42
6.4 - Variable flow evaporator
Variable evaporator flow can be used in standard 30XB chillers.
The chillers maintain a constant leaving water temperature 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
N
Normal air conditioning
3,25
Process type cooling
6,5
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
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.
30XB & XBP
Sizes 250 to 450
500
Static pressure
bar
1
2
2,5
1
2
2,5
Pure water
l
2400 1600 1200 3960 2640 1980
10% EG
l
1800 1200
900
2940 1960 1470
20% EG
l
1320 880
660
2100 1400 1050
30% EG
l
1080 720
540
1740 1160 870
40% EG
l
900
600
450
1500 1000 750
EG :
Ethylene Glycol
6.7 - Evaporator water flow rate
30XB & 30XBP
Minimum flow rate
(1)
(l/s) Maximum flow rate
(2)
(l/s)
250
3,6
37,5
300
4,0
40,5
350
4,3
40,5
400
5,3
34,1
450
6,0
36,9
500
6,7
42,0
600
8,1
45,0
700
8,9
56,1
750
9,6
59,1
800
10,4
67,1
850
11,0
67,1
900
11,8
73,9
1000
13,1
83,9
1100
15,1
87,8
1200
16,4
126,5
1300
17,5
92,9
1400
16,4
132,1
1500
18,8
107,4
1550
19,9
109,4
1700
22,0
107,4
(1) Minimum flow rate for maximum allowable water temperature difference conditions
(10K) under Eurovent conditions
(2) Maximum flow rate for a pressure drop of 100 kPa in the exchanger”
6 - APPLICATION DATA
Summary of Contents for AquaForce 30XB series
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