There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Heat and fluid flow in high-power LED packaging and applications

A heat dissipation device includes a primary heat sink ( 10 ) contacting a central processing unit and a secondary heat sink ( 20 ) attached on heat-generating electronic components adjacent the central processing unit. The primary heat sink includes a base ( 12 ) and a heat-dissipation portion ( 14 ) disposed on a middle of the base. The secondary heat sink includes a substrate ( 22 ) and a plurality of fin assemblies ( 24 ) arranged on the substrate. The base is laid on the substrate with the fin assemblies arranged around the heat-dissipation portion. The primary heat sink is partly superposed on the secondary heat sink with a compact structure. The heat-dissipation portion can simultaneously dissipate heat from the central processing unit and its adjacent heat-generating electronic components.

Heat dissipation device

Thermal behavior in solar air heater channel fitted with combined rib and delta-winglet

Various microchannel heat sinks for dissipating heat loads have received great attention. Wavy channels are recognized to be suitable to enhance the heat transfer, and are successfully applied in heat-exchange devices. In this article, three kinds of water-cooled microchannel heat sinks, such as a rectangular straight microchannel heat sink, a single-layer wavy microchannel heat sink and a double-layer wavy microchannel heat sink, have been designed and the corresponding laminar flow and heat transfer have been investigated numerically. The effects of the wave amplitude on heat transfer, pressure drop, and thermal resistance are also observed. Results show that for removing an identical heat load, the overall thermal resistance of the single-layer wavy microchannel heat sink decreases with increasing volumetric flow rate, but the pressure drop is increased greatly. At the same flow rate, the double-layer wavy microchannel heat sinks can reduce not only the pressure drop but also the overall thermal resist...

Numerical Predictions of the Flow and Thermal Performance of Water-Cooled Single-Layer and Double-Layer Wavy Microchannel Heat Sinks

In this study, an approximate analytical-numerical procedure is used to model natural convection cooling of heat sinks using electronics cooling software. The analysis evolves in two stages: a numerical simulation of the detailed heat sink, and a simulation of a compact model that exhibits similar thermal and flow resistance characteristics to those of the actual heat sink. From the analysis, the thermal resistance of the heat sink is evaluated. Subsequently, the effective thermal conductivity that must be assigned to the compact heat sink is determined using the Nusselt number correlation for free convection over a vertical plate. Due to the algebraic form of the Nusselt number correlation, the effective thermal conductivity is determined in an iterative fashion. The purpose of a compact heat sink is to reduce computational effort while retaining a desired level of accuracy. In this article, the compact modeling scheme is first applied to either an extruded or a pin-fin heat sink in order to validate the procedure under laminar conditions. Subsequently, the same approach is applied to a multichip system consisting of a set of pin-fin heat sinks placed in series. At both individual and system-level models, it is found that the compact approach results in substantial savings in mesh size and computing time. These savings are accompanied by a small acceptable error that is less than 10% relative to the detailed model predictions.

Characterization of compact heat sink models in natural convection

An electronic system includes a chassis defining a substantially plane-shaped cavity. The chassis is arranged to contain an air stream (e.g., provided by a cooling subsystem) which flows from an air intake side of the chassis to an air exhaust side of the chassis through the substantially plane-shaped cavity. The air intake side of the chassis is opposite the air exhaust side of the chassis. The electronic system further includes a jacket circuit board disposed within the plane-shaped cavity, and a set of pluggable electronic modules. The jacket circuit board is oriented within the plane-shaped cavity to receive cooling from the air stream. Each pluggable electronic module is arranged to (i) electronically connect to the jacket circuit board through a front of the chassis and (ii) define a supplemental ventilation port through which air passes to augment the air stream.

Techniques utilizing thermal, emi and fips friendly electronic modules

Steady flow characteristics and surface Nusselt number distributions of heat sinks with smooth, ribbed, and dimpled surfaces are investigated in laminar flow using the numerical code FLUENT 6.2.16. Presented are local and spatially averaged surface Nusselt numbers, as well as distributions of numerically predicted flow characteristics within the heat sink passages. These include distributions of static pressure, velocity, and streamwise vorticity in flow cross-sectional planes. These results are valuable because of the design information provided to optimize heat sink thermal performance, without the use of costly and time-consuming experiments.

Numerical Predictions of Heat Transfer and Flow Characteristics of Heat Sinks with Ribbed and Dimpled Surfaces in Laminar Flow

Different numerical approaches have been proposed in the past to solve the Navier-Stokes equations. Conventional methods have often relied on finite-difference, finite-element, and boundary-element techniques. Multigrid methods have been recently introduced because they help to obtain a faster convergence rate of the error residual. A difficulty plaguing numerical methods today is the inability to treat singularities at or near boundaries. Such difficulties become even more pronounced when coupled with the need to handle semi-infinite and infinite domains. Sinc-based numerical algorithms have the advantage of handling singularities, boundary layers, and semi-infinite domains very effectively. In addition, they typically require fewer nodal points and are proven to provide an exponential convergence rate in solving linear differential equations. This study involves a first step in applying the Sinc-based algorithm to solve a nonlinear set of partial differential equations. The example we consider arises in...

/pdf/a-first-step-in-applying-the-sinc-collocation-method-to-the-31vxniw4c0.pdf

A first step in applying the sinc collocation method to the nonlinear navier± stokes equations

The heat sink of the present invention includes a device portion, a bend portion, and a support portion that thermally couples the circuit board component to a support member, thereby allowing for heat transfer from the circuit board component to the support member. The bend portion of the heat sink allows for displacement of the device portion relative to the support portion to limit the amount of stress generated by the heat sink on the circuit board component. The geometry of the heat sink further allows placement of the heat sink within the relatively narrow space conventionally formed between the circuit board and the support member.

Susheela Narasimhan

Papers

Characterization of compact heat sink models in natural convection

Techniques utilizing thermal, emi and fips friendly electronic modules

Numerical Predictions of Heat Transfer and Flow Characteristics of Heat Sinks with Ribbed and Dimpled Surfaces in Laminar Flow

A first step in applying the sinc collocation method to the nonlinear navier± stokes equations

Methods and apparatus for cooling a circuit board component