[BLDG-SIM] natural ventilation analysis tools

[Jon Hand]

Those interested in natural ventilation and mixed mode ventilation
might wish to check <http://www.esru.strath.ac.uk> for details
about ESP-r. It has long offered integrated thermal and CFD analysis,
integrated thermal and mass flow (bulk) analysis as well as
(more recently) the possibility to integrate thermal CFD and mass flow
assessments. It is open source so you can check out
the underlying numerical processes and add in your
own home-cooked wall functions or mass flow components.

Natural and nixed mode ventilation has been of long-standing
interest in Europe and ESP-r is regularly used for such
assessments. We know of quite a few practitioners who
also use TAS. 

Most often engineering questions of natural 
ventilation problems can be addressed via integrated mass
flow and thermal assessments (there is minimal overhead
in solving thousands of timesteps). There is still an
art in configuring a flow network and there are gaps
in the available components (e.g. single sided ventilation
is a challenge) but practitioners are using simulation to
address this routinely. 

When questions of mean age of air and local discomfort arise, CFD
may be appropriate (for somewhat fewer timesteps). There
is also much of an art to CFD use so some preparation is 
required prior to real-time deployment.  

CIBSE has issued a Mixed mode ventilation applications
manual (CIBSE AM13:2000) which covers various
methods of evaluation, procedures for professional practice
and information sources. It discusses in detail how one
might deal with uncertainty in flow rates as well as 
fall-back systems for extreme conditions. A definite must-read!

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