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Author Topic: sprinkler and hss  (Read 2047 times)

tricia

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sprinkler and hss
« on: April 01, 2015, 12:29:33 am »

Hi, i am new to pyrosim and need some help in this. I had created a simple model with sprinkler and burner. The HSS didnt go to zero when sprinkler is activated. Could anyone advise what could have gone wrong with the attached model? Thanks.
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Dave McGill

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Re: sprinkler and hss
« Reply #1 on: April 02, 2015, 06:15:46 am »

Hi Tricia,

Short Answer
This feature doesn't work very well, has no predictive value and isn't worth spending time on.

Long Answer
When I was teaching, I had my students do a model using this feature. Over the years, I've looked at several hundred examples. Sometimes the fire is diminished a  lot, sometimes only a little. It was rarely put out completely. There is no predictable pattern. The E_COEEFICIENT has to be determined experimentally, and, to my knowledge, no one has ever done that. So, it is an unvalidated feature, with no predictive value.

I compared your example to the e_coefficient example provided with FDS. There are several differences that cause the fire to not decline in your example.
  • the HRR is 5x greater
  • the flow rate is 1/10th
  • the spray pattern is almost horizontal, and most of the water leaves the domain
I think this combination of factors explains why the fire is not extinguished in your example.

If you want to approximate the effect of sprinklers on a fire, then there are several other options.
  • The hrr_freeze feature will hold the HRR steady when a device, like a sprinnkler activates. This is a common conservative strategy.
  • The old way was to let the fire grow, note when a sprinkler activated, stop the model and adjust the HRR via RAMP to stop growing, or decline at the time of sprinkler activation, and re-run the model

Dave
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Dave McGill
firemodel.ca

tricia

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Re: sprinkler and hss
« Reply #2 on: April 05, 2015, 08:24:05 pm »

Hi dave, thanks for your reply. I had adjusted the hss, flow rate and flow angle and the hss drops by half though it dont go to zero.
« Last Edit: April 05, 2015, 09:37:56 pm by tricia »
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