To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and p...To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and performance of the heat pump part of this new heating system are studied.Based on a SASHP with 10 kW,the mathematical model of this system is built,and the characteristics and performance are concluded from the simulation analysis at different environmental temperatures and output water temperatures.The results show that the performance of heat pumps can be greatly improved based on the new SASHP.When the environmental temperature is 7 ℃,the coefficient of performance（COP）of the air-source heat pump（ASHP）can be increased by 26% at most.This paper sets up a base for further study on the heating system with this new SASHP in the heating season.展开更多
With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial ...With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial for the environment and alleviates air pollution.However,the large-scale application of airsource heat pumps has brought power quality problems such as voltage sags,harmonic pollution,and three-phase imbalance to the distribution network.This paper studies the fixed-frequency and variablefrequency air-source heat pump,introduces its working principle,analyzes the mechanism of its power quality problem.Moreover,the paper establishes a simulation model for the fixed-frequency heat pump and variable-frequency heat pump to connect to the distribution network.This research mainly studies the impact of large-scale fixed-frequency heat pumps on the depth of voltage sags in the distribution network and the impact of large-scale variable-frequency heat pumps on the harmonic content of the distribution network under different penetration rates and uses measured data to verify the reliability of the simulation results.This paper uses experimental data for the first time to verify the real power quality problems of large-scale heat pumps,which can provide a reference for determining the power quality standards for heat pumps connected to the power grid.At the same time,it can also provide a reference for the power quality management of the distribution network that is actually connected to electric heating.展开更多
The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in...The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.展开更多
Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the perform...Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation temperature of-20oC,and an experimental setup was established to test the prototype.The measured results demonstrated that the heating EER(energy efficiency ratio)of the EVIe could reach about 4%higher than that of the system without the ejector when the heating capacity remained nearly constant.The design method is helpful to development of a heat pump system coupled with scroll compressor and ejector.展开更多
Carotenoids are lipophilic isoprenoid pigments with essential roles in plants.While the cultivated allotetraploid cottons exhibit distinct mature anther coloration—yellow in Gossypium barbadense versus predominantly ...Carotenoids are lipophilic isoprenoid pigments with essential roles in plants.While the cultivated allotetraploid cottons exhibit distinct mature anther coloration—yellow in Gossypium barbadense versus predominantly white in G.hirsutum—the genetic basis of this divergence remains unclear.The purpose of this study was to identify the genetic basis of anther-color variation in cotton(Gossypium)species.We firstly identified carotenoids as the primary pigments underlying yellow-anthers coloration.Comparative transcriptomics of anthers revealed that the carotenoid biosynthesis gene GbPSY4 was expressed as a key regulator in G.barbadense.Functional validation via tissue-specific expression,subcellular localization,in vivo enzymatic assays,and virus-induced gene silencing confirmed its role in carotenoid biosynthesis and yellow pigmentation.Genome-wide association studies in a G.hirsutum population revealed GhPSY4_At,an ortholog of GbPSY4,as the causal gene of anther-color variation.We conclude that PSY4-regulated carotenoid biosynthesis governs yellow pigmentation.Furthermore,a finding that G.hirsutum accessions with yellow anthers showed greater pollen viability under high-temperature stress than those with white anthers suggests that the same pathway that governs yellow pigmentation influences heat tolerance.PSY4 is a promising target for breeding stress-tolerant cotton varieties.展开更多
Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate indiv...Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.展开更多
The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF...The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.展开更多
Extreme heat events contribute to high mortality[1,2]and overwhelm emergency medical services through increased ambulance calls and overcrowded emergency departments.[3]Because morbidity and mortality are directly rel...Extreme heat events contribute to high mortality[1,2]and overwhelm emergency medical services through increased ambulance calls and overcrowded emergency departments.[3]Because morbidity and mortality are directly related to both the degree and duration of hyperthermia,timely recognition and management of heat exhaustion and heat stroke are critical for preventing death and reducing healthcare burdens.展开更多
In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditi...In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditional energy to clean energy heating modes,the feasibility of a heating system coupling traditional and clean energies was studied using the heating system of an office building in a cold region of China as the research object.The air-source heat pump(ASHP)heating system used in the office building in this study was field-tested.The problems existing in the heating system were analysed using testing data combined with the existing conditions of the building.Solar-air source heat pump coupled heating system based on heat grid(NH-SASHP)was proposed,and the system model was established using TRNSYS software.The operation effect of the NH-SASHP coupling system was analysed,and the control strategy of the coupling system was optimized.The results showed that NH-SASHP system possessed certain advantages over the ASHP system during the heating season,and the energy saving rate is 50.79%compared with the ASHP system.Under the most unfavourable working conditions in the middle of severe cold,the indoor temperature compliance rate was 100%.The average coefficient of performance of the heat pump system(COPsys)of NH-SASHP system and ASHP system were 6.27 and 3.55,respectively.The operating cost of the NH-SASHP system is approximately 72.3%of the ASHP system.展开更多
Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and sh...Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.展开更多
Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to t...Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to their outstanding properties,including high thermal conductivity,tunable thermal expansion coefficients,excellent mechanical strength,and low density.However,the industrial-scale application of these composites faces critical challenges during the fabrication of components with complex structures,such as inhomogeneous dispersion of graphene within the copper matrix and poor interfacial bonding between the two phases,which substantially undermine the overall performance of graphene/copper-based composites.To address these issues,the preparation methods for graphene/copper-based composite heat sinks were reviewed.For each method,a rigorous analysis was presented to clarify its inherent advantages and unavoidable restrictions.Furthermore,the latest research progress in addressing three core scientific challenges was synthesized,including uniform dispersion of graphene,interfacial optimization mechanisms,and molecular dynamics simulations for elucidating the structure-property relationships.Finally,the future development directions of graphene/copper-based composite heat sinks in engineering applications were prospected.展开更多
This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in...This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.展开更多
The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to...The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.展开更多
Urban populations are increasingly exposed to extreme heat due to climate change and rapid urbanization,heightening health risks in cities worldwide.Accurate heat exposure assessment is essential for public health pla...Urban populations are increasingly exposed to extreme heat due to climate change and rapid urbanization,heightening health risks in cities worldwide.Accurate heat exposure assessment is essential for public health planning and risk reduction.Most existing approaches rely on a single threshold temperature(e.g.,35℃of daily max temperature),applied uniformly to the entire population.However,this one-size-fits-all assumption overlooks substantial differences in heat sensitivity across population subgroups.In this study,we address this limitation by quantifying subgroup-specific temperature-mortality relationships and using corresponding minimum mortality temperatures(MMTs)to assess heat exposure.Results show that the population-wide MMT was 27.5℃,but it varied greatly across population subgroups.The elderly population(≥65)had an MMT of 24.6℃,much lower than the 28.6℃observed in younger individuals(<65).Females also exhibited a lower MMT that males(25℃versus 28.2℃).However,educational attainment did not significantly affect MMT.Using a uniform MMT resulted in substantial underestimation of heat exposure,ranging from 25.3%in 1990 to 13.9%in 2020,reflecting demographic shifts over time.Spatially,nearly half of the city experienced underestimated heat risk,especially in central and northeastern regions where heat-vulnerable populations are concentrated.These findings underscore the need for more nuanced heat exposure assessments that account for demographic and spatial variability,paving the way for targeted public health interventions to protect the most vulnerable urban populations.展开更多
Enhancing the efficiency of phase-change heat storage is vital for maximizing the utilization of renewable energy.This study examines the synergistic effect of non-uniformly shaped fins and nanoparticles on the meltin...Enhancing the efficiency of phase-change heat storage is vital for maximizing the utilization of renewable energy.This study examines the synergistic effect of non-uniformly shaped fins and nanoparticles on the melting performance of phase-change storage tanks.The problem is addressed using a finite volume framework coupled with the enthalpy–porosity method,with the numerical model rigorously validated against experimental data.The analysis explores the influence of varying fin deflection angles and nanoparticle concentrations on melting dynamics.It is shown that a downward fin deflection of 6◦reduces melting time to 570 s,representing a 20.8% improvement over uniform fins.Introducing 1% nanoparticles further accelerates melting,reducing time by 36.54% compared to the nanoparticle-free case.The combined strategy of 6◦fin deflection and 1%nanoparticle addition shows the most economic heat storage rate,achieving an exceptional 80.74% enhancement relative to a tank with uniform fins.展开更多
The atmospheric surface layer of the tropical coastal ocean is commonly very unstable and experiences weakwind conditions.How the latent(LE)and sensible(H)heat fluxes behave under such conditions are unclear because o...The atmospheric surface layer of the tropical coastal ocean is commonly very unstable and experiences weakwind conditions.How the latent(LE)and sensible(H)heat fluxes behave under such conditions are unclear because of the lack of observation stations in the tropics.Thus,this study aims to analyze LE and H and the microclimate parameters influencing them.The authors deployed an eddy covariance system in a tropical coastal region for seven months.The microclimate parameters investigated were wind speed(U),vapor pressure deficit(Δe),temperature difference(ΔT),wind-vapor pressure deficit(UΔe),wind-temperature difference(UΔT),and atmospheric stability(z/L),where z is height and L is the Monin–Obukhov length.On the daily time scale,the results show that LE was more associated with U thanΔe,while H was more related toΔT than U.Cross-wavelet analysis revealed the strong coherence in the LE-U relationship for periods between one and two days,and for H–ΔT,0.5 to 1 day.Correlation and regression analyses confirmed the time series analyses results,where strong positive correlation coefficients(r)were obtained between LE and U(r=0.494)and H andΔT(r=0.365).Compared to other water bodies,the transfer coefficient of moisture(CE N)was found to be small(=0.40×10^(-3))and independent of stability;conversely,the transfer coefficient of heat(CH N)was closer to literature values(=1.00×10^(-3))and a function of stability.展开更多
The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This stud...The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This study examines all long-lived MHWs(>10 days)in the SCS from 1982 to 2021,categorizing them into intensified and attenuated MHWs based on the overall trend of sea surface temperature during an MHW event.A mixed-layer heat budget analysis reveals that the thermal processes primarily driven by the latent heat flux are crucial in modulating the SCS MHWs,particularly for attenuated MHWs.However,under intensified conditions,the proportions of dynamically dominated MHWs(40%)is approximately comparable to that of thermally dominated ones(47%).This study highlights the significance of dynamic processes in shaping SCS MHWs and discusses the potential impacts induced by tropical cyclones on these MHWs.展开更多
To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-ge...To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.展开更多
The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhua...The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhuakeng uranium deposit has a high radioactive heat production rate(avg.5.50μW/m³)and a low Th/U ratio(avg.2.62).Uranium-rich granite and its alteration zone within the upper crust(0-5 km depth)contribute about 45%of the total radioactive heat production,wich is crucial for controlling geothermal resource distribution.For uranium-thermal at tectonic plate margins,a symbiotic geological model was proposed:Firstly,subduction of the Pacific Plate caused upwelling of the asthenosphere,generating a high heat-flow background.Secondly,heat transfer is enhanced by major faults such as the Youdong and Mianhuakeng faults.Subsequently,uranium was mobilized,transported,and enriched within the granite through deep siliceous hydrothermal activity and associated alteration.Ultimately,the uranium enrichment in granite leads to increased radioactive heat production,resulting in local thermal anomalies.This model provides a theoretical support for exploring and developing uranium-thermal symbiotic resources in South China.展开更多
The dual-probe heat pulse(DPHP)is a well-established method for estimating soil moisture(θ)using soil thermal conductivity(λ)and volumetric heat capacity(C_(v)).Recently,monitoringθhas been improved by integrating ...The dual-probe heat pulse(DPHP)is a well-established method for estimating soil moisture(θ)using soil thermal conductivity(λ)and volumetric heat capacity(C_(v)).Recently,monitoringθhas been improved by integrating the DPHP method with distributed temperature sensing(DTS)technology.In the DPHP-DTS approach,a single fiber optic(FO)cable with embedded metallic constituents functions as a heating element,while a parallel cable serves to monitor the temperature.Despite ongoing advancements,challenges such as the difficulty in positioning heating and sensing cables and high energy requirements hinder the widespread adoption of the DPHP-DTS method.As alternative heating materials are seldom used,this study evaluated the feasibility of employing a resistive metallic alloy as the heating element in a laboratory DPHP-DTS application.Overall,higher errors were observed when assessing C_(v)andλat higherθvalues(>0.2),but using C_(v)data produced more accurateθestimates(with the root mean square error(RMSE)≤0.06).Based on C_(v)values,a low-power,long-duration heat pulse(8.07 W/m for 300 s)yielded more consistentθestimates(RMSE=0.04)than a high-power,shortduration pulse(15.93 W/m for 180 s,with RMSE=0.06).The findings of this study also indicated that variations in heating uniformity and electrical power fluctuations potentially affected measurement accuracy.Nevertheless,the resistive alloy proved advantageous for DPHP-DTS due to its independent power connection,ability to maintain linear positioning within the soil,and potential for energy savings,all while providing reliableθestimates.展开更多
基金The National Natural Science Foundation of China(No.50676018)the National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2008BAJ12B02)
文摘To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and performance of the heat pump part of this new heating system are studied.Based on a SASHP with 10 kW,the mathematical model of this system is built,and the characteristics and performance are concluded from the simulation analysis at different environmental temperatures and output water temperatures.The results show that the performance of heat pumps can be greatly improved based on the new SASHP.When the environmental temperature is 7 ℃,the coefficient of performance（COP）of the air-source heat pump（ASHP）can be increased by 26% at most.This paper sets up a base for further study on the heating system with this new SASHP in the heating season.
基金Science and Technology Project of State Grid Corporation of China,Scale application and benefit evaluation of typical power substitution technology considering the influence of power quality(52182018000H).
文摘With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial for the environment and alleviates air pollution.However,the large-scale application of airsource heat pumps has brought power quality problems such as voltage sags,harmonic pollution,and three-phase imbalance to the distribution network.This paper studies the fixed-frequency and variablefrequency air-source heat pump,introduces its working principle,analyzes the mechanism of its power quality problem.Moreover,the paper establishes a simulation model for the fixed-frequency heat pump and variable-frequency heat pump to connect to the distribution network.This research mainly studies the impact of large-scale fixed-frequency heat pumps on the depth of voltage sags in the distribution network and the impact of large-scale variable-frequency heat pumps on the harmonic content of the distribution network under different penetration rates and uses measured data to verify the reliability of the simulation results.This paper uses experimental data for the first time to verify the real power quality problems of large-scale heat pumps,which can provide a reference for determining the power quality standards for heat pumps connected to the power grid.At the same time,it can also provide a reference for the power quality management of the distribution network that is actually connected to electric heating.
基金supported by the National Key R&D Program of China(No.2021YFB1507203)the National Natural Science Foundation of China(No.51838007).
文摘The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.
基金supported by the National Natural Science Foundation of China(Grant No.50776001)
文摘Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation temperature of-20oC,and an experimental setup was established to test the prototype.The measured results demonstrated that the heating EER(energy efficiency ratio)of the EVIe could reach about 4%higher than that of the system without the ejector when the heating capacity remained nearly constant.The design method is helpful to development of a heat pump system coupled with scroll compressor and ejector.
基金the National Natural Science Foundation of China(32170271,32470277)the Project of Sanya Yazhou Bay Science and Technology City(SCKJ-JYRC-2023-52)the Natural Science Foundation of Henan Province(252300421076,222300420024).
文摘Carotenoids are lipophilic isoprenoid pigments with essential roles in plants.While the cultivated allotetraploid cottons exhibit distinct mature anther coloration—yellow in Gossypium barbadense versus predominantly white in G.hirsutum—the genetic basis of this divergence remains unclear.The purpose of this study was to identify the genetic basis of anther-color variation in cotton(Gossypium)species.We firstly identified carotenoids as the primary pigments underlying yellow-anthers coloration.Comparative transcriptomics of anthers revealed that the carotenoid biosynthesis gene GbPSY4 was expressed as a key regulator in G.barbadense.Functional validation via tissue-specific expression,subcellular localization,in vivo enzymatic assays,and virus-induced gene silencing confirmed its role in carotenoid biosynthesis and yellow pigmentation.Genome-wide association studies in a G.hirsutum population revealed GhPSY4_At,an ortholog of GbPSY4,as the causal gene of anther-color variation.We conclude that PSY4-regulated carotenoid biosynthesis governs yellow pigmentation.Furthermore,a finding that G.hirsutum accessions with yellow anthers showed greater pollen viability under high-temperature stress than those with white anthers suggests that the same pathway that governs yellow pigmentation influences heat tolerance.PSY4 is a promising target for breeding stress-tolerant cotton varieties.
基金National Natural Science Foundation of China(52172108)National Key R&D Program of China(2022YFB3707700)Strategic Priority Research Program of the Chinese Academy of Sciences(XDC0144005)。
文摘Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.
基金National Natural Science Foundation of China(11875039)Shanxi Scholarship Council of China(2023-033)+2 种基金Fundamental Research Program of Shanxi Province(202303021221071)China Baowu Low Carbon Metallurgical Innovation Foundation(2022)2023 Anhui Major Industrial Innovation Plan Project。
文摘The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.
文摘Extreme heat events contribute to high mortality[1,2]and overwhelm emergency medical services through increased ambulance calls and overcrowded emergency departments.[3]Because morbidity and mortality are directly related to both the degree and duration of hyperthermia,timely recognition and management of heat exhaustion and heat stroke are critical for preventing death and reducing healthcare burdens.
文摘In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditional energy to clean energy heating modes,the feasibility of a heating system coupling traditional and clean energies was studied using the heating system of an office building in a cold region of China as the research object.The air-source heat pump(ASHP)heating system used in the office building in this study was field-tested.The problems existing in the heating system were analysed using testing data combined with the existing conditions of the building.Solar-air source heat pump coupled heating system based on heat grid(NH-SASHP)was proposed,and the system model was established using TRNSYS software.The operation effect of the NH-SASHP coupling system was analysed,and the control strategy of the coupling system was optimized.The results showed that NH-SASHP system possessed certain advantages over the ASHP system during the heating season,and the energy saving rate is 50.79%compared with the ASHP system.Under the most unfavourable working conditions in the middle of severe cold,the indoor temperature compliance rate was 100%.The average coefficient of performance of the heat pump system(COPsys)of NH-SASHP system and ASHP system were 6.27 and 3.55,respectively.The operating cost of the NH-SASHP system is approximately 72.3%of the ASHP system.
文摘Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.
基金Research Start-Up Fund Project of Anhui Polytechnic University(S022023017)University Research Project of Anhui Province(2023AH050937)+1 种基金Anhui Polytechnic University Research Foundation for Introducing Talents(2022YQQ003)Anhui Province Key Laboratory of Intelligent Vehicle Chassis by Wire。
文摘Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to their outstanding properties,including high thermal conductivity,tunable thermal expansion coefficients,excellent mechanical strength,and low density.However,the industrial-scale application of these composites faces critical challenges during the fabrication of components with complex structures,such as inhomogeneous dispersion of graphene within the copper matrix and poor interfacial bonding between the two phases,which substantially undermine the overall performance of graphene/copper-based composites.To address these issues,the preparation methods for graphene/copper-based composite heat sinks were reviewed.For each method,a rigorous analysis was presented to clarify its inherent advantages and unavoidable restrictions.Furthermore,the latest research progress in addressing three core scientific challenges was synthesized,including uniform dispersion of graphene,interfacial optimization mechanisms,and molecular dynamics simulations for elucidating the structure-property relationships.Finally,the future development directions of graphene/copper-based composite heat sinks in engineering applications were prospected.
文摘This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.
基金supported by the Tianjin Education Commission Research Program Project(No.2024KJ105)。
文摘The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.
基金supported by the National Natural Science Foundation of China(Grant No.42225104)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-086).
文摘Urban populations are increasingly exposed to extreme heat due to climate change and rapid urbanization,heightening health risks in cities worldwide.Accurate heat exposure assessment is essential for public health planning and risk reduction.Most existing approaches rely on a single threshold temperature(e.g.,35℃of daily max temperature),applied uniformly to the entire population.However,this one-size-fits-all assumption overlooks substantial differences in heat sensitivity across population subgroups.In this study,we address this limitation by quantifying subgroup-specific temperature-mortality relationships and using corresponding minimum mortality temperatures(MMTs)to assess heat exposure.Results show that the population-wide MMT was 27.5℃,but it varied greatly across population subgroups.The elderly population(≥65)had an MMT of 24.6℃,much lower than the 28.6℃observed in younger individuals(<65).Females also exhibited a lower MMT that males(25℃versus 28.2℃).However,educational attainment did not significantly affect MMT.Using a uniform MMT resulted in substantial underestimation of heat exposure,ranging from 25.3%in 1990 to 13.9%in 2020,reflecting demographic shifts over time.Spatially,nearly half of the city experienced underestimated heat risk,especially in central and northeastern regions where heat-vulnerable populations are concentrated.These findings underscore the need for more nuanced heat exposure assessments that account for demographic and spatial variability,paving the way for targeted public health interventions to protect the most vulnerable urban populations.
文摘Enhancing the efficiency of phase-change heat storage is vital for maximizing the utilization of renewable energy.This study examines the synergistic effect of non-uniformly shaped fins and nanoparticles on the melting performance of phase-change storage tanks.The problem is addressed using a finite volume framework coupled with the enthalpy–porosity method,with the numerical model rigorously validated against experimental data.The analysis explores the influence of varying fin deflection angles and nanoparticle concentrations on melting dynamics.It is shown that a downward fin deflection of 6◦reduces melting time to 570 s,representing a 20.8% improvement over uniform fins.Introducing 1% nanoparticles further accelerates melting,reducing time by 36.54% compared to the nanoparticle-free case.The combined strategy of 6◦fin deflection and 1%nanoparticle addition shows the most economic heat storage rate,achieving an exceptional 80.74% enhancement relative to a tank with uniform fins.
基金supported by a PETRONAS-Academia Collabora-tion Dialogue 2022 Grant[Grant number PACD 2022]from PETRONAS Research Sdn.Bhd。
文摘The atmospheric surface layer of the tropical coastal ocean is commonly very unstable and experiences weakwind conditions.How the latent(LE)and sensible(H)heat fluxes behave under such conditions are unclear because of the lack of observation stations in the tropics.Thus,this study aims to analyze LE and H and the microclimate parameters influencing them.The authors deployed an eddy covariance system in a tropical coastal region for seven months.The microclimate parameters investigated were wind speed(U),vapor pressure deficit(Δe),temperature difference(ΔT),wind-vapor pressure deficit(UΔe),wind-temperature difference(UΔT),and atmospheric stability(z/L),where z is height and L is the Monin–Obukhov length.On the daily time scale,the results show that LE was more associated with U thanΔe,while H was more related toΔT than U.Cross-wavelet analysis revealed the strong coherence in the LE-U relationship for periods between one and two days,and for H–ΔT,0.5 to 1 day.Correlation and regression analyses confirmed the time series analyses results,where strong positive correlation coefficients(r)were obtained between LE and U(r=0.494)and H andΔT(r=0.365).Compared to other water bodies,the transfer coefficient of moisture(CE N)was found to be small(=0.40×10^(-3))and independent of stability;conversely,the transfer coefficient of heat(CH N)was closer to literature values(=1.00×10^(-3))and a function of stability.
基金supported by the National Key R&D Program of China[grant number 2022YFF0801400]the National Natural Science Foundation of China [grant numbers 42376027 and W2441014]+2 种基金the Development Fund of the South China Sea Institute of Oceanology of the Chinese Academy of Sciences [grant number SCSIO202208]the Special Fund of the South China Sea Institute of Oceanology of the Chinese Academy of Sciences [grant number SCSIO2023QY01]the Science and Technology Projects in Guangzhou [grant number 202201010367]。
文摘The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This study examines all long-lived MHWs(>10 days)in the SCS from 1982 to 2021,categorizing them into intensified and attenuated MHWs based on the overall trend of sea surface temperature during an MHW event.A mixed-layer heat budget analysis reveals that the thermal processes primarily driven by the latent heat flux are crucial in modulating the SCS MHWs,particularly for attenuated MHWs.However,under intensified conditions,the proportions of dynamically dominated MHWs(40%)is approximately comparable to that of thermally dominated ones(47%).This study highlights the significance of dynamic processes in shaping SCS MHWs and discusses the potential impacts induced by tropical cyclones on these MHWs.
基金supported by the Henan Provincial Key Research and Development Special Project(251111220200)Natural Science Foundation of Henan Province Project(252300420446).
文摘To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.
基金supported by the National Natural Science Foundation of China(41902310,42372348,42372286)Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(2024ZD1003607)+2 种基金China Geological Survey Projects(DD20230700802,DD20221819)the Basic Research Fund of the Chinese Academy of Geological Sciences(JKYQN202306)Key Research and Development Program of Shanxi Province,China(202102090301009).
文摘The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhuakeng uranium deposit has a high radioactive heat production rate(avg.5.50μW/m³)and a low Th/U ratio(avg.2.62).Uranium-rich granite and its alteration zone within the upper crust(0-5 km depth)contribute about 45%of the total radioactive heat production,wich is crucial for controlling geothermal resource distribution.For uranium-thermal at tectonic plate margins,a symbiotic geological model was proposed:Firstly,subduction of the Pacific Plate caused upwelling of the asthenosphere,generating a high heat-flow background.Secondly,heat transfer is enhanced by major faults such as the Youdong and Mianhuakeng faults.Subsequently,uranium was mobilized,transported,and enriched within the granite through deep siliceous hydrothermal activity and associated alteration.Ultimately,the uranium enrichment in granite leads to increased radioactive heat production,resulting in local thermal anomalies.This model provides a theoretical support for exploring and developing uranium-thermal symbiotic resources in South China.
基金funded in part by the Coordination for the Improvement of Higher Education Personnel(CAPES,Finance Code 001)in part by the Brazilian National Council for Scientific and Technological Development(CNPq,Grant No.131511/2020-3)/Ministry of Science,Technology and Innovation(MCTI)in part by the State of São Paulo Research Foundation(FAPESP)(Grant Nos.2015/03806-1 and 2023/08756-9).
文摘The dual-probe heat pulse(DPHP)is a well-established method for estimating soil moisture(θ)using soil thermal conductivity(λ)and volumetric heat capacity(C_(v)).Recently,monitoringθhas been improved by integrating the DPHP method with distributed temperature sensing(DTS)technology.In the DPHP-DTS approach,a single fiber optic(FO)cable with embedded metallic constituents functions as a heating element,while a parallel cable serves to monitor the temperature.Despite ongoing advancements,challenges such as the difficulty in positioning heating and sensing cables and high energy requirements hinder the widespread adoption of the DPHP-DTS method.As alternative heating materials are seldom used,this study evaluated the feasibility of employing a resistive metallic alloy as the heating element in a laboratory DPHP-DTS application.Overall,higher errors were observed when assessing C_(v)andλat higherθvalues(>0.2),but using C_(v)data produced more accurateθestimates(with the root mean square error(RMSE)≤0.06).Based on C_(v)values,a low-power,long-duration heat pulse(8.07 W/m for 300 s)yielded more consistentθestimates(RMSE=0.04)than a high-power,shortduration pulse(15.93 W/m for 180 s,with RMSE=0.06).The findings of this study also indicated that variations in heating uniformity and electrical power fluctuations potentially affected measurement accuracy.Nevertheless,the resistive alloy proved advantageous for DPHP-DTS due to its independent power connection,ability to maintain linear positioning within the soil,and potential for energy savings,all while providing reliableθestimates.
