Author: Robin Bornoff

Sometimes the ability to apply artistic interpretation of your virtual product to your simulation model of it is limited or dictated (take your pick) by the available capabilities of that simulation tool. CFD simulation is quite a young technology, application to electronics cooling newer still, a mere 21 years old. Always pushing the limit of available computing resource, always adapting to the ever increasing need for accurate AND fast predictions, such tools continue to adapt. Couple this to the prevalence, and relative complexity, of fans in electronics cooling and you’ll be faced with a few options regarding their representation. (more…)

Never trust a TLA (three-letter acronym) or those who use them, unless the abbreviation provides some value in terms of repetitive usage  or is accepted as an industry standard. Too often TLAs are used as a screen between those who are listening and the incompetence of the person talking. TIGs (thermally insignificant geometries) as a TLA is neither useful nor accepted, I just made it up. Thermally insignificant geometries however are at the heart of the art of CFD based electronics cooling modelling.

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Larry Grayson’s famous high camp catchphrase would be well heeded by those wanting to ensure good thermal insulation. You can make it difficult for heat to leave a room, thus maintain a warm room temperature, by constructing walls and floors of sandwiched layers of various materials, restricting heat transfer to conduction and (in cavities) radiation methods only. Open a door however and cold air will rush in. Open a door just a crack and even a trickle of cold air can result in a substantial decrease in U-value. (more…)

The Mentor ‘IDEAS for Mechanical’ site allows users of FloTHERM, FloVENT, FloTHERM PCB and FloEFD to post their software enhancement requests (access via their SupportNet login credentials), comment on other people’s and most importantly vote on those ideas that they believe would  be of benefit to them. The result is a prioritised list of possible software features that product management can use to help determine a short term roadmap of the products that has the best chance of ensuring continued satisfaction of the userbase.  (more…)

Conduction, the transfer of heat through a solid object. Convection, the transfer of heat in moving air/fluid. Radiation, the transfer of heat from one solid surface to cooler solid surface in ‘line of sight’. The 3 modes of heat transfer are your enemy when it comes to thermal insulation of built environments. Heat is as sly as a fox when it comes to squirming its way out of a space to the cool outside. That’s a European talking. For those in sunnier climes think of ‘Cold’ as the fox, added to a room, desperate to make its way to the hot outside. Heat transfer is pretty symmetric in that respect. (more…)

Electronics cooling involves ensuring that IC package temperatures do not exceed maximum rated values. If they do the probability of thermo-mechanical related failure increases dramatically. The accuracy of any electronics thermal simulation will be determined by how well the IC package is represented in the solution. These are simple and evident truths. As the leading supplier of electronic thermal simulation tools we have an obligation to the industry to both provide the ability to simulate and also to facilitate the creation of good quality thermal representations of IC packages, by vendors, to be supplied to end users. (more…)

Why is it that when you increase a cavity air gap size beyond ~30mm is there no subsequent detrimental affect on the overall U-Value? Why is it that the U-Value of the cavity gap nearly doubles when the air gap reduces to such as size so as to stagnate the air? Questions that come begging after observing the FloVENT simulation results discussed in the previous blog posting. Let’s find out…. (more…)

100mm block, 50mm insulation, 50mm cavity air gap then 100mm block make up an external wall that in theory comply with a building regulation overall wall U-Value of 0.3 (W/m^2K). This got me thinking about the 50mm air gap. Why 50mm? What if it was 75mm or 10mm? Stagnant air is a great insulator, a small gap would tend to stagnate the air and might improve, reduce, the overall U-Value. A large gap would have lots of air, ok, it’d be moving more freely but intuitively a bigger gap should make it more difficult for the cold to penetrate from the outside. With FloVENT at my disposal I’d be mad to consider actually building some walls and doing some physical testing. CFD based software simulation makes such studies achievable, quickly, easily and requires no building skills (thank goodness as I have none).

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As covered in the previous blog, air that sticks to the inside and outside walls offers a resistance to the heat that passes from the room to the inside of the wall and from the outside of the wall to the outside air. These two resistances make up part of the overall U-value, the overall ease by which heat can pass through the entire wall (or window or door etc.). The rest of the U-value is made up of the ease by which the heat passes through the inside of the wall itself. (more…)

It might well be that a single U-value is quoted, in reality though that single value describes the ease by which heat can pass through various stages, from an ‘inside’, passing through a ‘wall/window’ and going to the ‘outside’. The resistance (inverse of the ease, resistance = 1/ease) the heat experiences as it passes from the inside air to the inner solid surface of the wall construction (and from the outer surface to the outside air)  is due to the fact that air sticks to the solid surface. How strange is that? . (more…)

I never trust a quoted value without having at least a little understanding as to what the value truly represents and how it was measured or derived. If you’ve ever felt inferior when someone quotes values or ranges of values at you take solace in the fact that there’s a fair chance they live on the surface of the pond of understanding and really don’t know how deep that pond is. (more…)

We knapped our first flints about 2,000,000 years ago and started to shelter from the elements in caves and simple huts about 200,000 years ago. As industries go the building industry is probably the oldest, well maybe second oldest. Our ability to both adapt to and manipulate our surroundings has set us apart from the beasts on a path of science, art and technology. (more…)

Computational Fluid Dynamics, CFD, is a simulation technology that provides 3D predictions of fluid flow and heat transfer for a modelled system. Be it an electronics enclosure or a building, insights into the often complex air flow patterns can help designers better understand the physical behaviour of their design. Communication of such insights helps others to appreciate the sometimes painful design modification decisions. To meet these needs we have made available a fully functional 3D CFD results viewer that can be used to view the output of FloVENT, FloTHERM and FloTHERM.PCB. Download and try it, it’s free!  (more…)

Heatsinks aren’t a novel energy efficient type of washing bowl, they are parts that are placed on high powered IC packages to help remove the heat more effectively and thus lower the operating temperature of the package which in turn increases reliability, can improve performance etc.  etc. Such approaches are observed in nature, from Elephants ears to the low sun apparent surface area of homo erectus. It could well be that the evolution of heatsinks also take a leaf out of nature’s book. (more…)

The ability of FloTHERM to resolve a massive disparity in geometric length scale in a single model is for me its greatest strength. By not having to make simplifying assumptions to ignore either extremely small or truncate extremely large geometric parts and features, simulation accuracy can be better assured. The ‘die in a city’ model in the previous blog resolved a length scale of 1,000,000,000:1. Admittedly not a common type of model (unless you are a deviant simulation masochist) but it does prove a point.  But just how does FloTHERM do it…? (more…)

We have recently published a new xml schema and associated xml reader for FloTHERM that offers some exciting new possibilities. Unlicensed and freely available it’s well worth checking out. Introducing my first guest blogger, my colleague Byron Blackmore explains more… (more…)

Electronics are small and getting smaller. The world in which we live is tending to stay at the same size. The one thing that typifies electronic thermal simulation models is the disparity of length scale that has to be accommodated. FloTHERM has been evolved to handle this disparity for over 20 years.  I, my fellow FloTHERM apostles and hopefully the FloTHERM userbase appreciate this. To prove this point I thought I’d push FloTHERM to the limit by creating … “The Most Extreme CFD Model Ever Ever”. (more…)

This series, despite being somewhat lengthy, is by no means a complete overview of the various methods, options and approaches to predicting component temperatures. Here is some stuff I didn’t cover…

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