Heat exchange – With retainer for removable article – Electrical component
Reexamination Certificate
1999-03-05
2001-07-17
Flanigan, Allen (Department: 3743)
Heat exchange
With retainer for removable article
Electrical component
C361S704000, C361S710000
Reexamination Certificate
active
06260610
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to heat transfer devices and, more particularly, to the thermal performance and manufacturability of convoluted fin heat sinks.
Heat transfer devices, such as heat sinks and heat exchangers, are widely used for absorptive thermal protection. To achieve this, heat transfer devices are made of various types of corrugated fin material to allow energy transfer during passage of air and/or fluid through the device.
Compact, lightweight heat dissipators have become increasingly important with the constant trend of microprocessor and electronic device miniaturization. Traditionally, the highest performing heat sinks comprise thin folded fin structures for heat dissipation and a flat base, providing structural support for the assembly, as well as the interface to the electronic device. Such heat sinks are generally considered to have excellent performance, but at a very high cost. The high cost comes in part from the labor-intensive process of fixturing the fin and base assembly for precise alignment during the joining procedure. However, with electronic devices becoming ubiquitous, cost pressure virtually excludes traditional convoluted fin heat sinks from wide commercial use.
The long-used thin, lightweight convoluted fin for typical heat exchangers and dissipators is folded into a square wave shape with squared or rounded corners. In most cases, the structural base is a planar element with smooth surfaces. The interface between the fin and the base is a narrow contact area at the trough of the wave. When the fins are thin, the interface covers only a very narrow area. Furthermore, although a perfectly square wave shape will encourage higher contact with the base plate than a rounded or radiussed wave shape, perfectly squared corners at the trough of the fin material wave are unrealistic for the material used in fin forming.
It is known in the art that heat transfer can be improved in various applications by increasing the surface area of the fin material. The surface area of the fin material can be increased by either increasing the height of the fin material; increasing the number of fins per inch of the fin material; or increasing the width or flow length of the fluid along the fin. However, each of these improvements has tangible limits. For example, the part incorporating the fin material typically has a height and width limitation, which the fin material must adhere to in order to fit in the part. This is particularly the case with compact parts such as medical equipment, space applications, and computers, where increasing the size of the fin material and, therefore, the heat transfer device, is extremely undesirable. Additionally, increases in the height and/or width of the fin material does not create a directly proportional increase in the performance or efficiency of the heat transfer device. The other improvement technique, increasing the number of fins per inch, is theoretically sound, but realistically limited. The number of fins per inch is limited by the performance and ability of the corrugation means for corrugating the fin material.
It would be desirable, therefore, to have a fin heat sink with improved thermal performance and ease of assembly, without requiring a consequent increase in the surface area of the fin material.
SUMMARY OF THE INVENTION
This need is met by the fin heat sink of the present invention, wherein a base topography is proposed to enhance thermal performance of the fin heat sink by maximizing the contact area between the fin trough and the base plate. The base topography configuration of the present invention improves the heat transfer capability of the heat transfer device incorporating the fin material. Generating a heat sink according to the present invention provides a heat transfer device having increased contact area and, consequently, improved thermal performance, without increasing the height, width, or number of fins per inch.
In accordance with one aspect of the present invention, an improved heat transfer device comprises a fin generated from a flat sheet of metal, the fin having a plurality of radiussed conduit top portions and a reciprocal plurality of radiussed conduit bottom portions, for transferring heat. The radiussed conduit bottom portions of the fin are attached to a base plate. The base plate comprises a series of grooves and risers for closely approximating the shape of the radiussed conduit portions. The radiussed fin portions nest in the configuration of grooves and risers to maximize the contact area between the fin and the base plate.
The present invention also includes a method for improving heat transfer. The method comprises the steps of providing a sheet of metal and forming a plurality of corrugations in the metal to generate a fin pack. Certain of the troughs of the fin pack are then received by and nested within a combination of a plurality of grooves and risers associated with the topographical configuration of a base plate, creating a heat sink with improved thermal performance.
Accordingly, it is an object of the present invention to provide an improvement in the thermal performance of a heat transfer device. It is also an object of the present invention to provide such an improvement wherein the volume of space required for the heat transfer device is not increased. It is a further object to provide such an improvement wherein thermal impedance of the joining area between the fin and the base plate is minimized by maximizing the contact area between the fin and the base plate.
REFERENCES:
patent: 5771966 (1998-06-01), Jacoby
patent: 5791406 (1998-08-01), Gönner et al.
patent: 6000462 (1998-08-01), Gönner
“Convoluted Fin Heat Sinks” from Wakefield Engineering website at: http://www.wakefield.com/products/convoluted.htm and a data sheet at: http://www.wakefield.com/products/folded%20fin.pdf dated 1998.
Biber Catharina R.
Campanella Vincent
Flanigan Allen
Haushalter Barbara Joan
Thermal Form & Function
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