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In this study, an experimental method was used to determine, following an identification method, the intrinsic spectral properties of glass samples in the mid and long infrared wavelength range, such as index of refraction and absorption coefficient. The method is based on an experimental set-up using FT-IR spectrometers to obtain the spectral distributions of the transmittance and reflectance of the samples. Some uncertainties associated with the analysis are determined and some experimental results are presented and discussed.

The wood energy conversion into power and heating processes concerning the chips and pellets production chain is analyzed. An exergy analysis and a life cycle assessment are performed, considering the wood chips for electricity generation in a central power plant and wood pellets for distributed generation. The consumption of diesel oil, electricity and biomass itself were carried out along both production chains. The results showed the best way to avoid exergy destruction and environmental impacts based on carbon dioxide emissions. Considering the same energy conversion plant efficiency, the exergetic performance and the environmental impact are very close when both the technological routes are compared. However, taking into account a distributed generation and the high efficiency characteristic of micro cogeneration plants (combined heat and power), the pellets technological route presents a better exergetic and environmental performance. Also, a sensitivity analysis along the production chain stages have demonstrated that large variations of about 50% on the specific fuel consumption represents a very small influence on the overall exergetic efficiency, in order of just 1.5%.

Estimating temperature is essential both to design reliable CubeSats and to keep it under maximum operating efficiency. This paper presents the transient thermal simulation of a CubeSat 1U, where the heat transfer by conduction and radiation (external and internal) are solved considering a typical CubeSat mission launched from the International Space Station. The objective is to obtain the temperature field based on the Finite Volume Method (FVM), with inner heat transfer by radiation. The Gebhart method computes the internal heat exchange through successive reflections, and an obstruction model supports the calculation of view factors. Three boundary conditions for the inner side of the CubeSat are tested: without internal heat transfer by radiation, or zero emissivity ( ϵ = 0 . 0 ), with intermediate internal heat transfer by radiation ( ϵ = 0 . 5 ), and maximum internal heat transfer by radiation ( ϵ = 1 . 0 ). The results show a significant impact of the internal heat transfer by radiation in the temperature field of both inner and outer parts of the satellite, and therefore it should not be ignored. Good agreement of transient temperature is found between the FVM and another more straightforward formulation based on the Lumped Method, although the three-dimensional effects are significant and cannot be obtained with such a simplified model.

During satellite development, engineers need to simulate and understand the satellite’s behavior in orbit and minimize failures or inadequate satellite operation. In this sense, one crucial assessment is the irradiance field, which impacts, for example, the power generation through the photovoltaic cells, as well as rules the satellite’s thermal conditions. This good practice is also valid for CubeSat projects. This paper presents a numerical tool to explore typical irradiation scenarios for CubeSat missions by combining state-of-the-art models. Such a tool can provide the input estimation for software and hardware in the loop analysis for a given initial condition and predict it along with the satellite’s lifespan. Three main models will be considered to estimate the irradiation flux over a CubeSat, namely an orbit, an attitude, and a radiation source model, including solar, albedo, and infrared emitted by the Earth. A case study illustrating the tool’s abilities is presented for a typical CubeSats’ two-line element set (TLE) and five attitudes. Finally, a possible application of the tool as an input to a CubeSat task-scheduling is introduced. The results show that the complete model’s use has considerable differences from the simplified models sometimes used in the literature.

Oxy-fired and air-fired furnaces are commonly employed in the ceramic and glass industry due to the high temperature and intensive energy required for the melting of glassy material. In this work an experimental analysis of a 0.96 MW oxy-fired furnace is presented and compared to the experimental analysis of two others: a 1.3 MW air-fired furnace and a 1.0 MW oxy-fired furnace. All three furnaces are used in the ceramic industry with operational temperature between 1200 and 1500 °C, processing a similar product and with equivalent dimensions. Experimental results for the presented oxy-fired furnace indicate an elevated mass flow infiltration of ambient air due to negative manometric pressure inside the combustion chamber. The release of CO2 by the load was detected and quantified. Comparison between the three furnaces show that the oxy-fired furnaces have higher efficiency with an energy input per kilogram of product of approximately one half of the one encountered for the air-fired furnace. Emission of CO2 and NO were measured and results indicate higher emission of tons of CO2 per ton of product for the air-fired furnace, while higher concentration of NO ppm per kg/h of product for the oxy-fuel furnace. Dissimilar behavior was found in the energy distribution among furnaces. For the air-fired furnace most of the energy is lost through the flue gas while for the oxy-fired furnaces most of the energy leaves the furnace with the load, indicating more available energy for the load processing. The results are interesting for understanding the behavior of industrial furnaces with different oxidizers and can be used for operational cost estimation and design of new equipment.

A comprehensive but simple formulation for the attitude of a nanosatellite is presented herein with a focus on problems associated with spin and heat transfer. Sequential matrices of rotation predict the position and orientation of the spacecraft, which govern the heat fluxes composed of solar, albedo and infrared radiation. These fluxes are boundary conditions for the energy equation and are implemented to solve the temperature field based on the finite volume method. Common spins are used as benchmark cases to study their effect on the temperature of CubeSats. The attitude of nadir, detumbling, high speed, arbitrary motion and maximum exposure to the Sun are simulated for orbits with and without eclipse, at an altitude of 650 km and inclination of 90°. Results for total heat influx and temperature of the external surfaces are shown for single full orbits. Low spins are associated with the largest temperature gradients, due to the unequal distribution of heat fluxes. High angular speed homogenizes the temperature, especially for a spin around three axes. In general, for high spin, temperatures are nearly constant and appropriate for regular operational temperatures. Data collect from CubeSats in orbit are compared with the numerical values and satisfactory agreement is observed, despite differences in the designs and geometries. The model presented is comprised of a formulation for the spin and for the thermal irradiation over a CubeSat and can be implemented in traditional programming languages to investigate different orbital parameters for CubeSats and Picosats.

Experimental data on the thermal behavior of a continuous-operation sodium silicate furnace obtained from in situ measurements are reported herein. Three cases with different load material compositions were investigated. The furnace energy balance was obtained from the measured data, indicating energy losses of around 12% through the wall and 60–70% in the flue gas in relation to the total energy input. Results obtained from the determination of the flue gas composition indicated the release of CO 2 from the load inside the furnace combustion chamber during operation. This released reached 20–46% of the total CO 2 produced during the manufacturing of the glassy load. Given the similarity of the processes involved, these results will be of interest to the glass manufacturing industry.

This paper describes a methodology for the modeling and simulation of a pulsed thermography inspection of carbon fiber-reinforced composites. A thermal–numerical model based on the 3D transient heat conduction equation for heterogeneous media is proposed to model the thermal response of the composite medium when a thermal pulse is applied to its surface. The solution of the model is developed using the finite volume method, in which the approximated equations are obtained by performing energy balances for each elementary volume. The experimental validation of the thermal–numerical model consisted of a comparison of the thermal decay curves for defective areas obtained through numerical simulation and with a pulsed thermography inspection of a laminated composite specimen with simulated defects (Teflon inserts). A parametric study was carried out in order to analyze the influence of the irradiation power density, non-uniform heating and characteristics associated with the defects on quantitative variables such as the onset time and thermal contrast. Numerical results showed that the variable thermal contrast is highly sensitivity to changes in the defect thickness, aspect ratio and parameters related to the external stimulation. Furthermore, an increase in the detectability of defects – especially those with lower aspect ratios – can be achieved by increasing the irradiation power.

This paper introduces and tests a statistical correlation method for the optimization of the pulsed thermography inspection. The method is based on partial least squares regression, which decomposes the thermographic PT data sequence obtained during the cooling regime into a set of latent variables. The regression method is applied to experimental PT data from a carbon fiber-reinforced composite with simulated defects. The performance of the regression technique is evaluated in terms of the signal-to-noise ratio. The results showed an increase in the SNRs for 96% of the defects after processing the original sequence with PLSR.

This paper presents a thermal analysis of a tunnel kiln used for the production of roof tiles, fueled by firewood and shale oil. A tridimensional numerical model based on the finite volume method is presented and applied to model the thermal behavior of the kiln. The fuel combustion was treated as a one-step complete reaction. Surface to surface radiation between the kiln walls and load surfaces with non-participating media was considered. A prescribed flow of flue gas and air was used to surpass the obstacle of high computational cost due to the large dimensions of the numerical domain. Experimental measurements for an operating tunnel kiln were compared with numerical results and a good agreement was observed. Temperature profiles and heat fluxes for the walls and load are reported and discussed.

This paper describes a methodology for the study and modeling of the thermal energy in ceramic frit melting kilns with an oxy-fired combustion process through the development of a numerical simulation in CFD software. Ceramic frits are vitreous compounds that provide glazes with specific properties for use in the coating of other ceramics, especially those of the ceramic tile industry. The aim of this study is to generate technical subsidies in order to support economically viable proposals for the ceramic industry. The CFD modeling is performed using the commercial software Ansys CFX 11.0, which is based on the method of finite volumes. The geometric domain of resolution consists of the internal cavity of the kiln. The CFD resolution is coupled to a three-dimensional heat conduction code along the kiln walls to determine the external temperature distribution. The thermal problem is composed of the combustion of natural gas with oxygen, the internal turbulent flow of exhaust gases, the energy loss by convection and radiation to the environment through the walls and the radiation within the kiln cavity with participating media. Data collected in an operating kiln are used to verify the numerical solution, achieving a good agreement in the general analysis of the kiln. The numerical solution provides physically consistent results, making it possible to predict the behavior of the kiln as a whole in similar cases with changes in the parameters of the manufacturing process or in the geometry. Other specific results, such as heat flux inside the kiln, are presented and discussed.

Fast firing has been used to produce relatively dense ceramics in periods of time shorter than 5 min. High heat inputs during fast firing originates changes in the internal structure of the ceramic compact. The amount of energy available for sintering increases by the formation of a dense outer layer which controls the heat flux to the interior of the compact. In this paper, a numerical model based on the method of finite volumes was developed to simulate the fast firing process in an alumina compact. The heat transfer inside the ceramic sample was modeled through the whole process in order to predict the density changes induced by the fast furnace's heat transfer and compared to conventional sintering.

An inverse heat transfer method is developed to characterize subsurface defects in ceramic materials through the reconstruction of the IR image obtained by numerical simulation. This study focuses on the application of the Conjugate Gradient Method (CGM) of minimization for the determination of the thermal conductivity and the depths of defects present in ceramic materials. To this aim, an inspection method which consists of imposing a transient regime process in the sample test is proposed, starting from an elevated and uniform temperature and applying a cooling process over the time. Surface thermal images are collected during the cooling process using an infrared camera. A mathematical model based on the transient behavior of the ceramic sample during the inspection is proposed to study the different heat transfer mechanisms and detectability levels of the simulated defects. The numerical solution of the model was developed using the Finite Volume Method (FVM), in which the approximated equations are obtained by performing energy balances for each elementary volumes. Experimental and simulated temperature decay curves of defective areas are used to determine the properties of the above-mentioned defects.

Pulsed Thermography (PT) is one of the most widely used approaches for the inspection of composites materials, being its main attraction the deployment in transient regime. However, due to the physical phenomena involved during the inspection, the signals acquired by the infrared camera are nearly always affected by external reflections and local emissivity variations. Furthermore, non-uniform heating at the surface and thermal losses at the edges of the material also represent constraints in the detection capability. For this reason, the thermographics signals should be processed in order to improve – qualitatively and quantitatively – the quality of the thermal images. Signal processing constitutes an important step in the chain of thermal image analysis, especially when defects characterization is required. Several of the signals processing techniques employed nowadays are based on the one-dimensional solution of Fourier’s law of heat conduction. This investigation brings into discussion the three-most used techniques based on the 1D Fourier’s law: Thermographic Signal Reconstruction (TSR), Differential Absolute Contrast (DAC) and Pulsed Phase Thermography (PPT), applied on carbon fiber laminated composites. It is of special interest to determine the detection capabilities of each technique, allowing in this way more reliable results when performing an inspection by PT.

The available technology for tunnel kilns in Brazil is practically empirical and there is a lack of fundamental studies developed as an aid for the design of new kilns or for the retrofit of old ones. Here, a thermal model of a tunnel kiln is developed allowing the numerical simulation of kilns and dryers aiming toward a more efficient and less energy consuming design. The model is then systematically applied in the design of a new kiln to be used for firing clay tiles, bricks and similar products, with natural gas and sawdust as fuels. The results include the three-dimensional temperature distribution within the walls, gas and load along the kiln and a complete thermal energy balance including all energy fluxes related to the process. The strategies for kiln design are discussed and the advantages of combining the low cost of the wood sawdust and the ease of adjustment and quality of the natural gas combustion are evidenced.