Q1 (a) Differentiate between free and forced convection with examples. (b) Define Nusselt (Nu), Prandtl (Pr), Reynolds (Re) and Grashof (Gr) dimensionless numbers. State which numbers are used in free...

Extracted text: Q1 (a) Differentiate between free and forced convection with examples. (b) Define Nusselt (Nu), Prandtl (Pr), Reynolds (Re) and Grashof (Gr) dimensionless numbers. State which numbers are used in free and forced convection to determine the heat transfer coefficient. (c) A vertical pipe 90 mm diameter and 2.5 m height is maintained at a constant temperature of 125 °C, The pipe is surrounded by still atmospheric air at 25 °C. Find heat loss by natural convection. Properties of water at 75 °C: Density = 1.0145 kg/m³ Kinematic viscosity = 20.55 x10-6 m²/s Prandtl number (Pr) = 0.693 Thermal conductivity (k) = 30.06 x 10-3 W/m K g × ß x L³ × AT Grashof number, Gr = V² Nu = 0.10(GrPr)0.333