Viessmann VITOSOL SERIES Technical Manual page 130

Information regarding design and operation
Note
For vacuum tube collectors based on the heat pipe principle, a steam
production capacity of 100 W/m
the collectors are installed.
The pipe run that holds steam during stagnation (steam range) is cal-
culated from the balance between the steam production capacity of
the collector array and the heat losses of the pipework. For the losses
from a solar circuit pipe made from copper 100 % insulated with com-
mercially available material, the following practical values are
assumed:
Dimensions
12 x 1/15 x 1/18 x 1
22 x 1/28 x 1.5
Expansion vessel and heat sink in the return
The steam can propagate in the flow and return.
A
B
C
P
D
12
E
A Collector
B Safety valve
C Solar-Divicon
D Heat sink
E Expansion vessel
The necessary residual cooling capacity is determined from the differ-
ential between the steam production capacity of the collector array and
the heat dissipation of the pipework up to the connection point for the
expansion vessel and the heat sink.
Note
The "SOLSEC" program is available at www.viessmann.com for cal-
culating the residual cooling capacity and sizing the heat sink.
The program offers three options:
■ Sufficiently long, uninsulated pipework branching to the expansion
vessel
■ A sufficiently large pre-cooling vessel, in relation to the cooling
capacity
■ A correctly sized stagnation heat sink
Specification
Stagnation heat sink
– Type 21
– Type 33
Pre-cooling vessel
VIESMANN
130
2 can be expected, no matter where
Heat loss in W/m
Output at 75/65 °C in W
482
835
—
(cont.)
■ Steam range less than the pipe run in the solar circuit (flow and
return) between the collector and the expansion vessel:
The steam cannot reach the expansion vessel in the event of stag-
nation. The displaced volume (collector array and pipework filled
with steam) must be taken into account when sizing the expansion
vessel.
■ Steam range greater than the pipe run in the solar circuit (flow and
return) between the collector and the expansion vessel:
Planning a cooling line (heat sink) to protect the expansion vessel
diaphragm against thermal overload (see figures below). Steam
condenses again in this cooling line and reduces the liquefied heat
transfer medium to a temperature below 70 °C.
25
30
Expansion vessel and heat sink in the flow
The steam can propagate only in the flow.
C
D
E
For the heat sink, standard radiators with an output calculated at 115
K are assumed. To make things clearer, the heating output is given as
75/65 °C in the program.
Note
As contact protection, Viessmann stagnation heat sinks (see
page 97) are equipped with a plate without flow due to the anticipated
high temperature on the surface. When using commercially available
radiators, contact protection must be provided and the connections
must be diffusion-proof. All components must be able to withstand
temperatures of up to 180 °C.
Cooling capacity during stagnation
in W
1668
A
B
P
Liquid content in l
964
450
VITOSOL
1
2
12