Application Guidelines
18
AB141686422149en-US0401
Sound and vibration management
Running sound level
Stopping sound level
Sound generation in a
refrigeration system and air
conditioning system
Compressor sound radiation
During start-up transients, it is natural for the
compressor sound level to be slightly higher
than during normal running. Danfoss scroll
compressors exhibit very little increased start-up
transient sound.
VRJ scroll compressors are designed with
optimised discharge ports and wrap geometry
to reduce the sound level when a compressor is
running.
VRJ scroll compressors have very low shutdown
sound due to minimal volume of discharge
volume to push scrolls in reverse at shutdown.
Due to this small re-expansion, there is no
internal break mechanism required to prevent
reverse spin of the scroll set.
Typical sound and vibration in refrigeration and
air conditioning systems encountered by design
and service engineers may be broken down into
the following three source categories.
Sound radiation:
This generally takes an
airborne path.
Mechanical vibrations:
These generally extend
along the parts of the unit and structure.
Gas pulsation:
This tends to travel through the
cooling medium, i.e. the refrigerant.
The following sections will focus on the causes
and methods of mitigation for each of the above
sources.
For sound radiating from the compressor, the
emission path is airborne and the sound waves
are travelling directly from the machine in all
directions.
The VRJ scroll compressor is designed to be quiet
and the frequency of the sound generated is
pushed into the higher ranges, which not only
are easier to reduce but also do not generate the
penetrating power of lower-frequency sound.
Use of sound-insulation materials on the inside of
unit panels is an effective means of substantially
reducing the sound being transmitted to the
outside. Ensure that no components capable
of transmitting sound/vibration within the unit
come into direct contact with any non-insulated
parts on the walls of the unit.
Because of the Danfoss unique design of a full-
suction gas & oil cooled motor, compressor body
insulation across its entire operating range is
possible.
Starting sound level
Sound level vs Speed
56
58
60
62
64
66
68
70
72
74
76
78
45/130
4200
45/130
3600
45/100
3600
45/100
2400
45/100
1800
45/100
900
Condition (Tsat(suction) / Tsat (discharge) and speed (RPM)
S
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Summary of Contents for VRJ
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