14
Water heat exchanger pressure drop curves,
standard units
Pr
essur
e dr
op, kPa
Water flow rate l/s
legend
1
30RQ 262-302
2
30RQ 342
3
30RQ 372-522
6.4 - variable flow water heat exchanger
Variable water heat exchanger flow can be used in standard
heat pumps. 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 2.5 l/kW.
6.5 - Minimum system 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
2.5
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.
It can be 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.
6.6 - Maximum system water volume
Units with hydronic 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.
Maximum water loop volume, litres
30RQ
262
302-522
static pressure
bar 1
2
2.5
1
2
2.5
Pure water
2400 1600 1200 3960 2640 1980
EG 10%
1800 1200 900
2940 1960 1470
EG 20%
1320 880
660
2100 1400 1050
EG 30%
1080 720
540
1740 1160 870
EG 40%
900
600
450
1500 1000 750
EG - Ethylene glycol
6.7 - Water heat exchanger flow rate
30RQ
Water flow rate, l/s
Minimum
Maximum*
262
3.5
26.7
302
3.9
26.7
342
4.4
29.4
372
4.9
31.1
402
5.2
31.1
432
5.8
31.1
462
6.1
31.1
522
6.9
31.1
*
The maximum flow rate corresponds to a pressure loss of 100 kPa (heat
exchanger without hydronic module).
Bad
Good
Connection to a buffer tank
Bad
Good
10
100
10
20
30
40
20
30
40
50
60
70
80
90
3
