Assignment 3

From Table 14.2 and Figure 14.5, match the water vapor content at saturation of a kilogram of air with each of the following temperatures.

40^oC - 47 g/kg

68^oF - 14 g/kg

0^oC - 3.5 g/kg

-20^oC - 0.75 g/kg

From Table 14.2, raising the air temperature of a kilogram of air 5^oC, from 10^oC to 15^oC, ________ the amount of water vapor needed for saturation by _____ grams.

Increases / 3

Raising the air temperature of a kilogram of air 5^oC, from 35^oC to 40^oC, ______ the amount of water vapor needed for saturation by ____ grams.

Increases / 12

_________ temperatures require ________ water vapor for saturation.

Higher / more

For an air temperature of 15^oC, match the following relative humidity values with the appropriate water vapor content

20% - 2 g/kg

50% - 5 g/kg

70% - 7 g/kg

If the temperature remains constant, adding water vapor will _____ the relative humidity, while removing water vapor will ______ the relative humidity.

raise / lower

Assuming a constant water vapor content of 5 g/kg, match each of the following air temperatures with the corresponding relative humidity.

25^oC - 25%

15^oC - 50%

5^oC - 100%

If the amount of water vapor in the air remains constant, cooling will _________ the relative humidity while warming will _______ the relative humidity

raise / lower

Heating a home during winter _____ the relative humidity inside the home.

Lowers

What can be done to lessen the effect of changing relative humidity resulting from heating a home during the winter?

Use a humidifier to add water vapor to the air

Explain why the air in a cool basement is humid (damp) in the summer

Warmer summer air holds more water vapor: Outside air entering the basement cools and relative humidity increases

Changing the temperature and/or water vapor content of air will change the relative humidity.

True

Using Table 14.2, what is the water vapor content for summer air with a temperature of 77^oF and 40% relative humidity?

Content = 8 g/kg

Using Table 14.2, what is the water vapor content for winter air with a temperature of 41^oF and 90% relative humidity?

Content = 4.5 g/kg

Explain why relative humidity does not give an accurate indication of the actual amount of water vapor in the air.

Relative humidity is a ratio of the amount of water vapor in the air compared to the amount that the air can hold, but the latter varies with temperature

By referring to Table 14.2, what is the dew-point temperature of a kilogram of air that contains 7 grams of water vapor?

Dew Point = 10^oC

What is the relative humidity of a kilogram of 25^oC air that contains 10 grams of water vapor?

Relative humidity = 50%

What is the dew-point of a kilogram of 25^oC air that contains 10 grams of water vapor?

Dew-point temperature = 15^oC

Using Table 14.3, what is the relative humidity for psychrometer readings of Dry-bulb temperature = 20^oC and Wet-bulb temperature = 18^oC?

Relative humidity = 82%

Using Table 14.3, what is the relative humidity for psychrometer readings of Dry-bulb temperature = 32^oC and Wet-bulb temperature = 25^oC?

Relative humidity = 56%

The greater the difference in the dry-bulb and wet-bulb temperatures, the higher the relative humidity.

False

Using Table 14.4, what is the dew-point temperature for a Dry-bulb temperature = 8^oC and Wet-bulb temperature = 6^oC?

3^oC

Using Table 14.4, what is the dew-point temperature for a Dry-bulb temperature = 30^oC and Wet-bulb temperature = 24^oC?

21^oC

Referring to Table 14.2, how many grams of water vapor will condense on a surface if a kilogram of 50^oF air with a relative humidity of 100% is cooled to 41^oF?

2 grams

Assume a kilogram of 25^oC air that contains 10 grams of water vapor. Using Table 14.2, how many grams of water will condense if the air's temperature is lowered to 5^oC?

5 grams

Assume a kilogram of 25^oC air that contains 10 grams of water vapor. Using Table 14.2, how many grams of water will condense if the air's temperature is lowered to -10^oC?

8 grams