US2753932A

US2753932A - Liquid distributing bell for vertical tubes

Info

Publication number: US2753932A
Application number: US239364A
Authority: US
Inventors: Albert W Eckstrom; James G Moore
Original assignee: Blaw Knox Co
Current assignee: Blaw Knox Co
Priority date: 1951-07-30
Filing date: 1951-07-30
Publication date: 1956-07-10
Anticipated expiration: 1973-07-10

Description

y 1956 A. w. ECKSTROM ET AL 2,753,932

LIQUID DISTRIBUTING BELL FOR VERTICAL TUBES Filed July so. 1 51 ww m m we M United States Patent LIQUID DISUTING BELL FOR VERTICAL TUBES Albert W. Eckstrom and James G. Moore, Buffalo, N. 1.,

assignors, by mesne assignments, to BiElW-KHOX Company, Pittsburgh, Pa., a corporation of Delaware Application July 39, 1951, Serial No. 239,364

2 Claims. (Cl. 159-13) This invention relates to a liquid distributing bell for vertical tubes and more particularly for distributing viscous or semi-viscous liquids, especially food products, on the inside surfaces of the tubes in vertical heat exchangers.

Such heat exchangers are of the type in which a shell is provided with upper and lower tube sheets into which the ends of the tubes are firmly fixed. When used as a downfiow evaporator or the like, the liquid to be concentrated is fed into the top chamber above the upper tube sheet and runs down the tubes in heat exchange relation with steam surrounding the tubes and out through the lower chamber below the lower tube sheet. For this type of equipment to operate satisfactorily, it is important that the liquid be distributed to each of the tubes and that the entire inside surface of each of the tubes be wetted with a continuous film of liquid. It is also important to provide a generally equal flow of the liquid down each tube surface and with a minimum head or level of liquid on the top tube sheet.

It is one of the principal objects of the invention to provide bells for distributing viscous and semi-viscous liquids to the tubes of a downfiow evaporator or the like which apply uniform and peripherally continuous annular films to the inside surfaces of the several tubes for the full length thereof.

Another object is to provide such bells which will operate with a minimum head of the liquid above the bells thereby to decrease the holding volume of the steam chest to a minimum.

Another object is to provide such a bell which is free from such protuberances as would break the annular stream discharged by the bell which break would result in uneven distribution and streaks of the liquid on the tube surface.

Another object is to provide such bells which are easily removed in cleaning the heat exchanger and are of simple configuration so as to be readily cleaned and also readily cast in the form of stainless steel or plastic bodies.

Another object is to provide such a bell which is firmly seated and in particular will not oscillate in use with resultant erratic distribution of the liquid.

Another object is to provide such a bell which will handle satisfactorily liquids of very high viscosity.

Another object is to provide such a bell which provides positive liquid film distribution through its entire range of capacities and in which the only limiting factors are (1) the minimum amount of liquid that can flow through its tube and still provide an unbroken film and (2) the minimum hydrostatic head above the bell that can be applied to provide the flow of liquid between the bell and the tube wall.

Another object is to provide such a bell which prevents the liquid from overshooting the top edge of its tube and falling without contact with the tube walls.

Another object is to provide such a bell providing adequate clearance to prevent clogging with small suspended solids'in the liquid and which has a minimum resistance to flow of the liquid. 1

Another aim is to provide such a bell which will, for a given tube, distribute the exact amount of liquid to provide maximum concentration in the heated tubes and form a uniform, unbroken film over the entire inside surface thereof.

Other objects and advantages of the invention will be apparent from the following description and drawings in which:

Fig. 1 is a fragmentary vertical section through the upper part of a downfiow evaporator having distributing bells embodying the present invention fitted within the upper ends of its tubes.

Fig. 2 is a fragmentary enlarged view similar to Fig. 1 and illustrating the bell in greater detail.

Fig. 3 is a fragmentary horizontal section taken on line 3-3, Fig. 2.

Fig. 4 is a perspective view of one of the bells.

The invention is illustrated in conjunction with the downfiow evaporator shown in greater detail in my copending patent application for Apparatus for Supplying and Distributing Liquids, Serial No. 229,006, filed May 31, 1951, nowPatent 2,713,895, and to which reference is made for a more detailed description of the evaporator. As here shown the evaporator comprises an upright cylindrical shell 6 having an annular flange 8 at its upper end. An upper tube sheet 9 is welded to and extends across the interior of the shell at its upper end and vertical evaporator tubes 10 extend through this tube sheet, the upper ends of these tubes being expanded into openings in the upper tube sheet. Steam is introduced into the space or steam chest 11 around these tubes so that the liquid flowing down the inside walls of these tubes 10 is concentrated.

A dome or upper cover 12 encloses a distribution chamber 13 above the upper tube sheet 9. For ready access this cover or dome 12 is removable and for this purpose it is shown as provided with a marginal flange 14 secured by swing bolts 15 to the upper flange 8 of the shell 6.

The liquid to be concentrated is fed downwardly from the center of the dome 12 and for this purpose an inlet pipe for the liquid to be evaporated is shown as terminating in an elbow 17 the downwardly turned end of which is removably connected with an inlet neck 18 rising from the center of the dome 12. a

To distribute the liquid uniformly over the tube sheet 9, a horizontal circular plate or basket 19 is provided which has an upturned rim 2% of slightly smaller diameter than the inside diameter of the shell 6 so that when it is placed within the upper end of this shell it is automatically centered in concentric relation thereto. To so center the plate or basket 19 and at the same time provide a slight annular space or clearance between the rim 20 and the shell 6, protuberances in the form of weldments 21 are applied to the rim 20 andengage the inside of the shell 6. This distributing plate 19 is preferably made of two sections 1911 and 19b, and is supported on the tube sheet 9 by a plurality of short legs 22 which are secured to the under side of the distributing plate 19 and rest upon the tube sheet 9. The distributing plate 19 also is provided with a plurality of uniformly spaced perforations 21's. Each section of the perforated distributing plate 19 is also preferably provided with handles 24 for ready removal.

Desirably, a head of the liquid to be concentrated is maintained on the upper surface of the perforated distributing plate or basket 19 and it is also desirable that the liquidforming this head be supplied in such manner as to reduce splashing and to maintain the under surface of the dome 12 free fromencrustations'of material drying thereon. To this end a plurality of radially disposed hangers 25 are shown as welded to the underside "of the dome 12 around and adjacent the opening from the neck 18. An upper distributing plate or baffle 26 is welded to the lower edges of these hangers 25. This upper distributing. plate or baffle 26 is shown as being of circular form and as provided at its center with an enlarged central opening 23 surrounded by an upturned neck or flange 29. This upper distributing plate 26 is preferably of generally flat and horizontal form but its marginal portion 30 is upturned so as to direct liquid flowing radially outwardly along its upper surface upwardly and thereby strike the under surface of the dome 12.

A plurality of radially disposed vertical hangers 31 are welded to the under surface of the upper distributing plate or bafiie 26, To the lower edges of this second series of hangers 31 is welded a second or lower distributing plate or baflie 32. This second or lower distributing plate or baffie 32 is disposed in a horizontal plane and is preferably of circular upwardly dished form so as to be in the form of a section of a sphere. At its lower end this distributing plate is provided with an opening 33 which is of substantially smaller diameter than the opening 23 of the upper distributing bafiie 26, and is provided with an upstanding marginal flange or rim 34.

The present invention is directed to the liquid distributing bells, indicating generally at 40, and which are inserted in the upper ends of all of the tubes to provide a uniform and peripherally continuous annular film flowing down the inner surfaces of these tubes. These bells are preferably each made in the form of a one-piece stainless steel or plastic casting, the use of breakable materials being undesirable.

Each of these bells comprises an upper horizontal spider 41 having a central vertical stem 42 from which three arms 43 radiate. Each of these arms is of substantial vertical extent as compared with its thickness and is provided at its outer end with a rectangular recess or indentation 44 forming a downwardly facing shoulder 45 and a radially outwardly facing shoulder 46. The three radially outwardly facing shoulders 46 are equidistant from the axis of the stem 42 and are located to closely fit the internal diameters of the several tubes 10. Accordingly, it will be seen that the spiders 41 can be partly inserted, interchangeably, into the upper ends of the tubes 10 with the shoulders 45 supporting the spiders on the upper ends of these tubes, as best shown in Fig. 2. It will also be seen that the radially facing shoulders 46 closely lit the tubes so as to hold these spiders in centered relation to the tubes. It will also be noted that these radially facing shoulders 46 are of substantial vertical extent so that the spiders are prevented from oscillating under the influence of the passing liquid.

A downwardly and outwardly flaring button 48 is integrally attached at its apex to the lower end of each of the stems 42. This button can be of the simple frustoconical form shown and has its lower edge 49 arranged in close concentric relation to the internal diameter of its tube 10. A feature of the invention resides in the condition that this edge 49 and the upper surface of the button adjacent this edge must be unbroken and free from any protuberance. It has been found that any protuberance on the upper surface of the button 48 adjacent its edge 49 divides the liquid flowing down this button so as to break the annular stream discharged from the edge 49 and thereby form a dry streak on the interior of the tube 10.

In the operation of the downflow evaporator as above described and equipped with the liquid distributing bells embodying the present invention, a part of the liquid to be concentrated, from the supply pipe 16, strikes the upper baflie or distributing plate 26. This portion is directed radially outwardly and strikes the upturned outer edge 39 thereof. This upturned outer edge serves to deflect this portion of the liquid slightly upwardly but in a generally horizontal direction. This liquid leaves this edge in the form of a generally solid or peripherally continuous annular curtain which strikes the under side of the dome 12. This curtain protects the central area of the dome against the formation of encrustations drying thereon.

The peripherally continuous annular curtain of liquid so leaving the upper bafile or distributing plate 26 and impinging against the under side of the dome 12 continues to move in a radial direction along the under side of this dome, portions of. this liquid falling from the dome in the form of drops into the perforated bottom plate or distributing basket 19. Because of the small size of these drops they cause a relatively slight amount of turbulence in the slight head of liquid maintained within the perforated basket 19. The liquid travelling along the under side of the dome 12 and which does not fall as drops into the basket 19 continues to flow down the inner surface of the rim or cover 12 and through the small space between the rim 20 of the basket 19 and the interior of the shell 6, this space being ensured by the projecting weldments 21 on the rim 20 of the basket 19. This liquid passes downwardly to the rim of the tube sheet 9 and thence flows radially inwardly on this tube sheet to ensure an adequate supply of liquid to the outermost rows of tubes 19.

A portion of the liquid from the inlet pipe 16 passes through the central opening 28 in the upper distributing plate or baffle 26. A fraction of this portion strikes the upper surface of the upwardly dished lower distributing plate or baflie 32. On so striking this lower distributing plate or bafiie 32, this fraction of the liquid is directed radially outwardly for distribution to the intermediate part of the perforated plate or basket 19 so as to ensure an adequate supply of the liquid to the tubes 10 under this intermediate part of the basket 19.

Another fraction of the liquid passing through the central opening 28 of the upper distributing plate or batiie 26 passes through the opening 33 in the lower distributing plate or baflie 32. This fraction strikes the central part of the bottom plate or basket 19 and thence flows radially outwardly in this basket so as to ensure an adequate supply of the liquid to the central tubes 10.

A slight head of the liquid is maintained on the tube sheet 9 and hence the upper ends of the tubes 10 are substautially filled with the liquid down to the lower edges 49 of the buttons 48. On flowing downwardly in the tubes this liquid is deflected radially to be brought forceably into contact with the full inside diameter of the tubes and hence form a continuous film in each tube which flows downwardly, without break, except for the vapor bubbles formed as a consequence of the application of heat to the exteriors of the tubes, to the lower extremity of each tube. This continuous film is subjected to the heat of the steam surrounding the tubes and hence is concentrated, the vapors also being removed downwardly through the tubes.

The liquid distributing bells completely prevent the free fall of liquid through the tubes 10 as well as overshooting of the liquid entering the tubes or washing free one side of any tube. Instead a peripherally continuous annular film is applied which remains unbroken, except for vapor bubbles, for the full length of travel down each tube. With a very slight hydrostatic head on the tube sheet 9, such as is desirable to avoid an excessive amount of liquid in the system for operation, it has been found that a uniform peripherally continuous film is applied to the interior of the full length of all of the tubes 10. The distributing bells are particularly useful where viscous liquids are being concentrated to provide the minimum amount of liquid required to produce a peripherally continuous film the full length of the tubes and with a minimum head above the tubes. At the same time the clearance between the edges 49 of the buttons 48 is not critical, clearances of from one tenth to one sixteenth inch having been successfully used with liquids of different viscosities. Thus with a four foot long tube having an internal diameter of 2.37 inches and with the base of the button of the distributing bell 2.14 inches outside diameter, leaving an open slot of .115 inch or a free area of .80 square inch, it was found to be satisfactory with liquids having viscosities of 580, 400, 280, 140 and 80 centipoises as well as water.

It will also be seen that the distributing bell of the present invention is firmly seated against both oscillation and blowing out due to air being initially in the feed line or any flash from the liquid being fed and at the same time is readily removable. The exterior is also free from irregularities both such as would cause streaking of the films flowing down the tubes, and also such as would render it dilficult to keep it in a clean and sanitary condition.

We claim:

1. In a downflow evaporator having an upper tube sheet on which a low head of liquid is maintained and having downflow tubes the upper ends of which are severally secured in openings provided in said tube sheet, the combination therewith of a liquid distributing bell for applying a peripherally continuous annular film of liquid to the inner surface of each of said downflow tubes from said head of liquid on said tube sheet, comprising a onepiece casting including a symmetrical button of circular horizontal cross section adapted to be arranged in the upper end of said tube and having a generally frustoconical downwardly and outwardly flaring upper conical surface having a central apex and terminating in a horizontal edge arranged in closely spaced relation to said inner surface of said tube, said upper conical surface of said button, adjacent said edge, being of regular conical downwardly and outwardly flaring form and free from protuberances tending to divide the liquid flowing toward said edge, a spider having at least three radial arms each fitted at its outer end against said inner surface of said tube and adapted to rest loosely thereon, and a vertical stem integrally uniting the central part only of said spider with the apex only of said button and forming the sole connection between said spider and button.

2. In a downflow evaporator having an upper tube sheet on which a low head of liquid is maintained and having downflow tubes the upper ends of which are severally secured in openings provided in said tube sheet, the combination therewith of a liquid distributing bell for applying a peripherally continuous annular film of liquid to the inner surface of each of said downflow tubes from said head of liquid on said tube sheet, comprising a one-piece casting including a symmetrical button of circular horizontal cross section adapted to be arranged in the upper end of said tube and having a generally frusto-conical downwardly and outwardly flaring upper conical surface having a central apex and terminating in a horizontal edge arranged in closely spaced relation to said inner surface of said tube, said upper conical surface of said button, adjacent said edge, being of regular conical downwardly and outwardly flaring form and free from protuberances tending to divide the liquid flowing toward said edge, a spider having at least three radial arms of substantial extent lengthwise of said tube, the end of each of said arms being notched to provide a downwardly facing shoulder adapted to rest loosely on the end of said tube and a radially outwardly facing shoulder of substantial vertical extent arranged to closely fit said inner surface of said tube, and a vertical stem integrally uniting the central part only of said spider with the apex only of said button and forming the sole connection between said spider and button.

References Cited in the file of this patent UNITED STATES PATENTS 1,253,234 Haas Jan. 15, 1918 2,424,441 Edmonds July 22, 1947 2,437,625 Taylor Mar. 9, 1948 2,570,210 Cross Oct. 9, 1951 2,580,646 Belden Jan. 1, 1952 FOREIGN PATENTS 581,636 Great Britain Oct. 18, 1946 592,361 Great Britain Sept. 16, 1947