24 TRG-TRC010-EN
notes
period three
Compressor Capacity Control
refrigerant. Recall that kinetic energy is converted to static energy, or static
pressure.
The radial velocity (V
r
) for a given compressor is directly proportional (∝) to the
flow rate of refrigerant vapor through the compressor.
The tangential velocity (V
t
) is proportional to the product of impeller rotational
speed and impeller diameter.
Therefore, the static-pressure-producing capacity of a compressor can be
adjusted by changing the flow rate of refrigerant, the impeller speed, or the
diameter of the impeller.
Impeller Dynamics
diameter
diameter
V
V
r
r
∝
refrigerant flow rate
refrigerant flow rate
V
V
t
t
∝
rotational speed × diameter
rotational speed × diameter
rotational
rotational
speed
speed
V
V
r
r
R
R
V
V
t
t
refrigerant
refrigerant
flow rate
flow rate
Figure 35
trgtrc010_book.book Page 24 Wednesday, September 1, 1999 10:39 AM
