Chapter 8, Problem 8.102P

An engineer proposes to insert a solid rod of diameter $D_i$ into a circular tube of diameter $D_o$ to enhance heat transfer from the flowing fluid of temperature $T_m$ , to the outer tube wall of temperature $T_{s,o}$ Assuming laminar flow, calculate the ratio of the heat flux from the fluid to the outer tube wall with the rod to the heat flux without the rod, $q_o^n/q_{o,wo}^n$ , for $D_i/D_o=0,0.10,0.25$ and 0.50. The rod is placed concentrically within the tube.