Example: Oil at 150'C flows slowly through a long, thin walled pipe of 30-mm inner diameter. The pipe is suspended in a room for which the air temperature is 20 C and the convection coefficient at the outer tube surface is 11 W/mK Estimate the heat loss per unit length of tube KNOWN: Oil flowing slowly through a long, thin-walled pipe suspended in a room. FIND: Heat loss per unit length of the pipe, conv SCHEMATIC: oom air 11W =20eC conv conv Pipe. D:30mm-.m 150° ASSUMPTIONS: (I)Steady-state conditions, (2) Tube wall thermal resistance negligible, 3) Fully developed flow, (4) Radiation exchange between pipe and room negligible PROPERTIES: Table A-5, Unused engine oil(m150C=423 K ): k=0.133 W/m-K Heat Transfer Su Yongkang School of Mechanical EngineeringHeat Transfer Su Yongkang School of Mechanical Engineering # 9 Example: Oil at 150℃flows slowly through a long, thin￾walled pipe of 30-mm inner diameter. The pipe is suspended in a room for which the air temperature is 20 ℃ and the convection coefficient at the outer tube surface is 11W/m2 .K. Estimate the heat loss per unit length of tube