with such heat exchangers because of the expansion and contraction of the tubes and shell and the forces produced thereby.

It has heretofore been common practice to provide heat exchangers wherein the entrance and dischargeports for both the hotter and colder fluids are arranged at one end of the apparatus so that the metal of the shell and, also the metal of the tubes is free to expand longitudinally away from the end of the heater having the intake and outlet ports. However, in handling fluids at comparatively high temperatures, particularly when a large temperature change occurs in the passage of the fluids through the apparatus, the expansion of the tubes and shell on opposite sides of the central plane of the exchanger will be different, thereby producing in the apparatus a tendency toward lateral distortion with resulting strains on the metal, and particularly on the joints between the shell and the header as Well'as on the tubes in the header. In the apparatus forming the subject-matter of this application this difficulty is avoided even when handling fluids at high'temperature and with a difference of several hundred degrees between the entrance and exit temperatures of the fluids being treated.

The essential feature of my improved heat exchanger lies in the provision of means whereby, although the metal of the tubes and shell on opposite sides of the longitudinal axes ofthe heater are subjected to fluids of widely different temperatures, the longitudinal extension of the tubes and shell due to heat expansion will be substantially the same.

'One particular object of the present invention is to provide an improved construction of tube and shell heat exchanger wherein all thermal expansion stresses are substantially compensated for in the heat exchanger itself and the provision of flexibility in the piping to the exchanger is obviated.

Another object of the invention is to provide a tube and shell heat exchanger construction in which no temperature gradient exists circumferentially of the shell.

A further object of the invention is to provide a tube and shell type of heat exchanger in which the stresses produced by thermal expansion are negligible.

The invention will be understood through refer- 1 Claim.-' (01. 25779234).

ence to the accompanying drawings which show, by way of example, a preferred embodiment of the invention and one modification thereof. 1 In these drawings: 1 Fig." 1 isa view in vertical longitudinal section through the preferred construction of heat exchanger; and

Fig. 2 is 'a similar section of the right-hand end portion of the exchanger illustrating a modification. i

Referring first to Fig. l of the drawings, the heat exchanger comprises two legs of unequal length indicated generally by reference numerals l and 2, respectively. Leg I has a shell 3 preferably cylindrical in cross section and made of suitable metal, such, for example,-as steel. The shell 4 of leg 2 is similar to-shell 3 but is substantially greater in length fora purpose which-will be more fully explained below. The right ends of shell sections-3 and 4 are permanently mounted in apertures'in a heavy metal plate 5 in which the may be secured by welding, as indicated. V

The ends of the two shell sections are interconnected by means of a hollow dome-shaped header 6 which is provided with a supporting flange 1 in order that it may be secured to the outer periphery of plate 5 by means of a series of bolts 8. Thus, the interiors of shells 3 and 4 are placed in communication with one another, making in effect a single heat exchanger shell having a length equivalent to the combined lengths of the two shell sections. i

As the shell of the heat exchanger is divided into two unequal legs orsections as above described, so also is the tube bundle of the heat exchanger. That is to say, the heat exchanger tube bundle is divided into two unequal length sections indicated generally byreference numerals 9 and I0, respectively. These tube bundle sections correspond in lengthwith the effective lengths of their'respective shells 3 and 4, that is, the length of these shells from about the center of header 6 to the'respective tube sheets H and I2 in which theleft-hand ends of the tube bundle'sections 9 and H] are respectively mounted. The tubes are of metal such as steel or a non-ferrous alloy. In the preferred form of the apparatuses shown in Fig. 1, tube bundle sections 9 and H! are formed by a bundle of U-tubes with the return bends thereof indicated generally by numeral l3, arranged within the header 6, the shorter'legs of these U-tubes forming the tube bundle section 9 and thelonger legs, tube bundle section In, these tube bundle-sections being interconnected by means of the return bends l3. Tube sheets I -l and I2 are preferably welded to the interior of shell sections 3 and 4, respectively.

The hot fluid is introduced into the short le of the heat exchanger and the cold fluid into the longer leg of the exchanger, the two fluids passing through the exchanger in countercurrent relation. The :hot fluid may be sent through the tube-side or the'shell-side of the exchanger, as desired. As shown in Fig. 1, the hot fluid is introduced into the tube-side of the exchanger through a flange T-connection M of welded construction and which is welded onto the" outer side of tube sheet H. The inlet is through'the side passage of T-member l4 and the longitudinal passage is closed by a cover plate I'd-which may be removed for the purpose of cleaning or removing the tubes connected to tube sheet ll. Similarly, the outlet for the tube side of the ex- 4 vision for flexibility in the piping connecting these members is necessary or desirable. Also. no packed gland for a floating head is required, nor any expansion joints in the heat exchanger shell. Moreover, since the hot fluid enters one leg of the shell and the cold fluid enters the other leg, these connections are separated from one another so that there is no temperature. gradient circumferentially of any part of the shell.

In Fig. 2 there is shown merely a modification ofthe means of interconnecting the right-hand ends of the two tube bundle sections. Instead of employing U-tubes connected by the return bends l3 as in Fig. 1, the two tube bundle sections 9a and Illa of Fig. 2 are connected together at their right ends by means of an internal header 22. The right ends of the tubes in the two tube bundles are mounted in a common tube changer, which is at the left end of the longer leg 2, consists of a secondjflanged T-member I6 which is welded to tube sheet 12 and closed by a cover plate I1.

The inlet and outlet for the shell-sideof the exchanger are shown, respectively, as flanged connections 18 and 19. Flanged connection I8 is welded in an aperture in'shell 4 adjacent tube sheet l2, and connection I 9 is welded in an aperture in shell 3 adjacent tube sheet ll. p

The shell side of the exchanger is preferably provided with spaced transverse baflle .plates. These are shown at 20 for short leg I and at 2| forlong leg 2. .They are {suitably perforated and the perforations are staggered to produce a crosswise flow of the shell fluidsomewhat as indicated by the arrows.

Under. conditions frequently met with. in practree the relative. temperatures of the hotter fluid and the colder fluid, as well as the actual temperatures of these fluids, are such that the temperature of metal shell 3 of the shorter leg l will be considerably higher than that of shell 4 of the longer-leg 2. This is also true of the tube metal temperatures of the twotube bundle sections9 and H) of the short and long legs, respectively. Accordingly, the lengths of these short and long legs I and 2, both theshell lengths and the tube bundle section lengths, depends upon the increase in the average metal temperature above the temperature of fabrication and the coeflicientof thermal expansion of the metal used for theshell and tor the 'tubes,;as the case may be. The length of the legs is so chosen'that the product of length times the-co'eiflcient of thermal expansion times the increase in average metal temperature above the temperature of fabrication is the same for both-legs. The rate =of'expansion of theshell and tube metaliof the shorter and hotter leg will be greater than,forthe .-longer and cooler leg. However, the actual extension in the lengths -of the two tube bundle sections when the heat exchanger is brought to operating "temperature is substantially equal. 'Hence, although the right-hand end of the exchanger tends to move away fromthe respective left-hand end portions'of the two heat exchanger legs, the amount of movement of the return bends-13 which interconnect the tube bundle sections :9 and 1-0 is substantially the-same as the amount 'of movement'of the header -6, ,so that there-is very little, :if any, relative.movementbetween the tubes of bundles 5 and 1-0 and ytheir respective shells. x I 3 v With this arrangementvot the heat-exchanger, the cflang-ed inlet and =outlet con.nections 14,.)16, -18 and l9 remainflxed inlpositionrso that-noyproin "the appended claim.

sheet 23 to which header 22 is removably secured by means of a series of bolts 24. It will be understood that the remaining parts of the heatexchanger are constructed as previously described. With this modification, just. as in the construction shown in Fig. 1, there is no substan tial movement of tube sheet 23 and header 22 with respect to the header 6,, as the apparatus is brought up to operating temperature.

While the principal advantage of-my improved heat exchanger is obtained when designed as above described withone leg shorter than the other to compensate for. unequal heat expansion.

the structure is also useful when constructed with legs of equal length. The two separate she'll sections of small diameter have structural advantages over a single shell section of a diameter large enough to receive both branches of the U-tubes. Also the temperature change :is more uniform through the entire circumference of the "small shells than can be obtained with a single shell divided by b'afiles or otherwise.

It will also be understood that the invention is not limited 'to the precise forms of construction illustrated, as changes may be made within the scope 'and spirit of the invention as set vforth 'I claim: A heatexchanger for :fluids having two legs of unequal length, each including ashell section with a tube bundle section therein, a header .ior interconnecting said shell sections at one .end, means within the header forinterconnecting said tube bundle sections, said legs :being separated from onev another to permit independent longitudinal extensions resulting .from thermal expan si'on, thes'hellsec'tion hf said legs and the header forming .a continuous .passage for a fluid about the tubes, the tube bundles and ithemean inter.- connecting the tubes forming a continuous ,passage within the tubes and connecting means therefor for-.asecond fluid,-.-means.-for introducing the"ho'tter fluid .into one of said passages in the shorter leg and discharging it .from said passage from the longer..leg, and means .for introducing the colder fluid into the other passage r-inithe longer leg and discharging it from said otherpassagerfrom the shorter vleg, the respective :lengths of said .leg-s being such .that at 'a" predetermined operating temperature there will be substantially equal extension of the lengths of :the :legs idn'e to thermal expansion. g a I WALT-ER :L. s'rnnnan. 1

.(Referenccs -.on following ,pa'geg REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 10,179 Crawford Nov. 1, 1853 1,032,236 Patten July 9, 1912 1,605,987 Richey et a1 Nov. 9, 1926 Number Number Name Date Pew, Jr. Dec. 30,1930 Schneider Jan. 21, 1941 Bowman Oct. 20, 1942 FOREIGN PATENTS Country Date France June 22, 1922

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