Some refrigerants have begun to be replaced due to their strong greenhouse effects. The waste refrigerants should be degraded. China is the main producer and consumer of refrigerants, so there will be a huge demand for destruction of waste refrigerants in the coming decades. This paper presents a review of the main destruction technology for waste refrigerant destruction, including the summary and analysis for the combustion method, plasma method, and catalysis method. Further research trends of waste refrigerant destruction are also discussed in this paper.

As a new type of functional material, open-cell metal foam has developed rapidly in the field of heat and mass transfer in recent years due to its small specific gravity, large specific surface area, high porosity and high thermal conductivity, especially the composite material formed after filling the medium. With its high thermal conductivity, the thermal conductivity of the filling medium was greatly improved. The current research mainly focuses on the flow and heat transfer process, and the systematic research on the effective thermal conductivity was not comprehensive, especially based on the complex three-dimensional structure. And most of the research was also focused on the experimental measurement, there were different gaps in the test conditions and errors. Effective thermal conductivity is an important parameter for the heat transfer and thermal properties of open-cell metal foam composites. Therefore, exploring the effective thermal conductivity and its influencing factors from the structural aspect is one of the ways to solve the problem. Based on the complexity of the three-dimensional structure, starting from the boundary model and the unit cell analysis model, a more comprehensive overview of the current research status of the effective thermal conductivity of open-cell foam metal composites was given. The methods and main models currently used in the research were summarized. It was pointed out that the influence of microscopic pore structure was ignored by the boundary model of macroscopic analysis of heat conduction problems by homogenization method. The empirical correlation analysis method of the cube model and the Kelvin model in the unit cell analysis model were emphasized. Its key point was pointed out that the shape parameters of the porous structure were fitted to the expression of adjustable empirical parameters in the form of porosity. In addition, 3D computed tomography was combined with numerical simulation methods. The research methods of the effective thermal conductivity of the real open-cell foam structure under high-precision calculation were proposed, especially the lattice-Boltzmann method for the study of the open-cell foam structure. The influence and law of the anisotropy of the real pore structure on the effective thermal conductivity were mainly analyzed. For 3D reconstruction numerical analysis, a simplified comparative analysis model needs to be sought to greatly reduce the computational cost. Relying on the existing scientific and technological research methods, the focus of the later research is the accurate fitting method of the empirical correlation model, the unification of the feature correlation, and the simplified comparative analysis model in the high-precision numerical simulation calculation.

Applications of transparent superhydrophobic surface can block the adhesion of atmospheric dust, reduce the surface reflectivity and improve the transmittance rate. Compared with the traditional anti-reflection film, the superhydrophobic anti-reflection film has the advantages of self-cleaning, low reflectance and high transmittance rate. The basic concept and principle of transparent superhydrophobic surface was introduced. The advantages and disadvantages of four preparation methods (deposition method, etching method, self-assembly method and sol-gel method) of superhydrophobic anti-reflection films in recent years were compared and the research progress of functional superhydrophobic surfaces in recent years was reviewed. Finally, the potential application of superhydrophobic anti-reflection coatings was prospected. The future research will focus on improving the performance of superhydrophobic anti-reflection films and developing advanced superhydrophobic anti-reflection films suitable for various applications.

This paper summarizes the research status of vapor-liquid separation technology and its device. Separations using gravity, inertia, filtration, centrifugation and distillation are detailed analyzed. Attentions are paid to their implementation to heat exchangers and refrigeration systems. Moreover, the advantages and disadvantages are compared. Results show that the mechanisms of the vapor-liquid separation technology are unclear and not universally adopted. Combination of the vapor-liquid separation and vapor-liquid phase change heat transfer has great potential in enhancing heat transfer and improving system efficiency.

Anion exchange membrane fuel cell (AEMFCs) have attracted worldwide attention because of several inherent advantages such as environmental friendliness, the utilization of less expensive metallic catalysts and the rapid electrode reaction rate. Anion exchange membrane is the core component of AEMFCs, and its properties determine the performance, energy efficiency and service life of fuel cell. In this paper, the preparation, properties and applications of anion exchange membranes with different skeleton structures which included poly(phenylene oxide), poly(arylene ether sulfone), polyolefin and polybenzimidazole are described, and the main problems and developmental trend of polymer-based AEM are also discussed.

The fugitive emission of dust seriously affects the surrounding air quality and workers' health in the process of wind erosion, unloading and reclaiming of iron and steel works' raw material piles. This paper described technologies and problems of dust emission control used in raw material piles of iron and steel works. Through the estimation formula of static dust and dynamic dust shown that the fugitive emission of dust can be effectively reduced by decreasing the difference between the ambient wind speed of environment and the critical wind speed of the raw material piles. Introduced watering dust suppression, spraying dust suppressants, windbreak dust suppression, closed stockyard dust suppression and new biological nano-film dust suppression, cloud dust suppression technologies. Compared the aspects of dust suppression mechanism, dust suppression efficiency, influencing factors, technical advantages and disadvantages to obtain the optimal structure parameters of dust suppression effect. Proposed the research direction in the future.

The electrodialysis based air dehumidification technology utilizes a high-voltage electric field to charge gas molecules, and realizes the separation of water molecules and other charged molecules, such as oxygen molecules, through nanoporous graphene oxide membranes. The interlayer spacing between the double-layered membrane will affect the transport characteristics and thermodynamic properties. This paper adopts Molecular Dynamics simulation to study the diffusion and adsorption of charged water and oxygen molecules through the membrane with different membrane spacings. The results show that the membrane spacing mainly affects the formation of interlayer hydrogen bonds, and consequently affects the adsorption energy between the nanoporous graphene oxide and gas molecules. There exists an optimal interlayer distance of 1.25 nm, resulting in the best water molecule penetration performance that the selectivity of water/oxygen has achieved the highest value of 1.14, a three times increasement compared to the case without an electric field.

Atmospheric water harvester based solar sorption technology uses widespread solar energy and air to obtain fresh water, which is an effective method to solve the shortage of fresh water. However, the traditional technology of water absorption and desorption sets need to be operated separately, which is inefficient and requires manual operation. To solve this problem, this paper proposes continuous atmospheric water harvester based on solar interfacial evaporation of hygroscopic salt solution. On the one hand, LiCl solution is used to absorb moisture in the air. On the other hand, solar interfacial evaporation is used to achieve solution desorption and water vapor condensation collection. Interfacial evaporation can achieve local heating and desorption, and the two processes of absorption and desorption can be performed simultaneously. In this paper, the solar interfacial evaporation of LiCl solution and continuous atmospheric water harvester were separately studied. The experimental results show that LiCl solution with a mass fraction of 30% can perform efficient absorption/desorption work, and can achieve an evaporation rate of 0.44 kg/(m²·h) and an efficiency of 39.3% under one solar light intensity. The device can achieve continuous solar atmospheric water harvest, and the water intake rate reaches 2 L/(m²·d).

Distributors are widely used in room and commercial air conditioners for the refrigerant flow distribution among multi-paths of micro-channel heat exchangers. The most common problem in the distributor application is the non-uniform distribution of refrigerant flow. In this paper a novel distributor with a cyclic channel was proposed to achieve the uniform refrigerant distribution. Based on a traditional cylinder-type distributor, the cyclic channel was designed to construct a dispersed bubble flow pattern and allocate the dispersed bubble flow evenly into each flat tube. The key geometric size of the novel distributors includes the diameter of spray holes and the hydraulic diameter of upward channel. In this paper, the spray diameter is deduced from the formation criterion of dispersed bubble flow and the hydraulic diameter of upward channel is deduced from the formation condition of circulating flow. A design case is provided by using the deduced equations, and the distribution performance of the proposed distributor is tested by experiments. The experimental results prove that the unevenness of the proposed distributor is 46.8%, 32.0% and 24.4% lower than that of the traditional distributor respectively when the mass flow rate of inlet is 14.0, 18.0 and 22.0 g/s.

With the implementation of the coal-to-electricity policy of China, efficient and eco-friendly heating methods are demanded for heating in northern China in winter. Air source heat pump is paid more attentions in recent years as a promising heating method, in which its efficiency under low ambient temperatures is urgent to be improved. In this paper, eco-friendly mixed refrigerant (CO₂ and 2,2-difluoropropane) is applied in a recuperative heat pump with simple structure, low cost and easy control, whose heating performances under different ambient temperatures are analyzed through theoretical optimization. When ambient temperature varies from -30℃ to 10℃, its COP varies from 1.87 to 3.51 while its volumetric heating capacity varies from 1773 kJ/m³ to 5516 kJ/m³. Through the comparison with common vapor-injection cycle, the potential and feasibility of the proposed heat pump cycle and refrigerant for winter heating are demonstrated. Besides, the excessive high operating pressure of regular CO₂ systems is well reduced due to the addition of 2,2-difluoropropane, which is beneficial for practical applications.

Microchannel heat exchangers (MCHXs) have the advantages of compact structure and high heat transfer efficiency. However, the performance of MCHXs may deteriorate due to the difficulty in defrosting water drainage when MCHXs are applied to heat pump air conditioners. The louver fins used in inserted microchannel heat exchanger add a special structure of drainage channel, which can improve the drainage performance of microchannel heat exchanger. In this paper, the structure of tubes with two-row fins is selected as the modelling object. The contact angle model of water droplets and the surface tension model are developed to predict the movement characteristic of water on the fin surface, and the proposed model is validated by the experiments. The simulation results show that, the effect of louver angle of the fins on the mass of retaining water is not obvious; the mass of retaining water increases with the increase of the louver number of the fins, and the water retention mass increases up to 31.89% as the louver number increases from 5 to 14.

This paper presents the dynamic heat transfer model of a R1233zd(E) horizontal condenser. Compared with the steady-state model, the dynamic model has obvious advantages in predicting the system operating performance and understanding the working principle. This article introduces the equations, discrete methods and model calculation logic in detail. From the results, the state parameters of the refrigerant, tube wall, and cooling water in every control volume of the condenser at each time step can be obtained. Since the model covers the geometric parameters of the heat exchange tubes, the geometric parameters variation of the heat exchange tubes can cause the great effect of heat transfer performance of the condenser. The study compares the phase area, heating capacity and output water temperature under different heat exchange tubes. For the results, when a low-rib heat exchange tube with the fin pitch of 1.3 mm is used, the temperature of the outlet water is increased by more than 1.5℃ than that of the light tube, the time to reach stable output is more than 1 minute earlier, and the heating capacity is increased by 2.3 times. R1233zd(E) acts as a new environmental protection working fluid, and there are not too much studies about the heat pump model. So this condenser model is an important basis for the further research of R1233zd(E) high temperature heat pump.

Throttling is widely used in refrigeration, and is also involved in cryogenic liquefaction cycles such as Linde cycle, Claude cycle, J-T helium refrigeration cycle, and cryogenic propellant thermodynamic vent systems. In order to reveal the particularity of throttling effect of cryogenic fluids compared to ambient temperature gases and refrigerants, an experimental setup was designed and established to visualize two-phase cryogenic fluid throttling process. Taking a Laval nozzle as the testing element, the effects of inlet subcooling and pressure on throttling behavior of liquid nitrogen were investigated. The study showed that at given certain inlet pressure, the temperature drop and gas mass fraction increase with the inlet subcooling degree; at given certain inlet subcooling, the temperature drop and gas mass fraction increase with inlet pressure; higher inlet pressure and lower subcooling lead to lower refrigerating capacity.

In this paper, a structure of double row folded type microchannel heat exchanger is presented, and a three-dimension distribution parameter model is established to analyze the performance of microchannel heat exchanger with this configuration. Based on the unique structure of double row folded heat exchanger, control volume of microchannel tube and header were divided respectively, and a path-to-path description method was used to describe the flow path of the refrigerant inside the tube. The correlations of heat transfer and pressure drop for refrigerant side and air side for microchannel heat exchanger, which are recorded in the published literature, were investigated and sorted out, so that the model could be applied to various working conditions. The governing equation of the model is established, and a fast algorithm of alternating iteration of heat transfer and pressure drop is developed. The results show that the average heat transfer error calculated based on the simulation model is less than 5%, and the average pressure drop error on the refrigerant side is less than 10% compared with experimental results, which meets the actual engineering requirements.

Various technologies on heat transfer enhancement have been exploited to develop more efficient compact heat exchanging devices. In this research, turbulent heat transfer and flow characteristics in a circular tube, with longitudinal vortex generators (LVG) on the wall, were numerically investigated. The effects of LVG shapes and number of pairs on Nusselt number, friction factor and performance evaluation criteria were numerically studied. The results showed that pairs of longitudinal vortexes were generated behind the LVG, which enhanced the fluid mixing in the tube, and promoted the momentum and energy exchange between the wall boundary layer and the main flow. Further analysis indicated that the tube with 4 pairs of rectangular winglets on each row held the best heat transfer performance, and the Nusselt number was improved by 27.2% compared with smooth tube on average. The tube with 4 pairs of trapezoidal winglets on each row presented the best performance evaluation criteria, and the value reached 0.97 — 1.07.

This paper experimentally studied the influence of lithium bromide concentration on the coefficient of performance (COP) of the ternary working fluid ammonia-water absorption refrigeration system (AARS) under different working conditions. The huge rectifier and low COP are two main shortcomings that limits the usage of AARS. The lithium bromide, as the third working fluid, can shift the vapor-liquid equilibrium (VLE) state of ammonia-water binary solution, and the ammonia concentration in vapor phases can be elevated to reduce the distillation thermal load. An AARS experiment platform was established to research the influence of lithium bromide on COP. The lithium bromide concentrations in the ternary working fluid were set to 5%, 10%, 15%, and 20%. The generation temperatures ranged from 90℃ to 130℃, evaporation temperature ranged from -19℃ to -4℃, cooling water temperature ranged from 22℃ to 33℃. The experiment results showed that lithium bromide can promote COP compared with the binary system and 15% is the optimum lithium bromide concentration in the ternary working fluid. The COP can reach 0.408, 0.410 and 0.412 when the generation temperature, evaporation temperature and cooling water temperature are 130℃, -4℃ and 22℃. As a consequence, applying ammonia-water-lithium bromide ternary working fluid in ammonia absorption refrigeration system can improve the heat utilization efficiency and promote COP of AARS directly.

The thermal short-circuiting problem between adjacent buried pipes is the key factor to restrain the efficient and sustainable operation of ground heat exchanger (GHE). In this paper, based on the constructal theory, a novel bionic tree-shaped GHE is proposed to solve the thermal short-circuiting problem and improve performance of GHE. The thermal performance and comprehensive performance of the bionic tree-shaped GHE were simulated by Fluent, and a comparison between the bionic tree-shaped GHE and serpentine GHE was conducted. The feasibility of the bionic tree-shaped GHE for solving the thermal interference problem of adjacent buried pipes and improving the system efficiency was analyzed. The results indicated that the new bionic tree-shaped GHE can effectively mitigate the thermal short-circuiting problem of adjacent buried pipe and avoid local heat accumulation. Meanwhile, the uniformity of soil temperature was improved. Furthermore, when the inlet velocity is in the range of 0.4—1.2 m/s, the comprehensive performance of bionic tree-shaped GHE is obviously better than that of serpentine GHE, with a value of 33.4%—38.3%.

Absorption heat pump is one of the ways to recover low-grade heat. In a diffusion absorption heat transformer, the diffusion gas is introduced to a dual entrances and exits bubble pump, which can replace the mechanical pump to realize the full thermal drive of the heat transformer. In this paper, water-potassium formate-R134a is used as the working fluids. The pumping performance of the bubble pump with different motive head (H=0.42 m and 0.55 m), generating temperature and diffusion gas flow rate is studied experimentally. The results show that pumping ratio increases with the increase of generating temperature and motive head, or the decrease of diffusion gas flow rate. The decrease of generating temperature and diffusion gas flow rate, or the increase of motive head lead to more energy-saving system. The uncertainty of m_R, m_G and α are 0.06078 g/s, 0.06081 g/s and 1.64799, respectively. In addition, the reduction of diffusion gas flow rate leads to the increase of the gross temperature lift. These research results will be contribute to the design of bubble pump in the future.

Under the condition of low evapouration temperature, the difference between the highest and the lowest pressure of CO₂ transcritical cycle is excessively large, and the operating efficiency decreases. For CO₂ transcritical cycle characteristics, a CO₂ transcritical refrigeration system with an ejector and an economiser is proposed. Recycling part of the refrigerant expansion work using the ejector reduces energy loss and increases the refrigerating capacity. Better design of the CO₂ compressor and the vapour injection port, and use of economizer for intermediate air supplement can reduce the energy loss of the system compression process. Research shows that the system performance can be increased by about 40% compared with the basic CO₂ transcritical refrigeration system under the condition of lower evaporating temperature,the compressor discharge temperature can be reduced by about 40℃, which is conducive to the stable operation of the system. And an approximate formula is proposed for the calculation of the segmentation efficiency in the quasi-two-stage compression process, and the error is reduced from 5% to 2% in a certain range compared with the traditional calculation method.

There are many applications about cryogenic multiphase flow in various industry situations. In this paper, the precooling flow of liquid nitrogen in a mini pipe was discussed with numerical simulation, some characteristics were displayed such as, bubbles formation, critical heat flux, and temperature profiles, etc. The employed mathematical and physical methods were verified with some experimental data in the previous literature. According to simulation results about precooling processes, the temperature drop of internal fluid happened early with the pipe diameter decreasing, and the temperature drop happened lately with the liquid nitrogen mass flow increasing. The amplitude of the wall temperature drop decreased with the pipe diameter decreasing. In the range of calculation conditions, the higher CHF values occurred with less inner diameter tubes and higher mass flow rate.

Utilizing expander instead of throttle valve in high pressure ratio CO₂ trans-critical refrigeration cycle has great potential to improve cycle efficiency. Compared with other expanders, the Wankel expander has a series of advantages in terms of compactness, economy and reduced mechanical vibrations, the working process consists of intake process, expand process and exhaust process. In this paper, the operation mechanism of Wankel expander in the refrigeration system is theoretically analyzed, including the working process, the influence of shape factor, rotor profile, intake angle, eccentric distance and wheelbase coefficient. A non-isentropic model which introduces isentropic efficiency is used to calculate the physical properties of cavity according to the change of volume. In this paper, by expanding supercritical CO₂ from 10 MPa, 313.15 K to 3.485 MPa, 273.69 K, the Wankel expander can increase the refrigeration coefficient by 23.7% in the discussed conditions; the shape factor and the intake angle are the main factors that affect the performance of Wankel expander. It is necessary to select appropriate parameters in order to optimize the efficiency.

The thermal management of the battery pack inside an electric vehicle is crucial to its safety and performance. Usually, a small and compact chiller with internal turbulence-generating structure is installed in parallel with the evaporator of the vehicle air-conditioning system, so as to cool down the coolant that circulates in the battery cooling plate. However, the establishment of specific testing facilities for the chiller and its experimental analyses have seldom been seen in the literature. In order to provide a steady and reliable chiller performance testing platform and to evaluate and analyze the heat exchanging capacity of a newly-designed chiller, a complete experimental system was thoroughly designed and established, and its stability and repetitiveness were then validated. Based on such a testing facility, the small chiller for the battery coolant was experimentally tested under different working conditions, and its heat exchanging performance and pressure drops were analyzed against the variations of the parameters of both refrigerant side and coolant side. Results reveal that the evaporating pressure of the refrigerant possesses bigger impact on the heat exchange than the superheated temperature at the outlet, and the pressure drop of the refrigerant always has similar trend with the heat exchanging capacity. On the coolant side, the inlet temperature and flowrate both have positive influence on the heat exchange. Finally, the highest heat exchanging capacity reached 5.6 kW, and the calculated efficiency of the compressor varied between 0.6 and 0.8.

A frost-free air cooled refrigerator with series-parallel refrigeration cycle is studied, and the refrigerating capacity of the refrigerator and energy saving ability is optimized. Also, the influence of optimal charge quantity and optimal mass fraction of zeotropic refrigerant mixture on system performance are analyzed by experimental methods. The results shows that there exist optimal charge quantity and optimal mass fraction of zeotropic refrigerant mixture cause the power consumption and freezing chamber temperature achieve the minimum, which is 1.51 kW·h/d and -40.7℃, respectively. Besides, the experiments data shows that the optimal voltage of the fan fixed in 7.5V can make the power consumption of the refrigerator reduced 10% to 1.16 kW·h/d.

As a kind of clean and efficient renewable energy with high colorific value, liquid hydrogen has been widely used in the fuel cell vehicles, explorer propelling and so on. Besides, liquid hydrogen can also be used for the cooling of devices working in cryogenic environment, for example High Temperature Superconducting (HTS) magnets. During the storage, transport and application, flow boiling of hydrogen can be easily triggered due to its extremely low saturation temperature. Heat transfer performance of hydrogen flow boiling is of significant importance and needs to be carefully studied. In conjunction with the two-fluid model, liquid hydrogen flow boiling model is developed according the Rensselaer Polytechnic Institute (RPI) model. In the model, heat transfer mechanism of hydrogen nucleate flow boiling can be divided into three parts, the evaporative heat transfer, the quenching heat transfer and the single liquid-phase convectional heat transfer. Some key parameters in the hydrogen flow boiling model, such as the bubble nucleation site density, bubble departure diameter and bubble departure frequency are carefully discussed and determined. Simulations of hydrogen flow boiling heat transfer in round tubes are conducted with the Re in 67000—660000, wall heat flux in 16300—317800 W/m², saturation temperature in 22—29 K, inlet subcooling degree in 0—8 K and channel diameter in 5.95—6.35 mm. The simulated flow boiling heat transfer coefficients agree considerably well with the experimental data with the mean absolute error (MAE) of 7.79%. About 94% of the simulated results fall in the ±20% error band. It is reasonable to conclude that the new developed model successfully captures some basic heat transfer mechanisms of hydrogen flow boiling and can be expected to be used for the further study of hydrogen flow boiling heat transfer.

A simulation study was carried out for the chiller, which is a key component of the secondary loop liquid battery cooling system. The coolant side flow channel was taken as the research object to analyze the influences of corrugated plate structure, coolant mass flow rate and inlet temperature on the flow and heat transfer characteristics. It is found that the second flow generated by the ripple and the contact structure between the upper and lower plates will enhance the turbulence and weaken the thickness of the boundary layer, thus enhancing the heat transfer effect, even when Reynolds number is as low as 739. And, the fitting equation between Nusselt number and Reynolds number showed that average heat transfer coefficient (HTC) of the plate increases with mass flow rate, but this will inevitably enlarge the pressure drop, so it need balance the heat transfer effect and power consumption. In addition, the variation of inlet temperature, which leads to the change of coolant thermal physical properties, caused a slight effect on the HTC and pressure drop. Therefore, the effects of seasonal and operating condition on the heat transfer performance need not consider.

As a new type of high-efficiency micro-channel heat exchanger, printed circuit heat exchanger (PCHE) has great potential for its application in floating LNG storage and gasification unit (FSRU). The flow and heat transfer characteristics of supercritical methane in the PCHE channel were simulated. The simulation results show that the heat transfer coefficient first increases and then decreases with temperature, and reaches a peak near the pseudocritical temperature (202—212 K). The pressure drop first remains unchanged with the temperature, then rises sharply near the pseudocritical temperature, and then increases with the temperature. When the temperature is near the pseudocritical temperature, increasing the heat flux under low mass flux density will deteriorate heat transfer coefficient. The heat transfer coefficients under different pressures all reach the peak at the pseudocritical temperature under each pressure. When the temperature is lower than the pseudocritical temperature, the influence of pressure on the pressure drop is negligible, and when the temperature is higher than the pseudocritical temperature, the pressure drop increases with the pressure. When the pressure is increased from 6.4 MPa to 8.5 MPa, the heat transfer coefficient is reduced by 32.5% and the pressure drop is reduced by 28.5%. The average errors of the developed heat transfer and pressure drop correlation equations are 5.6% and 4.2%, respectively.

The influence mechanisms of circulation solution flow (G_cir), cold/heat capacity (Q_c/Q_h) and systemic process on the air state changes and dehumidification effect in typical cross-flow liquid desiccant dehumidification systems were researched. Through simulation and analysis, the air process lines in the enthalpy and humidity diagram under different working conditions were exhibited, and the influence degrees of various factors were compared. The results show that under design conditions, the liquid desiccant system achieves optimal dehumidification effect when G_cir is about 0.05 kg/s; as the total Q_c and Q_h increase from 29.4 kW to 48.9 kW with close ratio, the dehumidification amount increases from 3.7 g/kg to 5.7 g/kg; in the different processes, the liquid desiccant dehumidification amount is relatively large when the cooling object is solution. Compared with G_cir and Q_c/Q_h, the systemic process has greater influence on air state changes and dehumidification effect. The air process lines in each process have significant characteristics, and the liquid desiccant process is the core factor that influences the air state changes and the dehumidification effect.

Compared with the traditional thermal regeneration, electrodialysis (ED) regeneration has greater energy-saving potential and has attracted more and more attention in recent years. At present, the research on the regeneration of ED solution is mainly focused on the system analysis, and there is a lack of the understanding of mass transfer mechanism in ED. To this end, a theoretical model describing the mass transfer in ED at high salt concentrations was established, and the effects of different current densities, volume ratios and initial concentrations on system performance were experimentally investigated. The results show that the model and the experimental results are in good agreement, and the errors are less than ±4%. The larger the volume ratio, the better the system regeneration performance, but the lower the solution production; the larger the current density, the better the system regeneration performance, but the higher the energy consumption; the higher the initial concentration, the lower the current efficiency and regeneration performance of the system, and the lower the concentration polarization coefficient. In practical applications, the above factors should be balanced to achieve higher performance and efficiency of system.

Microwave-enhanced thin film evaporation promoting the separation of mixture with the difference in polarity still faces the challenges of low energy efficiency and uneven heating, where electric field distribution is generally seen as a significantly related factor. However, considering that the factors affecting the electric field distribution are very complicated and uncontrollable, it is advisable to solve the bottleneck of efficient utilization of microwave energy from the perspective of evaporator structure and fluid flow pattern design. For this reason, a liquid-bridge spiral falling film evaporator is proposed in this study. The three-dimensional model is established first by COMSOL and then to simulate the process of water spiral falling film flow and evaporation on the designed evaporator. Evaporation efficiency and coefficient of temperature variation (COV) are used as evaluation indicators to explore the influence of liquid film thickness, the width of the spiral channel, evaporator diameter, flowrate and time on microwave energy utilization efficiency. The results show that at a certain microwave input power, the evaporation efficiency of the liquid film finally reaches 29.26% and the corresponding COV is reduced to 0.0867, which will provide foundation for the design of microwave-enhanced evaporation and separation devices.

As the working fluid of heat pump systems, water has the advantages of cheap, safe, stable, no toxicity and no flammability. It is a promising working fluid in the application of heat pumps. To find and study the water vapor heat pump system cycle with the best performance, three water vapor heat pumps with different system cycles and auxiliary equipment (the single-stage system with water-injection, the single-stage system with ejector, the two-stage system with internal heat exchanger) were designed and analyzed with simulation models. In the simulation, the twin-screw compressor was used as the power equipment in these systems. The simulation results indicated that compared with other systems, the two-stage system with internal heat exchanger is the best choice and has the best system performance including the discharge superheat, heating capacity, power consumption and COP. The single-stage system with water-injection has better performance than the conventional cycle, especially it can effectively decrease the discharge superheat. At 80℃ evaporation temperature and 140℃ condensation temperature, COP of the conventional cycle was 3.01. Meanwhile, COP of the single-stage system with water-injection and the two-stage system with internal heat exchanger was 3.15 and 4.07, which are 4.7% and 35.2% higher than that of the conventional cycle, respectively. For the single-stage system with ejector, it has better COP than the conventional cycle at high condensation temperature conditions with higher temperature lift. At 80℃ evaporation temperature and 145℃ condensation temperature, COP of the single-stage system with ejector was 2.53, which is higher than COP of the conventional cycle, 2.42. So it is also a good choice for high temperature lift conditions when used in water vapor heat pumps.

Frost build-up on the heat exchanger results in an increase in heat transfer resistance and pressure drop, leading to additional energy consumption and operational costs of heat pump systems. Superhydrophobic surface has been shown to retard frosting significantly due to its efficient removal of condensed droplets prior to freezing via coalescence induced droplet jumping. Recently, heat exchangers and fin pitch are designed elaborately to balance heat transfer and pressure drop. Exploring the effect of fin pitch and surfaces wettabilities on frosting rates on surfaces is crucial when designing high efficient heat exchangers. In this paper, frosting dynamics between two parallel heat exchangers with different wettabilities were studied experimentally. Frost growth was continually recorded through high-resolution optical camera from the side and top of the gap between the parallel fins. Average frost thickness was calculated visually by high resolution images and MATLAB image processing techniques. Test experiments were conducted for hydrophilic, superhydrophilic and superhydrophobic surfaces under different frosting conditions with fin pitch of 2, 4, 6, and 8 mm. Results indicated that frost process could be divided into two different regimes, called rapidly frosting and slowly frosting regime. Frost growth rates were distinctly higher under higher relative humidity and lower surface temperature. In addition, frost growth rates on superhydrophobic surface was lower than the hydrophilic and superhydrophilic surfaces significantly. This work here not only help to optimize the design of high efficient coated heat exchangers of heat pump systems, but also provide insights into understanding the complex thermodynamics theory of governing the condensation frosting process on surfaces.

The condensing flow widely appeared in compact thermal management system. Thus, this work modelled and discussed the pressure drop oscillation of working fluids to reveal the flow instability of condenser. The mechanism of pressure drop oscillation of condensing flow was analyzed based on Lyapunov instability principle. The flow drift would occur and trigger the flow instability in the condenser channel, when the working fluid operates on the negative slope region of pressure-drop flow curve. The results indicated that the onset-instability of condensing flow with the outlet quality by 1, and flow instability would be ended for the outlet quality of working fluid with the quality of 0.8. In addition, the much higher inlet super, smaller pipe diameter and lower heat flux would be easier to generate the negative slope on the pressure-drop flow curve of the condenser. As a result, the pressure drop oscillation and the unstable operation would be occurred in the condensing flow system.

A coupled multi-physical field model of electromagnetic field, fluid flow, heat transfer and species transport is developed in COMSOL Multiphysics to simulate the microwave distillation reactor. The thermal evolution, phase change, temperature distribution of water load under microwave irradiation are investigated. The whole process includes the water load heated from 293 K to boiling. The simulation results show that the temperature of the water sample is hierarchically distributed during the microwave heating stage, with the temperature of the upper section of the reactor being significantly higher than that of the lower section. At the same time, the generation of natural convection improves the temperature uniformity. During the microwave boiling stage, the boiling will not start immediately due to that the lower region of the sample with nucleation sites does not reach the saturation temperature. The accumulation of heat within the reactor leads to overheating in the water load. However, it is worth noting that the free surface of the water load maintains at the saturation temperature due to the high evaporation rate. After the temperature of the lower region of the reactor reaches the saturation temperature, the turbulence caused by the boiling bubbles improves the temperature uniformity, while the boiling eliminates this overheating phenomenon to a certain extend. Furthermore, the surface evaporation plays a major role in the dissipation of superheat compared to internal boiling evaporation. The final temperature depends on the relative value of the heat energy converted by microwave and the evaporative dissipation energy. This study can provide theoretical guidance for microwave-assisted separation, reaction and other chemical processes.

A three-dimensional transient CFD model of multi-row plane finned-tube heat exchanger considering gravity, surface tension and gas-liquid interfacial friction source terms was established firstly based on the VOF method. And then gas-liquid falling film flow characteristics on the surface of the heat exchanger was investigated to provide a theoretical basis for the study of heat and mass transfer enhancement in the closed-type heat source tower. The simulation results of liquid film thickness were agreement with the experimental data in the reference, showing that the established CFD model was reliable. The flow characteristics of liquid film on the fin surface with contact angle of 30° were studied under different gas and liquid Reynolds numbers. The results showed that the critical film Reynolds number and critical spray density of complete film flow on the finned-tube surface are 239 and 0.06 kg/(m·s), respectively. Its mean liquid film thickness is 16.8%—35.1% higher than Nusselt's theoretical solution within the liquid film Reynolds number of 239 to 995. In order to prevent the liquid film break-up and drop falling off from deteriorating the heat transfer process of the equipment, the Reynolds numbers of counter-current and co-current air flow should be less than 2190.7 and 3286.0, respectively. The main reason is that the high Reynolds number of gas phase will lead to the rapid increase of gas-liquid interfacial friction. In a word, the co-current gas-liquid flow is more beneficial to achieve the thin complete film flow at higher air Reynolds number.

As aircraft and spacecraft continues to evolve toward higher performance, the compactness and heat dissipation efficiency of thermal control system need to be improved. Metal foam has great potential in the application of aviation and aerospace thermal control due to its large specific area and high thermal conductivity. The pool boiling heat transfer characteristics on hydrophilic and hydrophobic metal foam covers were studied experimentally, and compared with those of uncoated metal foams. The effect of hydrophilicity and hydrophobicity on the pool boiling heat transfer performance of metal foams with different pore densities and porosities is analyzed. The test samples are copper foams with pore densities of 5 PPI, 20 PPI and 40 PPI, and porosities of 85% and 95%. The results show that hydrophobic modification can reduce the incipient boiling superheated degree by 20%—30%, while hydrophilic modification has no significant effect on the onset of nucleate boiling. Hydrophobic metal foams and hydrophilic metal foams have the optimum pool boiling heat transfer performance under low heat flux (q<4×10⁵ W/m²) and high heat flux (q≥4×10⁵ W/m²) conditions, respectively. Surface modification has a more significant effect on pool boiling heat transfer enhancement for low porosity metal foams, and hydrophilic modification is more effective than hydrophobic modification in improving thermal performance.

In this paper, a one-dimensional transient model is constructed by using COMSOL multiphysics to investigate the single-layer, double-layer and three-layer regenerator composed of three kinds of magnetocaloric materials (a, b, c) with different Curie temperatures. The effects of different filling ratios and high temperature end temperature on the performance of active magnetic regenerators are studied. The simulation results show that when the active magnetic regenerator is uniformly filled, the performance of the three-layer regenerator is better than that of the single-layer and double-layer regenerator. When the double-layer regenerator is filled with non-uniform proportion, the performance is the best when the filling ratio is 3∶7. Compared with the double-layer regenerator filled with 5∶5, the cooling capacity of the regenerator filled with 3∶7 ratio is increased by 6.02% and the corresponding COP is increased by 3.5%. Meanwhile, the maximum cooling capacity is increased by 1.13% compared with the three-layer AMR (i.e. example c). In order to investigate the influence of different hot end temperature on the performance of the three regenerators, the different filling methods at different hot end temperatures have a great influence on the performance of AMR.

For an array composed of 5 cylinders of the same specification in an infinite space, the natural convection heat transfer of diverters placed between the cylinders is numerically simulated. Considering the difference between the natural convection heat transfer when Ra is in the range of 10³—10⁴, the diverter's deflection angle is from 0° to 60°, and the cylinder spacing is from 2 to 4 cylinder diameters. The analysis of the local Nusselt number (Nu_loc) and the average Nusselt number (Nu_ave) of 5 cylinders shows that the natural convection heat transfer of the diverter to the array is reflected in two aspects. First, it is equivalent to an obstacle for the cylinders under the diverter to reduce the heat transfer, the second is to isolate the plume flow from the bottom of the cylinder above the diverter, thereby increasing the overall heat transfer of the array. In the case of large cylinder spacing, compared with the cylinder array without diverter, the heat transfer trend of C1—C4 cylinders has slowed down significantly, and the heat transfer trend of C4,C5 cylinders has increased, and the overall heat exchange of the system has been enhanced. The cylinder spacing S=2D, Ra=10³, the diverter mainly acts as an obstacle, weakening the heat transfer of the C1—C4 cylinders, resulting in a decrease in the overall heat transfer of the array. When the diverter deflection angle is 45°, the heat transfer of the array reaches its maximum value, which is up to 21% higher than that without the diverter.

With a certain type of steam ejection device as the research object, the mathematical model of the thermodynamic process of the system and the mechanical model of the aircraft was established. The simulation model was built and was verified, the dynamic performance of the steam ejection device with fast opening valve, linear valve, parabolic valve and logarithmic valve was simulated by the simulation model. The simulation results showed that, when the other parameters were consistent, chose different flow characteristics of the valve, the ejection steam consumption were similar, all of which were about 560 kg, the time required for ejection had the relation of quick-opening valve < linear valve < parabolic valve < logarithmic valve, and ejection time were all within 3 s, when choosing the linear valve and parabola valve, the pressure curve in the cylinder were more stable, and the maximum acceleration of the aircraft were smaller too, respectively were 40.97 and 42.80 m/s², the final took off speed of the aircrafts were all larger than 75 m/s.

According to the heating requirements of electric vehicles (EVs) heat pumps in low ambient temperatures and extending the mileage of EVs, a waste heat recovery system in which the heat exchanger branch outside the vehicle and the branch of the waste heat exchanger are connected in parallel was developed and an experimental study on the heating performance was conducted. The experimental results show that, for the vapor injection heat pump system with parallel waste heat recovery branches, the pressure and mass flow of the vapor injection branch are significantly increased with the increase of the waste heat, while the mass flow of the main-branch is affected by the superheat at the outlet of the waste heat exchanger. The flow ratio of the out-door heat exchanger and the waste heat exchanger has a linear relationship, and the slope of the flow ratio is related to the outlet phase state of the waste heat exchanger. Under the relatively high ambient working conditions of 7℃, the increase of waste heat is beneficial to the increase of heating performance, but COP has no advantage; under the lower ambient working conditions of -20℃, the increase of waste heat increases the flow of injection mass large, but the suction mass flow is seriously attenuated, and the heating performance of the system is not significantly improved; under ambient working conditions of about -10—0℃, the heating performance and COP are greatly increased with the increase of waste heat, at -10℃, the heating performance with 1.8 kW waste heat increased by 11.6% compared to that with 0.9 kW waste heat, and the COP increased by 9.18%.

The evenness distribution of liquid film in helical channel is very important to reduce gas leakage, and ensure the efficient of the expander. In this paper, the numerical VOF model is used to analyze the influence of helical channel structure parameters on the film thickness evenness distribution in y direction. According to the experimental data of the two-phase annular flow in the helical channel obtained in the previous experiment, the accuracy of the numerical model is verified, and the evolution process of the liquid film distribution in the helical channel is revealed. It is pointed out that the influence of torsion effect on the liquid phase distribution of the helical channel is negligible as η=0.90β, and the thickness of the liquid film on the outside of the helical channel is evenness in the y direction. Theoretical analysis of dimensionless pitches and curvature ratios on the change of liquid film thickness shows that the evenness index of liquid film thickness increases obviously with the increase of the dimensionless pitch, and decreases with the increase of the curvature ratio.

According to the application demand like electrical cooling, an R290 linear compressor prototype is designed and developed for small scale refrigeration unit. The performance of this compressor is investigated under different working conditions. On the condition of 8.0, 2.7 and -3.4℃ evaporating temperature,the cooling capacity at TDC of the linear compressor is 1633.4, 1417.4 and 943.4 W, respectively. COP is 6.67, 4.24 and 2.63, respectively. Correspondingly, the cycle efficiency is 67.5%, 70.9% and 69.3%, respectively and the efficiency on the rate condition is higher than the others. When the cooling capacity changes from 35% to 100%, the polytropic index ranges from 0.968 to 0.983. During the process of capacity adjustment, the equivalent gas spring, natural frequency and equivalent damping change nonlinearly with the piston stroke and has an extremum at the TDC.

The data center cooling system needs a multi-stage heat transfer process to dispatch the heat from the electronics equipment to the outdoor environment. This process is analyzed with the method of entransy and temperature difference, and some conclusions are drawn. Data center cooling is a process using the coolant to transport the heat generated in the chip to the outdoor under the driven temperature difference (ΔT), which includes the temperature difference of the heat acquisition from the chip (ΔT₁) and the temperature difference of the heat extraction to the outdoor environment (ΔT₂). Reducing the chip heat transfer loss, air mixing loss and heat exchanger loss can decrease the total heat transfer temperature difference (ΔT), and the cooling system can make full use of free cooling and operate in the complete free cooling mode. When the cooling system operates in the heat pipe mode in the fully free cooling area, the gravity driven heat pipe gets the highest COP, followed by the liquid pump driven heat pipe, whose COP can be as high as 40—80 generally, even more than 400, and the lowest is the gas pump driven heat pipe, whose highest COP can reach 15—30. When the temperature difference between indoor and outdoor is less than ΔT₂, the principle of the compensation temperature difference is used to make the refrigeration cycle closer to the heat pipe cycle and realize the lowest energy consumption operation of the refrigeration system. It puts forward a new solution for energy conservation and emission reduction of the data center.

Air source heat pump units are widely used in HVAC in China, however, when air source heat pumps are operating in winter, frosting of outdoor heat exchangers is an operating problem that cannot be ignored. Under frosting conditions, the heating capacity of air source heat pumps is significant reduced, and must undergo periodic defrost to ensure its normal operation. When the air source heat pump defrosts, the defrost water drops will cause the overall defrost of the heat exchanger to be uneven and affect the defrost performance. In order to study the influence of the defrost on the heat exchanger tube fin surface on the defrost performance of the air source heat pump during the defrost process, a dynamic model of the hot gas defrosting of the outdoor heat exchanger was established, at the same time, the heat and mass transfer analysis of the defrosting process is carried out, and the energy balance equation of the defrosting stage is established. The model is solved by MATLAB to obtain the tube wall temperature, the defrost rate and remaining frost quality and other parameters change with time. The results show that the defrost rate of heat exchanger decreases rapidly under the influence of defrost water, and the remaining frost mass in the upper area becomes 0 at 67 s, while the frost layer in the area affected by falling water does not melt until 78 s. The defrost time in the lower area is obviously affected by the falling water of defrost, and the defrost time is extended by 11 s.

Ultrasound plays an important significance in enhancing the boiling heat-transfer of lithium bromide aqueous solution in the generator of absorption refrigeration system, there are few theoretical and experimental studies about the application of ultrasound heat-transfer enhancement technology in the boiling heat-transfer of lithium bromide aqueous solution in the generator, especially in the field of solution bubble dynamics with multi-ultrasonic vibrators at present. In order to investigate the influence of the quantities of ultrasonic vibrators on the characteristics of solution cavitation bubble dynamics, a mathematical model of lithium bromide aqueous solution bubble dynamics is constructed, in addition, the accuracy of the mathematical model is verified with the degassed water, and the effect of different influencing factors on the characteristics of solution cavitation bubble dynamics are discussed. The results indicate that, when the total sound intensity of 1 W/cm², as the quantities of ultrasonic vibrators rise from 1 to 5, the maximum radius of a cavitation bubble is increased by 44.12%, while the maximum radius of cavitation bubble is increased by no more than 1% at the quantities of ultrasonic vibrators of 24—25; The effect of the generating pressure (ambient pressure) on the solution cavitation effect would be increased with the quantities of ultrasonic vibrators increase, in the absorption refrigeration system, the lithium bromide aqueous solution in vacuum generator is more likely to produce steady cavitation process with the single-ultrasonic vibrator, nevertheless, the solution in vacuum generator is more likely to produce transient cavitation process with the multi-ultrasonic vibrators; when the ultrasonic frequency uniformities of ultrasonic vibrators decrease, the intensity of solution cavitation effect would be increased, while the ultrasonic intensity uniformities of ultrasonic vibrators on the intensity of solution cavitation effect could be neglected.

Demulsification of emulsion is a difficult technical problem to be solved in the process of oilfield production in high water cut period. Electric field demulsification is an effective ways to solve this problem because of its advantages of clean and high efficiency. In this paper, numerical simulation and experimental verification were applied to study the coalescence and separation characteristics of double droplets induced by the step and ramp signal electric field in the process of electric dehydration. The results show that under the action of ramp signal electric field, the pumping suction effect caused by interfacial tension is far greater than the necking effect caused by electric field, which is conducive to the coalescence of droplets, and reduces the probability of secondary emulsification of droplets. While applying the step signal electric field, the demulsification of the droplet can be achieved within a certain range, but the droplet is prone to secondary emulsification during coalescence. From the perspective of the effect of electric field on the continuous phase, it is found that the step signal electric field not only drives the droplet deformation and coalescence, but also has an obvious effect on the continuous phase. The step signal electric field increases the turbulence effect in the continuous phase, which is unfavorable to the electric dehydration process. Therefore, applying ramp signal to induce droplet coalescence could reduce the probability of secondary emulsification in the electric dehydration process.

The flow and heat transfer characteristics of air around the column were studied numerically for equilateral triangular cylinder with blockage ratios of 1/5, 1/4 and 1/3 in a two-dimensional horizontal channel, and the variation of drag coefficient, lift coefficient, Nusselt number and Strouhal number with Reynolds number were analyzed for different blockage ratios for top-angle windward and top-angle leeward arrangements. The study shows that the drag coefficient and lift coefficient of the trigonal top corner leeward arrangement are significantly larger than that of the top corner windward arrangement, and the rate of change of lift coefficient increases with the increase of obstruction ratio. When the obstruction ratio is 1/3, the two trailing rows of vortices appear to be staggered influence, and the drag coefficient and Strouhal number increase significantly. The Strouhal number basically tends to a constant value as the Reynolds number increases due to the joint influence of the channel and the column. The obstruction ratio increase has less effect on the Nusselt number and is much larger at the top corner windward than at the top corner leeward, with a maximum difference of 24.5%. Finally, the correlation equation of the Nusselt number criterion for the built-in trigonal channel winding is given.

Free piston Stiring cooler has the advantages of environmental friendliness, wide cooling temperature range, and flexible and controllable cooling capacity. In the paper, a small free piston Stirling cooler suitable for the room temperature was experimental studied. In the experiment, laminated stainless steel wire mesh and rolled stainless steel wire mesh were used as regenerators, and the cooling performance at diffident cooling temperature were investigated. Among them, when using the laminated wire mesh, the cooling coefficient of the cooler was 0.94 at a cooling temperature of 235 K and a cooling capacity of 100 W, and a cooling coefficient of 0.49 could be obtained at 200 K and 80 W. When using the rolled wire mesh, the cooling coefficient of the cooler was 0.8 at a cooling temperature of 235 K and a cooling capacity of 100 W, and a cooling coefficient of 0.32 could be obtained at 200 K and 55 W. Finally, the loss of each component was analyzed to provide directions for later optimization.

Oxygen evolution reaction (OER) is the rate-determining step for water electrolysis. Manganese oxides (MnO_x) possess five valence states, hence with multiple steps to reduce the activation energy, and semiconductor titanium dioxide (TiO₂) exhibits corrosion resistance. Here we demonstrate OER performance over three catalysts, of MnO_x synthesized by gliding arc plasma (pM) and commercial MnO_x (cM), and commercial TiO₂ (cT). Of non- Faradiac process, using ideal polarized electrode (IPE), it expresses the electrode-solution interface, hence reveals the association between triple phase boundary (TPB) and activity. It suggests that, the MnO_xof pM shows better activity than cM. In alkali, the former has 180 mV lower potential vs RHE, and nearly half Tafel slope. In acid, both the MnO_x catalysts show step-current polarization with similar activity. Moreover, cM shows higher activity than cT, e.g., 420 mV lower potential. The revealed solution resistance, R_s is consistent with activity. For the same catalyst, the fraction in voltage drop of capacitance f_Cd, is also in accordance with the activity in terms of ionomer to catalyst ratio (I/C), loading and single/double layer(s). However, for the varied catalysts, e.g., cM versus cT, or pM versus cM, the f_Cd is inconsistent with the activity, which might result from involving the non-Faradiac process of MnO_x.

In recent years, with the rapid development of microwave technology, microwave energy as an efficiently clean energy has been widely used in many fields, such as chemical synthesis, industrial catalysis, biopharmaceuticals, food processing, etc. Especially in the field of chemical synthesis, microwave technology shows obvious advantages of high efficiency, easy control, safety, and no pollution. In this work, microwave-assisted technology is utilized to investigate the hydrothermal ion exchange reaction between NaNH₄Y molecular sieve and rare earth solution and develops the method of synthesis REY molecular sieve without high-temperature roasting process. Compared with the traditional industrial preparation methods of rare earth-containing molecular sieve, the preparation process is greatly shortened, the production efficiency of molecular sieve ion exchange process is greatly improved, and the production energy consumption is reduced. The main physical and chemical property parameters of REY molecular sieve prepared by the developed new method meet the quality index requirements of the same type of molecular sieves in industrial production, and the activity stability of the prepared catalyst is not lower than that of the traditional industrial molecular sieve catalyst. The process method studied in this work has important guiding significance for optimizing the industrial production of catalytic cracking molecular sieves and realizing the short-process industrial preparation of molecular sieves.

In this paper, polyethylene glycol dimethyl ether (NHD) was used as absorbent to treat the tail gas with high concentration of H₂S and CO₂ from the coal to hydrogen process. The solubility parameters of H₂S and CO₂ in NHD were fitted with the PC-SAFT equation of state. A two-stage absorptive separation process was built with the application of Aspen Plus process simulation software to realize the high effective separation of H₂S and CO₂. The results show that the concentration of the separated H₂S and CO₂ could be reached from 30% to 98.7% and 55% to 99.4%, respectively. Hence, the acid gas pollution control can be done by high efficient separation of H₂S and CO₂ to get high single concentration for reuse and resource.

Polyvinylidene fluoride (PVDF) membrane is widely used in the field of wastewater treatment due to its excellent chemical and mechanical stability. However, the hydrophobicity of the PVDF membrane makes it easy to be contaminated by oil droplets during the treatment of oily wastewater, which causes the pores of the membrane to be blocked and the decrease in permeation flux. In this study, we developed an approach for preparing a hydrophilic PVDF membrane. Specially, the co-deposition of tannic acid (TA) and polyethyleneimine (PEI) on the PVDF membrane was conducted for the formation of TA/PEI adhesive layer, which was covalently grafted with cysteine via glutaraldehyde to fabricate a modified PVDF membrane (PVDF@TA/PEI-Cys). The PVDF@TA/PEI-Cys membrane has good hydrophilicity and underwater superoleophobicity. The water contact angle and underwater oil contact angle were 22.2° and 150.2°, respectively. The pure water flux of the PVDF@TA/PEI-Cys membrane reached 6328 L/(m²·h) under 0.09 MPa and the separation efficiency of the oil-in-water emulsions was as high as 99.9%. In addition, the modified PVDF membrane can also be used for the adsorption of mercury ions with the maximum adsorption capacity of 24.7 mg/g.

Aiming at the problems that bearing signals in aircraft are simple and mixed with many noises, which require targeted features and high interpretability, a fault diagnosis model composed of complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and automatic feature engineering and random forest was developed. Bearing vibration signal is converted into intrinsic mode functions (IMF) through the decomposition method. The core of the model is the feature engineering that automatically performs feature generation and extraction based on 65 kinds of manually designed structural features. This feature engineering can automatically extract the effective features of different objects according to the signal difference of different objects, which has universality between objects. Besides, it can adjust the number of effective features according to different sample sizes, enrich the feature space, and have flexible scalability. Validation shows that the fault classification accuracy of the model based on automatic feature engineering and random forest classification model is 95.32%, which performs better than common model based on singular value entropy, energy entropy, envelope sample entropy feature engineering and support vector machines classification model. Result shows that automatic feature engineering fault diagnosis model can better distinguish different faults on compressor bearings under a large sample size.

An integrated system of PRICO natural gas liquefaction-membrane distillation (MD) seawater desalination is proposed. The system utilizes the waste heat from compressor outlet of the PRICO process to drive MD seawater desalination. A mathematical model of the integrated system is formulated using Aspen Plus and GAMS. The model simultaneously considers the system structure, streams properties, equipment sizing, operating parameters, and other system design variables. The model is capable of optimizing the system design that achieves the optimal investment costs, energy consumption, operating costs, and MD unit water production costs with different system configurations. A case study of a PRICO process with processing capacity of 1 kmol/s integrated with MD process is investigated. Computational results show that the optimal system design is able to achieve a minimum water production cost of 1.98 USD/m³ with a freshwater production rate of 5.78 m³/h, demonstrating that MD is economically competitive compared with reverse osmosis and other seawater desalination technologies.

Recently, the extensive use of heating, ventilation and air conditioning systems contribute 50% of building consumption, which causes the rapid growth of building consumption. Absorption cycle, which uses low grade energy likes solar heat energy and industrial heat to generate cooling effect, could lower the large amount of high grade electric power for cooling demand in summer. The most common working pair used in absorption chiller, i.e. LiBr-H₂O, owes the highest COP but has narrow evaporation temperature range and high crystallization risk, making the limitation for miniaturization and air-cooled design. Although the NH₃-H₂O can operate in wide range of evaporation temperature, the rectifier is indispensable for increasing the concentration of ammonia gas, that is disadvantageous to performance. The new working pair NH₃-LiNO₃ has a crystallization temperature which is much higher than that of LiBr-H₂O. And the chiller uses it as working medium operates without rectifier. In addition, the high pressure of ammonia gas makes the cycle using it is more suitable to coupled with compressor for performance improvement and operation temperature widening. Therefore, the performance analysis of absorption heat recovering cycle with high-pressure booster using NH₃-LiNO₃ as the working pair was carried out in this paper, to deeply research the improvement effect of the compressor introduction. As shown in results, with the assist of compressor, the driven temperature of the new cycle can decline to 34℃, and the evaporation temperature decreases to -34℃ as well. Furthermore, the circulating ratio reduced by 52.16%, which means the adaptability for miniaturization and air-cooled design.

Biogas and the associated gas produced by CO₂ flooding oil recovery contain large amount of CO₂. In order to reduce the energy consumption of high CO₂-content natural gas liquefaction process, a natural gas liquefaction system that uses activated methyldiethanolamine (MDEA) to remove CO₂ is proposed, and the waste heat of exhaust from the gas turbine driving the compressors in the liquefaction plant is utilized in the regeneration process of the absorbent. The HYSYS software is used to simulate the system and analyze the key parameters of the decarbonization process. The results show that waste heat of gas turbine exhaust can provide all the heat load for the regeneration system with a CO₂ content not exceeding 10% in feed gas. Even if the CO₂ is up to 30%, it can also provide nearly 50% regenerative heat load. Furthermore, when the CO₂ content in feed gas is 1% — 30%, the specific power consumption of the system is 0.577 — 0.611 kW·h/kg.

Before refueled in to the vehicle-mounted gas cylinder, the high-pressure hydrogen gas needs to be pre-cooled to prevent the structural damage of the cylinder by the high temperature gas. In the present study, a novel pre-cooling process integrating a vortex tube in replace of the traditional chiller is proposed. Then a numerical study of the vortex tube behavior is carried out for a high-pressure hydrogen flow. Obtained results from the numerical simulation show that the energy separation effect exists in the vortex tube with hydrogen flow at the pressure level of tens of megapascals. Moreover, it is found that the energy separation performance of the vortex tube improves as the pressure ratio increases. In other words, the temperature drop of the cold exit of vortex tube decreases as the pressure ratio decreases in the refueling process, which just matches the slowing-down temperature rise during the cylinder charge. Based on the obtained results, it is concluded that the integration of a vortex tube into the pre-cooling process has feasibility in the hydrogen fueling station.

Denitrification is a key step in sewage denitrification. Adding denitrifying microbial agents is an effective method to improve the removal efficiency of total nitrogen. In this experiment, Pseudomonas aeruginosa F5 (F5 in short hereafter) was harvested from the anaerobic/anoxic tank of an A²/O process in a municipal sewage treatment plant. A culture medium based on actual domestic sewage was prepared to cultivate F5, and the optimal dosage of key nutrients were determined through orthogonal experiments. The optimum dosage of beef extract, K₂SO₄ and MgSO₄·7H₂O were 5.0 g/L, 6.7 mg/L and 5.0 mg/L, respectively. In order to verify the feasibility of denitrification, F5 was added continuously to a pilot-scale (50 m³) A²/O reactor at a ratio of 1∶10000 (V_inoculant/V_{daily sewage}). The addition of F5 increased the total nitrogen removal rate by 19.6%—24.0%. For further improving denitrification efficiency, two mutant strains A75 and A82 were obtained after mutagenizing F5 by atmospheric and room-temperature plasma method (ARTP). The results showed that the total nitrogen removal rate increased by 14.5%—16.2% and 16.8%—18.0%, respectively, by adding A75 and A82 compared with F5. This research provides a reliable and theoretical basis for sewage treatment plants to improve denitrification capability.

In order to solve the condensing performance of boiler flue gas containing SO₂ on the vertical wall, based on the Fluent numerical simulation software, according to the calculation formula of the acid dew point temperature of the boiler flue gas, the user-define function(UDF) was used to solve this problem. On the working condition with sulfuric acid vapor fraction of 1%—10% and wall temperature of 300—450 K, numerical simulation results showed that even a small quantity of SO₂ could form H₂SO₄ with water vapor and condense on the wall surface. Therefore the low-temperature corrosion on the wall was produced. Simulation results revealed that when the condensing wall temperature was constant and the volume fraction of sulfuric acid vapor was small, the increase of volume fraction of sulfuric acid vapor caused an approximately linear increase of the condensation of sulfuric acid vapor. When the volume fraction of sulfuric acid vapor was constant, the increase of subcooling generated the increase of the sulfuric acid vapor condensation, but when the degree of subcooling reached a certain value, the effect of the subcooling was negative.

Metallic nickel asymmetric hollow fiber membranes with an inner dense skin on the outer porous layer were fabricated by spinning-phase inversion technique. The membrane was used to produce hydrogen via autothermal reforming of ethanol. The operating conditions including temperature, feeding flow rate, sweeping rate, steam-to-carbon molar ratio (S/C) and oxygen-to-carbon ratio (O₂/C) were investigated and optimized. The results have shown that the asymmetric nickel hollow fibers have excellent catalytic activity to EATR and high hydrogen permeation performance as well. Operated at 500—1000℃ with a steam-to-carbon ratio of 4 and an oxygen-to-carbon molar ratio of 0.8, the ethanol was completely consumed with 81.59% hydrogen yield, and the hydrogen permeation rate reached up to 13.99 mmol/(m²·s). With the increase of oxygen concentration in feed, the carbon deposition on the membrane surface was remarkably inhibited, while the hydrogen yield and CO selectivity were decreased.

The pure electric vehicle integrated thermal management (ITM) system could effectively improve the energy efficiency of vehicles. However, the structure of the ITM system considering the thermal requirements of battery and cabin is complex. Aiming at the series and parallel configuration of the ITM system, the system simulation model is built based on AMESim software, and the performance of the two ITM systems is compared and analyzed from the perspective of thermodynamic energy and exergy analysis. The results show that: the coefficient of performance and exergy efficiency of the series system are significantly higher than those of the parallel system, with an average increase of 7.6% and 23.6% in the refrigeration mode and 13% and 7.6% in the heat pump mode, respectively. With the increase of compressor speed, the total exergy loss of components in the two systems increases significantly. The exergy loss of compressor and outdoor heat exchanger became the main exergy loss. In addition, the exergy loss of electronic expansion valve accounts for a large proportion in the parallel system.

The mathematical model of residential grid-connected photovoltaic (PV) battery system is developed, to study the effect of technical and economic indicators on system performance. Two operation strategies, including basic strategy to maximize self-consumption rate as well as improved strategy via valley grid first and battery charging, have been considered. A novel sizing method for battery in the grid-connected PV battery system is then proposed based on the correlation curves which illustrates the relationship between net present value (NPV), self-consumption rate, self-sufficiency rate, as well as battery size. After developing the model in MATLAB, the simulation results demonstrate that there is a tradeoff relationship between technical and economic indicators especially when the battery size is less than 10.5 and 6.5 kW·h respectively for basic and improved strategies, denoting that the correlation curve between the indicators before the inflection point can be regarded as the reference curve for the given system when sizing the battery. Furthermore, the operation performance of PV battery system on a typical sunny day in Shanghai is examined, presenting that the electricity export and import between the 3.06 kW (peak value) system and the grid can be reduced obviously when the battery bank is 4.8 kW·h, finally enhancing peak-load shifting.

The exergy distribution of different heat exchanger combinations and the heat exchanger in the thermal system were studied, and an advanced exergy analysis model was established to further divide the exergy destruction into unavoidable parts and avoidable parts. The main energy loss in the heat exchanger and thermal system were determined by the calculation of the corresponding exergy destruction and exergy efficiency. It was verified in the organic Rankine cycle (ORC) system text rig, which provided a scientific basis for the optimization of the heat exchangers and thermal system operation. The results showed that different area of heat exchanger had a great impact on the energy efficiency of heat exchanger. And the traditional exergy analysis and the advanced exergy analysis provided different optimization sequences. The advanced exergy analysis showed that the avoidable exergy destruction in evaporator accounted for 41.2%—60.0% while the condenser could avoid 91%—97%. The ORC system had 52.5%—66.3% exergy destruction that could be avoided, which had great potential for optimization. In addition, it was found that unreasonable design of the pipeline would also affect the ORC system performance.

With the increasing demand for indoor environmental quality, air purification technology has become an indispensable project. In this paper, a new preparation technology of air purification material based on wood pulp fiber paper is proposed. The adsorbent is coupled to its surface by impregnation method, and its performance is tested and studied. Firstly, wood pulp fiber paper impregnated with different quality silica gel is prepared and their benzene adsorption properties are tested. The results show that the wood pulp fiber paper impregnated by silica gel three times has high adsorption capacity and good material stability, so we conclude that for benzene adsorption, the best impregnation times are three times. In addition, when the relative pressure is lower than 0.5, the static experimental data and dynamic experimental data of benzene adsorption can be well fitted by Freundlich model and LDF model, and their square correlation coefficients R² are greater than 0.97 and 0.94 respectively. As for CO₂ adsorption, silica gel was used as adhesive to coat 13X molecular sieve powder on the surface of fiber paper. The material shows good CO₂ capture performance and stability. The CO₂ adsorption capacity of the composite fiber paper material at 15 kPa and 100 kPa can reach 1.17 mmol/g and 1.92 mmol/g respectively. It can be seen that this material can effectively capture different gas and provide ideas and reference for the production of air filter.

More and more attentions have been paid to synthesize the graphene quantum dots by the biomass “bottom-up” approach because of the outstanding features, such as low-cost and environmentally friendly. Nitrogen and sulfur codoped graphene quantum dots (N, S-GQDs) were synthesized from soy protein through hydrothermal method. And ethanol precipitation was adopted as the purification method. Chemical structures and optical properties of the synthesized N, S-GQDs were carefully investigated by transmission electron microscopy (HRTEM), atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrum. The N,S-GQDs showed good water dispersibility and bright blue fluorescence. When the mass ratio of the soy protein to citric acid-urea was 5%(mass), the fluorescence quantum yield of the N, S-GQDs was as high as 9.23%. A 0.34 nm crystal lattice spacing was observed and the thickness of the N, S-GQDs was around 2—5 nm. The detection limit of the N, S-GQDs for Fe³⁺ was as low as 0.95 μmol/L. This work provided a facile method to synthesize N, S-GQDs from soy protein with high quantum yield.

Aiming at the problem that leakage always happen in the phase change process of octadecane, olefin block copolymer (OBC) is used as the packaging structure to prepare composite stereotyped phase change materials (PCMs). Meanwhile, the low thermal conductivity of octadecane is improved by adding expanded graphite (EG). The results show that when the mass fraction of OBC is 10%, the leakage will happen in the phase change process. However, leakage has not been observed when the mass fraction of OBC is equal to or higher than 20%. When the mass fraction of OBC is 20%, the phase change enthalpy of the composite PCM is 166.87 J/g, and lower than that of pure ocadecane (227.40 J/g) by 26.62%. The thermal conductivity of composite phase change materials with different mass fraction of EG increases with the increase of the content of EG. When the mass fraction of EG is 5%, the thermal conductivity of the composite PCM is 4.179 W/(m?K), which is about 16 times higher than that of the pure PCM [0.24 W/(m?K)], indicating that EG could effectively improve the thermal conductivity of the composite PCM. In addition, the phase change enthalpy of composite PCM with 5% EG was about 149.54 J/g, and there was no significant change in phase change temperature and enthalpy after 50 cycles, indicating that the thermal stability of the composite PCM is great. Therefore, the composite phase change material has the utilization potentiality in building energy conservation.

In order for efficient chemisorption heat storage system, an activated carbon fiber (ACF)-LiCl composite sorbent was developed while silica sol (SS) was used for shaping. Morphologies records, sorption kinetics and heat storage performance of ACF-LiCl composite sorbent were investigated. Samples with different salt contents were fabricated to store low-temperature thermal heat by impregnation methods. According to the test of the solution leakage phenomenon, the best sample was determined to be ACFLi30. Through the experimental study, thermal conductivity, specific surface area, pore volume and pore diameter were obtained. Sorption kinetics and equilibrium sorption capacity under conditions of multi temperature and relative humidity were studied by utilizing constant temperature and humidity chamber. The water uptake of ACFLi30 sample can be up to 1.1 g/g. Energy storage density was measured by simultaneous thermal analyzer. ACFLi30 sample had the good energy storage performance with 1.08 kW·h/kg mass energy storage density and 588.2 kW·h/m³ volumetric energy storage density. Compared with expanded vermiculite and activated alumina matrix, composite sorbent with ACF matrix has advantage in volumetric energy storage density. As a consequence, ACF-LiCl is promising sorbent in the field of chemisorption heat storage.

In order to obtain a satisfactory gating property of the membrane, the grafting yield must be kept in a proper range. In order to determine the optimal mass ratio of fatty acids in fatty acids composite phase change energy storage materials, three methods were proposed, the visual approaching method, the weighing measurement method and the percentage determination of penetration diameter method. And taking capric-myristic acid/expanded graphite (CA-MA/EG) composite phase change material for example, the optimum mass ratio of CA-MA in CA-MA/EG was determined by three methods. The results showed that the visual approximation method is easy to operate and mainly depends on experience and subjective judgment; the weighing measurement method is precise, but it is more complex; the determination standard can be set flexibly on the basis of the facts, and the results can accurately reflect the stability of composite phase change materials by the percentage determination of penetration diameter method.