US2711881A

US2711881A - Heat exchanger

Info

Publication number: US2711881A
Application number: US424963A
Authority: US
Inventors: Ernest A Rose
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-04-22
Filing date: 1954-04-22
Publication date: 1955-06-28
Anticipated expiration: 1972-06-28

Description

E. A. ROSE HEAT EXCHANGER June 28, 1955 Filed April 22, 1954' 2 Sheets-Sheet l IN VENTOR @wmf ATTORNEYS A E. A. ROSE HEAT EXCHANGER June 28, 1955 2 Sheets-Sheet 2 Filed April 22, 1954 IN VENTOR BY me@ i fini Ld/w ATTORNEYS United States Patent C HEAT EXCHANGER Ernest A. Rose, New Orleans, La.

Application April 22, 1954, Serial No. 424,963l

7 Claims. (Cl. 257-80) The present invention relates in general to heat exchange apparatus, and more particularly to rapid heat transfer sugar crystallizers of the type employed in the manufacture of sugar and like crystalline substances.

Many varieties of apparatus have been devised to promote crystallization in massecuite and similar sugar crystallization solutions. Primarily, apparatus of this type has relied upon rotary movement of highly thermally conductive bodies or radial conduits through a mass of solution under treatment with the heat exchange medium, the medium usually constituting a suitable liuid circulated through the conductive bodies or radial conduits. The rotary movement of these thermal exchange elements is provided to simultaneously effect slight agitation of the solution during cooling of the same to promote rapid crystallization.

ln many instances, prior art apparatus of this type have been subject to objection in that they employ as thermally conductive bodies elements of relatively large surface area in comparison to the total space in which the treatment is performed, which tends to precipitate rotation of the mass of solution under treatment. This is objectionable because anything other than a very gentle agitation of the solution will have the effect of either breaking up or grinding crystals already formed by gradual reduction of the temperature of the`solution. The optimum goal to be achieved in sugar crystallizers is the rapid production of large crystals from the massecuite or mother liquor. Achievement of this condition requires careful design to insure that crystals are produced by gradual growth rather than by abrupt formation of batches of minute crystals. The larger the Vcrystals which are obtained, the easier and more efiicient is the subsequent separation and consequently the better yield of sugar.

Attempts have been made to overcome the above described disadvantages incident to thermally conductive elements which have a large surface area producing an undesirable degreeof agitation of the solution on rotation or" the elements. One expedient has been to provide a series of spaced relatively small rectilinear radial conduits projecting from a central driven shaft, a cooling uid being circulated through the shaft and into the radial conduits during rotation of the conduits to effect the desired heat exchange action. These, however, have been found to be objectionable, since the limited uid capacity of these small conduits provides rapid exchange of cooling iiuid in the conduits and therefore in heat exchange relation wththe solution, and immersion of these small conduits having comparatively limited surface area eifects localized sudden chilling in the solution which promotes rigid formation of minute new crystals rather than gradual growth of larger crystals from crystal nuclei. Continuous forced-circulation heat exchangers have likewise been employed as rapid sugar crystallizers, but the multitude of small diameter conduits and orifices in the network of valves required in such continuous forced-circulation systems, are in many instances vulnerable to becoming obstructed or otherwise inoperative, thereby destroy- 2,7 l 1,88 Patented June 28, 1955 ing or diminishing the heat exchange efficiency of that portion of the system and therefore the uniformity of the heat exchange action throughout the solution.

An object of the present invention, therefore, is the provision of a novel heat exchanger of simple design and durable construction, which is largely free of the above enumerated objections.

Another object of the present invention is the provision of a novel heat exchange apparatus in which a mass of solution to be treated may be cooled or heated in a uniform manner throughout the mass.

Another object of the present invention is the provision of a novel heat exchange apparatus of the rapid sugar crystallizer type, in which a mass of solution is brought into heat exchange relation with a cooling or heating uid substantially uniformly throughout the bulk of the mass.

Another object of the present invention is the provision of a novel heat exchange apparatus of the sugar crystallizer type for circulating a treating fluid in heat exchange relation with the solution, wherein circulation of the fluid is effected by gravitational forces.

Another object of the present invention is the provision of novel heat exchange apparatus for sugar solutions and the like wherein the heat exchange iiuid is circulated through a plurality of radiating heat exchange elements of relatively small diameter to promote gradual growth of large crystals, wherein the use of small orifices, passages and valves is minimized.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing, showing only a preferred embodiment of the invention.

In the drawings:

Figure l is a vertical longitudinal section view of a rapid sugar crystallizer apparatus embodying the present invention showing the thermally conductive heat exchange elements in elevation.

Figure 2 is a vertical transverse section View of the sugar crystallizer apparatus, taken along the lines 2-2 of Figure l.

Figure 3 is a horizontal longitudinal section of one of the radiating heat exchange elements illustrating the liuid condition within the element at the initiation of a cycle of operation wherein its inlet end portion lies in a horizontal plane.

Figures 4, 5 and 6 are corresponding section views of one of the radial heat exchange elements illustrating the iiuid content conditions in the element at various sub-` sequent positions of the same during a cycle of operation.

Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, the sugar crystallizer apparatus comprises an upwardly opening tank or receptacle 10 having opposite end walls 11 and l2 and a side wall 13. The lower half of the tank 19 is preferably shaped to define a 180 degree cylindrical surface segment simulating a half drum, while the upper portions of the side wall 13 preferably extend in parallel vertical planes.

Centrally located within the tank 1t) in alignment with the medial longitudinal axis thereof is a hollow rotatable drum 14 which is slightly shorter than the length of the tank 10. A plurality of radiating heat exchange elements 15 formed of bent pipes of much smaller diameter than the drum 14 are closed at their outermost end 16 and are welded or otherwise suitably fixed in complementary apertures formed in the Wall of the drum 14 at the inner end portion 17 of the element 15, a portion 13 of the open end 17 of the element 15 projecting a short distance inwardly of the inner surface of the wall of the drum 14. It will be noted from the drawings that the elements 1S are substantially U-shaped, with the inlet or inner portion 17 forming one leg of the U and disposed on a radial axis of the drum 14. Au air relief conduit 19 of very small diameter is provided in each of the elements 15 and projects within the hollow of the drum 14 a distance at least as great as the radius of the inner wall of the drum 14.

Each end of the drum 14 is provided with a series of thrust collars and thrust washers generally indicated at 20 surrounding hollow supporting trunnions 21 at opposite ends of the drum, projecting through suitable apertures in the end walls 11 and 12 of the tank 10. The trunnious 21 terminate in a liquid inlet pipe 22 and liquid outlet pipe 23, respectively, and are supported for rotation in bearings 24 and packing glands 25 supported on the end walls 11 and 12 of the tank. The thrust collars and thrust washers 20 are provided on each trunnion in order to take up any thrust that might occur during operation.

The outer end of the inlet pipe 22 is connected by a flexible coupling 26 with a stationary main feed line 27 connected to hot and cold liquid supply reservoirs through a hot liquid control valve 2S and a cold liquid control valve 29. A worm wheel 30 is keyed on the trunnion 21 and is driven by a driven worm 31 to impart the desired rotary movement to the drum 14 and heat exchange elements 15. The outer end of the fluid outlet pipe 23 is provided with a liquid drip ring 32 and is disposed within a stationary liquid drain box 33 having a drain pipe 34 extending therefrom, the outlet pipe 23 being rotatably supported within the liquid drain box 33.

Operation of the rapid crystallizer will be more fully understood by specific reference to Figures l and 3-6, inclusive. Water or other heat exchange uid is admitted in desired quantities by'adjustrnent of either the hot liquid valve 28 or cold liquid valve 29 into the main feed line 27 and thence through the flexible coupling 26, inlet pipe 22 and the hollow conduit in the trunnion 21 into the hollow drum 14. `On continuous admission of the fluid into the drum 14, the liuid level rises in the drum until it reaches the lower edge of the bore in the outlet pipe 23, after which the liquid level is maintained at this point slightly below the longitudinal medial axis of the drum 14 by overflow of liquid through the outlet pipe 23 and into the liquid drain box 33.

The apparatus is operative to eiect substantially a complete change of the heat exchange fluid in the heat exchange elements 15 for each cycle of rotation of the elements 15 in the following manner:

Beginning the description of the operating cycle of one of the heat exchange elements 15 illustrated in Fig- "1' ures 3-6 with the inlet portion of leg 17 of the U-shaped element 15 extending horizontally to theI left of the medial axis of the drum 14, as illustrated in Figure 3, the leading portion of the inlet leg 17 is disposed immediately below the level of the uid in the hollow drum 14 so that iiuid begins to flow into the inlet portion 17 of the heat exchange element 15. Upon progressive counterclockwise rotation of the heat exchange element 15 from the position illustrated in Figure 3 to a position in which the axis of the inlet leg portion 17 is disposed slightly to the right of the vertical plane through the medial axis of the drum 14, as shown in Figure 4, increasing quantities of the heat exchange iiuid from the hollow drum 14 are drawn under the influence of gravity through the inlet leg portion 17 and into the medial bow and the end portion 16 of the U-shaped heat exchange element 15 to completely till the element. During this portion of the operating cycle, the entering fluid which begins to fill the element 15 gradually displaces the air occupying the interior of the element. The vent tube 19 facilitates this action and permits complete filling of the element 15 as the air displaced by the liquid entering the element is relieved back to the portion of the hollow drum 14 above the fluid level therein. The air relief tube 19 is open at both ends and alfords a complete conduit.

Cil

and a ready passage for all of the air being displaced during this period of filling the U-shaped element with the heat exchange uid. This affords the maximum volume of fresh heat exchange fluid to be traversing through the massecuite solution at all times. As the U-shaped heat exchange element 15 continues to rotate in a counterclockwise direction, the inlet leg portion 17 advances to a position inclined slightly above the horizontal plane through the medialaxis of the drum 14 following which progressively increasing portions of the heat exchange tluid in the inlet leg portion 17 and the inlet half ofthe bow of the heating element are returned to the drum under the influence of gravity to mingle with fresh heat exchangev uid constantly entering the drum 14. Progressive rotation of the element 15 from a position with the inlet leg portion 17 disposed vertically through the position illustrated in Figure 6 to the posi- :ion illustrated in Figure 3 progressively discharges most of the remaining fluid in the outer halfof the heat exchange element 15. The liquid flowing from the outer half of the element 15 through the inner half of the element and into the drum flows over the empty inner portion of the element 1S to remove the heat which is stored up in the inner portion during the period the heat exchange uid has been vexhausted from that portion.

lt is to be noted that at the instant that all of the heat exchange fluid is exhausted from the outer half of thc U-shaped element 1.5, element 15 has completed one cycle of operation and is again in the position illustrated in Figure 3 where a fresh charge of heat exchange fluid begins to enter the inlet leg portion 17 from the drum 14. By this arrangement, the U-shaped heat exchange element 14 is never totally empty at any point throughout the heat exchange cycle of 360 degrees of rotation.

The above described cycle of filling the U-shaped heat exchange elements 15 with the heat exchange fluid and the transferring of the heat through the medium of the heat exchange uid contained within the elements 15 together with the draining from the elements 15 of the heat exchange fluid is repeated throughout the full length of the heat exchanger.

At the end of a grinding season it is desirable for the heat exchange uid contained in the heat exchange elements of the apparatus to be completely drained, particularly if the apparatus is located in a climate where a hard freeze is likely to fracture the elements 15. To facilitate this draining procedure, the inlet ends 17 of the heat exchange elements 15 are projected as indicated at 18 a slight distance inwardly of the hollow bore in the drum 14, so that when the drain plug 35 in the drum 14 is opened, the heat exchange fluid will drain from the drum 14 until the only fluid retained is in the heat exchange elements 15 that are in a downward position. By rotating the drum 14 to elevate the downwardly directed heat exchange elements 15 and exhaust uid from them, the uid draining from the upwardly projecting elements 15 is prevented from returning to the downwardly projecting elements 15 by the inwardly projecting lips on the heat exchange elements. Thus all of the heat exchange fluid within the apparatus can be quickly and effectively exhausted from the device.

It will be appreciated that the group of heat exchange elements 15 will be disposed in either a spiral or helical pattern along the length of the rotating drum 14 to reduce the wear on the various moving parts caused by the shock of exposed heat exchange elements striking the surface ot the solution within the tank 10 when the tank is not completely filled.

While but one particular embodiment of the invention has been particularly shown and described, itis apparent that various modifications may be made in the invention without departing from the spirit and scope thereof, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and are set forth in the appended claimsf I claim: 1,- Heat texcihanae appar. us., comprisinglaftafienary receptacle, a hollow rotary,drum journalled in said `receptacle-for rotation about ahorizontalaxis, meausforcontinurouslyl rotating said drum', fluid ,conduitmeans delivering aheat transfer fluid totheinterior ofsaiddrunnmeans maintaining appreselected fluid,levelrinsaiddrum, and a ,seriesV of hollow heat exchangeelements radially disposed on said drum ,for rotationztherewith, each of said elements comprisingabent pipe closed at `one end Lremote from said drumand an air relief -conduit meansextending the length of-saidV pipe .forwrelieving any air `trapped in the closed end of said pipe to theinteriorofvsaid drum, said ,pipe having a leading.,portiorradjaent the inner end of said pipe extending ,on a radialaxis of said drum opening therein and` a trailing portion:V adjacent saidl closed end spaced fromand located onan axissubstantially parallel to said rstrnentioned portion ,wherebypsaid elements will be completely-filled with theheat Itransfer fluidduring the descending lrotationof theirleadingportions below said fluid levelandv. will retainatleast a portion. of said fluid throughout subsequent rotation to aposition :whereby their leading portions .descend ,intol a-xialr,alignment V with said uid level to admit a new charge of uid into the p1pe.` y t' 1 t if i 2.- Heat exchangeapparatus comprisingga stationary receptacle, a hollow rotarydrum"journalled Vin `said receptacle for rotation about; `a horizontal axis,- means for continuously rotating said drum, fluid conduitmeans deliver ing a heat transfer iiuid to the interior of said drum, means 1 maintaining )a preselectedgiiuidlevel in said drum, and a series of hollow heat exchange .elementspradially disposed on said drum for rotation therewith, each of said elements comprising a bent pipe-closedat one-end remote-from said drumand Van-airreliefconduitmeans extending the length off; saidpiperforrelievi-ngany Vair trappedin. the closed end of said pipe to the interior of said drum, said pipe having a leading portion adjacent the inner end of said pipe extending on a radial axis of said drum opening therein and a trailing portion adjacent said closed end spaced from and located on an axis substantially parallel to said first mentioned portion whereby said elements will be completely filled with the heat transfer uid during the descending rotation of their leading portions below said uid level and will retain at least a portion of said uid throughout subsequent rotation to a position wherein their leading portions descend into axial alignment with said fluid level to admit a new charge of fluid into the pipe.

3. Heat exchange apparatus comprising, in combinav tion, an upwardly opening receptacle, a hollow rotary drum journalled in said receptacle for rotation about a horizontal axis, means for continuously rotating said drum, fluid conduit means delivering a heat transfer fiuid to the interior of said drum, means maintaining a preselected uid level in said drum, and a series of holiow heat exchange elements radially disposed in longitudinally and angularly spaced relation on said drum for rotation therewith, each of said elements comprising a U-shaped pipe of small cross section relative to the cross section of said drum and having an inner end fixed to and opening within the interior of said drum and a closed outer end, an air relief conduit opening at both ends disposed within said pipe and extending from a point adjacent the closed end thereof through the open end and into the interior of said drum to prevent air lock in the closed end of said pipe, the leg of said U-shaped pipe adjacent said inner end constituting a leading portion extending along a radial axis of said drum and the other leg of said U-shaped pipe connected to said leading portion by the bow of the U constituting a trailing portion disposed parallel to said leading portion whereby said elements will be completely filled with the heat transfer iluid during the descending rotary movement of their leading portions below said uid level and will retain at least a portion of said uid throughoutl subsequentrotation toY a position wherein theirleading portions descend into axial alignment with said fluid level to admit a new charge of uid into said elements..v ,Y t, Y ,t l',

4. Heat` exchange apparatus comprising, in combinatiornan upwardly opening receptacle, a hollowjrotary druml journalled in Vsaid receptacle for rotation abouta horizontal axis, means for continuously rotating said drum, liuid conduit means delivering a heat transfer uid to the interior-of saidv drum, means maintaining a preselected uid level in said drum, and a series of hollow heat exchange elements radially disposed in longitudinally and angularly spaced relation on said drum for rotation therewith, eachy ofjsaid elements comprising a,U-sha'petl pipe of small cross section relative to the crosshsection of said drum and having an inner end fixed to and opening within the interior of said drum and a closed louter end, `an air relief conduit open lat both endsv disposed within said pipe and extending from a point adjacent the closed end thereof throughvthe open end and into the interior of said drum to prevent air lock in ihe closed end of said pipe, the legof said U-shaped pipe adjacent said inner end constituting a leading portion extending alongv a radial axis of said drum and the otherleg of saidK Ur-shapedvpipe connected to 4said leading portionby the bow of the U constituting a trailing portiondisposed parallel to said leading portion whereby said elements will4 be Vcompletely filled with the heat transfer iiuid d uringl ,the descending rotary ymovement of their leading portions below saidliuidlevel and vrwill retain at least a Vportion of said ,uid Vthroughout subsequent rotation to a positionpwhereinV their leading portions descend into axial alignment,withsaidfluid level to admit a new charge of uid into said` elements, j h 4 y y, 5. Heat exchange apparatus comprising, in combination, anl upwardly opening receptacle, a hollow rotary drum journalled in said receptacle for rotation about a horizontal axis, means for continuously rotating said drum, fluid conduit means delivering a heat transfer uid to the interior of said drum, means maintaining a preselected iiuid level in said drum, and a series of hollow heat exchange elements radially disposed in longitudinally and angularly spaced relation on said drum for rotation therewith, each of said elements comprising a U-shaped pipe of small cross section relative to the cross section of said drum and having an inner end fixed to and opening within the interior of said drum and a closed outer end, an air relief conduit open at both ends disposed within said pipe and extending from a point adjacent the closed end thereof through the open end and into the interior of said drum a distance at least as great as the radius of the hollow of said drum to prevent air lock in the closed end of said pipe, the leg of said U-shaped pipe adjacent said inner end constituting a leading portion extending along a radial axis of said drum and the other leg of said U-shaped pipe connected to said leading portion by the bow of the U constituting a trailing portion disposed parallel to said leading portion whereby said elements will be completely filled with the heat transfer fluid during the descending rotary movement of their leading portions below said fluid level and will retain at least a portion of said iluid throughout subsequent rotation to a position wherein their leading portions descend into axial alignment with said uid level to admit a new f charge of uid into said elements.

6. Heat exchange apparatus comprising a stationary upwardly opening tank, a hollow rotary drum extending longitudinally of and disposed centrally within said tank, trunnion means on opposite ends of said drum having hollow conduits extending the length of said trunnion means and opening into the interior of said drum, journal means mounted in the end walls of said tank for rotatably supporting said trnnnions and said rotary drum, means for continuously rotating said drum, fluid conduit means communicating with the conduit in one of said trunnions for delivering a heat transfer fluid to the interior of said drum, fluid draining means communicating with the conduit in the other of said trunnions for maintaining a preselected fluid level within said drum substantially aligned with the medial axis thereof, and a series of hollow heat exchange elements radially disposed in longitudinally and angularly spaced relation on said drum for rotation therewith, each of said elements comprising a U-shaped pipe of small cross section relative to the cross section of said drum and having an inner end fixed to and opening within the interior of said drum and a closed outer end, an air relief conduit open at both ends disposed within said pipe and extending from a point adjacent the closed end thereof through the open end and into the interior of said drum to prevent air lock in the closed end of said pipe,` the leg of said U-shaped pipe adjacent said inner end constituting a leading portion extending along a radial axis of said drum and the other leg of said U-shaped pipe connected to said leading portion by the bow of the U constituting a trailing portion disposed parallel to said leading portion whereby said elements will be completely filled with the heat transfer fluid during the descending rotary movement of their leading portions below said uid level and will retain at least a portion of said iiuid throughout subsequent rotation to a position wherein their leading portions descend into axial alignment with said fluid level to admit a new charge of fluid into said elements.

7. Heat exchange apparatus comprising a stationary upwardly opening tank, a hollow rotary drum extending longitudinally of and disposed centrally within said tank, trunnion means on opposite ends of said drum having hollow conduits extending the length of said trunnion means and opening into the interior of said drum, journal means mounted in the end walls of said tank for rotatably supporting said trunnions and said rotary drum, means for continuously rotating said drum, fluid conduit means communicating with the conduit in one of said trunnions for delivering a heat transfer iiuid to the interior of said drum, iiuid draining means communicating with the conduit in the other of said trunnions for maintaining a preselected uid level within said drum substantially aligned with the medial axis thereof, and a series of hollow heat exchange elements radially disposed in longitudinally and angularly spaced relation on said drum for rotation therewith, each of said elements comprising a U-shaped pipe of small cross section relative to the cross section of said drum and having an inner end fixed to and opening within the interior of said drum and a closed outer end, an air relief conduit open at both ends disposed within said pipe and extending from a point adjacent the closed ond thereof through the open end and into the interior of said drum a distance at least as great as the radius of the hollow of said drum to prevent air lock in the closed end of said pipe, the leg of said U-shaped pipe adjacent said inner end constituting a leading portion extending along a radial axis of said drum and the other leg of said U-shaped pipe connected to said leading portion by the bow of the U constituting a trailing portion disposed parallel to said leading portion whereby said elements will bc completely filled with the heat transfer uid during the descending rotary movement of their leading portions below said tiuid level and' will retain at least a portion of said fluid throughout subsequent rotation to a position wherein their leading portions descend into axial alignment with said fluid level to admit a new charge of iiud into said elements.

References Cited in the file of this patent UNITED STATES PATENTS 203,004 Cutler Apr. 30, 1878 1,740,192 McNeil Dec. 17, 1929 2,650,175 Rodriguez Aug. 25, 1953