[esp-r] Re: FW: surface fluxes

[Achim Geissler]

Dear Daisy (?)

that all the said values are zero is strange. I just checked the  
results of a double facade model and e.g. conduction(inside) is not  
zero for the glass surfaces both facing the zone and the facade gap.  
Which save level are you using? 4?

Also, WIS calculates U-values for double facades both unventilated and  
ventilated (based on the approach described in ISO 15099). So, as  
"facade description", this may suffice.

For the combination "building and facade", it is tricky. Any loads  
reported by ESP-r take storage effects into account, also. So it will  
be very difficult if not impossible to derive a meaningful U-value for  
a double facade (loads, gains, losses across two or more zones) from  
the results given. Additionally, all the convective heat transfer  
coefficients in ESP-r are not the same as used in standard U-value  
calculation by default.

However, in my experience, the facade must be described by the  
standard numbers (non-transient U-value, g-value) anyway, so a  
contractor can deliver to those numbers. Which values are most  
beneficial to the system "building" must be derived from the overall  
model based on loads and / or comfort criteria results from ESP-r.  
Going back and forth, one could optimize the facade parameters to meet  
the building situation in this way and have a "contractor-ready"  
description of the facade parameters to hand.

Best
Achim



On May 16, 2010, at 3:15 AM, 王菊花 wrote:

> Dear Achim,
>     I am sorry I have't expressed my minds clearly.I know there is  
> no  straightforward way to calculate U-value,which is exactly what I  
> mean.So I want to find an easy way to do that,U=Q/⊿T.Q is the heat  
> conduction of the double-skin facade.⊿T is the temperature  
> difference of interior and exterior surfaces.As you say,using a  
> simple tool like WIS can calculate U value.But there are many  
> openings for the exterior glass of double-skin facade in my model,so  
> there is ventilation between the air gap and environment.I realize  
> this by building zones for the air gap area and flow connections for  
> the openings.I try to  use result analysis >surface fluxes>  
> conduction(inside) or conduction(other face) facility in esp-r,the  
> output results are all zero.Maybe it is not practical to calculate U  
> value in this way,I thought out another way to do this.I can use  
> WINDOW5.0 to calculate U value of double-skin facade without  
> ventilation,then campare loads of double-skin facade with and  
> without ventilation in esp-r,divide the load difference by  
> ⊿T.Suppose the result is ⊿U,then plus ⊿U with U value of double- 
> skin facade without ventilation.Does the final result make sense? 
> Anxiously expecting your kind answers.Many thanks.
>
>
>
>
>
> CC: esp-r at lists.strath.ac.uk
> From: achim.geissler at intergga.ch
> To: luckygrass100 at hotmail.com
> Subject: Re: [esp-r] surface fluxes
> Date: Sat, 15 May 2010 19:20:29 +0200
>
> Hi
>
> not sure what you mean. What turned out zero? All the values in the  
> res-variables you name? Or your subsequent calculations? Anyway,  
> there is no straightforward way to extract the U-value (if that is  
> what you mean with comprehensive transfer coefficient) of a double  
> facade construction.
>
> I would recommend using a simple tool like WIS to compare your  
> window / facade constructions in regard to basic parameters (g- 
> value, U-value). And look at overall loads to compare the impact on  
> the building as a system.
>
> Regards
> Achim
>
>
> On May 15, 2010, at 1:31 PM, 王菊花 wrote:
>
> Dear Dear all，
>    I am puzzled again.I am simulating an low-carbon building with  
> double-skin facade for the south facade.I need calculate out the  
> comprehensive transfer coefficient h(W/m2.K),then compare it with  
> that of normal single window.I was thinking maybe I can output the  
> temperature and heat conduction of the interior and exterior  
> surfaces.But when I used the surface fluxes facility,and choosed  
> conduction(inside) or conduction(other face),it turned out all  
> zero.Why?
>
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achim.geissler at intergga.ch




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