Error check weather files for valid psychrometric conditions

[jmaguire1]

Issue overview

We've recently used some AMY weather files generated for us by someone else that had some wetbulb temperatures that were psychrometrically invalid (in the worst case, there was an outdoor drybulb of 37 C and wetbulb >0 C). The RH and outdoor air pressure were correct. The simulations were able to run despite having a weather file that had some data that should have resulted in invalid psychrometric calculations. I'm not sure what sort of error checking for weather files currently exists, but it feels like we should be making sure that any combination of variables used to determine your psychrometric state results in valid and identical conditions. I've included a weather file that includes "bad" wet bulb values, but there should really be a check that the psychrometric calculations come out the same no matter which variables you use from the weather file. bad_weather_example.zip

Details

• Platform Win64
• Version of EnergyPlus 8.9

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• [ ] Defect file added (list location of defect file here)
• [ ] Ticket added to Pivotal for defect (development team task)
• [ ] Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)

[jasondegraw]

See also #4644

[mjwitte]

@jcyuan2020 Please review this and #4644 and suggest a plan to address.

[jcyuan2020]

I checked the attached weather file and the weather data outputs seems fine. The wetbulb temperatures are not included in the original weather data file; but are calculated (and can be reported) based on DBT (dyrbulb), RH, and barometric pressure input from the weather data. There are quite some low humidity data in the weather but EnergyPlus seems to processed them fine to get a reasonable wetbulb temperature. For example, a DBT = 37.2C RH = 8%, P = 84793Pa will yield a wetbulb of 15.08 C and a dwepoint of -2.23C. The wetbulb is very close to the the result got from a third party psychometric calculator (15.05C, -2.18C).

The dewpoint using the EnergyPlus routine calculation is very close to the original weather file entry of -2C (within a -0.23C from routine calc) for above check point. Speaking of the dewpoint descrepancy (diffs between routine calculated dwp and weather file dwp), in many high quality Class I weather files (eg. Chicago airport), the dew point difference could be around 0.5C or more. In this regard, it looks the attached weather file for this site looks pretty fine in general.

I wonder at what context or what wetbulb values were observed to have abnormal behavior, e.g. some individual calls at some component simulation modules?