Self-pumped cooling device

Abstract

A vapor conduit having a first cross sectional area is connected to an evaporator for refrigerant exiting the evaporator. The evaporator is connected to a reservoir by a filling conduit having a second cross sectional area. A first liquid plug is disposed in the vapor conduit and a second liquid plug is disposed in the filling conduit. A first sum of forces acting on the first liquid plug is less than a second sum of forces acting on the second liquid plug (56) causing the refrigerant to expand into the vapor conduit to a greater extent than into the filling conduit causing continuous circulation of the refrigerant in the same direction. The first cross sectional area of the vapor conduit is greater than the second cross sectional area of the filling conduit for causing the first sum of forces to be greater than the second sum of forces.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

A closed-looped heat exchanger assembly for cooling an electronic device.

2. Description of the Prior Art

All electronic devices generate waste heat. Dissipation of that heat is necessary for the optimum and reliable operation of electronics. With increasing power density of micro-electronic devices, dissipation of the heat load becomes a critical factor in overall system design. Available approaches for electronics cooling include air-cooling, liquid-cooling, and refrigeration.

As an example, for cooling of computer microprocessors, forced air-cooling of finned heat sinks attached to the processor package has been sufficient for several years. However, the relentless increase in processor speed and corresponding heat dissipation has made air-cooling impractical from the standpoint of heat sink size and the noise associated with forced air convection, e.g., fans. Liquid cooling can meet or exceed the power dissipation demands for present and future computer systems. Approaches include forced liquid flow through heat sinks attached to electronic device packages, and the use of thermosiphons that incorporate a closed liquid/vapor flow system.

Heat pipes are attractive since they do not require any mechanical pump, either external or internal, thus reducing size, cost, and noise. They also can accommodate high heat loads since they use the large latent heat of vaporization of the working fluid, and thus “pin” the device temperature to the vapor saturation temperature. However, the maximum power dissipation is limited by the rate of condensing the vapor and returning liquid to the vaporization area to repeat the cycle. The liquid return rate usually uses gravity, wicking or capillary structures that are limited by orientation and flow rate.

Examples of pulsating heat exchangers are included in an article entitled “Passive Oscillatory Heat Transport Systems” by Weislogel, and an article entitled “Thermal Modeling of Unlooped and Looped Pulsating Heat Pipes” by Shafrii et al.

The Shafrii et al. article discloses a method for determining the movement of a liquid plug in an open heat pipe and in a closed heat pipe. Shafrii discloses a first liquid plug having a first sum of forces acting thereon and a second liquid plug having a second sum of forces acting thereon but fails to disclose a given relationship between the first and second sums of forces.

The Weislogel article discloses four pulsating systems: the Tamburini's T-System, the Akachi's Pulsating Heat Pipe, the Weislogel's Pulse Thermal System, and the Cargille's Thermal Transport Oscillator.

The T-System includes a condenser, an evaporator, and a reservoir. A vapor conduit interconnects the evaporator and condenser. A filling conduit interconnects the evaporator and the condenser. The reservoir is disposed along the filling conduit between the evaporator and condenser. A first valve is disposed along the filling conduit between the evaporator and the reservoir and a second valve is disposed along the filling conduit between the condenser and the reservoir for causing the circulation of the refrigerant.

The Pulsating Heat Pipe teaches an evaporator and a condenser and a closed looped conduit winding back and forth between the evaporator and the condenser. A plurality of liquid plugs each having a sum of forces acting thereon are enclosed in the conduit. The heat pipe relies on capillary forces in order to oscillate each liquid plug back and forth between the evaporator and condenser.

The Pulse Thermal System includes a plurality of evaporators in series with a plurality of condensers broken up by two way valves and check valves in order to produce a one way self pumping acting. The Thermal Transport Oscillator discloses an evaporator connected to a three way valve. Two condensers are connected in parallel between the evaporator and the three way valve. The Thermal Transport Oscillator produces a self pumping action via the three way valve which alternates between the two condensers.

Although the prior art discloses self pumping heat exchanger systems, there remains a need for a self pumping system that does not rely on capillary forces or on check valves, and the like, in order to produce the one way self pumping action.

SUMMARY OF THE INVENTION AND ADVANTAGES

The invention provides for a closed looped heat exchanger comprising a refrigerant for undergoing liquid-to-vapor cyclical transformations and an evaporator attached to the electronic device for evaporating the refrigerant by transferring heat from the electronic device to the refrigerant. A vapor conduit having a first cross sectional area defines a flow path for the refrigerant exiting the evaporator. A reservoir holds the refrigerant and has an inlet and an outlet. A filling conduit having a second cross sectional area defines a flow path for refrigerant entering the evaporator. A first liquid plug of the refrigerant is disposed in the vapor conduit and has a first sum of forces acting thereon. A second liquid plug of the refrigerant is disposed in the filling conduit and has a second sum of forces acting thereon. The first sum of resistive forces acting on the first liquid plug is less than the second sum of resistive forces acting on the second liquid plug for creating a head pressure during expansion of the refrigerant causing the refrigerant to expand more into the vapor conduit than into the filling conduit during vaporization of the refrigerant. The refrigerant in the evaporator evaporates and expands into the filling conduit and into the vapor conduit and thereafter condenses in the filling conduit and the vapor conduit causing additional refrigerant to enter the evaporator from the filling conduit. The additional refrigerant causes a cyclical expansion of the refrigerant into the vapor conduit to a larger extent than into the filling conduit for continuously circulating the refrigerant in the same direction through the assembly.

The present invention entails a cooling system that advances the pulsating heat pipe principle by incorporating the ability to self pump coolant vapor and hot coolant liquid at the same time. Because the system does not require a pump its weight, size, and cost are reduced. Furthermore, conduits having a larger diameter can be used for conveying the working fluid to and from the evaporator because the system does not rely on capillary forces. This can result in higher heat dissipation within a simplified package.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a schematic of a self-pumped cooling device illustrating the first conduit cross sectional area being greater than the second conduit cross sectional area;

FIG. 2 is an enlarged and fragmentary view of the embodiment of FIG. 1;

FIG. 3 is an enlarged and fragmentary view of an alternative embodiment of the invention illustrating the first cross sectional are being equal to the second cross sectional area;

FIG. 4 is a schematic view of an alternative embodiment of a self-pumped cooling device;

FIG. 5 is a schematic view of an alternative embodiment of the embodiment shown in FIG. 4 illustrating the evaporator vertically aligned with the condenser and the reservoir;

FIG. 6 is a schematic view of another embodiment of the invention illustrating the evaporator and condenser defining the vapor conduit and intermediate conduit;

FIG. 7 is a perspective view in cross-section of an alternative embodiment of the embodiment shown in FIG. 6 illustrating a plurality of partitions in the evaporator; and

FIG. 8 is a top view of the embodiment shown in FIG. 7 taken at A-A illustrating the arrangement of the partitions, the outlets and the vapor conduits.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a closed-looped heat exchanger assembly 20 is generally shown for cooling an electronic device 22.

A refrigerant 24 is disposed in the assembly 20 for undergoing liquid-to-vapor cyclical transformations. As shown in FIGS. 4, 5, and 6, an evaporator 26 generally indicated is attached to the electronic device 22 for evaporating the refrigerant 24 by transferring heat from the electronic device 22 to the refrigerant 24. The assembly 20 includes a condenser 28 for condensing the refrigerant 24.

The assembly 20 further includes a reservoir 30 for holding the refrigerant 24. The reservoir 30 includes at least one inlet 32 and at least one outlet 34. The refrigerant 24 defines a surface 36 in the reservoir 30. The inlet 32 of the reservoir 30 is disposed above the surface 36 of the refrigerant 24 and the outlet 34 of the reservoir 30 is disposed below the surface 36 of the refrigerant 24.

The evaporator 26 is also disposed below the surface 36 of the refrigerant 24 in the reservoir 30. Although, the assembly 20 can operate with the evaporator 26 at or above the surface 36 of the refrigerant 24, it is preferable to have the evaporator 26 below the surface 36 to allow the force of gravity to assist the circulation of the refrigerant 24.

A vapor conduit 38 defines a flow path for refrigerant 24 exiting the evaporator 26. The vapor conduit 38 has a first cross sectional area A_vc and is made of a material having a first high thermal conductivity. The first cross sectional area A_vc of the vapor conduit 38 is circular but can be of various other shapes such as a ring, as shown in FIG. 6, or a plurality of shapes, as shown in FIGS. 4, 5, 7 and 8. Reference to a conduit includes any fluid communication.

A filling conduit 40 defines a flow path for the refrigerant 24 entering the evaporator 26. The filling conduit 40 has a second cross sectional area A_fc and is made of a material having a second high thermal conductivity. The second cross sectional area A_fc is circular but can be of various other shapes, including a plurality of shapes as shown in FIGS. 6, 7 and 8.

As shown in FIGS. 2, 3, and 6 a first connector 42 interconnects the vapor conduit 38 and the evaporator 26 and has a first low thermal conductivity. The first high thermal conductivity of the vapor conduit 38 is greater than the first low thermal conductivity of the first connector 42 of the vapor conduit 38 which insulates the evaporator 26 from the vapor conduit 38. Similarly, as shown in FIG. 2 and 3, a second connector 44 interconnects the filling conduit 40 and the evaporator 26 and has a second low thermal conductivity. The second high thermal conductivity of the filling conduit 40 is greater than the second low thermal conductivity of the second connector 44 of the filling conduit 40 which insulates the evaporator 26 from the filling conduit 40. The high thermal conductivities of the vapor conduit 38 and filling conduit 40 allow heat transferred from the refrigerant 24 into the vapor and filling conduits 38, 40 to dissipate. The low thermal conductivities of the connectors 42, 44 restrict heat from transferring from the evaporator 26 into the conduits 38, 40 which can cause the refrigerant 24 in each conduit 40, 38 to vaporize prematurely.

In the embodiments shown in FIGS. 1, 6, 7 and 8, an intermediate conduit 46 interconnects the inlet 32 of the reservoir 30 and the condenser 28 for conveying the refrigerant 24 from the condenser 28 to the reservoir 30. The cross-section of the intermediate conduit 46 is circular, as in FIG. 1, but can be of various other shapes, such as a ring as shown in FIG. 6 or a plurality of circles as shown in FIGS. 7 and 8. The vapor conduit 38 defines a flow path extending between the evaporator 26 and the condenser 28 for conveying the refrigerant 24 from the evaporator 26 to the condenser 28. The filling conduit 40 defines a flow path between the outlet 34 of the reservoir 30 and the evaporator 26 for conveying the refrigerant 24 from the reservoir 30 to the evaporator 26.

In the embodiment shown in FIG. 1, the vapor conduit 38 and the intermediate conduit 46 are tubes.

In the embodiments shown in FIGS. 6, 7 and 8, the reservoir 30 has a plurality of holes therethrough defining the filling conduit 40. The condenser 28 is disposed about the reservoir 30 and is axially aligned with the vapor conduit 38 and the reservoir 30. The condenser 28 and the reservoir 30 define the vapor conduit 38 and the intermediate conduit 46 between the condenser 28 and the reservoir 30. These embodiments are compact designs which do not require any tubes.

In FIG. 6, the inlet 32 of the reservoir 30 extend along the periphery of the reservoir 30. The vapor conduit 38 extends about the reservoir 30 and the intermediate conduit 46 extends along the periphery of the reservoir 30.

In FIGS. 7 and 8 the inlet 32 is a plurality of holes extending radially and equally spaced about the reservoir 30. Similarly, the intermediate conduit 46 is a plurality of holes extending radially and equally spaced about the reservoir 30. The condenser 28 has a plurality of cavities defining the vapor conduit 38 and the intermediate conduit 46. The evaporator 26 includes a plurality of partitions 48 defining a plurality of pie-shaped chambers 50. Each of the cavities of the condenser 28 fluidly interconnects one of the chambers 50 of the evaporator 26 and the reservoir 30. Each of the holes in the reservoir 30 fluidly interconnects one of the chambers 50 of the evaporator 26 and the reservoir 30 with at least one hole leading into each of the chambers 50.

In two embodiments, respectively shown in FIGS. 4 and 5, an intermediate conduit 52 interconnects the outlet 34 of the reservoir 30 and the condenser 28 for conveying the refrigerant 24 from the reservoir 30 to the condenser 28. The vapor conduit 38 defines a flow path between the evaporator 26 and the reservoir 30 for conveying the refrigerant 24 from the evaporator 26 to the reservoir 30. The filling conduit 40 defines a flow path between the condenser 28 and the evaporator 26 for conveying refrigerant 24 from the condenser 28 to the evaporator 26.

The embodiment in FIG. 5 is a compact embodiment of the embodiment in FIG. 4, wherein the condenser 28 is vertically aligned with the reservoir 30 and the evaporator 26.

A first liquid plug 54 of the refrigerant 24 is disposed in the vapor conduit 38 and has a first sum of forces F_vc acting thereon. A second liquid plug 56 of the refrigerant 24 is disposed in the filling conduit 40 and has a second sum of forces F_fc acting thereon.

As illustrated in FIG. 1, a thermal valve 58 interconnects the filling conduit 40 and the evaporator 26 for restricting flow of the refrigerant 24 until the refrigerant 24 reaches a predetermined temperature. A thermal valve 58 can avoid failure during startup when the temperature of the evaporator 26 is low. The thermal valve 58 causes the first liquid plug 54 to expand into the vapor conduit 38 and the second liquid plug 56 to remain stationary during startup of the system when the temperature of the refrigerant 24 is below the predetermined temperature.

The assembly 20 is distinguished by the first sum of forces F_vc acting on the first liquid plug 54 being less than the second sum of forces F_fc acting on the second liquid plug 56 for creating a head pressure during expansion of the refrigerant 24. The forces F_fc, F_vc cause the refrigerant 24 to expand more into the vapor conduit 38 than into the filling conduit 40 during vaporization of the refrigerant 24 causing continuous circulation of the refrigerant 24 in the same direction.

The first sum of flow restrictive forces F_vc acting on the first liquid plug 54 can be determined using the following equations one through five:

F_vc=[F_g]_vc+[F_τ]_vc+[F_σ]_vc+[F_e]_vc   (1)

[F_g]_vc=ρ_vcgh_vc   (2)

[F_τ]_vc=πr_vcl_vcC_fvcv_vc²   (3)

[F_σ]_vc=2σ_vcA_vc/r_vc cos θ_vc   (4)

[F_e]_vc=0.5ρ_vcA_vcK_vcv_vc²   (5)

wherein ρ_vc is the density of the first liquid plug 54, h_vc is the height of the reservoir 30 above the first liquid plug 54, g is the gravitational constant, r_vc is the radius of the vapor conduit 38, and l_vc is the length of the first liquid plug 54 in the vapor conduit 38. C_fvc is the coefficient of friction between the refrigerant 24 and the vapor conduit 38, v_vc is the velocity of the first liquid plug 54 into the vapor conduit 38, and σ_vc is the surface 36 tension of the first liquid plug 54 in the vapor conduit 38. A_vc is the first cross sectional area of the vapor conduit 38, cos θ_vc is a geometric factor of the first liquid plug 54 found experimentally, and K_vc is the expansion loss coefficient for the inlet 32 of the reservoir 30.

The second sum of flow restrictive forces F_fc acting on the second liquid plug 56 can be determined using the following equations six through ten:

F_fc=[F_g]_fc+[F_τ]_fc+[F_σ]_fc+[F_e]_fc   (6)

[F_g]_fc=ρ_fcgh_fc   (7)

[F_τ]_fc=πr_fcl_fcC_ffcv_fc²   (8)

[F_σ]_fc=2σ_fcA_fc/r_fc cos θ_fc   (9)

[F_e]_fc=0.5ρ_fcA_fcK_fcv_fc²   (10)

wherein ρ_fc is the density of the second liquid plug 56, h_fc is the height of the reservoir 30 above the second liquid plug 56, r_fc is the radius of the filling conduit 40, and l_fc is the length of the second liquid plug 56 of the filling conduit 40. C_ffc is the coefficient of friction between the refrigerant 24 and the filling conduit 40, v_fc is the velocity of the second liquid plug 56 into the filling conduit 40, and σ_fc is the surface 36 tension of the second liquid plug 56 in the filling conduit 40. A_fc is the second cross sectional area, cos θ_fc is a geometric factor of the second liquid plug 56 found experimentally, and K_fc is the expansion loss coefficient for the outlet 34 of the reservoir 30.

Preferably, the first cross sectional area A_vc of the vapor conduit 38 is greater than the second cross sectional area A_fc of the filling conduit 40, as shown in FIGS. 1 and 2, for causing the first sum of forces F_vc acting on the first liquid plug 54 to be less than the second sum of forces F_fc acting on the second liquid plug 56.

In operation, heat is transferred from the electronic device 22 to the evaporator 26 causing the refrigerant 24 to boil. The refrigerant 24 evaporates in the evaporator 26 forming the first liquid plug 54 in the vapor conduit 38 and the second liquid plug 56 in the filling conduit 40 as the vapor expands into the filling conduit 40 and vapor conduit 38. The expanding vapor volume pushes the first liquid plug 54 in the vapor conduit 38 and the second liquid plug 56 in the filling conduit 40. The refrigerant 24 expands into the filling conduit 40 and into the vapor conduit 38. The first sum of forces F_vc acts on the first liquid plug 54 less than the second sum of forces F_fc acting on the second plug during the expanding stage. After the refrigerant 24 enters the filling conduit 40 and the vapor conduit 38, the heat is transferred from the refrigerant 24 to the respective conduits 38, 40 and thereafter dissipated causing the refrigerant 24 to condense and contract back into the evaporator 26. Contraction of the refrigerant 24 causes additional refrigerant 24 from the filling conduit 40 to enter the evaporator 26. The additional refrigerant 24 evaporates upon making contact with the hot surfaces 36 of the evaporator 26 and once again expands causing a cyclical expansion of the refrigerant 24. Because the first flow restrictive forces F_vc acting on the first liquid plug 54 in the vapor conduit 38 are less than the second flow restrictive forces F_fc acting on the second liquid plug 56 in the filling conduit 40, the refrigerant 24 expands into the vapor conduit 38 to a larger extent than into the filling conduit 40 causing a continuous circulation of the refrigerant 24 in the same direction through the assembly 20, thereby eliminating the need for a mechanical pump or valves.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A closed-looped heat exchanger assembly for cooling an electronic device comprising;

a refrigerant for undergoing liquid-to-vapor cyclical transformations,

an evaporator attached to the electronic device for evaporating said refrigerant by transferring heat from the electronic device to said refrigerant,

a vapor conduit having a first cross sectional area defining a flow path for said refrigerant exiting said evaporator,

a reservoir for holding said refrigerant and having an inlet and an outlet,

a filling conduit having a second cross sectional area defining a flow path for said refrigerant entering said evaporator,

a first liquid plug of said refrigerant in said vapor conduit having a first sum of forces acting thereon,

a second liquid plug of said refrigerant in said filling conduit having a second sum of forces acting thereon,

said first sum of forces acting on said first liquid plug being less than said second sum of forces acting on said second liquid plug for creating a head pressure during expansion of said refrigerant causing said refrigerant to expand more into said vapor conduit than into said filling conduit during vaporization of said refrigerant for evaporating said refrigerant in said evaporator and expanding said refrigerant into said filling conduit and into said vapor conduit and condensing said refrigerant in said filling conduit and said vapor conduit causing additional refrigerant to enter said evaporator from said filling conduit causing a cyclical expansion of said refrigerant into said vapor conduit to a larger extent than into said filling conduit for continuously circulating said refrigerant in the same direction through said assembly.

2. An assembly as set forth in claim 1 wherein said first cross sectional area of said vapor conduit is greater than said second cross sectional area of said filling conduit for causing said first sum of forces acting on said first liquid plug to be less than said second sum of forces acting on said second liquid plug.

3. An assembly as set forth in claim 1 wherein Fvc=[Fg]vc+[Fτ]vc+[Fσ]vc+[Fe]vc,

wherein [Fg]vc=ρvcghvc,

wherein [Fτ]vc=πrvclvcCfvcvvc2,

wherein [Fσ]vc=2σvcAvc/rvc cos θvc,

wherein [Fe]vc=0.5ρvcAvcKvcvvc2, and

wherein ρvc is the density of said first liquid plug, g is the gravitational constant, hvc is the height of said reservoir above said first liquid plug, rvc is the radius of said vapor conduit, lvc is the length of said first liquid plug in said vapor conduit, Cfvc is the coefficient of friction between said refrigerant and said vapor conduit, vvc is the velocity of said first liquid plug into said vapor conduit, σvc is the surface tension of said first liquid plug in said vapor conduit, Avc is said first cross sectional area, cos θvc is a geometric factor of said first liquid plug found experimentally, and Kvc is the expansion loss coefficient for said inlet of said reservoir, wherein Ffc=[Fg]fc+[Fτ]fc+[Fσ]fc+[Fe]fc,

wherein [Fg]fc=ρfcghfc,

wherein [Fτ]fc=πrfclfcCfvvfc2,

wherein [Fσ]fc=2σfcAfc/rfc cos θfc,

wherein [Fe]fc=0.5ρfcAfcKfcvfc2,

wherein ρfc is the density of said second liquid plug, hfc is the height of said reservoir above said second liquid plug, rfc is the radius of said filling conduit, lfc is the length of said second liquid plug in said filling conduit, Cffc is the coefficient of friction between said refrigerant and said filling conduit, vfc is the velocity of said second liquid plug into said filling conduit, σfc is the surface tension of said second liquid plug in said filling conduit, Afc is said second cross sectional area, cos θfc is a geometric factor of said second liquid plug found experimentally, and Kfc is the expansion loss coefficient for said outlet of said reservoir.

4. An assembly as set forth in claim 3 wherein said first cross sectional area of said vapor conduit is greater than said second cross sectional area of said filling conduit for causing said first sum of forces acting on said first liquid plug to be less than said second sum of forces acting on said second liquid plug.

5. An assembly as set forth in claim 4 wherein said refrigerant defines a surface in said reservoir and said inlet of said reservoir is disposed above said surface of said refrigerant in said reservoir and said outlet of said reservoir is disposed below said surface of said refrigerant in said reservoir.

6. An assembly as set forth in claim 5 wherein said evaporator is disposed below said surface of said refrigerant in said reservoir.

7. An assembly as set forth in claim 4 including a condenser for condensing said refrigerant.

8. An assembly as set forth in claim 7 including an intermediate conduit interconnecting said inlet of said reservoir and said condenser for conveying said refrigerant from said condenser to said reservoir,

wherein said vapor conduit defines a flow path between said evaporator and said condenser for conveying said refrigerant from said evaporator to said condenser, and

wherein said filling conduit defines a flow path between said outlet of said reservoir and said evaporator for conveying said refrigerant from said reservoir to said evaporator.

9. An assembly as set forth in claim 8 wherein said reservoir has a plurality of holes therethrough defining said filling conduit,

wherein said vapor conduit defines a flow path about said reservoir, and

wherein said condenser is disposed about said reservoir and is axially aligned with said filling conduit and with said reservoir.

10. An assembly as set forth in claim 9 wherein said condenser and said reservoir define said filling conduit between said condenser and said reservoir, and

wherein said inlet extends along a periphery of said reservoir.

11. An assembly as set forth in claim 9 wherein said condenser has a plurality of cavities defining said vapor conduit and said intermediate conduit.

12. An assembly as set forth in claim 11 wherein said evaporator includes a plurality of partitions to define a plurality of chambers,

wherein each of said holes in said reservoir fluidly interconnects one of said chambers of said evaporator and said reservoir, and

wherein each of said cavities of said condenser fluidly interconnects one of said chambers of said evaporator and said reservoir.

13. An assembly as set forth in claim 7 including;

an intermediate conduit interconnecting said outlet of said reservoir and said condenser for conveying said refrigerant from said reservoir to said condenser,

wherein said vapor conduit defines a flow path between said evaporator and said reservoir for conveying said refrigerant from said evaporator to said reservoir, and

wherein said filling conduit defines a flow path between said condenser and said evaporator for conveying said refrigerant from said condenser to said evaporator.

14. An assembly as set forth in claim 13 wherein said condenser is vertically aligned with said reservoir and with said evaporator.

15. An assembly as set forth in claim 4 including;

a first connector having a first low conductivity and interconnecting said vapor conduit and said evaporator,

a second connector having a second low conductivity and interconnecting said filling conduit and said evaporator,

said vapor conduit being of a material having a first high conductivity,

said filling conduit being of a material having a second high conductivity,

wherein said first high conductivity of said vapor conduit is greater than said first low conductivity of said first connector of said vapor conduit for insulating said evaporator from said vapor conduit, and

wherein said second high conductivity of said filling conduit is greater than said second low conductivity of said second connector of said filling conduit for insulating said evaporator from said filling conduit.

16. An assembly as set forth in claim 4 including;

a thermal valve interconnecting said filling conduit and said evaporator for restricting flow of said refrigerant until said refrigerant reaches a predetermined temperature,

wherein said refrigerant has a temperature, and

whereby said first liquid plug expands into said vapor conduit and said second liquid plug is stationary during startup of said system when said temperature of said refrigerant is below the predetermined temperature.

17. A closed-looped heat exchanger assembly for cooling an electronic device comprising;

a refrigerant for undergoing liquid-to-vapor cyclical transformations,

an evaporator attached to the electronic device for evaporating said refrigerant by transferring heat from the electronic device to said refrigerant,

a condenser for condensing said refrigerant,

a vapor conduit being of a material having a first high conductivity and having a first cross sectional area defining a flow path for said refrigerant exiting said evaporator,

a reservoir for holding said refrigerant and having an inlet and an outlet,

said refrigerant defining a surface in said reservoir,

said evaporator being disposed below said surface of said refrigerant in said reservoir,

said inlet of said reservoir being disposed above said surface of said refrigerant in said reservoir,

said outlet of said reservoir being disposed below said surface of said refrigerant in said reservoir,

a filling conduit being of a material having a second high conductivity and having a second cross sectional area for said refrigerant entering said evaporator, defining a flow path between said outlet of said reservoir and said evaporator for conveying said refrigerant from said reservoir to said evaporator,

a first liquid plug of said refrigerant in said vapor conduit having a first sum of forces acting thereon,

a second liquid plug of said refrigerant in said filling conduit having a second sum of forces acting thereon, and

a thermal valve interconnecting said filling conduit and said evaporator for restricting flow of said refrigerant until said refrigerant reaches a predetermined temperature,

wherein said refrigerant has a temperature,

whereby said first liquid plug expands into said vapor conduit and said second liquid plug is stationary during startup of said system when said temperature of said refrigerant is below the predetermined temperature,

said first sum of forces acting on said first liquid plug being less than said second sum of forces acting on said second liquid plug for creating a head pressure during expansion of said refrigerant causing said refrigerant to expand more into said vapor conduit than into said filling conduit during vaporization of said refrigerant for evaporating said refrigerant in said evaporator and expanding said refrigerant into said filling conduit and into said vapor conduit and condensing said refrigerant in said filling conduit and said vapor conduit causing additional refrigerant to enter said evaporator from said filling conduit causing a cyclical expansion of said refrigerant into said vapor conduit to a larger extent than into said filling conduit for continuously circulating said refrigerant in the same direction through said assembly, wherein Fvc=[Fg]vc+[Fτ]vc+[Fσ]vc+[Fe]vc,

wherein [Fg]vc=ρvcghvc,

wherein [Fτ]vc=πrvclvcCfvcvvc2.

wherein [Fσ]vc=2σvcAvcrvc cos θvc,

wherein [Fe]vc=0.5ρvcAvcKvcvvc2,

wherein ρvc is the density of said first liquid plug, g is the gravitational constant, hvc is the height of said reservoir above said first liquid plug, rvc is the radius of said vapor conduit, lvc is the length of said first liquid plug in said vapor conduit, Cfvc is the coefficient of friction between said refrigerant and said vapor conduit, vvc is the velocity of said first liquid plug into said vapor conduit, σvc is the surface tension of said first liquid plug in said vapor conduit, Avc is said first cross sectional area, cos θvc is a geometric factor of said first liquid plug found experimentally, and Kvc is the expansion loss coefficient for said inlet of said reservoir, wherein Ffc=[Fg]fc+[Fτ]fc+[Fσ]fc+[Fe]fc,

wherein [Fg]fc=ρfcghfc,

wherein [Fτ]fc=πrfclfcCffcvfc2.

wherein [Fσ]fc=2σfcAfcrfc cos θfc,

wherein [Fe]fc=0.5ρfcAfcKfcvfc2,

wherein ρfc is the density of said second liquid plug, hfr is the height of said reservoir above said second liquid plug, rfc is the radius of said filling conduit, lfc is the length of said second liquid plug in said filling conduit, Cffc is the coefficient of friction between said refrigerant and said filling conduit, vfc is the velocity of said second liquid plug into said filling conduit, σfc is the surface tension of said second liquid plug in said filling conduit, Afc is said second cross sectional area, cos θfc is a geometric factor of said second liquid plug found experimentally, and Kfc is the expansion loss coefficient for said outlet of said reservoir,

said first cross sectional area of said vapor conduit being greater than said second cross sectional area of said filling conduit for causing said first sum of forces acting on said first liquid plug to be less than said second sum of forces acting on said second liquid plug,

a first connector having a first low conductivity and interconnecting said vapor conduit and said evaporator,

a second connector having a second low conductivity and interconnecting said filling conduit and said evaporator,

wherein said first high conductivity of said vapor conduit is greater than said first low conductivity of said first connector of said vapor conduit for insulating said evaporator from said vapor conduit, and

wherein said second high conductivity of said filling conduit is greater than said second low conductivity of said second connector of said filling conduit for insulating said evaporator from said filling conduit.

18. An assembly as set forth in claim 17 including;

an intermediate conduit interconnecting said inlet of said reservoir and said condenser for conveying said refrigerant from said condenser to said reservoir,

said vapor conduit defining a flow path between said evaporator and said condenser for conveying said refrigerant from said evaporator to said condenser,

said condenser and said reservoir define said vapor conduit,

wherein said vapor conduit defines a flow path about said reservoir,

said filling conduit defining a flow path between said outlet of said reservoir and said evaporator for conveying said refrigerant from said reservoir to said evaporator,

said reservoir having a plurality of holes therethrough defining said filling conduit,

said inlet of said reservoir extending along a periphery of said reservoir,

said condenser being disposed about said reservoir and being axially aligned with said filling conduit and said reservoir and having a plurality of cavities defining said vapor conduit and said intermediate conduit,

said evaporator including a plurality of partitions to define a plurality of chambers,

wherein each of said holes in said reservoir fluidly interconnects one of said chambers of said evaporator and said reservoir, and

wherein each of said cavities of said condenser fluidly interconnects one of said chambers of said evaporator and said reservoir.

19. An assembly as set forth in claim 17 including;

an intermediate conduit interconnecting said outlet of said reservoir and said condenser for conveying said refrigerant from said reservoir to said condenser,

said vapor conduit defining a flow path between said evaporator and said reservoir for conveying said refrigerant from said evaporator to said reservoir,

said filling conduit defining a flow path between said condenser and said evaporator for conveying said refrigerant from said condenser to said evaporator,

said condenser being vertically aligned with said reservoir and with said evaporator,

wherein said vapor conduit defines a flow path between said evaporator and said reservoir,

wherein said reservoir is vertically aligned with said reservoir and said evaporator,

wherein said reservoir has a plurality of holes therethrough defining said filling conduit,

wherein said vapor conduit defines a flow path about said reservoir, and

wherein said condenser is disposed about said filling conduit and about said reservoir.

20. A method of cooling an electronic device using a closed looped assembly comprising the steps of;

transferring heat generated from the electronic device to an evaporator,

boiling refrigerant in the evaporator,

forming a first liquid plug in a vapor conduit and a second liquid plug in a filling conduit from the refrigerant,

expanding refrigerant in the evaporator into the vapor conduit and into the filling conduit,

dissipating heat from the refrigerant in the vapor conduit and filling conduit,

contracting the refrigerant from the vapor conduit and from the filling conduit into the evaporator in response to said dissipating step,

adding refrigerant from the vapor conduit into the evaporator,

applying a first sum of forces to the first liquid plug and applying a second sum of forces to the second liquid plug greater than the first sum of forces during said expanding step for expanding refrigerant into the vapor conduit more than into the filling conduit.

21. A method as set forth in claim 20 including the step of repeating said steps of boiling, expanding, dissipating and contracting in response to said adding step for continuously circulating the liquid plugs in the same direction.

22. A method as set forth in claim 21 wherein Fvc=[Fg]vc+[Fτ]vc+[Fσ]vc+[Fe]vc,

wherein [Fg]vc=ρvcghvc,

wherein [Fτ]vc=πrvclvcCfvcvvc2.

wherein [Fσ]vc=2σvcAvcrvc cos θvc,

wherein [Fe]vc=0.5ρvcAvcKvcvvc2,

wherein ρvc is the density of the first liquid plug, hvc is the height of the reservoir above the first liquid plug, rvc is the radius of the vapor conduit, lvc is the length of the first liquid plug in the vapor conduit traveled by the first liquid plug, Cfvc is the coefficient of friction between the refrigerant and the vapor conduit, vvc is the velocity of the first liquid plug into the vapor conduit, σvc is the surface tension of the first liquid plug in the vapor conduit, Avc is the first cross sectional area, cos θvc is a geometric factor of the first liquid plug found experimentally, and Kvc is the expansion loss coefficient for the inlet of the reservoir, wherein Ffc=[Fg]fc+[Fτ]fc+[Fσ]fc+[Fe]fc,

wherein [Fg]fc=ρfcghfc,

wherein [Fτ]fc=πrfclfcCffcvfc2.

wherein [Fσ]fc=2σfcAfcrfc cos θfc,

wherein [Fe]fc=0.5ρfcAfcKfcvfc2,

wherein ρfc is the density of the second liquid plug, g is the gravitational constant, hfc is the height of the reservoir above the second liquid plug, rfc is the radius of the filling conduit, lfc is the length of second liquid plug in the filling conduit, Cffc is the coefficient of friction between the refrigerant and the filling conduit, vfc is the velocity of the second liquid plug into the filling conduit, σfc is the surface tension of the second liquid plug in the filling conduit, Afc is the second cross sectional area, cos θfc is a geometric factor of the second liquid plug found experimentally, and Kfc is the expansion loss coefficient for the outlet of the reservoir.

23. A method as set forth in claim 22 wherein said applying steps are further defined by forming the first plug in the vapor conduit with a first cross sectional area and forming the second plug in the filling conduit with a second cross sectional area less than the first cross sectional area.