Variable Flow Evaporator; System Minimum Water Volume; Evaporator Water Flow Rate; Evaporator Pressure Drop Curve - Carrier AquaForce 30XAV 500 Installation, Operation And Maintenance Instructions

6.4 - Variable flow evaporator

Variable evaporator flow can be used as standard with
30XAV 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

N
3.25
6.5
One pass Evaporator pressure drop curves (option 100C)
40
30
20
10
0
10 20 30 40 50
Note: Standard evaporator and coolant = water

6.6 - Evaporator water flow rate

30XAV
500
600
700
800
950
1050
1150
* Standard evaporator and coolant = water
Sizes 500 to 1150
3
4
800
600-700
500
60 70 80 90 100
Water flow rate, L/s
Water flow rate, L/s
Connection to a buffer tank
Bad
Bad
Good
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
950
1050
1150
Legend:
1 500
2 600
3 700
4 800
5 950
6 1050
7 1150
110 120 130
Good
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
21