## MCQs

Total Questions : 75 | Page 1 of 8 pages
Question 1. Consider the following statements pertaining to heat transfer through fins
(i) They must be arranged at right angles to the direction of flow of working fluid
(ii) The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements
(iii) Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid
(iv) Fins are made of materials that have thermal conductivity higher than that of wall
Identify the correct statements
1.    3 and 4
2.    1 and 3
3.    2 and 3
4.    1 and 2
Answer: Option D. -> 1 and 2
Answer: (d).1 and 2
Question 2. The handle of a saucepan, 30 cm long and 2 cm in diameter, is subjected to 100 degree Celsius temperature during a certain cooking operation. The average unit surface conductance over the handle surface is 7.35 W/m² degree in the kitchen air at 24 degree Celsius. The cook is likely to grasp the last 10 cm of the handle and hence the temperature in this region should not exceed 38 degree Celsius. What should be the thermal conductivity of the handle material to accomplish it? The handle may be treated as a fin insulated at the tip
1.    18.36 W/m degree
2.    17.36 W/m degree
3.    16.36 W/m degree
4.    15.36 W/m degree
Answer: Option B. -> 17.36 W/m degree
Answer: (b).17.36 W/m degree
Question 3. An increase in fin effectiveness is caused by high value of
(i) Convective coefficient
(ii) Thermal conductivity
(iii) Circumference
(iv) Area
Identify the correct statement
1.    1 and 3
2.    3 and 4
3.    2 and 4
4.    2 and 3
Answer: Option C. -> 2 and 4
Answer: (c).2 and 4
Question 4. Choose the correct option regarding fin efficiency and fin effectiveness
1.    2 Fin effectiveness = A FIN/A B (Efficiency of fin)
2.    3 Fin effectiveness = A FIN/A B (Efficiency of fin)
3.    Fin effectiveness = A FIN/A B (Efficiency of fin)
4.    ½ Fin effectiveness = A FIN/A B (Efficiency of fin)
Answer: Option C. -> Fin effectiveness = A FIN/A B (Efficiency of fin)
Answer: (c).Fin effectiveness = A FIN/A B (Efficiency of fin)
Question 5. Let us assume a square section fin split longitudinally and used as two fins. This will result in
1.    Increase or decrease in heat transfer depending on material of fin
2.    Heat flow remains constant
3.    Decrease in heat transfer
4.    Increase in heat transfer
Answer: Option D. -> Increase in heat transfer
Answer: (d).Increase in heat transfer
Question 6. Mark the false statement regarding effectiveness of fin
1.    A high value of film coefficient adversely affects the fin effectiveness
2.    Fin effectiveness is improved if fin is made from a material of low conductivity
3.    Fin effectiveness is improved by having thin fins
4.    It can also be improved by having closely spaced fins
Answer: Option B. -> Fin effectiveness is improved if fin is made from a material of low conductivity
Answer: (b).Fin effectiveness is improved if fin is made from a material of low conductivity
Question 7. The thermometric well is treated as a fin of
1.    It is not treated as a fin
2.    Infinite length
3.    Finite length
4.    It depends on the amount of heat dissipation
Answer: Option C. -> Finite length
Question 8. The convective coefficient in boilers and condenser is
1.    Low
2.    High
3.    Moderate
4.    Depends on time and temperature
Answer: Option B. -> High
Question 9. Thermometric well apparatus doesn’t consists of
1.    Thermometer
2.    Pipe line
3.    Oil
4.    Ammeter
Answer: Option D. -> Ammeter