Reference temperature and Ignition temperature

[woodfire]

Hello everybody,

I am a bit confused about the difference
between material property REFERENCE_TEMPERATURE and surface property
IGNITION_ TEMPERATURE. can anyone make me clear what happens when I
specify a both the properties for a surface with definite material?
Reference_temp is the burning point for a material and Ignition_temp
is the ignition point for a surface, I think. But what happens when I
set both the properties? Thanks.


Shankar,
Germany.

[Kevin]

The parameters HRRPUA, IGNITION_TEMPERATURE, and HEAT_OF_VAPORIZATION
are all telling FDS
that you want to control the burning rate yourself, but you still want
to simulate the heating up and "ignition"
of the fuel. When these parameters appear on the SURF line, they are
acting in concert. If HRRPUA appears
alone, the surface will begin burning at the start of the simulation,
like a piloted burner. The addition of
an IGNITION_TEMPERATURE delays burning until your specified
temperature is reached. The addition of
HEAT_OF_VAPORIZATION tells FDS to account for the energy used to
vaporize the fuel. For any of these
options, if a MATL line is invoked by a SURF line containing a
specified HRRPUA, then that MATL ought to
have only thermal properties. It should have no reaction parameters,
product yields, and so on, like those
described in the previous sections. By specifying HRRPUA, you are
controlling the burning rate rather than
letting the material pyrolyze based on the conditions of the
surrounding environment.

Briefly -- IGNITION_TEMPERATURE is ONLY used when you specify the
burning rate yourself with HRRPUA. In this case, NEVER specify any
reaction parameters, like REFERENCE_TEMPERATURE.