US3887759A

US3887759A - Evaporative cooling system employing liquid film evaporation from grooved evaporator surface and vapor push pump for circulating liquid

Info

Publication number: US3887759A
Application number: US452945A
Authority: US
Inventors: Fred W Staub; Philip G Kosky
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1972-11-29
Filing date: 1974-03-20
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03

Abstract

Within a vaporization chamber which houses apparatus to be cooled (e.g., a transformer) a film of liquid flowing over a heated surface of said apparatus is evaporated thereby cooling the apparatus. The surface includes grooves which stabilize the distribution of a flowing liquid film so that all sections of the surface are maintained in a wetted condition by the flowing film thereby eliminating, or significantly reducing, the occurrence of dry, and therefore hot, spots on the surface. A vapor push pump within the vaporization chamber recirculates liquid so that the liquid can be redistributed as a flowing film over the aforesaid grooved surfaces. The use of a vapor push pump in combination with grooved evaporator surfaces, inter alia, enables significant efficiencies and economies respecting, among other things, the circulation rate of liquid coolant required.

Description

United States Patent- 1191 Staub et al.

[ June 3,1975

[75] Inventors: Fred W. Staub; Philip G. Kosky,

both of Scotia, N.Y.

[73] Assignee: General Electric Company,

Schenectady, NY.

22 Filed: Mar. 20, 1974 21 Appl.No.:452,945

Related US. Application Data [63] Continuation of Ser. No. 310,323, Nov. 29, 1972,

abandoned.

[52] US. Cl 174/15 R; 165/105 [51] Int. Cl. H01f 27/18 [58] Field of Search. 174/15 R, 15 C, 16 R, 16 DH; 165/105; 417/134, 135, 136, 138,208, 209; 336/55, 57, 58, 61

[56] References Cited UNITED STATES PATENTS 1,708,600 4/1929 Beckman 174/15 R 2,924,635 2/1960 Narbut 174/15 R 3,261,905 7/1966 Allen 417/209 X 3,402,767 9/1968 Bohdansky et a1. 165/105 3,452,147 6/1969 Narbut et a1. 174/16 R Primary ExaminerArthur T. Grimley Attorney, Agent, or Firm-Paul R. Webb, 11; Joseph T. Cohen; Jerome C. Squillaro [5 7] ABSTRACT Within a vaporization chamber which houses apparatus to be cooled (e.g., a transformer) a film of liquid flowing over a heated surface of said apparatus is evaporated thereby cooling the apparatus. The surface includes grooves which stabilize the distribution of a flowing liquid film so that all sections of the surface are maintained in a wetted condition by the flowing film thereby eliminating, or significantly reducing, the occurrence of dry, and therefore hot, spots on the surface. A vapor push pump within the vaporization chamber recirculates liquid so that the liquid can be redistributed as a flowing film over the aforesaid grooved surfaces. The use of a vapor push pump in combination with grooved evaporator surfaces, inter alia, enables significant efficiencies and economies respecting, among other things, the circulation rate of liquid coolant required.

3 Claims, 4 Drawing Figures PATEHTEMuz-a [975 4 7 SHEET EVAPORATIVE COOLING SYSTEM EMPLOYING LIQUID FILM EVAPORATION FROM GROOVED EVAPORATOR SURFACE AND VAPOR PUSH PUMP FOR CIRCULATING LIQUID This is a continuation of application Ser. No. 310,323, filed Nov. 29, 1972, now abandoned.

CROSS-REFERENCES TO RELATED APPLICATIONS Hereinafter disclosed, but not claimed herein, is a vapor push pump which may, advantageously, be employed as the liquid recirculation pump in the combination forming the liquid film evaporative cooling system of the subject invention; said vapor push pump being both disclosed and claimed in the U.S. patent application, Ser. No. 310,662, filed Nov. 29, 1972, on even date herewith, now U.S. Pat. No. 3,819,301 in behalf of the inventors H. .Iaster and P. G. Kosky, titled SIN- GLE VALVE VAPOR PUSH PUMP.

A related novel vapor push pump is also disclosed in the U.S. patent application Ser. No. 310,437, filed Nov. 29, 1972, on even date herewith, now U.S. Pat. No. 3,834,835 in behalf of the inventors H. Jaster, P. G. Kosky and F. W. Staub, titled DOUBLE VALVE VAPOR PUSH PUMP.

Also, an example of a liquid film evaporative cooling system, with which the subject invention is concerned, as well as some sophistications which may be included therein is to be had by referring to the earlier-filed U.S. patent application, Ser. No. 266,065, filed June 26, 1972, now abandoned in behalf of F. W. Staub titled VAPORIZATION COOLING SYSTEM USING A SEGREGATED NON-CONDENSIBLE DIELECTRIC GAS FOR PRESSURIZING A VAPOR COOLANT AND MAINTAINING DIELECTRIC STRENGTH WITHOUT SIGNIFICANTLY INTERFERING WITH CONDENSATION OF THE VAPOR.

The entire right, title and interest in and to the inventions described in the aforementioned patent applications, as well as in and to the aforementioned patent applications, and the entire right, title and interest in and to the invention herein disclosed, as well as in and to the patent application of which this specification is a part, are assigned to the same assignee.

BACKGROUND OF THE INVENTION 1. Field of the Invention The subject invention pertains, in general, to the cooling of apparatus (e.g., transformers, etc.) by evaporating a film of liquid from the surface, or surfaces, of the apparatus; and, in particular, to a film evaporation cooling system including, inter alia, liquid pumping means for supplementing condensate coolant, film flow over said surfaces, said surfaces including grooves therein for stabilizing the distribution of the flowing film of liquid coolant.

Although the subject invention is hereinafter described, and illustrated in the accompanying drawing figure, in connection with the liquid film evaporation cooling of static heat producing electrical apparatus, such as a transformer, it is to be understood that the invention may be otherwise employed. For example, the heat producing apparatus need not be electrical and, if electrical, it need not be static. However, for purposes of illustration the subject invention is hereinafter disclosed as being incorporated in the hereinbefore identi- .fied vaporization cooling system disclosed in U.S. pa-

tent application Ser. No. 266,065, filed June 26, 1972, in behalf of F. W. Staub.

2. Description of Prior Art Closed, or hermetically sealed, film evaporation cooling systems employing two-phase fluid coolants have been proposed. In such systems the fluid coolant is distributed while in its liquid phase as a liquid film over a surface, or surfaces, of the apparatus to be coded. Heat transfer from the heated surface of the apparatus to the liquid film evaporates the film thereby cooling the surface and the apparatus. Where the apparatus to be cooled is electrical in nature (e.g., a transformer, etc.) the two-phase fluid coolant is a dielectric and, sometimes, an inert non-condensible dielectric gas is used in addition to the aforesaid two-phase fluid; the inert non-condensible gas serving to maintain adequate system pressure and dielectric strength. In the aforementioned film evaporation cooling system the vapor produced subsequently condenses and is redistributed as a liquid film over the surfaces of the apparatus to be cooled. The evaporation-condensation cycle causes a natural recirculation of the coolant. However, it has been found that the flowing liquid coolant cannot normally be maintained intact on smooth surfaces unless substantial liquid coolant is caused to fiow in addition to the aforementioned natural recirculation rate. If the aforesaid rupture of the liquid film occurs then large dry and therefore hot spots are formed on the surfaces to be cooled resulting in undesirably high temperatures. To reduce the said undesirable situation either excess liquid may be pumped to the cooling surfaces in addition to the condensate flow, or the apparatus to be cooled may be partially submerged in a pool of the liquid coolant.

SUMMARY OF THE INVENTION One object of the invention is to provide a cooling system wherein apparatus to be cooled by evaporation of a film of liquid coolant therefrom need not have substantial portions of the apparatus immersed in a pool, or reservoir, of the liquid coolant.

Another object of the invention is to provide a film evaporation cooling system wherein the quantity of the two-phase fluid coolant required is, under the circumstances, the minimum quantity.

Another object of the invention is to provide a film evaporation cooling system which can satisfactorily perform the required cooling of apparatus throughout a wide range embracing a relatively low heat flux condition of the apparatus to a design heat flux condition of the apparatus.

Another object of the invention is to provide a film evaporation cooling system wherein liquid film is maintained intact to insure intact liquid film flow in order to at least reduce to a minimum the formation of hot, or dry, spots on the surfaces of the apparatus to be cooled.

In accordance with the invention there is provided a film vaporization cooling system comprising: a vaporization chamber containing heat producing apparatus to be cooled and a two-phase fluid coolant comprising a liquid and a vapor, said liquid residing at a bottom portion of the chamber and having a liquid level above the bottom of the chamber, said liquid also being distributed as a film which coats said apparatus, said vapor being produced by vaporization of said liquid by the heat produced by said apparatus, said vapor occupying space in said chamber above said liquid level; a condenser coupled with said vaporization chamber for receiving vapor from said vaporization chamber, condensing the received vapor and enabling its return as a liquid to said chamber; means in said vaporization chamber for receiving the liquid from said condenser and enabling the distribution of said liquid as a film coating said apparatus; and, a vapor push pump for pumping liquid from said liquid residing at the bottom portion of said chamber to said means for enabling the distribution of liquid as a film.

An additional feature of the invention is the inclusion of a number of grooves in the surfaces of the heat pro ducing apparatus to be cooled. The grooves enable the liquid which is coating the apparatus to maintain an intact liquid film thereon thereby significantly reducing the occurrence of hot or dry spots on said surfaces for a minimum liquid coolant rate.

Other objects and features, as well as the many advantages of the invention, appear hereinafter whereat the invention is disclosed by means of an illustrative example with reference to accompanying drawing figures.

THE DRAWINGS FIG. 1 is a schematic diagram of the film vaporization cooling apparatus according to the invention showing a vaporization chamber, a condenser, and an inert gasholding reservoir, a transformer to be cooled within the vaporization chamber and'a vapor push pump.

FIG. 2 is a cross section view taken on section line 2-2 of FIG. 1.

FIG. 3 is another cross section view taken on section line 33 of FIG. 2.

FIG. 4 is a schematic diagram of one form of vapor push pump which may be employed in the combination shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT In the schematic diagram shown in FIG. 1 a transformer designated, generally, by the reference number 11 includes a core 13 of laminated magnetic steel on which a number of conductor windings embedded in a matrix 15 of insulating material are disposed. The transformer 11 may be mounted on a suitable pedestal (not shown) of dielectric material. As shown the transformer 11 is located within a vaporization chamber 17 of a transformer casing 19. A surface condenser 23 is coupled in series between chamber 17 of casing 19 and a gas-holding reservoir 25. The system including the vaporization chamber 17, the condenser 23 and gasholding reservoir 25 form a closed, or hermetically sealed, system. The system is charged with a mass of vaporizable dielectric liquid, such as an inert fluorocarbon liquid; e.g., perfluoro-2-butyltetrahydrofuran which is marketed under the designation FC-75 of the 3M Company. The system is also charged with an inert non-condensible dielectric gas such as sulfur hexafluoride (SP The fluorocarbon liquid coolant has a high dielectric strength. Howeover, the dielectric strength of its vapor varies directly with its density. Accordingly, at low system temperatures when the vapor density is low little dielectric protection is provided. Accordingly, the non-condensible inert dielectric gas is charged into the system to regulate the system pressure for the purpose of maintaining the dielectric strength in the vapor phase in the chamber 17 when the system temperature is low. It is to be understood that the aforementioned inert fluorocarbon liquid coolant and inert gas are specifically named herein as examples and that other liquid coolants and inert non-condensible gases may be employed. The operation of a film vaporization cooling system employing the combination of a non-condensible dielectric gas and a dielectric two phase fluid coolant is disclosed in the U.S. patent application Ser. No. 266,065 of F. W. Staub, hereinbefore more fully identified.

In FIG. 1 the condenser 23 is illustrated as an aircooled surface condenser comprising a plurality of condenser tubes, such as the

tubes

27 and 29. Each of the

tubes

27 and 29 may be provided with spaced cooling fins 31 31 which are connected to the outer wall surfaces of the tubes and, as is well known, such cooling fins promote heat transfer from the tubes. The tube 27 is open at both ends, 27a and 2717; the opening 27a serves as a vapor inlet as well as a condensate outlet port. As indicated the tube opening 27a is coupled to and communicates with the top of the vaporization chamber 17. The tube opening 27b is coupled to and communicates with the gas-holding reservoir 25. Similarly, the condenser tube 29 is open at both ends, 29a and 29b. The opening 29a serves as both a vapor inlet and condensate outlet port and is coupled to and communicates with the top of the vaporization chamber 17. The tube opening 2% is coupled to and communicates with the gas reservoir 25. Mounted within the vaporization chamber 17 near the top thereof and situated di rectly below the

tube openings

27a and 29a is a perforated drip pan 33 which is arranged to receive condensate exiting from the

openings

27a and 29a of the surface condenser 23. Being perforated the pan 33 enables condensate collected therein to be distributed over the surfaces of the transformer 11. The liquid collected in the pan 33 drips or falls on the core 13 which may contain one or more cooling ducts and on insulating matrix 15 where is formed a liquid film which coats the surfaces of the transformer 11. FIGS. 2 and 3, hereinafter discussed, illustrate grooved surfaces. The excess liquid collects in a pool 18 or body of liquid in the bottom of vaporization chamber 17. The pool 18 of liquid coolant, having the liquid level II measured from the bottom of the chamber 17 of casing 19 includes the bottom portion of the core 13 immersed therein.

In FIG. 1 two

condenser tubes

27 and 29 of surface condenser 23 have been shown diagrammatically. However, it is to be understood that more than, or less than, two condenser tubes may be employed for connecting the vaporization chamber 17 with the gas holding reservoir 25, depending on the heat transfer rate required for the specific purpose.

At, for example, median ambient design temperatures the vaporizable dielectric liquid coolant pool 18 fills the bottom portion of vaporization chamber 17 of casing 19 to the level H, as indicated. Heat produced by the transformer 11 vaporizes the liquid film thereby cooling the transformer. The vapor moves upwardly in the vaporization chamber 17 and enters the condenser 23 through the

inlet openings

27a and 29a. The noncondensible dielectric gas is normally largely confined in the reservoir 25 if its vapor density is less than that of the dielectric vapor. The dielectric gas in effect, closes off the opposite ends 27b and 29b of the

condenser tubes

27 and 29. With the

ends

27b and 29b closed by the gas, the vapor moves upwardly in the

tubes

27 and 29 and condenses on the inner wall surfaces of these tubes. The condensate, thus formed, on

the inner wall surfaces of the

tubes

27 and 29 flows downwardly and ultimately exits as a liquid condensate from the

openings

27a and 29a and collects in the perforated drop pan 33. From the pan 33 the condensate is distributed over the surfaces of the transformer 11. Thus, the condensate formed in the condenser tubes returns by gravity, in countercurrent flow relationship with the vapor in the tubes, to the pan 33 where, again, by means of gravity it is distributed within the core 13 and matrix as a film. Subsequently, the heat producing transformer 11 again vaporizes the liquid film thereby rejecting its heat. This vaporizationcondensation cycle is repeated and the temperature of the transformer 11 is maintained within safe operating limits.

Also located within the vaporization chamber 17 is a vapor push pump 10 for recirculating condensate from the pool 18 or body of liquid back to the drip pan 33. The inclusion of a vapor push pump such as the vapor push pump 10 is advantageous. Without a pump 10 to recirculate the condensate from the pool 18 to the drip pan 33 the only liquid return is by the process of the vaporization and subsequent condensation cycle. In such a situation a large mass of the apparatus to be cooled (e.g., transformer 11) must then be immersed in the liquid 18. The details of the vapor push pump 10 are illustrated to the schematic cross section drawing of FIG. 4. As indicated, the pump 10 includes a housing 12 within which there is defined a chamber 14. Housing 12 has a port 16 at the top thereof so that liquid from the external body 18 or pool of liquid may enter port 16 and at least partly fill the chamber 14. The housing 12 is adapted to be submerged in the external body of coolant liquid 18 whose head H, is shown in FIGS. 1 and 4 as being the distance from the liquid level of the body of liquid 18 to the top of the housing 12. Also, at the top of the housing 12 two additional openings 20 and 22 are provided. The opening 20 has one end of a conduit 24 coupled thereto. The conduit 24 has another opening 21 at an opposite end thereof. The opening 21 is above the level of the body of liquid 18. The opening 20 with conduit 24 serves as a vapor vent, the action of which is hereinafter described. Another conduit 26 which is relatively long passes through the opening 22 in the housing 12. The conduit 26 is sealed to the housing 12 where it passes through opening 22. As indicated conduit 26 has an inlet opening 28 at the lower end thereof and an outlet opening 30 at the upper end thereof. The conduit 26 acts as a liquid delivery tube in that the liquid within housing 12 (in chamber 14) is pushed through inlet opening 28 and flows upwardly in conduit 26 where it is discharged at the outlet opening 30 and into the drip pan 33 (of FIG.

- 1) in vaporization chamber 17 (of FIG. 1). The outlet opening 30 is above the external body 18 of liquid. Inlet opening 28 is submerged in liquid in chamber 14 in housing 12. Situated in chamber 14 is a body 32 of low thermal conductivity and low thermal diffusivity. The body 32 includes a bore 34 within which an electric cartridge type heater 36 is located. A pair of electrical leads 38 having an end thereof electrically connected with the heater 36 extends in sealed relationship through the housing 12 to the outside thereof. If desired, the leads 38 may also extend through the transformer casing 19 so that electrical energization of the heater 36 may be initiated entirely from without the .transformer housing 19. The upper portion of the bore 34 communicates with a wider diameter cylindrical space 40 which is closed at its upper end by a seal 60,

or cover. Body 32 also includes a cylindrical well 42 within which the inlet opening 28 of conduit 26 is positioned. Between an outside wall surface of the body 32 and the inside wall surface of housing 12 there is provided the space 44 as shown. Body 32 also includes another bore 46 which communicates the aforesaid space 44 with the other bore 34 within which heater 36 is positioned.

Mounted by suitable means (not shown) at the upper portion of the cylindrical space 40 is a bent vapor outlet tube 48, an inlet end 50 of which is within the cylindrical space 40 and an outlet end 52 of which extends above the uppermost part of the sealing cover 60.

Mounted within chamber 14 is a valve body 54. Valve body 54 is buoyant and may float upwardly or downwardly depending on the liquid level in chamber 14. The upward and downward movement of the valve body 54 is indicated by the arrows in the drawing. Valve body 54 includes a number of openings 58 therein to allow for the passage of vapor therethrough.

Suitable stop members (not shown) limit the downward, as well as lateral movement of valve body 54. In its uppermost position the valve body 54 seals and closes off the port 16 and opening 20. Valve body 54 includes a flexible diaphragm 56 at the top thereof which facilitates closure of port 16 and opening 20. The diaphragm 56 flexes and thereby enters a short distance into the port 16 and into opening 20 for closing these apertures. One suitable material, among others, for fabricating the diaphragm 56 is a thin sheeting of silicone rubber.

Heat generated by heater 36 efficiently raises the temperature of the liquid surrounding the heater and is not wastefully employed in heating body 32 which is fashioned of thermal insulation material. Moreover, heat is not wastefully employed in heating the housing 12 or the body of liquid 61, inter alia.

Operationally, the valve body 54 due to its own weight is situated more or less in the position shown in FIG. 4 and is retained by stop members. In such a position the port 16 and the opening 20 are open. As a result liquid from body 18 enters port 16. The liquid thus admitted fills the chamber 14. When the liquid level in chamber 14 reaches the valve body 54 the buoyancy of the valve body 54 causes it to float upwardly in the liquid thereby closing the port 16 and the opening 20. Some of the liquid within chamber 14 enters space 44 and thereafter enters bore 46 from whence it passes to the other bore 34 to surround heater 36. Heater 36 adds heat to the surrounding liquid and converts it to vapor which rises into the space 40. Vapor from space 40 enters inlet opening 50 and passes therethrough to the outlet opening 52. From outlet opening 52 the vapor exits through openings 58 in valve body 54. Vapor exiting from openings 58 enters the main chamber 14 where it accumulates and exerts pressure on the liquid 61 therebelow. The vapor contained in the upper portion of chamber 14 also acts on the underside of diaphragm 56 to help maintain diaphragm 56 in a position closing port 16 and opening 20. Also, vapor in the upper portion of chamber 14 exerts pressure on the liquid in the lower portion of the chamber 14 thereby pushing or forcing the liquid into riser conduit 26 and through the inlet opening 28 thereof. The liquid entering the inlet opening 28 passes outwardly through con- 7 duit 26 and is discharged at opening 30 into the drip pan 33. (See FIG. 1) When the liquid level within chamber 14 has fallen to a level a little below the lower periphery or rim of the conduit 26 within the well 42 the conduit 26 drains free of liquid and the vapor within chamber 14 and within conduit 26 is in effect vented through conduit 26 and discharged at outlet opening 30. Accordingly, the vapor pressure within the chamber 14 is relieved and the valve body 54 falls due to its own weight, thus opening the port 16 and the opening '20. Also included in combination with vapor push pump 10 is a vapor venting conduit 24. If such a conduit 24 were not provided then float valve body 54 when moved downwardly to open inlet port 16 would not permit vapor in chamber 14 to escape other than through the port 16 during the time that liquid from body 18 was also being admitted through the same port 16. By incorporating a vapor venting conduit 24 with its opening 20 the vapor finds a low impedance path through opening 20 in conduit 24 to escape from pump The vapor push pump 10 will operate even though dielectric gas is occluded in the liquid coolant 18 and is later on enabled to escape.

Another feature of the invention is illustrated in FIGS. 2 and 3 where different sectional views of the insulation matrix are shown. As shown in FIG. 2 the matrix 15 has a plurality of longitudinal ducts 35 extending therethrough vertically. The ducts 35 serve as cooling ducts. The liquid from the drip pan 33 falls onto the matrix 15 and enters the cooling ducts 35, forming therein on the side wall surfaces thereof liquid films which flow downwardly within the ducts 35 to the body of liquid 18. Although a specific number of cooling ducts 35 are indicated in FIG. 2 it is to be understood that more than or less than the specifically illustrated number of ducts 35 may be employed, depending on the maximum temperatures allowed. In the vertical cross section view shown in FIG. 3 a section of one such duct 35 is clearly illustrated. As indicated, the duct 35 has a plurality of grooves 37 formed, or otherwise provided, in its side wall. The longitudinally extending vertical grooves 37 serve to maintain the film of liquid intact so that film will not break into rivulets (as would be the case with a smooth surface) thereby preventing rupture of the film. The aforesaid rupture by the coolant film would allow dry and therefore hot spots to exist.

Although one more or' less specific embodiment of the invention has been described and illustrated in the accompanying drawings, it is to be understood that this has been done for purposes of providing a working example of the invention and that many changes, not departing from the inventive principles involved, will occur to those skilled in the art. The scope of the invention is to be determined from the claims hereinafter set forth. V

What is claimed is:

1. In combination: a vaporization chamber containing heat producing electrical apparatus to be cooled while dielectrically protected and a two phase dielectric fluid comprising a liquid and a vapor, said apparatus including at least one cooling duct extending vertically therethrough, said duct having a plurality of longitudinal extending vertical grooves in its side wall, said liquid residing at a bottom portion of the chamber and having a liquid level above the bottom of the chamber,

said liquid also being distributed as a film which coats said apparatus and coats the vertical grooves of said duct, said vapor being produced by vaporization of said liquid by said heat produced by said apparatus, said vapor occupying space in said chamber above said liquid level, a condenser having one end thereof connected to and communicating with an upper portion of said vaporization chamber occupied by said vapor, a reservoir containing a predetermined mass of noncondensable dielectric gas positioned above said condenser, said condenser having another end connected to and communicating with said reservoir and said gas therein, said gas forming an interfacial contact with said vapor in said condenser at a region therein between said ends of said condenser, said vapor condensing to form liquid condensate in the condenser on one side of said interfacial contact so that the effective condensation area of said condenser lies between said one end of said condenser and said interfacial contact; distribution means in said chamber positioned above said electrical apparatus for receiving liquid condensate from said condenser and distributing the liquid condensate as a film coating said apparatus and coating the vertical grooves of said duct, and a condensate makeup pump for pumping liquid from the bottom portion of the chamber to said distribution means.

2. A hermetically sealed system comprising a chamber including heat producing electrical apparatus therein, said apparatus having at least one surface which includes a plurality of grooves therein, said at least one surface and said plurality of grooves therein being inclined toward a vertical axis of said apparatus, a reservoir located above said chamber, a condenser connected between said chamber and said reservoir and establishing communicationtherebetween, a two phase fluid coolant comprising a dielectric liquid and its dielectric vapor confined in said system, a noncondensible dielectric gas, said gas being largely combined in said reservoir and making contact with said vapor in said condenser, said vapor being largely confined within said chamber and extending into said condenser to the region of contact with said gas, said vapor condensing to form liquid condensate, distribution means for receiving said liquid condensate from said condenser and distributing the liquid condensate as a film coating the grooves of said at least one internal surface and coating said apparatus, and a condensate make-up pump in said chamber for pumping liquid therein between a lower portion of said apparatus to said distribution means.

3. In combination: a vaporization chamber having upper and lower portions, heat-producing apparatus within said chamber, said apparatus having at least one surface which includes a plurality of grooves therein, said at least one surface and said plurality of grooves therein being inclined toward a vertical axis of said apparatus, a two-phase fluid coolant within said chamber, said fluid coolant having a liquid phase and a vapor phase, part of the liquid phase coolant residing at the lower portion of said chamber, the vapor phase coolant being produced by vaporization of the liquid phase coolant by said apparatus, a condenser coupled with the top portion of said chamber for receiving vapor phase coolant therefrom and returning liquid phase coolant thereto, means within said chamber at the top portion thereof for receiving liquid phase coolant from the condenser and distributing said coolant as a liquid 3,887,759 9 l film on said at least one surface and in the grooves for transporting liquid phase coolant from the lower therein so that the liquid film stays intact, without forming rivulets, as the liquid film migrates downwardly in said grooves for collection at the lower porher at the top porno thereof tion of said chamber, and a condensate make-up pump portion of the chamber to said means within the cham-

Claims

1. In combination: a vaporization chamber containing heat producing electrical apparatus to be cooled while dielectrically protected and a two phase dielectric fluid comprising a liquid and a vapor, said apparatus including at least one cooling duct extending vertically therethrough, said duct having a plurality of longitudinal extending vertical grooves in its side wall, said liquid residing at a bottom portion of the chamber and having a liquid level above the bottom of the chamber, said liquid also being distributed as a film which coats said apparatus and coats the vertical grooves of said duct, said vapor being produced by vaporization of said liquid by said heat produced by said apparatus, said vapor occupying space in said chamber above said liquid level, a condenser having one end thereof connected to and communicating with an upper portion of said vaporization chamber occupied by said vapor, a reservoir containing a predetermined mass of non-condensable dielectric gas positioned above said condenser, said condenser having another end connected to and communicating with said reservoir and said gas therein, said gas forming an interfacial contact with said vapor in said condenser at a region therein between said ends of said condenser, said vapor condensing to form liquid condensate in the condenser on one side of said interfacial contact so that the effective condensation area of said condenser lies between said one end of said condenser and said interfacial contact; distribution means in said chamber positioned above said electrical apparatus for receiving liquid condensate from said condenser and distributing the liquid condensate as a film coating said apparatus and coating the vertical grooves of said duct, and a condensate makeup pump for pumping liquid from the bottom portion of the chamber to said distribution means.

1. In combination: a vaporization chamber containing heat producing electrical apparatus to be cooled while dielectrically protected and a two phase dielectric fluid comprising a liquid and a vapor, said apparatus including at least one cooling duct extending vertically therethrough, said duct having a plurality of longitudinal extending vertical grooves in its side wall, said liquid residing at a bottom portion of the chamber and having a liquid level above the bottom of the chamber, said liquid also being distributed as a film which coats said apparatus and coats the vertical grooves of said duct, said vapor being produced by vaporization of said liquid by said heat produced by said apparatus, said vapor occupying space in said chamber above said liquid level, a condenser having one end thereof connected to and communicating with an upper portion of said vaporization chamber occupied by said vapor, a reservoir containing a predetermined mass of non-condensable dielectric gas positioned above said condenser, said condenser having another end connected to and communicating with said reservoir and said gas therein, said gas forming an interfacial contact with said vapor in said condenser at a region therein between said ends of said condenser, said vapor condensing to form liquid condensate in the condenser on one side of said interfacial contact so that the effective condensation area of said condenser lies between said one end of said condenser and said interfacial contact; distribution means in said chamber positioned above said electrical apparatus for receiving liquid condensate from said condenser and distributing the liquid condensate as a film coating said apparatus and coating the vertical grooves of said duct, and a condensate make-up pump for pumping liquid from the bottom portion of the chamber to said distribution means.

2. A hermetically sealed system comprising a chamber including heat producing electrical apparatus therein, said apparatus having at least one surface which includes a plurality of grooves therein, said at least one surface and said plurality of grooves therein being inclined toward a vertical axis of said apparatus, a reservoir located above said chamber, a condenser connected between said chamber and said reservoir and establishing communication therebetween, a two phase fluid coolant comprising a dielectric liquid and its dielectric vapor confined in said system, a noncondensible dielectric gas, said gas being largely combined in said reservoir and making contact with said vapor in said condenser, said vapor being largely confined within said chamber and extending into said condenser to the region of contact with said gas, said vapor condensing to form liquid condensate, distribution Means for receiving said liquid condensate from said condenser and distributing the liquid condensate as a film coating the grooves of said at least one internal surface and coating said apparatus, and a condensate make-up pump in said chamber for pumping liquid therein between a lower portion of said apparatus to said distribution means.