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6.4 - Variable flow evaporator
Variable evaporator flow can be used as standard with
30XAV-ZE chillers. The chillers maintain a constant
leaving water temperature under all flow conditions. For
this to happen, the flow rate must be higher than the
minimum flow given in the table of permissible flow rates
and must not vary by more than 10% per minute.
If the flow rate changes more rapidly, the system should
contain a minimum of 6.5 litres of water per kW instead of
3.25 l/kW.
The flow can also be controlled by the unit through option
299 : Variable Water Flow Control. This option allows the
unit to control an external pump in order to maintain a
constant inlet/outlet temperature difference, a constant
outlet pressure or an unoccupied mode.
6.5 - system minimum water volume
Whichever the system, the water loop minimum capacity is
given by the formula:
Capacity = Cap (kW) x N litres
application
Normal air conditioning
Process type cooling
Where Cap is the nominal system cooling capacity (kW) at
the nominal operating conditions of the installation.
This volume is necessary for stable operation and accurate
temperature control.
It is often necessary to add a buffer water tank to the circuit
in order to achieve the required volume. The tank must
itself be internally baffled in order to ensure proper mixing
of the liquid (water or brine). Refer to the examples below.
6.7 - Evaporator pressure drop curve
40
30
20
10
22
n
3.25
6.5
sizes 401 to 901
0
10
20
30
40
50
Water flow rate, l/s
note: Standard evaporator and coolant = water
6.6 - evaporator water flow rate
30XaV-ZE
401
501
551
651
701
851
901
*
Standard evaporator and coolant = water
3
4
651
501-551
401
60
70
80
90
100
Water flow rate, L/s
Connection to a buffer tank
Bad
Mauvais
Bad
Mauvais
evaporator water flow rate, l/s*
dual pass
Minimum
Maximum
7.1
51.5
8.9
63.1
8.9
63.1
11.2
73.1
12.4
82.2
13.1
93.9
15.4
95.5
5
6
7
701
851
901
legend:
1
401
2
501
3
551
4
651
5
701
6
851
7
901
110
120
130
good
Bon
good
Bon
single pass
Minimum
Maximum
17
57.6
21
69.1
21
80.6
25.5
92.1
28.3
109.4
31.1
120.9
34.2
132.5
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