Davis 12 investigated heat transfer to fluids flowing in the annular section between concentric tubes. He proposed the following correlation for the heat-transfer coefficient when considering the film...

Davis¹²
investigated heat transfer to fluids flowing in the annular section between concentric tubes. He proposed the following correlation for the heat-transfer coefficient when considering the film on the inner tube:

where d₁
and d₂
are the outer diameter of the inner tube and the inner diameter of the outer tube, respectively,
 is the viscosity of the fluid at the bulk temperature of the fluid, and
s is the viscosity of the fluid at the heating surface temperature. Use this equation to predict the mass-transfer coefficient from a naphthalene rod used to form the inner tube of an annular duct.