Heat Sink Geometry Research Articles

스트립휜 히트싱크의 냉각특성

Air-cooled heat sinks are employed in many eletronic cooling applications since they provide significant heat transfer enhancement and operational flexibility. Strip-shaped fin heat sink is of interest and needs to be investigated as general cooling products for more applicability. The purposes of this study are to evaluate heat sink performance without bypass flow condition and to determine optimal heat sink geometries. The results show that the decreasing rate of thermal resistance of a heat sink decreases with increasing inlet air velocity, and the increasing rate of pressure drop increases with increasing inlet air velocity, but is not affected by input power. The increasing rate of optimal longitudinal fin spacing is larger than that of transverse fin spacing. The strip fin heat sink tested in this study showed better cooling performance compared to that of other plate fin type.

Compact Modeling of Forced Flow in Longitudinal Fin Heat Sinks With Tip Bypass

This paper introduces a compact model to predict the interfin velocity and the resulting pressure drop across a longitudinal fin heat sink with tip bypass. The compact model is based on results obtained from a comprehensive study into the behavior of both laminar and turbulent flow in longitudinal fin heat sinks with tip bypass using CFD analysis. The new compact flow prediction model is critically compared to existing compact models as well as to the results obtained from the CFD simulations. The results indicate that the new compact model shows at least a 4.5% improvement in accuracy predicting the pressure drop over a wide range of heat sink geometries and Reynolds numbers simulated. The improved accuracy in velocity distribution between the fins also increases the accuracy of the calculated heat transfer coefficients applied to the heat sinks.

Flow and pressure field characteristics in the porous block compact modeling of parallel plate heat sinks

Growing complexity has resulted in an increased computational effort in CFD modeling of electronic systems. To reduce the computational effort, one or several heat sinks can be represented by a compact "porous block" model, with an effective thermal conductivity and pressure loss coefficient. In this study of parallel plate heat sinks in laminar forced convection, a methodology is developed to analytically determine the fluid properties of compact heat sink models that provide acceptable levels of approximation. The results of an extensive set of CFD simulations for a three heat sink channel, covering three distinct heat sink geometries, air velocities from 0.25 m/s to 2 m/s and various spacings between the heat sinks, were used to create and evaluate the effectiveness of compact models. Use of a two term, equivalent loss coefficient-reflecting the linear and quadratic components in the pressure drop of a porous block-has led to good agreement between the detailed numerical and compact model predictions, with compact heat sink pressure drops usually slightly higher (<10%) than detailed heat sink pressure drops.

Thermal compact modeling of parallel plate heat sinks

Growing complexity of electronic systems has resulted in an increased computational effort in CFD modeling of electronic systems. To reduce the computational effort, one or several heat sinks can be represented by a compact "porous block" model, with an effective thermal conductivity and pressure loss coefficient. In this study of parallel plate heat sinks in laminar forced convection, a methodology is developed to rigorously determine the thermal properties of compact heat sink models that provide a high level of accuracy. The results of an extensive set of CFD simulations for a three heat sink channel covering two distinct heat sink geometries, air velocities from 0.25 m/s to 2 m/s and various spacings between the heat sinks, were used to create and evaluate the fidelity of compact models. The results of this study establish the validity and value in using the porous block compact model representation for noncritical heat sinks in an electronic assembly. The results also reveal that a location-independent porous-block representation can yield excellent agreement in the prediction of the thermal characteristics of state-of-the-art heat sinks.

Heat transfer from square pin-fin heat sinks using air impingement cooling

Experimental and numerical results are presented for heat transfer from a C4 mounted organic land grid array (OLGA) thermal test chip cooled by air impingement. Five heat sink geometries were investigated for Reynolds numbers ranging from 9,000 to 26,000. The dimensionless nozzle-to-heat sink vertical spacing z/D was varied between 2 and 12. In this study, we investigate the interactions between heat sink geometry, flow conditions and nozzle setting and how they affect the convective heat transfer and overall cooling of the test chip as measured by total thermal resistance /spl theta//sub ja/. Optimizing fin arrays by minimizing the overall heat sink thermal resistance instead of focusing solely on maximizing the heat transfer from the fins is shown to be a better design criterion. We also provide results that show cooling performance gains can be obtained by inserting a deflector plate above the heat sink.

FDTD modeling of heatsink RF characteristics for EMC mitigation

Due to their size and complex geometry, large heatsinks such as those used in the power electronics industry may enhance the radiated emissions produced by the circuits employing them. Such enhancement of the radio frequency (rf) radiation could cause the equipment to malfunction or to contravene current EMC regulations. In this paper, the electromagnetic resonant effects of heatsinks are examined using the finite-difference time-domain (FDTD) method and recommendations are made concerning the optimum geometry of heatsinks and the placement of components so as to mitigate potential EMC effects.

ANALYTICAL FORCED CONVECTION MODELING OF PLATE FIN HEAT SINKS

An analytical model is presented that predicts the average heat transfer rate for forced convection, air cooled, plate fin heat sinks for use in the design and selection of heat sinks for electronics applications. Using a composite solution based on the limiting cases of fully-developed and developing flow between isothermal parallel plates, the average Nusselt number can be calculated as a function of the heat sink geometry and fluid velocity. The resulting model is applicable for the full range of Reynolds number, , and accurately predicts the experimental results to within an RMS difference of 2.1%.

A Computational Method To Design Heat Sinks

A computationally economical method for the design of aluminum heat sinks is presented. The motivation for this project arose from a growing need in the electronics industry to find efficient ways of improving the design of heat sinks. A three-dimensional finite-difference simulation using curvilinear boundary fitted grids is used to model the conduction heat transfer in the heat sink. Analytical and empirical models for the boundary conditions take into account the effects of natural or forced convection, as well as radiation to the surroundings. Flow bypass is included in the analysis for forced convection. The solution methodology enables solution times of less than 30 seconds for most heat sink geometries. The quick analysis and accurate results verified by experimentation indicate that the techniques developed and implemented can be used in the design and selection of heat sinks.

Optimization of heat sink geometries for impingement air‐cooling of LSI packages

This paper describes the use of our previous study's prediction procedures for calculating thermal resistance and pressure drop. The procedures are used in the optimization of heat sink geometries for impingement air-cooling of LSI packages. Two types of heat sinks are considered: ones with longitudinal fins and ones with pin fins. We optimized the heat sink geometries by evaluating 16 parameters simultaneously. The parameters included fin thickness, spacing, and height. For the longitudinal fins, the optimal fin thicknesses were found to be between 0.12 and 0.15 mm, depending on which of the four types of fans were used. For pin fins, the optimal pin diameters were between 0.39 and 0.40 mm. Under constant pumping power, the optimal thermal resistance of the longitudinal fins was about 60% that of the pin fins. For both types of heat sinks, the optimal thermal resistance for four off-the-shelf fans was only slightly (maximum about 1%) higher than the theoretical optimum for the same pumping power. When manufacturing cost performance is considered, the most economical fin thickness and diameter are about 5 to 10 times higher than the optimal values calculated without respect for manufacturing costs. These values almost correspond to the actual limits of extrusion and press heat-sink manufacturing processes. © 1999 Scripta Technica, Heat Trans Asian Res, 28(2): 138–151, 1999

Optimization of heat sink geometries for impingement air-cooling of LSI packages

This paper describes the use of our previous study's prediction procedures for calculating thermal resistance and pressure drop. The procedures are used in the optimization of heat sink geometries for impingement air-cooling of LSI packages. Two types of heat sinks are considered: ones with longitudinal fins and ones with pin fins. We optimized the heat sink geometries by evaluating 16 parameters simultaneously. The parameters included fin thickness, spacing, and height. For the longitudinal fins, the optimal fin thicknesses were found to be between 0.12 and 0.15 mm, depending on which of the four types of fans were used. For pin fins, the optimal pin diameters were between 0.39 and 0.40 mm. Under constant pumping power, the optimal thermal resistance of the longitudinal fins was about 60% that of the pin fins. For both types of heat sinks, the optimal thermal resistance for four off-the-shelf fans was only slightly (maximum about 1%) higher than the theoretical optimum for the same pumping power. When manufacturing cost performance is considered, the most economical fin thickness and diameter are about 5 to 10 times higher than the optimal values calculated without respect for manufacturing costs. These values almost correspond to the actual limits of extrusion and press heat-sink manufacturing processes. © 1999 Scripta Technica, Heat Trans Asian Res, 28(2): 138–151, 1999

Optimization of heat sink geometries for impingement air-cooling of LSI packages

Optimization of heat sink geometries for impingement air-cooling of LSI packages

LSIパッケージの噴流冷却におけるヒートシンク形状の最適化

This paper describes the use of our previous study's prediction procedures for calculating thermal resistance and pressure drop. The procedures are used in the optimization of heat sink geometries for impingement air-cooling of LSI packages. Two types of heat sinks are considered: ones with longitudinal fins and ones with pin fins. We optimized the heat sink geometries by evaluating 16 parameters simultaneously. The parameters included fin thickness, spacing, and height. For the longitudinal fins, the optimal fin thicknesses were found to be between 0.12 and 0.15 mm, depending on which of the four types of fans were used. For pin fins, the optimal pin diameters were between 0.39 and 0.40 mm. Under constant pumping power, the optimal thermal resistance of the longitudinal fins was about 60% that of the pin fins. For both types of heat sinks, the optimal thermal resistance for four off-the-shelf fans was only slightly (maximum about 1%) higher than the theoretical optimum for the same pumping power. When manufacturing cost performance is considered, the most economical fin thickness and diameter are about 5 to 10 times higher than the optimal values calculated without respect for manufacturing costs. These values almost correspond to the actual limits of extrusion and press heat-sink manufacturing processes. © 1999 Scripta Technica, Heat Trans Asian Res, 28(2): 138–151, 1999

Thermal modeling of isothermal cuboids and rectangular heat sinks cooled by natural convection

Thermally-induced buoyancy effects are not always sufficient to adequately cool high density microelectronic packages found in modern circuit boards. In many instances thermal enhancement techniques, such as heat sinks, must be used to increase the effective surface area for heat transfer and lower the thermal resistance between source and sink. The irregular surfaces of heat sinks present a formidable challenge for designers in determining the boundary conditions along the fluid-solid interface. A simple yet accurate method for calculating the thermal performance of rectangular heat sinks using a flat plate boundary layer model is presented. Several heat sink geometries are examined over a range of Rayleigh number between 10/sup 3/ and 10/sup 10/. The heat-transfer performance of the heat sinks, as given by the Nusselt number, is determined for each test based on the isothermal body temperature and the square root of the wetted surface area. Results obtained using a conjugate model, META, are compared against an analytically-based correlation and experimental data. In addition to the rectangular heat sinks, isothermal cuboids of various sizes are modeled using META, where the cuboid is approximated as a thin uniformly-heated base plate with an attached extended surface. The cuboid results are compared with experimental data and an analytically based correlation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Two-Phase Electronic Cooling Using Mini-Channel and Micro-Channel Heat Sinks: Part 1—Design Criteria and Heat Diffusion Constraints

Mini-channel (D = 2.54 mm) and micro-channel (D = 510 μm) heat sinks with a 1-cm2 heated surface were tested for their high heat flux performance with flow boiling of R-113. Experimental results yielded CHF values in excess of 200 W cm−2 for flow rates less than 95 ml min−1 (0.025 gpm) over a range of inlet subcooling from 10 to 32°C. Heat diffusion within the heat sink was analyzed to ascertain the optimum heat sink geometry in terms of channel spacing and overall thickness. A heat sink thickness to channel diameter ratio of 1.2 provided a good compromise between minimizing overall thermal resistance and structural integrity. A ratio of channel pitch to diameter of less than two produced negligible surface temperature gradients even with a surface heat flux of 200 W cm−2. To further aid in determining channel diameter for a specific cooling application, a pressure drop model was developed, which is presented in the second part of the study.

Forced Convection Air Cooling of Simulated Low Profile Electronic Components: Part 2—Heat Sink Effects

Forced convection air cooling of an array of low profile, card-mounted components has been investigated. A simulated array is attached to one wall of a low aspect ratio duct. This is the second half of a two-part study. In this second part the presence of a longitudinally finned heat sink is considered. The heat sink is a thermally passive “flow disturbance”. Laboratory measurements of the heat transfer rates downstream of the heat sink are reported and compared with the measured values which occur when no heat sinks are present. Data are presented for three heat sink geometries subject to variations in channel spacing and flow rate. In the flow range considered laminar, transitional and turbulent heat transfer behavior has been observed. The presence of a heat sink appears to “trip” the start of transition at lower Reynolds numbers than when no heat sinks are present. A Reynolds number based on component length provides a good correlation of the heat transfer behavior due to variations in flow rate and channel spacing. Heat transfer is most strongly effected by flow rate and position relative to the heat sink. Depending on the flow regime (laminar or turbulent) both relative enhancement and reductions in the component Nusselt number have been observed. The impact of introducing a heat sink is greatest for flow rates corresponding to transitional behavior.

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

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 &lt; Re &lt; 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.

Factors Involved in the Design and Manufacture of Bonded Heat Sinks

A review has been made of the various factors involved in the design and manufacture of bonded heat sinks for printed circuit boards. Among the factors discussed are the design of heat sink thicknesses and the interrelationship with component lead geometry, the design of heat sink geometry as related to the fabrication of the heat sinks and bonding media, and the complexities of the bonding process itself.

On induced elastic waves in fiber‐optic sensors and laser diodes

Experimental observations of induced elastic waves propagating along the optical fibers of fiber‐optic hydrophones are presented. Extentional velocities and attenuation coefficients of longitudinal waves measured from single and multimode optical fibers are discussed in relation to fiber‐optic hydrophone noise. Experimental observations of magnetostrictively, thermoelastically, and electromagnetically induced elastic waves in laser diode heat sinks and leads are also presented. The importance of the findings is discussed in relation to the interaction between the elastic waves present in both laser diodes and optical fiber sensors, and the potential undesirable acousto‐optical modulations in integrated optics where the laser diode is mechanically coupled to the integrated chip. The magnetostrictively induced elastic waves were much larger than the thermoelastic waves in laser diodes using steel heat sinks. The effects of the laser diode heat sink geometry on focusing the elastic waves on the GaAs crystal ...

Thermal properties of annular and array geometry semiconductor devices on composite heat sinks

The thermal spreading resistance and temperature-profile properties of a circular semiconductor device mounted on a composite heat sink are considered theoretically. The results are applied to annular and array-geometry contacts by the principle of superposition. It is found that considerable reductions in thermal resistance can be achieved which are due both to contact geometry, and the composite heat sink. Substantial improvements in the uniformity of the temperature profile in the contact due to the composite nature of the heat sink is also demonstrated and optimum heat sink geometries are illustrated. An annular-geometry structure (inner radius to width ratio of 8) with an area of 3·14 × 10 −4 cm 2 has a predicted thermal resistance of 2·6°C/W and a temperature difference at the interface of only 7·5 per cent, when the main heat sink is copper, the conductivity ratio is 3, and the heat sink geometry is optimum. The results are shown to agree in the special case of a single-medium heat sink with those of Frey. The results are also applicable to the case where interface layers are present in the heat sink with conductivity lower than the main heat sink and in which heat-spreading is not negligible.