Rémi,
Does anyone know if and how Type109 manipulates the data that it reads? I am using Type109 to read the CA-QC-Montreal-716270.tm2 that comes with TRNSYS. The output values from type 109 don't match the data that is in thefile. It seems to only be right on the first hour of the year.Also doesn't wind direction in TMY give N=0? TRNSYS output is supposed to be N=180, but it doesn't seem to be changed from the input data.
What you are observing is just a difference between instantaneous values and hourly averages. In TRNSYS, all variables are average values over the simulation time step (and the convention is that values are reported at the end of the time step). So if TRNSYS outputs an ambient temperature of 2.32 at TIME=2, it means the average temperature between 01:00 and 02:00 on January 1st was 2.32. Weather data files typically include instantaneous values for temperature, humidity, etc. so all data readers in TRNSYS calculate the average value from 2 instantaneous values. Type 109 also applies a spline interpolation to Temperature, which explains that the average is not the exact mean value between 2.4 and 2.2. Note that solar radiation is usually provided as an average value in weather data files so that variable is not modified when you use an hourly time step (it is interpolated "intelligently" by Type 109 or Type 16 if you use a shorter time step).
There are several threads about this in the TRNSYS Mailing list archive, e.g: http://sel.me.wisc.edu/trnsys/mailinglist/archive1999-2002/msg00735.html
The reason I tried to beat the new TRNSYS engineer in answering you is that we noticed a problem in the Meteonorm-generated TMY2 file for Montréal (if you plot the temperature you will see what I mean). Meteotest has confirmed that this was a bug in the Meteonorm version that was used at the time TRNSYS files were generated and they have fixed it in Version 5.102. I will send you the corrected file in a separate email.
The TRNSYS convention for azimuth angles is indeed to have South = 0 in the Northern hemisphere (North = 0 in the Southern hemisphere) and positive values towards the West (i.e. East = -90). This convention applies to sun angles, walls, windows, solar collectors, etc. but not to the wind direction because weather files typically use 0 for North and positive towards East. To my knowledge the components that really care about wind direction are consistent with this convention (e.g. TRNFLow, the version of Type 56 with multizone airflow calculation).
Kind regards, Michaël Kummert -- _________________________________________________________________ Michaël Kummert École Polytechnique de Montréal - Génie Mécanique Case Postale 6079, succursale Centre-Ville Montréal QC H3C 3A7 Canada Tel: +1 (514) 340-4711, Ext. 3367 Fax: +1 (514) 340-5917 Email : michael.kummert à polymtl.ca