It has been performed a simple simulation and calculation on solar energy collection which is used indirectly to power a thermoacoustic prime mover by producing pressurized hot steam which would supply thermal energy to the prime mover via sealed-off hot heat exchangers. The solar energy collection took place in Yogyakarta City - Indonesia where the average energy of solar global radiation of 4.8 kWh/m 2 /day (17.3MJ/m 2 /day) is available around the year. The calculation including the amount of the remaining heat stored, steam pressure, and steam temperature for various areas of the collector unit (Fresnel lens) and volume of water, were done as a function of time for several days. We found that appropriate combinations of lens area and water volume would enable us to operate the thermoacoustic prime mover continuously all day and night.

This study numerically investigated the one-dimensional freeze drying of a solution product assisted with infrared radiation heating. In order to accurately consider the spectral radiative transfer inside the moisture-rich product, the two-flux radiation model was incorporated with our previous freeze drying analysis model based on the fixed grid method. Thus, this model fully takes into account the spectral absorption characteristics of ice and the spectral composition of light emitting from an infrared heater. The infrared-assisted freeze drying characteristics were investigated in detail, along with the spatial variation of radiation intensity inside the product. Then, the effects of infrared heater temperature on freeze drying behaviors were parametrically studied, and the results were discussed in relation with the spectral effects in the radiative transfer in the moisture-rich product.

This paper deals with the modeling of aero-thermal aspects of a space vehicle during its entry phase into an atmosphere. We treat the numerical coupling techniques between the external and internal aero-thermo-dynamics (ATD) produced by the interaction of ATD fields with the structural components. The thermal properties induced within the structure via heat transfer mechanisms of convection, conduction and radiation is taken into account presenting multi-disciplinary coupling between the aero-thermo-dynamics, the heat loads and the structural thermal response.

During atmospheric (re-)entries, planetary probes encounter huge heat fluxes due to their significant speed (up to 13 km/s for an Earth re-entry). The total heat flux received by the probe can be divided into two main components: a convective one (coming from the conduction and diffusion phenomena occuring in the shock layer) and a radiative one (due to the radiation of certain species). Numerical simulations have been performed for both Titan (Huygens mission) and Earth (Fire II mission) entries. The main parameters influencing the results are the atmosphere composition, the chemical reaction scheme, the transport model and the radiative model. The results obtained gave us information on the flowfield (temperature, pressure, species densities...) and values for the heat fluxes on the wall that are useful for experimental or flight data comparison.

This research focuses on the interaction of surface radiation with laminar mixed convection heat transfer for thermally developing airflow in horizontal ducts. The duct cross section is made of two differentially heated isothermal vertical walls and two adiabatic horizontal walls. In a series of experiments, the Reynolds number is varied from about Re = 800 to Re = 1200, for two aspect ratios of the duct cross section. The hot wall temperature ranges from 27°C to 100 °C, and the emissivity of internal walls are 0.05 and 0.85. The total heat transfer from the hot wall to the cold wall of the duct depends on the mixed convection and also on the surface radiation heat transfer that takes place within the duct. Therefore, it is important that the effects of surface radiation must be properly understood, and accounted for, in the design and analysis of flow and heat transfer through ducts. The results presented here show the effect of surface radiation and mixed convection on the total heat transfer rate within the duct. The flow field within the duct is also made visible by a suitable smoke flow visualization method.

The accuracy and computational expense of various radiation models in the simulation of turbulent jet flames are compared. Both nonluminous and luminous methane-air non-premixed turbulent jet flames are simulated using a comprehensive combustion solver. The combustion solver consists of a finite-volume/probability density function-based flow–chemistry solver interfaced with a high-accuracy spectral radiation solver. Flame simulations were performed using various k -distribution-based spectral models and radiative transfer equation (RTE) solvers, such as P-1 , P-3 , finite volume/discrete ordinates method (FVM/DOM), and Photon Monte Carlo (PMC) methods, with/without the consideration of turbulence-radiation interaction (TRI). TRI is found to drop the peak temperature by close to 150 K for a luminous flame (optically thicker) and 25–100 K for a nonluminous flame (optically thinner). RTE solvers are observed to have stronger effects on peak flame temperature, total radiant heat source and NO emission than the spectral models. P-1 is found to be the computationally least expensive RTE solver and the FVM the most expensive for any spectral model. For optically thinner flames all radiation models yield excellent accuracy. For optically thicker flames P-3 and FVM predict radiation more accurately than the P-1 method when compared to the benchmark line-by-line (LBL) PMC.

Near-field radiation that has a high intensity of electric field was applied to enhance conversion from thermal energy to electricity in a wavelength range less than 1.1 μm or 1.8 μm. A commercial Si-photovoltaic cell and a thermophotovoltaic cell made of GaSb semiconductors were used to confirm that the near-field radiation effect (the evanescent wave effect) can be applied to enhance generation of electricity. As a result, an increase in output power generation of electricity by the evanescent wave effect was detected and the short-circuit current density increased about 1.3 times for the Si-PV cell and 3.0 times for the GaSb-TPV cell as larger than those obtained by the conventional propagating-wave radiation.

This work proposes a comprehensive and efficient optimization approach for designing surface patterning for increasing solar panel absorption efficiency using near field radiation effects. Global and local optimization methods, such as the Broyden–Fletcher–Goldfarb–Shanno Quasi-Newton (BFGS-QN) and Simulated Annealing (SA), are employed for solving the inverse near field radiation problem. In particular, a thin amorphous silicon (a-Si) solar panel with periodic silver nano-wire patterning is considered. The design of the silver patterned solar panel is optimized to yield maximum enhancement in photon absorption. The optimization methods reproduce results found in previous literature but with reduced computational expense. Additional geometric parameters not discussed in previous work are included in the optimization analysis, further allowing for increased absorption enhancement. Both the BFGS-QN and SA methods give efficient results, providing designs with enhanced absorption.

Building of a model which could be used for optimization of design of nuclear waste storage, is one of biggest challenges in field of coupled processes modeling. Such a model have to take in consideration several fully-coupled processes. These processes are from field of Thermal, Hydro, Mechanical and Chemical science in short, they are described as THMC processes. Most of all, it is interaction of heat, generated by residual radiation in the waste, reacting with underground water and eventual chemical reaction in these water-solution. And all these actions being still a subject of eventual physical movements in the bedrock. In addition, model must take into consideration that values of a given process can change dramatically importance of this process characteristics for the safety of the storage. None of existing models is reaching the level of model complexity needed to address these issues. In this article is presented an object oriented model ISERIT. Model ISERIT is able to solve multidimensional task THH, where HH is for water, and water being present in 2 phases. The first phase is water vapor and the second phase is water absorbed by clay particles of the container buffer. In theoretical part of the article are defined governing equations. The governing equations are based on the conservation equations of heat and mass. The continuum equations are discretized in space by using the Galerkin finite element formulation. The time discretization is solved by implicit finite difference scheme. The main part of the article describes implementation of model ISERIT. Main structure of the model is defined with functionality of significant classes. The temperature, the water vapor concentration and the water concentration in solid phase are chosen as the three primary variables. The parameters, such as heat conductivity, heat capacity and water vapor diffusion coefficient, could be taken to be constants, or could be allowed to vary with temperature and water vapor concentration, without requiring fundamental modifications to the code. Article also describes how model can be enlarged to incorporate eventually other processes. This thanks to the fact, that model was build as object designed. At the end, article presents verification of the model against the experimental results, laboratory experiment BenchMark 1.3, as well as against full-scale experiment BenchMark 2.1.

Importance of turbulence and radiation interaction (TRI) has been investigated in a turbulent channel flow by using direct numerical simulation (DNS) to clarify detailed turbulent flow structure and heat transfer mechanisms. To investigate the effect of correlation functions between gas absorption and temperature fluctuation, the two cases of correlation are tested. Consequently, the TRI effect can be clearly observed when the correlation is positive. This fact provides the evidence that radiative intensity is enhanced by the turbulent fluctuation. The DNS results suggest the significance in the fundamental aspect of TRI. Furthermore, effects of frictional Reynolds number, Re τ , are investigated. Comparing with the case of Re τ = 150, the location of the enhancement peaks of Re τ = 300 shifts toward the walls. It is found that the relative importance of the TRI correspond to the structure of temperature fluctuation intensity originated from the differences of the Re τ .

The accuracy with which the solidification and cooling of a continuously cast billet is investigated depends on the setting of the boundary conditions of the numerical model of the temperature field. An in-house numerical model of the 3D temperature field of a concast billet had been used. This model enables the analysis of the temperature field of the actual blank as it passes through the zero-, primary-, secondary- and tertiary-cooling zones, i.e. through the entire caster. This paper deals with the derivation of transfer phenomena under the cooling nozzles of the secondary zone. These phenomena are expressed by the values of the heat transfer coefficients (HTCs). The dependences of these coefficients on surface temperature and other operational parameters must also be given. The HTCs beneath the nozzles are given by the sum of the forced convection coefficient and the so-called reduced convection coefficient corresponding to heat transfer by radiation. The definition of the boundary conditions is the most difficult part of the numerical and experimental investigation of the thermokinetics of this process. Regarding the fact that on a real caster, where there are many types of nozzles (with various settings) positioned inside a closed cage, it is practically impossible to conduct measurement of the real boundary conditions. Therefore, an experimental laboratory device was introduced in order to measure the cooling characteristics of the nozzles. It simulates not only the movement, but also the surface of a blank and for the necessary range of water flow in the operation and the casting speeds. The transfer phenomena beneath the water cooling nozzles are presented on a simulated temperature field for a real 150×150 mm steel billet under different operational conditions. This is ensured by the correct process procedure: real process → input data → numerical analysis → optimization → correction of process. The presented model is a valuable computational tool and accurate simulator for investigating transient phenomena in caster operations, and for developing control methods, the choice of an optimum cooling strategy to meet all quality requirements, and an assessment of the heat-energy content required for direct rolling.

The Modified Differential Approximation (MDA) was originally proposed for solution of the radiative transfer equation (RTE) in order to remove the shortcomings of the P 1 approximation in scenarios where the radiation intensity is strongly directionally dependent. In the original MDA approach, the wall-emitted component of the intensity is determined using a surface-to-surface exchange formulation that makes use of geometric viewfactors. Such an approach is computationally very expensive for complex geometry and/or inhomogeneous media. This article presents a new formulation in which the wall-emitted component is solved using the Discrete Ordinates Method (S N approximation), while the medium-emitted component is solved using the P 1 approximation, resulting in a hybrid S N -P N RTE solver. Results show that the hybrid Discrete Ordinates-P 1 method (DOM-P 1 ) is computationally very efficient, but its accuracy is poor in optically thin situations where ray effects, inherent in the Discrete Ordinates Method, are pronounced. To circumvent this problem, the control-angle Discrete Ordinates Method (CADOM) is finally employed, and the accuracy of the hybrid CADOM-P 1 method is found to be far superior to the hybrid DOM-P 1 method.

As part of the DOE Existing Plants, Emissions and Capture (EPEC) program, oxy-combustion is being investigated as a method to simplify carbon capture and reduce the parasitic energy penalties associated with separating CO 2 from a dilute flue gas. Gas-phase radiation heat transfer in boilers becomes significant when shifting from air-firing to oxy-combustion, and must be accurately represented in models. Currently, radiative property data are not widely available in the literature for conditions appropriate to this environment. In order to facilitate the development and validation of accurate oxy-combustion models, NETL conducted a series of studies to measure radiation properties of oxy-fuel flames at adiabatic flame temperatures of 1750–1950K, and product molar concentrations ranging from 95% CO 2 to 100% steam, determined by equilibrium calculations. Transmission coefficients were measured as a function of wavelength using a mid-IR imaging spectrometer and a blackbody radiation source. Additionally, flame temperatures were calculated using data collected within CO 2 and H 2 O absorption bands. Experimental results were compared to two statistical narrow-band models and experimental data from literature sources. These comparisons showed good overall agreement, although differences between the models and experimental results were noted, particularly for the R branch of the 2.7 μm H 2 O band.

Overall transmittance of porous cerium dioxide is measured in the spectral range of 900–1700 nm using dispersive spectroscopy. Dense and porous samples of cerium dioxide with average porosities of 0.08 and 0.72, respectively, are investigated. The transmittance of both sample types increases with decreasing thickness, and this trend is more pronounced for the dense samples. The on-average spectrally increasing transmittance of the dense samples is attributed to the decreasing absorption by bulk cerium dioxide with radiation wavelength. The transmittance of the porous samples, on the other hand, remains a constant over the spectrum. Porous samples attenuate radiation stronger than the dense samples at any wavelength in the considered range, and it is hypothesized that this effect is due to more intense scattering. Sharp local variations of the transmittance are observed for both sample types.

Many energy systems rely on flat surfaces for energy conversion. The simplest example is the solar thermal collector which absorbs solar irradiance on a flat plate and then transfers heat via conduction, convection and radiation to both the surroundings and more importantly to the working fluid. Conversely a night-sky radiator tries to lose heat via convection and radiation to ambient and night sky respectively while being coupled either via convection or conduction to higher temperature system. The recent advent of nanoparticles, particularly liquid-nanoparticle suspensions termed nanofluids, have led to novel systems that can reduce some of these heat transfer steps by utilizing the whole fluid volume directly. This study looks at the advantages afforded by using the volumetric approach on both the radiative properties of the system and the simplification of the heat transfer networks within these systems.

A method for the application of importance sampling to wavelength selection in ray tracing Monte Carlo solvers is introduced. In this method individual lines are treated independently, and probability distribution and weighting functions are applied to individual lines. The method reduces the number of photons required to reach the same statistical precision as the standard Monte Carlo method.

This study describes nanoparticles pigmented coatings used in controlling the radiative properties of surfaces exposed to sunlight. An optimization method that embraces both thermal and aesthetic requirements has been proposed. The proposed coatings maximize the reflectivity of the near infrared (NIR) region to reduce thermal heating, while for aesthetic appeal they minimize the visible (VIS) reflected energy. This spectral behavior can be achieved by controlling the size and concentration of pigment particles and coating thickness. In this study, both experimental and numerical approaches are applied on Fe 2 O 3 pigmented coating samples with 0.2 μm and 1 μm of average particle size and different particle concentrations and coating thicknesses. For numerical part the radiation analysis using the Radiation Element Method by Ray Emission Model (REM 2 ) in a one dimensional parallel plane model is conducted. From the numerical results, it is shown that the optimum size of Fe 2 O 3 particles for our desired spectral behavior is about 0.8 μm. The experimental results also show that the samples made from 1 μm particles have better performance for our objective.