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working.
In practice, for heating, it assumes the conventional value of 0,035;
C = the total water content of the system (l);
Pi = initial absolute pressure (bar) at an elevation that is installed on the vessel,
represented by the hydrostatic pr 0,3 bar + atmospheric pressure (1 bar).
In practice it is the preload pressure of the vessel increased from 1 bar;
Pf = final absolute pressure (bar) represented by the maximum system pressure plus
atmospheric pressure (1 bar). In practice it is the regulation of increased safety valve
of 1 bar.
Table 2 - Water Expansion Ratios
Scale an expansion vessel for a heating system with the following characteristics:
C = water content = 600 l
Phyd = hydrostatic pressure at the installation site = 1 bar
Pseg = set pressure of the safety valve = 3 bar
Solution:
Applying the formula above, where:
e = 0,035 valor convencional
Pi = Phid + 0,3 + Patm = 1 + 0,3 + 1 = 2,3 bar
Pf = Pseg + Patm = 3 + 1 = 4 bar
Therefore:
V = (0,035 · 600) ÷ [1 - (2,3 ÷ 4)] ≈ 49.41 l
We have to check in a manufacturer's catalog of expansion vessels and therefore
choose a vessel with a capacity equal to or greater than the calculated value.
