Showing papers on "Radiative transfer published in 2022"

The HITRAN2020 molecular spectroscopic database

Abstract: The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

Ternary Strategy Enabling High-Efficiency Rigid and Flexible Organic Solar Cells with Reduced Non-radiative Voltage Loss

Abstract: Ternary strategy has been identified as a feasible and effective way to obtain high-efficiency organic solar cells (OSCs). However, for most ternary OSCs, the voltage loss (Vloss) lies between those...

Protecting ice from melting under sunlight via radiative cooling

Abstract: As ice plays a critical role in various aspects of life, from food preservation to ice sports and ecosystem, it is desirable to protect ice from melting, especially under sunlight. The fundamental reason for ice melt under sunlight is related to the imbalanced energy flows of the incoming sunlight and outgoing thermal radiation. Therefore, radiative cooling, which can balance the energy flows without energy consumption, offers a sustainable approach for ice protection. Here, we demonstrate that a hierarchically designed radiative cooling film based on abundant and eco-friendly cellulose acetate molecules versatilely provides effective and passive protection to various forms/scales of ice under sunlight. This work provides inspiration for developing an effective, scalable, and sustainable route for preserving ice and other critical elements of ecosystems.

Highly‐Scattering Cellulose‐Based Films for Radiative Cooling

Abstract: Passive radiative cooling (RC) enables the cooling of objects below ambient temperature during daytime without consuming energy, promising to be a game changer in terms of energy savings and CO2 reduction. However, so far most RC surfaces are obtained by energy‐intensive nanofabrication processes or make use of unsustainable materials. These limitations are overcome by developing cellulose films with unprecedentedly low absorption of solar irradiance and strong mid‐infrared (mid‐IR) emittance. In particular, a cellulose‐derivative (cellulose acetate) is exploited to produce porous scattering films of two different thicknesses, L ≈ 30 µm (thin) and L ≈ 300 µm (thick), making them adaptable to above and below‐ambient cooling applications. The thin and thick films absorb only ≈5%${\approx}5\%$ of the solar irradiance, which represents a net cooling power gain of at least 17 W m−2, compared to state‐of‐the‐art cellulose‐based radiative‐cooling materials. Field tests show that the films can reach up to ≈5 °C below ambient temperature, when solar absorption and conductive/convective losses are minimized. Under dryer conditions (water column = 1 mm), it is estimated that the films can reach average minimum temperatures of ≈7–8 °C below the ambient. The work presents an alternative cellulose‐based material for efficient radiative cooling that is simple to fabricate, cost‐efficient and avoids the use of polluting materials.

The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022

Abstract: Abstract The underwater Hunga Tonga-Hunga Ha-apai volcano erupted in the early hours of 15th January 2022, and injected volcanic gases and aerosols to over 50 km altitude. Here we synthesise satellite, ground-based, in situ and radiosonde observations of the eruption to investigate the strength of the stratospheric aerosol and water vapour perturbations in the initial weeks after the eruption and we quantify the net radiative impact across the two species using offline radiative transfer modelling. We find that the Hunga Tonga-Hunga Ha-apai eruption produced the largest global perturbation of stratospheric aerosols since the Pinatubo eruption in 1991 and the largest perturbation of stratospheric water vapour observed in the satellite era. Immediately after the eruption, water vapour radiative cooling dominated the local stratospheric heating/cooling rates, while at the top-of-the-atmosphere and surface, volcanic aerosol cooling dominated the radiative forcing. However, after two weeks, due to dispersion/dilution, water vapour heating started to dominate the top-of-the-atmosphere radiative forcing, leading to a net warming of the climate system.

Clouds and the Earth’s Radiant Energy System (CERES) FluxByCldTyp Edition 4 Data Product

Abstract: The Clouds and the Earth’s Radiant Energy System (CERES) project has provided the climate community 20 years of globally observed top of the atmosphere (TOA) fluxes critical for climate and cloud feedback studies. The CERES Flux By Cloud Type (FBCT) product contains radiative fluxes by cloud-type, which can provide more stringent constraints when validating models and also reveal more insight into the interactions between clouds and climate. The FBCT product provides 1° regional daily and monthly shortwave (SW) and longwave (LW) cloud-type fluxes and cloud properties sorted by 7 pressure layers and 6 optical depth bins. Historically, cloud-type fluxes have been computed using radiative transfer models based on observed cloud properties. Instead of relying on radiative transfer models, the FBCT product utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) radiances partitioned by cloud-type within a CERES footprint to estimate the cloud-type broadband fluxes. The MODIS multi-channel derived broadband fluxes were compared with the CERES observed footprint fluxes and were found to be within 1% and 2.5% for LW and SW, respectively, as well as being mostly free of cloud property dependencies. These biases are mitigated by constraining the cloud-type fluxes within each footprint with the CERES Single Scanner Footprint (SSF) observed flux. The FBCT all-sky and clear-sky monthly averaged fluxes were found to be consistent with the CERES SSF1deg product. Several examples of FBCT data are presented to highlight its utility for scientific applications.

A Solution‐Processed Inorganic Emitter with High Spectral Selectivity for Efficient Subambient Radiative Cooling in Hot Humid Climates

Abstract: Daytime radiative cooling provides an eco-friendly solution to space cooling with zero energy consumption. Despite significant advances, most state-of-the-art radiative coolers show broadband infrared emission with low spectral selectivity, which limits their cooling temperatures, especially in hot humid regions. Here, an all-inorganic narrowband emitter comprising a solution-derived SiOx Ny layer sandwiched between a reflective substrate and a self-assembly monolayer of SiO2 microspheres is reported. It shows a high and diffusive solar reflectance (96.4%) and strong infrared-selective emittance (94.6%) with superior spectral selectivity (1.46). Remarkable subambient cooling of up to 5 °C in autumn and 2.5 °C in summer are achieved under high humidity without any solar shading or convection cover at noontime in a subtropical coastal city, Hong Kong. Owing to the all-inorganic hydrophobic structure, the emitter shows outstanding resistance to ultraviolet and water in long-term durability tests. The scalable-solution-based fabrication renders this stable high-performance emitter promising for large-scale deployment in various climates.

Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

Abstract: Passive daytime radiative cooling (PDRC) is emerging as a promising cooling technology. Owing to the high, broadband solar reflectivity and high mid‐infrared emissivity, daytime radiative cooling materials can achieve passive net cooling power under direct sunlight. The zero‐energy‐consumption characteristic enables PDRC to reduce negative environmental issues compared with conventional cooling systems. In this review, the development of advanced daytime radiative cooling designs is summarized, recent progress is highlighted, and potential correlated applications, such as building cooling, photovoltaic cooling, and electricity generation, are introduced. The remaining challenges and opportunities of PDRCs are also indicated. It is expected that this review provides an overall picture of recent PDRC progress and inspires future research regarding the fundamental understanding and practical applications of PDRC.

A Highly Settled Disk around Oph163131

Abstract: High dust density in the midplane of protoplanetary disks is favorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. Vertical settling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin and high-density regions. In this work, we aim to study these mechanisms in the highly inclined protoplanetary disk SSTC2D J163131.2-242627 (Oph 163131, i ∼ 84°). We present new high-angular-resolution continuum and 12CO ALMA observations of Oph 163131. The gas emission appears significantly more extended in the vertical and radial direction compared to the dust emission, consistent with vertical settling and possibly radial drift. In addition, the new continuum observations reveal two clear rings. The outer ring, located at ∼100 au, is well-resolved in the observations, allowing us to put stringent constraints on the vertical extent of millimeter dust particles. We model the disk using radiative transfer and find that the scale height of millimeter-sized grains is 0.5 au or less at 100 au from the central star. This value is about one order of magnitude smaller than the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of the large grains is occurring in the disk. When adopting a parametric dust settling prescription, we find that the observations are consistent with a turbulent viscosity coefficient of about α ≲ 10−5 at 100 au. Finally, we find that the thin dust scale height measured in Oph 163131 is favorable for planetary growth by pebble accretion: a 10 M E planet may grow within less than 10 Myr, even in orbits exceeding 50 au.

Thermal improvement in magnetized nanofluid for multiple shapes nanoparticles over radiative rotating disk

Abstract: In the present time, thermal transportation in the colloidal suspensions under various scenario becomes an influential research direction due to their extensive applications. Therefore, investigation of thermal transport over a rotating disk under the impacts of thermal and velocity slip, imposed Lorentz forces and thermal radiation is conducted for multiple shape effects of the nanomaterial. The nanofluid model suspended by Al2O3, TiO2 and Cu nanomaterial is reduced in dimensionless version via similarity variables. After that, RK scheme is implemented and handle the model effectively. The outcomes of various parameters for the velocity, thermal transport, skin friction and local heat transport are sketched and explained broadly. It is examined that the heat transport for the nanofluids becomes dominant throughout the analysis in comparison with conventional liquid. The temperature of the nanofluids significantly enhances due to the velocity slip effects. Moreover, thermal radiation and the volumetric fraction of the nanomaterials favor the local heat transfer rate.

A Universal Strategy for Tunable Persistent Luminescent Materials via Radiative Energy Transfer

Abstract: In this work, a universal strategy for solid, solution, or gel state organic persistent luminescent materials via radiative energy transfer is proposed. The persistent luminescence (τ>0.7 s) could be remotely regulated between different colors by controlling the isomerization of the energy acceptor. The function relies on the simple radiative energy transfer (reabsorption) mechanism, rather than the complicated communication between the excited state of the molecules such as Förster resonance energy transfer or Dexter energy transfer. And the "apparent lifetime" for the energy acceptor is the same as the lifetime of the energy donor, which was different with a traditional radiative energy transfer process. The simple working principle endows this strategy with huge universality, flexibility, and operability. This work offers a simple, feasible, and universal way to construct various persistent luminescent materials in solid, solution, and gel states.

MHD mixed convection flow of a hybrid nanofluid past a permeable vertical flat plate with thermal radiation effect

Abstract: The magnetohydrodynamic (MHD) radiative flow of a hybrid alumina-copper/water nanofluid past a permeable vertical plate with mixed convection is the focal interest in this present work. Dissimilar to the traditional nanofluid model that considers only one type of nanoparticles, we consider the hybridization of two types of nanoparticles in this work which are alumina and copper. The governing flow and heat transfer equations are simplified to the ordinary differential equations (ODEs) with the adaptation of conventional similarity transformations which are then evaluated by the bvp4c solver (MATLAB) to generate the numerical solutions. The solutions are generated and illustrated in the form of graph to be easily observed. Although dual solutions are obtained in this study, only one solution is determined to be stable. By reducing the concentration volume of copper and increasing the magnetic and radiation parameters, the boundary layer separation can be hindered. With the occurrence of opposing flow due to the mixed convection parameter, the heat transfer can be enhanced when the concentration volume of copper is being reduced and when the magnetic and radiation parameters are being proliferated.

Thermal improvement in magnetized nanofluid for multiple shapes nanoparticles over radiative rotating disk

Abstract: In the present time, thermal transportation in the colloidal suspensions under various scenario becomes an influential research direction due to their extensive applications. Therefore, investigation of thermal transport over a rotating disk under the impacts of thermal and velocity slip, imposed Lorentz forces and thermal radiation is conducted for multiple shape effects of the nanomaterial. The nanofluid model suspended by Al2O3, TiO2 and Cu nanomaterial is reduced in dimensionless version via similarity variables. After that, RK scheme is implemented and handle the model effectively. The outcomes of various parameters for the velocity, thermal transport, skin friction and local heat transport are sketched and explained broadly. It is examined that the heat transport for the nanofluids becomes dominant throughout the analysis in comparison with conventional liquid. The temperature of the nanofluids significantly enhances due to the velocity slip effects. Moreover, thermal radiation and the volumetric fraction of the nanomaterials favor the local heat transfer rate.

Ultralong organic phosphorescence from isolated molecules with repulsive interactions for multifunctional applications

Abstract: Abstract Intermolecular interactions, including attractive and repulsive interactions, play a vital role in manipulating functionalization of the materials from micro to macro dimensions. Despite great success in generation of ultralong organic phosphorescence (UOP) by suppressing non-radiative transitions through attractive interactions recently, there is still no consideration of repulsive interactions on UOP. Herein, we proposed a feasible approach by introducing carboxyl groups into organic phosphors, enabling formation of the intense repulsive interactions between the isolated molecules and the matrix in rigid environment. Our experimental results show a phosphor with a record lifetime and quantum efficiency up to 3.16 s and 50.0% simultaneously in film under ambient conditions. Considering the multiple functions of the flexible films, the potential applications in anti-counterfeiting, afterglow display and visual frequency indicators were demonstrated. This finding not only outlines a fundamental principle to achieve bright organic phosphorescence in film, but also expands the potential applications of UOP materials.

Low-Energy Supernovae Severely Constrain Radiative Particle Decays

Abstract: The hot and dense core formed in the collapse of a massive star is a powerful source of hypothetical feebly interacting particles such as sterile neutrinos, dark photons, axionlike particles (ALPs), and others. Radiative decays such as a→2γ deposit this energy in the surrounding material if the mean free path is less than the radius of the progenitor star. For the first time, we use a supernova (SN) population with particularly low explosion energies as the most sensitive calorimeters to constrain this possibility. These SNe are observationally identified as low-luminosity events with low ejecta velocities and low masses of ejected ^{56}Ni. Their low energies limit the energy deposition from particle decays to less than about 0.1 B, where 1 B(bethe)=10^{51} erg. For 1-500 MeV-mass ALPs, this generic argument excludes ALP-photon couplings G_{aγγ} in the 10^{-10}-10^{-8} GeV^{-1} range.

Opportunistic experiments to constrain aerosol effective radiative forcing

Abstract: Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well-defined sources provide "opportunistic experiments" (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatiotemporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite datasets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Opportunistic experiments have significantly improved process-level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change.

Non-singular fractional computations for the radiative heat and mass transfer phenomenon subject to mixed convection and slip boundary effects

Abstract: In this study, we have investigated the magnetohydrodynamics(MHD) fluid flow through a porous medium flowing on anerect vertical plate. The effects of mass and heat transfer through ramped temperature, thermal radiation, and slip conditions in the energy equation are also considered. To enhance the innovation of this article, the recent definition of fractional derivative operator i.e. Atangana-Baleanu (AB) time-fractional derivative, is used to explore the numerical results of the problem.The semi-analytical solution of fractional dimensionless leading equations is obtained by using the Laplace scheme and some numerical methods namely Stehfest and Tzou's algorithms. Some specialcases of velocity distribution are discussed whose physical applications are well-defined in the literature. The obtained results are illustrated graphically and numerically by changing the values ofdifferent parameters. A decayinh change in heat transfer and velocity profile is noticed for fractional parameter β.

Thermal prospective of Casson nano-materials in radiative binary reactive flow near oblique stagnation point flow with activation energy applications

Abstract: The flow of nanoparticles presents many dynamic applications in thermal sciences, solar systems, cooling and heating phenomenon, energy resources and much other multidisciplinary significance. Following to such valuable applications and motivations in mind, this research pronounced the thermal applications of radiative Casson nanoparticles in presence of radiative phenomenon and activation energy. The oblique stagnation point flow has been considered due to the stretching cylinder. To analyze the flow problem, the problem is formulated in the cylindrical coordinates. The numerical solution is computed via bvp4c built solver by using the MATLAB software. The impact of different involved parameters on skin fraction, heat transfer rate and mass transfer rate is reported and discussed in tables.