Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Chapter 5, Problem 5.7P
The average Reynolds number for air passing in turbulent flow over a 2-m-long, flat plate is
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Consider atmospheric air at 25?C and a velocity of 25 m/s flowing over both surfaces of a 1-m-long flat plate that is maintained at 125?C. Determine the rate of heat transfer per unit width from the plate for values of the critical Reynolds number corresponding to 5×105
. Castor oil at 36 °C flows over a 6 m long and 1 m wide heated plate at 0.06 m/s. For a surfacetemperature of 96 °C, determine (i) the thermal boundary layer thickness at the end of the plate,(ii) the local heat transfer coefficient at the end of the plate, and (iii) the rate of heat transfer fromthe entire plate
For laminar flow over a hot flat plate, the local heat transfer coefficient decreases with distance because (select all that are correct)
The thickness of the heated region near the plate is increasing.
The velocities near the plate are decreasing.
The fluid temperatures near the plate are increasing.
Chapter 5 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 5 - Evaluate the Reynolds number for flow over a tube...Ch. 5 - 5.2 Evaluate the Prandtl number from the following...Ch. 5 - Evaluate the Nusselt number for flow over a sphere...Ch. 5 - 5.4 Evaluate the Stanton number for flow over a...Ch. 5 - Evaluate the dimensionless groups hcD/k,UD/, and...Ch. 5 - 5.6 A fluid flows at 5 over a wide, flat plate 15...Ch. 5 - 5.7 The average Reynolds number for air passing in...Ch. 5 - Prob. 5.8PCh. 5 - When a sphere falls freely through a homogeneous...Ch. 5 - 5.10 Experiments have been performed on the...
Ch. 5 - 5.13 The torque due to the frictional resistance...Ch. 5 - The drag on an airplane wing in flight is known to...Ch. 5 - 5.19 Suppose that the graph below shows measured...Ch. 5 - Engine oil at 100C flows over and parallel to a...Ch. 5 - For flow over a slightly curved isothermal...Ch. 5 - Air at 20C flows at 1 m/s between two parallel...Ch. 5 - Air at 1000C flows at an inlet velocity of 2 m/s...Ch. 5 -
5.43 A refrigeration truck is traveling at 130...Ch. 5 - The air-conditioning system in a Chevrolet van for...Ch. 5 - Determine the rate of heat loss from the wall of a...
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- Oil flow in journal bearing can be approximated as parallel flow between two large plates with one plate moving and the other stationary. Determine the velocity, temperature distributions, the maximum temperature, the rate of heat transfer and the mechanical power wasted in oil. Take properties of oil at 50°C are given to be, k=0.17W/m. K, and u=0.05N.s/m2.arrow_forwardWater at 43.3°C flows over a large square plate at a velocity of 28 cm/s. The plate is 1.2 m long (in the flow direction) and its surface is maintained at a uniform temperature of 10.0°C. The width of the plate is 1.2 m. Calculate the steady rate of heat transfer for the entire width of the plate in watts (W). The properties of water at the film temperature of (Ts + T∞)/2 = (10 + 43.3)/2 = 27°C are ρ = 996.6 kg/m3, k = 0.610 W/m·°C, μ = 0.854 × 10–3 kg/m·s, and Pr = 5.85. The steady rate of heat transfer per unit width of the plate is ___ W.arrow_forwardAir (1 atm) entered into a 5-mm-diameter circular tube at an average velocity of 5 m/s. The tube wall is maintained at a constant surface temperature. Determine the convection heat transfer coefficient for (a) a 10-cm-long tube and (b) a 50-cm-long tube. Evaluate the air properties at 50°C.arrow_forward
- Laminar flow normally persists on a smooth flat plate until a critical Reynolds number value is reached. However, the flow can be tripped to a turbulent state by adding roughness to the leading edge of the plate. For a particular situation, experimental results show that the local heat transfer coefficients for laminar and turbulent conditions are hx,lam = (1.74 W / m¹.5 · K ) x-0.5 and hx,turb= (3.98 W/m² 1.8 K ) x-0.2, respectively. Calculate the average heat transfer coefficients, in W/m².K for laminar and turbulent conditions for plates of length L = 0.1 m. ₁,Jam h₁.turb || = || = i i W/m².K W/m².Karrow_forwardDuring air cooling of oranges, grapefruit, andtangelos, the heat transfer coefficient for combined convection,radiation, and evaporation for air velocities of0.11 < V < 0.33 m/s is determined experimentally and isexpressed as h = 5.05 kair Re1/3/D, where the diameter Dis the characteristic length. Oranges are cooled by refrigeratedair at 5°C and 1 atm at a velocity of 0.3 m/s. Determine(a) the initial rate of heat transfer from a 7-cm-diameterorange initially at 15°C with a thermal conductivity of0.50 W/m·K, (b) the value of the initial temperature gradientinside the orange at the surface, and (c) the value of theNusselt number.arrow_forwardQ : Engine oil at 80°C flows over a 10-m-long flat plate whose temperature is 30°C with a velocity of 2.5 m's. Determine the rate of heat transfer over the entire plate per unit width. Take the properties of the oil at film temperaturearrow_forward
- Laminar flow normally persists on a smooth flat plate until a critical Reynolds number value is reached. However, the flow can be tripped to a turbulent state by adding roughness to the leading edge of the plate. For a particular situation, experimental results show that the local heat transfer coefficients for laminar and turbulent conditions are hlam (x) = Alamæª htur (x) - Aturæb Alam = 1.98 a = -0.5 Atur = 4.15 b = -0.3 Calculate the average heat transfer coefficients for laminar and turbulent conditions for plates of length L = 0.2 m and 2.5 m.arrow_forwardOil flow in a journal bearing can be treated as parallel flow between two large isothermal plates with one plate moving at a constant velocity of 8 m/s and the other stationary. Consider such a flow with a uniform spacing of 0.7 mm between the plates. The temperatures of the upper and lower plates are 40°C and 15°C, respectively. By simplifying and solving the continuity, momentum, and energy equations, determine (a) the velocity and temperature distributions in the oil, (b) the maximum temperature and where it occurs, and (c) the heat flux from the oil to each plate.arrow_forward2. Consider airflow over a plate surface maintained at a temperature of 215°C. The temperature profile of the airflow is given as T(y) = Too (Too - T,) exp (- V fluid The airflow at 1 atm has a free stream velocity and temperature of 5 cm/s and 25°C, respectively. Determine the heat flux on the plate surface and the convection heat transfer coefficient of the airflow.arrow_forward
- Air at 1 atm and 20°C is flowing over the top surface of a 0.2 m x 0.5 m-thin metal foil. The air stream velocity is 100 m/s and the metal foil is heated electrically with a uniform heat flux of 6100 W/m2. If the friction force on the metal foil surface is 0.3 N, determine the surface temperature of the metal foil Evaluate the fluid properties at 100°C. Air, T 20°C Metal foil 4eler = 6100 W/m?arrow_forwardConsider a fluid with a Prandtl number of 7 flowing through a smooth circular tube. Using the Colburn, Petukhov, and Gnielinski equations, determine the Nusselt numbers for Reynolds numbers at 3500, 104, and 5 * 105. Compare and discuss the results.arrow_forwardFor flow over a flat plate of length L, the local heat transfer coefficient hx is -1/2 known to vary as x2, where x is the distance from the leading edge of the plate. What is the ratio of the average Nusselt number for the entire plate ( Nu1) to the local Nusselt number at x = L( Nu,)?arrow_forward
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