hi everyone, this is the first topic for me.

i have question regarding insulation thickness calculation for pipe going to flare and having a light HC gas flowing inside.

i used this equation Q=(2π*k*L*(T1-T2))/(ln(r2/r1))

where

Q, heat transfer

k, thermal conductivity

L lenght of pipe

T1, inlet temp

T2, outlet temp

r1, inner dia

r2 outer dia, must be found

k,T1,T2,r1,L are given but to find r2 i have to assume Q/L( heat loss per unit of length)

my question is how to assume of find the heat loss per unit of length