250+ TOP MCQs on Unit Operations – Heat Transfer by Conduction and Answers

Food Engineering Multiple Choice Questions on “Unit Operations – Heat Transfer by Conduction”.

1.
‘a’ refers to ______ and ‘b’ refers to _____
a) Steady state heat transfer, Unsteady state heat transfer
b) Unsteady state heat transfer, Steady state heat transfer
c) None of the mentioned
d) All of the mentioned
Answer: a
Clarification: ‘a’ refers to Steady state heat transfer and ‘b’ refers to unsteady state heat transfer.

2. The equation

View Answer

Answer: b Clarification: The equation dq/dA= (k(-dT))/dx is called Fourier’s law conduction.

3. Statement 1: The heat transfer co-efficient in ice is four times that of water.
Statement 2: k in conductance is for thermal conductivity.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Both the statements are true.

4. Frozen foods have a higher transfer co-efficient hence they lose heat faster than other food items when exposed to the outside environment.
a) True
b) False
Answer: a
Clarification: Frozen foods have a higher transfer co-efficient hence they lose heat faster than other food items when exposed to the outside environment.

5. Statement 1: When the average radius gives an error, log mean radius is used.
Statement 2: Log mean radius is given by r_L= ( r₀– r_i )/(ln(r₀/r_i))
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Both the statements are true.

6. Statement 1: α=k/(ρC_p)
Statement 2: α stands for thermal conductivity.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: a
Clarification: α=k/(ρC_p). α stands for thermal diffusivity.

7. Statement 1: N_Fo stands for Fourier number.
Statement 2: N_Fo= (αt_T)/s²
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Both the statements pertaining to Fourier number are true.

8. N_Fo= (αt_T)/s². Here ‘s’ stands for half slab thickness. Based on this data, ‘s’ for a chapatti/ dosa will be _____
a) Half slab thickness
b) Full slab thickness
c) One and a half slab thickness
d) Double slab thickness
Answer: b
Clarification: ‘s’ for a chapatti/ dosa will be Full slab thickness. This is because ‘s’ equals half slab thickness only when heating takes place from both sides. But, for a chapatti/ dosa, heating takes place only from one end hence‘s’ becomes ‘2s’.

9. _____ is the equation for unsteady state heat conduction through solid materials.
a) dT/dx= α (d² T)/ (dt)²
b) dT/dx= α (d² T)/ (dx)²
c) dT/dt= α (d² T)/ (dx)²
d) dT/dt= α (d² T)/ (dt)²
Answer: c
Clarification: dT/dt= α (d² T)/ (dx)² is the equation for unsteady state heat conduction through solid materials.

10. For a copper pipe, k = 0.3534, temperature difference = 60, B = 0.0125 and A = 850. What is the value of q?
a) 1442 W
b) 1442 kW
c) 1565 W
d) 1565 kW
Answer: b
Clarification: q=kA ∆T/B.