Temperature Distribution Profile Research Articles

Experimental investigation on the coal combustion in a pressurized fluidized bed

Pressurized oxy-coal combustion is considered as one of the most promising carbon capture technologies in terms of high carbon capture efficiency and low cost. However, practical operational experience with pressurized coal combustion in a fluidized bed, especially with continuous coal feeding, is still very limited. In this study, a pressurized fluidized bed combustion system was developed and a series of coal combustion experiments were carried out with continuous coal feeding under the pressures from 0.1 to 0.4 MPa. The effects of the combustion pressure and stoichiometric air coefficient on the fluidized bed combustion performances of a Chinese lignite in terms of the temperature distribution profile, apparent solid holdup, combustion efficiency, conversion ratio of carbon in coal to CO2 and ash composition were investigated. The experimental results show that an increase in pressure is beneficial to the improvement of combustion efficiency, and the positive effect of increasing stoichiometric air coefficient on the conversion ratio of carbon in coal to CO2 is more obvious with a lower combustion pressure. The bottom ash and fly ash have similar chemical compositions under different pressures. Based on the experimental data, a correlation as the functions of pressure and stoichiometric air coefficient is proposed to predict the conversion ratio of carbon in coal to CO2.

Effect of BaTiO3/CoFe2O4 micro-topological textures on the coupled static behaviour of magneto-electro-thermo-elastic beams in different thermal environment

The use of composite materials with multifunctional capabilities is an increasing requirement for structures or components where the sensory function is accompanied by the diagnosis and the actuation functions, such as autonomic, adaptive or self-sustaining systems. In this context, the present study aims to characterize the coupled response of magneto-electro-thermo-elastic (METE) beams made from Barium Titanate (BaTiO3) and Cobalt Ferric Oxide (CoFe2O4) composite having various micro-topological textures, as well as their static response when submitted to different temperature distribution profiles. To this purpose, a three-dimensional finite element accounting for the coupling between the multiple physical fields in presence, is developed and implemented. The spatial heterogeneous BaTiO3/CoFe2O4 microstructure is also assessed by considering typical Body Centered Cubic (BCC), Face Centered Cubic (FCC) and Simple Cubic (SC) spatial packing arrangements. A special attention is paid to the influence of these micro-topological structures on the pyroeffects and its contribution towards the direct and derived quantities of the METE beam. The results obtained, suggest that the composite heterogeneous microstructure have a relevant influence on the static response of the METE beam in thermal environment.

Effects of post combustion temperature on the wear of the supersonic nozzles in BOF lance tip

Abstract This paper studies the influence of post-combustion on supersonic lance tip nozzles wear for an 80t converter, using CFD (Computational Fluid Dynamics) simulations. These analyses were based on flow profile determination of supersonic jet at minimum and maximum operation flow rates, where it could be verified post-combustion inside the nozzles at lowest flow rates. Additionally, thermal input generated by post-combustion was exported as heat flow in order to serve as a boundary condition in CFD thermal exchange simulations, also considering nozzle internal cooling. With these simulations, it was shown that copper actually reaches its melting point, at which the lowest operating flow allows post-combustion inside the nozzle. The temperature distribution profiles and the high temperatures found were also relevant for a considerable grain growth found in the wear region, according to metallographic analyses. It was thus concluded that wear occurs due to the progressive melting of copper after continuous heats with low oxygen flow rates; post-combustion inside the nozzles is the root cause for this failure.

A three-dimensional numerical model to simulate Iranian NW Sabalan geothermal system

The plan for electricity generation from north-west (NW) Sabalan geothermal field, Iran has been presented since 1994. Now construction of the first pilot plant is running with a capacity of 5 MWe in this site. A three-dimensional (3D) numerical model of fluid flow and heat transfer of the geothermal reservoir was developed using Tough2 simulator code on the basis of the updated conceptual model from the field recent data. The aim of this study was to present an updated 3D model of the geothermal reservoir in this area by taking ten deep wells data into account and validate an existing model in which the data obtained from only three wells were included. The model covers an area of 92 km2 and extends to an approximate depth of 5.11 km from the land surface. The model includes 17 horizontal layers, (AA through QQ). The thickness of the layers range between 100 m and 1000 m. The model extends from a minimum level of -1000 to a maximum level of 4110 masl. The model has 12,784 grid blocks, in total. Each layer has 752 grid blocks with horizontal dimensions of 250 m × 250 m and 500 m × 500 m. Altogether, 21 rock types were used in the model to assign different horizontal permeability values from 1.0 × 10−17 to 9.0 × 10-13 m2 based on the conceptual model. The model was first calibrated by varying the permeability, the total magnitude and location of the recharges and well bottom pressure of discharge zones. It was further validated by the profiles of temperature and pressure distribution at 10 deep exploration wells data. A close agreement was obtained between the model predictions and the measured downhole temperature and pressure data in the exploration wells. In the best-fitted model, the natural state simulation proved the presence of a high temperature upflow zone in the southern part (Below the ground, between Pads D and E). High temperature fluid at a rate of 108 kg/s and with an enthalpy of 1056.43 kJ/kg (244 °C) recharged over an area of 2.25 km2 from 36 grid blocks from the bottom layer in southern part of the field. The overall natural discharge is about 43 kg/s from hot springs which was simulated using the pressure dependent deliverability method. The results show that there is mostly one inflow of geothermal water at the level of -1000 m at southeast below the land surface between the Pad D and Pad E. The fluid flow moves upward by the fracture zones and faults toward the northwest of area. The faults NW5, NW3 and NNW2 play a major role in this system. Finally, the geothermal fluid discharging by the surface manifestations can be seen as hot springs at the land surface. This model can be used to simulate future production scenarios to evaluate the sustainability of the reservoir.

Unsteady two-dimensional flows of a nanofluid over a vertical plate with time-exponential temperature

A two dimensional natural convective flow of nanofluid over a vertical plate in the presence of time-exponential temperature has been studied analytically. We have incorporated the effects of thermophoresis and Brownian motion in the considered nanofluid model. Moreover on the boundary of plate, it is assumed that the volumetric concentration of nanoparticles is passively controlled. The non-linear coupled governing equations have been solved with the help of the modified simple function equation method. Exact expressions for the concentration, temperature and velocity distribution profile have been established. Numerical computations are carried out in order to see the influence of different physical parameters like Lewis number, Pradtl number, buoyancy ratio parameter, thermophoresis parameter and Brownian motion parameter on the volumetric concentration of nanoparticles, temperature and velocity distribution profile and results are illustrated graphically and with tables. It is found that for decreasing values of the Brownian diffusion coefficient, therefore for increasing values of the Lewis number, the values of temperature and of particles concentration decrease. The temperature decreases with Prandtl number; while the nanoparticles concentration increases with Prandtl number (the thermal diffusivity has different influence on temperature and concentration).

3d cfd simulation of combustion in furnaces using mixture gases with variable composition

In the petroleum refining industry, furnaces are key equipment because they provide the necessary heat to carry out different processes. These furnaces are designed to use natural gas as fuel, but in most cases they use a mixture of waste gases known as refinery gases (RG), which molar composition varies depending on the process in which they are generated, in most cases with high content of propane, hydrogen, propylene, among others. This is done in most cases to save energy and reduce storage cost. However, this variation in molar composition also produces a change in calorific power that can be as high as 1,200 Btu/ft3, producing alterations in the combustion process, affecting efficiency and increasing pollutant emissions. In this work, the Computational Fluid Dynamics (CFD) technique is used to simulate the combustion process in a representative segment of a typical refinery furnace using RG as fuel with 3 different molar compositions. Comparative CFD 3D simulation cases are performed to study the effect of molar composition variability in the temperature and chemical species profiles inside the furnace. The obtained results show that high contents of gases like propane, propylene or hydrogen increase the calorific power and peak temperature inside the furnace, but temperature profile distribution is less uniform. The chemical species profiles inside the furnace show that there is an increase in CO when using mixture gases with low CH4 content, which indicates that a more detailed study regarding air excess and flow is needed. The results are very important because they can be used as a tool for decision-making regarding the convenience to use or not refinery waste gases as fuels in furnaces and to stablish a starting point for a detailed study about the improvement of furnaces operation and process safety.

Experimental investigation and finite element simulation of AISI 304 during electro discharge machining

In this paper, a two-dimensional axisymmetric thermal model using finite element method (FEM) has been established for predicting the temperature distribution profile on the work piece during electro discharge machining (EDM) and obtained material removal rate (MRR) from the temperature isotherm. For prediction of MRR, the model utilizes some important features viz. size and shape of the heat source (Gaussian heat distribution), thermal properties of workpiece, amount of heat distribution among the dielectric fluid, workpiece and tool, material flushing efficiency and pulse off/on time, etc. ANSYS software was used for developing the thermal model for the single spark operation. For this investigation, AISI 304 stainless steel and tungsten carbide was used as workpiece and electrode material, respectively. A comparison study has been carried out for theoretical and experimental MRR for the effect of each process parameter viz. gap voltage, pulse on time and peak current. The temperature distribution along the radial and depth direction of the workpiece has been reported. The model was validated by comparing the theoretical MRR with the experimental MRR and found a good correlation between them.

Effect of the particle size of pulverized olive cake on combustion parameters in Stirling engine in Morocco

Morocco is one of the richest countries with olive tree. Annually, about 675,000 t of Olive Cake are produced and injected which leads to damaging the environment especially the groundwater as well as the water table itself. To remedy this problem, and because olive cake has a high caloric value, the idea of this paper comes to valorize this waste through the Stirling engine in order to produce clean energy with low greenhouse emissions.To fulfill this purpose, the impact of the particle size of pulverized olive cake (OC) on the flow behavior and combustion parameters in a 3D vertical chamber was investigated. The spherical OC particles are injected through two injectors perpendicularly to the air inlet jets. Two particle sizes are chosen to conduct this study (PS1, PS2). The numerical approach is based on Reynolds averaged Navier–Stokes (RANS) method using the realizable k–ε turbulence model. For gas phase a non-premixed combustion model is used, and for the discrete second phase a Lagrangian approach is chosen. Temperature distribution, flow topology, velocity contours, and species concentrations profiles in the burner are obtained for the two cases. Results show that the first case particle size gives optimal results and is more suitable for this study.

Process intensification of honeycomb fractal micro-reactor for the direct production of lower olefins from syngas

Inspired by the nature fractal structure, a novel honeycomb fractal micro-reactor was designed and applied to intensify both heat and mass transfer in the exothermic conversion of syngas to olefins. The results show that the honeycomb fractal micro-reactor provides more even distribution of temperature profiles, a narrower reactant residence time distribution, and relative smaller pressure drop per unit length, compared with parallel straight microchannel reactor and mini-fixed bed reactor under the same reaction conditions. Owning to the reinforcement of flow separation and convergence in the honeycomb structure, the contact between reactants and catalyst particles were enhanced, leading to a better heat and mass transfer. Under the current range of temperature, pressure and standard GHSV, the honeycomb fractal micro-reactor leads to supreme CO conversion and lower olefins yield.

Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions.

The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

Thermal analysis of TIG welded Ti-6Al-4V plates using ANSYS

The exceptional properties of Titanium push it for research activities. A perfect and efficient welding of Titanium in similar and dissimilar manner is also a difficult task for manufacturing companies. Although there are so many ways for welding of Titanium but the most reliable method is Tungsten Inert Gas Welding (TIG). This study is based on the TIG welding and main focus is on temperature distribution. The aim of the study presented in this paper is to determine the temperature distribution profile by using effective and reliable method of simulation. Simulation was performed for Titanium-G5 alloy (Ti-6Al-4V), the most commonly used alloy of titanium. The used analysis was “transient analysis”. The concept of “Moving heat source” and “element birth & death model” technique is used to simulate welding Process. An experiment was also carried out on Titanium-G5 alloy (Ti-6Al-4V) for validation of ANSYS results. In this experiment a noncontact thermal image camera was used for temperature measurement. After the experiment and simulation it was found that temperature varies inversely with welding speed.

Prevention of boiler performance degradation under large primary air ratio scenario in a 660 MW brown coal boiler

To study how to prevent the boiler performance degradation under large primary air ratio (PAR) condition, a three dimensional computational fluid dynamics model was established on the basis of a 660 MW wall-fired brown coal boiler. Accuracy of simulation models was established by carrying out a mesh independence test and a comparison with real-life data. Then it was used to investigate the effects of proposed measures on boiler performance. The distribution profiles of combustion temperature, heat flux, CO mass fraction and unburnt char particles were selected to analyze the boiler performance under different cases. Results show that boiler performance deteriorates evidently when PAR is increased to 0.425, and the overall heat flux decreases by 37.0 MW. The three proposed measures can indeed improve the boiler performance that has been deteriorated when PAR is increased, and the overall heat flux was increased by 6.42 MW, 6.59 MW and 15.53 MW respectively. Among the proposed measures, the method of closing part of secondary air nozzles is recommended in regular boiler operation, due to its operability and convenience. The findings of this research and recommended measures can be used as guidelines in the actual operation in brown coal power plant.

Verification of hybrid mixture theory based two-scale unsaturated transport processes using controlled frying experiments

Involvement of unsaturated transport and high temperatures during frying of foods makes it a challenging process to study via experiments and computer simulations. The objective of this research is to validate the hybrid mixture based unsaturated transport theory of Takhar (2014) via controlled frying experiments. A hollow Teflon disc is used to insulate the edges of potato disc to ensure that frying is controlled, one-dimensional, and oil uptake and moisture loss happen only through top and bottom surfaces. The model was used to predict moisture and oil content, evaporation rates, temperature distribution, and pore and gas pressure profiles as a function of frying time and temperature. Percentage average absolute difference (AAD) between predicted and experimental values for moisture content was 3.89%, 5.7% and 5.5% and oil content was 14%, 31% and 20% at 150, 170 and 190°C respectively. Simulations showed that oil penetrated to only 0.5mm into the potato disc. Removal of surface oil improved the prediction of experimental oil content. Maximum evaporation rate of 0.13kg/m3s was observed near the surface of potato slice at 150s frying time resulting in rapid moisture loss. Pore pressure remained negative beyond 90s frying time, which may act as a driving force for oil uptake.

Comparison of the thermo-hydraulic performance and the entropy generation rate for two types of low temperature solar collectors using CFD

In this work, a comparison of the thermo-hydraulic performance and the entropy generation rate for two different types of low temperature solar collectors: flat plate solar collector (FPC) and water-in-glass evacuated tube solar collector (ETC), is addressed. The absorber area for both solar collectors were considered to be equal for a reliable comparison. The operation of the solar collectors was simulated under different volumetric flow rates and solar radiation values for the state of Guanajuato in Mexico. The volumetric flow rate for both collectors ranged from 1 to 9 L/min. The variation of the solar radiation was based on: (1) the solar radiation taken from several experimental tests reported elsewhere, (2) the month with the lowest average solar radiation in one year, (3) the average solar radiation of one year and (4) the month with the highest average solar radiation in one year. The buoyancy effects were considered in the CFD simulations using the Boussinesq approximation (BA) model. The distribution profiles of temperature, pressure, and velocity inside the tubes of the solar collectors, along with the local entropy generation rate distribution due to heat transfer and the fluid viscosity, are shown in detail. The results show a better thermal performance for the solar water-in-glass evacuated tube collector (ETC) than for the flat plate solar collector (FPC) at low flow rates (under 3.0 L/min). The outlet temperature reached is similar in both collectors for volumetric flow rates higher than 3.0 L/min. The analysis of the entropy generation rate shows that the generation due to the transfer of heat is higher for the ETC than for the FPC, and this contribution is up to 10% of the total entropy generation rate; on the other hand, the generation rate due to the fluid viscosity is higher for the FPC than the ETC at high volumetric flow rates (above 3.5 L/min), however, this contribution is negligible. Finally, the total entropy generation rate is higher for the FPC than the ETC at low volumetric flow rates (below 3.0 L/min) and this is increased if the solar radiation increases.

A Combined Hybrid 3-D/2-D Model for Flow and Solidification Prediction during Slab Continuous Casting

A combined hybrid 3-D/2-D simulation model was developed to investigate the flow and solidification phenomena in turbulent flow and laminar flow regions during slab continuous casting (CC). The 3-D coupling model and 2-D slicing model were applied to the turbulent flow and laminar flow regions, respectively. In the simulation model, the uneven distribution of cooling water in the width direction of the strand was taken into account according to the nozzle collocation of secondary cooling zones. The results from the 3-D turbulent flow region show that the impact effect of the molten steel jet on the formation of a solidification shell is significant. The impact point is 457 mm below the meniscus, and the plug flow is formed 2442 mm below the meniscus. In the laminar flow region, grid independence tests indicate that the grids with a cell size of 10 × 10 mm2 are sufficient in simulations to attain the precise temperature distribution and solidification profile. The liquid core of the strand is not entirely uniform, and the solidification profile agrees well with the integrated distribution of cooling water in secondary cooling zones. The final solidification points are at a position of 400–500 mm in the width direction and are 17.66 m away from the meniscus.

A mathematical study of magnetohydrodynamic Casson fluid via special functions with heat and mass transfer embedded in porous plate

This article is proposed to investigate the impacts of heat and mass transfer in magnetohydrodynamic casson fluid embedded in porous medium. The generalized solutions have been traced out for the temperature distribution, mass concentration and velocity profiles under the existence and non-existence of transverse magnetic field, permeability and porosity. The corresponding solutions of temperature distribution and mass concentration, velocity profiles are expressed in terms of newly defined generalized Robotnov-Hartley function, wright function and Mittage-Leffler function respectively. All the corresponding solutions fulfill necessary conditions (initial, natural and boundary conditions) as well. Caputo Fractionalized solutions have been converted for ordinary solutions by substituting . Some similar solutions for the temperature distribution, mass concentration and velocity profiles have been particularized form generalized solutions. Owing to the rheology of problem, graphical illustrations of distinct parameters are discussed in detail by depicting figures using Mathcad software (15).

A numerical and experimental investigation of temperature field in place of anchors in ETICS system

The aim of the paper is to determine the thermal quality of recycling connectors and to assess their application effectiveness in thermal insulation systems. Four types of connectors were used, differing in the share of the added recyclate, and two different ways of their mounting were presented. The connectors used in the work were produced on the basis of polypropylene recyclate. The initial tests determined their strength and other features required for mount connectors in the ETICS systems. The article presents the results of infrared measurements for envelopes insulated with the material of different thicknesses and mounted with the use of recycling connectors. In the numerical tests (THERM program), envelope models with a thermal connector were made for the selected variants of the connector and its mounting, treating it as a point bridge. Temperature distribution profiles were determined at the places of point thermal bridges, the thermal coupling coefficient and the value of the point thermal bridge were calculated. Throughout this work, the term ‘recyclate connector’ is understood by the authors as a sleeve made from recyclate and a pressure plate.

Numerical Investigation on Magnetohydrodynamics (MHD) Free Convection Fluid Flow over a Vertical Porous Plate with induced Magnetic Field

In this paper, investigate a two dimensional unsteady Magneto hydro dynamics (MHD) free convection flow of viscous incompressible and electrically conducting fluid flow past an vertical plate in the presence of Grashof Number, Modified Grashof Number, Prandtl Number, Schamidt Number as well as Dufour effects. The governing equations of the problem contain a system of non-linear partial differential equations; have been transformed into a set of coupled non-linear ordinary differential equations which is solved numerically by applying well known explicit finite difference method. The Finite-difference method is an enormously used technique to investigate of the general non linear partial differential equation. Partial differential equations occur in many branches of applied mathematics for example, in hydrodynamics, elasticity, quantum mechanics. Hence, the proposed study is to investigate the numerical results which are performed for various physical parameters such as velocity profiles, temperature distribution and concentration profiles within the boundary layer are separately discussed in graphically.

Study on thermal field of a laser heated gemstone matrix by finite element method

This paper presents the finite element modelling of the thermal field of a gemstone matrix by laser beam local heating. By using a continuous Gaussian beam of infrared laser a 3D temperature distribution in the gemstone material in the time domain is obtained. A tetrahedral mesh is used to solve the heat conduction equation in the entire 3D-structure. A transient thermal analysis of the interaction of the laser beam with the gemstone matrix reveals the temperature distribution profile throughout the volume of the material. The temperature profile of the computational model of the gemstone is in good agreement with the experimental observations.

US: Venator – iron oxide pigments

In non-isothermal flows through porous media, the rate of heat transport across the domain and the distribution of temperature profile are strongly affected by the thermal properties of the fluid and solid phases, flow conditions, and the topological geometry of the pore structure. The combined effect of these parameters on the dynamics of heat transfer is generally characterized by the thermal dispersion coefficient. In this study, we model thermal dispersion in granular porous media using pore-scale numerical simulations. The flow and heat transport equation are solved in a porous domain at the pore-level to obtain the distribution of temperature inside the fluid phase and solid grains. The effluent temperature profile at the outlet is then fitted to the analytical solution of the macroscale heat advection-dispersion equation to determine the longitudinal component of the effective thermal dispersion tensor. Several simulation runs are carried out to investigate the effect of Peclet number, fluid to solid thermal conductivity and heat capacity ratios, and the temperature-dependent viscosity on the variation of the longitudinal thermal dispersion coefficient. The results indicate the existence of different thermal dispersion regimes separated by a threshold Peclet number. Below the threshold, thermal dispersion is dominated by conduction and longitudinal dispersion coefficient is equal to the effective thermal conductivity of the porous medium. Above the threshold, there is a transition region in which both conduction and advection are responsible for the heat ttansport. At higher Peclet numbers, dispersion regime is advection-dominated and normalized dispersion coefficient increases with the Peclet number and thermal conductivity ratio whereas it decreases with the heat capacity ratio. In this regime, the relationship between dispersion coefficient and Peclet number follows a power-law functionality with the exponent decreasing with the heat capacity ratio. To summarize the results, a characterization diagram is constructed for thermal dispersion regime based on the values of Peclet number and thermal conductivity ratio. Finally, the presence of viscous fingering due to the monotonically increasing viscosity along the flow is observed to further increase the longitudinal thermal dispersion. The outcomes of this study are of great importance in the design, implementation, and performance optimization of thermal processes in granular porous media.