Open AccessExperimental heat transfer evaluation in a porous media
Author(s) -
Simone Pedrazzi,
Giulio Allesina,
Marco Puglia,
Nicolò Morselli,
Filippo Ottani,
Massimiliano Parenti,
Paolo Tartarini
Publication year - 2021
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1868/1/012016
Subject(s) - pellets , exothermic reaction , heat transfer coefficient , heat transfer , endothermic process , inert , materials science , pyrolysis , inert gas , convective heat transfer , carbonization , thermodynamics , sawdust , nuclear engineering , chemistry , waste management , composite material , adsorption , organic chemistry , engineering , scanning electron microscope , physics
The evaluation of the heat transfer coefficient between hot gases and biomass particles is not easy to estimate because of the concomitance of exothermic and endothermic reactions. However, a proper evaluation of this coefficient is fundamental to design pyrolysis apparatus. This paper presents an experimental study regarding wood pellets heating up in a batch reactor using hot exhaust gases from an engine. Temperature and flow of hot gases entering the reactor were measured over time. A first test was carried out using hemp hurd pellets with 15% of sawdust, and a second one using the carbonized pellets obtained from the previous test. Fresh pellets have a higher thermal capacity compared to carbonized pellets that is almost inert and follow a more regular heating trend. Heat transfer was calculated considering the energy released by the exhaust passing through the biomass as the sum of the energy absorbed by the pellets and the thermal losses. Convection is the predominant heat transfer mechanism and the convective heat transfer coefficient was evaluated. Finally, the energy for the pyrolysis of 1 kg of fuel was evaluated. About 0.7 kWh/kg are necessary to pyrolyze this kind of pellets while an heat transfer coefficient of 110 W/(m 2 K) was estimated for the inert packed bed.