Yes in the documentation, I've understood that shortwaves absorptance is solar absorptance and Infrared emittance, Thermal absorptance, but I can't figure out why I've found big differences between results with convection coefficients fixe according to 140 test protocole and those which use algorythm as TARP or DOE-2 to calculate the coefficients. Do you know if there is a way to find how are used convection coefficients or how are calculate those coefficients in the algorythm (with the absorptance ?)?
On Monday, June 13, 2016 9:05 PM, "Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
I'm not too familiar with the 140 test protocol, however these kind of validation tests often use simplifications to cancel out unwanted variance. Fixing the film coefficients as static values is not uncommon.
As for the definitions of which bands of radiation are considered for "solar" and other key words...I think the new documentation set has made this a bit clearer...at least that was the plan. If you don't find it to be so, log it to the helpdesk and let me know. I have an email discussion about this with Mike (e+) that I can dig up if you don't find it.
On 10 Jun 2016 1:48 pm, "raphael.peronnet@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Thanks for the answer, but when I've tried to use the algorithms, I found huge differences between my results and the ASHRAE datas. That's why I've fixed convection coefficients with values given by ASHRAE 140-2001. I'm still out of range but the evolution of the results seems to fit to the datas. So with this method I change the convection coefficients when I change absorptance using the linearized gray-body radiation equation also given in ASHRAE document.On Thursday, June 9, 2016 5:58 PM, "Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Surface to air heat transfer is via "convection". You can select one of several algorithms available that calculate the convection coefficients used in the calculation at each time step.On 6 Jun 2016 2:16 pm, "raphael.peronnet@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:Hi everyone,I'm currently working on the modelisation of tests from the ASHRAE Standard 140-2001 and I have some issues with the in-depth cases. For those cases I put a door to modelise the opaque window as briefly described in a report from energy plus. For the two first cases (195, 200) it gives results that sound right according to the datas from ASHRAE Standard 140-2001 but with the introduction of IR emittance in cases 210 and 215, I find heating loads quite importants. For IR emittance inputs on opaque surface I used the Thermal absorptance and solar absorptance for shortwaves absorptance. But I wonder if there is a mix for IR emittance. My question is, are IR emittance and shortwaves absorptance strictly equal to Thermal absorptance and Solar absorptance on energy plus ?And then i would like to know if there is a document which explain how are heat transfers modelised on energy plus (not just in the walls which are described on energy plus documentation but between each surface of the zone and the air).Many thanks.Raphaël
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Posted by: <raphael.peronnet@xxxxxxxxx>
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