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Re: [EnergyPlus_Support] Re: modelling night sky cooling
For HEAT EXCHANGER:DESICCANT:BALANCEDFLOW, there are two sets of data in
Datasets\PerfCurves.idf
For DESICCANT DEHUMIDIFIER:SOLID, you can use the DEFAULT performance model, or
develop your own user-defined curve fits.
Mike
On 18 Feb 2008 at 10:09, Abdul Murad Zainal Abidin wrote:
> Dear Ms Lawrie,
>
> I am doing research on desiccant HVAC system and hygrothermal properties of
> building materials at Loughborough University, UK, and a novice when it comes to
> E+. I have looked into the datasets for the desiccant system but there are no
> input files for desiccant system. Do I need to search and put in any
> manufacturer data regarding solid desiccant?
>
> Please advice. Thank you.
>
> Yours sincerely,
>
> Murad
>
>
>
>
> ----- Original Message ----
> From: Linda Lawrie <linda@xxxxxxxxxx>
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Sent: Monday, February 18, 2008 10:59:24 PM
> Subject: Re: [EnergyPlus_Support] Re: modelling night sky cooling
>
> At 11:28 PM 2/17/2008, bish.dj61 wrote:
> >1) Does the sky temp come with a standard weather file?
>
> Sky temperature is calculated from conditions presented on the
> weather file or design day. Horizontal IR from Sky is (or can be
> present) on weather files. If not, it is calculated as follows:
>
> ! Missing, use sky cover
> OSky=OpaqueSkyCover
> TDewK=MIN(DryBulb, DewPoint) +TKelvin
> EmissSky= (.787 +.764*LOG((TDewK) /TKelvin) )*(1. +
> ..0224*OpaqueSkyCove r- 0.0035*(OpaqueSkyCo ver**2) + .00028*(OpaqueSkyCo
> ver**3)) SkyTemp=(DryBulb+ TKelvin)* (EmissSky* *.25)-TKelvin where TKelvin is
> the conversion from C to Kelvin, i.e., 273.15
>
> when HorizIR is present on the weather file,
> SkyTemp=(HorizIRfro mSky/Sigma) **.25 -TKelvin
>
> !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.
>
> !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/m^2
>
> Linda
>
> EnergyPlus WebSite: http://www.energypl us.gov
> Owner: EnergyPlus_Support list
> Member: EnergyPlus Development Team
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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