Radiative Energy Transfer Research Articles

Thermal and emission characteristics of reverse air flow CAN combustor

Relative assessment of thermal and emission characteristics of conventional and reverse air flow CAN type gas turbine combustor is reported. Large Eddy Simulations (LES) are carried out with Wall Adaptive Local Eddy (WALE) viscosity model for sub grid scale stresses. Turbulence-chemistry interaction is modelled using presumed shape Probability Density Function (PDF) approach. Discrete Ordinates (DO) model is used for radiative heat transfer. Experimental measurement of temperature and NOx emission level at the exit of combustors are reported. Flow pattern and flame shape obtained from numerical analysis for conventional and reverse air flow combustor are correlated to combustor liner wall heating, exit temperature characteristics and NOx emission. The liner wall region of conventional combustor is dominated by hot combustion gases whereas the location of hot flame in reverse air flow combustor is in the vicinity of centreline. The exit temperature measurement shows that the wall side temperature in reverse air flow combustor is relatively low compared to conventional combustor. Reverse air flow arrangement in combustor eliminates the hot spots of high temperature gradient from primary region of combustor which results into significant reduction in NOx emission level in reverse air flow combustor as compared to conventional combustor. Thermal imaging of outer wall of combustors demonstrates that the radiative energy transfer from liner wall to outer wall is small in reverse air flow combustor compared to conventional combustor. This depicts that the wall-cooling requirement decreases in reverse air flow combustor.

Adapting Three Classic Demonstrations To Teach Radiant Energy Trapping and Transfer As Related to the Greenhouse Effect

Three concepts necessary for understanding the greenhouse effect are infrared radiation, absorption of infrared radiation by greenhouse gases, and steady-state energy flow. Herein, we describe adaptations to three classic demonstrations for teaching these concepts. William Hershel’s discovery of infrared radiation has been adapted into a fast and reliable demonstration using a pyranometer. We provide guidelines for building a ball-and-spring model of carbon dioxide that demonstrates the absorption of IR and the three fundamental vibrational modes of carbon dioxide and their relative frequencies. Finally, we describe an adaptation of Blanck’s plastic water-flow device to demonstrate how adding greenhouse gases can alter the steady-state flow of energy through the atmosphere.

Strategies for Plasmonic Hot‐Electron‐Driven Photoelectrochemical Water Splitting

AbstractPhotoelectrochemical water splitting (PEC‐WS) was inspired by the natural photosynthesis process that utilizes sunlight energy to produce chemical energy through splitting water to form hydrogen and oxygen. One recent promising and innovative approach in this field is to implement the concept of plasmonic to PEC‐WS devices. This Review provides a systematic overview of the plasmonic and hot‐electron‐driven PEC‐WS and elucidates their possible mechanisms for plasmon‐mediated energy transfer. In the first section, we provide a brief summary of the basics of PEC‐WS and the strategies employed to maximize its conversion efficiency. Highlighting the advantages of the plasmonic‐based PEC system, in the next part we cluster our discussion based on the basics of plasmonics and the involved energy transfer mechanisms, which are classified as radiative (scattering, optical near field coupling) and nonradiative energy transfer (hot electron injection, plasmon resonant energy transfer) processes for plasmonic metal–semiconductor junctions as a photoactive material. Then, the recent research efforts in this field are categorized and discussed in three main sections: 1) nanoplasmonic units, 2) nanostructured support scaffolds, and 3) interface engineering with state‐of‐the‐art demonstrations. Finally, we conclude our Review with pointing out the challenges and perspectives of the plasmonic‐based architectures for future water‐splitting devices.

Unravelling radiative energy transfer in solid-state lighting

Today, a wide variety of organic and inorganic luminescent materials (e.g., phosphors, quantum dots, etc.) are being used for lighting and new materials (e.g., graphene, perovskite, etc.) are currently under investigation. However, the understanding of radiative energy transfer is limited, even though it is critical to understand and improve the performance levels of solid-state lighting devices. In this study, we derived a matrix approach that includes absorption, reabsorption, inter-absorption and their iterative and combinatorial interactions for one and multiple types of fluorophores, which is simplified to an analytical matrix. This mathematical approach gives results that agree well with the measured spectral and efficiency characteristics of color-conversion light-emitting diodes. Moreover, it also provides a deep physical insight by uncovering the entire radiative interactions and their contribution to the output optical spectrum. The model is universal and applicable for all kinds of fluorophores.

A coherent description of thermal radiative devices and its application on the near-field negative electroluminescent cooling

Using the transimissivity between two thermal reservoirs and the generalized Planck distributions, we describe the devices that use radiative energy transfer between thermal reservoirs in a unified formalism. Four types of devices are distinguished. For power generators that use the temperature difference between reservoirs, photovoltaic (PV) and thermoradiative (TR) devices respectively use the low-temperature photovoltaic cell and high-temperature thermoradiative cell to generate electricity. For active cooling, the electroluminescent (EL) cooling devices apply a forward bias voltage on the object we want to cool, whereas the negative EL cooling devices apply a reverse bias voltage to the heat sink. The relationship among these four devices is explicated. The performance of the negative EL cooling is analyzed, both in the Shockley-Queisser (blackbody spectrum and radiative recombination) framework and the near-field enhancement. The “impedance match” condition derived for PV systems is applied to the negative EL devices. One advantageous feature of the negative EL cooling is that it does not apply the voltage to the target object which we want to cool, and the near-field enhancement can apply to various target materials that support the surface resonant modes.

Improving the Performance of Gold-Nanoparticle-Doped Solid-State Dye Laser Using Thermal Conversion Effect

Energy transfer between spherical gold nanoparticles with size of more than 15 nm and molecules of organic dye 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) has been studied. Such radiative energy transfer led to high local temperature, giving rise to a bleaching effect that resulted in rapid degradation of the laser medium. Gold nanoparticles were dispersed at concentrations from 5 × 109 particles/mL to 5 × 1010 particles/mL in DCM polymethylmethacrylate polymer using a radical polymerization process with 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Using the fast thermoelectric cooling method, the laser medium stability was significantly improved. The output stability of a distributed feedback dye laser pumped by second-harmonic generation from a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was investigated. Moreover, bidirectional energy transfer between gold nanoparticles and dye molecules was observed.

Correction: Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties.

Correction for 'Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties' by Guo-Hui Pan, Jiahua Zhang et al., Nanoscale, 2018, DOI: 10.1039/c8nr07360k.

Нобелевский лауреат С. Чандрасекар: к 65-летию первой монографии по переносу лучистой энергии (Посвящается 65-летию ИПМ имени М.В.Келдыша и памяти профессора Е.С. Кузнецова, основателя отечественной научной школы и создателя отдела «Кинетические уравнения»)

Нобелевский лауреат С. Чандрасекар: к 65-летию первой монографии по переносу лучистой энергии (Посвящается 65-летию ИПМ имени М.В.Келдыша и памяти профессора Е.С. Кузнецова, основателя отечественной научной школы и создателя отдела «Кинетические уравнения»)

Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties.

The most common yellow phosphor for wLEDs, Y3Al5O12:Ce3+ (YAG:Ce3+), suffers from a deficiency of red in its spectral content of light. In this paper, a new strategy is provided to tailor the Ce3+ spectral profile through surface-located dye molecules of ATTO-Rho101, which feature intense, broad absorption in the green-yellow spectral region of Ce3+ emission as well as bright red emission. Sphere-shaped and highly dispersed micrometer and nanometer-sized YAG:Ce3+ (micro/nano-YAG:Ce3+) was synthesized through a modified solvothermal method. Surface SiO2 coating and simultaneous dye embedding were performed on the solvothermally derived YAG:Ce3+, heat-treated micro-YAG:Ce3+ and commercial phosphors. Efficient radiative transfer/reabsorption from Ce3+ in the inner core of YAG to the dye molecules in the SiO2 outer shell, irrespective of the size of the phosphors, was demonstrated in the accumulated YAG:Ce3+@SiO2 + dye powder upon blue light excitation; this enhanced its red emission. Fluorescence microscopy was demonstrated to be a powerful tool to identify the reabsorption phenomenon of the powdered materials. Packaging the heat-treated micro-YAG:Ce3+@SiO2 + dye phosphors on blue LED chips yielded a warm wLED (Ra∼ 93), but an Ra of only ∼79 was obtained for the wLED with commercial YAG:Ce3+@(SiO2 + dye)5 due to the low concentration of phosphors dispersed in the epoxy resin and the resulting decreased reabsorption by dye molecules. Surface-protonated amine species were found to induce Ce3+→ Ce4+ oxidation upon activation by heating or photoirradiation and then quench the photoluminescence (PL) of micro-YAG:Ce3+ even after surface modification by SiO2, YAG or being embedded in an epoxy resin matrix. High calcination temperatures greatly improved the PL stability of micro-YAG:Ce3+ through the removal of surface-capped species. The dye in the silica matrix showed high stability against heating and irradiation due to the so-called "caging effects"; however, decreased photo-stability was found in commercial YAG:Ce3+@(SiO2 + dye)5 due to the incomplete and/or loose SiO2 layer grown during multiple surface modifications.

A 2D Ray-Tracing Based Model for Wave Propagation Through Forests at Micro-and Millimeter Wave Frequencies

This paper proposes the extension of a 2-D ray-tracing-based model for radiowave propagation in the presence of trees and vegetation areas to include real-sized trees and outdoor forest scenarios. The original propagation model proved to be suitable to characterize the electromagnetic behavior in the presence of indoor tree formation scenarios, despite some limitations found when applied to real-sized trees. In addition, the original propagation model requires the prior knowledge of the trees’ re-radiation function to extract the relevant propagation input parameters, which is not always possible to obtain in outdoor scenarios. Therefore, an empirical method to extract the relevant input propagation parameters based on simple measurements is proposed. The performance of the proposed propagation model extension is extensively assessed in both the line-of-trees and tree formation scenarios, including various (and mixed) species, both in- and out-of-leaf foliation states, and at three signal frequencies. Finally, depending on the type of scenario, a benchmark between the proposed propagation model and both the radiative energy transfer (RET) and discrete RET (dRET) models, for line-of-trees and tree formation, respectively, is presented.

Solar radiation exergy and quality performance for Iraq and Turkey

The present study is conducted with two primary objectives: First, a new formulation for the maximum efficiency of the solar radiation conversion is developed by considering the radiative energy transfer between two surfaces at different temperatures for a constant volume system. Second, a new methodology is introduced for estimating the exergy value of the monthly average daily horizontal global radiation, including many parameters, such as monthly average daily value of the horizontal extraterrestrial radiation, the number of sunny hours, the day length, the mean temperature and the mean wind velocity. Seven statistical parameters are used to validate the accuracy of all models. The results of the two new models are found to be more reliable than the results obtained from other models. This study, which was conducted for four locations in Iraq and Turkey. The findings would help in predicting the maximum availability of solar radiation based on weather parameters.

Visualization of complex DNA damage along accelerated ions tracks

The most deleterious DNA lesions induced by ionizing radiation are clustered DNA double-strand breaks (DSB). Clustered or complex DNA damage is a combination of a few simple lesions (single-strand breaks, base damage etc.) within one or two DNA helix turns. It is known that yield of complex DNA lesions increases with increasing linear energy transfer (LET) of radiation. For investigation of the induction and repair of complex DNA lesions, human fibroblasts were irradiated with high-LET 15N ions (LET = 183.3 keV/μm, E = 13MeV/n) and low-LET 60Co γ-rays (LET ≈ 0.3 keV/μm) radiation. DNA DSBs (γH2AX and 53BP1) and base damage (OGG1) markers were visualized by immunofluorecence staining and high-resolution microscopy. The obtained results showed slower repair kinetics of induced DSBs in cells irradiated with accelerated ions compared to 60Co γ-rays, indicating induction of more complex DNA damage. Confirming previous assumptions, detailed 3D analysis of γH2AX/53BP1 foci in 15N ions tracks revealed more complicated structure of the foci in contrast to γ-rays. It was shown that proteins 53BP1 and OGG1 involved in repair of DNA DSBs and modified bases, respectively, were colocalized in tracks of 15N ions and thus represented clustered DNA DSBs.

Localized hydroxyl radical generation at mmol/L and mol/L levels in water by photon irradiation.

The generation of localized hydroxyl radical (•OH) in aqueous samples by low linear energy transfer irradiation was investigated. Several concentrations of 5,5-dimethyl-1-pyrroline-N-oxid solution (from 0.5 to 1,680 mmol/L) were prepared and irradiated with an identical dose of X-ray or γ-ray. The density of •OH generation in aqueous solution was evaluated by the electron paramagnetic resonance spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxid as an electron paramagnetic resonance spin-trapping agent. The relationship between the molecular density of 5,5-dimethyl-1-pyrroline-N-oxid in the samples and the concentration of 5,5-dimethyl-1-pyrroline-N-oxid-OH generated in the irradiated samples was analyzed. Two different characteristic linear trends were observed in the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots, which suggested •OH generation in two fashions, i.e., mmol/L- and mol/L-level local concentrations. The dose, dose rate, and/or the energy of photon irradiation did not affect the shapes of the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots. Moreover, the addition of 5 mmol/L caffeine could cancel the contribution of mmol/L-level •OH generation, leaving a trace of mol/L-level •OH generation. Thus, the localized mmol/L- and mol/L-level generations of •OH, which were independent of experimental parameters such as dose, dose rate, and/or the energy of photon of low linear energy transfer radiation, were established.

Performance comparison between photovoltaic and thermoradiative devices

Photovoltaic (PV) and thermoradiative (TR) devices are power generators that use the radiative energy transfer between a hot and a cold reservoir. For PV devices, the semiconductor at the cold side (PV cell) generates electric power; for TR devices, the semiconductor at the hot side (TR cell) generates electric power. In this work, we compare the performance of the photovoltaic and thermoradiative devices, with and without the non-radiative processes. Without non-radiative processes, PV devices generally produce larger output powers than TR devices. However, when non-radiative processes become important, the TR can outperform the PV devices. This conclusion applies to both far-field and near-field based devices. A key difference in efficiency between PV and TR devices is pointed out.

Activatable Hybrid Nanotheranostics for Tetramodal Imaging and Synergistic Photothermal/Photodynamic Therapy.

A multifunctional core-satellite nanoconstruct is designed by assembling copper sulfide (CuS) nanoparticles on the surface of [89 Zr]-labeled hollow mesoporous silica nanoshells filled with porphyrin molecules, for effective cancer imaging and therapy. The hybrid nanotheranostic demonstrates three significant features: (1) simple and robust construction from biocompatible building blocks, demonstrating prolonged blood retention, enhanced tumor accumulation, and minimal long-term systemic toxicity, (2) rationally selected functional moieties that interact together to enable simultaneous tetramodal (positron emission tomography/fluorescence/Cerenkov luminescence/Cerenkov radiation energy transfer) imaging for rapid and accurate delineation of tumors and multimodal image-guided therapy in vivo, and (3) synergistic interaction between CuS-mediated photothermal therapy and porphyrin-mediated photodynamic therapy which results in complete tumor elimination within a day of treatment with no visible recurrence or side effects. Overall, this proof-of-concept study illustrates an efficient, generalized approach to design high-performance core-satellite nanohybrids that can be easily tailored to combine a wide variety of imaging and therapeutic modalities for improved and personalized cancer theranostics in the future.

Practical indicators for assessing the magnitudes of wall radiative flux and of coupling effects between radiation and other heat transfer modes on the temperature law-of-the wall in turbulent gaseous boundary layers

Practical indicators are derived to compare radiative and conductive fluxes and the coupling effects of conduction, convection and radiation in turbulent gaseous boundary layers. A first criterion controlling the weight of wall radiative flux compared to wall conductive flux is introduced to assess the necessity of performing radiation simulation under given flow conditions. A second criterion based on the variation of the non-dimensional temperature due to radiation (scaled in wall units) is also developed to predict whether a wall model accounting for radiation is required when coupling effects become significant. These criteria are built from turbulent channel gaseous flow field simulations for many typical conditions, based on a k-∊ model, a given turbulent Prandtl number expression and a spectral CK model for radiation. They have been validated from the comparison with corresponding fully-coupled results where turbulent fields are solved numerically with direct numerical simulations and where the radiative energy transfer is solved with a Monte Carlo approach.The obtained criterion results are then presented and thoroughly analyzed on a large set of conditions, which would not have been feasible with direct numerical simulations or large-eddy simulations. The influence of system size, Reynolds number, wall emissivity and pressure is synthesized in 2D contour plots of interest for engineers and researchers to assess the magnitude of radiation effects in wall bounded flows.

Radiative energy transfer from MoS2 excitons to surface plasmons

In this work, we demonstrated the energy transfer process from few-layer MoS2 to gold dimer arrays via ultrafast pump-probe spectroscopy. With the overlap between the MoS2 exciton and the designed plasmon dipolar modes in the frequency domain, the exciton energy can be radiatively transferred to plasmonic structures, excited the localized surface plasmon resonance, and then enhanced the oscillation of coherent acoustic phonons. Power-dependent differential reflection signals and an analytical model based on the rate equation of exciton density were carried out to quantitatively study the energy transfer process. Our finding explores the energy flow between MoS2 excitons and surface plasmons, and can be contributed to the design of exciton-plasmon structures utilizing ultrathin materials.

Near-field enhancement of thermoradiative devices

Thermoradiative (TR) device has recently been proposed for noncontact direct photon-electricity energy conversion. We investigate how the near-field effect can boost the performance of a TR device. For a near-field TR device, a heat sink is placed close to the TR cell, with the separation being small compared to the characteristic photon wavelength. It is demonstrated that the TR device, like the thermophotovoltaic device, can be formulated using the transmissivity and the generalized Planck distribution. We quantitatively show that δ-function transmissivity is a very good approximation (capturing up to 90% of total radiative energy transfer) when the radiative energy transfer is governed by resonances. Three practical types of heat sinks are considered, a metallic material described by the Drude model, a polar dielectric material described by the Lorentz oscillator model, and a semiconductor material that is identical to the TR cell. The blackbody heat sink serves as the far-field reference. By properly choosing the resonant frequencies supported by the heat sink, we show that the heat sink made of a Drude or Lorentz material can enhance the output power by about 60 and 20 times, respectively, as compared to the blackbody reference. Even with a heat sink made of the same material as the TR-cell, which does not support any resonant modes, the output power can be enhanced by about 10 times. The mechanisms can be elucidated from the impedance matching condition derived from the coupled-mode theory.

A novel approach to calculate radiative thermal exchange in coupled particle simulations

We present a novel algorithm to calculate radiative energy transfer rates in Discrete Element Method (DEM)-based simulations of mono-disperse spheres. To verify our algorithm we use the Finite Volume Method (FVM) which enables us to picture relevant radiation phenomena in a dense bed of particles. These phenomena include (i) shadowing, (ii) emission and (iii) adsorption by a constant gray medium. After careful verification, we embed our algorithm in LIGGGHTS, a solver for the DEM. A combination of LIGGGHTS and a solver for intra-particle temperature gradients, i.e., ParScale, is then used to quantify the relevance of radiative heat transfer rates in sheared particles beds. Specifically, we evaluate the relative contributions of conductive, convective and radiative thermal fluxes in granular shear flows of frictional inelastic spheres. We find that the radiative flux can be collapsed onto single curve if it is related to an appropriate dimensionless group. Our analysis establishes a rationale on when radiative heat transfer in dense granular flows should be considered or not. Also, our results can be used to close continuum-based granular dynamics model that aim on predicting the particle temperature distribution under extreme temperature scenarios.

Control of the luminescent properties of Eu2-xDyx(WO4)3 solid solutions for scintillator applications

Crystalline materials containing tungsten and europium ions are frequently used as scintillators because tungsten complexes show a high absorption cross section for high energy radiation and efficient energy transfer to europium ions, which relax radiatively in the visible spectral range according to the 5D0→7F2 transition. However, this intra-configurational transition is forbidden on spin and parity and, consequently, shows a slow decay rate (hundreds of microseconds to milliseconds). In order to use this kind of materials in high repetition rate processes, faster luminescence decays are required. A set of Eu2-xDyx(WO4)3 solid solutions has been synthesized. Rietveld refinement of X-ray diffraction patterns has been performed in order to determine the crystalline structure of the samples and particularly the distance between rare earth cations. The morphology and composition was characterized with scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Optical absorption, emission spectra and decay rates have been systematically measured to analyze the luminescent properties of the materials. Cross-relaxation processes between Eu3+ and Dy3+ ions are responsible of the reduction of the 5D0 decay rate. The average lifetime of the Eu3+5D0 excited state can be decreased in the range of one order of magnitude. However, the 5D0→7F2 emission intensity decreases in the same range too. Nevertheless, the proposed strategy of Eu3+5D0 lifetime reduction can be of interest for those opto-electronic detection applications, which are not limited by sensitivity but by time resolution, such as it occurs in many cases for high energy-high repetition rate photon pulses.