Question

An automotive travels at a velocity of 60 km/hr in the rainfall season where the surrounding temperature falls to 15 °C. While traveling, heat is dissipated from the bottom surface of the hot automotive engine block to its surrounding. Given the automotive engine block size is 800 mm (L) x 400 mm (W) x 500 mm (H) and the bottom surface temperature is approximately 95 °C.
(a) Determine the heat transfer rate from the bottom surface of the automotive engine block to its surrounding.
(b) Will the heat transfer rate increase or decrease when the automotive has stopped traveling but the automotive engine is still powered on? Justify your answer with proper calculation.​

Answer 1

Answer:

Consider a hot automotive engine, which can be approximated as a 0.5-m-high, 0.40-m-wide, and 0.8-m-long rectangular block. Thebottom surface of the block is at a temperature of 100°C and has an emissivity of 0.95. The ambient air is at 20°e. and the road surface is at 25°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 80km/h. Assume the flow to be turbulent over the entire surface because of the constant agitation of the engine block.

Step 1 of 3

Given: - Size of engine

Temperature of bottom surface of block

Emissivity of surface

Road surface temperature

Ambient air temperature

Answer 2

Answer:

hzksksjslahskshskshdjdhshsvsbevs