US20120205080A1

US20120205080A1 - Pump-Less Cooling Using a Rotating Disk

Info

Publication number: US20120205080A1
Application number: US13/028,089
Authority: US
Inventors: Kristian Debus; Tom Gielda
Original assignee: Caitin Inc
Current assignee: Caitin Inc
Priority date: 2011-02-15
Filing date: 2011-02-15
Publication date: 2012-08-16

Abstract

Cooling in the supersonic region of a compressible fluid is disclosed. The fluid is accelerated by a rotating disk to a velocity equal to or greater than the speed of sound in the fluid in a rotating evaporator tube. No conventional mechanical pump is required to accelerate the fluid. A phase change of the fluid due to a pressure differential may be utilized to transfer heat from an element to be cooled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention generally relates to cooling via a supersonic fluid flow cycle. More specifically, the present invention is related to cooling systems that establish a supersonic cooling cycle using a rotating disk.
2. Description of the Related Art
A vapor compression system as known in the art generally includes a compressor, a condenser, and an evaporator. These systems also include an expansion device. In a prior art vapor compression system, a gas is compressed whereby the temperature of that gas is increased beyond that of the ambient temperature. The compressed gas is then run through a condenser and turned into a liquid. The condensed and liquefied gas is then taken through an expansion device, which drops the pressure and the corresponding temperature. The resulting refrigerant is then boiled in an evaporator. This vapor compression cycle is generally known to those of skill in the art.
FIG. 1 illustrates a vapor compression system 100 such as might be found in the prior art. In the prior art vapor compression system 100 of FIG. 1, compressor 110 compresses the gas to (approximately) 238 pounds per square inch (PSI) and a temperature of 190° F. Condenser 120 then liquefies the heated and compressed gas to (approximately) 220 PSI and 117° F. The gas that was liquefied by the condenser 120 is then passed through the expansion valve 130 of FIG. 1. By passing the liquefied gas through expansion valve 130, the pressure is dropped to (approximately) 20 PSI. A corresponding drop in temperature accompanies the drop in pressure, which is reflected as a temperature drop to (approximately) 34° F. in FIG. 1. The refrigerant that results from dropping the pressure and temperature at the expansion valve 130 is boiled at evaporator 140. Through boiling of the refrigerant by evaporator 140, a low temperature vapor results, which is illustrated in FIG. 1 as having (approximately) a temperature of 39° F. and a corresponding pressure of 20 PSI.
The cycle related to the system 100 of FIG. 1 is sometimes referred to as the vapor compression cycle. Such a cycle generally results in a coefficient of performance (COP) between 2.4 and 3.5. The coefficient of performance, as reflected in FIG. 1, is the evaporator cooling power or capacity divided by compressor power. It should be noted that the temperature and pressure references that are reflected in FIG. 1 are exemplary and illustrative.
Such a system 100, however, operates at an efficiency rate (i.e., COP) that is far below that of system potential. To compress gas in a conventional vapor compression system 100 like that illustrated in FIG. 1 typically takes 1.75-2.5 kilowatts for every 5 kilowatts of cooling power generated. This exchange rate is less than optimal and directly correlates to the rise in pressure times the volumetric flow rate. Degraded performance is similarly and ultimately related to performance (or lack thereof) by the compressor 110.
Haloalkane refrigerants such as tetrafluoroethane (CH₂FCF₃) are inert gases that are commonly used as high-temperature refrigerants in refrigerators and automobile air conditioners. Haloalkane refrigerants have also been used to cool over-clocked computers. These inert, refrigerant gases are more commonly referred to as R-134 gases. The volume of an R-134 gas can be 600-1000 times greater than the corresponding liquid.
In light of the theoretical efficiencies of systems using haloalkanes or other fluids, there is a need in the art for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance. There is a further need for a cooling system that operates without the use of a conventional mechanical pump.

SUMMARY OF THE CLAIMED INVENTION

A cooling system that operates in a supersonic region of a selected working fluid is disclosed. The system includes an enclosure defining a fluid pathway that contains a fluid. A rotating disk positioned in the fluid pathway accelerates the fluid across a face of the rotating disk. The fluid flows in the critical flow regime to generate a compression wave that helps to change the pressure of the fluid, thereby reducing the temperature of the fluid. The cooled fluid is used to exchange heat with an element to be cooled.
A supersonic cooling method is also disclosed. The method includes rotating a disk so that it affects the flow of a fluid in a fluid pathway. The rotation of the disk accelerates the fluid so that the fluid flows across a face of the disk at a velocity greater than or equal to the speed of sound in the fluid, thereby establishing a low pressure region in the pathway. This causes a compression wave to form in the fluid as the fluid passes from a high pressure region to the low pressure region. The cooling effect created by the fluid flow is used to exchange heat with an element to be cooled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a vapor compression system in the prior art.

FIG. 2 illustrates an exemplary cooling system.

FIG. 3 is an exploded view of the cooling system illustrated in FIG. 2.

FIG. 4 illustrates a cross sectional view of the cooling system illustrated in FIG. 2.

FIG. 5 illustrates a method of supersonic cooling.

DETAILED DESCRIPTION

Embodiments of the present invention implement a supersonic cooling method that increases efficiency as compared to prior art cooling systems. A system utilizing the present invention may operate at a COP of 2 or greater, 3 or greater, 4 or greater, 5 or greater, 6 or greater, 7 or greater, 8 or greater, 9 or greater, 10 or greater, or or greater due to the elimination of certain hardware elements. Nor do embodiments of the present invention require a compressor or a conventional mechanical pump to operate. Only an electric motor or some other driving mechanism to impart a rotating force is required.
FIGS. 2-4 illustrate an exemplary cooling system 200. The cooling system 200 does not need to compress a gas as otherwise occurs at compressor 110 in a prior art vapor compression system 100 like that shown in FIG. 1. Cooling system 200 operates by accelerating a working liquid, which may be water, in an acceleration chamber 410. Because cooling system 200 utilizes liquid, the compression cooling system 200 does not require the use of a condenser 120 as does the prior art compression system 100 of FIG. 1. The compression cooling system 200 instead utilizes a rotating disk 210 that accelerates the working fluid to generate a compression wave.
The cooling system 200 operates in the critical flow regime of the working fluid. In this regime, the pressure of the fluid in the system 200 will remain almost constant and then ‘jump’ or ‘shock up’ to the ambient pressure. Further, because cooling system 200 accelerates the working fluid through rotational movement of the disk 210, cooling system 200 does not require the use of a conventional mechanical pump. The reduced amount of hardware required to operate the system 200—there is no need for a compressor or a conventional mechanical pump—gives rise to a greatly improved coefficient of performance (COP) for the system 200.
The rotating disk 210 may be mounted in a system housing 220. The motive force required to spin the rotating disk 210 may be supplied by any number of driving mechanisms known to those skilled in the art. Examples of suitable driving mechanisms include an electric motor with a drive axis coaxial with the center of the rotating disk 210 and magnetic elements installed in adjacent faces of the rotating disk 210 and a base of a housing enclosing the system.
An upper section 230 of the housing 220 may include a pair of spaced apart annular walls 420 sealed at an upper end to form a portion of a fluid pathway 430 (see FIG. 4). The upper section 230 of the housing 220 may include one or more hollow spokes 240. The hollow spokes 240 extend from an inner annular wall of the upper section 230 to a central throughway 310. The hollow spokes 240 may form a part of the fluid pathway 430, and may channel fluid from the outer circumference of the upper section 230 to the central throughway 310.
A lower section 250 of the housing 220 includes a base plate 260 with an upwardly extending annular wall 320 (see FIG. 3). The annular wall 320 of the lower section 250 contacts the outer annular wall 420 of the upper section 234, thereby continuing the fluid pathway 430 from the annular walls 420 of the upper section 230. The contact line—the seam—between the upper section 230 and the lower section 250 may be sealed to prevent leakage of the working fluid from the fluid pathway 430.
The underside of the rotating disk 210 is spaced apart from the base plate 260 to form the acceleration chamber 410. The height of the acceleration chamber 410 may be chosen so that shear forces generated in the acceleration chamber 410 create a cavitation effect in the working fluid as the fluid accelerates across the face of rotating disk 210.
An upper surface of the base plate 260 may include one or more grooves 330 that form a secondary flow path. Outer ends of the grooves 330 may open into the fluid pathway 430 bounded by the annular wall 320. Inner ends of the grooves 330 open into the central throughway 310. Fluid flowing through the grooves 330 may behave like a hydraulic bearing to assist fluid flow through the acceleration chamber 410. The grooves 330 may be arced to compensate for axial velocity of the rotating disk 210.
In an embodiment of the system 200 that utilizes a rotating disk 210 that is approximately 0.2 m in diameter, the height of the acceleration chamber 410—the separation between the rotating disk 210 and the base plate 260 of the lower section 250 of the housing 220—may be 1.6 mm. The rotational speed necessary to generate the desired shear force in the acceleration chamber is a function of the system parameters, including size, material and conformation of the rotating disk 210, and the working fluid selected. When water is used as the working fluid in a system 200 with a 0.2 m rotating disk 210 and an acceleration chamber 410 that is 1.6 mm in height, the desired shear force may be generated by spinning the rotating disk 210 at between approximately 7,500 rpm and approximately 10,000 rpm. Any and all of the physical dimensions and operating characteristics of the system 200 may be modified to meet the requirements of any particular installation.
The base plate 260 that forms the bottom of the lower section 250 of the housing 220 may be mounted directly on an element to be cooled 280. A thermally conductive element may be placed between the base plate 260 and the element to be cooled 280. As long as the base plate 260 is in thermal communication with the element to be cooled 280, the system 200 will achieve the desired heat exchange between the cooled working fluid and the element to be cooled 280. Materials used to construct the system 200 may be chosen on the basis of their thermal conductivity and physical properties. Aluminum may be selected as the primary material from which the system 200 is constructed.
The fluid pathway 430 may be seen as beginning at a point at which the central throughway 310 opens into the acceleration chamber 410. Fluid is accelerated outward from this point by the rotation of disk 210. The fluid flows toward the annular wall 320 of the lower section 250 of the housing 220. Suction (vacuum) created by the acceleration of the fluid causes the fluid to flow upward between the annular walls 420 of the upper section 230. The fluid then flows inward through the spokes 240 back to the central throughway 310.
As is explained in further detail below, a phase change occurs in the working fluid as the fluid is accelerated in the acceleration chamber 410. The phase change involves a sudden and significant change in volume in the fluid. To accommodate the volume change, a mechanism 270 to compensate for volume change may be provided. The volume change compensation mechanism 270 is installed in fluid communication with the fluid pathway. One volume change compensation mechanism 270 that may be utilized is an expandable bladder coupled to the central throughway 310.
As the working fluid travels through the fluid pathway 430, the system 200 generates a cooling effect via the method delineated in FIG. 5. In a step 510, the motive force for the fluid is provided by spinning the rotating disk 210 mounted in the housing 220. The desired rotational speed of the rotating disk 210 is determined by the parameters of the system and the selected working fluid. In one embodiment of the system 200, the rotating disk 210 may be spun at from approximately 7,500 rpm to approximately 10,000 rpm.
In a step 520, the working fluid is introduced through the central throughway 310 to a point near or at the center of the rotating disk 210. In a further step 530, the fluid is accelerated across the face of the rotating disk 210. It may be desirable to construct the acceleration chamber 410 that includes the rotating disk 210 such that a cavitation effect is created by shear forces generated between the face of the rotating disk 210 and the base plate 260 forming the bottom of the acceleration chamber 410.
The centrifugal force generated by spinning the rotating disk 210 accelerates the working fluid across the face of the rotating disk 210. Pressure drop and phase change result in a lowered temperature of the working fluid to create a cooling effect in the acceleration chamber 410 in step 540.
Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime established in the acceleration chamber 410. Critical flow occurs when the velocity of the fluid is greater than or equal to the speed of sound in the fluid. In critical flow, the pressure in the acceleration chamber 410 will not be influenced by the exit pressure. In step 550, at the annular wall 320 of the acceleration chamber 410, the fluid may ‘shock up’ to the ambient conditions.
The pressure change of the fluid in the system 200 may include a range of approximately 20 PSI in the low pressure region to 100 PSI in the high pressure region. In some instances, the pressure may be increased to more than 100 PSI, and in some instance, the pressure may be decreased to less than 20 PSI. Depending upon the characteristics of a given system, the pressure change range may vary from that described immediately above.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

1. A cooling system, the system comprising:

an enclosure defining a fluid pathway;

a rotating disk positioned in communication with the fluid pathway; and

a driving mechanism to provide a motive force to drive the rotating disk, wherein acceleration of the fluid across a face of the rotating disk causes the fluid to flow in the critical flow regime to generate a compression wave, the compression wave changing the pressure of the fluid so that the temperature of the fluid is reduced, thereby allowing heat to be exchanged with an element to be cooled.

2. The system of claim 1, wherein the rotating disk is separated from a base of the enclosure to form an acceleration chamber.

3. The system of claim 1, wherein the rotating disk is spaced apart from a base of the enclosure to form an acceleration chamber, and wherein fluid flow within the acceleration chamber creates a shear force that generates cavitation in the fluid as the fluid flows across the face of the rotating disk.

4. The system of claim 1, further comprising a volume change compensation mechanism in fluid communication with the fluid pathway, the volume change mechanism receiving a portion of the fluid during a phase change.

5. The system of claim 1, wherein a base of the enclosure is in thermal communication with the element to be cooled.

6. The system of claim 1, wherein the fluid pathway includes a region in which the fluid undergoes a phase change as the pressure of the fluid changes.

7. The system of claim 6, further comprising a volume change compensation mechanism in fluid communication with the fluid pathway, the volume change mechanism receiving a portion of the fluid during a phase change.

8. The system of claim 1, wherein a surface of a base of the enclosure includes at least one groove that forms a secondary flow path.

9. The system of claim 1, wherein the fluid pressure change between a high pressure region and a low pressure region created by the acceleration of the fluid is from approximately 100 PSI to approximately 20 PSI.

10. The system of claim 9, wherein the high pressure region of the fluid is at a pressure greater than 100 PSI.

11. The system of claim 10, wherein the low pressure region of the fluid is at a pressure less than 20 PSI.

12. A cooling method, the method comprising:

rotating a disk to affect the flow of a fluid in a fluid pathway, the disk accelerating the fluid so that the fluid flows across a face of the disk at a velocity greater than or equal to the speed of sound in the fluid, thereby establishing a low pressure region in the pathway;

forming a compression wave in the fluid as the fluid passes from a high pressure region to the low pressure region; and

exchanging heat introduced into the fluid pathway via the cooling effect created during a phase change of the fluid.

13. The method of claim 12, further comprising exchanging heat by placing at least one heat conductive surface in thermal communication with the fluid pathway.

14. The method of claim 12, further comprising positioning the disk apart from a base of an enclosure containing the fluid pathway to form an acceleration chamber.

15. The method of claim 12, further comprising creating a cavitation effect through shear forces generated by the rotation of the disk, the cavitation assisting the formation of the compression wave.

16. The method of claim 12, further comprising placing a volume change compensation mechanism in fluid communication with the fluid pathway, the volume change mechanism receiving a portion of the fluid during a phase change.

17. The method of claim 12, further comprising providing a secondary flow path via grooves formed in a base of the enclosure.

18. The method of claim 12, further comprising moving the fluid from the high pressure region to the low pressure region with the aid of suction.

19. The method of claim 12, further comprising effectuating a phase change in the fluid corresponding to a pressure change.

20. The method of claim 19, wherein the pressure change of the fluid occurs within a range of approximately 20 PSI to 100 PSI.

21. The method of claim 19, wherein the pressure change of the fluid involves a change to a pressure greater than or equal to 100 PSI.

22. The method of claim 19, wherein the pressure change of the fluid involves a change to a pressure less than or equal to 20 PSI.