Influence Of Radiation Absorption Research Articles

Exact Analysis of MHD Casson Fluid Flow Past an Exponentially Accelerated Vertical Plate in a Porous Medium with Radiation Absorption, Heat Generation, and Diffusion-Thermo Effects with Thermal and Solutal Ramped Conditions

The current investigation aims at to examine the effect of radiation absorption, heat generation and Dufour number on MHD Casson fluid flow past an exponentially accelerated vertical plate in a porous medium with chemical reaction. The governing equations for momentum, energy and concentration are solved by implementing the Laplace transformation method. Skin friction, rate of heat transfer and rate of mass transfer expressions are also extracted and depicted in tabular form. Investigation simulates that Casson parameter diminished the fluid velocity, whereas energy flux due to a mass concentration gradient improves the temperature field of the flow problem. In addition to this, temperature field is observed to be developed under the influence of radiation absorption and heat generation. Furthermore, the effects of different non-dimensional parameters on velocity field, temperature fluid and species concentration are exhibited graphically.

Exploration of Heat and Mass Transfer in the Convective Slip Flow of Non-Newtonian Casson Fluid

The present aim is concerned with heat and mass transfer of an unsteady convective slip flow of Casson fluid flow through a permeable vertical plate with heat source. The influence of radiation absorption and chemical reaction is also taken into consideration. Time depending governing equations are solved by implicit finite difference method using MATLAB. Results for various fluid flow parameter characteristics such as Casson fluid parameter, velocity slip parameter, Biot number, convection diffusion parameter, porosity parameter, Grashof number, heat source and radiative absorption parameter are presented through graphs and tables delineating the effect of various parameters characterizing the flow.

Effects of radiation absorption on spherical flame propagation and radiation-induced uncertainty in laminar flame speed measurement

Outwardly propagating spherical flames are popularly used to measure the laminar flame speed, especially for high pressure conditions. Since radiation always exists in spherical flame experiments, the accuracy of laminar flame speed measurement is inherently affected by radiation. In this study, the radiation-induced uncertainty in laminar flame speed measurement was investigated numerically. We focused on CO2 diluted mixtures in which the radiation absorption effects are important. The outwardly propagating spherical flames of different CO2 diluted mixtures at a broad range of pressure up to 25atm were simulated. Different fuels (hydrogen, methane, dimethyl ether and iso-octane) with different amounts of CO2 dilution were considered and detailed chemistry was included in simulation. Two radiation models were used: one is the optically thin model considering only radiation emission and the other is the statistical narrow band model considering both radiation emission and absorption. The effects of radiation absorption on spherical flame propagation and radiation-induced uncertainty in laminar flame speed measurement were quantified through comparison among results predicted by these two radiation models. It was found that for CO2 diluted mixtures, radiation absorption has great impact on spherical flame propagation: it greatly reduces the radiation-induced thermal and flow effects. The influence of radiation absorption was show to be stronger at higher pressure. When only radiation emission is considered and radiation absorption is neglected, the radiation-induced uncertainty in laminar flame speed measurement is substantially over-predicted for CO2 diluted mixtures. When radiation absorption is included, the radiation-induced uncertainty in laminar flame speed measurement is nearly negligible (within 2.5%) for all the CO2 diluted mixtures considered in this study.

Droplet burning rate enhancement of ethanol with the addition of graphite nanoparticles: Influence of radiation absorption

A droplet stream flame was used to measure the burning rate of ethanol droplets with the addition of graphite nanoparticles. Two particle sizes, 50 nm and 100 nm, were used for this study. Results indicate that as particle concentration is increased, the burning rate of the resulting nanofluid droplet also increases. The maximum enhancement of 62% was observed with the addition of 3 wt.% 50 nm graphite nanoparticles. To understand the burning-rate-enhancement phenomenon, a model was developed to estimate the radiation absorptivity by the hybrid droplet from the stream flame. The computational models determine the ratio of radiation retention by the entire depth of the fluid (volumetric absorptivity) using optical properties of both the particles and the fluid along with the penetration of radiation within the nanofluid using the well-known Monte Carlo algorithm that incorporates the aforementioned calculated optical properties of the nanofluid. Results indicate that radiation absorption by the hybrid droplet does play a role in the enhancement of burning rate. More importantly, the absorption is not uniform within the hybrid droplet. It is localized in the region near the droplet surface, promoting boiling at the droplet surface. This mechanism is believed to be responsible for the observed increased burning rate.

MHD Convective Heat and Mass Transfer Flow of a Newtonian Fluid Past a Vertical Porous Plate with Chemical Reaction, Radiation Absorption and Thermal Diffusion

In this manuscript, we have investigated the influence of radiation absorption on an unsteady MHD convective heat and mass transfer flow of a Newtonian fluid past a vertical porous plate in the presence of thermal radiation and chemical reaction. The non dimensional governing equations have been solved by using a multiple perturbation method, subject to the corresponding boundary conditions. The effects of various physical parameters such as velocity, temperature and concentration are studied through graphs. The expressions for local skin friction, Nusselt number and Sherwood number are derived and discussed with the help of a table. It is noticed that velocity increases when an increase in modified Grashof number Gm, radiation absorption parameter χ, Sorret number S0, time t whereas it decreases when an increase in Schmidt number Sc, chemical reaction parameter Kr and radiation parameter F. Temperature increases with an increase in radiation parameter χ and Sorret number S0whereas it decreases with an increase in chemical reaction parameter Kr, F and ϕ. Concentration is observed to be decreased when chemical reaction parameter Kr and Schmidt number Sc increase whereas it increases with an increase in Sorret number S0. Skin friction increases with an increase modified Grashof number Gm, radiation parameter χ and Sorret number S0whereas it has reverse effect in the case of Schmidt number Sc, chemical reaction parameter Kr. Nusselt number increases with an increase in Sc, S0, χ whereas it has reverse effect in the case of Kr. Sherwood number gets decreased when Sc, χ and Kr both are increased whereas it has shown revere effect in the case of S0.

An enhanced multi-component vaporization model for high temperature and pressure conditions

An enhanced multi-component vaporization model was proposed to simulate the vaporization process of fuel droplets under high ambient temperatures and pressures. In the present model, the heat flux of conduction, enthalpy diffusion, and radiation absorption in the gas phase are calculated by Fourier’s law, the multi-component diffusion sub-model, and a simplified analytical solution of the radiative heating, respectively. A surface temperature sub-model was employed to evaluate the average temperature within the droplet and the surface temperature of the droplet. For calculation of vapor–liquid phase equilibrium, a real and an ideal gas approach was used for high and low ambient temperatures and pressures, respectively. Moreover, the dependence of gas physical properties on temperature and pressure is also considered. Based on the enhanced vaporization model, extensive verifications for different multi-component droplets were conducted, and the results indicate that satisfactory agreements between the predictions and measurements can be achieved. Finally, the multi-component vaporization model was applied to investigate the vaporization characteristics of practical fuel droplets with a wide range of diameters at high ambient temperatures and pressures, and the effects of radiation absorption and real gas behavior on the vaporization process were understood. It is found that the influence of radiation absorption on the vaporization behavior strongly depends on the droplet diameter and the ambient temperature, and the effect of ambient pressure on the average vaporization rate is determined by the ambient temperature. Considering the compromise between computational accuracy and efficiency, a pressure criterion (P′) was introduced for the choice of ideal or real gas approaches, and a diameter criterion (D′) was also defined to decide whether to consider the radiation absorption in the vaporization model.

Influence of radiation absorption by microparticles on the flame velocity and combustion regimes

Thermal radiation of the hot combustion products usually does not influence noticeably the flame propagating through gaseous mixture. the situation is changed drastically in the presence even small concentration of particles, which absorb radiation, transfer the heat to the surrounding unburned gaseous mixture by means of heat conduction, so that the gas phase temperature in front of the advancing flame lags that of the particles. It is shown that radiative preheating of unreacted mixture ahead of the flame results in a modest increase of the advancing flame velocity for a highly reactive gaseous fuel, or to considerable increase of the flame velocity in the case of a slow reactive mixture. The effects of radiation preheating as stronger as smaller the normal flame velocity. The radiation heat transfer can become a dominant mechanism compared with molecular heat conduction, determining the structure and the speed of combustion wave in the case of a small enough velocity of the advancing flame. It is shown that in the case of non-uniform distribution of the particles, such that time of the radiation heating is longer so that the maximum temperature in the region of denser particles cloud ahead of the advancing flame is sufficient for ignition, the thermal radiation may trigger additional independent source of ignition. Depending on the steepness of the temperature gradient formed in the unburned mixture, either deflagration or detonation can be initiated via the Zeldovich's gradient mechanism. Ignition of different combustion regimes, depending on the radiation absorption length, is illustrated for the particle-laden hydrogen-oxygen flame.

The influence of radiation absorption on unsteady free convection and mass transfer flow of a polar fluid in the presence of a uniform magnetic field

The influence of radiation absorption on unsteady free convection and mass transfer flow of a polar fluid in the presence of a uniform magnetic field

The influence of radiation absorption on solar pond stability

This paper presents a study of the gravitational stability of a salty layer of a fluid subject to an adverse temperature gradient as a result of heat absorption. This is intended to model solar ponds where an artificial gradient of salt concentration in water is used to prevent convective motions induced by the absorption of solar radiation. The stability of the Boussinesq approximation of the Navier-Stokes equations is analysed for perturbations of a certain kind imposed on the stationary solution. The marginal states for the onset of convection are obtained using a Galerkin method based on a weak formulation of the governing equations. The analysis considers solar energy absorption in the layer and assumes prescribed heat flux values as boundary conditions for the temperature equation. Results are compared with those obtained earlier by different authors for a layer of fluid, heated from below, with linear profiles of both salt concentration and temperature.

Radiation absorption effects on the transient free-convection currents of a laminar boundary-layer

The influence of radiation absorption on the free-convection currents on a vertical porous flat plate has been considered. A steady transverse magnetic field has been assumed, while the absorption is the result of the presence of a strong radiation-absorbing second material, in a small concentration within the main fluid. The analytical solution is in terms of the very small Eckert number, which expresses the viscous dissipation term. The solution shows small influence on the general velocity and temperature profile, but a strong one in the skin friction and the heat flux.

Free convection and mass transfer in the hydromagnetic oscillatory flow past an infinite vertical porous plate with internal heat generation due to radiation absorption

the influence of radiation absorption on the flow-field of an unsteady laminar boundary layer due to free convection is considered. The flow is that of an incompressible viscous dissipative and electrically conducting fluid past an infinite vertical porous plate, when the flow is subjected to the action of a transverse magnetic field and the mainstream is oscillating around a mean value and an oscillating suction. The radiation is absorbed by a second material in a small concentration within the fluid and the absorption rate is proportional to the local concentration. The solution of the problem is obtained in the form of power series of Eckert numberE, which is very small for incompressible fluids, analytical expression for the velocity, temperature and the induced magnetic field are given for both the steady and the unsteady flows. The solution is also given in a number of figures that present the combined influence of the absorption withE,G r , and the frequency of oscillation. In addition the influence of the absorption on the skin friction the heat flux is given. The results indicate the importance of the absorption which can be significant under certain conditions.