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 mesumon203 June 7, 2010 22:12

Fire simulation

Hello world,

I am trying to model a fire of 100kw inside a completely sealed room. Can anyone please help me how to put a constant heat release rate in a fire zone?

And i am very confused with the boundary condition of the fire region. can i use wall b.c for inputting a 100kw source for fire simulation

pls help me.Have a nice day

 newdate4 June 8, 2010 01:53

Well, if you know the volume of the room. the heat input can be given in W/m3 but you need to have solid elements representing the volume of the room..In fluent it can represented as vol heat generation on the solid mesh.

As for B.C on the walls you can set to heat flux transfer =0 this is default condition in fluent.

 mesumon203 June 8, 2010 03:30

Thanks for the reply.

Ya i know the volume.its about 8 m3. So you mean the wall of the room should be solid. But actually i am trying to put a heat source at the bottom of the room for producing fire and my room is empty and full of air. so i am not understanding how to define the cell zones and how many cell zones there should be??

 newdate4 June 8, 2010 11:59

Please clarify what exactly you are looking for in this simulation..
if its sealed room with no heat transfer to outside then you need not model thickness of the room walls.. you can just set the adiabatic condition on the boundary layer of the volume. I guess you are studying the temperature distribution inside the room, then you have to represent the air inside using solid elements..I m not sure about how you are representing the heat source, if you have the exact dimensions of the heat source then model it as solid or shell & then input the heat value in w/m3 or w/m2 respectively. On the contrary if you are initiating fire directly on the floor of the room then you need to just input heat flux with proper sign in W/m2(area of the floor).
Number of cells depends on solving capacity of your machine can handle..
Build a corse mesh first & then refine it further until you feel the result arent changing much.

 mesumon203 June 9, 2010 05:52

Thanks very much for your reply.It is really helping me friend. Let me clarify a little bit more.

My room is sealed and with a dimension of 3*3*3 m and full of only air inside it. and i want to put a fire source at the bottom of the room with a small cubic box and wanna define the box as the heat source with as you said in w/m3 or w/m2 as heat flux and want to check out the temperature distribution in the air because of the source.

I am confused how many cell zones do i need?
if the small solid heat source box is solid zone then does it mean that inside that box is it solid material or air??

Ya do u have any idea.

Again thanks for you interest and co-operation.

have a nice day

 newdate4 June 10, 2010 01:12

ok..if you have the thermal properties of the heat source then you can model it as solid(inside of the heat box filled with solid elements representing the actual material)...Heat input in W/m3(vol of the heat box).
if you are using shell to model then leave the inside of box empty & apply heat flux to the shells (w/m2(surface area of the box shell).
there is no thumb rule for number of cells to be modelled..since your model is a regular geometric shape it shouldn't be difficult to iterate starting with coarser mesh & refine it further until you are satisfied.

 mesumon203 June 10, 2010 01:49

Thanks very much.

 Vignesh V July 4, 2012 06:40

Fire simulation

Hi,

I'm trying to simulate fire in a room.

can u help me out in doing the simulation.

Tell me what are the conditions needed to be imposed to the model.

Thank you in advance.

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