8 Function of the check valves [specialist]
2016/05
996091425-mub-en – V04
27
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The density of the solar fluid decreases considerably with rising temperature. In the case of
high installations and large temperature differences, the difference in density causes gravity
circulation. This circulation can lead to a cooling down of the storage tank.
Calculation example: Δp = Δρ * g * h
Collector temperature: 5 °C
Density of the solar fluid 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
Δp = 3875 Pa = 395 mm wc
The two check valves of 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 storage tank.