1. In flow over a surface, velocity and temperature profiles are of the forms u(y)=Ay+By²-Cy³ and T(y)=D+Ey+Fy²+Gy³ where the coefficients A through G are constants. Obtain expressions for the friction coefficient Cf and the convection coefficient h in terms of u∞, T∞, and appropriate profile coefficients and fluid properties. Answer: h = -krE D T∞

1. In flow over a surface, velocity and temperature profiles are of the forms u(y)=Ay+By²-Cy³ and T(y)=D+Ey+Fy²+Gy³ where the coefficients A through G are constants. Obtain expressions for the friction coefficient Cf and the convection coefficient h in terms of u∞, T∞, and appropriate profile coefficients and fluid properties. Answer: h = -krE D T∞

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.35P

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1. In flow over a surface, velocity and temperature profiles are of the forms u(y)=Ay+By²-Cy³ and T(y)=D+Ey+Fy²+Gy³ where the coefficients A through G are constants. Obtain expressions for the friction coefficient Cf and the convection coefficient h in terms of u∞, T∞, and appropriate profile coefficients and fluid properties. Answer: h= -k[E D To
Q2) In flow over a surface, velocity and temperature profiles are of the forms u(y) = Ay + By² + Cy3 and T(y) = D+ Ey + Fy? - Gy3 where the coefficients A through G are constants. Obtain expressions for the friction coefficient C, and the convection coefficient h in terms of uo, To, and appropriate profile coefficients and fluid properties. Q3) Water at a temperature of T = 25°C flows over one of the surfaces of a steel wall (AISI 1010) whose temperature is Ts1 = 40°C. The wall is 0.35 m thick, and its other surface temperature is Ts,2 = 100°C. For steady state conditions what is the convection coefficient associated with the water flow? What is the temperature gradient in the wall and in the water that is in contact with the wall? Sketch the temperature distribution in the wall and in the adjoining water.
Please answer and explain why each statement must be true or may not be true.
Cooling water for a power plant is stored in a pond 900 m in length and 400 m wide. A dry wind at 300 K blows in a horizontal direction parallel to the 900 m side of the pond at a velocity of 2 m/s. The cooling water is at 300 K. Known the air dynamic viscosity v= 1.67 x10m?/s.; the Re transition from laminar flow to turbulent flow is 500,000; and the saturated water vapor pressure at 300 K is 3580 Pa; gas constant R= 8.3144 J/mole.K. 1.) At what position across the pond is the air flow no longer laminar? Would it reasonable to assume that the mean gas-film mass transfer coefficient for water vapor in air is dominated by turbulent flow mass transfer? 2.) As part of an engineering analysis to predict the evaporation rate of water from the pond, determine the mean gas film mass transfer co-efficient. 3.) Calculate the rate of water evaporation from the pond.
Air flows inside a tube 60 mm in diameter (d) and 2.1 m long (l) at a velocity w = 5 m/sec. Find the heat-transfer coefficient α if the mean air temperature tf = 100oC. Note: Write your answer in space provided without the unit (the answer is in kcal/m2-hr-oC, one decimal places)
2. In a particular application involving airflow over a heated surface, the boundary layer temperature distribution may be approximated as T − Ts T∞ — Ts - = 1 – exp (−Pr- uooy ט where y is the distance normal to the surface and the Prandtl number, Сри Pr = = : 0.7 k is a dimensionless fluid property. If T∞= 400 K, Ts= 300 K, and u∞/v = 5000 m²¹, what is the surface heat flux?
Conduct thorough a research on Reynolds Number, laminar and turbulent flow as it relates to mechanics of fluids
Required information Water at 20°C is flowing with velocity of 0.89 m/s between two parallel flat plates placed 1 cm apart. Given: The properties of water at 20°C are p= 998.0 kg/m3, µ = 1.002 x 103 kg/m-s and Pr = 7.01 Determine/the distance from the entrance at which the velocity boundary layers meet. (Round the final answer to one decimal place.) The distance from the entrance at which the velocity boundary layers meet is m.
Forced air at T0 = 25°C and V = 17 m/s is used to cool electronic elements on a circuit board. One such element is a chip, 4 mm x 4 mm, located 129 mm from the leading edge of the board. Experiments have revealed that flow over the board is disturbed by the elements and that convection heat transfer is correlated by an expression of the form Nuz = 0.04RE0.85 Pr3 V, T. Chip Board L mm Estimate the surface temperature of the chip if it is dissipating 38 mW.
As a process engineer, you are designing a new drinking water treatment plant using conventional treatment process including Two Trains of Flocculators as follows: The design flow is 0.35 m³/s. The average temperature of water is 5°C with a dynamic viscosity, μ = 1.519 x 10-3 Pa.S and p = 999.967 kg/m³. The major target of the WTP is to remove color from water using alum as coagulant. GAvg 0 = 120,000. In each train of flocculators, it includes three same size compartments in series with the tappered velocity gradients G: 80, 50, and 20 Sec-¹. Length = Width = Depth for each Comparment. The type of impeller is axial-flow with three blades. The available impeller diameters are 1.0, 1.8 and 2.7 m. The water depth below the impeller, B = 1/3 H. H is the water depth in flocculator.
k An empirical correlation for the Nusselt number (Nu = hd) for flow past tubes is Nu= 0.25Re 0.6 pp.0.38, where Re = is the pud μ k Reynolds number and Pr = p; pH is the Prandtl number. Here, µ is the viscosity and k is the thermal conductivity. Using the simple expressions for the transport properties that we derived in class, determine the temperature and pressure dependency of the convective heat transfer coefficient h.
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