Radiative Heat Research Articles

A Semi-implicit Stochastic Multiscale Method for Radiative Heat Transfer Problem in Composite Materials

A Semi-implicit Stochastic Multiscale Method for Radiative Heat Transfer Problem in Composite Materials

Initial Performance Outlook on the Sliding Particle Receiver (SlideRec)

The next generation of central receivers is expected to reach high outlet temperatures of 800 °C and above, maintain stable operation and react to a varying incoming flux magnitude caused by hourly and seasonal variations, endure high-temperature operation, and remain cost-effective. Particle-based central receivers are being considered due to their high-temperature durability and favorable thermal properties of particle materials such as bauxite particles. This paper describes a new particle-based central receiver concept and provides an initial exploration of its performance in comparison with the existing CentRec® technology. Discrete Element Method (DEM) simulations demonstrated that a stable falling and sliding particle film can be achieved inside the SlideRec. The residence time of particle flow within the SlideRec is estimated to be higher than a falling particle receiver and similar to that of an obstructed-flow receiver. The results of the thermal model (incorporating reflective, radiative, convective and conductive heat losses) indicate that the SlideRec demonstrates a higher thermal efficiency than the CentRec® under an incoming aperture flux of between 0.1 MW/m2 and 1.7 MW/m2. The concept therefore is promising and is recommended for further experimental exploration.

LES of blockage of thermal radiation to the pool surface in large double pool fires.

Thermal radiation blockage to the pool surface plays a major role in assessing the fire growth and heat feedback to the pool surface and thereby intensity of pollution to the environment. In this work, large eddy fire simulations are performed to quantify the thermal radiation blockage to the pool surface of 0.6 m n-heptane double pool fires (DPF). The interspace between the two pools is varied from 0 to 0.6 m. The results of the air entrainment show that the considered double pool configuration is radiation dominated irrespective of the separation distances between the pools. The predicted heat feedbacks are in good agreement with the experimental results. A radiation influencing zone (RIZ) is introduced based on the percentage of the radiation contribution from the flame. RIZ is directly proportional to the flame height. Based on the opacity through the RIZ, the thermal radiation blockage is calculated. The blockage of radiation from standalone fire to double fire increased to 20%. The calculated radiative heat flux to the pool surface is in good agreement with the reported measurements. In addition, the maximum deviation between calculated and measured heat fluxes of the studied DPF is 6.8%. Further, the accuracy of the present methodology is shown better than the reported literature estimations.

Dynamics of Viscous Jeffrey Fluid Flow Through Darcian Medium With Hall Current and Quadratic Buoyancy.

This contribution builds on existing studies by investigating the dynamics of Hall current in Jeffery fluid under radiative heat, convective boundary conditions, Joule heating, and Darcy dissipation. Hall current, an important phenomenon in engineering applications involving strong magnetic fields, highlights the impact of electromagnetic force in examining blood flow rate, determining charge drift velocity, density, and movement, and is used in power generators and high-voltage transformers. This analysis incorporates dissipative and thermal radiative heat and employs the effects of Hall current and Joule heating, resulting from porous medium resistance, to derive the partial differential equationsgoverning the dynamic systems. These equationsare then reduced to ordinary differential equations (ODEs) through similarity variables. The Galerkin weighted residual method (GWRM) is employed to examine the dynamics of Hall current and quadratic thermal buoyancy, shedding light on the thermal properties and hydrodynamics of Jeffrey fluid convection within a porous medium. The analysis reveals that in the presence of an applied magnetic field, the contribution of Hall current to flow and heat dynamics induces a magnetic force that enhances fluid motion and negatively impacts heat energy patterns. The imposition of dissipative heat physically increases the fluid temperature, owing to an increase in buoyancy current. The occurrence of thermal radiation, Hall current, viscous dissipation, and Joule heating can efficiently optimize the rate of heat transfer and shear stress. Moreover, the tabular results indicate that Jeffrey fluid, exhibiting higher relaxation time, will experience a lower friction coefficient and heat transferrate.

Enhanced Catalytic Probe Design for Mapping Radical Density in the Plasma Afterglow.

The electrification of chemical processes using plasma generates an increasing demand for sensors, monitoring concentrations of plasma-activated species such as radicals. Radical probes are a low-cost in situ method for spatially resolved quantification of the radical density in a plasma afterglow using the heat from the exothermal recombination of radicals on a catalytic surface. However, distinguishing recombination heating from other heat fluxes in the system is challenging. In this study, we present a heat flux analysis based on probe measurements inside the reactor, with simultaneous IR imaging monitoring of the temperature of the reactor wall. The impact of radiation heat on a single thermocouple as well as the advantage of a dual thermocouple setup (using a catalytic unit together with a reference thermocouple) is shown. We add a heat sink with a monitored temperature to the dual thermocouple setup, allowing the determination of conductive and radiative heat fluxes. The heat sink gives more information on the measurement and reduces ambiguities in the evaluation used by others. The probe was tested by mapping N atom densities throughout the plasma afterglow of our reactor, enabling evaluation of the recombination kinetics of the radicals in the gas phase. Three-body recombination was shown to be the main pathway of recombination, with a recombination rate of krec = (2.0 ± 0.9)·10-44 m6/s, which is in line with the known literature findings, demonstrating that the measured species are N radicals and the probe did not influence the plasma or recombination reactions in the afterglow.

Estimation of thermal emission from mixture of CO2 and H2O gases and fly-ash particles

Abstract In the present work the thermal emission from gases and particle mixture is studied comprehensively. The mixture consist of CO2 and H2Ogases along with fly-ash particles and their spectral radiative properties are obtained from HITEMP database and Mie theory, respectively. The Line-by-line method, known for high accuracy is used to estimate radiative heat transfer from gases and particle mixture. Three distinct cases, i.e, pure absorption/emission, pure scattering, and their combined effects are investigated. The spectral radiative transfer equation is solved by finite angle method (FAM) and the correctness of the results is ensured by principle of energy conservation. The anisotropic scattering is modeled using the Henyey-Greenstein method. The influence of radiative properties of the participating medium, along with wall and cavity temperatures, on heat transfer and emission spectrum is evaluated. The radiative heat transfer enhances with introduction of the particles in the gaseous mixture. For pure scattering medium, the emission spectrum on each wall differs and also varies from the emission spectrum of the emitting wall. The particle influence grows notably with higher volume fractions in gaseous mixture. While there is a notable contribution of anisotropic scattering in a purely scattering medium, its significance diminishes in an absorbing, emitting, and scattering medium.

Application Research of Infrared Technology in Safety Detection in Ship Field

Abstract. This paper studies infrared technology and its application in the field of ship detection, mainly studying infrared thermal imaging of failure equipment refueling oil spill and ship safety problems because infrared technology is a high precision contact thermal measurement method through infrared camera infrared objects, the infrared spectrum wavelength range of infrared radiation heat, on the receiver into electronic signals, through electronic attenuation and electronic scanning form the corresponding heat map or temperature field image, to intuitively reflect the temperature distribution and heat focus of the object. In addition, the infrared detection device can be reasonably installed in the ship without affecting the work of other equipment, and it has been found that infrared technology has significantly improved the solution to the safety problems of ships.

Thermophoretic particle deposition effect on a squeezed flow of radiative Jeffrey fluid past a sensor surface with uniform heat source/sink and chemical reaction

Abstract This anticipated model investigates the time-dependent, and incompressible 2D magnetized Jeffrey liquid flowing on a sensor surface placed between two infinite parallel plates with the existence of a uniform heat source/sink. The lower plate remains fixed while the upper plate is subject to squeezing. For the heat and mass transmission processes, the consequences of radiative heat flux, chemical reaction, and thermophoretic particle deposition are applied and analyzed. The envisioned model is supported by prescribed heat and mass flux conditions. The uniqueness of the proposed model is the analysis of the unsteady squeezed flow of Jeffrey liquid over a sensor surface, accounting for radiative heat flux, thermophoretic particle deposition, and variable thermal conductivity. The model possesses applications in microfluidic sensors, biomedical devices, thermal management systems, and inkjet printing. The equations comprising the model are subject to similarity transformations. The bvp4c package is utilized to analyze the dynamic flow system. The connotation of arising parameters with the associated profiles is depicted through graphs and tables. It is examined that fluid velocity, temperature, and concentration profiles are dwindling functions of squeezed parameter. It is also witnessed that the concentration of liquid drops with an enhancement of thermophoretic and chemical reaction parameters. The validation of the truthfulness of the envisioned model is an added feature of this study.

Accurately measuring slowly propagating flame speeds: Application to ammonia/air flames

Environmental concerns have driven the development of alternative fuels and refrigerant working fluids with low global warming potential. Ammonia (NH3) is a potential zero-carbon fuel, while hydrofluorocarbons (HFCs) like R-32 and R-1234yf are being adopted as refrigerants. When mixed with air, these compounds can sustain slowly propagating flames with laminar flame speeds less than 10 cm/s. Unlike typical hydrocarbon-fueled flames, these slow flames are influenced by buoyancy-induced flow and radiation heat loss. In this study, we experimentally investigate the flame speeds of NH3/air mixtures using the constant-pressure spherically expanding flame method, while circumventing gravity-induced natural convection, and account for radiation-induced inward flow. To mitigate buoyant convection, a low-cost drop tower was built and used to study slow spherically expanding flames in free fall. A computational model (SRADIF) is utilized that combines thermodynamic equilibrium and finite rate optically thin limit radiation heat loss calculations to estimate the inward flow. The developed methodology is utilized to investigate slowly propagating NH3/air flames over a range of equivalence ratios. A systematic approach was undertaken to understand and quantify the errors that could arise when deriving the laminar flame speed. It was found that attempting to study slowly propagating flames in a static configuration, as opposed to in free fall, results in large differences in flame dynamics and subsequently all derived quantities. It is necessary to study slowly propagating flames in free-fall. Additionally, using experimental data that has not been corrected for radiation-induced flow leads to large errors in all derived quantities. Furthermore, direct comparisons of experimental measurements and detailed flame simulations are found to be necessary to determine if existing extrapolation approaches are applicable to these slowly propagating flames, which are challenging to study.

Electrochemical Nanoimprinting of Colored Infrared Reflective Patterns for Radiative Heating

AbstractMetallic nanostructures hold immense promise for radiative heating technology because of their distinctive capability to simultaneously achieve high mid‐infrared reflectance and generate vibrant colors through structural or plasmonic effects. However, fabricating metallic nanostructures remains challenging using traditional top–down techniques. Here, the solid‐state superionic stamping (S4) process is demonstrated as a scalable and economical tool to electrochemically imprint metallic grid nano‐patterns onto flexible substrates. With precise control over grid width and length at the nanoscale, the S4 approach enables the fabrication of nano‐patterned grid coatings exhibiting a spectrum of colors. These coatings also show high mid‐infrared reflectance exceeding 80% at 9.5 µm, leading to radiative heating effects of 5.9 and 3.1 °C compared to bare skin and cotton, respectively. This work introduces a viable strategy for creating colored infrared‐reflective patterns, paving the way for diverse thermal management applications.

Experimental Study on Cryogenic Compressed Hydrogen Jet Flames

Cryogenic compressed hydrogen (CcH2) technology combines the advantages of high pressure and low temperature to achieve high hydrogen storage density without liquefying the hydrogen, which has broad application prospects. However, the safety concerns related to cryogenic hydrogen need to be carefully addressed beforehand. In the present work, cryogenic hydrogen jet flames are experimentally investigated for various release pressures and initial temperatures. The flame length and thermal radiation flux were measured for horizontally releasing with nozzle diameters of 0.5–2 mm, temperatures ranging from 93 to 298 K, and initial pressures of 2–10 MPa. The results show that the flame length is dependent on the nozzle diameter, stagnation pressure and temperature. At a given pressure, the flame length, size and total radiant power increase with decreasing temperature, which is attributed to the lower jet flow velocity and higher density of low-temperature hydrogen. The normalized flame length Lf/D is correlated with the pressure ratio and temperature ratio. The correlation can be used to predict the flame length at various hydrogen pressures and temperatures. The normalized flame length of the cryogenic hydrogen jet flame is greater than that of the room-temperature hydrogen jet flame. The radiative heat flux of the flame can be predicted by the mass flow rate of the jet flow.

Heat transfer and entropy generation analysis of ternary nanofluid

Abstract In light of the rising demand for improved heat transfer in thermal systems, this work offers a unique technique for boosting heat transfer capacity and reducing entropy generation using a ternary nanofluid. Moreover, constant pressure gradient, magnetic field, Joule heating, and thermal radiation also contribute to the flow dynamics. The 2D mathematical model is solved numerically using a finite difference method and the simulations are done in MATLAB. The obtained results show that ternary nanoparticles not only increase the thermal rates but are also helpful in maintaining the irreversibility of a system. It is also observed that the heat transfer of the base fluid increased by 7.5%, 8.3%, and 8.5% on adding TiO2, CuO-TiO2, and MgO-CuO-TiO2 nanoparticles, respectively.

Hybrid heating in the fused filament fabrication process

AbstractAltering the heating regime of the polymer during the fused filament fabrication (FFF) process can lead to changes in both the behaviour of the polymer and the characteristics of the printed product. This study proposes replacing the traditional resistive heating system with two hybrid systems that introduce an additional temperature of 120–160 °C: one combining resistive and hot air jet heating, and the other combining resistive and infrared radiation heating. The samples printed using these hybrid systems were analysed using differential scanning calorimetry (DSC) and visually inspected. Commercial ABS and PLA filaments were used in the experimental programme. A model to evaluate the polymer’s melting during the printing process was proposed and experimentally validated. Visual testing revealed that the printed lattice structure had smaller voids, characterised by depositions that were flattened rather than circular in cross-section due to the extended time in a viscous/partially molten state. The elongation viscosity and storage modulus decreased by approximately 10%, with a slightly smaller decrease observed for the infrared radiation heat source. The glass transition temperature remained unchanged, and the molecular mobility was not affected by the additional heat. Similarly, the energy required for crystal formation was unaffected by the supplementary heat. The mechanical behaviour of the printed pieces during compression tests was also influenced by the addition of a second heat source. For both materials, a decrease in deformability was observed as the temperature of the hot air jet increased.

Heat transfer characteristics of petroleum coke particle packed bed: An experimental and CFD simulation study

AbstractDue to the complexity of the internal pore structure of petroleum coke loose particle‐packed beds, measuring their thermal conductivity has always been a challenging problem. This work independently developed an experimental apparatus for testing the thermal conductivity of petroleum coke particle‐packed beds and constructed a forward calculation model for the heat transfer process, which was based on one‐dimensional unsteady heat transfer. Using the Sparse Nonlinear OPTimizer (SNOPT) algorithm, a mathematical relationship between the thermal conductivity λ of the coke bed, temperature T, and equivalent particle diameter dp was established through inverse modeling. Concurrently, a digital model of the petroleum coke particle packed bed was derived utilizing three‐dimensional computed tomography (CT) scanning technology, and a pore‐scale gas–solid radiation heat transfer model was formulated based on CFD simulation technology, thereby further elucidating the heat transfer mechanism within the petroleum coke particle packed bed. The research results indicate that the temperature predicted by the established thermal conductivity model aligns well with experimental data. Further CFD simulation studies demonstrate that a smaller particle size leads to a larger temperature difference between the wall and the center of the packed bed, while a higher gas velocity results in a smaller temperature difference, with a linear correlation observed between these two factors. At high temperatures, thermal radiation between particles in the porous petroleum coke‐packed bed plays a dominant role. The research outcomes can offer significant theoretical support for a profound analysis of the heat transfer behavior of petroleum coke‐packed beds within a vertical shaft calciner.

Numerical simulation of magnetically driven nanomaterial rotating flow configured by convective-radiative cone with chemical reaction

Indeed, nanoliquids have acquired substantial consideration in heat transference field because of their inimitable thermal attributes and favorable application likelihoods. In contrast to orthodox liquids, the haphazard movement of nanoparticles within nanoliquid strengthens fluid turbulence, accomplishes superior thermal effectiveness and declines thermal resistance. Nanoliquids have ample utilization, for illustration, solar energy, electronic chips, automotive radiators and heat exchangers etc. This communication reports chemically reactive electro-magnetized nanomaterial dissipative flow confined by rotating cone. Flow expressions include thermo-solutal buoyancy, varying viscosity and magneto-hydrodynamics. Radiative heat, thermophoresis, viscous dissipation, Brownian diffusion, thermal source and first order chemical reaction are pondered to model transport expressions. Relevant variables are introduced to transfigure partial differential mathematical expressions to mathematical ordinary ones. Numerical outcomes for non-dimensional mathematical expressions are reported via bvp4c algorithm in MATLAB. The comprehensive results featuring dimensionless quantities are explored through graphs and arithmetic representations. It is evaluated that escalating values of variable viscosity, Prandtl number and unsteady parameter decline temperature but temperature is improved as a consequence of progressive variation in radiation parameter, Eckert number, thermophoresis parameter, heat generating and Brownian diffusive variables. The study is relevant to cooling industry, electroconductive, thermal collector and nano-materials processing.

Diversified characteristics of the dissipative heat on the radiative micropolar hybrid nanofluid over a wedged surface: Gauss-Lobatto IIIA numerical approach

The present examination focuses on the Falkner-Skan flow of micropolar hybridized nanofluid via a wedge surface. The proposed study examines thermal radiative fluxing and heat dissipation in hybridized nanoparticle aqueous solutions. Simulations of uni-directional radiative transport in optically dense fluids use Rosseland's diffusion model. This study created a Cu-TiO2/water hybrid nanofluid by mixing Cu and TiO2 nanomolecules with H2O. Partial differential equations from Naiver-Stokes theory are used to generate the regulating flow phenomena, then convert them into ordinary differentiation equations using an appropriate similarity approach. Additionally, the three-stage Lobatto IIIA method is used to compute the formulae. Calculations are done using MATLAB's built-in bvp5c function. We found that increasing material characteristics slows fluid flow because micropolar nanofluids minimize drag. These alterations alter fluid flow and boost temperature. However, boosting thermal radiation and Eckert number slows heat movement but improves temperature profiles. Much prior research ignored thermal radiative fluxing and heat dissipation in the aqueous solution of hybrid nanomolecules (Cu and TiO2) in Falkner-Skan micropolar flow via a wedge surface. Tables show wall frictional factor and Nusselt quantity results. Micropolar fluid characteristic decreases velocity but increases micro-rotational velocity. Power-law parameters, volume fractions, radiation, heat source, and Eckert amount affect thermal contours.

Implicit modular coupled heat transfer analysis for functionally graded materials using the SVC-FMC method

Functionally graded materials have found extensive applications in the aerospace industry and solar energy systems due to their excellent performance in enhancing heat transfer/insulation. Developing corresponding theoretical frameworks for the coupled radiation and conduction heat transfer (CRCHT) is crucial for unlocking their full potential and expanding their applicability in various high-performance and critical applications. Considering the limitations of existing frameworks in addressing CRCHT problems in practical applications, such as the explicit iteration procedure and the linearization assumption, a fully implicit framework as the source value caching function Monte Carlo (SVC-FMC) method is proposed based on the null collision reverse Monte Carlo and the Green's Function Markov Superposition Monte Carlo, which are suitable for solving the radiative transfer equation and the energy equation within non-uniform media. The accuracy of the proposed method is validated with different heat transfer systems. It was observed that the maximum root mean square error during the verification process did not exceed 0.08, thereby demonstrating the efficacy of SVC-FMC in analyzing CRCHT processes involving gradient materials. Results reveal that the material properties that transcend the functional distribution form will augment the strengthening effect of heat transfer/insulation. The scattering characteristics significantly influence the strengthening effect caused by refractive index distribution.

Thermal processes affected by carbon dioxide near ground surface

This study provides penetrative investigation of the effects of carbon dioxide concentration on time-dependent temperature and energy fluxes on the ground surface subject to solar irradiation. While global warming significantly impacts human life, the factors responsible remain controversial. This work considers unsteady one-dimensional heat conduction and radiative heat transfer, including collimated and diffuse components as functions of longitude, latitude, and altitude. Diffuse radiation depends on the different absorption bands of carbon dioxide and water vapor, as functions of wavelength, temperature, concentrations or pressure. The predicted results using COMSOL computer code show that the effects of carbon dioxide concentration on ground surface temperature are negligibly small, for example, over a 5-year period. Time-dependent ground surface temperature strongly depends on the absorption or dissipation of diffuse radiation and heat conduction. Diffuse radiation has a damping effect on temperature variation. Temperature changes due to solar irradiation absorption in the atmosphere are also negligibly small, despite solar irradiation being much greater than diffuse radiation and heat conduction. The absorption or dissipation of diffuse radiation depends on the dominant absorption bands centered at 4.3 and 15 μm of carbon dioxide at different times. This study, from the viewpoint of energy conservation, identifies diffuse radiation as a critical factor influencing the rate of temperature change at the ground surface, without assuming radiative or thermal equilibrium or modeling convection. Poor management of this radiation would hinder efforts to avoid droughts, water scarcity, severe fires, rising sea levels, flooding, catastrophic storms, and biodiversity loss.

Experimental study on the thermal insulation performance of semi-transparent materials based on convection heating method

Radiation heat transfer inside the aerogel materials belongs to medium radiation, so different heating methods have different measurement results of thermal conductivity. For aerogel materials applied in high temperature air flow environment (aerospace field), since the real boundary conditions of aerogel materials during operation can be simulated by convection heating method (CHM), the combustion-gas wind tunnel device based on two-stages atomization, two-stages combustion/mixing mode is constructed, and the performance test is conducted. The operation safety and combustion performance of the device meet the test requirements, so the thermal conductivity test of aerogel materials can be carried out. When the average temperatures are 469 K, 622 K and 763 K respectively, the effective thermal conductivity (ETC) measured by the CHM is smaller than that measured by the thermal conduction heating method (TCHM), which decreases by 2.7 %, 7.84 % and 9.23 % respectively. The CHM solves the limitations of the TCHM, so the ETC of aerogel materials measured by CHM is more valuable for the design of thermal protection system.

Experimental study on radiative heat flux from annular pool fires under the cross airflow

Experimental study on radiative heat flux from annular pool fires under the cross airflow