Showing papers by "Ralph L. Webb published in 2006"
TL;DR: The thermal performance of plate fin, round pin-fin, and offset strip-fin heat sinks with a duct-flow type fan arrangement was analytically evaluated in this article.
Abstract: The thermal performance of plate fin, round pin-fin, and offset strip-fin heat sinks with a duct-flow type fan arrangement was analytically evaluated. Heat sinks of 65mmtimes60 mm plan areatimes50 mm height with a 4300-RPM dc fan (60mmtimes15mm) were chosen for the performance comparison. A constant temperature, 6-mm thick heat sink base plate is assumed so that thermal spreading resistance is not involved. The operating point on the fan curve is based on the flow pressure drop impedance curve through a heat sink using the friction factor correlation for the chosen heat sink. The loss coefficients at both the entrance and the exit of the heat sink are included in the flow impedance curve. The operating point is defined by the balance point of the flow impedance curve and the fan performance curve. After determining the operating air velocity, the convective thermal resistance of heat sinks is evaluated from the Nusselt number correlation for the chosen heat sink. Results obtained show that optimized round pin-fin heat sinks provide 32.8%-46.4% higher convective thermal resistance compared to an optimized plate-fin heat sink. The optimized offset strip-fin heat sink shows a slightly lower convective thermal resistance than the plate-fin heat sink. As the offset strip length decreases, however, thermal performance seriously deteriorates
27 citations
TL;DR: In this article, the authors presented an analysis that allows the accurate calculation of K c and K e values with parallel plate channels in the developing flow region, as a function of contraction ratio and 4x+ (= 4x/D h Re).
Abstract: An analysis is presented to calculate the entrance and exit losses for developing flow in parallel plate channels. Such an analysis is of value for air-cooled heat sinks with short flow length, such as electronic heat sinks. These predictions are typically done using inlet (K c ) and exit (K e ) loss coefficients for parallel plate channels from the Kays and London book, Compact Heat Exchangers. However, the information presented in Compact Heat Exchangers assumes fully developed flow at the exit. Electronic heat sinks operate in the developing flow region. Thus, the use of the published K c and K e from Compact Heat Exchangers will result in an overestimation of the actual K c and K e values. The present author has completed an analysis that allows the accurate calculation of K c and K e values with parallel plate channels in the developing flow region. The results are presented in graphical and equation form as a function of contraction ratio and 4x+ (= 4x/D h Re). Entrance and exit losses can account f...
13 citations