bUOYANCY DRIVEN NATURAL CONVECTION FLOW IN SOLAR CHIMNEY

Surajtalele · April 17, 2013, 13:09

Hello,
I am modelling a solar chimney which is a part of Net Zero energy building. Here, the dimensions of the chimney are 14'2" X 6'11" X 7'4". the chimney is rectangular in shape and the top 6' of the chimney on three surfaces has low emission windows and the bottom part is face brick wall. The absorber wall is a wall of gypsum board and is painted with white paint. The model is 3D and I am using ANSYS 14.5 for modelling the chimney

The flow in chimney is laminar flow and I am using S2S radiation model in solar ray tracing for the solar ray data.

In this case, I want suggestion how can I model low emission windows in fluent? and how can i give boundary condition for the low emission windows and white painted absorber wall? I want constant temperature boundary condition at all surfaces. Currently for the Low E surfaces I have used internal emissivity as 0.029 and temperature as was measured, is this enough? I did the same thing for the white painted wall. Please suggest how can I model Low E windows and white painted wall?

Also, at velocity inlet boundary i have specified 0 pressure and at pressure outlet boundary static atmospheric pressure of 747.8 mmHg is specified. In operating conditions dialog box, i specified pressure as 0. Please suggest if this is correct? And also suggest what should be appropriated pressure in this case and at which boundary?

and also, in materials when I use ideal gas for air and specified operating density as 0, when i initialize the case and run simulation there is error message as "Error: Divergence detected in AMG solver: pressure correction" Please suggest what should I change to correct this error

I am new to ANSYS FLUENT so i am facing some difficulties

Surajtalele · April 17, 2013, 15:56

Can you please reply in English?
Thanks

billwangard · April 19, 2013, 17:10

I think the way you need to do this is solve radition using the DO model, use 2 Bands, one for small wavelengths (visible light) and one for large wavelengths (IR). Then set the emissivity of the windows to high (0.9) for the high band and (0.1) for the visible band.

Hope this helps

Sincererly,
Bill Wangard, Ph.D.
Engrana LLC

Dorasemon · April 26, 2013, 11:09

Hi, Bill.
I think in this case most of large wavelengths(IR) are reflected which means low emissivity for the high band.
I am also beginner and I am still confused about this.

April 17, 2013, 13:09	bUOYANCY DRIVEN NATURAL CONVECTION FLOW IN SOLAR CHIMNEY	#1
Surajtalele New Member SURAJ H TALELE Join Date: Apr 2013 Posts: 3 Rep Power: 13	Hello, I am modelling a solar chimney which is a part of Net Zero energy building. Here, the dimensions of the chimney are 14'2" X 6'11" X 7'4". the chimney is rectangular in shape and the top 6' of the chimney on three surfaces has low emission windows and the bottom part is face brick wall. The absorber wall is a wall of gypsum board and is painted with white paint. The model is 3D and I am using ANSYS 14.5 for modelling the chimney The flow in chimney is laminar flow and I am using S2S radiation model in solar ray tracing for the solar ray data. In this case, I want suggestion how can I model low emission windows in fluent? and how can i give boundary condition for the low emission windows and white painted absorber wall? I want constant temperature boundary condition at all surfaces. Currently for the Low E surfaces I have used internal emissivity as 0.029 and temperature as was measured, is this enough? I did the same thing for the white painted wall. Please suggest how can I model Low E windows and white painted wall? Also, at velocity inlet boundary i have specified 0 pressure and at pressure outlet boundary static atmospheric pressure of 747.8 mmHg is specified. In operating conditions dialog box, i specified pressure as 0. Please suggest if this is correct? And also suggest what should be appropriated pressure in this case and at which boundary? and also, in materials when I use ideal gas for air and specified operating density as 0, when i initialize the case and run simulation there is error message as "*Error: Divergence detected in AMG solver: pressure correction*" Please suggest what should I change to correct this error I am new to ANSYS FLUENT so i am facing some difficulties

April 19, 2013, 17:10	Low E windows question	#3
billwangard New Member Bill Wangard Join Date: Jan 2011 Posts: 21 Rep Power: 0	I think the way you need to do this is solve radition using the DO model, use 2 Bands, one for small wavelengths (visible light) and one for large wavelengths (IR). Then set the emissivity of the windows to high (0.9) for the high band and (0.1) for the visible band. Hope this helps Sincererly, Bill Wangard, Ph.D. Engrana LLC

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April 17, 2013, 15:56		#2
Surajtalele New Member SURAJ H TALELE Join Date: Apr 2013 Posts: 3 Rep Power: 13	Can you please reply in English? Thanks

April 26, 2013, 11:09		#4
Dorasemon New Member Emon P Join Date: Mar 2013 Posts: 22 Rep Power: 13	Hi, Bill. I think in this case most of large wavelengths(IR) are reflected which means low emissivity for the high band. I am also beginner and I am still confused about this.