[BLDG-SIM] external louvres

[Pueltz, Gunter]

Vic,

you have to split the simulation of external louvres into following two
parts:

1) Calculating the energetic properties of the louvers by special software:
The energetic properties - usually the angle dependant overall-transmission 
(over all single layers of the facade) and absorption (at each layer of the
transparent component) - must be calculated by a tool, which considers
multiple reflections between all layers (i.e. the external louvers and
usually two glaz panes) as well as the spectral distribution of
transmission,
reflectance and absorption of each layer. This means that the calculations
must be done for several wavelength intervalls (multiband calculations)
within
the wavelength-range of solar radiation (appr. 300 - 2500 nm) and at last a
weigted integration of the single-band results must be done.
These complex calculations are described in ISO 15099: Thermal performance 
of windows, doors and shading devices - Detailed calculations.
If you don´t want to code these complexe calculations for yourself, the
cost-free European software WIS can be recommended to you. See
http://windat.ucd.ie/wis/html/index.html

The American people from LBNL also are working on enhancing their
WINDOW-software
with a model for louvres. See
http://windows.lbl.gov/software/window/window.html

As results you will get integral energetic properies (integrated over the
complete range of solar radiation) as a function of incident angle; these
values take into account all multiple reflections between the layers as well

as the spectral distribution of all considered layers (i.e. glaz panes or 
inclined louvres). 

2) Using these angle dependant transmission and absorption at each layer of
the facade as input data for the simulation tool (condition: It is a high
quality simulation tool, which includes a model for heat conduction within
even the transparent components based upon 1-D-finite-Element heat
conduction)

You see multiple reflections (as well as spectral distributions) can
be taken into account for thermal simulations.

Regards,
Gunter 


--------------------------------------------
Dr.-Ing. Gunter Pültz
Müller-BBM GmbH
Robert-Koch-Str. 11
82152 Planegg bei München
Telefon +49 (89) 85602-336
Telefax +49 (89) 85602-111
http://www.mbbm.de
email:plz at mbbm.de




> -----Original Message-----
> From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Victor
> Hanby
> Sent: Friday, November 19, 2004 12:47 PM
> To: BLDG-SIM at gard.com
> Subject: [BLDG-SIM] external louvres
> 
> 
> Are there any simulation programs that handle external louvres by 
> calculating multiple reflections, or is it normal to e.g. factor down 
> the exposed area of glass?
> 
> Vic Hanby
> -- 
> -------------------------------------------------
> Professor V I Hanby
> Institute of Energy and Sustainable Development
> De Montfort University
> The Gateway
> Leicester LE1 9BH, UK
> +44 (0)116 257 7980,  7977 (fax)
> -------------------------------------------------
> 
> 
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