Heat Loss by Free Convection from a Horizontal Pipe
Estimate the rate of heat loss by free convection from a unit length of a horizontal pipe, 6 in. in outside diameter, if the outer surface temperature is 100°F and the surrounding air is at 1 atm and 80°F.
http://cse.gre.ac.uk/coursinf/cfd_exp.html
Since the specified pressure is 1 atm, air can be considered a low density fluid and the MATLAB programs grcalc and prcalc can be used.
Converting to SI units:
80°F = 299.817 K
100°F = 310.928 K
6 inches = 0.1524 m
>> start301 (specify new session, E&M balances, ceng301 database, K as temperature, 1 compound: air)
>> Gr=grcalc(0.1524,299.817,310.928)
ans =
4.8315e+06
The flow is laminar, and this value is in agreement with the book answer of 4.68e06 and can be used in combination with prcalc to determine the Nusselt number, heat transfer coefficient, and rate of heat loss.
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