RE: [EnergyPlus_Support] Re: Window blinds - conductance of shading layer in heat balance equations

["Griffith, Brent" <brent.griffith@xxxxxxxx>]

I like your idea, but that is not what the program is doing.  The blind model is only for relatively normal slat configurations with low conductance. 

 

 

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From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of tboomgaert
Sent: Thursday, April 23, 2009 3:49 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Window blinds - conductance of shading layer in heat balance equations

 

Thank you for your answer.

I don't understand this completely however. Do you mean that the shading layer conductance k is just equal to lambda/t (with lambda the slat conductivity and t the slat thickness)? I find it strange that the distance between the slats is nowhere included in this, as well as width of the slats (and equivalent shading layer).

I was thinking that the conductance would have to be calculated somewhat like this:
k=lambda/((t/(h+t))*w)
so that:
- for slats with no thickness, the conductance would be infinite (because there is no material)
- for h=0 (no distance between slats), the conductivity of the shading layer would be equal to the slat confuctivity, so that k=lambda/w

Can you tell me if I'm right or not?

Thanks in advance,
Thomas

--- In EnergyPlus_Support@yahoogroups.com, "Griffith, Brent" <brent.griffith@...> wrote:
>
> Blind layer conductance is calculated by dividing slat conductivity by
> slat thickness.
>
>
>
> ________________________________
>
> From: EnergyPlus_Support@yahoogroups.com
> [mailto:EnergyPlus_Support@yahoogroups.com] On Behalf Of tboomgaert
> Sent: Friday, April 10, 2009 4:13 AM
> To: EnergyPlus_Support@yahoogroups.com
> Subject: [EnergyPlus_Support] Window blinds - conductance of shading
> layer in heat balance equations
>
>
>
>
>
>
>
>
> Hello,
>
> In the Engineering Reference on p.228-230 (heat balance equations for
> shading device and adjacent glass), it states that shading devices are
> treated as a uniform layer with a conductance k_sh.
>
> I was wondering how this k_sh is calculated for window blinds (with
> horizontal slats)? I can't seem to find anything on this in the
> engineering reference.
>
> Thanks in advance!
> Thomas
>

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