Module 4: Psychrometry

Question 1

the study of the properties of mixtures of air and water vapor

Answer 1

psychrometry

Question 2

air and water vapor at diff conditions affects the product during drying and storage operations

true or false

Answer 2

true

Question 3

it is a binary mixture of dry-air and low-pressure water vapor

Answer 3

moist air

Question 4

components of dry-air

Answer 4

• nitrogen
• oxygen
• argon
• carbon dioxide
• rare gases

Question 5

for pure substances, two properties are sufficient, while for binary mixtures, three properties are needed to completely define their state

true or false

Answer 5

true

Question 6

the major physical properties of air that affect the drying rate of grains are

Answer 6

• RH or humidity ratio
• dry-bulb & wet-bulb temperature
• specific volume
• enthalpy
• dew point temp

Question 7

physical properties of air that affect the drying rate of grains

measured by the ordinary thermometer

Answer 7

dry bulb temp

Question 8

physical properties of air that affect the drying rate of grains

dry bulb temp is the horizontal lines in the chart

true or false

Answer 8

false; it’s the vertical lines

Question 9

physical properties of air that affect the drying rate of grains

air temp measured by an ordinary thermometer whose glass bulb is covered by a wet cloth or gauze

Answer 9

wet bulb temp

Question 10

physical properties of air that affect the drying rate of grains

air temp at which moisture condenses at the surface

Answer 10

dewpoint temp

Question 11

physical properties of air that affect the drying rate of grains

scale is the same as the wet bulb scale which is on the face of the shoe

Answer 11

dewpoint temp

Question 12

physical properties of air that affect the drying rate of grains

dewpoint temp are lines parallel to the x axis

true or false

Answer 12

true

Question 13

physical properties of air that affect the drying rate of grains

amount of water vapor per unit dry air

Answer 13

absolute humidity

Question 14

physical properties of air that affect the drying rate of grains

y-axis or the ordinate (the back of the shoe)

Answer 14

absolute humidity (or HR)

Question 15

physical properties of air that affect the drying rate of grains

relative humidity and dew points are at the same lines

true or false

Answer 15

false; dew point temp are the horizontal lines while RH are the lines sloping upwards

Question 16

physical properties of air that affect the drying rate of grains

lines are the same as the dew point temp lines

Answer 16

absolute humidity

Question 17

physical properties of air that affect the drying rate of grains

ratio of partial pressure of water vapor to the saturation pressure of pure water at the same temperature

Answer 17

relative humidity

Question 18

physical properties of air that affect the drying rate of grains

face of the shoe

Answer 18

relative humidity

Question 19

physical properties of air that affect the drying rate of grains

defined as the volume occupied by a kilogram of dry air

Answer 19

specific volume

Question 20

physical properties of air that affect the drying rate of grains

these are the diagonal lines having a higher slope compared to wet bulb lines

Answer 20

specific volume

Question 21

physical properties of air that affect the drying rate of grains

heat content of the air (denoted by h)

Answer 21

enthalpy

Question 22

physical properties of air that affect the drying rate of grains

it is essential in the calculation of the energy requirement of any process involving air a the medium

Answer 22

enthalpy

Question 23

_______ ______: cubic meter/kg dry air
enthalpy : ___________

Answer 23

specific volume: cubic meter/kg dry air
enthalpy : kilo Joules/kg

Question 24

psychrometric processes

Answer 24

1. sensible heating or cooling
2. humidification
   a. adiabatic humidification
   b. non adiabatic humidification
3. cooling and dehumidification
   a. moisture condensation

Question 25

psychrometric processes involves the increase or decrease in the air temp without changing its humidity ratio

Answer 25

sensible heating or cooling

Question 26

psychrometric processes sensible heating or cooling is a process that's depicted as a horizontal line in the chart extended to the _______ for sensible heating and to the _______ for cooling

Answer 26

right; left

Question 27

psychrometric processes process of adding water to the air

Answer 27

humidification

Question 28

psychrometric processes on heat exchange with surroundings, constant wet bulb temperature, dry bulb temperature decreases

Answer 28

adiabatic humidification

Question 29

psychrometric processes heat is added, net heat added is positive, dry bulb temperature can increase along with moisture content

Answer 29

non adiabatic humidification

Question 30

psychrometric processes decrease in dry bulb temp and HR

Answer 30

cooling and dehumidification

Question 31

psychrometric processes cooling and dehumidification, the total heat removed is equal to the total heat removed in the ________ ____

Answer 31

cooling coil this principles is referred as the refrigeration capacity

Question 32

psychrometric processes occurs when moist air is cooled to a temperature below its initial dew point

Answer 32

moisture condensation

Question 33

is the process where ambient air is heated to a desired drying temperature at a constant humidity and vapor pressure

Answer 33

heating

Question 34

process where the temperature of the heated air decreases during drying, approaching 100% RH and constant wet bulb temp

Answer 34

cooling

Question 35

where are psychrometric principles applied?

Answer 35

- load calculations - air-conditioning systems - cooling and dehumidifying coils - cooking towers - evaporative condensers

Question 36

component of moisture air consisting of composition of gases

Answer 36

dry-air

Question 37

component of moisture air which is a very low-pressure steam, the amount of which could vary from zero to a mac value for a given pressure and temp

Answer 37

water-vapor

Question 38

major physical properties of air that affect the drying rate of grains

Answer 38

- RH - dry-bulb temp - specific volume - enthalpy

Question 39

refers to the mole fraction of water vapor in moist air to the mole fraction of water vapor in saturated air at the same temperature and pressure

Answer 39

relative humidity

Question 40

process by which the wet-bulb thermometer cools due to water evaporation

Answer 40

evaporative cooling

Question 41

knowing both the dry-bulb and wet-bulb temperatures allows you to determine the ______ _______ of the air using a psychrometric chart

Answer 41

relative humidity

Question 42

________ ______ of the drying air affect the power required by the fan

Answer 42

specific volume

Question 43

enthalpy of the mixture of dry air and water vapour is the sum of the enthalpy of the dry air and the enthalpy of the water vapour true or false

Answer 43

true

Question 44

the zero value of the water vapour is saturated liquid water at __ degree Celsius, this is the same reference point used for steam

Answer 44

0