To overcome the issue of requiring additional heat sources during the expansion stage of advanced adiabatic compressed air energy storage (AA-CAES) systems, a combined cooling and power system with compressed air energy storage and auxiliary heating via parabolic trough solar collectors is proposed. The turbine inlet temperature of the CAES system is increased using the solar trough energy, thereby increasing its storage capacity and reducing the consumption of high-temperature heat transfer oil. The heat transfer oil saved via the first coupled parabolic trough solar system is used to drive the [mmim]DMP/CH₃OH compression-absorption refrigeration system. A dynamic mathematical model of the Combined Cooling with Solar Auxiliary (CCSA) system was established based on the conservation laws of mass and energy of each subsystem. The operating conditions of the CCSA system during the energy release phase under design conditions were simulated, and energy and exergy analyses were conducted. The impacts of months, latitude, high-pressure generator temperature, and auxiliary compressor pressure ratio of the refrigeration system on the thermodynamic performance of the CCSA system were investigated. The effective solar utilization efficiency of the CCSA system was compared with that of a conventional solar-driven ammonia power system. Moreover, its energy and exergy efficiencies were compared with those of the AA-CAES and Solar Auxiliary Reheating Compressed Air Energy Storage (SAR-CAES) systems. The results revealed that the effective solar utilization efficiency of the CCSA system was 8.44% to 13.87% higher than that of the solar-driven ammonia power system and its energy and exergy efficiencies were higher than those of the AA-CAES and SAR-CAES systems.

Mass concrete structures are extensively used in large-scale infrastructure projects; however, temperature cracks after concrete pouring severely affect structural durability and pose safety risks. This study focuses on a 5 MW wind turbine foundation at the Changqing Oilfield, China, to investigate the temperature evolution and spatial distribution of mass concrete after pouring. Based on the dynamic balance between hydration heat release and heat dissipation, the temperature evolution of mass concrete can be divided into three phases: rapid heating, peak maintenance, and slow cooling. The internal temperature of the concrete exhibits a distinct spatial heterogeneity, with higher temperatures at the center and lower temperatures at the edges. The maximum central temperature reaches 74.3 ℃, whereas the edge regions are considerably affected by ambient temperature(5 ℃ to 23 ℃). Theoretical calculations show that the temperature difference between the interior and exterior of the mass concrete after 3 days of pouring is 30.15 ℃. However, when plastic films and burlap are used as insulators, the maximum temperature difference within 10 days after pouring is only 25.2 ℃, thus indicating an effective reduction in the risk of temperature cracks. These findings offer theoretical and practical guidance for temperature control of mass concrete in similar environments, and the proposed insulation measures after pouring are critical for enhancing the durability of large-scale infrastructure projects, such as wind power foundations.

To address the issues of reduced available capacity and shortened lifespan in lithium battery packs caused by inconsistent capacities of individual cells, this paper proposes a lithium battery management system based on hybrid passive-active balancing. The system employs passive balancing for “peak clipping” during the charging phase by dissipating excess energy from the highest-voltage battery cell through a load resistor. During the discharging or idle phase, active balancing is used for “valley filling” by charging the battery cell with the lowest voltage using the energy from the entire pack, thereby enhancing the overall performance. Compared with traditional flyback transformer-based solutions, the proposed design features a simpler circuit and can meet the real-time balancing requirements during charging and discharging processes. The experimental results show that the system significantly improves the voltage consistency of the battery cells and facilitates capacity recovery, thus providing reliable support for the efficient and stable operation of the battery pack.

To address the low accuracy and reliability of existing power cable fault-location methods, a new cable fault-location method based on APO-MVMD-Transformer is proposed in this study. The collected cable fault signal is decoupled through phase-mode transformation to obtain the fault traveling wave signal. The Arctic puffin optimization (APO) optimized multivariate variational mode decomposition (MVMD) parameters are then used to decompose this traveling wave signal. The Teager energy operator is applied to extract instantaneous energy variations in the high-frequency modal components, allowing the identification of the wavefront arrival times. The sampling points corresponding to these times are then used as feature values to construct a feature dataset, which is further employed to optimize the APO-Transformed-based model. Finally, feature dataset are input into the APO-Transformer-based location model to locate cable faults. Results showed that the proposed model exhibited a coefficient of determination as high as 0.999 91, a relative fault-location error within 1%, and a distance error within 100 m, thereby demonstrating high fault location accuracy.

Under the national dual-carbon policy and energy transition，the need for coordinated development between compressed air energy storage （CAES） technology and renewable energy has grown significantly. A solar auxiliary reheating compressed air energy storage （SAR-CAES） system is proposed. The system integrates a parabolic trough solar collector with an advanced adiabatic CAES system for achieving energy release. A mathematical model of the trough solar collector and a three-stage expansion advanced adiabatic compressed air energy storage system were established. Using the discretization algorithm in Matlab，the models were coupled to analyze the impact of months and latitudes on key system parameters. Results show that the resultant dynamic model satisfies the first and second laws of thermodynamics. After auxiliary heating，the heat load of the auxiliary heat exchanger increased clearly. Medium regenerator and Low regenerator barely participated in heat exchange，but generated considerable exergic loss. The efficiency of compressed air energy storage clearly improved after auxiliary heating，reaching its peak during the summer solstice at the Tropic of Cancer. The effective utilization efficiency of the solar energy in this system is higher than that of a solar-driven ammonia-water regenerative Rankine cycle system，with a maximum efficiency during the winter solstice—67.86% higher than that of the ammonia-water power cycle.

Carbon dioxide energy storage （CCES），which has evolved from compressed air energy storage，offers advantages such as zero carbon emissions，high energy storage density，safety and reliability. To further utilize the advantages of easy liquefaction and the high energy density of carbon dioxide，a transcritical carbon dioxide energy storage system （TC-CCES） with gas-liquid two-phase changes was proposed. The low-pressure storage tank in the system contains a gas-liquid mixture that remains in transcritical state throughout the operation. Energy and exergy analyses were conducted on TC-CCES，and simulations were performed to obtain the dynamic properties of the system during its operation. In addition，the impact of the initial temperature of the high-pressure gas storage tank on the system was analyzed. The study revealed that lowering the initial temperature of the high-pressure tank enhanced the system efficiency. When the system ran in a stable state，it achieved an efficiency of 56.93% and an energy storage density is 3 510 kJ/m³.

Fouling is a common problem in the efficient conversion and utilization of energy as it significantly reduces heat transfer efficiency and jeopardizes the operational safety of equipment. In recent years, with the application of polymer oil drive technology in recent years, the fouling problem caused by HPAM in the recovered fluid has gradually attracted attention. Scaling processes are more complex and fouling is more stubborn in HPAM-containing environments than in HPAM-free environments. Herein, to address the fouling of polymer-bearing wastewater on the surface of heat-exchanger equipment, we experimentally investigated the impacts of factors such as heat-exchanger surface temperature, HPAM mass concentration, hydrolysis degree, fluid salinity, and surface roughness on the fouling rate and identified the fouling patterns of polymer-bearing wastewater on such surfaces. It was found that polymer concentration is the most important factor affecting the fouling rate of polymer-bearing wastewater. The fouling rate decreases and then increases with increasing HPAM mass concentration, and HPAM exerts an antagonistic effect on the fouling rate. The fouling rate increases with increasing heat-exchanger surface temperature, and boiling accelerates the surface fouling rate. In addition, there is a critical degree of HPAM hydrolysis at which the fouling rate is the highest, while the surface roughness has no significant effect on scaling rate.

To address the energy shortages problem, in addition to developing new and renewable energy sources, the recovery and utilization of waste heat resources have gained increasing attention, particularly low-grade industrial waste heat. Traditional integrated waste heat adsorption beds suffer from slow heat transfer and uneven temperature distribution, severely limiting the efficiency of waste heat storage. This study proposes a staggered adsorption bed that utilizes thermochemical hydration salts for low-grade waste heat recovery. Results show that the heat-storage rate of this adsorption bed is three times that of traditional adsorption beds. In terms of the heat transfer, it effectively mitigates the issue of uneven heating duration of materials across the adsorption bed. In terms of the mass transfer, a multidirectional mass transfer reduces the contact time between water vapor and materials, avoiding conditions for the secondary hydration of heat-storage materials. Therefore, the “staggered adsorption bed” has unique advantages in heat and mass transfer, providing a novel approach for the design and improvement of adsorption heat-storage beds for waste heat recovery.

With the rapid increase in the scale of new energy installations, the role of thermal power units in grid peak regulation has become crucial. Swift and precise prediction of the duration of the “startup-grid connection” process for thermal power units is essential for dispatchers to promptly adjust grid operation status. To address the current reliance on human experience for predicting the duration of the “startup-grid connection” process, this paper proposes a method for predicting the duration of this process for thermal power units. First, the startup-grid connection process of thermal power units is analyzed to identify key operational parameters at each stage. Then, logical calculations are leveraged to predict the duration of the “startup-grid connection” process. Results of a pilot test on a typical unit on the “Net-Source platform” indicate that the proposed model can accurately monitor the response state of the units during the “startup-grid connection” process and successfully predict its duration. This method provides timely decision support for dispatchers, helping to ensure the safety and stability of grid operations.

In the pursuit of bridging the energy demand gap and striving for a pristine environment, ammonia fuel has emerged as one of the most promising fuels of the future. Zero carbon emissions, high energy density, and low production and transportation costs make it a promising candidate. However, challenges persist regarding the overall efficiency of pure ammonia combustion. This paper proposes a regenerative cycle in an ammonia gas turbine that matches the reheat Rankine cycle, considering the maximum temperature of the exhaust gas from the turbine and phase transition temperature of liquid ammonia in the turbine cycle. We conducted a thermodynamic analysis and evaluated the system performance based on the first and second laws of thermodynamics and analyzed the influence of the inlet temperature and pressure of the ammonia gas turbine on the overall cycle performance. The results indicate that the combined cycle has improved the efficiency of the ammonia gas turbine by up to 33.38% and the maximum efficiency achieved by the combined thermodynamic cycle is 60.13%,when the inlet temperature of an ammonia gas turbine does not exceed 1 400 ℃ and the inlet pressure remains below 0.5 MPa. Furthermore, the combined cycle exhibits outstanding thermodynamic properties and energy recovery rates. Additionally, the efficiency of the regenerative cycle increases with increasing the inlet temperature and pressure of the ammonia gas turbine, provided that the inlet pressure does not exceed 5 MPa. New perspectives have been proposed to enhance the operational efficiency of ammonia-powered gas turbines and promote the efficient utilization of ammonia as a fuel. This study proposes novel perspectives towards enhancing the efficient utilization of ammonia fuel and the actual efficiency of ammonia gas turbine cycles, providing a forward-looking exploration for the energy utilization of ammonia gas turbine systems.

Currently, the steam pipelines in cigarette factories are characterized by numerous points, extensive lengths, and broad coverage. The thermal conversion factor of these pipelines is high, and their steam energy consumption accounts for a large proportion of the total energy consumption. Therefore, investigating the performance of the insulation layer of steam pipes is of considerable importance for improving steam utilization efficiency and reducing heat loss in the steam pipe network. In this study, the thermal conductivities of insulation layers made of four insulation materials were measured using the steady-state method at different temperatures to elucidate the relationship between the thermal conductivity of an insulation material and the steam temperature, thereby identifying the efficient insulation materials suitable for application scenarios. The appropriate insulation layer thickness was determined using the maximum allowable heat loss method and economic thickness method. Moreover, the thermal conductivities of insulation layers with different service lives were measured. Results indicate that the thermal conductivity increased linearly with the increasing service life. Factors causing the deterioration of insulation layer performance were incorporated into the model to study the relationship between the operating cost of an insulation layer and its outer diameter and service life. For insulation layers with different designed service lives, their optimal outer diameters and operating costs were calculated using the economic thickness method. Results show that considering material aging factors in the design of insulation layer thickness can reduce cumulative costs by 10.7% within the designed service life. However, when the service life expires, the operating cost of a design that considered the aging issue is higher than that of a design that did not consider the aging issue owing to increased heat loss as a result of aging of the insulation layer. The insulation layer can be designed to reduce steam heat loss and improve steam utilization efficiency as well as provide theoretical guidance for the green, low-carbon, and high-quality development of cigarette factories.

Supercritical CO₂ plays an important role in many applications such as nuclear power generation, solar power generation, cryogenic refrigeration, and aerospace. Currently, the majority of studies on supercritical CO₂ convective heat transfer in tubes focus on the temperature range near the critical point, while the heat transfer patterns at high temperature and pressure far from the critical point remain unclear and need to be further studied. In this study, numerical simulations were performed to analyze the effects of mass flow, inlet temperature, system pressure, heat flux density, and tube diameter on the convective heat transfer coefficient at high temperature and pressure, as well as the effects of buoyancy and flow acceleration caused by operating conditions on the heat transfer characteristics. The results show that the convective heat transfer coefficient increases with increasing mass flow, inlet temperature, system pressure, and heat flux density. The difference in convective heat transfer coefficient gradually grows along the flow direction under different heat flux densities. Convective heat transfer coefficient decreases with increasing tube diameter. Compared with the heat transfer patterns near the critical point, heat flux density and tube diameter exert different effects on the convective heat transfer coefficient. In general, the effects of pressure on the convective heat transfer coefficient are small. This study provides significant values to understand the law of supercritical fluid heat transfer and guide the design of efficient and safe heat exchanger.

Energy and environment problems are becoming increasingly prominent, renewable energy is developing rapidly, and its intermittency is one of the key problems restricting its development. Advanced adiabatic compressed air energy storage (AA-CAES) is an effective method to address the intermittency of renewable energy. In this study, a mathematical model for the energy storage stage of AA-CAES is established, and dynamic and sensitivity analysis of the conservation of energy, energy balance, and key parameters of each component are conducted. The results reveal that the proposed mathematical model follows the laws of conservation of energy and exergy balance; the exergy loss of the compressor is greater than that of the heat exchanger; energy and heat are mainly stored in heat transfer oil and high-pressure air, respectively; the deviation between compressor operating and design condition reduces the efficiency; the effect of the air flow rate and inlet temperature of the first-stage turbine on the operation time is greater than that of the storage temperature, adiabatic efficiency and stored air mass. This paper provides reference for adjusting parameters and optimizing energy storage system according to actual demand.

Submerged combustion evaporation technology is a heat exchange technology that uses high-temperature flue gas as the heat source to evaporate the liquid in direct contact with it. However, existing research lacks thermal state simulations of the immersed combustion evaporation process and investigations on the impact of the inclination angle of the distribution disc inside the evaporator on the evaporation. In this study, we conducted a thermal state numerical simulation on the structural parameters of the distributed disc-type submerged combustion evaporator using the Euler method. Herein, the flue gas distribution inside the evaporator was obtained by studying the gas-liquid two-phase flow. Additionally, the impact of different distribution disc inclination angles on the evaporation amount and pressure fluctuation was explored. The numerical simulation results indicate that the angle of the distribution disc affects the distribution of flue gas in the liquid. Moreover, the pressure fluctuation at the inlet of the submerged tube can be reduced by increasing the distribution disc’s angle, thereby increasing backpressure stability in the burner. Conversely, the heat exchange effect between gas and liquid can be enhanced by decreasing the distribution disc’s angle, thereby enhancing evaporation efficiency.

To overcome the shortcomings of traditional absorption refrigeration working pairs, ionic liquid refrigeration working pairs have been widely developed and used as ideal substitutes. Herein, the gas-liquid phase equilibrium properties of the [EMIM]BF₄/CH₃OH ionic liquid binary system were investigated using static experiments and molecular dynamics simulations. The results reveal that this binary solution shows favorable gas-liquid phase equilibrium properties, and its saturated vapor pressure is experimentally measured to be approximately 21% lower than that of other alcohol-based ionic liquid solutions. In addition, the simulation results exhibit the same order of magnitude and trend as the experimental results, and the relative errors are generally less than 8%. These findings provide physical property database for screening ionic liquid refrigeration working pairs and studying the theoretical cycle system as well as a new method for simulating and predicting the basic properties of ionic liquids.

As a novel energy storage method, compressed supercritical carbon dioxide (sCO₂) energy storage offers several advantages, such as high energy storage density, compact structure, long service life, and negative carbon emissions. Therefore, it has a broad application prospect in the energy storage and conversion. In this study, a dynamic mathematical model for the compressed sCO₂ energy storage system (SC-CCES) was established based on the mass conservation and energy conservation laws and the reliability of the model was verified. Additionally, dynamic simulations of the SC-CCES system with single-stage compression and single-stage expansion were performed using Matlab/Simulink. Under the designed operating conditions, the energy storage efficiency of the SC-CCES system was found to be 51.98%, with an energy storage density of 447.8 kWh/m³. The energy storage density of the SC-CCES system was more than 20 times higher than that of a traditional compressed air energy storage system. Furthermore, the impact of different high-pressure tank inlet pressures on system performance was analyzed. The results showed that the energy storage efficiency increases with the increase of the inlet pressure of the high-pressure storage tank, while the energy storage density is exactly the opposite. This study provides a basis for the development of compressed carbon dioxide energy storage.

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.