Performance Prediction for Partially-Confined Heat Sinks

2003 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Meng-Ping Wang ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Velocity ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Thermal Conductance ◽  
Optimal Number ◽  
Performance Parameter ◽  
Heat Sinks ◽  
Fin Spacing

In the present study, the forced air convection heat transfer for unconfined and confined heat sinks by considering flow bypass effect is studied on a semi-empirical basis. The flow bypass effect for unconfined heat sinks is firstly investigated. For unconfined heat sinks with specified fin spacing and fin height, the results reveal that the value of Ui/(ε·Us), which represents the flow bypass capability, increases from a very small Reynolds number up to a certain Reynolds number, say Rei = 60–200; and then gradually decrease with further increasing Reynolds number. At a specified Reynolds number, the Ui/(ε·Us) will generally increase when the fin spacing decreases or the fin height increases. For heat sinks partially confined in a channel, a novel concept to estimate an imaginative flow domain, in which the flow is influenced due to the existence of heat sink in the channel, is postulated in the study. Accordingly, an effective method for predicting the flow velocity between fins, flow rate through the heat sink and the fin heat transfer coefficient in both unconfined flow and confined flow is presented. Finally, in order to explore the optimal number of fins, a performance parameter defined as the ratio of thermal conductance to the required pumping power is introduced; an optimal procedure to determine the maximum performance parameter for a heat sink partially confined in a channel is postulated. The results manifest that the optimal number of fins increases with increasing inlet flow velocity.

Fluid Flow and Heat Transfer of Liquid Sodium in Small-Scale Heat Sinks With Different Geometries

2021 ◽  
Author(s):  
Mahyar Pourghasemi ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Sections ◽  
Heat Sink ◽  
Volume Ratio ◽  
Heat Sinks ◽  
Liquid Sodium ◽  
Small Scale ◽  
Nusselt Numbers ◽  
The Difference

Abstract 3-D numerical simulations are performed to investigate liquid sodium (Na) flow and the heat transfer within miniature heat sinks with different geometries and hydraulic diameters of less than 5 mm. Two different straight small-scale heat sinks with rectangular and triangular cross-sections are studied in the laminar flow with the Reynolds number up to 1900. The local and average Nusselt numbers are obtained and compared against eachother. At the same surface area to volume ratio, rectangular minichannel heat sink leads to almost 280% higher convective heat transfer rate in comparison with triangular heat sink. It is observed that the difference between thermal efficiencies of rectangular and triangular minichannel heat sinks was independent of flow Reynolds number.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

Numerical Simulation of Heat Sink Performance With Interrupted and Staggered Fins

2009 ◽  
Author(s):  
Suabsakul Gururatana ◽  
Xianchang Li
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Flow Direction ◽  
Heat Sinks ◽  
High Heat Transfer

Extended surfaces (fins) have been used to enhance heat transfer in many applications. In electronics cooling, fin-based heat sinks are commonly designed so that coolants (gas or liquid) are forced to pass through the narrow straight channel. To improve the overall heat sink performance, this study investigated numerically the details of heat sinks with interrupted and staggered fins cooled by forced convection. Long and narrow flow passages or channels are widely seen in heat sinks. Based on the fundamental theory of heat transfer, however, a new boundary layer can be created periodically with interrupted fins, and the entrance region can produce a very high heat transfer coefficient. The staggered fins can take advantage of the lower temperature flow from the upstream. The tradeoff is the higher pressure loss. A major challenge for heat sink design is to reduce the pressure loss while keeping the heat transfer rate high. The effect of fin shapes on the heat sink performance was also examined. Two different shapes under study are rectangular and elliptic with various gaps between the interrupted fins in the flow direction. In addition, studies were also conducted on the parametric effects of Reynolds number and gap length. It is observed that heat transfer increases with the Reynolds number due to the feature of developing boundary layer. If the same pressure drop is considered, the heat transfer rate of elliptic fins is higher than that of rectangular fins.

Natural Convection From Finned Heat Sinks

2007 ◽  
Author(s):  
L. T. Yeh ◽  
Joseph Yeh ◽  
B. T. F. Chung
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Plate Thickness ◽  
Heat Sinks ◽  
Cfd Model ◽  
Practical Applications ◽  
Computational Fluid Dynamics Analysis ◽  
Fin Spacing ◽  
Fin Length

A CFD (computational fluid dynamics) analysis is performed on the finned heat sinks. For convenience, a commercial CFD code, Flotherm, is utilized in the analysis. Though the code can handle the radiation heat transfer, the present analysis is limited to the natural convection with the base of the heat sink at a constant temperature. The continuous fin configuration is first considered due to the importance of its applications. Several experimental data are available for the vertically straight-fin heat sink and a useful correlation is also developed. For given overall fin dimensions of 15″ × 10.341″ × 2.2″, the correlations are first employed to determine the optimal fin spacing. This optimal fin spacing of 0.439 in is then used to develop the baseline CFD model. The dimensions of the baseline CFD model are as follows: Fin width (in): 10.341. Heat sink length (in): 15. Fin spacing (in): 0.439. Fin height (in): 2.0. Fin thickness (in): 0.1. Fin base plate thickness (in): 0.2. Fin numbers: 20. The baseline model with various fin spacing is analyzed and the results (heat loss from the finned heat sink) compare well with those obtained through the correlations. The analysis is extended to the staggered and in-line fin configurations because of their practical applications. Three different fin lengths, including 1″, 3″ and 5″ fin length for the staggered fin array are examined. The results indicate that the effectiveness of heat transfer is increased as the fin length increasing. The continuous fin configuration is the most efficient, and is followed by the staggered fins and then by the in-line fins.

Conjugate Mixed Convection Heat Transfer From a Shrouded Vertical Nonisothermal Heat Sink

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
Biplab Das ◽  
Asis Giri ◽  
Suman Debnath
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Parametric Studies ◽  
Mixed Convection Heat Transfer ◽  
Fin Spacing

A computational analysis of conjugate mixed convection heat transfer from shrouded vertical nonisothermal heat sink on a horizontal base is performed. The overall Nusselt number and the product of friction factor (f) and Reynolds number (Re) are found to vary significantly with the spacing of heat sink as well as with the clearance between shroud and heat sink. By increasing the fin conductance by 200%, an enhancement of Nusselt number is noted to be around 58%, while the same Nusselt number enhancement is 134% for isothermal fin, within the range of parametric studies. The fRe value for smaller fin spacing shows a maximum with clearances, while the same for higher fin spacing remains the same or increases with clearances. Finally, overall Nusselt number and friction factor are well correlated with the governing parameters of the problem.

scholarly journals Experimental analysis of effect of base with different inner geometries filled nano PCM for the thermal performance of the plate fin heat sink

2021 ◽  
pp. 243-243
Author(s):  
Periyannan Lakshmanan ◽  
Saravanan Periyasamy ◽  
Mohan Raman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Phase Shift ◽  
Experimental Research ◽  
Thermal Performance ◽  
Heat Sink ◽  
Electronic Devices ◽  
Base Plate ◽  
Heat Sinks

Experimental research demonstrates the performance of electronic devices on plate fin heat sinks in order to guarantee that operating temperatures are kept as low as possible for reliability. Paraffin wax (PCM) is a substance that is used to store energy and the aluminum plate fin cavity base is chosen as a Thermal Conductivity Enhancer (TCEs). The effects of PCM material (Phase shift material), cavity form base (Rectangular, Triangular, Concave and Convex) with PCM, Reynolds number (Re= 4000-20000) on heat transfer effectiveness of plate fin heat sinks were experimentally explored in this research. The thermal performance of concave base plate fin heat sink with PCM is increased up to 7.8% compared to other cavity base heat sinks.

Study of Flow and Heat Transfer Characteristics in Asymmetrically Heated Sintered Porous Heat Sinks With Periodical Baffles

2005 ◽  
Vol 128 (3) ◽  
pp. 226-235 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Sheng-Chung Tzeng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Heated Surface ◽  
Heat Sinks ◽  
Heat Transfer Characteristics ◽  
Fluid Medium ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer

This work numerically examined the mechanism of heat transfer in a sintered porous heat sink with baffles. A channel filled with the sintered porous heat sink was asymmetrically heated and metallic baffles were periodically mounted on the heated surface. The fluid medium was air. The results indicate that no recirculation occurred between baffles. The metallic baffle obtained heat from the heated surface by conduction directly from the heated surface and indirectly through the porous media. It dissipated heat to the fluid that passed over the zone above the baffle. The Nusselt numbers in the cases with baffles exceeded those in cases without a baffle. The enhancement in the average Nusselt numbers of sintered porous heat sinks with baffles increased as the Reynolds number (Re) declined; the baffle height (h∕H) increased; the baffle length (w∕H) increased, or the baffle pitch (XL) decreased. However, at Re=500, the average Nusselt number in the case with h∕H=0.3 was higher than those with h∕H=0.7, 0.5, and 0.1. Additionally, the minimum enhancement appeared at around Re=3000 for various h∕H, w∕H, and XL. For the cases with h∕H⩽0.3 and various w∕H as well as XL, at Re>3000, sintered porous heat sinks with baffles insignificantly improved heat transfer.

Natural and forced convection heat transfer coefficients of various finned heat sinks for miniature electronic systems

2018 ◽  
Vol 233 (2) ◽  
pp. 249-261 ◽  
Author(s):  
SW Pua ◽  
KS Ong ◽  
KC Lai ◽  
MS Naghavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Cooling Mode ◽  
Heat Transfer Coefficients ◽  
Experimental Heat

Downward lighting light-emitting diodes require cooling with cylindrical fin heat sinks to be mounted on top and cooled under natural convection air cooling mode. Performance simulation would involve specification of the heat transfer coefficient. Numerous methods are available to simulate the performance of conventional plate fin heat sinks including computational fluid dynamics packages. It would be feasible to perform simulation based on conventional flat plate fin heat sinks. A cylindrical fin heat sinks could be simply treated as a plate fin heat sink, if we imagine it cut open and laid out horizontally. A theoretical model is proposed in this paper. An experimental investigation is conducted here to validate its accuracy. Convective heat transfer coefficients were experimentally determined for a horizontally and vertically inclined bare plate operating under natural and forced air cooling modes. In addition, a vertical plate fin heat sink and a vertical cylindrical fin heat sink under natural convection were investigated. Power inputs were kept from 5 to 40 W in order to keep operating temperatures below 100 ℃. Comparison of the experimental heat transfer coefficients and those obtained from well-known existing Nusselt number correlations show that agreement was poor for the bare plate but satisfactory for the plate and cylindrical fin heat sinks. Although they are within the generally accepted range, it would be advisable for actual measurements to be carried out in order to provide more accurate sizing for thermal measurements.

A Three-Dimensional Simulation Analysis of Fluid Flow and Heat Transfer in Microchannel Heat Sinks with Different Structures

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jienan Shen ◽  
Xiuxiu Li ◽  
Yongsheng Zhu ◽  
Boya Zhang ◽  
Hang Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Heat Sink ◽  
Simulation Analysis ◽  
Heat Sinks ◽  
Mixing Efficiency ◽  
Microchannel Heat Sink ◽  
Flow And Heat Transfer ◽  
Microchannel Heat Sinks

Abstract Numerical studies have been performed to analyze the fluid flow and heat transfer characteristics of nine microchannel heat sinks (MCHS) with different shapes and different arrangements of the ribs and cavities on the sidewalls, using three common shapes (square, triangle, and circular) of ribs or cavities as the basic structure in this work. The boundary conditions, governing equations, friction factor (f), Nusselt number (Nu), and performance evaluation criteria (ξ) were considered to determine which design was the best in terms of the heat transfer, the pressure drop, and the overall performance. It was observed that no matter how the circular ribs or cavities were arranged, its heat sink performance was better than the other two shapes for Reynolds number of 200–1000. Therefore, circular ribs or cavities can be considered as the best structure to improve the performance of MCHS. In addition, the heat sink performance of the microchannel heat sink with symmetrical circular ribs (MCHS-SCR) was improved by 31.2 % compared with the conventional microchannel heat sink at Re = 667. This was because in addition to the formation of transverse vortices in the channel, four symmetrical and reverse longitudinal vortices are formed to improve the mixing efficiency of the central fluid (low temperature) and the near-wall fluid (high temperature). Then, as the Reynolds number increases, the heat sink performance of MCHS-SCR dropped sharply. The heat sink performance of microchannel heat sinks with staggered ribs and cavities (MCHS-SCRC, MCHS-STRC, and MCHS-SSRC) exceeded that of MCHS-SCR. This indicated that the microchannel heat sink with staggered ribs and cavities was more suitable for high Reynolds number (Re > 800).

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