Internal Energy Generation Research Articles

Entropy Generation Analysis on a Metal Foam in an Automotive Exhaust Line with Thermoelectric Generator

Abstract In the present paper, an entropy generation analysis on a 2-D steady state problem in convective regime of an aluminum foam partially and totally filled channel with an external TEG element is solved in numerical way. The numerical analyses are accomplished with the assumption of the local thermal equilibrium (LTE) hypothesis in order to model the metal foam and heat transfer inside the channel. The working fluid is exhaust gas characterized by the same properties of the air in correspondence to the TEG upper surface temperature. The TEG is considered as a solid component characterized by an internal energy generation. The thermophysical properties are assumed temperature independent. Ansys-Fluent code is employed in order to resolve the governing equations for exhaust gas, metal foam and TEG. Different exhaust gas mass flow rates on the inlet section are assumed. Several thicknesses of aluminum foam values are employed. The porous media are characterized by a porosity from 0.90 to 0.978 and number of pores per inch (PPI) equal to 5, 10, 20, 40. Results are given in terms of global entropy generations related to the thermal and viscous effects. The total global entropy generation increases with increasing of exhaust gas flow rate for all pore density and porosity values. Bejan number decreases with the increment of mass flow rate and thickness. It increases when the porosity value increases whereas at high mass flow rate and for assigned porosity the values present small difference for different pore density values.

Simulation for bloodstream conveying bi-nanoparticles in an endoscopic canal with blood clot under intense electromagnetic force

In the current era, the electromagnetic pumping flow of hybrid nano-biofluid features in myriad magneto-biomedical engineering applications. In this scenario, the current disquisition is centralized to unfold the electro-magneto-hemodynamic distinctive features of ionized bloodstream conveying silver and aluminium oxide hybridized nanoparticles driven by electroosmosis via an endoscopic conduit (space between two coaxial tubes) formed by a uniform and rigid endoscope and a complaint walled artery. The formulation involves the dominance of Hall and ion-slip factors, internal energy generation, Joule warming, a blood clot (coagulation), and convective wall condition. The contribution of nanoparticles' shape is dissected in this examination. The Poisson-Boltzmann equation is utilized to emulate the conduit's electric double layer (EDL). The lubrication and Debye-Hückel linearization principles are opted to simplify the normalized complicated leading equations. The homotopic series solutions of the consequent coupled nonlinear dimensionless equations are computed. A critical examination of significant flow-controlling parameters over the relevant hemodynamical characteristics is executed via graphs and tables. From the obtained outcomes, it is worthy of imparting that a discernible lesson is viewed in the blood velocity profile against the intensified estimates of Hall and ion-slip, and electro-osmotic factors. Blood is warmed with a positive Joule heating factor, whereas it is cooled with negative values of this factor. Upraised volumetric proportions of hybridized nanoparticles cool the blood in the conduit. Streamline patterns are also graphically displayed to see the blood flow pattern and the formation of entrapped boluses in the endoscopic domain. This research study considering multiple physical aspects such as electromagnetic phenomena, electromagnetic force, inclusion of hybridized nanoparticles, and coagulation is an innovative approach. Our findings in this simulation are expected to open up a new opportunity in biomedical engineering applications, including magneto-endoscopic operation, cheap devices for drug distribution, bio-magnetic therapy, electromagnetic hyperthermia treatment for cancer, etc.

Numerical investigation on a thermoelectric generator in an exhaust automotive line with convergent metal foam

In the present paper, a 2-D steady state convective heat transfer problem in a convergent channel partially filled with aluminum foam with an external thermoelectric generator (TEG) component is numerically solved. The channel is characterized by a length equal to 272 mm and by a height of 60 mm. The TEG has the dimensions equal to 65 mm and 8.5 mm. The investigation is executed considering the Darcy-Forchheimer-Brinkman assumption and the local thermal equilibrium (LTE) hypothesis for modelling the metal foam. The exhaust gas is considered to have the same properties of the air in corresponding to the assigned temperature of the upper surface of the thermoelectric generator. The thermophysical properties are temperature independent and the thermoelectric generator is studied as a solid with an internal energy generation. The governing equations for gas, porous media and thermoelectric generator are solved by finite volume method using the Ansys-Fluent code. Different configurations of convergent metal foam are analyzed. The aluminum foams are characterized by 5 PPI and porosity equal to 0.905, 0.946 and 0.971. Results are presented in terms of temperature distributions, thermoelectric efficiency, power density, and the Energy Performance Ratio (EPR) for different gas flow rates and aluminum foam configurations. Furthermore, a comparison with the use of the same foam samples characterized by a constant section is showed for the same system. From the comparison, it is possible to deduce how the configuration with convergent channel has a more uniform temperature profile than the geometry with constant section.

ELECTRICAL CONDUCTIVITY APPLICATION IN OHMIC PASTEURIZATION OF ORANGE JUICE

The conversion of electrical energy into heat energy, which results in internal energy generation, is the underlying premise of Ohmic heating. An experimental batch Ohmic heating unit was built and manufactured for this study. The effect of voltage gradient of alternating current during batch Ohmic heating on orange juice was investigated. Parameters such as temperature, electrical current, time consumption, system performance coefficient, and heating rate of orange juice under Ohmic heating process were studied. The time consumption such as (23.02, 11.25, and 2.19 minutes) to reach the Ohmic pasteurization temperature (95 °C) was decreased as the voltage gradients (9.20 V/cm, 12.64 V/cm, and 25.28 V/cm) increased respectively. The electrical current was rapidly increased (4.46 Amp.) in accordance with the higher voltage gradient (25.28 V/cm) to attain the pasteurization temperature. With rising voltage gradients, Ohmic heating resulted in greater system performance coefficient values. The heating rate appears to have grown dramatically as the voltage gradients increased.

Influence of metachronal ciliary wave motion on peristaltic flow of nanofluid model of synovitis problem

In this article, we have considered the effect of metachronal ciliary wave motion on the peristaltic flow of the Buongiorno nanofluid model for the synovitis problem. This study is additionally limited by the assumption of a low Reynolds number and lubrication theory approximations. An internal energy generation is also taken into account. Shear-thinning (model I) and shear-thickening (model II) for the concentration fluids are considered. The obtained dimensionless rheological equation is solved by using the homotopy perturbation Sumudu transformation method. The influence of various physical parameters on the dimensionless velocity, pressure rise, temperature, volume fraction, multi-sinusoidal waves, triangular waves, and streamlines has been analyzed. A trapping phenomenon is thoroughly examined. It is observed from the investigation that the shear-thinning (model I) and shear-thickening (model II) have completely distinct characteristics. The synovial fluid parameter shows opposite behavior on velocity and pressure rise profiles for models I and II, whereas the multi-sinusoidal wave and triangular wave forms retain the same shape of the waves as in the pressure gradient. These models can be used to treat rheumatoid arthritis as synovial fluids are present in joints. Fluid transfer in biological organs is improved by metachronal ciliary motion. Patients with rheumatoid arthritis can be treated with nanoparticles and ciliary motion. It is primarily due to their biocompatibility, low toxicity, and controlled release as well as their capacity to boost bioavailability and bioactivity of treatments and enable targeting the injured joints through the use of nanoparticles. In the limited scenario, the current work is in good accord with the earlier research, and it is analyzed through a graph.

Conjugate MHD natural convection in a square cavity with a non-uniform heat source thick solid partition

This paper aims to investigate the effect of a non-uniform internal volumetric energy generation on the conjugate MHD natural convection in a square cavity filled by an electrically conducting fluid. The uniform magnetic field is applied horizontally; the two horizontal and vertical left walls are thermally insulated, whereas the right vertical wall is kept at constant cold temperature. The governing conservation equations are solved numerically using an in house program based on the finite-volume method and the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The effects of internal Rayleigh, Hartmann and Prandtl numbers, thermal conductivity ratio, inclination angle of the cavity, and the thickness of heat source partition are discussed. The obtained results show that regardless of Kr , α and Δ, an almost pure conduction state is observed for low RaI without MHD and for high RaI with MHD at high magnetic field intensity.

Quantification of thermal energy generation in annular hyperbolic porous-finned heat sinks using inverse optimization

The present paper introduces an accurate numerical procedure to assess the internal thermal energy generation in an annular porous-finned heat sink from the sole assessment of surface temperature profile using the golden section search technique. All possible heat transfer modes and temperature dependence of all thermal parameters are accounted for in the present nonlinear model. At first, the direct problem is numerically solved using the Runge–Kutta method, whereas for predicting the prevailing heat generation within a given generalized fin domain an inverse method is used with the aid of the golden section search technique. After simplifications, the proposed scheme is credibly verified with other methodologies reported in the existing literature. Numerical predictions are performed under different levels of Gaussian noise from which accurate reconstructions are observed for measurement error up to 20%. The sensitivity study deciphers that the surface temperature field in itself is a strong function of the surface porosity, and the same is controlled through a joint trade-off among heat generation and other thermo-geometrical parameters. The present results acquired from the golden section search technique-assisted inverse method are proposed to be suitable for designing effective and robust porous fin heat sinks in order to deliver safe and enhanced heat transfer along with significant weight reduction with respect to the conventionally used systems. The present inverse estimation technique is proposed to be robust as it can be easily tailored to analyse all possible geometries manufactured from any material in a more accurate manner by taking into account all feasible heat transfer modes.

On electroosmosis in peristaltic activity of MHD non-Newtonian fluid

Electroosmosis in peristalsis of non-Newtonian fluid in a microchannel is considered. Magnetohydrodynamics (MHD), thermal radiation and mixed convection are adopted. Momentum, mass and temperature equations for third grade fluid are derived for long wavelength and small Reynolds number. Formulation is further completed by considering the velocity, temperature and concentration slip conditions. An internal energy generation is also taken into account. The physical parameters involved in flow characteristics are graphically analyzed. This work finds its utility in micro-fabrication technique, reservoir engineering and chemical industry where the electro-osmotic energy and mass exchanges play a vital role.

Analysis of transient thermoelastic temperature distribution of a thin circular plate and its thermal deflection under uniform heat generation

Analysis of transient thermoelastic temperature distribution of a thin circular plate and its thermal deflection under uniform internal heat generation is investigated. The upper and lower surfaces are thermally insulated, while the perimetric surface is subjected to convection heat transfer with convection coefficient hc and fluid temperature while the plate is also subjected to uniform internal energy generation g0 (W.m–3). The integral transform method is used to obtain the analytical solution for the temperature field and thermal deflection. As a special case, the mathematical model is prepared for copper material, and temperature distribution is analyzed for two different initial conditions. The results for temperature changes and the thermal deflection are computed numerically and illustrated graphically.

Numerical investigation on thermoelectric generators in an exhaust automotive line with aluminium foam

In the present paper a two-dimensional convective heat transfer problem in a partially filled channel with metal foam is numerically solved in steady state regime. An external thermoelectric generators (TEG) component is placed on the top surface of the channel. The numerical analyses are accomplished assuming the local thermal equilibrium (LTE) model to simulate the presence of the aluminum foam. The working fluid is exhaust gas with properties equal to the air for fixed temperature of the upper surface of the thermo-electric generator (TEG). The thermophysical properties are assumed temperature independent and the TEG component is considered as a solid with an internal energy generation. The Ansys-Fluent code is applied in order to resolve the governing equations for gas, porous media and TEG. Several mass flow rates of exhaust gas on the inlet section of the channel are considered. Different thicknesses of aluminum foam are assumed into the duct. The foam is characterized by different porosity equal to 0.90, 0.95, 0.97. Moreover, the number of pores per inch also changes and assumes the following values of 5, 20, 40. Results are showed in terms of temperature distributions, pressure drop, thermoelectric efficiency for different exhaust gas flow rates and metal foam characteristics and thicknesses. The results highlight that the use of metal foams significantly increases the heat transfer between the surface of exhaust gas tube and hot gas. Consequently, the effectiveness improves, and it increases between three-ten times with respect to the one for tube without metal foams. It is shown that the pore density does not affect the effectiveness.

Analytical investigation of workpiece internal energy generation in peripheral milling of titanium alloy Ti–6Al–4V

Energy management is crucial to the cutting process where generation and conversion of various forms of energy is occurring. Reducing the energy that stored in the machined surface layer can significantly improve the quality of processing and dimensional stability of machined structures. To achieve this, an accurate energy conversion model is required. In the present study, energy generation and conversion process during peripheral milling titanium alloy Ti–6Al–4V are investigated. Analytical model of cutting energy that acted on the machined surface is first established. And then, energy criteria for machining-induced residual stress field are proposed, and the energy that stored in the machined surface layer is calculated on the basis of the measured residual stress. Finally, a Q-factor is proposed to relate cutting energy to workpiece internal energy. By experimental analysis, there is about 10.86% of the energy that acted on the machined surface converted to the workpiece internal energy. On the basis of the proposed energy conversion model, the influences of milling processing parameters on the machining-induced material internal energy are revealed. According to the research results, the increase in cutting speed, feed rate and radial depth of cut increase the machining-induced material internal energy, and it is the cutting speed and feed per tooth that turn out to be the chief reasons for energy conversion in peripheral milling.

Assessing the efficiency of the off-gas network management in integrated steelworks

The European Steel industry is spending considerable efforts in order to improve the socio-economic and environmental sustainability of its processes by promoting any development, which can increase efficiency and lower the environmental impact of the steel production processes. In particular, the European iron and steel sector is strongly committed toward the reduction of energy consumptions and CO2emissions. Process gases are a very valuable resource: possibilities exist to consider these gases as an intermediate by-product for the production of other valuable energy carriers or products with an associated environmental benefit. Therefore, the process gas networks, especially inside the integrated steelworks, have a fundamental function, as they allow meeting the demand of many processes and producing energy through dedicated facilities. They can also support the production processes by internal electric energy generation and often by supplying energy outside the plant boundaries. On the other hand, such networks are very complex systems interacting with many different production steps and the management of such complex systems is a very difficult task, where many often-counteracting factors need to be jointly taken into account. This paper presents the first outcomes of the research project entitled “Optimization of the management of the process gas network within the integrated steelworks (GASNET)”, which aims at developing a Decision Support System helping the energy managers and other concerned technical personnel to implement an optimized off-gases management and exploitation considering environmental and economic objectives. A series of Key Performance Indicators has been elaborated, in order to monitor the efficiency of the gas management and the objectives of the optimization have been defined. The overall structure of the project and the ongoing work will also be outlined in the paper.

SURF ZONE WAVE HEATING BY ENERGY DISSIPATION OF BREAKING WAVES

This study investigates surf zone wave heating due to the dissipation of breaking wave energy by using the Smoothed Particle Hydrodynamics method. We evaluate the surf zone wave heating by examining the increase of internal energy of the system, which is computed based on the conservation of energy. The equivalent temperature profile is calculated based on a simple conversion relationship between energy and temperature. We first examine the surf zone wave heating based on long-crested wave breaking over a planar beach, and we consider spilling breaker and weakly plunging breaker. Numerical results show that breaking of water waves in the surf zone increases the internal energy of water body. Furthermore, the dissipation of incident wave energy is fully converted into the internal energy in a thermally isolated system, confirming the energy conservation of the present numerical approach. It is further found that the long-crested wave breaking generates undertow, which transports the generated wave heating from the surf zone to deep waters. We further carry out numerical experiments to examine surf zone wave heating due to short-crested wave breaking over a beach. The internal energy generation mainly follows the isolated wave breakers, and there is a 3D pattern of wave heating due to the complicated wave breaking process and current system. In general, the magnitude of the generated internal energy or temperature by dissipation of breaking wave energy in the surf zone is relatively small. The present study shows that the generated water temperature is in the order of 10^-3 Kelvin for wave breaking over a typical coastal beach.

Exactness of measured/predicted temperature distributions for heat generation in arbitrary non-variable cross-section bar using entropy generation method

• A novel application of second law of thermodynamics. • Usable for validation purposes in every study which involves heat transfer. • Presenting a unique value of non-dimensional total entropy generation rate. • Investigating the effect of cross sectional geometry on lost work. The purpose of the present study is to introduce the entropy generation method as a new validation tool of numerical and experimental studies in the heat transfer field where there exist no similar solutions with which to compare results. Analysis of temperature profiles has been conducted in bars with internal thermal energy generation, constant temperature boundary condition and arbitrary non-variable cross section. The bars have steady state Fourier heat conduction and uniform thermal energy generation. The total rate of entropy generation can be calculated using two different methods: The 1st method is based on integrating local entropy generation rate on the solution domain, and the 2nd one is based on the thermodynamic definition of entropy and the Clausius theorem. The equality of these two results depends on the exactness of the applied temperature profile. The closer the entropy generation rates in the control volume (EGRCVs), the more accurate the predicted temperature profile would be and thus, the obtained results are more reliable. Seven different geometries have been examined for the bar cross section and a correlation between error of temperature distribution and error of entropy generation has been obtained. Moreover, the effect of the cross section geometry on entropy generation has been studied and the distribution of local entropy generation rate for the selected geometries was plotted.

Effect of variable thermal conductivity on entropy generation in a plate with internal energy generation

The current numerical investigation aims at analyzing the effect of variable thermal conductivity on local and global entropy generation rates in an energy generating plate dissipating heat by conjugate conduction-forced convection heat transfer. In order to fulfill this objective, the physical model of the plate dissipating heat into surrounding coolant is transformed into a mathematical model governing the temperature field in the plate as well as flow and thermal fields in the fluid. The resulting mathematical model, being a set of coupled and non linear partial differential equations, is solved by adopting stream function-vorticity formulation and by employing Alternating direction implicit scheme. Keeping Prandtl number of the fluid, temperature of the free stream coolant and maximum permissible plate temperature as fixed, numerical predictions are obtained for wide range of values of aspect ratio, conduction-convection parameter, energy generation parameter and flow Reynolds number. It is concluded that unrealistic constant thermal conductivity assumption leads to underestimation of entropy generation rates. It is also found that an increase in energy generation parameter results in significant increase in underestimation of global entropy generation rate.

Effect of variable thermal conductivity on entropy generation in a plate with internal energy generation

The current numerical investigation aims at analyzing the effect of variable thermal conductivity on local and global entropy generation rates in an energy generating plate dissipating heat by conjugate conduction-forced convection heat transfer. In order to fulfill this objective, the physical model of the plate dissipating heat into surrounding coolant is transformed into a mathematical model governing the temperature field in the plate as well as flow and thermal fields in the fluid. The resulting mathematical model, being a set of coupled and non linear partial differential equations, is solved by adopting stream function-vorticity formulation and by employing Alternating direction implicit scheme. Keeping Prandtl number of the fluid, temperature of the free stream coolant and maximum permissible plate temperature as fixed, numerical predictions are obtained for wide range of values of aspect ratio, conduction-convection parameter, energy generation parameter and flow Reynolds number. It is concluded that unrealistic constant thermal conductivity assumption leads to underestimation of entropy generation rates. It is also found that an increase in energy generation parameter results in significant increase in underestimation of global entropy generation rate.

Numerical investigation of Prandtl number effect on heat transfer and fluid flow characteristics of a nuclear fuel element

This paper investigates the heat transfer and fluid flow characteristics of liquid metal coolants (such as Sodium, Sodium potassium, Bismuth, Lead, and Lead–bismuth) flowing over a nuclear fuel element having non-uniform internal energy generation numerically using finite difference method. The Full Navier Stokes Equations governing the flow were converted into stream function-Vorticity form and solved simultaneously along with energy equation using central finite difference scheme. For the two dimensional steady state heat conduction and Stream-Function Equation, the discretization was done in the form suitable to solve using ‘Line-by-Line Gauss-Seidel’ solution technique whereas the discretization of Vorticity transport and energy equations were done using Alternating Direction Implicit (ADI) scheme. After discretization the systems of equations were solved using ‘Thomas Algorithm’. The complete task was done by writing a computer code. The results were obtained in the form of variation of Maximum temperature in the fuel element (hot spots) and its location, mean coolant temperature at the exit .The parameters considered for the study were aspect ratio of fuel element, Ar, conduction-convection parameter Ncc, total energy generation parameter Qt, and flow Reynolds number ReH. The results obtained can be used to minimize the Maximum temperature in the fuel element (hot spots).

Passivity analysis of linear physical systems with internal energy sources modelled by bond graphs

Integrated dynamic systems such as mechatronic or control systems generally contain passive elements and internal energy sources that are appropriately modulated to perform the desired dynamic actions. The overall passivity of such systems is a useful property that relates to the stability and the safety of the system, in the sense that the maximum net amount of energy that the system can impart to the environment is limited by its initial state. In this paper, conditions under which a physical system containing internal modulated sources is globally passive are investigated using bond graph modelling techniques. For the class of systems under consideration, bond graph models include power bonds and active (signals) bonds modulating embedded energy sources, so that the continuity of power (or energy conservation) in the junction structure is not satisfied. For the purpose of the analysis, a so-called bond graph pseudo-junction structure is proposed as an alternative representation for linear time-invariant (LTI) bond graph models with internal modulated sources. The pseudo-junction structure highlights the existence of a multiport coupled resistive field involving the modulation gains of the internal sources and the parameters of dissipative elements, therefore implicitly realizing the balance of internal energy generation and dissipation. Moreover, it can be regarded as consisting of an inner structure which satisfies the continuity of power, and an outer structure in which a power scaling is performed in relation with the dissipative field. The associated multiport coupled resistive field constitutive equations can then be used to determine the passivity property of the overall system. The paper focuses on systems interconnected in cascade (with no loading effect) or in closed-loop configurations which are common in control systems.

The influence of welding processes on the weld strength of flame-retardant materials

Due to continually rising fire-safety standards, the use of plastics containing flame-retardant additives has increased strongly in recent years and is continuing to increase. The flame-retardant reaction of these materials prevents flames and the associated thermal energy from using the polymer as a source of flammable material, thus suppressing and slowing the spread of the flames. This, however, works (so to speak) against the energy needed to melt the polymer, which in turn can cause a reduction in weld strength. In this study, the behavior of flame-retardant plastics is examined for the four standard welding processes hot plate welding, vibration welding, ultrasonic welding, and laser welding. During the experiments, both a halogen and a nitric flame retardant are investigated in Polyamide 6.6, Polyamide 6, and polybutylene terephthalate, and their effect on weld strength was determined. It transpired that the activation of the flame retardant and the directly related loss of weld strength in the joint depend considerably on the welding process and its parameters. For hot plate welding, the temperature of the heated tool as well as the heating time is of considerable significance for the joint quality. Reaching a temperature above the activation temperature of the flame retardant resulted in notable reductions in weld strength, caused by the activated additive. These weld strength reductions can be to some extent held in check by suitable process parameters; in this case, there are boundary levels of activation which must not be exceeded, in order to ensure a sufficiently high joint strength. This behavior varies, however, from that shown in ultrasonic welding. Here, no activation of the flame retardant was observed, meaning that the flame-retardant additive acts only as a filler material on the joint strength. For vibration welding, there is an observable effect resulting from concentrations of flame retardant; this effect can be partially or entirely neutralized by a suitably high joining pressure, which pushes the concentrated areas into the welding bead and thus reduces or eliminates the damage to the weld itself. Laser welding leads to a high degree of activation in the flame retardant and therefore results in a significant drop in joint strength. To briefly summarize, it can be said that welding processes with external heat sources are to be more critically evaluated than processes with internal energy generation when welding flame-retardant polymers.

Two-dimensional steady-state temperature distribution of a thin circular plate due to uniform internal energy generation

This article is concerned with the determination of temperature, displacement, and thermal stresses in a thin circular plate due to uniform internal energy generation within it. The fixed circular edge (r=a) is kept at zero temperature and the upper (z=h) and lower (z=0) surfaces are thermally insulated. The governing heat conduction equation has been solved using finite Hankel transform technique. The results are obtained in a series form in terms of Bessel’s functions. The results for temperature, displacement, and stresses have been computed numerically and illustrated graphically.