# Food Engineering Questions and Answers – Unit Operations – Heat Transfer by Conduction

This set of Food Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Unit Operations – Heat Transfer by Conduction”.

1.
‘a’ refers to ______ and ‘b’ refers to _____
c) None of the mentioned
d) All of the mentioned

Explanation: ‘a’ refers to Steady state heat transfer and ‘b’ refers to unsteady state heat transfer.

2. The equation

$dq/dA= \left(k\left(-dT\right)\right)/dx is called _____ a\right) Kirchhoff’s law of conduction b\right) Fourier’s law conduction c\right) Kirchhoff’s & Fourier’s law conduction d\right) None of the mentioned$View Answer
Answer: b Explanation: 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

Explanation: 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

Explanation: 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 rL= ( r0– ri )/(ln(r0/ri))
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: Both the statements are true.
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6. Statement 1: α=k/(ρCp)
Statement 2: α stands for thermal conductivity.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: α=k/(ρCp). α stands for thermal diffusivity.

7. Statement 1: NFo stands for Fourier number.
Statement 2: NFo= (αtT)/s2
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: Both the statements pertaining to Fourier number are true.

8. NFo= (αtT)/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

Explanation: ‘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

Explanation: 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

Explanation: q=kA ∆T/B.

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