US2324837A - Electric heater - Google Patents

Description

July2o,1943.y C., HALL 2,324,837

ELECTRIC HEATER Filed Aug. 29 ;l942

Patented July 20, 1943 ELECTRIC HEATER Chester I. Hall, Rexford, N. Y., assigner to General Electric Company, a corporation of New York Application August 29, 1942, Serial No. 456,660

7 Claims. (Cl. 21S-40) Y This invention relates to electric heaters, more particularly to electric heaters of the electrode type which function to heat a substance by pass ing current through it, and it has for its object the provisionof an improved electric heater of this character.

This invention is particularly applicable to an electric heater of the electrode type for heating liquids, such as milk, vegetable and fruit juices, beer and the like in order to pasteurize the liquid. In order to pastcurize liquids of this character, it is extremely important that every part of the liquid be heated to the critical pasteurizing temperature and that this temperature be held for a predetermined period of tin e. If thisis not done, particles of the liquid may retain a colony or colonies of bacteria which later will grow and contaminate the whole.

In certain commercial pasteurizers now on the market, the liquid isv forced to ow upwardly continuously through an electrode chamber, the walls of which are defined in part by spaced electrodes. .As the liquid Vpasses through ythe wchamber itis heated to a predetermined temperature by the passage of alternating current through it from one electrode to the other. Generally, these electrode chambers have had a pair of opposed electrodes which subjected the liquid stream of a uniform current density, and consequently heated all particles of the liquid uni formly to insure complete pasteurization.

These electrode chambers inherently impose a single phase load on the power system.k This Was not objectionable as long' as the capacity of the apparatus was relatively small; thus, a milk pasteurizer, which handled about 150 gallonsper hour, has an electrical rating of about 18 kilowatts, which is not great enough to irnposeV too unfavorable conditions on the generating equipment. However, it has been repos-ed to increase the capacity cf certain milk pasteurizing apparatus to about 100G to 12130 gallons per hour. Such an apparatus requires an electrical supply of more than 100 kilowatts.

Such a large single phase heater when connected to a three-phase power system imposes a serious unbalanced load upon the transmitting and generating equipment, which as is well known is attendant with undesirable operating conditions in the equipment.

This invention contemplates the provision of an improved pasteurizer electrode chamber which will obviate this objectionable feature of the single phase double electrode chamber.

In accordance with this invention, the electrode chamber is provided with three electrodes which are adapted to be connected to the three supply Wires of a three-phase power source; the

load imposed on the electrode supply system therefore is balanced.

It further contemplates the provision of such a chamber' which will give uniform current density throughout the liquid stream, thus insuring uniform heating of all particles of the liquid. This is accomplished by giving the ectrode surfaces in contact with the liquid a predetermined convex curvature with relation to the spacing between them.

In addition, another object ci this invention is the provision of an improved coolingr system for preventing overheating of the electrode surfaces that contact the liquid stream.. one form of this invention, this system includes cooling liquid passageways directed through the interior of the electrodes themselves.

Other objects of this invention include the provision of an electrode chamber structure which lends itself to easy assembly and disassembly, and which is inexpensive in construction.

For a more complete understanding of this invention, reference should be had to the accompanying drawing in which l is a vertical sectional View of a threeephase electrode pasteurizing chamber embodying this invention; Fig. 2 is a sectional View taken through the line 2 2 of Fig. l and looking in the direction of the arrows; Fig. 3 is a sectional View taken through the line 3-3 of Fig. l and looking in the direction of the arrows; and Fig. 4 is a diagrammatic representation of the electrode chamber of Figs. 1-3 illustrating the manner in which it is connected into the liquid pasteurizing circuit, and also the way in which it is connected to a three-phase electrical power source.

Referring to the drawing, this invention has been shown in one form as applied to a three-v phase electrode chamber for pasteuriginz milk. This chamber, as shown, comprises pair of opposed end membersan upper member Il! and a lower member il. These are formed of any suitable mechanically streng, electrically insulating material, such porcelain.

Mounted in the space between the end members il] and li is an electrode chamber iid. This defined by the end members il; and i l, by three electrodes spaced 120 apart, and by three electrically jnsulatine walls i3 inserted between the electrodes. The electrodes i2, as shown, are substantially homogeneous, and are formed of any suitable material-#preferably carbon; and while the walls I3 may be made of any suitable non-conducting materiaLI prefer to form them of glass. Suitable gaskets Id are interposed between the electrodes I2 and the walls I3 in order to make fluid-tight joints between these members. i It will be observed that the electrodes I2 and glass walls I3 extend throughout the` full distance between the two end members Il) and II,

which members preferably will be provided with recesses I5 and I6 respectively in their opposedsurfaces to receive the end sections of the electrodes and walls. Inserted in these recesses' between the end surfaces of the electrodes I2 and Walls I3, and the bottom walls ofthe .recesses are sealing gaskets Ia and I6a.

As shown, the outside surfaces Iib of the electrodes I2 have an arcuate shape. these surfaces so as to secure the electrodes I2 and walls I3 together are upper and lower clampirrg rings,Y II and I8`. Each of these members is in the form of a brokenv ring provided with outwardly extending flanges YI9l atv the ends. These flanges are clamped together byfmeans' of bolts zu.

The clamping rings Ilv andv I3 also function to clamp-suitable relectrical supply contact mem-V bers 2l to the' outer surfaces Ib of the electrod'es.V These members have vabout the same length as the electrodes and extend fromV one Y edge thereof to the' other, and have iianges 2Ia Yformed on their lower ends with which to make electrical connections with a source of electrical supply. Interposed between the endle'dges of the contacts 2l are arcuate-shaped insulating sheets 22, which will be made of any suitable rmaterial, such as Textolite. Preferably andY as material, such as Textolite.

Surrounding the contacts ZI and the insulating sheets 22' is a cylinder 2d formed of la suitable electrically insulating material, suchV as *'Iextolite. This cylinder also is secured by the rings Il andY I8; as shown.

.The outer insulating cylinder 24 is provided with three windows 25" opposite the glass insulating walls I3 so that the milk stream may be viewed. Y Y v Y The two end sections Ill and II are clamped together by means of a plurality of elongated bolts 2l? which, as shown, are directed through upper and lower metallic endV plates 28 and- 29 fittedl to the top and bottom surfaces of the end members Illand I I so as to clamp themA together. Interpcsed between these surfaces of the end members andthe plates 28 and .'29 are suitableseallng gaskets 313 and 3l respectively.

The end member II hasV afluid supply passageway 32 connected withzthe electrode chamber I-Ia while the end member IIB is provided withA a fluid discharge passageway 33 connected with this chamben It will be understood that inthe operation ofr the apparatus, the milk stream to be treated is forced upwardly through the passageway 32 into the 'electrode chamber Ilf andV thence is discharged out throughthe passageway to conduct the milk awayfrom Ythe apparatus; as shown, a SuitableV milk supply pipe 34? communicates with the passageway 32, while a suitable dischargepiper isconnected with the discharge passageway. It will' be Encir'cling observed, therefore, that the electrodes I2 and insulating walls I3 extend upwardly parallel to the direction of ow of the liquid stream.

It is contemplated that the three electrode contact plates 2l will be electrically connected respectively with the three conductors of a threephase supply system 36, as shown in Fig. 4. In order that the electrodes I2 thus supplied will subject the liquid stream flowing. opposite them to a uniform current density throughout, I give the electrode surfaces 3'I which contact the liquid stream a convex curvature, as shown in Fig. 3'; the curvature of the surfaces 31 is such thatv the current density in the liquid stream in any area normal to the direction of flow is substantially imiform, whereby the liquid flowing through the electrode chamber is uniformly heated. It will'be observed that the surfaces 38 of the-walls I3 contacting the liquid stream will be given a plane surface normal to the milk ilow. TheA electrodes I2 must be cooled in order to prevent them from attaining too high a tem'- peraturewhi'ch might result in burning particles of the liquid. The cooling systemarranged in accordance with this invention includes passage'- ways 39 which are formed in the electrodes themselves. YIn other words, the electrodes'are hollow' and are so arranged that a relatively large liquid passageway is formed through them. Cool'- ing waterv is forced through the electrodes in a direction opposite! to the direction of ow of the fluid in the electrodechamber IIcr.VY Thecooling water is forced continuously into the upper ends of the electrodes', is caused to ow downthrough them, and then is discharged from the electrodes at the bottom.V In order to supply the electrodes with the cooling water' the upper endy member III is provided with a ycircular passageway 6I! vinto which the water is fed by means of a supply'pipe 4I. The circular passageway` All is connected withA the three electrodeV chambers 39 by three vertical passageways 42. The lower Vend member I`I is provided with asimilar circular passageway 43 connected with the lower endsV of the channels 39' by means of three passagewaysY '46. Connected with the discharge passageway 43 is a discharge piperiwhich has a pinched section I6 that functions to keep full columns of the cooling water in the hollow electrodes.

Y hold the temperature constant.

' are connected to the three conductorsV respectivelyV of a three-phase alternating current supply source 36. The voltage of this source is controlled* by means of aY temperature-responsive element d'9 which responds to thetemperature of the milk streamflowing away from the electrode chamber so that a substantially constant temperature is held in the milk stream.V While any suitable temperature responsive elementV may be used, I prefer to use an element of the type described and claimed in my Patent No. 2,271,975; dated February 3, 19.42. As there described, this element issuch that its electrical resistance varies widely with temperature changes. Any suitable controller 50 which will operate responsively to such changes in resistance may be used to control the Voltage applied to the electrodesin order to It will be observed that one of the features of this invention is the provision' of means for readily disassembling the electrode chamber and for reassembling it. To disassemble the chamber, it

' is merely necessary to vremove the large bolts 21 These walls may be separated merely by removing the bolts 2li of the clamping rings. To reassemble, it is of course only necessary to place the walls I2 and i3 together, along with the supply contacts 2l, insulating members 22, and insulating cylinder 24, and then clamp these members together by the two rings I1 and I 8.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modications may be made, and I, therefore, contemplate by the appended claims to cover any such modications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. An electric pasteurizing device comprising a pair of electrically insulating end members, a plurality of spaced hollow electrodes extending between said end members, said end members having fluid passageways therein arranged to interconnect said electrodes so that a cooling fluid may be circulated between said end members through the interior of said electrodes, insulating members extending between said electrodes, and said end members, electrodes and insulating members being arranged to define a heating chamber for heating liquid circulated therethrough.

2. Electric pasteurizing apparatus adapted to be energized from a polyphase source of electric power comprising an electric heater having a plurality of spaced electrodes adapted to be connected to the various phases of said source of power, and also havingl a plurality of spaced electrically insulating members interposed between said electrodes, said electrodes and insulating members deiining a chamber in which the liquid to be heated is received, all of the surface areas of said electrodes that Contact with the liquid have a predetermined form such that the current density through the liquid is substantially uniform whereby the liquid is substantially uniformly heated.

3. Pasteurizing apparatus comprising an electric heater having an electrode chamber through which liquid to be heated is circulated in a predetermined direction, a plurality of spaced electrodes disposed in said chamber and extending in the direction of ilow of liquid through said chamber, said electrodes being hollow so as to define internal passageways extending therethrough, and means for circulating a cooling fluid through said electrodes so that it iiows in the direction opposite of the direction of ilow of said liquid.

4.-. An electric heater comprising a pair of opposed end members formed of electrically .insulating material, said members having shallow circular recesses in their faces opposing each other, an electrode assembly having a plurality of spaced electrodes having arcuate-shaped exterior surfaces, a plurality of insulating members between said electrodes, readily detachable bands clamping said electrodes and insulating members together, said assembly being interposed between said end members so that its ends are received in said recesses, and readily detachable clamping means securing end members together.

5. A device for heating liquid by passing an electric current therethrough comprising a pair of end members formed oi electrically insulating material, a plurality of spaced electrodes extending between said end members, insulating members extending between said electrodes, said end members, electrodes, and insulating members being arranged to dV ne an electrode chamber for heating liqu'd contained therein, said electrodes having cooling passageways extending through them and said end members having uid passageways therein arranged to interconnect said electrodes so that a cooling iiuid may be circulated between said end members through the interior of said electrodes.

5. Electric pasteurizing apparatus adapted to be energized from a source cf three-phase electric power comprising an electric heater having a chamber through which liquid to be heated is circulated, said chamber having three equally spaced electrodes and three equally spaced electrically insulating members between said electrodes, said electrodes and insulating members dening the chamber through which the liquid to be heated is circulated, and said electrodes and insulating members extending substantially parallel to the direction of the liquid flow, the surfaces of said insulating members in contact with the liquid being substantially at, and the surfaces of said electrodes in Contact with said liquid having a convex curvature such that the current density through the liquid in any area normal to the direction of flow is substantially uniform whereby liquid flowing through said chamber is substantially uniformly heated.

7. A milk pasteurizing electrode having substantially homogeneous walls formed of carbon, one of said walls having a surface adapted to be exposed to the milk stream, and said walls defining an internal passageway through the electrode for receiving a cooling iluid.

CHESTER I. HALL.

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