Wright State University Spring 2014

Department of Mechanical and Materials Engineering

ME 3360/5360 HEAT TRANSFER: QUIZ 6

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

Show All Work for Partial Credit

Problem 1 (10 points): 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 75ºC and has an emissivity of

0.92. The ambient air is at 5ºC, and the road surface is at 10ºC. 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/hr.

Assume the flow to be turbulent over the entire surface.

Problem 2 (10 points): Combustion air in a manufacturing facility is to be preheated before entering a furnace

by hot water at 90ºC flowing through the tubes of a tube bank located in a duct. Air enters the duct at 15ºC and

1 atm with a mean velocity of 4.5 m/s, and flows over the tubes. The outer diameter of the tubes is 2.2 cm, and

the tubes are arranged in-line with longitudinal and transverse pitches of SL = ST = 5 cm. There are eight rows in

the flow direction with eight tubes in each row. Determine the rate of heat transfer per unit length of the tubes,

and the pressure drop across the tube bank.