Influence of Prandtl Number on Thin Film Condensation in Forced Convection in an Inclined Wall Covered with a Porous Material

The numerical study of thin film type condensation in forced convection of a saturated pure vapor in an inclined wall covered with a porous material is presented. The generalized Darcy-Brinkman-Forchheimer (DBF) model is used to describe the flow in the porous medium while the classical boundary layer equations have been exploited in the case of a pure liquid. The dimensionless equations are solved by an implicit finite difference method and the iterative Gauss-Seidel method. The objective of this study is to examine the influence of the Prandtl number on the hydrodynamic and thermal fields but also on the local Nusselt number and on the boundary layer thickness. For Pr ≤ 0.7 (low) the velocity and the longitudinal temperature increase with the Prandtl number. On the other hand, when Pr ≥ 2 (high) the Prandtl number no longer influences the velocity and the longitudinal temperature. The local Nusselt number increases as the Prandtl number increases and the thickness of the hydrodynamic boundary layer increases as the Prandtl number decreases.

Numerical Study of Thin Film Condensation in Forced Convection on an Inclined Wall Covered with a Porous Material

The present work presents a study of forced convection condensation of a laminar film of a pure and saturated vapor on a porous plate inclined to the vertical. The Darcy-Brinkman-Forchheimer model is used to write the flow in the porous medium, while the classical boundary layer equations have been exploited in the pure liquid and in the porous medium taking into account inertia and enthalpy convection terms. The problem has been solved numerically. The results are mainly presented in the form of velocity and temperature profiles. The obtained results have been compared with the numerical results of Chaynane et al. [1]. The effects of different influential parameters such as: inclination (ϕ), effective viscosity (ReK), and dimensionless thermal conductivity λ* on the flow and heat transfers are outlined.

Characterization of the Omni-Processor Sewage Sludge Ash for Reuse as Construction Material

Omni Processors(OP)are machines which use sludge as a fuel to generate electricity and clean water,but create ash at the same time.In the present study,fly ash and bottom ash are investigated as materials for potential reuse in the construction field.First,the granular size,density and Blaine finesse are determined.Then,the chemical composition and microstructure are obtained by means of X-ray fluorescence and Scanning Electron Microscopy-Energy Dispersive Spectroscopy(SEM-EDS),respectively.Finally,ashes reactivity is determined by two chemical methods(modified Chapelle test,bound water content R3)and a mechanical method(pozzolanic activity index).The characterization results indicate two material types:fly ash similar to cement and bottom ash similar to fine sand.That’s why the mortars mechanical strength with fly ash 0%-30%is better than that with bottom ash at the same rate.Fly ash slightly decreases the mechanical strength of mortars while bottom ash induces a much more significant decrease.

Modeling of the Photovoltaic Module Operating Temperature for Various Weather Conditions in the Tropical Region

The operating temperature is a critical factor affecting the performances of photovoltaic(PV)modules.In this work,relevant models are proposed for the prediction of this operating temperature using data(ambient temperature and solar irradiance)based on real measurements conducted in the tropical region.For each weather condition(categorized according to irradiance and temperature levels),the temperatures of the PV modules obtained using the proposed approach is compared with the corresponding experimentally measured value.The results show that the proposed models have a smaller Root Mean Squared Error than other models developed in the literature for all weather conditions,which confirms the reliability of the proposed framework.

Effects of Chemical Treatment on the Physical Properties of Typha

Plant-based concretes are produced from plant aggregates and a binder.Plant fibers are mainly composed of saccharides(sugars)and these sugars can decrease the concentration of Ca2+ions in the cement pore solution and delay the formation of hydration products.To improve the interfacial bond between fibers and matrix a chemical treatment is widely used.This study investigates the effect of sodium hydroxide treatment on physical and hygroscopic properties of Typha aggregates.In particular,a 5%sodium hydroxide solution is used to treat these aggregates and their bulk and absolute densities,porosity,water content and water absorption are evaluated accordingly.Results indicate that bulk and absolute densities increase after treatment from 56.44 kg/m^(3) to 122.57 kg/m^(3) and 541.93 kg/m^(3) to 555.17 kg/m^(3),respectively.NaOH treatment reduces porosity of Typha from 89.58%to 77.92%and decreases water content from 1.4%to 1%.The treatment with sodium hydroxide reduces substantially the water absorption of the aggregates.

Two-Dimension Numerical Simulation of Parabolic Trough Solar Collector: Far North Region of Cameroon

Cameroon lives in the era of great infrastructures in order to reach the economic emergence by 2035. These infrastructures require a solid framework of energy provisions from many natural energy sources and resources that the country possesses. Speaking of natural energy resources, the country is particularly gifted by solar energy potential in the far north. This region of the land is densely populated but much of the populations do not have access to electricity since they live in remote areas far from national electricity grid. Solar thermal energy appears then as real potential to fulfill the growing demand of energy and reduce fossil fuel use dependence. Moreover, it would also be a grandiose opportunity for hospitals in these regions to provide hot water for Sterilization. As the design of a solar thermal plant strongly relies on the potential of direct solar irradiance and the performance of a solar parabolic trough collector (PTC) estimated under the local climate conditions, in this paper, we annually compute direct solar radiation based on monthly average Linke turbidity factor and various tracking modes in two chosen sites in the far north region of Cameroon. Also, a detailed two dimensional numerical heat transfer analysis of a PTC has been performed. The receiver has been divided into many control volumes along his length and each of them is a column consisting of glass, vacuum, absorber and fluid along which mass and energy balance have been applied. Direct solar irradiation, ambient temperature optical and thermal analyses of the collector receiver takes into consideration all modes of heat transfer and the nonlinear algebraic equations were solved simultaneously at each instant during a day of computation using Engineering Equation Solver (EES). To validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL). It has shown a great concordance with a maximum relative error value of 0.35% and thermal efficiency range of systems about 66.67% - 73.2%. It has also been found that the one axis polar East-West and horizontal East-West tracking with 96% and 94% of full tracking mode respectively, were most suitable for a parabolic trough collector throughout the whole year in the two towns considered.