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Re: [EnergyPlus_Support] Weather Data

Here is the formula:

    ! Calculate Sky IR
    !HIR = ESKY * SIGMA * (TOUT**4)
    !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) +
    !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/m^2

    !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.

I suppose the manual should be changed to just say "opaque sky cover".


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