To investigate surface movement and deformation characteristics due to continuous mining and continuous backfilling (CMCB)of coal under artificial lakes, laboratory and field coring mechanical tests were conducted on the CMCB area to verify the feasibility of the filling body. Based on the equivalent mining height probability integration method, the surface subsidence of the CMCB area was predicted. The height of the water-conducting fracture zone was analyzed using numerical simulation, and its results were compared with those of the probability integration method. The results show that the strength of the filling body is 5.063 MPa, which is higher than the designed strength of 2.0 MPa, ensuring safe mining.Owing to continuous mining and backfilling in the area, the maximum inclination value of the surface was 0.3 mm/m and the maximum horizontal deformation value of the surface was -0.2 mm/m, respectively, which is less than the range of grade Ⅰ damage to brick and concrete structures. The surrounding surface subsidence was gentle, and there was no safety hazard. The height of the water-conducting fracture zone was about 49.7 m, and the distance from the waterproof layer was about 160.3 m, indicating the safety of underwater coal mining. Results of the FLAC^3D numerical simulation and probability integration method were close, thereby verifying that the CMCB technology can effectively slow down surface movement and deformation.

The traditional maximum power point tracking (MPPT) algorithm is prone to fall into local optimization in the case of a multipeak photovoltaic array. The butterfly optimization algorithm has a strong global search capability and a relatively stable convergence process; however, it has not been widely used due to its low convergence accuracy. This paper proposes an MPPT algorithm that combines the improved butterfly optimization algorithm with the perturbation and observation method. The traditional butterfly optimization algorithm was optimized by introducing the chaotic mapping theory to improve the distribution of the initial butterfly population. Besides, the dynamic switching probability was used to optimize the switching strategy. Herein, first, the global search capability of the butterfly optimization algorithm was used to locate the range of the maximum power point, and then the small step size perturbation and disturbance observation method were used to accurately locate the maximum power point. This algorithm combines the advantages of the global optimization of the butterfly optimization algorithm and the precise optimization of the perturbation and observation method. Furthermore, Simulink simulation experiments were conducted, and the results were compared with the traditional butterfly optimization algorithm and particle swarm optimization algorithm. The results show that the improved algorithm can adapt to complex and changing light conditions and has certain advantages in both convergence accuracy and speed.

In this paper, we have used the observed data of annual total solar radiation from 1961 to 2016 in Jinan, Shandong Province, and compared and analyzed the fitting results of time series models AR(5) and ARIMA((1,2,4),1,0) via model identification and statistical tests. As per the residual test results, the sparse coefficient model ARIMA((1,2,4),1,0) can be used to predict the total annual surface solar radiation. The prediction results show that the overall interannual variation of surface solar radiation in Jinan from 2017 to 2025 follows an increasing trend and the utilization of solar energy resources can be further explored. Compared to the results of the multiple linear regression model, the time series sparse coefficient model has less error and higher prediction accuracy.

Currently, Shengli Oilfield has entered the period of ultrahigh water cut, thereby increasing the difficulty of exploitation and raising the cost of oil production. Energy conservation has become the main factor for controlling the cost of oil-production plants. The distributed energy system based on natural gas can be constructed by combining gas turbine or gas internal combustion engine for power generation and flue gas-driven heat pump for the recovery from sewage and heating crude oil. Energy-flow analysis and optimization can be achieved through pinch analysis of a traditional joint station and a joint station distributed energy system. Based on the energy-flow model of a gas internal combustion engine under variable working conditions, the combustion calculation of a gas internal combustion engine is performed via thermal simulation and the pinch analysis is conducted for a traditional joint station that heats crude oil via water jacket heating furnace. Based on the lithium bromide-absorption heat pump energy-flow model driven via flue-gas heat, the pinch point analysis is conducted for the distributed energy system of the joint station. A comparative analysis of the joint station distributed energy system and the traditional joint station is performed. The energy-saving potential of the joint station distributed energy system can reach 24%, contributing to the realization of the “carbon peaking and carbon neutrality” goal.

A combined cooling, heating, and power system based on solar hydrogen production and high-temperature proton-exchange membrane fuel cell is developed in this study. A mathematical model of the system is built using the Matlab software to analyze the operation conditions of the system under rated working condition. The key design parameters, such as the pressure swing adsorption separation rate, current density, and working temperature of the high-temperature proton-exchange membrane fuel cell are studied emphatically to explore their impact on exergy efficiency; primary energy efficiency; and the cooling, heating, power loads of the system. The results demonstrate that the combined cooling, heating, and power system can provide the power load of 236.68 kW, heating, and cooling loads of 1 180.30 kW, and 165.14 kW, respectively, during a 6 h hydrogen production period under the design flow rate of input methanol. The system can output power, heating, and cooling loads of 2.30 × 10⁷, 2.55 × 10⁷,and 1.43 × 10⁷ kJ every 24 h. The 24 h exergy and the primary energy efficiency of the system are 69.18% and 91.96% respectively. Further, it is observed that the largest exergy loss occurs in the burning room, heat exchanger 3, and solar reforming-reaction generator.

For the continuous decrease in the wellhead pressure of natural gas containing moisture and sulfur in gas fields with high quantities of sulfur, low-pressure gases are transported owing to the surplus pressure from high-pressure gas wells via ejectors. Herein, the Fluent software is used to numerically simulate temperature and pressure profiles for single- and two-phase flows of natural gas containing moisture and sulfur in an ejector. The ZahediⅠmodel is used to predict the formation area of natural gas hydrates in the ejector. The effect of the inlet temperature of the working fluid, sulfur content, and moisture content on the formation of natural gas hydrates is predicted and analyzed. With increasing inlet temperature of the working fluid, the generation area range of natural gas hydrates in the ejector decreases. When the sulfide content is high, the generation area range of natural gas hydrates is large. The working fluid contains water droplets. The generation area of natural gas hydrates in the ejector is smaller than that under a single-phase working medium. Based on these results, measures for reducing natural gas hydrates are proposed.

Currently, the leakage of drain pipeline values in power plants is detected automatically using the principle of heat transfer. However, existing studies have not yet analyzed the flow and heat transfer of the fluid in a pipeline during valve leakage. Furthermore, research on the arrangement of temperature measurement points and the accuracy requirements of temperature measurements is lacking. To address these shortcomings, this study uses a computational fluid dynamic simulation to investigate heat transfer and flow in pipelines when valve leakage occurs. In addition, the influence of different pipeline diameters and insulation materials on differences in the measured temperatures and the amount of leakage is analyzed. The findings of this study provide a reference for the real-time monitoring of dynamic changes in the flow near the valve and the diagnosis of leakage faults of drain valves on engineering sites.

In the process of deepwater drilling, early and accurate monitoring of gas invasion is crucial for drilling safety. Based on Hagdorn and Brown’s method, this study establishes a model for increasing gas velocity after gas invasion in deepwater drilling, optimizes the influence of well deviation angle on the division principle of gas-flow pattern and gas slippage velocity in deviated wells, and realizes the real-time calculation of the time when the gas reaches subsea wellhead in accordance with the gas-liquid flow law in the wellbore after gas invasion. The results can effectively reflect the flow law of wellbore annulus after the gas invasion in deepwater-deviated well drilling and are of great significance for gas-invasion monitoring and well control.

A novel method for measuring the mixing characteristics of dissimilar particles in dense gas-solid two-phase flow based on a capacitance probe was developed. In the mixing process, the variation in the micromixing ratio of dissimilar particles in a bubbling fluidized bed was studied. The influence of convection and diffusion on the mixing of particles at a series of locations in the bubbling fluidized bed and its micromechanism were analyzed. Results show that with increasing bed height, the influence of convective mixing on the mixing of particles first increases and then decreases. The mixing ratio near the wall fluctuates slightly with the mixing time and mainly shows diffusion mixing behavior. No considerable difference is observed in the time required for particles to reach mixing equilibrium at different bed heights, and the time required for particles to reach mixing equilibrium near the wall is approximately twice as long as that at the axial positions. However, the final micromixing indices are similar in the mixing equilibrium state.

In the passive improvement of heat transfer technology, the use of inserts in tubes is a very common and practical technique. Inserting a central inclined rod in a heat exchanger tube can realize multilongitudinal vortex flow, similar to the optimized flow field in the tube, and effectively improve the heat exchange performance of the heat exchanger tube while retaining a small increase in flow resistance. In this study, a heat exchanger tube with an inserted central inclined rod is examined based on the numerical simulation method. The influence of the number, pitch, and diameter of inclined rods on the heat transfer performance and resistance characteristics is investigated. Results show that the heat transfer tube with the inserted central inclined rod achieves considerably better heat transfer performance than the smooth tube. The Nusselt number of the heat transfer tube with the inserted central inclined rod increases within a certain range with an increasing number of inclined rods, and the pressure drop increases with the number of inclined rods. When the number of inclined rods is three, the comprehensive heat transfer performance of the heat transfer tube with the inserted central inclined rod is better. The Nusselt number and pressure drop decrease with increasing pitch of the inclined rod. When the pitch of the inclined rod is 20 mm, the comprehensive heat transfer performance of the heat transfer tube with the inserted central inclined rod is better. The Nusselt number and pressure drop increase with the inclined rod diameter. When the inclined rod diameter is 2.0 mm, the comprehensive heat transfer performance of the heat exchange tube with the inserted central inclined rod is better.

In this study, two production modes of oil-collecting pipeline transportation and oil-pulling single-well oil storage tanks are modeled and dynamic simulations are performed. Moreover, the heating load-variation rules and optimal heating parameters of the two modes are further explored. The distributed energy system schemes of crude oil transportation in single-well oil-collecting pipelines and oil-pulling oil storage tanks are designed, which involve a water jacket heating furnace, electric heat tracing, a solar heat-collecting device, a solar heat storage device, and an air source heat pump. Thermodynamic calculations of five types of heat sources are performed, and the objective function and constraint conditions for the two types of distributed energy systems are established to optimize the systems. Results show the required electric heat-tracing proportion of different modes, seasons, and times to achieve the rational use of the heat source and minimize investment and operational costs. Furthermore, economic analysis of several distributed heat sources is performed.

To improve the throttling loss of an electric water feed pump during the deep peak shaving operation of northeast coal-fired units, and the utilization rate of electric energy and coal consumption, a 600 MW electric water feed pump unit in power plant is taken as an example, using a frequency conversion scheme, under different working conditions (100%, 92%, 83%, 67%, 60%, 53%, and 50% rated loads), to analyze the power and frequency conversion conditions of single and double water feed pumps and identify the relationship between the flow rate, load, electrical efficiency, and active power of the motor. The test results show that the lower the flow, the more greater will be the improvements in the electrical efficiency and active power of the motor, up to 30% and 33%, respectively, subsequent to frequency conversion. Frequency conversion transformation is suitable for this unit, reducing the plant power consumption rate by 0.45%~0.87%, the power saving rate is 21%~33%. The variable frequency drive has a significant energy-saving effect on the deep peak shaving operation of the unit, providing a certain degree of reference for the transformation of the same type of unit.

Flash evaporation refers to the abrupt vaporization of liquid when it undergoes a sudden pressure drop. It has broad application prospects in the field of waste heat recovery in energy-intensive industries. Motivated by the lack of research on internal flow and phase-change phenomena inside the nozzle in a waste heat power generation system, in this work, we conduct numerical research on the internal flashing in a typical nozzle with two S-shaped internal vanes. The mathematical description of this problem is given by coupling the Volume of Fluent model and the pressure-driven phase-change model, and a numerical solution is obtained using CFD software. Results show that the fluid starts to rotate and accelerate when it flows through the S-shaped vanes. Downstream the vanes, the rotation speed is low in the middle and high near the wall. After that, the fluid accelerates and ejects through the contraction section of the nozzle. Pressure drop downstream the vanes leads to flash evaporation inside the nozzle, and fluid leaves the nozzle as a liquid-vapor mixture. In addition, a modified nozzle structure is proposed from the perspectives of improving atomization, reducing fouling, and enlarging passage area. The proposed structure can promote the complete and rapid progress of spray flash evaporation and help to further improve the efficiency of the waste heat power generation system.

Considering different types of power output characteristics and the complementarity and contradiction between them, a multiobjective optimal dispatching model is built for a power generation system that includes hydropower, thermal power, wind power, and an energy storage system. The proposed model is characterized by minimal system cost, minimal air pollution emission, and maximal clean energy utilization. A Monte Carlo simulation and a genetic algorithm are combined to validate the effectiveness of the proposed model using an improved 39-node system. Both the hydropower and energy storage system can fulfill their regulatory functions to the greatest extent in different situations, thus stabilizing the fluctuation of wind power, reducing air pollution emission and wind abandonment, and implementing the allocation of various types of energy sources.

Based on the concept of representative elementary volume (REV) proposed by Bear, the heat transfer in oil reservoirs containing multiple fluids was studied. Moreover, the “three box” analysis method was used to simplify the heat transfer model of the reservoir REV. Because the multifield coupling mechanism in porous media of the oil reservoir is complex and difficult to analyze, a new “gray box” analysis model was proposed for estimating thermal conductivity and the corresponding calculation formula was provided. Finally, the model was combined with CMG（computer modelling group) software to simulate the operating conditions of the horizontal well injection with multiple thermal fluids. Furthermore, the physical parameter distribution of the ground was obtained, which verified the usability of the proposed model.

In this study, a new type of microporous surface for copper foam was prepared using an improved electroplating method. Further, the microstructure of the microporous surface of copper foam was evaluated using a scanning electron microscope (SEM). In the experiment, deionized water was used as the working medium to investigate the pool boiling heat transfer characteristics of smooth and microporous surfaces, thereby obtaining their pool boiling heat transfer curves. Results show that under identical heat flux conditions, the vaporization core of the microporous surface has a high density in the nucleate boiling zone, which can effectively reduce the superheat associated with the initial boiling point of the wall and considerably increase the pool boiling heat transfer coefficient. Thus, this study proves that the microporous surface of copper foam can be used for the heat dissipation of high-power electronic devices such as semiconductor refrigeration systems.

A double-layer belt conveyor, which conveys coal on the upper belt and ash powder on the lower belt, is placed higher than the conventional singe-layer belt conveyor. To determine the most appropriate height of the rain shield to prevent ash powder from blowing out under strong crosswinds (velocity is 17 m/s), the Fluent software is used to numerically simulate the distribution of the flow fields and the dust concentration fields within the rain shield with or without crosswind based on the theory of gas-solid two-phase flow. The calculation results show that crosswinds strengthen the vortex formed between the double-layer belts and the ash powder may thus be blown out. When the crosswind velocity is 17 m/s, the vortex formed is not too strong and the ash powder will not be blown out of the rain shield. Under crosswind conditions, there is wind blowing with very high velocity(up to 55 m/s) on the top of the rain shield; as such, the stress exerted by the strong winds should be considered in the process of designing the strength of the rain shield. In the presence of crosswinds, the dust concentration in the rain shield is the highest at the junction of the coal conveying belt and coal pile, and is the second highest at the junction of the ash powder conveying belt and ash powder pile. When the crosswind velocity is 17 m/s, the dust concentration outside the rain shield is less than 4×10^-6 kg/m³, which meets the requirements of the Coalmine Safety Regulations. 

To effectively evaluate the remaining service life of a power lithium battery system, key factors affecting its remaining service life must be accurately obtained. In this paper, the current of the battery during charging and discharging, temperature, and real-time voltage were determined as the key factors. The influence of each factor on the remaining service life of the power lithium battery was analyzed using the principal component analysis method to perform a quantitative analysis. The values of each factor were collected during the processes of repeated charging and discharging cycle. Through the verification and comparison of the remaining service life prediction, it was observed that the cumulative contribution rate of the first five factors accountted for 99% (the error range was within 3%) and the cumulative contribution rate of the first four factors accountted for 90% (the error range was within 4%).

Based on a miniature car as a prototype, a numerical simulation of the aerodynamic characteristics of the car's three-dimensional external flow field is carried out. By analyzing the pressure field between the original car and the improved streamlined car at different speeds, and comparing the aerodynamic drag values.The results show that the pressure distribution of the improved streamlined car has been effectively improved at the normal driving speed of 20 m/s or the limiting driving speed of 50 m/s. The aerodynamic drag of the car is 6.67% at the normal driving speed of 20 m/s, and it can still reduce the resistance by 4.55% at the limiting driving speed of 50 m/s. The improved car can effectively reduce the aerodynamic drag value, and improve the power and fuel economy of the car. 

Based on the Angstrom-Prescott model and spatial interpolation method, an estimation method of monthly solar radiation in Shandong Province is constructed herein, and the accuracy of the proposed method is verified using the radiation observation data from three national stations （Jinan, Juxian, and Fushan） and those from Heze, Liaocheng, Zibo, and Qingdao. First, based on the observation data of radiation and sunshine percentage between 1992 to 2015 from the three national stations, the Angstrom-Prescott model coefficients (A-P coefficients) in different months are obtained using the least square fitting method and verified using the observation data in 2016. Then, the solar radiation in Heze, Liaocheng, Zibo, and Qingdao is estimated using different spatial interpolation methods, and an optimal spatial interpolation method is selected based on these results. Finally, this method is compared with other methods in literature. The estimation results of monthly solar radiation in the national stations in 2016 show that the monthly average σMRE is approximately 3.5%, and the monthly average σ_RMSE is approximately 17 MJ/m²~24 MJ/m², proving that the A-P coefficient has a high accuracy. From the estimation results of monthly solar radiation in Heze, Liaocheng, Zibo, and Qingdao stations, the minimum curvature method with the least error (σ_MRE is approximately 7.22%, σ_RMSE is approximately 16 MJ/m²~69 MJ/m²) is selected as the optimal spatial interpolation method. Compared with other methods in literature, results show that the accuracy of monthly solar radiation estimation based on the proposed method is higher, and it can be extended to other regions.

To investigate the energy saving effect of servo press in stamping production, the energy consumption and the slide power of a 6300 kN multi-link mechanical servo press used in the stamping production of washing machines were quantitively measured, and the energy consumption was calculated and analyzed. The results showed that the single energy consumption of the tested press was 0.094 5 kW·h, and the single specific energy consumption was 15.0×10^-6 kW·h/kN. The energy transfer efficiency from the machine input to the slide was 39.5%. Based on these results, the single energy consumption of the tested press was observed to be 86.4% lower than that of the traditional 8000 kN hydraulic press replaced, and the energy transfer efficiency was at least 25% higher than that observed in the literature data. Furthermore, along with its high shaping performance, the proposed method of using servo press technology has also achieved remarkable energy saving effect.

Focusing on the optimization of a building-type natural gas distributed energy system, in this study，the dynamic electric load averaging algorithm and multidimensional iterative algorithm were combined to determine the capacity of a basic generator set. The optimal power range of the generator set was determined to be 2297~2477 kW. Results of the analysis of the project’s energy consumption showed that the primary energy saving ratio of the optimized model increased by 14.3%, the economic cost of energy increased by 20.14%~20.85%, and the comprehensive energy utilization rate was greater than 70%.

In order to increase the wellhead pressure in Puguang gas field that had high sulfur containing natural gas, a plan of using natural gas ejector to improve the pressure of low-pressure natural gas formation then transport was expressed. Due to the change of temperature and pressure in the process of ejection supercharging, high sulfur containing natural gas may produce sulfur release in ejector, the deposition of elemental sulfur can cause clogging and increase the corrosion of equipment. In this paper, a mathematical model for ejection supercharging of high sulfur containing natural gas was established to study the pressure, temperature and velocity distribution characteristics of natural gas in the ejector. The factors affecting the entrainment ratio were studied, and the possibility of sulfur release in the process of ejection supercharging was analyzed. The result shows that sulfur release occurs in the ejector under the design condition. The analysis results can provide guidance for ejection supercharging technology of high sulfur containing natural gas field.

The micro-cylinder-group is an efficient heat dissipation structure, which has great application prospects for solving the cooling problems in micro space. The flow characteristics in the channel with micro-cylinder-group are the foundation for the design and optimization of the heat dissipation structure. Micro particle image velocimetry (Micro-PIV) was used to study the flow past the micro-cylinder-group and the flow field around micro-cylinders with different Reynolds numbers was measured. The velocity field of the micro-cylinder-group and the effects of Reynolds number on the vortex structure and the backflow length were analyzed. The results show that vortex structure appears in the wake region of micro-cylinder and the backflow length increases gradually with the increase of Reynolds number. The boundary layer separation phenomenon in flow past the micro-cylinder has a certain lag compared with the macro-scale.

An experiment study has been conducted to investigate the onset of nucleate boiling (ONB) characteristics of deionized water in circular, diamond and elliptic micro pin fin heat sinks. The experiments were carried out in a range of mass flux from 292.8 to 412.2 kg/(m²·s), inlet temperature from 50.6 to 81.5 °C, heat flux from 10.1 to 87.1 W/cm². The wall temperature and pressure drop distributions of the micro pin fin heat sinks were analyzed from singlephase forced convection to twophase flow boiling heat transfer. The experiment results indicate that the ONB can be identified as the point at which deviations from singlephase trend is shown as a sudden change in temperature and pressure drop versus the heat flux. A parametric study was explored to investigate the effects of the experimental parameters on ONB. The heat flux at the ONB increases with an increase in mass flux. However, raising the inlet temperature can cause a reduction on the heat flux at the ONB. Besides, the heat flux at the ONB in circular, diamond and elliptic micro pin fin heat sink decreases successively under the same experimental condition.

In this paper, the phase separation and coke granularity of Liaohe atmospheric residuum (LHAR) and Karamay atmospheric residuum (KLAR) in the coking reaction were investigated. The effects of additives on the phase process and coke particle size were also investigated. The results showed that when sodium dodecyl benzene sulfonate (SDBS) and 4-Dodecylbenzenesulfonic acid (DBA) were added in LHAR,it could obviously change the phase separation process during the process of thermal reaction, the capacity of coking was increased and the size of coke was obviously reduced. The coke yield of KLAR in the coking reaction was decreased dramatically due to the addition of DBA. DBA could interact with the polar functional groups of asphaltene colloid in the process of thermal reaction. Therefore, the aggregation of asphaltene was inhibited and the phase separation of the system was delayed. The coke was smaller and the number of coke centers increased with the addition of DBA, So the coke size was reduced greatly when the total coke amount was similar.

This study proposed a new kind of mini/microchannel heat sink fabricated by flat aluminum multiport extruded tubes, which was reliable for structure and simple for manufacturing process. In order to investigate the thermal characteristics of heat sinks, a threedimensional conjugated heat transfer model was developed. Meanwhile, an experiment was conducted to verify the reliability of the model, which included channel aspect ratio, channel width ratio and channel number on thermal resistance under pumping power consumption(Ω=0.03 W). In addition, the overall resistance of heat sink was divided into three parts (conduction resistance, convective resistance, and heat capacity resistance) and calculated in detail. Moreover, the effect of width and height of fins on enhancement of heat transfer factor (PEC) was discussed, and the optimized width of fins was calculated. This study provides a reference for the design of this kind of heat sink.

For a sunflower radiator with a length of 10 cm, a fin number of 18, a fin thickness of 0.7 mm, and a fin height of 14 mm, numerical simulation model was established. The simulation was verified by experiments and errors were within 3.5%, which proved that the simulation result was reliable. Based on this, numerical simulation was carried out to study the quantitative relationship between radiator length, fin number, fin height and fin thickness vs. fin temperature and heat transfer coefficient. The results show that under the same amount of heat dissipation, the fin temperature and heat transfer coefficient decrease with the increase of the radiator length, while the fin temperature decreases first and then increases with the increase of fin number. Therefore, there is an optimal number of fins to maximize heat dissipation. The fin temperature decreases with height, while the fin thickness has little effect on the fin temperature.

 In this work, the intrinsic kinetics of the first reduction stage of a hematite as oxygen carrier (OC) reduced by carbon monoxide (CO) has been investigated. For the intrinsic kinetics analysis, the BET surface area and the pore size distribution tests showed that the porosity of this kind of OC was 0.031, which revealed that the OC had dense structure with undeveloped pore structure. The temperature programmed reduction experiments were conducted in the thermo gravimetric analyzer, which showed that the reduction of OC was conducted in stages, and the appropriate experimental temperature range for testing the intrinsic kinetics of the first reduction stage was 400~650 °C. Furthermore, a series of formal experiments were conducted in a batch fluidized bed system with different temperatures and different CO concentrations. The intrinsic activation energy and the preexponential factor were determined as 138.55 kJ/mol and 6.8×1013 s^-1 respectively, after the internal and external diffusion factor been eliminated. The analysis to the internal and external diffusion factors deepened the acknowledgement to the reaction properties of this kind of hematite OC reduced by CO. The researching results of this paper had good compatibility with many previous research conclusions such as shrinking core model, external diffusion control and smaller apparent activation energy.

The Ebsilon software was employed to establish a thermodynamic cycle model of a typical heat pump heating system by utilizing the waste heat in marine aquaculture. Simulations were carried out to find out the defects of the heat pump system for a typical engineering case. The optimization of the heat pump system was carried out, and a doubled energy efficiency was obtained. In the case of an indoor sea cucumber seedling plant in Qingdao sea area, electricity saving is up to 2 000 kW·h each day in winter. The energy saving potential is tremendous, and the economic benefit is remarkable. The case analysis shows that the critical point is to follow the essential scientific principle of"temperature counterpart and cascade utilization" when reusing the waste heat of drainage in mariculture by a heat pump system.

We established a fractal model for the microstructure of NaK-BASE tube with the transport of Na+ and K+ in NaK-BASE tube as a subject. We simulated the transport of Na+ and K+ in NaK-BASE tube with PoissonNernstPlanck multiions transport model. We also investigated ion transport process in NaK-BASE tube with different temperatures. Results show that cation transport concentration and surface charge density of Na+ and K+ have direct relationship with the temperature of NaK-BASE tube. Peak value of cation concentration in NaK-BASE tube will decrease with the increase of BASE tube temperature. Peak value of Na+ and K+ can be enhanced by the increase of NaK-BASE tube tortuosity. Moreover, surface charge density of Na+ and K+ in BASE tube gradually increases with the increase of temperature. Discrepancy of surface charge density gradually increases with the increase of tortuosity.

We performed numerical simulation for bubble formation process in a T-junction microchannel with volume of fluid method (VOF). We also analyzed the impact of gas/liquid fluid velocity, fluid properties and microchannel diameter on bubble length based on bubble formation mechanism. Results demonstrate that the bubble length exponentially increases with the increase of gas fraction in T-junction microchannel, but gas/liquid fluid velocity has little effect on bubble length for fixed gas fraction. Liquid viscosity and surface tension comparatively have less effect on bubble length. When surface tension of liquid phase reduces from 0.072 N·m-1 to 0.01 N·m-1, the bubble length in T-junction microchannel decreases by 18%. This is because that maximum neck width and collapse time decrease in expansion stage of bubble formation process. The bubble length increases with the increase of microchannel diameter, but dimensionless length of the bubble is less influenced by microchannel diameter.

Thermalboundary resistance of nano-film is predominant in thermal transport process of nano-scale structure. Compared with metal nano-film, thermal transport process of nonmetal nano-film is more complicated. We measure thermal boundary resistance between metal, nonmetal nano-film and different dielectric substrates with improveddual-color femosecond laser time-domain thermoreflectance ( TDTR) method. Debye temperature ratio of film and substrate can serve as a measurement of acoustic mismatch degree. For the same Debye temperature ratio, thermal boundary resistance of nonmetal nano-film is about 2 ~3 times greater than that of metal nano-film. This is mainly because electric-phonon coupling enhances thermal transport capability of metal nano-film.

Hydrophobic micro-pin fins with different contact angles are obtained by solidifying nano-particles involved hydrophobic coating on the surface of oval micro-pin fins. Pressure drop, friction factor f and Nusselt number Nu for different Reynolds numbers are measured. The impact of the variation of contact angles on heat sink flow resistance and heat transfer of micro-pin fins and energy efficiency characteristics are also analyzed comprehensive. Results demonstrate that hydrophobic coating has significant resistance reduction effect. Pressure drop and flow resistance coefficient decrease with the increase of contact angles. However, Nu in hydrophobic micro-pin fins also decreases, and Nu deviation in the three hydrophobic micro-pin fins increases with the increase of heat power. Although hydrophobic surface reduces Nu in micro-pin fins, superhydrophobic micro-pin fins with contact angle of 151.5° have better energy efficiency characteristics. Compared with those without hydrophobic coating, required pump power can be reduced by more than 200% for the same convective heat transfer.

We construct highly efficient ejectorabsorption composite gas water heater with operating principle of an ejector. We further design its physical and mathematical models with ammoniawater solution as working fluid. We also calculate the proportion of each heat exchanger based on the selection of reasonable matching parameters. Results indicate that high temperature heat exchanger can absorb the maximum gas heat, more than 40% of total transferred heat. However, low temperature heat exchanger can absorb the minimum gas heat, no more than 25% of the total transferred heat. Thermal efficiency of the heater can attain more than 110% in winter, and even more than 120% in summer. High efficiency and energy saving can therefore be practically implemented.

We measured thermogravimetric curve for ionic liquid ［bmim］Zn₂Cl₅ at T= (323.15~1 173.15) K. Results show that ［bmim］Zn₂Cl₅ has higher thermal stability at T < 637.15 K. We acquired heat capacity data of ［bmim］Zn2Cl5 through DSC scan, which could be well fitted with a conic curve at T= (251.15~383.15) K. We measured mole excess enthalpy of binary system ［bmim］Zn₂Cl₅ (2) + NH₃ (1) for ammonia molar fractions x1 = (0.60 ~ 0.95) at T=288.15 K,303.15 K,318.15 K,333.15 K.We employed NRTL model to fit excess enthalpy data and acquired binary adjustable parameters and nonrandom parameters. Measurement error and maximum fitting deviation of excess enthalpy data are respectively less than 4.8% and 4.3%. Based on heat capacity of ［bmim］Zn₂Cl₅ and excess enthalpy data of ［bmim］Zn₂Cl₅/NH₃, we also calculated the enthalpy of ［bmim］Zn₂Cl₅/NH₃ solution for ammonia mass fractions of w1 = (0 ~1) and temperature scope T=(273.15 ~ 343.15) K. The obtained enthalpyconcentration diagram is essential to the investigation of the thermodynamic performances of ［bmim］Zn₂Cl₅/NH₃ absorption refrigeration system.

Thermal boundary conductance (TBC) is predominant in interior thermal transport with the increasing minimization of nanometer components. We theoretically predicted phonon transmission coefficient and TBC between graphene and Si substrate with diffuse mismatch model (DMM) and inelastic scattering model and conducted analysis with phonon transport theory. Results show that both phonon transmission coefficient and TBC increase with the increase of temperature. They gradually converge at high temperature due to mode saturation of excited phonon. Inelastic scattering provides extra channels for phonon transmission,which cause the increase of phonon transmission coefficient and TBC capacity.

We designed a condensing heat pipe heat exchanger installed at the rear funnel of conventional gas water heater. We analyzed the impact of heat load and inlet flow volume on the exhaust sensible and latent heat recovery as well as the thermal efficiency of gas water heater. Experimental results show that heat load of the gas water heater has important impact on the recycled heat of heat pipe heat exchanger.With the increase of heat load of the gas water heater from 051 m3/h to 0.59 m3/h, the recovered sensible heat and latent heat respectively increase from 2 671 kJ/h to 3 283 kJ/h and 735 kJ/h to 1 126 kJ/h. The average thermal efficiency of the gas water heater can reach 94%, and the highest thermal efficiency can attain 101%.