The potential industrial applications of curved tubes for single- and two-phase flow are reviewed within the context of physics of flow, trends in the development of technology, and its laboratory to industrial-scale commercialization. Comparison of the performance of curved tube configurations demonstrates its edge over the conventional motionless mixers, heat exchangers, and reactors. Alongside, their respective advantages and limitations are also highlighted. Further, a compendium of the available correlations for single- and two-phase friction factor and heat- and mass-transfer coefficient in curved tubes has also been presented. Key issues regarding the design parameters governing the performance of the curved tubes for mixing and heat- and mass-transfer that impact the research, development, and scale-up or scale-down of such devices are also analyzed. Emerging trends for the development of a new class of curved tubes, namely, inverters and serpentine and chaotic devices are also presented.

A Review on the Potential Applications of Curved Geometries in Process Industry

Investigation of nanofluid mixed convection in a shallow cavity using a two-phase mixture model

Techno-economic analysis of bioethanol production from lignocellulosic residues in Colombia: a process simulation approach.

Reaction pathways of glucose during esterification: effects of reaction parameters on the formation of humin type polymers.

https://www.frre.utn.edu.ar/quimobi/clean/files/get/item/2281

Optimization of the acid pretreatment of rice hulls to obtain fermentable sugars for bioethanol production

Kinetics of sequential reaction of hydrolysis and sugar degradation of rice husk in ethanol production: effect of catalyst concentration.

Some aspects on gas–solid flow in a U-bend: Numerical investigation

The incompressible, single-phase and multiphase, isothermal and steady-state flows in a U-bend are studied numerically using FLUENT 6.0. A basic understanding of gas–solid flow and pressure behavior in a U-bend is frequently required to obtain better U-bend design, for example, in pneumatic conveying dryers. Fyhr and Rasmuson found that U-bends significantly influence the drying behavior in such a dryer since they enhance velocity differences (slip) between suspended material and the drying medium. For single-phase flow, influences of the gas inlet velocity and the bend radius ratio on the velocity and pressure profiles in a U-bend are studied. The numerical calculations were validated against experimental data from the literature. The gas inlet velocity varies from 5 up to 25 m s−1 while the bend radius ratio varies from 2 up to 8 m m−1, The gas inlet velocity has a strong influence on the total pressure drop of the system and the bend radius ratio strongly affects the velocity and pressure profiles in a U-bend. For multiphase flow, the bend radius ratio was varied from 3 up to 8 with constant gas velocity of 15 m s−1. There are three important effects of the U-bend: increase in slip velocity; an accumulation of particles along the outer walls of the U-bend and the beginning of downstream pipe; and an increase in pressure drop. A higher slip velocity and a better dispersion of particles are desired for a pneumatic conveying drying system while an increase in pressure drop is not favorable. Choice of the appropriate velocity and bend shape can, therefore, be utilized in the overall optimization of the operating conditions of pneumatic conveying systems.

Numerical assessment of gas-solid flow in a U-bend.

Lignocellulosic materials sustainability in ethanol production could be supported by the use of mixed raw materials. Therefore the effect of mixed raw materials to hydrolysis kinetics needs to be studied. For this purpose each raw material was hydrolyzed and the mixed raw materials were also hydrolyzed. As a result, a comparison of the kinetics models of dilute sulfuric acid hydrolysis between various lignocellulosic materials (leaf, twig, corn cob, sawdust) and its mixture was obtained. It was observed that a pseudo-homogeneous model can quantitatively describe individual materials as well as mixed materials with different levels of accuracy. Besides the kinetics model, the influence of various lignocellulosic materials on sugar yield was also investigated. The results showed that the lignin content of the raw material influenced the sugar yield of the hydrolysis. Moreover the mixed lignocellulosic materials did not proportionally provide a yield based on its composition. Some hydrolyzates were fermented...

Sulfuric acid hydrolysis of various lignocellulosic materials and its mixture in ethanol production

Computational fluid dynamics (CFD) modelling with the Eularian–Eularian formulation is used to describe the drying phenomena occurring in pneumatic conveying drying particularly in the U-bend. Two user defined scalar equations (UDSs) are inserted into the solution to take into account the solid particle moisture content and the mass fraction of water in the gas phase, respectively. The drying kinetics cover the two periods of drying: the constant drying rate and the falling drying rate. The investigation emphasized influences of the parameters (solid loading ratio, gas velocity, bend radius ratio, feed moisture content and geometry arrangement of a U-bend) on the drying rate and moisture content. A validation of the drying model is accomplished by comparing calculation results with experimental data. In general, the drying rate decreases along the axial direction of pipe due to the decrease in driving force (the air humidity increases). The mass-weighted average drying rate shows a slight decrease in and just after the U-bend, which is mainly due to the high accumulation of solid particles at the outer U-bend wall. Solid particles disperse and the slip velocities are high in the area after the U-bend. This causes the mass-weighted average drying rate to slightly increase.

Muslikhin Hidayat

Papers

Kinetics of sequential reaction of hydrolysis and sugar degradation of rice husk in ethanol production: effect of catalyst concentration.

Some aspects on gas–solid flow in a U-bend: Numerical investigation

Numerical assessment of gas-solid flow in a U-bend.

Sulfuric acid hydrolysis of various lignocellulosic materials and its mixture in ethanol production

Heat and Mass Transfer in U-Bend of a Pneumatic Conveying Dryer