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Hi, I want to know how do we integrate the air resistance between window and internal shading device, for instance : drapes. Do we integrate the air resistance with the shading resistance and put it as a additional resistance factor for shading?
Also, considering that there is big enough distance between the shading and the window the air resistance technically does not work since there is lot of heat transfer via convection air hysteresis like loop.
Any suggestion or comments from experts/trnsys team on this specific modeling part would be appreciated, thanks!
Abir,
The impact that the drapes have on solar shading and the impact that they have on air resistance will need to be treated independently.
The shading impact would be accomplished by setting the drapes up as an internal shading device so that their presence will be taken into account when Type56 computes the amounts of short and long wave solar radiation getting through the glazing system.
How you handle the the resistance to airflow that the drapes cause depends somewhat on how you are handling the overall air flow through the building.
If you are using either CONTAM (Type97/98) or TRNFlow then your open window is an element in the air flow balance model. That open window element will need to be modified as the simulation progresses to account for whether the drapes are open or closed. It is much the same case as when the window is open or closed.
If you are handling air infiltration in Type56 without the aid of CONTAM or TRNFlow then the impact of the drapes is to change the infiltration rate into your building. Presumably you have set the infiltration rate either as a schedule or as an input so you'd need to make an estimate of what the infiltration rate will be with the window closed, window open/drape closed, window open/drape open.
It may be that the estimates will need to come from some other modeling such as CFD. You might also start out by trying the make a couple of "goal post" assumptions about how the drapes will impact the air flow. Perhaps you guess that they will reduce the airflow by only 10%. Run the simulation and take a look at what conclusions are suggested. Then guess that the drapes will reduce the airflow by 90%. Run the simulation again and see if the conclusions change. If the Trnsys model is very sensitive to the assumption then you can invest some time in coming up with a more rigorous model. If the overall conclusions don't change then make a middle-of-the road assumption about the drapes and invest time elsewhere in the model.
kind regards,
David
Hi David
Thanks for your detailed response. You have always been super helpful.
Best
Abir
