Problem 3. A tractor-trailer rig has a frontal area of A = 102 ft² and drag coefficient CD = 0.9. The ratio ofrolling resistance to vehicle weight is CR = FR/W = (6 lbf)/(1000 lbf). The specific fuel consumption(defined as mass of fuel consumed divided by power, or thrust, produced times the time period) for the dieselengine is SFC= mƒ/(P▲t) = 0.34 lbm/(hp hr) and the drivetrain efficiency is na = 92%. The densityof diesel fuel is pf = 6.9 lbm/gal. (a) Estimate the fuel economy, FE, for a rig traveling at a speed ofU = 55 mph with a weight of W = 72,000 lbs. (b) For a fairing system that reduces the aerodynamic drag by15%, estimate the improved fuel economy, FE faired. (c) Calculate the annual fuel savings, FS, for a rig thattravels 120,000 miles per year. (d) Plot FE and FEƒfaired versus speed, U, assuming SFC and nd areconstant.

Given Information:Frontal area, A = 102 square feetDrag coefficient, C_D = 0.9Rolling resistance…

Answered: Problem 3. A tractor-trailer rig has a…

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.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.26P

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3.) Automotive engineers work very hard to improve the value of the drag coefficient for cars. Suppose you have a car with a mass of 3000. kg and an effective surface area of 4.00 m^2. The engine can generate a maximum force of 28,000. N. Let the coefficient of kinetic friction be 0.200, and the coefficient of static friction be 0.400. Air has a density of 1.21 kg/m^3. (back on earth) (3a) Draw a free-body diagram for your car, including both drag and friction, when the car is moving at its maximum velocity. (3b) If the maximum value of your car's velocity is 150.0 m/s, then what is the drag coefficient for the car? (3c) Suppose your engineers change the drag coefficient to 0.300 - what would be your maximum velocity then with the same force from your engine.
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Correctly solve it.

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