Thermal Radiation Characteristics Research Articles

Nonlinear heat radiation and mass transfer characteristics on MHD Walters’ B fluid flow through a porous medium over a stretching sheet

To handle the continuous thermal power supply is very important in thermal systems and industries, so magnetized heat transport with non-Newtonian fluid is an appropriate platform for thermal power energy. In view of this usefulness, this paper provides a numerical assessment of electrically conducting Walter's B fluid flow through nonlinear permeable stretching sheet subject to mixed convective, porous medium, and Newtonian heating phenomena. Thermophoresis and Brownian motion effects have been included in energy and species diffusion equations to account for the impacts of nonlinear thermal radiation, joule heating, heat source and chemical reaction. The system of governing equations has been reduced to dimensionless nonlinear coupled equations using similarity transformations. The bvp4c technique has been used to obtain the solution for velocity, temperature, and concentration distributions. We consider both regions of assisting and opposing flow and provide various tables and graphs to examine the impact of varying values of emerging factors. Heat source and thermal radiation characteristics are found to enhance the thermal boundary layer thickness, which may be used to dissipate heat. The magnetic parameter augmented the fluid temperature and decelerated the velocity field. The chemical reaction parameter accelerated the concentration distribution. Further, the Sherwood number, Nusselt number, and skin friction coefficient have been determined and compared well to prior research that has been published.

The Influence of Reinforced Fibers and Opacifiers on the Effective Thermal Conductivity of Silica Aerogels.

Fiber-particle-reinforced silica aerogels are widely applied in thermal insulation. Knowing their effective thermal conductivity (ETC) and radiative characteristics under high temperatures is necessary to improve their performance. This article first analyzes the radiation characteristics of silica aerogels doped with opacifier particles and reinforced fibers, and then a universal model is established to predict the ETC. Furthermore, the impacts of different parameters of opacifier particles and reinforced fibers on the thermal insulation performance of silica aerogels are investigated. The results indicate that SiC exhibits comparatively strong absorption characteristics, making it a good alternative for opacifiers to improve thermal insulation performance under high temperatures. For the given type and volume fraction of opacifier particles, there exists an optimal diameter and volume fraction to achieve the best insulation performance of silica aerogel under a certain temperature. Considering that SiO2 fibers exhibit a limited extinction capability and higher conductive thermal conductivity under high temperatures, for fiber-particle-reinforced silica aerogels, it is beneficial for their insulation performance to reduce the fiber volume fraction when the required mechanical properties are satisfied.

Thermally tunable nonreciprocal radiation in lithography-free vanadium dioxide-dielectric-Weyl semimetal stack

Nonreciprocal thermal radiation (NTR) holds great promise in revolutionizing energy harvesting and conversion process, has become a hot topic of various research fields ranging from renewable energy, molecular sensing, to thermal circuitry and camouflage. Despite intensive effort into enhance the nonreciprocal response, static manipulation of NTR has limited the potential application, dynamic control of thermal radiation is highly demanded. Here, by using a multilayered stack comprised of vanadium dioxide (VO2) thin film, germanium (Ge) spacer layer, Weyl semimetal (WSM) layer terminated by molybdenum (Mo) substrate, we propose a thermally tunable nonreciprocal emitter. The effects of the incident angle (θi), azimuthal angle (ϕi), and the thickness of each layer for the VO2/Ge/WSM stack on the characteristics of thermal radiation have been discussed thoroughly. Dominant peaks and dips of nonreciprocity have been obtained with an incident angle of θi=60° and azimuthal angle of ϕi=0°. A switching effect between the near-unity nonreciprocity (”ON”) and zero nonreciprocity (”OFF”) states are induced when the temperature increases from 20 °C to 68 °C. It is shown that the magnitude and sign of the nonreciprocity can be managed simultaneously for transverse electric (s-) and transverse magnetic (p-) polarizations. The proposed structure shows good near-unity nonreciprocity stability in a wide range of θi and ϕi. This structurally lithography-free nonreciprocal thermal emitter not only provides the ability to tune nonreciprocal radiative properties, but also leads to the possible development of power scavenging and conversion devices.

Impact of Arrhenius activation energy on magnetic nanofluid flow over a slendering stretchable sheet with nonlinear radiative heat transfer: A machine learning algorithm

Thermal systems in the contemporary world need effective cooling and heating methods. Heat transfer technology plays a vital role in various industries, including aerospace, electronic equipment, automobiles, and transportation. Considering the importance of effective cooling and heating processes, this framework explores the hydromagnetic stagnation point flow with binary chemical reactions, ohmic heating, Arrhenius activation energy, nonlinear thermal radiation, thermophoresis, and Brownian motion. At first, the flow equations are determined in a formal way as dimensional partial differential equations. Then, they are transformed into simpler, dimensionless ordinary differential equations using self-similar variables. The present study describes a novel approach to intelligent numerical computing, utilizing a Levenberg-Marquard algorithm-based MLP (Multi-Layer Perceptron) feed-forward back-propagation ANN (Artificial Neural Networks) implementation. The collection of data was conducted to facilitate the evaluation, validation, and instruction of the artificial neural network model. The utilization of appropriate self-similarity variables has facilitated the conversion of fluid transport equations into ordinary differential equations. The Runge–Kutta–Fehlberg (RKF) technique was used to solve these equations. The numerical results are presented visually for numerous constraints of the governing parameters. The increased values of the velocity ratio enhanced the fluid velocity. The nonlinear thermal radiation and temperature differential characteristics significantly raise the temperature of the fluid. Increasing the nonlinear radiation and magnetic field parameters improves the rate of heat transfer. The temperature of the fluid decreases as the size of stagnation increases. The skin friction coefficients decrease as the wall thickness and magnetic parameters increase.

ON THE ISSUE OF THE COMPREHENSIVE IMPACT OF NEGATIVE AND HARMFUL FACTORS ON THE OCCURRENCE OF OCCUPATIONAL DISEASES

Most of the time, a person spends indoors, and up to 40 % of this time is spent at their workplace. Therefore, the environmental conditions, whether at home or at work, have a significant impact on the human body and their performance. The modern world is influenced by more than a hundred real existing negative factors that affect industry, daily life, and the natural environment. According to the standards defined in DSTU-N B A.3.2-1:2007 “Occupational Safety Standards. Guidelines for Identifying Hazardous and Harmful Factors and Protection Against Their Impact in Production”, environmental factors are divided into several groups: physical, chemical, biological and psychophysiological. The presence of these factors affects the health and safety of individuals while performing their professional duties. The purpose of the article. Conducting a comprehensive analysis of the impact of negative and harmful factors on the occurrence of occupational diseases in the workplace with the aim of developing recommendations for improving working conditions and preventing occupational diseases. Conclusion. 1. A comprehensive approach is necessary to address the tasks of creating safe working conditions and providing a normal working environment for enterprise personnel. 2. The significant complexity of the comprehensive impact of harmful factors on production workers requires the provision of optimal working conditions and the preservation of workers' health. 3. It is important to study the combined effect of various production environment factors on the worker's body in manufacturing processes involving high temperatures. 4. The assessment of working conditions in areas with elevated thermal radiation is not yet complete because it does not consider qualitative characteristics of thermal radiation, such as spectral composition, vector energy distribution, the influence of splashes, and particles of molten metal, and the operating mode of heat radiation sources. 5. Based on the analysis of collected data in the workshops of petrochemical and metallurgical enterprises, it has been found that the most dangerous and challenging working conditions, with limited research from the standpoint of working conditions, are the workplaces and areas with elevated thermal radiation, where sanitary norms are exceeded by more than 100 times. 6. Quantitative and qualitative characteristics of excessive thermal radiation, such as spectral composition (direct and transformed radiation) and vector distribution, as well as the influence of splashes and particles of molten metal, were not taken into account when addressing protection from thermal radiation. 7. There is currently no unified methodology for researching working conditions and developing recommendations for their improvement.

Controlling Thermal Radiation in Photonic Quasicrystals Containing Epsilon-Negative Metamaterials

The transfer matrix approach is used to study the optical characteristics of thermal radiation in a one-dimensional photonic crystal (1DPC) with metamaterial. In this method, every layer within the multilayer structure is associated with its specific transfer matrix. Subsequently, it links the incident beam to the next layer from the previous layer. The proposed structure is composed of three types of materials, namely InSb, ZrO2, and Teflon, and one type of epsilon-negative (ENG) metamaterial and is organized in accordance with the laws of sequencing. The semiconductor InSb has the capability to adjust bandgaps by utilizing its thermally responsive permittivity, allowing for tunability with temperature changes, while the metamaterial modifies the bandgaps according to its negative permittivity. Using quasi-periodic shows that, in contrast to employing absolute periodic arrangements, it produces more diverse results in modifying the structure’s band-gaps. Using a new sequence arrangement mixed-quasi-periodic (MQP) structure, which is a combination of two quasi periodic structures, provides more freedom of action for modifying the properties of the medium than periodic arrangements do. The ability to control thermal radiation is crucial in a range of optical applications since it is frequently unpolarized and incoherent in both space and time. These configurations allow for the suppression and emission of thermal radiation in a certain frequency range due to their fundamental nature as photonic band-gaps (PBGs). So, we are able to control the thermal radiation by changing the structure arrangement. Here, the We use an indirect method based on the second Kirchoff law for thermal radiation to investigate the emittance of black bodies based on a well-known transfer matrix technique. We can measure the transmission and reflection coefficients with associated transmittance and reflectance, T and R, respectively. Here, the effects of several parameters, including the input beam’s angle, polarization, and period on tailoring the thermal radiation spectrum of the proposed structure, are studied. The results show that in some frequency bands, thermal radiation exceeded the black body limit. There were also good results in terms of complete stop bands for both TE and TM polarization at different incident angles and frequencies. This study produces encouraging results for the creation of Terahertz (THz) filters and selective thermal emitters. The tunability of our media is a crucial factor that influences the efficiency and function of our desired photonic outcome. Therefore, exploiting MQP sequences or arrangements is a promising strategy, as it allows us to rearrange our media more flexibly than quasi-periodic sequences and thus achieve our optimal result.

Thermal Radiation Characteristics of Cylindrical Porous Burner with Axial Supply of Combustible Mixture

Thermal Radiation Characteristics of Cylindrical Porous Burner with Axial Supply of Combustible Mixture

Thermal radiative transfer characteristics of a single water droplet

Direct heating of water droplets by thermal radiation is the key process in incorporating solar energy to achieve green production in many industrial applications, such as desalination, carbon capture, and energy storage. The radiative transfer characteristics of a single water droplet under given irradiation, including reflection, absorption, and transmission were investigated through a calculation model built with the zone method. The ranges of the equivalent diameter and length–width ratio of the droplet were 0.1 – 1.0 mm, 1 – 10 respectively. The absorption coefficient was 10 – 15 000 m−1 and the refractive index was 1.2 – 2.0. Results suggested that, (1) the reasonable irradiating angle between external irradiation and droplet's long axis was 30° – 150°, in which the energy allocation among reflection, absorption and transmission was almost fixed. (2) The absorption mode of the droplet could be classified into surface absorption (SA) and volumetric absorption (VA). In VA, the droplet could achieve a uniform and rapid temperature increase, but it required the optical thickness of droplet to be less than 1. (3) Scattering included reflection and transmission. Compared with incident irradiation, reflection was distributed mainly on the same side as droplet's long axis, whereas transmission was distributed mainly on the opposite side. The overall reflectivity increased depended mainly on refractive index, but was independent on droplet size. Transmissivity increased with increasing length–width ratio or decreasing equivalent diameter. (3) In VA, at least 40% of incident irradiation was scattered out. The total amount of scattering could be adjusted by changing the absorption coefficient in VA or the refractive index in SA. At last, an empirical formula of droplet's absorptivity was proposed when the irradiating angle was in the range of 30° – 150°

Regional Thermal Radiation Characteristics of FY Satellite Remote Sensing Based on Big Data Analysis.

It is of great significance to study the thermal radiation anomalies of earthquake swarms in the same area in terms of selecting abnormal characteristic determination parameters, optimizing and determining the processing model, and understanding the abnormal machine. In this paper, we investigated short-term and long-term thermal radiation anomalies induced by earthquake swarms in Iran and Pakistan between 2007 and 2016. The anomalies were extracted from infrared remote sensing black body temperature data from the China Geostationary Meteorological Satellites (FY-2C/2E/2F/2G) using the multiscale time-frequency relative power spectrum (MS T-FRPS) method. By analyzing and summarizing the thermal radiation anomalies of series earthquake groups with consistency law through a stable and reliable MS T-FRPS method, we first obtained the relationship between anomalies and ShakeMaps from USGS and proposed the anomaly regional indicator (ARI) to determine seismic anomalies and the magnitude decision factor (MDF) to determine seismic magnitude. In addition, we explored the following discussions: earthquake impact on regional thermal radiation background and the relationship between thermal anomalies and earthquake magnitude and the like. Future research directions using the MS T-FRPS method to characterize regional thermal radiation anomalies induced by strong earthquakes could help improve the accuracy of earthquake magnitude determination.

Effect of Pore Evolution on Thermal Diffusivity and Radiation Characteristics of Thermal Barrier Coatings after High-Temperature Exposures

Studying the impact of pores is crucial to enhancing the service performance of coatings, since they are a typical microstructure feature of thermal barrier coatings. In this paper, a coating prepared by the APS method was employed as the study object, and a scanning electron microscope and optical microscope were used to calculate the porosity after spraying or high-temperature exposures. Based on this, numerical calculations and simulations were used to evaluate the impacts of the pore structure and porosity on the heat conductivity and radiation characteristics of the coating. The results showed that, at high-temperature exposures, the horizontal pores inhibited thermal conductivity and radiation, but the column pores increased heat conductivity and radiation. The heat conductivity of the coating linearly decreased as the porosity increased, whereas the extinction coefficient increased, although at a slower and slower pace. When the porosity reached 15%, if the porosity was further increased, the thermal radiation energy did not change much, indicating that increasing the porosity would only block the heat radiation to a certain amount. This new and time-saving technique for materials research utilizing simulation and numerical computing may be utilized to optimize the microstructure of coatings to increase their service performance.

Effectiveness of thermal radiations and homogeneous–heterogeneous reactions in Maxwell flow field across a rotating cylinder

This paper investigates the impact of cubic autocatalysis on energy transport in Maxwell fluid flow induced into a rotating cylinder inspired by a solar radiative surface. The homogeneous-reaction is assumed to be furnished by the kinetics of isothermal cubic autocatalytic and the heterogeneous reaction by kinetics of first order. To prevent induced axial secondary flow, the cylinder's rotation is maintained at a constant rate. The characteristics of thermal radiation are also investigated to regulate the pace of heat transmission. A magnetic beam is projected in the upward radial direction to control the fluid momentum. A suitable flow ansatz is used to convert the entire physical problem of thermal energy transmission and fluid flow from partial differential equations (PDEs) to nonlinear ordinary differential equations (ODEs). Results obtained numerically with the bvp4c approach are presented graphically and explained physically. It is observed that by flourishing the Reynolds parameter, the penetration depth decreases. Further, when the thermal relaxation period increases, the temperature field degrades. Moreover, when the homogeneous–heterogeneous reaction's strength is increased, a reduction in fluid concentration is shown.

Multicolored Displays with Selective Visible‐Infrared Spectral Modulation for Optical Information Transmission

AbstractPolyaniline (PANI) can achieve reversible optical modulation in visible and infrared (IR) bands under the action of voltage. However, PANI‐based electrochromic devices cannot cope with the dual detection of visible and IR light to realize the transmission of information due to the linkage restriction between the spectral modulation in the visible and IR region. Here, IR low‐absorptive inorganic pigments as colorants and IR high‐transparent polymer as a binder are utilized to prepare colored films with high transparency. A camouflage layer against visible light detection is constructed on the surface of IR electrochromic devices, and the information transmission is realized in the IR band by controlling the thermal radiation characteristics. Furthermore, thermochromic microcapsules (TMs) that change color under external thermal stimuli are introduced to fabricate a thermochromic and IR transparent functional layer, which is attached to the surface of IR electrochromic devices and endows the devices with separate spectral modulation ability in the visible and IR region. Multicolored displays are fabricated by arraying various devices. Moreover, visual patterns are prepared on the surface of IR electrochromic devices by dispensing technology. This configuration endows the device with a promising potential for anti‐counterfeiting, optical security, and related applications.

Effect of Particle Size Distribution and Complex Refraction Index of Alumina on Infrared Rocket Plume Signatures

ABSTRACT Although there are several studies existing in the literature modeling the infrared radiation signatures of solid motor rocket plumes, none of them investigate the effect of some simplifying assumptions such as using gray optical properties, Sauter-mean/mass-mean diameters, temperature-independent optical properties, etc., on thermal radiation characteristics of rocket plumes. These assumptions have the potential to improve the computational efficiency of the radiative transfer calculations by reducing the CPU time required by the solution of Mie theory. Therefore, the objective of this study is to investigate the influence of using (i) mean diameters instead of a particle size distribution (PSD), (ii) optical properties for different phases and crystal structures of Al2O3, (iii) temperature-independent optical properties of Al2O3, and (iv) gray optical properties of Al2O3 particles instead of spectral ones on the radiative heat transfer predictions under rocket plume conditions. For this purpose, a 3-D radiation model based on discrete ordinates method (DOM) coupled with statistical narrow band correlated-k (SNBCK) and Mie theory is utilized. Based on the outcomes of this study, it can be concluded that utilizing mean diameters, temperature-independent optical properties, and gray optical properties of Al2O3 for the calculation of particle radiative properties provides reasonably accurate radiative heat transfer predictions. Moreover, presence of different phases and crystal structures of Al2O3 in the rocket plume leads to significantly different infrared radiation signatures.

Segmented Line Heat Source Model for Thermal Radiation Calculation of Jet Fires in Chemical Plants

Abstract The jet fire caused by the leakage of combustible materials is one of the biggest threats to the safety of chemical plants. Thermal radiation of the jet fire brings severe damage to nearby facilities and people's health. To evaluate the damage of jet fires, a precise model for the calculation of thermal radiation is indispensable. Classical thermal radiation models of jet fires either have a lower prediction accuracy or a higher computation complexity. To overcome such deficiencies, this paper proposes a novel segmented line heat source (SLHS) model for jet fires. Because the length of the jet fire is often much larger than the width, the jet fire is viewed as a line heat source, with all the heat radiated from the centerline of the jet fire. The jet fire is divided into three segments along the flame length according to the temperature distribution and thermal radiation characteristics of the flame. Based on the SLHS model, three types of thermal radiation models called cone-cylinder-cone, ellipsoid-cylinder-ellipsoid, and ellipsoid-cylinder-cone models are built for computing the radiant heat flux distribution around the jet fire. The effectiveness and advantages of the proposed models are illustrated with the experimental data and a numerical simulation.

Strong nonreciprocal thermal radiation based on topological edge state in one-dimensional photonic crystal with Weyl semimetal

Kirchhoff's law is the theoretical basis for characterizing thermal radiation. The construction of nonreciprocal thermal radiation needs to violate Kirchhoff's law, in which its existing methods usually utilize the magneto-optical effect with an external magnetic field. However, natural materials' relatively weak magneto-optical response in the thermal wavelength range requires a strong or moderate magnetic field. Fortunately, the unique topologically nontrivial electronic state and inherent time-reversal symmetry breaking of Weyl semimetals can exhibit highly unusual and extremely large gyrotropic optical responses in the mid-infrared band without an external magnetic field, which provides a new way to violate Kirchhoff's law. This work theoretically investigates the nonreciprocity of a multilayer structure in which a Weyl semimetal is embedded in two one-dimensional photonic crystals. The results show that the absorptivity and emissivity of the structure almost completely violate Kirchhoff's law over a broad range of angles (7° ∼ 51°) and frequencies (56.4 THz ∼ 65.3 THz) without any external magnetic field. We also discuss the effects of the incident angle, the axial vector of the Weyl semimetal, and the thickness of the Weyl semimetal on the characteristics of nonreciprocal thermal radiation. Furthermore, the electric field distribution reveals that the structurally excited topological edge states significantly enhance the local electric field in the vicinity of the Weyl semimetal, providing positive conditions for the realization of perfect strong nonreciprocal thermal radiation. We hope this work may contribute to the design of strong nonreciprocal thermal emitters.

Computational and Stability Analysis of MHD Time-Dependent Thermal Reaction Flow Impinging on a Vertical Porous Plate Enclosing Magnetic Prandtl Number and Thermal Radiation Effect

The aim of the present study is to investigate magnetohydrodynamic (MHD) time-dependent flow past a vertical slanted plate enclosing heat and mass transmission (HMT), induced magnetic field (IMF), thermal radiation (TR), and viscous and magnetic dissipation characteristics on a chemical reaction fluid flow. A boundary layer estimate is taken to develop a movement that exactly captures the time-dependent equations for continuity, momentum, magnetic induction, energy, concentration, generalized Ohm’s law, and Maxwell’s model. Partial differential equations designate the path occupied by the magnetized fluid as it passes through the porous matrix. In addition, a heat source is included in the model in order to monitor the flow nature in the current study. Because of the nonlinearity in the governing equations, the mathematical models are computed numerically by RK4 method. Further, tables and graphs are depicted to elucidate the physical influence of important factors on the flow characteristics. The novelty of the present work is investigating the irregular heat source and chemical reaction over the porous rotating channel. It is perceived that high thermal radiation occurs with increases in temperature and concentration. It is witnessed that the IMF effect is diminished for large values of magnetic Prandtl number (MPN). It is also analyzed that with increasing the heat source factor, the velocity of the fluid enhances. For stability analysis, the existing effort is compared with the published work and good agreement is found. Moreover, the residue error estimation confirms our solution.

Polyaniline-Based Infrared Dynamic Patterned Encoder with Multiple Thermal Radiation Characteristics.

A high-level infrared dynamic patterned encoder (IR-DPE) possesses prospective applications for energy-harvesting and information, but a simple and reliable method for fabrication remains challenging. Herein, we first report an IR-DPE with multiple thermal radiation characteristics based on polyaniline (PANI). Specifically, the electron-beam evaporation technique is introduced to obtain the divanadium pentoxide (V2O5) coating, and then the V2O5 film acts as an oxidant to drive in situ polymerization of the PANI film. During the process, we experimentally explore the relationship between the thickness of V2O5 and the emissivity of PANI to obtain up to six emissivity levels and achieve the IR pattern integrated into multiple thermal radiation characteristics. The device shows multiple thermal radiation characteristics at the oxidized state, realizing a pattern visible with the IR camera and the same thermal radiation properties at the reduced state, leading to the pattern concealed in the IR regime. In addition, the highest emissivity tunability of the device is to be tuned from 0.40 to 0.82 (Δε = 0.42) at 2.5-25 μm. Meanwhile, the device exhibits a maximum temperature control of up to 5.9 °C. The results show the enormous potential of IR-DPEs for IR information transfer and thermal management.

Microwave Thermal Radiation Analysis of King Crater on the Lunar Farside Using CE-2 MRM Data

King crater is a Copernican crater located near the equator in the western highlands of the lunar farside. The study of the microwave brightness temperature (TB) in this region is of great significance for exploring the interior structure of the lunar farside. The Chang’e-2 (CE-2) microwave radiometer (MRM) is mainly used to obtain TB data on the lunar surface under four channels. This study uses the ordinary Kriging algorithm to interpolate the midday and midnight MRM data of this region and generates the TB maps and TB difference (dTB) maps for each channel in two moments. Combined with UVVIS data from Clementine satellite and Diviner data from LRO satellite, the characteristics of microwave thermal radiation are discussed. The results show that (FeO+TiO2) abundance (FTA) and rock abundance (RA) are important factors affecting thermal radiation anomalies in the King crater. It also provides evidence for the formation of the King-Bruno anomalous belt, which is believed to be significantly related to the formation of the King crater.

Nonlinear radiation phenomena for Casson–Maxwell nanoliquid flow with chemical reactions

The viscoelastic characteristics of an incompressible, axisymmetric Casson–Maxwell nanoliquid flow between two stationary discs were examined in this paper. Two porous discs are constrained for uniform injection. The Christov model is used in conjunction with the Buongiorno model. In an energy equation with a nonlinear form, thermal radiation characteristics are used. In the current continuation, the impact of chemical reactions is taken into account, making the work more adaptable. Using appropriate transformations, the constructed model was transformed into a dimensionless form. The solution is obtained by employing the FEM technique. The related parameters are described using physical results. The radial velocity distribution at the center line was reduced using a magnetic parameter and a Casson parameter. When the Brownian motion constant and radiation parameter are increased, the temperature distribution of nanoparticles enhances. Furthermore, the rate of the reaction increases in the presence of a chemical reaction. Pearson's correlation coefficient was used to discover a relationship between the Sherwood and Nusslet numbers. To determine the linear relationship between variables, the t-test method is used.

Investigation on the radiation heat transfer in dilution zone of a 100 kWth oxy-fuel pressurized circulating fluidized bed

Due to high pressure, complicated flue gas components and high particle concentration in dilute phase region, radiation heat transfer in the oxy-fuel combustion pressurized circulating fluidized bed (PCFB) is complex. To indicate the radiation heat transfer, both experiments and numerical simulations were carried out, where the Computational Fluid Dynamics (CFD) modelling was based on the full spectrum correlated k-distribution model (FSCK) combined with Mie theory. The multiphase flow behaviors, combustion reactions and radiation heat transfer of the PCFB under oxy-fuel combustion at 0.6 MPa were revealed with good agreement between the simulated result and the experimental data. The predictions of radiation heat transfer were accomplished under different oxygen concentration and operating pressure. The results illustrated that the existence and accumulation of particles lead to the increase of flue gas optical thickness, which hinders more radiation energy transmitted to the wall. Various oxygen concentration leads to the different distribution of temperature and radiative medium concentration, which all have an impact on total radiation intensity. Compared with temperature, particle radiation and gas radiation have less effect on radiation heat transfer under different atmosphere. In addition, the operating pressure affected the flue gas temperature as well as particle concentration and radiative gas concentration in the dilution zone, and the combustion atmosphere also has an influence on the above characteristics. Complicated thermodynamic states lead to dissimilar thermal radiation characteristics under different operating condition.