Advanced civil aero-engines tend to adopt lean burn combustors to meet emission requirements.The exit of a lean burn combustor experiences highly non-uniformities in both temperature(Hot Streak,HS)and flow(swirl).This...Advanced civil aero-engines tend to adopt lean burn combustors to meet emission requirements.The exit of a lean burn combustor experiences highly non-uniformities in both temperature(Hot Streak,HS)and flow(swirl).This paper presents a numerical investigation on the behaviors of a High-Pressure(HP)turbine under a combined effect of swirl and hot streak.The investigation was conducted on a GE-E3 HP turbine with unsteady numerical simulations,which considered the realistic clocking position of the HP Nozzle Guide Vane(NGV)relative to the combustor.The influences of swirl orientations on the HS migration and thermal performances on the blade surface were examined.Results indicate that,inside the NGV passage,the swirl’s induced incidence angle effect dominates the HS radial migration.The transversal movement of HS follows the cross flow and thus makes itself approach the Suction Side(SS)and keep away from the Pressure Side(PS)as passing through the NGV,so that HS near the SS is more influenced by the incidence angle effect than that near the PS.As for the heat transfer,swirl affects the Heat Transfer Coefficient(HTC)on the NGV’s PS and SS mainly through the incidence angle effect.Different from the NGV,the inlet swirl and HS have limited effect on the HTC on the rotor blade’s PS,while on the rotor blade’s SS,the original vortex system dominates;therefore,the inlet non-uniformities merely enhance the HTC on the SS rather than alter its distribution characteristics.展开更多
This study proposes three possible keel-surface layer combinations to implement a new type of thermally insulating decorative wall system.A set of 8 samples has been studied.In particular,through theoretical calculati...This study proposes three possible keel-surface layer combinations to implement a new type of thermally insulating decorative wall system.A set of 8 samples has been studied.In particular,through theoretical calculations,simulations,and experimental verification,the influence of different types of connecting structures on the overall thermal performance of the wall system has been determined.It has been found that a proper combination of these elements can meet existing energy-saving standards and effectively reduce the energy loss caused by thermal bridges due to the installation of steel keels at the edges of integrated wall panels.展开更多
Pre-cooling the inlet air of a dry cooling tower by means of a spray can improve the tower performance during periods of high temperature.To study the spray effect on the thermal performance of natural draft dry cooli...Pre-cooling the inlet air of a dry cooling tower by means of a spray can improve the tower performance during periods of high temperature.To study the spray effect on the thermal performance of natural draft dry cooling towers(NDDCTs),in this study 3-D numerical simulations of such a process have been conducted using Fluent 16.2(a two-way coupled Eulerian-Lagrangian approach).The considered NDDCT is 120 m high and only half system is simulated due to its structural symmetry.Three different spray strategies have been investigated at a typical crosswind speed of 4 m/s,which is the most frequent wind speed.The results have shown that:(1)The three implemented spray strategies can improve the thermal performance of the studied NDDCT with a vary-ing degree of success.In one case,the heat rejection rate can be increased by 35.2%,and the tower outlet water temperature can be decreased by 2.1℃ when compared with the no spray case;(2)To improve the thermal per-formance of the NDDCT using a small amount of water,the design of the spray pre-cooling system must include more nozzles on the windward and fewer or even no nozzles on the leeward sides of the NDDCT.展开更多
Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TB...Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.展开更多
The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heat...The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heater(SAH)integrated with an internal thermal storage unit using Waste Automotive Oil(WAO).The SAH was designed based on the circulation of confined air around the internal thermal storage unit due to the updraft effects of hot air.Two SAHs were tested to compare the performance of WAO and water,with the results being compared to previous work that utilised phase change material.Results showed that WAO responds faster in the early stage,while water has slightly higher daytime efficiency,with a maximum temperature of 60℃,while WAO reached a maximum temperature of 76℃.During the discharge cycle,WAO achieved an efficiency of 65.7%,while the water’s efficiency 73.2% within the same period.The highest outlet air temperatures recorded were 43℃ for WAO and 33.8℃ for water.These findings support that water is suitable for applications requiring rapid thermal charging,while WAO offers extended thermal stability.The study highlights the feasibility of using low-cost materials,such as WAO and water,to enhance the performance of solar energy systems,thereby making them more viable for industrial applications like drying and heating.展开更多
Enhancing solar photovoltaic and thermal conversion performances may help develop more environmentally friendly hybrid photovoltaic/thermal(PV/T)systems that can be used in applications ranging from household to indus...Enhancing solar photovoltaic and thermal conversion performances may help develop more environmentally friendly hybrid photovoltaic/thermal(PV/T)systems that can be used in applications ranging from household to industrial scales.Owing to their enhanced thermal and optical properties,nanofluids have proven to be good candidates for designing PV/T systems with superior performances.As smart nanofluids,magnetic nanofluids(MNFs)can further enhance the performances of PV/T systems under external magnetic fields.This paper reviews recent developments in enhancing the electrical and thermal performances of PV/T systems using magnetic nanofluids.Various parameters affecting the performances are highlighted,and some areas for further investigations are discussed.The reviewed literature shows that PV/T systems with MNFs are promising.However,their performances need further investigation before they can be used in applications.展开更多
Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excell...Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.展开更多
Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles l...Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles limits its application in advanced flip chip ball gray array(FCBGA)packaging.Former researchers place a seal or dam structure to prevent In leakage,leading to the risk of In explosion,thermal degradation,or require additional keep-out zones.In this work,a copper foam(CF)matrix was embedded in In to absorb the liquid In and eliminate the leakage of In TIM1 during the multiple reflow cycles,as the CF capillary force.Au/Ni/Cu-Au/Ni/Cu joint was fabricated by soldering with the composite solder at 190℃for 2 min.After reflow cycles,good metallurgical bonding was formed at interfaces of joint.Rod-like Cu_(11)In_(9) formed at the CF and In interface,due to the re-dissolved of Cu_(11)In_(9) crystal.Small amount of Cu atoms from CF can reduce the activity of In,which inhibits the growth of Ni_(3)In_(7) intermetallic compound(IMC)at the interface of In and Au/Ni/Cu substrate.The CF matrix also improved the shear strength(22.9%)and thermal conductivity of the solder joints.Besides,the fracture behavior of solder joints without CF matrix was classified to be ductile type while that with CF matrix was changed to be ductile-brittle mixed type.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
To integrate insulation and load-bearing functions in prefabricated composite wall structures,a novel design based on fiber-reinforced expanded polystyrene(EPS)con-crete is proposed.The research focuses on three key a...To integrate insulation and load-bearing functions in prefabricated composite wall structures,a novel design based on fiber-reinforced expanded polystyrene(EPS)con-crete is proposed.The research focuses on three key as-pects:material properties,seismic performance,and ther-mal performance.Firstly,the compressive strength and thermal conductivity of fiber-reinforced EPS concrete were analyzed at different sand ratios,leading to the development of an optimal mix design and a damage constitutive model.Secondly,a combination of experimental and numerical analysis methods was used to investigate the seismic perfor-mance of prefabricated composite walls with different infill materials,including autoclaved aerated fly ash and fiber-reinforced EPS concrete.Finally,thermal perfor-mance studies were conducted on prefabricated composite wall panels with different infill materials.The results indi-cate that the specimens underwent elastic,elastoplastic,and failure stages during loading.While specimens using EPS concrete exhibited a slightly lower overall bearing capacity,they demonstrated superior ductility,energy dissipation ca-pacity,and enhanced insulation and thermal stability.展开更多
This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal ...This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).展开更多
The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areex...The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.展开更多
Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of pr...Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of primary-secondary thermally conductive network was designed by water-suspension granulation, surface coating, and hot-pressing procedures in the graphene-based PBXs composites to greatly increase the thermal conductive performance of the composites. The primary network with a threedimensional structure provided the heat-conducting skeleton, while the secondary network in the polymer matrix bridged the primary network to increase the network density. The enhancement efficiency in the thermally conductive performance of the composites reached the highest value of 59.70% at a primary-secondary network ratio of 3:1. Finite element analysis confirmed the synergistic enhancement effect of the primary and secondary thermally conductive networks. This study introduces an innovative approach to designing network structures for PBX composites, significantly enhancing their thermal conductivity.展开更多
This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed...This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed (PFB) combustion and the other two based on atmospheric circulating fluidized bed (CFB) combustion. The results show that the first scheme avoids high temperature gas filter, but has the lower cycle efficiency and syngas heating value. The second scheme can gain the highest cycle efficiency, however it is better to now lower the filter operating temperature. The third and fourth schemes, based on CFB, have lower efficiencies than the second one. But the fourth one, with preheating air/steam for gasification, can obtain the highest heating value of syngas and gain higher efficiency than the third one.展开更多
Operating Lithium-ion batteries at their temperature limits is a challenging design task due to explosion risk at high temperatures and rapid degradation at low temperatures.Depending on the battery package design,tho...Operating Lithium-ion batteries at their temperature limits is a challenging design task due to explosion risk at high temperatures and rapid degradation at low temperatures.Depending on the battery package design,those risks can be solved with passive solutions,which require no active cooling or heating.Thecurrentwork aims to optimize the pack design and materials of the type-NCR18650B battery based on a wide range of operation temperature.The lower limit was denoted by cold case while the maximum limit was expressed by hot case.A combined analyticalnumerical approach was developed to model the heat generation inside the battery.A thermal resistance analysis was used to determine the boundary conditions of the numerical model.The governing differential equations for the 1-D heat generation model were solved analytically.The numerical analysis was considered to determine the best battery pack design based on material parameters,number of batteries,and geometrical arrangement.The analytical results revealedthat the cold case canbe selectedas theworst case and thebestmodel wasobtainedusing thehexagonal-shaped 10-battery pack that was covered with Delrin of 1.8 mm in thickness.The numerical results showed that the best model was the hexagonal-shaped 10-battery pack with Delrin of 2 mm in thickness that achieved the largest temperature of−20.6℃ in the cold case.展开更多
Thermal performance of envelopes and indoor thermal environment were technologically improved for traditional wooden vernacular dwellings of Tujia Minority in Western Hunan, China, on the premise of protecting their c...Thermal performance of envelopes and indoor thermal environment were technologically improved for traditional wooden vernacular dwellings of Tujia Minority in Western Hunan, China, on the premise of protecting their conventional styles. Thermal insulation boards and wooden boards were added to the interior side of external walls of vernacular dwellings to form two layers of air cavities, so as to gain excellent thermal performance. The indoor temperature of such dwellings after reconstruction was apparently improved compared with the data before reconstruction both in winter and summer, which verified the feasibility and the effectiveness of the reconstruction technologies proposed.展开更多
A geothermal demonstration exploitation area will be established in the Enhanced Geothermal System of the Qiabuqia field, Gonghe Basin, Qinghai–Xizang Plateau in China. Selection of operational parameters for geother...A geothermal demonstration exploitation area will be established in the Enhanced Geothermal System of the Qiabuqia field, Gonghe Basin, Qinghai–Xizang Plateau in China. Selection of operational parameters for geothermal field extraction is thus of great significance to realize the best production performance. A novel integrated method of finite element and multi-objective optimization has been employed to obtain the optimal scheme for thermal extraction from the Gonghe Basin. A thermal-hydraulic-mechanical coupling model(THM) is established to analyze the thermal performance. From this it has been found that there exists a contraction among different heat extraction indexes. Parametric study indicates that injection mass rate(Q_(in)) is the most sensitive parameter to the heat extraction, followed by well spacing(WS) and injection temperature(T_(in)). The least sensitive parameter is production pressure(p_(out)). The optimal combination of operational parameters acquired is such that(T_(in), p_(out), Q_(in), WS) equals(72.72°C, 30.56 MPa, 18.32 kg/s, 327.82 m). Results indicate that the maximum electrical power is 1.41 MW for the optimal case over 20 years. The thermal break has been relieved and the pressure difference reduced by 8 MPa compared with the base case. The optimal case would extract 50% more energy than that of a previous case and the outcome will provide a remarkable reference for the construction of Gonghe project.展开更多
Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of th...Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of the effective techniques to solve high temperature leakage and corrosion.In this paper,commercial Al-10Si alloy micro powders were encapsulated with flexible ceramic shells whose total thickness is below 1μm by hydrothermal treatment and heat treatment in N_(2) atmosphere.The compositions and microstructures were characterized by XRD,SEM and TEM.The shell was composed of AlN fibers network structure embedded withα-Al_(2)O_(3)/AlN which prevented the alloy from leaking and oxidizing,as well as had excellent thermal stability.The latent heat of microcapsules was 351.8 J g^(-1)for absorption and 372.7 J g^(-1)for exothermic.The microcapsules showed near zero thermal performance loss with latent heat storage(LHS)/release(LHR)was 353.2/403.7 J g^(-1)after 3000 cycles.Compared with the published Al-Si alloy microcapsules,both high heat storage density and super thermal cycle stability were achieved,showing promising development prospects in high temperature thermal management.展开更多
The multiple jets impingement heat transfer is widely applied in the wing anti-icing system.It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat ...The multiple jets impingement heat transfer is widely applied in the wing anti-icing system.It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior.In the present study,the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m×3 m icing wind tunnel of China Aerodynamics Research and Development Center.The effects of icing parameters Liquid Water Content(LWC)and Median Volume Diameter(MVD)and hot air parameters(mass flow rate and temperature)on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied.The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms.The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters.The temperature of impingement hot air and that of wing skin are approximately linear correlated.The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion.The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.展开更多
Solar water heaters(SWH) are widely used in urban areas because of their advantages in reducing energy consumption and mitigating greenhouse gas emissions. However, the performance of SWH subjected to obstructions is ...Solar water heaters(SWH) are widely used in urban areas because of their advantages in reducing energy consumption and mitigating greenhouse gas emissions. However, the performance of SWH subjected to obstructions is unclear yet. In this study, we present a numerical evaluation on thermal performance of fa?ade-installed SWH under three typical obstructed scenarios, based on various levels of sunshine duration. This study is carried out for four locations with various latitudes across China. Thermal performance is measured by solar fraction for annual and monthly evaluation. The results show that the obstruction can seriously degrade annual solar fraction of SWH, even in the 4-hour sunshine duration scenario, for all the studied locations. Interestingly, only lengthening sunshine duration in the standard day(e.g., from 2 h to 4 h) may not result in increasing annual solar fraction markedly. In terms of the monthly performance, solar fraction in January and December decreases significantly, while from May to August it just declines slightly, except for Guangzhou having a swift reduction. This study can provide insights into the behavior and promote the appropriate application of SWH in urban areas.展开更多
基金funded by the National Science Foundation of China(No.61890923)the National Science and Technology Major Project,China(No.J2019-VIII-0001-0162).
文摘Advanced civil aero-engines tend to adopt lean burn combustors to meet emission requirements.The exit of a lean burn combustor experiences highly non-uniformities in both temperature(Hot Streak,HS)and flow(swirl).This paper presents a numerical investigation on the behaviors of a High-Pressure(HP)turbine under a combined effect of swirl and hot streak.The investigation was conducted on a GE-E3 HP turbine with unsteady numerical simulations,which considered the realistic clocking position of the HP Nozzle Guide Vane(NGV)relative to the combustor.The influences of swirl orientations on the HS migration and thermal performances on the blade surface were examined.Results indicate that,inside the NGV passage,the swirl’s induced incidence angle effect dominates the HS radial migration.The transversal movement of HS follows the cross flow and thus makes itself approach the Suction Side(SS)and keep away from the Pressure Side(PS)as passing through the NGV,so that HS near the SS is more influenced by the incidence angle effect than that near the PS.As for the heat transfer,swirl affects the Heat Transfer Coefficient(HTC)on the NGV’s PS and SS mainly through the incidence angle effect.Different from the NGV,the inlet swirl and HS have limited effect on the HTC on the rotor blade’s PS,while on the rotor blade’s SS,the original vortex system dominates;therefore,the inlet non-uniformities merely enhance the HTC on the SS rather than alter its distribution characteristics.
基金The research content of this paper comes from the Urban and Rural Construction Science and Technology Project of Shandong Province,China,Subject No.2018-K9-07.
文摘This study proposes three possible keel-surface layer combinations to implement a new type of thermally insulating decorative wall system.A set of 8 samples has been studied.In particular,through theoretical calculations,simulations,and experimental verification,the influence of different types of connecting structures on the overall thermal performance of the wall system has been determined.It has been found that a proper combination of these elements can meet existing energy-saving standards and effectively reduce the energy loss caused by thermal bridges due to the installation of steel keels at the edges of integrated wall panels.
基金supported by the Shandong Provincial Science and Technology SMEs Innovation Capacity Improvement Project(2022TSGC2018)the Shandong Natural Science Foundation(Grant No.ZR2022ME008)+3 种基金the Shenzhen Science and Technology Program(KCXFZ20201221173409026)the“Young Scholars Program of Shandong University”(YSPSDU,No.2018WLJH73)the Open Project of State Key Laboratory of Clean Energy Utilization,Zhejiang University(Program Number ZJUCEU2020011)the Shandong Natural Science Foundation(Grant No.ZR2021ME118).
文摘Pre-cooling the inlet air of a dry cooling tower by means of a spray can improve the tower performance during periods of high temperature.To study the spray effect on the thermal performance of natural draft dry cooling towers(NDDCTs),in this study 3-D numerical simulations of such a process have been conducted using Fluent 16.2(a two-way coupled Eulerian-Lagrangian approach).The considered NDDCT is 120 m high and only half system is simulated due to its structural symmetry.Three different spray strategies have been investigated at a typical crosswind speed of 4 m/s,which is the most frequent wind speed.The results have shown that:(1)The three implemented spray strategies can improve the thermal performance of the studied NDDCT with a vary-ing degree of success.In one case,the heat rejection rate can be increased by 35.2%,and the tower outlet water temperature can be decreased by 2.1℃ when compared with the no spray case;(2)To improve the thermal per-formance of the NDDCT using a small amount of water,the design of the spray pre-cooling system must include more nozzles on the windward and fewer or even no nozzles on the leeward sides of the NDDCT.
基金Supported by Scientific and Technological Innovation of Shaanxi Provincial State-Owned Capital Operation Budget(2022-056)Institute's Self-Developed Technology Program(0801YK2317)+4 种基金Qin Chuangyuan Cites High-Level Innovation and Entrepreneurship Talent Program(QCYRCXM-2023-120)Qin Chuangyuan Industry Cluster Zone“Four Chains”Integration Program(2024CY-JJQ-46)National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.
文摘The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heater(SAH)integrated with an internal thermal storage unit using Waste Automotive Oil(WAO).The SAH was designed based on the circulation of confined air around the internal thermal storage unit due to the updraft effects of hot air.Two SAHs were tested to compare the performance of WAO and water,with the results being compared to previous work that utilised phase change material.Results showed that WAO responds faster in the early stage,while water has slightly higher daytime efficiency,with a maximum temperature of 60℃,while WAO reached a maximum temperature of 76℃.During the discharge cycle,WAO achieved an efficiency of 65.7%,while the water’s efficiency 73.2% within the same period.The highest outlet air temperatures recorded were 43℃ for WAO and 33.8℃ for water.These findings support that water is suitable for applications requiring rapid thermal charging,while WAO offers extended thermal stability.The study highlights the feasibility of using low-cost materials,such as WAO and water,to enhance the performance of solar energy systems,thereby making them more viable for industrial applications like drying and heating.
基金This work was supported by the World Bank through the East Africa Higher Education Centers of Excellence(Project ID:PI 51847)and the African Center of Excellence in Energy for Sustainable Development(ACE-ESD).
文摘Enhancing solar photovoltaic and thermal conversion performances may help develop more environmentally friendly hybrid photovoltaic/thermal(PV/T)systems that can be used in applications ranging from household to industrial scales.Owing to their enhanced thermal and optical properties,nanofluids have proven to be good candidates for designing PV/T systems with superior performances.As smart nanofluids,magnetic nanofluids(MNFs)can further enhance the performances of PV/T systems under external magnetic fields.This paper reviews recent developments in enhancing the electrical and thermal performances of PV/T systems using magnetic nanofluids.Various parameters affecting the performances are highlighted,and some areas for further investigations are discussed.The reviewed literature shows that PV/T systems with MNFs are promising.However,their performances need further investigation before they can be used in applications.
基金supported by the National Natural Science Foundation of China(grant no.52231004 and 52072305).
文摘Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.
基金Project(2023GK2063)supported by the Key R&D Program of Hunan Province,ChinaProject(2023GXGG006)supported by the Key Products in Manufacturing Industry of Hunan Province,ChinaProject(kq2102005)supported by Key Project of Science and Technology of Changsha,China。
文摘Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles limits its application in advanced flip chip ball gray array(FCBGA)packaging.Former researchers place a seal or dam structure to prevent In leakage,leading to the risk of In explosion,thermal degradation,or require additional keep-out zones.In this work,a copper foam(CF)matrix was embedded in In to absorb the liquid In and eliminate the leakage of In TIM1 during the multiple reflow cycles,as the CF capillary force.Au/Ni/Cu-Au/Ni/Cu joint was fabricated by soldering with the composite solder at 190℃for 2 min.After reflow cycles,good metallurgical bonding was formed at interfaces of joint.Rod-like Cu_(11)In_(9) formed at the CF and In interface,due to the re-dissolved of Cu_(11)In_(9) crystal.Small amount of Cu atoms from CF can reduce the activity of In,which inhibits the growth of Ni_(3)In_(7) intermetallic compound(IMC)at the interface of In and Au/Ni/Cu substrate.The CF matrix also improved the shear strength(22.9%)and thermal conductivity of the solder joints.Besides,the fracture behavior of solder joints without CF matrix was classified to be ductile type while that with CF matrix was changed to be ductile-brittle mixed type.
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The National Natural Science Foundation of China (No. 52168022)。
文摘To integrate insulation and load-bearing functions in prefabricated composite wall structures,a novel design based on fiber-reinforced expanded polystyrene(EPS)con-crete is proposed.The research focuses on three key as-pects:material properties,seismic performance,and ther-mal performance.Firstly,the compressive strength and thermal conductivity of fiber-reinforced EPS concrete were analyzed at different sand ratios,leading to the development of an optimal mix design and a damage constitutive model.Secondly,a combination of experimental and numerical analysis methods was used to investigate the seismic perfor-mance of prefabricated composite walls with different infill materials,including autoclaved aerated fly ash and fiber-reinforced EPS concrete.Finally,thermal perfor-mance studies were conducted on prefabricated composite wall panels with different infill materials.The results indi-cate that the specimens underwent elastic,elastoplastic,and failure stages during loading.While specimens using EPS concrete exhibited a slightly lower overall bearing capacity,they demonstrated superior ductility,energy dissipation ca-pacity,and enhanced insulation and thermal stability.
文摘This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).
基金funded by the Project of the Hubei Provincial Department of Science and Technology(Grant No.2022CFB957)the Project of Hubei Engineering University of Teaching Research(Grant No.JY2024032)+1 种基金Ministry of Education University-Industry Cooperation Collaborative Education Project(Grant No.220903584161245)College Students’Innovation and Entrepreneurship Training Program(Grant Nos.DC2024031,DC2024032).
文摘The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.
基金supported by the National Natural Science Foundation of China (Grant Nos. 22475179 and 22275173)。
文摘Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of primary-secondary thermally conductive network was designed by water-suspension granulation, surface coating, and hot-pressing procedures in the graphene-based PBXs composites to greatly increase the thermal conductive performance of the composites. The primary network with a threedimensional structure provided the heat-conducting skeleton, while the secondary network in the polymer matrix bridged the primary network to increase the network density. The enhancement efficiency in the thermally conductive performance of the composites reached the highest value of 59.70% at a primary-secondary network ratio of 3:1. Finite element analysis confirmed the synergistic enhancement effect of the primary and secondary thermally conductive networks. This study introduces an innovative approach to designing network structures for PBX composites, significantly enhancing their thermal conductivity.
文摘This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed (PFB) combustion and the other two based on atmospheric circulating fluidized bed (CFB) combustion. The results show that the first scheme avoids high temperature gas filter, but has the lower cycle efficiency and syngas heating value. The second scheme can gain the highest cycle efficiency, however it is better to now lower the filter operating temperature. The third and fourth schemes, based on CFB, have lower efficiencies than the second one. But the fourth one, with preheating air/steam for gasification, can obtain the highest heating value of syngas and gain higher efficiency than the third one.
文摘Operating Lithium-ion batteries at their temperature limits is a challenging design task due to explosion risk at high temperatures and rapid degradation at low temperatures.Depending on the battery package design,those risks can be solved with passive solutions,which require no active cooling or heating.Thecurrentwork aims to optimize the pack design and materials of the type-NCR18650B battery based on a wide range of operation temperature.The lower limit was denoted by cold case while the maximum limit was expressed by hot case.A combined analyticalnumerical approach was developed to model the heat generation inside the battery.A thermal resistance analysis was used to determine the boundary conditions of the numerical model.The governing differential equations for the 1-D heat generation model were solved analytically.The numerical analysis was considered to determine the best battery pack design based on material parameters,number of batteries,and geometrical arrangement.The analytical results revealedthat the cold case canbe selectedas theworst case and thebestmodel wasobtainedusing thehexagonal-shaped 10-battery pack that was covered with Delrin of 1.8 mm in thickness.The numerical results showed that the best model was the hexagonal-shaped 10-battery pack with Delrin of 2 mm in thickness that achieved the largest temperature of−20.6℃ in the cold case.
基金Project(51308548)supported by the National Natural Science Foundation of ChinaProject(2014M552155)supported by China Postdoctoral Science FoundationProject(2013RS4054)supported by the Science and Technology Fund of Hunan Province,China
文摘Thermal performance of envelopes and indoor thermal environment were technologically improved for traditional wooden vernacular dwellings of Tujia Minority in Western Hunan, China, on the premise of protecting their conventional styles. Thermal insulation boards and wooden boards were added to the interior side of external walls of vernacular dwellings to form two layers of air cavities, so as to gain excellent thermal performance. The indoor temperature of such dwellings after reconstruction was apparently improved compared with the data before reconstruction both in winter and summer, which verified the feasibility and the effectiveness of the reconstruction technologies proposed.
基金the National Key R&D Program of China(Grant No.2018YFB1501804)the National Natural Science Funds for Excellent Young Scholars of China(Grant No.51822406)+2 种基金the Sichuan Science and Technology Program(2021YJ0389)the Program of Introducing Talents of Discipline to Chinese Universities(111 Plan)(Grant No.B17045)the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201911414038)。
文摘A geothermal demonstration exploitation area will be established in the Enhanced Geothermal System of the Qiabuqia field, Gonghe Basin, Qinghai–Xizang Plateau in China. Selection of operational parameters for geothermal field extraction is thus of great significance to realize the best production performance. A novel integrated method of finite element and multi-objective optimization has been employed to obtain the optimal scheme for thermal extraction from the Gonghe Basin. A thermal-hydraulic-mechanical coupling model(THM) is established to analyze the thermal performance. From this it has been found that there exists a contraction among different heat extraction indexes. Parametric study indicates that injection mass rate(Q_(in)) is the most sensitive parameter to the heat extraction, followed by well spacing(WS) and injection temperature(T_(in)). The least sensitive parameter is production pressure(p_(out)). The optimal combination of operational parameters acquired is such that(T_(in), p_(out), Q_(in), WS) equals(72.72°C, 30.56 MPa, 18.32 kg/s, 327.82 m). Results indicate that the maximum electrical power is 1.41 MW for the optimal case over 20 years. The thermal break has been relieved and the pressure difference reduced by 8 MPa compared with the base case. The optimal case would extract 50% more energy than that of a previous case and the outcome will provide a remarkable reference for the construction of Gonghe project.
基金financial support from the National Natural Science Foundation of China(No.52072276)Hubei Important Project on Science and Technology(No.2022BECO20).
文摘Al-Si alloy,a high temperature phase change material,has great potential in thermal management due to its advantages of high heat storage density and thermal conductivity.Microencapsulation of Al-Si alloy is one of the effective techniques to solve high temperature leakage and corrosion.In this paper,commercial Al-10Si alloy micro powders were encapsulated with flexible ceramic shells whose total thickness is below 1μm by hydrothermal treatment and heat treatment in N_(2) atmosphere.The compositions and microstructures were characterized by XRD,SEM and TEM.The shell was composed of AlN fibers network structure embedded withα-Al_(2)O_(3)/AlN which prevented the alloy from leaking and oxidizing,as well as had excellent thermal stability.The latent heat of microcapsules was 351.8 J g^(-1)for absorption and 372.7 J g^(-1)for exothermic.The microcapsules showed near zero thermal performance loss with latent heat storage(LHS)/release(LHR)was 353.2/403.7 J g^(-1)after 3000 cycles.Compared with the published Al-Si alloy microcapsules,both high heat storage density and super thermal cycle stability were achieved,showing promising development prospects in high temperature thermal management.
基金co-supported by the National Numerical Wind Tunnel Project(No.NNW2018-ZT2B04)the “973”Program of China(No.2015CB755800)。
文摘The multiple jets impingement heat transfer is widely applied in the wing anti-icing system.It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior.In the present study,the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m×3 m icing wind tunnel of China Aerodynamics Research and Development Center.The effects of icing parameters Liquid Water Content(LWC)and Median Volume Diameter(MVD)and hot air parameters(mass flow rate and temperature)on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied.The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms.The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters.The temperature of impingement hot air and that of wing skin are approximately linear correlated.The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion.The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.
基金Projects(2017JJ3517,2017JJ3090)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2018NK2066)supported by the Key Research and Development Program of Hunan Province,ChinaProject(QJ2017007B)supported by the Youth Scientific Research Foundation of Central South University of Forestry and Technology,China。
文摘Solar water heaters(SWH) are widely used in urban areas because of their advantages in reducing energy consumption and mitigating greenhouse gas emissions. However, the performance of SWH subjected to obstructions is unclear yet. In this study, we present a numerical evaluation on thermal performance of fa?ade-installed SWH under three typical obstructed scenarios, based on various levels of sunshine duration. This study is carried out for four locations with various latitudes across China. Thermal performance is measured by solar fraction for annual and monthly evaluation. The results show that the obstruction can seriously degrade annual solar fraction of SWH, even in the 4-hour sunshine duration scenario, for all the studied locations. Interestingly, only lengthening sunshine duration in the standard day(e.g., from 2 h to 4 h) may not result in increasing annual solar fraction markedly. In terms of the monthly performance, solar fraction in January and December decreases significantly, while from May to August it just declines slightly, except for Guangzhou having a swift reduction. This study can provide insights into the behavior and promote the appropriate application of SWH in urban areas.
