Enhancement of Near-Field Radiative Heat Transfer based on High-Entropy Alloys

The enhancement of near-field radiative heat transfer(NFRHT)has now become one of the research hotspots in the fieldsof thermal management and imaging due to its ability to improve the performance of near-field thermoelectric devices and near-field imaging systems.In this paper,we design three structures(multilayer structure,nanoporous structure,and nanorod structure)based on high-entropy alloys to realize the enhancement of NFRHT.By combining stochastic electrodynamicsand Maxwell-Garnett's description of the effective medium,we calculate the radiative heat transfer under different parametersand find that the nanoporousstructure has the largest enhancement effect on NFRHT.The near-field heat transfer factor(q)of this structure(q=1.40×10^(9)W/(m^(2)·K))is three times higher than that of the planestructure(q=4.6×10^(8)W/(m^(2)·K)),and about two orders of magnitude higher than that of the SiO2plate.Thisresult providesa freshidea for the enhancement of NFRHT and will promote the application of high-entropy alloy materials in near-field heat radiation.

NUMERICAL MODELING OF BIOMASS GASIFICATION USING COW DUNG AS FEEDSTOCK

In this study,a biomass gasification model was developed and simulated based on Gibbs free energy minimization by using software Aspen Plus.Two reactors,RYIELD and RGIBBS,were moslty used.The biomass feedstock used was cow dung.The model was validated.The composition,H_(2)/CO ratio and low heating value(LHV)of the resulting synthetic gas(also known as syngas)was estimated by changing the operating parameters of gasification temperatures,steam and biomass ratios and pressures.Simulation results showed that increased gasification temperature helped to elevate H_(2) and CO content and H_(2) peaked at 900℃.When steam increased as the gasification agent,H_(2) production increased.However,the steam/biomass(S/B)ratio negatively affected CO and CH4,resulting in lower LHV.The optimal S/B ratio was 1.5.An increase in pressure lead to a decrease in H_(2) and CO content,so the optimal pressure for gasification was 0.1 MPa.

Effect of wet flue gas desulfurization(WFGD) on fine particle(PM_(2.5)) emission from coal-fired boilers

In this study, the characteristics of fine particles before and after wet flue gas desulfurization(WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%–56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094–0.946 μm was observed. The watersoluble ion content accounted for a very large proportion of PM_(2.5) mass, and its proportion in PM_(2.5) increased from 28.39%–41.08% to 48.96%–61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component(Ca^(2+) for unit A, Mg^(2+) for unit B, and Na+for unit C) and the proportion of SO_4^(2-) in PM_(2.5), and it increased the CE/AE values of PM_(2.5) from 0.82–0.98 to 0.93–1.27 for the three study units.

Optimal economic operation of isolated community microgrid incorporating temperature controlling devices

With the increasing connection of controllable devices to isolated community microgrid,an economic operation model of isolated community microgrid based on the temperature regulation characteristics of temperature controlling devices composed of wind turbine,micro-gas turbine,energy storage battery and heat pump is proposed.With full consideration of various economic costs,including fuel cost,start-stop cost,energy storage battery depletion expense and penalty for wind curtailment,the model is solved by hybrid particle swarm optimization(HPSO)algorithm.The optimal output of the micro-sources and total operating cost of the system in the scheduling cycle are also obtained.The case study demonstrates that temperature adjustment of temperature controlling devices can adjust the power load indirectly and increase the schedulability of the isolated community microgrid,and reduce the operating cost of the microgrid.