US1770375A - Heat-interchanging apparatus - Google Patents

Description

July 15, 1930. D. G. BRANDT HEAT INTERCHANGING APPARATUS Filed Feb. 6, 1928 2 Sheets-Sheet l nvenfow DA W0 6. BRANDT July 15, 1930. D. a. BRANDT HEAT INTERCHANGING APPARATUS Filed Feb. 6, 1928 2 Sheets-Sheet 2 51-41mm DAV/U 6. BRANDT Patented July 15, 19.30

UNITED STATES masts PATENT OFFICE DAVID G. BRANDT, OF WESTFIELD, NEW JERSEY, ASSIGNOR TO DOHEBTY RESEARCH COMPANY, OF NEW YORK, N. 'Y.,

A CORPORATION OF DELAWARE HEAT-INTERCHANGING APPARATUS This invention relates to improvements in heat interchange apparatus, and more particularly to heat interchange apparatus of the recuperator type designed for use in effecting eflicient indirect heat interchange between two confined bodies of fluid flowing continuously across opposite faces of a heat conductant partition wall or diaphragm.

The capacity of a heat interchange alpparatus of this type is dependent particu arly -on the extent of the heat conductant diaphragm surface between the two bodies of fluid undergoin indirect heat interchange, and on the rapidity and uniformity with which the bodies of'fluid are circulatedin contact with the surfaces of the diaphragm.

An object of the present invention is to provide heat interchange apparatus of the recuperator type having a lar e heat interchanging heat conductant diap ra-gm surface capable of withstanding substantial pressure differentials obtaining between the heating and heat receiving fluids passed over opposite facesthereof. I I

Another object of the invention is to provide heat interchange apparatus of the recuperator type in which the heat conductan-t diaphra ms form long sinuous pressure resistant fines of extensive surface WhlCl'l may be assembled in compact and accessible form within an outer enclosed cylindrical shell.

More specific objects of the invention are: To provide a recuperator assembly of the above character so designed as to permlt ready access through the outer shell to every portion of the inner flues; to so construct theinner fines of the recuperator as to provide long devious paths for the fluid to be heated and a proportionately large heat transfer surface per unit of space occupied separating the fluid to be heated from the heating fluid; to provide a form of high pressure resistant recuperator flue which can be assembled from a plurality of uniformly-shapedindividual-- ly removable segments into a compact nest of annular cross section; to providerecuperatorflue segments of uniform, sinuous and contact sha e that can be readily castin mol' assem led in multiple into coils and the other fluid flows.

nests of annular cross section, and cleaned without dismantling.

WVith these and other objects in View, the invention consists in the improved heat interchange apparatus hereinafter described and more particularly defined in the claims.

The various features of the invention are illustrated in the accompanying drawings, in which:

Fig. 1 is a view in vertical section, with parts broken away, of the upper part of a cylindrical dephlegmator column in which there is incorporated a recuperator assembly illustrative of a preferred form of embodiment of the present invention, taken on the line 11 of Fig. 2;

Fig. 2 is a cross section of the recuperator, taken on the line 22 of Fig. 1;

Fig. 3 is an enlarged plan view of one of the flue or tube segments which, assembled in multiple, make up the sinuous annular {(pcuperator flues or flue sections shown in Fig. 4 is a side elevation of the flue segments shown in Fig. 3;

Fig. 5 is a plan view of one of the U-sha ed flue segments shown in side elevation in ig.

*1 as connecting two adjacent vertically spaced tiers of annular sinuous flue coils in the assembled recuperator.

Fig. 6- is an end elevation of the U-shaped flue segment shown in Fig. 5.

According to the present invention the warmer and cooler fluids between which a heat interchange is to be affected are caused to flow, usually under pressure, in sinuous or baflied streams separated by relatively thin but strong heat conductant diaphragms through which the interchange of heat takes place. I The heat interchanging diaphragm is preferably formed into one or more long sinuous flues through which one of the fluids flows, a number of restricted passages bein formed around and among the bends an straight portions of said flues through which 05 p The flues are in turn mounted in outer enclosed, re'ferably cylindrical, casings or shells capable of withstanding the pressures under which the fluids are supplied, in such a manner as to be accessible .100,

. around the fines.

for cleaning or repairs without being removed from the shell.

The recuperator has been illustrated as incorporated in the upper part of a dephlegmator column of a type used in the fractional distillation of petroleum oils and like fluid mixtures, and accordingly it will be assumed in the interest-s of clarity in the following description that the recuperator is to be used for heating oil in the liquid state as it is passed downwardly through the inner flues of the recuperator by indirect heat interchange with hot oil vapors and gases passed upwardly through the recuperator and It will be understood, however, that the recuperator is not limited to such use; but on the contrary is applicable generally for eflecting indirect heat inter change between any two bodies of fluid passed in either direction therethrough in contact with opposite faces of the heat conductant flue-shaped diaphragms.

In the accompanying drawings (Fig. 1) the numeral 10 designates the integral closed cylindrical outer shell and end closures of the dephlegmator column which also serve as the outer shell of the recuperator forming the subject of the invention. The recuperator shell-10 is preferably constructed of heavy metal capable of withstanding high internal pressures and may advantageously be lined, externally or internally or both, with some good heat-insulating and/or corrosion-resistant material (not shown). A manhole entrance 12, closed by a removable cover 14, is provided in one end of the shell 10 in position to afford ready access from outside the shell to a passage 16 extend .ing through the recuperator section of the dephlegmator along its longitudinal axis (Fig. 2) as far as the top tray or bubble plate 18. From this point access is had to the lower trays of the dephlegmator and to lower I tiers or coils E of the recuperator flue which are mounted between the trays of the dephlegmator (shown in Fig. 1) through combined reflux overflow and as and vapor uptake pipes 20. A gas am? vapor ofitake 22 leads oil from thevtop of the recuperator adjacent the manhole opening 12, and one or more pipes 24 (two are shown in Fig. 1) serve to introduce oil (or other fluid) to be heated from some outside source through the shell 10 and into the first of a connected series of W-shaped tube sections 26, a plurality of which when assembledend to end make up continuous flues 28, the walls of which comprise the heat conductant diaphragms of the recuperator.

The fiues 28 (Figs. 1 and 2) are disposed in the recuperator structure in the form of a nest of vertically separated and closely spaced connected tiers A, B, G, D, E, etc.; each tier lying in a plane at right angles to the longitudinal axis of shell 10 in the form of an annular sinuous coil disposed concentrically about the axial manhole passage 16. Each of the tiers A, B,.C, D, etc., comprises a plurality of thetube sections 26 assembled end to end. In the recuperator design illustrated in the drawings two continuous enclosed flues 28 are shown for conducting oil to be heated through the recuperator. Each flue 28 is supplied with oil by one of the two pipes 24, and each of the horizontally placed tiers A, B, C, D, E, etc. of each pair of fiues is semi-circular in form, occupying in the assembled recuperator substantially one-half the annular space between the central opening 16 and the inner lining of the shell.

Each of the W-shaped tube sections 26 embodies in an integral structure two substantially 90 bends 30 and 32 disposed back to back, one on the open end of each of two outside legs 34 and 36 of the structure, together with three return or U-bcnds 38, 40 and 42 successively disposed in 'the structure and with their appurtenant connecting legs 44 and 46 forming a closed connection between the ends of legs 34 and 36 opposite those on which bends 30 and 32 are placed. The two outside U-bcnds thus face in one direction and form the base of the W-shaped structure while the inside U-bend 40 faces in the opposite direction and lies in the center of the structure. The longitudinal axis through the center of the W-shaped tube section 26, including all of its appurtenant legs and all of the five bends, lies in a single plane. The outer legs 34 and 36 are preferably of substantially equal length, and in the assembled recuperator the substantially right angle bends 30 and 32 are disposed at opposite ends of the legs 34-and 36 in .the periphery of passage 16, while the return bends 38 and 42 lie in an arc paralleling and closely spaced from the inner periphery of shell 10. The return bends 38 and 42 lie in closely spaced but not abuttingl relationship, and the legs appurtenantt ereto are disposed in a closely spaced relationship approaching the parallel but converging slightly in the direction of the open top 0 the structure, thus imparting a roughly isosceles triangle form to the structure viewed as a whole. While the longitudinal axes of the outer legs 34 and 36 of the sections 26 as they are illustrated converge toward a point located some distance beyond the bends 30 and 32 at the open ends thereof (such point lying in about the longitudinal axis of the shell 10 in the assembled recuperator) the backs of the bends 30 and 32 are not brought by such convergence into abutting relationship, though they are brought into a closely spaced or compact relationship. It will be observed that legs 34 and 36 are somewhat longer than the appurtenant legs 44 and 46 of the inner return bend 40, with the re sult that bend 40 lies some distance from bends 30 and 32 and nearer the base of the structure-formed by bends 38 and 42. In the assembled recuperator all of the legs 34, 36, 44 and 46 of each W-shaped tube section 26 lie in closely spaced relationship in substantially radial axes diverging from and at right an les to the'lon itudinal axis of shell 10.

ach W-shape tube section 26 is preferably formed by casting it as an integral unit from material such as cast iron, brass or other relatively strong heat-conductant pressureand-corrosion-resistant substance. In casting sections 26, openings 48 are preferably left in the mold at the back of each of the U-bends 38, 40 and 42-of the section in order to accomnodate supports for the refractory core which is employed in the casting operation. After the casting has been completed and this core has been removed the holes 48 thus left in the casting are drilled to a suitable uniform size and tapped, and plugs orequivalent closures 50 are inserted and sealed in place therein.

Since one of the principal features of design of thew-shaped tube'sections 26 is to provide a heat-interchanging surface of proportionately large area per unit of space occupied, it is sometimes advantageous to embody in the outer legs 34 and 36 thereof angles or equivalent moderate curvatures 52, with the object of drawing their free ends more closely together-above the inner return bend 40 to thereby reducethe cross-sectional area of the spaces 54 lying between-the outer and inner legs of the structure. For the same reason the inner legs 44 and 46 appurtenant to the return bend 40 are disposed in compact closely spaced relationship with the object of reducing as far as practicable the cross sectional area of spaces 56 lying therebetwcen. The preferred form of tube section 26 illustrated in the drawings has-a shape resembling that ofthe letter W except that the outer legs 34 and 36 depart somewhat from the analogywith the letter W by diverging toward rather than away from the base of the structure.

'Bolting cars 58 or their equivalents are formed at intervals about the circumference of each of the open ends of sections 26 as an integral part thereof, and spacer bosses 60 are also preferably cast as an integral part of these sections at points immediately above and/or below the return bends38, 40 and 42 or at other suitable points of the structure.

Each of the tiers A, B, C, D, E, etc., composed of connected W-shaped sections 26, is in turn connected to the tier immediately above or below the same by an especially designed return bend 64 (see Figs. 1, 5 and 6), such bendsin the assembled 'recuperator lying ina vertical plane at right an les to the horizontal plane of the tiers whic it connects. Two right angle or substantially 90 tubular bends 66 are formed as an integral part of the bends 64, one on the open end of each of its legs 68, the open faces of the bends 66 being faced in a horizontal direction at right angles to the vertical plane occupied by the return bend in the assembled recuperator. Bolting cars 58 are formed as an integral part of the bends 66 thereby afiording means for attaching the return bend section 64 to the open ends of the first and last in the series of W- shaped sections 26 comprising the respective tiers to be connected. These return bends 64 are preferably formed of cast metal in much the same manner as that employed in forming sections 26, openings 48 being left at the back of the return bend which are later tapped and sealed with plugs 50.

While the foregoing description sets forth in more or less detail the preferred shape of the tube sections 26 and the preferred number and relative positions of the bends and connecting legs embodied in their structure, it will be evident that such tube units may be formed in other ways than that described and may embody bends and appurtenant straight or curved legs assembled in an integral or multiple part tube section having a preferably uniform' shape more or less closely analogous to that of the letters V and W, without departing from the spirit of the invention. The tube sections 26 with their bends and appurtenant connecting legs are designed to compactly fill the area of an annulus segment. The widest part of each of the preferred form of W-shaped tube sections 26 illustrated lies in the plane of the longitudinal axes passing through the tubes which form the section and is measured by the distance bet-ween the outsides of the two outer return bends 38 and 42 formin the closed base of the section, and the maximum width of the section is practically limited. to a dimension which will permit insertion of the section as a unit into the shell 10 through the manhole 12. The size and form of the unit flue section also depends somewhat upon the size and Weight of the flue of which these sections form a part. In the same way the maximum allowable width of each of the return bends 64 is preferably such as to allow of its insertion as a unit through the manhole opening 12 for assembly within the shell 10.

In assembling the recuperator the W- shaped tube sections 26 and the return bends 64 are inserted into the shell 10 through the manhole 12, and are then connected in end to end relationship inthe manner illustrated to form in order the superimposed tiers E, D, C, B, A connected by the return bends 64. In case the sections 26 are to be assembled to form two continuous flues 28 through the (see the drawing). If on the other hand all of the sections 26 and bends 64 are to be assembled in the form of only one continuous flue 28, the nest of tiers A, B, C, D, E, etc. will occupy all the annular space between the opening 16 and the inner periphery of the shell. It will be understood that if desired the sections 26 and return bends 64; may be assembled into three, four or even more continuous flues 28 traversing the length of the recuperator.

The opposite open ends of each of the W- shaped sections 26 and of each of the return bends 64 are provided respectively with male and female joints comprising respectively annular noses 69 and sockets 70 to fit said noses (Fig. 3). Sealing rings or gaskets of asbestos, soft metal or the like may be disposed between the opposed surfaces of the nose 69 and socket 70 making up the joint between the adjacent flue sections, and sections 26 and 64*- may then be drawn and held rigidly together by bolts 72 passed through the cars 58 on the'outside of each of the opposed connected faces of the sections. AL ternatively such connections may be made by forming sockets similar to, but somewhat deeper than, the socket 70 illustrated, on both open faces of each tube section, and by then drawing the sections together over a tight fitting sleeve collared by said sockets in the opposed ends of the adjacent sections 26 and welded or swedged into place (not shown).

Referring more particularly to Figs. 1 and 2 of the accompanying drawings, one of the heat interchanging fluids, preferably the cooler heat receiving fluid, for example oil, is

admitted to the upper end of the shell 10 through the inlet pipes 24 and flows in a devious horizontal path through the tube sections 26 making up the upper tiers A of the two continuous fines 28 extending through the recuperator in the direction of the arrows (see Fig. 2). After traversing 'the semicircular devious horizontal path occupied by the tiers A, the oil passes downwardly through the first return bends 64 into. the underlying tiers B of the recuperator fines and follows a devious path through the sections 26 composing tiers B in a reverse'horizontal direction to the path followed in traversing tiers A. From tiers B the oil passes downwardly into tiers C through the connecting return bends 64 and passes through tiers C in horizontal paths paralleling those previously traversed in tiers A. Fromtiers C the oil passes downwardly into tiers D and after traversing the same again passes downwardly into tiers E, and so on through the recuperator. In thus passing through the fines 28 of the recuperator the oil is rapidly heated by indirect transfer of heat abstracted from the heating fluids through the walls of the fines and is finally removed at the lower end of the recuperator through an outlet pipe (not.

D, E and the spaces 54 and 56 lying between and around the legs of the W-sha'ped tube sections composing the recuperator fines; In thus passing through the recuperator the heating fluid is rapidly cooled by contact with the outside walls of the flues 28, with resultant indirect heat transfer to the fluid receiving heat as it passes through said fiues; the thus cooled gases and vapors being finally received at the upper end of the shell 10 and removed through the outlet 22. In order to prevent the heating fluid from passing upwardly through the central aperture 16 formed in the major axis of the recuperator shell 10, a deflector 74 having an end closure 76 over its top is mounted in the opening 16. The deflector 74 serves to blank off the passage 16 and thus prevent the heatingfluid from bypassing the passages 54 and 56 surrounding the fiues carrying the heat receiving fluid. The deflector 7 4 is preferably constructed in three or more segments 78 having inwardly extending lugs 80 (Fig. 2) which are suitably drilled to enable segments 78 to be bolted together. By building the deflector in segments it can be readily inserted strong and which at the same time lends itself to close spacing of the legs and bends making up the tube sections 26, thereby providing a larger heat transferring surface per unit of space occupied.

As indigated above, the cross sectional area of the opening 16 is preferably such that it will permit access to every portion of the recuperator for the purpose of cleaning, replacing or repairing each individual segment of the assembled fiues. When access to the fines of the recuperator is desired the closure 7 6 of the deflector 7 4 is first removed and the rest of the deflector is then removed or placed to one side after dismantling it into its several sections 78. If it is desired to clear the fines this can be readily accomplished without disconnecting the individual flue sections 26 simply by drilling out or otherwise remove ing the plugs 50 in the ends of the inner re- The purpose of this design,

cry of opening 16 and the opening 48 in the end of the inner return bends 40 of the section 26 is suiiicient to permit insertion and manipulation of drill spindles and other tools employed in removing plugs 50 and in cleaning the tube sections or repairing same.

The heat receiving and heating fluids are caused to pass only through flues 28 and through passages 54 and 56 between and around the fines in close heat transferring relationship thereto; flow through other portions of the apparatus being prevented by baffles or blanketing devices such as deflector 74. Since it is desirable to maintain the same velocity of flow of the fluids on both sides of the heat conductant diaphragm through which heat is being transferred in the recuperator, it is preferred to so adjust the ratio between the sum of the cross sectional areas of the flues in one tier and the sum of the areas of the spaces between and around said flues as to maintain substantially the same velocity of flow of fluid through the flues and through the passages surrounding the fines.

In the recuperator design illustrated in the drawing, each W-shaped tube section is shown as occupying a 30 segment of theannular space surrounding the central opening 16. It will be understood, however, that the invention is not limited to the use of any particular number of sections 26 in a tier or to any particular number of tiers in a bank or nest, nor to any particular number of flues. The number of flues and the number of tiers making up the flues will depend primarily on the volume of oil or other fluid to be heated and/or on the amount of heat contained in the hot gases and vapors or other heating fluid.

There is no preferred manner of supporting the flues, or the tube nests and tiers making up the fines, within the shell. The flues may for example be supported within the shell by deflector brackets 82 projecting from the inner walls of the shell 10 immediately above the top dephlegmator tray 18 (see Fig. 1). Similarly the deflector 74 may be supported within the shell by simply resting brackets 84: on its outer periphery on the tops of the joints between connecting legs of the W- shaped sections making up the upper tiers of the flues 28-. Each of the tiers A, B, G is supported in the structure and spaced from the tier immediately below it by the spacer bosses 60 forming an integral part of the W- shaped sections of which the tiers are composed. In order to avoid undue crowding of the disclosure only a few tiers and only a, few

of the spacers between the tiers have been shown.

As already indicated, the fluid to be heated is preferably passed through the recuperator in a direction which is in general countercurrent to the direction followed by the heating fluid in traversing the recuperator. One of the fluids, however, and preferably the heat receiving fluid, is forced to follow a long devious course in traversing the recuperator through paths which extend at right angles as Well as countercurrent to the paths followed by the heating gases.

The above invention having been thus described what is claimed as new is:

1. A W-shaped tube section embodying in an integral compact structure lying in one plane, two outer converging legs, the diverging end of each of said legs being joined to the other by three successive return bends and by the connecting legs appurtenant thereto.

2. A W-shaped tube section embodying in an integral structure lying in one plane, three successive return bends with their appurtenant connecting legs and two outer converging legs each open at one end and connected at its other end to the two outside return bends, said two outside return bends forming the base of the structure and the converging open ends of said outer legs forming the top of the structure.

3. A W-shaped tube section embodying in an integral structure lying in one plane, two moderately bent converging outer legs of uniform length, one end of each of which is joined to the other by three successive return bends and by two inner connecting legs appurtenant thereto.

4. A W-shaped tube section embodying in an integral structure lying in one plane, two outer converging legs of uniform length, one end of each of which is joined to the other by three successive return bends and by two inner converging legs appurtenant thereto,

' said inner legs being of substantially equal but shorter length than said outer legs.

5. A Ll-shaped tube section embodying in an integral structure lying in one plane, three successive return bends with their appurte nant connecting legs and two outer converging legs each open at one end and connected at its other end to the twooutside return bends, said two outside return bends forming the base of the structure and the open converging ends of said outer legs forming the top of the structure, all of said legs and bends being disposed in closely spaced relationship.

6. A tube section embodying in an integral structure lying in one plane, two outer legs of substantially equal length, one end of each of which is joined to the other by an inner connecting leg, the unconnected ends of said outer legs converging and having right angle bends formed thereon in closely spaced back to back relationship.

7. A W-shaped tube section embodying 1n an integral structure lying in one plane, three successive return bends with their appurtenant connecting legs, and two outer legs each open at one end and connected at its other end to the two outside return bends, said two outside return bends forming the base of the structure and the open ends of said outer legs forming the top of the structure, and spacer bosses extending laterally from said section.

8. A W-shaped tube section embodying in an integral structure lying in one plane, two outer converging legs of uniform length, one end of each being joined to the other by three successive bends and by two inner converging legs appurtenant thereto, said inner legs being of substantially equal but shorter lengths than said outer legs, and tapped and plugged openings in the end of each of said return bends.

9. A recuperator tube section embodying, in an integral structure lying in one plane and disposed in compact form within the area of an annulus segment, two outer converging legs each having a closed end joined to the other by appurtenant inner connecting legs and each having a free end, the axes of said legs converging substantially toward the center of the annulus, and each leg having a substantially right angle bend, each bend faced back to back in closely spaced relation to the corresponding bend on the other leg.

10. A W-shaped tube section embodying in a. structure lying in one plane, two outer legs of substantially equal length one end of each of which is joined to the other by three successive return bends and by the connecting legs appurtenant thereto, the unconnected open ends of said outer legs having substantially right angle bends placed in spaced back to back relationship thereon, and bolting ears formed on eac right angle bend.

'11. A tube section embodying in an inte ral structure lying in one plane, two outer e s of substantially equal length one end of eac of which is joined to the other by inner connecting legs appurtenant thereto, the unconnected open ends of said outer legs having substantiall right angle bends placed in back to bee relationship thereon, and male and female joints formed respectively on the open ends of said outer legs for attachment to a corresponding section.

12. W-shaped tube section embodying in an integral structure lying in one plane, two outer legs of substantially uniformlength, each connected at one end to the other by three successive return bends and two shorter connecting legs appurtenant thereto and each outer leg having at its open end a right an 1e bend faced in the opposite direction to t e corresponding bend on the other leg, all of said structure being arranged to form a compact triangular shaped annulus section, the two outer legs converging substantially toward the center of the annulus.

13. In heat interchanging apparatus, in combination, an outer closed c lindrical shell, and a plurality of integral eat conductant uniformly-shaped flue sections connected end to end to form a sinuous flue disposed in a plane at right angles to the longitudinal axis of said shell concentricall between the inner periphery of said shel and an axial passage through the same.

14. In heat interchanging apparatus, in combination, an outerclosed cylindrical shell, a plurality of integral uniformly-shaped fiue sections connected end to end to form a sinuous flue tier, a number of said tiers being disposed in closely spaced parallel planes concentrically between the inner periphery of said shell and an axial manhole passage through the same, and return bends connecting adjacent pairs of said flue tiers.

15. In heat interchanging apparatus, in combination, an outer closed cylindrical shell, a plurality of integral uniformlyshaped flue sections connected end to end to form a sinuous flue disposed in a plane at right angles to the longitudinal axis of the shell and concentrically between the inner periphery of said shell and a manhole passage along said longitudinal axis, fluid inlets and outlets respectively for said flue and for passages surrounding said line and a deflector in said manhole passage for preventin fluid from by-passmg the passages aroun said flue.

16. In heat interchanging apparatus, in combination, an upright closed cylindrical shell, a continuous heat conductant interchanger flue disposed concentrically in the annular space between the inner walls of said shell and a manhole passage extending along the longitudinal axis of said shell, said flue comprising a number of superimposed, sinuous, horizontally lying flue tiers connected to each-other by Vertically placed return bends, and each tier in turn comprising a plurality of uniformly shaped tube sections connected end to end.

1'1, In heat interchanging apparatus, in combination, a heat conductant diaphragm member comprisin a plurality of integral uniformly-shaped ue sections assembled end to end in parallel tiers, means connecting adjacent tiers in multi le to form a nest of annular cross-section 'sposed concentrically between the inner wall of a closed cylindrical shell surrounding said nest and an axial longitudinal manhole passage through said shell, a manhole opening in the end wall of said shell inline with said axial passage of sufiicient area to pass said integral has 1 sections and return bends, a closure for said manhole o ening, a deflector mounted in said axial man ole passa e, and separate inlets and outlets for fiui s to said has and to passages through said nest surrounding said 18. A combined dephlegmator and heat interchanger apparatus unit embodying, in combination an upri ht closed cylindrical shell, 9. m ole opening in the top of said shell, an axial manhole passage extending along the longitudinal axis of said shell between said manhole opening and a top tray of said'dephlegmator, a heat conductant interchanger flue disposed concentrically in the space between the inner walls of said shell and said manhole passage and comprising a plurality of compactly arranged sinuous flow tiers, each tier being connected 'to the adjacent tiers by return bends, and each tier comprising a plurality of integralW-shaped flue sections connected end to end to form an annulus section, the legs of the flue section converging toward the center of the annulus,

fluid inlets and outlets respectively to said lines and to passages surroundin said flues, and deflector means for forcing uid to flow through rather than by-pass said passages. 19. In heat interchanging apparatus, in combination, an outer closed cylindrical shell and a continuous heat conductant inner flue disposed in the form of a nest' of closely spaced connected parallel tiers concentrically between the inner periphery of said shell and an axial passage, therein, each of said tiers comprising a plurality of integral uni- ,formly shaped flue sections connected end to end to form an annulus section placed in a plane at right angles to said axial passage, the means connecting each pair of tiers comprising an integral uniformly shaped tubular return bend having right angle bends on the open ends of each of its appurtenant legs, each right angle .bend faced in a direction at right angles to the axis of the return bend for attachment to the open-ends of the respective tiers to be connected.

20. In heat interchanging apparatus, in combination, an outer closed cylindrical shell, a manhole opening in one end of said shell,

a manhole passage extending from said 0 ening along the inner longitudinal axis 0 the shell, and a plurality of uniformly shaped compact sinuous fiues assembled in multiple Within said shell into a nest of annularcross section disposed in readily accessible compact form concentricall in the space between the inner periphery 0 said shell and said manhole passage. Y 5: In testimony whereof I aflix my signature.

DAVID G. BRANDT. I

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