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ibpsa / modelica-ibpsa

Modelica library for building and district energy systems developed within IBPSA Project 1
https://ibpsa.github.io/project1
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ReaderTMY3 allows inconsistent results #1449

Open mwetter opened 3 years ago

mwetter commented 3 years ago

In IBPSA.BoundaryConditions.WeatherData.ReaderTMY3, if a user specifies dry bulb temperature and relative humidity as inputs to the model, then the dew point temperature will still be the one from the weather data file. Hence, results can be inconsistent because the dew point temperature depends on dry bulb temperature and relative humidity.

The underlying reason is that the TMY3 data specifies all three variables, but only two are independent.

As a fix, it probably would be best to disable specification of TDewPoi by an input or parameter, and overwrite the value from the weather data file whenever a user prescribes TDryBul or relHum. Using TDryBul or relHum, rather than TDewPoi, as an input has also the advantage that any combination of TDryBul or 0 <= relHum <= 1 is always well defined.

Mathadon commented 3 years ago

Sounds good. An alternative would be to add asserts that checks invalid combinations. That way the user is better informed of the internal workings/overrides, which would now be happening without notice.