Vapor pressure, mixing ratio, and the concept of saturation help us to understan

Question

Vapor pressure, mixing ratio, and the concept of saturation help us to understand a much more commonly used measure of moisture-relative humidity. Remember that a point on the saturation vapor pressure curve represents the vapor pressure that saturated air would exert, and a point on the saturation muting ratio curve show s the mass of water vapor for a saturated sample. Since the atmosphere typically is not saturated, relative humidity (RH) measures how close an air sample is to the saturation point Specifically, relative humidity is the ratio of the actual amount of water vapor in the air to the saturation level at a given temperature In terms of vapor pressure: RH = vapour pressure/saturation vapor pressure - 100% In terms of mixing ratio: RH = mixing ratio/saturation mixing ratio - 100% Consider a sample of air with a temperature of 20 degree C and a mixing ratio of 10 g kg^-1. The saturation mixing ratio of the sample (derived from Table 5-2) is 14.956 g kg^-1 Thus, we have: RH = [mixing ratio/saturation mixing ratio] - 1.00% = [10 g kg^-1/14.956 g kg^-1] * 100% = 66.8% Determine the saturation mixing ratio of the following air samples, and calculate the relative humidity of each. In the winter, cold air is brought into homes and heated. How does this change the relative humidity of the air? Explain why the basement of a house often has high relative humidity In the summer. Rank each of the following air samples from l (highest) to 5 (lowest) in order of water vapor content. (From the above example, can you suggest one disadvantage to using relative humidity?

Explanation / Answer

ANS 14: Saturation mixing ratio and relative humidity of air samples:

In terms of mixing ratio,

Relative humidity = (mixing ratio / saturation mixing ratio) *100

Saturation mixing ratio is determined by the air temperature . Higher the air temperature, greater the saturation mixing ratio. There is a pre-computed table of saturation mixing ratio at various temperatures which is used to solve such problems.

so using that table( from internet), we get to know that

so using the above data we can compute Relative Humidity(RH):

i) T= 14 0C , mixing ratio (U) =5, Saturation mixing ratio(Us) = 10.14

RH = (Mixing ratio/ saturation mixing ratio) * 100

Therefore , RH =5/ 10.14 * 100 = 49.30%

ii) T= 14 0 C , U = 9 , Us = 10.14

RH = 9/ 10.14 * 100 = 88.75 %

iii) T= 240C , U= 5 , Us = 19.21

RH= 5/ 19.21 * 100 = 26.02 %

iv) T=24 0 C, U= 2 , Us =19.21

RH = 2/ 19.21 * 100 = 10.41%

v) T= 34 0C, U =7 , Us = 35.134

RH = 7/35.134 * 100 = 19.9%

so the final answer table is:

19.9 %

b) Relative humidity is a measure of amount of moisture in the air compared to the maximum amount of moisture in the air could be.

Now when in the winter cold air is brought into the homes and is heated, heating decreases the humidity in the home compared to outside and when air is heated the difference b/w temperature and dew point increase dramatically as dew point reamain the same but the temperature of air increases. since the amount of moisture is same in inside air and outside air but inside air will b much drier dure to higher rate of evaporation .

Relative humidity = (mixing ratio / saturation mixing ratio) *100

Related Questions

Navigate

• Browse (All)
• Browse V
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.