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Hi all,
I'm currently working on developing a spreadsheet to provide basic flare stack sizes/radiation levels for times when we do not have access to simulation software (eg. Flaresim).
API 521 provides a couple of sizing methods to size stacks with sub-sonic flare tips based on radiation levels, but does not present any methods relating to sonic flare tips. The empirical equation by Hajek and Ludwig (eq. 24, pg 80, 5th edition) is applicable to both sonic and sub-sonic flare tips, but the factor representing the fraction of heat radiated (F) is only given for sub-sonic flares (in Table 10).
API 521 states that flare manufacturers should be consulted for sonic tips, however I was hoping that given the wide acceptance of sonic flare tips in designs these days that there might be some more information available in the public domain regarding the associated flare stack sizing.
Any input would be appreciated.
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Flare Stack Sizing With Sonic Flare Tip
Started by Guest_tmarsh1811_*, Feb 10 2009 04:03 AM
7 replies to this topic
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#2
JoeWong
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Posted 10 February 2009 - 05:02 PM
For sonic tip, typically can try F=0.1-0.12 Heavy gas i.e. C3, higher F factor may be experienced. Above just for your prelim studies, please get confirmation from flare vendor
#3
Guest_tmarsh1811_*
Guest_tmarsh1811_*
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Posted 10 February 2009 - 10:18 PM
QUOTE (JoeWong @ Feb 10 2009, 06:02 PM) <{POST_SNAPBACK}>
For sonic tip, typically can try F=0.1-0.12 Heavy gas i.e. C3, higher F factor may be experienced. Above just for your prelim studies, please get confirmation from flare vendor
Great, thanks for the advice Joe.
#4
JoeWong
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Posted 11 February 2009 - 04:45 PM
Appreciate you can come back with vendor used F factor for sonic tip for future reference.
#5
Guest_tmarsh1811_*
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Posted 11 February 2009 - 07:42 PM
Will do Joe. We have contacted some vendors and are awaiting feedback at the moment.
However, we are still missing one piece of information. The F factor for sonic tips will allow us to calculate the radius from the flame centre for a specific radiation isopleth, but we are still left with the problem of locating the flame centre. I am assuming the charts presented in API 521 for the Brzustowski/Sommer's approach are applicable only for sub-sonic flares, so we need to find out whether similar charts exist for sonic flares. Again, we've posed this question to the vendors and await feedback, but if you have any thoughts on the matter I'd been interested to hear them.
However, we are still missing one piece of information. The F factor for sonic tips will allow us to calculate the radius from the flame centre for a specific radiation isopleth, but we are still left with the problem of locating the flame centre. I am assuming the charts presented in API 521 for the Brzustowski/Sommer's approach are applicable only for sub-sonic flares, so we need to find out whether similar charts exist for sonic flares. Again, we've posed this question to the vendors and await feedback, but if you have any thoughts on the matter I'd been interested to hear them.
#6
JoeWong
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Posted 13 February 2009 - 04:22 AM
As far as i aware, it is not available. Probably the flare manufacturer have it (non-publish)
#7
Guest_tmarsh1811_*
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Posted 23 February 2009 - 01:17 AM
Just an update on what we have recieved from the vendors.
As expected, the vendors all use their own proprietary software to model flame shapes from sonic flares. As such, they caution that the F-factor they use would not be applicable to the model presented in API 521. One vendor did suggest an F-factor of 0.05-0.1, but went on to say that it is "difficult to generalise".
Flaresim was considered acceptable for modelling sonic flares, with an accuracy of around 90% at peak flows.
My feeling is that the API-521 model can be used to model existing/new sub-sonic flares, and predicting radiation levels associated with light-off of existing vent stacks. Where sonic flare tips are involved, an F-factor of 0.05 to 0.1 could be used, but this would should not be used for anything other than feasibility-type studies (as JoeWong suggested). In the case of both sub-sonic and sonic flares, the API-521 method should only be be used in the event that Flaresim (or similar simulation software) was not available.
As expected, the vendors all use their own proprietary software to model flame shapes from sonic flares. As such, they caution that the F-factor they use would not be applicable to the model presented in API 521. One vendor did suggest an F-factor of 0.05-0.1, but went on to say that it is "difficult to generalise".
Flaresim was considered acceptable for modelling sonic flares, with an accuracy of around 90% at peak flows.
My feeling is that the API-521 model can be used to model existing/new sub-sonic flares, and predicting radiation levels associated with light-off of existing vent stacks. Where sonic flare tips are involved, an F-factor of 0.05 to 0.1 could be used, but this would should not be used for anything other than feasibility-type studies (as JoeWong suggested). In the case of both sub-sonic and sonic flares, the API-521 method should only be be used in the event that Flaresim (or similar simulation software) was not available.
#8
JoeWong
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Posted 01 March 2009 - 05:47 PM
QUOTE (tmarsh1811 @ Feb 23 2009, 02:17 AM) <{POST_SNAPBACK}>
As expected, the vendors all use their own proprietary software to model flame shapes from sonic flares. As such, they caution that the F-factor they use would not be applicable to the model presented in API 521.
Yeap... this is my common experiences too...
QUOTE
One vendor did suggest an F-factor of 0.05-0.1, but went on to say that it is "difficult to generalise".
Flaresim was considered acceptable for modelling sonic flares, with an accuracy of around 90% at peak flows.
My feeling is that the API-521 model can be used to model existing/new sub-sonic flares, and predicting radiation levels associated with light-off of existing vent stacks. Where sonic flare tips are involved, an F-factor of 0.05 to 0.1 could be used, but this would should not be used for anything other than feasibility-type studies (as JoeWong suggested). In the case of both sub-sonic and sonic flares, the API-521 method should only be be used in the event that Flaresim (or similar simulation software) was not available.
Flaresim was considered acceptable for modelling sonic flares, with an accuracy of around 90% at peak flows.
My feeling is that the API-521 model can be used to model existing/new sub-sonic flares, and predicting radiation levels associated with light-off of existing vent stacks. Where sonic flare tips are involved, an F-factor of 0.05 to 0.1 could be used, but this would should not be used for anything other than feasibility-type studies (as JoeWong suggested). In the case of both sub-sonic and sonic flares, the API-521 method should only be be used in the event that Flaresim (or similar simulation software) was not available.
I have seriously doubt on F<0.1. I have read many articles on experiments of flare. Still yet to find any experiments with F<=0.1
Hope this experiences help.
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