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Re: OT: Where to learn about airflow/temperature?

Specifically, I'm wondering, if I have an airflow of, say,

>between 1 and 5 LPM (liters per minute), in a known tube, >and a heating element, assuming the tube is either insulated >or reaches operating temp. OK; how would I find out how many >watts it would take to heat that air to, say, 160C? > >Of course, 1 to 5 LPM is quite a range, but I can do PWM >from 1-99%, so no worries there - I just need to know how >much nichrome wire to use in my heating element. > >And if there's some kind of formula, like the heat capacity >of air, that wouldn't be unwelcome. :-) > >Thanks, >Rich
1 LPM heats about 50 degrees C per watt.

John

Reply to
John Larkin
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I found this starting with the wikipedia entry for Anemometer:

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The figure that is important is velocity. Take your LPM figure and the size of the orifice involved and see what that gives you.

Hint: 1 to 5 LPM isn't terribly bad compared to automotive applications, both in terms of absolute value and range. Look up Mass Airflow Sensors for specifics in this area.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Reply to
Paul Hovnanian P.E.

So maybe 30W if you expect to run 50% duty cycle at 5lpm.

This sounds like the sort of project where work slows down once you begin the testing phase.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Rich Grise snipped-for-privacy@example.net posted to sci.electronics.design:

The math and the physics(heat capacities and transfer functions) are readily available if not in particularly convenient forms. If i were faced with that issue i might try getting a grad student to give me a theoretical or numeric approximation and finish off with curve fitting the actual device. Of course i would tell the student that i wanted a parameterized answer.

Reply to
JosephKK

Farnell has glass-encapsulated (both in SMD and SOD-27) ones that are good for -40 to +300 deg. IIRC, they are associated with Newark?

Barry

Reply to
Barry Lennox

Grad student? I was taught that stuff in my second year undergraduate thermodynamics course.

It's pretty straightforward, provided that you can assume that rotations are fully thermalised, and vibrations aren't thermalised at all, which is usually good enough.

-- Bill Sloman, Nijmegen

Reply to
bill.sloman

I can send you a couple of K thermocouples; we have a bunch of them.

T/c's are fairly cheap from Omega, but you have to buy a dozen at a time or something like that.

John

Reply to
John Larkin

snipped-for-privacy@ieee.org snipped-for-privacy@ieee.org posted to sci.electronics.design:

The way i could get into the courses it was in my third year. I remember being exposed to the materiel but have not used it in decades. I have always had consideration for imperfections in memory, it is a childhood experience thing.

Reply to
JosephKK

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