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A computational model capable of simulating heat and mass transfer in conjugate fluid-porous domains is utilized to simulate forced convective drying. The material to be dried is considered as the porous region, which is coupled through interfaces to the surrounding pure fluid region. The computational model solves transport equations for mass and momentum, energy, and moisture in all regions simultaneously. The model includes non-equilibrium heat and moisture transport in the porous region such that the fluid and solid constituents, and the exchanges between them, are captured. The interfacial moisture transfer condition between phases in the porous region, and between the porous and pure fluid regions, is developed to show the level of detail required for modeling. The study considers the drying of apple flesh to validate the developed drying model against available experimental data. The results show accurate prediction of moisture content as a function of drying time for different airflow velocities, and correctly capture the influences of temperature, relative humidity and initial moisture content on the drying rate. Thus, the model is considered viable for taking steps towards implicit dynamic coupling of the constituents in the porous region.

The gas-liquid two-phase slug flow regime phenomenon is commonly encountered in the chemical engineering industry, particularly in oil and gas production transportation pipelines. Slug flow regime normally occurs for a range of pipe inclinations, and gas and liquid flowrates. A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flowrates at the outlet. Therefore, the monitoring of slugs and the measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. In this paper, a correlation between gas void fraction, absolute acoustic emission energy, and slug velocities in a two-phase air/water flow regime was developed using an acoustic emission technique. It is demonstrated that the gas void fraction can be determined by measurement of acoustic emission.

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The two-phase liquid/gas slug flow regime phenomenon can be encountered over a range of gas and liquid flowrates. Monitoring of slugs and measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. This article presents experimental results correlating acoustic emission measurements with gas void fraction in a two-phase water/air flow regime. It is concluded that the gas void fraction can be determined by the measurement of acoustic emission, which hitherto has not been investigated.

SUMMARY The present research is focused on the two‐step ZnO/Zn thermochemical water splitting cycle for hydrogen production. In the present paper, the numerical modeling of the first step, which involves endothermic reduction of zinc oxide (ZnO), is carried out in a cylindrical reactor using Computational Fluid Dynamics (CFD). The parametric study shows that the fractional conversion of ZnO increases with an increase in the flow rate of ZnO, while it decreases with an increase in the ZnO particle diameter and carrier gas mass flow rate. Six different reactor configurations are also assessed comprehensively. It is observed that a cylindrical reactor with a tangential inlet at the top plane and a tangential outlet at the bottom plane has higher robustness to the variation of various operating parameters with consistently high ZnO fractional conversion. Copyright © 2013 John Wiley & Sons, Ltd.

Due to the depleting reserves of fossil fuels and their harmful effects on the environment, there is an urgent need to explore clean alternative energy resources to fulfil the growing energy demand. Sunlight is an abundant source of energy, and its storage and utilization in the form of hydrogen is considered to be effective and cleanest. The present research is focused on the numerical investigation of hydrogen production through thermo-chemical decomposition of water. In this paper we report on the first step reaction which is the endothermic reduction of zinc oxide in a solar reactor/receiver coupled with a parabolic dish type solar energy concentrator. The simulations were conducted in a three-dimensional reactor model using the commercial CFD software FLUENT. The results of parametric study showed an increase in the fractional conversion of zinc oxide with a decrease in the diameter of the zinc oxide particles, while this fractional conversion decreased with a decrease in the zinc oxide mass flow rate. It was also observed that the particle initial temperature has no effect on the fractional conversion of the zinc oxide. The outlet temperature of the fluid mixture was also not influenced significantly by the zinc oxide fractional conversation and remained over 1800K for the entire fractional conversion range of zinc oxide.