What are the parameters that effect the convection heat transfer? What are the effects of turbulence?

What are the significances of Nusselt number (Nu) and Prandtl (Pr) number?

Derive an expression of the mass continuity equation for the Laminar boundary layer on a flat plate.

Define hydrodynamic and thermal boundary layer. Why are they formed? Draw the hydrodynamic boundary layer profile for a flow over the flat plate.

What do you mean by Stanton Number? Derive an expression for Reynolds-Colburn analogy based on fluid friction and heat transfer?

Air is flowing over a flat plate 5m long and 2.5m wide with a velocity of 4 m/sec at 15°C. Calculate:

• Length of the plate over which the boundary layer is laminar, and thickness of the boundary layer (Laminar).
• Shear stress at the location where boundary layer ceases to be laminar.
• Total drag force on the both sides on that portion of the plate where boundary layer is laminar.

Define Reynolds number, Nusselt number, Boundary layer and Prandtl number. Describe their physical significances. Also define "no slip" condition.

Air at 25°C and atmospheric condition having no moisture is blowing with a velocity of 2.5 m/s over a squared flat plate of 3m × 3m. The plate is maintained at 90°C throughout the length. Calculate :

• boundary layer thickness at a distance of 0.5m from the leading edge,
• the local friction coefficient and shear stress at x = 0.5m,
• heat transfer rate from the first 0.5m of the plate.
  Assuming ρ = 1.02 kg/m³, cₚ = 1010 J/kg-K, μ = 19.90×10⁻⁶ kg/m-s, k = 0.03 W/m-K, Pr = 0.69.

Why heat transfer coefficient is important for convection heat transfer? On what factors does the heat transfer coefficient depend? Explain two factors.

Dry air at atmospheric pressure and 20°C is flowing with a velocity of 3 m/s along the length of a long flat plate of 0.3m wide, maintained at 100°C. Calculate:

• boundary layer thickness at x=0.3m.
• local friction coefficient at x=0.3m.
• local shear stress at x=0.3m and
• thickness of thermal boundary layer at x=0.3m.
  Properties of air at 60°C are: ρ=1.025 kg/m³, Cp=1017 J/kg-K; µ=19.91×10⁻⁶ kg/m-s; k=0.028 W/m-K; Pr=0.7.

Describe the mechanism of force convection. Why is boundary layer formed? Define velocity and thermal boundary layer thickness.

For a flat plate 3 m × 2 m having uniform temperature 50 °C. Air flows over the flat plate with 2.5 m/s at atmospheric pressure. Find the critical boundary layer thickness. Also find the boundary layer thickness at 1.5 cm from the leading edge. (Use $\nu = 1.68 \times 10^{-5}$ m²/s).

What is physical mechanism that causes the friction factor to be higher in turbulent flow?

What is the physical significance of the Reynolds number? How it is defined for external flow over a plate of length L?

Calculate the ratio of thermal boundary layer thickness to hydrodynamic boundary layer thickness of air at 1 atm and 300 K.

What is convection heat transfer? How Nusselt's number and Reynold's number are defined? What are the significances of these numbers?

Consider a flat plate of length 2 m and 1 m wide having temperature of 40 °C. Air flows over the flat plate with 2 m/s at 1 atm. Find where the critical Reynolds number occurred? Determine boundary layer thickness at a distance 20 cm from the leading edge. (v= 1.69 × 10⁻⁵ m²/s)

What is hydraulic diameter? How is it defined? What is equal to for a circular tube diameter?

What fluid property is responsible for the development of the velocity boundary? For what kind of fluid will there be no velocity boundary layer in a pipe?

Air flows across a 5 cm diameter smooth pipe with free stream conditions of 20 °C, 1 atm and u∞ = 25 m/s. If the tube surface temperature is 120 °C, Calculate the heat loss per unit length.