Temperature Distribution Profile Research Articles

A Computational Modeling of the Influence of Different Oxy-fuel Combustion Environment on Combustion Characteristics and Particles Temporal History

ABSTRACT In the present article, CFD simulation of various oxy-fuel combustion cases has been performed to find out the influences of oxy-fuel combustion environment on temperature distribution, char consumption, radiative properties and temporal variation of particle phase variables such as particle temperature, volatile and char mass fraction. The oxy-fuel combustion cases are obtained by varying O2 and CO2 concentrations while keeping the total volume flow rate constant. Four oxy-fuel cases are considered in the present work having oxygen concentration 21%, 25%, 30%, and 35%. The present article also investigates the influence of char gasification reactions on temperature distribution, species concentration and temporal profile of particle char mass fraction. The predicted temperature distribution and radiative properties under oxy-fuel cases are compared with the corresponding values obtained under air-fired combustion as for retrofit existing power plants comparable values are desirable. The oxy-30 case having 30% oxygen has almost identical temperature and radiative profiles. With an increase in oxygen concentration in oxy-fuel cases leads to an increased peak temperature and surface incident radiation due to the rise in local stoichiometry, which results in enhanced reaction kinetics and burning rate. The peak temperature obtained in oxy-25, oxy-30 and oxy-35 cases is around 10%, 18%, and 24% higher than the oxy-21 case. Reduced char burnout time is obtained due to the presence of gasification reactions.

MHD natural convection in cadmium telluride nanofluid over a vertical cone embedded in a porous medium

An investigation for the effects of cadmium telluride (CdTe) nanoparticles on magnetohydrodynamic natural flow over a cone is considered. The cone is assumed to be in a porous medium. The effects of thermal radiation on thermal and fluid flow properties are also examined. The solution of dimensionless, coupled, nonlinear system of partial differential equations is obtained by using unconditionally stable method, namely, Crank Nicolson method combined with well known tri-diagonal Thomas algorithm. The influence of the governing parameters on features of temperature distribution and velocity profile are determined and reported graphically. The current research is more focused on CdTe nanoparticles. However, thermal boundary layer and momentum for CdTe-nanoparticles with four different nanoparticles, namely, alumina, copper, gold and silver are compared. The results show that thermal performance of ethylene glycol is higher for CdTe nanoparticles than other nanoparticles.

Primary air ratio affects coal utilization mode and NOx emission in lignite pulverized boiler

Through a previously validated numerical model, seven combustion scenarios were simulated to study the effects of primary air ratio (PAR) on coal utilization mode and NOx formation characteristics of a wall-fired lignite boiler. Distribution profiles of combustion temperature, concentration of gas components, mole fractions of NO and volatile N-intermediates were discussed. Results show that the effects of PAR on coal utilization mode, i.e. char-O2 oxidation and char-H2O gasification process, differ in two separate ranges. When PAR is slightly increased from 0.35 to 0.41, char-O2 oxidation deteriorates in the lower furnace region while char-H2O gasification is enhanced. However, when PAR is largely increased from 0.44 to 0.53, char-O2 oxidation behavior gets re-improved but char-H2O gasification becomes weaker. Besides, NOx emission at the furnace exit rises monotonously with PAR increasing. Variation of coal utilization mode is attributed to the changes of mixing process between coal particles and secondary air, while the increase of NOx emission is ascribed to the increased initial oxygen around coal particles. The results thoroughly reveal the influence of air distribution between primary and secondary air on coal utilization process and NOx-related characteristics, which can be used as theoretical guidance for the practical operation of lignite-fired boilers.

Nanosecond Pulsed Laser Ablation on Stainless Steel − Combining Finite Element Modeling and Experimental Work

In the present work, finite element simulations to investigate nanosecond pulsed laser ablation of stainless steel under low laser fluence conditions is performed. The laser has a wavelength of 1064 nm as well as a Gaussian spatial and temporal energy distribution. The utilized model of heat transfer consists of thermal conduction, thermal convection, and thermal irradiation. Temperature‐dependent material's properties including absorptivity and the instantaneous material removal by evaporation are considered. Corresponding laser ablation experiments on stainless steel are also conducted, demonstrating good agreement in the widths of the evaporated area and the heat affected zone obtained by simulation results. The 2D simulation results of single pulse laser ablation demonstrate that low laser fluences ranging from 26.53 to 46.42 J cm−2 have a significant impact on both temperature distribution and material removal profile. Particularly for the width of the evaporated area, the maximum deviation of predicted values from experimental results is smaller than 10%. The 3D simulation results of groove texturing using multiple laser pulses also shows an excellent agreement with the experimental work in terms of the resulting groove morphology.

Thermoplasmonic of Single Au@SiO2 and SiO2@Au Core Shell Nanoparticles in Deionized Water and Poly-vinylpyrrolidoneMatrix

Metal nanoparticles can serve as an efficient nano-heat source with confinement photothermal effects. Thermo-plasmonic technology allows researchers to control the temperature at a nanoscale due to the possibility of precise light propagation. The response of opto-thermal generation of single gold-silica core-shell nanoparticle immersed in water and Poly-vinylpyrrolidone surrounding media is theoretically investigated. Two lasers (CW and fs pulses) at the plasmonic resonance (532 nm) are utilized. For this purpose, finite element method is used via COMSOL multiphysics to find a numerical computation of absorption cross section for the proposed core –shell NP in different media. Thermo-plasmonic response for both lasers is studied. The heat profile of different nanostructures is estimated. The results revealed that the temperature distribution profile was varied due to changing in the relative volume fraction between the core and the shell of nanoparticle.

Thermoplasmonic of Single Au@SiO2 and SiO2@Au Core Shell Nanoparticles in Deionized Water and Poly-vinylpyrrolidoneMatrix

Metal nanoparticles can serve as an efficient nano-heat source with confinement photothermal effects. Thermo-plasmonic technology allows researchers to control the temperature at a nanoscale due to the possibility of precise light propagation. The response of opto-thermal generation of single gold-silica core-shell nanoparticle immersed in water and Poly-vinylpyrrolidone surrounding media is theoretically investigated. Two lasers (CW and fs pulses) at the plasmonic resonance (532 nm) are utilized. For this purpose, finite element method is used via COMSOL multiphysics to find a numerical computation of absorption cross section for the proposed core –shell NP in different media. Thermo-plasmonic response for both lasers is studied. The heat profile of different nanostructures is estimated. The results revealed that the temperature distribution profile was varied due to changing in the relative volume fraction between the core and the shell of nanoparticle.

Study on Solar Air Collector with Perforated Strips in the Baffles

In this paper, a three-dimensional study of incompressible turbulent flow through a canal of a solar air collector has been carried out. The canal is provided with two solid baffles in the first case and two perforated baffles in the second case fixed on the absorber and the insulator. The models of the perforations are in the forms of perforated strips in the baffles and they have a diameter of d=0.005m; their number is 12 per baffle. The working fluid used is air. The form and the position of its perforations allow the creation of secondary flows with the orientation of the flow towards the absorber. The numerical resolution of the transport equations is carried out by using the finite volume method and the k-( turbulent model. The results are compared with experimental data. The evolution of axial velocity fields, the pressure coefficients fields, the friction coefficients profiles, the local Nusselt numbers profiles and the temperature distribution profiles are discussed in this work.

Heat transfer performance of a novel tubular oscillating heat pipe with sintered copper particles inside flat-plate evaporator and high-power LED heat sink application

Abstract A novel tubular oscillating heat pipe (OHP) with sintered copper particles (SCPs) inside a flat-plate evaporator for the thermal management of high-power LED chips was designed and fabricated. The thermal performance of designed OHP, temperature distribution and illumination profiles of LED array were experimentally tested and evaluated. Results showed that the addition of SCPs on the evaporator of OHP can facilitate the startup and make oscillating motions of liquid-plugs/vapor-bubbles inside copper tubes more easily. A lowest thermal resistance of 0.168 K/W was achieved by the OHP with SCPs when the input power to the LED array was 60 W, and the corresponding maximum LED temperature can be controlled below 70 °C. The temperature distribution of LED array at different inclination angles was almost coincident and achieved good uniformity if the designed OHP was operated at low filling ratios, indicating that the gravity action can be partially neglected. It was also found that the temperature of LED array was inversely proportional to the illumination intensity, and a high filling ratio can cause the degradation of illumination intensity of LED chips. A low filling ratio of 30% was preferred for the designed OHP applied in high-power LED cooling.

Microscale Temperature Shaping Using Spatial Light Modulation on Gold Nanoparticles

Heating on the microscale using focused lasers gave rise to recent applications, e.g., in biomedicine, biology and microfluidics, especially using gold nanoparticles as efficient nanoabsorbers of light. However, such an approach naturally leads to nonuniform, Gaussian-like temperature distributions due to the diffusive nature of heat. Here, we report on an experimental means to generate arbitrary distributions of temperature profiles on the micrometric scale (e.g. uniform, linear, parabolic, etc) consisting in illuminating a uniform gold nanoparticle distribution on a planar substrate using spatially contrasted laser beams, shaped using a spatial light modulator (SLM). We explain how to compute the light pattern and the SLM interferogram to achieve the desired temperature distribution, and demonstrate the approach by carrying out temperature measurements using quantitative wavefront sensing.

Numerical modeling of Flux assisted Gas Tungsten Arc Welding (F-GTAW) process of Duplex Stainless Steel (DSS)

A three dimensional transient Finite Element Model (FEM) of Flux assisted Gas Tungsten Arc Welding (F-GTAW) to predict the temperature cycle at the weld lineof Duplex Stainless Steel (DSS2205) is proposed in this study using gaussian moving source. Theproposed finite element model is validated using theexperimental results published in the literature. The temperature history plot obtained from the FEM is compared with the experimental data. The results shows that the peak temperature value at a surface node of the FEM is matching with the maximum temperature obtained at the surface of the weld. The proposedmodel has the capability to predict the temperature history of the entire welding cycle. The temperature distribution profile obtained from the FEM of F-GTAW is also compared with the conventional GTAW model. The proposed FEM model has been developed using Ansys software.

The temperature effect of the muon component observed on A.I. Kuzmin cosmic ray spectrograph in Yakutsk

An estimation and accounting of a temperature effect in data of the complex of muon detectors of the Yakutsk cosmic ray spectrograph after A.I. Kuzmin are carried out. The results of determination of altitudinal distribution of the temperature from the database of world network of muon telescopes (MDDB), which are obtained using a model of the atmosphere developed in the National Centers for Environmental Prediction NCEP, are used. It is shown, that the vertical profiles of temperature distribution in the atmosphere that are presented in MDDB and the estimated temperature coefficients are allow qualitatively exclude the temperature effect from the data of registration of the muon component of secondary cosmic rays. The results of observation of the Yakutsk spectrograph and accounting of the temperature effect are presented in the Internet through the link http://www.ysn.ru/ipm.

Pore-level modeling of effective longitudinal thermal dispersion in non-isothermal flows through granular porous media

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.

Experimental and simulation studies of heat transfer in high-humidity hot air impingement blanching (HHAIB) of carrot

A mathematical model was presented to characterise heat transfer in high-humidity hot air impingement blanching (HHAIB) of cuboid carrots. The model accounts for condensation heat transfer and predicts the sample’s core temperature evolution with time. The simulation was performed at different relative humidity of 20%, 40%, 60%, 80% with constant temperature of 383K. Results showed that the heat transfer process of HHAIB is divided into two stages based on vapor–liquid phase transition, namely a condensing heat transfer segment and a non-condensing heat transfer segment. In the initial stage of HHAIB, a comprehensive and intense condensation occurred on the sample surface leading to high heat transfer coefficient and greatly enhancing heat transfer, but at the same time creating a huge temperature gradient in the sample. The relative humidity of 40%–60% at 383K could not only enhance the heat transfer rate but also improve the homogeneity of temperature distribution in the sample. Simulated core temperatures were compared with experimental measurements, showing good agreement with a coefficient of determination R2 of 0.991. The findings of current work provide theoretical basis to better design and control of the process conditions of HHAIB as it elucidates the heat transfer characteristic taking account condensation phenomenon and illustrates the temperature distribution and evolution profiles.

Impacts of Anthropogenic Aerosols on Fog in North China Plain

AbstractFog poses a severe environmental problem in the North China Plain, China, which has been witnessing increases in anthropogenic emission since the early 1980s. This work first uses the WRF/Chem model coupled with the local anthropogenic emissions to simulate and evaluate a severe fog event occurring in North China Plain. Comparison of the simulations against observations shows that WRF/Chem well reproduces the general features of temporal evolution of PM2.5 mass concentration, fog spatial distribution, visibility, and vertical profiles of temperature, water vapor content, and relative humidity in the planetary boundary layer throughout the whole period of the fog event. Sensitivity studies are then performed with five different levels of anthropogenic emission as model inputs to systematically examine the comprehensive impacts of aerosols on fog microphysical, macrophysical, radiative, and dynamical properties. The results show that as aerosol concentration increases, fog droplet number concentration and liquid water content all increase nonlinearly; but effective radius decreases. Macrophysical properties (fog fraction, fog duration, fog height, and liquid water path) also increase nonlinearly with increasing aerosol concentration, with rates of changes smaller than microphysical properties. Further analysis reveals distinct aerosol effects on thermodynamic and dynamical conditions during different stages of fog evolution: increasing aerosols invigorate fog formation and development by enhancing longwave‐induced instability, fog droplet condensation accompanying latent heat release, and thus turbulence, but delay fog dissipation by reducing surface solar radiation, surface sensible, and latent heat fluxes, and thus suppressing turbulence during the dissipation stage.

Thermo-Mechanical Stress Simulation of Unconstrained Region of Straight X20 Steam Pipe

Abstract The thermo-mechanical stress, strain and temperature distribution across the thickness of X20 steam pipe at region less susceptible to thermo-mechanical failure was simulated using finite element analysis software, Abaqus. The mesh convergence studies conducted showed that 10 mm mesh size was suitable for the simulation. The temperature distribution profile across the thickness of Pyrogel showed that pyrogel is an excellent insulation jacket for steam pipes. The maximum stress value obtained from the simulation shows that the pipe is operating below the yield strength of X20 steel at the region under study. Hence, the pipe’s failure at this region due to thermo-mechanical stress or strain only is practically impossible over a long period of time. A deviation of 0.5% was found to exist between the analytical and simulated stress value obtained. This indicates a strong correlation between the simulated and analytical stress results.

Thermal Optimization for Al12SiMg with Influence of Magnesium Oxide Particulate Composites

Abstract The current study engross on the effect of thermal behavior in the Al alloys of Al12SiMg with MgO particulate metal matrix composites. The casting of Al-12Si alloy and its composites were developed using liquid metallurgy technique by an amount 2 to 10% volume fraction by steps of two of particulate of magnesium oxide reinforcements. Thermo mechanical analyzer is used to establish the coefficient thermal expansion of Al-12Si with magnesium oxide composites using an instrument as per ASTME-831-34(TMA400).Through this numerical investigation, we estimated the temperature distribution profiles by finite element program (ANSYS) for different composition of composites. The 3-D solid element is used to create model and meshed nodes are integrates with temperatures upto5000c to magnify the thermal capability of alloy and its composites. These results of theoretical and analytical studies are reasonably harmony with experimental approach.

The effect of operating parameters on regeneration characteristics and particulate emission characteristics of diesel particulate filters

Due to stringent emission standards, diesel particulate filter (DPF) is used to reduce and control particulate matter (PM) emissions for engine manufacturers. The periodical regeneration the DPF by oxidizing the accumulated PM is able to avoid pressure drop build-up and fuel efficiency decrease. This paper discusses the influence of regeneration temperature, regeneration flow rate and regeneration time on both regeneration and emission performance by regeneration test bench. From the temperature distribution profiles, the maximum temperatures were achieved at rear and center part of DPF in all the regeneration tests. When the regeneration temperature was higher than 525 °C, it was benefit to emit the large diameter particles. Increasing the flow rate had negative effect for the maximum temperature, maximum temperature gradient, and regeneration performance ratio. The trends for regeneration efficiency, total mass concentration and emitted particle average diameter were similar under different regeneration flow rates. Increasing regeneration time was benefit for improving regeneration efficiency, but it had negative effect for the performance ratio. The optimization active regeneration operating parameters were achieved after considering both regeneration and emission characteristics.

A CFD based comprehensive study of coal-fired updraft gasifier in ceramic industry

Coal is the most versatile conventional fuel which was used for many years by human beings for domestic purpose, in heavy industries and power plants. Particular in the ceramic industry, heating requirements have been satisfied by coal. Gasification of coal is the promising and convenient technology of converting the coal into synthesis gas which is a mixture of many combustible species. Gasifier used in present study was updraft type coal-fired gasifier which has been used by ceramic industries of Morbi (India). Experimental works have been carried out for various values of equivalence ratio (E.R.) from 0.24 to 0.36 and for specified boundary conditions. Also, numerical simulations have been compared with experimental works for the same E.R. values and boundary conditions. ANSYS Fluent software has been used to carry out numerical modeling and simulation. For coal-fired gasifier, Euler-Lagrange approach has been used for numerical modeling. The temperature distribution profile on gasifier wall has been compared with experimental and numerical data and it shows good agreement. Optimum E.R. for best syngas quality for Indonesian bituminous type coal was found as 0.28. Syngas composition has been determined at E.R. 0.28 with CO as 23.6 mol%, CO2 as 7.9 mol%, H2 as 19.6 mol%, H2O as 4.8 mol% and CH4 as 0.3 mol%. Carbon Convergence (C.C.) and Cold Gas Efficiency (C.G.E.) have also been determined in the present study with maximum values C.C. as 97.4% and C.G.E. as 87.5%. Also, the effect of steam/air ratio for E.R. 0.28 has been determined. The increment in steam/air ratio improves hydrogen production but resists overall gasification process.

Sensitivity Studies of the Red Sea Eddies Using Adjoint Method

AbstractAdjoint sensitivity analysis is applied to a set of eddies in the Red Sea using a high‐resolution Massachusetts Institute of Technology general circulation model and its adjoint model. Previous studies have reported several eddy events in the Red Sea, namely, a dipole captured on 17 August 2001 in the southern Red Sea, a cyclonic eddy in November 2011 in the northern Red Sea, and an anticyclonic eddy in April 2010 in the central Red Sea. Sensitivity analysis is applied here to investigate the governing factors that control the intensity and evolution of these eddies. The eddies are first reproduced by running the Massachusetts Institute of Technology general circulation model forward and their sensitivities to external atmospheric forcing and previous model states are then computed using the adjoint model. In the experiments, (relative) surface vorticity (curl of horizontal velocity) is defined as the objective function. The contributions of forcings and model states are quantified and investigated. The sensitivities to external forcings are distinct in different eddy events. The dipole in the central Red Sea is dominantly sensitive to the cross‐basin eastward wind jet. The anticyclonic eddy in the central Red Sea is most sensitive to the along‐basin wind stress. The cyclonic eddy in the northern Red Sea is sensitive to the net heat flux and to surface elevation perturbations even from the remote southern Red Sea, which is attributed to the propagation of baroclinic Kelvin waves along the coast. Analysis of the sensitivity to model state variables suggests that these eddies are also modulated by the boundary currents and the temperature profile distributions.

Sensitivity study of hardness profile of 4340 steel disc hardened by induction according to machine parameters and geometrical factors

An adequate induction heat treatment operation should always identify, previously, the probable temperature distribution and hardness profile behavior in specific regions of the treated component according to heating process parameters. This paper presents an analysis of the effects of some geometrical factor related to the component and the coil and machine parameters on temperature distribution and case depth of an AISI 4340 low-alloy steel disc heated by induction. A Comsol model was created, defined as a group of process parameters followed by a mesh study. A Matlab algorithm coupled to the simulation model was designed to handle a large number of simulations and export temperature profile data. The case depth is then interpolated from collected temperature data and a statistical analysis was developed to create the hardness prediction model. The experimental tests conducted under the same process parameters support the numerical model results and approve the simulation, the prediction modeling, and the statistical study.