Resumo A normatização brasileira relacionada ao desempenho termoenergético de edificações tem procurado inserir a refletância ou a absortância solar em seus critérios de análise. O objetivo deste artigo é analisar a exatidão e a repetibilidade de medições de refletância com o espectrômetro Alta II, bem como a influência da luminosidade do ambiente e da rugosidade da superfície sobre os valores medidos. Foram realizadas três séries de medições, variando os espectrômetros utilizados, a exposição à luz, e a rugosidade da superfície avaliada. Medições com o espectrofotômetro Lambda 1050 serviram de referência. A análise demonstrou que os resultados podem apresentar imprecisão elevada, com incerteza de ±0,10 nos valores absolutos de refletância solar. Sendo assim, o usuário do espectrômetro Alta II deve utilizá-lo com precaução, considerando tal erro. Também foi possível observar neste estudo que o Alta II pode ser usado especialmente para análise de superfícies planas e lisas. Além disso, deve-se garantir que as medições sejam realizadas com o cuidado de evitar a infiltração de luz através da superfície de contato entre o equipamento e a amostra.

Abstract Solar reflectance and solar absorptance are directly responsible for the behaviour of surfaces concerning incident solar radiation. The Brazilian regulation related to the thermal and energy performance of buildings has sought to include such properties in its analysis criteria. The objective of this paper is to analyse the accuracy and repeatability of reflectance measurements using the Alta II spectrometer, as well as the influence of ambient light and surface roughness on the measured values. Three series of measurements were performed by varying: the spectrometers used, the exposure to light, and the roughness of the measured surface (flat painted samples or texture painted walls). Measurements were also performed using the Lambda 1050 spectrophotometer as a reference. The analysis showed that the results may be highly inaccurate. Therefore, the Alta II spectrometer should be used with caution. The experiments showed uncertainty of about ±0.10 in the absolute values of solar reflectance (for reflectance ranging from 0-1). Thus, the Alta II spectrometer user must consider such an error. It was also concluded that Alta II should only be used to analyse flat surfaces and it is important to ensure that measurements are carried out preventing light leakage through contact between the equipment surface and the sample.

The aim of this study was to obtain and evaluate the electrical, thermal and mechanical properties of iron oxide-filled castor oil polyurethane (PU/Fe2O3). The iron oxide used in this study was a residue derived from the steel pickling process of a Brazilian steel rolling industry. Polymeric composites with different iron oxide volume fractions (2.5, 5.0, 7.5, 10.0 and 12.5%) were prepared through the casting process followed by compression molding at room temperature. The composites were analyzed by FTIR, XRD and densities, tensile strength, Young's modulus, electrical and thermal conductivities measurements. By increasing the iron oxide content, the apparent density, tensile strength, Young's modulus and electrical conductivity values of the composites were also increased. The iron oxide additions did not change significantly the value of thermal conductivity (from 0.191 W.mK-1 for PU up to 0.340 W.mK-1 for PU enriched with 12.5% v/v of iron oxide). Thus, even at the higher iron oxide concentration, the compounds as well as the pure polyurethane can be classified as thermal insulators.

As trocas de calor determinam o balanço térmico das edificações, afetando a temperatura interna. O desempenho térmico pode ser analisado em função dos somatórios de graus-hora de resfriamento e aquecimento, obtidos a partir de simulações computacionais. Este trabalho visa selecionar algoritmos de condução e convecção disponíveis no software EnergyPlus v.6.0, para aplicação na simulação computacional da Casa Eficiente, localizada em Florianópolis, SC. As simulações foram calibradas para o verão, com base em dados medidos in loco, analisando-se o balanço térmico das superfícies e os somatórios de graus-hora de resfriamento de um ambiente interno. Para a condução, os ganhos de calor simulados superestimaram as medições em até 4,4 vezes, com o método das diferenças finitas. Com o algoritmo CTF, os ganhos foram subestimados em até 90%. O somatório de graus-hora de resfriamento (período de 22 a 25/01/2008, temperatura-base de 26 ºC) variou de 12,1 ºC a 21,5 ºC, em função dos coeficientes de convecção. O emprego dos algoritmos Simple para as paredes e Adaptive para o teto e o piso resultou nos menores desvios da temperatura do ar: 0,3 ºC a 0,9 ºC. Essa análise possibilitou uma seleção acurada dos algoritmos de condução e convecção, sendo eficaz para reduzir os desvios nas simulações do ambiente estudado.

The heat transfer components define the thermal balance of buildings, affecting their internal temperatures. Cooling and heating degrees-hours, obtained from simulations, are parameters for building thermal performance analysis. This study aims to determine the most appropriate conduction and convection algorithms available in the EnergyPlus v. 6.0, for computer simulation of the Casa Eficiente, an experimental dwelling located in Florianopolis, SC. EnergyPlus 6.0 simulations were calibrated against field measured data during summer, analyzing surfaces inside heat balance and room cooling degree hours. The simulation results for the Conduction Finite Difference Solution algorithm overestimated the measured heat gains by up to 4.4 times. For the CTF algorithm, the measured heat gains were underestimated by up to 90%. The cooling degree hours (period: 22 to 25/01/2008, base temperature = 26 ºC) ranged from 12.1 ºC to 21.5 ºC, depending on convection coefficients. Lower air temperature deviations were obtained by using the Simple algorithm for the walls and the Adaptive algorithm for the ceiling and floor: ranging from 0.3 ºC to 0.9 ºC. This analysis enabled the selection of accurate conduction and convection algorithms for this building's thermal simulation, reducing the deviations in results for the studied environment.

Ceramic floor tiles are widely used in buildings. In places where people are bare feet, the thermal sensation of cold or hot depends on the environmental conditions and material properties including its microstructure and crustiness surface. The introduction of the crustiness surface on the ceramic floor tiles interfere in the contact temperature and also it can be an strategy to obtain ceramic tiles more comfortable. In this work, porous ceramic tiles were obtained by pressing an industrial atomized ceramic powder incorporated with refractory raw material (residue from porcelainized stoneware tile polishing) and changing firing temperature. Raw materials and obtained compacted samples were evaluated by chemical analysis, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Thermal (thermal conductivity and effusivity) and physical (porosity) measurements were also evaluated.

In places where people are bare feet, the thermal sensation of cold or hot depends on the environmental conditions and material properties including its microstructure and crustiness surface. The uncomforting can be characterized by heated floor surfaces in external environments which are exposed to sun radiation (swimming polls areas) or by cold floor surfaces in internal environments (bed rooms, path rooms). The property named thermal effusivity which defines the interface temperature when two semi-infinite solids are putted in perfect contact. The introduction of the crustiness surface on the ceramic tiles interferes in the contact temperature and also it can be a strategy to obtain ceramic tiles more comfortable. Materials with low conductivities and densities can be obtained by porous inclusion are due particularly to the processing conditions usually employed. However, the presence of pores generally involves low mechanical strength. This work has the objective to evaluate the thermal comfort of ceramics floor obtained by incorporation of refractory raw materials (residue of the polishing of the porcelanato) in industrial atomized ceramic powder, through the thermal and mechanical properties. The theoretical and experimental results show that the porosity and crustiness surface increases; there is sensitive improvement in the comfort by contact.