Radiation
 

Hi everybody, I'm modelling a fire in a road tunnel as a volumetric source of heat and smoke (it's the simplest way and the first step), and I would like to model also the effects of radiation transport in the tunnel. I have two approaches: the detailed one, using a radiation model, or the radiative fraction approach, which ignores the thermal radiation in the medium and assumes that a fixed fraction of the total heat release rate in the fire is to be lost to the surroundings without affecting the temperature distribution within the tunnel. What I would like to know, concerning the second approach, is: which is the fraction of the total heat that I have to consider lost due to radiation ? I hope I've been clear enough. Thanks, Gabriel.

Re: Radiation
 

Hi, I have some questions to understand your approach better.

1) Will you solve mass, momentum and energy equations simultaneously?

2) Dou you know temperature distribution within the medium?

You may define either wall temperatures or heat fluxes at the wall. This will effect temperature profile within the medium

Nuray

Re: Radiation
 

1)Yes, I solve the three equations. 2)I know the distribution of the temperatures whithin the medium.

I also made an attempt defining the wall heat-fluxes, better than lowering the heat release rate of the source(fire), but I think that I gave these losses at the wall a too high value.

Thank you. Gabriel

Re: Radiation
 

I calculated radiative heat fluxes at walls of a combuster. The temperature distribution within the system and some part of walls was available. The temperature distribution at the walls really affect incident wall heat fluxes. You should measure either wall temperatures or radiative heat fluxes. If you measure wall temperatures you can calculate incident wall heat fluxes using temperature distribution within the medium. Then you may compare predicted incident (not net)wall heat fluxes with measured values. The summation of all source terms within the medium is equal to heat removal from all walls. After this check you can be sure that you calculated the source term sufficiently.

Nuray