Viessmann VITODENS 242-F Technical Manual page 72

Design information
Expansion vessel
The expansion vessel can be calculated once the steam spread has
been determined and any heat sinks that may be used have been
taken into consideration.
The required volume is determined by the following factors:
■ Expansion of the heat transfer medium in its liquid state
■ Liquid seal
■ Expected steam volume, taking account of the static head of the
system
■ Pre-charge pressure
V = (V + V + V
dev col dpipe e
V Rated volume of the expansion vessel in l
dev
V Liquid content of the solar collectors in l
col
V Content of the pipework subject to steam loads in l
dpipe
(Calculated from the steam spread and the pipework content
per m pipe length)
To determine the steam volume in the pipework, the content per m of pipe must be taken into consideration.
Copper pipe
Contents
Corrugated stainless
steel pipe
Contents
For the liquid content of the solar collectors, see the Vitosol technical
guide.
Quick selection of expansion vessel and heat sink
The details in the following table are standard values. They allow quick
estimates at the design and calculation stage. We recommend verify-
ing the values with appropriate calculations. The selection refers to a
hydraulic system with a liquid "bag" and the use of a 6 bar safety
valve.
Vitosol 200-F/300-F, type SV
2
Absorber area in m
2.3
6
4.6
6.9
Vitosol 200-F/300-F, type SH
Absorber area in m 2
2.3
4.6
6.9
VIESMANN
72
(cont.)
+ V )·Df
fv
Dim.
l/m pipe
Dim.
l/m pipe
Static head in m System capacity in l
5
10
15
5
10
15
5
10
15
Static head in m System capacity in l
5
10
15
5
10
15
5
10
15
V Increase in the volume of the heat transfer medium in its liquid
e
state in l
V = V · β
e a
V System volume (content of the solar collectors, the heat
a
exchanger and the pipework)
β Expansion factor
β = 0.13 for Viessmann heat transfer medium from −20 to
120 °C
V Liquid seal in the expansion vessel in l
fv
(4 % of the system volume, min. 3 l)
Df Pressure factor
(p + 1): (p
e
p Max. system pressure at the safety valve in bar (90 % of
e
the safety valve response pressure)
p System pre-charge pressure
o
p = 1 bar + 0.1 bar/m static head
o
12 × 1 15 × 1 18 × 1
DN 10 DN 13 DN 16
0.079 0.133 0.201
DN 16
For further information, see the Vitosol technical guide.
Note
Check the size of the expansion vessel on site.
Recom. capacity of the ex-
pansion vessel in l
22.3
25.7
29.2
24.7
27.6
31.0
28.5
29.6
32.9
Recom. capacity of the ex-
pansion vessel in l
22.9
26.4
29.8
26.0
28.9
32.3
30.5
31.5
34.8
− p )
e o
22 × 1 28 × 1.5 35 × 1.5
DN20 DN25
0.314 0.491
0.25
Recom. heat sink
(see page 71)
18 —
25
25 2 m uninsulated pipe
—
—
40 Type 21
0.6 m uninsulated pipe
—
Recom. heat sink
(see page 71)
18 —
25
40 2 m uninsulated pipe
—
—
40 Type 21
0.6 m uninsulated pipe
50 —
42 x 1.5
DN32 DN40
0.804 1.195
VITODENS