Enter the HHV value for the fuel (e.g., Btu/ft³) and the specific gravity of the fuel (relative to air) into the Wobbe Index Calculator. The calculator will evaluate the Wobbe Index.
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Wobbe Index Formula
The following example problem outlines the steps and information needed to calculate the Wobbe Index.
WI = Vc / (Gs)^{1/2}Variables:
- WI is the Wobbe Index (same units as Vc, e.g., Btu/ft³ or kJ/m³)
- Vc is the HHV value for the fuel per unit volume (e.g., Btu/ft³)
- Gs is the specific gravity (relative density) of the fuel gas relative to air at the same reference conditions (dimensionless)
To calculate a Wobbe Index, divide the HHV value for the fuel by the square root of the specific gravity of the fuel.
How to Calculate Wobbe Index?
The following steps outline how to calculate the Wobbe Index.
- First, determine the HHV value for the fuel (Btu/ft³).
- Next, determine the specific gravity of the fuel (relative to air).
- Next, gather the formula from above = WI = Vc / (Gs)^1/2.
- Finally, calculate the Wobbe Index.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
HHV value for the fuel (Btu/ft³) = 1050
specific gravity of the fuel = .61
WI = Vc / (Gs)^1/2 = ?
