The drag coefficient of a vehicle increases when its windows are rolled down or its sunroof is opened. A sports car has a fronta
l area of 18 ft2 and a drag coefficient of 0.32 when the windows and sunroof are closed. The drag coefficient increases to 0.41 when the sunroof is open. Determine the additional power consumption of the car when the sunroof is opened at (a) 35 mi/h and (b) 70 mi/h. Take the density of air to be 0.075 lbm/ft3 .
2 answers:
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Answer:
Q = -68.859 kJ
Explanation:
given details
mass
initial pressure P_1 = 104 kPa
Temperature T_1 = 25 Degree C = 25+ 273 K = 298 K
final pressure P_2 = 1068 kPa
Temperature T_2 = 311 Degree C = 311+ 273 K = 584 K
we know that
molecular mass of
R = 8.314/44 = 0.189 kJ/kg K
c_v = 0.657 kJ/kgK
from ideal gas equation
PV =mRT
WORK DONE
w = 586*(0.1033 -0.514)
W =256.76 kJ
INTERNAL ENERGY IS
HEAT TRANSFER
= 187.902 +(-256.46)
Q = -68.859 kJ