US3187802A - Recirculating heat transfer apparatus - Google Patents

Description

June 8, 1965 F. D. l-ucKEY 3,187,802

RECIRCULATING HEAT HANS FER APPARATUS Filed Jan. 23, 1961 FIE 1 INVENTOR FRANK D. HICKEY BY QQIM/W ATTO RNEY United States Patent ran .ncincnrAriN-o uni tr inarqsrnn arranarns Frank D. Hickey, San Jose, Cniiil, assignor to FM Corporation, a corporation of Deiaware Filed .ian. 23, 1961, Ser. No. 84,485 4 laims. (til. 165-2) The present invention appertains to continuously operating heat transfer apparatus and relates more particularly to apparatus adapted to treat highly viscous materials.

Many problems exist when processing materials such as pureed pumpkin or squash, and baby foods which have a high viscosity in the normal temperature ranges at which such materials are ordinarily handled. As an example, pureed squash or pumpkin is heated for purposes of sterilization before being sealed into cans, or it is ch lled before being packaged for freezing. Since such material does not flow readily during the heating or chilling process, it has been the general practice heretofore to handle the material in batches even though production is very limited. If the heating or chilling operation is performed in certain known apparatus of the continuously operating type, the energy required for advancing the material through the apparatus and for heating or refrigerating the material, and the time required to perform the operation, are disproportionately high even though production may be increased in comparison to the batch process. Another problem results from the tendency of the material to become aerated in continuous equipment either from intrained air or from the formation of gas therein during heating.

An object of the present invention, therefore, is to provide improved apparatus for rapidly heating or chilling highly viscous material on a continuous production basis and at lower cost than heretofore possible.

Another object is to provide improved apparatus for rendering material of the type mentioned temporarily less viscous than it ordinarily is at temperatures within a particular range, thereby improving its flow characteristics to facilitate the processing operation.

Another object is to provide improved apparatus for increasing the rate of heat transfer to or from the viscous material over that obtained in known continuous apparatus of the character mentioned. 7

Another object of the invention is to provide improved apparatus arranged to de-aerate the viscous material.

These and other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings, in which:

FIG. 1 is an axial section through the heat transfer or exchange apparatus of the present invention, with cer-' tain parts broken away and other parts shown in elevation.

FIG. 2 is a transverse section taken along the lines 22 of FIG. 1.

The embodiment of the heat transfer apparatus of the present invention that is illustrated in FIG. 1 is indicated generally by reference numeral 4 and comprises a shell or vessel 6, having an inner cylindrical'side wall 8 enclosing a processing chamber 9. A jacket 11, which will be described more fully hereinafter, is disposed around the inner wall 8 and is adapted to receive a heating or cooling medium for heating or cooling the chamber 9. A U-shaped recirculation conduit 11), through which a portion of the viscous material to be treated is recirculated from one end to the other of the chamber 9, comprising a bight portion 12 and two branch pipes 14 and 16. The branch pipe 14 communicates with one end of the chamber 9 and is disposed in a radial plane of the chamber to direct material into the chamber, and the branch pipe 16 leads tangentially from the side wall 8 of the chamber adjacent the other end. A rotor or impeller 18, which includes a tubular shaft g 9 E 8? ,802 Fatented June 8, 1965 19, is mounted for rotation coaxially in the cylindrical chamber 9 and is driven by a pulley and belt arrangement 20 (FIG. 1 connected thereto and to a source of power (not shown).

The heavy viscous material, which is to be either heated or chilled in the chamber 9, is conducted under controlled, positive pressure from a supply thereof (not shown) through a pipe 22 leading into the recirculation conduit 11) adjacent the juncture 23 of the bight portion 12 and the branch pipe 14. A valve 24 in the supply pipe 22 permits further regulation and control of the material entering the chamber 9. The end of the vessel 6 adjacent the branch pipe 16 is provided with a material outlet pipe as having a valve 28 for controlling the rate at which the processed material is discharged from the chamber 9.

Upon entering the cylindrical chamber 9 through the branch pipe 14, the material is centrifugally impelled, i.e., thrown by centrifugal force, outwardly from the axis of the chamber 9 against the cylindrical wall 8 by the rotor 13 which spins rapidly in the direction indicated by the arrow 29 (FIG. 2). The outlet valve 28, may be closed so that the material entering the chamber through the supply pipe 22 will build up quickly in a rapidly moving uniformly thick layer against the cylindrical wall 8, thus forming a high velocity vortex. The material contacting the wall 8 is thereby heated or chilled, as the case may be. Entrained air or gas in the material is expelled therefrom due to the centrifugal action of the rotor 18 and due to the natural tendency of rapidly rotating material to throw the heavy particles outwardly, causing the light particles to move towards the center of the vortex. The air or gas, referred to hereinafter as gas, is discharged from the vessel 6 through the tubular rotor shaft 19.

The centrifugal action of the rotor 18, in impelling the material outward from its point of entry into the chamber from the branch pipe 14 toward the wall 8, creates a pressure differential between the ends of the branch pipes 14 and 16 in the chamber 9. For this reason, a portion of the material is constantly impelled from the chamber 9 into the branch pipe 16 and is drawn through the recirculation conduit 10 to mix with additional material entering from the supply pipe 22 and re-enter the chamber 9 through the branch pipe 14.

When the material in the chamber 9 first reaches the desired temperature, the discharge valve 28 is opened enough to establish a continuous flow of material out of the chamber 9 but not enough to lower the temperature of the material in the chamber 9.

Referring to FIG. 1 the vessel 6 comprises an outer cylindrical wall 319 of the jacket 11 fixed to the inner wall 3 in spaced, concentric relation by opposite, annular end members 32 and 34. This construction provides the fluid tight jacket 11 in which a suitable temperature controlling medium such as steam, hot or cold water, or refrigerating fluid is circulated around the chamber 9. It will be under stood that the jacket 11 is provided with suitable piping (not shown) having adequate controls (not shown) to regulate the temperature controlling fluid and thereby control the processing temperature of the chamber 9. A spiral fin or rib 38, fixed to the outside of the inner wall 8 within the jack 11, aids in conducting heat to or from the material in the chamber 9 and also strengthens the wall 8.

Que end of the vessel 6 (at the left in FIG. 1) is closed by a circular head 459 fixed in fluid tight relation to the annular member 32 by a plurality of circumferentially spaced cap screws 42 (only one shown, FIG. 1). Centrally of the head 41 is an outwardly directed cylindrical projection 44-, provided at its inner end with'a cylindrical are /e02 recess or extension 46 of the chamber 9. A short drive shaft 43, extending coaxially of the vessel 6, is journaled by bearings (not shown) of any well known type in the outer end portion of the projection 44 and is held therein against axial displacement. Seals 5d of a suitable,.commercially obtainable type are provided in the projection 44 about the drive shaft 48. The shaft 43 is driven by the previously mentioned belt and pulley drive 20.

The bight portion 12 of the recirculation conduit 19 extends generally longitudinally of the vessel 6 outside the jacket 11 with the branch pipe 14 leading into the cylindrical recess 46 through. an opening 51 in the wall of the cylindrical projection 44. Adjacent the other end of the chamber 9, the branch pipe it) leads tangentially from the chamber through an opening 52. (FIGS. 1 and 2) in the inner wall 3 and extends through an opening 53 in the outer wall of the vessel 6. It will be understood that since food products are processed in the apparatus of the present invention, access must be provided to its interior so that it can be adequately cleaned. Accordingly, as shown in FIG. 1, the supply pipe 22 is removably attached to the recirculation conduit ill by means of a union 54 at one end of the bight portion 12 while an access opening (not shown) at the other end of the bight portion 12 is provided with an easily removable cap 54a.

, The end of the vessel 6 opposite the head 4% is pro video. with a removable, circular head 55' disposed against an annular seat 56 in the annular end member 34. Each of a plurality of circumferentially spaced head retaining clamps 53 (only one shown, FIG. '1) is pivoted at 59 to the outer wall 3% and threadedly receives a hand screw 60. When the clamps 58 are positioned as shown in FIG. 1 with the screws 60 forcing the head 55 against the seat 56, the head is held in fixed, operative position in fluid tight relation against the annular end member 34 to close the end of the chamber 9. The head 55 is provided at its center with a bearing housing 62 which projects axially outward from the chamber 9. The material outlet pipe 26 is fixed to the head 55 and leadsfrom the upper part of the chamber 9 adjacent the wall 8.

The rotor 18 comprises the tubular shaft 19 which has a reduced diameter end portion 68 journalled in suitable bearings 69 in the housing 62 in coaxial relation with the drive shaft 48. A shoulder 76 (FIG. 1) on the shaft 19 seats against the innermost one of the bearings 59 to hold the rotor 18 against axial displacement. Seals 71 are mounted in a well known manner in the head 55 about the rotor shaft 19. The inner end 72 of the shaft 19 is drivingly and removably connected to the inner end of the drive shaft 48 by a splined coupling 73 (FIG. 1) of well 7 6b of the tubular shaft 19 with a gas discharge line leading to a suitable location maintained at atmospheric pressure. The line Stl is provided with a normally closed valve 82 which can beopened when desired to establish communication with the interior of the chamber 9 through the tubular shaft 19 and the holes 76. It will be apparent that, upon rotation of the drive shaft 48 by the belt and pulley drive 29 in the direction indicated by the arrow 29 (FIG. 2), the rotor 18 will be rotated in the same direction with the peripheries of the discs '74 moving rapidly adjacent the inside of the stationary cylindrical wall 8.

When the apparatus 4- of the present invention isinitially set in operation to heat or sterilizematerial such peripheral velocity of about feet per second. Steam is supplied to the jacket 11 to maintain the desired processing or sterilizing temperature in the chamber 9. The pureed material, supplied to the apparatus 4 through the supply pipe 22, enters the processing chamber 9 through the branch pipe 14 which leads into the cylindrical recess 3-3. The recess 4-6 functions as a suction inlet whereby the viscous material is delivered into contact with the first disc '74 (FIG. 1) adjacent its center. The rapidly rotating disc, acting somewhat like an impeller in a centrifugal pump, impels or flings the material centrifugally from the suction inlet 46 and against the heated wall 8 of the processing chamber 9. The material continuing to enter the chamber 9 through the pipe 22 is advanced by the pumping action of the discs along the chamber between the wall 8 and the edges of the discs 74 toward the opposite end of the chamber. This material assumes the form of a rapidly rotating, cylindrical vortex extending the length of the chamber 9 and having what will be referred to hereinafter as an eye at its center.

The action of the rotor '18 in impelling the material with considerable velocity away from the recess or suction inlet. 45 places the opening 51 under a relatively low pressure and the opening '52 under a higher pressure. Thus, the material will be sucked away from the pipe 14 into chamber and centrifugally impelled by the discs 74 into the branch pipe 16 to advance. the material through the recirculation conduit 19. The heated material in the conduit, upon reaching the branch pipe 145, mingles with the colder material entering the same through the supply pipe Thereafter, this combined material progresses through the branch pipe 14 andenters the processing chamber 9 as previously described.

The continuous supply of material entering the chamber9 is allowed to incease therein until the inner surface of the rapidly rotating vortex of material is close to but spaced radially from the tubular rotor shaft 19 throughout the length of the chamber 9. During this time, the material is constantly recirculated in the manner heretofore described. When the desired quantity of material has reached the desired processing temperature, the valve 28, it previously closed, is opened to an extent permitting a portion of the processed material to be discharged from the chamber 9 at a rate substantially equal to the rate at which material is supplied through the pipe 22. Processed material leaving the chamber .9 is routed through the pipe 26 to equipment such as a container-filling machine (not shown).

As mentioned previously, the vortex of material is driven by the impeller discs 74 at a high velocity and is in contact with the stationary heated chamber wall 8. Be-

cause of slippage between the discs 74 and the vortex of material, the impeller discs '74 travel rapidly through the mass of material of which the vortex is composed. In this-way, the. impeller discs cooperate with the stationary wall d to vigorously agitate the material. This material, while being agitated and a very short time thereafter, is more fluid in nature and, therefore, flows more readily diu'ing this temporary period than the same material would when not agitated. The vigorous agitation of the material by theimpeller discs 74, in addition to imparting the more fluid condition to the material, improves the transfer of heat between the material and the temperature controlling medium in the jacket 11.

It has been found that in order to recirculate the material at a satisfactory rate through the apparatus 4, the diameter of the recirculation conduit 10 is preferably in the range of from one-fifth to one-fourth the diameter of as pureed pumpkin or squash, the valve 28" in the discharge the chamber 9. With a recirculation conduit 10 of this proportion, it is possible for the material having the more fluid quality to flow longitudinally of the chamber 9 from the end adjacent the suction inlet 46 to the branch pipe 16 under the pumping action of the impeller discs 74 without a large pressure drop which might adversely effectoperation of the apparatus 4. Thus, it is possible to obtain a continuous mass flow or recirculation of the material through the chamber 9 and the recirculation conduit 10.

Because of the agitation of the material and the mass movement thereof relative to the stationary heated chamber wall 8, the rate of heat transfer to the material is high. For instance, when the jacket 11 is supplied with steam at a temperature of 330 F. and when the chamber 9 is 3 feet long and 18 inches in diameter and the recirculation conduit is four inches in diameter, it is possible to raise the temperature of 10,000 lbs. of material 100 F. in an hour, for instance from 180 F. to 280 F.

Material of the type mentioned becomes aerated during its preparation prior to entry into the apparatus and gas is formed therein during heat sterilization. In order to produce a high quality product it is desirable that this material be de-aerated before being canned or packaged. For this reason, the apparatus 4 of the present invention has been constructed to de-aerate the material rather than having to employ separate apparatus for this purpose. The fact that the material is centrifuged, coupled with the fact that the material is made more fluid due to the agitation by the impeller discs 74, results in a tendency of the lighter air and gas entrained in the material to move to the low pressure zone Within the eye of the vortex. Therefore, the eye of the vortex, along which the rotor shaft 19 extends, provides a convenient collecting area for the gas released from the material forming the vortex. Whereas the pressure within the eye of the vortex is higher than atmospheric pressure it is normally relatively lower than the pressure at the periphery of the vortex. If the pressure at the eye of the vortex is allowed to build up it may reach a pressure equal to that existing at the outer periphery of the vortex. If this condition is reached, the processed material would be discharged from the apparatus 4 without being de-aerated.

When the valve 82 is opened the eye of the vortex is vented to the atmosphere through the holes 76 in the tubular shaft 19 and the vent line 80. By occasionally opening the valve 82 it is possible to maintain a lower pressure within the eye of the vortex than at its outer periphery so that the gas expelled from the material being treated collects in the eye thereof. In this way all the material in the chamber 9 is spaced from the shaft 19, very little material will pass through the holes 76 and out vent line 80. However, any material that may be discharged through the line 80 can be salvaged if desired.

Since many different materials may be handled with the apparatus of the present invention, it is apparent that the viscosity of the materials and the amount of heat required to raise the temperature of the materials to the desired level will vary. The apparatus is adapted to meet these conditions by providing means for varying the rate and pressure at which the material is supplied to the chamber 9 and the rate at which it is discharged therefrom. Further, it may be necessary to vary the peripheral velocity of the impeller discs 74 in order to suitably agitate and recirculate the material. Under some conditions it may be necessary to temporarily close the inlet valve 24 in the supply pipe 22 if the chamber 9 fills to capacity before the material therein reaches the desired temperature. Under such a condition and when the desired temperature of the material is reached, both valves 24 and 28 can then be adjusted to regulate the rate at which the material is processed in accordance with the rate at which it reaches the processing temperature.

While only one example of an operation of treating material in the apparatus 4 of the present invention by the use of heat has been described, it is to be understood that the apparatus 4 can just as successfully be used to cool or chill the material. When performing a material cooling operation the jacket 11 is supplied with a refrigerant or other suitable cooling fluid. Under such a condition the apparatus 4 will function in the same manner as previously described except that heat will be 6 conducted from the material in the chamber 9 to the fluid in the jacket 11.

In order to gain access to the interior of the apparatus 4, the recirculation conduit 10 can be opened as previously described. By releasing the clamps 58 in a manner apparent from FIG. 1, the head 54 and the rotor 18 can be Withdrawn from the chamber 9 as a unit. It will be understood that the splined coupling 73 enablcs the rotor shaft 19 to be withdrawn axially from the drive shaft 48 in order to remove the rotor 18 from the chamber 9. The manner in which the apparatus 4 is reassembled preparatory to its operation is the reverse of the above-described procedure.

It will be apparent from the foregoing description that the apparatus of the present invention is capable of either rapidly heating or cooling highly viscous liquids at low cost because of the high rate of heat transfer to or from the viscous material obtained as a result of agitating the material to improve its fluid characteristics and by recirculating the material through the processing chamber 9. Additionally, a superior product is obtained by use of the apparatus 4 of the invention because the, material is de-aerated 'by the time it is discharged from the vessel 6.

A modified form of the present invention may provide means for introducing material into the chamber 9 separately from the branch pipe 14 of the conduit 10 so that recirculation is performed independently of supplying material to the chamber.

While a particular embodiment of the present invention has been shown and described it will be understood that the apparatus of the present invention is capable of modification and variation without departing from the principles of the invention and that the scope of the invention should be limited only by the scope and proper interpretation of the claims appended thereto.

The invention having thus been described, what is believed to be new and desired to be protected by Letters Patent is:

-1. A method of heating viscous material comprising the steps of violently agitating and desaerating the material and forming it into a vontex, moving the vortex along a heated surface with the material in heat-transfer contact with the surface, moving the material out of contact with said surface and breaking up the vortex to permit the particles of material to become reoriented relat1ve to the surrounding particles, and deaerating the material and reforming the vortex and moving it along said heated surface in contact therewith.

2. In a heat exchange apparatus for treating viscous material, a vessel having a material outlet and a sidewall providing a heat transfer surface defining a cylindrical processing chamber for heating or cooling the material therein, a recirculation conduit disposed exteriorly of said vessel and leading at its inlet end out of the processing chamber adjacent one end at the periphery of the chamber and leading at its discharge end coaxially Into the processing chamber at the opposite end thereof, means providing a material inlet leading into said recirculation conduit, impeller means comprising a plurality of axially spaced discs mounted in the chamber in coaxial relation thereto for rotation to impel material from within said conduit at its discharge end and against the side wall of the chamber to create a low pressure area in said conduit adjacent the discharge end to draw material through the material inlet in said conduit and through said conduit from adjacent said one end of the processing chamber for the return of the material into the processing chamber at said opposite end to recircula-te the material, and drive means connected to said impeller to operate the same.

3. In apparatus for deaerating viscous materials such as pureed pumpkin, a vessel having a material inlet and a material outlet and a side wall providing a heat transfer surface defining a horizontally extending cylindrical processing chamber, a coaxial perforate hollow shaft ro tatably mounted in said chamber, impeller means comprising a plurality of axially spaced discs secured 'coaxially to said perforate hollow shaft for impelling the material centrifugally into a cylindrical, vortex against the cylindrical Wall of the chamber, said perforate hollow shaft establishing communication between the interior of the chamber and the outside atmosphere, the cylindrical vortex having an eye extending along said perforate, hollow shaft with the material formingsthe vortex defining the eye being spaced outward from the outer surface of said perforate hollow shaft, said perforate hollow shaftincluding outlet means arranged to vent the eye of the vortex to the outside atmosphere, and drive means connected to said impeller means to operate the same.

4. In a heat transfer apparatus for treating viscous material, a vessel having a material inlet and a material outlet and a side wall providing a heat transfer surface defining a cylindrical processing chamber, a recirculation conduit disposed exteriorly of said vessel and communicating between a first location in the processing chamber at theside thereof and a second location in one end of the processing chamber spaced radially inwardly from the side Wall of the chamber, a coaxial perforate shaft rotatably mounted in said chamber, impeller means comprising a plurality of axially spaced discs secured coaxially to said perforate hollow shaft for impelling material centrifugally from within said conduit at said second location and into a cylindrical vortex againstthe cylindrical wall of the processing chamber and into the end of said recirculation conduit at said first location to create a low pressure area in said conduit adjacent said second location to circulate the material in the processing chamber and through said conduit to recirculate the material, outlet means for said perforate hollow shaft establishing communication between the interior of said processing chamber and the outside atmosphere, the cylindrical vortex having an eye extending along said perforate hollow shaft with the material forming the vortex defining the eye being spaced radially outward from the outer surface of said perforate hollow shaft, said perforate hollow shaft being arranged to vent the eye of the vortex to the outside atmosphere, and drive means connected to said impeller means to operate the same.

References Cited by. the Examiner UNITED STATES PATENTS De Haven Miller et al. 165108 CHARLES SUKALO, Primary Examiner.

HERBERT L. MARTIN, PERCY L; PATRICK, JAMES W. WESTHAVER, Examiners..

Claims (2)

1. A METHOD OF HEATING VISCOUS METAL COMPRISING THE STEPS OF VIOLENTLY AGITATING AND DE-AERATING THE MATERIAL AND FORMING IT INTO A VORTEX, MOVING THE VORTEX ALONG A HEATED SURFACE WITH THE MATERIAL IN HEAT-TRANSFER CONTACT WITH THE SURFACE, MOVING THE MATERIAL OUT OF CONTACT WITH SAID SURFACE AND BREAKING UP THE VORTEX TO PERMIT THE PARTICLES OF MATERIAL TO BECOME REORIENTED RELATIVE TO THE SURROUNDING PARTICLES, AND DEAERATING THE MATERIAL AND REFORMING THE VORTEX AND MOVING ITS ALONG SAID HEATED SURFACE IN CONTACT THEREWITH.

2. IN A HEAT EXCHANGE APPARATUS FOR TREATING VISCOUS MATERIAL, A VESSEL HAVING A MATERIAL OUTLET AND A SIDEWALL PROVIDING A HEAT TRANSFER SURFAE DEFINING A CYLINDRICAL PROCESSING CHAMBER FOR HEATING OR COOLING THE MATERIAL THEREIN, A RECIRCULATION CONDUIT DISPOSED EXTERIORLY OF SAID VESSEL AND LEADING AT ITS INLET END OUT OF THE PROCESSING CHAMBER ADJACENT ONE END AT THE PERIPHERY OF THE CHAMBER AND LEADING AT ITS DISCHARGE END COAXIALLY INTO THE PROCESSING CHAMBER AT THE OPPOSITE END THEREOF, MEANS PROVIDING A MATERIAL INLET LEADING INTO SAID RECIRCULATION CONDUIT, IMPELLER MEANS COMPRISING A PLURALITY OF AXIALLY SPACED DISCS MOUNTED IN THE CHAMBER IN COAXIAL RELATION THERETO FOR ROTATION TO IMPEL MATERIAL FROM WITHIN SAID CONDUIT AT ITS DISCHARGE END AND AGAINST THE SIDE WALL OF THE CHAMBER TO CREATE A LOW PRESSURE AREA IN SAID CONDUIT ADJACENT THE DISCHARGE END TO DRAW MATERIAL THROUGH THE MATERIAL INLET IN SAID CONDUIT AND THROUGH SAID CONDUIT FROM ADJACENT SAID ONE END OF THE PROCESSING CHAMBER FOR THE RETURN OF THE MATERIAL INTO THE PROCESSING CHAMBER AT SAID OPPOSITE END TO RECIRCULATE THE MATERIAL, AND DRIVE MEANS CONNECTED TO SAID IMPELLER TO OPERATE THE SAME.

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