Energy Transfer Equations Research Articles

THE IMPACT OF SOLAR RADIATION ON THE TEMPERATURE REGIME OF A ROOM IN WINTER

The article is devoted to the computational studies of the air-thermal state of office premises taking into account the effect of solar radiation coming through window openings. The study was conducted for a room with two windows using two heating devices installed under them. The air-temperature regime of premises in winter, characterized by the highest thermal energy consumption for heat supply, is considered. The study is based on the solution of a three-dimensional nonlinear heat transfer problem described by a system of equations of turbulent momentum and energy transfer. The k-e turbulence model is used to close this system. The results of numarical modeling of the physical situation under study are presented. The research data on the features of the air-thermal state of the premises under solar radiation conditions are given. The results of a comparative analysis of the air-temperature conditions of office premises corresponding to the solution of the specified heat exchange problems in the presence and absence of solar radiation are presented and the effects of solar radiation on the structure of the air flow and the thermal state of the premises are established. It is shown that in the presence of solar radiation, the air flow picture and the character of the temperature fields in the premises change significantly. In particular, in these conditions, the increase in the average temperature of the premises for the studied period is 2.5 °С. The possibility of a certain reduction of the load on the heating system in the presence of solar radiation is noted. Bibl. 17, Fig. 5.

Numerical Analysis of MHD Casson Fluid Flow over a Stretching Surface with Chemical Reaction and Variable Thermal Conductivity

The motivation of the current article is to explore the Numerical analysis of MHD Casson fluid flow over a Stretching surface. Three dimensional, non-linear of an incompressible fluid flow in the presence of chemical reaction and variable thermal conductivity is considered. The mathematical model effectively describes the current flow analysis. The Governing equations are simplified with the help of boundary layer approximations. Non-linear coupled equations for momentum, energy and mass transfer are tackled with MATLAB bvp4c. The behavior of various non-dimensional parameters which are involved in the derived set of equations are described and explained in detailed through graph.

Modeling of artificial neural network to analyze heat and mass transfer of ternary hybrid nanofluid between two parallel plates with inclined magnetic field

The applications of the artificial neural network (ANN) have become the focus of interest of researchers due to their convenience for accurate modeling, simulation, and efficiency of evaluation. The primary objective of this study is to investigate the characteristics of heat and mass transfer of the ternary hybrid nanofluid flow (THNF), which is squeezed between two parallel plates, using ANN. The plate which lies on x-axis is stretching while the upper plate (UP) can move in upward and downward direction. An inclined magnetic field (MF) is also applied to the lower plate (LP). A system of partial differential equations of flow, energy, and mass transfer is used to simulate the THNF, which is then condensed using similarity substitution to a collection of ordinary differential equations (ODEs). Using the differential transform method (DTM), the resultant nonlinear ODEs in dimensionless form are further solved. The influence of the different varying physical parameters on velocity, temperature, and concentration is graphically presented and discussed. It becomes apparent that the velocity, heat, and mass transfer in squeezing flows are significantly impacted by the inclination angle of the applied MF. To demonstrate the validity of the study, the numerical findings of the Nusselt and the Sherwood numbers are provided. For the accuracy of the used approach, DTM results are compared with results from the numerical approach. The novelty of the current work is to train the neural network with the Levenberg–Marquardt algorithm in the model. To get the estimated output of the model, different scenarios are set for training, testing, and validation. The analysis is done by mean square error (MSE), histogram, fitness curve, and regression (RG). The created ANN model is shown to be reliable due to its exceptional accuracy throughout the training, validation, and testing stages.

Enhancement of Heat and Mass Transfer in 2D-Mixed Convection Nano-Liquid Flow Over a Flexible Riga Plate with Heat Source/Sink and Chemical Reaction

This study delves into the complex dynamics of two-dimensional (2D) hydro-magnetic nano-fluidic flow over an elastic Riga plate, aiming to elucidate the interactions among thermal energy, concentration transfer, pressure gradient, and convective & zero mass flux at the boundary. Notably, the investigation incorporates concentration and temperature buoyancy forces, integrating them into the analysis with a comprehensive energy transfer equation and essential nanofluid properties in the species concentration. Further, the internal heat source/sink and rate of first order chemical reaction are considered. Employing the advanced capabilities of MATHEMATICA12 software, the study applies the Optimal Homotopy Analysis Method (OHAM), reducing the governing equations partially to ordinary ones. Furthermore, the study reveals intriguing patterns, highlighting the significant impact of the modified Hartmann number on velocity and concentration gradients, while displaying contrasting effects on thermal profiles. Moreover, the dual nature of pressure gradient behavior underscores the complexity of the studied phenomenon, offering valuable insights for further research and practical applications in nano-fluidic systems.

Thermo-fluid characteristics and lock-on range efficiency of infrared suppression (IRS) devices with diathermic funnels in the presence of surface radiation: A comparative study

This investigation examines the influence of surface radiation on the thermo-fluid characteristics of three distinct infrared suppression (IRS) mechanisms employing diathermic funnels. Managing the flow and heat transfer attributes within an IRS apparatus becomes increasingly intricate owing to the convergence of frigid ambient mass entering via inter-funnel apertures and the high-temperature flue gas generated by the turbine on naval or cargo vessels. Conducting a three-dimensional analysis involving conical, louvered conical, and louvered cylindrical funnels, computational simulations based on the Navier-Stokes equation, encompassing the energy and radiative transfer equations, are conducted. This study offers a comprehensive elucidation of how the Reynolds number (ranging from 6.1 × 105 to 3.18 × 106), FOL (negative, zero, and positive), and NOL collectively influence the temperature variations at the system’s exit. Louvered cylinder-shaped funnels, specifically in zero-overlap scenarios, emerge as the optimal configuration for the IRS system. The computations undertaken aim to gauge the ship’s lock-on range, accounting for the presence or absence of the IRS system.

Analysis of Entropy Generation for MHD Heat Transfer Flow of Viscous Fluid Embedded in a Porous Channel Due to Thermal Radiation

The study investigates the effect of convective flow on entropy generation for MHD heat transfer flow of viscous fluid embedded in a porous channel due to thermal radiation. The governing equations were transformed using the non-dimensional parameters. The solution of the resulting coupled dimensionless differential equations with a constant coefficient describing the momentum, energy, and mass transfer equations was obtained by using the method of undetermine coefficient. The parameters embedded in the flow are thermal radiation , Prandtl number, entropy generation , Suction/injection parameter , heat source/sink , porous material . In addition, physical quantities of engineering interest such as the Bejan number , Brinkman number , volumetric flow rate , skin friction coefficient, and heat transfer rate were computed. It is noticed that velocity and temperature increase significantly with an increase in heat source and suction parameters, while a reverse trend is observed when heat sink and injection are present. It is also evident that, the heat source increases the temperature profile in the presence of injection parameter, and a reverse trend is observed when the heat sink increases in the presence of the suction parameter. skin friction is decreasing with increase higher values of porous material in both at when injection and , volume flow rate reduces with increasing values of heat source and shot-up with decreasing values of heat sink, its observed that entropy generation is increasing for higher values of ...........

CFD simulation of drag-reducing fluids in a non-Newtonian turbulent pipe flow

The conveyance of fluids from one terminal to another incurs considerable expenses primarily due to the significant costs associated with addressing pressure losses arising from shear stresses and friction along the inner surface during the pumping operations within pipelines. This study was conducted with the objective of simulating turbulent flow in pipes containing drag-reducing fluids. This was achieved through the utilization of both RKE and RNG versions of a non-Newtonian model for low Reynolds numbers, based on the k-ε model, along with a non-Newtonian damping function. The outcomes were subsequently compared to simulations carried out by Pinho and experimental data sourced from the existing literature. To simulate the flow in pipelines, computational fluid dynamics (CFD) software was employed, which incorporated non-linear molecular viscosity and a damping function to accurately account for near-wall effects. In addition, this research entailed the optimization of C and C0 parameters in the damping function and the stress term, which quantifies the cross-correlation between fluctuating viscosity and the fluctuating rate of strain. Furthermore, non-Newtonian terms were incorporated into the equations for turbulent kinetic energy (k), dissipation rate (ε), and momentum transfer. The study involved a comprehensive comparison of model predictions with experimental data across various flow parameters, including friction factor, axial velocity, turbulent kinetic energy, and Reynolds shear stresses. The results revealed a significant enhancement in the model's ability to predict critical flow parameters, such as friction factor, mean axial velocity, and Reynolds stress profiles. Nevertheless, the model displayed some limitations in predicting turbulent kinetic energy. Notably, the average error in calculating the friction factor for the fluids under investigation was found to be 5.45%, marking a substantial improvement compared to the Pinho model, which exhibited an average error of 32.49%.

Energy Conversion in Systems-Contained Laser-Irradiated Metallic Nanoparticles – Comparison of Results from Analytical Solutions and Numerical Methods

Abstract This work introduces the theoretical method of metallic nanoparticles’ (NPs’) heat and mass transfer where the particles are coated on a surface (base), together with considering the case wherein nanoparticles move freely in a pipe. In order to simulate the heat transfer, energy and radiative transfer equations are adjusted to the considered issue. NPs’ properties are determined following the nanofluidic theories, whereas absorption and scattering coefficients are described using either Mie-Lorenz theory or Rayleigh-Drude approximation. Thermal boundary conditions are implemented based on the microscale heat transfer and Smoluchowski theory. Results are compared with the classical Fourier transport differential solutions that have been adjusted to laser irradiation.

Matematyczne modele hydromechaniki przepływu wielofazowego o zmiennej masie

The paper discusses the mathematical model of hydromechanics of multiphase flows with varying mass. A multiphase flow is considered a continuum consisting of a set of a large number of different groups of particles. The derivation of motion equations and similarity criteria are given taking into account both the externally attached (or detached) mass and phase transitions within the medium. The equations of mass, momentum and energy transfer for individual phases and the medium as a whole are derived based on fundamental conservation laws. It was demonstrated that in the absence of sources (or flow-offs) of mass, momentum and energy, the known equations of single- and multi-phase flow hydromechanics follow as a special case from the obtained systems of motion equations and similarity criteria. The obtained motion equations are valid for the description of an ingredient of mixture and the medium as a whole, regardless of their physical and mechanical properties. Thermodynamic and rheological state equations, as well as expressions for heat flow, interfacial mass forces phase transitions, and heat exchange between phases can be used to close them. The implemented models make it possible to simulate both the stationary distribution of parameters along the wellbore during production and non-stationary processes that occur, for example, when the pump shaft speed changes during oil production. The developed approaches were implemented in the DataFlow software tool for analysis of the hydrodynamics of multiphase hydrocarbon flows, taking into account heat exchange with the rocks surrounding the well, and phase transitions in the fluid. Using the software package, test calculations were carried out to demonstrate the performance of the proposed and implemented models.

Numerical simulation of the particle wall mass transfer rates on rough surfaces confining turbulent natural convection flows

We performed numerical simulations of the particle mass transfer rates on the horizontal and vertical thermally active rough walls confining a turbulent natural convection flow. We considered the air flow conditions in a cubical cavity (L=1.22m, Ra=5.4·108, Pr=0.71) with two opposed pairs of consecutive walls at different temperatures, for which measurements of the particle deposition velocities are reported in the literature. The simulations were carried out by solving the momentum, thermal energy and particle mass transfer equations using a series of two-dimensional computational cell units to determine spatial evolution and development of the particle concentration boundary layer in the vicinity of hot and cold rough walls. Different flow conditions, wall orientations, sizes of roughness elements, particle diameters and temperature increments between the wall and the bulk fluid, typically found in indoor environments, have been considered and consequently, results can be used to estimate the particle deposition rates in real scenarios. At large mass transfer particle Péclet numbers, corresponding to spherical particles with diameters of 0.5–1 μm, the wall mass transfer rates of particles on rough textures typically increase by a factor of about 3 in comparison with the deposition on smooth surfaces. The thermophoretic effect significantly decreases the particle deposition on hot surfaces and increases it on cold surfaces, especially at large particle Péclet numbers. The numerical predictions of the deposition velocities are in good agreement with the measurements reported in the literature for the same flow conditions considered.

Coaxially swirled porous disks flow simultaneously induced by mixed convection with morphological effect of metallic/metallic oxide nanoparticles

This study focuses on the numerical modeling of coaxially swirling porous disk flow subject to the combined effects of mixed convection and chemical reactions. We conducted numerical investigations to analyze the morphologies of aluminum oxide (Al2O3) and copper (Cu) nanoparticles under the influence of magnetohydrodynamics. For the flow of hybrid nanofluids, we developed a model that considers the aggregate nanoparticle volume fraction based on single-phase simulation, along with the energy and mass transfer equations. The high-order, nonlinear, ordinary differential equations are obtained from the governing system of nonlinear partial differential equations via similarity transformation. The resulting system of ordinary differential equations is solved numerically by the Runge–Kutta technique and the shooting method. This is one of the most widely used numerical algorithms for solving differential equations in various fields, including physics, engineering, and computer science. This study investigated the impact of various nanoparticle shape factors (spherical, platelet and laminar) subject to relevant physical quantities and their corresponding distributions. Our findings indicate that aluminum oxide and copper (Al2O3-Cu/H2O) hybrid nanofluids exhibit significant improvements in heat transfer compared to other shape factors, particularly in laminar flow. Additionally, the injection/suction factor influences the contraction/expansion phenomenon, leading to noteworthy results concerning skin friction and the Nusselt number in the field of engineering. Moreover, the chemical reaction parameter demonstrates a remarkable influence on Sherwood’s number. The insights gained from this work hold potential benefits for the field of lubricant technology, as they contribute valuable knowledge regarding the behavior of hybrid nanofluids and their associated characteristics.

Heat and mass transfer for MHD nanofluid flow on a porous stretching sheet with prescribed boundary conditions

A theoretical study is conducted in order to scrutinize the thermodynamic first law of the MHD nanofluid flow with an inclined magnetic field, radiation, heat source/sink, viscous dissipation, Joule heating, concentration power-law exponent, and the chemical reaction on a porous stretching surface immersed within a permeable Darcian medium. Cobalt ferrite nanoparticles (CoFe2O4) have been combined with pure water to form a nanofluid called CoFe2O4/H2O. The controlling mathematical equations for MHD nanofluid flow are transformed through similarity transformation into non-dimensional equations. The exact solutions for the energy and mass transfer equations are provided in terms of confluent hypergeometric function. The effects of controlling parameters on the velocity, temperature, and concentration profiles are discussed and illustrated with figures and tables. According to the results, increasing the concentration power-law exponent yields a rise in the Sherwood number (PSC) magnitude and the wall concentration (PMF). Furthermore, the 3-D plots showed that the skin friction coefficient is directly related to the Hartmann number, suction parameter, and nanoparticle volume fraction parameter.

Numerical Simulation of The Influence of Geometric Parameter on The Flow Behavior in a Solar Chimney Power Plant System

Numerical simulations have been carried out on the solar chimney power plant systems. This paper gives the flow field analysis for a solar chimney power generation project located in Baghdad. The continuity, Naver-stockes, energy and radiation transfer equations have been solved and carried out by Fluent software. The governing equations are solved for incompressible, 3-D, steady state, turbulent is approximated by a standard k -  model with Boussiuesq approximation to study and evaluate the performance of solar chimney power plant in Baghdad city of Iraq. The different geometric parameters of project are assumed such as collector diameter and chimney height at different working conditions of solar radiation intensity (300,450,600,750 and 900 W/m2) to gain the optimal designed structure. The results show that the change of collector diameter and chimney height has considerable effects on the performance of the system. The velocity increase when the collector diameter and chimney height increase and reach to the maximize value at H=D 12 m and when solar intensity (900 W/m2). The study shows that Iraqi weather are suitable for this system.

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.

A fluid model of pulsed direct current planar magnetron discharge

We simulated a pulsed direct current (DC) planar magnetron discharge using fluid model, solving for species continuity, momentum, and energy transfer equations, coupled with Poisson equation and Lorentz force for electromagnetism. Based on a validated DC magnetron model, an asymmetric bipolar potential waveform is applied at the cathode at 50–200 kHz frequency and 50–80% duty cycle. Our results show that pulsing leads to increased electron density and electron temperature, but decreased deposition rate over non-pulsed DC magnetron, trends consistent with those reported by experimental studies. Increasing pulse frequency increases electron temperature but reduces the electron density and deposition rate, whereas increasing duty cycle decreases both electron temperature and density but increases deposition rate. We found that the time-averaged electron density scales inversely with the frequency, and time-averaged discharge voltage magnitude scales with the duty cycle. Our results are readily applicable to modulated pulse power magnetron sputtering and can be extended to alternating current (AC) reactive sputtering processes.

Modeling and simulation of an industrial adsorption process of dehydration of natural gas in 4A molecular sieves: Effect of adsorbent aging

Adsorption in molecular sieves is the number one choice for the dehydration of natural gas in offshore platforms. Many phenomenological and mathematical approaches have been used to describe this unit operation. However, the effect of aging on the operation performance, and consequently the adequacy of these models to describe operational field conditions, has been seldom assessed. This work presents the simulation of an industrial unit of natural gas dehydration with 4A molecular sieves in different cycle numbers using a phenomenological model. First, the most adequate equilibrium isotherm to describe experimental data of pure compound adsorption (viz., the dual-site Langmuir isotherm) was determined. Second, momentum, mass, and energy transfer equations were implemented, and the modeling of literature adsorption data was used to verify the adequacy of the developed equations. Finally, an industrial dehydration unit was modeled using the same approach, and calculated breakthrough times were compared to field data. In conclusion, the premature aging of molecular sieves in industrial operation appears as a defining factor in equipment performance.

A dynamic model of tablet film coating processes for control system design

Aqueous film coating is a common and important step in the production of most pharmaceutical tablets. Controlling this process is beneficial to maintain stable and optimal operation and the use of a model capable of describing its main physical phenomena is fundamental for control system design. This paper presents the development of a dynamic macro scale model of a pan coater based on energy and mass transfer equations. Model complexity is kept low to simplify parameterization and allow for real-time applications, such as the development of system observers to estimate critical unmeasured variables. Pilot plant data from seven batches, ran according to designed experiments, are used for model calibration and validation. The final model adequately captures the global trajectories of the main process variables; mean differences between experimental and simulated values are below 2 °C for the outlet gas and tablet bed temperatures, and 2% for the outlet gas relative humidity.

Numerical analysis of the fluid flow and heat transfer of a hybrid PV-thermal collector and performance assessment

In recent years, new materials and absorber configurations have been proposed to improve the performance of hybrid photovoltaic-thermal (PV-T) collectors. This work analyses the fluid flow and the energy performance of an uncovered water-based PV-T collector with a roll-bond thermal absorber. A detailed CFD model was developed and the results were compared with the experimental performance features provided by the PV-T manufacturer. The fluid flow results show uneven flow distribution among the roll-bond microchannels which leads to areas with larger PV cell temperatures and thus a lower electricity generation. The PV-T collector layers were also modelled using the energy transfer equations layer-by-layer. The model was run for several water inlet temperatures and water flow-rates to obtain the thermal performance curve. The results show that the electrical efficiency of the PV-T collector is 14.5–10.3% larger than for a PV-only system for water inlet temperatures of 20–30 °C, respectively. The developed CFD model reproduces accurately the thermal performance of the PV-T collector, with a maximum error of 6.5% for inlet water temperatures of 20–60 °C. Therefore, this model can be used with confidence to propose alternative designs that achieve a homogeneous temperature distribution in the PV layer and improve the overall PV-T collector performance.

Evaporation characteristics of ethanol droplet in different gases under force convection condition

Ethanol is recognized as one of the finest alternative bio-fuels due to its natural characteristics. Fundamental studies on ethanol droplet evaporation process are mainly either in stagnant environment or using some semi-empirical co-relations. Here, a fully numerical model based on the first principle is solved to investigate the effects of various atmospheric gases (Ar, N2, O2 and CO2) on droplet evaporation phenomenon under force convective situation. Two-dimensional governing equations of species, momentum and energy transfer of spherical coordinate system are solved, and the simulation is validated quantitatively with the literature. Uniform convective strength (Re = 100) is maintained for all cases examined at T∞ = 500 K and P∞ = 0.1 MPa. From the simulation results, it is observed that the viscosity ratio (liquid to gas) has effect on droplet life time. The ethanol droplet life time increases in less viscous atmospheric gases. The ethanol droplet life time is shorter in Ar gas, but heat-up period, wet-bulb temperature, and the surface blowing effect are higher in Ar compared to other atmospheric gases. The heat-up periods of the ethanol droplet in Ar, CO2, N2 and O2 atmosphere occupy around 30%, 20%, 17% and 16.5% of the total life time of the droplet, respectively. It is also noticed that, the heat-up period increases with increase in the thermal conductivity ratio (liquid to gas) and vice versa. Furthermore, the flow pattern of both gas- and liquid-phase in terms of streamline and the internal temperature distributions of the droplet are visualized at various time instants.

Study of the Possibility of Stimulating Cloud Convection by Solar Radiation Energy Absorbed in an Artificial Aerosol Layer

We consider the possibility of creating artificial clouds similar to Pyro clouds formed in nature over large forest and other fires. It is assumed that the creation of an artificial surface aerosol layer that absorbs solar radiation can lead to the heating of local air volumes and initiate thermal convection. The possibility of such convection was examined theoretically using the computational fluid dynamics software package suite FlowVision, in which the equations of motion, energy and mass transfer are solved in relative variables. Numerical experiments showed the principal possibility of initiating cloud convection only under some favorable atmospheric conditions (low wind speeds, temperature lapse rate greater than 8–9 °C/km), with an aerosol layer area of at least 5–10 km2 and a duration of its existence (heating) of at least 30 min. To assess the possibility of the practical implementation of this method, eight variants of highly efficient smoke compositions were developed and tested, and two batches of aerosol checkers weighing 25 kg, creating an aerosol of optimal size to absorb solar radiation, were produced. Calculations of the required dose based on the results of laboratory and field tests of the checkers showed that for one experiment to initiate cloud convection several thousand checkers need to be burned. The consumption of pyrotechnic aerosol composition (tens of tons) is about 1.5 times less than the burning of petroleum products in previously tested meteotrons. However, for environmental safety purposes, full-scale tests and the application of the aerosol layer method is advisable to conduct away from populated areas.