Daikin VRV Plus Series General Information Manual page 33

Si33-003.book Page 29 Monday, June 25, 2001 9:06 AM
SiE33-003
3.2.6 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.
General Information
Key points
Lower the degree of vacuum to below –755mmHg
Pressure
Boiling point
∗cmHg
of water (˚C)
40 –70.5 7333
30 –72.4 4800
26.7 –73.5 3333
24.4 –73.8 3066
22.2 –74.0 2666
20.6 –74.2 2400
17.8 –74.5 2000
15.0 –74.7 1733
11.7 –75.0 1333
→
7.2 –75.2 1066
0 –75.5 667
Above figures (cmHg) are gauge pressure readings.
(V1216)
: http://splitoff.ru/tehn-doc.html
Installation
Pa Torr
55
36
25
22
20
18
15
13
10
8
5
29