Table of Contents
Advertisement
Installation 1
3.2.11
Vacuum Drying
What is vacuum
Vacuum drying is:
drying?
"The use of a vacuum pump to vaporize (gasify) the moisture (liquid) inside the pipes and expel it leaving
the pipes completely dry inside."
At 1 atm (760 mmHg) the boiling point (evaporating temperature) of water is 100°C but if a vacuum is
created inside the pipes using a vacuum pump then the boiling point is rapidly reduced as the degree of the
vacuum is increased. If the boiling point is reduced to a level below that of the ambient temperature then
the moisture in the pipes will evaporate.
<Example>
When outside temperature is 72°C
As shown in the table on the right, the degree
of vacuum must be lowered below –75.2cmHg.
The evacuation of air conditioner piping provides the following effects.
1. Vacuum drying
2. Removes air and nitrogen (used in air-tightness test) from the inside of pipes.
Therfore, it is necessary to ensure that the both purposes have been achieved in the vacuum drying
operation.
48
Key points
Lower the degree of vacuum to below –755mmHg
PACD011001G2 / PACD011004G3
Boiling point
of water (°C)
∗cmHg
40
–70.5
30
–72.4
26.7
–73.5
24.4
–73.8
22.2
–74.0
20.6
–74.2
17.8
–74.5
15.0
–74.7
11.7
–75.0
→
7.2
–75.2
0
–75.5
Above figures (cmHg) are gauge pressure readings.
(V1216)
Urban Multi Inverter "MX1" Series
Pressure
Pa
Torr
7333
55
4800
36
3333
25
3066
22
2666
20
2400
18
2000
15
1733
13
1333
10
1066
8
667
5
Advertisement
Table of Contents
