Relative Humidity Relative humidity is a term used to describe the amount of wat

Question

Relative Humidity Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions. The relative humidity of air thus changes not only with respect to the absolute humidity (moisture content) but also temperature and pressure, upon which the saturated vapor pressure depends. Relative humidity is often used instead of absolute humidity in situations where the rate of water evaporation is important, as it takes into account the variation in saturated vapor pressure.

Explanation / Answer

Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. Its unit is g/m3

or The relative humidity is defined as the ratio of the partial pressure of water vapor in the mixture to the equilibrium vapor pressure of water over a flat surface of pure water at a given temperature:

Rh=e/es(T)

Absolute humidity is the measure of water vapor in the air, regardless of temperature. It is expressed as grams of moisture per cubic meter of air.

a) we KNOW RH=moisture content in air /moisture content at particulare temperature

=>85=x/18 gm/m3

So x =1530 gm/m3

Now temperature changes to 10 degree

and Rh=45%

so Rh=45=y/7.20

means y=45*7.20=324 gm/m3

so changes water content 1530-324=1206 gm/m3 absolute humidity of the outside air.

b) Volume of air initial =1525 m3 at 25 C and so what will be at 10 C

  V2/V1 = T2/T1 so V2/1525=283/298 or  1448.2 m3

c) mass of water removed per m3 =1206 gm/m3

change in volume =1525-1448.2=76.8000 m3

So total water removed=1206*76.8= 92621.0gm

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