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Re: [EnergyPlus_Support] Re: Heat balance model: Zone air mass
The air volume in each zone is considered constant. The air mass is:
Mass = Volume (m3) * Density (kg/m3) at temperature and humidity ratio
from last time step
Multiply this mass by the specific heat of air (J/Kg-C) and the Zone
Volume Capacitance Multiplier (usually equal to 1) gives the capacitance
of air (Joules/Celcius) used in the heat balance equation. The Cz(dT/dt)
term in equation 2 and 5.
See the source code at the end of the Zone Volume Capacitance Multiplier
section just after equation 11.
anarui.oliveira wrote:
>
> So, the actual air mass considered for each zone is constant, based
> on zone volume and initial density conditions?
> Ana.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> <RRaustad@...> wrote:
> >
> > Equation 2 is the heat balance equation without the impact of HVAC
> > equipment. So this equation is not impacted by airflow through
> > inlet/outlet nodes in the zone. The actual air mass flow rates used
> are
> > shown in the equation as Mi (interzone mixing caused by mixing and
> > cross-mixing objects) and Minf (infiltration). Each of these mass
> flow
> > rate terms represent the mass flow rate of air "entering" each zone
> and
> > are specified by the user. The impact of the zone inlet node mass
> flow
> > rate on the heat balance is shown in Equation 5 as Msys. This is
> the
> > actual mass flow rate "entering" the zone through the zone inlet
> node
> > and is a result of HVAC system operation.
> >
> > anarui.oliveira wrote:
> > >
> > > Hi.
> > >
> > > A question about E+ heat balance model:
> > > - What is the actual air mass (I believe it is hidden in "Cz" in
> Eq.
> > > (2)?) E+ considers for each zone? Is it constant? Is it affected
> by any
> > > of the airflows that use inlet/outlet nodes or zones nodes?
> > >
> > > Regards,
> > > Ana.
> > >
> > >
> >
> > --
> > Richard A. Raustad
> > Senior Research Engineer
> > Florida Solar Energy Center
> > University of Central Florida
> > 1679 Clearlake Road
> > Cocoa, FL 32922-5703
> > Phone: (321) 638-1454
> > Fax: (321) 638-1439 or 1010
> > Visit our web site at: http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>
> >
> > UCF - From Promise to Prominence: Celebrating 40 Years
> >
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
UCF - From Promise to Prominence: Celebrating 40 Years
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