Orientation insensitive multi chamber thermosiphon

A hermetically sealed housing includes a plurality of inner walls extending radially from a central post to a circular outer wall, thereby defining a plurality of pie shaped chambers, each independently containing a refrigerant. At least one of the chambers is always in position to remove heat from an electronic device regardless of the orientation of the heat exchanger assembly. A plurality of side fins are disposed on the outer wall of the housing, and a plurality of top fins extend radially from a central axis (A) and are disposed on top of the housing. A wicking material is disposed on the interior of each chamber. A fan assembly is disposed on top of the top fins to blow air radially down into the fins.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an orientation insensitive heat exchanger assembly for cooling an electronic device.

2. Description of the Prior Art

The operating speed of computers is constantly being improved to create faster computers. With this, comes increased heat generation and a need to effectively dissipate that heat. As laptop computers become more universal, the ability to position these heat exchangers and other parts in any one of numerous orientations become of greater importance.

Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to dissipate heat from electronic devices that are highly concentrated heat sources such as microprocessors and computer chips; however, air has a relatively low heat capacity. Thus, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids have been used to remove heat from these types of heat sources. Although, LCUs are satisfactory for moderate heat flux, increasing computing speeds have required more effective heat sink assemblies.

Accordingly, thermosiphon cooling units (TCUs) have been used for cooling electronic devices having a high heat flux. A typical TCU absorbs heat generated by the electronic device by vaporizing a working fluid housed on the boiler plate of the unit. The boiling of refrigerant constitutes a phase change from liquid-to-vapor state as such the refrigerant of the TCU is considered to be a two phase fluid. Vapor generated during boiling of the refrigerant is then transferred to a condenser, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into a stream of air flowing over fins extending from the condenser and the condensed liquid is returned back to the boiler plate by gravity. As a result, most TCUs must be positioned in a predetermined orientation in order for the refrigerant to continue the boiling-condensing cycle, thus making the TCU orientation sensitive.

To solve this problem orientation insensitive thermosiphons, or heat exchangers, have been used. An example of a thermosiphon is U.S. Pat. No. 6,695,039 to Reyzin et al. Also relevant is U.S. Pat. No. 6,085,831 to DiGiacomo et al.

The '039 patent is a thermosiphon assembly including a housing for holding a refrigerant for liquid-to-vapor transformation, and heat transfer fins disposed in the housing. The housing includes one chamber which is in contact with a boiler plate for transferring heat from the electric device. The chamber extends upwardly at an angle such that the thermosiphon can operate in both a vertical and a horizontal position and any angle of tilt there between. However, the assembly cannot be rotated a full revolution while in a tilted or horizontal position and remain operational.

The '831 patent is a heat exchanger assembly including a housing for holding refrigerant and a top wall wherein heat transfer fins are disposed on the top wall. The housing includes a plurality of condensing chambers extending upwardly and outwardly along a single vertical plane. Although this assembly has a plurality of condensing chambers, refrigerant is not present in all chambers, nor are the chambers hermetically sealed.

SUMMARY OF THE INVENTION AND ADVANTAGES

The invention provides an orientation insensitive heat exchanger assembly for cooling an electronic device comprising a hermetically sealed housing having inner walls defining a plurality of chambers. A refrigerant is disposed in each of the chambers of the housing for liquid to vapor transformation. The refrigerant in each of the chambers is independent of the refrigerant in the other chambers.

The assembly of the present invention is suitable for operation not only in the horizontal and vertical orientations, but additionally at any angle of tilt therebetween. The assembly also offers a compact arrangement while providing enhancement of heat transfer through the use of heat transfer fins.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate like parts throughout the several views, an orientation insensitive heat exchanger assembly is generally shown for cooling an electronic device20.

The assembly includes a boiler plate22for transmitting heat from an electronic device20through a thermal grease24disposed between a bottom surface of the boiler plate22and the electronic device20, as illustrated inFIG. 2. The thermal grease24fills in surface defects to form a better contact between the boiler plate22and the electronic device20.

A hermetically sealed housing26generally indicated is disposed about a central axis A. The housing26is shown to have a cylindrical shape having a circular cross-section, but can also have other shapes such as a cube. The housing26has at least one outer wall28and a bottom wall30and a top wall32sealed to one another, as shown inFIG. 4. The housing26includes a post34disposed about the central axis A and extending upwardly from the bottom wall30to the top wall32. The post34has a conical shape, as shown inFIGS. 2,3and5, but may also have a cylindrical shape having a circular cross-section, as shown inFIG. 4, or other cross-sections.

A plurality of side fins36are equally spaced from one another circumferentially around the outer wall28. The side fins36extend radially outwardly from the outer wall28to the axially extending first outer edges38at an outer imaginary cylinder C having a circular cross-section. The side fins36extend axially from the top wall32to the bottom wall30and dissipate heat from the housing26to the ambient air moving between and over the side fins36.

A plurality of top fins40generally shown are also shown inFIG. 4and extend upwardly from the top wall32of the housing26and extend radially outwardly from the central axis A to second outer edges42at the outer imaginary circular cylinder C. These fins dissipate heat from the top wall32to the ambient air moved over the top fins40. The top fins40include a set of inner fins44and a set of outer fins46disposed on the top wall32of the housing26. The inner fins44extend radially outwardly from the central axis A to an imaginary inner circle and are equally spaced circumferentially. The outer fins46, also equally spaced circumferentially, extend radially outwardly from the inner circle of the inner fins44to the second outer edges42at the outer imaginary circular cylinder C. The top fins40and the side fins36can align vertically or axially as seen inFIG. 1.

A fan assembly48generally indicated is disposed on the top fins40and along the central axis A and, is included for blowing air downwardly into and radially outwardly between the top fins40. The fan assembly48includes a plurality of fan blades50disposed about the central axis A for blowing air. The fan blades50draw air axially into the fan and downward to the top fins40. A shroud52, having a circular cylindrical shape, is disposed on the top fins40and surrounds the fan blades50. A motor54is included in the fan assembly48for rotating the fan blades50. A cage56extends radially inwardly from the shroud52and supports the motor54. The cage56is open between the spokes openings for allowing outside air to flow into the fan assembly48.

As mentioned, the fan is included for blowing air between the top fins40. When the top fins40and side fins36are aligned vertically, straight or aligned chambers58are formed through which the air can flow. When the top fins40and side fins36have a circular offset, the air flow would be interrupted, thus creating a turbulent or non-linear flow.

The assembly is distinguished by including a plurality of inner walls60disposed in the housing26which extend radially from the central axis A to the outer wall28to define a plurality of pie shaped chambers58. Each inner wall60intersects and extends radially from the central axis A to a curved segment of the outer wall28. The chambers58are independently hermetically sealed from one another. A refrigerant62is disposed in each of the chambers58of the housing26for liquid to vapor transformation. Each chamber58holds an equal amount of refrigerant62and includes an interior surface defined by the top wall32, bottom wall30and outer wall28. The chambers58are not entirely filled by the refrigerant62and the remaining empty portion accommodates the boiled off vapor.

A plurality of interior fins64are disposed on the post34and extend radially outwardly from the bottom wall30to the top wall32with each of the interior fins64being associated with one of the chambers58.

A wicking material66is disposed on the interior surfaces of each chamber58. The wicking material66performs an essential function by absorbing a portion of the refrigerant62disposed in the chambers58. This in turn cools the walls in contact with the wicking material66. This especially aids in cooling when the electronic device20is in a position other than a horizontal one. InFIG. 3. only a portion of the refrigerant62directly cools the electronic device20without the aid of the wicking material66. The refrigerant62on the bottom of the lower chamber58is wicked to aid in the cooling of the device. In an upside down position, as seen inFIG. 5, the wicking material66is essential and wicks the refrigerant62to the walls in contact with the electronic device20.

A plurality of charge ports68are disposed on the outer wall28of the housing26interleaved with the side fins36. Each of the chambers58are associated with one of the charge ports68which extend into the chambers58for supplying refrigerant62to each of the chambers58independently of the other chambers58. When operating, the electronic device20generates of heat to be dissipated. The heat is transferred from the electronic device20to the boiler plate22and thereafter causes the refrigerant62in the chambers58to boil. Vapor boiled off the refrigerant62rises and condenses. Heat is transferred from the walls to the fins and is then released from the fins into the ambient air.

When the assembly is positioned horizontally, as seen inFIG. 2, the wall in contact with the electronic device20is entirely covered by the refrigerant62in the chambers58. When the assembly is rotated 90 degrees as seen inFIG. 3, or any angle there between, a portion of the refrigerant62remains in contact with the wall engaging the electronic device20. InFIG. 5, the assembly is in an upside down position. The electronic device20is cooled by the wicked refrigerant62; accordingly the device is orientation insensitive.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims. The reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.