A mathematical model of principal elements of the aircraft hydraulic system is presented based on the heat transfer theory. The dynamic heat transfer process of the hydraulic oil and the pump shells within an aircraft...A mathematical model of principal elements of the aircraft hydraulic system is presented based on the heat transfer theory. The dynamic heat transfer process of the hydraulic oil and the pump shells within an aircraft hydraulic system are analyzed by the difference method. A kind of means for the prediction to variational trends of the aircraft hydraulic system temperature is provided during operation. The numerical prediction and simulation under the operational conditions are presented for ground trial running and the decelerated operation in flight. Computational results show that there is a good coincidence between the experimental data and the numerical predictions.展开更多
In the relativistic σ-ω model, including the vacuum fluctuation of nucleons and σ mesons, the effect of the temperature to the composition and equation of state of protoneutron star matter, nucleon effective mass a...In the relativistic σ-ω model, including the vacuum fluctuation of nucleons and σ mesons, the effect of the temperature to the composition and equation of state of protoneutron star matter, nucleon effective mass and chemical potential of neutrons and electrons are studied. We find that the influence of the temperature on the equation of state of protoneutron star matter is indeed small, however, its influence on the composition of protoneutron star, which will contribute to the evolution of protoneutron star, cannot be neglected in low density region. The chemical potentials of neutrons and electrons also depend on the temperature in almost the same density region.展开更多
Delivering energy flexibility at the district scale entails coordinating control actions across many buildings to shape aggregate demand;this coordination depends on training and deploying control policies and optimiz...Delivering energy flexibility at the district scale entails coordinating control actions across many buildings to shape aggregate demand;this coordination depends on training and deploying control policies and optimization routines,which in turn require predictive models that can be queried efficiently over large building clusters.However,conventional physics-based simulators are computationally prohibitive for large-scale control training,and simple data-driven surrogates often lack the generalization needed for heterogeneous clusters.This paper introduces ScaleONet,a deep operator network framework designed for scalable,control-oriented modeling of building-cluster thermal dynamics.ScaleONet leverages the DeepONet paradigm to decouple and share learning across buildings:an LSTM-based branch network encodes outdoor climate and individual HVAC control signals,while a multilayer perceptron(MLP)-based trunk network embeds prediction timestamps,enabling fast predictions for growing clusters with negligible extra cost for each additional building or timestep.To the authors’knowledge,this is the first operator-learning method tailored to indoor air temperature forecasting in heterogeneous building clusters.Validation on thirty Belgian buildings(GenkNet)simulated in Dymola shows that,although a non-operator-learning LSTM baseline slightly outperforms ScaleONet for single-building cases,its error grows monotonically with cluster size.In contrast,ScaleONet’s median per-building-per-day RMSE decreases from 0.59°C at three buildings to 0.53°C at ten and 0.47°C at thirty,compared to 0.95°C for the LSTM at thirty buildings-a 51%reduction in prediction error.Error analysis across envelope heat-loss coefficients(UAbuilding)further reveals that while the LSTM’s RMSE increases for high-𝑈𝐴structures,ScaleONet maintains uniformly low error.With millisecond-scale inference(approximately 4 ms per sample for thirty buildings),ScaleONet is well suited for large-scale reinforcement learning,receding-horizon optimization,and real-time model predictive control.展开更多
Rapid population growth in recent decades has intensified both the global energy crisis and the challenges posed by climate change,including global warming.Currently,the increased frequency of extreme weather events a...Rapid population growth in recent decades has intensified both the global energy crisis and the challenges posed by climate change,including global warming.Currently,the increased frequency of extreme weather events and large fluctuations in ambient temperature disrupt thermal comfort and negatively impact health,driving a growing dependence on cooling and heating energy sources.Consequently,efficient thermal management has become a central focus of energy research.Traditional thermal management systems consume substantial energy,further contributing to greenhouse gas emissions.In contrast,emergent radiant thermal management technologies that rely on renewable energy have been proposed as sustainable alternatives.However,achieving year-round thermal management without additional energy input remains a formidable challenge.Recently,dynamic radiative thermal management technologies have emerged as the most promising solution,offering the potential for energy-efficient adaptation across seasonal variations.This review systematically presents recent advancements in dynamic radiative thermal management,covering fundamental principles,switching mechanisms,primary materials,and application areas.Additionally,the key challenges hindering the broader adoption of dynamic radiative thermal management technologies are discussed.By highlighting their transformative potential,this review provides insights into the design and industrial scalability of these innovations,with the ultimate aim of promoting renewable energy integration in thermal management applications.展开更多
The district heating system(DHS)consumes a lot of energy in winter,and its control accuracy needs to be improved urgently.To apply advanced process control(APC)in DHS,the thermal dynamic model of the existing building...The district heating system(DHS)consumes a lot of energy in winter,and its control accuracy needs to be improved urgently.To apply advanced process control(APC)in DHS,the thermal dynamic model of the existing buildings is essential.This paper uses the subspace method which is a data-driven approach for modelling the thermal dynamics of the building.The model’s performance is analyzed using the collected data,and the differences compared to the classical methods are also analyzed.The method reduces the RMSE by about 20%compared with the ARX model for the same complexity.Subsequently,the analysis of the training residuals indicates that the estimate of periodic intra-building disturbance can be obtained by minimizing the training residuals.By introducing the estimated disturbance function,the RMSE on the test set is further reduced by 26%.At the end of the article,a simple parameter extrapolation experiment is conducted,and the result shows that the parameters can be extrapolated to other buildings without large errors.展开更多
The essential task of integrated electricity-heat systems(IEHSs)is to provide customers with reliable electric and heating services.From the perspective of customers,it is reasonable to analyze the reliabilities of IE...The essential task of integrated electricity-heat systems(IEHSs)is to provide customers with reliable electric and heating services.From the perspective of customers,it is reasonable to analyze the reliabilities of IEHSs based on the ability to provide energy services with a reasonable assurance of continuity and quality,which are termed as service-based reliabilities.Due to the thermal inertia existing in IEHSs,the heating service performances can present slow dynamic characteristics,which has a great impact on the service satisfaction of customers.The neglect of such thermal dynamics will bring about inaccurate service-based reliability measurement,which can lead to the inefficient dispatch decisions of system operators.Therefore,it is necessary to provide a tool which can analyze the servicebased reliabilities of IEHSs considering the impacts of thermal dynamics.This paper firstly models the energy service performance of IEHSs in contingency states.Specifically,the nodal energy supplies are obtained from the optimal power and heat flow model under both variable hydraulic and thermal conditions,in which the transmission-side thermal dynamics are formulated.On this basis,the energy service performances for customers are further determined with the formulation of demandside thermal dynamics.Moreover,a service-based reliability analysis framework for the IEHSs is proposed utilizing the timesequential Monte Carlo simulation(TSMCS)technique with the embedded decomposition algorithm.Furthermore,the indices for quantifying service-based reliabilities are defined based on the traditional reliability indices,where dynamic service performances and service satisfactions of customers are both considered.Numerical simulations are carried out with a test system to validate the effectiveness of the proposed framework.展开更多
In this paper,we propose a graph model embedded with compact physical equations for modeling the thermal dynamics of buildings.The principles of heat flow across various components in the building,such as walls and do...In this paper,we propose a graph model embedded with compact physical equations for modeling the thermal dynamics of buildings.The principles of heat flow across various components in the building,such as walls and doors,fit the message-passing strategy used by Graph Neural networks(GNNs).The proposed method is to represent the multi-zone building as a graph,in which only zones are considered as nodes,and any heat flow between zones is modeled as an edge based on prior knowledge of the building structure.Furthermore,the thermal dynamics of these components are described by compact models in the graph.GNNs are further employed to train model parameters from collected data.During model training,our proposed method enforces physical constraints(e.g.,zone sizes and connections)on model parameters and propagates the penalty in the loss function of GNN.Such constraints are essential to ensure model robustness and interpretability.We evaluate the effectiveness of the proposed modeling approach on a realistic dataset with multiple zones.The results demonstrate a satisfactory accuracy in the prediction of multi-zone temperature.Moreover,we illustrate that the new model can reliably learn hidden physical parameters with incomplete data.展开更多
A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain p...A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.展开更多
This research focused on the dynamic mechanical and thermal properties of woven mat jute/kenaf/jute(J/K/J)and kenaf/jute/kenaf(K/J/K)hybrid composites.Dynamic mechanical analysis(DMA)and Thermo-gravimetric Analysis(TG...This research focused on the dynamic mechanical and thermal properties of woven mat jute/kenaf/jute(J/K/J)and kenaf/jute/kenaf(K/J/K)hybrid composites.Dynamic mechanical analysis(DMA)and Thermo-gravimetric Analysis(TGA)were used to study the effect of layering sequence on the thermal properties of kenaf/jute hybrid composites.The DMA results;it was found that the differences in the stacking sequence between the kenaf/jute composites do not affect their storage modulus,loss modulus and damping factor.From the TGA and DMA results,it has been shown that stacking sequence has given positive effect to the kenaf/jute hybrid composite compared to pure epoxy composite.This is because kenaf and jute fibre has increased the Tg values of the composites,thus affect the thermal degradation.Results showed that the storage modulus for kenaf/jute hybrid composites increased compared with pure epoxy composites with increasing temperature and the values of remained almost the same at glass transition temperature(Tg),the hybrid composite perhaps due to the improved fibre/matrix interface bonding.The preliminary analysis could provide a new direction for the creation of a novel hybrid composite which offers unique properties which cannot be accomplished in a single material system.展开更多
An analytical method is developed to determine the transient response of dynamic thermostress in a two-layered cylinder with initial interface pressure. At first, the initial interface pressure in a two-layered cylind...An analytical method is developed to determine the transient response of dynamic thermostress in a two-layered cylinder with initial interface pressure. At first, the initial interface pressure in a two-layered cylinder caused by a heat-assembling method is considered as the initial condition of a thermal elastodynamic equilibrium equation. Thus, a thermal elastodynamic solution for a separate hollow cylinder with the initial stress field is found out by means of a series of simply mathematical transform. By making use of the boundary conditions and continuity conditions of a layered cylinders, the solution for the thermal shock exerting an influence on the initial interface pressure in a two-layered cylinder is also discussed.展开更多
With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperatur...With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperature drop in storage tanks under actual dynamically changing environments, this paper considers the influence of dynamic thermal environment and internal crude oil physical properties on the fluctuating changes in crude oil temperature. A theoretical model of the unsteady-state temperature drop heat transfer process is developed from a three-dimensional perspective. According to the temperature drop variation law of crude oil storage tank under the coupling effect of various heat transfer modes such as external forced convection, thermal radiation, and internal natural convection, the external dynamic thermal environment influence zone, the internal crude oil physical property influence zone, and the intermediate transition zone of the tank are proposed. And the multiple non-linear regression method is used to quantitatively characterize the influence of external ambient temperature, solar radiation, wind speed, internal crude oil density, viscosity, and specific heat capacity on the temperature drop of crude oil in each influencing zone. The results of this paper not only quantitatively explain the main influencing factors of the oil temperature drop in the top, wall, and bottom regions of the tank, but also provide a theoretical reference for oil security reserves under a dynamic thermal environment.展开更多
Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysila...Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane （VTES）, vinyl trimethoxysilane （VTMS） and γ-methacryloylpropyl trimethoxysilane （MPS）. The treated glass fibers were analyzed by fourier transform infrared spectroscopy （FTIR）. Dynamic mechanical thermal analysis （DMTA） and thermo-gravimetric analysis （TGA） were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy （SEM）. The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.展开更多
The heat conduction and thermal conductivity for methane hydrate are simulated from equilibrium molecular dynamics. The thermal conductivity and temperature dependence trend agree well with the experimental results. T...The heat conduction and thermal conductivity for methane hydrate are simulated from equilibrium molecular dynamics. The thermal conductivity and temperature dependence trend agree well with the experimental results. The nonmonotonic temperature dependence is attributed to the phonon inelastic scattering at higher temperature and to the confinement of the optic phonon modes and low frequency phonons at low temperature. The thermal conductivity scales proportionally with the van der Waals interaction strength, The conversion of a crystal-like nature into an amorphous one oecurs at higher strength. Both the temperature dependence and interaction strength dependence are explained by phonon inelastic scattering.展开更多
Using molecular dynamics （MD） simulation, we study the thermal shock behavior of tungsten （W）, which has been used for the plasma facing material （PFM） of tokamaks. The thermo-elastic stress wave, corresponding ...Using molecular dynamics （MD） simulation, we study the thermal shock behavior of tungsten （W）, which has been used for the plasma facing material （PFM） of tokamaks. The thermo-elastic stress wave, corresponding to the collective displacement of atoms, is analyzed with the Lagrangian atomic stress method, of which the reliability is also analyzed. The stress wave velocity corresponds to the speed of sound in the material, which is not dependent on the thermal shock energy. The peak pressure of a normal stress wave increases with the increase of thermal shock energy. We analyze the temperature evolution of the thermal shock region according to the Fourier transformation. It can be seen that the “obvious” velocity of heat propagation is less than the velocity of the stress wave; further, that the thermo-elastic stress wave may contribute little to the transport of kinetic energy. The heat propagation can be described properly by the heat conduction equation. These results may be useful for understanding the process of the thermal shock of tungsten.展开更多
Silicene, a silicon analogue of graphene, has attracted increasing research attention in recent years because of its unique electrical and thermal conductivities. In this study, phonon thermal conductivity and its iso...Silicene, a silicon analogue of graphene, has attracted increasing research attention in recent years because of its unique electrical and thermal conductivities. In this study, phonon thermal conductivity and its isotopic doping effect in silicene nanoribbons（SNRs） are investigated by using molecular dynamics simulations. The calculated thermal conductivities are approximately 32 W/mK and 35 W/mK for armchair-edged SNRs and zigzag-edged SNRs, respectively, which show anisotropic behaviors. Isotope doping induces mass disorder in the lattice, which results in increased phonon scattering, thus reducing the thermal conductivity. The phonon thermal conductivity of isotopic doped SNR is dependent on the concentration and arrangement pattern of dopants. A maximum reduction of about 15% is obtained at 50% randomly isotopic doping with ^（30）Si. In addition, ordered doping（i.e., isotope superlattice） leads to a much larger reduction in thermal conductivity than random doping for the same doping concentration. Particularly, the periodicity of the doping superlattice structure has a significant influence on the thermal conductivity of SNR. Phonon spectrum analysis is also used to qualitatively explain the mechanism of thermal conductivity change induced by isotopic doping. This study highlights the importance of isotopic doping in tuning the thermal properties of silicene, thus guiding defect engineering of the thermal properties of two-dimensional silicon materials.展开更多
Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study o...Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation （R） and determination （R2） coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.展开更多
We improved the thermal equivalent-circuit model of the laser diode module（LDM） to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal p...We improved the thermal equivalent-circuit model of the laser diode module（LDM） to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.展开更多
he temperature distnbution on the surface of a flight vehicle and the va-riation of the modulus of elasticity with respect to temperature are considered. The minimum weight structural design with constraints on freque...he temperature distnbution on the surface of a flight vehicle and the va-riation of the modulus of elasticity with respect to temperature are considered. The minimum weight structural design with constraints on frequency, on the coordinates ofmodal nodes and on the upper and lower bounds of the design vanables are studied us-ing Kuhn-Tucker conditions as optimal cntenon. The vanation of the flrst three ordernatural frequencies, modal shapes and minimum structural weight vs temperature gra-dient are discussed. It is pointed out that it is imperative to take into account the effectof aerodynamic heating on structural dynamic optimization. Calculation example showsthat the method obtained is feasible and efficient.展开更多
The lattice thermal conductivity of boron nitride nanoribbon（BNNR） is calculated by using equilibrium molecular dynamics（EMD） simulation method. The Green–Kubo relation derived from linear response theory is used...The lattice thermal conductivity of boron nitride nanoribbon（BNNR） is calculated by using equilibrium molecular dynamics（EMD） simulation method. The Green–Kubo relation derived from linear response theory is used to acquire the thermal conductivity from heat current auto-correlation function（HCACF）. HCACF of the selected BNNR system shows a tendency of a very fast decay and then be followed by a very slow decay process,finally,approaching zero approximately within 3 ps. The convergence of lattice thermal conductivity demonstrates that the thermal conductivity of BNNR can be simulated by EMD simulation using several thousands of atoms with periodic boundary conditions. The results show that BNNR exhibit lower thermal conductivity than that of boron nitride（BN） monolayer,which indicates that phonons boundary scatting significantly suppresses the phonons transport in BNNR. Vacancies in BNNR greatly affect the lattice thermal conductivity,in detail,only 1% concentration of vacancies in BNNR induce a 60% reduction of the lattice thermal conductivity at room temperature.展开更多
A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results...A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.展开更多
文摘A mathematical model of principal elements of the aircraft hydraulic system is presented based on the heat transfer theory. The dynamic heat transfer process of the hydraulic oil and the pump shells within an aircraft hydraulic system are analyzed by the difference method. A kind of means for the prediction to variational trends of the aircraft hydraulic system temperature is provided during operation. The numerical prediction and simulation under the operational conditions are presented for ground trial running and the decelerated operation in flight. Computational results show that there is a good coincidence between the experimental data and the numerical predictions.
文摘In the relativistic σ-ω model, including the vacuum fluctuation of nucleons and σ mesons, the effect of the temperature to the composition and equation of state of protoneutron star matter, nucleon effective mass and chemical potential of neutrons and electrons are studied. We find that the influence of the temperature on the equation of state of protoneutron star matter is indeed small, however, its influence on the composition of protoneutron star, which will contribute to the evolution of protoneutron star, cannot be neglected in low density region. The chemical potentials of neutrons and electrons also depend on the temperature in almost the same density region.
基金supported by KU Leuven,Belgium through the TECHPED-C2 project(C24M/21/021)which investigates tech-nically feasible and effective solutions for Positive Energy Districts.Additional support was provided by the National University of Singa-pore,Singapore through the Start-Up Grant(A-0009876-00-00)the Ministry of Education,Singapore,under the Academic Research Fund Tier 1(A-8003235-00-00).
文摘Delivering energy flexibility at the district scale entails coordinating control actions across many buildings to shape aggregate demand;this coordination depends on training and deploying control policies and optimization routines,which in turn require predictive models that can be queried efficiently over large building clusters.However,conventional physics-based simulators are computationally prohibitive for large-scale control training,and simple data-driven surrogates often lack the generalization needed for heterogeneous clusters.This paper introduces ScaleONet,a deep operator network framework designed for scalable,control-oriented modeling of building-cluster thermal dynamics.ScaleONet leverages the DeepONet paradigm to decouple and share learning across buildings:an LSTM-based branch network encodes outdoor climate and individual HVAC control signals,while a multilayer perceptron(MLP)-based trunk network embeds prediction timestamps,enabling fast predictions for growing clusters with negligible extra cost for each additional building or timestep.To the authors’knowledge,this is the first operator-learning method tailored to indoor air temperature forecasting in heterogeneous building clusters.Validation on thirty Belgian buildings(GenkNet)simulated in Dymola shows that,although a non-operator-learning LSTM baseline slightly outperforms ScaleONet for single-building cases,its error grows monotonically with cluster size.In contrast,ScaleONet’s median per-building-per-day RMSE decreases from 0.59°C at three buildings to 0.53°C at ten and 0.47°C at thirty,compared to 0.95°C for the LSTM at thirty buildings-a 51%reduction in prediction error.Error analysis across envelope heat-loss coefficients(UAbuilding)further reveals that while the LSTM’s RMSE increases for high-𝑈𝐴structures,ScaleONet maintains uniformly low error.With millisecond-scale inference(approximately 4 ms per sample for thirty buildings),ScaleONet is well suited for large-scale reinforcement learning,receding-horizon optimization,and real-time model predictive control.
基金the Institute of Biomass & Functional Materials of Shaanxi University of Science and Technology for funding this research workfinancially supported by the National Natural Science Foundation of China (2207081675, 22278257, 22308209)+1 种基金the Key R&D Program of Shaanxi Province (2024SF-YBXM-586)the Project of Innovation Capability Support Program in Shaanxi Province (2024ZC-KJXX-005)
文摘Rapid population growth in recent decades has intensified both the global energy crisis and the challenges posed by climate change,including global warming.Currently,the increased frequency of extreme weather events and large fluctuations in ambient temperature disrupt thermal comfort and negatively impact health,driving a growing dependence on cooling and heating energy sources.Consequently,efficient thermal management has become a central focus of energy research.Traditional thermal management systems consume substantial energy,further contributing to greenhouse gas emissions.In contrast,emergent radiant thermal management technologies that rely on renewable energy have been proposed as sustainable alternatives.However,achieving year-round thermal management without additional energy input remains a formidable challenge.Recently,dynamic radiative thermal management technologies have emerged as the most promising solution,offering the potential for energy-efficient adaptation across seasonal variations.This review systematically presents recent advancements in dynamic radiative thermal management,covering fundamental principles,switching mechanisms,primary materials,and application areas.Additionally,the key challenges hindering the broader adoption of dynamic radiative thermal management technologies are discussed.By highlighting their transformative potential,this review provides insights into the design and industrial scalability of these innovations,with the ultimate aim of promoting renewable energy integration in thermal management applications.
文摘The district heating system(DHS)consumes a lot of energy in winter,and its control accuracy needs to be improved urgently.To apply advanced process control(APC)in DHS,the thermal dynamic model of the existing buildings is essential.This paper uses the subspace method which is a data-driven approach for modelling the thermal dynamics of the building.The model’s performance is analyzed using the collected data,and the differences compared to the classical methods are also analyzed.The method reduces the RMSE by about 20%compared with the ARX model for the same complexity.Subsequently,the analysis of the training residuals indicates that the estimate of periodic intra-building disturbance can be obtained by minimizing the training residuals.By introducing the estimated disturbance function,the RMSE on the test set is further reduced by 26%.At the end of the article,a simple parameter extrapolation experiment is conducted,and the result shows that the parameters can be extrapolated to other buildings without large errors.
基金supported by the Science and Technology Project of State Grid Corporation of China(No.5108-202218280A-2-448-XG)。
文摘The essential task of integrated electricity-heat systems(IEHSs)is to provide customers with reliable electric and heating services.From the perspective of customers,it is reasonable to analyze the reliabilities of IEHSs based on the ability to provide energy services with a reasonable assurance of continuity and quality,which are termed as service-based reliabilities.Due to the thermal inertia existing in IEHSs,the heating service performances can present slow dynamic characteristics,which has a great impact on the service satisfaction of customers.The neglect of such thermal dynamics will bring about inaccurate service-based reliability measurement,which can lead to the inefficient dispatch decisions of system operators.Therefore,it is necessary to provide a tool which can analyze the servicebased reliabilities of IEHSs considering the impacts of thermal dynamics.This paper firstly models the energy service performance of IEHSs in contingency states.Specifically,the nodal energy supplies are obtained from the optimal power and heat flow model under both variable hydraulic and thermal conditions,in which the transmission-side thermal dynamics are formulated.On this basis,the energy service performances for customers are further determined with the formulation of demandside thermal dynamics.Moreover,a service-based reliability analysis framework for the IEHSs is proposed utilizing the timesequential Monte Carlo simulation(TSMCS)technique with the embedded decomposition algorithm.Furthermore,the indices for quantifying service-based reliabilities are defined based on the traditional reliability indices,where dynamic service performances and service satisfactions of customers are both considered.Numerical simulations are carried out with a test system to validate the effectiveness of the proposed framework.
文摘In this paper,we propose a graph model embedded with compact physical equations for modeling the thermal dynamics of buildings.The principles of heat flow across various components in the building,such as walls and doors,fit the message-passing strategy used by Graph Neural networks(GNNs).The proposed method is to represent the multi-zone building as a graph,in which only zones are considered as nodes,and any heat flow between zones is modeled as an edge based on prior knowledge of the building structure.Furthermore,the thermal dynamics of these components are described by compact models in the graph.GNNs are further employed to train model parameters from collected data.During model training,our proposed method enforces physical constraints(e.g.,zone sizes and connections)on model parameters and propagates the penalty in the loss function of GNN.Such constraints are essential to ensure model robustness and interpretability.We evaluate the effectiveness of the proposed modeling approach on a realistic dataset with multiple zones.The results demonstrate a satisfactory accuracy in the prediction of multi-zone temperature.Moreover,we illustrate that the new model can reliably learn hidden physical parameters with incomplete data.
文摘A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.
基金This work is supported by UPM under GP-IPS Grant 9486400.
文摘This research focused on the dynamic mechanical and thermal properties of woven mat jute/kenaf/jute(J/K/J)and kenaf/jute/kenaf(K/J/K)hybrid composites.Dynamic mechanical analysis(DMA)and Thermo-gravimetric Analysis(TGA)were used to study the effect of layering sequence on the thermal properties of kenaf/jute hybrid composites.The DMA results;it was found that the differences in the stacking sequence between the kenaf/jute composites do not affect their storage modulus,loss modulus and damping factor.From the TGA and DMA results,it has been shown that stacking sequence has given positive effect to the kenaf/jute hybrid composite compared to pure epoxy composite.This is because kenaf and jute fibre has increased the Tg values of the composites,thus affect the thermal degradation.Results showed that the storage modulus for kenaf/jute hybrid composites increased compared with pure epoxy composites with increasing temperature and the values of remained almost the same at glass transition temperature(Tg),the hybrid composite perhaps due to the improved fibre/matrix interface bonding.The preliminary analysis could provide a new direction for the creation of a novel hybrid composite which offers unique properties which cannot be accomplished in a single material system.
文摘An analytical method is developed to determine the transient response of dynamic thermostress in a two-layered cylinder with initial interface pressure. At first, the initial interface pressure in a two-layered cylinder caused by a heat-assembling method is considered as the initial condition of a thermal elastodynamic equilibrium equation. Thus, a thermal elastodynamic solution for a separate hollow cylinder with the initial stress field is found out by means of a series of simply mathematical transform. By making use of the boundary conditions and continuity conditions of a layered cylinders, the solution for the thermal shock exerting an influence on the initial interface pressure in a two-layered cylinder is also discussed.
基金supported by the National Natural Science Foundation of China(52104064)(52074089)the China Postdoctoral Science Foundation(2020M681074)+3 种基金Heilongjiang Provincial Natural Science Foundation of China(YQ2023E006)University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(UNPYSCT-2020152)Postdoctoral Science Foundation of Heilongjiang Province in China(LBH-TZ2106)(LBH-Z20122)Northeast Petroleum University Talents Introduction Fund(2019KQ18).
文摘With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperature drop in storage tanks under actual dynamically changing environments, this paper considers the influence of dynamic thermal environment and internal crude oil physical properties on the fluctuating changes in crude oil temperature. A theoretical model of the unsteady-state temperature drop heat transfer process is developed from a three-dimensional perspective. According to the temperature drop variation law of crude oil storage tank under the coupling effect of various heat transfer modes such as external forced convection, thermal radiation, and internal natural convection, the external dynamic thermal environment influence zone, the internal crude oil physical property influence zone, and the intermediate transition zone of the tank are proposed. And the multiple non-linear regression method is used to quantitatively characterize the influence of external ambient temperature, solar radiation, wind speed, internal crude oil density, viscosity, and specific heat capacity on the temperature drop of crude oil in each influencing zone. The results of this paper not only quantitatively explain the main influencing factors of the oil temperature drop in the top, wall, and bottom regions of the tank, but also provide a theoretical reference for oil security reserves under a dynamic thermal environment.
基金Supported by National Natural Science Foundation of China (No.50872101,A3 Foresight Program-50821140308)National Basic Research Program of China (No.2009CB939704)a joint project of National Nature Science Foundation of China and Russian Foundation for Basic Research(No.NSFC-RFBR 51011120252)
文摘Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane （VTES）, vinyl trimethoxysilane （VTMS） and γ-methacryloylpropyl trimethoxysilane （MPS）. The treated glass fibers were analyzed by fourier transform infrared spectroscopy （FTIR）. Dynamic mechanical thermal analysis （DMTA） and thermo-gravimetric analysis （TGA） were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy （SEM）. The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.
基金Supported by the National Natural Science Foundation of China under Grant Nos U1262112 and 51176205
文摘The heat conduction and thermal conductivity for methane hydrate are simulated from equilibrium molecular dynamics. The thermal conductivity and temperature dependence trend agree well with the experimental results. The nonmonotonic temperature dependence is attributed to the phonon inelastic scattering at higher temperature and to the confinement of the optic phonon modes and low frequency phonons at low temperature. The thermal conductivity scales proportionally with the van der Waals interaction strength, The conversion of a crystal-like nature into an amorphous one oecurs at higher strength. Both the temperature dependence and interaction strength dependence are explained by phonon inelastic scattering.
基金Project supported by the National Magnetic Confinement Fusion Science Program of China(Grant No.2013GB109004)the National Natural Science Foundation of China(Grant Nos.51071095 and 50971077)
文摘Using molecular dynamics （MD） simulation, we study the thermal shock behavior of tungsten （W）, which has been used for the plasma facing material （PFM） of tokamaks. The thermo-elastic stress wave, corresponding to the collective displacement of atoms, is analyzed with the Lagrangian atomic stress method, of which the reliability is also analyzed. The stress wave velocity corresponds to the speed of sound in the material, which is not dependent on the thermal shock energy. The peak pressure of a normal stress wave increases with the increase of thermal shock energy. We analyze the temperature evolution of the thermal shock region according to the Fourier transformation. It can be seen that the “obvious” velocity of heat propagation is less than the velocity of the stress wave; further, that the thermo-elastic stress wave may contribute little to the transport of kinetic energy. The heat propagation can be described properly by the heat conduction equation. These results may be useful for understanding the process of the thermal shock of tungsten.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504418 and 11447033)the Natural Science Fund for Colleges and Universities in Jiangsu Province,China(Grant No.16KJB460022)the Fundamental Research Funds for the Central Universities of CUMT,China(Grant No.2015XKMS075)
文摘Silicene, a silicon analogue of graphene, has attracted increasing research attention in recent years because of its unique electrical and thermal conductivities. In this study, phonon thermal conductivity and its isotopic doping effect in silicene nanoribbons（SNRs） are investigated by using molecular dynamics simulations. The calculated thermal conductivities are approximately 32 W/mK and 35 W/mK for armchair-edged SNRs and zigzag-edged SNRs, respectively, which show anisotropic behaviors. Isotope doping induces mass disorder in the lattice, which results in increased phonon scattering, thus reducing the thermal conductivity. The phonon thermal conductivity of isotopic doped SNR is dependent on the concentration and arrangement pattern of dopants. A maximum reduction of about 15% is obtained at 50% randomly isotopic doping with ^（30）Si. In addition, ordered doping（i.e., isotope superlattice） leads to a much larger reduction in thermal conductivity than random doping for the same doping concentration. Particularly, the periodicity of the doping superlattice structure has a significant influence on the thermal conductivity of SNR. Phonon spectrum analysis is also used to qualitatively explain the mechanism of thermal conductivity change induced by isotopic doping. This study highlights the importance of isotopic doping in tuning the thermal properties of silicene, thus guiding defect engineering of the thermal properties of two-dimensional silicon materials.
文摘Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation （R） and determination （R2） coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.
基金Project supported by the Key Program of the National Natural Science Foundation of China (Grant No. 60938002)the Special-funded Program on National Key Scientific Instruments and Equipment Development of China (Grant No. 2012YQ06016501)the Tianjin Research Program of Application Foundation and Advanced Technology,China (Grant No. 11JCYBJC04900)
文摘We improved the thermal equivalent-circuit model of the laser diode module（LDM） to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.
文摘he temperature distnbution on the surface of a flight vehicle and the va-riation of the modulus of elasticity with respect to temperature are considered. The minimum weight structural design with constraints on frequency, on the coordinates ofmodal nodes and on the upper and lower bounds of the design vanables are studied us-ing Kuhn-Tucker conditions as optimal cntenon. The vanation of the flrst three ordernatural frequencies, modal shapes and minimum structural weight vs temperature gra-dient are discussed. It is pointed out that it is imperative to take into account the effectof aerodynamic heating on structural dynamic optimization. Calculation example showsthat the method obtained is feasible and efficient.
基金Supported by the Natural Science Foundation of Hubei Province(2014CFB610)the Excellent Young Innovation Team Project of Hubei Province(T201429)
文摘The lattice thermal conductivity of boron nitride nanoribbon（BNNR） is calculated by using equilibrium molecular dynamics（EMD） simulation method. The Green–Kubo relation derived from linear response theory is used to acquire the thermal conductivity from heat current auto-correlation function（HCACF）. HCACF of the selected BNNR system shows a tendency of a very fast decay and then be followed by a very slow decay process,finally,approaching zero approximately within 3 ps. The convergence of lattice thermal conductivity demonstrates that the thermal conductivity of BNNR can be simulated by EMD simulation using several thousands of atoms with periodic boundary conditions. The results show that BNNR exhibit lower thermal conductivity than that of boron nitride（BN） monolayer,which indicates that phonons boundary scatting significantly suppresses the phonons transport in BNNR. Vacancies in BNNR greatly affect the lattice thermal conductivity,in detail,only 1% concentration of vacancies in BNNR induce a 60% reduction of the lattice thermal conductivity at room temperature.
文摘A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.
