Variable Flow Evaporator; System Minimum Water Volume; Maximum System Water Volume; Evaporator Water Flow Rate - Carrier AquaForce 30XB series Installation, Operation And Maintenance Instructions

6 - APPLICATION DATA
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
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
42
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.
30XB & XBP
Static pressure
Pure water
10% EG
20% EG
30% EG
40% EG
EG : Ethylene Glycol
6.7 - Evaporator water flow rate
30XB & 30XBP Minimum flow rate
250
300
350
400
450
500
600
700
750
800
850
900
1000
1100
1200
1300
1400
1500
1550
1700
(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"
Sizes 250 to 450
bar 1 2 2,5 1
l 2400 1600 1200 3960 2640 1980
l 1800 1200 900 2940 1960 1470
l 1320 880 660 2100 1400 1050
l 1080 720 540 1740 1160
l 900 600 450 1500 1000
(1)
(l/s) Maximum flow rate
3,6 37,5
4,0 40,5
4,3 40,5
5,3 34,1
6,0 36,9
6,7 42,0
8,1 45,0
8,9 56,1
9,6 59,1
10,4 67,1
11,0 67,1
11,8 73,9
13,1 83,9
15,1 87,8
16,4 126,5
17,5 92,9
16,4 132,1
18,8 107,4
19,9 109,4
22,0 107,4
500
2 2,5
870
750
(2)
(l/s)