[TRNSYS-users] thermal resistance of external shading device

Thu Nov 3 09:50:07 PDT 2011

Thanks a lot for your detailed answer Marion.

I actually got confused by the name of TrnBuild variable “External Shading
factor” which I thought referred to radiation transmission factor and not to
fraction of occultation (shdout in the formula I suppose).

I understand from your explanations why the additional thermal resistance is
also lower than expected (only affects glazing which is kind of surprising
though).

(PS : I also thank you for your interest in my idea of generating 3D data
with third party software. I send you an example of DesignBuilder idf as
soon as I have a moment).

Thanks for all

--

Antoine Gautier
Solamen
+33 6 98 78 56 46

antoine.gautier at solamen.fr

De : Marion Hiller [mailto:hiller at transsolar.com] 
Envoyé : jeudi 3 novembre 2011 10:17
À : antoine.gautier
Cc : trnsys-users
Objet : AW: [TRNSYS-users] thermal resistance of external shading device

Dear Antoine, 

looking at the calculation, it the resistance is always active when the
shading is active. 

Maybe you confused due to the influence of the frame? 

The u-value of the frame is not influenced by the additional resistance of
the shading. 

The NTYPE 50 UWIN is calculated of three different parts: 

a)   Centre of glass 

b)    Edge of glass (influenced by the spacer) 

c)     Frame 

The Uglas (centre of glass and edge of glass) without the inner and out
outer heat transfer is calculated by 

      Redge=(1/alfain+(rshdin*shdin)+1/uedge 

     .                   +(rshdout*shdout)+1/alfout)/fe 

      Rcenter=(1/alfain+(rshdin*shdin)+1/ucentr 

     .                   +(rshdout*shdout)+1/alfout)/fg 

      Rges=Redge*Rcenter/(Redge+Rcenter) 

      UGLAS=1/(Rges-1/alfain-1/alfout) 

Then the frame is included: 

          UGL(N)=UGLAS* (1.-FFRAM)+UFRAM*FFRAM ! total window u-value
without inner and outer heat transfer 

Finally the NTYPE 50 is calculated by: 

         CASE (50) ! u-value of window (glass+frame)with standard inner and
outer heat trasnfer coefficients 

            IF (HO.GT.30.) RO=0.04 

            IF (HO.LT.0.005) RO=0.0 

            IF ((HO.LE.30.).AND.(HO.GE.0.005)) RO=0.13 

            UGLK=1./(1./(UGL(NWI)/3.6)+0.13+RO) 

          ENDIF 

          OUT(IOUT)=UGLK*3.6 

Best, 

Marion 

Dipl.-Ing. Marion Hiller 
TRANSSOLAR: KlimaEngineering - Technologien für energieeffizientes Bauen und
Nutzerkomfort in Gebäude 
Munich - New York - Stuttgart + 49.711.67976.0 

Transsolar Energietechnik GmbH, Curiestrasse 2, 70563 Stuttgart 
Amtsgericht Stuttgart - HRB 23347, Steuernummer 99073/00911, USt-IdNr.:
DE152272639 

Geschäftsführer: Dipl.Ing. Matthias Schuler, Dipl.Ing. Thomas Auer,
Dipl.Phys. Stefan Holst, Prof. Dipl.-Ing. Bleicher  

  _____  

Von: Antoine Gautier [mailto:antoine.gautier at solamen.fr] 
Gesendet: Montag, 31. Oktober 2011 18:36
An: trnsys-users at cae.wisc.edu
Betreff: [TRNSYS-users] thermal resistance of external shading device 

Dear all 

I use the surface output Uwin to assess the thermal impact of an external
shading device. 

As you know the thermal properties entered for the shading devices are
effective only if a shading device is actually defined for the window in the
zone description. 

I get the following results whereas I specified DeltaR = 0.06 m2.K.h/kJ in
input. Does anybody understand this better than I do? i.e. why does the
shading factor modify the thermal impact though the shading device is only
active during periods of time with zero irradiation? Why do I not get the
expected DeltaR in output but half the value? 

Shading factor  - Uwin w/o shading - Uwin with shading [kJ/h.m2.K] - DeltaR
[m2.K.h/kJ] 

1          - 4.93 - 4.22 - 0.034 

0.75      - 4.93 - 4.36 - 0.027 

Thanks for your help 

-- 

Antoine Gautier
Solamen
+33 6 98 78 56 46 

antoine.gautier at solamen.fr 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20111103/66ee3867/attachment-0001.htm>