Chapter 8, Problem 8.29P

Engine oil flows at a rate of $\text{1 kg}/\text{s}$ through a $\text{5}-\text{mm}$ diameter straight tube. The oil has an inlet temperature of $\text{45}°\text{C}$ and it is desired to heat the oil to a mean temperature of $0°\text{C}$ at the exit of the tube. The surface of the tube is maintained at $1\text{5}0°\text{C}$ . Determine the required length of the tube. Hint: Calculate the Reynolds numbers at the entrance and exit of the tube before proceeding with your analysis.