Search Results (135)

The use of semi-transparent photovoltaic (Solar PV) glass in buildings is an effective strategy for integrating renewable energy generation, solar control, and thermal comfort. However, conventional simulation models rely on global optical properties, neglecting spectral radiation and its propagation within the material. This limits the accurate assessment of thermal comfort, light distribution, and performance in complex systems such as multi-layer glazing. This study presents the development, implementation, and experimental validation of a numerical model that reproduces the thermal, electrical, and optical behaviour of semi-transparent Solar PV glass, explicitly incorporating radiative transfer. The model simultaneously solves the conduction, convection, and electrical generation equations together with the radiative transfer equation, solved via the finite volume method across two spectral bands. The refractive index and extinction coefficient, derived from manufacturer-provided optical data, were used as inputs. Experimental validation employed 10% semi-transparent a-Si glass, comparing surface temperatures and electrical power generation. The model achieved average relative errors of 3.8% for temperature and 3.3% for electrical power. Comparisons with representative literature models yielded errors between 6% and 21%. Additionally, the proposed model estimated a solar factor of 0.32, closely matching the manufacturer’s 0.29. Full article

High-speed impact is a critical mechanism for structural damage. The infrared signatures generated during fragment formation provide essential data for damage assessment, protective system design, and target identification. This study investigated an aluminum alloy blunt projectile penetrating a target plate by employing smoothed particle hydrodynamics to simulate the debris ejection thermal and infrared properties. The infrared signatures of the debris clouds were calculated using Mie scattering theory under a spherical particle approximation. The reverse Monte Carlo methodology was applied to solve the radiative transfer equations and quantify the infrared emission characteristics. The infrared radiation characteristics of the debris cloud were investigated for projectile impact velocities of 800, 1000, and 1200 m/s. The results showed that the anterior debris regions reached peak temperatures of approximately 1200 K, with a temperature rise of 150–200 K per 200 m/s velocity increase behind the target. The medium-wave (3–5 μm) infrared intensity of the debris cloud was higher than the long-wave (8–12 μm) infrared intensity. The development of debris clouds enhanced the dispersion effect and slowed the increase in infrared radiation intensity in the same time interval. This study provides theoretical foundations for the dynamic infrared radiation characteristics of fragments generated by high-velocity projectile impacts. The infrared radiation characteristics within typical spectral bands can be utilized to assess hit probability and kill effectiveness. Full article

To enhance the field calibration capability of ground-based lunar observation instruments for long-term continuous monitoring and to optimize the stability and traceability of lunar observation data, this manuscript presents the development of a SI traceable Portable Self-calibrating Absolute Radiation Source (PSARS) based on an electrical substitute radiometer. A self-calibrating radiation transfer model has been established. The system features a “+” structure layout centered around an integrating sphere, which ensures uniformity of the light source while improving system integration. Preliminary performance testing results indicate that PSARS achieves excellent radiative planar uniformity and angular uniformity within the targeted area, both exceeding 99%. During the self-calibration cycle of PSARS, the detector demonstrates high measurement stability for the built-in light source. Ultimately, through comparative validation and uncertainty assessment, the self-calibration accuracy of spectral irradiance for PSARS in the 400–1000 nm wavelength range is better than 2%, meeting the demands for high-frequency, high-stability, and high-precision real-time on-site radiometric calibration under ground-based lunar observation field test conditions. This provides technical support for the construction of high-precision lunar models and the widespread application of lunar calibration technologies. Full article

Monitoring and accurately forecasting ultraviolet (UV) radiation is of great importance especially due to its adverse effects on human health. In this study, we develop a numerical model to estimate the UV surface solar radiation with the overarching goal of providing a fully automated UV forecasting tool in the region of Epirus, Greece, and especially at the city of Ioannina. The UV surface solar radiation (SSR) is estimated based on detailed radiative transfer (RT) calculations. To ensure their accuracy, we employ the well-established UVSPEC model included in the libRadtran RT routines. LibRadtran provides a variety of options to set up and modify an atmosphere with molecules, aerosol particles, water and ice clouds and a surface as the lower boundary. As a first step, we performed a sensitivity study of the surface solar UV radiation with respect to ozone, precipitable water, aerosol optical properties and surface albedo. Our calculations are performed initially under clear-sky conditions to eliminate the uncertainties induced by clouds. All our calculations are performed spectrally within the UV spectral range, for a specific date and time at Ioannina, Epirus. Full article

The research objectives of engine plume radiation calculation primarily encompass two aspects: (1) addressing the additional heating induced by plume radiation on rocket thermal protection systems and (2) elucidating the variation patterns of spectral radiation intensity for infrared signature identification and tracking. Focusing on the thermal effects of radiation, this study first calculates the radiative properties of high-temperature combustion gases and particles separately. Subsequently, the radiative properties of mixed droplets with alumina caps are computed and analyzed. Building upon this and incorporating empirical formulas for aluminum droplet combustion, the engine’s radiative properties are calculated, accounting for the presence of mixed droplets. Ultimately, an integrated computational method for engine radiative properties (both internal and external flow fields) is established, which considers the non-equilibrium processes during droplet transformation. The radiative property parameters are then embedded into the fluid dynamics software via multidimensional interpolation. The radiation transfer equation is solved using the discrete ordinates method (DOM) to obtain the radiation intensity distribution within the plume flow field. This work provides technical support for investigating the radiative characteristics of solid rocket engine plumes. Full article

In the present study, the reflection and transmission of radiation in submicron indium tin oxide (ITO) films deposited on a borosilicate glass substrate are experimentally investigated for a wide spectral range, including ultraviolet, visible, infrared and terahertz regions. Theoretical modeling of the spectra is performed using the transfer matrix method. The interaction of electromagnetic radiation with ITO is considered in the framework of the Drude model. The simulated spectra are in good agreement with the experimental ones. New non-destructive methods for determining the ITO film parameters (sheet resistivity, thickness, electron concentration and mobility) have been developed. They are based on a fitting procedure for reflectivity and/or transmittance spectra. Full article

When vehicles fly at hypersonic speeds, a high-temperature flow field forms and emits intense radiation across some spectral bands. This strong flow field can be seen as a point source and is transmitted to high altitudes through the radiative transfer process. In this study, the corresponding atmospheric profiles were introduced, the databases in high-temperature conditions were established, and the corresponding gas absorption characteristics were further calculated using the line-by-line method. Correspondingly, the radiative transfer processes were calculated by a Monte Carlo model with surface and point sources. The Monte Carlo model is rigorously validated against the VLIDORT model through detailed comparisons. For radiative simulations in the near-space environment, both high-temperature conditions and 3D scenarios are considered. The simulations reveal that the use of high-temperature databases could introduce an error of approximately 3%, and the radiation field exhibits stronger inhomogeneity in the infrared band. Full article

Atmospheric climate science lacks the capacity to integrate thermodynamics with the gravitational potential of air in a classical quantum theory. To what extent can we identify Carnot’s ideal heat engine cycle in reversible isothermal and isentropic phases between dual temperatures partitioning heat flow with coupled work processes in the atmosphere? Using statistical action mechanics to describe Carnot’s cycle, the maximum rate of work possible can be integrated for the working gases as equal to variations in the absolute Gibbs energy, estimated as sustaining field quanta consistent with Carnot’s definition of heat as caloric. His treatise of 1824 even gave equations expressing work potential as a function of differences in temperature and the logarithm of the change in density and volume. Second, Carnot’s mechanical principle of cooling caused by gas dilation or warming by compression can be applied to tropospheric heat–work cycles in anticyclones and cyclones. Third, the virial theorem of Lagrange and Clausius based on least action predicts a more accurate temperature gradient with altitude near 6.5–6.9 °C per km, requiring that the Gibbs rotational quantum energies of gas molecules exchange reversibly with gravitational potential. This predicts a diminished role for the radiative transfer of energy from the atmosphere to the surface, in contrast to the Trenberth global radiative budget of ≈330 watts per square metre as downwelling radiation. The spectral absorptivity of greenhouse gas for surface radiation into the troposphere enables thermal recycling, sustaining air masses in Lagrangian action. This obviates the current paradigm of cooling with altitude by adiabatic expansion. The virial-action theorem must also control non-reversible heat–work Carnot cycles, with turbulent friction raising the surface temperature. Dissipative surface warming raises the surface pressure by heating, sustaining the weight of the atmosphere to varying altitudes according to latitude and seasonal angles of insolation. New predictions for experimental testing are now emerging from this virial-action hypothesis for climate, linking vortical energy potential with convective and turbulent exchanges of work and heat, proposed as the efficient cause setting the thermal temperature of surface materials. Full article

The mechanism for the upscale deposition of energy into the atmosphere from molecules and photons up to organized wind systems is examined. This analysis rests on the statistical multifractal analysis of airborne observations. The results show that the persistence of molecular velocity after collision in breaking the continuous translational symmetry of an equilibrated gas is causative. The symmetry breaking may be caused by excited photofragments with the associated persistence of molecular velocity after collision, interaction with condensed phase surfaces (solid or liquid), or, in a scaling environment, an adjacent scale having a different velocity and temperature. The relationship of these factors for the solution to the Navier–Stokes equation in an atmospheric context is considered. The scale invariant version of Gibbs free energy, carried by the most energetic molecules, enables the acceleration of organized flow (winds) from the smallest planetary scales by virtue of the nonlinearity of the mechanism, subject to dissipation by the more numerous average molecules maintaining an operational temperature via infrared radiation to the cold sink of space. The fastest moving molecules also affect the transfer of infrared radiation because their higher kinetic energy and the associated more-energetic collisions contribute more to the far wings of the spectral lines, where the collisional displacement from the central energy level gap is greatest and the lines are less self-absorbed. The relationship of events at these scales to macroscopic variables such as the thermal wind equation and its components will be considered in the Discussion section. An attempt is made to synthesize the mechanisms by which winds are generated and sustained, on all scales, by appealing to published works since 2003. This synthesis produces a view of the general circulation that includes thermodynamics and the defining role of turbulence in driving it. Full article

A significant portion of energy losses in industrial systems arises from the inefficient use of high-temperature exhaust gases, emphasizing the need for enhanced heat recovery strategies. This study aims to improve energy efficiency by examining the effects of radiation-intensifying inserts on combined radiative and convective heat transfer in flue-gas heated channels. A systematic literature review revealed a research gap in understanding the interaction between these mechanisms in flue-gas heat exchangers. To address this, analytical calculations were conducted for two geometries: a radiation-intensifying plate between parallel plates and the same insert in a circular pipe. The analysis covered a range of gas-flue and wall temperatures (560–1460 K and 303–393 K, respectively), flow velocities, and spectral emissivity values. Key performance metrics included Reynolds and Nusselt numbers to assess flow resistance and heat transfer. Results indicated that flue-gas temperature has the most significant effect on total rate of heat transfer, and the insert significantly enhanced radiative heat transfer by over 60%, increasing flow resistance. A local Nusselt number minimum at a length-to-diameter ratio of approximately 26 suggested transitional flow behavior. These results provide valuable insights for the design of high-temperature heat exchangers, with future work planned to validate the findings experimentally. Full article

In response to the pressing need for long-range, non-contact detection in hazardous gas leakage monitoring within chemical industrial parks, this study proposes a gas detection algorithm based on an infrared radiation physical model that utilizes dual-band infrared radiation background reconstruction. The proposed method addresses the issues of the existing detection methods’ lack of physical model support. First, appropriate filter wavelength ranges are selected based on the absorption spectral characteristics of the target gas. Subsequently, a physical model incorporating atmospheric attenuation, background radiation, and gas absorption properties is established based on gas radiative transfer theory. The non-absorption band data are then employed to reconstruct the theoretical background radiation of the absorption band. Furthermore, leveraging the synergistic observation advantages of a dual-band infrared imaging system, gas morphology identification is achieved by inverting the difference between the theoretical background and the actual measured values in the absorption band. Experimental results demonstrate that this method enables gas morphology detection through background reconstruction without requiring pre-collected gas-free background images. By implementing dual-band infrared radiation background reconstruction, this study achieves effective gas detection, providing a reliable technical approach for real-time monitoring and early warning of industrial gas leaks. The proposed algorithm enhances detection capabilities, offering significant potential for applications in industrial safety and environmental monitoring. Full article

Radiation transfer in layers of densely packed aggregates of hydroxyapatite nanoparticles was studied for a spectral range from 300 to 1100 nm using diffuse reflectance measurements and the modeling of the light transfer properties of the layers. The studied samples of dispersed biogenic hydroxyapatite were obtained from animal bone material (bovine bones) using fast pyrolysis followed by grinding and pressing into tablets. A distinctive feature is the high reflectivity (high albedo) of the obtained samples, which is practically independent of the wavelength in the studied spectral range and comparable to the reflectivity of the diffuse reflectance standard based on Spectralon. The modeling of the light transfer properties of the studied samples within the framework of the effective medium theory (using coherent potential approximation) made it possible to establish the weak dependence of the mean scattering-free path and the mean transport-free path of light propagation in the medium on the wavelength, which is consistent with the features observed in the experiment. Possible prospects for the use of nanostructured hydroxyapatite as photonic material are discussed. Full article

Microporous metal materials have promising applications in the high-temperature industry for their high heat exchange efficiency. However, due to their complex internal structure, analyzing the heat transfer mechanisms presents a great challenge. This I confirm work introduces a mathematical model to accurately calculate the radiative thermal conductivity of microporous open-cell metal materials. The finite element and lattice Boltzmann methods were employed to calculate the thermal conduction and thermal radiation conductivities separately and validated for aluminum foams, with the relative errors all less than 9.3%. The results show that the thermal conductivity of microporous metal materials mainly increased with an increase in temperature and volume-specific surface area but decreased with an increase in porosity. Analysis of the spectral radiation characteristics shows that the surface plasmon polariton resonance and the magnetic polariton resonance appearing at the gas–solid interface of the metal foam significantly increase the dissipation effect of the gas–solid interface, further reducing the metal foam’s heat transfer efficiency. This indicates the potential of this work for use in the design of specific microporous metal materials like energy management devices or heat transfer exchangers in the aerospace industry. Full article

Accurate solar spectral irradiance (SSI) input is key to modelling climate systems. Traditional SSI data used in the climate modelling community are based on solar model calculations joined by limited observations. Recent advances in spaceborne high-resolution solar spectrum observations, such as the National Administration for Space and Aeronautics (NASA)’s Total and Spectral Solar Irradiance Sensor (TSIS), have provided more accurate and reliable SSI alternatives. Here, we investigate the differences between the observed and the model-based SSIs, and how these affect the modelled downward surface shortwave radiation (DSSR) over different regions of China. Special interest is dedicated to the implications for solar power estimation from solar farms. We conduct idealized calculations using the RRTMG_SW radiative transfer model, with the traditional China Meteorological Administration standard solar spectrum (CMA_STD) and the observed TSIS-1 Hybrid Solar Reference Spectrum (TSIS-1_HSRS). Results show that the CMA_STD SSI yields 4.45 Wm⁻² less energy than the TSIS-1_HSRS, and systematically overestimate energy in the infrared bands and underestimate that in the visible bands. These discrepancies result in an annual regional mean DSSR underestimation of ~0.44 Wm⁻², with localized underestimation for a particular month exceeding 2 Wm⁻². The estimated solar power productions with the two SSIs differ by 0.25~0.32% and 0.36~0.52% of the total power production capacity for fixed-angle and solar tracking panels, respectively. These findings suggest that long-term and high-resolution spaceborne SSI observations are crucial to improve surface climate modelling, especially on local scales, and to service climate change mitigations. Full article

The analysis of natural and artificial chiral compounds is vital wherever the nuances in the three-dimensional structure are decisive for the possibility of their further use, e.g., as pharmaceuticals or catalysts. The qualitative determination of the structure of a chiral entity requires either an anomalous scattering of X-ray radiation or chiroptical techniques, of which electronic circular dichroism (ECD) is one of the most useful. Chiroptical sensing that uses stereodynamic probes remains one of the remedies for the problem of the lack of a suitable chromophore in the molecules of the chiral compound. A covalent or non-covalent binding of an ECD-silent chiral molecule (the inducer) to the UV-active chromophoric system (chiroptical probe) led to obtaining complex ECD active at a given spectral region. The transfer of structural information from a permanently chiral inducer molecule to the structurally labile chromophoric system of the probe results in adjusting the latter’s structure to the chiral environment. This contribution focuses on some fundamental aspects of chirality sensing using conformationally labile probes. It discusses the mechanism of action of arbitrarily chosen stereodynamic chirality sensors, with particular emphasis on probes based on di- and triarylmethyl derivatives and biphenyl and its congeners. Full article