Hi，
How can you know that "The surface and air temperatures start at 23C"?
I did not found it in engineering manual.....
If both the surface and air temperature start at 23C, then the convection to zone from surface can not happen. Right?
Thanks,
Best,
Na
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Griffith, Brent" <brent.griffith@...> wrote:
>
> The surface and air temperatures start at 23C.
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx [ mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of bokelai1989
> Sent: Thursday, August 16, 2012 10:34 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: 3rdOrderBackwardDifference in Energy Plus
>
>
>
> Hi,
> But in the initial calculation, where do the history temps come from when we are just provided with one desired zone temperature?
>
> To be specific, to solve the ODES of temperature using the predictor-corrector approach, how does energy plus initialize the temperature values for the ODES? For example, given a weather data and ground temp, we know the outside temperature and the ground temperature. Also given the zone temperature schedule, we know the desired temperature for each zone.
>
> My question is , in the energy equation, will the temperatures of inside and outside surface of each wall be also calculated through the integration method? How can we initialize these temperatures?
>
> Thanks!
> Best,
> Na
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx< mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad <RRaustad@<mailto:RRaustad@>> wrote:
> >
> > E+ saves the previous zone temps in history terms, t-1, t-2, t-3, and
> > uses those as needed. Of course these are updated every time step (i.e.,
> > using first in last out).
> >
> > On 8/16/2012 11:58 AM, bokelai1989 wrote:
> > > Hi, All,
> > > In the Engineering Manual of Energy Plus, it mentions a method of "3rdOrderBackwardDifference".
> > >
> > > It says "This algorithm requires zone air temperatures at three previous time steps and uses constant temperature coefficients. The assumption is that three previous time steps lengths are the same."
> > >
> > > I would like to know in terms of its inner calculation mechanism, how energy plus acquires the zone air temperature at three previous time steps?
> > >
> > > Thanks!
> > > Na
> > >
> > >
> > >
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> > --
> > Richard A. Raustad
> > Senior Research Engineer
> > Florida Solar Energy Center
> > University of Central Florida
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