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Question: a transmission case measures w 030 m on each...

Question details
A transmission case measures W =
0.30 m on each side (for a total heat
transfer area of 0.54 m2
) and receives a
power input Pi = 150 hp from the engine.
The transmission efficiency is h = 0.93 (this
means that 93% of the engine power is
transmitted to the wheels while 7% is
dissipated as heat). Air at 30o
C flows over
the case with a convection heat transfer
coefficient h. The emissivity of the case is
0.80 and the ground/chassis may be
approximated as large surroundings at
30o
C. Assume that the surface
temperature of the transmission case is
uniform and conduction heat transfer is
minimal.
a) First, find the surface temperature of the transmission case using a convection heat transfer
coefficient of 250 W/m2
-K and assuming negligible radiation heat transfer. (88.0o
C)
b) Now, find the surface temperature of the transmission case using a convection heat transfer
coefficient of 250 W/m2
-K and accounting for radiation heat transfer. (86.5o
C)
c) Repeat your calculations from a) and b) using a convection heat transfer coefficient of 50
W/m2
-K.
d) Based on your results from a)-c), discuss the assumption you made to neglect radiation.
How did the assumption impact your results? Under what conditions might it be a good
assumption?
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