RESUMO Este estudo teve como objetivo avaliar diferentes tipos de máquinas adaptadas para as atividades de colheita florestal mecanizada, de forma a quantificar o grau de atendimento aos princípios ergonômicos aplicáveis às máquinas florestais, bem como os riscos ergonômicos aos quais os trabalhadores estão expostos. Foram avaliadas as seguintes máquinas: um feller buncher adaptado em uma pá carregadeira de rodas; um mini skidder acoplado a um trator agrícola; e um carregador florestal adaptado a um trator agrícola; operando nos estados do Paraná e Minas Gerais. As condições biomecânicas do trabalho foram avaliadas através da aplicação de um check-list para avaliação simplificada das condições biomecânicas do posto de trabalho. A avaliação das posturas forçadas foi realizada utilizando o método REBA - "Rapid Entire Body Assessment". Por sua vez, a classificação ergonômica foi através das diretrizes contidas no manual de classificação ergonômica "Ergonomic Guidelines for Forest Machines". Ainda, foram avaliados os fatores ambientais ruído, temperatura e vibração aos quais os operadores destas máquinas estavam expostos. Os resultados apontaram que todas as máquinas avaliadas apresentaram padrões ergonômicos abaixo dos indicados em todos os aspectos avaliados, principalmente relacionados ao acesso e dimensões do posto de trabalho, necessidade de adoção de posturas forçadas durante a jornada de trabalho, e exposição aos fatores ambientais avaliados acima dos limites de tolerância. Conclui-se que as máquinas adaptadas para utilização em processos de colheita florestal tem apresentado importantes lacunas em relação aos aspectos ergonômicos, apresentando elevado e iminente risco de desenvolvimento de doenças ocupacionais em seus operadores.

ABSTRACT This study aimed to assess different types of machines adapted for mechanized forest harvesting activities in order to quantify the degree of compliance with ergonomic principles applicable to forest machines, as well as the ergonomic risks to which workers are exposed. The following machines were evaluated: a feller buncher adapted into a wheel loader; a mini skidder coupled to an agricultural tractor; and a forest loader adapted to an agricultural tractor; operating in the states of Paraná and Minas Gerais. Biomechanical working conditions were assessed by applying a checklist for simplified assessment of the workplace biomechanical conditions. The forced postures assessment was performed using the REBA - "Rapid Entire Body Assessment" method. In turn, ergonomic classification was through guidelines contained in the ergonomic classification manual "Ergonomic Guidelines for Forest Machines". Moreover, the environmental factors noise, temperature and vibration to which the operators of these machines were exposed were assessed. The results showed all assessed machines had ergonomic standards below those indicated in all assessed aspects, mainly related to access and dimensions of the workplace, need to adopt forced postures during working hours, and exposure to environmental factors assessed above tolerance limits. It is concluded that machines adapted for use in forest harvesting processes have shown significant gaps in relation to ergonomic aspects, presenting high and imminent risk of development of occupational diseases in their operators.

Abstract A few decades ago, the product development process was just based on a trial and error procedure, and the designer's experience. The need for a new way to design and manufacture more economical and sustainable products corroborates increasingly to a new vision of how to create new products for the benefit of society. Modern numerical tools allow greater knowledge about the physical phenomena involved in engineering problems and enable cost reduction with trials and time of manufacture and projection. Among the equipment that can be mentioned where numerical simulation is used, can be found heat exchangers, which are capable of accomplishing the heat transfer between two fluid medias with different temperatures. Within the range of existing exchangers, this work will address a compact model with louvered fins, widely used in the automotive and aerospace industries, mainly due to their high thermal exchange surface vs occupied volume ratio. The heat exchanger surface is analised using computational fluid dynamics tecniques disposable in the commercial code ANSYS CFX14® to reproduce the flow at service condition. Genetic optimization routines are used to increase the performance of heat exchanger. As a result, a heat transfer surface is obtained with about a 25% better performance according to the selected objective function. The dimensionless factor of the convective heat transfer coefficient (Colburn factor, j) and the friction factor (Fanning factor, f) used in (Wang et al.,1998), are employed for simulation. Experimental data are also used for validation.

Abstract The objective of this research is to assess how much the improvement in the combustion reaction efficiency can reduce fuel consumption, maintaining the same thermal energy rate provided by the reaction in a pelletizing furnace. The furnace for pelletizing iron ore is a complex thermal machine, in terms of energy balance. It contains recirculation fan gases and constant variations in the process, and the variation of a single process variable can influence numerous changes in operating conditions. This study demonstrated how the main variables related to combustion in the burning zone influence fuel consumption (natural gas) from the furnace of the Usina de Pelotização de Fábrica (owned by VALE S/A), without changing process conditions that affect production quality. Variables were analyzed regarding the velocity and pressure of the fuel in the burners, the temperature of the combustion air and reactant gases, the conversion rate and the stoichiometric air/fuel ratio of the reaction. For the analysis, actual data of the furnace in operation was used, and for the simulation of chemical reactions, the software Gaseq® was used. The study showed that the adjustment of combustion reaction stoichiometry provides a reduction of 9.25% in fuel consumption, representing a savings of US$ 2.6 million per year for the company.