Buckley Rumford Fireplaces


Date: Thu, 17 Feb 2005
From: Gerald Maxwell
To: Jim Buckley
Subject: radiation laws


Looking at your "ramblings on radiation", a few picky comments. Old profs are like that! picky, picky!

Planck's law needs a "delta nu" attached to both sides of the equation, to be mathematically precise. You mention the "delta nu" in your definition of terms under the equation but it is absent both sides in the actual equation above.

In Stephan-Boltzmann's equation under the definition of terms you use F +460 to convert to absolute temp (deg. Kelvin). I think the 460 must be a typo. The conversion from F to K is a bit more complicated. I like to use a temp converter found on the internet. Easier! However, converting from C to K is a bit easier, just add 273.15 and you are in the ballpark.

Further down you set up an example of radiation of a fire and start with a temp of 80F, or "540 absolute", and then double the 540 to get 1080, etc. etc. However, 80 F is actually 299.82 K which when doubled would be about 600K, not 1080K, so the numbers that follow couldn't conform to the physics of the example proposed.

Also I can't follow the logic that finally leads to the statement, "an open fire radiates at about 16 times more than that radiated when behind glass doors." As I continue to assert, my experience says IR has a non-zero transmittance through glass.

Then, I found a real typo, somewhere, i.e. "power" spelled as "pawer". Finding that a is left as an exercise for the author. I don't think it detracts at all from the science, since spelling is english, not science! he he he he he he!

Finally a disclaimer. I am many years rusty on all this but reading and trying to get up to speed. It is fun to get out the books and I shall run hard. I feel a bit like someone who has jumped from a vehicle that is moving much faster than he can run. My legs are trying hard to keep my body from pitching onto the pavement and falling flat on my face. Is that the same as getting egg on one's face? How can pavement taste like egg?????


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