# 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?