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- Book Review: Hot Air Rises and Heat Sinks, by Tony Kordyban
- Hot air rises and heat sinks : everything you know about cooling electronics is wrong
- Hot Air Rises and Heat Sinks
Through anecdotes and stories based on his experiences at Tellabs Operations, Inc. Tony Kordyban covers basic dimensions of heat transfer concepts—mostly from real problems which were incorrectly solved at least once before a correct technique was applied. The book's 31 chapters, each on an important and relevant topic, contain simple line drawings to help illustrate the basic concepts, while the text provides accurate and complete technical explanations.
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Book Review: Hot Air Rises and Heat Sinks, by Tony Kordyban
By Tony Kordyban. Ifirst met Herbie in my early days at TeleLeap, Inc. The name TeleLeap comes from the idea that we leapfrog current technology to develop new telecommunications products. Some say it comes from our habit of releasing a new product every leap year.
It was that awkward time between learning where the bathrooms were and actually having some work to do. The first job that falls on your desk, and the way you handle it, sets the tone for how the rest of them will go.
For better or for worse, the first person to drop into my sparsely furnished office was Herbie. I smiled weakly. About three puns can be made about thermal engineering, and in three days I had heard them all. Herbie jumped up to the whiteboard and uncorked a smelly green marker. Yeah, and here it is in a nutshell. He drew a box, and then inside of it he drew four vertical lines.
The Crosser system has been tested and out on the market for about nine months. But now we want to do this — He drew four more lines sandwiched between the old ones.
We want to double the number of ports in the system. Will it get too hot? I got up and looked more closely at the problem definition on the whiteboard.
From the improved angle it still only looked like a box with eight lines in it. TeleLeap looks like any company that makes electronics. It is a chaotic maze of corridors, copy machines, and cubicles crammed with people busy leaving voice mail messages for each other.
In some invisible way this all adds up to an organization that makes electronics for the telecommunication industry. TeleLeap makes quite a pile of money on products that For example, we sell a lot of Echo Cancelers. Phone calls through satellites used to have an annoying echo, but not after we apply our technology. Another problem phone companies have that nobody would ever imagine is that to save wire they often multiplex several different phone conversations on one wire.
Between the time you can say No and Thanks several other people have already hung up on other telemarketers. There are different, incompatible ways to do this, with cute acronyms like Tl and DS3. When the phone companies need to connect these different lines to each other and still have them make sense, TeleLeap sells them a digital cross-connect system like Crosser. This means that a lot of the people at TeleLeap are engineers: software writers, electronic hardware developers, and a handful of mechanical engineers.
The hardware developers are very talented with their flip-flops and phase-locked loops, but they have only a vague notion that heat is bad for electronics. They want somebody else to get rid of it for them, the way a homeowner calls a plumber to rod out the sewer line. Besides my experience and education in the field, my main qualification for the job was that I was one of the few people in North America willing to do it.
Down the hall was the lab. No test tubes, no bubbling liquids or spinning reels of tape. It was just another office-type room with a few work benches and a row of six-foot tall, steel racks filled with cages of circuit boards. It looked something like Figure Herbie swept his hand dramatically toward one of the racks, like a model pointing out a box of Rice-a-Roni on The Price Is Right.
He said, This is a port Crosser. What it does is His detailed description has NOT been removed to protect company secrets, but only because I really have no idea what he said. He used a lot of English words such as megahertz, bit, coaxial cable, time slot interchange, and frame relay, but he might as well have been explaining the rules of Australian football. I smiled and nodded and looked at the pretty blinking LEDs on the front panels. I probed my hand into a space between a pair of card cages and wiggled my fingers in the warm air and made a concerned face.
Hmm, I said. I said, Is there a temperature test report for this system? Herbie tilted his head back and forth as if he were trying to make his brain roll back into its socket. Oh, sure! He was pretty good. Used to work the grill when we had our department barbecues. Must have been good at thermal if he knew how to barbecue, right? The test report was in an old filing cabinet, behind some scope probes. It was only a few pages long, including a drawing of the system and a table of temperature measurements.
I took it back to my office for further study. The report was, to put a good face on it, concise. It forced me to read between the lines. The more I did, the more worried I got. It simply stated that the Crosser System met the temperature requirements contained in the Product Definition Document. I dug up the Product Definition, which referred to a corporate standard, which in turn called out an industry standard.
After a day and a half of digging and reading, I thought I had found the problem. Setting a precedent for our future adventures, it was not the original problem that Herbie had first posed. I was about to find out whether TeleLeap really was like the other companies I had worked for. I had not found a mere mistake in a test report, or a single component that was too hot. What I had seen was a fundamental flaw in the way TeleLeap had been doing thermal engineering, written right into their engineering standards.
Know-It-All — but how would the company react? Would they listen to me? I thought it best to try out my arguments on Herbie first. Herbie answered. I later found he was not fond of the phrase more work. You want to know how the Double Crosser would work, based on the assumption that the original Crosser does not have any temperature problems. He was just following the standard. You measure the air temperature at the inlet grill, and the air temperature at the exit grill, and if the difference is less than 20 degrees, you say the electronics are cool enough.
After all, this is an air-cooled system. The air goes in and picks up heat and comes out. The hotter the circuit boards are, the hotter the air is coming out. If the circuits are too hot, the air coming out will be too hot. Maybe the printed circuit board could catch on fire. By short time I mean before the warranty runs out. Oh, no kidding! Those phone company guys are nuts on reliability. So we need to keep the temperature down for reliability.
But the temperature of what? The air? Who cares how hot air gets? The reliability, and even whether a component will flip its flip-flops, is based on the junction temperature of that component. The junction is the guts of a component where all the action is, you know, the silicon chip.
Herbie still frowned. But my experience is that on a typical circuit board, most of the components are cool, and only a few parts get hot, because they do all the work. When you measure the exit air temperature, you are more or less averaging all of the components together. Do you want me to say your temperature is OK based on the temperature of those puny little chips? I mean — wait, I think I get your point. By measuring only the air, we could be missing some localized hot spots. And it only takes one component to fail for the whole circuit board, and maybe the whole system, to fail.
Herbie made a face like he had just dropped his sandwich on the floor, peanut butter side down. I shook my head a little in disbelief. You buy my story?
Just like that? There is no journal called Hard Lessons Learned, and I think it is a shame. Because as much as we learn from reading about all of the new discoveries and triumphs of successful projects, we could learn so much more by reading about the things people have done wrong over time. Not to ridicule, or to feel superior, but to save ourselves from the same waste of time and effort.
Hot air rises and heat sinks : everything you know about cooling electronics is wrong
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Hot Air Rises and Heat Sinks
This popular book is a collection of myths, mistakes, and lessons learned from practicing engineers involved in the field of electronic equipment cooling. Through entertaining anecdotes and stories based on his experience at Tellabs Operations, Inc. Tony Kordyban covers basic dimensions of heat transfer concepts--mostly from real problems which were incorrectly solved at least once before a correct technique was applied. The book's 31 chapters, each on an important and relevant topic, contain simple line drawings to help illustrate the basic concepts, while the text provides accurate and complete technical explanations.
By Tony Kordyban. Ifirst met Herbie in my early days at TeleLeap, Inc. The name TeleLeap comes from the idea that we leapfrog current technology to develop new telecommunications products. Some say it comes from our habit of releasing a new product every leap year. It was that awkward time between learning where the bathrooms were and actually having some work to do.
Topics and Articles in Electronics Cooling
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Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Rafanelli Published Engineering. Hot Air Rises and Heat Sinks: Everything You Know About Cooling Electronics Is Wrong is a collection of myths, mistakes, and "lessons learned" from practicing engineers involved in the field of electronic equipment cooling. Through anecdotes and stories based on his experiences at Tellabs Operations, Inc.
Видишь? - спросил Бринкерхофф, наклоняясь над ней и показывая цифру. - Это СЦР. Миллиард долларов. Мидж хмыкнула. - Кажется, чуточку дороговато, не правда. - Да уж, - застонал. - Чуточку.
No lo se, senor. He знаю. Но уж определенно не здесь! - Он улыбнулся.
- НБ - это, конечно, не болтай. Вот такое агентство. На другой стороне авениды Изабеллы он сразу же увидел клинику с изображенным на крыше обычным красным крестом на белом поле. С того момента как полицейский доставил сюда канадца, прошло уже несколько часов.
Выкладывай. - Может быть, все это чепуха, - сказала Мидж, - но в статистических данных по шифровалке вдруг вылезло что-то несуразное. Я надеюсь, что ты мне все объяснишь. - В чем же проблема? - Джабба сделал глоток своей жгучей приправы.
Четыре года назад конгресс, стремясь создать новый стандарт шифрования, поручил лучшим математикам страны, иными словами - сотрудникам АНБ, написать новый супералгоритм. Конгресс собирался принять закон, объявляющий этот новый алгоритм национальным стандартом, что должно было решить проблему несовместимости, с которой сталкивались корпорации, использующие разные алгоритмы. Конечно, просить АН Б приложить руку к совершенствованию системы общего пользования - это все равно что предложить приговоренному к смертной казни самому сколотить себе гроб.
- Я видела твою электронную почту. Хейл замер, потом повернул Сьюзан лицом к. - Ты вскрыла мою электронную почту.
Странно, но его очки ничуть не пострадали. Странные очки, подумал Беккер, увидев проводок, который тянулся от ушных дужек к коробочке, пристегнутой к брючному ремню. Но он настолько устал, что ему было не до любопытства. Сидя в одиночестве и собираясь с мыслями, Беккер посмотрел на кольцо на своем пальце.