[Bldg-sim] Natural Ventilation

Cheney chenyu73 at gmail.com
Thu Feb 10 09:55:37 PST 2011


Hi Shambav,

Both Eric and Chris offered very good points. I'd like to remind you that no
matter how your get the boundary condition, it must be reasonable. I know
some simulation programs can generate boundary condition through
dynamic thermal calculation or bulk air model, such IES VE or TAS. However,
you'd better verify the boundary condition based on your common sense and
experience. I did some natural ventilation related study before and
noticed the results from CFD simulation could be logical only when the
boundary condition is well established. That's why I highly recommend field
measurements or wind tunnel test as a starting point. What's the difference
between them and those dynamic calculation results:

1. Natural ventilation is quite micro-climate oriented. Surrounding
buildings, topography, landscape, etc will have very significant impact on
it. However, most dynamic calculation will use a standard weather file
generated from nearby airport or open sapce. As a result, a misleading
boundary condition could be generated.

2. Some variables, such as surface temperatures, may vary a lot between real
world and computational one. Most time I have a feeling that simplified
thermal engine could not trace the complicity of the real world perfectly
and underestimate the surface temperatures. I did mention it in one of my
recent post.

Regards,

Cheney

LinkedIN @ http://ca.linkedin.com/pub/yu-cheney-chen/27/637/72b
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