ME 436 (Heat Transfer) Final UPDATED
ACTUAL Exam Questions and CORRECT
Answers
Which of the following statements provides the best physical interpretation of the Biot number?
(A) A ratio of the heat conduction rate to the thermal energy storage rate.
(B) A measure of the temperature difference in the solid relative to the temp difference between
the solid surface and the fluid
(C) A relationship between the volume and surface area of an object
(D) A ratio of inertial to viscous forces - CORRECT ANSWER - (B) A measure of the
temperature difference in the solid relative to the temp difference between the solid surface and
the fluid
The eigenvalues ζn are the positive roots of the transcendental equation ζn*tan(ζn) = Fo.
T/F? - CORRECT ANSWER -F
The Fourier number may be described as
Length
Time
Mass
Temp - CORRECT ANSWER - Time
When Bi << 1, the resistance to conduction within the solid is much less than the resistance to
convection across the fluid boundary layer
T/F - CORRECT ANSWER -T
, If the conduction resistance within the solid is assumed to be negligible, then this implies that we
are considering an infinite thermal conductivity
(T/F) - CORRECT ANSWER -T
When Bi >> 1, the temperature distribution across the solid can be considered spatially uniform
(T/F) - CORRECT ANSWER -F
If temperature gradient within the solid can be neglected, a comparatively simple approach,
termed the lumped capacitance method, may be used. (T/F) - CORRECT ANSWER -T
The first step in performing a transient conduction analysis is to calculate the Biot number. If it is
less than _______, then we can use the lumped capacitance method.
1.0
0.2
0.1
10 - CORRECT ANSWER - 0.1
The lumped capacitance method is more likely to be more applicable for cooling a hot solid by
forced convection in air - than in water. (T/F) - CORRECT ANSWER -T
As the Biot number ______, temperature gradients within the solid become ______. For these
cases we can often use a one-term approximation of the exact solution to find the temperature
distribution, if Fo_____ .
increases / insignificant / > 0.2
increases / significant / > 0.2
increases / insignificant / < 0.2
decreases / significant / > 0.2 - CORRECT ANSWER - As the Biot number INCREASES,
temperature gradients within the solid become SIGNIFICANT. For these cases we can often use
a one-term approximation of the exact solution to find the temperature distribution, if Fo > 0.2
ACTUAL Exam Questions and CORRECT
Answers
Which of the following statements provides the best physical interpretation of the Biot number?
(A) A ratio of the heat conduction rate to the thermal energy storage rate.
(B) A measure of the temperature difference in the solid relative to the temp difference between
the solid surface and the fluid
(C) A relationship between the volume and surface area of an object
(D) A ratio of inertial to viscous forces - CORRECT ANSWER - (B) A measure of the
temperature difference in the solid relative to the temp difference between the solid surface and
the fluid
The eigenvalues ζn are the positive roots of the transcendental equation ζn*tan(ζn) = Fo.
T/F? - CORRECT ANSWER -F
The Fourier number may be described as
Length
Time
Mass
Temp - CORRECT ANSWER - Time
When Bi << 1, the resistance to conduction within the solid is much less than the resistance to
convection across the fluid boundary layer
T/F - CORRECT ANSWER -T
, If the conduction resistance within the solid is assumed to be negligible, then this implies that we
are considering an infinite thermal conductivity
(T/F) - CORRECT ANSWER -T
When Bi >> 1, the temperature distribution across the solid can be considered spatially uniform
(T/F) - CORRECT ANSWER -F
If temperature gradient within the solid can be neglected, a comparatively simple approach,
termed the lumped capacitance method, may be used. (T/F) - CORRECT ANSWER -T
The first step in performing a transient conduction analysis is to calculate the Biot number. If it is
less than _______, then we can use the lumped capacitance method.
1.0
0.2
0.1
10 - CORRECT ANSWER - 0.1
The lumped capacitance method is more likely to be more applicable for cooling a hot solid by
forced convection in air - than in water. (T/F) - CORRECT ANSWER -T
As the Biot number ______, temperature gradients within the solid become ______. For these
cases we can often use a one-term approximation of the exact solution to find the temperature
distribution, if Fo_____ .
increases / insignificant / > 0.2
increases / significant / > 0.2
increases / insignificant / < 0.2
decreases / significant / > 0.2 - CORRECT ANSWER - As the Biot number INCREASES,
temperature gradients within the solid become SIGNIFICANT. For these cases we can often use
a one-term approximation of the exact solution to find the temperature distribution, if Fo > 0.2
