High Temperatures

Resumo: O clima possui uma variabilidade natural, que resulta das interações entre o sistema terra-atmosfera e que culmina, muitas vezes, com a deflagração de eventos extremos que são intensificados pela ação humana, que podem causar grandes impactos negativos à sociedade. O objetivo deste estudo foi produzir uma análise da variabilidade das temperaturas máximas anuais no estado do Paraná no período de 1976 a 2015, visando identificar períodos mais quentes. As análises constantes no trabalho foram feitas por meio da aplicação de diferentes índices: 1- primavera - verão (P-V); 2 - índice diário (ID) e 3 - índices de extremos térmicos propostos pela OMM. Como resultado da análise da variabilidade anual das temperaturas, o Método Gráfico Cronológico de Tratamento de Informação (MGCTI) possibilitou uma análise conjunta dos dados das estações e mostra um aquecimento após a década de 2000. O índice P-V detecta somente os eventos mais extremos que ocorrem com frequência nos meses de novembro a fevereiro. O índice ID identifica os eventos de aquecimento anômalo que ocorrem durante todo o ano e, no Paraná, foi verificado que os maiores registros ocorrem nas estações de outono e inverno. Por meio da análise dos índices dos extremos térmicos da OMM foi possível identificar que as estações localizadas na região norte e oeste do estado, principalmente, aquelas localizadas ao norte do trópico de Capricórnio apresentaram ondas de calor mais significativas, de maior duração e com temperaturas mais elevadas. Por outro lado, as estações situadas no centro-sul do estado demonstram ondas de calor com menor intensidade e duração. Pelo fato de que as ondas de calor são caracterizadas de formas diferentes pelos métodos aplicados, destaca-se que os resultados são dependentes do índice utilizado, sendo assim, a seleção do critério para determinar as ondas de calor depende do propósito do estudo.

Abstract: The climate has a natural variability, which results from the interactions between the earth-atmosphere system and culminating, often, with the outbreak of extreme events that are intensified by human action, which can cause great negative impacts to society. The objective of this study was to produce an analysis of the variability of annual maximum temperatures in the state of Paraná from 1976 to 2015, seeking to identify warmer periods. The analyzes in the work were done through the application of different indexes: 1 - spring - summer (P-V); 2 - daily index (ID) and 3 - thermal extremes indices proposed by WMO. As a result of the analysis of the annual variability of temperatures, the chronological graphic method of information processing (MGCTI) allowed a joint analysis of the data of the seasons and shows a warming after the decade of 2000. The P-V index detects only the more extreme events that occur frequently in the months of November to February. The ID index identifies the events of anomalous warming occurring throughout the year, and in Paraná, it was verified that the largest records occur in the autumn and winter seasons. Through the analysis of the thermal extremes indexes of the WMO, it was possible to identify that the stations located in the north and west of the state, mainly those located north of the Tropic of Capricorn, presented more significant heat waves of longer duration and with higher temperatures. On the other hand, the stations located in the center-south of the state show heat waves with less intensity and duration. Because the heat waves are characterized in different ways by the applied methods, it is emphasized that the results are dependent on the index used, so, the selection of the criterion to determine the heat waves depends on the purpose of the study.

The thermophysical properties of Cu-based industrial alloys in the liquid phase have been determined in the framework of ThermoLab project. Four commercial copper alloys provided by one member of the industrial user group, Cu-Sn-X (X= P; Ti), Cu-Ni-Si and Cu-Ni-Si-Mg ...

In the first part of this paper, we present a transient model of radial heat conduction in infinitely large media to model the hot-wire technique. Pulse and a Heaviside heat sources are investigated. The general instantaneous solution is generated using Green's functions ...

Abstract. A new method, based on the modified Enskog theory, is presented for the calculation of viscosity of some supercritical fluids, including refrigerants R152a and HFC-125 at high temperatures and pressures. For this purpose, new correlation functions for the calculation of the ...

ABSRACT The present study aims at comparing the compressive strengths between standard concrete and steel fibre reinforced standard concrete subjected to high temperatures. The grade of concrete designed for investigation is M30. The fibres used for investigations are hook end steel fibres with aspect ratio 50. The dosage of fibres added was 3% by weight of cement. The specimens of size 150x150x150 mm are cast for testing. The samples are cured for 3, 7, 28 and 56 days. The specimens were air dried and then exposed to 27, 100, 200, 300 and 400°C for duration of one hour and cooled to room temperature and then tested under 2000 kN digital compression testing machine. When exposed to elevated temperatures, standard concrete with steel fibres of 3% by weight of cement performs better than that standard concrete without steel fibres. All the results and observations are analysed and presented in the paper.

Aim: The article describes different types of coverings utilized in the protection of steel building constructions and reveals
results from research, designed to assess the effectiveness and behaviour of silicone coatings intended to provide heat resistant protection for steel alloys.
Methods: Research was focused on the influence of high temperatures and impact of direct fire on the change in the thickness of protective coating. High temperature tests were performed in a Nabertherm furnace, which was equipped with an electronic temperature control mechanism. Changes to the surface appearance were recorded by an optical microscope, Zeiss Stereo Discovery v20. In order to determine changes in the concentration of coating elements, formed during heating of samples in the furnace and under influence of direct fire, the elements were examined using a scanning electron microscope
with a field emission, FEI Company Nova Nanos 200, equipped with an X-ray probe. Results from an analysis of the coating
surface revealed a state of decomposition in the concentration of coating elements.
Results: The study revealed a variation in protective effectiveness of tested silicone coatings. Silicone varnish presented a greater protective ability in conditions involving direct fire as well as high temperatures in a furnace. Examined silicone coatings belong to a group, which slow down the spread of fire and protect the steel substrate, and do not reveal significant
changes to the thickness of the protective layer. In the case of silicone paint a reduction in of the thickness of coatings ranged
between 13% and 20% at temperatures of 500°C and 820°C respectively. Silicon varnish, applied as a surface coating for
steel, under the same temperature conditions, showed changes in the thickness of 13% and 51% respectively. Action by direct fire caused lesser changes to the thickness of the coating and ranged from 9% (paint) to 5% (varnish). The average decrease in coating thickness was partially associated with the melting as well as sublimation of coating components, whereby the heat flow reaching the protected surface is slowed down. In the make-up of examined material significant differences were identified during analysis of surface decomposition of component elements. These differences were mainly associated with the content of aluminium, iron and carbon. The elements content in the silicone painting were respectively 7% to Al and about 20% to Fe, while the same elements content in the silicone varnish were 51% to Al and less than 1% to Fe. The carbon content was approximately 20% in silicone paint and about 10% in varnish respectively. As a result of direct fire application, the main changes were associated with the carbon content in both types of coating. The carbon content decreased in silicone paint from 3 times (direct fire) to 10 times in case of the furnace heating action. Whereas with silicone varnish, regardless of the type of temperature level, the content was reduced by only 2.5 times.