Graphite phase carbon nitride (g-C₃N₄) is a kind of metal-free semiconductor material with a forbidden band width of about 2.7 eV and has visible light response capability. Attributed to its good thermal and chemical stability, adjustable morphology and chemical structure, it is widely used in the field of photocatalysis. However, due to its low specific surface area and wide band gap, its response range to visible light is narrow and the recombination rate of photogenerated carriers is high, resulting in a low photocatalytic efficiency, which can be effectively improved by modification. The two-dimensional material Ti₃C₂ has a narrower band gap compared with other semiconductor materials, and the heterogeneous junction between Ti₃C₂ and g-C₃N₄ is expected to obtain a wider range of visible light absorption and higher photocatalytic efficiency. This article reviews the modification methods of g-C₃N₄ including morphology control, doping and constructing heterojunctions, as well as the action mechanism, preparation methods and applications of g-C₃N₄/Ti₃C₂ heterojunction in photocatalytic hydrogen evolution, organics degradation and synthesis, etc.

Hemoperfusion is one type of extracorporeal blood purification therapy. Based on adsorption, the toxins in blood of patients can be efficiently removed by hemoadsorbents. The core of hemoperfusion therapy is the hemoadsorbent materials. The development of high-performance hemoadsorbents will improve the therapeutic efficiency and effect, and reduce or eliminate the severe side effect, thus boosting the development of hemoperfusion technology. Herein, the recent studies of hemoadsorbents are reviewed, including carbon-based materials, polymer-based materials, silica-based materials, molecularly imprinted polymer (MIP)-based materials, adsorption membrane-based materials, novel hemoadsorbents, etc., and the future direction is prospected to provide a guideline for the development of novel hemoadsorbents.

Packed beds of particles are widely used in chemical industrial production as core units of fixed bed reactors, dryers, filters and other equipment. Based on traditional structured packed beds, this paper proposes some novel grille-support structured packed beds. The novel grille-support packed beds can be quickly constructed by using the new grille, including grille-support simple cubic (G-SC), grille-support body center cubic (G-BCC), grille-support loose face center cubic (G-LFCC) and grille-support compact face center cubic (G-CFCC) packing. In this paper, the flow and heat transfer characteristics of grille-support structured packed beds are numerically studied. Results show that, the packed beds with different packing forms have diverse flow and heat transfer performance. Under the same face center cubic packing form, the flow and heat transfer could be also significantly different with disparate grilles. It is also revealed that, compared with the traditional structured packed bed, the pressure drop of the grille-support structured packed bed is reduced while the heat transfer coefficient is similar, so the overall heat transfer efficiency is notably improved.

Membrane-type total heat exchanger (THX) is a device that can recover both heat and moisture, it is often used to reduce the building energy consumption and improve the indoor air quality. The effects of membrane transport properties on the moisture condensation of a THX has been numerically studied, the condensation characteristics curves and the critical condensation temperature are obtained to represent the moisture condensation characteristics, and the optimal membrane properties are recommended based on the combined consideration of safety and economy. The results show that the higher the outdoor air temperature and relative humidity, the more likely the moisture condensation takes place. The membrane thermal conductivity has a slight influence on the condensation characteristics and performance of the THX, the increase of the in-membrane moisture diffusivity can significantly improve the anti-condensation characteristics and effectiveness of the THX, with the moisture condensation occurring more easily at the membrane surfaces at the junction of the supply outdoor and exhaust indoor airstreams.

Heat dissipation design and optimization of cold and hot end is a key link to improve the performance of thermoelectric cooling devices and promote their application. This paper focuses on the thermoelectric cooling device, and studies the influence of the thermal conductance distribution between the cold and hot end on the cooling performance. In order to comprehensively consider the influence of various physical factors of heat, electricity and its conversion process, the distribution ratio parameter of the thermal conductance of the cold end in the total thermal conductance (w) is introduced, and the relationship between the cooling performance parameters of the thermoelectric cooling device and the distribution ratio are solved using the one-dimensional analytical method. On this basis, the optimal distribution ratio corresponding to the maximum cooling capacity and the highest cooling coefficient of performance (COP) under different operating currents, thermoelectric arm structure, external fluid temperature and total thermal conductance is analyzed. The result show that there is an optimal w between 0.35 and 0.45 that the cooling performance of the thermoelectric cooling device reaches the optimal. The cooling capacity and COP always have the same trend and will firstly increase, and reach up to the maximum, and then decrease with the increase of w, and there is an optimal w so that the cooling performance of the thermoelectric cooling device is optimized. The change of operating current has the greatest influence on the optimal w, and as the operating current increases, the optimal w decreases. The greater the temperature difference between the hot and cold fluids, the smaller the optimal w. The geometrical parameters of the thermoelectric arm and the total thermal conductance of the cold and hot ends of the thermoelectric cooling device have negligible influence on the optimal w.

The laser interferometric method and high-speed camera technology are combined to study the dynamic characteristics of a single ethanol bubble generated by the hydrophobic ITO heating surface, and to study the microlayer at the bottom of the bubble. The process of bubble growth and detachment was compared and analyzed with previous hydrophilic heating surface experiments. In this experiment, two high-speed cameras were used at the same time: one recorded the interference fringes of microlayer at the bottom of the bubble, and the other recorded the growth and detachment images of the single bubble from the side view. By comparing these images frame by frame and comparing with the hydrophilic heating surface experiment, it is found that the growth period of the hydrophobic surface bubble has no waiting period, and the time of the detachment period is much longer than the growth period, the microlayer at the bottom of the bubble is unstable and random slip occurs during the growth and detachment process of the bubble.

In electric vehicles, a battery thermal management system is essential to guarantee the safety of the battery pack. In the present study, an optimization method is developed to design the shape of the divergence and convergence plenums in an air-cooled battery thermal management system (BTMS) with parallel channels. The control points are used to describe the plenum shape, and the numerical simulation method is introduced to evaluate the performance of the BTMS. The height distribution of the control points is adjusted one step by one step, with the target of minimizing the temperature difference of the battery pack. Finally, the designed plenum shape is obtained according to the optimized height distribution of the control points. The results of typical cases show that the heat dissipation performance of the air-cooled BTMS with Z-type flow can be significantly improved after the plenum shape optimization using the proposed optimization method. Compared with those in the original system, the maximum temperature of the battery pack in the optimized system is more than 3.7 K lower, and the temperature difference is reduced by more than 85%, while the pressure drop of the system is only increased by 20% under different inlet flow rates. Compared with those in the optimized system in the literature, the temperature difference of the battery pack in the present optimized system is reduced by more than 48% without increasing the pressure drop.

A new phase change model based on VOF (volume of fluid) method is proposed to calculate the energy and mass source terms in the equations describing the vapor-liquid phase change process. The heat transfer occurring near the interface is considered as a transient thermal diffusion process. The phase change model calculates the energy and mass source terms in terms of the temperature of the interfacial cell, thermal physical properties of gas and liquid phases, and the time step. One-dimension Stefan problem and two-dimension horizontal film boiling were adopted to verify this new phase change model. Simulation results of the interface position and temperature distribution agree well with analytical solutions. The effect of the time step on the simulation accuracy is discussed. The results show that the deviations between the simulation results and the theoretical results decrease with the decreasing time step.

Taylor flows in mini tubes have been widely adopted in energy and chemical industrials. In order to study characteristics of two-phase interfaces and frictional pressure drops, the liquid-liquid Taylor flow in mini channels with circular and flat cross sections are studied numerically using the moving frame reference method. Effects of Reynolds number, ratio of width to height, and volume fraction of the dispersed phase on two-phase interfaces, liquid film thickness, and pressure drops are analyzed. The numerical results show that the dispersed droplets in circular tubes are consist of spherical nose and tail. The dispersed flows in flat tubes are confined by the channel wall, leading to flat droplets. The two-phase interfaces shrink with increasing Re for all tubes, leading to a higher liquid film thickness between interfaces and channel walls at a higher Re. The liquid film thickness is uniformly distributed along the circumferential direction in circular tubes, while the liquid film in flat tube is much thinner at the flattened part compared with the arc corner. Two-phase pressure drops increase with increasing Re and ratio of width to height, while they decrease with increase in droplet volume fraction. Three components contribute to the two-phase pressure drops, which are the continuous pressure drop, the dispersed pressure drop, and the interfacial pressure drops. Compared with the other two, the interfacial pressure drop contributes more to the total pressure drop. A new correlation to predict the pressure drops in circular and flat tubes is developed.

At present, the cooling requirement of the high-powered, time-vary and large heat flux airborne avionics on military helicopters is increasing exponentially. In order to improve the performance of military helicopters and solve the cooling requirement of avionics, a new type of liquid cooling system, consisted of a liquid cooling loop and a vapor loop subsystem is developed. Steady state experiments with evaporator and condenser have been carried out on ground. The method of combining simulation with experiment is adopted in research process. The steady-state simulation calculation and experimental performance of evaporator and condenser are carried out in refrigeration cycle. The simulation model is validated and the parameters are revised. The above research can provide some references for the design of key components of helicopter liquid-cooling/evaporative refrigeration system.

A physical mathematical model of oil sand packed bed thermal energy storage (TES) which can be applied in high temperature TES system is established. The charge/discharge outlet temperature and thermocline thickness are investigated when charge and discharge process are operated simultaneously. The results indicate that the small charging power and lower increasing rate of charge outlet temperature are obtained in the end of simultaneous charge and discharge. The smaller the net TES flow rate, the longer it takes to reach a stable charge outlet temperature under the condition of the same TES medium in the TES tank. The conventional TES tank thermocline thickness is thinner than oil sand packed bed when operated at the same net charge flow rate. The stable/unstable simultaneous charge and discharge are investigated based on cycle process of square wave thermal source. The discharge outlet temperature and the thermocline thickness gradually increase after the end of each cycle due to the effect of the superposition of the cycle process. The discharge outlet temperature fluctuates periodically.

Experimental study of jet impingement heat transfer with molten salt under the influence of external constant magnetic field was generated by permanent magnets. Both stagnation correlation and radial distribution of Nusselt number under magnetic field were obtained. The results showed that the Nusselt number with magnetic field became higher than that without magnetic field at stagnation region and jet impingement heat transfer was comparatively enhanced, while in wall jet region, the enhancement of heat transfer was gradually weakened. In addition, when the Reynolds number was constant, the Nusselt number of molten salt increased with increasing of the intensity of magnetic field, and the most enhanced heat transfer existed at the stagnation point. Under the conditions of Reynolds number Re=6400 and the intensity of magnetic field B=2800 Gs, the stagnation Nusselt number of molten salt was about 6 % higher than that without magnetic field. It can be seen that the magnetic field may promote the jet impingement heat transfer of molten salt.

A complex function composed of linear weighted sum of the entransy dissipation rate (EDR) caused by heat transfer and total pumping power is established in this paper. Under the conditions of fixed total condensation rate and heat transfer area, constructal optimization of a shell-and-tube condenser (STC) with organic fluid is carried out by taking minimum complex function as optimization objective. The minimum complex function and the optimal external diameter of the condensation tube are obtained. The results show that compared with the initial design construct, the optimal construct of the STC increases the total EDR caused by heat transfer by 10.70%, and reduces the total pumping power and complex function by 54.94% and 6.46%, respectively. This illustrates that the complex function sacrifices a certain heat transfer performance, and improves the fluid flow performance evidently, which leads to the overall performance improvement of the STC. The twice minimization of the complex function can be realized by choosing an appropriate number of the condensation tubes. New guidelines for the optimal structure designs of the STCs are provided by introducing entransy theory into constructal optimizations of the organic fluid STCs, and this method can be further extended to the optimal designs of the cycle systems with organic fluids.

Traditional numerical simulation methods have shortcomings of large amount of calculation, longer calculating time, so they can not meet the development requirement of modern industry. A POD reduced-order model for flat tube fin heat exchanger is constructed by combining body-fitted coordinates with proper orthogonal decomposition. The flow and heat transfer process of flat tube fin heat exchanger is calculated under unique heat flux boundary conditions. And its calculation results are compared with calculation results of the finite volume method (FVM). Results show that the POD method is feasible for solving the flow and heat transfer problems in complex structures such as flat tube fin heat exchangers and that can accurately capture the temperature field and velocity field information for different parameters. The relative deviation increases with the number of variables between the POD and FVM. The relative average maximum error of reconstructed velocity fields and temperature fields are 1.90% and 0.308%, respectively. Both cases are three-variable conditions. The POD method can increase the calculating speed of the traditional FVM by 3093.4 times under the premise of ensuring the calculating accuracy. This study has certain theoretical reference for improving the numerical design efficiency of flat tube fin heat exchangers and expanding the engineering application field of POD method.

In order to explore the performance of the multistage pin-mesh ionic wind cooling system and optimize the design for the multistage ionic wind heat dissipation device, a multistage pin-mesh ionic wind cooling system device was proposed to study the effect of multistage number, stage clearance, and discharge voltage on the maximum wind velocity of the ionic wind and the heat dissipation temperature drop of the heating plate. The results show that at the same voltage, the multistage heat dissipation performance is better than the single-stage, which can reduce the 11 W heating plate to a lower temperature and obtain a larger maximum wind velocity of the ionic wind. When the maximum wind velocity of the ionic wind reaches the maximum value, it does not mean that the heat dissipation performance is the best, because the optimal heat dissipation performance can be achieved when the average wind velocity reaches the maximum value. The multistage device using the pin-mesh integrated structure has a maximum wind velocity of 2.6 m/s, which can reduce the temperature of the 11 W heating plate to about 90℃ and the temperature drop to about 105℃, while the single-stage can only drop to 110℃ and the temperature drop is about 85℃.

The structures and the heat and mass transfer processes are complex and variable in porous media. Therefore, the further study should be taken on the precise analysis models for describing micro-pore distributions characteristics. Based on the concept of REV (representative elementary volume), two microphysical models for porous media (hollow skeleton primitive model, solid particle primitive model) were proposed. And the formulas for thermal conductivity calculation on two microphysical models were established respectively. In view of the micro-structure characteristics of porous media, the fractal method was used for fractal correction of these two primitive models, which was better represented micro-pore structures. Based on these models, the parameter influences on the thermal conductivity of porous media were analyzed by numerical simulation. The accuracy of the models were verified by the experiments of the self-developed experimental equipment.

The heat and mass transfer of fluid in a square cavity with a solutal and thermal source is numerically investigated. For different Rayleigh numbers, buoyancy ratio, Soret and Dufour numbers, the bifurcation characteristics of heat and mass transfer in a symmetrical square cavity are studied systematically. The results show that there is a critical Ra_c for onset of bifurcation that changes the fluid flow pattern. When Ra < Ra_c, the streamline, temperature and concentration are symmetrically distributed; when Ra > Ra_c, the transition from a symmetrical state to a stable asymmetric state is observed. The fluid is more prone to bifurcation with increasing of buoyancy. An increment to the Soret and Dufour effects enhances heat transfer symmetry and increases the critical Rayleigh number for breaking symmetry.

The influence of non-condensable gas on the direct contact condensing behavior and heat transfer characteristics of steam jet in subcooled water is investigated by two-dimensional axisymmetric numerical model. Based on Euler-Euler two-fluid model in CFX, the steam condensation is calculated with thermal phase change model. The composition variation of steam-air mixture is realized using species transport equation for the gas phase. The gas mass flow at nozzle outlet is 300 kg/(m²·s), and non-condensable gas is within 15%. The results show that non-condensable gas obstructs the direct contact between steam and subcooled water, forming the thermal resistance and deteriorating the condensation heat transfer. The thermal resistance and the length of jet region increase with the increase of non-condensable gas. While the condensation rate decreases with the increase of non-condensable gas. The presence of non-condensable gas prevents vapor from being condensed completely, and the remaining vapor is independent of the original non-condensable gas.

Printed circuit heat exchanger (PCHE) is a promising candidate in the field of supercritical CO₂ Brayton cycle due to its high thermal efficiency and compactness. In this paper, the effects of wave angles (15°—30°) on the heat transfer performance of sinusoidal channels under turbulent conditions are numerically studied at first. The results show that the heat transfer performance increases with the increase of wave angle (the maximum increase of the heat transfer rate is 7.1%), while the pressure drop on the hot side increases more significantly when compared with that on the cold side. Secondly, the local flow and heat transfer characteristics in the different regions of the channels are analyzed by pitches. Zones with large and small temperature differences are observed in the inlet zones on the hot and cold sides, respectively. Meanwhile, the inlet zones are found to be related to great pressure drops and should be carefully optimized. Finally, a novel hybrid structure of sinusoidal channel combined with straight channel is designed and its thermal hydraulic performance is tentatively investigated.

The interaction between high-enthalpy/chemical-nonequilibrium flow and surface materials brings complex coupling convective heat transfer characteristics, leading to weak applicability of hot-wall correction method (HWC) for rapid evaluation of aerodynamic thermal environment. In view of the above problems, this paper deals with HWC improvement via coupling numerical simulation of catalytic heating on carbon-based materials in carbon-oxygen dissociation environment. On the basis of the numerical simulation of hypersonic aerodynamic heating/structural heat transfer interaction, the chemical non-equilibrium effect and the interface high-temperature chemical effect were deeply analyzed. The coupling results show that the linearity of wall chemical heatflux and temperature is weakened due to interface thermochemistry, while the temperature-gradient part maintains high linearity. Accordingly, a new idea to improve HWC was proposed by decomposing the contribution of heatflux into two physical processes: one obeying the conventional HWC, and the other independent of boundary layer profiles. In-depth analysis shows that the latter can be simply dealt with by computing reaction rates from chemistry mechanism, eliminating the need for full CFD/CHT coupling computation.

The gas concentration detection method based on laser absorption spectrum technology has the advantages of non-contact, rapid response and high sensitivity. However, on-line detection of industrial gas by laser spectroscopy is susceptible to temperature changes, resulting in an increase in concentration measurement deviation. In this paper, an experimental platform for water vapour laser detection at various temperatures (373—393 K) is built. The gas concentration is inverted by direct absorption method. The mechanism of temperature effect on the absorption spectroscopy characteristics of ammonia is explored, and a new method is proposed to correct the inversion concentration at various temperatures. The results show that the inversion error of concentration measurement value is reduced from 35% to 0.9%—3.5%.

Two kinds of square microchannel heat sinks with different structures were established based on CFD software, and numerical calculations were carried out to simulate the temperature field and pressure field of the heat sink. On this basis, the effects of different microchannel distribution patterns, different mass flow rates and different heat fluxes on the temperature and pressure drop of the heat sink are studied. At the same time, based on the comparison analysis of the entransy dissipation theory, a better optimization scheme of heat sink in square microchannel is obtained. A better optimization scheme, under the fixed boundary heat flow condition, the smaller the entransy dissipation, the better the heat exchange effect. The calculation results show that with the increase of mass flow rate, the heat sink temperature gradually decreases, the pressure drop increases gradually, the PEC gradually increases, and the entransy dissipation decreases; as the heat flux density increases, the heat sink temperature gradually increases, the pressure drop gradually decreases, the PEC gradually increases, and the entransy dissipation gradually decreases. The microchannel distribution pattern is the upper inscribed circle radius-lower layer circumcircle radius distribution, the temperature of the heat sink is lower, the PEC is larger, the entransy dissipation is smaller, and the heat transfer efficiency is higher.

Placing twisted inserts into tubes is a common method of high maneuverability to enhance tube side heat transfer. The mechanism of heat transfer enhancement is mainly to induce secondary flow by twisted inserts in the tube. Under a uniform wall temperature (UWT) thermal boundary condition, the laminar flow and heat transfer characteristics in a circular tube inserting different twisted vortex generators are numerically studied. It is found that when the geometric area of material cut from the traditional twisted tape to form different vortex generator inserts is identical, the tube-side heat transfer capability that inserting the isosceles trapezoidal vortex generators is the best, followed by that of the right-angle trapezoidal vortex generators, and the circular tube inserting rectangular vortex generators has the worst heat transfer capacity. The peak value of the local Nusselt number on the tube wall and its circumferential position is related to the shape of the vortex generator. However, the influence of the shape of vortex generators on the tube-side resistance coefficient is small. For the studied cases of different vortex generators placed inside a circular tube, both the secondary flow intensity parameter Se and the averaged Nusselt number Nu_m increase with the increase of Reynolds number, and the law of their change with Re are close to consistent. The averaged Nusselt number Nu_m is related to the secondary flow intensity parameter Se as a power function. The intensity of secondary flow in a circular tube fitted with vortex generator inserts determines its convective heat transfer intensity.

In this paper, the thermal degradation kinetics of soybean was studied by dynamic thermogravimetry (TGA). The thermal decomposition characteristics and kinetics of soybean under different pyrolysis conditions were explored by changing the heating rate (5, 10, 20 and 40℃/min) and the atmosphere conditions (nitrogen and air). According to the trend of TGA and DTG curves, the pyrolysis of soybean can be divided into four stages: the first two stages correspond to the removal of free water and crystal water, and the last two stages correspond to the secondary decomposition stage and the main decomposition stage of main components (starch, protein and fat). In the latter two stages, due to the presence of oxygen, the thermal decomposition process of soybean appeared different, and the activation energy and carbon residue rate of the reaction decreased. Compared with pyrolysis in nitrogen atmosphere, soybean showed lower activation energy and fire safety in air atmosphere. In this paper, the difference of pyrolysis kinetics of soybean in different atmosphere was studied for the first time, and the intrinsic law of pyrolysis and its fire safety were revealed.

The development of coalbed methane is an important part of unconventional natural gas in China. Methane gas in coal mainly occurs in the form of adsorption in a series of nanopores. The dynamic process of adsorption is of great significance for the exploitation of coalbed methane. The low field nuclear magnetic resonance experimental system for measuring the dynamic adsorption characteristics is built, and the dynamic adsorption process of methane with time and pressure is quantitatively analyzed by NMR transverse relaxation map. The methane in coal samples in the transverse relaxation map of NMR presents the multi-peak distribution. The relaxation time peak of 0.1—1 ms contains the information of methane gas content in nanopores. With the increase of time, the gas is gradually converted to the adsorption state. The isothermal adsorption curve of the sample can be obtained from the equilibrium adsorption amount at each pressure, which conforms to the fitting of Langmuir model.

The separation efficiency of cyclone separator for fine particles under 5 μm needs to be improved. In this paper, the concentration distribution of 1 μm particles in cyclone was studied by Reynolds stress model and stochastic trajectory model. The results showed that fine particles were gathered in the annular region where the upstream and quasi-free vortex overlap, forming a concentration peak. By analyzing the radial distribution of particles at different axial positions and at different times, it was found that there were two formation mechanisms. Firstly, the mismatch between the height of separation space and the nature vortex length led to the vortex end sweep the particles on the wall, resulting in a strong backmixing of particles. Then, backmixing particles moved outward due to the separation effect of internal swirl. The other mechanism was the convergence effect of downward flow entrained fine particles. Moreover, the former contributed more to the formation of particle concentration peak. Most of the particles in the dense ring would continue to move outward during running up, and then they would be separated by the external swirling flow again after entering the downflow. A few particles escape due to the entrainment of upflow or short-circuit flow. Inhibition of particle backmixing is the key to ameliorate particle dense ring. It can be achieved by optimizing the height or the internals.

The hollow polypyrrole nanoparticle with porous shell was incorporated into poly(ethylene oxide) monomer to fabricate the mixed matrix membrane by free radical polymerization. Morphology of the membranes showed the polymeric filler had good interfacial compatibility with the polymeric matrix without obvious defect. The results showed that the gas permeability of membranes increased at first and then decreased as the filler loading increased, while the permselectivity of CO₂/N₂ decreased_{andthat of CO2/CH4 maintained constant basically. The research showed that the diffusion coefficients decreased due to the blockage of the pore in shell of nanoparticles by polymeric matrix, the improvement of the gas permeability was mainly contributed by the improvement of the solubility coefficient, which also affected the solubility selectivity and then the permselectivity. The optimum nanoparticle loading was around 0.5%. In this case, the permeability of CO2 was about 6.5×10^-11 cm³?cm?cm^-2?s^-1?Pa^-1 (31% higher than the pristine polymeric membranes), while the permselectivity of CO2/N2 was about 30 (34% lower than that of the pristine polymeric membranes) and the permselectivity of CO2/CH4 was about 14 without significant sacrifice. The result showed the polypyrrole nanoparticles with porous shell was potential for application in CO2/CH4 separation.}

Slowly-time-varying characteristics are common in chemical processes, and the changes of slowly-time-varying parameters in an operating cycle gradually decrease the performance of chemical process. So, enough margins must be added for design variables during the phase of process design according to the possible worst-case influence of slowly-time-varying parameters. The design margins will be released gradually compensating the worse influence of slowly-time-varying parameters in an operating cycle. It can be called as a perfect operation that the operating point is on the boundary of process constraints when an operating cycle is ending. In this paper, the margin release mechanism of slowly-time-varying chemical processes is analyzed. Based on the universal dynamic model containing slowly-time-varying parameters, the full cycle operation optimization is solved by minimum principle of optimal control. It is found that the optimal margin release trajectory is related to the curve of slowly-time-varying parameter, ensuring that the optimal margin release is only dependent on the operating cycle. This mechanism is verified by the example of acetylene hydrogenation reactor. For slowly-time-varying chemical processes, the shorter the operating cycle is set, the faster the design margin is released, the higher temporary economic benefit is obtained; otherwise, the longer the operating cycle is set, the more integrated economic benefit is accomplished.

For a kind of nonlinear affine systems, an economic model predictive control algorithm for online estimation of switching time is proposed and extended to the long period control process. In a limited time, the switching time is used as a variable to estimate in real time, and the optimal switching point is determined, so as to ensure that the economic performance is optimal at every moment under the premise that the control objective is reachable. The situations of unreachable control objective and poor economic performance caused by traditional switching economic model predictive control strategy are avoided. Furthermore, the strategy is applied as a single cycle to the long period optimization control process. Once the disturbance occurs, a new optimization control cycle is started. The flexible switching between the optimized mode and the control mode can be realized, and the disturbance can be dealt with in time. The simulation results show the effectiveness of the method.

Due to the stratification of sludge particles in the ultrasonic field, the acoustic interaction forces the particles to agglomerate on a plane perpendicular to the direction of ultrasonic propagation. Therefore, the thickness of sludge can significantly influence the characteristics of ultrasound-assisted hot air convective drying municipal sewage sludge. In this paper, the stratified aggregation phenomenon of sludge with different thicknesses was observed in the ultrasonic field using the experimental method. It was found that the stratification of the internal structure of sludge became more obvious with the increase of its thickness. The effects of ultrasound on the drying time and the drying rate of sludge with various thicknesses were studied. Meanwhile, the effective moisture diffusivity (D_eff) was analyzed. The experimental results demonstrated that the larger the sludge thickness, the longer the time length of the first falling rate stage and the promotion of the drying rate was worse when the ultrasonic power was less than 135 W. The situation was opposite at the constant rate stage. Among the sludge with the thicknesses of 5, 10, and 15 mm, the total drying time and energy consumption of the sludge with a thickness of 10 mm decreased the most substantially under the condition of ultrasonic power less than 90 W. The smaller the thickness of sludge is, the less obvious the effect of ultrasound on the effective moisture diffusivity, and vice versa.

Regeneration using low-grade thermal energy is one of the most important components of the thermal regenerative battery (TRB) system. In this study, the effects of the regenerative electrolyte on the performance of TRB and the effects of temperature and mass transfer on the thermal regeneration are studied. The experimental results showed that the maximum power of TRB using regenerated electrolyte was 5.7 mW, which was 14% lower than that of TRB using initial electrolyte (6.5 mW). In the process of thermal regeneration, the increasing of temperature can obviously strengthen the process of thermal regeneration, and the performance of thermal regeneration can also be effectively improved by using glass balls bed and stirring.

To improve the value of power battery modules retried from electric vehicles, and to decrease the utilization cost and mitigate the related environmental pollution, it is of great importance to study the cascade utilization of the retired power batteries. With respect to the scenario of applying the retired power battery for the electricity storage in power grid, we measured the capacity and studied experimentally the electric and thermal performance of a retired LiFePO₄ battery module under various charge and discharge C-rates. Further, to ensure adequate uniformity in-between cells of the battery module during charging/discharging, we employed the active electric balancing strategy, and did a comparison study on the discharged electricity, and voltage and temperature behaviors during discharge, for the battery module having implemented the active-balance operation or not. The results indicate it benefits to the battery??s electro-thermal performance, lifespan, and safety if constraining the SOC of the battery module within a proper range during charge/discharge operations.

A library of poly(N-isopropylacrylamide-co-N-tert-butylacrylamide-co-acrylic acid) (P-NIPAm-tBAm-AAc) hydrogel nanoparticles with good dispersion and uniform size were prepared by precipitation polymerization method. Their hydrodynamic diameters were controlled from 71 nm to 304 nm proved by dynamic light scattering (DLS) with adjusting the polymerization formulation, while the PDI values are all below 0.1. Due to the charge repulsion, the particle size increased from 71 nm to 219 nm when the feeding of electrophilic monomer AAc increased from 5% to 50%(mol) in polymerization. Meanwhile, the inverse effect was also revealed on the hydrophobic monomer tBAm, that is, the nanoparticle size decreased along with increasing its feeding ratio. Besides, the increased usage of the surfactant SDS resulted in the microspheres being smaller to 71 nm. It is proved that the NPs size greatly affected their affinity to the target peptides (LEVLFQGP), and the results showed that the adsorption rate increased with decreasing the nanoparticle size. When the molar ratio of AAc was 20% and the diameter was 128 nm, the adsorption rate could reach 90%. Furthermore, the adsorption and desorption experiment was performed with changing the environmental temperature from 35℃ to 5℃ since the volume phase transition temperature (LCST) of NPs is (20±2)℃ proved by DLS. After five times adsorption/desorption circulation experiments, the reduction of NPs adsorption rate on target peptide was below 7%. Therefore, the prepared and screened NPs are size controlled and reusable.

Since the thermal insulation structure with foam layer is one issue in current refrigerator production, the physical parameters in polymer foaming process are studied, and the simulation method of foam layer based on changing these physical parameters is proposed to optimize the structural design of refrigerator doors. Informed by theoretical analysis of polymer foaming process, these physical parameters related to foaming layer structure is discussed, and their changing and expression is analyzed. Based on the statistical data from literature and the polymer foaming experiments, the simulation model of foaming process with CFD-UDF is established, to analyze the refrigerator door structure. At last, one refrigerator door is proposed as the instance to discuss its physical parameters and foam layer structure, and to validate this CFD-UDF model.

To reveal the role of interface micro-concentration distribution on the evolution of materials structure, silver crystallization was investigated by the in-situ optical microscopy and lattice Boltzmann simulations. Silver particles were synthesized by electrodeposition, in which silver oxide colloid particles were generated as the by-products. The migration velocity of colloid particles in the electrolyte was regulated by the electric field. With the increase of migration velocity of colloid particle, mass transfer increased, the diffusion layer in the front of the growth became thinner, and the concentration gradient became sharper. As a result, the morphology of silver particles changed from spherical nanocrystals to symmetrical dendrites, and the growth rate increased from 10 μm²/s to 60 μm²/s simultaneously. Finally, it was proposed that the micro-concentration field in the diffusion layer is the main mechanism dominating the evolution of particle morphology, which was verified by the lattice Boltzmann simulation of convection diffusion and phase transition.

In order to clean the ultrafiltration membrane in the process of seawater desalination, this paper studied the cleaning effects of backwash water and chemical agents on the ultrafiltration membrane by using the ultrafiltration pilot equipment. Effects of different backwash water on the transmembrane pressure difference were studied. The results showed that the cleaning effect was in the order of fresh water (tap water) > ultrafiltration water > reverse osmosis concentrated water. In addition, cleaning effect was as follows: citric acid > oxalate > hydrochloric acid > sodium hypochlorite > sodium hydroxide. Citric acid had the best cleaning effect, and the pure water penetration rate could be restored from 283.24 L/(m²·h) to 571.56 L/(m²·h). Moreover, the effect of alkali washing and acid washing together is better than that of cleaning alone. After cleaning with sodium hydroxide and then citric acid, the pure water transmission rate can recover from 283.24 L/(m²·h) to 818.81 L/(m²·h). The results of this study have a good application prospect for the maintenance of ultrafiltration membrane in seawater desalination.

As novel functional materials, metal-organic framework (MOF) and graphene oxide (GO) have received great attentions in recent years. In this work, MOF@GO nanocomposite (MOF-199@GO) is prepared by an in-situ growth method. A novel and highly efficient nanofiltration (NF) membrane can be facilely fabricated via surface decoration of MOF-199@GO onto poly(vinylidene fluoride) (PVDF) substrate before interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) in order to overcome the hydrophobicity of PVDF membrane. The structure and morphology of MOF-199@GO and MOF-199@GO modified PVDF polyamide composite membrane are characterized by XRD, SEM, TEM, AFM and zeta potential. MOF-199@GO modified PVDF composite NF membrane which possesses dense and uniform polyamide thin-layer exhibits higher negative surface potential (up to ~37 mV) at pH 9.5. The performance of MOF-199@GO modified PVDF polyamide composite NF membrane has been investigated by determination of pure water flux and salt rejection. The prepared NF membrane MG3 exhibited highly efficient rejection of MgSO₄, Na₂SO₄, NaCl and MgCl₂, which are 93.56%, 93.04%, 87.48% and 87.11%, respectively. This work provides a worthy reference for designing highly efficient NF membranes modified by MOF and relevant materials.

In order to settle the membrane fouling of reverse osmosis membranes in seawater desalination process, this study reported a novel strategy based on forward-osmosis process and discussed the effects of different factors like different cleaning combination among reverse osmosis product, simulated reverse osmosis concentrate and simulated seawater, as well as cleaning time on the membrane permeate flux and salt rejection. For irreversible fouling, the effects of different chemical cleaning agents, immersion time and concentration were also investigated in this study. The results exhibited that the cleaning combination between diluted water and simulated reverse osmosis concentrate possessed the best cleaning performance in the process of forward-osmosis cleaning. Such approach also enhanced normalized flux from 9.48 L/(m²·h·MPa) to 13.6 L/(m²·h·MPa) and enhanced NaCl rejection from 80.59% to 92.80%. Furthermore, the normalized flux was enhanced from 9.48 L/(m²·h·MPa) to 14.3 L/(m²·h·MPa) and NaCl rejection was also enhanced from 80.59% to 96.27% after soaking in 2%(mass) citric acid solution for 2h, soaking with 1%(mass) ethylenediamine tetra-acetic acid tetrasodium salt and 0.3%(mass) sodium tripolyphosphate solution for 1.5 h. According to the result of SEM images and AFM images, the forward-osmosis cleaning strategy could not cause the damage of selective layer of membrane surface and caused the drop of inorganic and organic fouling on the membrane surface. Hence, cleaning fouled RO membranes by such approach could prolong the chemical cleaning cycle and reduce the amount of chemical cleaning agent, which has certain industrial application perspectives.

In this paper, nitrate (KNO₃, NaNO₃) and carbonate (Li₂CO₃, K₂CO₃, Na₂CO₃ and CaCO₃), which are composite inorganic phase change thermal storage materials suitable for industrial thermal storage, non-toxic and less corrosive, are used as phase change components, respectively. The thermal properties (melting point, latent heat) of 4 different ratios of nitrate phase change components and 6 different ratios of carbonate phase change components were studied, and a distribution ratio of molten salt phase change components was selected respectively. Using the principle of porous carrier adsorption, two types of composite molten salt thermal storage materials with the best ratio were prepared. The ease of decomposition of the thermal storage materials in different media atmospheres (Ar and air) was analyzed. TG-DSC-MS tested high temperature thermal decomposition products show that the composite nitrate thermal storage materials have stable physical and chemical properties and good safety when storing thermal at medium temperature (300℃), but they are easy to decompose NO and high temperature (500℃) or higher. NO₂ and air atmosphere are more likely to generate toxic gases, and composite carbonate thermal storage materials are more likely to generate CO in air than Ar, which affects the safety of the thermal storage process.