# Food Processing Unit Operations Questions and Answers – Drying – Psychrometry

This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Drying – Psychrometry”.

1. What is psychometric chart?
a) It is the graphical representation of thermodynamic properties
b) It is the graphical representation of chemical properties
c) It is the graphical representation of drying properties
d) It is the graphical representation of mechanical properties

Explanation: Psychometric chart is a graphical representation of thermodynamic properties of moist air at one atmosphere like wet bulb temperature, dry bulb temperature, dew point temperature, humidity ratio, relative humidity, specific volume and enthalpy.

2. Who invented the psychometric chart?
a) Dr Richard Seligman
b) George Babcock
c) George Brayton
d) Willis H. Carrier

Explanation: Dr Richard Seligman invented heat exchanger. George Babcock invented boiler. George Brayton invented engine. Willis H. Carrier invented psychometric chart.

3. Which lines indicate wet bulb temperatures in the psychometric charts?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves

Explanation: The temperature read by the thermometer where the bulb of thermometer is enclosedwith a wet cloth is called as wet bulb temperature. If the reading of the wet bulb temperature is lower, this indicates that the surroundings have lower humidity.When the relative humidity is 100%, then wet bulb temperature is equal to the air temperature.

4. Which lines indicate dry bulb temperatures in the psychometric chart?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves

Explanation:The dry-bulb temperature is defined as the temperature of air which is measured by a thermometer that is freely exposed to the air, but protected from radiation and the moisture content. It is the true thermodynamic temperature.Dry bulb temperatures in the psychometric charts areindicated by vertical lines.

5. Which lines indicate relative humidity in the psychometric charts?
a) Diagonals lines
b) Vertical lines
c) Horizontal lines
d) Curves

Explanation: The relative humidity is defined as the amount of water vapor present in air.It is normally expressed as a percentage of the amount needed for saturation at the same temperature. Relative humidity in the psychometric charts is indicated by curves.
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6. What is another name for humidity ratio?
a) Mixing ratio
b) Water ratio
c) Relative humidity ratio
d) Bound water ratio

Explanation: Humidity ratio is the fraction of mass of water vapor per unit mass of dry air at the given conditions thermodynamic conditions. It is known as the moisture content or the mixing ratio. It is typically plotted as the ordinate on the vertical axis of the graph.

7. Who invented the sling psychrometrer?
a) Sir John Leslie
b) Leonardo da Vinci
c) George Babcock
d) George Brayton

Explanation: Sir John Leslie invented the sling psychrometrer. A sling psychrometer is an instrument that measures the dew point and relative humidity in an area. It has two thermometers, they are a wet bulb and a dry bulb.

8. What is wet bulb depression?
a) Difference between dry bulb temperature and wet bulb temperature at any point
b) Difference between relative humidity and wet bulb temperature at any point
c) Difference between dew point and wet bulb temperature at any point
d) Difference between dry bulb temperature and dew point temperature at any point

Explanation: The wet bulb depression is defined as the difference between dry bulb temperature and wet bulb temperature at any point. It indicates relative humidity of the air.

9. What is dew point depression?
a) Difference between dry bulb temperature and dew point temperature of air
b) Difference between wet bulb temperature and dew point temperature of air
c) Difference between relative humidity and dew point temperature of air
d) Difference between wet bulb depression and dew point temperature of air

Explanation: The dew point depression is defined as the difference between dry bulb temperature and dew point temperature of air. As the dew point depression deals with the moisture in the atmosphere, it is very important in forest, agricultural and particularly in forecasting wildfires.

10. Is dew point same as wet bulb?
a) True
b) False

Explanation: The wet bulb temperature is defined as the temperature that a wet bulb which is covered by wet cotton wick will reach from evaporative cooling. Whereas the dew point temperature is the temperature that the atmosphere would have to be cooled for complete saturation of air with water.

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