illogical heat transfer simulation

asked 2023-11-17 09:26:56 -0600

Mateo's avatar

updated 2023-11-17 12:26:56 -0600

Hi, i'm new in the openstudio developing and i'm working with OS application. I made a simple box case with 3 stories, each one constitude with a two components envelope and a couple of simple windows. The envelope is composed of a low conductivity concrete in the outside and a mean conductivity concrete in the inside face (Both with 0.21 Btu/lb.R of specific heat, 0.9 on thermal alpha and 0.7 on solar alpha). No schedules, space types, internal loads or HVAC system was applied. It is only compose by single thermal zone.

When i run the simulation, the results is seems to be illogical:

  • The interior temperature is attenuated throught-out the day and for all the year. The amplitude of the daily temperatures (comparing day and night) is less than one or two celsius degrees . I'm comparing outdoor drybulb temperature with zone mean radiant and air temperature (witch are the same).

  • Another issue i see is that the solar irradiated outside face temperature has peaks of twenty celsius degrees highers than the ambient temperature on the midday and then has also lowers temperatures than the outdoor on the night.

These circunstance doesn't match together, because the boundary conditions makes me think that the internal temperature must oscilate between peaks, and the manual/excel calculation of the heat transfer confirms me that.

I'm thinking on a hypotesis but i want to know first if i'm missing some important steps on the definition of the model and this is a trivial issue or not.

This is my first interaction on the forum so i don't know if it is possible to share the model and the EPW file. I thank you in advice.

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@Mateo you can upload your model and EPW file to a file sharing service like Google Drive, Dropbox, etc. and then share the URL to those files here for others to access.

Aaron Boranian's avatar Aaron Boranian  ( 2023-11-17 12:26:40 -0600 )edit

@Mateo, you raise 2 issues. The first one is indeed suspect, given the addition of windows. A glance at the .osm file would help, as @Aaron Boranian suggests. Ultimately, E+ simulates a single (albeit tall) thermal zone in your case. What are the ground floor construction + boundary condition? Surfaces in direct contact with the ground can be great temperature moderators. The second observation would not be unexpected in (moderately to very) dry climates (night radiative cooling).

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-11-17 14:09:10 -0600 )edit