Dear all:
I need help, I hope there is someone out there who can help me.
I finish drawing the 2D geometry of an Air Solar Collector with an undulated absorber plate (in contrast with a flat plate absorber). This is a ~~~~~ shape plate to capture the sun radiation.
So I already added the materials and (try to) add the Physics to my model:
- Single Phase FLuid Flow - Laminar Flow
- Heat Transfer in Solids
- Heat Transfer in Fluids
But when I run the simulation, even though I have the Heat Transfer in Solids and the Heat Transfer in Fluids modules included in my model, the Results doesn't show whatsoever the Graphs for the Temperature Distribution, or contrours. Also the Pressure Results Graph doesn't shows anything
I'am attaching two images: on of my model's geometry, and one with the solution of the Velocities distribution, but this is as much as I can arrive to.
I'm sure I am doing something wrong with the Boundary Conditions I'm entering.
These are all the Boundary Conditions I'm trying to use :
i. Constant Radiation Heat Flux at the top of the glass cover.
ii. Constant Convection Heat Flux as Losses from the top of the glass cover to the ambient.
iii. Tried to establish a Constant Conduction Heat Flux from the bottom of the collector to the surroundings (to represent the Heat Conduction Losses from the bottom of the Collector to the roof and environment).
iv. Isothermal Walls at both of the sides of the air cavity.
v. The No-slip Boundary Condition (u=v=0) at the inside of all the walls of the air cavity.
vi. An entering Air Mass Flow from the left to the right of the bottom air cavity.
vii. I wanted to establish also and exiting Mass Flow at the right side of the bottom cavity, but couldn't. So instead, I established this Condition as a Pressure at the Outlet, as the Boundary Condition.
So I'm pretty sure I am doing something wrong with one or several of the BC.
I hope someon can give me some help me. I'll appreciate it
Thank You !
You may need adding the physics of radiation heat transfer as wee. Radiation heat transfer between solid-fluid and fluid-fluid inside the collector are necessary to be considered. See the attached file. See the attached file.
Dear Muneer:
I see, so this model cannot be ran (computed) without including the Radiation physics ?
Best Regards,
Thank you !
Dear Franklin,
Previously, we tried to make a validation with: Article Geometry optimization of a nanofluid-based direct absorption...
but we didn't get acceptable results, when we reviewed the paper carefully, we concluded that the radiation calculation must be included. Therefore, we postponed our work in this field.
Best Wishes,
Muneer
Ahmed Mahmood Abdullah Daabo
Dear Franklin,
I can help you with setting up your model.
First, I see that you used three modules rather than using a coupled Non-isothermal laminar flow within it you can add heat transfer in solids and all necessary BCs. Second, I don't know what the warning message is about in the screenshot. Alternatively, you can clear all studies and meshes and send me your model to check the settings (send to: [email protected]).
Regards,
Dear Suliman S Alfarawi :
Thank you so much for your help.
I realised the problem is not evident at all, and may scale up in complexity fast, so I decied to reduce the problem and try first to simulate just one of the parts of the solar collector, before moving up to the whole collector in a single model.
So I built the geometry just for an encloes air cavity with the wavy plate absorber at the bottom, and with motion of air underneath the wavy plate.
I completed the model but I stil trying to understand the physics and conditions.
one of the problems I was having first, is that I was establishing a turbulent flow of air (in both domains; inside the enclosed cavity and underneath the wavy plate), so when I started to read abouth the Grashof and Rayleigh numbers this part abouth the regimes of forced and natural convection and laminar or turbulent regimes became a little more clear.
So, I adjusted the model for it to be within the regime of laminar flow.
So I think I got to compute correctly the Gr and Ra numbers ...
My first understanding is this :
firstly, what you have to do is to compute the Ra to ensure what you have Natural convection and you can neglect the part of Forced convection , then, the Gr number has to be computed to ensure you are working inside the laminar regime ...
So, my results for the Gr and Ra for the air inside the enclosed cavity were:
Ra = 3.78 x10^7
Gr = 7.8 x10^7
Do you think Im going in the right direction with this part I'm describing here ?
Can I consider the problem to be a Laminar flow problem and keep going ?
Next what I need to do is compute the Nusselt number for the air underneath the wavy absorber plate
Dear Franklin Uriel Parás Hernández
Useful information can be found in the attached files.
Regards,
Dear Suliman S Alfarawi :
Thankyou for the sent documents :)
The first one, I have already read it, and I followed the criteria mentioned there.
The second one I haven't, I will read it to get to my understanding anything may be useful.
sadly, nowadays, with all the situation of emergency and the lockdown, I cannot go to the Center anymore, so I cannot use COMSOL now. So, for all this upcoming time I won't be able to make progress on the models. But I want to use my time in searching for more literature and alike examples.
I hope I will be able to resume the models and the numerical simulations when the lockdown ends, I hope I can communicate with you again after have given a review to my models again.
However, I can sent my lastest model to you, so if you are kind enough to review if I am doing the corresponding considerations correctly (namely, the Boussinesq Approx., Non-Isothermal flow, etc. ) I will really appreciate it.
Can I send it you to the e-mail address you gave me above ?
Kind Regards ! :)
Dear Franklin Uriel Parás Hernández
Yes, no problem at all.
Regards,
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