US2703225A

US2703225A - Heat transfer apparatus for granular material

Info

Publication number: US2703225A
Application number: US229238A
Authority: US
Inventors: Albert L Cooper
Original assignee: Holly Sugar Corp
Current assignee: Holly Sugar Corp
Priority date: 1951-05-31
Filing date: 1951-05-31
Publication date: 1955-03-01
Anticipated expiration: 1972-03-01

Description

March 1, 1955 A. L. COOPER 2,

HEAT TRANSFER APPARATUS FORIGRANULAR MATERIAL Failed May 31. 1951 s She'efcs-Sheet 1 Clttornegs March 1, 1955 A. COOPER u 2,703,225

HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Filed May 31, 1951 3 Sheets-Sheet 2 Zhwentor ALBERT L. COOPER (Ittornegs March 1, 1955 A. L. COOPER HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Filed May 31, 1951 3 Sheets-Sheet 3 Snuentor ALBERT L COOPER attorney United States Patent HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Albert L. Cooper, Colorado Springs, Colo., assignor to Holly Sugar Corporation, Colorado Springs, Colo., a corporation of New York Application May 31, 1951, Serial No. 229,238

6 Claims. Cl. 257-228) This invention relates to heat transfer apparatus for granular material, and more particularly to apparatus for cooling granular material such as sugar.

In the production of a granular material such as sugar, which is crystallized from solution and separated in centrifugal separators, being washed with clear water during such centrifugal separation, it is customary to heat the sugar, as in a dryer, to drive off moisture, and then separate the sugar granules in accordance with size. If packed immediately in bags or sacks containing relatively small quantities, the heat contained in the sugar does not unduly complicate the problems involved, but immediate packing into bags requires a relatively large labor force, thus adding considerably to the cost of operation of a sugar factory, since the sugar is produced over a period of perhaps only a few months, whereas it is sold or distributed throughout the entire year. However, cooled sugar does provide better scale operation and more accurate weights, and reduced heat results in longer life of paper containers. More recently, it has become the practice to store the sugar in huge bins or towers, but if the sugar is placed in the towers immediately after drying, the heat in the sugar produces a number of difliculties. Warm sugar stored in large bulk bins tends to cause residual surface moisture to migrate to cooler zones, as in the lower portion of the bin, thus producing caking or hard cores. When cakes or cores of considerable extent occur, about the only manner in which the sugar can be handled is to redissolve the sugar in hot water, and recrystallize. This, of course, involves a comparatively large expense, since it is one of the principal operations of the sugar factory, and when it is necessary for the same sugar to go through crystallization twice, the second crystallization cost is a loss.

Additional difficulty is introduced by the fact that the production rate of sugar in a sugar factory or refinery is not uniform at all times. That is, when a white pan, for instance, is struck or discharged, the centrifugal separators are in operation continuously for a period of time, until all the sugar from that pan has passed therethrough. This means that the production is periodic, and while dryers generally have suflicient capacity and are effective over a comparatively large load range, a cooler for the sugar must be able to handle the production of the heated sugar as it comes from the dryer, i. e. a relatively large flow for a period of time, then a smaller flow, dwindling perhaps to an extremely low rate or perhaps nothing before the next white pan is struck or discharged.

Because of its granular nature, it is difficult to cool effectively any large amount of sugar, since heat transfer through the sugar is relatively slow. Also, uniformity of coolingthat is, the cooling of each small part of a relatively large mass of sugar to the same temperature-is diflicult.

Among the objects of this invention are to provide a novel heat transfer apparatus for granular material; to provide such apparatus which is particularly adapted for the cooling of sugar; to provide such apparatus which may be constructed to have a comparatively large capacity; to provide such apparatus which tends to cool each part of a relatively large mass of granular material to a substantially uniform temperature; to provide such apparatus which can produce uniform cooling, irrespective of whether the amount of sugar passing therethrough is small or large, up to its ultimate capacity; to provide such apparatus which is adapted to handle granular material in amounts which change periodically, and particularly in amounts which periodically reach a maximum and then diminish to a minimum of little or no material, such as following a strike of a sugar pan; to provide such apparatus which requires a comparative minimum of attention; and to provide such apparatus which is effective and efiicient in operation.

Additional objects and the novel features of this invention will become apparent from the following description, tallierli1 in connection with the accompanying drawings, in w 1c Fig. 1 is a side elevation, broken away at the center, of a sugar cooler embodying the principles of heat transfer apparatus for granular material of this invention;

Fig. 2 is an enlarged vertical section, broken away at the center, of a heat transfer tube forming a part of the sugar cooler of Fig. 1;

Fig. 3 is a vertical section, on a slightly larger scale than Fig. 1, taken along line 3-3 of Fig. l, and also broken away at the center;

Fig. 4 is a partial horizontal section, taken along line 4 4 of Fig. 1, on a slightly larger scale than Fig. 1;

Fig. 5 is a horizontal section taken along line 5-5 of Fig. 1, on a slightly larger scale than Fig. 1;

Fig. 6 is a further enlarged fragmentary vertical section taken along line 6-6 of Fig. 5;

Fig. 7 is a fragmentary horizontal section taken along line 77 of Fig. 6; and

Fig. 8 is a diagram of an installation of the sugar cooler of Fig. 1 in a sugar factory.

Heat transfer apparatus for granular material, constructed in accordance with this invention, may be embodied in a sugar cooler which, as in Fig. 1, may comprise a generally cylindrical shell S disposed in vertical position and closed at its lower end by an inverted, generally conical outlet housing 0, and closed at its upper end by an inlet housing I. A series of relatively long, vertically extending heat transfer tubes T are enclosed within shell S, and each tube T is constructed individually to provide an adequate transfer of heat from the sugar to be cooled. A heat transfer liquid, such as water for cooling purposes, may be introduced into the lower end of the shell S through a water inlet manifold 10, and discharged from the upper end of the shell through a water outlet manifold 11. In passing from the lower to the upper end of the shell S, the water not only circulates around each of the tubes T, but also through the tubes, but without contacting the sugar, as will be explained below.

As in Fig. 2, each of the tubes T is provided with an inner tube 12, which forms an annular sugar cooling space within the tube T and around the inner tube 12, an inlet connection 13 for each tube 12 extending between the inner tube 12 at its lower end and the tube T at a circular opening provided for the purpose, to each of which the inlet connection 13 may be welded, brazed or otherwise attached. A similar outlet connection 14 may be attached at one end to the inner tube 12 and at its opposite end to the tube T at an opening provided for the purpose, again as by welding, brazing or the like. The inlet and

outlet connections

13 and 14 for the inner tubes 12 are disposed at points relatively close to the lower and upper ends, respectively, of the tubes T, it being understood that most of the tube T of Fig. 2 is included in the portion broken away in the center, since the tube T, for instance, may have a diameter of 3 inches and a length of 30 feet. As in Fig. 3, the lower ends of the tubes T are attached and sealed, as by rolling, to a lower tube sheet 15, which is provided with spaced holes corresponding to the location of the tubes, against which the tubes may be expanded, while the upper ends of the tubes T are similarly attached and sealed to an upper tube sheet 16 by expanding. The

tube sheets

15 and 16 may extend laterally beyond the shell S, to form flanges for attachment of the outlet housing 0 and inlet housing I, respectively, as througha flange 17 of housing 0 and a flange 17' of housing I, while the ends of shell S may be attached to

tube sheets

15 and 16 in a suitable manner, as by welding. The cooling water is fed into the lower end of the shell S, from the box-like, water inlet manifold 10, through a series of spaced openings 18 in the shell S, as in Figs. 1 and 3, while the water may be discharged at the upper end of the shell through a series of similar openings 19 into the box-like, water outlet manifold 11. As will be evident, the cooling water will tend to fill the space within shell S completely, except for the sugar cooling space between tubes T and tubes 12, the water flowing upwardly around the tubes T and also through the inner tubes 12.

The annular space, or ring thickness, between each inner tube 12 and tube T is preferably sufficiently narrow that an adequate transfer of heat to all portions of the sugar passing downwardly through each tube T will be produced, and so that all of the sugar will be cooled to substantially the same temperature by the time the sugar reaches the bottom of each tube T. Preferably, sufiicient water is passed through the shell S so that the rise in temperature is on the order of a few degrees or a fraction of a degree only, whereas the sugar itself may be cooled over a much wider range of temperature, such as from 55 C. down to about 30 C. Thus, for an outside diameter of tubes T of 3 inches and an inside diameter of 2 inches, the inner tubes 12 may have an outside diameter of 1 inches, or approximately half the diameter of the tube T. With such dimensions, the ring thickness of the annular space between the tubes will be 1 inches, and this is generally sufiicient to accommodate granular sugar, since there will ordinarily be no lumps greater than ,6, inch in diameter. For uniform cooling it is desirable that the sugar fiow evenly and without interruption through each tube T. Also, if the fiow can be controlled so that each tube T remains full of sugar while in operation, the rate at which sugar is discharged from the lower end of each tube T will determine not only the amount of sugar flowing through the tube but also the rate at which it flows. For controlling the flow of sugar through each tube, i. e. to provide means at the lower end of each tube for controlling the flow of granular material therethrough, any suitable individualized control device may be used, but a preferred control means consists of an inverted cone having a diameter at its upper end larger than the tube T, as in Fig. 2, and conveniently attached to the tube sheet 15. although the cone 20 may be formed by or attached to the lower end of a tube T. The included angle between the sides of the inverted cone 20 is preferably such that the sides of the cone slope at an angle greater than the angle of repose of the sugar. An included angle of 60 is convenient for use, since the sides of the cone will be disposed at 60 to the horizontal, i. e. at an angle considerably greater than the angle of repose of mill run sugar of approximately 33. In addition, the lower end of the inverted cone 20 is provided with an orifice 21 having a diameter D, the orifice preferably being reamed or otherwise accurately dimensioned, to a size which will permit the sugar to be discharged from the lower end of the tube T at a rate which will produce the desired retention time or rate of flow of the sugar down through the tube. The diameter D at the orifice 21 preferably has a size such that the cross sectional area of the orifice 21 is less than the cross sectional area of the annular splace between the outside of tube 12 and the inside of tu e T.

The cross sectional area of the discharge opening 22 of the inverted conical outlet 0, as in Fig. 3, is preferably greater than the combined cross sectional area of the orifices 21, so that when the cooler is operating at .full capacity, the flow through the discharge opening 22 can be as reat or greater than the flow from all of the control orifices 21. The cross sectional area of the inlet opening 23 of the inlet housing I may, of course, be any desired value sufficient to accommodate the maximum flow into the cooler, being generally greater than the area of outlet opening 22, and equal to or slightly greater than the area of the inlet tube or pine 24 leading thereto.

In further accordance with this invention, an inlet plate 25, constructed so that it is self-cleaning, is preferably mounted on the upper tube sheet 16, and provided with surfaces which are inclined with respect to the horizontal at an angle greater than the angle of repose of the sugar, or other granular material being cooled or to or from which heat is transferred. Again, an angle of 60 is convenient, since it is considerably greater than the angle of repose of mill run sugar of approximately 33. Thus, the inlet plate is provided with a series of apertures or orifices, corresponding in diameter to the tubes T, but having angularly inclined sides, such as at an angle of 60 to the horizontal. Also, the plate 25 is sufiiciently thick that the ridges between the tubes T will be pointed, as

will be evident also from Fig. 2. The inlet plate 25 may be made of plastic or similar material readily formed or machined, since there is no great stress thereon.

During operation of the cooler, whenever a white pan, for instance, is struck, and the granulated sugar begins to be delivered from the dryer to the cooler, a valve 26, as in Fig. 1, such as a butterfly valve and installed in the outlet pipe 27 leading from the lower end of outlet housing 0, is preferably closed, so that sugar will build up in the outlet 0, and then build up in the tubes T. When the tubes T become filled with sugar, a pile 28 of sugar will then begin to build up to inlet plate 25, as in Fig. 3. When this pile 28 reaches a predetermined height, corresponding to the probable or average maximum flow of sugar from the pan involved, or to all of the tubes T being full, the valve 26 may be opened. This insures that the tubes T necessary for the operation will be full before discharge is started. The level of sugar in the inlet housing I, such as defined by the pile 28, may be observed through a transparent window 29 of Fig. l, or a telegauge or other level device, such as a Bin-Dicator, may be installed within the inlet housing I, and the valve 26 opened automatically when the pile reaches a predetermined height. Assuming that all or less than the total number of tubes T are full, when the sugar discharge valve 26 is opened, the level of sugar in the outlet 0 will drop, until the flow through the valve 26 corresponds to the amount of sugar being discharged through the tubes in use. Of course, the discharge orifices 21 will determine the rate of flow of the sugar through the tubes T. If the flow of sugar through the inlet pipe 24 should decrease, it will be evident that the pile 28 will tend to decrease in size, so that the tubes around the edges of the pile will begin to be uncovered. However, whenever a tube T is uncovered, the sugar will merely flow downwardly therethrough, at a rate determined by the discharge orifice 21 at its lower end, until the tube is empty. Thus, as the amount of sugar from the dryer, previously received from the centrifgugals, decreases during a strike, there will be a smaller number of tubes T in operation. However, the flow through each of the tubes T in service will be the same, so that all of the sugar will tend to be cooled to the same temperature.

Furthermore, if the amount of sugar tends to increase, the pile 28 will increase in size, whereupon additional tubes T will begin to receive sugar, and these will tend to become full, since the fiow at the lower end is restricted by the discharge orifice 21, so that the time of passage of this sugar down the tubes T will tend to become the same as through the tubes more centrally located with respect to pile 28. In general, however, during a strike, the flow of sugar will tend to increase rather quickly to a maximum, and perhaps level off for some time, and then taper off while the strike is being finished. After the strike is finished, valve 26 may be closed for the next strike, and the operation repeated.

When a telegauge, Bin-Dicator, or other automatic device is utilized to indicate or measure the height or extent of the pile 28 of sugar at the beginning of the strike, the outlet valve 26 may be solenoid or fiuid operated, so that it may be closed manually prior to a strike, as by remote control, and will be automatically opened after the sugar in the inlet housing I has reached a predetermined level or pile size. In such case, the level indicator may be electrically connected to a solenoid which opens an air valve controlling the release of air pressure on a cylinder or the like holding the valve 26 closed, and the indicator may be reset manually to cause the valve 26 to close automatically, after one strike and prior to the next. In addition, an orifice 30, such as having a 60 approach section, may be installed in a vertical section of outlet pipe 27 below valve 26, as in Fig. l, in the event that a sudden flow of sugar from outlet housing 0, at the time valve 26 is opened, may tend to cause overloading or clogging of subsequent equipment, such as elevators, conveyors, separators, and the like. It will be understood, of course. that when the flow of granular material to the heat transfer apparatus of this invention is substantially continuous and does not consist of periodically heavy loads, the inlet plate 25 will accommodate variations in flow, and that the control of the valve 26, as described above, may be unnecessary.

As shown in Figs. 4 and 5, a hexagonal arrangement of the tubes has been found to be convenient, particularly for design purposes, since the flow and distribution of water through the tubes T may bemade on the basis of six similar triangular arrangements. Thus, the ninetyone tubes shown in Figs. 4 and 5 may be disposed in six similar triangular arrangements of fifteen tubes each, with one tube in the exact center. The inlet housing I, as in Figs. 1 and 4, may be provided with side walls 32 disposed in hexagonal relationship, and the flange 17 therefor provided with a hexagonal aperture into which the sides 32 extend for attachment to the flange, as by Welding. The inlet plate 25 thus may be hexagonal and may be provided with straight edges, thereby avoiding a shelf formed by the segments around the edges of the hexagonal configuration of the tubes on which sugar might tend to remain. For uniform flow of heat transfer fluid, each of the inlet connections 13 and outlet connections 14 of the inner tubes 12 face outwardly, with the openings of all tubes of each triangular arrangement facing in the same direction and the center tube in any desireddirection, and, as in Fig. 5, the water inlet openings 18 may be so spaced that there is no opening immediately in front of a tube T nearest the shell S. As shown in Figs. 1 and 6, the flow of water through the space within shell S may be controlled by suitable baffle means for directing the flow of liquid through the inner tubes 12 as well as around the tubes T. Thus, the flow of water around the tubes T may be restricted by horizontal bafile plates 33, which may be placed in vertically spaced relation from the lower to the upper end of the shell S, such as in the positions indicated in Fig. 1, and corresponding positions over the remainder of the shell. For example, when the tubes T are approximately 30 feet in length, the baffle plates 33 may be spaced about 2 feet apart and may be attached at their edges to the inside of the shell, as by welding, either continuous or spot. Each baflie plate 33 is provided with a series of holes 34, as in Figs. 6 and 7, through which the tubes T extend and whichform around each tube T an annular space which preferably has a cross sectional area slightly less than the cross sectional area of the tube 12 inside the tube T. Thus, for 1 /2 inch 0. D., 16 gage, inner tubes 12, each hole 34 may leave an annular space having a ring thickness of approximately inch around a 3 inch 0. D. tube T, or a cross sectional area of approximately 0.911 sq. inch, in comparison to approximately 1.486 sq. inches for the inner tube 12. As will be evident, the incoming water is forced to flow, by the lowermost baffle 33, into the inlet openings of the inner tubes 12, and also into the center of the nest of tubes. The additional bafiles produce turbulence and mixing of the coolant, thus preventing hot spots, and also retard the upward flow sufficiently so that an adequate rate of fiow through the inner tubes 12 is assured.

The inner tubes 12 may also be maintained in position within the tubes T, as in Fig. 7, by outwardly extending spacing rods 35 welded or otherwise secured to the inner tubes 12, in units of three rods spaced 120 apart around the tube 12, which may in turn be spaced any desired distance apart vertically of the tubes 12, such as approximately 5 feet. The rods 35 do not require a precision fit, but the ends may be machined or rough ground merely within reasonably accurate'dimensions, such as to within approximately 1 inch of the distance to the inner surface of the tube T.

The water inlet manifold 10 may be provided with two inlets 37, as in Fig. 5, and the water outlet manifold 11 may be similarly provided with two outlets 38, as in Fig. 1, the same being diametrically opposed in each instance, to insure a more uniform distribution and supply of the water to the interior of the shell S. As in Fig. 5, the water opening 18 opposite each inlet 37 may be omitted, to prevent a direct flow of water from the inlet straight into the adjacent tubes and produce a more uniform distribution of the water, while a similar provision may be made in the case of the upper water openings 19. The water circulated through the cooler may be natural water sufiiciently cool to accomplish the desired cooling, or may be artificially cooled, as by means of a spray pond or refrigeration, when necessary. As indicated previously, a comparatively large amount of water preferably is passed through the cooler, so that the rise in temperature of the water between the inlet and the outlet is not great. When the supply water'is at a lower temperature than necessary, a portion of the water may be recirculated through the cooler, as by an automatically operating, temperature responsive regulat ing valve. The pressure of the water supply to the cooler inlet need not be great, but only sufficient to force the water up through the cooler to the outlet, as for a distance of 30 feet, since the water may be permitted to flow with only slight pressure into the outlet manifold 11 from the shell S.

The diameter D of each tube orifice 21 may be proportioned in accordance with the length and the cross sectional area of the annulus within tube T, around the inner tube 12, correlated with the retention time desired. These factors may, of course, vary for different materials, but for mill run granulated sugar to be cooled, for instance, from an average temperature of 55 C. to 29 C., each tube T may be a 3 inch 0. D., 16 gage tube, and each tube 12 a 1%. inch 0. D., 16 gage tube, with the tube T being approximately 30 feet long and the inlet connection 13 and outlet connection 14 each being spaced at a center line 6 inches from the lower and upper end of the tube T, respectively. In tests, the flow of mill run sugar was found to be 9.72 lbs. per minute, or approximately 10 lbs. per minute or 0.3 tons per hour, when thediameter D of the cone orifice 21 was 0.8 inches. For a tube unit having the same dimensions as given above, except that the length of the tube T was only 20 feet instead of 30 feet, it was found that the amount of sugar contained in the tube was approximately 32.85 lbs., and the retention time was approximately 972 3.37 minutes for an average temperature drop of the sugar from 55.2 C. to 35.5 C. and an average rise in the cooling water temperature from 14.6 C. to 15.1 C. Thus, for a tube 30 feet long, it would be expected that the sugar contained in each tube would be approximately 49.2 lbs. and that the retention time would be 5 minutes, for a temperature drop of 55 C. to 29 C. for the sugar and a cooling water temperature rise from 13 C. to 14 C. The diameter D, shown in Fig. 2, of the flow control orifice for the tube T may vary in accordance with the rate of flow desired, and in turn be affected by the type of material being cooled. However, on tests on mill run sugar, the following results were secured, which will provide a basis for the selection of a desired orifice diameter for any desired rate of flow or material, it being understood that the axis must be vertical and the angle included between the sides of the cone above the orifice was 60, and that a variation in this angle will affect the rate of flow through the orifice.

Flow, pounds Diameter of orifice, inches per minute Flow, tons per hour From the above results, some of which are extrapolated, the following formula was deduced:

F=Flow in lbs. sugar per minute K=18.13 (constant for granulated sugar) D=Diameter of orifice in inches.

maximum capacity of a cooler having ninety-one tubes, as illustrated, when an 0.8 inch diameter orifice below a 60 cone is installed below each tube, would be 91 9.72=874.52' lbs. per minute, or 29.1 tons per hour, and assuming that the six tubes at the points of the hex would not be filled, so that only 85 tubes were in operation, the maximum rated capacity would be or, to be conservative, approximately 25 tons per hour.

A sugar cooler constructed in accordance with this invention may be installed in a sugar factory in a manner similar to that illustrated in Fig. 8, wherein sugar is delivered from a dryer (not shown), as through a scroll conveyor, to the lower end of an elevator 40, transported to the upper end of the elevator 40 and discharged through pipe 24 into the inlet I of the cooler. After downward passage through the tubes T within the shell S, the cooled sugar may be discharged through pipe 27 to the lower end of a cooled sugar elevator 41, and discharged from the upper end thereof through a pipe 42 to a horizontal scroll conveyor 43, which feeds the cooled sugar into one or more separators 44, such as two, as shown. Separators 44 classify the sugar into sizes or grades, such as fine, bakers or superfine, and scalpings, and preferably discharge into temporary or permanent storage bins or the like.

The material of which the various parts of the heat transfer apparatus of this invention are made may vary considerably, although certain materials may be preferred where available and also economically feasible. The shell S, of course, may be made of sheet or plate steel, while the inlet and outlet water manifolds may be made of similar material, as by an upper and lower flat ring welded to the outside of the shell S and to an outer annular ring, to form a box-like structure. The tubes T, and also inner tubes 12 and their inlet and outlet connections, are made of material which will not rust, have no harmful effect on the sugar, and have a comparatively high coeflicient of heat transmission. Brass or other copper containing metal are preferred materials, although other materials, such as stainless steel or aluminum, may be used when the preferred materials are not available. The orifice cones 20 and the inlet and outlet housings may be made of the same or similar material, or of galvanized steel. The inlet plate 25, as indicated previously, may be made of plastic, such as a synthetic resin, while the baffle plates 33 may be made of mild steel. The

tube sheets

15 and 16, which also provide flanges for the shell S, may be made of stainless clad steel, with the stainless layer facing the inlet and outlet housings, respectively, and the shell S welded to the mild steel side. The outlet housing and inlet housing I may be made of galvanized steel plate, or of brass or stainless steel if desired, and as indicated previously, may be welded to the

flanges

17 and 17, respectively. It will be understood, of course, that other materials may be found suitable, and utilized when desired, as well as other methods of constructing the parts and assembling or attaching them together.

From the foregoing, it will be evident that the heat transfer apparatus for granular material of this invention, fulfills to a marked degree the requirements and objects hereinbefore set forth. As will be evident, such apparatus is particularly adapted for the cooling of sugar, although it may be utilized for the cooling or heating of other granular material. As will also be evident, the apparatus has a comparatively large capacity, but can produce uniform cooling, irrespective of the amount of material passing therethrough, by virtue of the controlled restrictive flow through each tube, which insures that the material will remain in each tube for a period of time sufiicient to cool the same the desired amount. Thus, the individual flow control means at the lower end of each heat exchange tube will restrict the downward descent of granular material in each tube to less than free flow, so that granular material is adequately maintained in contact with the heat exchange tubes during descent. As will be further evident, each tube in operation produces substantially the same amount of cooling for the material passing therethrough, due to the uniform flow, and therefore each part of a relatively large mass of granular material may be cooled to a substantially uniform temperature. As will be additionally evident, the apparatus is effective and efficient in operation, since cooling of all parts of the material is substantially uniform for various rates of flow, and the apparatus also may be operated to achieve substantially uniform cooling when the flow is periodic, as in the case of sugar in a sugar factory, when the flow is heavy immediately succeeding a white pan strike, and diminishes thereafter, but again becomes heavy when another white pan is struck.

Although a specific embodiment of this invention has been described with particularity, and certain possible variations therein indicated, it will be understood that other variations may be made, and that other and different embodiments of this invention may exist, all without departing from the spirit and scope thereof.

What is claimed is:

1. Heat transfer apparatus for granular material, comprising a shell defining a space for a heat transfer fluid; means for supplying such heat transfer fluid to said space adjacent one end of said shell and for removing such heat transfer fluid from said space adjacent the opposite end of said shell; a first plurality of tubes extending through said space in sealed relation thereto and disposed generally vertically; an inner tube disposed within each of said first tubes and having a connection with said space adjacent the upper and lower ends of said first tube, said inner tubes being sealed with respect to the interior of said first tubes; and an inverted cone at the lower end of each of said first tubes for restricting the flow of granular material, each said inverted cone having sides disposed at an angle to the horizontal greater than the angle of repose of said granular material, each said cone being provided at its lower end with a discharge orifice having a cross sectional area less than the cross sectional area of the granular material space between said first tube and said inner tube therein and thereby restricting the downward descent of granular material through the corresponding tube to less than free fall so as to maintain granular material in contact with said tube during such descent.

2. Apparatus for cooling granular material such as sugar, comprising an upright cylindrical shell; upper and lower tube sheets having a plurality of circular apertures and closing the respective ends of said shell; a plurality of first tubes disposed generally within a hexagon and registering with said apertures, said tubes extending between said tube sheets and sealed thereto at said apertures; a cylindrical inner tube disposed within each of said first tubes and extending in concentric relation thereto, each said inner tube having a plurality of sets of laterally extending rods, said sets being disposed in spaced vertical relation and said rods maintaining said inner tube in concentric relation to said first tube, each said inner tube having an inlet liquid connection adjacent the bottom of said first tube and a liquid outlet connection adjacent the top of said first tube, each of said connections facing outwardly toward said shell; an inverted conical flow control device having side walls forming an included angle of substantially 60 and provided at the lower end with a circular orifice having a cross sectional area less than the cross sectional area of the annular space between an inner tube and a first tube, each said inverted conical flow control device being attached to the underside of said lower tube sheet in substantially axial alignment with a first tube; means for supplying cooling water to the space within the periphery of said shell adjacent the lower end thereof; means for removing water from the space within said shell adjacent the upper end thereof; and a series of horizontal baffles disposed in spaced vertical relation within said shell, each bafile having a series of circular apertures therein disposed substantially concentrically with respect to said first tubes and through which said first tubes extend, the annular cross sectional area formed by said apertures around each of said first tubes being less than the area of the inner tube therewithin.

3. Apparatus for cooling granular material such as sugar, comprising an upright cylindrical shell; upper and lower tube sheets having a plurality of circular apertures disposed generally Within a hexagon and closing the respective ends of said shell; a plurality of first tubes registering with said apertures, said tubes extending between said tube sheets and sealed thereto at said apertures; an outlet housing connected to the lower end of said shell having an inverted conical form and an outlet opening at the bottom; an outlet valve below said outlet housing; a discharge pipe leading from said valve and provided with a flow control orifice; an inlet housing connected to the upper end of said shell and having sides forming a hexagon at said upper tube sheet; a cylindrical inner tube disposed within each of said first tubes and extending in concentric relation thereto, each said inner tube having a plurality of sets of laterally extending rods, said sets being disposed in spaced vertical relation and said rods maintaining said inner tube in concentric relation to said first tube, each said inner tube having an inlet liquid connection adjacent the bottom of said first tube and a liquid outlet connection adjacent the top of said first tube, each of said connections facing outwardly toward said shell; an inverted conical flow control device having side walls forming an included angle of substantially 60 and provided at the lower end with a circular orifice having a cross sectional area less than the cross sectional area of the annular space between an inner tube and a first tube, each said inverted conical flow control device being attached to the underside of said lower tube sheet in substantially axial alignment with a first tube; a horizontal series of water inlet holes spaced about the periphery of said shell adjacent the lower end thereof; a water inlet manifold encircling said shell and enclosing said inlet holes; a horizontally disposed series of water outlet holes in said shell adjacent the upper end thereof; a horizontally disposed water outlet manifold surrounding said shell and enclosing said outlet holes; a hexagonal inlet plate mounted on said upper tube sheet and having a series of spaced circular apertures registering with said first tubes, said first tubes being disposed generally within a hexagon, said inlet plate having surfaces extending upwardly and outwardly away from each said aperture at an angle of approximately 60 to the horizontal, the thickness of said inlet plate being such that the sloping surfaces from adjacent apertures intersect in pointed ridges; a series of horizontal bafiles disposed in spaced vertical relation within said shell, each bafiie having a series of circular apertures therein disposed substantially concentrically with respect to said first tubes and through which said first tubes extend, the annular cross sectional area formed by said apertures around each of said first tubes being less than the area of the inner tube therewithin; and means in said upper housing for determining the extent of a pile of granular material filling said first tubes and extending upwardly within said inlet housing.

4. Apparatus for cooling granular material such as sugar, comprising an upright cylindrical shell; upper and lower tube sheets having a plurality of circular apertures and closing the respective ends of a fluid space within said shell; a plurality of first cylindrical tubes registering with said apertures, said tubes extending between said tube sheets and sealed thereto at said apertures; a cylindrical inner tube disposed within each of said first tubes and extending in concentric relation thereto, each said inner tube having an inlet liquid connection adjacent the bottom of said first tube and a liquid outlet connection ad acent the top of said first tube; an inverted conical flow control device for each said first tube and provided at the lower end with a circular orifice having a cross sectional area less than the cross sectional area of the annular space between the corresponding inner tube and first tube, each said inverted conical flow control device being attached to the underside of said lower tube sheet in substantially axial alignment with a first tube; means for supplying cooling water to the fluid space within said shell adjacent the lower end thereof; and means for removing water from the fluid space within said shell adjacent the upper end thereof.

5. Apparatus for cooling granular materials such as sugar, as defined in claim 4, including a series of horizontal baflles disposed in spaced vertical relation Within said shell, each bafiie having a series of circular apertures therein disposed substantially concentrically with respect to said first tubes and through which said first tubes extend, the annular cross sectional area formed by said aperture around each of said first tubes being less than the cross sectional area of the inner tube therewithin.

6. Apparatus for cooling granular material, as defined in claim 4, including an inlet plate above said upper tube sheet and having apertures registering with the apertures of said upper tube sheet, said inlet plate having surfaces leading to each said tube sheet aperture, inclined at an angle to the horizontal greater than the angle of repose of said granular material, said inlet plate having sufiicient thickness that the surfaces between adjacent apertures intersect in ridges.

References Cited in the file of this patent UNITED STATES PATENTS