An automotive engine can be approximated as a 0 4 m high, 0 60 m wide, and 0 7 m long rectangular block The bottom surface of the block is at a temperature of 75 deg C and has an emissivity of 0 92 The ambient air is at 5 deg C, and the road surface is at 10 deg C Determine the rate of heat transfe...

A car travels at a velocity of 60 kmh The rate of heat transfer from the bottom surface of the hot a ...

An automotive engine can be approximated as a 0.4-m-high, 0.60-m-wide, and 0.7-m-long rectangular block. The bottom surface

Question:

An automotive engine can be approximated as a 0.4-m-high, 0.60-m-wide, and 0.7-m-long rectangular block. The bottom surface of the block is at a temperature of 75°C and has an emissivity of 0.92. The ambient air is at 5°C, and the road surface is at 10°C. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a velocity of 60 km/h. Assume the flow to be turbulent over the entire surface because of the constant agitation of the engine block. How will the heat transfer be affected when a 2-mmthick gunk (k = 3 W/mˆ™K) has formed at the bottom surface as a result of the dirt and oil collected at that surface over time? Assume the metal temperature under the gunk still to be 75°C.

-Engine block Air 60 km/h 75°C 5°C Gunk ↑2 mm Road E= 0.92 10°C