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Re: [EnergyPlus_Support] problem with thermal radiation



thank you for your answer
1-this solution that you said in reality is different form that i said.
because amount of radiation reflection inside layers is different from radiation refection at the internal reflective cavity what should i do ?
2- do you know where can i find the correct value of solar and thermal and visual absorption for materials?
thank for you time
REZA

On Sun, Dec 12, 2010 at 4:27 PM, Griffith, Brent <brent.griffith@xxxxxxxx> wrote:
 

The  model for surface heat transfer in EnergyPlus is not what you seem to imagine.  Trying to assemble an internal reflective cavity using Construction and Material objects does not work.  You would need to develop equivalent properties for that portion of the assembly and collapse them into a single Material layer.

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of reza m
Sent: Sunday, December 12, 2010 8:15 AM


To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] problem with thermal radiation

 

 


i saw many details that they use 3 or 4  metal layers with foam as insulation layers.

 

On Sun, Dec 12, 2010 at 4:09 PM, Griffith, Brent <brent.griffith@xxxxxxxx> wrote:

 

Your metal layers are inside the construction and will not do anything to affect thermal radiation.  Only the first and last Materials affect the surface radiation properties of the Construction.   

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of reza m
Sent: Saturday, December 11, 2010 4:31 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] problem with thermal radiation

 

 

Hi,
I investigate on thermal radiation and its effects
I have two alternative materials
1- external wall ( with two metal layers)
2- external wall2 (with out metal)
The difference between two simulations  was very poor and thermal radiation energy loos by the wall that has this material wasn't change.

A9C38D:Surface Ext Thermal Radiation Heat Loss to Outdoors [kWh](Monthly)

 

with out Reflector

 with Reflector

January

108.8691475

108.8541296

February

128.5922864

128.6258381

March

251.0705809

250.9363295

April

395.7446768

395.1045226

May

566.9424429

567.0461548

June

587.9205448

587.9979196

July

638.0636581

638.0444506

August

516.8364084

516.6539877

September

348.7579962

348.6593856

October

215.2195033

215.3210677

November

122.2107265

122.2722356

December

90.07916896

90.1409641



do you have any idea?


what should i do to have better result for radiation
i attached my IDF file
thank you in advance for your time
REZA

 




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