M. Chirtoc et al., RAYLEIGH-BENARD-MARANGONI INSTABILITIES DURING EVAPORATION OF AQUEOUSALCOHOL-SOLUTIONS, DETECTED BY PYROELECTRIC SENSORS, Instrumentation science & technology, 26(2-3), 1998, pp. 133-144
A simple pyroelectric Sensor is presented for on-line monitoring of Ra
yleigh-Benard-Marangoni convective instabilities in methanol, ethanol
and isopropanol aqueous solutions, caused by alcohol evaporation from
the free surface of the liquid. The signals measured at the liquid-sub
strate interface represent thermal fluctuations of the order of 10(-2)
K, having a frequency spectrum between 0.08 Hz and 0.4 Hz. The numeri
cal estimation of the Rayleigh and Marangoni numbers leads to the conc
lusion that the latter is dominant in the conditions of the experiment
. The amplitude and duration of the thermal noise are investigated as
a function of alcohol concentration. An attempt is made to determine c
haracteristic invariant quantities.