In refrigerating industry,frost commonly deposits on the confined cold surfaces of heat exchangers,which affects the heat transfer *** the confined flow path of the heat exchanger,the frosting at downstream is affecte...
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In refrigerating industry,frost commonly deposits on the confined cold surfaces of heat exchangers,which affects the heat transfer *** the confined flow path of the heat exchanger,the frosting at downstream is affected by the parameters from the *** this study,a numerical model considering the confinement effect has been proposed to predict frosting characteristics in plate-fin heat ***-diffusion equations for humid air and empirical correlations for local frost density are employed in the numerical *** behavior and heat transfer in the confined channel are investigated with different humid air parameters and cold surface *** results indicate that frost thickness in the confined channel is thicker than that in open space under the same inlet *** frost layer is thicker and fluffier along the confined *** addition,the air temperature difference between inlet and outlet of the confined channel enlarges with *** the same average temperature of upper and lower surfaces,the heat and mass transfer of frosting are enhanced with diminishing temperature difference of upper and lower *** such condition,frosting is mainly influenced by the cold surface with the lower temperature.
In this paper,a novel system integrating chemical-looping hydrogen generation(CLH)system and solid oxide fuel cell(SOFC)has been *** new methane-fuelled energy system was investigated with energy balance and exergy **...
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In this paper,a novel system integrating chemical-looping hydrogen generation(CLH)system and solid oxide fuel cell(SOFC)has been *** new methane-fuelled energy system was investigated with energy balance and exergy *** produces the hydrogen as the fuel of the SOFC,and the Fe O and Fe3O4 are selected as the looping *** heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of *** to the cascade utilization of the fuel between the CLH and SOFC,the net efficiency of this novel system can achieve 62.8%considering CO_(2)separation,more than 10 percentage points higher than a methane reforming fuelled SOFC ***,by using the CLH to produce the hydrogen,the CO_(2)can be recovered without an energy *** the analysis of the graphical exergy,the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high *** novel system also has the advantage of CO_(2)capture without energy penalty,so this combined system is an advantaged method to accomplish the efficient utilization of methane.
The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been *** particular,the exp...
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The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been *** particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°*** material of the tube is *** experimental investigation,the near critical pressure CHF test data of water are *** find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is *** the experimental data,a correlation function for the CHF is established via regression and machine *** established via machine learning greatly improved the regression *** study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type *** the development of the CHF model,the friction resistance coefficient is determined according to our test *** comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type *** calculation results of the model can provide reference for the optimal design of the USCFB boiler.
Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting *** this study,a numerical model is developed to predict the spatio-temp...
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Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting *** this study,a numerical model is developed to predict the spatio-temporal frosting habits on curved surfaces in combination with the correlations of frost density and thermal *** the model,frost melting is *** verification,the frosting and heat transfer characteristics along the flow path are investigated under various structural and operating *** thickness along the path is mainly affected by the cooling surface temperature,while the heat and mass transfer rates are strongly correlated with the humidity *** proportions of latent heat and sensible heat are distributed more unevenly in parallel flow case than in counter flow *** deposition is facilitated by a smaller radius of curvature of the cooling *** uniform frosting characteristics along the path and smaller heat transfer obstruction are presented with a smaller length-to-height ratio of the flow path.
Cryogen spray cooling has been applied to protect epidermis from thermal damage in laser dermatology. However, present cryogen R134a shows insufficient cooling capacity on minimizing the laser energy absorption by the...
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*** Noble metal nanocrystals serve as exceptional catalysts across a wide spectrum of industrial processes[1].Moreover,there exists a substantial demand for noble metal catalysts in emerging clean-energy applications,...
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*** Noble metal nanocrystals serve as exceptional catalysts across a wide spectrum of industrial processes[1].Moreover,there exists a substantial demand for noble metal catalysts in emerging clean-energy applications,such as water-splitting hydrogen production and fuel *** non-noble transition metals or main-group metals into noble metal nanocrystals can reduce the weight of noble metals in the catalysts,thus remarkably lowering the ***,alloy nanocrystals offer intriguing catalytic properties that surpass those of their monometallic counterparts,thanks to the charge transfer between the constituent components and the expansion or shrinkage of the lattice size[2].
Machine learning combined with density functional theory(DFT)enables rapid exploration of catalyst descriptors space such as adsorption energy,facilitating rapid and effective catalyst ***,there is still a lack of mod...
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Machine learning combined with density functional theory(DFT)enables rapid exploration of catalyst descriptors space such as adsorption energy,facilitating rapid and effective catalyst ***,there is still a lack of models for predicting adsorption energies on oxides,due to the complexity of elemental species and the ambiguous coordination *** work proposes an active learning workflow(LeNN)founded on local electronic transfer features(e)and the principle of coordinate rotation *** accurately characterizing the electron transfer to adsorption site atoms and their surrounding geometric structures,LeNN mitigates abrupt feature changes due to different element types and clarifies coordination *** a result,it enables the prediction of^(*)H adsorption energy on binary oxide surfaces with a mean absolute error(MAE)below 0.18 ***,we incorporate local coverage(θ_(l))and leverage neutral network ensemble to establish an active learning workflow,attaining a prediction MAE below 0.2 eV for 5419 multi-^(*)H adsorption *** findings validate the universality and capability of the proposed features in predicting^(*)H adsorption energy on binary oxide surfaces.
Elbow wear, which is most likely occurring in pneumatic conveying, becomes a key factor in development of pneumatic conveying. This paper used 3D DEM-CFD to simulate the elbow wear in pneumatic conveying system. Simul...
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In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are desi...
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In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are designed by using the orthogonal design method. The Eulerian-Lagrangian formulation is employed for modeling the droplets-crossflow two-phase flow while the realizable k-ε turbulence model is used to describe the turbulence. A new index, mixedness quality, is proposed to assess the overall mixing of the droplets in the crossflow. The simulation results demonstrate that the counter-rotating vortex pair (CVP) imposes a more significant impact on the spatial distribution than on the size distribution of the droplets. Pairs of CVP with smaller scales are preferable for achieving a better mixing. The influencing factors are listed in the following order in terms of the degree of their impact from the greatest to the least: the Sauter diameter of the initial droplets, the mixing tube diameter, the spray angle, the velocity of the inlet crossflow, and the vertical velocity of the initial droplets. A moderate droplet diameter, a smaller tube diameter, a moderate spray angle, a greater crossflow velocity and a moderate vertical velocity of the droplet are favorable for achieving a higher mixedness quality of the jet spray in a confined crossflow.
The continuous growth of CO2 emissions is one of the global problems facing humanity, and how to convert and exploit the stock of CO2 has become an urgent issue. Biomass as an activity of CO2 thermal reduction medium ...
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