Numerical study of the influence of the atmospheric pressure on the thermal environment in the passenger cabin

The cabin air pressure remains lower than the horizontal atmospheric pressure when the airplane is in flight.Air pressure is one of the parameters that must be taken into consideration while studying the thermal environment of an airplane cabin.There are still no reference values for aircraft cabins despite the fact that numerous studies on low pressure heat transfer have demonstrated the connection between convective heat transfer coefficient(CHTC)and air pressure.In this paper,a correction method for CHTC under low pressure conditions was established by using the dummy heat dissipation in the low-pressure cabin experiment.On this basis,a thermal environment simulation model was developed,then was applied to the simulation of a seven-row aircraft cabin containing 42 passengers,and the CHTC and heat loss of dummy surface in the cabin were obtained.Finally,the results of PMV calculated by using heat dissipation and air parameters at sampling points were compared.The results show that the modified CHTC can accurately reflect the cabin thermal environment under low pressure conditions,and the correction of CHTC can be realized by adjusting the turbulent Prandtl number,which is nonlinear correlated with the pressure.The simulation results of the thermal environment in the seven-row cabin show that the CHTC changes by about 42%before and after modification.The air pressure decreases during take-off,which reduces the average CHTC of the crew surface from 5.09 W/(m^(2)·K)to 4.56 W/(m^(2)·K),but the air temperature rises by about 0.2°C as a whole.The deviation of PMV results calculated by using simulated heat loss data and using air parameters of measuring points in space is up to 0.5,but the latter is representative for calculating the thermal comfort level of the whole cabin.

Oxidation Characteristics of the Reactivity Between Pyrite and Aqueous Arsenate

Natural pyrites contain high levels of adsorbed and structurally incorporated arsenic(As),which may simultaneously result in the release of As and affect the oxidation process of pyrite.However,the oxidation and electrochemical behaviors of As on the oxidation reactivity of pyrites are still not clear.In this study,pyrite was prepared by a hydrothermal method and applied to study the oxidation mechanism between pyrite and aqueous arsenate.Analyses of X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy demonstrate that the as-prepared sample is an octahedron-like pyrite with high purity and crystallinity.The interaction between As(V)and pyrite as well as the electrochemical behaviors of pyrite oxidation in the presence of aqueous arsenate were investigated under acidic conditions by an ion analysis method,cyclic voltammetry(CV),Tafel,and electrochemical impedance spectroscopy(EIS).The results of the chemical reaction indicate that electrons are transferred from S 22-to dissolved oxygen with the formation of SO 42-in the initial As(V)concentration range of 0–0.3 mmol/L.In the initial As(V)concentration range of 0.4–1.2 mmol/L,electrons are transferred from S 22-to As(V)with the formation of elemental S 0 and As(III).The CV,the Tafel plot and EIS analyses indicate that aqueous arsenate in an electrolyte promotes oxidation reactivity and passivation of the pyrite electrode.Moreover,the electron transfer rate increases with increasing aqueous arsenate concentration in the electrolyte.

Catalytic Activity of Cr（Ⅵ） in the Degradation of Phenol by H2O2 Under Acidic Conditions

Cr(Ⅵ)and phenol are toxic contaminants that need to be treated,and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater.In this study,Cr(Ⅵ)was used as a novel Fenton-like catalyst in phenol degradation by H2O2.In the pH range of 3.0-11.0,the degradation efficiency of phenol decreased with elevated pH.At pH=3.0,100 mg/L phenol was effectively degraded by 2 mmol/L Cr(Ⅵ)and 20 mmol/L H2O2.At pH=7.0 and the same conditions as those of pH=3.0,79%of 100 mg/L phenol was removed within 6h,which was an improvement in pH limitation compared with the Fe(Ⅱ)-mediated Fenton reaction.Quenching experiments indicated that·OH generated from the catalysis of H2O2 by Cr(Ⅴ)instead of Cr(Ⅵ)was the primary oxidant that degraded phenol.When pyrophosphate was added in the Cr(Ⅵ)/H2O2 system,complexes with the Cr(Ⅴ)intermediate rapidly formed and inhibited H2O2 decomposition,implying that the decomposition of H2O2 to·OH was catalyzed by Cr(Ⅴ)instead of Cr(Ⅵ).The presence of anions such as chloride and sulfate had insignificant effect on the degradation of phenol.TOC and UV analyses suggest that phenol could not be completely oxidized to CO2 and H2O,and the intermediates identified by high performance liquid chromatography further indicates that maleic acid and benzoquinone were intermediates which may be further degraded into short chain acids,primarily maleic,formic,acetic,and oxalic acids,and eventually into CO2 and H2O.Considering that more than 50%Cr(Ⅵ)can also be removed during this process,the Cr(Ⅵ)/H2O2 system is more appropriate for the simultaneous removal of Cr(Ⅵ)and phenol contaminants from industrial wastewater.

Determining V-I characteristics of energy-efficient electrostatic assisted air filtration system by utilizing the back-corona induced current model

The widely utilized high efficient particulate air filters(HEPA)and electrostatic precipitator(ESP)respectively has the shortcomings of relatively high energy consumption and low filtration efficiency.In order to overcome the disadvantages of two traditional air filtration system,electrostatic assisted air filtration system(combining HEPA and ESP)has been proven to achieve high filtration efficiency and low energy consumption simultaneously.Predicting of V-I characteristics of electrostatic filtration system with configuration of“pin to filter medium to grounded device”is very essential and challenging due to the back corona phenomenon.This study utilized the back-corona based current model to predict the V-I characteristics of electrostatic system with different filter medium types and“pin-to-filter”distances.Experiments are conducted to provide data for model validation by changing filter types and locations of discharge pin.The results indicated that both of the predicted values of total discharge current and back-corona induced current agreed well with the experimentally measured data.This validated mathematical model could be used for preliminary design of electrostatic assisted filtration system with configuration of“pin to filter to grounded device”.Based on the V-I characteristics predicted by the semi-empirical model,the electrostatic filtration efficiency could be estimated.

Potential applications of porous organic polymers as adsorbent for the adsorption of volatile organic compounds

Volatile organic compounds(VOCs)with high toxicity and carcinogenicity are emitted from kinds of industries,which endanger human health and the environment.Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency.In recent years,activated carbons,zeolites,and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity.However,the hydrophilic nature and low desorption rate of those materials limit their commercial application.Furthermore,the adsorption capacities of VOCs still need to be improved.Porous organic polymers(POPs)with extremely high porosity,structural diversity,and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption.This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs.Moreover,the mechanism of competitive adsorption between water and VOCs on the POPs was discussed.Finally,a concise outlook for utilizing POPs for VOCs adsorption was discussed,noting areas in which further work is needed to develop the next-generation POPs for practical applications.

Multiple indicators and analytic hierarchy process(AHP)for comprehensive performance evaluation of exhaust hood

Indicators are the basis for judging the working performance of exhaust hood and capture performance are usually used as the only indicator.An evaluation index system including three factors of cooking oil fumes(COF)instantaneous capture,health risk impact and thermal comfort was proposed to assess the comprehensive performance of exhaust hood in the present study.The primary capture efficiency(PCE)of formaldehyde,the PCE of particulate matter with the diameter less than or equal to 2.5μm(PM_(2.5)),the incremental lifetime cancer risk(ILCR)of formaldehyde,the ILCR of PM_(2.5)and the predicted mean vote(PMV),which can all be quantified with the aid of computational fluid dynamics(CFD),were selected as the indicators.And the analytic hierarchy process(AHP)method was introduced to perform the comprehensive performance evaluation of exhaust hood.The performance of two exhaust hood structures(grille and orifice type)with three exhaust rates(3000,4000,and 5000 m^(3)/h)in two cooking zones of a university canteen kitchen were evaluated.The result showed that the reduction of ILCR of COF exposure is the most important to the performance of exhaust hood.The comprehensive performance of orifice exhaust hood with exhaust rate of 4000 and 5000 m^(3)/h are optimal;the orifice exhaust hood with exhaust of 3000 m^(3)/h and grille exhaust hood with exhaust rate of 5000 m^(3)/h are moderate;the grille exhaust hood with exhaust rate of 3000 and 4000 m^(3)/h are low.Decision-making priorities based on comprehensive and individual performance are not exactly the same in the two cooking zones.It is necessary to use the index system to evaluate the comprehensive performance of exhaust hood that considers the impact on human health and thermal comfort.

Experimental study of oil mist characteristics generated from minimum quantity lubrication and flood cooling

The use of metalworking fluids during machining can generate oil mist and endanger the health of workers.In order to study the characteristics and emission laws of oil mist generated by machining,this study constructed a test bench to simulate the turning process.Parameters affecting the oil mist generated in the minimum quantity lubrication(MQL)mode and flood cooling mode were studied by means of single-factor experiments,and the formation mechanisms of oil mist were analyzed.The results show that the oil mist generated by the MQL system has two main sources,the initial escape of oil mist into the air and the evaporation/condensation of oil mist.The centrifugation has almost no effect on oil mist formation in the MQL mode.The mass concentration of oil mist generated by the MQL system is proportional to the cutting oil flow rate.When the work-piece is at room temperature,increasing the air supply pressure and nozzle distance,increases the oil mist mass concentration.For the flood cooling mode,the concentration of centrifugal aerosol is linearly and positively correlated with the relative centrifugal force generated by the work-piece,and the coefficient of determination(R 2)is above 0.97.The oil mist mass concentrations in MQL mode is 8.33 mg/m^(3)~305.88 mg/m^(3).The MMD and SMD are 0.74μm to 4.42μm and 0.31μm to 2.14μm,respectively.The oil mist mass concentrations in flood cooling mode is 0.2 mg/m^(3)~22.42 mg/m^(3).The MMD and SMD are 1.81μm to 6.58μm and 0.45μm to 5.13μm,respectively.

Phthalate levels in Chinese residences:Seasonal and regional variations and the implication on human exposure

Indoor pollution of manmade semivolatile organic compounds(SVOCs)such as phthalates are a growing threat to human health.Herein we summarize the dust-phase phthalate concentrations in Chinese residences reported from 2011 to 2021and simulate corresponding airborne concentrations based on equilibrium models.The simulation considers seasonal and regional variations in indoor temperature and PM_(2.5)concentration,in contrast to the common practice of using constant values.Results show that variations in these two environmental factors lead to up to ten-and six-fold variations in the monthly median gas-and particle-phase concentrations of phthalates,respectively,in residences in individual climate zones.For higher-vaporpressure species di-n-butyl phthalate and di-isobutyl phthalate,the resultant seasonal and regional variations in aggregate nondiet intake can reach six-and three-fold,respectively.These results have important implications on exposure assessment of SVOCs and epidemiological evaluation of their health effects.

Cooking grease particles purification review and technology combination strategy evaluation for commercial kitchens

Effective emission control of cooking oil fumes(COFs),particularly for grease particles,has always been a cause of great concern for catering industry.The review and evaluation of combinations of purification technology are urgently required.This work presents a literature review and combination strategy evaluation of purification technology of grease particles of commercial kitchens.A variety of mainstream purification technologies,such as mechanical separation(M),filtration(F),washing absorption(W)and electrostatic deposition(E)are discussed.In order to establish a complete and efficient fume purification system for commercial kitchen,this study proposes the four-point principles of combined purification technologies as:(1)from easy to difficult(for grease particle diameter);(2)fire prevention and noise reduction;(3)electrostatic deposition postposition;(4)Absorption and dissolution(by-product from electrostatic).Based on the above principles and separation characteristics,the recommended combinations of purification strategies are M-E,F-E,M-F-E and M-E-F.The combination strategy of M-F-E is adopted as an example to evaluate and optimize COFs purification system use life cycle assessment approach.The results indicate that the optimization of the M-F-E purification system using rotating mesh plate instead of baffle filter can reduce the environmental impact of global warming and eutrophication by about 35%which reduces the emissions of CO_(2)and SO_(2)from 92.533 kg and 0.110 kg to 60.214 kg and 0.072 kg,respectively.Besides the review of relevant purification technologies,the study also proposes the combination of principles of purification technologies and the evaluation and optimization of life cycle assessment for the optimal design of combined purification system.

A metal-OH group modification strategy to prepare highly-hydrophobic MIL-53-Al for efficient acetone capture under humid conditions

A series of highly-hydrophobic MIL-53-Al(MIL = Materials of Institut Lavoisier) frameworks synthesized via decoration of the Al-OH groups by alkyl phosphonic acid were developed as adsorbents for removing acetone from humid gas streams.The newly prepared materials were characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscope(SEM), N_(2) adsorption-desorption and thermogravimetric analysis(TGA).Their adsorption behaviors toward acetone vapor under dry and wet conditions were studied subsequently.Results showed that alkyl phosphonic acid was successfully grafted into MIL-53-Al skeleton through coordinating interaction with Al3+generating MIL-53-Al@C_(x)(x = 12, 14, 18).The MIL-53-Al@C_(x) exhibited similar crystal structure and thermal stability to parent MIL-53-Al.Furthermore, the modified materials showed significantly enhanced hydrophobicity.The water vapor uptake of MIL-53-Al@C_(14) decreased by 72.55%at 75% relative humidity(RH).Dynamic adsorption experiments demonstrated that water vapor had almost no effect on the acetone adsorption performance of MIL-53-Al@C_(14).Under the condition of 90% RH, the acetone adsorption capacity of MIL-53-Al@C_(14) was 102.98% higher than that of MIL-53-Al.Notably, MIL-53-Al@C_(14) presented excellent adsorption reversibility and regeneration performance in 10 adsorption-desorption cycles.Taken together, the strategy of metal-OH group modification is an attractive way to improve the acetone adsorption performance over metal-organic frameworks(MOFs) under humid conditions.Besides, MIL-53-Al@C_(14) would be deemed as a promising candidate for capturing acetone in high moisture environment.

An efficient 3D ordered mesoporous Cu sphere array electrocatalyst for carbon dioxide electrochemical reduction

The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions.However,this solution has been challenged by the lack of active and selective catalysts.Here,we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays,which is fabricated by a dual template method using a poly methyl methacrylate(PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal.Therefo re,the well-ordered 3D interconnected bi-continuous mesopore s structure has advantages of abundant exposed catalytically active sites,efficient mass transport,and high electrical conductivity,which result in excellent electrocatalytic CO2 RR perfo rmance.The prepared 3D ordered mesoporous Cu sphere array(3 D-OMCuSA) exhibits a low onset potential of-0.4 V at a 1 mA cm^-2 electrode current density,a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate.These distinct features of 3 D-OMCuSA render it a promising method for the further develo p ment of advanced electrocatalytic materials for CO2 reduction.