Heat-removal device

Abstract

A heat-removal device for removing heat from a hot surface includes a housing containing a cooling fluid. The housing has a heat-absorption section, which is in contact with the hot surface. The housing also has a heat-dissipation section, which is cooled by natural or forced convection with ambient air. An internal impeller circulates the cooling fluid in a closed loop between the heat-absorption section and the heat-dissipation section to transport heat away from the hot surface to the ambient air.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/920,203, filed Mar. 27, 2007

FIELD OF THE INVENTION

This invention relates to a device for efficiently removing large quantities of heat generated within a relatively small area such as Electronic Devices, Integrated Circuits, Bearings, etc.

BACKGROUND OF THE INVENTION

The problem of efficiently removing heat generated within relatively small areas such as Integrated Circuits, Bearings, etc. has long plagued engineers. If generated heat is not removed efficiently from such parts, the performance or longevity of the part can be adversely affected.

A common problem is heat removal from integrated circuits (ICs). As ICs get smaller, they generate more heat within smaller volumes. If this heat is not removed, the IC overheats causing loss of performance and malfunction. A specific example is the common problem of reduction of performance of a computer due to overheating of its Central Processing Unit (CPU).

Typically a finned aluminum or copper block, with or without reticulated metallic foam, such as that described in U.S. Pat. Nos. 6,424,529, 6,424,531, and others is used to transfer heat generated within an Integrated Circuit (IC) to the external environment by natural or forced convection with ambient air. However such IC Coolers are relatively inefficient at transferring the heat, especially from modern computer chips which generate tremendous amounts of heat. The overheating of the computer chips reduces the processing ability of the chips. Furthermore, reticulated metallic-foam is relatively expensive.

Other designs, which incorporate heat-pipes, are also used to attempt to remove the generated heat from ICs. However, they are complicated and expensive to manufacture. U.S. Pat. No. 5,949,648 to Liao describes such a heat-pipe design.

Other designs, which are similar to automotive radiator systems, use circulated water and a remote heat-exchanger and cooling-fan. These designs, while able to provide good cooling, are very large, are assembled from a number of parts, and are expensive to produce.

Similarly, as rotating equipment gets miniaturized, it generates large quantities of heat from miniaturized bearings. If the heat is not removed from these bearings, they are liable to overheat and seize. The higher operating temperature of these bearings reduces their operating life. There is therefore also a great need for a heat-removal device that will efficiently transfer the generated heat away from a bearing or other small machine part.

Many other mechanical, electrical and chemical devices generate large amounts of heat in a small area and would benefit from a high efficiency heat-removal device described in this invention.

SUMMARY OF THE INVENTION

In one aspect of the present invention a device for removing heat from a hot-surface comprises a generally closed housing, the housing having a heat-absorbing section and a heat-dissipation section, the heat-absorbing section having an external surface in contact with the hot-surface and an internal surface, the heat-dissipation section having an external surface which is exposed to the external environment and an internal surface and a heat-conducting fluid located within the housing, the heat-conducting fluid generally contacting both the internal surface of the heat-absorbing section and the internal surface of the heat-dissipation section.

In another aspect of the present invention, the Heat Removal Device further includes a fluid-circulation means (FCM) for circulating the heat-conducting fluid past the internal surface of the heat-absorbing section and the internal surface of the heat-dissipation section of the housing.

In yet another aspect of the present invention, the Heat Removal Device further includes an open fluid-flow-passage (FFP) which has a first open end submerged in the heat-conducting fluid adjacent to the internal surface of the heat-absorbing section of the housing and a second open end submerged in the heat-conducting fluid adjacent to the internal surface of the heat-dissipation section of the housing.

In another aspect of the present invention, the fluid-circulation means is an impeller, which is submerged within the heat-conducting fluid.

In another aspect of the present invention, the Heat Removal Device further includes a fluid-circulation means (FCM) for circulating the heat-conducting fluid through the fluid-flow-passage.

In another aspect of the present invention, the fluid-circulation means is an impeller, which is located between the first and second open ends of the fluid-flow-passage.

In another aspect of the present invention, the impeller draws the heat-conducting fluid (HCF) into its second open end and impels it through the first open end against the internal-surface of the heat-absorbing section.

In another aspect of the present invention, the impeller impels the heat-conducting fluid (HCF) at a generally perpendicular orientation against the internal-surface of the heat-absorbing section.

In another aspect of the present invention, the impeller draws the heat-conducting fluid (HCF) into its first open end and expels it through the second open end.

In another aspect of the present invention, the Heat Removal Device further includes a rotating-movement-generating device (RMGD) which has a rotating element, which is rotationally coupled to the impeller.

In another aspect of the present invention, the RMGD is located outside the housing and the rotational-coupling is effected by a shaft which is connected through the housing at its first end to the rotating element and at its second end to the impeller.

In another aspect of the present invention, the RMGD is located outside the housing and the rotating element and the impeller are magnets and the rotational-coupling is effected by a magnetic force connecting the rotating element to the impeller.

In another aspect of the present invention, the rotating element is an electromagnet.

In another aspect of the present invention, the external surface of the heat-dissipation section has heat-transfer fins.

In another aspect of the present invention, the internal surface of the heat-dissipation section is heat-transfer enhanced.

In another aspect of the present invention, the internal surface of the heat-dissipation section has heat-transfer fins.

In another aspect of the present invention, the internal surface of the heat-absorption section is heat-transfer enhanced.

In another aspect of the present invention, the internal surface of the heat-absorption section has heat-transfer fins. In another aspect of the present invention, the heat-conducting fluid comprises water.

In another aspect of the present invention, the heat-conducting fluid comprises ethylene-glycol.

In another aspect of the present invention, the Heat Removal Device further includes a rotating-magnetic field-generating device (RMFGD) which has a rotating magnetic field, which is magnetically coupled to the impeller.

In another aspect of the present invention, heat is transferred from the external surface of the heat-dissipation section to the external environment by natural convection.

In another aspect of the present invention, heat is transferred from the external surface of the heat-dissipation section to the external environment by forced convection.

In another aspect of the present invention, the heat-conducting fluid undergoes a thermodynamic phase. In another aspect of the present invention, the heat-conducting fluid stays in the same thermodynamic phase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a cross-sectional elevation-view representation of the Heat Removal Device of the present invention as used to remove heat from the CPU of a computer.

FIG. 1b is a sectional plan-view representation of the Heat Removal Device of FIG. 1a.

FIG. 2 is a cross-sectional elevation-view representation of another embodiment of the Heat Removal Device of the present invention, which uses a direct-driven impeller.

FIG. 3 is a cross-sectional elevation-view representation of another embodiment of the Heat Removal Device of the present invention which uses a magnetic field generating device to rotate the impeller shown in FIG. 1a.

FIG. 4 is a cross-sectional elevation-view representation of another embodiment of the Heat Removal Device of the present invention, which has a flattened or pancake elevational profile.

DESCRIPTION OF THE INVENTION

The present invention is directed to a Heat-Removal Device, which combines conductive and convective heat-transfer in a simple and inexpensive design to rapidly transfer large amounts of heat from a small area or a point source to the external environment.

Referring to FIGS. 1a and 1b, Heat Removal Device 12 comprises a closed housing 12h, which contains a cooling fluid, and a cooling-air circulation fan 15. The cold and hot states of the cooling fluid are represented as 14c and 14h in FIGS. 1a and 1b. In one embodiment of the invention shown in FIG. 1a, housing 12h is configured as a chamber which comprises a first end-closure floor member 12c, a second end-closure roof member 12p, and an intermediate vertical walled hollow member 12w, to define a closed, internal, hollow space 12v. As shown in FIGS. 1a and 1b, vertical member 12w is configured from a short piece of extruded, circular cross-sectioned tube made of a metal, such as aluminum or copper or aluminum plated with copper or other such heat-conductive material. Other design refinements could include plating the inside of an extruded aluminum tube with a non-corroding, highly-conductive surface such as copper, silver, gold, diamond, or other suitable highly conductive non-corroding material to provide high heat-transfer at an economical price.

To dissipate heat efficiently, a plurality of fins 12f is provided on the exterior surface of vertical member 12w. Such fins can also be provided on the exterior surface of roof member 12p if additional heat-transfer area is desired. While only 12 fins have been shown in FIG. 1b, it will be obvious that the maximum possible number of fins that can be physically accommodated on the external surface of vertical member 12w will be advantageous to provide the maximum heat-dissipation from vertical member 12w. Vertical member 12w and roof member 12p therefore comprise the heat-dissipation section of Heat Removal Device 12.

Located within internal volume 12v is a volume displacement member (VDM) 12s, which is configured as a short length of a thick-walled tube made of Styrofoam or other such material. VDM 12s has an outside diameter which is less than the inside diameter of vertical member 12w to provide an annular flow passage 12a between the outside diameter of VDM 12s and the inside diameter of vertical member 12w. While a thick walled tube is shown, VDM 12s could also be fabricated of a thin-walled tube depending on the required dimensions for housing 12h. Also VDM 12s has a vertical length that is less than the vertical length of vertical member 12w. The outside diameter and vertical length of VDM 12s are chosen to provide a top flow passage 12t which is connected to an outer annular flow passage 12a which in turn is connected to a bottom flow passage 12b. It will be obvious to one of ordinary skill in the art that these flow-passages have to have adequate dimensions to allow the cooling fluid to flow there-through without excessive pressure drop. The dimensions are also selected to provide an optimum heat-transfer coefficient between the liquid and the internal wall of vertical member 12w. The optimum value of these dimensions can be chosen through theoretical calculations, or experimental trial-and-error, or computer-aided computational fluid dynamic calculations. Such methods are considered to be within the knowledge base of one of ordinary skill in the art.

Further VDM 12s has an inside diameter, which is chosen to accommodate a fluid-circulation means (FCM), such as cooling-fluid pump impeller 16i, described below, therein. The inside diameter of VDM 12s is also chosen to provide a concentric, circular fluid flow-passage 12cf connecting upper flow channel 12t to lower flow channel 12b. It will be obvious that fluid flow-passage 12cf has to have a suitable diameter to allow the cooling fluid to flow there-through without excessive pressure drop while providing an optimum impinging jet on floor 12c to transfer heat away from the hot surface.

Thus the placement of VDM 12s within internal volume 12v creates a toroidal flow-path for the cooling fluid within housing 12h. In this flow-path, the cooling fluid is impelled downwards through the central flow passage 12cf and impinges the internal surface 12ci of floor 12c, and is then deflected outwards radially into lower flow passage 12b towards the internal surface 12wi of vertical member 12w. It will be obvious that some stand-off means (not shown for clarity), such as legs or supports, for raising VDM 12s away from bottom floor plate 12c needs to be provided to create the lower flow passage 12b. The cooling fluid then passes upwards within annular flow passage 12a and then radially inwards in top flow passage 12t from where it is inducted into central flow passage 12cf by the suction action of impeller 16i.

During operation of Heat Removal Device 12, cooling air fan 15 is activated to create forced convection by blowing cold cooling air 15c through flow channels 12fc between adjacent fins 12f of vertical member 12w. While not shown, flow directing means, such as a cowl, can be provided around the periphery of fan 15 to direct the maximum amount of air over fins 12f. The cooling-air fan has blades 15b, which are connected to a rotating movement generating device, such as electric motor 15z. In FIG. 1a, blades 15b are shown connected to rotating shaft 15s of motor 15z. At its free end, shaft 15s is also connected to a magnetic coupling member 15m. Magnetic coupling member 15m is located so that its magnetic surface can rotate freely over the upper surface of top plate 12p of housing 12h. Ideally, to reduce friction, a small gap is provided between the magnetic surface of magnetic coupling member 15m and the upper surface of top plate 12p of housing 12h. As will be described below, magnetic coupling 15m non-contactingly rotates cooling fluid impeller 16i.

During operation of Heat Removal Device 12, the heat, (represented by “Q” in FIG. 1a), generated by the hot-surface is transferred to the cold cooling fluid 14c through its contact with internal surface 12ci of heat-conductive floor plate 12c of housing 12h. Heat-conductive floor plate 12c therefore comprises the heat-absorption section of Heat Removal Device 12. The heated cooling fluid 14h then passes upwards through annular flow channel 12a and transfers its heat through its contact with cooler internal surface 12wi of vertical wall 12w. The heat is then conducted away from wall 12w by fins 12f, which transfer the heat to the ambient air of the external environment, either by natural or forced convection. If cooling-air fan 15 is in operation, the cold air 15c absorbs the heat from hot fins 12f by forced convection, as shown in FIG. 1a. If cooling-air fan 15 is not in operation, the ambient air surrounding hot fins 12f absorbs the heat from hot fins 12f by natural convection, as shown in FIG. 3. The cooled cooling fluid 14c is then recirculated back to central fluid flow passage 12cf for removing additional heat from the hot surface as previously described.

To rotate impeller 16i, a magnetic coupling 16m is provided within volume 12v. Magnetic coupling 16m is attached to impeller 16i by shaft 16s. While a fan-propeller type of impeller is shown, other impeller forms such as an Archimedes Screw can also be used to move the cooling fluid. Coupling 16m is non-contactingly coupled to mating magnetic coupling 15m, which was described above. Thus the rotational motion of external mating magnetic coupling 15m is non-contactingly transferred to internal mating magnetic coupling 16m by magnetic forces that pass through roof member 12p. This arrangement provides a hermetically sealed housing 12h and prevents leakage of the cooling fluid.

Roof member 12p is plastic or non-ferrous metal or other material, which will not substantially obstruct the magnetic force linkage between coupling members 15m and 16m.

While impeller 16i is shown as magnetically driven by cooling fan motor 15z, it could also be direct coupled to shaft 15s of motor 15z, as shown in FIG. 2. In this situation, a liquid-tight shaft-seal (not shown) will be needed in roof member 12p for the through-insertion of shaft 15s into central flow passage 12cf to attach to impeller 16i. Alternatively, impeller 16i can be rotated by its own dedicated, hermetically sealed motor that is located within housing 12h. The dedicated motor could be connected to the external electrical power source by wires that penetrate housing 12h in a liquid-tight manner. All of these modifications for rotating impeller 16i will be obvious to one of ordinary skill in the art and are considered to fall within the scope of the present invention.

The cooling fluid 14c can be a gas such as Freon or it can be a liquid such as water or ethylene-glycol, or other such liquid. Any other fluid or mixture of fluids that can meet the required heat-transfer, non-corrosiveness, non-toxicity, and other desired characteristics of the application can also be used. Further, the fluid may or may not undergo a thermodynamic phase-change. Yet other configurations and modification of Heat Removal Device 12 disclosed herein will be obvious to persons skilled in the art. These configurations are considered to fall within the scope of the present invention.

While the above disclosure relates to the use of the Heat Removal Device of the present invention for cooling ICs, it could also have other applications for removal of spot heat. For example, it could be used for cooling bearings or other machine parts.

Yet further refinements can be provided to enhance the performance of Heat Removal Device 12 of the present invention.

For example, liquid flow straighteners can be used to maintain the toroidal flow-path within housing 12h and thereby enhance the pumping efficiency of impeller 16i.

Further, housing 12h may have other cross-sections besides the circular cross-section shown in FIG. 1b. Vertical section 12w of housing 12h could take on other geometric or non-geometric shapes. For example, the vertical section 12w could be hexagonal and the fins could create a square profile if desired.

Yet further, as shown in FIG. 1a, heat-transfer enhanced surfaces 12ce on internal surface 12ci of bottom plate 12b and 12we on internal surface 12wi of vertical member 12w can be provided to increase the heat-transfer from the hot surface to the cooling fluid and cooling air. Such means to enhance the heat-transfer from between a surface and a fluid includes dimples, etchings, grooves, fins, pins or any other means of disturbing the laminar flow boundary of the fluid to create turbulent flow, which is known to enhance heat-transfer. Such an enhanced heat-transfer surface can be provided on the internal side of floor plate 12c, where floor plate 12c contacts the hot surface, to increase heat-transfer from floor plate 12c to cooling fluid 14c.

Similar, heat-transfer enhancement means 12we can be provided on the internal side of vertical section 12w, opposite the location of fins 12f, to enhance heat-transfer from hot cooling-fluid 14h to fins 12f.

Yet further, additional means of creating and maintaining turbulent flow of cooling-fluid 14c to enhance heat transfer can be provided. For example, the internal wall of vertical section 12w or the surfaces of internal fluid displacer 12s can be roughened to create turbulent flow. Alternately, protrusions can be provided on these surfaces to create turbulent flow in cooling-fluid 14c.

Similarly, the heat-transferring surfaces of fins 12f could be roughened by methods such as sand-blasting or other such processes, to create a turbulent flow of cold air 15c over fins 12f to enhance heat transfer. All such heat-transfer enhanced surfaces are considered to fall within the scope of the present invention.

While the preferred embodiment of the invention has been shown and described with the internal volume displacement device 12s, there could be other means of creating largely toroidal flow to achieve substantially the same results. All such means of creating toroidal flow are considered to fall within the spirit of this invention. The invention may even be practiced without volume displacement means 12s as it is highly likely that even random or uncontrolled flow pattern pumping of cooling-fluid 14c within housing 12h would produce at least some of the heat-transfer effects described above.

In the preferred embodiment, the toroidal flow is directed through central fluid flow passage 12cf of VDM 12s to impinge on internal surface 12ci of Heat Removal Device 12. However, in another embodiment of the present invention shown in FIG. 2, the flow is reversed with cooling fluid 14c moving upwards in central flow passage 12cf, away from heated absorption section 12c. As shown in FIG. 2, to maintain the counter-current flow between the cooling fluid 14c and the cooling air 15c, the rotation of cooling air fan blades 15b can also be reversed. Alternately, though less efficient from a heat-transfer point of view, a co-current flow can be maintained between cooling fluid 14c and cooling air 15c.

In the description of the Heat Removal Device of the present invention, a propeller type pump is depicted. However, other arrangements may also be conceived to incorporate other types of pumps such as centrifugal pumps, mixed flow pumps, etc. It is also not necessary that the pump be located in central flow passage 12cf. The pump could be located anywhere in the fluid circulation flow-path to circulate the fluid past the heat-absorption and heat-dissipation sections. A further refinement to the design would be a nozzle, which could be fitted to the bottom flow-opening 12cx of fluid flow-passage 12cf to enhance the impingement of cooling fluid 14c on floor plate section 12c of Heat Removal Device 12.

The pump, pump housing, magnetic drive and bearings may be manufactured as a complete sub-assembly that will easily be fitted into VDM 12s. For example, for lower cost and ease of assembly, a centrifugal pump with an integrated magnetic coupling could be provided in upper flow opening 12cy.

Yet other modifications can be made to Heat Removal Device 12 of the present invention to suit specific applications. For example, the vertical height of Heat Removal Device 12 could be shortened to suit headroom constraints, such as in laptop computers. Thus, in this design represented by FIG. 4, Heat Removal Device 12 would have a flattened or pancake elevational profile. The location and orientation of fins 12f can also be adjusted to fit specific design constraints. All of these modifications are considered to fall within the scope of the present invention.

Yet further, as shown in FIG. 3, magnetic coupling 16m could be rotated by a rotating magnetic field generating device 15zm, which would include a plurality of stationary electromagnetic poles 15zp. For example, a stator of an electric motor could be used to create a rotating magnetic field to rotate magnetic coupling 16m.

Further, as shown in FIG. 4, impeller 16im could itself be magnetized to eliminate the magnetic coupling member and connecting shaft. Thus impeller 16im would be directly magnetically coupled to the rotating magnetic field created by rotating magnetic field generating device 15zm.

Further, the heat recovery device of the present invention can be used with more than one heat-source. For example, FIG. 4 shows the pancake version of Heat Removal Device 12 being used with a plurality of Liquid Crystal Display (LCD) elements. Heat Removal Device 12 can also used with a plurality of Light Emitting Diode (LED) elements.

All of these design alternatives and refinements are considered to fall within the scope of the present invention, which should be limited, only by the scope of the following claims.

Claims

1) A device for removing heat from a hot-surface, the device comprising:

a generally closed chamber, the chamber having a first end-closure member, a second end-closure member, and an intermediate-member connecting the first end-closure member to the second end-closure member, the first end-closure member having a heat-absorbing section, the heat-absorbing section having an external surface in contact with the hot-surface and an internal surface, the second end-closure member and intermediate-member together or individually functioning as a heat-dissipation section which is exposed to the external environment; and a heat-conducting fluid located within the chamber, the heat-conducting fluid generally contacting both the internal surface of the heat-absorbing section and the internal surface of the heat-dissipation section.

2) The device of claim 1, further including a fluid-circulation means for circulating the heat-conducting fluid past the internal surface of the heat-absorbing section and the internal surface of the heat-dissipation section of the chamber.

3) The device of claim 1, further including an open fluid-flow-passage having a first open end submerged in the heat-conducting fluid adjacent to the internal surface of the heat-absorbing section of the chamber and having a second open end submerged in the heat-conducting fluid adjacent to the internal surface of the heat-dissipation of the chamber.

4) The device of claim 2, wherein the fluid-circulation means is an impeller, which is submerged within the heat-conducting fluid.

5) The device of claim 3, further including a fluid-circulation means for circulating the heat-conducting fluid through the fluid-flow-passage.

6) The device of claim 5, wherein the fluid-circulation means is an impeller which is located between the first and second open ends of the fluid-flow-passage.

7) The device of claim 6, wherein the impeller draws the heat-conducting fluid into its second open end and impels it through the first open end against the internal-surface of the heat-absorbing section.

8) The device of claim 7, wherein the impeller impels the heat-conducting fluid at a generally perpendicular orientation against the internal-surface of the heat-absorbing section.

9) The device of claim 6, wherein the impeller draws the heat-conducting fluid into its first open end and expels it through the second open end.

10) The device of claim 6, further comprising a rotating-movement generating device which has a rotating element which is rotationally-coupled to the impeller.

11) The device of claim 10, wherein the rotating-movement generating device is located outside the chamber and the rotational-coupling is effected by a shaft which is connected through the chamber-wall at its first end to the rotating element and at its second end to the impeller.

12) The device of claim 10, wherein the rotating-movement generating device is located outside the chamber and the rotating element and the impeller are magnets and the rotational-coupling is effected by a magnetic force connecting the rotating element to the impeller.

13) The device of claim 12, wherein the rotating element is an electromagnet.

14) The device of claim 1, wherein the external surface of the heat-dissipation section has heat-transfer fins.

15) The device of claim 1, wherein the internal surface of the heat-dissipation section is heat-transfer enhanced.

16) The device of claim 1, wherein the internal surface of the heat-dissipation section has heat-transfer fins.

17) The device of claim 1, wherein the internal surface of the heat-absorption section is heat-transfer enhanced.

18) The device of claim 1, wherein the internal surface of the heat-absorption section has heat-transfer fins.

19) The device of claim 1, wherein the heat-conducting fluid comprises water.

20) The device of claim 1, wherein the heat-conducting fluid comprises ethylene-glycol.

21) The device of claim 6, further comprising a rotating-magnetic field generating device which has a rotating magnetic field which is magnetically-coupled to the impeller.

22) The device of claim 1, wherein heat is transferred from the external surface of the heat-dissipation section to the external environment by natural convection.

23) The device of claim 1, wherein heat is transferred from the external surface of the heat-dissipation section to the external environment by forced convection.

24) The device of claim 1, wherein the heat-conducting fluid undergoes a thermodynamic phase-change.

25) The device of claim 1, wherein the heat-conducting fluid stays in the same thermodynamic phase

26) A device for removing heat from a hot-surface, the device comprising:

a generally closed housing, the housing having a heat-absorbing section and a heat-dissipation section, the heat-absorbing section having an external surface in contact with the hot-surface and an internal surface, the heat-dissipation section having an external surface which is exposed to the external environment and an internal surface; and a heat-conducting fluid located within the housing, the heat-conducting fluid generally contacting both the internal surface of the heat-absorbing section and the internal surface of the heat-dissipation section.

27) A device for removing heat from a hot-surface, the device comprising:

a generally closed liquid-filled chamber, a first external surface of which is in contact with the hot-surface to receive heat therefrom, a second external surface of which is exposed to the external environment to transfer heat thereto.