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:
Helium at 1 atm and 200K is used to cool a 1-m-square plate maintained at 310K. The flow velocity is 75 m/sec. Calculate the total heat-loss from the plate. What is the boundary layer thickness as the flow leaves the plate.
In an Industrial facility, air is to be preheated before entering a furnace by geothermal water at 120°C flowing through the tubes of tube bank located in a duct. Air enters the duct at 20°C and 1 atm with a mean velocity of 4.5 m/sec, and flows over the tubes in normal direction. The outer diameter of the tube is 1.5 cm, and the tubes are arranged in-line with longitudinal and transverse pitches of SL=ST=5m. There are 6 rows in the flow direction with 10 tubes in each row.
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 "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.
Air at 25°C flows across a circular tube of diameter 6 cm, perpendicular to the tube axis with a velocity of 3 m/s. Tube surface is maintained at 55°C. Determine the value of convection heat transfer coefficient. Air properties at 40°C, v=18×10⁻⁶ m²/s, Pr=0.7, k=0.027 W/m-K.
Water at 20°C flows through a tube, 4 cm diameter, 9 m length, tube surface being maintained at 90°C. Temperature of water increases from 20°C to 60°C. Find the mass flow rate. Use the equation Nu=0.023 Re⁰.⁸ Pr⁰.⁴. Properties of water at 40°C: ρ=993 kg/m³, cp=4170 J/kg-K, k=0.64 W/m-K and v=0.6×10⁻⁶ m²/s.
A thin walled, steel pipe of 6 cm length and 50 mm internal diameter is heated by condensing steam from the outside, which maintains the internal wall temperature at 100 °C. The tube has 2.5 × 10⁻⁴ m³/s of water flowing through it, that is heated from 20 °C to 60 °C. What is the mean heat transfer coefficient over the pipe length?
Air flows across a 4 cm diameter smooth pipe with 20 °C, 1 atm and velocity 20 m/s (free stream condition). If the tube surface temperature is 150 °C. Calculate the heat transfer from the tube per meter length.
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?
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.