Heat exchange – With retainer for removable article – Electrical component
Reexamination Certificate
1999-08-02
2001-01-16
Flanigan, Allen (Department: 3743)
Heat exchange
With retainer for removable article
Electrical component
C165S080400, C165S185000, C361S697000, C361S710000
Reexamination Certificate
active
06173758
ABSTRACT:
TECHNICAL FIELD
This invention relates to an apparatus for dissipating heat from a surface and more specifically, to pin fin heat sinks and arrangement designs for the pin fins.
BACKGROUND OF THE INVENTION
Heat sinks comprise extended surfaces that are used to enhance cooling of heat dissipating surfaces. By increasing the overall surface area exposed to a cooling medium (fluid), the rate of heat transfer may be increased. Heat sinks may be fabricated using a variety of materials which employ a number of designs which act to enhance the cooling of the heat dissipating surfaces. Generally, the designs of the heat sinks are intended to decrease the impedance of the fluid flow through the heat sink and, thereby, reduce pressure losses. One commonly used heat sink apparatus is a pin fin heat sink. Pin fin heat sinks are also generally designed to maximize surface area and induce turbulent flow near the pin fins.
A conventional pin fin heat sink apparatus includes a base surface having a plurality of pin fins perpendicular to and protruding from the base surface. The heat sink apparatus is designed so that fluid flows through the plurality of pins which act to enhance the cooling of the heat dissipating surfaces. The plurality of pin fins may be provided in staggered rows on the base surface or the pin fins may be in equally aligned rows on the base surface. Conventional pin fin heat sink apparatuses have used a number of types of pin fins which have a variety of shapes, including, square, triangular, rectangular, diamond, circular, or helical. Typically, a single type of pin fin is used to exchange heat to the cooling medium.
As is known, one of the associated limitations of a heat sink apparatus is that the fluid flow loses a significant amount of its inertial force after entering the heat sink apparatus at one side and the fluid tends to slow as the fluid encounters rows of pin fins and flows toward an opposite side of the heat sulk apparatus. A circular pin fin design which is used in many conventional heat sinks works very well at lower flow rates. However as the flow rate of the system increases, a pressure drop begins to rapidly increase in the heat sink apparatus. Each circular pin fin creates a turbulent wake on the downstream side of the pin at high flow rates contributing to the system pressure drop. In effect, the circular pin fin creates more turbulence than is needed at high flow rates and the turbulence within the heat sink prevents the fluid from effectively flowing through the heat sink increasing the inefficiency of the heat transfer between the pin fin and the cooling medium (fluid). Prior heat fin apparatuses which include an elliptical pin fin design generally do not cause a large drop in pressure; however, the elliptical shape of the pin fin may not cause enough turbulence to provide optimal heat transfer between the pin fin and the cooling medium.
Consequently, there is a need to provide a pin fin arrangement in a heat sink apparatus which offers near optimal heat transfer at high flow rates.
SUMMARY OF THE INVENTION
The present invention comprises a pin fin heat sink and more specifically, relates to mixed geometry pin fin configurations which optimize the positive attributes of each individual pin fin geometry to provide a low cost overall system and provide better system performance in high flow rate systems. In an exemplary embodiment, the pin fin heat sink comprises a base surface having a plurality of pin fins perpendicular to and protruding therefrom. The plurality of pin fins actually comprises a plurality of pin fins having a first configuration and a plurality of pin fins having a second configuration. The first configuration pin fins are selected so that the geometric cross section of the pin fins causes turbulence as the fluid encounters the pin fins and the second configuration pin fins are selected so that the geometric cross section is such that the pin fins help streamline the turbulent fluid so that the fluid continues to move through the heat sink. Preferably, the first configuration comprises substantially circular shaped pin fins and the second configuration comprises substantially elliptical shaped pin fins.
In accordance with one exemplary embodiment of the present invention, the substantially circular shaped pin fins and the substantially elliptical shaped pin fins are arranged in staggered rows in which adjacent rows include pin fins having different configurations. In other words in the one exemplary embodiment, the heat sink includes an alternating pin fin design, wherein at least one row of the substantially circular pin fins alternates with at least one row of substantially elliptical pin fins. In a preferred embodiment, the pin fin configuration comprises disposing two rows of substantially elliptical pin fins downstream from a row of substantially circular pin fins. This alternating pattern is repeated over the base surface to form the heat sink of the present invention.
The above-described alternating pin fin arrangement is designed to reduce the pressure drop observed in high flow rate systems while at the same time, the mixed geometry arrangement creates enough turbulence to provide near optimal heat transfer at high flow rates and high Reynolds number conditions.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
REFERENCES:
patent: 2892618 (1959-06-01), Holm
patent: 5158136 (1992-10-01), Azar
patent: 5195576 (1993-03-01), Hatada et al.
patent: 5845399 (1998-12-01), Dewar et al.
Downer Scott D.
Ward Terence G.
Flanigan Allen
General Motors Corporation
Simon Anthony Luke
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