How to dimension the expansion tank for a Dualsun installation?
SPRING 4
Expansion tank is mandatory with SPRING4 installation.
In order to size it properly you can follow the rule :
Vexpansion_fluid = Vinstallation x Cexpansion_fluid
Vinstallation = Total volume of the installation
= Pipes volume + Panels volume + Thermal exchanger volume thermique
Cexpansion_fluid = Expansion coefficient of the heat transfer fluid (warning : Value in below table is %)
Usefull_effect= [(Pfilling + 1) - (Ptank inflation + 1)] / (Pexpansion + 1)
Pfilling = cominssionning pressure at the height of solar station
Pfilling = 2 + H/10 [bar]Ptank_inflation = Inflation pressure of the tank before hydrauliuqeu expansion of the installation
Ptank_inflation = 0,1 + H/10 [bar]
Vvase = (Vexpansion_fluide x 1,25 ) / Effet_utile
As an example you can find the following volume of tank necessary with 20m of DN16 pipe:
Number of panels | 2 | 3 | 4 | 5 | 6 |
Tank volume (L) | 2 | 2 | 3 | 3 | 4 |
SPRING3
The expansion tank is only recommended for installations of more than 12 Dualsun SPRING hybrid panels in a pressurized system.
The expansion tank is used to store heat transfer fluid during hydraulic commissioning and to improve the filling quality of the system.
After numerous tests, the DualSun engineering team has defined the following calculation formula to determine the volume of the expansion tank to be connected to a system equipped with DualSun SPRING panels.
Panels in portrait mode
Vvessel = [Vexpansion_fluid + (Number_SPRING_panels x 0,33)] / Acceptance_factot
Panels in landscape mode
Vvessel = [Vexpansion_fluid + (Number_SPRING_panels x 0,93)] / Acceptance_factor
Vvessel = Total volume of vessel in Liters [L]
Number_SPRING_pannels = Total number of SPRING panels connected to the installation
The choice of vessel volume must be rounded to the superior standard vessel volume
Vexpansion_fluid = Vinstallation x Cexpansion_fluid
Vinstallation = Total volume of installation
Vinstallation = Transfer lines volume + Panels volume + Heat exchanger volumeCexpansion_fluid = Expansion coefficient of heat transfer fluid
Expansion coefficient of heat transfer fluid (%) | ||||||||||||
Glycol content (%) | Temperature (°C) | |||||||||||
-20 | -10 | 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | |
0 |
|
| 0 | 0,1 | 0,2 | 0,4 | 0,8 | 1,2 | 1,7 | 2,3 | 2,9 | 3,6 |
10 |
|
| 0,1 | 0,3 | 0,5 | 0,7 | 1,1 | 1,5 | 2 | 2,6 | 3,2 | 3,9 |
20 |
|
| 0,2 | 0,5 | 0,8 | 1,1 | 1,4 | 1,8 | 2,3 | 2,9 | 3,5 | 4,2 |
30 |
| 0,1 | 0,4 | 0,7 | 1 | 1,3 | 1,6 | 2,1 | 2,6 | 3,1 | 3,8 | 4,4 |
40 | 0,4 | 0,7 | 1 | 1,3 | 1,5 | 1,7 | 2,1 | 2,5 | 3 | 3,6 | 4,2 | 4,9 |
50 | 0,6 | 0,9 | 1,2 | 1,5 | 1,8 | 2 | 2,4 | 2,8 | 3,3 | 3,9 | 4,5 | 5,2 |
Acceptance_factor = [(Pfilling + 1) - (Pvessel_inflation + 1)] / (Pfilling + 1)
Pfilling = Hydraulic commissioning pressure of the installation at the level of the solar station
Pfilling = 1,5 + H/10 [bar]Pvessel_inflation = Inflation pressure of the expansion tank before hydraulic filling of the installation
Pvessel_inflation = 0,1 + H/10 [bar]
H = Height of the installation in meters [m] (distance between expansion tank and panels)
>To go further : Why use a 6 bar valve if the maximum operating sensor pressure is 1.5 bar?