In the latest Qpedia Thermal eMagazine, we discuss the latest developments in the industry on thermally conductive polymers. The article explores the importance, uses and advantages of thermally conductive polymers in providing heat transfer in various applications, such as lighting and automotive, and provides a summary of recent developments in industry and research underway at MIT.
Read the “Thermal Conductive Polymers” article by downloading the latest Qpedia.
Posted in materials, polymers, Qpedia Thermal eMagazine
Passive Thermal Management Technology for Fuel Cells
Part 1: Control Valve Tests
Last Month’s Qpedia featured part 1 of the two-part article series, “Passive Thermal Management Technology for Fuel Cells”, which discussed control valve tests. The article discussed tests performed by Burke et al, which demonstrated that the 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. Read Part 1 in the December 2013 Issue by downloading it at: http://www.qats.com/Qpedia-Thermal-eMagazine/Back-Issues-Content/114.aspx
Part 2: Passive Cooling Plates
The second part of “Passive Thermal Technology for Fuel Cells” is featured in this month’s Qpedia, focusing on passive cooling plates. The author discusses the importance of fuel cells by illustrating a description of Burke’s study using passive thermal management technology to regulate the PEMFC stack temperature. This study demonstrated that passive thermal control of fuel cell stacks is feasible and that the passive removal of heat is controllable and provides the highly uniform thermal environment desired for fuel cell operation. This revolutionary thermal control approach was shown to reduce the components and parasitic power compared to the traditional pumped loop thermal control approach.
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The latest Qpedia Thermal eMagazine has just been released and can be downloaded at www.qats.com. This issue marks the eighth year Qpedia has been publishing the highly regarded magazine for the thermal engineering community.
One of this issue’s featured articles is “Thermal Conductivity of Printed Circuit Boards.”
Some components are designed to dissipate most of their heat through the PCB, and their packages are not necessarily designed to minimize Θjc. It may also be the case that the environment renders a heat sink less effective, and the heat dissipation depends on both the heat sink and the PCB. In these cases, how should the thermal performance of the PCB be analyzed? PCBs have their own copper traces, different numbers of fiberglass layers and copper planes, and many different patterns of vias. The question is what are the effects of these PCB features on the thermal conductivity of the board?
Read the “Thermal Conductivity of Printed Circuit Boards” article now by downloading the latest Qpedia at http://www.qats.com/Qpedia-Thermal-eMagazine/Current-Issue
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The latest Qpedia Thermal eMagazine has just been released and can be downloaded at: http://www.qats.com/Qpedia-Thermal-eMagazine/Back-Issues
Featured articles included in this month’s issue are:
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.
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In light of ATS’ new release of the ethermVIEW, a high resolution liquid crystal thermography system, we sat down with Dr. Tavassoli, Chief Technologist at ATS to ask a few questions about liquid crystal thermography. Below is the Q & A session on commons questions that are asked about liquid crystal thermography.
Q: What are Liquid Crystals? How do they work?
A: Liquid Crystals reflect incident light at the visible wave length based on the temperature of the surface to which they are applied.
Q: Does the chip or the board get destroyed as the result of the ink/Liquid Crystal (LC) application?
A: No, ink and LC can be washed off with de-ionized water
Q: Can you reuse the LC treated surface?
A: Yes, as long as the surface is kept in a clean environment.
Q: How often do I need to calibrate?
A: Typically every time the LC is applied to a new surface, which is a good measurement practice.
Q: Are Liquid Crystals harmful?
A: No, but we do not recommend consuming them!
Q: Can you use LC’s for board level measurement?
A: Yes, LC’s can be used for any surface that can be treated with LC’s and trackable lighting.
Q: Can you mix different Liquid Crystal compounds?
A: Yes, however, it will be difficult to determine the temperature because the same colors, reflecting a temperature, will appear repeatedly as the surface is heated.
Watch liquid crystals in action! Check out the video demo
To learn more about the newly released ethermVIEW, and other surface thermography systems offered by ATS, visit http://www.qats.com/Products/Temperature-and-Velocity-Measurement/Surface-Thermography.