Romeu Miqueias Szmoski's research while affiliated with Federal University of Technology - Paraná/Brazil (UTFPR) and other places

A thermosyphon is a gravity-assisted heat pipe used to improve heat transfer in several applications. Its main feature is the use of latent heat of vaporization to transmit heat at high rates over considerable distances with a small decrease in temperature. In this work, the experimental performance of a thermosyphon was compared with its thermal design, in order to verify its correct operating. The thermosyphon was manufactured from a copper tube with an outer diameter of 22.23mm, an inner diameter of 20.80mm, and a total length of 840mm. The working fluid used was distilled water with a filling ratio of 50% of the evaporator volume. The evaporator has a length of 650mm, while the adiabatic section and condenser have lengths of 80mm and 110mm, respectively. The condenser was cooled by water forced convection and the evaporator was heated by Joule’s effect. Experimental tests were performed for a heat load of 80 to 140W in a position at 25º from the horizontal (evaporator above the condenser). The thermal analysis of the thermosyphon was performed from thermocouples arranged in their regions, as well as the value of the thermal load dissipated by it. Some specific points of the experimental apparatus were identified for possible adjustments, such as better insulation, different manifold, and different water flow conditions. The thermosyphon operated as expected in all the analyzed aspects – temperature distribution, thermal resistance, thermal design’s heat load, and thermal and exergy efficiencies – which showed that the methodology used to its construction is adequate.

Neste trabalho foi realizada uma análise térmica experimental de termossifões distintos para aplicação em um sistema híbrido fotovoltaico/térmico. Os termossifões foram fabricados a partir de tubos de cobre possuindo comprimento total de 840mm. O fluido de trabalho utilizado foi água destilada com razão de preenchimento de 50% do volume do evaporador. O evaporador tem comprimento de 650mm, enquanto a seção adiabática e o condensador têm comprimentos de 80mm e 110mm, respectivamente. O condensador foi resfriado por convecção forçada de água, a seção adiabática foi isolada e o evaporador foi aquecido por um resistor elétrico. Testes experimentais foram realizados para uma carga térmica de 80W a 140W em uma posição a 25° da horizontal (evaporador acima do condensador). A análise térmica foi baseada na distribuição de temperaturas ao longo dos dispositivos passivos de transferência de calor, sua resistência térmica e eficiência térmica. O Termossifão B, que possui maior diâmetro, apresentou melhores resultados nas condições testadas, se mostrando assim a melhor escolha entre os dois termossifões para compor um sistema híbrido fotovoltaico/térmico.

The basic physics of traveling waves and standing waves are fundamental topics in the education of science and engineering students. These concepts are found in many areas, including classical mechanics, quantum mechanics, and electromagnetism. Typically, laboratory demonstrations of traveling waves and standing waves are based on mechanical systems such as vibrating strings and sound waves. This paper presents a simple benchtop experiment for producing and observing electromagnetic standing waves in a coaxial cable and determining the phase velocity of their underlying component traveling waves. We also discuss the experimental requirements for this experiment.

Resumo Os conceitos de ondas estacionárias e modos normais são dos mais fundamentais da física, tanto da mecânica clássica como da quântica e do eletromagnetismo. Demonstrações usuais da existência de modos normais de oscilação incluem quase que exclusivamente modelos mecânicos, como por exemplo, cordas vibrantes. Neste artigo propomos um experimento simples para a geração e observação de ondas eletromagnéticas estacionárias em um cabo coaxial.

In the present work, an experimental analysis was performed to obtain the calibration curve of three load cells connected in series. The control of the load applied on a given component is an important factor in some engineering applications, for example, in cases where it is desired to increase the heat exchange between two surfaces. One of the ways to control the applied load is the use of load cells, which has as its principle of use a strain gauge that has its resistance varied when it undergoes a deformation, thus causing a voltage variation due to the application of load. This study used an ArduinoTM microcontroller as a data acquisition system and blocks with known mass for load application. In this way it was possible to obtain the calibration curve of the load cells by means of linear regression between the mass of the blocks and the data obtained by the ArduinoTM microcontroller and verify their applicability according to their measurement uncertainties.