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6 - APPLICATION DATA
6.4 - Variable flow evaporator
Variable evaporator flow can be used in standard 30XAS chillers.
The chillers maintain a constant leaving water tem-perature under
all flow conditions. For this to happen, the minimum 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.
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.
Connection to a buffer tank
Bad
Bad
N
3,25
6,5
Good
Good
6.6 - Maximum system water volume
Units with hydraulic module incorporate an expansion tank that
limits the water volume. The table below gives the maximum loop
volume for pure water or ethylene glycol with various system
concentrations, as well as the static pressures. If the maximum
volume is insufficient, compared to the minimum system water
loop volume, an additional expansion tank must be added to the
system.
30XAS
Static pressure
Maximum water loop volume
Pure water
Ethylene glycol 10%
Ethylene glycol 20%
Ethylene glycol 30%
Ethylene glycol 40%
6.7 - Evaporator water flow rate
Evaporator water flow rate, l/s
30XAS
Min, flow rate
242
3,2
282
3,7
342
4,4
442
5,8
482
6,5
(1) The maximum water flow rate corresponds to a pressure drop of 100 kPa.
6.8 - Evaporator pressure drop curve
Legend
1
30XAS 242-342
2
30XAS 442-482
242-482
bar
1
l
2400
1800
1320
1080
900
Max, flow rate
30,7
30,7
30,7
41,0
41,0
Water flow rate, l/s
2
1600
1200
880
720
600
(1)
19
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