Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich

5. METHODS OF PROCESSING OF RAW EXPERIMENTAL DATA
There are two values which have to be estimated from experimental data of burps,
namely: energy release in a burp per gram of a sample, QV, and temperature of «ignition»,
Tign. As to the second value, there was no problem to get it known as duration of a burp is
always short - from 0.4 to 2 sec. Energy release in a burp was estimated by four different
ways:
• for thin layer of methane QV can be estimated by making balance of energy within 1 sec
after ignition of a burp assuming adiabatic character of heating of a sample and copper
walls of the chamber (that is, neglecting helium cooling as only small portion of energy is
removed by a coolant during a burp. In this case, QV -value is assumed to be uniform
through a sample due to only small variation of temperature.
• by integrating a heat removed by helium during and after a burp until temperature returns
to an equilibrium value, and subtracting thermal power induced by neutrons (4.5-5.2
Watts). In this case, Q -value is actually averaged over a sample.
• for segmented samples, QV -value near a place of the central thermocouple can be estimated
directly knowing its records before and after a burp, Tign and Tmax:
Q = [ H ( T ) − H ( T )],
V sample max sample ign
•
where H is heat content in sample material at given temperature T.
By computer simulation of nonstationary heat diffusivity process, it was possible also to
calculate QV -value by making several iterations of QV (t) until heat transfer power (experimental,
time-dependent value) coming into the copper walls of the capsule is equal to
the calculated heat transfer power going out of a sample:
dT
dT
Cu
sample
cCu ( TCu) ⋅ ⋅ mCu + λsample
⋅ ⋅ Ssample
= 0,
dt dt
where Ssample is an area of a boundary surface between a sample and the copper walls of the
capsule, and cCu is a specific heat of copper.
This procedure enables one also to estimate duration of energy release in a burp and distribution
of energy release in time (though, quite roughly) as well.
6. RESULTS AND ANALYSIS OF SOLID METHANE EXPERIMENTS
6.1. Stored energy and Saturated curves
Let us call a concentration of radicals (or: «stored energy», which is identical), versus
irradiation time by a ‘saturation curve’, and a saturated amount of stored energy - by ‘saturated
stored energy’, Q∞.. Relation between molar concentration of radicals n and stored energy
Q, J/g, is: Q = n ⋅1.08E+4 , if radicals are CH3, and Q = n ⋅1.35E+4, if radicals are H, see
Appendix.
Amount of stored energy was estimated by methods described above. All methods are
based on estimation of a magnitude of energy released during a burp which appeared to be not
strictly reproducible. That is why a reconstruction of an exact saturation curve was
impossible.
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