I'm sorry to bother you, but I have a doubt about this argument.
SkyTemp=(DryBulb+TKelvin)*(ESky**.25)-TKelvin
Also in absolute temperatures: Tsky = Tdrybulb * (ESky^0.25)
Isn't it?
What is the physical meaning of that _expression_?
With Regards
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie <linda@...> wrote:
>
> It uses the Horizontal IR from sky as a basis (we calculate this on
> the weather files and design days)
>
> ! Calculate sky temperature, use IRHoriz if not missing
> IF (IRHoriz == "missing") THEN
> ! Missing, use sky cover
> OSky=OpaqueSkyCover
> TDewK=MIN(DryBulb,DewPoint)+TKelvin
> ESky= (.787 +.764*LOG((TDewK)/TKelvin))*(1. + .0224*OSky -
> 0.0035*(OSky**2) + .00028*(OSky**3))
> SkyTemp=(DryBulb+TKelvin)*(ESky**.25)-TKelvin
> ELSE ! Valid IR from Sky
> SkyTemp=(IRHoriz/Sigma)**.25 -TKelvin
> ENDIF
>
> Sky IR is calculated as:
> ! Determine Sky Temp ==>
> ! Function of DryBulb, DewPoint, OpaqueSkyCover
> ! Calculate Sky IR
> !HIR = ESKY * SIGMA * (TOUT**4)
> !
> !where
> !
> !HIR = horizontal IR intensity (W/m2)
> !ESKY = sky emissivity
> !SIGMA = Stefan-Boltzmann constant = 5.6697e-8 W/m2-K4
> !TOUT = drybulb temperature (K)
> !
> !The sky emissivity is given by
> !
> !ESKY = [0.787 + 0.764*ln(TDEW/273)]*[1 + 0.0224*N -
> 0.0035*(N**2) + 0.00028*(N**3)]
> !
> !where
> !
> !TDEW = dewpoint temperature (K)
> !N = opaque sky cover (tenths)
> !
> !Example: Clear sky (N=0), TOUT = 273+20=293K, TDEW = 273+10=283K:
> !
> !ESKY = 0.787 + 0.764*0.036 = 0.815
> !HIR = 0.815*5.6697e-8*(293**4) = 340.6 W/m2
>
> !References:
> !
> !George N. Walton, "Thermal Analysis Research Program
> Reference Manual,"
> !NBSIR 83-2655, March 1983, p. 21.
> !
> !G. Clark and C. Allen, "The Estimation of Atmospheric
> Radiation for Clear and
> !Cloudy Skies," Proc. 2nd National Passive Solar Conference
> (AS/ISES), 1978, pp. 675-678.
>
>
> Linda
>
> EnergyPlus WebSite: http://www.energyplus.gov
> Owner: EnergyPlus_Support list
> Member: EnergyPlus Development Team
>
>
>
> [Non-text portions of this message have been removed]
>
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