Operating Range Bw10; Minimum Chilled Water Flow; Maximum Chilled Water Flow; Variable Flow - Danfoss BW10 020-090 Installation, Operation And Maintenance Instructions

5.2 - Operating range BW10

65
60
55
50
Option 272
45
40
35
30
25
20
15
-8 -6 -4 -2 0 2
Evaporator leaving water temperature, °C
BW10 standard unit
BW10 unit with option 272 (brine to water)

5.4 - Minimum chilled water flow

If the system water flow rate is lower than the minimum water
flow rate, recirculation of the evaporator flow may occur. The
temperature of the mixture leaving the evaporator must never be
less than 2.5 K lower than the chilled water entering
temperature.

5.5 - Maximum chilled water flow

The maximum chilled water flow is limited by the maximum
permitted pressure drop in the evaporator. It is provided in the
tables in chapter 5.7. If the flow exceeds the maximum value,
two solutions are possible:
• Modify the flow rate with a control valve.
• Bypass the evaporator to obtain a highter temperature
difference with a lower evaporator flow rate.

5.6 - Variable flow

A pump with variable flow can be used in these units. The units
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 the
values below.

5.7 - Water flow rate

5.7.1 - Standard BW10
BW10 Evaporator water flow rate, l/s
Minimum* Minimum** Maximum***
Low High
pressure pressure
020 1.1 0.9 0.4
025 1.0 1.0 0.4
030 1.0 1.0 0.5
035 1.1 1.1 0.6
040 1.1 1.1 0.6
045 1.2 1.1 0.8
050 1.6 1.4 0.8
060 1.5 1.5 1.0
070 1.6 1.5 1.1
080 1.6 1.5 1.3
090 2.0 1.6 1.5
* Minimum flow rate for an available pressure of 10 kPa (unit with hydronic module)
** Minimum flow rate for a water temperature difference of 10 K (unit without
Standard
4 6 8 10 12 14 16
Maximum****
Low High
pressure pressure
3.1 3.6 3.8
3.3 3.8 4.1
3.3 3.8 4.1
3.6 4.2 4.7
3.8 4.4 5.0
4.0 4.6 5.4
5.4 7.8 9.2
6.1 8.0 9.9
6.2 8.1 10.3
6.3 8.3 10.9
7.8 8.7 12.5
hydronic module)
*** Maximum flow rate for an available pressure of 20 kPa (unit with low-pressure
hydronic module) or 50 kPa (unit with high-pressure hydronic module)
**** Maximum flow rate for a pressure drop of 100 kPa in the plate heat exchanger (unit
without hydronic module)
BW10 Condenser water flow rate, l/s
Minimum*
Low pressure
020 0.3
025 0.3
030 0.3
035 0.4
040 0.4
18 20
045 0.4
050 0.4
060 0.5
070 0.5
080 0.6
090 0.6
* Minimum flow rate for a water temperature difference of 18 K (unit with or without
hydronic module)
** Maximum flow rate for an available pressure of 20 kPa (unit with low-pressure
hydronic module) or 50 kPa (unit with high-pressure hydronic module)
*** Maximum flow rate for a pressure drop of 100 kPa in the plate heat exchanger (unit
without hydronic module)
5.7.2 - BW10 with option 272
BW10 Minimum evaporator water flow rate - option 272*, l/s
Minimum**
Low pressure
020
0.5
025
0.6
030
0.7
035
0.8
040
0.8
045
0.9
050
0.8
060
1.0
070 1.0
080 1.1
090 1.1
* Option 272: Condenser side high-temperature water production, with glycol
solution, evaporator side
** Minimum flow rate for a maximum permitted temperature difference at the
minimum leaving water temperature (unit with hydronic module)
*** Minimum flow rate for a water temperature difference of 5 K (unit without hydronic
module)

5.8 - Minimum water volume

Whichever the system, the water loop minimum capacity is
given by the formula:
Capacity = Cap (kW) x N Liters
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.
Application
BW10
ATTENTION: Minimum water volume required between the
unit and possible customer-supplied valves to the outside of
the unit.
Industrial process applications
Certain industrial processes may require high leaving water
stability. In these cases the values above must be increased.
Maximum**
Low pressure High pressure
3.1 3.5
3.3 3.8
3.3 3.8
3.5 4.1
3.7 4.3
3.9 4.5
4.8 6.8
5.5 7.0
5.6 7.2
5.8 7.4
7.2 7.9
Minimum***
High pressure
0.6 0.3
0.6 0.3
0.7 0.3
0.8 0.4
0.8 0.4
1.0 0.5
0.9 0.5
1.0 0.5
1.1 0.6
1.2 0.7
1.4 0.7
N
2.5
Maximum***
3.8
4.1
4.1
4.7
5.0
5.4
7.0
7.5
7.8
8.2
9.3
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