THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

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Movement of water drops in a forest fuel layer in the course of its thermal decomposition

ABSTRACT
In this paper, we conducted an experimental investigation on water droplets gravitating in a layer of typical forest fuel (as illustrated by pine needle litter) in the course of its thermal decomposition. We used a high-speed (200 fps) video recording system, Tema Automotive software with continuous tracking of a moving object as well as a set of low-inertia (no more than 0.1 s) thermocouples. Similar experiments were performed at moderate temperatures (below the onset temperature of forest fuel pyrolysis, i.e. about 300 K). Two approaches were used: continuous tracking of a moving water droplet using high-speed video recording; and registration of a droplet path using the readings of thermocouples placed at different levels in a forest fuel (FF) layer. We determined the typical depths of an FF layer that water droplets reach with the initial volume of these droplets ranging from 90 to 900 μL. The typical velocities of water droplets were calculated at different depths of the FF layer. We also determined the share of the mass of water spent in an FF layer on evaporation and cooling of the material down to the temperatures below those of thermal decomposition. Finally, we identified the physical processes influencing water droplets moving through the layers of forest fuel heated up to the high temperatures similar to those of thermal decomposition.
KEYWORDS
PAPER SUBMITTED: 2016-08-18
PAPER REVISED: 2017-04-01
PAPER ACCEPTED: 2017-04-19
PUBLISHED ONLINE: 2017-05-06
DOI REFERENCE: https://doi.org/10.2298/TSCI160818110V
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