# Question: a 45 mm diameter tube is insulated with a layer...

###### Question details

A 4.5 mm diameter tube is insulated with a layer of k = 0.05
W/mK material. Heat is lost from the tube by convection only (no
radiation) with ℎ̅ 𝑐 = 1.3( ∆𝑇/ D ) ^{1/4}
W/m^{2}K. ∆𝑇 = 𝑇_{𝑆} − 𝑇_{𝑒} where
𝑇_{𝑆} is at the outer surface of the insulation and D is
outer diameter in meters. Find the critical radius of the
insulation and the corresponding heat loss for a surface
temperature of 350K and an ambient temperature of 300K.