Turbulently burning fuel-rich fireballs cool both by
thermal radiation and by mixing with ambient cold air.
Both mechanisms have been considered important. In this
work we first study their relative effectiveness By
re-analyzing published, small scale experimental results
and by two simple analytical models, which take into
account only one of the cooling mechanisms at a time. The
models indicate that mixing dominates over radiation.
Detailed analytical calculations of thermal radiation are
prohibitively complicated due to the fact that the
temperature of the fireball, including its effective
surface temperature, can not be determined by averaging
in spite of the strong turbulence present.
However, using some plausible assumptions we are able to
extrapolate the empirical, thermally radiating fraction
of the energy from experimentally available firehall
sizes to such larger masses that are relevant in
industrial accidents. This is done by scaling the
relevant parameters (fireball radius, its burning and
cooling time) with the released fuel mass Mf. The
radiating fraction turns out to be a weakly decreasing
function of the mass (~Mf-1/6).
In the end we estimate the
health hazards from thermal radiation to people at
different distances as a function of Mf.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||29|
|Publication status||Published - 1984|
|MoE publication type||D4 Published development or research report or study|
|Series||Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports|
- thermal radiation