{"id":272,"date":"2012-07-08T20:04:41","date_gmt":"2012-07-09T01:04:41","guid":{"rendered":"http:\/\/tonykordyban.com\/?page_id=272"},"modified":"2014-04-13T20:22:28","modified_gmt":"2014-04-14T01:22:28","slug":"everything-you-know-is-wrong-august-2001","status":"publish","type":"page","link":"http:\/\/tonykordyban.com\/?page_id=272","title":{"rendered":"Everything You Know Is Wrong August 2001"},"content":{"rendered":"

Answers to those Doggone Thermal Design Questions<\/strong><\/p>\n

By Tony Kordyban<\/strong><\/p>\n

Copyright by Tony Kordyban 2001<\/p>\n

 <\/p>\n

Dear Mr. Tony Kordyban,<\/em><\/p>\n

What’s with the crack about PE’s in your last column?\u00a0 (See EYKIW July 2001,<\/a> “P.S.\u00a0 Sorry, I couldn’t think up a clever pseudonym.\u00a0 I thought having PE after my name was amusing enough.”)<\/em><\/p>\n

We have a hard enough time trying to convince people there’s a difference between engineers and air conditioning repair technicians, without you dumping on our profession, too!<\/em><\/p>\n

PE from Peoria<\/em><\/p>\n

 <\/p>\n

Dear PE,<\/p>\n

Sorry.\u00a0 I guess that was unprofessional of me.\u00a0 I suppose I should warn my readers that I am not licensed by any state to practice humor either.<\/p>\n

\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014<\/strong><\/p>\n

Hi Tony,<\/em><\/p>\n

[In regard to last month’s column about mounting a thermocouple inside a blind hole in an aluminum plate] To check if a thermocouple is making good contact with a surface (such as in the “drill a hole and fill it with glue” scenario), attaching an ohm’s meter across either lead of the thermocouple and the metal it is fed into will indicate a good or bad connection. Zero or very low resistance reading is good contact, high reading or no reading is a poor contact. Hope this helps.<\/em><\/p>\n

\u00a0Regards, <\/em>
\n \u00a0Les Fisher <\/em>
\n \u00a0Snr Thermal and EMC engineer <\/em>
\n \u00a0Intel<\/em><\/p>\n

 <\/p>\n

Dear Les,<\/p>\n

What a great idea!\u00a0 They always sound so obvious after someone else says them.<\/p>\n

Your idea would work especially well if you form the bead of the thermocouple as close to the insulation as possible.\u00a0 That way it should not make any electrical contact with the aluminum plate except at the junction.<\/p>\n

P.S.\u00a0 The name Les Fisher is real, not some lame attempt at a pun about “fishing a wire into a hole”, so I don’t want to hear any complaints from fishermen (fisherpersons? fishcatchers? fishers?\u00a0 — you see the trouble you get into once you start apologizing for things?)<\/p>\n

\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014<\/strong><\/p>\n

Dear Temperature Helping Guy,<\/em><\/p>\n

\"\"<\/a>I belong to a laptop computer hobbyist club.\u00a0 Our hobby is figuring out how to make laptops do stuff they were never meant to.\u00a0 Like in this picture, we crack open an old 486 laptop, upgrade the processor, duct tape the video display to the dashboard, stuff the keyboard section under the driver seat, and wire it up to the car stereo.\u00a0\u00a0 Presto! —\u00a0 an MP3 player for the ’73 Vega!\u00a0 The trouble is, half the time we crack open a laptop, the darn thing locks up, sometimes forever.\u00a0 The club members say it’s a thermal thing.\u00a0 They have lots of wacky ideas for boosting the cooling.\u00a0 One guy says to bore a hole in the case and shoot CO2 cartridges into it.\u00a0 Can you give us a little bit more professional help?<\/em><\/p>\n

\u00a0Overclocker from Knickerbocker<\/em><\/p>\n

Dear Over,<\/p>\n

AAARRRGGGHHH!<\/p>\n

That is the collective sound of all the engineers pulling out their hair (for me, what’s left of it.)\u00a0 A team of engineers agonized for a year and a half, designing that laptop to meet conflicting design requirements.\u00a0 They babied it through the thermal tests, safety tests, electromagnetic interference (EMI) tests, and performance tests, all the time trying to predict how the customer might reasonably use it.<\/p>\n

And them some bozos buy it second-hand and decide to “crack open the case”?!\u00a0 There go safety and EMI out the window.\u00a0 And once the chassis is disassembled, the jigsaw puzzle of heat transfer paths carefully designed into it is completely kaput.\u00a0 You destroy the end product of a multi-million dollar development effort just for kicks, and you want some “professional help”?<\/p>\n

Well, OK.\u00a0 Sure.<\/p>\n

Compared to personal computer thermal engineers, I’ve got it easy, in one respect.\u00a0 In the telecom biz, where I work, the thermal environment is well-defined.\u00a0 In aUStelephone central office, for example, the room air temperature is controlled between 0 and 50 degrees C.\u00a0\u00a0 It’s all spelled out in an industry standard published by Telcordia.\u00a0 It even tells exactly how big the aisle space around my equipment will be.<\/p>\n

But what is the industry standard for a lap?\u00a0 That’s the nominal environment for a laptop computer, isn’t it?\u00a0 I pity the engineer that has to cool a laptop, with such a\u00a0 vague definition of the operating environment.\u00a0 What is the maximum air temperature?\u00a0 What is the worst case air flow?\u00a0 How much of the surface area is in contact with air, and how much with the lap of the user?\u00a0 How hot do the user’s legs get?\u00a0 With shorts on?\u00a0 Or no shorts at all?\u00a0 And how hot can the laptop surface get before the lap gets uncomfortable?\u00a0 TV commercials show laptops in use at the beach.\u00a0 What is the worst case solar load?<\/p>\n

Somehow the laptop engineers decide what the reasonable worst case environment should be.\u00a0 Then they design and test their computer to not overheat in it.\u00a0 I don’t know how they do it, exactly, but I think the general cooling concept is that the whole chassis is a single heat sink, and sometimes there is a tiny fan to help out in peak temperature situations.<\/p>\n

Then you guys go not one, but a hundred steps farther than those engineers ever imagined.\u00a0 You bump up the processor performance AND shove it under a car seat.\u00a0 Your photo shows a laptop designer’s nightmare thermal scenario — you have placed the laptop on top of a bed.\u00a0 The whole bottom surface is literally blanketed with a conformal insulator.\u00a0 You took away 50% of the heat path surface area, and probably blocked any vent holes, too.<\/p>\n

The same thing would probably happen under a car seat.\u00a0 The carpet (and the inevitable collection of fast food wrappers) under the driver seat would smother the heat transfer from the bottom of the chassis.\u00a0 The processor would likely overheat even if you didn’t upgrade it.\u00a0 Breaking open the case probably disrupted any heat transfer path out the top side or through the keyboard, so you are in for big thermal trouble.<\/p>\n

Although, again, I am not a professional engineer, even I am leery about getting involved in a project with such a huge chance for something seriously to go wrong.\u00a0 Not just thermally.\u00a0 When you crack the case, you break the EMI seal, and will probably interfere with radio and TV broadcasts (a federal offense).\u00a0 When you play with batteries, you risk burns, explosions, chemical poisoning, and environmental damage.\u00a0 There may be other toxic substances in there.\u00a0 I especially hope that the guy who wants to cool his laptop with CO2 cartridges does not discharge them in his car with the windows rolled up.\u00a0 He could end up seriously suffocated (dead).<\/p>\n

So my first recommendation is to get a new hobby (something safe, like watching Food TV<\/a> on cable).\u00a0 But I know that my paternalistic warnings are not going to stop guys like you from tinkering.\u00a0 So I am going to give you some real thermal advice.\u00a0 Just don’t take that as an endorsement of what you are doing.\u00a0 Everything you try, even my advice, is totally at your own risk.<\/p>\n

Here goes.\u00a0 Preserve as much of the original cooling design as possible.\u00a0 Those laptop engineers really did put a lot of thought into it.\u00a0 That means use the outside of the case, as intact as possible, as the heat sink for the processor.\u00a0 If you open the case to do an upgrade, close it back up just the way it was, if you can.\u00a0 If you put it under the car seat, attach some legs, maybe a half inch tall, to get the bottom of the case off the carpet.\u00a0 Then blow air across the whole thing.\u00a0 Run a dryer hose down from the air conditioning vent.\u00a0 Or mount a fan nearby.\u00a0 Here are some fans I recommend (not because I know they will work, but because they look hard to misuse, but I bet you’ll find a way.)<\/p>\n

\"\"<\/a>

This fan clips onto a baby's highchair. How much trouble could an overclocker get into with this?<\/p><\/div>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

\"\"<\/a>

This one doesn't have the cute face, but it plugs into the car cigarette lighter, so you don't have to duct tape it to a car battery.<\/p><\/div>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

I found these on Google with a little clicking around.\u00a0 I suppose your club members would prefer to find some used ones on ebay.<\/p>\n

If you think you can stand any more “professional” advice like this, feel free to come back.<\/p>\n

\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014<\/strong><\/p>\n

Isn\u2019t Everything He Knows Wrong, Too?<\/strong><\/p>\n

The straight dope on Tony Kordyban<\/em><\/strong><\/p>\n

\"Tony<\/a>Tony Kordyban has been an engineer in the field of electronics cooling for different telecom and power supply companies (who can keep track when they change names so frequently?) for the last twenty years.\u00a0 Maybe that doesn\u2019t make him an expert in heat transfer theory, but it has certainly gained him a lot of experience in the ways NOT to\u00a0cool electronics.\u00a0 He does have some book-learnin\u2019, with a BS in Mechanical Engineering from the University of Detroit (motto:Detroit\u2014 no place for wimps) and a Masters in Mechanical Engineering from Stanford (motto: shouldn\u2019t Nobels count more than Rose Bowls?)<\/p>\n

In those twenty years Tony has come to the conclusion that a lot of the common practices of electronics cooling are full of baloney.\u00a0 He has run into so much nonsense in the field that he has found it easier to just assume \u201ceverything you know is wrong\u201d (from the comedy album by Firesign Theatre), and to question everything against the basic principles of heat transfer theory.<\/p>\n

Tony has been collecting case studies of the wrong way to cool electronics, using them to educate the cooling masses, applying humor as the sugar to help the medicine go down.\u00a0 These have been published recently by the ASME Press in a book called, \u201cHot Air Rises and Heat Sinks:\u00a0 Everything You Know About Cooling Electronics Is Wrong.\u201d\u00a0 It is available direct from ASME Press at 1-800-843-2763 or at their web site at\u00a0http:\/\/www.asme.org\/pubs\/asmepress<\/a>,\u00a0\u00a0<\/em><\/strong>Order Number 800741.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Answers to those Doggone Thermal Design Questions By Tony Kordyban Copyright by Tony Kordyban 2001   Dear Mr. Tony Kordyban, What’s with the crack about PE’s in your last column?\u00a0 (See EYKIW July 2001, “P.S.\u00a0 Sorry, I couldn’t think up a clever pseudonym.\u00a0 I thought having PE after my name was amusing enough.”) We have […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-272","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/272","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=272"}],"version-history":[{"count":14,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/272\/revisions"}],"predecessor-version":[{"id":288,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/272\/revisions\/288"}],"wp:attachment":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=272"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}