Robin Bornoff's blog

Views and insights into the concepts behind electronics cooling with a specific focus on the application of FloTHERM to the thermal simulation of electronic systems. Investigations into the application of FloVENT to HVAC simulation. Plus the odd foray into CFD, non-linear dynamic systems and cider making.

19 December, 2014

Sure, most modern homes have much more advanced water heating systems than a big tank with an electric heater element. Systems that work on ‘point of use’ heating concepts that heat the water as it is being delivered, not heating up a large storage container for later use. One day I hope to live in such a house! Until then I’m going to worry and fret about the amount of money spent on heating water and subsequently the amount of money lost as that energy leaks away. So, can simulation predict how much money it takes to heat a water tank? Well yes!


Hysteresis Thermostatic ControlBasic thermostatic control approaches relate the amount of (heating) power to the difference between a set point temperature and the temperature of the system being heated. This type of proportional control can be further enhanced to also take into account the rate at which the temperature is changing (derivative) as well as some history of what how the system has changed up to now (integral). Such PID control systems require constants that need to be tuned to achieve the most efficient approach to ensuring the set point temperature is achieved without under or over shoots. For this study I’ve adopted just a proportional control but including the effects of hysteresis using standard transient features in FloTHERM.

A maximum power (in this case 2000W) is derated once a nominated point in the tank exceeds 55 degC. Once it exceeds 60degC the power is limited to 100W. If the temperature starts to drop then a different curve is used to determine the required increase in power. This offset between the two is intended to stop rapid changes to the power as the water temperature tends towards its intended set point.

Power Temperature Warm UpThe FloTHERM transient simulation covers a period of about 2 hours, during which the temperature is seen to stabilise at ~60degC. It takes just over an hour to settle down to this value. The changing power over that time is also stored.

Power is energy per time. The integral of the power history is the amount of energy (Joules) used. We pay for Joules, Joules = $£. About 7,800,000 Joules are used to raise the water temperature from 25 to 60 degC.

Does that sound about right? There’s a simple hand calculation that can also be used to double check: This 60 litre tank contains 60kg of water. The specific heat of water is ~ 4200 J/kgK. It takes 4200 Joules to raise 1kg of water 1 K (a 1 Kelvin increase is the same as a 1 degC increase). So, it will take 60*4200*(60-25) Joules to raise the entire tank to the required level. This works out at 8,820,000 Joules.

A bit higher than the simulation predicts. Why might that be? Let’s have a look at the temperature distribution within the tank during warm up:

WarmUpTemps

The red dot is the point at which the water temperature is measured. As can be seen there is quite a variation in water temperature, it does not heat up equally throughout. As is often the case with such simple approaches, the hand calc used above assumes that the water heats up uniformly, just as doesn’t happen in reality. The 11% or so difference between hand calc and 3D CFD simulation is due to the fact that not all the water is heated to achieve the 60degC at the single thermostat control point, less energy is required. You can see a pool of much colder water at the bottom of the tank.

A good example of the value of 3D simulation over simpler assumption prone equations.

Next time we’ll look at how good the tank is at holding onto those 7.8 million Joules.

19th December 2014. Ross-on-Wye.

(p.s. tagged with ‘electronics cooling’ as for sure the water is doing its best to cool the electrically heated element just as much as the element is battling to heat the water :) )

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15 December, 2014

Human technical prowess relies heavily on the conversion of energy from one form to another, to meet our needs. Physiological needs underpin  Maslow’s pyramid of all our other ones. The availability of hot water is in turn important for that. Likely we’ve been heating water since the early Neolithic, converting chemical energy stored in wood to heat (radiative and convective) which in turn raises the temperature of a vessel of water. Despite some forays to the moon and a landing on a comet, the intervening years of human endeavour have seen little evolution of this water heating approach.


Temp and Outside FlowWhat is considered socially acceptable has changed much in the last few decades. Smoking was commonplace on TV and in film up to the 80s, today such on-screen behaviour is rare and roundly condemned. I wonder what will be considered similarly abhorrent in 40 years time? May well be wastage generally, for energy especially.

“Look Dad, look at them on holo-vid heating their water in a tank and leaving it there to cool down before they even used it. Yuck!”

EnergyUsageSunnovations, hopes to address hot water heating energy wastage through a kickstarter supported product called Aquanta. It’s neat in that it will learn when best to heat the water so that energy is converted as close to the time of use as possible. Limiting how those Joules you add might otherwise float away over time, like money in a casino. The ability to compare your energy efficiency with your peers might well be the start of a social revolution in acceptable behaviour.

Simulation plays a critical role in predicting the energy efficiency of a proposed boiler tank design. Be it the cost effectiveness of lagging, the balance between a hot enough temperature to achieve pasteurization of for example Legionella pneumophila but not so hot as to scald, the time it takes for the temperature in a water tank to drop back down to ambient, all of these and maybe more I’ll investigate using the CFD (computational fluid dynamics) simulation capabilities of our tools such as FloTHERM, FloEFD and Flowmaster.

Steady State Boiler Flow15th December 2014, Ross-on-Wye

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25 November, 2014

A lot of engineering involves the management of energies, converting them from one form to another, channeling off useful work to power our cars, planes, phones, lights etc. To date we haven’t come up with a system to channel all energy into a desired task. Even the most advanced power generation systems still end up heating water to steam to drive turbines, a cycle that is no more than about 38% efficient. The rest of the energy mostly lost to heat. Electronics are no different. A lot of power is consumed just to move electrons and photons about. That useful work doesn’t require much energy (what’s the kinetic energy of an electron?), nearly all the input energy is lost to heat in the process. If you’re going to lose it, why not use it?


Electronics dissipate energy as heat power and thus get hot. Too hot and they start to malfunction then ultimately fail completely. Getting the heat out as fast as it’s generated keeps the temperatures down. This is at the heart of electronics thermal management. Tools such as FloTHERM were designed to help simulate such heat transfer and resulting temperature levels. The heat still has to end up somewhere, usually an assumed ‘ambient’. A pool of cool so big that it tends to keep at just about the same temperature even when heat is dumped into it. A good enough engineering assumption most of the time. However if you want that ambient to heat up then the engineering challenge of dealing with waste heat becomes an engineering opportunity!

qrad

Qarnot Computing Q.rad Computer Architecture

A French company, Qarnot Computing,  provides a computer called Q.rad that is designed to be a room heater, provided as part of a cost effective distributed HPC cloud deployment system.  Their HPC customers are linked to their heating customers so that HPC demand is automatically distributed to the Q.rad farm. An ingeniously green approach, in recognition of the inefficiencies that blight our modern world.

Until such time as a room temperature superconductor is developed (http://bestsf.net/greg-egan-zero-for-conduct-twelve-tomorrows/), or we all go live inside a mega data center, we will be faced with the more pressing challenge of determining where to place Q.rad in our home to ensure efficiency from the heat leaving Q.rad to it reaching your extremities. Keep warm everyone!

Window_and_radiator

25th November 2014, Ross-on-Wye

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28 October, 2014

There are 475,000 Google search hits for ‘thermal bottleneck’. It’s a well recognised phrase playing on a very obvious analogy. Despite this there were few attempts to quantify such a parameter. Spurred on by its relevance in electronic thermal design, we did just that, put hard numbers to the concept. FloTHERM now has the ability to plot distributions of  thermal bottleneck, enabling thermal design engineers to predict not just how hot a product might become in operation, but also the culprit locations that cause that temperature rise.


When determining how to quantify a thermal bottleneck we knew that it should combine both the amount of heat that flows as well as the difficulty the heat experiences as it flows. The amount of heat flowing is simply the heat flux, W/m^2. The difficulty was a little more difficult to figure out. In the end we selected the temperature gradient as being indicative of the difficulty. The bigger the temperature difference, the more the difficulty experienced that gave rise to that dT/dx. Both are vector quantities. How best to combine both? (a lot of heat flowing AND finding it difficult). Dot product seemed best. Finally normalised by its maximum to show the relative distributions in a single simulation model.  And that was the invention process, full details can be found in US patent US8628236.

Take a section through a typical FloTHERM application (in this case a wall mounted repeater unit):

Hot_and_Why

On the left is temperature. On the right is thermal bottleneck, Bn. Showing clearly where the bottlenecks are makes for a compelling demonstration as to why design changes might be needed, and where. Much design work comes down to influence and balance. Having such a Bn capability is a useful influencing tool for the thermal design engineer.

Analogies have always played an important role in the evolution of science and technology. As Einstein said: “Growth comes through analogy; through seeing how things connect, rather than only seeing how they might be different.” It was therefore rather gratifying when we discovered that the thermal bottleneck is analogous to the Joule heating power density in a DC current flow (current density x voltage gradient). W/m^3 compared to the thermal bottleneck degC W/m^3. If Joule heating is the energy required to force the current through where its flowing, then bottleneck is the energy required to get the heat over a 1 degC hurdle. Neat.

You can find out more details in this webinar I gave on this subject.

28th October 2014, Hampton Court.

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21 October, 2014

Lighting accounts for ~20% of the world’s total energy consumption. This is a staggering statistic. Why so much? Historically a lot of energy had to be consumed to produce the required amount of visible light. Incandescent bulbs, where electric current is used to heat a metal filament, resulted in most of the energy being dissipated as heat. More a hot bulb than a light bulb. Even worse for a candle. LEDs mark a step change in the efficiency by which energy is converted into light, they’re cooler as a consequence and thus more reliable. Win/win/win. Their ubiquity today is due to the breakthrough in creating an LED capable of emitting blue light (red and green having already been achieved). With the ability to create those 3 colours, they could be combined to produce white and all colours in between. The 2014 Nobel prize in Physics was awarded to 3 scientists who ‘invented’ the blue LED in the 1990s, despite the fact that a 1974 US patent indicates otherwise.


A Lumen (lm) is a measure of the energy contained in that part of the EM spectrum that your eye can sense, the visible spectrum. A luminous ‘efficiacy’ of radiation is a measure of how much visible light power there is compared to the power in all frequencies of the light. More the better. LEDs are on their way to becoming x1000 better than historic forms of lighting:

Lumens_per_Watt

Ironically, LEDs perform better if they are cooler. At higher (junction) temperatures the brightness decreases, the emitted frequency shifts and the reliability is compromised as well. Good thermal management, in terms of the physical characterisation of their optical and thermal properties as well as a simulation based design methodology, is essential. The LED vendor market is coalescing through acquisition, maintaining a competitive product edge is as important as it ever was. Such thermo-optical applications are a real sweet spot for the technology in the Mechanical Analysis Division of Mentor Graphics. The MCAD embedded CFD technology of FloEFD coupled with the T3Ster and TeraLED physical test and measurement equipment is especially well suited to automotive lighting applications where the use of LEDs is now commonplace.

Cluster_LEDsAn interface between T3Ster and FloEFD enables temperature dependent LED optical properties, measured by TeraLED, to be imported into FloEFD whereupon a ‘hot lumen’ prediction can be simulated based on a specified driving current. That, coupled with a choice of 3 optical radiation models in FloEFD and the ability to handle complex MCAD assemblies directly within the MCAD environment, make for a unrivalled industrial strength capability.

W_Rhines

Wally Rhines, CEO, Mentor Graphics

One of the authors of the overlooked 1974 US patent “Gallium nitride metal-semiconductor junction light emitting diode was Wally Rhines, CEO of Mentor Graphics. Wally is one of those rare captivating keynote speakers who can take you on a roller-coaster of a ride into the world of EDA and deposit you at the end feeling intrigued yet satisfied. It would have been cool to have a Nobel Laureate as CEO. It’s a bit of a shame it didn’t work out that way this time.

21st October 2014, Ross-on-Wye.

p.s. Wally’s not only a keynote speaker of course, his CEO track record at Mentor speaks for itself. Thought I’d clarify that in case he stumbles on this blog… :)

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6 October, 2014

“How thick is a leg hair” is not a question I thought I’d be posing when I woke up today. Reading this article about the effect of leg hair on the overall drag of a performance cyclist prompted me to investigate the physics behind this observation. For the sake of expediency I steered clear of a full body MAMIL simulation, focussing instead on just a small patch of a particularly hairy leg subjected to an oncoming air flow.


BoundaryLayerAir will ‘stick’ to any solid surface, even a silky smooth leg. Away from the wall it speeds up until it reaches free stream speeds. That thin sliver of slow moving air, hugging each solid surface, is called a boundary layer, often graphically indicates as a series of velocity vectors, running parallel to a wall, increasing in size away form it. This stickiness offers a resistance, more for treacle, less for air. So, even a shaved leg will offer some resistance to the air flow.

HiarDistributionAdd to the wall (skin) a whole forest of hairs then you’ve added loads of new solid surface area to which the air will stick. I did go looking for a MCAD file of hair but to no avail. Instead I mocked up a random distribution of stubble type hairs of a density pretty high up the Chewbacca scale. Nice and simple, no moving hairs, no curly hairs, no solid fluid interaction. Such stubborn stubble being an extreme case in cycling aerodynamic drag, rather lack of it.

In addition to the increase in surface area and the resulting increased stick of the fluid, the more tortuous a path the fluid has to travel through the hairy obstruction, the more difficult it finds it to do so. This fluid difficulty manifests itself as a pressure drop, effectively the energy required to achieve that flow.

SpeedBetweenLegHairsSo, using FloTHERM (though FloEFD would have been more appropriate, old dog, new tricks etc.), I simulated air approaching the segment of hairy skin to see just how tortuous a path it would be made to follow. The red areas are high speed flow, the blue/green areas low speed, especially obvious in the slow moving recirculating wakes behind each hair. Even more evident if we look at the flow animation:

leghair

Each twist and turn of the flow equates to a force required to overcome it. The more hairs you have on your legs, the more force you’ll need to overcome it, the more energy you’d need to expend. For Chewbacca this equates to the difference between changing from a round-tube frame to an aero-style one.

FloEFD has a proven track record for sports applications as this fascinating webinar by Olympian Professor Kristan Bromley shows.

6th October 2014, Ross-on-Wye

p.s. Diameter of a human hair is between 17 and 180 microns (millionths of a meter). For the case above I chose a particularly hirsute 200 microns (0.2 mm).

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1 October, 2014

There are a handful of quoted and re-quoted drivers, concepts and technologies in the electronics cooling industry.  Be it a presentation, peer reviewed paper, press release, thermal design guide or webinar the same core material keeps popping up in various guises. This is by no means a bad thing. The challenges faced when cooling electronics are clear, clearly described and need to be constantly reiterated. If, when viewing such presentations, reading the articles or attending a travel budget friendly webinar you might like to partake in this electronics cooling ‘metaphorical’ drinking game to pass the time.


The following items, should they be encountered, will score the following drinking game points penalty… I’ll leave it up to you to decide how those penalty points should be paid.

  • MooresLawMoore’s Law. The number of transistors in an IC doubles approximately every two years. More an observation than a law though it has, until recently, stood the test of time very well. Considering that it is the thermally dissipated power of the transistors that causes the temperature rise and subsequent performance and reliability issues in electronic products, it’s not surprising that this graph is shown again and again. Very common: Penalty Points = 1

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  • HeatFlux_vs_YearFollowing on from Moore’s law, the actual heat dissipation divided by the area over which it occurs is the heat flux and has been rising recently, quite dramatically. Analogies are always good, especially when you’re trying to scare the pants off an audience. Although for just a small area (of the order of a few mm^2), the heat flux values in tomorrow’s processors will be ‘as hot at the sun’ (as I’m sure the media will spin it as). Getting to be a more popular graph and it’s fun: Penalty Points = 2

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  • ThermalResistancesIn 1822 Joseph Fourier published Théorie analytique de la chaleur in which he postulated that heat flow is proportional to the temperature difference between two points and the thermal resistance between them. Nearly 200 years later and the electronics thermal community thrives on such simple abstractions of what in reality are complex 3D heat flow patterns. Thermal resistor network descriptions of systems are as common as muck and almost twice as useful: Penalty Points = 1

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  • Fixing Problems WhenNot unique to the electronics cooling industry, the cost of fixing mistakes at various stages of the product development process is well documented. As any good sales person will be at pains to point out, anything that can front load the design process with risk identification will have a very obvious and evident return on investment. And sure, we’re no different. A graph as valuable as it is overused: Penalty Points = 1

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  • Structure_FunctionIn recent years transient thermal test characterisation has become a popular non-destructive approach to investigate the physical construction of a packaged IC or discrete. A thermal equivalent to the use of X-rays, the T3Ster measurement technology is now frequently referenced in the industry. One key aspect of the value of the T3Ster approach is in the determination of a thermal ‘structure function’, a graph that indicates the thermal resistances and capacitances that exist within the package and system in which it is placed. Banded to show what parts of the graph refer to what physical part of the package/system, to understand and appreciate a structure functions is now a prerequisite for all thermal engineers: Penalty Points = 3

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  • TSVsTSVs! (through silicon vias) The next big thing. Enabling die to be stacked efficiently, no need for inter-die interposers or peripheral wire bonding. From a thermal perspective you’ve just massively increased the effective heat flux. How to get that heat out is a question that has to be answered before this technology can hit the mainstream. The very high heat transfer coefficients that over-chip liquid microchannel cooling can provide seems the most promising concept. Likely that any material you see or read on this topic will have a picture that looks much like an apartment block with too many elevators.  The future is always fascinating: Penalty Points = 4

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  • Equivalent CircuitsThévenin’s equivalent circuit theory is fundamental to many electronics cooling simulation approaches, be they spreadsheet based or modelling methodologies employed for full 3D simulation. Maybe too simple or too well recognised to be described in any detail nowadays, assumed thermal resistances in series or parallel can be used to determine effective resistances and thus, say, effective thermal conductivities.  No different to an electrical circuit and surely everyone knows this stuff by now?: Penalty Points = 0.5

There are many more graphics and phrases you’ll come across when involved in electronics thermal management but the above should provide some amusement next time you’re sitting there, watching presentations late on the 2nd day of a 3 day conference.

1st October 2014, Ross-on-Wye

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19 September, 2014

A recently issued patent describes a process by which the critical IC temperature (junction temperature, Tj) can be determined in an end user environment. A critical junction temperature is one that, should the IC temperature go beyond it, will continue to increase in a thermal runaway scenario. In other words the environment in which the IC is operating can’t get the heat out quick enough. The thermal equivalent of an uncontrolled nuclear fission event.

Thermal runaway generally leads to fusing, a melting of the conductor. Temperature increases -> electrical resistivity increases -> Joule heating power dissipation increases -> temperature increases … and so on. As the name indicates, this is precisely how a fuse works. Same effect in digital electrical circuitry can have disastrous consequences.

The power dissipated in a IC comprises two parts, a dynamic part (due to all the turning off and on of the transistors including frequency and capacitive affects) and a static, or leakage, part (that is the power that is drawn when the transistors are in an off state). The static proportion increases with smaller transistor sizes AND is temperature dependent. Temperature first affects functional performance then, as runaway thermal feedback is encountered, it quickly escalates to a full smoking thermal catastrophe. All of which is shown in this (albeit a bit old) video:

P-QThe key to determining the point at which runaway might occur is consideration of both the static power vs. temperature relationship AND the system performance in same terms, determining where they meet, and this is what the patent focusses on. This bears a striking and quite lovely similarity to fan sizing, where the fan P Q curve intersects with the system P Q behaviour is the operating point of the fan, and thus also of the system.

Chip Temperature Distribution Predicted by FloTHERM

Chip Temperature Distribution Predicted by FloTHERM

Be it fan sizing or specification of a temperature dependent power dissipation, FloTHERM can simulate it all. Quickly, early and easily.

This white paper on our chip-package solutions will hopefully provide some additional insights.

19th September 2014, Ross-on-Wye

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8 September, 2014

Develop 3D is a UK based Magazine and Website focussing on the technologies involved in product design. The latest copy had a fascinating article on Dell’s Precision Workstation labs. This blog is being written on a Precision M4500 which I’ve lugged around countless airports and dumped, wearily, on numerous hotel beds. The fact that it works as well now as when I first got it a few years ago is testament to Dell’s design processes and technologies.


The article, http://www.develop3d.com/features/a-peek-inside-dells-workstation-labs , looks into Signal Integrity and Thermal design. Both are key aspects in achieving competitive product performance. From a thermal perspective the overall power dissipation is related to the frequency at which the PC will operate (well, the dynamic portion of the power dissipation is). Increased power leads to increased temperatures. If the temperatures get too high things start to break, the supplier gets a bad reputation, warranty costs spiral, other very bad things ensue. This catastrophe can be diverted by throttling down the power before the temperatures get too high. Downside is that performance is limited. Having a cooling architecture that is sufficiently effective at removing the heat quickly can therefore have a marked and direct effect on the competitive nature of the product (read $$).

As the article quotes, “[We do] simulation way early on, looking at how thermals are going to work, almost in turn figuring out how the whole box is going plug in together and work together before we even build the first one.” An excellent example of doing design at the right time. A mature design process is one where simulation is used at a conceptual, pre ‘concept commit’ stage to determine at a high level what the major design constraints will be. Interesting that at this stage in the design, before the green light has been given and lots and lots of engineers and detailed engineering tools are deployed, there is very little detailed design data. From a simulation perspective this is actually quite liberating. Good engineering judgement can be applied to drive the simulation tool, in the context of little or no IDF or STEP, to answer questions such as “how many vents will we need?”, “one micro blower or two?”, “heatpipes?” etc.

Generic Laptop SectionFloTHERM was adopted early on for telecomms, networking and computing applications and is especially well suited to conceptual design. It’s simple CAD type interface, building block approach to 3D model construction, instant grid calculation and fast+robust CFD solution technology really comes into their own. Here’s some output from an application example we install with FloTHERM. A corner section of a generic laptop with a double inlet/outlet blower, convection cooling a couple of ducted heatsinks that are supplied the heat via a couple of heatpipes connected to a PLCC package.

The animated air flow behaviour enables appreciation of how the design is working, is all the cold air ingested that could be? Is any hot air recirculated back inside?

Generic Laptop Section Top

Generic Laptop Section Below

If you’d like to find out more about FloTHERM this introduction to FloTHERM webinar gives a good overall impression as to what it can do, worth checking out.

One final thought, if you are ‘lucky’ enough to have highly detailed EDA and MCAD design data to hand when using FloTHERM maybe you should ask yourself if it’s a bit late in the day simulating the design for the first time.

8th August 2014, Ross-on-Wye

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4 September, 2014

A release so good it has 11 best top 10 features, very Spinal Tap. I thought I’d wrap up this series with a list of more minor, but imo, very useful features and finish off with some words on cultural idioms.


FloTHERM V10.0 and V10.1 together satisfy about 60 software enhancement requests as voted for on the Mentor IDEAS site for Mechanical Analysis Products, a strategy we’ve been committing to for a number of years now. It’s not always the big headline grabbing features that the most interesting though. Here are some of my personal less well known favourites:

  • Indication of whether a loaded model has results or not. Done via a coloured icon in the bottom status bar in the Project Manager. ResultsYesNo No more having to load a model and open the Profiles window to see whether there is any residual history.

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  • NomObjectsHow many objects are selected? Now given directly, again in the Project Manager bottom status bar. If no objects are selected this changes to the total number of objects in a model. I benefit from this often in my use of FloTHERM, though to tell you the truth I’m not exactly sure why!

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  • AlignI like the simplicity of shape moving and editing in Microsoft products. Needs no training. One thing that is missing from Office (but now not form FloTHERM!) is a double align on both centers, in one operation. Now a one button operation in V10.

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  •  Having a RecentProjectslist of recently used files/documents for quick access to recent data is quite standard nowadays. FloTHERM’s had this for a while. However it only worked if the selected project was in the current project solution directory. This has now been rectified. Loading a previous project will automtically force change of the solution directory and load the project.

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  • AbortSolver So many times I’ve started a solve only to suddenly realise that I’d forgotten to make some required tweak or modification to the model. The solver stops slowly as it finishes its current iteration then writes out all the solution data to disk. Sure, we could have added an ‘Are you sure?’ dialog each time the GO button was pressed. We’d be lynched though. Instead we’ve added an ‘Abort Solver Action’ feature that will terminate the solver executable immediately, no results written but you can get back and make the change asap. Hands up who remembers ‘kill -9′ on Unix?

Well, that’s it for V10. Development for V11 is well underway. FloTHERM ploughs ahead!

4th September 2014, Ross-on-Wye

p.s. O yes, idioms. Not sure where the phrase ‘odds and sods’ comes from, it’s in common use in the the UK though. ‘Odds and ends’ is the more common variant I suppose. There are a number of phrases that are perfectly acceptable to use in the UK but would raise eyebrows elsewhere, normally in the US. Yep, in the UK it’s perfectly acceptable to go out of the pub and ask someone if you could ‘bum a fag’. Also, a private school in the UK is referred to as a public school (well, it’s open to any member of the public to pay to send their children to!). This and other US/UK travel word tips can be found here.

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Meet Robin Bornoff

With a mechanical engineering background and CFD foundation, I have 20 years of experience in the field of electronics cooling design and simulation. Beyond my vocation I enjoy making my own cider, appreciating fractals and prime numbers, running (slowly) and will only ever read Sci-Fi.

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