11 Definition of Terms
11-2. Definition of terms used in "Measuring gas specification sheet"
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11-2. Definition of terms used in "Measuring gas
specification sheet"
Instrument air
Dry, clean air. Use Classes 1.1.1 to 1.6.2 stipulated in JIS B8392-1:2003 (ISO
8573-1:2001). In cold climates, use Classes 1.1.1 to 1.3.2.
MJ/m
3
Calorific value per cubic meter expressed in SI units.
Gross
(HHV, SCV)
All of these terms are synonymous, which are abbreviations for Gross calorific
value (Gross), Higher Heating Value (HHV) and Superior Calorific Value (SCV).
This calorific value includes "latent heat" obtained when water vapor generated
during combustion is compressed.
Net
(LHV, ICV)
All of these terms are synonymous, which are abbreviations for Net calorific value
(Net), Lower Heating Value (LHV) and Inferior Calorific Value (ICV).
This calorific value does not include "latent heat" obtained when water vapor
generated during combustion is compressed.
Standard
temperature
Temperature of a gas to be used as a reference for measuring and displaying
calorific value and density in units per unit volume.
Standard pressure
Pressure of a gas to be used as a reference for measuring and displaying calorific
value and density in units per unit volume.
kg/m
3
Mass per cubic meter expressed in SI units.
Specific gravity
[AIR = 1]
Value obtained by dividing the density of a certain substance by that of a
reference substance.
To obtain the specific gravity of a gas, it is a common practice to use air as the
reference. The OHC-800 also derives a specific gravity using air as the reference.
WOBBE index
The WOBBE index (W.I.) is one of the combustion quality indexes. This value is
obtained by dividing a calorific value by the square root of a specific gravity.
This value is in proportion to the calorific value released per unit of time when a
gas is supplied under a certain pressure to a nozzle with a certain orifice.
