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Re: [EnergyPlus_Support] Surface:HeatTransfer:ExteriorNaturalVentedCavity
I'm working on a masters thesis using a validated CFD model to develope a
method in EnergyPlus to model a DSF. There are bascially two ways to model a
DSF in EPlus now (with passive airflow)...neither of them are accurate, but
I'm not sure about the total error in an annual analysis.
1) You could model the cavity as a separate zone, using COMIS to calculate
passive airflow. With this method, just make windows in both facades, and
EPlus takes care of all the solar issues. This method isn't accurate because
EPlus doesn't have an appropriate convection coefficient for the interior
facade, so the heat loss from the space is not accurate. Also, the airflow
rate isn't correct because COMIS uses an average zone air temp for buoyancy
calcs, instead of the peak temperature.
2) You could use the 'airflow window' module. With this, you can't model
passive airflow - the user has to enter an airflow rate schedule. But, you
can put the cavity air into the space, into the HVAC system, or vented to
outside.
As far as I can see, these are the best options in EPlus right now.
I'm working on some correlations for airflow & convection coefficients that
could be inputted into any annual simulation.....but it'll be a few months
before I'm done.
Aleka
Building Systems Program
Department of Civil Engineering
University of Colorado at Boulder
(720) 635-0281
Quoting Ian Doebber <ian.doebber@xxxxxxxx>:
> I'm investigating a double skin façade and want essentially to calculate the
> overall SC and U-value that varies hourly across my design day. I started to
> use the
> Surface:HeatTransfer:ExteriorNaturalVentedCavity but can this input
> incorporate an transparent material. From the only material inputs of solar
> absorptivity and emmissivity, I'm assuming that E+ treats the baffle as an
> opaque surface. Is there a way that I can model this baffle as transparent.
> If not, what other modules can I use to model double skin façade that
> transmits light.
>
> THanks
>
> Ian
>
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