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.
Define convective heat transfer coefficient. How does it vary? Why is higher heat transfer occurred in turbulent flow than in laminar flow?
Define Stanton number. Derive an expression for Reynolds-Colburn analogy.
A 2m×3m flat plate is suspended in a room and is subjected to air flow parallel to its surfaces along its 3m long side. The free stream temperature and velocity are 25°C and 6 m/s. The total drag force acting on the plate is measured to be 0.82N. Determine the average convection heat transfer coefficient for the plate.
What is the physical significance of Prandtl number (Pr)? How Pr behaves on the following cases
The convection heat transfer coefficient for a clothed person standing in moving air is expressed as h = 14.8v⁰.⁶⁹ for 0.15 < v < 1.5 m/s where v is the air velocity. For a person with a body surface area of 1.7 m² and average surface temperature of 29°C, determine the rate of heat loss from the person in a windy air at 10°C by convection for air velocity of 1.5 m/s.
For laminar free convection from a heated vertical surface, the local convection coefficient is expressed as hₓ = Cx⁻ⁿ. Obtain an expression for hₓ / h.
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:
Why "Colburn analogy" is significant and important? Explain.
How "Reynolds analogy" is different from "Colburn analogy"? When "Reynolds analogy" can be used?
Air at 27°C and 1 atm flows over a flat plate at a speed of 2 m/s. Assuming that the plate is heated over its entire length to a temperature of 60°C. Calculate the heat transfer for the first 0.4 m of the plate. Properties of air at 316.5K: v=17×10⁻⁶ m²/s, Cp=1006 J/kg-K, Pr=0.7, k=0.027 W/m-K and ρ=1.12 kg/m³.
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 do you mean by Prandtl's number? Explain the physical significance.
Engine oil at 60 °C flows over the upper surface of a 6 m long flat plate whose temperature is 20 °C with a velocity of 2 m/s. Determine the total drag force and rate of heat transfer per unit width of the entire plate.
Differentiate between laminar flow and turbulent flow. Why is higher heat transfer in turbulent flow than laminer flow?