MEEN 464 Final Exam | UPDATED Questions with 100% Verified
Answers
Question:
A thermistor is a temperature sensor that contains metallic
wire that changes its electrical resistance when the
temperature changes.
Answer:
True
Question:
A Bi-metallic Dial Thermometer is a temperature sensor that
contains the liquid that changes its volume when the
temperature changes.
Answer:
FALSE --> contains metal strips, not liquid
Question:
Due to harsh conditions, a sheath may be used to protect a
thermocouple. The time constant of the thermocouple will be
smaller due to the sheath
Answer:
FALSE --> TC's will be HIGHER
Question:
Which thermocouple will have the shortest time constant?
Answer:
30-gage T-type thermocouple with an exposed junction
***Not sheathed, more diameter increases time constant, K <
T
Question:
Time Constant
, Answer:
T = (t1 +t2) / 2 find t it takes for T = t1 subtract --> t1 -ti =
t(1/2) TIME CONSTANT = t(1/2) / ln(2)
Question:
Heat Transfer through a rod (lab 2)
Answer:
Q = -kA(dt/dx)
Question:
The two collinear rods are then subjected to long exposure in
salt water, and thus pitting corrosion has occurred at the
interface. If the rods are used for further testing, the thermal
contact resistance should be expected to increase. (lab 3)
Answer:
surface pitting involves defects on the surface, thus
substantially increasing the roughness. The thermal contact
resistance should be expected to increase.
Question:
The thermal contact resistance should be expected to increase
when the rods are pressed against each other (lab 3)
Answer:
FALSE (gap is closing --> increasing pressure means
decreasing resistance)
Question:
Dimensionless Temperature (Lab 4)
Answer:
(T - T_inf) / (T_base - T_inf)
Question:
Biot number equation/rule (Lab 5)
, Answer:
(h *(V/A_s)) / k Bi MUST BE < 0.1 for Lumped Capacitance
Question:
Counter-flow concentric tube heat exchanger problem (Lab 7)
Answer:
mc(delta_T) = m1c1(delta_T1) --> solve for specific
inlet/outlet temp Thi - Tho = delta_T Tco - Tci = delta_T1
--> Total Rate of HT = (mh)(mc)(delta_Th)
Question:
Explain why the IR thermal image of the heated plate at a
uniform temperature looks different in temperature scales
(LAB 8)
Answer:
because of the varying emissivities
Question:
emissivity estimation equation (LAB 8)
Answer:
q'' · ··T4 sigma cancels out, CONVERT TO KELVIN
Question:
When the heater temperature is further increased, a large
number of bubbles form at a very high rate. Explain how the
vapor bubbles affect the rate of heat transfer in Nucleate
Boiling (LAB 9)
Answer:
Vapor bubbles increase/enhance the rate of Heat Transfer, it is
a form of heat transport, and more bubbles increase the HT
coefficient and slope of boiling curve (DECREASE IN
WALL TEMPERATURE)
Answers
Question:
A thermistor is a temperature sensor that contains metallic
wire that changes its electrical resistance when the
temperature changes.
Answer:
True
Question:
A Bi-metallic Dial Thermometer is a temperature sensor that
contains the liquid that changes its volume when the
temperature changes.
Answer:
FALSE --> contains metal strips, not liquid
Question:
Due to harsh conditions, a sheath may be used to protect a
thermocouple. The time constant of the thermocouple will be
smaller due to the sheath
Answer:
FALSE --> TC's will be HIGHER
Question:
Which thermocouple will have the shortest time constant?
Answer:
30-gage T-type thermocouple with an exposed junction
***Not sheathed, more diameter increases time constant, K <
T
Question:
Time Constant
, Answer:
T = (t1 +t2) / 2 find t it takes for T = t1 subtract --> t1 -ti =
t(1/2) TIME CONSTANT = t(1/2) / ln(2)
Question:
Heat Transfer through a rod (lab 2)
Answer:
Q = -kA(dt/dx)
Question:
The two collinear rods are then subjected to long exposure in
salt water, and thus pitting corrosion has occurred at the
interface. If the rods are used for further testing, the thermal
contact resistance should be expected to increase. (lab 3)
Answer:
surface pitting involves defects on the surface, thus
substantially increasing the roughness. The thermal contact
resistance should be expected to increase.
Question:
The thermal contact resistance should be expected to increase
when the rods are pressed against each other (lab 3)
Answer:
FALSE (gap is closing --> increasing pressure means
decreasing resistance)
Question:
Dimensionless Temperature (Lab 4)
Answer:
(T - T_inf) / (T_base - T_inf)
Question:
Biot number equation/rule (Lab 5)
, Answer:
(h *(V/A_s)) / k Bi MUST BE < 0.1 for Lumped Capacitance
Question:
Counter-flow concentric tube heat exchanger problem (Lab 7)
Answer:
mc(delta_T) = m1c1(delta_T1) --> solve for specific
inlet/outlet temp Thi - Tho = delta_T Tco - Tci = delta_T1
--> Total Rate of HT = (mh)(mc)(delta_Th)
Question:
Explain why the IR thermal image of the heated plate at a
uniform temperature looks different in temperature scales
(LAB 8)
Answer:
because of the varying emissivities
Question:
emissivity estimation equation (LAB 8)
Answer:
q'' · ··T4 sigma cancels out, CONVERT TO KELVIN
Question:
When the heater temperature is further increased, a large
number of bubbles form at a very high rate. Explain how the
vapor bubbles affect the rate of heat transfer in Nucleate
Boiling (LAB 9)
Answer:
Vapor bubbles increase/enhance the rate of Heat Transfer, it is
a form of heat transport, and more bubbles increase the HT
coefficient and slope of boiling curve (DECREASE IN
WALL TEMPERATURE)
