Hi Peter,

Thanks for your reply on the matter. I have began looking a little at TRNSYS, and from what you are describing about its air movement analysis, it sounds tempting to use this program for the dynamic simulation. How does TRNSYS model the temperature stratification in the atrium? Can it predict the air flow if the solar gain is "captured" by interior screens at the top of the atrium, (which thereby adds to the air movement at this location) instead of the solar gain being added near the walls and floors by tracking the solar irradiation? What about diffuse radiation? In short: What is your experience using TRNSYS? Can it do what you want it to do? What about stratification?

My client expects presentation of results regarding temperature in the occupied zone as well as air velocity. However I will not make a CFD stating that the air velocity on the occupied zone is 0,1435 m/s (...which is shown in this CFD calculation etc. ...) because the calculation is only steady state and is not valid for a whole year, because of the uncertainties in the input in the CFD calculations. Moreover I can't present the results from the thermal calculations as these are very uncertain due to the uncertainty about stratification in the atria. Can TRNSYS take care of these problems?

I would rather not make more than 4 CFD simulations, and the simulations should have the necessary input from TRNSYS in order to achieve the correct results more or less in the first simulation. What's your comment on transient simulation? Is it worthwhile? From what I know of these simulations, the computing time is more or less the same as the results are based on the constant boundary conditions and is therefore only showing the uncertainties in the solving of the different differential equations. The results presented in the transient calculations can then be used to illustrate the variation of the results... or can it?

The CFD calculations are extremely expensive and if it is to be of any use for any client the uncertainties should also be presented. Your efforts on LA courthouse confirms that CFD is expensive. When was this work done? What was the tasks on this building? It would be nice if I could glance at the papers you made at that time.

I haven't been able to find the program "ROOM"? Do you have a link? Thanks for your help.

Kind regards

Frederik Vildbrad Winther (FRW)