In This Issue
Optimization of Evaporator to Condenser Length Ratio for Heat Pipe Maximum Performance
Heat pipes have a multitude of applications in the thermal management of electronics. The thermal resistance of a heat pipe strongly depends, among other parameters, on so-called L-ratio, which is the ratio between the evaporator length and condenser length. The optimal L-ratio is defined as being the value for which the heat pipe thermal resistance is minimal, for a certain heat pipe assembly configuration. Finding the optimal L-ratio offers a valuable tool for thermal practitioners to most effectively deploy the heat pipe in their application. This article reviews an analytical approach for finding this optimum L-ratio.
Passive Thermal Management Technology for Fuel Cells – Part I: Control Valve Tests
The author discusses, in part one of this two part series, the Control Valve Tests run by Burke et al, which demonstrate that passive thermal control of fuel stacks is possible. They found that using either the electronic proportional control valve or the thermostatic valve can effectively control the fuel cell stack temperature. The proportional valve controls the temperature independently of the fuel cell stack power and can maintain the stack temperature within a small control band. The power level and the operating temperature are not independent, but they rise or fall together. Properly optimized for the fuel cell stack, it could provide an acceptable level of thermal control.
Industry Developments: Carbon and Graphite Foams for Thermal Management
Certain materials, such as diamond, provide substantially higher heat spreading capabilities compared with others. However, issues that include cost, availability and application make most of these materials unsuitable for conventional electronic cooling needs. One substance with excellent heat spreading properties is carbon. Improvements in carbon materials are increasing industry interest as cooling needs mount for components and PCBs. Carbon-based heat sink materials have included graphite strands, carbon nano-fibers and metal-graphite matrices.
Technology Review: Integrating Heat Pipes into Heat Sinks, 2012-2013
In this issue our spotlight is on integrating heat pipes into heat sinks. There is much discussion about this subject in the electronics industry, and these patents show some of the salient features that are the focus of different inventors.
