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
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in buildi...Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.展开更多
The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and conti...The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and continuously.The mechanical properties and surface appearance of the heated samples were also investigated.Continuous and intermittent microwave drying kinetic experiments were conducted at a frequency of 2.45 GHz using a microwave laboratory oven at 300,500,and 1000 watts.Drying rate curves indicated three distinct phases of MWH.Increasing the microwave power with a shorter drying time led to rapid increases in internal temperature and water evaporation rates of the heated samples.Mechanical results indicated that samples heated under continuous MW(Microwave)power at 300 watts had a modulus of rupture(MOR)and modulus of elasticity(MOE)in three static bending tests higher than 29%and 36%,respectively,than samples heated at 1000 watts.Intermittent microwave heating(IMWH)of samples at 300 and 1000 watts produced the highest MOR and MOE values of 31%and 51%,respectively,unlike those heated under continuous microwave heating(CMWH).External qualitative observation showed that samples heated at high microwave power had severe surface checks.These defects were missing when using IMWH.An analysis of variance(ANOVA)showed that mechanical properties were linked to both microwave power level and the heating scenario,except for MOR in axial compression under CMWH.展开更多
The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-...The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-air source heat pump heating system structure that is specifically designed for such regions.The two-stage heat storage device in this heating system expands the storage temperature range of solar heat.The utilization of the two-stage heat storage device not onlymakes up for the instability of the solar heating system,but can also directlymeet the building heating temperature,and can reduce the influence of low-temperature outdoor environments in severe cold regions on the heating performance of the air source heat pump by using solar energy.Therefore,the two-stage phase change heat storage coupled to the solar energy-air source heat pump heating system effectively improves the utilization rate of solar energy.A numerical model of the system components and their integration was developed using TRNSYS software in this study,and various performance aspects of the system were simulated and analyzed.The simulation results demonstrated that the two-stage heat storage device can effectively store solar energy,enabling its hierarchical utilization.The low-temperature solar energy stored by the two-stage phase change heat storage device enhances the coefficient of performance of the air source heat pump by 11.1%in severe cold conditions.Using the Hooke-Jeeves optimization method,the annual cost and carbon emissions are taken as optimization objectives,with the optimized solar heat supply accounting for 52.5%.This study offers valuable insights into operational strategies and site selection for engineering applications,providing a solid theoretical foundation for the widespread implementation of this system in severe cold regions.展开更多
The latent heat thermal energy storage system with solid-liquid phase-change material(SLPCM-LHTES)as energy storage medium provides outstanding advantages such as system simplicity,stable temperature control,and high ...The latent heat thermal energy storage system with solid-liquid phase-change material(SLPCM-LHTES)as energy storage medium provides outstanding advantages such as system simplicity,stable temperature control,and high energy storage density,showing great potential toward addressing the energy storage problems associated with decentralized,intermittent,and unstable renewable energy sources.Notably,effective heat transfer within the SLPCM-LHTES is crucial for extending its application potential.Therefore,a comprehensive understanding of the heat transfer processes in SLPCM-LHTES from a theoretical perspective is necessary.In this review,we propose a three-stage heat transfer pathway in SLPCM-LHTES,including external heating,interfacial heat transfer,and intrinsic phase transition processes.From the perspective of this three-stage pathway,the theoretical basis of heat transfer processes and typical efficiency enhancement strategies in SLPCM-LHTES are summarized.Moreover,an overview of the typical applications of SLPCM-LHTES in various fields,such as building energy efficiency,textiles and garments,and battery thermal management,is presented.Finally,the remaining challenges and possible avenues of research in this burgeoning field will also be discussed.展开更多
The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea...The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.展开更多
Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency...Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.展开更多
In this study,the flow boiling characteristics of R1234yf in parallel microchannels were experimentally investigated.The experiments were conducted with heat flux from 0 to 550 kW/m^(2),mass flux of 434,727,and 1015 k...In this study,the flow boiling characteristics of R1234yf in parallel microchannels were experimentally investigated.The experiments were conducted with heat flux from 0 to 550 kW/m^(2),mass flux of 434,727,and 1015 kg/(m2 s),saturation temperatures of 293,298,and 303 K,and inlet sub-cooling of 5,10,and 15 K.The analysis of the experimental results provides the following conclusions:a reduced mass flux and lower subcooling correspond to a diminished degree of superheat at the boiling inception wall;conversely,an elevated saturation temperature results in a reduced amount of superheat at the boiling inception wall.Furthermore,an increase in sub-cooling and saturation temperature will enhance heat transfer efficiency.The wall temperature is mostly influenced by variations in saturation temperature and is minimally related to changes in mass flux and subcooling degree.An increase in mass flux results in a greater pressure drop attributed to heightened frictional pressure loss.The variation in pressure drop with respect to sub-cooling is minimal,while an increased saturation temperature correlates with a reduced pressure drop due to the formation of smaller bubbles and lowered frictional pressure loss at high saturation pressures.This study thoroughly examines and summarizes the effects of mass flow rate,saturation temperature,and subcooling on the flow-boiling heat transfer and pressure drop characteristics of R1234yf.Furthermore,the new correlation has 93.42%of the predicted values fall within a 15%mean absolute error,exhibiting a mean absolute error of 5.75%.It provides a superior method for predicting the flow-boiling heat transfer coefficients of R1234yf in the heat sink of parallel microchannels compared to existing correlations.展开更多
Global warming poses a severe threat to rice production and food security.We identified a heat-sensitive mutant hs1 through largescale screening of an established rice mutant library,and subsequently cloned the corres...Global warming poses a severe threat to rice production and food security.We identified a heat-sensitive mutant hs1 through largescale screening of an established rice mutant library,and subsequently cloned the corresponding gene HS1,which confers thermotolerance in rice.HS1 is localized to the chloroplast and functions by preserving chloroplast integrity under elevated temperatures through stabilizing the photosystem I subunit protein PsaC.Loss of HS1 function in the hs1 mutant leads to severe structural damage to the chloroplast under heat stress,accompanied by intracellular accumulation of reactive oxygen species(ROS),which in turn triggers DNA damage and leaf albinism,ultimately manifesting as a heat-sensitive phenotype.展开更多
Heat stress is a major threat to maize(Zea mays L.)production worldwide.Heat shock transcription factors(HSFs)play vital roles in plant responses to heat stress.However,the molecular and genetic mechanisms underlying ...Heat stress is a major threat to maize(Zea mays L.)production worldwide.Heat shock transcription factors(HSFs)play vital roles in plant responses to heat stress.However,the molecular and genetic mechanisms underlying HSF-meditated thermotolerance in maize remain largely unexplored.In this study,we demonstrate that the alternative splicing of ZmHsf23 modulates heat stress tolerance in maize.Hsf23 produced two functional transcripts,Hsf23L and Hsf23S,which differ by the presence of a cryptic mini-exon in Hsf23L that is spliced out in Hsf23S.Both transcripts were strongly induced by heat stress.Mutants lacking Hsf23L alone(hsf23l)or both Hsf23L and Hsf23S(hsf23l23s)exhibited increased susceptibility to heat stress,whereas overexpression of Hsf23S enhanced heat stress tolerance in maize.Subsequently,we found that Hsf23S positively regulates heat stress tolerance by directly activating the transcription of three sHSP genes(Hsp16.9,Hsp17.2,and Hsp18a)and TIL1 gene.In addition,Hsf23L physically interacted with Hsf23S and enhanced the transcriptional activation of Hsf23S on the sHSPs and TIL1 promoters.Notably,genetic analysis suggested that co-overexpression of Hsf23L and Hsf23S further improves heat tolerance of the transgenic plants.Taken together,these results reveal two splicing variants of ZmHsf23 cooperatively regulate maize heat tolerance,thus highlighting potential value of ZmHsf23 in breeding heat-tolerant maize varieties.展开更多
Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigate...Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigated.Notably,the incorporation of surface corrugations is widely recognized as both effective and practical.Chevron corrugation is the most employed design.However,there remains a need to investigate alternative geometries that may offer superior performance.This study aims to find a novel corrugation design by conducting a comparative CFD analysis of flat,square,chevron,and cylindrical corrugated surfaces,assessing their impact on heat transfer enhancement within a plate heat exchanger.ANSYS Fluent software was used for simulation at four distinct Reynolds numbers(10,000,18,000,26,000,and 28,000),with a heat flux of 12,000 W/m^(2).A structured mesh was generated using Pointwise software.The material of the solid plates was modelled as aluminum,the fluid was modelled as water,and the flow was turbulent.To obtain a fully developed turbulent flow,a separate inlet duct was modelled,and the output velocity profile of the inlet duct was input into the plate heat exchanger.The Nusselt number(Nu)and heattransfer coefficient(h)were calculated to evaluate the performance of all surfaces.The results indicate that cylindrical corrugated surfaces exhibit higher Nusselt numbers than chevron,square,and flat plates.This higher performance is because of the generation of vortices in the middle of the cylindrical texture.Consequently,flow recirculation occurs,leading to reattachment to the mainstreamflow.This phenomenon induces increased turbulence,thereby enhancing the heat transfer efficiency.To validate the results,a grid-convergence independence test was performed for three different mesh sizes.In addition,empirical calculations were performed using the Dittus-Boelter and the Genilaski equations to validate the results of the flat-plate heat exchanger.It was concluded that the cylinder was the best corrugated surface and had a maximum heat transfer 35%higher than that of a flat plate.展开更多
This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable en...This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable energy,limited research has addressed the potential of ground-source heat pump(GSHP)systems under local climatic and soil conditions.To address this gap,the study employs GeoT*SOL simulation to evaluate systemperformance,incorporating site-specific parameters such as soil thermal conductivity,heating demand profiles,and regional weather data.The results show that the GSHP system achieves a maximum seasonal performance factor(SPF)of 5.62 and an average SPF of 4.86,indicating high operational efficiency.Additionally,the system provides an estimated annual CO_(2) emissions reduction of 1956 kg per household,highlighting its environmental benefits.Comparative analysis with conventional heating systems demonstrates considerable energy savings and emissions mitigation.The study identifies technical(e.g.,initial installation complexity)and economic(e.g.,high upfront costs)challenges to widespread implementation.Based on these insights,practical recommendations are proposed:policymakers are encouraged to support financial incentives and policy frameworks;urban planners should consider GSHP integration in regional heating plans;and engineers may adopt the simulation-based approach presented here for feasibility studies.This research contributes to the strategic advancement of renewable heating technologies in Azerbaijan.展开更多
This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency...This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency and efficacy of the lattice Boltzmann method associated with a single relaxation time and its possibility of studying the nanofluid and heat transfer with high accuracy.Key parameters,including nanoparticle type and concentration,Rayleigh number,fluid basis,and obstacle position and dimension,were examined to identify optimal conditions for enhancing heat transfer quality.Principal findings indicated that increasing the Rayleigh number boosts buoyancy forces and alters vortex structure,improving the heat transfer efficiency across all nanofluid configu-rations.Moreover,nanoparticles with higher thermal conductivity,particularly Cu nanoparticles,exhibit slight improvements in heat transfer quality compared to Al2O3 nanoparticles,while higher nanoparticle concentrations generally lead to enhanced heat transfer effectiveness.Water-Cu nanofluids also demonstrate superior heat transfer performance over ethylene glycol-Cu nanofluids.Furthermore,the presence of obstacles at cavity extremities hampers overall heat transfer,whereas those positioned centrally augment heat exchange rates.This research offers valuable insights into optimizing convective heat transfer in nanofluid-filled cavities crucial for various engineering applications.展开更多
Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparis...Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparison between direct heat exchange(DHE)and open-cycle mechanical heat pump(MHP)under various operating conditions is carried out in this work.The price ratios R_(ES)(electricity to steam)and R_(HS)(hot water to steam)are introduced to quantify regional impacts and conduct quantitative analysis.A semi-empirical formula is obtained to explore the exergoeconomic performance of the two systems.For waste heat within 373.15-423.15 K,the exergy efficiency of the DHE with a temperature difference of 10-90 K is always lower than that of the MHP with a temperature lift of 10-50 K.The economic performance of the two systems has a break-even point,depending on the operating parameters and relative prices of electricity,steam,and hot water.Under the average R_(ES)(3.8)in China,if R_(HS)is higher than 0.748,the annual revenue of the DHE is always higher,whereas the MHP is more economical when R_(HS)is lower than 0.110.In regions where R_(ES)is higher than 4.353,the annual revenue of the MHP will be negative in some cases.展开更多
This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficul...This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficult to model due to their complex geometries.The proposed method uses an equivalent convective heat transfer coefficient to represent the fins,significantly reducing the computational requirements of the simulations.Validation against the effectiveness-number of transfer units method showed average deviations of 4.4%for the novel louvered fin with two combined holes and 9.5%for conventional configurations,confirming the accuracy of the method.Further application to two-phase refrigerant scenarios using experimental data demonstrated the robustness of the method and its suitability for practical design and optimization of LFFTHXs.The approach not only improves the feasibility of thermal analysis in industrial applications but also provides a foundation for future research into more efficient heat exchanger designs.展开更多
The heat transfer coefficient of the water surface is an important parameter in the design of thermal discharge in nuclear power plant engineering.In this study,in situ observations were performed in the northwestern ...The heat transfer coefficient of the water surface is an important parameter in the design of thermal discharge in nuclear power plant engineering.In this study,in situ observations were performed in the northwestern South China Sea near a coastal nuclear power plant to evaluate the applicability of heat transfer coefficient calculation algorithms commonly used in marine thermal discharge engineering in China.The results show that the Regulation for Hydraulic and Thermal Model in Cooling Water Projects(SL 160-2012)is not applicable in calculating the heat transfer coefficient in offshore areas.SL 160-2012 significantly overestimates the heat loss at the sea surface.However,Code for Design of Cooling for Industrial Recirculating Water(GB/T 50102-2014)performs well,and its estimation coefficient is roughly consistent with the estimations of the COARE 3.6 bulk algorithm,which is extensively used in physical oceanography for calculating air-sea heat fluxes,and the Gunneberg formula.In a 3-day observation,the average heat transfer coefficients estimated using these three algorithms were 50.4,48.5,and 48.8 W m^(-2)℃^(-1),respectively,with a deviation of less than 4% among them,whereas that estimated using SL 160-2012 was as high as 176.3 W m^(-2)℃^(-1).The abnormally large value of SL 160-2012 is due to its additional cooling term,which is artificially increased by 100 times because of the incorrect unit conversion used when developing the regulation.If this error is corrected,the value will decrease to 50.5 W m^(-2)℃^(-1),which is very close to the estimation of GB/T 50102-2014.展开更多
The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of wat...The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of waterbased nanofluids containing TiO_(2),CuO,and graphene nanoplatelet(GNP)nanoparticles as they flow through a copper tube.Both the dynamic viscosity and thermal conductivity of these nanofluids were modeled and experimentally measured across varying nanoparticle concentrations(0.01,0.02,and 0.03 vol.%)and temperatures(25℃,35℃,and 45℃).The findings indicate that the behavior of nanofluids depends on the parameter used for comparison with the base fluid.Notably,both the friction factor and heat transfer coefficient increase with higher nanoparticle volume concentrations at a constant Reynolds number.The results further reveal that the GNP/water nanofluid,with a volume concentration of 0.03%at 45℃,exhibit the highest Nusselt number,followed by the CuO/water and TiO_(2)/water nanofluids,with respective increases of 17.8%,11.09%,and 8.11%.展开更多
The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinatio...The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinations of them were considered.The leaf-shaped design of the cooling pin fin enhances uniformity and synergy,effectively creating an optimized flow path that boosts cooling performance.Eight three-dimensional conjugate heat transfer models in staggered arrangement were developed using ANSYS-Fluent software.Aluminum6061material was used as the heat sinkmaterial and single-phase liquid water flowed through the rectangular channel where the Reynolds(R_(e))number varies from 40 to 100.Using the same boundary conditions as the software simulations,two leaf-shaped channels were printed to validate numerical models.Velocity field and temperature differences of the eight proposed leaf-shaped pin fins configurations were discussed by comparison with cylindrical pin fins.Based on the findings of this study,at a Reynolds number of 80,the Leaf B Staggered Array(LBSA)records a maximum temperature that is 0.72 K lower than that of the cylindrical pin fins arrangement.Additionally,the LBSA exhibits a reduction in the friction factor by approximately 33.3%relative to the circular pin fins array under the same R_(e).This implies that the design of LBSA has been optimized to provide better heat dissipation performance while maintaining lower energy consumption.Furthermore,the LBSA demonstrates the most favorable thermal-hydraulic performance index(TPI),which is 1.18 times higher than that of the circular pin fins arrangement at R_(e)=80.The temperature reduction and friction factor reduction of the lobed channel is more pronounced than that of the conventional cooling channel,highlighting its potential to increase heat transfer efficiency and reduce energy consumption in practical applications.展开更多
The escalating global temperature,with 2024 as the hottest year,emphasizes the critical link between climate change and kidney health.Extreme heat,a conse-quence of global warming,causes multifaceted effects on human ...The escalating global temperature,with 2024 as the hottest year,emphasizes the critical link between climate change and kidney health.Extreme heat,a conse-quence of global warming,causes multifaceted effects on human physiology,including renal function alterations.This review investigates physiological and molecular mechanisms of heat stress-induced kidney injury,including acute kidney injury,chronic kidney disease(CKD),and urinary stone formation.It highlights how heat stress contributes to renal dysfunction via dehydration,electrolyte imbalances,and activation of the renin-angiotensin-aldosterone system and antidiuretic hormone pathways,particularly in vulnerable populations like outdoor workers,the elderly,and pregnant women.The review also emphasizes the roles of heat shock proteins(HSPs)-HSP27,HSP60,HSP70,and HSP90-in maintaining cellular integrity by preventing protein aggregation and repairing damaged proteins in renal tissues.Dysregulation of these proteins under prolonged heat stress is implicated in CKD progression.This review highlights the urgent need for targeted public health interventions:(1)Hydration;(2)Workplace cooling;(3)Community education;and(4)Developing pharmaco-logical therapies targeting HSPs.A multidisciplinary approach involving nephrology,environmental science,and public health is essential to mitigate the increasing burden of heat-related kidney disease in the era of global climate change.展开更多
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financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金support by the Shanghai Engineering Research Center for Shallow Geothermal Energy(DRZX-202306)Shaanxi Coal Geology Group Co.,Ltd.(SMDZ-ZD2024-23)+4 种基金Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources,China(ZP2020-1)Shaanxi Investment Group Co.,Ltd.(SIGC2023-KY-05)Key Research and Development Projects of Shaanxi Province(2023-GHZD-54)Shaanxi Qinchuangyuan Scientist+Engineer Team Construction Project(2022KXJ-049)China Postdoctoral Science Foundation(2023M742802,2024T170721).
文摘Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.
文摘The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and continuously.The mechanical properties and surface appearance of the heated samples were also investigated.Continuous and intermittent microwave drying kinetic experiments were conducted at a frequency of 2.45 GHz using a microwave laboratory oven at 300,500,and 1000 watts.Drying rate curves indicated three distinct phases of MWH.Increasing the microwave power with a shorter drying time led to rapid increases in internal temperature and water evaporation rates of the heated samples.Mechanical results indicated that samples heated under continuous MW(Microwave)power at 300 watts had a modulus of rupture(MOR)and modulus of elasticity(MOE)in three static bending tests higher than 29%and 36%,respectively,than samples heated at 1000 watts.Intermittent microwave heating(IMWH)of samples at 300 and 1000 watts produced the highest MOR and MOE values of 31%and 51%,respectively,unlike those heated under continuous microwave heating(CMWH).External qualitative observation showed that samples heated at high microwave power had severe surface checks.These defects were missing when using IMWH.An analysis of variance(ANOVA)showed that mechanical properties were linked to both microwave power level and the heating scenario,except for MOR in axial compression under CMWH.
基金This work was supported by the project of the Research on Energy Consumption of Office Space in Colleges and Universities under the“Dual Carbon Target”(No.CJ202301006).
文摘The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-air source heat pump heating system structure that is specifically designed for such regions.The two-stage heat storage device in this heating system expands the storage temperature range of solar heat.The utilization of the two-stage heat storage device not onlymakes up for the instability of the solar heating system,but can also directlymeet the building heating temperature,and can reduce the influence of low-temperature outdoor environments in severe cold regions on the heating performance of the air source heat pump by using solar energy.Therefore,the two-stage phase change heat storage coupled to the solar energy-air source heat pump heating system effectively improves the utilization rate of solar energy.A numerical model of the system components and their integration was developed using TRNSYS software in this study,and various performance aspects of the system were simulated and analyzed.The simulation results demonstrated that the two-stage heat storage device can effectively store solar energy,enabling its hierarchical utilization.The low-temperature solar energy stored by the two-stage phase change heat storage device enhances the coefficient of performance of the air source heat pump by 11.1%in severe cold conditions.Using the Hooke-Jeeves optimization method,the annual cost and carbon emissions are taken as optimization objectives,with the optimized solar heat supply accounting for 52.5%.This study offers valuable insights into operational strategies and site selection for engineering applications,providing a solid theoretical foundation for the widespread implementation of this system in severe cold regions.
基金financial support was provided by the National Natural Science Foundation of China(Nos.52476146,52006008,and 52471219)the Guangdong Basic and Applied Basic Research Foundation(2023A1515140059 and 2025A1515011255)+2 种基金the Peking University Third Hospital Haidian transformation project(HDCXZHKC2023210)the National Foreign Expert Individual Human Project(Category H,No.H20240116)the State Key Laboratory of New Ceramic Materials Tsinghua University(No.KFZD202402).
文摘The latent heat thermal energy storage system with solid-liquid phase-change material(SLPCM-LHTES)as energy storage medium provides outstanding advantages such as system simplicity,stable temperature control,and high energy storage density,showing great potential toward addressing the energy storage problems associated with decentralized,intermittent,and unstable renewable energy sources.Notably,effective heat transfer within the SLPCM-LHTES is crucial for extending its application potential.Therefore,a comprehensive understanding of the heat transfer processes in SLPCM-LHTES from a theoretical perspective is necessary.In this review,we propose a three-stage heat transfer pathway in SLPCM-LHTES,including external heating,interfacial heat transfer,and intrinsic phase transition processes.From the perspective of this three-stage pathway,the theoretical basis of heat transfer processes and typical efficiency enhancement strategies in SLPCM-LHTES are summarized.Moreover,an overview of the typical applications of SLPCM-LHTES in various fields,such as building energy efficiency,textiles and garments,and battery thermal management,is presented.Finally,the remaining challenges and possible avenues of research in this burgeoning field will also be discussed.
基金supported by the National Key R&D Program of China (Grant No. 2024YFF0506603)the Independent Research Foundation of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. SML2023SP201 and SML2021SP306)+2 种基金the Natural Science Foundation of Guangdong Province, China (Grant No. 2024A1515012717)the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. 313021004, 313022009 and 313022001)the Program of Innovation 2030 on Smart Ocean, Zhejiang University
文摘The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.
基金supported by the National Natural Science Foundation of China(Nos.52275299,52105313)R&D Program of Beijing Municipal Education Commission(No.KM202210005036)+1 种基金Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-MSX0701)National Defense Basic Research Projects of China(No.JCKY2022405C002).
文摘Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.
基金supported by the Beijing Municipal Science&Technology Commission(Z231100006123010).
文摘In this study,the flow boiling characteristics of R1234yf in parallel microchannels were experimentally investigated.The experiments were conducted with heat flux from 0 to 550 kW/m^(2),mass flux of 434,727,and 1015 kg/(m2 s),saturation temperatures of 293,298,and 303 K,and inlet sub-cooling of 5,10,and 15 K.The analysis of the experimental results provides the following conclusions:a reduced mass flux and lower subcooling correspond to a diminished degree of superheat at the boiling inception wall;conversely,an elevated saturation temperature results in a reduced amount of superheat at the boiling inception wall.Furthermore,an increase in sub-cooling and saturation temperature will enhance heat transfer efficiency.The wall temperature is mostly influenced by variations in saturation temperature and is minimally related to changes in mass flux and subcooling degree.An increase in mass flux results in a greater pressure drop attributed to heightened frictional pressure loss.The variation in pressure drop with respect to sub-cooling is minimal,while an increased saturation temperature correlates with a reduced pressure drop due to the formation of smaller bubbles and lowered frictional pressure loss at high saturation pressures.This study thoroughly examines and summarizes the effects of mass flow rate,saturation temperature,and subcooling on the flow-boiling heat transfer and pressure drop characteristics of R1234yf.Furthermore,the new correlation has 93.42%of the predicted values fall within a 15%mean absolute error,exhibiting a mean absolute error of 5.75%.It provides a superior method for predicting the flow-boiling heat transfer coefficients of R1234yf in the heat sink of parallel microchannels compared to existing correlations.
基金supported by the National Natural Science Foundation of China(Grant Nos.32372118 and 32188102)the Zhejiang Natural Science Foundation,China(Grant No.LZ25C130010)+1 种基金the Qian Qian Academician Workstation,and the specific research fund of the Innovation Platform for Academicians of Hainan Province,China(Grant No.YSPTZX202303)the Central Public-Interest Scientific Institution Basal Research Fund from Chinese Academy of Agricultural Sciences(Grant No.Y2025YC93)。
文摘Global warming poses a severe threat to rice production and food security.We identified a heat-sensitive mutant hs1 through largescale screening of an established rice mutant library,and subsequently cloned the corresponding gene HS1,which confers thermotolerance in rice.HS1 is localized to the chloroplast and functions by preserving chloroplast integrity under elevated temperatures through stabilizing the photosystem I subunit protein PsaC.Loss of HS1 function in the hs1 mutant leads to severe structural damage to the chloroplast under heat stress,accompanied by intracellular accumulation of reactive oxygen species(ROS),which in turn triggers DNA damage and leaf albinism,ultimately manifesting as a heat-sensitive phenotype.
基金supported by the National Key Research and Development Program of China(2021YFF1000301)the National Natural Science Foundation of China(31771805)。
文摘Heat stress is a major threat to maize(Zea mays L.)production worldwide.Heat shock transcription factors(HSFs)play vital roles in plant responses to heat stress.However,the molecular and genetic mechanisms underlying HSF-meditated thermotolerance in maize remain largely unexplored.In this study,we demonstrate that the alternative splicing of ZmHsf23 modulates heat stress tolerance in maize.Hsf23 produced two functional transcripts,Hsf23L and Hsf23S,which differ by the presence of a cryptic mini-exon in Hsf23L that is spliced out in Hsf23S.Both transcripts were strongly induced by heat stress.Mutants lacking Hsf23L alone(hsf23l)or both Hsf23L and Hsf23S(hsf23l23s)exhibited increased susceptibility to heat stress,whereas overexpression of Hsf23S enhanced heat stress tolerance in maize.Subsequently,we found that Hsf23S positively regulates heat stress tolerance by directly activating the transcription of three sHSP genes(Hsp16.9,Hsp17.2,and Hsp18a)and TIL1 gene.In addition,Hsf23L physically interacted with Hsf23S and enhanced the transcriptional activation of Hsf23S on the sHSPs and TIL1 promoters.Notably,genetic analysis suggested that co-overexpression of Hsf23L and Hsf23S further improves heat tolerance of the transgenic plants.Taken together,these results reveal two splicing variants of ZmHsf23 cooperatively regulate maize heat tolerance,thus highlighting potential value of ZmHsf23 in breeding heat-tolerant maize varieties.
文摘Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigated.Notably,the incorporation of surface corrugations is widely recognized as both effective and practical.Chevron corrugation is the most employed design.However,there remains a need to investigate alternative geometries that may offer superior performance.This study aims to find a novel corrugation design by conducting a comparative CFD analysis of flat,square,chevron,and cylindrical corrugated surfaces,assessing their impact on heat transfer enhancement within a plate heat exchanger.ANSYS Fluent software was used for simulation at four distinct Reynolds numbers(10,000,18,000,26,000,and 28,000),with a heat flux of 12,000 W/m^(2).A structured mesh was generated using Pointwise software.The material of the solid plates was modelled as aluminum,the fluid was modelled as water,and the flow was turbulent.To obtain a fully developed turbulent flow,a separate inlet duct was modelled,and the output velocity profile of the inlet duct was input into the plate heat exchanger.The Nusselt number(Nu)and heattransfer coefficient(h)were calculated to evaluate the performance of all surfaces.The results indicate that cylindrical corrugated surfaces exhibit higher Nusselt numbers than chevron,square,and flat plates.This higher performance is because of the generation of vortices in the middle of the cylindrical texture.Consequently,flow recirculation occurs,leading to reattachment to the mainstreamflow.This phenomenon induces increased turbulence,thereby enhancing the heat transfer efficiency.To validate the results,a grid-convergence independence test was performed for three different mesh sizes.In addition,empirical calculations were performed using the Dittus-Boelter and the Genilaski equations to validate the results of the flat-plate heat exchanger.It was concluded that the cylinder was the best corrugated surface and had a maximum heat transfer 35%higher than that of a flat plate.
文摘This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable energy,limited research has addressed the potential of ground-source heat pump(GSHP)systems under local climatic and soil conditions.To address this gap,the study employs GeoT*SOL simulation to evaluate systemperformance,incorporating site-specific parameters such as soil thermal conductivity,heating demand profiles,and regional weather data.The results show that the GSHP system achieves a maximum seasonal performance factor(SPF)of 5.62 and an average SPF of 4.86,indicating high operational efficiency.Additionally,the system provides an estimated annual CO_(2) emissions reduction of 1956 kg per household,highlighting its environmental benefits.Comparative analysis with conventional heating systems demonstrates considerable energy savings and emissions mitigation.The study identifies technical(e.g.,initial installation complexity)and economic(e.g.,high upfront costs)challenges to widespread implementation.Based on these insights,practical recommendations are proposed:policymakers are encouraged to support financial incentives and policy frameworks;urban planners should consider GSHP integration in regional heating plans;and engineers may adopt the simulation-based approach presented here for feasibility studies.This research contributes to the strategic advancement of renewable heating technologies in Azerbaijan.
文摘This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency and efficacy of the lattice Boltzmann method associated with a single relaxation time and its possibility of studying the nanofluid and heat transfer with high accuracy.Key parameters,including nanoparticle type and concentration,Rayleigh number,fluid basis,and obstacle position and dimension,were examined to identify optimal conditions for enhancing heat transfer quality.Principal findings indicated that increasing the Rayleigh number boosts buoyancy forces and alters vortex structure,improving the heat transfer efficiency across all nanofluid configu-rations.Moreover,nanoparticles with higher thermal conductivity,particularly Cu nanoparticles,exhibit slight improvements in heat transfer quality compared to Al2O3 nanoparticles,while higher nanoparticle concentrations generally lead to enhanced heat transfer effectiveness.Water-Cu nanofluids also demonstrate superior heat transfer performance over ethylene glycol-Cu nanofluids.Furthermore,the presence of obstacles at cavity extremities hampers overall heat transfer,whereas those positioned centrally augment heat exchange rates.This research offers valuable insights into optimizing convective heat transfer in nanofluid-filled cavities crucial for various engineering applications.
基金Financial support from the National Natural Science Foundation of China(21736008)。
文摘Recovering waste heat is essential for primary energy savings and carbon emission reduction.To provide direct and reliable suggestions for factories to recover waste heat,energetic,economic and exergoeconomic comparison between direct heat exchange(DHE)and open-cycle mechanical heat pump(MHP)under various operating conditions is carried out in this work.The price ratios R_(ES)(electricity to steam)and R_(HS)(hot water to steam)are introduced to quantify regional impacts and conduct quantitative analysis.A semi-empirical formula is obtained to explore the exergoeconomic performance of the two systems.For waste heat within 373.15-423.15 K,the exergy efficiency of the DHE with a temperature difference of 10-90 K is always lower than that of the MHP with a temperature lift of 10-50 K.The economic performance of the two systems has a break-even point,depending on the operating parameters and relative prices of electricity,steam,and hot water.Under the average R_(ES)(3.8)in China,if R_(HS)is higher than 0.748,the annual revenue of the DHE is always higher,whereas the MHP is more economical when R_(HS)is lower than 0.110.In regions where R_(ES)is higher than 4.353,the annual revenue of the MHP will be negative in some cases.
基金supported by the National Natural Science Foundation of China(Grant No.12272345).
文摘This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficult to model due to their complex geometries.The proposed method uses an equivalent convective heat transfer coefficient to represent the fins,significantly reducing the computational requirements of the simulations.Validation against the effectiveness-number of transfer units method showed average deviations of 4.4%for the novel louvered fin with two combined holes and 9.5%for conventional configurations,confirming the accuracy of the method.Further application to two-phase refrigerant scenarios using experimental data demonstrated the robustness of the method and its suitability for practical design and optimization of LFFTHXs.The approach not only improves the feasibility of thermal analysis in industrial applications but also provides a foundation for future research into more efficient heat exchanger designs.
基金supported by the Laoshan Laboratory(No.LSKJ202201600)the National Natural Science Foundation of China(No.41821004)。
文摘The heat transfer coefficient of the water surface is an important parameter in the design of thermal discharge in nuclear power plant engineering.In this study,in situ observations were performed in the northwestern South China Sea near a coastal nuclear power plant to evaluate the applicability of heat transfer coefficient calculation algorithms commonly used in marine thermal discharge engineering in China.The results show that the Regulation for Hydraulic and Thermal Model in Cooling Water Projects(SL 160-2012)is not applicable in calculating the heat transfer coefficient in offshore areas.SL 160-2012 significantly overestimates the heat loss at the sea surface.However,Code for Design of Cooling for Industrial Recirculating Water(GB/T 50102-2014)performs well,and its estimation coefficient is roughly consistent with the estimations of the COARE 3.6 bulk algorithm,which is extensively used in physical oceanography for calculating air-sea heat fluxes,and the Gunneberg formula.In a 3-day observation,the average heat transfer coefficients estimated using these three algorithms were 50.4,48.5,and 48.8 W m^(-2)℃^(-1),respectively,with a deviation of less than 4% among them,whereas that estimated using SL 160-2012 was as high as 176.3 W m^(-2)℃^(-1).The abnormally large value of SL 160-2012 is due to its additional cooling term,which is artificially increased by 100 times because of the incorrect unit conversion used when developing the regulation.If this error is corrected,the value will decrease to 50.5 W m^(-2)℃^(-1),which is very close to the estimation of GB/T 50102-2014.
文摘The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of waterbased nanofluids containing TiO_(2),CuO,and graphene nanoplatelet(GNP)nanoparticles as they flow through a copper tube.Both the dynamic viscosity and thermal conductivity of these nanofluids were modeled and experimentally measured across varying nanoparticle concentrations(0.01,0.02,and 0.03 vol.%)and temperatures(25℃,35℃,and 45℃).The findings indicate that the behavior of nanofluids depends on the parameter used for comparison with the base fluid.Notably,both the friction factor and heat transfer coefficient increase with higher nanoparticle volume concentrations at a constant Reynolds number.The results further reveal that the GNP/water nanofluid,with a volume concentration of 0.03%at 45℃,exhibit the highest Nusselt number,followed by the CuO/water and TiO_(2)/water nanofluids,with respective increases of 17.8%,11.09%,and 8.11%.
基金supported by the Shandong Provincial Natural Science Foundation,China(Grant ZR2024ME136).
文摘The growing need for enhanced heat dissipation is compelling the development of more effective heat exchangers.Innovation inspired by nature bionics,four types of leaf-shaped pin fins were proposed and four combinations of them were considered.The leaf-shaped design of the cooling pin fin enhances uniformity and synergy,effectively creating an optimized flow path that boosts cooling performance.Eight three-dimensional conjugate heat transfer models in staggered arrangement were developed using ANSYS-Fluent software.Aluminum6061material was used as the heat sinkmaterial and single-phase liquid water flowed through the rectangular channel where the Reynolds(R_(e))number varies from 40 to 100.Using the same boundary conditions as the software simulations,two leaf-shaped channels were printed to validate numerical models.Velocity field and temperature differences of the eight proposed leaf-shaped pin fins configurations were discussed by comparison with cylindrical pin fins.Based on the findings of this study,at a Reynolds number of 80,the Leaf B Staggered Array(LBSA)records a maximum temperature that is 0.72 K lower than that of the cylindrical pin fins arrangement.Additionally,the LBSA exhibits a reduction in the friction factor by approximately 33.3%relative to the circular pin fins array under the same R_(e).This implies that the design of LBSA has been optimized to provide better heat dissipation performance while maintaining lower energy consumption.Furthermore,the LBSA demonstrates the most favorable thermal-hydraulic performance index(TPI),which is 1.18 times higher than that of the circular pin fins arrangement at R_(e)=80.The temperature reduction and friction factor reduction of the lobed channel is more pronounced than that of the conventional cooling channel,highlighting its potential to increase heat transfer efficiency and reduce energy consumption in practical applications.
文摘The escalating global temperature,with 2024 as the hottest year,emphasizes the critical link between climate change and kidney health.Extreme heat,a conse-quence of global warming,causes multifaceted effects on human physiology,including renal function alterations.This review investigates physiological and molecular mechanisms of heat stress-induced kidney injury,including acute kidney injury,chronic kidney disease(CKD),and urinary stone formation.It highlights how heat stress contributes to renal dysfunction via dehydration,electrolyte imbalances,and activation of the renin-angiotensin-aldosterone system and antidiuretic hormone pathways,particularly in vulnerable populations like outdoor workers,the elderly,and pregnant women.The review also emphasizes the roles of heat shock proteins(HSPs)-HSP27,HSP60,HSP70,and HSP90-in maintaining cellular integrity by preventing protein aggregation and repairing damaged proteins in renal tissues.Dysregulation of these proteins under prolonged heat stress is implicated in CKD progression.This review highlights the urgent need for targeted public health interventions:(1)Hydration;(2)Workplace cooling;(3)Community education;and(4)Developing pharmaco-logical therapies targeting HSPs.A multidisciplinary approach involving nephrology,environmental science,and public health is essential to mitigate the increasing burden of heat-related kidney disease in the era of global climate change.
