Based on a refrigeration cycle using R134a as a working fluid,the falling film evaporation on horizontal tubes was used in the evaporator.The heat transfer characteristics of the falling film evaporation were investigated experimentally under different conditions.The heat fluxes varied from 8 to 40 kW·m^-2 and the mass flow rate of the sprayed liquid ranged from 0.005 to 0.04 kg·m^-1·s^-1.The performance of a smooth tube and two enhanced tubes(a TJX tube and an EX tube)were tested in the experiment.The two enhanced tubes were designed for the falling film evaporation specifically.The experimental data were processed by using the modified Wilson method.The test results show that the heat transfer characteristics of the falling film evaporation are mainly associated with heat flux and mass flow rate.For all tubes,the heat transfer coefficient increases before the occurrence of the critical heat flux.The performance of enhanced tubes are better than that of smooth tube,especially the EX tube with grill channels on the surface.With the oil in the refrigeration system,the presence of oil in the experimental loop deteriorates the heat transfer coefficient significantly.Finally,a new heat transfer correlation is used to predict the heat transfer coefficient of the smooth tube,and correction factors for the heat transfer prediction of enhanced tubes are proposed.

A theoretical model was derived for the steady state one-dimensional velocity distribution and two-dimensional temperature distributions in annular laminar liquid films falling down on the wall outside a vertical tube with heat and mass transferring from the interface to counter-current gas flow.Based on the model,liquid film thickness and interfacial heat flux could be predicted if shear stress was obtained.From the good agreement of experimental data and predicted values of the interfacial heat fluxes within the range of gas flow Reynolds number Re_g<1200,the method of using interfacial friction factor to solve the model was reliable under laminar conditions of the two phases.The model simulation results revealed the non-linear characteristics of velocity and temperature distributions in the film.The sharp temperature gradient close to the gas-liquid interface indicated that it was an effective way to enhance heat and mass transfer by reducing film thickness.

A novel method using ultrasound is introduced for frost suppression on cold flat surface.The dynamic behavior of water droplets dropped on aluminum surface subjected to 20 kHz and 50W ultrasonic vibration was visually studied.The transient processes of deformation,spreading and atomization of water droplets on aluminum surface due to ultrasonic vibration were recorded.The experimental results indicate that the intense disturbance first occurs in the water droplet subjected to instantaneous incentive due to the effect of ultrasonic vibration and then the droplet deforms and spreads.When the liquid film thickness decreases to a critical value,the water droplet instantaneously atomizes.The interfacial shear force generated by ultrasonic mechanical effect and the high pressure impact induced by ultrasonic cavitation might be respectively the dominant factor for droplet deformation and atomization.The results preliminarily show that the ultrasonic vibration can instantaneously atomize the water droplet on aluminum surface in the initial stage of frosting,which provides a possibility for effective frost suppression on cold surface.

For helical blade rotors,the heat transfer enhancement mechanism was theoretically analyzed. Some enhancement mechanisms involve the strengthening effects of cross section contraction,spiral flow and secondary flow.Based on the empirical equations for the plain tube and theoretical derivation,the prediction correlations for Nusselt number and pressure drop of the tube with helical blade rotors were established in the turbulent region in order to predict the influence of geometric parameters on heat transfer enhancement and resistance characteristics of rotors,including rotor lead,rotor diameter and sectional dimension.The comparison between experimental results and predicted results shows that the maximum deviations of the Nusselt number and friction factor are 7.4% and 10.1%,respectively.

In order to discuss the mechanism of electrohydrodynamics enhanced boiling heat transfer,with water serving as the working medium the method combining numerical simulation with experimental study was used to research the behavior of cold nitrogen bubble under electric field.Numerical simulation was made for calculating the distribution of electric field intensity around the bubble,the cycle and instantaneous velocity when the bubble broke away under DC voltage 10 kV.The result showed that with increasing electric field intensity,the deformation of cold nitrogen bubble,i.e.,elongation was more obvious.The cycle got shorter when the bubble broke away.The electric field intensity gradually symmetrically decreased along the direction of the bubble outline.The velocity with which the bubble broke away increased with increasing electric field intensity and the velocity reached a maximum at the bottom of the bubble.

Bubble moving along an inclined surface is a common phenomenon in industry.A single bubble rising along an inclined adiabatic surface was simulated with the lattice Boltzmann method(LBM).The influences of initial bubble diameter,inclined angle and Eotvos number on bubble deformation and the vertical distance between its centroid and the surface,were studied.Under the condition of fixed initial bubble diameter,the relationships between bubble terminal velocity,inclined angle and Eotvos number were also investigated.The simulation revealed that the asymmetry of bubble became significant with the increasing of inclined angle.During the rising process,the trajectory of bubble's centroid remained parallel to the surface.When the inclined angle was greater than 45°,the vertical distance between its centroid and the surface increased with the Eotvos number, while when it was less than 45°,the variation was the opposite.Besides,the bubble's terminal velocity increased with increasing inclined angle and Eotvos number for the same initial diameter.

A new type of elastic wall distributor of outer annular falling film was developed.This method could create a uniform annular channel for the micron-size ultra-thin falling film flow,which could be precisely controlled.This distributor had homogeneity and stability of internal mechanism due to the axisymmetrical deformation coordination characteristics of elastic wall and it could generate negative feedback responses to fluid pressure changes sensitively.According to the theory of thin shell and Amonton law of friction,the linear relationship between initial film thickness and liquid height was given.Also,the equation of falling film flow was established.Experiments were performed using water and 30% glycerol aqueous solutions at lower flow rates.The results indicated that the two equations obtained were in good agreement with experimental data and could be used as the design equations for engineering applications. The experiments also revealed that the vertical tube with a length of 0.6 m and a diameter of 14 mm could be completely wetted by the ultra-thin falling film 0.157 mm thick using the elastic wall distributor.And the wetting performance of the distributor reached the dimensionless minimum wetting rate,which was dependent on the properties of the solid-liquid interface.Compared with other liquid distributors,the elastic wall distributor gave the best performance of hydrodynamics.

In this paper a mathematical model of mass diffusion during the cryoprotectant addition for neural stem cell sphere is presented.The mass diffusion equation is established separately for intracellular and extracellular spaces but taking into account the mass exchange across the cell membrane.The volume change of cells in different positions is also simulated when cryoprotectant is added step by step.The factors affecting volume change are analyzed.Different procedures of addition are used to investigate osmotic damage.The results shows that change of DMSO in extracellular space,which can attain stable within 10 s near the surface and 15 s close to the center of the ball,is faster than that in the intracellular element.Decreasing L_p and increasing ω can greatly improve the volume change while the impact on the size of neural stem cell spheres is limit.The multi-steps addition procedures,which keep the same osmotic pressure difference in each step while gradually reduced time durations,should be chosen.In addition,four-step addition is better than other stepwise additions.An ideal continuous addition should combine with low concentration difference and short loading time,and convex curve addition patterns are preferred.

Convective heat transfer can be enhanced effectively by longitudinal vortices,thus it is meaningful to study the swirling flow induced by longitudinal vortex generator in exploring the heat transfer enhancement mechanism.The structure of the flow field and the flow characteristics in a tube with trapezoid winglets embedded were investigated by performing particle image velocimetry(PIV)measurement in both transverse and longitudinal sections.The trapezoid winglets were uniformly distributed over the circumference upstream placed at an angle of 135° to the tube wall.The experimental results showed that multi-longitudinal vortices flow was induced downstream of the winglets with four symmetrical counter-rotating vortex pairs.Two different flow patterns were in the near wall region,one was the flow towards the wall and the other was the flow away from the wall,both of which effectively increased the component of the transverse velocity perpendicular to the mainstream.In a certain range of Reynolds number involved in the experiment,it could be drawn that the maximum value of transverse velocity and the radial velocity in the sections downstream the winglets could reach 27% and 20% of the averaged mainstream velocity respectively.The continuous disturbance to the flow induced by the longitudinal vortices proceeded downstream along the tube wall,which increased the velocity of the flow near the wall significantly,by 1.0-3.6 times of that in the smooth tube.The fields of velocity and vorticity showed that the disturbance turned out to be more powerful with the increase of Reynolds number.Compared with the flow field in the smooth tube,it was found that the flow mixing generated by the winglets enhanced mass transfer between the mainstream and the fluid in the near wall region due to its enhancement of radial velocity component perpendicular to the wall,which was beneficial for convective heat transfer enhancement in the tube.

To achieve the optimal use of the low-temperature waste heat,11 substances were adopted as the subcritical ORC working fluids,R245fa and R601a,as well as 9 non-azeotropic binary mixtures in different mass ratios.Thermodynamic and thermo-economic analyses ware employed to design a reasonable ORC system and optimize relevant parameters.The result shows that the ORC system presents better thermal performance with the parameters at the maximum exergy efficiency as the working conditions of system.Under the designed working conditions of system,R245fa/R601a of 0.6/0.4 makes the thermodynamic performance better while the ratio of 0.9/0.1 leads to the best thermo-economy.R245fa/R601a of 0.9/0.1 is little different from the ratio of 0.6/0.4 in the analysis of thermo-economy.Taking its excellent thermodynamic properties into account,the ratio of 0.6/0.4 should be considered as the working fluid when designing the system.Meanwhile,increase of the mass ratio of R245fa in the binary mixture reduces APR and LEC,improving the system economy.

Wet desulfurization of flue gas was investigated with Ca(OH)₂ slurry as absorbent in a water-sparged aerocyclone(WSA),new and high efficiency gas-liquid mass transfer equipment.The results show that the removal efficiency of SO₂ increases with the inlet gas velocity,first increases linearly with liquid jet velocity u_L,and then remains almost constant when u_L is equal to or greater than 0.29 m·s^-1.The removal efficiency of SO₂ decreases as SO₂ concentration in the flue gas increases,and presents a maximum value with the increase of liquid reflux ratio and Ca(OH)₂ concentration in the absorbent slurry.The removal efficiency of SO₂ can reach 88.9%-97.7% under the following conditions:flue gas flow rate of 24-72 m³·h^-1,absorbent recirculation flow rate of 0.4-0.8 m³·h^-1,Ca(OH)₂ concentration in absorbent of 7500 g·m^-3,and SO₂ concentration in flue gas of 1891-6373 mg·m^-3.No fouling and blocking were found in the WSA because of the self-cleaning ability of the cyclone gas and liquid jet.The mass transfer mechanism in the WSA was also investigated.The results show that the overall volumetric mass transfer coefficient K_Ga and the interfacial area a increase with the increase of inlet gas velocity u_G,the overall mass transfer coefficient K_G increases with u_G slowly.K_Ga and K_G increase quickly with liquid jet velocity u_L when u_L≤0.26 m·s^-1 and then increase slowly,and a increases almost linearly with the increase of u_L.As Ca(OH)₂ concentration c_L increases,K_Ga and K_G increase first and then decrease.The empirical formulae fit the experimental data well and could be used to predict the mass transfer characteristics for wet desulfurization in WSA.Under the experimental conditions,the mass transfer in wet desulfurization in the WSA is controlled by both gas film and liquid film,mainly by liquid film.

Visualized experiments were conducted by using a high speed video camera system to study slug flow in a narrow rectangular channel(3.25 mm×40 mm)with four inclination angles.For low two-phase superficial velocity,due to buoyancy slug nose deviated from the channel centerline and became sharper under inclined condition,resulting in the increase of slug velocity.The coefficient C₀ decreased with increasing inclination angle,while drift velocity V₀ varied inversely.For the case of high two-phase superficial velocity,the influence of inclination angle on slug velocity weakened with the flow tending to be stable,as was the same to C₀ and V₀.Four classical correlations for calculating slug velocity were evaluated against the experimental data.The correlations of C₀ and V₀ were given according to the threshold of 3.5 of Froude number.

Based on the fractal theory,the micro-scale geometric structure of nano-granule porous medium was illustrated and the equivalent fractal unit model was proposed.The effective thermal conductivity of the nano-granule porous medium under the vacuum condition has some relation with the thermal conductivity of solid substrate,vacancy porosity,fractal dimension,fractal diameter,pressure and thermal conductivity of rarefied air,and environmental condition.The calculation models for thermal conductivities of air phase and solid phase,the equivalent thermal radiation and the total effective thermal conduction were constructed.The results show that the effective thermal conductivity of nano-granule porous medium increases with the increase of fractal diameter and rarefied air pressure within the material,but decreases with the increase of vacancy porosity.The optional diameter of the nano-granule is recommended.The calculated results are in good agreement with the experimental data.The study is useful for enhancing the adiabatic performance of nano-granule porous medium and developing new vacuum adiabatic materials.

The fluid extracts or rejects heat from subsurface by downward leg of pipe(DLP)and upward leg of pipe(ULP)in vertical borehole heat exchangers(BHEs).As the borehole diameter is only 0.11 m to 0.2 m,the temperature difference between DLP and ULP inevitably leads to thermal short-circuiting.In order to build accurate heat transfer model for the BHEs,the vertical underground heat exchangers with different boreholes,pipe diameters and arrangements were investigated numerically,and a best-fit correlation for the thermal short-circuiting resistance was presented in dimensionless form.A 3-D equivalent rectangular numerical model for BHEs was established and the influences of velocity and borehole depth on the short-circuiting loss rate were analyzed.Smaller velocity leads to larger thermal short-circuiting loss rate and lower average heat flux per unit length,but too large velocity has no obvious effect on reducing short-circuiting loss rate.The temperature difference between inlet and outlet increases with the borehole depth,while the heat transfer between DLP and ULP also increases greatly.The relationship between the thermal short-circuiting and the fluid temperature change is explored. The geometric mean fluid temperature ignoring the short-circuiting is always higher than the integral mean fluid temperature.With an in situ thermal conductivity test rig established in Nanjing,the results indicate that lower velocity results in lower effective subsurface conductivity and smaller heat transfer capacity in the BHEs.The measured subsurface thermal conductivity with 50 m borehole is 2.50 W·(m·K)^-1,31.8% higher than that with 100 m borehole,which is 1.896 W·(m·K)^-1.The heat exchange amount,short-circuiting and investment should be taken into account while determining the borehole depth.

In order to prevent fire accident caused by leakage of liquid fuels in the process of storing,using and transporting,a schlieren system,CCD cameras and K-thermocouples were used to study the characteristics of flame spreading over sand bed wetted with 1-butanol.The effect of surface inclination angle of sand bed on the mechanism of flame spread was analyzed.The results indicate that the flame spreads on the sand bed at constant speed.When the flame spreads upward,its height,yellow luminous zone and spread rate increase with surface angle; when the flame spreads downward,they all decrease as the surface angle increases.As the surface inclination angle increases,the preheating zone magnifies,which is in front of the flame,and the thickness of thermal boundary layer decreases,which is in the sand layer.The investigation on flame spread characteristics and burning mechanism provide some guideline for fire suppression and environmental protection.

In order to investigate the over-reading prediction model of wet gas measurement using gas ultrasonic flow meter,a Z-shaped gas ultrasonic flow meter prototype was selected to analyze its measuring principle and mechanism of over-reading when metering wet gas flow.The laboratory tests were conducted in TJU adjustable medium-pressure wet gas test loop.The over-reading of Z-shaped gas ultrasonic flow meter was mainly related to the void fraction of the pipe under a uniform film assumption with annular flow.Meanwhile,the correlation between void fraction and over-reading was deduced.Five typical void fraction correlations of gas/liquid two-phase flow in horizontal circular pipe were selected to calculate the predicted value of over-reading.The most appropriate void fraction correlation for predicting over-reading of Z-shaped type gas ultrasonic flow meter was the Armand-Massina correlation.The over-reading prediction model based on this void fraction correlation had prediction relative errors ranging from-7.77% to 4.90%,with a standard uncertainty of 0.98% at 95% confidence interval.

Bis 2,4-dichlorobenzoyl peroxide(DCBP)is usually used as an initiator,a hardener,and a vulcanizing agent in rubber industry.As a kind of organic peroxides,the peroxy group(-O-O-)may cause the thermal instability and explosion likelihood of DCBP.To analyze the potential hazards of its thermal decomposition,the differential scanning calorimetry(DSC)was used to test the thermal behavior of DCBP under dynamic and isothermal conditions.Kinetic parameters calculated by the Friedman iso-conversional method indicated the autocatalysis possibility of this decomposition.DSC curves obtained at five constant temperatures confirmed a strong autocatalytic reaction of DCBP.Exothermic onset temperature of DCBP was 98℃ and activation energy was between 232 kJ·mol^-1 and 236 kJ·mol^-1 under dynamic evaluation.When scanning at 92℃ in isothermal mode,the time to maximum rate was less than 30 min,so the best constant temperature for evaluation under this mode should be no higher than 92℃ to prevent loss of heat-flow signal.By simulating the five isothermal curves,a kinetic model was established and the mechanism function was found.As all data showed that reaction progress was short and reaction rate was high,it is best to avoid external heating and sudden energy transfer during DCBP manufacture,transportation and storage.Meanwhile,emergency rescue plans should be prepared for minimization of loss once accident happens.

Polymeric Nb₂O₅ sols were successfully synthesized via sol-gel process by using niobium penta(n)butoxide as a precursor.Effects of synthesis parameters,including pH of system,hydrolysis ratio,reaction temperature,reaction time and chelating agent,on the state and size of Nb₂O₅ sols were investigated in detail.Microporous Nb₂O₅ membranes were deposited on defect-free γ-alumina membranes with an average pore size of ca.3 nm,by using polymeric Nb₂O₅ sol with an average size of 4.8 nm.The properties of Nb₂O₅ powder and the supported Nb₂O₅ membranes were characterized by TG,XRD,NH₃ adsorption-desorption,CO₂ adsorption,Fourier-transform infrared spectroscopy of pyridine adsorption(Py-IR)and single gas permeance test.Results showed that the single hydrogen permeance and H₂/CO₂ permselectivity of 350℃-calcined microporous Nb₂O₅ membrane were 3.1×10^-9 mol·m^-2·s^-1·Pa^-1 and 21,respectively,measured at 200℃ and 0.3 MPa.The single gas permeance and H₂/CO₂ permselectivity of the membrane remained fairly stable after in-situ exposure to 150 kPa steam for 8 h.

Vapor quality in static flash evaporation was studied experimentally,using aqueous solution of NaCl at a mass fraction range of 5%-26%,an initial temperature range of 74-104℃,an initial aqueous solution height range of 0.1-0.3 m,and a superheated range of 0.79-42 K.The results showed that increasing concentration of aqueous NaCl solution reduced the vapor quality at a given initial solution temperature and a final equilibrium flash chamber pressure.The effect of concentration became weak at a given superheat(ΔT)and the same aqueous solution height.Vapor quality increased with increasing initial aqueous solution height,but at the same time,vapor quality produced by per unit mass of aqueous NaCl solution decreased.Vapor quality increased linearly with increasing superheat.Based on the experimental results,the dimensionless correlation for vapor quality in static flash evaporation was established.

Based on the single-stage model for chiral extraction of naproxen(NAP)enantiomers and the law of mass conservation,a model for multi-stage countercurrent centrifugal extraction of naproxen enantiomers was built.The model was programmed with Matlab and the influence of process parameters such as phase ratio,extractant concentration,pH value of aqueous phase was examined.Increase of phase ratio(W/O)reduces the enantiomeric excess(ee_extract)and increases the yield(Y_extract)in the extract. With the increase of extractant concentration,ee_extract of extract increases quickly at first,then decreases slowly,and Y_extract increases continuously.As pH increases,Y_extract keeps increase,while ee_extract decreases.The experimental and simulation studies indicate that ee_extract of 45% and Y_extract of 60% are achieved under the optimal separation conditions:R,S-NAP concentration of 0.025 mol·L^-1,HP-β-CD concentration of 0.050 mol·L^-1,phase ratio of 7,pH of 2.5,and temperature of 5℃.

Adsorption equilibrium of pure methane and ethane on activated carbon 204-Ⅱ was determined by the volumetric method at 293 K and 0-4 MPa.Adsorption data,with the CH₄ concentration in the range of 34.0%-95.2%,were measured by the open flow method on activated carbon 204-Ⅱ at 293 K.The real adsorption solution theory(RAST)expressing the non-ideality of the local adsorbed phase was combined with the micro-pore size distribution(MPSD)model describing the energetic distribution of the adsorbent surface,and a MPSD-RAST model was put forward to predict adsorption equilibrium of binary CH₄-C₂H₆ system.The Wilson equation and the NTRL equation were adopted to calculate activity coefficients for the local adsorbed phase.The ideal adsorption solution theory(IAST)and the MPSD-IAST model were also used for prediction.The investigation demonstrates that the MPSD-RAST model greatly improves prediction accuracy of the adsorption amount and the mole fraction for CH₄,compared with the IAST and MPSD-IAST models.For the heavy component C₂H₆,prediction deviations with these three methods are all lower than 5%.It is important to consider non-ideality of the adsorbed phase in prediction models.

Gel filtration media play a very important role in separation and purification of bio-macromolecules such as proteins,polysaccharides.Their pore structure directly influences protein transport and adsorption in chromatographic separation column.The pore size distribution(PSD)plays a major role beyond simply the mean pore size.Various methods have been employed to determine the PSD of porous materials,including gas adsorption-desorption(BET),mercury intrusion porosimetry(MIP).Since most of gel filtration media is soft gel,so it is difficult to measure their PSD by conventional method.In this paper,a new method,low-field NMR,was explored to determine the pore size distribution of gel filtration media.First,the distribution range of internal water,external water and free water in transverse relaxation time(T₂)of low-field NMR were setting-out; then comparing the results with that from inverse size-exclusion chromatography(ISEC)and finding relationship between the pore size and relaxation time in internal water; finally,the pore size distribution of media was fitted by the Gaussian normal distribution.The results demonstrated that low-field NMR is an effective method for PSD determination of porous chromatographic media.The method is easy to operate,simple and quick,and can provide a reference for other determination of chromatography media pore size distribution.

CO₂ absorption by alkanolamine aqueous solution is an important method for biogas purification. A series of experimental tests were conducted in a packed tower using aqueous solution of MEA and DEA,in which the percent conversion η,absorption rate N and volumetric overall mass transfer coefficient in gas phase K_Ga_e were analyzed at various absorbent concentrations,gas flow rates,CO₂ concentrations and absorption temperatures.The results show that the increment of absorbent concentration can improve η,N and K_Ga_e effectively.With the increment of gas flow rate,the percent conversion η decreases obviously,while the absorption rate N increases within a certain range and then decreases,the change of K_Ga_e is similar to that of absorption rate N,but the value of K_Ga_e will maintain a relatively stable value when the gas flow rate is high enough.The percent conversion η and decrease as CO₂ concentration increases,while the absorption rate N increases.The effect of absorption temperature on η and K_Ga_e are approximately parabolic.The optimum absorption temperature of MEA and DEA is about 40-60℃,and it decreases with the increment of CO₂ loading.The experimental results of this study can provide some guidance for the further study and practical application of biogas purification technology by alkanolamine aqueous solution.

The characteristic of coagulation sludge was altered by the pretreatment of high temperature. The appearance and crystallization of coagulation were respectively characterized by SEM and XRD and the samples with pretreatment and without pretreatment were compared.The adsorption characteristic of pretreated sludge for adsorption of ammonia-nitrogen from the aqueous solution was also evaluated using the theory of thermodynamics and kinetics.The adsorption model of ammonia-nitrogen was fitted with the Freundlich equation.The kinetic equations of pseudo-first-order,pseudo-second-order and intra-particle diffusion were adopted to examine the mechanism of the adsorption process and the pseudo-second-order models provided the better correlation of adsorption data.Thermodynamic parameters including ΔG⁰,ΔH⁰,ΔS⁰,E_a, and S^* were calculated.The values of ΔG⁰ at 30,40 and 50℃ were-1.915,-1.744 and-1.719 kJ·mol^-1 respectively,indicating the spontaneous nature was happened in ammonia adsorption on altered coagulation sludge.The negative value of ΔH⁰ proved the existence of the exothermic nature in the modified sludge absorption process.The negative value of ΔS⁰ represented that the adsorption was a declining process for entropy.The S^* value at 0.0812 ranged from 0 to 1 demonstrated that the adsorption was a physical process.

Performance monitoring of model predictive control(MPC)technology has received much attention in both academic and industrial circles.For model-based control technique,model accuracy is a key factor to ensure its performance.So model-plant mismatch(MPM)is important in the procedure of control performance monitoring.In recent years,the multi-step prediction error approach for MPC performance potential has been developed without requiring the knowledge of plant model and interactor matrix.However,since the MPC controller has strong robustness to MPM and other uncertainties,the multi-step prediction error approach is not sensitive to performance potential change in MPC controller which is caused by MPM.Considering that model prediction residuals of MPC controller could effectively reflect the information of MPM,an improved approach based on model prediction residuals was developed to resolve this problem.Meanwhile,a performance benchmark and real-time performance monitoring strategy based on the improved approach was defined to monitor MPC control performance.Theoretical analysis and experimental results showed that the improved approach not only possessed the advantages of the original approach,but also could better detect the change in MPC controller performance potential by MPM.Simulation example in the continuous stirred tank heater(CSTH)system illustrated the feasibility and effectiveness of this approach.

A systematic procedure to integrate the heat exchanger network considering pressure drops and multiple shells is described.The shell-side pressure drop correlation without resorting to correction factors is developed from the Esso method.The number of shells is calculated by considering the temperature cross in a heat exchanger instead of the designer's choice for the ratio.The network spaghetti design is solved by the optimization of total annual cost with the genetic algorithm.The case study shows that the proposed method can handle more constraints and make the computation more reliable and optimized.

In order to study the variation of average film thickness of end faces in contacting mechanical seal in running-in period,the change of surface topography was studied by fractal parameters characterization.Based on the fractal model of mechanical seals,an average film thickness prediction model of end faces in contacting mechanical seal was established by solving the volumes of surface voids of end faces.Running-in tests of two mechanical seals of B104a-70 type were carried out with water as test medium.Test temperature was 20℃,test pressure was 0.5 MPa,rotating speed was 2900 r·min^-1,and spring pressures were 0.15 MPa and 0.3 MPa respectively.The results indicated that the end face of the soft ring tended to be smoothed rapidly and average film thickness decreased rapidly in running-in period.The average film thicknesses of two tested mechanical seals were both about 0.295 μm in the normal wearing stage.Surface topography had significant influence on average film thickness,while spring pressure had little influence on average film thickness.Studying the changes of surface topography and average film thickness has important significance both in the prediction of operating characteristics and in the design of end faces of contacting mechanical seals.

This research aims to study the stress corrosion cracking(SCC)behavior and its mechanism of 16Mn steel and heat-affected zone in alkaline(pH=11.7)sulfide solution with different concentrations using electrochemical technology and U-bent specimen immersing test.Original structure,coarse grain structure(air cooling structure)and hardening structure(quenching structure)turned into the state of passivation in alkaline sulfide solution,and the current density of passivation decreased gradually.The current density of hydrogen evolution of hardening organization was higher and corrosion rate was slower.And the corrosion near the fusion line part was deeper and the residual tensile stress area was exposed after long-term service,which caused stress corrosion cracking.The sensitivity of SCC lowered gradually when hardening organization,open grain structure and original structure of HAZ were in alkaline sulfide environment.Hardening structure exhibited high susceptibility to SCC.Coarse grain structure and original structure exhibited low susceptibility to SCC.The susceptibility increased by increasing the concentration of H₂S.The SCC mechanism of 16Mn steel was anodic dissolution(AD)and was intergranular fracturing when it was in the solution of alkaline sulfide.

Ionic liquids 1-vinyl-3-alkyl imidazolium bromide([VAIM]Br)were synthesized and characterized by FTIR,¹H NMR,TG and DSC,and their electrochemical properties were studied.The results indicated that the temperature dependence of conductivity(σ)obeyed Arrhenius type equation at a range from 298.15 K to 323.15 K and the activation energy for conductivity decreased with the extension of the alkyl chain of the[VAIM]⁺.The conductivities of[VAIM]Br solutions using water,methanol or ethanol as solvents respectively all increased remarkably with the increasing concentration of[VAIM]Br,and corresponded to σ(water)>σ(methanol)>σ(ethanol).The critical micelle concentrations of the[VAIM]Br in different solutions were confirmed by conductance method which were about 6.8×10^-6 mol·L^-1 in water,1.5×10^-5 mol·L^-1in methanol and 2.0×10^-5 mol·L^-1 in ethanol respectively.This showed superior surface activities of[VAIM]Br.Electrochemical window of[VAIM]Br were from 1.6 V to 2.5 V,and electrochemical stability decreased with the extension of the alkyl side chain of[VAIM]⁺.

In recent years,producing terpenoids in microbe by synthetic biology methods has become more and more popular.Inducible promoters and constructive promoters have both advantages and disadvantages. The choice of promoters depends on the specific systems and target compounds.In this research,regulations of heterologous modules by inducible and constructive promoters were studied respectively for the taxadiene synthesis in Saccharomyces cerevisiae.A yeast chassis was firstly constructed after expressing a truncated 3-hydroxyl-3-methylglutaryl-CoA reductase gene(thmgr),endogenous farnesyl diphosphate synthase gene(erg20)under the regulation of tdh3 promoter.After inserting the heterologous module in which ts was regulated by inducible promoter into the genome of chassis,an engineered strain which produced 5.2 mg·L^-1 taxadiene was obtained.When the promoter was replaced by constructive one-tdh3p,the yield increased to 11.5 mg·L^-1.That indicated the constructive promoter may be more suitable for the taxadiene synthesis system in yeast.After a simple fermentation optimization in shaking flask,the yield increased by 70% to reach 19.5 mg·L^-1.Strains regulated by constructive promoters can use glucose as carbon source which was suitable for large scale fermentation in future.

To evaluate the influence of remaining ionic liquid in fermentable sugars from lignocellulosic materials on subsequent ethanol fermentation,the toxicity of ionic liquid 1-ethyl-3-methylimidazolium acetate([Emim]Ac)to Saccharomyces cerevisiae AY93161 and its influence on ethanol fermentation process were investigated.After methylene blue staining,the morphological structure,budding and metabolic activity of Saccharomyces cerevisiae AY93161 at log growth phase in the presence of different concentrations of[Emim]Ac were observed under microscope-OLYMPUS CX41.The result showed that its single cell morphology changed when[Emim]Ac concentration was greater than 5 g·L^-1,and its reproduction rate by budding and its metabolic activity decreased with increasing[Emim]Ac concentration when[Emim]Ac concentration was greater than 0.1 g·L^-1.The half effective concentration(EC50)and the half inhibition concentration(IC50)of[Emim]Ac to Saccharomyces cerevisiae AY93161 were then measured by using solid and liquid suspension culture and their values were 4.45 and 7.70 g·L^-1 respectively.According to the parameters measured during the ethanol fermentation process at different[Emim]Ac concentrations,when[Emim]Ac in the medium was below 0.1 g·L^-1,there was almost no effect on the ethanol fermentation process,but when[Emim]Ac in the medium was greater than 0.1 g·L^-1,the ethanol fermentation was inhibited,resulting from its inhibitory effect on growth of the yeast Saccharomyces cerevisiae AY93161.

Consecutive batch fermentation with self-flocculating yeast realized recycling of cell and increased ethanol yield and productivity.Oxidoreduction potential(ORP)control was used in this process to automatically feed the fresh medium at the end of every batch by judging the uprising of ORP curve.When ORP value was controlled at-100 mV and initial glucose were chosen as 200 g·L^-1(industrial concentration)and 250 g·L^-1(very high gravity),compared with batch fermentation,accumulated biomass in consecutive batch sharply declined by 42.4%(～200 g·L^-1,5 batches)and 16.3%(～250 g·L^-1,6 batches),respectively.On the other hand,compared with manual consecutive batch fermentation,automatic process greatly shortened fermentation time by 17.8%(～200 g·L^-1)and 15.2%(～250 g·L^-1).Consequently,ethanol productivities were enhanced by 21.7% and 17.9%,respectively.

Chemical-looping combustion(CLC)is a promising technology with inherent separation of CO₂.Because coal is cheaper and more abundant than gaseous fuel,it is attractive to adapt CLC for use with coal.The gasification process of coal is the limiting step,so this study presented an enhancement of gasification rate of coal using Na-loaded iron ore as oxygen carrier in a 1 kW_th continuous reactor.The effect of fuel reactor temperature on the chemical-looping combustion of coal was investigated.The results showed that the catalytic effect of Na on coal gasification was obvious in the fuel reactor temperature range of 820-920℃.There was an obvious increase in the concentration of CO₂ from fuel reactor and a decrease in the concentration of CO with the increase of fuel reactor temperature.The CO₂ capture efficiency and carbon capture efficiency for Na-loaded iron ore were 78.60% and 80.54% respectively,whereas those for iron ore were 40.27% and 45.65%.The Na-loaded iron ore showed sintering and agglomeration on the oxygen carrier particles and the defluidization phenomena of the fuel reactor was observed at a fuel reactor temperature of 950℃.This was likely due to the low melting point of the sodium compounds and the over-reduction of the oxygen carrier.SEM and XRD analysis showed that the reduction degree of Fe₂O₃ in the oxygen carrier using Na-loaded iron ore was intensively enhanced.

At present,the emission of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)has hampered the application of combustion technology in waste clean treatment and waste to energy utilization.This study experimentally investigated the inhibition of PCDD/Fs formation from fly ash by ammonium sulfate and urea at different temperatures.Some key observations were reported.Both inhibitors had higher inhibition efficiency at a high temperature(650℃)than a low temperature(350℃),while the production of PCDD/Fs at 650℃ was quite small; the main reduction of PCDD/Fs was from PCDFs,as well as,the most significant reduction of homologue was TeCDF at a low temperature(350℃)and OCDF at 650℃.In a full scale incinerator,the chemical additives injected at the high temperature section could enter the low temperature area and continued to inhibit dioxin formation,so it is necessary to do more work to evaluate different inhibitors for PCDD/Fs formation and figure out the optimal injecting temperature.

The design of an external circulation reactor dealing with algae in Taihu lake was improved,and the performance of its quick start-up process and microbial properties of granular sludge were investigated. Cyanobacteria could be treated in around 35 d when running under the condition of dosing seed sludge,continuous operation with increasing load by steps,and intermittent agitation.When start-up finished,the removal rate of chemical oxygen demand(COD)by the reactor was about 85%,and gas production rate was about 380 ml·(g COD)^-1.In addition,the removal rate of microcystins reached 92%. Microorganisms in granular sludge were mainly cocci and filamentous bacteria,containing lots of Methanococcus,and plentiful holes in granular sludge provided the condition for transport of matter and degradation of microorganisms.The dominant methane-producing archaea in the granular sludge were Methanosphaera,Methanolinea,Thermogymnomonas,Methanoregula,Methanomethylovorans,Methanosaeta. Protease and coenzyme F₄₂₀ in the sludge particles showed higher activity.Intermittent stirring device and reflux system could overcome the drawbacks of floating and crusting of cyanobacteria in the reactor and at the same time accelerate mass transfer in the reactor so as to contribute to faster startup of the reactor.

Oil samples,obtained by retorting Indonesian oil sands at different end temperatures,were analyzed by ¹H nuclear magnetic resonance spectroscopy and elemental analyzer.Based on the assignments of hydrogen peaks,integrating each ¹H NMR peak can give hydrogen distribution in oil samples.The average structure parameters were calculated using modified Brown-Ladner method.The influence of retorting end temperature on chemical structure of the oil-sands oil could be revealed from an analysis for change tendency of structure parameters with retorting end temperature.The results showed that,with increasing end temperature,the chemical structure of oil-sands oil changed significantly,i.e.,the number of aliphatic carbons C_al,aromatic peripheral carbons C_p(us),aromatic carbons C_a(us),aromatic rings R_a(us),naphthenic rings R_n(us) and total rings R_t(us) all decreasing,mainly due to decomposition of alkanes,broken of alkyl side chains,condensation of aromatic and naphthenic rings and ring-opening.Owing to the different of oil constituents produced and that of influence degree of distillation-pyrolysis,average mass of unit structure and average relative molecular weight decrease first and then increase with rise of retorting end temperature.

Groundwater pollution of petroleum hydrocarbons is one of serious environment issues, which has potential great impact on human health and environment ecosystem.Although some efforts have been made to remove the petroleum contaminants, the results seem to be unsatisfied.There are a number of compounds in petroleum pollutants with different functional groups(chainalkanes: Chs,cycloalkanes:Cys,aromatics: Ars, and asphaltenes: Aps), and their existence phases and migration pathways are various in vadose zone.However, these diversities are often ignored in prediction of environmental impacts and in design of remedial measures.So, in the present paper based on a survey for real contaminated sites the experimental study was conducted in a soil column to simulate, during leaching by contaminated water, the residue and migration of petroleum fraction #em/em#.e.Chs, Cys, Ars and Aps, in vadose zone when they penetrate into the soil and water.While the distinctions caused by both compounds characteristics and media properties was discussed.The results demonstrated that differences in solubility, fugacity and viscosity of the compounds and relative permeability of media were mainly factors leading to their migration diversity.Leaching factors of Chs, Cys, Ars and Aps in fined soil were 38.2,11.7,83.6 and 7.4×10^-3 mg·L^-1, respectively.Hence, the migration of Chs and Ars (volatilizing factor 43.9 mg·L^-1) were significant and so they could be leached out of soil column.Especially, Ars (volatilizing factor up to 43.9 mg·L^-1) was easier to leach out.Conversely, Aps was inclined to remain or be entrapped in soil due to its powerful viscosity.Because the permeability was the lowest for fine soil column, the components and amount of hydrocarbons pollutants accumulated were more and great, mainly on its upper layers, and decreased rapidly with depth of column.In contrast, for medium and coarse soil column, the residues were main Aps, and distributed in the whole column.At the end of leaching, soil samples of three columns were collected to determine the types and concentrations of compounds remained in soil.The analysis results showed that Chs and Aps could be remained in vadose zone for a long period, which is useful and helpful for risk assessment and remedial implements.