Unit 27 - Chapter 125

Question 0

Dalton’s law of partial pressure states that

Answer 0

In a mixture of two or more gases each will exert a partial pressure which is equal to the pressure that it would exert if it filled that space alone

Question 1

Air is what composition by volume?

Answer 1

79% nitrogen and 21% oxygen

Question 2

Relative humidity is

Answer 2

The ratio if water vapour in the air compared to the total amount water vapour the air could contain at a given temperature

Question 3

The dew point is the

Answer 3

Temperature below which water vapour will start to condense out of the air

Question 4

The volume of standard air is

Answer 4

0.833 kg/cubic meters of dry air

Question 5

The heat content of air is called the

Answer 5

Enthalpy of the air

Question 6

Psychrometry is

Answer 6

The study of behaviour of mixtures of air and water

Question 7

The composition of pure dry air is

Answer 7

23.2% oxygen and 76.8% nitrogen by weight

Question 8

Air conditioning involves

Answer 8

The control of the air temperature, the control of humidity, air circulation, an the removal of contaminants

Question 9

The term relative humidity applies to

Answer 9

The percentage of moisture in the air compared to the amount of moisture the air can hold at a specific temperature

Question 10

A device for measuring relative humidity is called

Answer 10

A psychrometer

Question 11

The difference between the wet and dry bulb readings is called the

Answer 11

Wet bulb depression

Question 12

Which law describes the existence of moisture in the air in vapour or evaporated state?

Answer 12

Dalton’s law of partial pressure

Question 13

Absolute or specific humidity is

Answer 13

The actual mass of moisture present in a specific amount of air

Question 14

Relative humidity is

Answer 14

The ratio of the mass of moisture contained in a specific amount of air to the maximum amount of moisture this specific amount of air can contain

Question 15

Dew point can best be described as

Answer 15

The temperature at which air, upon cooling, becomes saturated and will begin to condense out water vapour below this temperature

Question 16

Dry bulb temp is

Answer 16

The temp of air measured with an ordinary thermometer

Question 17

Wet bulb temp is

Answer 17

The temperature indicated by a thermometer having its bulb covered by a water wetted wick or cloth and the wet bulb is exposed to a rapidly moving stream of air

Question 18

What is wet bulb depression?

Answer 18

Difference between dry bulb and wet bulb temperature

Question 19

Psychrometers are

Answer 19

Instruments used to determine relative humidity of air

Question 20

Which of the following instruments use a battery operated fan to draw air over the thermometer bulbs?

Answer 20

Aspiring psychrometer

Question 21

The specific volume of air is

Answer 21

The volume of 1 kg of air at atmospheric pressure expressed in cubic meters

Question 22

Standard air is

Answer 22

The volume of 1 kg of dry air at 21 degrees and at atmospheric pressure

Question 23

Enthalpy of air depends on

Answer 23

Pressure, temp, and relative humidity of air

Question 24

To find various properties of air

Answer 24

Use a psychrometric chart

Question 25

Enthalpy of air is measured in

Answer 25

KJ/kg of dry air

Question 26

The dry bulb temp scale is read in a psychrometric chart

Answer 26

Along the horizontal axis on the bottom of the chart

Question 27

The wet bulb temp scale is read in a psychrometric chart

Answer 27

Along the saturation line and slope downward to the right

Question 28

The dewpoint temp scale is read in a psychrometric chart

Answer 28

Along the horizontal line, same scale as wet bulb temperature but plotted along horizontal lines

Question 29

Relative humidity is read in a psychrometric chart

Answer 29

On lines curved upwards from the lower left to the right side of the chart

Question 30

Specific humidity is

Answer 30

The actual moisture content of air expressed as kg of moisture per kg of dry air

Question 31

Specific humidity scale is read in a psychrometric chart

Answer 31

Along the vertical axis of the chart and right side of chart

Question 32

Specific volume is read in a psychrometric chart

Answer 32

Has its lines originate on the volume scale along the horizontal axis and they slope steeply upwards to the left of the chart

Question 33

Enthalpy values are found on a psychrometric chart by

Answer 33

Plotting a line through the required point on the chart parallel to the lines of the two Enthalpy scales scales, one on the left side and one on the right side of the chart