Sound and vibration management
Running sound level
Sound generation in a
refrigeration system / air
conditioning system
Compressor sound
radiation
Danfoss Heat Pump scroll compressors are
designed with optimised discharge ports and
wrap geometry to reduce the sound level
when a compressor is running.
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 Danfoss Heat Pump 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’s unique design of a full-
suction gas & oil cooled motor, compressor body
insulation across its entire operating range is
possible.
Model
Code 4
Code 5
Sound power (dBA)
Without jacket
Sound power (dBA)
With jacket
Sound power (dBA)
Without jacket
Sound power (dBA)
With jacket
HHP015
70
62
70
62
HHP019
70
62
70
62
HHP021
71
63
71
63
HHP026
71
63
71
63
HHP030
72
64
72
64
HHP038
72
64
72
64
HHP045
73
65
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-
Mechanical vibrations
Vibration isolation constitutes the primary method
for controlling structural vibration. Danfoss Heat
Pump scroll compressors are designed to produce
minimal vibration during operations. The use of
rubber isolators on the compressor base plate or
on the frame of a manifolded unit is very effective
in reducing vibration being transmitted from
the compressor(s) to the unit. Rubber grommets
are supplied with all Danfoss compressors.
Once the supplied rubber grommets have been
properly mounted, vibration transmitted from
the compressor base plate to the unit are held
to a strict minimum. In addition, it is extremely
important that the frame supporting the mounted
compressor be of sufficient mass and stiffness to
help dampen any residual vibration potentially
transmitted to the frame. The tubing should be
designed so as to both reduce the transmission
of vibrations to other structures and withstand
vibration without incurring any damage. Tubing
should also be designed for three-dimensional
flexibility. For more information on piping design,
please see the section entitled "Essential piping
design considerations".
Gas pulsation
The Danfoss Heat Pump scroll compressors
have been designed and tested to ensure that
gas pulsation has been optimised for the most
commonly encountered pressure ratio. On heat
pump installations and other installations where
the pressure ratio lies beyond the typical range,
testing should be conducted under all expected
conditions and operating configurations to
ensure that minimum gas pulsation is present. If
an unacceptable level is identified, a discharge
muffler with the appropriate resonant volume and
mass should be installed. This information can be
obtained from the component manufacturer.
23
FRCC.PC.017.A2.02
Application Guidelines
