Pipe heat loss calculations are taken from the work done by Bailey and Lyell cited by McAdams, Kohli and Coker for the heat loss of oxidized pipe in an 80°F room. This work should be a conservative basis for actual nighttime heat losses because the emissivity of the oxidized pipe used by Bailey and Lyell is higher than the emmissivity of the aluminum or stainless steel cladding typically used for chemical plant and refinery piping. Direct sunlight on the cladding will reduce the heat loss and may lead to heat gain on process services operating below 60°C (140°F).
This calculation uses my regression of the table of total heat loss (convective and radiant), duplicated by McAdams, Kohli and Coker. I regressed the wind multiplier for thermal losses from another table, based on work by others, duplicated by Kohli and Coker. I also regressed thermal conductivity from the graph in Rubin. This graph's values are largely in agreement with other sources.
A 25% design margin should be included in the calculated heat loss.
Copyrighted 2003, 2004