How to calculate the amount of condensed water
Example) To obtain the amount of condensed water
when the inlet air of a compressor is pressuri-
sed to 0.7 MPa then cooled down to 25
°
C.
Given an ambient temperature of 30
°
C and a
relative humidity of 60%.
1. Trace the arrow mark from point A of ambient tem-
perature 30
°
C to obtain the intersection B on the
curved line for the relative humidity of 60%.
2. Trace the arrow mark from the intersection B to
obtain the intersection D on the curved line for the
0.7 MPa pressure characteristics.
3. Trace the intersection D to obtain the intersection
E.
4. The intersection E is the pressure dew point at 0.7
MPa with an ambient temperature of 30
°
C and a
relative humidity of 60%. The value for E is at
62
°
C.
5. Trace the intersection E upward to D and leftward
to obtain the intersection C on the vertical line.
6. The intersection C is the amount of water which is
included in the compressed air 1 m
3
at 0.7 MPa, a
pressure dew point of 62
°
C. The amount of water
is 18.2 g/m
3
.
7. Trace the arrow mark from F (cooling temperature
25
°
C (pressure dew point 25
°
C)) to obtain the in-
tersection G on the pressure characteristic line for
0.7 MPa.
8. From the intersection G, trace the arrow mark to
obtain the intersection H on the vertical line.
9. The intersection H is the amount of water which is
included in the compressed air 1 m
3
at 0.7 MPa,
pressure dew point of 25
°
C. The amount of water
is 3.0 g/m
3
.
10. Therefore, the amount of condensed water is as
following. (per 1 m
3
)
The amount of water at the intersection C
– the amount of water at the intersection H
= the amount of condensed water
18.2 – 3.0 = 15.2 g/m
3
How to read the dew point conversion chart
Example) To obtain the atmospheric dew point at a pressure dew point of
10
°
C, and a pressure of 0.7 MPa.
1. Trace the arrow mark from point A at a pressure dew point of 10
°
C
to obtain the intersection B on the pressure characteristic line for
0.7 MPa.
2. Trace the arrow mark from point B to obtain the intersection C on
the atmospheric pressure dew point.
3. The intersection C is the conversion value –17
°
C under atmosphe-
ric pressure dew point.
Dew Point Conversion Chart
Condensed Water Calculation
Atmospheric pressure dew point (
°
C)
Pressure dew point (
°
C)
0
10
20
30
40
50
60
–60
–50
–60
–50
–40
–30
–40
–30
–20
–10
–20
–10
0
10
20
30
A
C
B
Ambient temperature (Air compressor intake air temperature) (
°
C)
–20
–10
0
10
20
30
40
50
60
Relative humidity
100
%
80
%
60
%
40
%
20
%
A
B
0.2
Amount of condensed water
C–H
18.2 - 3.0 = 15.2 g /m
3
Pressure dew point (
°
C)
0
10
20
30
40
50
60
70
80
45
40
35
30
25
20
15
10
5
0
E
H
Amount of water in air (g
/m
3
)
0.3
0.4 0.5
0.6
0.7 0.8
1.6
1.0
1.4
0.1 M
Pa
C
G
F
D
Data
Atm
ospheric pressure
1.5 MPa
1.3 MPa
1.1 MPa
0.9 MPa
0.7 MPa
0.5 MPa
0.3 MPa
0.1 MPa
Atmospheric
pressure
13
