scispace - formally typeset
Search or ask a question

Showing papers on "Thermal radiation published in 2021"


Journal ArticleDOI
TL;DR: It is demonstrated that a hierarchically designed polymer nanofibre-based film, produced by a scalable electrostatic spinning process, enables selective mid-infrared emission, effective sunlight reflection and therefore excellent all-day radiative cooling performance.
Abstract: Traditional cooling systems consume tremendous amounts of energy and thus aggravate the greenhouse effect1,2. Passive radiative cooling, dissipating an object’s heat through an atmospheric transparency window (8–13 μm) to outer space without any energy consumption, has attracted much attention3–9. The unique feature of radiative cooling lies in the high emissivity in the atmospheric transparency window through which heat can be dissipated to the universe. Therefore, for achieving high cooling performance, the design and fabrication of selective emitters, with emission strongly dominant in the transparency window, is of essential importance, as such spectral selection suppresses parasitic absorption from the surrounding thermal radiation. Recently, various materials and structures with tailored spectrum responses have been investigated to achieve the effect of daytime radiative cooling6–8,10–15. However, most of the radiative cooling materials reported possess broad-band absorption/emission covering the whole mid-infrared wavelength11–15. Here we demonstrate that a hierarchically designed polymer nanofibre-based film, produced by a scalable electrostatic spinning process, enables selective mid-infrared emission, effective sunlight reflection and therefore excellent all-day radiative cooling performance. Specifically, the C–O–C (1,260–1,110 cm−1) and C–OH (1,239–1,030 cm−1) bonding endows the selective emissivity of 78% in 8–13 μm wavelength range, and the design of nanofibres with a controlled diameter allows for a high reflectivity of 96.3% in 0.3–2.5 μm wavelength range. As a result, we observe ~3 °C cooling improvement of this selective thermal emitter as compared to that of a non-selective emitter at night, and 5 °C sub-ambient cooling under sunlight. The impact of this hierarchically designed selective thermal emitter on alleviating global warming and temperature regulating an Earth-like planet is also analysed, with a significant advantage demonstrated. With its excellent cooling performance and a scalable process, this hierarchically designed selective thermal emitter opens a new pathway towards large-scale applications of all-day radiative cooling materials. A hierarchically designed polymer nanofibre-based film produced by a scalable electrospinning process enables selective mid-infrared emission and effective sunlight reflection, and thus realizes an excellent all-day radiative cooling performance.

302 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of thermal radiation and surface roughness on the complex dynamics of water conveying alumina and copper oxide nanoparticles, in the case where the thermophysical properties of the resulting mixture vary meaningfully with the volume fraction of solid nanomaterials, as well as with the Brownian motion and thermophoresis microscopic phenomena.
Abstract: Sequel to the fact that hybrid nanofluidic systems (e.g. scalable micro-/nanofluidic device) exhibit greater thermal resistance with increasing nanoparticle concentration, little is known on the significance of thermal radiation, surface roughness and linear stability of water conveying alumina and copper oxide nanoparticles. This study presents the effects of thermal radiation and surface roughness on the complex dynamics of water conveying alumina and copper oxide nanoparticles, in the case where the thermophysical properties of the resulting mixture vary meaningfully with the volume fraction of solid nanomaterials, as well as with the Brownian motion and thermophoresis microscopic phenomena. Based on the linear stability theory and normal mode analysis method, the basic partial differential equations governing the transport phenomenon were non-dimensionalized to obtain the simplified stability equations. The optimum values of the critical thermal Rayleigh number depicting the onset of thermo-magneto-hydrodynamic instabilities were obtained using the power series method and the Chock–Schechter numerical integration. The increase in the strength of Lorentz forces, thermal radiation and surface roughness has a stronger stabilizing impact on the appearance of convection cells. On the contrary, the stability diminishes with the increasing values of the volumetric fraction and diameter of nanomaterials. The partial substitution of the alumina nanoparticles by the copper oxide nanomaterials in the mixture stabilizes importantly the hybrid nanofluidic medium.

225 citations


Journal ArticleDOI
TL;DR: In this article, a mathematical analysis for three-dimensional Eyring-Powell nanofluid nonlinear thermal radiation with modified heat plus mass fluxes is investigated, and the slip condition is introduced to enhance the dynamical and physical study of structure.
Abstract: In this paper, a mathematical analysis for three-dimensional Eyring–Powell nanofluid nonlinear thermal radiation with modified heat plus mass fluxes is investigated. To enhance the dynamical and physical study of structure, the slip condition is introduced. A Riga plate is employed for avoiding boundary-layer separation to diminish the friction and pressure drag of submarines. To evaluate the heat transfer, the Cattaneo–Christov heat flux model is implemented via appropriate transformation. A comparison between bvp4c results and shooting technique is made. Graphical and numerical illustrations are presented for prominent parameters.

151 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the magnetic force and nonlinear thermal radiation on hybrid bio-nanofluid flow in a peristaltic channel under the influence of an applied magnetic field with high and low Reynolds number.

114 citations


Journal ArticleDOI
TL;DR: In this paper, a doubly holographic model of a black hole in two-dimensional JT gravity theory is coupled to an auxiliary bath system at arbitrary finite temperature, and a unitary Page curve is obtained by applying the usual prescription for holographic entanglement entropy.
Abstract: We study the doubly holographic model of [1] in the situation where a black hole in two-dimensional JT gravity theory is coupled to an auxiliary bath system at arbitrary finite temperature. Depending on the initial temperature of the black hole relative to the bath temperature, the black hole can lose mass by emitting Hawking radiation, stay in equilibrium with the bath or gain mass by absorbing thermal radiation from the bath. In all of these scenarios, a unitary Page curve is obtained by applying the usual prescription for holographic entanglement entropy and identifying the quantum extremal surface for the generalized entropy, using both analytical and numeric calculations. As the application of the entanglement wedge reconstruction, we further investigate the reconstruction of the black hole interior from a subsystem containing the Hawking radiation. We examine the roles of the Hawking radiation and also the purification of the thermal bath in this reconstruction.

113 citations


Journal ArticleDOI
TL;DR: In this paper, a numerical model is employed for the nanofluid flow and heat transfer from an infinite vertical plate in the presence of a magnetic field, thermal radiation and viscous dissipation.

93 citations


Journal ArticleDOI
TL;DR: In this article, the influence of hybrid nanoparticles on various physical quantities in a water-based hybrid nanofluid involved in a steady and fully developed forced convective flow generated over a stretched surface was investigated.
Abstract: We have investigated the influence of hybrid nanoparticles on various physical quantities in a water-based hybrid nanofluid involved in a steady and fully developed forced convective flow generated over a stretched surface. Nonlinear thermal radiation and melting heat transfer analysis are featured in this work. To obtain the solution of the governing equations, a standard transformation and numerical procedure are implemented. Then, a comprehensive discussion of the effects of the flow regime on several governing parameters is presented. The results indicated that increasing magnetic strength $$M$$ and nanoparticle volume fraction $$\phi_{1}$$ lead to a thicker thermal boundary layer. A similar trend takes place with increasing nonlinear thermal radiation while the reverse is noticed for Eckert number. The entropy generation rate increases with the increase in Brinkman number and Bejan number reduces with increasing Eckert number. The obtained results of this model closely match with those available in the literature as a limiting situation. It is demonstrated that hybrid nanofluids exhibit lower entropy generation rates. The results of this study are of importance in the assessment of the effect of some essential design parameters on heat transfer and, consequently, in the optimization of industrial processes.

91 citations


Journal ArticleDOI
TL;DR: In this paper, the behavior of buoyancy-driven flow in a Fe3O4 water ferrofluid-filled enclosure with two circular cylinders and subject to constant magnetic field and thermal radiation was investigated.

85 citations


Journal ArticleDOI
TL;DR: In this paper, the impacts of nonlinear thermal radiations on S W C N T − T i O 2 & M W C n T − C o F e 2 O 4 nanoparticles suspended in water-based hybrid type nanofluid flow over rotating disk are considered.

85 citations


Journal ArticleDOI
20 May 2021-ACS Nano
TL;DR: A scalable thermal insulating cooler (TIC) consisting of hierarchically hollow microfibers as the building envelope that simultaneously achieves passive daytime radiative cooling and thermal insulation to reduce environmental heat gain is proposed in this article.
Abstract: Daytime passive radiative cooling is a promising electricity-free pathway for cooling terrestrial buildings. Current research interest in this cooling strategy mainly lies in tailoring the optical spectra of materials for strong thermal emission and high solar reflection. However, environmental heat gain poses a crucial challenge to building cooling at subambient temperatures. Herein, we devise a scalable thermal insulating cooler (TIC) consisting of hierarchically hollow microfibers as the building envelope that simultaneously achieves passive daytime radiative cooling and thermal insulation to reduce environmental heat gain. The TIC demonstrates efficient solar reflection (94%) and long-wave infrared emission (94%), yielding a temperature drop of about 9 °C under sunlight of 900 W/m2. Notably, the thermal conductivity of the TIC is lower than that of air, thus preventing heat flow from external environments to indoor space in the summer, an additional benefit that does not sacrifice the radiative cooling performance. A building energy simulation shows that 48.5% of cooling energy could be saved if the TIC is widely deployed in China.

76 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the phenomenon of heat and mass transfer in 3D radiative flow of hybrid nanofluid over a rotational disk and found that the rate of heat transfer is proportional to Brinkman number, magnetic effect and concentration of nanoparticles.
Abstract: In this research, the phenomenon of heat and mass transfer in 3D radiative flow of hybrid nanofluid over a rotational disk is investigated. Nanoparticles of Al2O3 and Cu are being used with water (H2O) as base fluid. The mathematical flow model in terms of PDEs is constructed by considering the heat transport mechanism due to Joule heating and viscous dissipation. This set of PDEs is converted into a system of ODEs by introducing the proper similarity transformations, which is then solved with the computational strength of Lobatto IIIA method. Demonstrations of graphical and numerical data are offered to examine the variation of velocity and thermal field against various physical constraints. The variable trend of heat transfer rate and skin friction coefficient through numerical data are also investigated. It is found that rate of heat transfer is proportional to Brinkman number, magnetic effect and concentration of nanoparticles. Achieved accuracy in term of relative error upto the level of 1e-14 shows the reliability and worth of solution methodology.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated solar radiation influences on two-dimensional stagnation-point flow of nanofluid over a stretching sheet and found that increasing values of Brownian motion parameter make greater temperature values on the profile and thicker thermal boundary layer.

Journal ArticleDOI
TL;DR: In this paper, the irreversibility in MHD convection flow of viscous liquid with melting effect over a stretched surface is investigated and the obtained systems are solved for the convergent solutions through ND-solve method.
Abstract: Melting phenomenon of PCMs (phase change materials) is mostly complemented with resilient variation in density of thermal heat. Thermal energy created from numerous sources can be stored in form of latent heat combination throughout melting process of a phase change materials. Thermal energy can be unconfined during the solidification processes. MPCS (microencapsulated phase change slurry) has noteworthy advantages particularly in high energy density and narrow temperature range for various heat energy application. Melting heat transportation has attracted the consideration of scientists and engineers due to its tremendous applications of technological, solidification, casting and industrial processes. A variety of phase change materials with low cost are commercially accessible and do significant work in different circumstances of temperature. Main motivation here is to investigate irreversibility in MHD convection flow of viscous liquid with melting effect over a stretched surface. Slip condition and Lorentz force behaviors are accounted. Energy expression is developed through dissipation, heat radiation and Joule heating. Irreversibility exploration is modeled through second law of thermodynamics. Brownian diffusion and thermophoresis are taken. First order chemical reaction is deliberated. Nonlinear expressions are reduced to ordinary one employing transformation. The obtained systems are solved for the convergent solutions through ND-solve method. Variation of velocity field, entropy rate, temperature, Bejan number and concentration distribution are scrutinized. Velocity filed rises versus higher melting variable. Larger melting parameter decreases the temperature distribution. Concentration and temperature have similar effects against thermophoresis variable. Bejan number and entropy rate have opposite outcome via melting parameter. Higher radiation parameter reduces the entropy rate. For higher radiation both entropy rate and Bejan number have same effect. Main observations are concluded.

Journal ArticleDOI
TL;DR: In this paper, the authors have evaluated the numerical solution of the energy equation with the help of numerical scheme and the effects of physical parameters on temperature and velocity profiles are presented in terms of graphs.

Journal ArticleDOI
TL;DR: In this paper, the study of incompressible steady Williamson fluid flow is conducted in a curvilinear coordinate system, where the flow is bounded below through curves stretchable sheet.
Abstract: The study of incompressible steady Williamson fluid flow is conducted in a curvilinear coordinate system. The flow is bounded below through curves stretchable sheet. Linear thermal radiation effects are considered to observe the heat flow in the system. The model was designed as an application to solar energy in thermal engineering processes. Employing suitable similarity transformations, a set of partial differential equations obtained from the flow situations are converted into a system of non-linear coupled ordinary differential equations. The subsequent equations are elucidated numerically via Runge-Kutta-4 along with the shooting algorithm. The outcomes for different flow properties are displayed and discussed both graphically and numerically. The observations shows that the curvature parameter reduces both velocity and temperature. Radiation parameter boosts the temperature of the fluid but reduces the local Nusselt number. Williamson fluid parameter has a reverse impact on velocity field but it works as a provoking agent for the case of thermal profile. The visual effects in the form of streamlines and isotherms are also presented for different Reynolds number.


Journal ArticleDOI
TL;DR: In this article, the authors studied the stability analysis of heat transfer enhancement occurring due to the influence of significant properties variation of fluids in the presence of thermal radiation with the aid of suspended hybrid nanofluids.
Abstract: The intention of the present work is to study the stability analysis of heat transfer enhancement occurring due to the influence of significant properties variation of fluids in the presence of thermal radiation with an aid of suspended hybrid nanofluids. The mathematical equations are converted into a pair of self-similarity equations by applying appropriate transformation. Runge Kutta Fehlberg 45th order method is applied to solve the reduced similarity equivalences numerically. The flow and energy transfer characteristics are studied for distinct values of important factors to obtain better perception of the problem. According to graphical results, heat transfer enhancement is higher for larger values of radiation parameter (R) and higher values of Prandtl number resulted in heat transfer reduction.

Journal ArticleDOI
TL;DR: In this paper, a numerical study of flow and heat transport of nanoliquid with aggregation kinematics of nanoparticles is carried out using the modified Buongiorno model (MBM).

Journal ArticleDOI
TL;DR: In this paper, the authors examined the heat transfer attributes of magnetohydrodynamic hybrid nanofluid flow in the presence of radiation and found that the Nusselt number increases significantly for lower values of pressure and decreases for higher pressure gradients while keeping the radiation value at zero.

Journal ArticleDOI
TL;DR: In this article, the stagnation point flow of radiative micropolar nanofluid over an off centered rotating disk with applications of motile microorganisms is reported. And the appropriate transformations are utilized to reduce the partial differential equations into dimensionless forms.
Abstract: To improve the heat efficiency base fluids (water, engine oil, glycol), the interaction of nanoparticles (nanotubes, droplets, nanowires, metals and non-metals) into such traditional liquids is the most frequent mechanism and attained the researchers attention, especially in current decade. The nanofluid is a suspension of submerged solid particles in base fluids. The nano-materials convinced the applications in the field of nanotechnology, thermal engineering, industrial and bio-engineering. Following to such motivating applications in mind, current research reports the stagnation point flow of radiative micropolar nanofluid over an off centered rotating disk with applications of motile microorganisms. The novel dynamic of thermal radiation and activation energy are also incorporated. The appropriate transformations are utilized to reduce the partial differential equations into dimensionless forms. A numerical shooting scheme is used to obtain the approximate solution with MATLAB software. The effects of prominent parameter on velocity profile, nanofluid temperature, concentration of nanoparticles and microorganism profile are physically incorporated.

Journal ArticleDOI
TL;DR: In this paper, Prandtl-Eyring hybrid nanofluid (P-EHNF) was chosen as a working fluid in the SWP model for the production of SWP in a parabolic trough surface collector (PTSC).
Abstract: Nowadays, with the advantages of nanotechnology and solar radiation, the research of Solar Water Pump (SWP) production has become a trend. In this article, Prandtl-Eyring hybrid nanofluid (P-EHNF) is chosen as a working fluid in the SWP model for the production of SWP in a parabolic trough surface collector (PTSC) is investigated for the case of numerous viscous dissipation, heat radiations, heat source, and the entropy generation analysis. By using a well-established numerical scheme the group of equations in terms of energy and momentum have been handled that is called the Keller-box method. The velocity, temperature, and shear stress are briefly explained and displayed in tables and figures. Nusselt number and surface drag coefficient are also being taken into reflection for illustrating the numerical results. The first finding is the improvement in SWP production is generated by amplification in thermal radiation and thermal conductivity variables. A single nanofluid and hybrid nanofluid is very crucial to provide us the efficient heat energy sources. Further, the thermal efficiency of MoS2-Cu/EO than Cu-EO is between 3.3 and 4.4% The second finding is the addition of entropy is due to the increasing level of radiative flow, nanoparticles size, and Prandtl-Eyring variable.

Journal ArticleDOI
TL;DR: In this article, the boundary layer two-phase flow of Al2O3-H2O nanoliquid over a vertical flat plate is studied numerically subjected to the aspects of quadratic thermal convection and nonlinear thermal radiation.

Journal ArticleDOI
TL;DR: In this article, the effect of parameters such as Rayleigh number (103-105), Darcy number (0.001-0.1), Hartmann number ( 0,20), radiation parameter (0,1,0.3), angle of magnetic field ( 0 ∘ − 90 ∘ ), and nanoparticle concentration ( 0.01−0.04) on heat transfer performance and entropy generation (Sgen) is studied.

Journal ArticleDOI
TL;DR: It is observed that velocity increases with an increase in both micro-polar parameter and thermal buoyancy parameter, and for the temperature profiles opposite behavior is observed for increment in both unsteadiness parameter and Thermal buoyancy parameters.

Journal ArticleDOI
01 Dec 2021-Pramana
TL;DR: In this paper, the influence of non-uniform heat sink/source and thermal radiation effects on the nanoliquid flow past a stretching sheet is studied in the presence of chemical reaction and magnetic dipole.
Abstract: This study mainly focusses on the rheological properties of the nanofluids by using Koo–Kleinstreuer–Li model. The nanofluids have been proposed as viable replacements to traditional fluids due to their increased heat transport capacity. In this regard, the influence of non-uniform heat sink/source and thermal radiation effects on the nanoliquid flow past a stretching sheet is studied in the presence of chemical reaction and magnetic dipole. The defined flow equations are transformed to ordinary differential equations by using appropriate similarity variables and then they are numerically tackled with Runge Kutta Fehlberg-45 (RKF-45) scheme by adopting shooting process. The graphical outcomes of the velocity, thermal, concentration profiles, drag force, Sherwood number and Nusselt number are found to get an obvious insight into the existing boundary layer flow problem. The outcomes reveal that, the gain in values of radiation parameter improves the thermal profile due to the production of inner heat. The rise in Biot number improves the thermal boundary layer region which automatically boosts up the thermal profile. Further, the escalation in space-dependent internal heat sink/source parameter deteriorates the rate of heat transfer.

Journal ArticleDOI
TL;DR: In this paper, the effects of nonlinear thermal radiation and activation energy on the flow of modified second-grade fluid with the utilization of nanoparticles were investigated by using the theory of Cattaneo-Christov heat flux and generalized Fick's relations.
Abstract: The aim of the current contribution is to exploit the effects of nonlinear thermal radiation and activation energy on the flow of modified second-grade fluid with the utilization of nanoparticles. The induced flow has been considered by linear movement of stretched surface which is considered to be porous. Famous modified second-grade fluid enables one to capture the important rheological features of shear thinning and thickening. Following the modern aspects of heat and mass transportations, we have employed the theories of Cattaneo–Christov heat flux and generalized Fick’s relations. The additional features of thermal radiation are also utilized in the energy equations with nonlinear expressions. Further, the impact of activation energy is also considered in the current continuation which makes the study quite versatile. While operating the suitable variables, the constituted problem has been distracted in a dimensionless form. The solution procedure has been followed with the implementation of the famous shooting technique with desirable accuracy. The involved engineering parameters are explained graphically with interesting physical consequences. It is noted that velocity distribution declined with a stretching ratio constant and combined parameter. An improved nanoparticles temperature distribution is observed with increases in stretching parameter and Brownian motion constant. The study also reports that the presence of activation energy can be more useful to enhance reaction processes. Based on the obtained scientific computations, it is claimed that the reported results can play a useful role in manufacturing processes and improvement in energy and heat resources.

Journal ArticleDOI
TL;DR: In this article, a numerical solution for Darcy-Forchheimer flow of hybrid nanofluid with velocity slip condition is developed, where nonlinear thermal radiation and thermal stratification are also considered.
Abstract: This study develops numerical solution for Darcy-Forchheimer flow of hybrid nanofluid with velocity slip condition. Nonlinear thermal radiation and thermal stratification are also considered. Titanium dioxide and Aluminium oxide nanoparticles are considered for a comparative study. Flow is generated by a rotating disk. Porous space with variable porosity and permeability is characterized through Darcy-Forchheimer expression. Resulting systems of nonlinear equations are solved numerically by shooting technique. Numerical results are obtained to interpret the role of involved variables on physical quantities. It is observed that local heat transfer rate of Titanium dioxide nanofluid is higher when compared with hybrid nanofluid. Our results reveal that thermal radiation parameter augments the local Nusselt number.

Journal ArticleDOI
TL;DR: In this article, a numerical analysis of double diffusive convection in micropolar nanofluids flow governed by peristaltic pumping in an asymmetric microchannel, in the presence of thermal radiation and an external magnetic field is performed.
Abstract: A numerical computation is performed to analyze the double diffusive convection in micropolar nanofluids flow governed by peristaltic pumping in an asymmetric microchannel, in the presence of thermal radiation and an external magnetic field. The highly nonlinear governing equations are diluted by using desirable physical assumptions such as lubrication approximation and low zeta potential. Convective boundary conditions are employed. This enables us to determine numerical estimates of various physical flow variables such as velocity, pressure gradient, spin velocity, temperature of the nanofluid, concentration of solute, and volume fraction of nanoparticles for sundry parameters like micropolar parameter, coupling parameter, solutal Grashof number, thermophoretic diffusion coefficient, Grashof number, thermal radiation parameter and Helmholtz–Smoluchowski velocity with the aid of bvp4c function built-in command of MATLAB 2012b. Influence of each relevant parameter on flow, thermal and species characteristics are computed in this study. Influence of Soret and Dufour parameters are also simulated. This model is applicable to the study of chemical fraternization/separation procedures and various thermal management systems like of heat sinks, thermoelectric coolers, forced air systems and fans, heat pipes, and many more.

Journal ArticleDOI
TL;DR: In this article, the authors examined the flow of Maxwell nanoliquid embedded with SWCNT/MWCNT over a stretching sheet with the consideration of thermal radiation and magnetic dipole, and the reduced ODEs were numerically solved using Runge-Kutta Fehlberg 45 order (RFF 45) method with the aid of shooting scheme.

Journal ArticleDOI
TL;DR: In this article, boundary layer analysis of two-dimensional unsteady hybrid nanofluid flow over a flat/slendering stretching surface is addressed, where the transformed nonlinear ordinary differential equations are resolved using Runge-Kutta-Fehlberg technique.
Abstract: The pivotal aim of this research is to address the boundary layer analysis of two-dimensional unsteady hybrid nanofluid flow over a flat/slendering stretching surface Thermal radiation and magnetohydrodynamic analysis are featured in this work The transformed nonlinear ordinary differential equations are resolved using Runge–Kutta–Fehlberg technique Then, a complete discussion of the influences of the flow regime on several thermofluidic parameters is presented The significant outcome of the current investigation is that the increment in magnetic field and nanoparticle volume fraction parameters declines the skin friction Furthermore, it is shown that when the radiation and the nanoparticle volume fraction are improved, the heat transfer rate triggers considerable evolution The obtained results of this model closely match with those available in the literature as a limiting situation