Burner Surface Temperature

[Sarnia]

Hi all,

I need some help sorting out some confusion im having with the surface dialog box when creating a burner surface.

If I specify a burner with a HRRPUA, the dialog also gives the option to set the temperature of the burner (similar to the way you set the temperature of a heater/cooler). This sets the CONVECTIVE HEAT FLUX or NET HEAT FLUX values on the surf line in the FDS code. But am I corrrect in my understanding that this wont affect the mass loss rate or HRR of the surface.

Do these parameters have any effect in this scenario??

Is the effect of the fire (radiation and convection) ignored when the temperature of the surface is calculated.

When would one want to specify the temperature of a burner?

Any guidance would be greatly appreciated.

Sarnia

[Bryan Klein]

Hello Sarnia,

The HRRPUA parameter determines the mass flux of fuel ejected from the burner surface.
You are correct, setting burner surface temperature will not change this fuel release rate.

As for the question of why use burner temperature, I will let Jason Floyd answer you from a post on the FDS-SMV discussion group.

"Depends on what you are trying to do.  If you are interested in far
field quantities, the inlet fuel temperature is not very important.
c_p ~ 1 kJ/kg-K and deltah_combustion is ~ 20 - 50 MJ/kg.  So the
amount of energy added to by combustion is going to be much larger
than any energy change resulting from the inlet temperature.  However,
I have observed that near field fluxes for some configurations  (flux
to the wall when the burner is up agaisnt a wall) are impacted by the
burner temperature."

http://groups.google.com/group/fds-smv/msg/cb37511fe41e2393

I hope this helps,
-Bryan Klein