Lesson 4

Question 1

It is the study of the properties of air, and use of the psychrometric
chart are essential for an understanding of the processes involved in
drying and storage of grains and other agricultural crops, and for analyzing individual requirements for a particular climatic condition.

Answer 1

Psychometrics

Question 2

It is the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures.

Answer 2

Psychometrics

Question 3

A state of matter that is liquid at its core, but it is in a gaseous state. It has a lower temperature than gas.

Answer 3

Vapor

Question 4

A gaseous state
throughout.

Answer 4

Gas

Question 5

What is the main difference between vapor and gas?

Answer 5

Temperature

Question 6

Process 0-1

Answer 6

Sensible Heating

Question 7

Process 0– 2

Answer 7

Sensible cooling

Question 8

Process 0– 3

Answer 8

Humidifying

Question 9

Process 0– 4

Answer 9

Dehumidifying

Question 10

Process 0– 5

Answer 10

Heating and Humidifying

Question 11

Process 0– 6

Answer 11

Cooling and Dehumidifying

Question 12

Process 0– 7

Answer 12

Cooling and Humidifying

Question 13

Process 0–8

Answer 13

Heating and Dehumidifying

Question 14

A mechanical mixture of gases and
water vapor.

Answer 14

Air

Question 15

Types of air

Answer 15

Dry air
Moist air
Saturated air

Question 16

What is the relative molecular mass of all components
for dry air?

Answer 16

28.9645 g/mol

Question 17

Mixture of various gases in the absence of water vapour.

Answer 17

Dry Air

Question 18

The mixture of dry air and water vapour. The amount of water present in air depends on the pressure and temperature of the mixture.

Answer 18

Moist Air

Question 19

The mixture of dry air and water vapour when air has diffused maximum amount of water vapour into it.

Answer 19

Saturated Air

Question 20

When condensation and evaporation are
equal, this is called?

Answer 20

Saturation

Question 21

Also called Specific Humidity. The ratio of the weight of water vapor to the weight of completely dried air. It is the weight of the water vapor contained in the moist air per unit weight of dry air. Other term used for this is absolute humidity. Expressed as pound per pound or kg/kg or no unit.

Answer 21

Humidity Ratio

Question 22

A measure of its fractional saturation with moisture. It is defined as the ratio of the partial pressure of water vapor to the saturated vapor pressure.

Answer 22

Relative Humidity, %

Question 23

Temperature indicated by a thermometer which is unaffected by moisture or radiation. It is the temperature of the air as measured using an ordinary thermometer, such as a household thermometer. The bulb is the sensitive portion of the instrument. As the temperature of the bulb increases, the liquid in the bulb expands and rises in the stem (thermal expansion).

Answer 23

Dry Bulb Temperature

Question 24

Temperature of the air measured by a mercury thermometer whose glass bulb is covered by a wick or wet cloth or gauze. The clean cotton wick absorbs water. Also, and the airflow passing over the wick at least 5 m/s. Evaporation of this water reduces the temperature of the wick, and the resultant temperature is indicated by the mercury in the thermometer stem.

Answer 24

Wet Bulb Temperature

Question 25

Temperature of air at which water vapor in air starts condensing when the air is cooled at constant humidity and constant atmospheric pressure. It is the temperature at which moisture condenses on the surface.

Answer 25

Dew Point Temperature

Question 26

Defined as the total volume of 1 KG of dry air and its accompanying water vapor. The specific volume of moist air is defined as the volume per unit mass of dry air.(v = V/Mda). The specific density (kg/m3) of the moist air is equal to the reciprocal of its specific volume. It is expressed as (m3/kg).

Answer 26

Specific Volume

Question 27

The enthalpy of a dry-air-water-vapor mixture is the heat content of the moist air per unit weight of dry air above a certain reference temperature. The unit of measurement for enthalpy is thejoule. It is also the sum of internal energy and pressure times volume. (h = U + PV)

Answer 27

Enthalpy

Question 28

The unit of measurement used to determine the amount of moisture in the air; 7000 grains equal 1lb (0.45 kg) of water. This can be determined from any of the following combinations: dry-bulb temperature and relative humidity (RH); dry-bulb temperature and dewpoint; wet-bulb temperature and relative humidity; wet-bulb temperature and dewpoint; dry-bulb and wet-bulb temperatures; or dewpoint alone.

Answer 28

Grains of Moisture

Question 29

The chart used to find out the thermodynamic properties of moist air at one temperature. This chart is a device that simplifies the measurement of air properties and eliminates many time consuming and tedious calculations that would otherwise be necessary.

Answer 29

Psychrometric Chart

Question 30

A graphic presentation of the conditions or properties of air, such as temperature, humidity, and dewpoint.

Answer 30

Psychrometric Chart