Food Engineering Questions for entrance exams on “Mixing-2”.
1. Which of the following is NOT an application of mixing solids in the food industry?
a) Biscuit/bakery making
b) Poultry and cattle feed
c) Chips and snacks industry
d) None of the mentioned
Answer: d
Clarification: All the mentioned are applications of mixing in the food industry.
2. Which of the following is NOT a mixing involved with fluids in the food industry?
a) Soup powders
b) Carbonated drinks
c) Oxygen transfer in fermentation broths
d) None of the mentioned
Answer: a
Clarification: Soup powders involve mixing of solids. Carbonated drinks involve mixing of gas with a liquid. Oxygen transfer in fermentation broths involves mixing of gas in liquid again.
3. Which of the following does NOT include power required for mixing by an impeller?
a) Rheological nature of the fluid
b) Friction in the motor
c) Speed, nature and type of the impeller
d) None of the mentioned
Answer: b
Clarification: Friction in the motor does NOT include power required for mixing by an impeller.
4. Power required for a gassed system is more than that required for an ungassed system.
a) True
b) False
Answer: b
Clarification: Power required for an ungassed system is more than that required for a gassed system. This is because when gas is sent into the fluid via a nozzle, the density of the fluid near the impeller decreases and hence the power required for it is lesser.
5. Statement 1: Froude number relates the gravitational effect which is important when the liquid is agitated by an impeller.
Statement 2: When NRe,i < 300, NFr is ineffective.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Froude number relates the gravitational effect which is important when the liquid is agitated by an impeller. When NRe,i < 300, NFr is ineffective.
6. With respect to the relationship between the power number and the impeller Reynolds’s number, which amongst the following statements is true?
a) In the turbulent region, the NRe,i has no impact over NPo
b) In the transient region, the NRe,i has no impact over NPo
c) In the laminar region, the NPo continually falls as NRe,i increases
d) None of the mentioned
Answer: a
Clarification: In the turbulent region, the NRe,i, impeller Reynolds’s number, has no impact over NPo, power number.
7. Statement 1: In the transient zone, the power input depends on the density and viscosity of the fluid.
Statement 2: In the laminar zone, the power input depends on the density only. It is independent of the viscosity of the fluid.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: a
Clarification: In the laminar zone, the power input depends on the viscosity only. It is independent of the density of the fluid.
8. Statement 1: For non-Newtonian fluids, another term called apparent viscosity is used as their viscosity changes with the change in the shear rate.
Statement 2: For non-Newtonian fluids, between the transition region, the power number for non-Newtonian fluids is slightly higher than that for Newtonian fluids.
a) True, False
b) True, True
c) False, False
d) False, True