Question: In a production facility, thin square plates 2m × 2m in size coming out of the oven at 270°C are cooled by blowing ambient air at 18°C horizontally parallel to their surfaces. Determine the air velocity above which the natural convection effects on heat transfer are less than 10 percent and thus are negligible.
A 150-mm-diameter and 1-cm-long vertical rod has water flowing across its outer surface at a velocity of 0.5 m/s. The water temperature is uniform at 40°C, and the rod surface temperature is maintained at 120°C. Under these conditions are the natural convection effects important to the heat transfer process?