Thermal analysis of natural convective air drying of shrinking bodies

Rahman, Najmur; Kumar, Subodh

doi:10.1002/er.1236

Cited by 6 publications

(2 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results are similar to those results obtained by Bennamoun et al [5] and Rahman and Kumar. [37] Moreover, the convective mass transfer coefficient changed from 9.70 Â 10 À8 m=s for the original sludge to 8.67 Â 10 À8 m=s for the mixed sludge and then increased to 12.09 Â 10 À8 m=s for the mixture of a mass ratio of 4=6.…”

Section: Determination Of the Mass Transfer Coefficientmentioning

confidence: 98%

See 1 more Smart Citation

Analysis of the Shrinkage Effect on Mass Transfer During Convective Drying of Sawdust/Sludge Mixtures

Bennamoun

Fraikin

et al. 2014

Drying Technology

View full text Add to dashboard Cite

Convective drying of wastewater sludges and sawdust/sludge mixtures was studied. The first part of this work was an experimental study performed in a cross-flow convective dryer using 500 g of wet material extruded through a disk with circular dies of 12 mm. The results showed that the sawdust addition has a positive impact on the drying process from a mass ratio of 2/8, on a dry basis, with observed drying rates higher than the original sludge. The second part of this work consisted of developing a drying model in order to identify the internal diffusion coefficient and convective mass transfer coefficient from the experimental data. A comparison was made between fitted drying curves, well represented by the Newton's model, and the analytical solutions of the diffusion equation applied to a finite cylinder. Variations of dimensional characteristics, such as the volume and exchange surface of the sample bed, were obtained by X-ray tomography. This technique allowed us to confirm that shrinkage, which is an important phenomenon occurring during sludge and sawdust/sludge mixture drying, must be taken into account. The results showed that both the internal diffusion coefficient and convective mass transfer coefficient were affected by mixing and sawdust addition. The internal diffusion coefficient changed from 7.77 Â 10 À9 m 2 /s for the original sludge to 7.01 Â 10 À9 m 2 /s for the mixed sludge and then increased to 8.35 Â 10 À9 m 2 /s for the mixture of a mass ratio of 4/6. The convective mass transfer coefficient changed from 9.70 Â 10 À8 m/s for the original sludge to 8.67 Â 10 À8 m/s for the mixed sludge and then increased to 12.09 Â 10 À8 m/s for the mixture of a mass ratio of 4/6. These results confirmed that sawdust addition was beneficial to the sludge drying process as the mass transfer efficiency between the air and material increased. Reinforcing the texture of sludge by adding sawdust can increase the drying rate and decrease the drying time, and then the heat energy supply will be reduced significantly. The study also showed that neglecting shrinkage phenomenon resulted in an overestimation for the internal diffusion coefficient for the convective drying of sludges and sawdust/sludge mixtures.

show abstract

Section: Determination Of the Mass Transfer Coefficientmentioning

confidence: 98%

“…[11,36] It is not possible to use the infinite approach because the radius is near to the height of the product. We adopted an approach called a superimposition technique, [33,35,37] which consists of providing the solution as the product of two infinite analytical solutions. Therefore, mathematically, we can write:…”

Section: Mathematical Model Empirical Modelsmentioning

confidence: 99%