Explanation Write the expression for kinetic energy. ke = V 2 2 (I) Here, the kinetic energy of blowing air is ke , the velocity of air is V . Write the expression for the density of air. ρ = P R T (II) Here, the density of air is ρ , the pressure is P , the gas constant for air is R and the temperature is T . Write the expression for mass flow rate of air. m ˙ = ρ AV (III) The mass flow rate of air is m ˙ , the area is A . Write the expression for area. A = π D 2 4 (IV) Here, the diameter is D . Write the expression for available power. W avi = m ˙ ( ke ) (V) Here the available power is W avi . Calculate the minimum number of windmills for the power output of 1500 kW . N = W ˙ total W avi (VI) Here, the minimum number of windmills is N and total power W ˙ total . Conclusion: The temperature and pressure at standard condition is assumed to be 1 atm and 25 ° C . Refer Table A-1, obtain the gas constant for air is 0.287 kPa ⋅ m 3 /kg ⋅ K . Substitute 6 m/s for V in Equation (I). ke = ( 6 m/s ) 2 2 = 36 m 2 /s 2 2 ( 1 kJ 1000 m 2 /s 2 ) = 0.018 kJ/kg Substitute 101 kPa for P , 0.287 kPa ⋅ m 3 /kg ⋅ K for R and 25 ° C for T in Equation (II). ρ = ( 101 kPa ) ( 0.287 kPa ⋅ m 3 /kg ⋅ K ) ( 25 ° C ) = ( 101 kPa ) ( 0

8th Edition

ISBN: 9780073398174

Author: Yunus A. Cengel Dr., Michael A. Boles

Publisher: McGraw-Hill Education

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Applied Fluid Mechanics

A fluid is a substance that is continuously deformed by the application of shear stress. The rate of deformation of a fluid depends on its viscosity. The fluid tries to flow when it interacts with some other system.

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Chapter 8.8, Problem 12P

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The minimum number of windmills for the power output.

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