# Links between CFD or MZ and thermal simulations for simulating air and temperature distributions in atria

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Hi,

I am currently starting up on simulating a relatively large atrium in Denmark (app. 55?N) with a glazed roof (sloped towards the sun - clever), open balconies with working areas connected to the atrium, as well as a smaller atrium with smaller openings connecting the two atria together with each other. The main focus in the simulation is first of all the air velocity and temperature distribution in the occupied zone and on the balconies - describing the thermal comfort as well as draft rate. The next focus is on integrating the smaller atria as a heat exchanger in winter time as well as analyzing if this can be used for cooling in summer time, transporting the air from outside to the biggest atrium, via the smaller atrium with little heating of the air. The calculations I want to perform in CFD also regards simulations of the solar gain in the biggest atrium. However simulating radiation in CFD simulations require more computing power for bigger rooms with a lot of surfaces. Any advice on simulating solar gain in CFD? How can this dynamic gain be simulated in CFD? Another cool thing in this atrium would be the heat recovery of the extracted air in the top part of the atrium.

Simulating this in a thermal simulation software requires a lot of luck to obtain the correct (and true) result in the first couple of simulations. However I am thinking of integrating the results from a CFD calculation into the thermal simulation. I am thinking of doing this as an iterative process, integrating the results from CFD when needed in the thermal simulations. This will probably result in at least 4 different simulations over a whole year, giving detailed results (temperature gradient, flow between zones, convective heat-transfer coefficients etc.) which can be used in the thermal simulation for these 4 periods over a year. As mentioned above simulating radiation in CFD is tough, I am thinking of leaving this calculation in the thermal simulation.

Another simpler setup would be the integration of a multi-zone calculation in the thermal simulation giving a more coarse result of the main flow route in the atrium and mixing between balconies and the atrium. However these results could potentially give the same detailed results I am looking for.

Finally has any one worked on an uncertainty analysis of these coupling methods illustrating first of all the uncertainty in the results as well as the sensitivity in the input parameters?

Has anyone done something like this before and what tools were used? I have been given free hands with regards to choice of software so any feedback on this subject will be useful. I'm really looking forward to hear from you :-)

Kind regards

Frederik Vildbrad Winther (FRW)

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