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QUESTION: Solar collector boundary conditions in fluent

Solar collector boundary conditions in fluent 2 years 11 months ago #16

  • Vijay Mali
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Hi Manish,

I am getting an error while reading the tin file. That might be because I am using ANSYS ICEMCFD 13.0. I will try to open this in other version and let you know if I can see the geometry.

The zip file contains only mainboxcomplete.tin file. There is no allremesh.tin. Could you please check and upload allremesh.tin file.

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Vijay Mali
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Solar collector boundary conditions in fluent 2 years 11 months ago #17

I have attached the zip file with this message. It is not opening because i am using ansys 15.0 so this files are not getting read by the lower version. I will convert them in ansys and revert back to you with the files that can be opened in lower versions also.
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Solar collector boundary conditions in fluent 2 years 11 months ago #18

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Yes Manish,

Please provide both the files in lower version. I am unable to open this one too :(

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Solar collector boundary conditions in fluent 2 years 11 months ago #19

I am attaching the zip file of the geometry in 13.0 format.
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Last Edit: 2 years 11 months ago by Vijay Mali.
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Solar collector boundary conditions in fluent 2 years 11 months ago #20

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Hi Manish,

I could able to open both the files now.

By looking at the original geometry (mainboxcomplete.tin) and simplified version of it (allremesh.tin), I am not really sure about how you are trying to model this. Below are the images of original and simplified geometry.
org-solar-collector.jpg
Original Domain

simplified-solar-collector.jpg
Simplified Domain

The actual physics is : sun radiation will fall on glass, then get reflected, refracted and transferred inside the collector. The absorber plate will absorb the heat and transfer that to pipe and then to flow water (or air). I can understand that you have value of how much heat is absorbed by the plate. So you are not modeling the glass etc. But even in that case, the heat transfer even between absorber plate and tube is not only due to conduction. Radiation also plays an important role in this. So you have to account for radiation. So you need to change the approach of modeling this.

In your allremesh.tin, I see only solid part of absorber plate is modeled. You have solid parts for inlet and outlet header and pipes. So how are you planing to account for radiative heat transfer between absorber plate and tube ?

Now coming back to your original question of "Surface is not available for providing the heat flux boundary conditions"

I see that in allremesh.tin, you have only one material point (V_AIR). You need to model (create mesh in) solid portion of tube and solid portion of absorber plate. To model that, you need to create material points (may be V_PIPE_SOILD and V_ABS_PLATE - as shown below) and create the mesh. To provide the heat flux condition on top surface of absorber plate, you need to create a part and put top surface in that part.
zones.jpg
Zones

I think once you do above changes, you should able to get the top surface of absorber plate available in FLUENT to provide boundary condition.

I also see that there is line contact between absorber plate and pipe. Even if you want to only capture conductive heat transfer, how heat transfer would happen across line contact. There should be surface contact for heat transfer to happen.
line-contact.jpg
Line contact

So, please look at the way you are planing to model this problem. I think, you need to change the approach and hence the domain for CFD analysis.

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Vijay Mali
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Last Edit: 2 years 11 months ago by Vijay Mali.
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Solar collector boundary conditions in fluent 2 years 11 months ago #21

I have considered radiation in fluent by use of solar load calculator which is in radiation. By giving volumes to each pipes and headers pipes and absorber plate the no. of elements go upto 100 millions which is not possible for my computer which has a RAM of 16 Gb. So if you can suggest any other way to make it possible it will be of great help. If possible I want to do analysis of main box / geometry also.
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Solar collector boundary conditions in fluent 2 years 11 months ago #22

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Hi Manish,

Solar load model is not actually radiation. Its just gives you how much heat would be received giving the your geographical location, time and orientation of the model.

The radiation I am talking about is when heat is received by absorber plate, how it would be transferred to the water in tube. One is through conduction, but other important mode is radiation between absorber plate and tube. I think you need to consider that effect.

100 Millon cells, are you kidding !!! You are doing something really wrong. Its should not produce 100 million cells for this geometry. May be you are putting too many cells in solid zone. I think 4-5 layers would be sufficient.

You can even think of doing heat transfer analysis for only one tube. What you can do is just do a flow analysis of air inside tubes (including inlet and outlet headers). This analysis will give you flow rate going through each tube. Then you can do heat transfer analysis only for one tube with the flow rate estimated by flow analysis. This way, your domain will reduce to single tube. If you neglect the amount of heat absorbed by inlet and outlet header, I guess your temperature values predicted by single tube analysis should not be different that what you will get considering all the tubes.

So, as I said before, you really need to redefine the problem and solution approach. I don't think the current approach is going to give you any valuable results.

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The following user(s) said Thank You: raj

Solar collector boundary conditions in fluent 2 years 11 months ago #23

I did gave very fine meshing size of about 0.1 mm so it got upto that much value but afterwards I gave meshing size which i had given in allremesh.tin which i have mailed you. for which i got 1945947 cells (image 04) this no. of cells i got for surface meshing but the volume meshing was not going forward for 2 hrs I waited till 1 am. I am attaching the images of the no. of volume parts i made if it has to be reduced then please suggest.

Today i will do the analysis for one pipe as you have suggested in the earlier reply and will inform you with the same i.e what temperature I am getting at end and if it is nearer to the calculated value I can do the analysis for the other geometry of mine which is having little different geometry then this.

Thank You very much for your support until now.

IMG_01.jpg


IMG_02.jpg


IMG_03.jpg


IMG_04.jpg


IMG_05.jpg
Last Edit: 2 years 11 months ago by Vijay Mali.
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Solar collector boundary conditions in fluent 2 years 11 months ago #24

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Hi Manish,

You are using really fine mesh on the surfaces. Try coarsening the mesh. The volume mesh is stuck for 2 hrs is due to high number volume cells. I don't think you can even get volume mesh with such fine surface mesh.

Post the results of single pipe. But I am not sure if you are going to get any temperature difference between inlet and outlet. In your current geometry, you have line contact between absorber plate and tube. This will not give any heat transfer. So I will not be surprised if your inlet and outlet temperature will be same.

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Solar collector boundary conditions in fluent 2 years 11 months ago #25

I have found the value of heat transfer co-efficient for the individual pipes if i put it in boundary condition of pipe and start the radiation model will be it of help or by just giving heat flux can i get some improvement.
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Solar collector boundary conditions in fluent 2 years 11 months ago #26

I meshed the model today and the volume meshing happened but it showed the error of " there is a leak in the mesh material v_inheader.1 can reach material v_air.1" should I delete the volume of pipe i.e. inheader.
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Solar collector boundary conditions in fluent 2 years 11 months ago #27

I did the heat transfer analysis of single pipe but the temperature was not increasing so I gave radiation boundary condition on pipe with outer temperature of 400 k and the temperature profile I got also showed 400 k . Also as u directed me to give volume to pipes and header pipe and plate I did it but after meshing what volume meshing I got is seen in below figure and it is only due V_air. Without it the other volumes it do not comes like this.
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Solar collector boundary conditions in fluent 2 years 11 months ago #28

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Hi Manish,

Please post the latest condition of your simulation. Have you done heat transfer or are you still stuck at meshing stage ?

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Vijay Mali
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Solar collector boundary conditions in fluent 2 years 11 months ago #29

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Hi Manish,

There was some problem in your last post. Could you please post that again ?

Following is the text from your last post (if you want that as reference)
By just considering the volume of air i.e. V_AIR in pipes and header i did the prism meshing with 20 elements in the range 0-0.30 and rest all in the range 0.30-1.00(99.99%). But when i consider volume to pipes and header pipes after meshing i get the below image of my mesh. I will post the simulation for single pipe if it is required because what r the results i m getting i have told u above only.
In image i have put the boundary condition on pipe as constant heat flux i got the temperature error, I changed the boundary condition to constant heat transfer co-efficient the temperature remained same while when i put the condition as radiation with outer temperature as 400 K the result showed 400 k at outlet also.
Images 3 & 4 are the images which i got when i gave volume to all the pipes, plate and interior volume of air.

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Solar collector boundary conditions in fluent 2 years 11 months ago #30

when i considered the volumes for each pipe and for header as well as for the plate the volume meshing i got is shown in the images
IMG-20150723-WA0027.jpg


IMG-20150723-WA0050.jpg
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