During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- in...During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- ing techniques for electronic and microelectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection,liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.展开更多
A new cooling technique based on thermal driving in high centrifugal field （TDHCF） is developed for gas turbine rotational components, such as turbine blades. The key point of TDHCF is to enhance heat transfer by th...A new cooling technique based on thermal driving in high centrifugal field （TDHCF） is developed for gas turbine rotational components, such as turbine blades. The key point of TDHCF is to enhance heat transfer by the fluid thermal driving in closed loop small channels placed in the high centrifugal field. Heat transfer characteristics of the new cooling technique are analyzed. In experiments, two different fluids （liquid water and Freon R12） are used as thermal driving media （fluid inside the loop channel）. And the channel width d is 1 mm and the height h is 30 mm. The temperature is measured by thermocouples and an average heat transfer coefficient KH is defined to indicate heat transfer capacity of TDHCF. Experimental results show that KH is enhanced when heat flux and the rotating speed increase. And thermal properties of thermal driving media are also influenced by KH. Larger KH can be achieved by using Freon R12 as thermal driving medium compared with using liquid water. It can increase to 2 300 W/（m^2 · K） and it is much higher than that of the normal air cooling method （usually at the level of 600-1200 W/（m^2·K））. All fundamental studies of TDHCF show that there actually exists thermal driving in the closed loop small channel in the centrifugal field to improve heat transfer characteristics.展开更多
The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results i...The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results indicated that the large section bars were passed through the zone of secondary carbide precipitation quickly by ultra-fast cooling technology （UFC） at instantaneous cooling rate of about 200 ℃/s and the finishing cooling temperature was higher than Ms. The lamellar spacing of pearlite decreased and the microhardness increased with decreasing the rereddening temperature. The precipitation of network carbide was restrained when re-reddening temperature was 690 ℃. And fine laminated pearlite was obtained through transformation of pseudopearlition that induced the reduction of the diameter of pearlite grain and refinement of the lamellar spacing of pearlite, so ideal microstructures of promoting spheroidizing annealing were obtained.展开更多
Our societies are highly dependent on reliable cooling for air conditioning(AC)and refrigeration.Currently,modern cooling is supported by a 19th century technology:vapor compression cycle(VCC)-based cooling.Refrigeran...Our societies are highly dependent on reliable cooling for air conditioning(AC)and refrigeration.Currently,modern cooling is supported by a 19th century technology:vapor compression cycle(VCC)-based cooling.Refrigerants used in the VCC cooling are strong greenhouse gases and thus are among the leading causes of global warming.The electrocaloric(EC)cooling is attractive as an alternative to the VCC cooling.EC cooling is environmentally benign,compressor-free,highly scalable,and has the potential of achieving higher efficiency than VCC cooling.The active EC materials research since the late 2000s has created several EC materials that exhibit giant electrocaloric effect(ECE)(by direct measurement).These EC materials have enabled the demonstration of EC cooling devices that exhibit temperature lifts of more than 8 K.These EC materials and device research reveals the promise of fer-roelectric materials in generating giant ECE at low electric fields and EC cooling devices achieving high performance.This review highlights these advances and offers perspectives of the EC cooling technologies.展开更多
Based on the urgency of thermal hazard control in deep coal mines,we studied the status of deep thermal damage and cooling technology both at home and abroad,summarized the causes of deep thermal hazard,analysed and c...Based on the urgency of thermal hazard control in deep coal mines,we studied the status of deep thermal damage and cooling technology both at home and abroad,summarized the causes of deep thermal hazard,analysed and compared the control technologies for deep thermal hazards.The results show that the causes of deep thermal damage can be attributed to three aspects,i.e.,climate,geological and mining factors,of which the geological factors are deemed the major reasons for thermal hazards.As well,we compared a number of cooling technologies of domestic and overseas provenance,such as central air conditioning cooling technology,ice cooling technology and water cooling technology,with one other cooling technology,i.e.,the HEMS cooling technology,which has a large and important effect with its unique"pure air"cooling technology,realizes the utilizing of heat resources from underground to the ground.This technology makes use of heat obtained underground;thus the technology can promote low-carbon environmental economic development in coal mines,in order to achieve low-carbon coal production in China.展开更多
The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine ...The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine adopts various cooling techniques to ensure cooling,including a metal thermal barrier coating,multiple liquid film cooling slots,spiral milled regenerative cooling channels with high aspect ratio,a non-weld forming thrust chamber and an optimal cooling flow path design.In addition,the 480-ton LOX/kerosene engine for China’s future heavy-lift launch vehicle LM-9 will be larger in size,which makes it more difficult to be developed and will have more strict requirements in the cooling process.The main differences between the LM-5B and LM-5 are briefly described in this paper and the development process and working characteristics of YF-100 engines are introduced.The advantages and disadvantages of main cooling methods used in the thrust chambers of high-thrust liquid propellant engines are also described.Finally,the future challenges and countermeasures in cooling technology for China’s high-thrust LOX/kerosene engines and future reusable rocket engines are also presented.展开更多
Radiative cooling has emerged as an attractive passive cooling technology in energy and thermal management fields due to its zero-energy consumption and pollution-free characteristics[[1],[2],[3]].An ideal radiative c...Radiative cooling has emerged as an attractive passive cooling technology in energy and thermal management fields due to its zero-energy consumption and pollution-free characteristics[[1],[2],[3]].An ideal radiative cooling material should simultaneously exhibit high solar reflectance to minimize solar heat absorption and high infrared emissivity in the“atmospheric window”band(8–13μm)to directly radiate heat to outer space(∼3 K),achieving passive cooling without energy input[[4],[5],[6]].Photonic structures(such as nano-multilayers,nano-pores,and photonic crystals)have been proven to simultaneously achieve high solar reflectance and broadband infrared emissivity[7,8].For instance,commercial“cooling paints”(such as BaSO4 and TiO2-based reflective paints)can reduce surface temperatures by several degrees and moderately decrease building cooling loads.展开更多
High-power wireless power transfer(WPT)systems are pivotal for the widespread adoption of electric vehicles(EVs)and the decarbonization of transportation.However,thermal issues arising from Joule heating and hysteresi...High-power wireless power transfer(WPT)systems are pivotal for the widespread adoption of electric vehicles(EVs)and the decarbonization of transportation.However,thermal issues arising from Joule heating and hysteresis losses in high-power(≥100 kW)systems remain a critical bottleneck,compromising efficiency,reliability,and safety.This review comprehensively examines the fundamental principles and recent advancements in magnetic field-coupled WPT technology.We then provide a critical analysis of state-of-the-art thermal management solutions-including air cooling,immersion cooling,microchannel cooling,phase change materials,nanofluids,heat pipes,and composite systems-evaluating their thermal performance,electromagnetic compatibility,and carbon footprints.Notable achievements include microchannel cooling maintaining temperatures at 108◦C in megawatt-level coils,and phase change material-based solutions limiting heating plate temperatures below 80◦C.Despite progress,challenges persist in electromagnetic compatibility,system compactness,and dynamic response.Future research should prioritize developing advanced cooling architectures for efficiency-carbon trade-off optimization,focusing on low-eddy-current liquid cooling and electromagnetic compatibility-optimized phase change material enclosures.This review links thermal management breakthroughs to scalable,low-carbon EV infrastructure,offering actionable insights to accelerate the transition to carbon-neutral transportation.展开更多
Saturator is one of the core components of humid air turbine （HAT） and is the main feature of HAT making it different from other gas turbine cycles. Due to the lack of sufficient experience in commercial plant opera...Saturator is one of the core components of humid air turbine （HAT） and is the main feature of HAT making it different from other gas turbine cycles. Due to the lack of sufficient experience in commercial plant operation, HAT cycle has a great demand for modeling and simulation of the system and its components, especially the saturator, to provide reference for system design and optimization. The conventional saturator models are usually based on the theory of heat and mass transfer, which need two accurate coefficients to ensure convincing results. This work proposes a global heat and mass transfer coefficient based on cooling tower technology to model the saturator in small-scale HAT cycle. Compared with the experimental data, the simulation results show that the proposed model well predicts the dynamic humidity and temperature distribution characteristics of saturator at low air pressure and temperature.展开更多
With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has...With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.展开更多
Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-tempera...Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.展开更多
When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling t...When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield.However,little crucial review work was proposed to comment cooling technologies for PV modules.Therefore,this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules,and given appropriate comments,comparisons and discussions.According to the ways or principles of cooling,existing cooling technologies have been classified as fluid medium cooling(air cooling,water cooling and nanofluids cooling),optimizing structural configuration cooling and phase change materials cooling.Potential influential factors and sub-methods were collected from the review work,and their contributions and impact have been discussed to guide future studies.Although most cooling technologies reviewed in this paper are matured,there are still problems need to be solved,such as the choice of cooling fluid and its usability for specific regions,the fouling accumulation and cleaning of enhanced heat exchangers with complex structures,the balance between cooling cost and net efficiency of PV modules,the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas.To be advocated,due to efficient heat transfer and spectral filter characters,nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization.展开更多
The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effecti...The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.展开更多
Global warming and the increasing frequency of extreme weather events pose serious threats to natural ecosystems and human well-being,creating an urgent need for energy-efficient cooling technologies.Conventional cool...Global warming and the increasing frequency of extreme weather events pose serious threats to natural ecosystems and human well-being,creating an urgent need for energy-efficient cooling technologies.Conventional cooling approaches,such as vapor compression systems and cooling units,account for approximately 15%of global electricity consumption,with energy demand continuing to rise annually[1].Consequently,the development of advanced cooling technologies that reduce both energy usage and environmental impact has become a pressing priority.展开更多
The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and ch...The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder＇s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetra- tion of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the ＂necessary kinetic condition of the lubricating activity＂ is relayed.展开更多
文摘During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- ing techniques for electronic and microelectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection,liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.
文摘A new cooling technique based on thermal driving in high centrifugal field （TDHCF） is developed for gas turbine rotational components, such as turbine blades. The key point of TDHCF is to enhance heat transfer by the fluid thermal driving in closed loop small channels placed in the high centrifugal field. Heat transfer characteristics of the new cooling technique are analyzed. In experiments, two different fluids （liquid water and Freon R12） are used as thermal driving media （fluid inside the loop channel）. And the channel width d is 1 mm and the height h is 30 mm. The temperature is measured by thermocouples and an average heat transfer coefficient KH is defined to indicate heat transfer capacity of TDHCF. Experimental results show that KH is enhanced when heat flux and the rotating speed increase. And thermal properties of thermal driving media are also influenced by KH. Larger KH can be achieved by using Freon R12 as thermal driving medium compared with using liquid water. It can increase to 2 300 W/（m^2 · K） and it is much higher than that of the normal air cooling method （usually at the level of 600-1200 W/（m^2·K））. All fundamental studies of TDHCF show that there actually exists thermal driving in the closed loop small channel in the centrifugal field to improve heat transfer characteristics.
基金Sponsored by National Natural Science Foundation of China(50334010)
文摘The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results indicated that the large section bars were passed through the zone of secondary carbide precipitation quickly by ultra-fast cooling technology （UFC） at instantaneous cooling rate of about 200 ℃/s and the finishing cooling temperature was higher than Ms. The lamellar spacing of pearlite decreased and the microhardness increased with decreasing the rereddening temperature. The precipitation of network carbide was restrained when re-reddening temperature was 690 ℃. And fine laminated pearlite was obtained through transformation of pseudopearlition that induced the reduction of the diameter of pearlite grain and refinement of the lamellar spacing of pearlite, so ideal microstructures of promoting spheroidizing annealing were obtained.
基金supported by the U.S.Office of Naval Research under awards number N00014-19-1-2028 and N00014-23-1-2247.
文摘Our societies are highly dependent on reliable cooling for air conditioning(AC)and refrigeration.Currently,modern cooling is supported by a 19th century technology:vapor compression cycle(VCC)-based cooling.Refrigerants used in the VCC cooling are strong greenhouse gases and thus are among the leading causes of global warming.The electrocaloric(EC)cooling is attractive as an alternative to the VCC cooling.EC cooling is environmentally benign,compressor-free,highly scalable,and has the potential of achieving higher efficiency than VCC cooling.The active EC materials research since the late 2000s has created several EC materials that exhibit giant electrocaloric effect(ECE)(by direct measurement).These EC materials have enabled the demonstration of EC cooling devices that exhibit temperature lifts of more than 8 K.These EC materials and device research reveals the promise of fer-roelectric materials in generating giant ECE at low electric fields and EC cooling devices achieving high performance.This review highlights these advances and offers perspectives of the EC cooling technologies.
基金Financial support for this project,provided by the New Century Excellent Talent Program of the Ministry of Education(No.NCET-08-0833)the National Natural Science Foundation of China(No.41040027)+1 种基金the National Basic Research Program of China(No.2006CB202200)the Program for Changjiang Scholars and Innovative Research Team in Universities of China(No.IRT0656)
文摘Based on the urgency of thermal hazard control in deep coal mines,we studied the status of deep thermal damage and cooling technology both at home and abroad,summarized the causes of deep thermal hazard,analysed and compared the control technologies for deep thermal hazards.The results show that the causes of deep thermal damage can be attributed to three aspects,i.e.,climate,geological and mining factors,of which the geological factors are deemed the major reasons for thermal hazards.As well,we compared a number of cooling technologies of domestic and overseas provenance,such as central air conditioning cooling technology,ice cooling technology and water cooling technology,with one other cooling technology,i.e.,the HEMS cooling technology,which has a large and important effect with its unique"pure air"cooling technology,realizes the utilizing of heat resources from underground to the ground.This technology makes use of heat obtained underground;thus the technology can promote low-carbon environmental economic development in coal mines,in order to achieve low-carbon coal production in China.
文摘The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine adopts various cooling techniques to ensure cooling,including a metal thermal barrier coating,multiple liquid film cooling slots,spiral milled regenerative cooling channels with high aspect ratio,a non-weld forming thrust chamber and an optimal cooling flow path design.In addition,the 480-ton LOX/kerosene engine for China’s future heavy-lift launch vehicle LM-9 will be larger in size,which makes it more difficult to be developed and will have more strict requirements in the cooling process.The main differences between the LM-5B and LM-5 are briefly described in this paper and the development process and working characteristics of YF-100 engines are introduced.The advantages and disadvantages of main cooling methods used in the thrust chambers of high-thrust liquid propellant engines are also described.Finally,the future challenges and countermeasures in cooling technology for China’s high-thrust LOX/kerosene engines and future reusable rocket engines are also presented.
基金supported by the National Natural Science Foundation of China(52273085)the Natural Science Foundation of Henan Province(252300421087).
文摘Radiative cooling has emerged as an attractive passive cooling technology in energy and thermal management fields due to its zero-energy consumption and pollution-free characteristics[[1],[2],[3]].An ideal radiative cooling material should simultaneously exhibit high solar reflectance to minimize solar heat absorption and high infrared emissivity in the“atmospheric window”band(8–13μm)to directly radiate heat to outer space(∼3 K),achieving passive cooling without energy input[[4],[5],[6]].Photonic structures(such as nano-multilayers,nano-pores,and photonic crystals)have been proven to simultaneously achieve high solar reflectance and broadband infrared emissivity[7,8].For instance,commercial“cooling paints”(such as BaSO4 and TiO2-based reflective paints)can reduce surface temperatures by several degrees and moderately decrease building cooling loads.
文摘High-power wireless power transfer(WPT)systems are pivotal for the widespread adoption of electric vehicles(EVs)and the decarbonization of transportation.However,thermal issues arising from Joule heating and hysteresis losses in high-power(≥100 kW)systems remain a critical bottleneck,compromising efficiency,reliability,and safety.This review comprehensively examines the fundamental principles and recent advancements in magnetic field-coupled WPT technology.We then provide a critical analysis of state-of-the-art thermal management solutions-including air cooling,immersion cooling,microchannel cooling,phase change materials,nanofluids,heat pipes,and composite systems-evaluating their thermal performance,electromagnetic compatibility,and carbon footprints.Notable achievements include microchannel cooling maintaining temperatures at 108◦C in megawatt-level coils,and phase change material-based solutions limiting heating plate temperatures below 80◦C.Despite progress,challenges persist in electromagnetic compatibility,system compactness,and dynamic response.Future research should prioritize developing advanced cooling architectures for efficiency-carbon trade-off optimization,focusing on low-eddy-current liquid cooling and electromagnetic compatibility-optimized phase change material enclosures.This review links thermal management breakthroughs to scalable,low-carbon EV infrastructure,offering actionable insights to accelerate the transition to carbon-neutral transportation.
基金Project(2017YFB0903300)supported by National Key R&D Program of ChinaProject(2016M601593)supported by China Postdoctoral Science Foundation
文摘Saturator is one of the core components of humid air turbine （HAT） and is the main feature of HAT making it different from other gas turbine cycles. Due to the lack of sufficient experience in commercial plant operation, HAT cycle has a great demand for modeling and simulation of the system and its components, especially the saturator, to provide reference for system design and optimization. The conventional saturator models are usually based on the theory of heat and mass transfer, which need two accurate coefficients to ensure convincing results. This work proposes a global heat and mass transfer coefficient based on cooling tower technology to model the saturator in small-scale HAT cycle. Compared with the experimental data, the simulation results show that the proposed model well predicts the dynamic humidity and temperature distribution characteristics of saturator at low air pressure and temperature.
基金supported by the National Natural Science Foundation of China(No.52373085,U21A2095)Natural Science Foundation of Hubei Province(No.2023AFA828)+3 种基金Innovative Team Program of Natural Science Foundation of Hubei Province(No.2023AFA027)Department of Science and Technology of Hubei Province(No.2024CSA076)Open Fund for Hubei Key Laboratory of Digital Textile Equipment,Wuhan Textile University(No.DTL2023022)National Local Joint Laboratory for Advanced Textile Processing and Clean Production(No.17).
文摘With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.
文摘Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.
基金The authors gratefully acknowledge the funding support from the National Key R&D Program of China(No.2017YFC0702900).
文摘When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield.However,little crucial review work was proposed to comment cooling technologies for PV modules.Therefore,this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules,and given appropriate comments,comparisons and discussions.According to the ways or principles of cooling,existing cooling technologies have been classified as fluid medium cooling(air cooling,water cooling and nanofluids cooling),optimizing structural configuration cooling and phase change materials cooling.Potential influential factors and sub-methods were collected from the review work,and their contributions and impact have been discussed to guide future studies.Although most cooling technologies reviewed in this paper are matured,there are still problems need to be solved,such as the choice of cooling fluid and its usability for specific regions,the fouling accumulation and cleaning of enhanced heat exchangers with complex structures,the balance between cooling cost and net efficiency of PV modules,the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas.To be advocated,due to efficient heat transfer and spectral filter characters,nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization.
基金supports provided by Science Center for Gas Turbine Project (P2022-B-Ⅱ-028-001).
文摘The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.
基金supported by the China National Petroleum Corporation Innovation Fund(2024DQ02-0409)the National Key Research Program(2020YFC2201103 and 2020YFA0210702)the National Natural Science Foundation of China(220375163).
文摘Global warming and the increasing frequency of extreme weather events pose serious threats to natural ecosystems and human well-being,creating an urgent need for energy-efficient cooling technologies.Conventional cooling approaches,such as vapor compression systems and cooling units,account for approximately 15%of global electricity consumption,with energy demand continuing to rise annually[1].Consequently,the development of advanced cooling technologies that reduce both energy usage and environmental impact has become a pressing priority.
文摘The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder＇s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetra- tion of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the ＂necessary kinetic condition of the lubricating activity＂ is relayed.
