[EnergyPlus_Support] longwave radiation from the environment

["friedl decock" <friedl.decock@xxxxxxxxx>]

Dear,

I'm trying to get the different heat fluxes through a wall out of a
simulation.
Everything seems to be fine for the interior surface heat balance. But I
encounter some problems with the outside surface heat balance, especially
with the longwave radiation from the environment.

1. If I try to calculate qLWR with the formulas on p.36 (in the engineering
reference document) and with the output from a simulation (surface
temperatures, sky temperature, outside air temperature), there is a big
difference between the 'calculated qLWR' and the flux out of the simulation
( = [Surface Inside Face Conduction] - [qSOL] - [qconv,exterior]). (There is
no thermal storage (density = specific heat = 0)).

2. If I'm asking for the report variables: Surface Ext Rad to Air Coeff,
Surface Ext Rad to Sky Coeff, Surface Ext Rad to Ground Coeff, they are
always zero. Do you need to do something special to get those report
variables?

3. In the engineering reference document p.60 basic heat balance:
"TARP includes four possible representations for the basic outside surface
heat balance. The first two depend on which of the optimal surface
conductance algorithms the user selects. The simple outside surface
conductance that includes both the convective and thermal interchange
between the surface and the environment in a single coefficient, " ... " The
detailed outside surface conductance model considers convection and
radiation interchange with the sky and with the ground as seperate factors."

3a. How can you chose the optimal surface conductance algorithm?
3b. What's the value of the single coefficient? Does it take the emissivity
of the surface into account?
3c. The detailed outside surface conductance seems to be almost the same
as mentioned on p.35, accept that I don't see the radiative heat transfer
coeff to the air in figure 28 on p.62. (HA = outside convection coefficient)
(Or is HA a single value for radiation and convection?)

Regards,
Friedl


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