This work investigates the heat transfer characteristics of particle clusters under the effects of the complex properties of supercritical water(SCW).It analyzes the heat transfer characteristics of sub-particles and ...
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This work investigates the heat transfer characteristics of particle clusters under the effects of the complex properties of supercritical water(SCW).It analyzes the heat transfer characteristics of sub-particles and the average heat transfer characteristics of particle *** results reveal a phenomenon of shifting positions of high specific heat *** led to variations in the dimensionless heat transfer coefficient ***,the results indicate that as the heat transfer process strengthens,the effects of variations in property distribution on heat transfer tends to *** on this conclusion,the effects of variations in property distribution on heat transfer are categorized into Stable Effects Region and Non-Stable Effects *** utilizing the principles of fluid flow-heat transfer coupling and similarity,a heat transfer prediction model for particle clusters in SCW is established.
In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical *** Shear Stress Transport(SST)k-ωmode...
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In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical *** Shear Stress Transport(SST)k-ωmodel was adopted for describing *** operating parameters are chosen according to a 660 MW ultra-supercritical CFB *** heat transfer performances under different operating parameters,such as boiler load,flow direction and heat flux distribution are *** temperature and heat flux on inner wall varies along the circumference and show symmetric *** overall heat transfer performances at each cross section are better than the local heat transfer performance of midpoint of heating *** direction has a great influence on heat transfer performance;it changes the radial distribution of axial velocity and then affects the turbulence ***,upward flow condition shows a better heat transfer *** heat flux improves both the overall and local heat transfer *** the heat flux area is not conducive to the overall heat transfer,but does not affect the local heat transfer at the midpoint of heating ***,a new correlation is fitted based on the simulated results of supercritical water heat transfer with circumferential non-uniform heat flux distributions.
Cold-end systems are heat sinks of thermal power cycles,which have an essential effect on the overall performance of thermal power *** enhance the efficiency of thermal power plants,multi-pressure condensers have been...
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Cold-end systems are heat sinks of thermal power cycles,which have an essential effect on the overall performance of thermal power *** enhance the efficiency of thermal power plants,multi-pressure condensers have been applied in some large-capacity thermal power ***,little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be ***,the design optimization methods of coldend systems with single-and multi-pressure condensers are developed based on the entropy generation rate,and the genetic algorithm(GA)is used to optimize multiple *** parameters,including heat transfer area of multi-pressure condensers,steam distribution in condensers,and cooling water mass flow rate,are optimized while considering detailed entropy generation rate of the cold-end *** results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is ***,the economic performance can be improved with the adoption of the multi-pressure cold-end *** compared with the single-pressure cold-end system,the excess revenues gained by using dual-and quadruplepressure cold-end systems are 575 and 580 k$/a,respectively.
Bunsen burner is a typical geometry for investigating the turbulence-flame *** most experimental studies,only turbulence intensity u′and integral scale l0 are used to characterize the turbulent flow field,regardless ...
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Bunsen burner is a typical geometry for investigating the turbulence-flame *** most experimental studies,only turbulence intensity u′and integral scale l0 are used to characterize the turbulent flow field,regardless of the perforation geometry of perforated ***,since the geometry influences the developing process and vortex broken,the plate geometry has to be considered when discussing the flame-turbulence *** order to investigate conditions at the same l0 and u′using different geometries,large eddy simulation of CH_(4)/air flames with dynamic TF combustion model was *** model validation shows good agreement between Large Eddy Simulation(LES)and experimental *** the non-reacting flows,the Vortex Stretching of circular-perforated plate condition is always larger than that of slot-perforated plate condition,which comes from the stresses in the flow fields to stretch the vorticity *** reacting flows,at the root of the flame,the Vortex Stretching plays a major role,and the total vorticity here of circular-perforated plate condition is still larger(53.8%and 300%larger than that of the slot-perforated plate at x/D=0 and x/D=2.5,respectively).More small-scale vortex in circular-perforated plate condition can affect and wrinkle the flame front to increase the Probability Density Function(PDF)at large *** 3D curvature distributions of both cases bias to negative *** negative trend of curvatures at the instant flame front results from the Dilatation ***,the value of the Vortex Stretching and the Dilatation at the flame front of circular-perforated plate condition is obviously larger.
Objective Port-wine stains (PWS) are congenital vascular malformations caused by the abnormal dilation of capillaries and venules in the skin. Affecting 0.3%‒0.5% of newborns, PWS typically manifest as pinkish patches...
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Objective Port-wine stains (PWS) are congenital vascular malformations caused by the abnormal dilation of capillaries and venules in the skin. Affecting 0.3%‒0.5% of newborns, PWS typically manifest as pinkish patches on the face and neck that darken and thicken over time, significantly impacting patients’physical and mental well-being. Pulsed dye laser (PDL) therapy, based on selective photothermolysis, is the gold standard for PWS treatment. By targeting hemoglobin in abnormal blood vessels with specific wavelengths, PDL induces thermal damage to the vasculature while sparing surrounding tissues. However, due to variability in skin types, lesion depths, and laser parameters, clinical outcomes often depend on subjective evaluations and physician experience. These limitations underscore the urgent need for objective, quantitative, and noninvasive methods to assess skin structure and monitor treatment efficacy. This study integrates reflectance spectroscopy with an inverse Monte Carlo radiation method to quantify changes in key skin parameters before and after laser treatment. By measuring and reconstructing parameters such as epidermal thickness, melanin volume fraction, blood volume fraction, and blood oxygen saturation, this study establishes a robust framework for evaluating treatment outcomes and optimizing laser parameters. Additionally, it investigates differences in treatment responses between pediatric and adult patients, providing critical insights for personalized therapeutic strategies. Methods Eleven patients with PWS underwent pulsed dye laser (PDL) therapy at a wavelength of 595 nm, with an energy density of 8 J/cm2 and a fixed spot diameter of 7 mm. Reflectance spectra of the skin were measured before and after treatment using an HR400 CG-UV-NIR spectrometer (Fig. 1.. To enhance efficacy, a double-irradiation strategy was employed, in which the second laser exposure followed the first after five minutes. For spectral analysis, an inverse Monte Carlo r
Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst *** performance of the catalysts was tested to study the effect of suppor...
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Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst *** performance of the catalysts was tested to study the effect of support on Mn-based catalyst *** of the catalysts followed as Mn_(0.4)/Al>Mn_(0.2)/Al>Mn_(0.4)/Ti>Mn_(0.2)/Ti>MnO_(x)>Al_(2)O_(3)on the whole,indicating the synergism of MnO_(x)and Al_(2)O_(3)for NO catalytic *** were analyzed according to characterization *** oxygen on catalyst rather than lattice oxygen was detected as the active oxidizer for NO *** catalyst support,Al_(2)O_(3)provided more sites to carry surface adsorbed oxygen than TiO_(2),resulting in the presence of more active oxygen on Mn O_(x)/Al_(2)O_(3)than on MnO_(x)/TiO_(2).Moreover,MnO_(x)/Al_(2)O_(3)possessed high surface area and pore volume,which greatly benefited the adsorption of NO on catalyst and further favored the oxidation of NO by active *** these advantages helped Mn_(0.4)/Al exhibited the best catalytic efficiency.
The safe and efficient combustion of high-alkali coal under deep peaking conditions remains a critical research focus. Boiler operating parameters under such conditions frequently fluctuate, markedly though incomplete...
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The safe and efficient combustion of high-alkali coal under deep peaking conditions remains a critical research focus. Boiler operating parameters under such conditions frequently fluctuate, markedly though incompletely understood in their influence on fouling and slagging, necessitating further investigation. Here, mineral transformation and ash fusion characteristics during high-alkali coal combustion in the main combustion zone were simulated through thermodynamic equilibrium calculations, addressing its fouling issues under deep peaking conditions. Variable loads were decomposed into distinct factors for analysis due to challenges of direct simulation. Additionally, the plasma ashing method was employed to prepare ash samples. High-alkali coals with distinct properties exhibit significant variations in mineral distribution, elemental evolution, ash fusion temperature, and viscosity. Abundant fayalite (Fe2SiO4) was observed in Hongshaquan (HSQ) coal, forming stable mineral phases with other components. In Shaerhu (SEH) coal, sodium primarily exists in the gaseous phase at high temperatures, significantly contributing to fouling. Meanwhile, Jiangjunmiao (JJM) and Wucaiwan (WCW) coals demonstrate limited mineral phases but higher ash fusion temperatures, with over 30 % of iron in the gaseous phase. The mineral transformation and ash fusion behaviors in various local combustion atmospheres follow consistent trends. The formations of gaseous sodium hydroxide (NaOH(g)) and sodium oxide in the slag phase (Na2O(slag)) are promoted with weakening reducing atmospheres, while total gaseous sodium content decreases. The slag phases of calcium, magnesium, and iron increase, accompanied by a decline in ash viscosity. However, unburned carbon inversely influences mineral transformation and ash fusion characteristics compared to excess air coefficients. This research provides theoretical support for overcoming the key technical challenges associated with high-alkali coal combus
The methanation of CO 2 and supercritical CO 2 (scCO 2 ) fracturing represent effective approaches for CO 2 utilization and greenhouse effect mitigation. In these process, light gases like H 2 , O 2 , CO, CH 4 are com...
The methanation of CO 2 and supercritical CO 2 (scCO 2 ) fracturing represent effective approaches for CO 2 utilization and greenhouse effect mitigation. In these process, light gases like H 2 , O 2 , CO, CH 4 are commonly involved. However, limited studies have focused on the diffusion behavior of these gases in scCO 2 under high-pressure conditions, as well as a shortage of self-diffusion coefficient data and prediction equations specifically designed for scCO 2 solvents. To address this gap, molecular dynamics (MD) simulations were employed to compute the self-diffusion coefficients of several light gases in scCO 2 across a wide temperature range (31. K–71. K) and at high pressures (75.994 bar, 1.1.325 bar and 1.6.656 bar) under infinitely dilute conditions. The effects of temperature, density, viscosity, molecular mass, and solute–solvent interaction energy on the self-diffusion behavior were systematically analyzed. Two empirical equations (a Speedy–Angell-type power-law equation and a newly developed equation incorporating temperature, density, and viscosity) were refitted based on simulation data. The overall relative errors are 4.52% and 4.44%, respectively, indicating an improved accuracy compared to conventional experimental and MD-based empirical equations.
The transient two-fluid model has been used to develop a general relation for acoustic waves. The analysis is valid in principle over the whole void fraction region. flow pattern transitions from one flow regime to th...
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The transient two-fluid model has been used to develop a general relation for acoustic waves. The analysis is valid in principle over the whole void fraction region. flow pattern transitions from one flow regime to the other are assumed to occur at certain void fractions. Different correlations are used to calculate the interfacial area and interfacial drag force per unit mixture volume for bubbly flow,slug flow and annular flow respectively. The Vapour-liquid interphase heat flux is derived from the one dimensional Fourier heat conduction equation to evaluate the interphase evaporation or condensatior *** on the present theory, a program has been carried out. Calculations are performed for pressure from 0.07 MPa to 1..0 MPa, void fractions from 0.0 to 1.0. The predicted sound speeds are compare with some experimental data for low pressures, good agreement has been achieved between sound speed predictions and experimental data.
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