Re: [TRNSYS-users] Blinds

[Adrien JEZEQUEL - ITF <a.jezequel@itf.biz>]

Dear Julie,

I suggest you to put an equation tool outside of Type56. In that equation tool, ESHAD (the ratio of non transparent area of the shading device to the whole glazing area, as defined in TRNBUILD) will be calculated depending on blinds position.
If you consider that :

• GWINDOW = solar shading factor of window only, which is constant (60% for example, which means that 60% of solar radiation goes through the window)
• FS = solar shading factor of your system Window + Shadings.
  FS depends on blinds use,
  
• if blinds are used, FS = 0.2 (for example)
  
• if not, FS = GWINDOW

In that way, FS is calculated as the product between :

• the amount of solar energy which pass through external shading device when they're used => (1-ESHAD)
  
• ESHAD = 0 means no shading
  
• ESHAD = 1 means zero transmission
• and window solar shading factor (GWINDOW)
• FS = GWINDOW.(1-ESHAD)    (1)
  Regarding (1)
  ESHAD = (1- FS/GWINDOW)   (2)

No you have a relation between ESHAD, FS and Window G-Value :

• When blinds are up, solar radiation are only blocked by the window solar shading factor => FS = GWINDOW and ESHAD = 0.
• When blinds are down, solar radiation are blocked by window and external shadings => FS = 0.2 (for the whole system in that example), ESHAD = (1-0.2/0.6) = 0.667 that means that 66.67% non transparent area of the shading device to the whole glazing area)
  Regarding (1) FS = 0.5*(1-0.0.667) = 0.5*0.4 = 0.2 which is the total shading factor you want.

Best

---

www.itf.biz	Adrien JEZEQUEL Simulations Thermiques Dynamiques
	ITF	62, Rue du Bolliet 73230 St Alban Leysse FRANCE
	Phone : Fax : Mail:	+33(0) 479 750 029 +33(0) 479 852 122 a.jezequel@itf.biz

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Le 22/06/2010 14:04, Julie Lestrade a écrit :

Dear TRNSYS users,

I was wondering about blinds in front of windows and how to take them into account.
In my case, they external blinds. They're up at certain time and down at other (depending on radiation on the wall, time of day, ...).

Should I take account of them in Type 56 ? on the windows considered with 'external shading factor'  (that would be convenient since i can use a schedule) ? If yes, I would like to have a total solar factor for the window of 0.2 when the blind is down. Does that mean I should put a shading factor 0.8 ? or is it more complicated than that ?

Thank you for your answers

Julie

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