User Manual

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Siemens Modulating refrigerant valves, PN 63 CE2N4717en
Smart Infrastructure 2019-11-25
Use of the MVS661..N as an expansion valve
Observe engineering notes page 7
• Typical control range 20...100 %.
• Increased capacity through better use of the evaporator
• The use of 2 or more compressors or compressor stages significantly increases
efficiency with low loads
• Especially suitable for fluctuating condensing and evaporating pressures
40153A
1
2
4
3
1 = MVS661..N
2 = evaporator
3 = compressor
4 = condenser
Electronic superheat control is achieved by using additional control equipment (e.g.
PolyCool).
Refrigerant R717C; Q
0
= 205 kW; t
o
= -5 °C; t
c
= 35 °C
The correct k
vs
value for the MVS661..N valve needs to be determined.
The important section of table KE for R717 is the area around the working point. The
correction factor KE relevant to the working point should be determined by linear inter-
polation from the 4 guide values.
In practice, the KE, KH or KS value can be estimated because the theoretical k
vs
-value
ascertained will be rounded off by up to 30 % to 1 of the 10 available k
vs
-values. So you
can proceed directly with Step 4.
Step 1: For t
c
= 35 °C, calculate the value for t
o
= -10 °C between values 20 °C and
40 °C in the table; result: 574
Step 2: For t
c
= 35 °C, calculate the value for t
o
= 0 °C between values 20 °C and 40
°C in the table; result: 553
Step 3: For t
o
= -5 °C, calculate the value for t
c
= 35 °C between correction factors
574 and 553; calculated in steps 1 and 2; result: 450
Step 4: Calculate the theoretical k
vs
value; result: 0.46 m
3
/h
Step 5: Select the valve; the valve closest to the theoretical k
vs
value is the
MVS661.25-0.4N
Step 6: Check that the theoretical k
vs
value is greater than 50 % of nominal k
vs
value
KE
R717C t
o
= –10 °C t
o
= 0 °C Interpolation at t
c
= 35 °C
t
c
= 20 °C
481
376
481 + [(605 - 481) x (35 - 20) / (40 - 20)]
574
t
c
= 35 °C
574
553
t
c
= 40 °C
605
612
376 + [(612 - 376) x (35 - 20) / (40 - 20)]
553
Interpolation at
t
o
= -5 °C
574 +[(553 - 574) x (-5 - 0) / (-10 - 0)]
450
k
vs
theoretical = 205 kW / 450 = 0.46 m
3
/h
Valve MVS661.25-0.4N is suitable, since: 0.46 m
3
/h / 0.4 m
3
/h x 100 % = 115 % (> 50 %)
a) Refrigerant valve MVS661..N for capacity control of a dry expansion evaporator.
4717Z07
+
-
MVS661..N
Suction pressure and temperature are moni-
tored with a mechanical capacity controller
and reinjection valve.
• Typical control range 0...100 %
• Energy-efficient operation with low loads
• Ideal control of temperature and dehumidi-
fication
Note
Capacity optimization
Application example
Note on interpolation
Capacity control