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View factor calculation

  1. Jun 25, 2012 #1
    hello, everybody, I try to use mcnp to calculate view factor of radiation heat
    transfer, could somebody give me some advice? I want to use surface
    source, but I do not know how to get the number of the particles
    emitted from the source from the output file? and I use F4 tally, I do
    not know how to use the values of the tally from the output file, the
    values seem to be very small?
    Thanks a lot. The attachment is the output file, Hope you can help me .

    Attached Files:

  2. jcsd
  3. Jul 1, 2012 #2
    It has been a while since I've used MCNP, but since no one else has responded I'll give it a shot answering your question.

    I believe the tally results are normalized to a single source particle. That actually explains both your questions in one. You don't need to know the number of source particles because the answer is PER source particle. It also explains why your answer is so small.
  4. Jul 5, 2012 #3
    Thanks so much for your respond. I know I should not care the magnitude about the value. I think F4 tally is not so good in my case, 'cause usually the sum of all value should be 1, but in my case it is far more than one, there should be some where I should modify in my input, F4 gives flux inside the cell, but what I really need is # of particles passing through the surface, even through I made everything is void, maybe scattering will influence the process, I tried to use boundary condition to solve the problem, but I still did not find the correct way to do so.
  5. Jul 5, 2012 #4
    Since you only care about the surfaces I believe you should be using the F2 tallies which are surface flux instead of F4 tallies which are cell (volume) flux. Give that a try and see if you get better results. Also, if all your materials are void than scattering in MCNP should not be an issue.
  6. Jul 5, 2012 #5
    OK, since scattering will not be an issue. Now I'm using F2 tally, since I should divide the whole surface into many segments, and I need the flux through individual segment, I try to use FSn to get it, I still try to find an way to calculate it in one time, since now I only can get one flux for one time, do you have some advice?
  7. Jul 5, 2012 #6
    My MCNP experience is pretty limited so I don't remember how segmenting surfaces work. I believe the segmentation lets you divide a surface (from the surface card) into smaller sections for the tally. You'll have to read the manual and play around. Maybe someone else here with more experience can help you.
  8. Jul 5, 2012 #7
    Sure, Thanks for your help. I am using the most time-assuming way to do so, I think. Maybe later I will find a better method, *.*
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