Artykuły w czasopismach: „Radiative Heat Flux Rate”

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Cheung, C. S., C. W. Leung i T. P. Leung. "Modelling Spatial Radiative Heat Flux Distribution in a Direct Injection Diesel Engine". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 208, nr 4 (listopad 1994): 275–83. http://dx.doi.org/10.1243/pime_proc_1994_208_048_02.

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In this paper, the spatial distribution of radiative heat flux from a luminous flame to various positions on the cylinder head of a direct injection diesel engine is modelled and the results compared with some published experimental investigations. The model is primarily based on measured pressure data, which are converted into fuel-burned rate data through a single-zone heat-release rate analysis. Coupled with appropriate soot formation and oxidation models, the fuel-burned rate data are converted into the soot contents in the cylinder. By separating the combustion chamber into a burned zone and an unburned zone, the radiation temperature, the absorption coefficient and the spatial distribution of radiative heat flux to the cylinder walls are calculated.

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Zhang, Chong, Zhongnong Zhang i Chun Lou. "Thermodynamic Irreversibility Analysis of Thermal Radiation in Coal-Fired Furnace: Effect of Coal Ash Deposits". Materials 16, nr 2 (13.01.2023): 799. http://dx.doi.org/10.3390/ma16020799.

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In this paper, a three-dimensional (3-D) high-temperature furnace filled with a gas-solid medium was investigated, and the radiative transfer equation and the radiative entropy transfer equation in the chamber were applied in order to analyze the effect of coal deposits on thermal radiation. The heat flux on the walls of the furnace and the entropy generation rate were determined due to the irreversibility of the radiative heat transfer process in the furnace. Furthermore, the effect of ash deposits on the wall surface on the irreversibility of the radiation heat transfer process was investigated. The numerical results show that when burning bituminous and sub-bituminous coal, ash deposits in the furnace led to a 48.2% and 63.2% decrease in wall radiative heat flux and a 9.1% and 12.4% decrease in the radiative entropy rate, respectively. The ash deposits also led to an increase in the entropy generation number and a decrease in the thermodynamic efficiency of the radiative heat transfer process in the furnace.

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Budaev, Bair V., i David B. Bogy. "The role of EM wave polarization on radiative heat transfer across a nanoscale gap". Journal of Applied Physics 132, nr 5 (7.08.2022): 054903. http://dx.doi.org/10.1063/5.0094382.

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This work presents a novel study of radiative heat transfer between closely separated plates based on an extension of Planck’s spectrum of thermal radiations to systems with a steady heat flux. This extension together with electromagnetic wave theory is chosen specifically to avoid the commonly used so-called fluctuation dissipation theory, which is also limited to equilibrium systems. The spectrum of thermal radiation with a heat flux is described by the introduction of an analog of a chemical potential, which creates a bias toward the direction of heat transfer. This is the first comprehensive study of radiative heat transfer based on the generalization of Planck’s spectrum for systems with a heat flux, which eliminates contradictions arising when a heat flux is described in terms of the laws limited to equilibrium systems. The total heat flux is split into fluxes carried by waves with different frequencies, directions of propagation, and polarizations. This simplifies the analysis because due to the stochastic independence, the energy fluxes of such waves are additive, and this also reveals that the heat carrying capacity of radiation with the parallel polarization is significantly higher than that of the perpendicularly polarized radiation. This suggests that the rate of radiative heat transfer may be noticeably increased by the control of the polarization of thermal radiation.

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Liu, L. H., i S. X. Chu. "On the Entropy Generation Formula of Radiation Heat Transfer Processes". Journal of Heat Transfer 128, nr 5 (21.10.2005): 504–6. http://dx.doi.org/10.1115/1.2190695.

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Because thermal radiation is a long-range phenomenon, the local radiative heat flux is dependent on the temperature distribution of the entire enclosure under consideration and is not determined by the local temperature gradient. In the community of heat transfer, traditionally, the conduction-type formula of entropy generation rate is used to calculate the entropy generation rate of radiation heat transfer. In the present study, three counterexamples are considered. The discrete ordinates method is employed to solve the radiative transfer equation and then solve the radiative entropy generation rate. The results show that the traditional formulas of entropy generation rate for heat transfer generally cannot be used to calculate the local entropy generation rate of radiation heat transfer. Only in optically extremely thick situations, the traditional formula of entropy generation rate for heat transfer can be approximately used to calculate the local entropy generation rate of radiation heat transfer.

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Liu, Cheng, Evgeni Fedorovich, Jianping Huang, Xiao-Ming Hu, Yongwei Wang i Xuhui Lee. "Impact of Aerosol Shortwave Radiative Heating on Entrainment in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study". Journal of the Atmospheric Sciences 76, nr 3 (1.03.2019): 785–99. http://dx.doi.org/10.1175/jas-d-18-0107.1.

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AbstractEntrainment is critical to the development of the atmospheric convective boundary layer (CBL), but little is known about how entrainment is impacted by the aerosol radiative effect. An aerosol radiation transfer model is used in conjunction with large-eddy simulation (LES) to quantify the impact of aerosol shortwave radiative heating on entrainment and thermodynamics of an idealized dry CBL under aerosol-loading conditions. An entrainment equation is derived within the framework of a zero-order model (ZOM) with the aerosol radiative heating effect included; the equation is then examined against the LES outputs for varying aerosol optical depths (AODs) and free-atmosphere stratification scenarios. The results show that the heat flux profiles become more nonlinear in shape as compared to the case of the clean (no aerosol pollution) CBL, with the degree of nonlinearity being highly dependent on the AOD of the layer for the given type of radiation-absorbing aerosols. As AOD increases, less solar radiation reaches the surface and thus the surface heat flux becomes smaller, and both actual (LES) and ZOM-derived entrainment flux ratios decrease. This trend is opposite to the clean CBL where the LES-predicted flux ratios show an increasing trend with diminishing surface heat flux, while the ZOM-calculated flux ratio remains constant. The modified dimensionless entrainment rate closely follows the −1 power law with a modified Richardson number. The study suggests that including the aerosol radiative effect may improve numerical air quality predictions for heavy-air-pollution events.

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Hayat, T., M. Waleed Ahmed Khan, M. Ijaz Khan i A. Alsaedi. "Nonlinear radiative heat flux and heat source/sink on entropy generation minimization rate". Physica B: Condensed Matter 538 (czerwiec 2018): 95–103. http://dx.doi.org/10.1016/j.physb.2018.01.054.

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GODBOLE, RV, i RR KELKAR. "Net Terrestrial Radiative Heat Fluxes over India during Monsoon". MAUSAM 20, nr 1 (30.04.2022): 1–10. http://dx.doi.org/10.54302/mausam.v20i1.5421.

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Infrared radiative heat flux and instantaneous rate of temperature change have been computed for Indian, subcontinent for monsoon season by making use of the numerical method developed for the purpose. The effects of water Vapour alone have been considered. It is found that the radiative beat loss near the surface is minimum over the Western Ghats. Over northeast and northwest India, the radiative heat loss is relatively high. Also, the radiative cooling integrated from the surface upto 300 mb indicates a large cooling over northeast and northwest India (>loC per day) and relatively small cooling over the southern Peninsula ( <0.25°C per day). Analysis of the day to day values of net flux and temperature suggest no cause-and-effect relationship. However, a good correspondence has been noticed between net flux, temperature and total moisture content as far as surface level is concerned. The day to day values of net flux at higher levels follow very closely to those at the surface.

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Palesskiy, F. S. "Numerical Study of Combustion Regimes and Heat Radiation of Cylindrical Porous Burner". Key Engineering Materials 685 (luty 2016): 94–98. http://dx.doi.org/10.4028/www.scientific.net/kem.685.94.

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Temperature and radiative characteristics of different regimes of premixed gas combustion in porous cylindrical burner are investigated numerically. Two-temperature thermal diffusion model with radiative heat transfer and external radiative heat losses described in the framework of Eddington model is applied. It is found that two different combustion regimes can be realized under the same mixture equivalence ratio and flow rate depends on ignition conditions. It is shown that total radiative heat flux from the external surface of the burner and burner’s radiative efficiency strongly depend on the combustion regime.

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Narahari, Marneni, i Noorhana Yahya. "Effects of Time Dependent Temperature and Thermal Radiation on Free Convection Flow in Unsteady Couette Motion". Applied Mechanics and Materials 249-250 (grudzień 2012): 15–21. http://dx.doi.org/10.4028/www.scientific.net/amm.249-250.15.

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The effect of thermal radiation on free convection flow in unsteady Couette motion between vertical parallel plates has been investigated subject to a time dependent temperature boundary condition at the moving plate. Rosseland diffusion approximation is used to describe the radiative heat flux in the energy equation. Analytical solutions of the dimensionless governing equations are derived using the Laplace transform technique. The velocity and temperature profiles are shown on graphs, the variation of skin-friction, Nusselt number, volume flow rate and vertical heat flux are presented in tabular form. The effects of system parameters such as Grashof number, radiation parameter and time on the flow fields have been discussed in detail.

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Dupuy, J. L., i J. Maréchal. "Slope effect on laboratory fire spread: contribution of radiation and convection to fuel bed preheating". International Journal of Wildland Fire 20, nr 2 (2011): 289. http://dx.doi.org/10.1071/wf09076.

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Two series of 16 and 18 laboratory fire experiments were conducted to explore the respective roles of radiation and convection heat transfer in slope effect on fire spread. The first series attempts to measure fuel temperature and gas temperature simultaneously and at the same location using an infrared camera and thermocouples respectively. The second series measures the incident radiant heat flux as would be received by a small fuel bed volume ahead of the fire line. These measurements are used to compute a fuel bed heat balance for each slope angle (0°, 10°, 20° and 30°). Overall, radiative heating is found to be the heat transfer mechanism that dominates in the slope effect between 0° and 20°, but close to the fire line (<10 cm), the flux due to convective heating is also significant, reaching one-third of the net heat flux at a 20° slope angle. When the slope angle increases from 20° to 30°, the rate of spread rises by a factor of 2.5 due to a marked increase in convective heating, while radiative heating no longer increases. Far from the fire line, cooling by convection is found to be substantial except at the 30° slope angle.

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Zhai, Chunjie, Fei Peng, Xiaodong Zhou i Lizhong Yang. "Pyrolysis and ignition delay time of poly(methyl methacrylate) exposed to ramped heat flux". Journal of Fire Sciences 36, nr 3 (14.02.2018): 147–63. http://dx.doi.org/10.1177/0734904118757742.

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Usually, the constant heat flux is used in the previous studies of polymeric pyrolysis. However, the ramped heat flux may be more realistic under a fire condition. For further understandings of polymer pyrolysis in the early stage of fire, the influences of ramped heat flux on pyrolysis of poly(methyl methacrylate) were experimentally and theoretically investigated. Linearly and quadratically ramped heat fluxes were controlled by the output power of a radiative heater. Surface temperature, mass loss rate, and ignition time were experimentally obtained to explore the thermochemical stability of poly(methyl methacrylate) under ramped heat fluxes. A one-dimensional model was used to predict the pyrolysis process, where kinetic parameters were evaluated by a genetic algorithm. Finally, ignition criteria including critical surface temperature and critical mass loss rate were revisited. We observed that the two ignition criteria give similar ignition time when the heat flux increases fast.

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Bianchi, Daniele, Giuseppe Leccese, Francesco Nasuti, Marcello Onofri i Carmine Carmicino. "Modeling of High Density Polyethylene Regression Rate in the Simulation of Hybrid Rocket Flowfields". Aerospace 6, nr 8 (9.08.2019): 88. http://dx.doi.org/10.3390/aerospace6080088.

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Numerical analysis of hybrid rocket internal ballistics is carried out with a Reynolds-averaged Navier–Stokes solver integrated with a customized gas–surface interaction wall boundary condition and coupled with a radiation code based on the discrete transfer method. The fuel grain wall boundary condition is based on species, mass, and energy conservation equations coupled with thermal radiation exchange and finite-rate kinetics for fuel pyrolysis modeling. Fuel pyrolysis is governed by the convective and radiative heat flux reaching the surface and by the energy required for the propellant grain to heat up and pyrolyze. Attention is focused here on a set of static firings performed with a lab-scale GOX/HDPE motor working at relatively low oxidizer mass fluxes. A sensitivity analysis was carried out on the literature pyrolysis models for HDPE, to evaluate the possible role of the uncertainty of such models on the actual prediction of the regression rate. A reasonable agreement between the measured and computed averaged regression rate and chamber pressure was obtained, with a noticeable improvement with respect to solutions without including radiative energy exchange.

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Sunahara, Hiroyuki, Takahiro Ishihara, Ken Matsuyama, Shin’ichi Sugahara i Masahiro Morita. "Relation between Heat Release Rate and Radiative Heat Flux of Wooden Crib Burning during Water Discharge". Fire Science and Technology 30, nr 1 (2011): 1–25. http://dx.doi.org/10.3210/fst.30.1.

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An, Chen, Alice Cunha da Silva i Jian Su. "Improved Lumped Models for Transient Combined Convective and Radiative Cooling of Multilayer Spherical Media". Mathematical Problems in Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/8303021.

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In this work, we studied the transient combined convection and radiation of multilayer spherical media with volumetric heat generation, extending the previous work on the particular case of a spherical body subjected to radiative cooling. The proposed lumped models were obtained through two-point Hermite approximations for the average temperature and heat flux in each layer. For the average temperature, the plain trapezoidal rule (H0,0 approximation) was employed in all layers, except for the innermost layer, where the second-order two-side corrected trapezoidal rule (H2,1 approximation) was utilized. For the heat flux, the plain trapezoidal rule (H0,0 approximation) was employed for all the layers. The transient heat conduction in a TRISO-coated fuel particle being composed of five layers (namely, fuel kernel, buffer of porous carbon, inner pyrocarbon, silicon carbide, and outer pyrocarbon) was analyzed using the proposed lumped models, the results of which were verified by comparison with the finite difference solution of the original distributed parameter model. Parametric studies were conducted to examine the effects of the dimensionless heat generation rate, the radiation-conduction parameter, and the Biot number on the temporal variations of the average temperatures.

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Osman, Abdel-Nasser A., S. M. Abo-Dahab i R. A. Mohamed. "Analytical Solution of Thermal Radiation and Chemical Reaction Effects on Unsteady MHD Convection through Porous Media with Heat Source/Sink". Mathematical Problems in Engineering 2011 (2011): 1–18. http://dx.doi.org/10.1155/2011/205181.

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This paper analytically studies the thermal radiation and chemical reaction effect on unsteady MHD convection through a porous medium bounded by an infinite vertical plate. The fluid considered here is a gray, absorbing-emitting but nonscattering medium, and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The dimensionless governing equations are solved using Laplace transform technique. The resulting velocity, temperature and concentration profiles as well as the skin-friction, rate of heat, and mass transfer are shown graphically for different values of physical parameters involved.

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Crnomarkovic, Nenad, Miroslav Sijercic, Srdjan Belosevic, Dragan Tucakovic i Titoslav Zivanovic. "Influence of application of Hottel’s zonal model and six-flux model of thermal radiation on numerical simulations results of pulverized coal fired furnace". Thermal Science 16, nr 1 (2012): 271–82. http://dx.doi.org/10.2298/tsci110627126c.

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Difference of results of numerical simulation of pulverized coal fired furnace when mathematical models contain various radiation models has been described in paper. Two sets of numerical simulations of pulverized coal fired furnace of 210 MWe power boiler have been performed. One numerical simulation has contained Hottel?s zonal model, whereas the other numerical simulation has contained six-flux model. Other details of numerical simulations have been identical. The influence of radiation models has been examined through comparison of selected variables (gas-phase temperature, oxygen concentration, and absorbed radiative heat rate of surface zones of rear and right furnace walls), selected global parameters of furnace operation (total absorbed heat rate by all furnace walls and furnace exit gas-phase temperature). Computation time has been compared as well. Spatially distributed variables have been compared through maximal local differences and mean differences. Maximal local difference of gas-phase temperature has been 8.44%. Maximal local difference of absorbed radiative heat rate of the surface zones has been almost 80.0%. Difference of global parameters of furnace operation has been expressed in percents of value obtained by mathematical model containing Hottel?s zonal model and has not been bigger than 7.0%. Computation time for calculation of 1000 iterations has been approximately the same. Comparison with other radiation models is necessary for assessment of differences.

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Singh, Khilap, i Manoj Kumar. "Influence of Chemical Reaction on Heat and Mass Transfer Flow of a Micropolar Fluid over a Permeable Channel with Radiation and Heat Generation". Journal of Thermodynamics 2016 (7.12.2016): 1–10. http://dx.doi.org/10.1155/2016/8307980.

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The effects of chemical reaction on heat and mass transfer flow of a micropolar fluid in a permeable channel with heat generation and thermal radiation is studied. The Rosseland approximations are used to describe the radiative heat flux in the energy equation. The model contains nonlinear coupled partial differential equations which have been transformed into ordinary differential equation by using the similarity variables. The relevant nonlinear equations have been solved by Runge-Kutta-Fehlberg fourth fifth-order method with shooting technique. The physical significance of interesting parameters on the flow and heat transfer characteristics as well as the local skin friction coefficient, wall couple stress, and the heat transfer rate are thoroughly examined.

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Chu, Yu-Ming, M. Ijaz Khan, M. Israr Ur Rehman, Seifedine Kadry i M. K. Nayak. "Flow and thermal management of MHD Cross nanofluids over a thin needle with auto catalysis chemical reactions". International Journal of Modern Physics B 34, nr 30 (28.10.2020): 2050287. http://dx.doi.org/10.1142/s0217979220502872.

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This research work concerns the investigation of electrically conducting stagnation point flow, heat and mass transport of magneto-Cross nanofluids towards a moving and stretched surface of thin needle. The Buongiorno nanofluid model is incorporated to model the governing expressions. The flow is conducted electrically and generated through stretching impact. Internal diffusion of particle, homogenous–heterogeneous reactions and radiative heat flux effects are utilized to examine the behavior of heat and mass transport on the surface of thin needle. Suitable similarity variables and boundary layer approximations are used to turn into dimensionless one. After that, numerical outcomes are computed by a Shooting method (bvp4c) package in MATLAB. The incentives of sundry relevant parameters on the flow field, skin friction coefficient, heat transfer rate, temperature field and concentration distribution are portrayed via graphical tactic and have been elucidated in detail. The outcomes indicate that the temperature distribution is more versus rising values of radiative heat flux, magnetic parameter and Eckert number.

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Bilal, M., M. Sagheer i S. Hussain. "On MHD 3D upper convected Maxwell fluid flow with thermophoretic effect using nonlinear radiative heat flux". Canadian Journal of Physics 96, nr 1 (styczeń 2018): 1–10. http://dx.doi.org/10.1139/cjp-2017-0250.

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In this study, three-dimensional upper-convected Maxwell fluid flow over a stretching surface in the presence of viscous dissipation and Joule heating is considered to examine the effects of thermophoresis and magnetohydrodynamics (MHD) on heat and mass transfer. Energy equation is formulated under the assumption of nonlinear radiative heat flux. Ordinary differential equations are deduced from the governing partial differential equations with the help of similarity transformation. These equations are then solved numerically using the shooting method, through the fourth-order Runge–Kutta integration procedure. To strengthen the reliability of our results, the MATLAB built-in function bvp4c is also used. Effects of some prominent physical parameters, such as Eckert number, Prandtl number, thermophoretic parameter, and magnetic parameter on the velocity, temperature, and concentration profiles are discussed graphically and numerically. It is found that concentration profile decreases for the higher values of thermophoretic parameter and Schmidt number. The heat flux rate is observed to enhance for increasing values of thermal radiation and Prandtl number.

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Istomin, Vladimir A., Elena V. Kustova i Kirill A. Prutko. "Heat and radiative fluxes in strongly nonequilibrium flows behind shock waves". Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy 9, nr 4 (2022): 705–19. http://dx.doi.org/10.21638/spbu01.2022.412.

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State-to-state and two-temperature theoretical models for high-temperature strongly nonequilibrium reacting and radiating air flows are developed in the framework of the generalized Chapman - Enskog method. In the theoretical approach, the sets of governing equations for coupled fluid dynamics, chemical kinetics, internal energy transitions and radiation are derived; the algorithms for the calculation of state-resolved transport coefficients are developed and implemented. The proposed models are applied for 1-D simulations of shock waves in air under high-temperature conditions observed in flight experiments. Nonequilibrium mixture composition, temperatures and pressure profiles are obtained and compared for various models of chemical reaction rate coefficients. Flow variables strongly depend on both the kinetic-theory approach and chemical reaction model; species molar fractions and temperature show significantly different behaviour for the state-to-state and two-temperature simulations. Transport properties and radiative fluxes are calculated as functions of the distance from the shock front. It is found that diffusion provides a major contribution to the total energy flux whereas the role of heat conduction is weak due to the compensation effects. It is shown that under considered conditions, two-temperature models are not applicable for correct predictions of radiative heating.

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Mackolil, Joby, i Basavarajappa Mahanthesh. "Exact and statistical computations of radiated flow of nano and Casson fluids under heat and mass flux conditions". Journal of Computational Design and Engineering 6, nr 4 (21.03.2019): 593–605. http://dx.doi.org/10.1016/j.jcde.2019.03.003.

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Abstract The statistical and exact analysis of the unsteady radiative flow of Nano and Casson fluids past a vertical plate with Dufour effect is carried out. The heat transport phenomenon is studied under uniform heat flux (UHF) and uniform wall temperature (UWT) conditions. The exact solution to the problem is found using the Laplace transform method (LTM). The effects of various parameters on velocity, temperature and concentration profiles are examined via graphs. The heat transfer rate and skin friction are analyzed through statistical tools like probable error and regression. The Dufour effect enhances the velocity and temperature profiles. It is also observed that the velocity profile is slightly greater in the case of UWT than the UHF case for both nanofluid and Casson fluid. From the regression analysis, it is established that the Dufour number and nanoparticle volume fraction have a negative impact whereas the radiative heat parameter has a positive impact on the rate of heat transfer. Highlights The statistical analysis of the unsteady radiated flow on a vertical plate with Dufour effect is performed. The uniform heat flux (UHF) and uniform wall temperature (UWT) conditions are accounted. The Nusselt number and friction factor are analysed through statistical tools. The velocity profile is greater for UWT case than the UHF case.

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Uddin, M. J., W. A. Khan, O. Anwar Bég i A. I. M. Ismail. "Non-Similar Solution of G-jitter Induced Unsteady Magnetohydrodynamic Radiative Slip Flow of Nanofluid". Applied Sciences 10, nr 4 (20.02.2020): 1420. http://dx.doi.org/10.3390/app10041420.

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We present a mathematical model and numerical simulation of the unsteady 2-D g-jitter-free and forced the convective flow of water-based nanofluid from a flat plate, considering both the velocity slip and thermal slip conditions imposed on the wall of the plate. The Darcian model is used, and both cases of a calm and moving free stream are considered. In place of the extensively used linearly varying radiative heat flux, the nonlinearly varying heat flux calculation is applied to produce practically useful results. Further, we incorporate the “zero mass flux boundary condition” which is believed to be more realistic than the earlier extensively used “actively” controlled model. The parameter influences the non-dimensional velocity, temperature, nanoparticle volume fraction, skin friction and heat transfer rates are visualized graphically and discussed in detail. Special cases of the results are benchmarked with those existing in the literature, and a good arrangement is obtained. It is found that the rate of heat transfer is lower for the calm free stream rather than the moving free stream.

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Bitz, C. M., M. M. Holland, E. C. Hunke i R. E. Moritz. "Maintenance of the Sea-Ice Edge". Journal of Climate 18, nr 15 (1.08.2005): 2903–21. http://dx.doi.org/10.1175/jcli3428.1.

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Abstract A coupled global climate model is used to evaluate processes that determine the equilibrium location of the sea-ice edge and its climatological annual cycle. The extent to which the wintertime ice edge departs from a symmetric ring around either pole depends primarily on coastlines, ice motion, and the melt rate at the ice–ocean interface. At any location the principal drivers of the oceanic heat flux that melts sea ice are absorbed solar radiation and the convergence of heat transported by ocean currents. The distance between the ice edge and the pole and the magnitude of the ocean heat flux convergence at the ice edge are inversely related. The chief exception to this rule is in the East Greenland Current, where the ocean heat flux convergence just east of the ice edge is relatively high but ice survives due to its swift southward motion and the protection of the cold southward-flowing surface water. In regions where the ice edge extends relatively far equatorward, absorbed solar radiation is the largest component of the ocean energy budget, and the large seasonal range of insolation causes the ice edge to traverse a large distance. In contrast, at relatively high latitudes, the ocean heat flux convergence is the largest component and it has a relatively small annual range, so the ice edge traverses a much smaller distance there. When the model is subject to increased CO2 forcing up to twice preindustrial levels, the ocean heat flux convergence weakens near the ice edge in most places. This weakening reduces the heat flux from the ocean to the base of the ice and tends to offset the effects of increased radiative forcing at the ice surface, so the ice edge retreats less than it would otherwise.

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Hussain, Azad, Aysha Rehman, Sohail Nadeem, M. Riaz Khan i Alibek Issakhov. "A Computational Model for the Radiated Kinetic Molecular Postulate of Fluid-Originated Nanomaterial Liquid Flow in the Induced Magnetic Flux Regime". Mathematical Problems in Engineering 2021 (8.06.2021): 1–17. http://dx.doi.org/10.1155/2021/6690366.

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The performance of mass transfer rate, friction drag, and heat transfer rate is illustrated in the boundary layer flow region via induced magnetic flux. In this recent analysis, the Buongiorno model is introduced to inspect the induced magnetic flux and radiative and convective kinetic molecular theory of liquid-initiated nanoliquid flow near the stagnant point. The energy equation is modified by radiation efficacy using the application of the Rosseland approximation. Through similarity variables, the available formulated partial differential equations are promoted into the nondimensional structure. The variation of the induced magnetic field near the wall goes up, and very far away, it decays when the size of the radiation characteristic ascends. The velocity amplitude expands by enlargement in the amount of the magnetic parameter, mixed convection, thermophoresis parameter, and fluid characteristic. The nanoparticle concentration reduces if the reciprocal of the magnetic Prandtl number expands. The temperature spectrum declines by enhancing the amount of the magnetic parameter. Drag friction decreases by the increment in the values of radiation and thermophoresis parameters. Heat transport rate increases when there is an increase in the values of Brownian and magnetic parameters. Mass transfer rate increases when there is incline in the values of the magnetic Prandtl and fluid parameter.

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BACONNEAU, OLIVIER, JAN BOUWE VAN DEN BERG, CLAUDE-MICHEL BRAUNER i JOSEPHUU HULSHOF. "Multiplicity and stability of travelling wave solutions in a free boundary combustion-radiation problem". European Journal of Applied Mathematics 15, nr 1 (luty 2004): 79–102. http://dx.doi.org/10.1017/s0956792503005333.

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We study travelling wave solutions of a one-dimensional two-phase Free Boundary Problem, which models premixed flames propagating in a gaseous mixture with dust. The model combines diffusion of mass and temperature with reaction at the flame front, the reaction rate being temperature dependent. The radiative effects due to the presence of dust account for the divergence of the radiative flux entering the equation for temperature. This flux is modelled by the Eddington equation. In an appropriate limit the divergence of the flux takes the form of a nonlinear heat loss term. The resulting reduced model is able to capture a hysteresis effect that appears if the amount of fuel in front of the flame, or equivalently, the adiabatic temperature is taken as a control parameter.

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Rahman, M. M., i T. Sultana. "Radiative Heat Transfer Flow of Micropolar Fluid with Variable Heat Flux in a Porous Medium". Nonlinear Analysis: Modelling and Control 13, nr 1 (25.01.2008): 71–87. http://dx.doi.org/10.15388/na.2008.13.1.14590.

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A two-dimensional steady convective flow of a micropolar fluid past a vertical porous flat plate in the presence of radiation with variable heat flux has been analyzed numerically. Using Darcy-Forchheimer model the corresponding momentum, microrotation and energy equations have been solved numerically. The local similarity solutions for the flow, microrotation and heat transfer characteristics are illustrated graphically for various material parameters. The effects of the pertinent parameters on the local skin friction coefficient, plate couple stress and the heat transfer are also calculated. It was shown that large Darcy parameter leads to decrease the velocity while it increases the angular velocity as well as temperature of the micropolar fluids. The rate of heat transfer in weakly concentrated micropolar fluids is higher than strongly concentrated micropolar fluids.

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SARMA, D., N. AHMED i H. DEKA. "MHD FREE CONVECTION AND MASS TRANSFER FLOW PAST AN ACCELERATED VERTICAL PLATE WITH CHEMICAL REACTION IN PRESENCE OF RADIATION". Latin American Applied Research - An international journal 44, nr 1 (31.01.2014): 1–8. http://dx.doi.org/10.52292/j.laar.2014.412.

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This paper deals with the study of the thermal radiation and chemical reaction effects on an unsteady MHD free convective mass transfer flow past an accelerated infinite vertical plate embedded in a porous medium. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The dimensionless governing equations of motion are solved by using Laplace transform technique in closed form. Expressions for the velocity, temperature and concentration are obtained. The resulting velocity and temperature profiles as well as the skin-friction, rate of heat and mass transfer are shown graphically for different values of the physical parameters viz., Grashof number, Prandtl number, Schmidt number, Chemical reaction parameter, Radiation parameter, Magnetic parameter and Porosity parameter.

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Xu, Yan Ying, Ruo Jun Wang, Jian Chen i Lu Chao Li. "Combustion Performance of Composite Floor with Different Radiant Heat Flux". Applied Mechanics and Materials 501-504 (styczeń 2014): 2415–18. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.2415.

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The combustion performance of engineered wood flooring and intensive composite floor under the different radiation heat flux were experimented by cone calorimeter. Fire parameters were measured including the ignition time and heat release rate. Experimental results show that the ignition time of engineered wood flooring is much lower than intensive composite floor, and the ignition time are decreased with the increase of radiation heat flux. The heat release rate (HRR) curve has two peaks under the same radiation heat flux, and the first peak of the heat release rate of engineered wood flooring occurs significantly earlier than intensive composite floor. The heat release rate is increased and the first peak significantly ahead of time with the increase of the radiation intensity

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29

Khan, Muhammad Ijaz, Sohail Ahmad Khan, Tasawar Hayat, Muhammad Faisal Javed i Ahmed Alsaedi. "Entropy generation in radiative flow of Ree-Eyring fluid due to due rotating disks". International Journal of Numerical Methods for Heat & Fluid Flow 29, nr 6 (3.06.2019): 2057–79. http://dx.doi.org/10.1108/hff-11-2018-0642.

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Purpose This study aims to examine the flow characteristics of Ree–Eyring fluid between two rotating disks. The characteristics of heat transfer are discussed in presence of viscous dissipation, heat source/sink and nonlinear radiative heat flux. Design/methodology/approach Nonlinear flow expressions lead to ordinary ones through adequate similarity transformations. The ordinary differential system has been tackled through optimal homotopic method. The impact of different flow variables on the velocity field, entropy generation rate and temperature fields is graphically discussed. The surface drag force and heat transfer rate are numerically examined via various pertinent parameters. Findings By minimization of values of stretching parameter and Brinkman number, the entropy generation rate can be controlled. The entropy generation rate enhances for higher values of magnetic parameter, while the Bejan number is decreased via magnetic parameter. Originality/value No such work is yet published in the literature.

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30

Takahashi, Ken. "Radiative Constraints on the Hydrological Cycle in an Idealized Radiative–Convective Equilibrium Model". Journal of the Atmospheric Sciences 66, nr 1 (1.01.2009): 77–91. http://dx.doi.org/10.1175/2008jas2797.1.

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Abstract The radiative constraints on the partitioning of the surface energy budget and, hence, on the strength of the hydrological cycle are analyzed in an idealized one-dimensional radiative–convective equilibrium model formulated in terms of the energy budgets at the top of the atmosphere, the subcloud layer, and the free atmosphere, which enables it to predict both surface relative humidity and the air–sea temperature difference. Using semigray radiative transfer, a semianalytical solution was obtained that explicitly shows how the surface latent heat flux (LHF) is related to the radiative properties of the atmosphere. This solution was also used in conjunction with a full radiative transfer code and was found to provide reasonably realistic quantitative estimates. In the model the LHF is fundamentally constrained by the net longwave flux divergence above the level of condensation by lifting (LCL) and by the atmospheric absorption of shortwave radiation, with only a weak indirect control by near-surface moisture. The latter implies that the Clausius–Clapeyron relation does not directly constrain the strength of the hydrological cycle. Under radiative perturbations, the changes in LHF are determined by the changes in the net longwave fluxes at the LCL, associated mainly with the changes in the longwave transmissivity, and by the changes in shortwave absorption by the atmosphere (e.g., by increased water vapor). Using a full radiative transfer model with interactive water vapor feedback with the semianalytical solution indicates a rate of change in LHF with greenhouse forcing of around 2 W m−2 K−1 of surface warming, which corresponds to the Planck feedback (∼3.2 W m−2 K−1) multiplied by a coefficient of order one that, to first approximation, depends only on the relative magnitudes of the net longwave radiation fluxes at the LCL and the top of the atmosphere (i.e., on the shape of the vertical profile of the net longwave flux).

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Ketchat, Niwat, i Bundit Krittacom. "Numerical Study of Radiative Heat Flux Emitted by Stainless Wire-Net Porous Media". Key Engineering Materials 861 (wrzesień 2020): 509–13. http://dx.doi.org/10.4028/www.scientific.net/kem.861.509.

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Numerical model of the convective-radiative heat transfer of porous media was proposed. A stainless wire-net was used as porous media. The physical properties, consisting of porosity (φ) and optical thickness (τ0), of porous media were independent variables. The air velocity was reported in the form of Reynolds number (Re). Two equations of the conservative energy with local thermal non-equilibrium were analyzed. The gas (θf) and solid (θs) phases of conservative energy equation inside porous media were investigated. The radiative heat flux (ψ) at down-stream of solid phase emitted into outside was dealt by the P1 approximation. From the study, it was found that the level of θf and θs decreased as Re increased because the effect of convection heat transfer. Inversely, the level of ψ increased as increasing Re. The level of θf, θs and ψ were decreased as φ increased owing to a lower volume of material depended on the increasing level of φ resulting to the heat transfer rate became lower. The level of θf, θs and ψ gave increased with τ0 becaues a wider distance in absorping energy leading to a higher emission energy from the porous media was achieved.

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Murer, Luc, Sarah Chatenet, Gaelle Fontaine, Serge Bourbigot i Olivier Authier. "Influence of model assumptions on charring polymer decomposition in the cone calorimeter". Journal of Fire Sciences 36, nr 3 (15.03.2018): 181–201. http://dx.doi.org/10.1177/0734904118761641.

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This article addresses the one-dimensional modeling of a charring polymer decomposition in the cone calorimeter used to reproduce at bench scale the radiative heating from a fire. The rate-controlling phenomena are first discussed in a preliminary analysis of dimensionless numbers. Then, the role of three critical assumptions is highlighted by simulations: (1) transport of the gaseous products within the material or instantaneous release of gaseous products, (2) volume variation or constant volume, and (3) absorption of applied heat flux at the exposed face or through the thickness. Their influence in thermally thick regime is shown in particular on mass loss rate and time to extinction. Under the conditions tested, the influence of internal transport by convection on mass loss rate and time to extinction is minor. The assumption of constant volume appears to have a moderate influence on the mass loss rate and time to extinction. Variations of optical properties affect the numerical results by an increase of the maximum peak of mass loss rate and a decrease of time to extinction. Finally, the effects of applied heat flux and initial material thickness on the mass loss rate and time to extinction are important. With a higher heat flux or a smaller thickness, the decomposition is earlier, faster, and more intense.

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Qasim, Muhammad, Tasawar Hayat i Saleem Obaidat. "Radiation Effect on the Mixed Convection Flow of a Viscoelastic Fluid Along an Inclined Stretching Sheet". Zeitschrift für Naturforschung A 67, nr 3-4 (1.04.2012): 195–202. http://dx.doi.org/10.5560/zna.2012-0006.

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This study concentrates on the heat transfer analysis of the steady flow of viscoelastic fluid along an inclined stretching surface. Analysis has been carried out in the presence of thermal radiation and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The equations of continuity, momentum and energy are reduced into the system of governing differential equations and solved by homotopy analysis method (HAM). The velocity and temperature are illustrated through graphs. Exact and homotopy solutions are compared in a limiting sense. It is noticed that viscoelastic parameter decreases the velocity and boundary layer thickness. It is also observed that increasing values of viscoelastic parameter reduces the thickness of momentum boundary layer and increase the heat transfer rate. However, it is found that increasing the radiation parameter has the effect of decreasing the local Nusselt number

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34

Mochizuki, Takashi, i Toshiyuki Awaji. "Summertime Evolution of Decadal Sea Surface Temperature Anomalies in the Midlatitude North Pacific". Journal of Climate 21, nr 7 (1.04.2008): 1569–88. http://dx.doi.org/10.1175/2007jcli1853.1.

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Abstract To clarify the summertime evolution of decadal sea surface temperature (SST) anomalies and related physical processes in the midlatitudes of the North Pacific, numerical solutions of a three-dimensional bulk mixed layer model are analyzed, focusing on the contribution of the net shortwave radiative forcing at the sea surface. A quantitative heat budget analysis for the ocean mixed layer relating to late-1980s decadal SST change reveals that the decadal SST anomalies decay from late spring to early summer over the entire midlatitudes of the North Pacific. This quasi-seasonal decay of the decadal SST anomalies is controlled by an anomalous local thermal damping (i.e., anomalous surface heat fluxes). From midsummer to early autumn the anomalous net shortwave radiation flux associated with a meridional shift of the storm track acts to induce strong seasonal damping of the decadal SST anomaly in the northern Kuroshio–Oyashio Extension region. In contrast, in the north of the subtropical frontal region, the net shortwave radiation flux anomaly, which results from changes in low-level stratiform cloud cover, plays a major role in seasonally enhancing the decadal SST anomaly. Consequently, the SST anomalies formed by these radiative forcings cause significant variations in the local thermal damping rate at the sea surface over the period from late summer to early autumn.

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SUNAHARA, Hiroyuki, Takahiro ISHIHARA, Ken MATSUYAMA, Shin'ichi SUGAHARA i Masahiro MORITA. "A STUDY ON RERATION BETWEEN HEAT RELEASE RATE AND RADIATIVE HEAT FLUX OF WOOD CRIB BURNING DURING WATER DISCHARGE". Journal of Environmental Engineering (Transactions of AIJ) 75, nr 658 (2010): 1009–17. http://dx.doi.org/10.3130/aije.75.1009.

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Zhang, Jia Qing, Bo Si Zhang, Ming Hao Fan, Liu Fang Wang, Xiang Jun Guo i Deng Yang Yu. "Effects of External Heat Radiation on Combustion and Toxic Gas Release of Flame Retardant Cables". Materials Science Forum 898 (czerwiec 2017): 2392–98. http://dx.doi.org/10.4028/www.scientific.net/msf.898.2392.

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The effects of external heat radiation on combustion and toxic gas release characteristics of flame retardant cables, which were XLPE insulated, flame retardant PVC sheathed and steel armoured cables, were investigated. The combustion characteristics of the level A and the level C flame retardant cables were explored by the cone calorimeter. For the level C cables, heat release rate (HRR) and CO concentration in cable fires increased and the ignition time decreased with increase of the external radiation heat flux. For level A cables, the HRR and CO concentration showed two-stage variations with the external radiation heat flux. When the external radiation heat flux was smaller than 35 kW/m2, the cable self-extinguished quickly after the ignition. When the external radiation heat flux was larger than 50 kW/m2, the cables showed continuous burning phenomena after the ignition. The level A cable had smaller HRRs compared with that of the level C cable under the same external radiation heat flux. However, the CO concentration of level A cable was remarkably higher than that of the level C cable in the present study. The high CO release rate of cable with well flame retardant ability under large external radiation heat flux requires more caution in the cable fires.

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37

Mjankwi, Musa Antidius, Verdiana Grace Masanja, Eunice W. Mureithi i Makungu Ng’oga James. "Unsteady MHD Flow of Nanofluid with Variable Properties over a Stretching Sheet in the Presence of Thermal Radiation and Chemical Reaction". International Journal of Mathematics and Mathematical Sciences 2019 (2.05.2019): 1–14. http://dx.doi.org/10.1155/2019/7392459.

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The unsteady magnetohydrodynamics (MHD) flow of nanofluid with variable fluid properties over an inclined stretching sheet in the presence of thermal radiation and chemical reaction is studied taking into account the effect of variable fluid properties in thermal conductivity and diffusion coefficient. The governing partial differential equations are transformed into ordinary differential equations by using similarity transformation. The numerical solutions of the problem are obtained by using the fourth order Runge-Kutta method in line with the shooting technique. It is found that the increase in both thermal conductivity and radiative heat flux decreases the heat transfer rate but increases the skin friction and mass transfer rates. It is further observed that the increase in porosity parameter and magnetic field reduces the skin friction, heat, and mass transfer rates.

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38

Azad, Masoud Torabi, Hesameddin Mehrfar i Mozhgan Emtyazjoo. "A Case Study of Heat Budget in the Southern Caspian Sea, Gorgan Bay, Iran". Marine Technology Society Journal 55, nr 5 (1.09.2021): 150–60. http://dx.doi.org/10.4031/mtsj.55.5.1.

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Abstract Gorgan Bay is one of the unique closed basins in the world and has a special geological and environmental status from a physical oceanographic perspective. In the present case study, local coefficients for heat budget of the area were extracted using in-situ measurements. According to the obtained findings in this study, the shortwave radiation flux, net longwave radiation flux, sensible heat flux, and latent heat flux have been estimated to be about 155 W/m2, −66 W/m2, −20 W/m2, and −187 W/m2, respectively. The rate of heat transfer through Caspian Sea to Gorgan Bay is estimated to be about 1.2 × 109 W. In addition, the rate of the heat transfer through rivers to Gorgan Bay is approximately 2.2 × 106 W, which is negligible. In addition, it was concluded that heat balance, which was investigated for different seasons, is caused by the heat loss through river flows as well as heat exchanges between the Caspian Sea and Gorgan Bay gaps. The amount of advection heat flux is about −31 W/m2, which is equal to the surface heat flux. The mentioned finding indicates that storms not only affect the latent heat flux and sensible heat flux but also have a significant impact on the total heat budget.

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Ko, Gwon Hyun. "Numerical Study on Heat Radiation Attenuation and Flow Characteristics by Water Mist Curtains". Fire Science and Engineering 36, nr 4 (31.08.2022): 1–7. http://dx.doi.org/10.7731/kifse.b677f696.

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A numerical study was conducted to investigate the attenuation effect of fire radiative heat and flow characteristics by water mist curtains. To shield a fire room with a diesel fire source with a maximum heat release rate of 1.8 MW, two mist curtain nozzles that operated at 1.0∼3.0 MPa were installed. The injection flow rate and mean diameter of droplets ranged from 9.1 to 15.8 lpm and from 87 to 58 <i>μ</i>m, respectively. The radiative heat flux through the mist curtain was μ attenuated by 50%∼76% based on the given injection pressure range and appropriately followed the trends of previous experimental results. Comparing the flow characteristics with and without mist curtain activation, the effect of smoke shielding using the mist curtain was partially evident at the early stage of the fire; however, the shielding effect decreased, as the speed of the smoke flow increased during the peak period.

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40

Gnaneswara, Reddy, i Reddy Bhaskar. "Radiation and mass transfer effects on unsteady MHD free convection flow of an incompressible viscous fluid past a moving vertical cylinder". Theoretical and Applied Mechanics 36, nr 3 (2009): 239–60. http://dx.doi.org/10.2298/tam0903239g.

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The interaction of free convection with thermal radiation of a viscous incompressible unsteady MHD flow past a moving vertical cylinder with heat and mass transfer is analyzed. The fluid is a gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing equations are solved using an implicit finite-difference scheme of Crank-Nicolson type. Numerical results for the transient velocity, the temperature, the concentration, the local as well as average skin-friction, the rate of heat and mass transfer for various parameters such as thermal Grashof number, mass Grashof number, magnetic parameter, radiation parameter and Schmidt number are shown graphically. It is observed that, when the radiation parameter increases the velocity and temperature decrease in the boundary layer. Also, it is found that as increase in the magnetic field leads to decrease in the velocity field and rise in the thermal boundary thickness.

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41

Su, Yun, Jiazhen He i Jun Li. "An improved model to analyze radiative heat transfer in flame-resistant fabrics exposed to low-level radiation". Textile Research Journal 87, nr 16 (9.08.2016): 1953–67. http://dx.doi.org/10.1177/0040517516660892.

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An improved heat transfer model, based on the two-flux model, in a multilayer flame-resistant fabric system with an air gap was proposed. The developed model considered the thermal radiation by absorbing, transmitting, emitting and reflecting in porous fabrics. The predicted results of the new model were compared with the previous Beer’s law model and the experimental results, and were found to be in good agreement with the experimental ones. The aim of this study is to investigate the mechanism of radiant heat transfer in the multilayer fabric system and the effects of the optical properties of flame-resistant fabric on heat transfer in the fabric system. The numerical results demonstrated that the self-emission in multilayer fabric system increases not only the rate of thermal energy transferred to human skin during thermal exposure, but also the rate of thermal energy transmitting to the ambience during cooling. The fabric’s optical properties have a complex influence on the transmitted and stored energy in multilayer protective clothing. The finding obtained in this study can provide references for the improvement of the thermal protective performance of flame-resistant fabrics.

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42

Jin, Xiaohua, Lingbo Zhang, Xiaoyan Li i Caixia Zhu. "Structural Features and Smoke Resistance of Water Mist Curtain of Upper Spray Nozzle". International Journal of Heat and Technology 38, nr 3 (15.10.2020): 758–66. http://dx.doi.org/10.18280/ijht.380321.

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Due to its structural limitation, the super-long tunnel faces the difficulty in smoke suppression on the ceiling. For this, the authors aim to develop a water mist curtain with an upward sprinkler head and analyze its smoke suppression performance. FDS numerical simulation was conducted to analyze the changes over time of different parameters such as temperature, smoke spread, radiative heat flux density, CO volume fraction, and the distance between the sprinkler head and the ceiling, and explore the smoke-proof and fire extinguishing effect of the improved water mist curtain together with the tunnel's smoke exhaust system. The results show that with the spray flow rate of 12L/min and droplet size of 300μm, the water mist system with upward sprinkler heads has a more efficient smoke suppression efficiency than the conventional one; the improved water mist system reduced the temperature at the tunnel ceiling by more than 40%, and the CO volume fraction by about 33%, thereby significantly decreasing the smoke density on the ceiling; it reduced the radiative heat flux density at a height of 2m by about 47%, and especially when coupled with the tunnel smoke exhaust system, the smoke suppression performance is better; the smoke volume fraction decreases with the distance between the sprinkler head and ceiling at the height of 5m from the ground. The research findings provide a reference for the smoke suppression of the water mist system and smoke exhaust system in the future.

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Mansoor, Saad Bin, i Bekir S. Yilbas. "Estimating Entropy Generation Rate for Ballistic-Diffusive Phonon Transport Using Effective Thermal Conductivity". Journal of Non-Equilibrium Thermodynamics 46, nr 3 (13.05.2021): 321–27. http://dx.doi.org/10.1515/jnet-2020-0113.

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Abstract The entropy generation rate in a low dimensional film is formulated incorporating the heat flux and effective thermal conductivity of the film material. In the analysis, the mathematical formulation employed is kept the same as that used in the diffusive regime. However, the entropy generation rate is corrected by replacing the bulk thermal conductivity with an effective thermal conductivity evaluated from the Boltzmann equation. The entropy generation rate using the phonon distribution from the equation of phonon radiative transport in the film material is employed. The results show that both formulations result in a very close match for the entropy generation rates.

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Ahmad, Salman, Khan Ijaz, Ahmed Waleed, Tufail Khan, Tasawar Hayat i Ahmed Alsaedi. "Impact of arrhenius activation energy in viscoelastic nanomaterial flow subject to binary chemical reaction and non-linear mixed convection". Thermal Science 24, nr 2 Part B (2020): 1143–55. http://dx.doi.org/10.2298/tsci180524212a.

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The computational investigations on mixed convection stagnation point flow of Jeffrey nanofluid over a stretched surface is presented herein. The sheet is placed vertical over which nanomaterials flowing upward direction. Arrhenius activation energy and binary chemical reaction are accounted. Non-linear radiative heat flux, MHD, viscous dissipation, heat source/sink, and Joule heating are considered. Initially the non-linear flow expressions are converted to ordinary one and then tackled for series solutions by homotopy analysis method. Consider flow problem are discussed for velocity, temperature and concentration through various flow variables. Furthermore, skin friction coefficient, Sherwood number, and heat transfer rate are computed graphically.

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Reddy, M. M. Gnaneswara, i N. Bhaskar Reddy. "Thermal radiation and mass transfer effects on MHD free convection flow past a vertical cylinder with variable surface temperature and concentration". Journal of Naval Architecture and Marine Engineering 6, nr 1 (27.03.2010): 1–15. http://dx.doi.org/10.3329/jname.v6i1.2615.

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The interaction of free convection with thermal radiation of a viscous incompressible unsteady MHD flow past a vertical cylinder with variable surface temperature and concentration is analyzed. The fluid is a gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing equations are solved using an implicit finite-difference scheme of Crank-Nicolson type. Numerical results for the transient velocity, the temperature, the concentration, the local as well as average skin-friction, the rate of heat and mass transfer are shown graphically. It is observed that the presence of as well as increase in the magnetic field leads to decrease in the velocity field and rise in the thermal boundary thickness. The numerical predications have been compared with the existing information in the literature and good agreement is obtained.Keywords: Heat Transfer, radiation, finite-difference Scheme, vertical cylinderDOI: 10.3329/jname.v5i2.2615Journal of Naval Architecture and Marine Engineering 6(1)(2009) 1-24

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46

Han, Haidong, Jian Wang, Junfeng Wei i Shiyin Liu. "Backwasting rate on debris-covered Koxkar glacier, Tuomuer mountain, China". Journal of Glaciology 56, nr 196 (2010): 287–96. http://dx.doi.org/10.3189/002214310791968430.

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AbstractA physically based energy-balance model with improved parameterization of solar radiation for a sloped ice surface has been developed to estimate the backwasting rate of an ice cliff in a debris-covered area. The model has been tested against observations between 5 August and 5 September 2008 on 38 ice cliffs in the debris-covered area of Koxkar glacier, Tuomuer mountain, China. We calculated that the energy-balance model gave a good estimate of the backwasting rates, with errors in the range ±1.96 cm d−1 and root-mean-square errors of 0.99 cm d−1. Errors arising from setting of surface albedo and turbulent flux parameterization were limited. We found that shortwave radiation is the most important heat source for ice-cliff ablation, contributing about 76% of the total heat available for ice melt, while the sensible heat flux provides nearly 24% of the total heat for ice-cliff wastage. The latent heat flux and net longwave radiation are comparatively small according to the model calculation. The mean backwasting rate of ice cliffs in the debris-covered area of Koxkar glacier is estimated at 7.64 m a−1 when the winter ablation is neglected. With this annual backwasting rate and given a mean slope angle of 46.4°, the backwasting of ice cliffs produces about 1.60 × 106 m3 of meltwater, accounting for about 7.3% of the total melt runoff from the debris-covered area.

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Budea, Sanda, i Viorel Badescu. "Fluid Flow Control in Domestic Hot Water Systems During Days with Different Radiative Stability Levels". Annals of West University of Timisoara - Physics 60, nr 1 (1.08.2018): 88–96. http://dx.doi.org/10.2478/awutp-2018-0009.

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AbstractThis paper presents models/strategies for optimum performance of solar collector in closed loop systems. These models aim to maximize the obtained energy by thermal conversion of solar energy. The mass flow rate of the fluid from the primary circuit of the system is the control parameter. The semi empirical models and optimal control methods are in brief presented. The volume of the storage tank is important and the ratio Vs/Ac between this volume and area of the collectors is a key factor in appropriate sizing of the DHW system. Therefore, the paper establishes a relationship between this ratio and the mass flow rate of the fluid in the collector This paper also analyses the variation of the energetic performance (useful heat flux transferred to the storage tank, heat flux transferred to the water, water temperature in the storage tank) with the volume of the storage tank. Analysis was performed on an extensive set of meteorological data from Timisoara, Romania, with instantaneous data (measured at 15 seconds) for summer days, from July 2009, with different relative sunshine values, σ. Important differences have been observed between days with different stability levels - days more or less stable.

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Đorđević, Milan, Velimir Stefanović, Mića Vukić i Marko Mančić. "EXPERIMENTAL INVESTIGATION OF THE CONVECTIVE HEAT TRANSFER IN A SPIRALLY COILED CORRUGATED TUBE WITH RADIANT HEATING". Facta Universitatis, Series: Mechanical Engineering 15, nr 3 (9.12.2017): 495. http://dx.doi.org/10.22190/fume171001027d.

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The Archimedean spiral coil made of a transversely corrugated tube was exposed to radiant heating in order to represent a heat absorber of the parabolic dish solar concentrator. The main advantage of the considered innovative design solution is a coupling effect of the two passive methods for heat transfer enhancement - coiling of the flow channel and changes in surface roughness. The curvature ratio of the spiral coil varies from 0.029 to 0.234, while water and a mixture of propylene glycol and water are used as heat transfer fluids. The unique focus of this study is on specific boundary conditions since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but in the axial direction as well. Instrumentation of the laboratory model of the heat absorber mounted in the radiation field includes measurement of inlet fluid flow rate, pressure drop, inlet and outlet fluid temperature and 35 type K thermocouples welded to the coil surface. A thermal analysis of the experimentally obtained data implies taking into consideration the externally applied radiation field, convective and radiative heat losses, conduction through the tube wall and convection to the internal fluid. The experimental results have shown significant enhancement of the heat transfer rate compared to spirally coiled smooth tubes, up to 240% in the turbulent flow regime.

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Abu-Hamdeh, Nidal H., Abdulmalik A. Aljinaidi, Mohamed A. Eltaher, Khalid H. Almitani, Khaled A. Alnefaie, Abdullah M. Abusorrah i Mohammad Reza Safaei. "Implicit Finite Difference Simulation of Prandtl-Eyring Nanofluid over a Flat Plate with Variable Thermal Conductivity: A Tiwari and Das Model". Mathematics 9, nr 24 (7.12.2021): 3153. http://dx.doi.org/10.3390/math9243153.

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The current article presents the entropy formation and heat transfer of the steady Prandtl-Eyring nanofluids (P-ENF). Heat transfer and flow of P-ENF are analyzed when nanofluid is passed to the hot and slippery surface. The study also investigates the effects of radiative heat flux, variable thermal conductivity, the material’s porosity, and the morphologies of nano-solid particles. Flow equations are defined utilizing partial differential equations (PDEs). Necessary transformations are employed to convert the formulae into ordinary differential equations. The implicit finite difference method (I-FDM) is used to find approximate solutions to ordinary differential equations. Two types of nano-solid particles, aluminium oxide (Al2O3) and copper (Cu), are examined using engine oil (EO) as working fluid. Graphical plots are used to depict the crucial outcomes regarding drag force, entropy measurement, temperature, Nusselt number, and flow. According to the study, there is a solid and aggressive increase in the heat transfer rate of P-ENF Cu-EO than Al2O3-EO. An increment in the size of nanoparticles resulted in enhancing the entropy of the model. The Prandtl-Eyring parameter and modified radiative flow show the same impact on the radiative field.

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Vijayakumar, G., i Ashwani Kumar Kachroo. "Temperature Prediction Methodology for a Missile Flying at Low and High Altitudes". Applied Mechanics and Materials 592-594 (lipiec 2014): 1794–800. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1794.

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Missiles fly at supersonic and hypersonic speeds. Airframe forms the aerodynamic shape of the missile and houses several components essential for mission with suitable structural supports. The missile airframe is subjected to high rate of heating caused by kinetic heating due to very high vehicle speed. Heat transfer analysis of the missile airframe structure is required to be performed for wall temperature predictions to select the material of missile construction with suitable wall thickness and also to check design adequacy for ensuring the safe operation in the severe thermal environment experienced during flight. This paper describes the methodology of evaluation of heat flux distribution over missile wall, prediction of missile wall temperature distribution considering airframe as heat sink and validation of the methodology against flight data. Heat flux has been estimated using classical engineering methods for both stagnation as well as off-stagnation regions including the effect of angle of attack, rarified flow, thermal radiation and solar heating. Transient three dimensional heat transfer analysis with convective and radiative boundary conditions has been carried out for predicting the missile wall temperature profiles. Parametric study has been carried out, considering various parameters such as material of construction, thickness and time duration. The prediction methodology has been validated and a close match is observed between the predictions and flight data.

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