US2794625A

US2794625A - Fluid cooled apparatus with natural and forced cooling

Info

Publication number: US2794625A
Application number: US329977A
Authority: US
Inventors: William C Sealey
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1953-01-07
Filing date: 1953-01-07
Publication date: 1957-06-04
Anticipated expiration: 1974-06-04

Description

June 4, 1957 w. c. sEALEY FLUID COOLED APPARATUS WITH NATURAL AND FORCED COOLING Filed Jan. 7. 1953 2 Sheets-Sheet 1 web. M mm June 4, 1957 w. c. sEALl-:Y

2,794,625 FLUID COOLED APPARATUS WITH NATURAL AND FORCED COOLING l Filed-Jan. '7. 195s 2 Sheets-Sheet 2 United States Patent O FLUID COOLED APPARAT US WITH NA AND FGRCED COOLING William C. Sealey, Wauwatosa, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, `Wis.

Application January 7, 1953, Serial No. 329,977

13 Claims. (Cl. 257-491) This invention relates generally to apparatus provided with fluid by which heat is dissipated and particularly to electrical apparatus, such las transformers, that are embodied in casings having heat dissipators and provided with cooling fluid, such as insulating oil, which is circulated under certain conditions by natural convection and under other conditions by a pump for increasing the rate of ow of the fluid through the heat dissipators.

Various heat exchange means or systems have been provided for cooling electrical apparatus, such as transformers. ln those systems heat of the transformer is transferred from the coils and core thereof to the oil or other cooling fluid by conduction, thereby causing that uid to flow by convection to eventually transfer the heat by conduction to the material of the casing and radiators attached thereto, from which the heat is transferred by radiation and conduction to the cooling air surrounding the casing and radiators. ln such apparatus, where the transformer heats the cooling uid to cause it to ow by convection in a natural circulatory path upwardly through the transformer disposed in the casing and downwardly through the radiator external of the casing, the system will be generally referred to hereinafter as a self-cooled system yhaving a self-cooled rating. And where a uid pump is provided to increase the rate of circulation of fluid, the system will be referred to as forced fluid, having a forced huid cooled rating.

While it has been suggested that encased transformers may have both these systems adapted thereto, such transformers have had to be provided with separate Vheat dissipators for the two systems involving considerable expense, or the flow of fluid by natural convection in the self-cooled system has been considerably restricted because of passing through the pump of the other system, or a bypass and valves or excessively large passages in the pump have had to be provided so as not to impede the natural convection system. lt has also been suggested that the pump and parts of its system may be embodied in the transformer casing, but that results in 'an increase of the size of the casing and complicates the design of the transformer because of the added insulation problems. And naturally, it is impractical to change transformers embodying only a self-cooled system to `add an internally arranged pump of a forced flow system.

ln accordance with the teachings of this invention those two systems may be combined in an improved way eliminating the necessity for separate heat exchangers in the forced fluid ow system and eliminating the necessity of an internal pump. The above mentioned disadvantages are avoided by constructing and larranging the apparatus, its casing and cooling systems in accordance with this invention in such manner as to provide a uid pump preferably disposed externally of the casing and arranging that pump and its intake and discharge with respect to the radiators so that the natural convection ilow of the fluid in the self-cooled system does not pass through the pump but still utilizes the same radiators as the forced fluid flow system Without providing 'a -specially arranged valve or a bypass of the pump. Further, in accordance with the teaching of this invention apparatus now provided with conventional radiators of only a self-cooled system may relatively easily and with minimum expense be provided with `an efficient forced huid system without additional radiators, valves or bypasses and without lessening the effectiveness of the self-cooled system.

It is therefore an object of this invention to provide an improved cooling system for apparatus subject to changes in temperature designed to have both the so-called forced uid `cooled rating 'and self-cooled rating.

Another object of this invention is to simplify the structure and construction of cooling system apparatus of transformers, or the like, designed to have self-cooled rating and forced fluid cooled rating.

Still another object of this invention is to provide for transformers or the like encased apparatus, selfcooled rating Iand forced uid cooled rating by such means for circulating the fluid in the forced uid system that does not interfere with the self-cooled rating and thereby does not lessen the effectiveness of the self-cooled system and in which the self-cooled system of the encased electrical apparatus is as e'icient and inexpensive as a similar selfcooled system designed for a similar electrical apparatus not provided with a forced uid system.

And another object of this invention is to provide an inexpensive forced uid apparatus to be easily and inexpensively added to self-cooled transformers.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. l is a diagrammatic view in elevation of an encased core type transformer made in accordance with the teaching of this invention. The transformer casing and part of one Winding of the transformer are shown in section;

Fig. 2 is an elevation view of a shell type transformer disposed in a liquid filled cas-ing and embodying a modication of the cooling system arranged in accordance with the teaching of this invention. The transformer and casing are diagrammatically illustrated and shown in section;

Fig. 3 is a diagrammatic illustration in elevation of another modification of a cooling system 'arranged in accordance with this invention, adapted to an encased transformer of the shell type which is shown in section;

Fig. 4 is a diagrammatic illustration in elevation of still another modification of Ia cooling system arranged in accordance with this invention, also adapted to an encased transformer of the shell type which is shown in section;

Fig. 5 -is lanother diagrammatic illustration in elevation of an encased transformer of the shell type which is shown in section with va cooling system adapted thereto in accordance with the teaching of this invention. While this cooling system is similar to that shown -in Fig. l the bafe arrangement in the casing is modified to provide better cooling of the shell type transformer disposed as shown in this gure;

Fig. 6 is a diagrammatic illustration in elevation of a modied showing of an encased transformer of the shell type shown in section, with the heat dissipating radiating surfaces comprising the external walls of the casing; and

Fig. 7 is a cross sectional view taken along the line VIl-Vll of Fig. 1.

An electrical apparatus is disposed in a casing provided with heat dissipating means through which the cooling iluid is directed. Suitable dissipating means may be associated with the casing to be substantially a part thereof with adequate bafing to effect lluid paths passing along a wall surface which radiates heat to the surrounding air. These auxiliary paths may be made in any suitable manner as by baling means within the casing but preferably are illustrated as radiators the ends of which ar@ attached to the main portion of the casing at different levels; whether these auxiliary paths be along an external wall surface, or through a radiator they may be said to be auxiliary portions of the casing. In Fig. l, a core type transformer 11 is disposed in a casing 12, with suitable heat dissipating radiators 13 and 14 disposed on opposite ends of the casing, being connected in iluid exchange relation with the casing by

upper iluid conduits

21 and 22, respectively, and by lower iluid conduits 23 and 24, respectively. A cooling and insulating iluid 16 illls the casing. f the iluid is a liquid such as oil, .its level is above the top of the upper iluid conduits, but a cooling and insulating gas would-lill the entire casing. Additional radiators may be disposed along the sides of the casing, having conduit connections to the casing at 19 and 20. Y e

As illustrated in Figs. l and 7, windings of the transforzner comprise axially spaced superposed disk coils 27, which are separated by radially extending arcuately spaced disk spacers 26. Adjacent spacers 26 combine with the disk coils 27 to form horizontally disposed ducts 35 between the disk coils 27 and disk spacers 26. In the bore formed by the superposed disk coils 27 are concentric

cylindrical barriers

29 and 29 which are separated to form vertically disposed

ducts

28 and 28. The spacing of these cylindrical barriers may be maintained by vertical spacing rods 30 between the

barriers

29 and 29 and additional vertical spacing rods 30 between outer barrier 29' and the superposed disk coils 27. Inner vertical duct 28 is formed between

barriers

29 and 29 and outer vertical duct 2S is formed between disk coils 27 and the outer barrier 29. In abutment with the top disk spacers 26 and the top of the

cylindrical barriers

29 and 29 are radially extending arcuately spaced end spacers 25. Adjacent end spacers 25 combine with the top disk coil 27 to form horizontally disposed inlet ducts 15. These inlet ducts 15 form passages for the flow of cooling iluid from the natural passageways in the casing 12 to the

vertical ducts

28 and 28. In similar manner radially extending arcuately spaced end spacers 25 are positioned in abutment with the bottom disk coil 27 and bottom of the

cylindrical barriers

29 and 29 to form horizontally disposed outlet ducts 15.

A part of the iluid entering inlet ducts 15 ilows into and downwardly through the outer vertical duct 28. The remainder of the iluid ilowing through inlet ducts 15 ilows into and downwardly through the inner vertical duct 28 and emerges from the outlet ducts'15.

Fluid also enters the horizontal ducts 35 in the upper half of the winding and ilows into the outer vertical duct 28. Part of the fluid in the outer vertical duct 28 will emerge from the horizontal ducts 35 in the lower half of the winding. The remainder of the iluid in the outer duct will emerge from the outlet ducts 15'.

Batlle means is provided in the casing to aid in directing the ilow of fluid to the ducts in the windings. In this instance, a horizontally disposed baille 31 extends from the approximate outer peripheral surface of the winding 17 to the adjacent sides of the casingY intermediate the upper and lower iluid conduits 21 and 23, providing a relatively small passageway 33 between the baille and outer surface of the winding. A similar horizontally disposed baille 32, which may be integral with `baffle 31, is similarly arranged with respect to winding 18 and the sides of the casing adjacent thereto, extending from the approximate outer peripheral surface of the winding to the adjacent sides of the casing intermediate vthe-upper and

lower iluid conduits

22 and 24.

ln Fig. l suitable means is provided for circulating the cooling iluid under suilicient head to move that iluid at a considerably increased rate through the radiators 13 and 14 when it is necessary to dissipate heat developed at an increased rate by the transformer. This includes Vintake 36, pump 33, and discharge 37. One end of the 4 intake is connected in iluid exchange relation with the lower portion of the casing near the connection of lower conduit 23, and the other end of the intake is connected in iluid exchange relation with the pump. The discharge has its opposite ends connected in iluid exchange relation with the pump and the opposite lower portion of the casing near the connection of lower conduit 24. Baille 34 is attached to the bottom of the casing and extends upwardly to the proximity of baffle 31, thereby separating the lower portion of the casing into two compartments, one of which constitutes an intake compartment for the forced iluid system and the other of which constitutes a discharge compartment of that system. This baille, however, is disposed in the casing so that it does not interfere with the natural convection ilow of the cooling iluid since it is upstanding intermediate the two windings.

Self-cooling by natural convection results in substantially identical iluid current paths on each side of this baille, and the direction of iluid llow through the Winding is generally vertical, When the transformer becomes heated, the fluid ilows by natural convection upwardly through the transformer coils 17 and 18 and from the upper portion of the casing it enters the upper ends of radiators 13 and 14 through

iluid conducting conduits

21 and 22, respectively. That iluid passes downwardly through the radiators as itcools, and then, of course, reenters the casing at the bottom thereof by passing through the lower iluid conducting conduits 23 and 24, respectively.

For forced cooling, that is, with the pump in operation, iluid is pumped into the casing from discharge 37. Some of this iluid passes upwardly through the winding while other of this iluid passes in a generally parallel path upwardly through radiator 14. Then this iluid passes from the upper portion of coil 18 and from the top of radiator 14 to the left hand side of the casing as viewed in Fig. 1 from which it is drawn by the pump to the intake in generally parallel paths that have a direction downwardly through the ducts in winding 17 and downwardly through radiator 13. Under conditions when forced iluid circulation is required for adequate cooling, it matters little whether the iluid circulates through the radiator 14 upwardly from the bottom of the casing or downwardly from the top ofthe casing as the temperature diierential of the iluid at the top and bottom of the casing is only a small percentage of the diilerential of temper- -ature of iluid pumped through the radiator and ambient, and it is this latter differential which is relied upon to cool the iluid.

The arrows shown in the figures represent iluid circulated by the forced iluid system; the arrow head indicates the direction of flow.

In Fig. 2 a sectional View of a three leg shell type transformer is taken in a plane in front of an insulating washer 51 on which there are glued radiallydisposed spacers 52. Washers of this type are conventional in transformers and provide ducts for insulating and cooling iluid to pass between conventional adjacent disk coils (not shown). Thelcooling ducts are across the face of the washer between spacers 52.

Radiators 53 and 54 are connected to opposite sides of the casing 55 to be in iluid exchange relation therewith. A baille 59 is attached to the sides of the casing intermediate the upper and lower connections to the radiators. This baille, like the horizontal bales of Fig. l, extends from the sides of the casing approximately to the winding of the transformer so as to influence the iluid to ilow through the winding.

' Intake 56 of the forced iluid system apparatus has one end thereof connected in iluid exchange relation with the upper portion of the casing and the other end thereof connected to pump 57, and discharge 58 has its lower end connected in fluid exchange relation with the bottom portion of the casing 55 and its upper end connected to pump 57. The intake and discharge are connected on 86, is illustrated in Fig. 4.

.Y nected thereto Vin huid exchange relation.

opposite sides of the horizontal bathe. `Lower leg .61 of the core may also constitute part of a baille upstanding from the bottom Vof Ythe casing which causes the fluid to how transverse the winding when pump 57 is in operation, thereby improving the huid how into the winding and increasing the dissipation of heat of the transformer.

The how of liquid by natural convection for the arrangement of Fig. 2 is conventional, taking similar paths on each side of the transformer, upwardly through the winding and into the radiators wherein it passes downwardly as it cools before reenter-ing the casing at the bottom thereof.

When pump 57 is in operation, intake 56 draws huid upwardly through both radiators, 53 and 54, and upwardly through the casing and transformer winding. This fluid passes through the pump to be discharged into the bottom portion of the casing, whence it passes in parallel Vpaths upwardly through radiators 53 and 54 and upwardly through the transformer. In addition to this upward flow, the :fluid hows transversely across the face of the washer because fluid discharged by the pump is directed by the bathes and influenced by impedance of the path through the winding to take the three parallel paths which means that some fluid Vmust traverse the transformer winding to get to radiator 53.

The view of transformer 66 shown in Fig. 3 is similar to that of Fig. 2, a shell type transformer disposed in similar relation to its casing 67. Bafhe 68 extends laterally between the transformer winding and the side walls ofthe casing approximately midway between the top and bottom of the casing. Lower leg, 71, of thercore may constitute part of a baille at the bottom of the casing extending upwardly to the approximate vicinity of vthe outer periphery of winding 69. In this modification only one heat dissipating unit is shown. This is radiator 72, external of the casing, disposed vertically with its upper end connected to header 76 that is in fluid exchange relation with the upper portion of the casing above baille 68 and with its lower end connected to header 77 that is in fluid exchange relation with the bottom portion of the casing below baille 68. In this embodiment the forced huid system apparatus is also connected to these headers. Intake conduit 78 has its lower end connected to header 77 and its upper end connected to pump 81, and discharge conduit 79 has its upper end connected to header 76 and its lower end connected to the pump.

As in the previously described figures, the conventional how of cooling huid 82 by natural convection in the transformer shown in Fig 3 is not Ainterfered with by the provisions of the forced fluid system apparatus. For forced huid circulation the pump, of course, is in operation and draws fluid from the casing on one side of bathe 68 and from one end of the radiator and discharges huid into the casing on the other side of that baille and into the other end of the radiator, thereby increasing the flow of fluid through the radiator and increasing the cooling ehect of that huid in contact with the transformer. rIn this illustration the intake conduit 78 -draws fluid into header 77 from the bottom of the radiator 72 and from the bottom portion of the casing Vcausing fluid to flow downwardly through winding 69 past bathe 68 and transversely of the winding above bathe 71. The fluid discharged by the pump .passes from the discharge conduit 79 into header 76 and from there in parallel paths into l radiator 72 and into the casing above baille 68.

Another shell type transformer, identified by number In the casing of this modification an upstanding baille 87 and a horizontal baille 88 disposed around the coil 90 are like the similar baffles described in connection with Fig. 3. Radiators 9S and 96 are disposed on opposite sides of the casing, being con- In this modillcation the forced fluid system apparatus includes,` lin addition to pump 91,'intak'e conduit I92 and discharge conduit 93, a vertical baille 94 intermediate the top of the Winding and at least the top of the fluid vlevel in the casing to cause some fluid entering the casing from the pump discharge to flow crosswise of the transformer wind ing. Further, the intake and discharge of the pump are on opposite sides of the vertical bafhes 87 and 94 and on opposite sides of the horizontal 'baille 88. Intake 92 is connected to the lower portion of the casing to the left of

bathes

87 and 94, and the discharge is connected to the upper portion of the casing to the right of bahles 87 and Vthe upper hal-f of 'the Winding (arrow 44).

94.

Radiators

95 and 96 have their respective opposite ends connected directly to the casing, and -preferably ythe upper ends of these radiators connect with the casing at a fluid level below the point where discharge conduit 93 connects to the casing and the lower ends of these radiators connect with the casing Vat a fluid level above the point where the intake conduit 92 connects to the casing.

Preferably, the direction of flow of fluid through the radiators when the pump is in operation is conventionally downward. Fluid discharged into the lupper portion of the casing by the pump takes several generally parallel paths, a feature common to the various embodiments of this invention. In one path some fluid hows downwardly into and through radiator 96; Vin another path some of the lluid hows in a generally diagonal direction downwardly through coil toward the intake conduit 92 disposed in the :left hand bottom portion of the casing, and in a third path huid traverses the upper portion of coil 90 below baille 94 and enters the upper end of radiator 95 through which this fluid passes downwardly and is cooled. The fluid cooled in passing through radiator 96 flows transversely through the lower half of coil 9d because that huid is discharged from the radiator into the bottom right 4hand portion of the casing from which it is drawn across the winding above baille 87 to the intake conduit 92.

In Fig. 5 the arrangement of the casing, the horizontal bathe, the lower lvertical bathe, the radiators'and vthe pump 'and its associated intake and discharge conduits is similar to the arrangement of those parts described with respect to Fig. l. However, the transformer shown in Fig. 5, is of the so-called shell type instead of core type of Fig. l, and a baille 97 is depended from the top of the casing to the approximate vicinity of the transformer core. Thus, this modification has the transformer and baille arrangement shown in Fig. 4, but the pump apparatus arrangement of Fig. l. The intake conduit of the pump apparatus 99 is connected in fluid exchange relation with the casing on the side of the lower upstanding baille opposite to the side of the connection of the discharge conduit, but both the intake and discharge of this apparatus are connected to the casing below the level of the bottom of the radiators. With the structure thus arranged, the pump circulates fluid transversely across the bottom portion of the winding above the bottom upstanding batlle from the discharge conduit to the intake conduit as illustrated by arrow 41. Other'of the huid is circulated upwardly in the casing directed by horizontal bathe 98 to -pass through the winding (arrow 42). Still other of the fluid (arrow 43) is circulated up through vthe radiator which has its intake nearest the discharge conduit of the pump, and from the upper end of that radiator the fluid pumped through that radiator enters the upper portion of the casing and is deflected by baille 9'7 at the top of the casing so as to pass transversely of The pump apparatus draws fluid from the bottom left portion of the transformer which results in fluid being drawn inparallel paths, some huid (arrow 46) going into the top of the radiator to the left of the casing and other fluid (arrow 47) passing diagonally downwardly through the winding in the casing. Thus, in this arrangement the `huid circulated by the pump takes parallel paths through the winding and one or the other radiator.

`sipation of the transformer heat.

Fig. 6 illustrates how the heat dissipating radiators may be incorporated into the casing by suitable bailling` Batlle or conduit means 101 are provided to separate the casing into a main portion 102 holding the transformer 103 and

auxiliary portions

104 and 106 through which a cooling fluid such as an inert gas passes along

heat dissipating surfaces

107 and 108, respectively. During selfcooling, the gas passes upwardly through the transformer in the main portion and downwardly through the auxiliary portions; whereas during forced ilow, pump 109 discharges gas into the bottom right hand side of the casing and the horizontal and vertical parts of the baille means cause thatrupwardly ilowing gas to be directed in parallel paths through the transformer and through auxiliary portion 106; Gas is drawn into the intake conduit 112 of thc pump apparatus from auxiliary portion 104 and lfrom the left side of the main portion.

In all the modiilcations embodying this invention, the construction of the transformer, the radiators and the 'pump may be such that the impedances to the flow of llluid through the transformer and through the radiators and the head on the pump assure a considerable ilow of fluid through all those paths eilecting relatively fast dis- That is, the impedance to iluid tiow preferably is generally balanced through the 'casing and through the radiators.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to one skilled in the art that various changes and modications may be made therein without departing from the .spirit kof the invention or from the scope of the appended claims.

It is claimed and desired to secure -by ILetters Patent: 1. `In combination, a device including a casing containing an apparatus subject to increases in temperature, -a radiator external of said casing, means connecting said radiator in iluid exchange relation with said casing, said device being substantially iilled with cooling lluid, said radiator disposed with said means comprising an upper condui-t interconnecting the upper end of said radiator to an adjacent upper portion of lsaid casing and a lower conduit interconnecting the lower end of said radiator to an adjacent lower portion of said casing whereby said fluid when heated flows 'by natural convection in series upwardly in said casing and downwardly in said radiator, and forced uid flow means disposed independently of said natural convection series fluid path comprising a conduit connected at its opposite ends to said device and a fluid pump disposed intermediate said opposite ends to circulate said iluid lfrom said pump through said casing and said radiator in Kthe same vertical direction Y in parallel paths.

2. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing, said apparatus spaced from the top and opposite sides of said casing, la pair of radiators external of said casing, a iirst :of said radiators rconnected in uid exchange relation With said casing at a first of said sides, a second of said radiators connected in iluid exchange relation with said casing at the other of said sides, said casing containing cooling iluid to a level above the connections to said `radiators, baille means disposed in said casing intermedi- V.ate said opposite sides extending between said apparatus and said casing, whereby said iluid when heated has `natural convection paths upwardly in said casing `and Adownwardly in said radiators, and forced iluid -ilow means external of said casing disposed independently of said radiators including an intake conduit, a pump and a discharge conduit, said intake connected in fluid exchange relation with'said casing on one side of said baille means, said discharge connected in uid exchange relation with said casing on the opposite side of said baille means, whereby said pump causes iluid to ilow :transversely in said casing.

3. In combination, a casing, an apparatus subject to 4'to said radiators, baille means disposed in said casing intermediate said opposite sides extending -between said apparatus and the bottom wall of said casing, whereby said iluid when heated has similar natural convection paths on each side of said baille means upwardly in said casing and downwardly in said radiators, and forced tluid llow means external of said casing disposed independently of said radiators including an intake conduit, a pump and a discharge conduit, said intake connected in iluid exchange relation with 4said casingon one side of said baille means, said discharge connected in lluid exchange relation with said casing on the opposite side of said baille means, whereby said pump causes transverse iluid ilow in said casing, said intake disposed to draw -fluid from the bottom of a llrst of said radiators and the adjacent bottom portion of said casing, said discharge disposed to expel iluid into the bottom of the second of said radiators and the adjacent bottom portion of said casing under suil'icient head to cause some of said ftluid to ilow upwardly through said second radiator and upwardly through said casing and whereby the lluid drawn from said irst radiator by said intake enters said first radiator from the upper portion of said casing.

4. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing spaced from one side of said casing, said apparatus provided with fluid passages therethrough, a radiator external of said casing connected lat its top and bottom in Iiluid exchange relation with said casing, said casing containing cooling fluid at a level above the connections to said radiator, baille means disposed in said casing intermediate the top Iand bottom of said radiator between said apparatus and said side to cause said fluid when heated to flow lby natural convection upwardly in said casing through said fluid passages in series hydraulic circuit with the downward tlow through said radiator, and

forced fluid ilow means independent of said natural convection path through said radiator, said forcedY ilow means including an intake conduit, a discharge conduit and a fluid pump connected between said conduits, said intake connected in fluid exchange relation with said casing on one side of said baille means at a level as low as the bottom of said radiator, said discharge connected in fluid exchange relation with said casing on the opposite side of said baille means at a level -as high as the top of said radiator to `cause fluid circulated by said pump .to pass through both said apparatus and said radiator in hydraulic parallel paths.

5. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing spaced from one side of said casing, said apparatus provided with iluid passages therethrough, a radiator external of said casing connected -at its top and bottom in iluid exchange relation with said casing, said casing containing cooling tluid at a level above the connections to said radiator to cause said fluid when heated to ilow by natural convection upwardly in said casing throughisaid fluid passages in series hydraulic circuit with the downward -ilow through said radiator, Vand forced iluid ilow means independent of said natural convection path through said radiator, said forced flow means including an intake, a discharge and a fluid pump connected between said intake and saiddischarge, said intake connected in Iiluid exchange relation with said casing ata level as low as the bottom of said radiator, said discharge connected in fluid exchange relation with -said casing at` a level as highfas the top ofv said radiator to cause uid circulated by said pump to pass through `both said apparatus and said radiator in hydraulic parallel paths.

6. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing and spaced from the top and opposite sides of said casing, a pair of radiators external of said casing', a first of said radiators connected in fluid exchange relation with said casing to a rst of said sides, a second of said radiators connected in fluid exchange relation with said casing to the other of said sides, said casing containing cooling uid to a level above the connections to said radiators, whereby saidv fluid when heated has natural convection paths upwardly in said casing through said apparatus and downwardly in said radiators, and forced uid means external of said casing disposed independently of said radiators including an intake, a pump and a discharge, said intake connected in uid exchange relation with said casing near the bottom portion of said rst side to draw uid from the bottom of said first radiator and from the adjacent bottom portion of said casing, said discharge connected in fluid exchange relation with said casing near the bottom portion of said other side to expel uid into the bottom of said second radiator and the adjacent bottom portion of said casing.

7. In combination, a casing, an apparatus subject to changes in temperature disposed in said casing, said apparatus having fluid passages therethrough, a pair of radiators external of opposite sides of said casing, a rst of said radiators connected in fluid exchange relation with said casing to a iirst of said sides, a second of said radiators connected in fluid exchange relation with said casing to the other of said sides, said casing containing cooling fluid to a level above the connections to said radiators, bafle means disposed in said casing intermediate the top and bottom of said casing extending between said apparatus and said opposite sides, and forced uid ow means external of said casing disposed independently of said radiators including an intake, a pump and a discharge, said intake connected in iluid exchange relation with said casing to one side of said bafe means, said discharge connected in uid exchange relation with said casing to the opposite side of said bale means, the head on said pump being suicient when said pump is in operation that uid discharge from said pump will flow in parallel paths through the passages in said apparatus and through said radiators.

8. In combination, a casing, an apparatus subject to changes in temperature disposed in said casing spaced from the top and opposite sides of said casing, a radiator external of said casing connected thereto at its opposite ends in fluid exchange relation at the top and bottom portions of a side of said casing, said casing containing cooling fluid to a level above the connections of said radiator to said casing, baffle means disposed in said casing intermediate the top and bottom of said casing extending between said Iapparatus and said sides, and forced uid low means external of said casing disposed independently of said radiator including an intake, a pump and a discharge, said intake connected in fluid exchange relation with said casing lat a level as high as the top of said radiator, said discharge connected in uid exchange relation with said casing at a level as low as the bottom of said radiator, whereby uid circulated by said pump passes through both said apparatus and said radiator.

9. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing, said apparatus spaced from the top and opposite sides of said casing, a pair of radiators external of said casing, a rst of said radiators connected in uid exchange relation with said casing at a rst of said sides, a second of said radiators connected in uid exchange relation with said casing at the other of said sides, said casing containing a cooling fluid to a level above the connections to said radiators, bafde means disposed in said casing intermediate said opposite sides extending between said apparatus and the 10 top of said casing, wherebyV said u'id when heated has similar natural convection paths on each side of said baie means upwardly in said casing and downwardly in said radiators, and forced fluid flow means external of said casing disposed independently of said radiators including an intake, a pump and a discharge, said intake connected in uid exchange relation with said casing on one side of said bae means, said discharge connected in fluid exchange relation with said casing on the opposite side of said baie means, whereby said pump causes fluid to flow transversely in said casing, said intake disposed to draw fluid from the bottom of said first radiator and the adjacent bottom portion of said casing, said discharge disposed to expel uid into the top of said second radiator v and the adjacent top portion `of said casing.

l0. In combination, a casing, an apparatus subject to increases in temperature disposed in said casing, said apparatus spaced from the top and opposite sides of said casing, a pair of radiators external of said casing, a first of said radiators :connected in fluid exchange relation with said casing at a rst of said sides, a second of said radiators connected in uid exchange relation with said casing at the other of said sides, said casing containing cooling uid to a level Iabove the connections to said radiators, baffle means disposed in said casing intermediate said opposite sides extending between said apparatus and the top of said casing, whereby said uid when heated has similar natural convection paths on each side of said bafe means upwardly in said casing and downwardly in said radiators, and forced uid flow means external of said casing disposed independently of said radiators including an intake, a pump and a discharge, said intake connected in uid exchange relation with said casing on one side of said baille means, said discharge connected in iiuid exchange relation with said casing on the opposite side of said baffle means, whereby said pump causes fluid to oW transversely in said casing.

ll. In combination, a casing containing cooling fluid, an apparatus subject to changes of temperature disposed in said casing, a heat exchanger disposed outside said casing and connected in fluid exchange relation at its opposite ends to the top and bottom of said casing, said apparatus being provided with fluid passages therethrough to cause said liuid when heated to ow by natural convection upwardly in said casing through said iluid passages in series hydraulic circuit with the downward flow through said heat exchanger and a forced fluid means connected in uid exchange relation with said casing, said forced iluid means including a uid pump external of said casing and independent of said heat exchanger so as not to interfere with natural convection flow of said uid when not in operation and being disposed in fluid exchange relation with said casing and said heat exchanger so as to cause uid to flow in the same vertical direction in hydraulic parallel paths through said passages and said heat exchanger when said pump is in operation due to the relative impedance to fluid ow in said two hydraulic parallel paths.

12. In combination, a device including a casing containing an apparatus having fluid passages therethrough and subject to changes of temperature, said device substantially filled with cooling uid and having a radiator external of said casing and means connecting opposite ends of said radiator in fluid exchange relation with the top portion and bottom portions of said casing to cause said llui-d when heated to flow by natural convection in series hydraulic circuit upwardly in said casing and downwardly in said radiator, the impedance to uid ilow in said casing being approximately equal to the impedance to uid ow in said radiator, and forced fluid flow means comprising a conduit connected at its opposite ends to said device and including a duid pump disposed intermediate said last mentioned opposite ends, said pump when in operation having sucient head to force said 11` uid to 110W through said casing and said radiator in the same vertical direction in hydraulic parallel paths.

13. In combination, a casing containing a cooling fluid,

an apparatus subject to increases in temprature' disposed in the same vertical direction as the forced flow of uid 15 through said exchanger, said forced uid ow means being external of said casing and independent of said exchanger so as not to interfere with naturalconvection of said fluid when said ovv means is not in operation.

References Cited in the le of this patent UNITED STATES PATENTS 1,706,574 Hodtumv Mar. 26, 1929 1,798,702 Y Roebel Mar. 31, 1931 1,800,163 Thompson Apr. 7, 1931 2,347,989 Burnham May 2, 1944 FOREIGN PATENTS l 348,794 Germany Feb. 18, 1922 France Nov. 9, 1927