Natural Ventilation

prwarren · Posts: 1

(a) I notice that when adding a new Cp data set to pressure coefficient data, the wind angle relative to the surface runs at 45deg intervals from 0 to 180deg, rather than to 315deg. This restriction seems to imply that the building is axisymmetric relative to the surface. Is my understanding correct? If so.how can one deal with more complex built forms for which Cp values are not axisymmetric?
(b) Is AIRNET implemented in 1.1.1.006?

Peter Warren

Andy Tindale · Posts: 1110 Location: Stroud

Peter,

a) The Cp data templates are used to provide standard AIVC default pressure coefficient arrays for 1:1 aspect ratio for each surface based on the slope of the surface and exposure of the building. The AIVC pressure coefficient data is axisymmetric and it is probably unrealistic to consider using asymmetric default Cp data sets because it would be almost impossible to apply. Clearly the use of such default data will provide only approximate Wind Cps but this is usually adequate for natural ventilation design calculations and is the recommended method described in the CIBSE A Guide.

For applications where you have building-specific data (which for nonsymmetric buildings will generally be asymmetric) then you can enter this asymmetric data at the surface level on the Openings tab for each surface.

b) Yes AIRNET is implemented in 1.1.1.006 when EnergyPlus version 1.3.0 is selected in the program options dialog on the EnergyPlus tab. But I would recommend using the current beta release version if you're planning to carry out AIRNET simulations because it contains an important EnergyPlus AIRNET bug fix.

Regards
Andy

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