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{ |
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The following calculation uses the BRTDfunc type to reproduce the |
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calculation used by LBL's Window 4 program for the transmittance |
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and reflectance of coated glazings. This calculation is based |
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on fits for the angular dependence for clear and bronze-coated |
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glazing, and is not terribly accurate. |
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|
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5/20/93 Greg Ward |
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|
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Arguments used for this material should look like: |
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|
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mod BRTDfunc my_glazing |
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10 rrho grho brho |
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rtau gtau btau |
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0 0 0 |
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glazing.cal |
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0 |
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18 0 0 0 |
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0 0 0 |
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0 0 0 |
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FRRHO FGRHO FBRHO |
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BRRHO BGRHO BBRHO |
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RTAU GTAU BTAU |
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|
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where: |
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FRRHO FGRHO FBRHO is front normal spectral reflectance |
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BRRHO BGRHO BBRHO is back normal spectral reflectance |
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RTAU GTAU BTAU is normal spectral transmittance |
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} |
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{ get normal reflectance } |
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rbase = if(Rdot,10,13); { different front and back } |
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Rred = arg(rbase)*CrP; |
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Rgrn = arg(rbase+1)*CgP; |
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Rblu = arg(rbase+2)*CbP; |
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{ get normal transmittance } |
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Tred = arg(16)*CrP; |
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Tgrn = arg(17)*CgP; |
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Tblu = arg(18)*CbP; |
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{ reflectance coefficients } |
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Rclear = .999 + RdotP*(-.563 + RdotP*(2.043 + RdotP*(-2.532 + RdotP*1.054))); |
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Rbronze = .997 + RdotP*(-1.868 + RdotP*(6.513 + RdotP*(-7.862 + RdotP*3.225))); |
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|
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{ transmittance coefficients } |
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Tclear = -.0015 + RdotP*(3.355 + RdotP*(-3.840 + RdotP*(1.460 + RdotP*.0288))); |
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Tbronze = -.002 + RdotP*(2.813 + RdotP*(-2.341 + RdotP*(-.05725 + RdotP*.599))); |
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|
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Tcutoff : .645; { transmittance cutoff constant } |
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{ returned spectral reflectance } |
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rrho = Rred*if(Tred-Tcutoff, Rclear, Rbronze); |
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grho = Rgrn*if(Tgrn-Tcutoff, Rclear, Rbronze); |
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brho = Rblu*if(Tblu-Tcutoff, Rclear, Rbronze); |
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{ returned spectral transmittance } |
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rtau = Tred*if(Tred-Tcutoff, Tclear, Tbronze); |
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gtau = Tgrn*if(Tgrn-Tcutoff, Tclear, Tbronze); |
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btau = Tblu*if(Tblu-Tcutoff, Tclear, Tbronze); |
