Saturation Vapor Pressure

Satisfactory Essays

Saturation vapor pressure is a unique function of temperature as given in Table 5.6. Each temperature in the table may be interpreted as a dew point temperature, because as the ground cools, dew will begin to form at the temperature corresponding to the vapor pressure.

Table 5.6: Saturated Vapor Pressure of Air at Various Temperature
(C) Temp (F) | Sat Vapor Pressure (mb) | (C) Temp (F) | Sat Vapor Pressure (mb)
-18
-15
-12
-09
-07
-04
-01
02
04
07
10
13
16 00
05
10
15
20
25
30
35
40
45
50
55
60 1.5
1.9
2.4
3.0
3.7
4.6
5.6
6.9
8.4
10.2
12.3
14.8
17.7 |
|
|
|
|
|
|
|
|
|
|
|
| 18
21
24
27
29
32
35
38
41
43
46
49
52 65
70
75
80
85
90
95
100
105
110
115
120
125 21.0
25.0
29.6
35.0
41.0
48.1
56.2
65.6
76.2
87.8
101.4
116.8
134.2

5.4.4 Absolute saturation (humidity) or percentage saturation (humidity)
This is define as the ratio of the number of moles of vapor per number of moles of vapor-free gas to the number of moles of vapor that would be present per mole of vapor-free gas if the mixture were completely saturated at a given temperature and total pressure.

Absolute Saturation (AS)=((number of moles of vapor)/(number of moles of vapor-free gas ))_actual/((number of moles of vapor)/(number of moles of vapor-free gas ))_saturated … (5.34)

Let subscripts 1 and 2 represent vapor and vapor-free gas respectively, then we have:

Percentage Absolute Saturation=(n_1/(n_2 ))_actual/(n_1/(n_2 ))_saturated ×100=(p_1/(p_2 ))_actual/(p_1/(p_2 ))_saturated ×100 … (5.35)

Let p1 saturated be represented by p_1^* or p_t=p_1+p_2 so that:

% AS=((p_1/(p_t-p_1 )))/(((p_1^*)/(p_t-p_1^* )) )×100=p_1/(p_1^* ) ((p_t-p_1^*)/(p_t-p_1 ))×100 … …show more content…

(5.37). Figure 5.5 show the relationships between relative humidity, wet and dry