The effects of moisture content, fiber length and compaction time on African oil palm empty fruit bunches briquette quality parameters.

In this paper a study on the process of densification of oil palm empty fruit bunches (OPEFB) is presented. An empirical-statistical model that allows the evaluation of densification process is obtained through an experimental factorial design. The main purpose of the experimental arrangement is to find the appropriate reference values for the experimental factors - moisture content, fiber length and compaction time-with which optimal performance responses of briquettes are achieved. Statistical models are obtained that explain in an acceptable way the influence of independent experimental factors on the mechanical properties of briquettes, such as briquettes density, durability index and compressive strength. It is possible to conclude that briquettes manufactured with the appropriate reference values, moisture content of 8% w.b., fiber length of 73.6 mm and a compaction time of 26.6 s respectively, meet mechanical and thermal requirements that are required in the most representative standards for biomass briquettes for energy purposes. Results obtained in the current investigation can be used as reference for the design of an industrial pilot plant destined to the densification of EFB of African oil palm.

Thermal, structural and mechanical characterization of Nephila clavipes spider silk in southwest Colombia.

Some physical properties of spider silks, including mechanical strength and toughness, have been studied in many laboratories worldwide. Given that this silk is organic in nature, composed of protein, and has similar properties to metal wires or polymers, it has the potential for application in medicine, nanoelectronics, and other related areas. In this study, we worked on spider silk from the Nephila clavipes species collected from the wild and kept it in the nursery of the Autonomous University of the West, Cali, Colombia, to determine its physical, thermal, and mechanical properties, seeking possible applications in the medical and industrial sectors and comparing the material properties of the silk from the species from southwestern Colombia with those of the previously studied species from other regions. The mechanical characterization of the material was performed using a universal testing machine; thermal behavior was captured by a thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry; and structural characterization was performed using diffraction X-rays. The results of the thermal characterization demonstrate that the spider silk loses 10 % of water content at 150 °C with significant changes at 400 °C, while the mechanical characterization indicates that the spider silk is much tougher than Kevlar 49 and Nylon 6 since it is capable of absorbing more energy before rupture.

Simulation of vorticity wind turbines.

There are a wide variety of devices behaving essentially as flexible and elastic systems while interacting dynamically with fluids, usually water or air, under normal operating conditions. Interactions of this kind involve a double complexity of the dynamics, as the systems go through large deformation due to the flow actions, and simultaneously, the flow dynamics is strongly influenced by the shape adopted by the systems. The present research adapts mathematical methods, still new to the field, to represent ways of dealing with flows of fluid in bidirectional interactions with those new technologies, and particularly applies them to the exploration of vorticity wind turbines (VWT), a new kind of vertical blade-less turbine that gathers energy from the vortex induced vibrations (VIV) of a relatively short and scalable mast. This research presents a framework for such modeling by coupling the discrete element method (DEM) with the Immersed Boundary Method (IBM), for the representation of VWT; and with the finite volume method (FVM), for solving the Navier-Stokes equations. Simulations show that the VWT achieves the lock-in effect for wind velocities between 9 and 15 m/s, with efficiency values between 20 and 30%. The preliminary results together with logistic and cost-related reasons, make these devices very promising, especially when considering the difficulties of implementing new approaches in developing countries.

A comparative study of the energy, exergetic and thermo-economic performance of a novelty combined Brayton S-CO2-ORC configurations as bottoming cycles.

This paper presents a comparative study on the energy, exergetic and thermo-economic performance of a novelty thermal power system integrated by a supercritical CO2 Brayton cycle, and a recuperative organic Rankine cycle (RORC) or a simple organic Rankine cycle (SORC). A thermodynamic model was developed applying the mass, energy and exergy balances to all the equipment, allowing to calculate the exergy destruction in the components. In addition, a sensitivity analysis allowed studying the effect of the primary turbine inlet temperature (TIT, PHIGH, rP and TC) on the net power generated, the thermal and exergy efficiency, and some thermo-economic indicators such as the payback period (PBP), the specific investment cost (SIC), and the levelized cost of energy (LCOE), when cyclohexane, acetone and toluene are used as working fluids in the bottoming organic Rankine cycle. The parametric study results show that cyclohexane is the organic fluid that presents the best thermo-economic performance, and the optimization with the PSO method conclude a 2308.91 USD/kWh in the SIC, 0.22 USD/kWh in the LCOE, and 9.89 year in the PBP for the RORC system. Therefore, to obtain technical and economic viability, and increase the industrial applications of these thermal systems, thermo-economic optimizations must be proposed to obtain lower values of the evaluated performance indicators.

A comparative energy and exergy optimization of a supercritical-CO2 Brayton cycle and Organic Rankine Cycle combined system using swarm intelligence algorithms.

This article presents a multivariable optimization of the energy and exergetic performance of a power generation system, which is integrated by a supercritical Brayton Cycle using carbon dioxide, and a Simple Organic Rankine Cycle (SORC) using toluene, with reheater ( S - C O 2 R H - S O R C ), and without reheater ( S - C O 2 N R H - S O R C ) using the PSO algorithm. A thermodynamic model of the integrated system was developed from the application of mass, energy and exergy balances to each component, which allowed the calculation of the exergy destroyed a fraction of each equipment, the power generated, the thermal and exergetic efficiency of the system. In addition, through a sensitivity analysis, the effect of the main operational and design variables on thermal efficiency and total exergy destroyed was studied, which were the objective functions selected in the proposed optimization. The results show that the greatest exergy destruction occurs at the thermal source, with a value of 97 kW for the system without Reheater (NRH), but this is reduced by 92.28% for the system with Reheater (RH). In addition, by optimizing the integrated cycle for a particle number of 25, the maximum thermal efficiency of 55.53% (NRH) was achieved, and 56.95% in the RH system. Likewise, for a particle number of 15 and 20 in the PSO algorithm, exergy destruction was minimized to 60.72 kW (NRH) and 112.06 kW (RH), respectively. Comparative analyses of some swarm intelligence optimization algorithms were conducted for the integrated S-CO2-SORC system, evaluating performance indicators, where the PSO optimization algorithm was favorable in the analyses, guaranteeing that it is the ideal algorithm to solve this case study.

A phenomenological base semi-physical thermodynamic model for the cylinder and exhaust manifold of a natural gas 2-megawatt four-stroke internal combustion engine.

This paper presents the application of a systematic methodology to obtain a semi-physical model of phenomenological base for a 2 MW internal combustion engine to generate electric power operating with natural gas, as a function of the average thermodynamic value normally measured in industrial applications. Specifically, the application of the methodology is focused on the cylinders, exhaust manifold, and turbocharger turbine sections. The proposed model was validated with actual operating data, obtaining an error rate not exceeding 5%, which allow a thermal characterization of the Jenbacher JMS 612 GS-N based on the model. A parametric analysis is conducted; considering the volumetric efficiency, the output electric power, the effective efficiency, the exhaust gas temperature, the turbine mass flow, the specific fuel consumption under the nominal operation conditions, which is 1.16 bar in the gas pressure, 65 °C in the cooling water temperature, 35 °C in the average ambient temperature, and 1500 rpm. The results of this model can be used to evaluate the thermodynamic performance parameters of waste heat recovery systems. On the other hand, new control strategies and the implementation of state observers for the detection and diagnosis of failures can be developed based on the proposed model.

Phenomenological models for the isothermal physical aging of PEEK.

Creep test is a useful tool to study thermal aging and deformation mechanisms of semi-crystalline polymers, such as polyether-ether-ketone (PEEK). Hou and Chen proposed a power law to fit creep data of PEEK aged at different temperatures and the master curve built from those data. This paper attempts to complement that analysis by introducing Kohlrausch function as an alternative to the fractional Maxwell's model associated to the power law. Although the fitting of experimental data and the mathematical conditions imposed to equations that describe curves that can be superimposed by translations, are obeyed by both models, this paper demonstrates that Kohlrausch function provides a better phenomenological description of the creep response of PEEK due to the physical interpretation of the fitting parameters and their dependence on the aging time and temperature.

A new method for characterization of small capacity wind turbines with permanent magnet synchronous generator: An experimental study.

This work presents a new and useful method to dimension wind turbines and control systems and to optimize their mechanical design. This method allows determining the principal curves for characterizing a small capacity wind turbine designed with a Permanent Magnet Synchronous Generator (PMSG). For the wind turbine characterization it was considered the losses in the process of energy transformation in the wind rotor, electric generator and in the bridge rectifier. The equivalent electric model of the synchronous generator was used to determine the electric parameter performance. The work of the wind rotor was considered in its maximum power curve and the PMSG performance in the linear region of its magnetization curve. This leads to develop a new methodology for the complete wind turbine characterization from the nominal parameters of the wind rotor and the electric generator. This method also allows obtaining the power curves and the parameters of voltage, current and efficiency around the wind speed domain and angular speed in the wind rotor. The method was tested for small-capacity wind turbine (1 kW and 10 kW) performances and the numerical and experimental results are described.