Wright State University Spring 2017

Department of Mechanical and Materials Engineering

ME 3360/5360 HEAT TRANSFER: FINAL EXAM

Open Book, Closed Notes, DO NOT Write on this Sheet

Show All Work for Partial Credit

Problem 1 (10 points): A hot automotive engine can be approximated as a 0.5-m-high, 0.40-m-wide, and 0.8-

m long rectangular block. The bottom surface of the block is at a temperature of 100°C and has an emissivity of

0.95. The ambient air is at 20°C, 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 80 km/hr.

Assume that the flow is fully turbulent over the entire surface.

Problem 2 (10 points): In a gas-fired boiler, water is being boiled at 120°C by hot air flowing through a 5-m-

long, 5-cm-diameter tube submerged in water. Hot air enters the tube at 1 atm and 300°C at a mean velocity of

8 m/s, and leaves at 150°C. If the surface temperature of the tube is 120°C, determine the average convection

heat transfer coefficient of the air and the rate of water evaporation, in kg/hr.

Problem 3 (10 points): Two infinitely long parallel plates of width w are located at w distance apart. The two

plates behave as black surfaces, where surface 1 has a temperature of 500°C and surface 2 has a temperature of

50°C. Determine the radiation heat flux between the two surfaces.

10 9 8 7 6 5 4 3 2 1 0

9 6 6 8 6 2 1 2 0 0 0

10 9 8 7 6 5 4 3 2 1 0

2 8 8 4 10 3 3 0 0 0 0

10 9 8 7 6 5 4 3 2 1 0

20 8 7 2 0 0 1 1 0 1 0