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TRG-TRC010-EN 27
period three
Compressor Capacity Control
notes
conditions that cause the compressor to surge. Any operating point that falls to
the right of this line is satisfactory for stable operation.
To balance the load on the chiller, the compressor must pump a certain quantity
of refrigerant vapor at evaporator pressure and elevate it to the pressure
dictated by the condensing conditions.
The intersection of the refrigerant flow rate and the pressure difference
between the inlet and outlet of the compressor identifies the compressor
operating point.
Superimposing the operating point on the previous compressor performance
curves establishes the point at which the compressor will balance the load. In
this example, the compressor will balance the load with its inlet vanes open
90°.
Operating Point
pressure difference
pressure difference
refrigerant flow rate
refrigerant flow rate
operating
operating
point
point
Figure 39
compressor map for a
2-Stage Compressor
25
25
75
75
10
10
14
14
63
63
pressure difference
pressure difference
refrigerant flow rate
refrigerant flow rate
s
u
r
g
e
s
u
r
g
e
90
90
36
36
51
51
operating
operating
point
point
vane position
vane position
(degrees)
(degrees)
Figure 40
trgtrc010_book.book Page 27 Wednesday, September 1, 1999 10:39 AM