Heat Transfer FE Review

Multiple Choice

A wall is constructed of 25 mm thick white pine boards and insulated with 75 mm thick fiberglass insulation. The thermal conductivities of the two materials are 0.11 W/mK and 0.048 W/mK, respectively. On a given day, the internal and external tempreatures are 22°C and -10°C, respectively. What is the rate of heat loss per unit area of wall?

• 6.7 W/m^2

• 18 W/m^2

• 19 W/m^2

• 32 W/m^2

Multiple Choice

Air flows at a velocity of 2m/s in an 8cm diameter and 7m long tube as the tube is subjected to uniform heat flux from all services. Using the air properties given below, the convection heat transfer coefficient is most nearly:

• 7.25 W/m^2K

• 10.44 W/m^2K

• 12.44 W/m^2K

• 5.23 W/m^2K

Multiple Choice

Surface A has a temperature of 100 degrees C and Surface B, 200 degrees C. The two surfaces are sufficiently close so that all the radiation leaving A is intercepted by B and vise-versa. Assuming black-body behavior, the net thermal radiation heat transfer between the two surfaces is most nearly:

• 1740 W/m^2

• 1540 W/m^2

• 1852 W/m^2

• 1956 W/m^2

Multiple Choice

The thermal resistance for one-dimensional steady conduction heat transfer through a cylindrical wall in the radial direction is which of the following?

• linear

• logarithmic

• exponential

• polynomial

Multiple Choice

If T is the absolute temperature, the intensity of radiation from an ideal radiator will be proportional to:

• T

• $$T^2$$  

• T

• $$T^4$$  

Multiple Choice

The heat transfer during an adiabatic process is

• reversible

• irreversible

• dependent on temperature

• zero

Multiple Choice

An isentropic process is one which:

• is adabatic but not resverisble

• is reversible but not adiabatic

• is adiabatic and reversible

• occurs at constant pressure and temperature

Multiple Choice

A well insulated solid copper wire 1 m long with a cross-sectional area of 0.0839 cm^2 connects two reservoirs, one with boiling water at 100°C and the other with ice at 0°C. How long does it take for 100 cal of energy to move through the wire?

• 3.5 min

• 21 min

• 80 min

• 240 min