Engineering Questions with Answers - Multiple Choice Questions
Primary Production of Milk Engineering MCQs
1 - Question
The evaporator in which the material to be evaporated boils outside the horizontal tube and steam condenses inside the tubes is called ________
a) Horizontal tube evaporator
b) Vertical tube evaporator
c) Vacuum pan evaporator
d) Forced circulation evaporator
View Answer
Explanation: In Horizontal tube evaporator, the material to be evaporated boils outside the horizontal tube and steam condenses inside the tubes. These evaporators are not considered effective as the heat transfer is lower especially if the liquid is viscous.
2 - Question
Evaporator which promotes natural circulation is?
a) Horizontal tube evaporator
b) Vertical tube evaporator
c) Vacuum pan evaporator
d) Forced circulation evaporator
View Answer
Explanation: In vertical tube evaporator, heating and boiling of liquid cause it to rise and flow upwards and un-evaporated liquid flows down through the central large diameter tube. Thus natural circulation is promoted in this type of evaporator.
3 - Question
Evaporators in which pumps are used to force the evaporating liquid through the tubes are called?
a) Horizontal tube evaporator
b) Vertical tube evaporator
c) Vacuum pan evaporator
d) Forced circulation evaporator
View Answer
Explanation: Forced Circulation Evaporator is a modified form of vertical tube evaporator. In this type a pumps is used to force the evaporating liquid through the tubes. This helps to further improve the evaporating capacity.
4 - Question
Name of the evaporator which consists of one pass vertical shell and tube heat exchanger discharging the product to be evaporated into a relatively small vapor head?
a) Horizontal tube evaporator
b) Long tube vertical evaporator
c) Vacuum pan evaporator
d) Forced circulation evaporator
View Answer
Explanation: In Long tube vertical evaporator, the feed enters at the bottom of the tube, starts boiling as it moves up the tube and the mixture of liquid and vapor leaving at the top at high velocity strikes against a deflector placed above the tube.
5 - Question
The deflector used in long tube vertical evaporator can be used as?
a) Vapor separator
b) Foam breaker
c) Pasteurizer
d) Vapor separator and foam breaker
View Answer
Explanation: Deflector placed above the tube. This deflector is effective both as a vapor separator and as a foam breaker. When the ratio of feed to evaporation is low, recirculation of liquid is provided.
6 - Question
Which of the following is the disadvantage of climbing film evaporator?
a) Severe scale formation
b) Over heating
c) Small concentration
d) Low pressure
View Answer
Explanation: The main disadvantage of climbing film evaporator is that a comparatively large volume of liquid is present in the evaporator at one time and most of it located at the bottom. Because of this, severe scale formation occurs more rapidly in this region.
7 - Question
As the film rises further evaporation occurs until they reach the top of the tubes. The mixture of vapor and milk then passes into a separate chamber from which the vapor passes to a condenser. Name the evaporator.
a) Climbing film evaporator
b) Falling film evaporator
c) Plate evaporator
d) Forced circulation evaporator
View Answer
Explanation: Climbing Film Evaporator, in this type the liquid to be evaporated is fed at the lower end of the vertical tubes, heated by the condensing steam on the outside of the tube. The liquid starts boiling at the bottom; the vapor along with the liquid tends to rise further up the tube in the form of a thin film. As the film rises further evaporation occurs until they reach the top of the tubes.
8 - Question
Which of the following is not the advantage of falling film evaporator?
a) Short residence time of liquid
b) Good performance with small temperature difference across heating surfaces
c) Operates at lower temperature difference than rising film evaporator
d) Long residence time of liquid
View Answer
Explanation: The advantages claimed for the falling film evaporator are short residence time of liquid, good performance with small temperature difference across the heating surface. More effects can be used with falling film evaporator as it will operate with a lower temperature difference than climbing film evaporator.
9 - Question
Great economies of operation may be made in large installations with ___________
a) Multiple effect evaporator
b) Centri-therm evaporator
c) Falling film evaporator
d) Rising film evaporator
View Answer
Explanation: Considerable saving in steam and water can be effected by using multiple effect evaporators. The vapors from one effect have considerable latent heat and may thus be used for heating second effect and vapors from the second effect to heat the third effect and so on. Thus great economies of operation may be made in large installations with multiple- effect evaporator.
10 - Question
Device used to improve thermal efficiency of an evaporator is called?
a) Thermo compressor
b) Deareater
c) Dryer
d) Pasteurizer
View Answer
Explanation: The vapor evolved from the product can be compressed and used as a heating medium. This improves the thermal efficiency of the evaporator. A thermo compressor is used for this purpose.
11 - Question
Evaporators in the dairy industry don’t concentrate which of the following?
a) Whole and skimmed milk
b) Whey
c) Condensed milk
d) Cheese
View Answer
Explanation: Evaporators are ideal partner for solutions for the concentration of Whole- and skimmed milk, Whey, Condensed milk and Lactose.
12 - Question
Ratio of capacity to economy is known as ________
a) Water consumption per hour
b) Steam consumption per hour
c) Sediment consumption per hour
d) Milk consumption per hour
View Answer
Explanation: Capacity of an evaporator is the amount of water vaporized in the evaporator per unit time. Ratio of capacity to economy is called the steam consumption per hour.
13 - Question
__________ is the total mass of water vaporized per unit mass of steam input to the evaporator.
a) Efficiency of evaporator
b) Economy of evaporator
c) Rate of evaporator
d) Capacity of evaporator
View Answer
Explanation: Capacity is defined as the number of kilograms of water vaporized per hour. Economy is the number of kilograms vaporized per kilogram of steam fed to the unit. In a single effect evaporator the economy is approximately always less than 1, but in multiple-effect equipment it may be considerably greater.
14 - Question
Single effect evaporation is simple and steam effective.
a) True
b) False
View Answer
Explanation: When a single evaporator is used, the vapour from the boiling liquid is condensed and discarded. Simple but does not use steam effectively.
15 - Question
________ Rule is often used to compare a pure liquid and a solution at a given concentration.
a) Duhring’s rule
b) Plank rule
c) Friction rule
d) Doppler rule
View Answer
Explanation: Duhring’s rule states that a linear relationship exists between the temperatures at which two solutions exert the same vapour pressure. The rule is mostly used to compare a pure liquid and a solution at a given concentration.
16 - Question
Aeration in milk doesn’t occur in which of the following states?
a) Dispersed state
b) Dissolved state
c) Chemically bound state
d) Crystal state
View Answer
Explanation: Air in milk occurs in three states namely Dispersed; Dissolved; and chemically bound.
17 - Question
Milk in udder contains what percentage of gases?
a) 4.5-6%
b) 7-8%
c) 4-5%
d) >10%
View Answer
Explanation: The total volume of air in milk in the udder can be some 4.5 – 6 %, of which O2 constitutes about 0.1%, N2 (nitrogen) about 1% and CO2 3.5 – 4.9%.
18 - Question
Dispersed air in milk cause problems.
a) True
b) False
View Answer
Explanation: It is not unusual for incoming milk to contain 10% air by volume or even more. Finely and coarsely dispersed air predominates at this stage. Dispersed air causes problems.
19 - Question
Aeration leads to ______ in volumetric measurement of milk.
a) Precision
b) Delay
c) Consistency
d) Inaccuracy
View Answer
Explanation: Inaccuracy in volumetric measurement of milk is observed due to dispersion of air in the milk.
20 - Question
Which among the following are the problem associated with aeration in milk? I) Incrustation of heating surfaces in pasteurizers (fouling) II) Reduced skimming efficiency in separators III) Loss of precision in automatic in-line standardization IV) Inaccurate in-line fat standardization
a) I), II) and III)
b) I) and II)
c) I), II), III) and IV)
d) I) only
View Answer
Explanation: The basic problems caused by dispersed air are Inaccuracy in volumetric measurement of milk, incrustation of heating surfaces in pasteurizers (fouling), reduced skimming efficiency in separators, loss of precision in automatic in-line standardization and concentration of air in cream, causing inaccurate in-line fat standardization.
21 - Question
In order to make milk pass through air eliminator, the inlet of the cylindrical vessel must be located at a ______ level than the outlet pipe of the milk tank on the vehicle.
a) Upper
b) Lower
c) Same
d) Tilted
View Answer
Explanation: The inlet of the cylindrical vessel must be located at a lower level than the outlet pipe of the milk tank(s) on the vehicle, as the milk should not be pumped into the vessel but transferred to it by gravity.
22 - Question
Efficiency of milk deaerator depends on which of the following factor?
a) Fat content
b) Nutrition
c) Fat globule size
d) Dispersion of air
View Answer
Explanation: The deaeration system can be manually or automatically operated. In both cases, the efficiency of air elimination depends very much on how finely dispersed the air is. The smallest air bubbles cannot be removed.
23 - Question
Which law forms the basis of working of deaerator?
a) James law
b) Planck law
c) Law of thermodynamic
d) Henry law
View Answer
Explanation: According to William Henry in 1803 its state, that gas solubility in a solution decreases as the gas partial pressure above the solution decreases. The solubility of a gas dissolved in a liquid is directly proportional to the partial pressure of the gas.
24 - Question
Solubility of gases decrease with ________ in solution temperature.
a) Increase
b) Decrease
c) No change
d) Increase and decrease
View Answer
Explanation: Solubility of gases decrease with an increase in solution temperature and or decrease in pressure. The solubility of gas in a solution decreases as the temperature of the solution rises and approaches saturation temperature.
25 - Question
Which of the deaerator have application in the dairy industry?
a) Tray type
b) Vacuum type
c) Spray type
d) Bubble type
View Answer
Explanation: Vacuum deaeration has been used successfully to expel dissolved air and finely dispersed air bubbles from milk. Warm (Preheated) milk is fed into an expansion vessel in which the vacuum level is adjusted to a level equivalent to a boiling point.
26 - Question
Components of vacuum deaerator are? I) Deaerator II) Vacuum pump III) Pump unit
a) I) only
b) II) only
c) III) only
d) I), II) and III)
View Answer
Explanation: A vacuum deaerator consists of three main components a vacuum deaerator, a vacuum pump unit and a pump unit.
27 - Question
What is the oxygen content of commercial mixed raw milk?
a) 0.47%
b) 1.29%
c) 4.45%
d) 6.21%
View Answer
Explanation: Commercial mixed raw milk constitutes about 0.47% of oxygen in it. The total volume of air in milk in the udder can be some 4.5 – 6 %, of which oxygen constitutes about 0.1%.
28 - Question
What is the nitrogen content of commercial mixed raw milk?
a) 0.47%
b) 1.29%
c) 4.45%
d) 6.21%
View Answer
Explanation: Commercial mixed raw milk constitutes about 1.29% of nitrogen in it. The total volume of air in milk in the udder can be some 4.5 – 6 %, of which nitrogen constitutes about 1%.
29 - Question
What is the carbon dioxide content of commercial mixed raw milk?
a) 0.47%
b) 1.29%
c) 4.45%
d) 6.21%
View Answer
Explanation: Commercial mixed raw milk constitutes about 4.45% of carbon dioxide in it. The total volume of air in milk in the udder can be some 4.5 – 6 %, of which carbon dioxide constitutes about 3.5- 4.9%.
30 - Question
Factors that lead to excess air in milk are?
a) Gravity and temperature
b) Temperature and atmospheric pressure
c) Temperature and volume
d) Volume and pressure
View Answer
Explanation: The equilibrium that prevails between three states of aggregation is determined by temperature and atmospheric pressure. The rise in temperature during pasteurization for instance, dissolved air goes from solution to dispersion causing the problem.