bchoate
I am going to outline a procedure for estimating steam tracing needs for piping. This procedure comes from "Applied Chemical Process Design", F. Aerstin & G. Street, 3rd printing 1982, Plenum Press.
Calculate the thermal conductance
C(i) = [ 1 ]
(12/2*pi*K)ln(d(o)/d(i))
where C(i) is the thermal conductance of the insulation, K is the thermal conductivity of the insulation {btu/hr/ft(2)/(F/in)}, d(o) is outside diameter of insulation(in.), and d(i) is inside diameter of insulation. If there is no insulation, then K and d's are for pipe wall metal. In insulated pipe, delta T across pipe wall is small.
calculate heat loss per foot of pipe
q = C(i)*(t(p)-t(a))
where t(p) is temperature in pipe and t(a) is air T.
estimate number of tracers needed
Heat output from a tracer per foot is shown by a nomograph in the book. Data is plotted as btu/hr/ft versus delta T between steam and pipe T. E.G. 3/8" copper tracer with heat transfer cement has factors of 110, 200, and 300 at delta T's of 50, 100, and 150 F, respectively. Factors can be calculated from heat transfer by conduction through the tube wall with a delta T of steam - pipe.
number of tracers = total heat loss/heat output from tracer.
steam usage can be estimated as heat transfer by condensation. Divide total heat loss by the heat provided by condensing 1 lb. of steam.
This may be overkill but it's here if it is any use to you.
