[EnergyPlus_Support] Re: Adiabatic wall

["careym.cosmaj" <mark.carey@xxxxxxxxxxxxx>]

Jason,

Thanks for the pointer to "Material:NoMass", we have also realised that we were reporting on the wrong variable to watch energy flow through a surface.  We are now seing zero heat flow through our adiabatic walls.

We needed to report on "Opaque Surface Inside Face Conduction" and ensure "Output:Diagnostics, DisplayAdvancedReportVariables" was set.

We dont have any information on the age of the existing envelope.  Plus New Zelandss legislative framework requiring thermal insulation does not have the ancestry buildings in other countries enjoy.

Thanks for the suggestion.

Regards,

Mark Carey

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jason Kirkpatrick <jason.alan.kirkpatrick@...> wrote:
>
> Mark,
> 
> Depending on the year of construction of the existing building, could you
> not just assume minimal code compliance for the wall?
> 
> If you definitely want to go the adiabatic route, you could define the
> construction as composed of a Material:NoMass object.
> 
> this material gave me convection less than 4 BTUh without changing the
> boundary condition to adiabatic
> 
>   Material:NoMass,
>     MAT-FLOOR-1,             !- Name
>     Rough,                   !- Roughness
>     1000000000000000,             !- Thermal Resistance {m2-K/W}
>     0.00001,                    !- Thermal Absorptance
>     0.00001,                    !- Solar Absorptance
>     0.00001;                    !- Visible Absorptance
> 
> Hope this helps,
> 
> Jason
> 
> 
> 
> 
> 
> 
> On Mon, Jan 10, 2011 at 6:41 PM, careym.cosmaj <mark.carey@...>wrote:
> 
> >
> >
> > Hi,
> >
> > Trying to comparitively simulate thermal envelope differences of an
> > extension to an existing large zone building (warehouse).
> >
> > We have two options;
> >
> > 1. Make educated guesses about the thermal performance of the existing
> > elements or,
> >
> > 2. Model the interface between the existing and new building sections as
> > adiabatic.
> >
> > There are pros and cons of each and both can be considered by purists as
> > fudges at some level.
> >
> > "Wall:Adiabatic" only permits rectagular elements (the building has a
> > pitched roof)
> >
> > We are trying to use, "BuildingSurface:Detailed" with "Adiabatic" Outside
> > Boundary Condition.
> >
> > Eplus requires a Construction be specified whihc is non-ideal as we dont
> > want the thermal mass effect of the adiabatic wall in the simulation as
> > there is no wall in reality.
> >
> > We are seeing non-zero "Surface Int Convection Heat Rate" for a wall which
> > should be adiabatic.
> >
> > We have defined a psuedo-material with very low specific heat capacity,
> > very low density, and very low conductivity and still see much larger than
> > expected Convection Heat Rates on the surface, any suggestions?
> >
> > Thanks,
> >
> > Mark Carey
> >
> >  
> >
>




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