engineering fundamentals List Replies
Directory | Career | News | Industrial
Home Membership Magazines Forum Search Member Calculators






List Recent Topics | Start a New Topic

Message No. 6 posted by canucme on 12/21/99 15:55 PST
This is a reply to message No. 5
To mimic a bald head exposed to the cold night sky, try these values:

Object 1 (Bald Head)
Temp:  95 deg F
Area:  0.3 ft^2 (a reasonable guess)
Emissivity:  0.9 (another reasonable guess)

Object 2 (night sky)
Temp:  -150 deg F
Area:   anything much larger than the area of object 1
Emissivity:  1 (sky acts like a blackbody)

ViewFactor:  1  (assume that the head sees nothing but sky)

This will give a heat loss of almost 12 watts, a reasonable estimate for this problem.  The earlier suggestion of 20 watts was probably an overestimate; object 1's area was chosen too large.
[ Messages on This Topic ] [ All Topics ]

There are 2 Direct Replies to This Message

canucme, Why is the night sky -150F? I have a co-worker who insists, de...
No. 20, Posted by quiche on 01/06/00, 16:25 PST.
Thanks for your response. I think i understand the example much better now...
No. 13, Posted by daffodil on 01/05/00, 09:03 PST.

Home  Membership  About Us  Privacy  Disclaimer  Contact  Advertise

Copyright © 2018 eFunda, Inc.