Assessment on thermal behavior of municipal sewage sludge thin-layer during hot air forced convective drying

Modelisation and Simulation of Heat and Mass Transfers during Solar Drying of Sewage Sludge with Introduction of Real Climatic Conditions

“…The comparison of the results obtained by this model with experimental data shows its effectiveness. Huang et al (2015 and2016) have used two models to predict the thin layer sludge drying. These models are the BackPropagation (BP) and the Generalized Regression Neural Network (GRNN) model.…”

One-Dimensional Mathematical Model for Solar Drying of Beds of Sludge

“…In recent years several papers concerning the convective drying kinetics of wastewater sewage sludge and porous material in general have been published (Reyes, Eckholt, Troncoso and Efremov, 2004;Font, Gomez-Rico and Fullana, 2011;Bennamoun, Crine and Léonard, 2013;Haghighi, Shahraeeni, Lehmann and Or, 2013;Bennamoun, Fraikin and Léonard, 2014;Huang, Chen and Jia, 2016). While some papers conclude that the moisture content of the drying material only affects the migration of moisture inside, newer studies link a decreased moisture content at the surface with a higher resistance for the mass transport from the surface to the atmosphere (Font, Gomez-Rico and Fullana, 2011;Bennamoun, Crine and Léonard, 2013;Haghighi, Shahraeeni, Lehmann and Or, 2013;Huang, Chen and Jia, 2016). Considering the complex and diverse structure of sewage sludge, the determination of universal empirical correlations for mass transfer, heat transfer and physical properties is difficult (Bennamoun, Crine and Léonard, 2013) Bennamoun, Crine and Léonard (2013) conducted drying experiments for sewage sludge in a convective belt dryer and determined transport coefficients by applying a mathematical model.…”

“…As recent research suggests the evaporation and heat transfer rate at the surface seem to not only be functions of the temperature and the properties of the drying air, but of the moisture content at the surface (Font, Gomez-Rico and Fullana, 2011;Bennamoun, Crine and Léonard, 2013;Haghighi, Shahraeeni, Lehmann, and Or, 2013;Huang, Chen and Jia, 2016).…”

“…The parameter A represents the conductivity at equilibrium moisture, while B is the proportionality factor for the moisture content at hand. Font, Gomez-Rico and Fullana (2011) On the other hand, correlations for the convective heat transfer at the surface dependent on the moisture content exist, they have often been determined through drying experiments at higher temperatures (Reyes, Eckholt, Troncoso and Efremov, 2004;Huang, Chen and Jia, 2016).…”

“…Noteworthy is especially the work of Huang, Chen and Jia (2016), in which such a correlation is derived through sludge drying experiments in the 100 °C -160 °C temperature range. But as the calculated Nusselt numbers show deviations up to more than 25% to the experimental data at considered temperatures, the applicability to the model at hand is questionable, as drying air temperatures for solar drying are considerably lower.…”