8 Function of the check valves [Expert]
28
997655810x-mub-en – V08
2020/10
Do you need to know it exactly?
The density of the solar fluid strongly decreases with increasing temperature. In systems of high
system heights and with large temperature differences, the difference in density causes gravity
circulation. This circulation can result in the storage tank cooling down.
Calculation example:
Δ
p =
Δρ
* g * h
Collector temperature: 5 °C
Solar fluid density
ρ
1 = 1042 kg/m³
Storage tank temperature: 67 °C
Density of the solar fluid
ρ
2 = 1002.5 kg/m³
Δρ
=
ρ
1 -
ρ
2 = 39.5 kg/m³
g = 9.81 m/s²
Installation height h = 10 m
Δ
p = 3875 Pa = 395 mm wc
The two check valves per storage tank circuit in the station (2 x 200 mm wc) are sufficient for an
installation height of 10 m and a temperature difference of up to 62 K between the collector and
the tank.
