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NREL / EnergyPlus

EnergyPlus™ is a whole building energy simulation program that engineers, architects, and researchers use to model both energy consumption and water use in buildings.
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Comment shows incorrect units for PsyCpAirFnWTdb #4632

Closed mjwitte closed 8 years ago

mjwitte commented 9 years ago

User notes that line 316 of Psychrometrics.hh should be

// This function provides the heat capacity of air {kJ/kg-C} as function of humidity ratio.

instead of

// This function provides the heat capacity of air {J/kg-C} as function of humidity ratio.

User has verified the result against published values for Cp of air and it also computes the same as another algorithm ...which also has units of kJ/kg-C. I think it's just a typo in the comment line.

Hopefully it's just a matter of fixing the comment, but we should confirm that calling routines are expecting kJ/kg-C.

Myoldmopar commented 8 years ago

For reference, I am finding 351 calls to this function. So we probably won't be able to spot check them all...I'll comment on which ones I check, and update the text in the source comment, and close this one unless I find a problem.

Myoldmopar commented 8 years ago

Adding a call to PsyCpAirFnWTdb in SimulationManager with reasonable values gives this:

Processing Data Dictionary
Processing Input File
1004.86
Initializing Simulation
Reporting Surfaces

Standard values of air for specific heat are approximately 1.0 kJ/kg-K. (source)

So this function is return J/kg-K, as the comment suggests, not kJ as the user noted. This is a non-issue, and I am closing it.