SLHV... ? What's the "S"

I came across the abbreviation SLHV, does anyone know what the “S” stands for?
This abbreviation is used when talking fuel and heating values - I like to think I understand the HHV, LHV and LCV,
I just cant seem to find anything on the “S”.


Standard, not to be confused with actual. Its an assumption rather than a measure.

A “standard” value is an assumption, a book value. It does not take into account variation in temperature, density, pressure, or chemical composition of the fuel in your tank. Its a “perfect world” engineering value. If I dont have any test data and need to run a calc I’m going to plug in a standard value. OTOH once I have actual test data I’m going to use actual, occasionally called the normal or measured value in all calcs. Sometimes you’ll see subscripts S or A used, sometimes software, laziness, or personal preference wont allow and you’ll see the S or A prior to the thermodynamic shorthand. SLHV = LHVS. ACFM = CFMA.

Liquid onroad fuel in the first world is the most chemically consistent fuel worldwide, but it still varies. In the second and third world even onroad fuel varies significantly as they aren’t regulated to the high standards the rest of us are. Offroad fuels everywhere vary significantly, head out into the US oil patch or even your local trash dump and you’ll see generators burning whatever comes out of the ground. When you get into the gaseous fuel world, composition and LHV vary significantly hence my quoting of “standard” above, book values often being rather optimistic. That variation might not seem important, but when you’re developing a large engine burning many thousands of gallons of third world fuel per year it impacts calibration and even hardware decisions as a 1% improvement in fuel economy can be tens of thousands of US$$$/year.

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