Turbulent natural convection of air that happens into inner square cavity with localized heating from horizontal bottom surface has been numerically investigated. Localized heating is simulated by a centrally located heat source on the bottom wall, and two values of the dimensionless heat source length ? are considered in the present work. Solutions are obtained for several Rayleigh numbers with Prandtl number Pr = 0.70. The horizontal top surface is thermally insulated and the vertical surfaces are assumed to be the cold isothermal surfaces whereas the heat source on the bottom wall is isothermally heated. In this study, the Navier-Stokes equations are used considering a two-dimensional and turbulent flow in unsteady state. The Finite Element Method (FEM) with a Galerkin scheme is utilized for solving the conservation equations. The formulation of conservation equations is carried out for turbulent flow and the implementation of turbulent model is made by Large-Eddy Simulation (LES). The distributions of the stream function and of the temperature are determined as functions of thermal and geometrical parameters. The average Nusselt number Num is shown to increase with an increase in the Rayleigh number Ra as well as in the dimensionless heat source length ?. The results of this work can be applied to the design of electronic components

Theoretical framework: A biodiesel fuel is made from long-chain fatty acids derived from vegetable oil or animal fat. Similarities between physical-chemical characteristics of diesel and biodiesel make their mixture feasible. Environmental benefits achieved by using biofuels to drive machines has increased their contribution in energetic matrixes. Objective: The aim of this research is to produce soybean and sunflower biodiesel in the laboratory using a transesterification reaction and to examine the biodiesel specifications for utilization in compression ignition engines. Method: The physical-chemical properties of the biodiesel measured in the present work are density, viscosity, cetane index, flash point, pour point, and cloud point. Results and conclusion: For soybean and sunflower biodiesel, density (867 kg/m³, 860 kg/m³), viscosity (5.29 mm²/s, 5.30 mm²/s), Centane index (53.88, 55.66), flash point (187°C and 135.6°C) are reported respectively. Regarding the pour point, cloud point, were only determined for sunflower biodiesel, respectively, -2°C and 13°C. The results indicate that these properties, density, kinematic viscosity, flash point, as determined from the soybean and sunflower biodiesel are within the limits established by The Brazilian National Agency of Petroleum, Natural Gas and Biofuels, Resolution No. 45 of the ANP of 08/25/2014 – DOU 08/26/2014. These values are, respectively, 850-900 kg/m³, 3-6 mm²/s, at least 100°C.The produced biodiesel presented behavior similar to diesel S10 proving its viability of use. Research implications: As a result of such thorough research, we are able to compare many characteristics of soybean and sunflower biodiesel with commercial diesel S10. This research is critical to the performance evaluation of a compression ignition engine and the potential reduction in greenhouse gas emissions associated with conventional diesel.

Objective: The objective of this study is to investigate the thermal behavior of coated cutting tools in industrial turning processes, aiming to enhance machining efficiency and prolong tool lifespan. Theoretical Framework: The study is grounded in the concepts of heat transfer, thermally insulating coatings, and their impact on cutting tool performance. Key theories and models include thermal conductivity, thermal insulation, and heat dissipation mechanisms. Methodology: The research employs numerical simulation using the COMSOL® Multiphysics package to model transient heat transfer within coated tools and their holders. Thermal contact resistance at the tool-holder interface is also considered. Two coating configurations (Model 1 and Model 2) with different materials are analyzed, resulting in six simulation scenarios. Results and Discussion: The simulations demonstrate significant temperature reductions in the coated tools compared to uncoated ones, with Model 2 showing the most substantial decrease. These findings indicate the effectiveness of thermally insulating coatings in mitigating heat generation and improving tool performance. Research Implications: The study's findings have practical implications for the manufacturing industry, suggesting that the use of specific coatings can lead to higher cutting velocities and prolonged tool lifespan. These insights can inform decision-making in tool selection and process optimization. Originality/Value: This research contributes to the literature by providing a detailed analysis of the thermal behavior of coated cutting tools under extreme temperatures. The study's innovative approach and practical implications offer valuable insights for improving machining processes and tool performance. Objetivo: El objetivo de este estudio es investigar el comportamiento térmico de herramientas de corte recubiertas en procesos industriales de torneado, con el fin de mejorar la eficiencia del mecanizado y prolongar la vida útil de las herramientas. Marco teórico: El estudio se basa en los conceptos de transferencia de calor, recubrimientos térmicamente aislantes y su impacto en el rendimiento de las herramientas de corte. Las teorías y modelos clave incluyen la conductividad térmica, el aislamiento térmico y los mecanismos de disipación de calor. Metodología: La investigación utiliza simulación numérica con el paquete COMSOL® Multiphysics para modelar la transferencia de calor transitoria dentro de las herramientas recubiertas y sus soportes. También se considera la resistencia térmica de contacto en la interfaz herramienta-soporte. Se analizan dos configuraciones de recubrimiento (Modelo 1 y Modelo 2) con diferentes materiales, lo que resulta en seis escenarios de simulación. Resultados y discusión: Las simulaciones muestran reducciones significativas de temperatura en las herramientas recubiertas en comparación con las no recubiertas, siendo el Modelo 2 el que muestra la disminución más sustancial. Estos resultados indican la eficacia de los recubrimientos térmicamente aislantes en la mitigación de la generación de calor y la mejora del rendimiento de las herramientas. Implicaciones de la investigación: Los hallazgos del estudio tienen implicaciones prácticas para la industria manufacturera, sugiriendo que el uso de recubrimientos específicos puede conducir a mayores velocidades de corte y una vida útil prolongada de las herramientas. Estos conocimientos pueden informar la toma de decisiones en la selección de herramientas y la optimización de procesos. Originalidad/Valor: Esta investigación contribuye a la literatura al proporcionar un análisis detallado del comportamiento térmico de herramientas de corte recubiertas en temperaturas extremas. El enfoque innovador del estudio y sus implicaciones prácticas ofrecen ideas valiosas para mejorar los procesos de mecanizado y el rendimiento de las herramientas. Objetivo: O objetivo deste estudo é investigar o comportamento térmico de ferramentas de corte revestidas em processos industriais de torneamento, visando melhorar a eficiência da usinagem e prolongar a vida útil das ferramentas. Referencial Teórico: O estudo está fundamentado nos conceitos de transferência de calor, revestimentos termicamente isolantes e seu impacto no desempenho das ferramentas de corte. Teorias e modelos-chave incluem condutividade térmica, isolamento térmico e mecanismos de dissipação de calor. Metodologia: A pesquisa utiliza simulação numérica usando o pacote COMSOL® Multiphysics para modelar a transferência de calor transiente dentro das ferramentas revestidas e seus suportes. A resistência térmica de contato na interface ferramenta-suporte também é considerada. Duas configurações de revestimento (Modelo 1 e Modelo 2) com diferentes materiais são analisadas, resultando em seis cenários de simulação. Resultados e Discussão: As simulações demonstram reduções significativas de temperatura nas ferramentas revestidas em comparação com as não revestidas, sendo o Modelo 2 o que apresenta a diminuição mais substancial. Esses resultados indicam a eficácia dos revestimentos termicamente isolantes na mitigação da geração de calor e melhoria do desempenho das ferramentas. Implicações da Pesquisa: As descobertas do estudo têm implicações práticas para a indústria de fabricação, sugerindo que o uso de revestimentos específicos pode levar a maiores velocidades de corte e vida útil prolongada das ferramentas. Esses insights podem informar a tomada de decisões na seleção de ferramentas e...