Heat sink system with fin structure
A heat sink apparatus includes a heat conductive base plate and a plurality of fins in thermal communication with the heat conductive base plate. The plurality of fins is configured to form a plurality of curved and branching channels extending radially on the base plate. At least two of the plurality of fins are configured with a gap between them to trip a gas boundary layer formed on a first one of the at least two fins, when a gas boundary layer is present.
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1. Field of the Invention
This invention relates to heat fins, and particularly to heat sinks having a plurality of fins.
2. Description of the Related Art
Integrated circuits and printed circuit boards used in electronics increasingly require high-performance heat sinks that have a heat conducting base plate in thermal communication with a fin structure. Air introduced to the resulting system, often times using a forced-air cooling assembly such as a fan, accomplishes the thermal transfer by carrying away heat energy from the heat sink and fins. The air is directed either at the base plate (in an impinging air flow configuration) or over the base plate (in a parallel flow configuration) and channeled through the fins to carry away the heat. Typically, the fins are metallic and may employ a combination of different lengths and widths to optimize such thermal transfer characteristics.
Unfortunately, such fin and base-plate arrangements typically suffer from high pressure drop challenges resulting in increased fan size and increased fan input power requirements. In addition, the power dissipation requirements of electronic devices are increasing at a rapid pace, while their sizes continue to shrink to meet consumer demand. Conventional air-cooling methods are currently limited to thermal transfer power dissipation densities of 5-10 Watts/cm2, while liquid cooling techniques that would allow greater power dissipation are expensive and may lower system reliability.
A need still exists, therefore, for an air-cooled heat sink with reduced pressure drop and increased thermal transfer characteristics.
SUMMARY OF THE INVENTIONA heat sink apparatus is disclosed for use with integrated circuits, printed circuit boards and other heat sources. In one embodiment, the heat sink includes a heat conductive base plate and a plurality of fins in thermal communication with the heat conductive base plate. The plurality of fins is configured to form a plurality of curved and branching channels extending radially on the base plate. At least two of the plurality of fins are configured with a gap between them to trip a gas boundary layer formed on a first one of the at least two fins, when a gas boundary layer is present.
In one embodiment of a method of cooling a heat conductive base plate, the method includes conducting heat from a heat conductive base plate to a plurality of curved fins, blowing air onto a face of the heat conductive base plate, directing the air through first-tier channels established by the plurality of curved fins to induce primary and vortex flow patterns, directing the air through second-tier branching channels formed by the plurality of curved fins to reduce buildup of back pressure as the air moves across the heat conductive base plate adjacent to the curved fins and passing the air across gaps formed in the plurality of curved fins to trip a developing thermal boundary layer.
The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Like reference numerals designate corresponding parts throughout the different views.
A heat sink, in accordance with one embodiment, includes a plurality of heat conducting fins coupled to a heat conductive base plate, with the fins arranged to form curved and branching channels that extend radially on the base plate. The fins are curved to produce primary and secondary flow characteristics when air is forced through them to provide advantageous thermal transfer characteristics between the air, fins and base plate. Each transition to a new tier of branching channels also results in development of a new thermal boundary layer to provide advantageous thermal transfer characteristics. Each subsequent tier of branching channel has a reduced cross section area for a reduced gas flow rate through such channel. The number of tiers of branching channels is preferably four or higher, but may be designed based on heat load requirement and available fan size. In the preferred embodiment, the adjoining and discontinuous fins are also configured with a gap between them to trip flow and thermal boundary layers to further improve thermal transfer characteristics. Although the preferred embodiment is described for use with gas, it is contemplated that the apparatus may also be used in a liquid environment to form a liquid-cooled heat exchanger. The curved fins, multi-scale branching channels and fin gaps provide a heat sink with reduced back pressure and increased thermal transfer characteristics verses previous heat sink designs allowing the use of smaller fans (in an air-cooled format) for the same heat transfer coefficient and improving overall system reliability.
The described repeating and multi-tiered branching pattern 204 preferably repeats about the periphery of the heat sink 200 to provide a heat sink with reduced back pressure and increased thermal transfer characteristics verses previous heat sink designs. In an alternative embodiment, the relative lengths and relative positions of the curved fins in other sectors of the heat sink are changed to modify flow characteristics according to the fins' use in a fan or fluid system to properly distribute heat energy absorbed from the heat conducting base plate 107.
During operation, the heat conductive base plate 107 is in thermal communication with a heat source such as an operating integrated circuit or printed circuit board to absorb dissipated heat energy. Dissipated heat energy is conducted from the conductive base plate to the plurality of curved fins 105 positioned radially across the base plate 107 to improve the heat removal capacity of the heat sink system. Air is blown directly onto the face of the conductive base plate (impinging air flow configuration). Air is directed in a primary flow pattern through channels (211, 217, 223) formed by the curved fins, with the curvature of the fins inducing a secondary flow pattern. Branching channels formed by the curved fins reduce buildup of back pressure as the air moves across the heat conductive base plate adjacent to the curved fins. Developing thermal and velocity boundary layers are repeatedly tripped by passing the air across gaps formed between the plurality of curved fins.
In
While various implementations of the application have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention.
Claims
1. A heat sink apparatus, comprising:
- a heat conductive base plate; and
- a plurality of fins in thermal communication with said heat conductive base plate, said plurality of fins configured to form a plurality of curved and branching channels extending radially on said base plate, at least two of said plurality of fins configured with a gap between them to trip a boundary layer formed on a first one of said at least two fins, when a boundary layer is present.
2. The apparatus of claim 1, wherein at least one of said plurality of fins comprises a plurality of pin fins.
3. The apparatus of claim 1, wherein said plurality of fins have respective fin heights that increase radially outward to provide a more uniform base plate temperature when used as a heat sink.
4. The apparatus of claim 1, wherein said gap extends substantially across the height of said at least one of said plurality of fins.
5. The apparatus of claim 1, further comprising a plurality of concave dimples configured on an upper surface of said heat conductive based plate to introduce a vortex flow on the said upper surface, when a flow is present.
6. A heat sink apparatus, comprising:
- a heat conductive base plate;
- first and second curved fins in thermal communication with said heat conductive base plate, said first and second curved fins forming a first channel inlet to receive a flow of gas for heat transfer;
- a third curved fin positioned between said first and second curved fins and extending from a position on said heat conductive base plate set back from said first channel inlet, said first curved fin and a proximal end of said third curved fin establishing a second channel inlet to receive a portion of the flow of gas for heat transfer; and
- a fourth curved fin positioned between said first and third curved fins and extending from a position on said heat conductive base plate set back from said second channel inlet, said first curved fin and a proximal end of said fourth curved fin forming a third channel inlet to receive a portion of the flow of gas for heat transfer;
- wherein said first, second, third and fourth fins establish a plurality of branching and curved channels to receive a gas flow and to induce primary and secondary gas flow for increased heat transfer at a reduced pressure drop between said first and third channel inlets.
7. The apparatus of claim 6, further comprising:
- a fifth curved fin positioned between said first and fourth curved fins and extending from a position on said heat conductive base plate set back from said third channel inlet, said first curved fin and a proximal end of said fifth curved fin forming a fourth channel inlet to receive a portion of the flow of gas for heat transfer at a reduced pressure drop between said first and fourth channel inlets.
8. The apparatus of claim 6, wherein at least one of said first, second and third curved fins comprises a plurality of fin segments to trip a gas boundary layer at each respective fin gap.
9. The apparatus of claim 6, wherein at least one of said first, second and third curved fins comprises a plurality of pin fins to trip a gas boundary layer at each respective pin gap.
10. The apparatus of claim 6, wherein at least one of said first, second and third curved fins have a fin height that increases radially outward to provide more uniformity of base plate temperature.
11. The apparatus of claim 10, further comprising a plurality of concave dimples configured on an upper surface of said heat conductive based plate to introduce a vortex flow on the said upper surface, when a flow is present.
12. A heat sink system, comprising:
- a heat conductive base plate;
- a fin structure in thermal communication with said base plate, said fin structure having a plurality of curved branching channels, said plurality of curved branching channels having a first tier channel inlet;
- a fan positioned in complementary opposition to said first tier channel inlet to provide a flow of air.
13. The system of claim 12, further comprising a metering port positioned between said first tier channel inlet and said fan to redirect air towards said first tier channel inlet.
14. The system of claim 12, further comprising a directing port positioned between said first tier channel inlet and said fan to redirect air towards said first tier channel inlet.
15. The system of claim 12, wherein said curved branching channels comprise a plurality of curved fins.
16. The system of claim 15, wherein at least one of said curved fins comprises a plurality of fin segments to trip a gas boundary layer at each respective fin segment intersection.
17. The system of claim 15, wherein at least one of said curved fins comprises a plurality of pins to trip a gas boundary layer at each respective pin intersection.
18. The apparatus of claim 15, further comprising a plurality of concave dimples configured on an upper surface of said heat conductive based plate to introduce a vortex flow on the said upper surface, when a flow is present.
19. A method of cooling a heat conductive base plate, including:
- conducting heat from a heat conductive base plate to a plurality of curved fins;
- blowing air onto a face of said heat conductive base plate;
- directing said air through at least one first-tier channel established by said plurality of curved fins to induce primary and vortex flow patterns;
- directing said air through a plurality of second-tier branching channels established by said plurality of curved fins to reduce buildup of back pressure as said air moves across said heat conductive base plate adjacent to said curved fins; and
- passing said air across gaps formed in said plurality of curved fins to trip a developing thermal boundary layer.
20. The method of claim 19, further comprising:
- passing said air across concave dimples formed on a surface of said heat conductive base plate to trip a developing thermal boundary layer.
21. The method of claim 19, further comprising:
- passing said air across a plurality of concave dimples formed on at least one of said plurality of curved fins to trip a developing thermal boundary layer.
Type: Application
Filed: Oct 31, 2008
Publication Date: May 6, 2010
Applicant:
Inventors: Avijit Bhunia (Agoura Hills, CA), Yuan Zhao (Thousand Oaks, CA), Chung-Lung Chen (Thousand Oaks, CA)
Application Number: 12/290,505
International Classification: F28F 7/00 (20060101);