We present the scheme of the structure of grading a resistor-heated system ofwarm compaction in powder metallurgy. The structure has the first heater and the second heater thatare heated by electrical tubes. Powder is...We present the scheme of the structure of grading a resistor-heated system ofwarm compaction in powder metallurgy. The structure has the first heater and the second heater thatare heated by electrical tubes. Powder is heated in turn in the first heater and the second heater,where there is the mass fluidity of powder under gravity. The dimensions of the first heater andthe second heater were calculated from the Fourier equation of heat conduction, and the boundarycondition was constant temperature. The drawings of the first heater, the second heater and thepowder-delivering device were given. The structure of the heat equipment is simple and easy tomanufacture. Finally, an exact warm compaction press system HGWY- II was developed for the heatingsystem.展开更多
Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heati...Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heating and viscous dissipation.Governing nonlinear problems of velocity, temperature and nanoparticle concentration are solved via homotopic procedure.Convergence is examined graphically and numerically. Results of temperature and nanoparticle concentration are plotted and discussed for various values of material parameters, Prandtl number, Lewis number, Newtonian heating parameter, Eckert number and thermophoresis and Brownian motion parameters. Numerical computations are performed. The results show that the change in temperature and nanoparticle concentration distribution functions is similar when we use higher values of material parameters β1 andβ2. It is seen that the temperature and thermal boundary layer thickness are increasing functions of Newtonian heating parameter γ.An increase in thermophoresis and Brownian motion parameters tends to an enhancement in the temperature.展开更多
This paper presents a hybrid graded element model for the transient heat conduction problem in functionally graded materials （FGMs）. First, a Laplace transform approach is used to handle the time variable. Then, a f...This paper presents a hybrid graded element model for the transient heat conduction problem in functionally graded materials （FGMs）. First, a Laplace transform approach is used to handle the time variable. Then, a fundamental solution in Laplace space for FGMs is constructed. Next, a hybrid graded element is formulated based on the obtained fundamental solution and a frame field. As a result, the graded properties of FGMs are naturally reflected by using the fundamental solution to interpolate the intra-element field. Further, Stefest＇s algorithm is employed to convert the results in Laplace space back into the time-space domain. Finally, the performance of the proposed method is assessed by several benchmark examples. The results demonstrate well the efficiency and accuracy of the proposed method.展开更多
A meshless numerical model is developed for analyzing transient heat conductions in three-dimensional （3D） axisymmetric continuously nonhomogeneous functionally graded materials （FGMs）. Axial symmetry of geometry ...A meshless numerical model is developed for analyzing transient heat conductions in three-dimensional （3D） axisymmetric continuously nonhomogeneous functionally graded materials （FGMs）. Axial symmetry of geometry and boundary conditions reduces the original 3D initial-boundary value problem into a two-dimensional （2D） problem. Local weak forms are derived for small polygonal sub-domains which surround nodal points distributed over the cross section. In order to simplify the treatment of the essential boundary conditions, spatial variations of the temperature and heat flux at discrete time instants are interpolated by the natural neighbor interpolation. Moreover, the using of three-node triangular finite element method （FEM） shape functions as test functions reduces the orders of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with the traditional two-point difference technique in the time domain. Two numerical examples are investigated and excellent results are obtained, demonstrating the potential application of the proposed approach.展开更多
Energy crisis make the effective use of low grade energy more and more urgent. It is still a worldwide difficult conundrum. To efficiently recover low grade heat, this paper deals with a theoretical analysis of a new ...Energy crisis make the effective use of low grade energy more and more urgent. It is still a worldwide difficult conundrum. To efficiently recover low grade heat, this paper deals with a theoretical analysis of a new power generation method driven by a low grade heat source. When the temperature of the low grade heat source exceeds the saturated temperature, it can heat the liquid into steam. If the steam is sealed and cooled in a container, it will lead to a negative pressure condition. The proposed power generation method utilizes the negative pressure condition in the sealed container, called as a condensator. When the condensator is connected to a liquid pool, the liquid will be pumped into it by the negative pressure condition. After the conden- sator is filled by liquid, the liquid flows back into the pool and drives the turbine to generate electricity. According to our analysis, for water, the head pressure of water pumped into the condensator could reach 9.5 m when the temperature of water in the pool is 25 ℃, and the steam temperature is 105 ℃. Theoretical thermal efficiency of this power generation system could reach 3.2% to 5.8% varying with the altitude of the condensator to the water level, ignoring steam leakage loss.展开更多
The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced th...The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.展开更多
As the installed capacity of renewable energy such as wind and solar power continues to increase,energy storage technology is becoming increasingly crucial.It could effectively balance power demand and supply,enhance ...As the installed capacity of renewable energy such as wind and solar power continues to increase,energy storage technology is becoming increasingly crucial.It could effectively balance power demand and supply,enhance allocation flexibility,and improve power quality.Among various energy storage technologies,liquid CO_(2)energy storage(LCES)stands out as one of the most promising options due to its advantages such as high round-trip efficiency(RTE),high energy storage density(ESD),safety,stability,and longevity.Within the system,the cold and heat storage units play a critical role in determining the overall performance of the system and are particularly important among its various components.In this paper,a novel LCES system is proposed and the heat transfer characteristics are analyzed in detail.Then,the impact of key parameters on the liquefaction ratio and RTE is discussed.The results indicate that the RTE,ESD,and exergy efficiency of the system are 56.12%,29.46 kWh/m^(3),and 93.73%under specified design conditions,respectively.During the gas-liquid phase change process of carbon dioxide or when it is in a supercritical state,the related heat transfer processes become more complex,leading to increased energy loss.The analysis of key parameters of the Linde-Hampson liquefaction unit reveals that as the liquefaction temperature decreases,both the liquefaction ratio and RTE increase.While the liquefaction pressure has a minimal impact on the liquefaction ratio,it significantly affects RTE,with an optimal liquefaction pressure identified.展开更多
Achieving rubber-like stretchability in cellulose ionogels presents a substantial challenge due to the intrinsically extended chain configuration of cellulose.Inspired by the molecular configuration of natural rubber,...Achieving rubber-like stretchability in cellulose ionogels presents a substantial challenge due to the intrinsically extended chain configuration of cellulose.Inspired by the molecular configuration of natural rubber,we address this challenge by using cyanoethyl as a substitute for 1.5 hydroxyl on the D-glucose unit of cellulose.This strategy innovatively triggers the transformation of cellulose molecules into a coiled chain configuration,facilitating the creation of an ultra-stretchable ionogel free from any petrochemical polymers.The resultant ionogel demonstrates mechanical ductility comparable to that of a rubber band,achieving an elongation strain of nearly 1,000%while maintaining a tensile strength of up to 1.8 MPa and exhibiting a biomodulus akin to that of human skin,recorded at 63 kPa.Additionally,this stretchable ionogel presents skin-like self-healing behavior,favorable biocompatibility,and noteworthy thermoelectric properties,highlighted by a Seebeck coefficient of approximately 68 mV K−1.This study delineates a feasible molecular approach for developing stretchable ionogels from biomass resources,potentially revolutionizing self-powered stretchable electronics for integration with human tissues and skin.展开更多
Carbon dioxide energy storage(CES)is an emerging compressed gas energy storage technology which offers high energy storage efficiency,flexibility in location,and low overall costs.This study focuses on a CES system th...Carbon dioxide energy storage(CES)is an emerging compressed gas energy storage technology which offers high energy storage efficiency,flexibility in location,and low overall costs.This study focuses on a CES system that incorporates a high-temperature graded heat storage structure,utilizing multiple heat exchange working fluids.Unlike traditional CES systems that utilize a single thermal storage at low to medium temperatures,this system significantly optimizes the heat transfer performance of the system,thereby improving its cycle efficiency.Under typical design conditions,the round-trip efficiency of the system is found to be 76.4%,with an output power of 334 kW/(kg·s^(-1))per unit mass flow rate,through mathematical modeling.Performance analysis shows that increasing the total pressure ratio,reducing the heat transfer temperature difference,improving the heat exchanger efficiency,and lowering the ambient temperature can enhance cycle efficiency.Additionally,this paper proposes a universal and theoretical CES thermodynamic intrinsic cycle construction method and performance prediction evaluation method for CES systems,providing a more standardized and accurate approach for optimizing CES system design.展开更多
In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficien...In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficiently finite thermal reservoirs.The exergy destructions(anergies) at various components of the system are theoretically investigated as well as the exergy efficiency.Results show that the anergy of heat exchanger or two-phase expander decreases while the anergy of throttle valve increases with increasing flash temperature,and the exergy efficiency has an optimum value with respect to the flash temperature.Under the optimal conditions with respect to the flash temperature,exergy efficiency increases with the heating temperature and the component having the largest exergy destruction varies with the flash temperature or heating temperature.展开更多
Organic thermoelectric materials have emerged as compelling candidates for harvesting low‐grade heat in flexible and lightweight energy systems.Compared to conventional inorganic thermoelectric materials,organic ther...Organic thermoelectric materials have emerged as compelling candidates for harvesting low‐grade heat in flexible and lightweight energy systems.Compared to conventional inorganic thermoelectric materials,organic ther-moelectric materials offer distinct advantages,including intrinsically low ther-mal conductivity,mechanical flexibility,and compatibility with large‐area and solution‐based processing.While p‐type materials such as poly(3,4‐ethyl-enedioxythiophene):polystyrene sulfonate(PEDOT:PSS)have been exten-sively optimized through solvent treatments and de‐doping strategies,recent advances in air‐stable n‐type polymers such as poly(benzodifurandione)(PBFDO)have greatly narrowed the performance gap and made it feasible to construct fully organic thermoelectric modules.This review highlights recent progress in organic thermoelectric materials with a focus on molecular design,doping mechanisms,and device‐level integration.We examine how novel polymers,dopant formulations,and emerging concepts have been driving improvements in the performance of organic thermoelectric materials toward practical application.Our group's previous contributions to module design such as thermal lamination techniques and integrated circuits are presented as case studies of system‐level implementation.Despite their relatively modest power factors and thermoelectric figures of merit,organic thermoelectric materials possess unique advantages in terms of low weight,processability,and scal-ability that make them especially suited for gram‐scale modules and powering small‐scale electronic devices and Internet‐of‐Things systems using ambient thermal energy.展开更多
文摘We present the scheme of the structure of grading a resistor-heated system ofwarm compaction in powder metallurgy. The structure has the first heater and the second heater thatare heated by electrical tubes. Powder is heated in turn in the first heater and the second heater,where there is the mass fluidity of powder under gravity. The dimensions of the first heater andthe second heater were calculated from the Fourier equation of heat conduction, and the boundarycondition was constant temperature. The drawings of the first heater, the second heater and thepowder-delivering device were given. The structure of the heat equipment is simple and easy tomanufacture. Finally, an exact warm compaction press system HGWY- II was developed for the heatingsystem.
基金funded by the Deanship of Scientific Research (DSR), King Abdulaziz University (KAU), under Grant No. 37-130-35-HiCi
文摘Two-dimensional boundary layer flow of an incompressible third grade nanofluid over a stretching surface is investigated.Influence of thermophoresis and Brownian motion is considered in the presence of Newtonian heating and viscous dissipation.Governing nonlinear problems of velocity, temperature and nanoparticle concentration are solved via homotopic procedure.Convergence is examined graphically and numerically. Results of temperature and nanoparticle concentration are plotted and discussed for various values of material parameters, Prandtl number, Lewis number, Newtonian heating parameter, Eckert number and thermophoresis and Brownian motion parameters. Numerical computations are performed. The results show that the change in temperature and nanoparticle concentration distribution functions is similar when we use higher values of material parameters β1 andβ2. It is seen that the temperature and thermal boundary layer thickness are increasing functions of Newtonian heating parameter γ.An increase in thermophoresis and Brownian motion parameters tends to an enhancement in the temperature.
文摘This paper presents a hybrid graded element model for the transient heat conduction problem in functionally graded materials （FGMs）. First, a Laplace transform approach is used to handle the time variable. Then, a fundamental solution in Laplace space for FGMs is constructed. Next, a hybrid graded element is formulated based on the obtained fundamental solution and a frame field. As a result, the graded properties of FGMs are naturally reflected by using the fundamental solution to interpolate the intra-element field. Further, Stefest＇s algorithm is employed to convert the results in Laplace space back into the time-space domain. Finally, the performance of the proposed method is assessed by several benchmark examples. The results demonstrate well the efficiency and accuracy of the proposed method.
基金Project supported by the National Natural Science Foundation of China(Grant No.11002054)the Foundation of Hunan Educational Committee(Grant No.12C0059).
文摘A meshless numerical model is developed for analyzing transient heat conductions in three-dimensional （3D） axisymmetric continuously nonhomogeneous functionally graded materials （FGMs）. Axial symmetry of geometry and boundary conditions reduces the original 3D initial-boundary value problem into a two-dimensional （2D） problem. Local weak forms are derived for small polygonal sub-domains which surround nodal points distributed over the cross section. In order to simplify the treatment of the essential boundary conditions, spatial variations of the temperature and heat flux at discrete time instants are interpolated by the natural neighbor interpolation. Moreover, the using of three-node triangular finite element method （FEM） shape functions as test functions reduces the orders of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with the traditional two-point difference technique in the time domain. Two numerical examples are investigated and excellent results are obtained, demonstrating the potential application of the proposed approach.
基金Project (No. 51109174) supported by the National Natural Science Foundation of China
文摘Energy crisis make the effective use of low grade energy more and more urgent. It is still a worldwide difficult conundrum. To efficiently recover low grade heat, this paper deals with a theoretical analysis of a new power generation method driven by a low grade heat source. When the temperature of the low grade heat source exceeds the saturated temperature, it can heat the liquid into steam. If the steam is sealed and cooled in a container, it will lead to a negative pressure condition. The proposed power generation method utilizes the negative pressure condition in the sealed container, called as a condensator. When the condensator is connected to a liquid pool, the liquid will be pumped into it by the negative pressure condition. After the conden- sator is filled by liquid, the liquid flows back into the pool and drives the turbine to generate electricity. According to our analysis, for water, the head pressure of water pumped into the condensator could reach 9.5 m when the temperature of water in the pool is 25 ℃, and the steam temperature is 105 ℃. Theoretical thermal efficiency of this power generation system could reach 3.2% to 5.8% varying with the altitude of the condensator to the water level, ignoring steam leakage loss.
基金the Majlesi Branch,Islamic Azad University for the support of this work
文摘The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.
基金supported by the National Natural Science Foundation of China(Grant Nos.52206032 and 21978308)Special Fund for Central Guiding Local Science and Technology Development,China(ZYYD2022B11&2022ZY0048).
文摘As the installed capacity of renewable energy such as wind and solar power continues to increase,energy storage technology is becoming increasingly crucial.It could effectively balance power demand and supply,enhance allocation flexibility,and improve power quality.Among various energy storage technologies,liquid CO_(2)energy storage(LCES)stands out as one of the most promising options due to its advantages such as high round-trip efficiency(RTE),high energy storage density(ESD),safety,stability,and longevity.Within the system,the cold and heat storage units play a critical role in determining the overall performance of the system and are particularly important among its various components.In this paper,a novel LCES system is proposed and the heat transfer characteristics are analyzed in detail.Then,the impact of key parameters on the liquefaction ratio and RTE is discussed.The results indicate that the RTE,ESD,and exergy efficiency of the system are 56.12%,29.46 kWh/m^(3),and 93.73%under specified design conditions,respectively.During the gas-liquid phase change process of carbon dioxide or when it is in a supercritical state,the related heat transfer processes become more complex,leading to increased energy loss.The analysis of key parameters of the Linde-Hampson liquefaction unit reveals that as the liquefaction temperature decreases,both the liquefaction ratio and RTE increase.While the liquefaction pressure has a minimal impact on the liquefaction ratio,it significantly affects RTE,with an optimal liquefaction pressure identified.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFD2200504)the Central Guidance Fund for Local Science and Technology Development Projects(Grant No.2024JH6/100700013)+1 种基金the National Natural Science Foundation of China(Grant Nos.32171720 and 32371823)the National Science Fund for Distinguished Young Scholars(Grant No.31925028).
文摘Achieving rubber-like stretchability in cellulose ionogels presents a substantial challenge due to the intrinsically extended chain configuration of cellulose.Inspired by the molecular configuration of natural rubber,we address this challenge by using cyanoethyl as a substitute for 1.5 hydroxyl on the D-glucose unit of cellulose.This strategy innovatively triggers the transformation of cellulose molecules into a coiled chain configuration,facilitating the creation of an ultra-stretchable ionogel free from any petrochemical polymers.The resultant ionogel demonstrates mechanical ductility comparable to that of a rubber band,achieving an elongation strain of nearly 1,000%while maintaining a tensile strength of up to 1.8 MPa and exhibiting a biomodulus akin to that of human skin,recorded at 63 kPa.Additionally,this stretchable ionogel presents skin-like self-healing behavior,favorable biocompatibility,and noteworthy thermoelectric properties,highlighted by a Seebeck coefficient of approximately 68 mV K−1.This study delineates a feasible molecular approach for developing stretchable ionogels from biomass resources,potentially revolutionizing self-powered stretchable electronics for integration with human tissues and skin.
基金supported by the National Natural Technology Development,China(Grant Nos.ZYYD2022B11 and 2022ZY0048).
文摘Carbon dioxide energy storage(CES)is an emerging compressed gas energy storage technology which offers high energy storage efficiency,flexibility in location,and low overall costs.This study focuses on a CES system that incorporates a high-temperature graded heat storage structure,utilizing multiple heat exchange working fluids.Unlike traditional CES systems that utilize a single thermal storage at low to medium temperatures,this system significantly optimizes the heat transfer performance of the system,thereby improving its cycle efficiency.Under typical design conditions,the round-trip efficiency of the system is found to be 76.4%,with an output power of 334 kW/(kg·s^(-1))per unit mass flow rate,through mathematical modeling.Performance analysis shows that increasing the total pressure ratio,reducing the heat transfer temperature difference,improving the heat exchanger efficiency,and lowering the ambient temperature can enhance cycle efficiency.Additionally,this paper proposes a universal and theoretical CES thermodynamic intrinsic cycle construction method and performance prediction evaluation method for CES systems,providing a more standardized and accurate approach for optimizing CES system design.
基金supported by Research Fund,Kumoh National Institute of Technology
文摘In this work exergetical performance analysis is carried out based on the second law of thermodynamics for organic flash cycle(OFC) using a two-phase expander instead of throttle expansion in order to recover efficiently finite thermal reservoirs.The exergy destructions(anergies) at various components of the system are theoretically investigated as well as the exergy efficiency.Results show that the anergy of heat exchanger or two-phase expander decreases while the anergy of throttle valve increases with increasing flash temperature,and the exergy efficiency has an optimum value with respect to the flash temperature.Under the optimal conditions with respect to the flash temperature,exergy efficiency increases with the heating temperature and the component having the largest exergy destruction varies with the flash temperature or heating temperature.
基金Japan Science and Technology Agency,Grant/Award Number:JPMJTR23R6。
文摘Organic thermoelectric materials have emerged as compelling candidates for harvesting low‐grade heat in flexible and lightweight energy systems.Compared to conventional inorganic thermoelectric materials,organic ther-moelectric materials offer distinct advantages,including intrinsically low ther-mal conductivity,mechanical flexibility,and compatibility with large‐area and solution‐based processing.While p‐type materials such as poly(3,4‐ethyl-enedioxythiophene):polystyrene sulfonate(PEDOT:PSS)have been exten-sively optimized through solvent treatments and de‐doping strategies,recent advances in air‐stable n‐type polymers such as poly(benzodifurandione)(PBFDO)have greatly narrowed the performance gap and made it feasible to construct fully organic thermoelectric modules.This review highlights recent progress in organic thermoelectric materials with a focus on molecular design,doping mechanisms,and device‐level integration.We examine how novel polymers,dopant formulations,and emerging concepts have been driving improvements in the performance of organic thermoelectric materials toward practical application.Our group's previous contributions to module design such as thermal lamination techniques and integrated circuits are presented as case studies of system‐level implementation.Despite their relatively modest power factors and thermoelectric figures of merit,organic thermoelectric materials possess unique advantages in terms of low weight,processability,and scal-ability that make them especially suited for gram‐scale modules and powering small‐scale electronic devices and Internet‐of‐Things systems using ambient thermal energy.
