66 research outputs found

    Feature investigation using micro computed tomography within materials

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    This work uses micro computed tomography, as a direct non-destructive tool, to investigate the internal 3D microstructure of different materials at multiple length scales to provide insights that are of interest to the scientific community on a variety of different problems.In the first chapter, the 3D microstructure of three types of manufactured biomass microsphere particles was investigated before and after fast pyrolysis. The results show that the particle size, biomass components, and volume of air decrease during fast pyrolysis.Next, concrete mixtures with different aggregate gradations and workability were prepared to study the aggregate packing in hardened concrete. The results show that low distance between aggregates and areas where no aggregates are observed correspond with mixtures of poor workability in the fresh concrete. These findings suggest that segregation of the coarse aggregate plays an important role in the workability of fresh concrete.In addition, the role of critical degree of saturation and air void system on the crack propagation of cement mortar subjected to freeze-thaw cycles was investigated. The results show that cracking occurred in non-air entrained mortar subjected to a single freeze-thaw cycle when the critical degree of saturation was near 100%. These microcracks mostly initiate and propagate from the paste-aggregate interface or from within aggregate. In addition, materials were observed to form within the pores after freezing.Finally, the role of air void system on the freeze-thaw damage of the cement paste was investigated. The results show that severe frost damage occurred in the surface of the non-air entrained cement paste ponded with KI solution after 63 freeze-thaw cycles. It was also observed that the average distance between air voids in the non-air-entrained was ~ 1.8x higher than the average distance between air voids in the air-entrained samples. In addition, most of the air voids (~75%) in both non-air-entrained and air-entrained samples are distributed in size ranges between 15 to 60 um. These observations show that X-ray imaging is a powerful method that provides new insights into physical properties and morphology of biomass particles, workability of flowable concrete, and freeze-thaw performance of concrete

    4E assessment of power generation systems for a mobile house in emergency condition using solar energy: a case study

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    In this study, a solar parabolic trough concentrator (PTC) was evaluated as a heat source of a power generation system based on energy (E1), exergy (E2), environmental (E3), and economic (E4) analyses. Various configurations of power generation systems were investigated, including the solar SRC (SRC) and solar ORC (ORC). Water and R113 were used as heat transfer fluids of SRC and ORC system, respectively. It should be mentioned that the proposed solar systems were evaluated for providing the required power of a mobile house in an emergency condition such as an earthquake that was happened in Kermanshah, Iran, in 2016 with many homeless people. The PTC system was optically and thermally investigated based on sensitivity analysis. The optimized PTC system was assumed as a heat source of the RC with two various configurations for power generation. Then, the solar RC systems were investigated based on 4E analyses for providing the power of the mobile house based on various numbers of solar RC units. It was concluded that the solar SRC system could be recommended for achieving the highest 4E performance. The highest value of its energy efficiency was found at 24.60% and of his exergy at 26.37%. On the other hand, the ORC system has energy and exergy efficiencies at 17.64% and 18.91%, respectively, which are significantly lower than the efficiencies of the SRC system. The optimum heat source temperature for the SRC system is found at 650 K, while for the ORC system at 499 K. Moreover, the best economic performance was found with the SRC system with a payback period of 7.47 years. Finally, the CO2 mitigated per annum (φCO2) was estimated at 5.29 (tones year−1), and the carbon credit (ZCO2) was calculated equal to 76.71 ($ year−1)

    Hybrid optimization algorithm for thermal analysis in a solar parabolic trough collector based on nanofluid

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    In recent years, many research works focused on improving and reducing the cost of solar collectors. This paper focuses upon the development of an efficient modeling and optimization of solar collector. The approach adopted in modeling utilizes a parabolic trough collector absorber tube with non-uniform heat flux, fully developed mixed convection flow and Al2O3/synthetic oil as a base fluid. Optimization of thermal analysis in a solar trough collector using nanofluid is non-convex, non-linear and computationally intensive process. In order to overcome these difficulties, a hybrid optimization method involving GA (genetic algorithm) and SQP (sequential quadratic programming) is introduced in the optimization process. The optimization problem used in this study involves maximization of a nondimensional correlation consisting of Nusselt number and pressure drop with Reynolds and Richardson number which are used as design constraints. The methodology implemented within an integrated environment involving Matlab, Gambit and Fluent. The results obtained show that heat transfer enhancement has a direct relationship with the nanoparticle concentration ratio whereas it has inverse relationship with the operational temperature. In addition, the results show that the proposed methodology provides an effective way of solving thermal analysis in a solar parabolic trough collectors based on simulation models
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