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Fan cooling , qualitative assessment

Without having to learn about pneumatics For an existing product with a 12V fan with ducted area across fan ie minus the central motor area, of about 6 square inches and current consumption of .2 amps. As it stands this fan would seem to waste a lot of power and increase in noise, blowing through a set of 14 slots in the case of total air-vented area 1.5 sq ins. If most of this grill section was totally cut away , fared off, and an external wire grill added would that allow the use of .1 amp fan for more, or less air throughput and a bonus of less audible noise.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook
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Without having to learn about pneumatics For an existing product with a 12V fan with ducted area across fan ie minus the central motor area, of about 6 square inches and current consumption of .2 amps. As it stands this fan would seem to waste a lot of power and increase in noise, blowing through a set of 14 slots in the case of total air vented area 1.5 sq ins. If most of this grill section was totally cut away , fared off, and an external wire grill added would that allow the use of .1 amp fan for more, or less air throughput and a bonus of less audible noise.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

That all makes sense. One ROT is that the grille area should be at least as big as the fan area, so 4:1 will seriously restrict flow.

Extech makes a nice, inexpensive air flow + temperature meter that lets you quantify things like this. Air flow can be counter-intuitive, and mere mortals can't afford to purchase or learn worthwhild airflow simulation software.

John

Reply to
John Larkin

A really sharp M.E. that I worked with at GenRad from '77 to '87 had a smoke generator that he used to examine airflow.

He would build a mock-up of the equipment with foam board, place cardboard obstacles shaped like components, add fans and observe the flow.

Then move things around and/or add baffles to shape the airflow.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
         America: Land of the Free, Because of the Brave
Reply to
Jim Thompson

Incense, joss sticks, work fine.

Right. A wood/plastic/cardboard/duct tape mockup can be done in an hour or two and is enormously instructive. You can also clamp some of those metal-case power resistors onto candidate heat sinks, crank in some power, and see what their operating temps will really be, and get an idea of how noisy the mess will be.

It's fun to test cardcages with fan trays, or PC enclosures. You'll often get dead spots directly above fan trays, or air flowing leisurely in the opposite direction to where high-velocity flow was expected. Air is funky stuff, and there's an incredible amount of really bad thermal designs, or rather "designs", around.

John

Reply to
John Larkin

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