Guide To The Sizing Of The Expansion Tank; Capacity Of Water Circuit - Uniflair RAN Series Instruction Manual

GUIDE TO THE SIZING OF THE EXPANSION TANK

The project elements to consider when selecting the dimensions of the buffer tank for a system are:
C The quantity of water in the system in litres
e the expansion coefficient of the water, calculated as the maximum temperature difference between
when the system is off and when the system is running (the values are given in the table below)
p The absolute initial pressure, equivalent to the pre-charge pressure of the buffer tank (normally 2.5 bar,
i
i.e. 1.5 bar-r);
p The absolute tolerated pressure, which must be less than the pressure at which the safety valve is set,
f
taking account of any difference in height between the valve and the tank.
The total capacity of the buffer tank is expressed as:
using the expansion coefficient values in the following table.
WATER EXPANSION COEFFICIENT
Water temp. [°C] Density
[kg/m
10
20
30
40
50
60
70
80
90
100

CAPACITY OF WATER CIRCUIT

The table below shows the capacity in litres of the water circuit.
RAL RAL
0360 0510
litres 6.1 9.8
RAN-RAL - Rev 1.0. - 11-10-2002 IT - EN
e
3
] (at 10°C)
999.6 -
997.9 0.0017
995.6 0.0040
992.2 0.0075
988.1 0.0116
983.2 0.0167
977.8 0.0223
971.8 0.0286
965.3 0.0355
958.4 0.0430
RAL RAN RA**
0700 0750 1000
13.6 12.1 14.2
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C ⋅ e
=
V
t
p
−
i
1
p
f
It is also possible to calculate the average value of 'e'
between the initial water temperature (generally
assumed to be 10°C) and the operating temperature,
using:
=
e 7 ,
RA** RAL RAL
1500 2300 3600
19.1 - -
( )
2
− 6
⋅ ⋅ −
5 10 T 4
RAL
5700
-
T [°C]
24 (32)