here - Daat Research Corp
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1. Although we sometimes import system geometry from our Solid Works CAD system the cooling software makes it so quick and easy to build models we often by pass the CAD program For exam ple an elliptical pin fin heat sink was created in the software be cause it provided a parametric model which made it easier to do an optimization study We built the model in Coolit included pa rameters for pin diameter spac ing and height specified a range of values for each and submitted the problems in batch mode The results guided further analysis Unfortunately the thermal pro gram s parametric features don t apply to imported CAD models An invaluable feature of the soft ware is its ability to accept any combination of units convert them and deliver results in the units of choice This should let us avoid conversion errors which have been a frequent source of irri tation To facilitate analysis the devel oper s technical support engineers recommended we first break the problem into parts to assess their sensitivity and the relative impor tance of various design parame ters They also suggested that dur ing the initial optimization process we stick to coarse grid models to shorten computational time Models at this stage aver aged 150 000 grid cells Models this size took under an The thermal analysis software can model complete electronic systems and subsystems such as individual heat sinks hou2. D i er review Edited by Paul Dvorak APRIL 5 2001 www machinedesign com A PENTON PUBLICATION Thermal analysis leads to cb designs Coolit CFD software predicts airflow and heat transfer in electronic equipment It works this way An engineer defines a model space and items in it such as enclosures fans vents and systems components These may be imported from a CAD system or assembled using building blocks from a component library Point and click operations dramatically shorten design tasks Material properties and component specifica tions are selected from an online material li brary or typed in After building the model the software creates an appropriate grid and calcu lates results These are displayed using a viewer called Cool Plot that comes with the software Plots can show a long list of variables including temperatures ve locity heat flux pressure and turbulence inten sity that are useful in analyzing problems Color coding highlights gradations in variable values and pinpoints hot spots Different variables such as temperature and pressure can be overlaid to visualize their interactions Animation in Coolit puts streamlines in motion showing nontechnical users how one design such as the finned heat exchanger might work better than another j The unusual heat sink was modeled in Coolit Arrows indicate streamlines Red is for hotter areas and blue cooler areas
3. The software s parametric features can run through a range of design considerations that more clearly pins point to a best one Users can examine results in 3D several ways For instance cross sections can show results or users can rotate models and zoom in on areas of concern When necessary animation puts streamlines in motion While working with NEC we tapped the soft ware to accelerate heat sink development for a new series of network servers These are pow ered by processors ranging from 600 MHz to gi gahertz chips The heat sinks must cool the processors should one of the three redundant system fans fail We faced an extremely tight introduction schedule and could not afford to spend develop ment time climbing a lengthy learning curve Consequently ease of use was a prime considera tion for selecting the CFD package We downloaded the software from the vendor installed it and had it running in 30 min The User Manual and online Help are succinct and to the point One particularly helpful tutorial in the manual steps through an entire problem setup and analysis in less than 2 hr We built and ana lyzed our first models in a half day This rapid ramp up exceeded expectations Previous experi User review ence suggested that it would take several days of training before get ting useful results And when we encountered difficulty the devel oper s technical support responds quickly to emailed questions
4. ich was spent building models The software has produced a more effective heat sink design and cut the per piece cost by over 80 Coolit is available for purchase or lease A one year license in cludes unlimited technical support and all upgrades from Daat Re search Corp Box 5484 Hanover NH 03755 5484 603 448 1302 www daat com Jason Welch Jason Welch formerly with NEC is a mechanical engineer specializing in advanced thermal solutions for Thermal Cast a division of Kennedy Die Castings Worcester Mass Copyright 2001 by Penton Media Inc Cleveland Ohio 44114
5. r to calculate on a dual Pen tium III 600 MHz NT based com puter with 512 Mbytes RAM The computer handled other engineer ing work in parallel with Coolit calculations We ran 8 to 10 design iterations overnight for several days which moved the design along quickly Cell count crept up as the design evolved and the model became more complex Fi nal stage calculations averaged 500 000 cells Such models let us analyze the reduction in cooling efficiency as air gets warmer and slower tra versing the heat sink This detailed analysis pointed the way to changes in pin thickness length and positioning that increased the cooling capacity The result is an unorthodox elliptical pin fin topog raphy that shaves 15 C off the processor die temperature Results have been repeatedly validated by physical testing In fact the match between analysis and testing has been so good that prototypes have been almost entirely eliminated It s often necessary to share thermal analyses with coworkers or superiors who are not CFD i users CoolPlot visualization soft ware lets anyone view case files The plotting module provides still views and flow animations Pic tures can be readily annotated marked up and incorporated into other MS Windows products such as Word and PowerPoint Prior to Coolit thermal analysis was a combination of common sense and mathematical calcula tions that took at least 10 times longer most of wh
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