Radiation Convection Heat Transfer Research Articles

Investigation of periodic heat transfer on the transient thermal characteristics of fully wet moving semi-spherical porous fin composed of functionally graded material

This study investigates the thermal behaviour of a fully wet, moving semi-spherical porous fin made of linear Functionally Graded Material (FGM). This investigation examines the fin response to convective-radiative heat transfer under periodic variations in base temperature across three different FGM scenarios: Homogeneous material (HM), Functionally Graded Material I (FGM I) and Functionally Graded Material II (FGM II). The resultant nonlinear partial differential equation is accurately solved using the Finite Difference Method (FDM) and outcomes are benchmarked against existing literature. This research pioneers an investigation into the effects of periodic heat transfer on the detailed thermal profiles of FGM fin, an area not been explored in existing literature. It significantly enhances understanding of the influence of oscillatory base temperatures on thermal management within FGMs, uncovering pivotal insights into the interaction between material grading, amplitude of temperature oscillation and their collective effects on thermal efficiency. Additionally, this research assesses the influence of variables such as the amplitude of input temperature, frequency of oscillation, thermal conductivity grading parameter and others on temperature distribution along the fin length and over dimensionless time. Notably, periodic heat transfer induces a dynamically wavy thermal profile in the fin over time, attributable to oscillating base temperatures. Moreover, the analysis demonstrates that FGM II fin exhibit the most significant temperature distribution, followed by FGM I and HM. The fin heat transfer rate is profoundly influenced by the amplitude of input temperature and the thermal conductivity grading parameter. These insights are pivotal for optimizing fin designs in critical applications, including electronics cooling, HVAC systems, automotive engine cooling and solar energy collection, substantially improving upon traditional designs.

Radiative flow of clay nanoparticles on the lubricity of Williamson drilling fluids across a vertical surface in a Darcy-Brinkman porous medium

Drilling fluids are essential for extracting gases and oils from rocks and soil. To increase drilling fluid efficiency, clay nanoparticles are crucial. The use of clay particles in drilling fluids increases their thermal conductivity, viscosity, and boiling point, hence giving resilience to high temperatures and controlling fluid costs. Therefore, this research examines the convection radiative flow and heat transfer incorporated in the Williamson nanofluid with a heat source/sink. The effective thermophysical properties of clay nanofluid are represented quantitatively by using Maxwell-Garnett and Brinkman's formulas. The leading PDEs with physical boundary conditions that control the flow phenomena are predetermined. These PDEs are converted into ODEs using the similarity method, and dual solutions are then found by using an effective bvp4c solver. The effects of mixed convective, permeability, Williamson constraint, heat source/sink, nanoparticle volume fraction, and radiation parameters were all thoroughly studied quantitatively and theoretically. The Nusselt number and skin friction are calculated and displayed in tabular form as well as graphical form along with the velocity and temperature profiles. Multiple solutions are observed in the shrinkable sheet as well as the buoyancy assisting flow. The findings demonstrate that the Nusselt number rises noticeably when volume concentration increases. In addition, the permeability parameter expands the boundary layer thickness in the lower solution, while the contrary behavior is observed in the upper solution.

Comparative analysis of thermal behaviour in functionally graded material fin under convective-radiative heat transfer: Homotopy perturbation method

In this study, the thermal characteristics of a fully wet, moving longitudinal fin made from linear Functionally Graded Material (FGM) is explored. The fin response to convective-radiative heat transfer is examined through three distinct FGM scenarios namely, a Homogeneous material (HM), Functionally Graded Material I (FGM I) having greater thermal grading near the base, and Functionally Graded Material II (FGM II) having increased thermal grading towards the tip. The derived energy equation is a second-order nonlinear ordinary differential equation is solved using the Homotopy Perturbation Method (HPM) compared with results found in the existing literature. The fin thermal profile has been graphically analysed for the thermal conductivity grading parameter (β), Peclet number (Pe) and other pertinent parameters. It is found that the temperature distribution along the fin is highest for the FGM II fin and lowest for the HM fin, with the FGM I fin displaying intermediate values. Efficiency of the fin (η) is discovered to be lowest in the case of HM fin structures followed by FGM I and FGM II fin structures at the base and vice versa at the tip. The results show significant potential of HPM which benefits the manufacture and design of FGM fin structures.

Radiation-convective heat transfer and performance analysis of a parallel-plates duct direct absorption solar heat collection system

Solar photo-thermal conversion and solar heat collection are hot topics today. However, which solar collection mode is the best? The question has puzzled scholars for many years. In this study, a direct absorption solar heat collection (DASC) duct system was investigated. Carbon quantum dots (CQDs) were selected as the heat absorption medium. Different absorption modes were clarified. It is found that the ratio of the radiation penetration depth of nanofluids to duct depth (duct penetration ratio, α) plays a key role in the duct heat transfer and system performance. Totally three solar heat collection modes can be classified depending on the value of α: volume absorption (partial volume 0<α<1 or whole volume α = 1), surface absorption (upper α → 0 or bottom α → ∞) and hybrid absorption for α > 1. Of them, the whole volume absorption has the best performance when α = 1, while the hybrid performs the best when the penetration ratio is not unity. Surprisingly, a higher fluid absorption coefficient does not necessarily lead to a higher photo-thermal performance. The extreme high fluid absorption coefficients (upper surface mode) are inferior to extreme low absorption coefficients (bottom surface mode). Of the different modes, the total Nusselt numbers in the whole volume absorption mode are 2–3 times higher than those in the bottom surface absorption mode. For solar heat collection, convective heat collection is better than standstill collection, and a certain flow velocity should be ensured to have a satisfactory efficiency. The findings were experimentally verified.

Activation energy with binary chemical reaction of convective radiative magnetized nanofluid flow with viscous dissipation and pressure gradient

ABSTRACT The present investigation deals with the study of activation energy with the binary chemical reaction on magnetohydrodynamic convective radiative heat and mass transfer of nanofluid flow with internal heat source/sink, viscous dissipation, pressure gradient force, and suction effects. The basic equations of conservation of momentum, energy, and mass diffusion are brought to a set of ordinary differential equations (nonlinear) using suitable similarity transformations, and these are then solved using the Homotopy Perturbation Method (HPM). The validity of the present results is established by comparing them with those obtained by the Runge-Kutta-Fehlberg method (RKFM). The results reveal that the temperature distribution increases with raising the value of the thermal radiation parameter. It is found that the concentration distribution increases by increasing the values of the activation energy parameter. In contrast, the reverse effect is observed by enhancing the chemical reaction parameter, Schmidt number, and pressure gradient parameter. Further, the skin-friction coefficient and Nusselt number decrement by enhancing the value of the Hartmann number, whereas the reverse trend is found by enhancing the pressure gradient and suction parameter values. Also, the Sherwood number retards with an enhancement in the Hartmann number, whereas it rises by increasing the pressure gradient and suction parameters.

Steady and Unsteady Complex Heat Transfer in Optically Thick Medium During Film Boiling

Abstract The paper presents the results of a study of radiative-convective heat transfer at film boiling of a liquid on a vertical heated plate. Both a steady-state problem of heat transfer and a transient problem were considered. The latter describes the instantaneous (flash) boiling up of a liquid on a heated surface. The novelty of the present study is the use of the optically thick medium approximation in a mathematical model when studying the process of radiation-convective heat transfer in the film boiling regime. For the first time, radiation heat transfer was considered for an optically thick medium. An analytical solution of the steady-state problems is obtained for boundary conditions involving a constant wall temperature and a constant wall heat flux. The effect of radiation and the temperature difference between the wall and liquid on the temperature profiles in the vapor phase is shown. The effect of radiation becomes more pronounced with an increase in the temperature difference between the wall and the liquid. As a result of solving the transient problem, the variation in time of the temperature profile and the heat transfer coefficient in the vapor film were obtained. The effect of radiation (Stark number) on the heat transfer coefficients is elucidated. An increase in the radiative heat flux leads to an increase in the Nusselt number, as well as the time it takes for the heat transfer process to reach a steady-state regime.

Temperature Reduction of a Hot Component Enclosed in a Ring Filled with Power-Law Ferrofluid Under the Effect of Magnetic Field and Heat Absorption: Benefit from LBM Ability to Simulate Radiation–Convection Heat Transfer

Temperature Reduction of a Hot Component Enclosed in a Ring Filled with Power-Law Ferrofluid Under the Effect of Magnetic Field and Heat Absorption: Benefit from LBM Ability to Simulate Radiation–Convection Heat Transfer

Дослідження методик розрахунку прогресуючого обвалення

Modeling of the progressive collapse of buildings under fire conditions was carried out using the LIRA-CAD software environment in order to increase the level of fire safety. Scientific works and standardization of requirements for the progressive collapse of buildings in fire conditions are analyzed, the causes of progressive collapse in fire conditions, modern methods and approaches to calculating progressive collapse in fire conditions in the USA and Ukraine are considered. It has been established that currently there is no single methodology for calculating "progressive collapse". Ensuring (development of calculation methodology) the necessary resistance of objects to progressive collapse under various combined special effects of fire and explosion is an urgent scientific and practical task. A numerical model of the progressive collapse of the building under fire conditions, which can lead to the progressive collapse of the building, has been developed. For this, the LIRA-SAPR software complex was used. A finite-element model of a three-story parking lot was created. The applied differential equation of thermal conductivity takes into account radiation-convective heat transfer from the gas medium to the heating surfaces of the column, heat transfer by thermal conductivity in the column. Stiffness types and corresponding characteristics were determined for the model. As a result of the numerical modeling, the place of the fire was established, the consequences of which will lead to the loss of the load-bearing capacity of the structures, and, as a result, to the loss of the overall stability of the parking building. It has been established that approaches to increase the area of reinforcement take place in the design of buildings and structures, but are generally not acceptable in the operation of already constructed buildings and in the case of the need to increase the fire resistance limits of reinforced concrete structures to standardized values.

Evolutionary Computing for the Radiative-Convective Heat Transfer of a Wetted Wavy Fin Using a Genetic Algorithm-Based Neural Network.

Evolutionary algorithms are a large class of optimization techniques inspired by the ideas of natural selection, and can be employed to address challenging problems. These algorithms iteratively evolve populations using crossover, which combines genetic information from two parent solutions, and mutation, which adds random changes. This iterative process tends to produce effective solutions. Inspired by this, the current study presents the results of thermal variation on the surface of a wetted wavy fin using a genetic algorithm in the context of parameter estimation for artificial neural network models. The physical features of convective and radiative heat transfer during wet surface conditions are also considered to develop the model. The highly nonlinear governing ordinary differential equation of the proposed fin problem is transmuted into a dimensionless equation. The graphical outcomes of the aspects of the thermal profile are demonstrated for specific non-dimensional variables. The primary observation of the current study is a decrease in temperature profile with a rise in wet parameters and convective-conductive parameters. The implemented genetic algorithm offers a powerful optimization technique that can effectively tune the parameters of the artificial neural network, leading to an enhanced predictive accuracy and convergence with the numerically obtained solution.

Implication of radiation on the thermal behavior of a partially wetted dovetail fin using an artificial neural network

The simultaneous convection-radiation heat transfer of a partially wetted dovetail extended surface is investigated in this study. Also, the temperature variance behavior of the dovetail extended surface (DES) is estimated through thermal models for partially wet and dry conditions using the neural network with the Levenberg-Marquardt scheme (NNLMS). The corresponding governing energy equations of a dovetail fin are presented as a set of ordinary differential equations (ODE), which are reduced to a non-dimensional form using dimensionless terms. Further, the resulting coupled conductive, convective, and radiative dimensionless ODEs are numerically solved utilizing the Runge-Kutta-Fehlberg fourth-fifth order (RKF-45) scheme. Using graphical illustrations, the resultant solutions are physically determined by considering the effects of various nondimensional variables on thermal behavior. From the outcomes, it is established that the thermal conductivity parameter enhances the thermal distribution in a partially wetted dovetail fin, and an upsurge in convection-conduction variable, temperature ratio parameter, radiation-conduction, and wet parameter diminishes the temperature profile of the considered extended surface. The modelled problem's NNLMS efficacy is demonstrated by achieving the best convergence and unique numerically assessed quantified results. The outcomes indicate that the strategy successfully resolves the partially wetted fin problem.

Radiative–Convective Heating of the Surface of the Martian Descent Vehicle MSL with Taking into Account the Turbulent Nature of Flow

The three-dimensional computer model based on the Reynolds-averaged Navier–Stokes equations together with the Baldwin–Lomax and Prandtl algebraic models of turbulent mixing is used to calculate radiative–convective heat transfer on the surface of the MSL descent space vehicle. The intensification of convective heat transfer on the leeward side of the frontal aerodynamic shield and the superiority of the radiative heat flux density over the convective one on the rear surface are demonstrated. The calculations are performed using the physically and chemically nonequilibrium gas model. The results are compared with the calculations based on other computational models and the flight data on the heat load to the descent vehicle obtained during MSL descent in the dense layers of the Martian atmosphere.

REDUCED HEAT LOSS THROUGH WINDOW STRUCTURES

The results of theoretical and experimental studies of heat transfer through the window structures of the building are presented, the thermal characteristics of the windows are established and the level of heat loss realized through them is estimated. To determine the heat transfer resistance of two-chamber double-glazed units, numerical modeling of radiative-convective heat transfer is performed, taking into account the thermal conductivity of the gas layer between the glasses. Natural free convection of the gaseous medium in the double-glazed chambers occurs as a result of the temperature difference between the side glass surfaces of the chamber. Modeling is performed by numerically solving the system of fluid dynamics and energy equations for the air layer and glass. On the inner surfaces of the chambers, conditions of the fourth kind are set, which take into account the radiation and conductive components of the total heat flow coming from the glass surface. The results of simulation of heat transfer through double-glazed windows with ordinary glass indicate that about 60 % of heat is transferred by radiation. Therefore, an effective measure to reduce heat loss through windows is to reduce the radiation component of the total heat flow by applying a low-emissivity coating to the inner surfaces of the glass unit. This makes it possible to reduce the total heat flow (and, accordingly, heat loss to the environment) by 20–34 %, depending on the number of glass surfaces with this coating. Conducted independent experimental studies confirm the modeling results. In order to comply with the current requirements of state building regulations and to achieve the energy efficiency class of type C buildings (specific heat consumption for heating 1 sq. m of usable area is less than 75 kWh), for the climatic conditions of Kyiv, it is recommended to use double-chamber windows with two low-emission coatings with the formula of the glass unit: 4M1-10-i4M1-10-i4M1. Bibl. 22, Fig. 8.

Analysis of mixed convective-radiative heat transfer in a porous square cavity filled with various nanofluids

The present study examines the numerical simulation of mixed convective fluid movement and heat transference within the square cavity with various nanofluids. In this work, the nanofluids are prepared by suspending zinc oxide (ZnO)/silicon dioxide nanoparticles into water /kerosene /ethylene glycol base liquids. Features of various nanofluids flow inside cavity are investigated and this kind of studies may be useful in automobile applications and electrical gadgets. The vertical walls of the cavity are hot, the bottom wall is partially cooled, and the top wall is considered to be adiabatic. The Marker-And-Cell (MAC) method is utilized to solve the governing non-dimensional partial differential equations. The impact of heat generation/absorption (Q), nanoparticle volume fraction Darcy number (Da), Richardson number (Ri), Reynolds number (Re), and the thermal radiation parameter (Rd) are scrutinized. The outcomes are displayed informs of streamlines, isotherms, and local and average Nusselt numbers. The comparative study is performed and it finds a good accordance with the literature. As fluid flow and heat transfer are concerned, ZnO-Ethylene Glycol(EG) nanofluid explores the optimum features among the considered nanofluids. When 5% ZnO/SiO 2 nanoparticles are suspended into water, compared to SiO 2-water nanofluid, ZnO-water nanofluid has more than 10.81% mean rate of heat transmission. Suspension of 5% ZnO in water/kerosene/EG has the tendency to enhance the mean heat transfer rates of water/kerosene/EG up to respectively. The highest mean heat transfer rate is attained when the cavity’s aspect ratio is fixed as 1:1.

Radiative-convective heating of the surface of the Martian descent vehicle MSL with allowance for the turbulent nature of the flow

A spatial computer model based on the Reynolds-averaged Navier-Stokes equations together with the Baldwin-Lomax and Prandtl algebraic models of turbulent mixing was used to calculate the radiative-convective heat transfer on the surface of the MSL descent vehicle. The intensification of convective heat transfer on the leeward side of the frontal aerodynamic shield and the superiority of the radiative heat flux density over the convective one on the rear surface are shown. The calculations were performed using the model of a physically and chemically nonequilibrium gas. A comparison is made with the results of calculations using other computational models and with flight data on the heat load on the descent vehicle obtained during the MSL descent in the dense layers of the Martian atmosphere.

Lattice Boltzmann scheme for coupled radiation–convection heat transfer in participating media

With the increasing scientific and engineering applications of coupled radiation and natural convection problems (CRNCP), it is required to develop more convenient numerical methods to solve the problems. In this paper, the equations of momentum, energy, and radiative transfer are all solved by the lattice Boltzmann method, and a lattice Boltzmann (LB) framework is established for the CRNCP. The influences of the Planck number, Rayleigh number, scattering albedo, and optical thickness in isotropic scattering media are analyzed. The results indicate that the radiation parameters significantly impact the CRNCP. In addition, the LB framework is extended to solve the problems of anisotropic scattering media. It is expected that the current work will provide a convenient numerical tool for various CRNCP.

Simulation of combined convective-radiative heat transfer of hybrid nanofluid flow inside an open trapezoidal enclosure considering the magnetic force impacts

In this research, the combined convective-radiative heat transfer for magnetohydrodynamics (MHD) hybrid nanofluid flow inside an open trapezoidal enclosure are numerically simulated. There are two diagonal side walls and a horizontal wall defining this open enclosure. This enclosure's inclined side walls are accurately modeled using the embedded boundary approach. Calculations of thermal radiation term in the energy equation are done based on the Roseland approximation. The nanofluid applied in this research is a mixture of hybrid Al2O3-CuO nanoparticles and H2O base fluid. To investigate the thermal treatment, distributions of dimensionless temperature in the enclosure and the variations of Nusselt numbers on its bottom hot wall are presented for various magnitudes of radiative parameter, hybrid nanoparticles volume fractions and magnetic force. The obtained findings indicate the highest magnitude of total heat transfer rate on the enclosure bottom hot wall is registered in absence of magnetic force Ha=0 and for highest values of radiative parameter Rd=1 and hybrid nanoparticles concentration ϕ=0.03Al2O3+0.03CuO.

Вопросы численного моделирования горения в диффузионном факеле

The study is devoted to mathematical models of mass transfer during diffusion combustion of gaseous fuel. A numerical approach is presented that makes it possible to estimate the effect of combustion conditions on the length of a direct-flow diffusion flame. A simplified method for calculating the heat release in a diffusion flame is applied, taking into account the fact that the chemical reactions of combustion are concentrated in it at the flame front. Some results of numerical simulation of diffusion combustion processes and complex radiative-convective heat transfer in industrial furnaces in the production of cement clinker are presented.

Research of the thermoelastic performance of the functionally graded sandwich slabs with convective-radiative boundary conditions based on FVM

<p indent="0mm">In this study, a two-dimensional control volume finite element method (CV-FVM) has been developed for the thermoelastic coupling problem of sandwich structures with functionally graded material core under a convection-radiation heat transfer environment. Based on a four-node quadrilateral element, the discrete process of the governing equation and the nonlinear heat transfer boundary are given in detail. Based on the staggered grid technology, the variables are stored at the node of the element, and the material parameters are defined at the center of the element. To ensure the convergence of the temperature solution, the radiation heat transfer boundary condition is handled by the linearization technique. The numerical method developed in this study is validated for the heat conduction problem of sandwich structures with an exponential core. The results showed that CV-FVM results are consistent with the analytical solution. The influences of the geometric and physical parameters, such as the Biot number, radiation conduction coefficient, environmental temperature ratio, panel thickness, and gradient index of the functionally graded core, on the thermoelastic performance of the structure are investigated. The results showed that the Biot number of the heating surface has only a slight effect on the thermoelastic response of the structure, whereas the Biot number of the cooling surface has a significant effect on the thermoelastic response. The cooling surface is more sensitive to the change in the environmental temperature than the heating surface. For sandwich structures with an exponential core, increasing the thickness of the upper panel can reduce the large gradient change of the stress at the junction between the upper panel and the core. The stress with a linear variation of the properties (<italic>p</italic> = 1) is smoother than that with a nonlinear variation of the properties (<italic>p</italic> = 0.1 and 10), and the large gradient change of the stress of the structure can be reduced significantly (<italic>p</italic> = 1).

Transient analysis of convective-radiative heat transfer through porous fins with temperature-dependent thermal conductivity and internal heat generation

In this research study, the transient study of heat transfer through a convective-radiative porous fin is carried out considering temperature-dependent thermal conductivity and internal heat generation. The unsteady Galerkin weighted residuals technique is employed to obtain the transient temperatures of the porous fin. The results indicate that increasing of the fin base temperature, internal heat generation and, thermal conductivity lead to increase heat transfer along the fin and consequently the higher temperature of the entire of the fin achieved. However, increasing of the porous and radiative parameters result in more heat dissipation from the fin and cause to lowering the fin temperature which leads to increase heat flux entering the fin through the base. Furthermore, the transient thermal analysis of the porous fin illustrates that by increasing the porous and the radiation parameters, the fin cools down faster, so in the applications that the time of cooling is more important, these parameters can be more noticeable.

Investigations of Couette Flow Unsteady Radiative Convective Heat Transfer in a Vertical Channel Using the Generalized Method of Lines (MOL)

This study describes a very efficient and fast numerical solution method for the non-steady free convection flow with radiation of a viscous fluid between two infinite vertical parallel walls. The method of lines (MOL) is used together with the Runge-Kutta ODE Matlab solver to investigate this problem numerically. The presence of radiation adds more stiffness and numerical complexity to the problem. A complete derivation in dimensionless form of the governing equations for momentum and energy is also included. A constant heat flux condition is applied at the left wall and a transient numerical solution is obtained for different values of the radiation parameter (&lt;i&gt;R&lt;/i&gt;). The results are presented for dimensionless velocity, dimensionless temperature and Nusselt number for different values of the Prandtl number (&lt;i&gt;Pr&lt;/i&gt;), Grashof number (&lt;i&gt;Gr&lt;/i&gt;), and the radiation parameter (&lt;i&gt;R&lt;/i&gt;). As expected, the results show that the convection heat transfer is high when the Nusselt number is high and the radiation parameter is low. It is also shown that the solution method used is simple and efficient and could be easily adopted to solve more complex problems.