A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building...A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.展开更多
An analysis of atmospheric SW-radiative forcing and local heating/cooling rate is made using a one year temporal and vertical profiles of aerosol and cloud over Yaoundé (11.51°E, 3.83°N). It appears tha...An analysis of atmospheric SW-radiative forcing and local heating/cooling rate is made using a one year temporal and vertical profiles of aerosol and cloud over Yaoundé (11.51°E, 3.83°N). It appears that the direct influence of aerosols on the surface compared to the TOA can be 3 times larger. Annual mean value obtained at 559 mb altitude is +27.74 W/m2 with range from 0 to +43 W/m2. At 904 mb, we obtained an annual mean of ﹣46.22 W/m2 with range from ﹣65 to ﹣9 W/m2. Frequency distribution indicates that more than 95% of ARF are between +10 and +70 W/m2 at 559 mb (upper limit of UL), and more than 85% of ARF are between ﹣70 and ﹣10 W/m2 at 904 mb (upper limit of PBL). This sign change is explained by the fact that the backscattering peaks at the upper limit of the aerosol PBL layer. The maximum CRF is noted at TOA where it reaches ﹣600 W/m2 based on the time interval and the structure of clouds. The highest values occur between 11.50 and 13.50 LST. Clouds lead to a general heating of the entire atmospheric column with a much greater effect near the surface. Aerosols effect on the heating rate profile show strong cooling during the day for the lower atmosphere, with slight heating at the upper atmosphere. This cooling contribution generally increases from the surface and peacks at the upper boundary of aerosol layer where reflectivity is the most important. Depending on the moment of the day, average heating effect of clouds peacks at surface or within the middle troposphere due to the absorption by clouds particles. Vertical profiles deeply evolve exhibiting differences that exceed ﹣3 K/day according to altitude from one hour to another during a given mean solar day.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimi...This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.展开更多
To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-ge...To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.展开更多
Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency...Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.展开更多
The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to...The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.展开更多
Switchable radiative cooling/heating holds great promise for mitigating the global energy and environmental crisis.Here,we reported a cost-effective,high-strength Janus film through surface optical engineering waste p...Switchable radiative cooling/heating holds great promise for mitigating the global energy and environmental crisis.Here,we reported a cost-effective,high-strength Janus film through surface optical engineering waste paper with one side decorated by a hydrophobic polymeric cooling coating consisting of micro/nanopore/particle hierarchical structure and the other side coated with hydrophilic MXene nanosheets for heating.The cooling surface demonstrates high solar reflectivity(96.3%)and infrared emissivity(95.5%),resulting in daytime/nighttime sub-ambient radiative cooling of 6℃/8℃with the theoretical cooling power of 100.6 and 138.5Wm^(−2),respectively.The heating surface exhibits high solar absorptivity(83.7%)and low infrared emissivity(15.2%),resulting in excellent radiative heating capacity for vehicle charging pile(~6.2℃)and solar heating performance.Impressively,the mechanical strength of Janus film increased greatly by 563%compared with that of pristine waste paper,which is helpful for its practical applications in various scenarios for switchable radiative thermal management through mechanical flipping.Energy-saving simulation results reveal that significant total energy savings of up to 32.4MJm^(−2) can be achieved annually(corresponding to the 12.4%saving ratio),showing the immense importance of reducing carbon footprint and promoting carbon neutrality.展开更多
This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without...This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without bespoke weather files.High-accuracy predictive models are developed to estimate seasonal heating and cooling loads and to derive convective heat transfer coefficients for transitional seasons.Models are calibrated against extended AMeDAS records for Kurume,Fukuoka Prefecture,demonstrating improved capture of local climatic variability compared with standard practice.Methodologically,the study establishes time-series regression relationships linking outdoor air temperature,incident solar radiation,and wind speed to instantaneous thermal demand and surface convective rates.These empirical relations feed a reconstruction algorithm that adjusts simulation outputs to standardized climatic conditions by rescaling heat flows and convective parameters rather than altering meteorological inputs.Results indicate that reframing simulation inputs in terms of heat enhances reliability and transferability of performance predictions and reduces uncertainty associated with variable weather.The paper examines essential assumptions affecting applicability,including the assumed linearity of convective correlations,representativeness of the reference building envelope,and the use of virtual walls for parameter identification.It further proposes a novel procedure to compute a physical adjustment coefficient for the convective heat transfer coefficient,addressing a parameter gap in macro-scale models while acknowledging challenges for conventional comparative validation.The authors recommend future work on automated calibration routines and on extending the method to tropical and arid climates to broaden applicability and support foundational reform of building energy simulation.展开更多
The aim of the present analysis concerns the magnetohydrodynamic flow of fluid which is natural convective and electrically charged through two vertical insulated walls.Influences of radiative heat flux,induced magnet...The aim of the present analysis concerns the magnetohydrodynamic flow of fluid which is natural convective and electrically charged through two vertical insulated walls.Influences of radiative heat flux,induced magnetic field,and the Newtonian heating/cooling are taken.We found exact expressions for the temperature field,the velocity field,and the induced magnetic field by solving the set of dimensionless coupled governing equations.Further,we obtained the equations for induced current density,Nusselt number,skin frictions as well as mass flux.The influences of the several constraints like the magnetic,the radiation and the Newtonian heating/cooling on the profiles of the velocity,the temperature field,the induced magnetic field as well as the current density display with graphics.Moreover,the influence of these non-dimensional parameters on the skin frictions,the Nusselt number,and the mass flux is explored in tabular form.The outcome of the radiation raised the velocity,the temperature field,the induced magnetic field and the current density field in view of enhancing the thickness of the boundary layer.Also,the impact of Newtonian heating is to raise the velocity,temperature,induced magnetic field and induced current density,whereas all these fields have opposite behaviors in case of Newtonian cooling.展开更多
The knowledge representation mode and inference control strategy were analyzed according to the specialties of air-conditioning cooling/heating sources selection. The constructing idea and working procedure for knowle...The knowledge representation mode and inference control strategy were analyzed according to the specialties of air-conditioning cooling/heating sources selection. The constructing idea and working procedure for knowledge base and inference engine were proposed while the realization technique of the C language was discussed. An intelligent decision support system (IDSS) model based on such knowledge representation and inference mechanism was developed by domain engineers. The model was verified to have a small kernel and powerful capability in list processing and data driving, which was successfully used in the design of a cooling/heating sources system for a large-sized office building.展开更多
An advanced control concept, Predictive Functional Control （PFC）, is applied for temperature control of a bench-scaled batch reactor equipped with monofluid heating/cooling system. First principles process models ar...An advanced control concept, Predictive Functional Control （PFC）, is applied for temperature control of a bench-scaled batch reactor equipped with monofluid heating/cooling system. First principles process models are developed. Based on achieved models, significant process variables, which are difficult or impossible to measure online, are estimated from easily measured variables, and cascade PFC control strategy has been projected and implemented in Matlab RI 4. The dynamics of individual subunits is explicitly taken into consideration by internal model in the control algorithms, and model uncertainty, various process disturbances are compensated by modifi- cation of internal model. The experimental results present an excellent capability of tracking the set point, and the success of PFC technique as a process control paradigm is illustratively demonstrated.展开更多
Radiative cooling textiles with spectrally selective surfaces offer a promising energy-efficient approach for sub-ambient cooling of outdoor objects and individuals.However,the spectrally selective mid-infrared emissi...Radiative cooling textiles with spectrally selective surfaces offer a promising energy-efficient approach for sub-ambient cooling of outdoor objects and individuals.However,the spectrally selective mid-infrared emission of these textiles significantly hinders their efficient radiative heat exchange with self-heated objects,thereby posing a significant challenge to their versatile cooling applicability.Herein,we present a bicomponent blow spinning strategy for the production of scalable,ultra-flexible,and healable textiles featuring a tailored dual gradient in both chemical composition and fiber diameter.The gradient in the fiber diameter of this textile introduces a hierarchically porous structure across the sunlight incident area,thereby achieving a competitive solar reflectivity of 98.7%on its outer surface.Additionally,the gradient in the chemical composition of this textile contributes to the formation of Janus infrared-absorbing surfaces:The outer surface demonstrates a high mid-infrared emission,whereas the inner surface shows a broad infrared absorptivity,facilitating radiative heat exchange with underlying self-heated objects.Consequently,this textile demonstrates multi-scenario radiative cooling capabilities,enabling versatile outdoor cooling for unheated objects by 7.8℃ and self-heated objects by 13.6℃,compared to commercial sunshade fabrics.展开更多
The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF...The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.展开更多
An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature unifor...An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature uniformity. To address the high energy consumption of secondary cooling loops in vehicles for cooling immersion oil, this paper proposes a method of immersion coupled cooling tubes. Battery heat is directly absorbed by the immersion liquid and rapidly dissipated via cooling water in the S-type cooling tube(SCT). This work investigated the effects of structural parameters, immersion fluid medium, and operating parameters on the cooling performance of the BTMS. The results showed that the fin height(h_(f)) has no significant effect on the cooling performance. Both Transformer Oil and HFE-7100 delivered outstanding thermal management, reaching a maximum of 36.73℃ and 41.39℃ while maintaining narrow temperature differences of only 3.70℃ and 2.09℃ apart, respectively. When the ambient temperature reached 40℃ and HFE-7100 was used as the immersion liquid, the maximum temperature difference remained consistently below 3℃. Subsequently, a sensitivity analysis was conducted on the respective influential parameters. It was found that inlet water temperature(T_(in)) and immersion fluids exert the most significant influence on the system performance. Finally, different immersion cooling schemes were compared, which demonstrated the advantages of the system proposed in this study under harsh condition, thereby supporting the application of different schemes under various scenarios. It can be directly integrated with the vehicle-mounted cooling circuit system, thereby reducing energy consumption and weight, and offering new insights for research on thermal management systems for EVs.展开更多
In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wa...In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wall.Fan-shaped holes,commonly used in gas turbines and aerospace applications,flare toward the exit to form a protective cooling film over hot surfaces,enhancing thermal protection compared to cylindrical holes.An initial hole configuration was used to improve adiabatic cooling efficiency.Design variables included the hole injection angle,forward expansion angle,lateral expansion angle,and aperture ratio,while the objective function was the average adiabatic cooling efficiency of the concave wall surface.Optimization was performed at two representative blowing ratios,M=1.0 and M=1.5,using the GPR-based surrogate model to accelerate exploration,with the Bayesian algorithm identifying optimal configurations.Results indicate that the optimized fan-shaped holes increased cooling efficiency by 15.2%and 12.3%at low and high blowing ratios,respectively.Analysis of flow and thermal fields further revealed how the optimized geometry influenced coolant distribution and heat transfer,providing insight into the mechanisms driving the improved cooling performance.展开更多
Methods allowing passive daytime radiative cooling(PDRC)to be carried out in an energy-efficient and scalable way are potentially important for various disciplines.Here,we report a sustainable strategy for scalable-de...Methods allowing passive daytime radiative cooling(PDRC)to be carried out in an energy-efficient and scalable way are potentially important for various disciplines.Here,we report a sustainable strategy for scalable-designed and color-regulating PDRC coating based on high-crystallinity photonic metamaterial(crystallinity:71.5%;enhanced assembly efficiency:72%),that is derived from the as-prepared 55 wt%solid content poly(methyl methacrylate-butyl acrylate-methacrylic acid)P(MMA-BA-MAA)monodispersed latexes(approaching theoretical limit:59 wt%).Robust meter-scale PDRC coatings are constructed by various industrial modes onto diverse surfaces,addressing bottlenecks like dull appearance,high cost,low efficiency,and hard construction.Notably,the solar reflectance,long-wave infrared emittance,and calculated theoretical cooling power of the designed PDRC coating,respectively,reach~0.94,~0.97,and~95.5 W m^(-2)under solar radiation,which can achieve an average 5.3℃sub-ambient daytime temperature drop in the summer in Nanjing.The cooling performance,scale preparation,and cost-effectiveness of the PDRC coating have extended into leading position compared with those of state-of-the-art designs.This work provides promising route to reduce carbon emissions and energy consumption for global sustainability.展开更多
This paper presents an experimental analysis of a solar-assisted powered underfloor heating system,designed primarily to boost energy efficiency and achieve reliable desired steady-state temperature in buildings.We th...This paper presents an experimental analysis of a solar-assisted powered underfloor heating system,designed primarily to boost energy efficiency and achieve reliable desired steady-state temperature in buildings.We thoroughly tested the system’s thermal and operational features by subjecting it to three distinct scenarios that mimicked diverse solar irradiance and environmental conditions.Our findings reveal a strong correlation between variations in solar input and overall system performance.The Solar Fraction(SF),our key energy efficiency metric,varied significantly across the cases,ranging from 63.1%up to 88.7%.This high reliance on renewables resulted in a substantial reduction in backup power;consequently,the auxiliary electric heater was only required to supply between 1.82 and 3.00 kWh over the test periods.The circulation pump operated on a precise control logic,engaging below 20℃ and disengaging at 21℃.Crucially,the experiments verified the system’s ability not only tomeet the air temperature setpoint but also to ensure the floor surface temperature stayed within required international comfort criteria.These robust results directly support the study’s main objective.For practical application,we advise increasing the total length of the embedded pipe network.This crucial adjustment would allow for a reduction in the required circulating water temperature,which in turn maximizes the utilization of low-grade solar heat and optimizes radiant heat delivery toward achieving the desired steady-state temperature.Ultimately,the study confirms that solar-assisted underfloor heating offers a technically viable,sustainable,and energy-efficient solution with the potential to significantly cut fossil fuel consumption.展开更多
Radiative cooling passively emits heat to outer space without energy input,offering promise for energy-efficient thermal management.It is an important solution to promote the low-carbon environmental protection strate...Radiative cooling passively emits heat to outer space without energy input,offering promise for energy-efficient thermal management.It is an important solution to promote the low-carbon environmental protection strategy.With the continuous development of radiative cooling technologies,the material selection,preparation process,structural design,and applica-tion fields have also made more diverse progress.Therefore,this review aims to systematically introduce the fundamental concepts and underlying principles of radiative cooling.A summary of the commonly used materials for radiative cooling is provided.In addition,the advanced fabrication processes and structural designs of radiative cooling materials are further explored and discussed.Subsequently,the unique functions of radiative cooling materials are highlighted to enhance their applicability and usefulness across various fields.An overview of combining radiative cooling materials with different fields is also provided.In reality,these applications hold the potential to improve thermal management across a range of fields.Finally,it summarizes the shortcomings and great potential of radiative cooling materials in various fields.It also looks forward to the future,aiming to promote the progress and widespread adoption of radiative cooling technologies.展开更多
Based on the Fluent numerical simulation method,this study systematically analyzed the structural parameters of the spiral tube heat exchanger and the influence of the external baffle on its heat transfer performance....Based on the Fluent numerical simulation method,this study systematically analyzed the structural parameters of the spiral tube heat exchanger and the influence of the external baffle on its heat transfer performance.The results show that when the equivalent diameter of the spiral tube increased from 16.68 to 21.23 mm,its surface heat transfer coefficient decreased from 22,040 to 17,230 W/m^(2)⋅K,and the outlet air temperature dropped from 822.3 to 807.3 K.However,the pressure loss decreased from 2.692 to 0.958 kPa.which reveals the contradiction between the heat transfer efficiency and the flow resistance.By adding a baffle to enhance the turbulent disturbance,the wall heat flux density is increased by 21.17%,the surface heat transfer coefficient is increased by 12.1%,and the outlet temperature is optimized,which verifies the significant improvement of the heat transfer performance by the countercurrent design.Comprehensive research shows that the collaborative optimization of spiral tube equivalent diameter parameters and baffle flow control is the key to improve the comprehensive performance of heat exchanger.Theresearch results provide a theoretical basis for energy-saving design of industrial heat exchangers.展开更多
基金The National Natural Science Foundation of China(No. 51036001 )the Natural Science Foundation of Jiangsu Province(No. BK2010043)
文摘A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.
文摘An analysis of atmospheric SW-radiative forcing and local heating/cooling rate is made using a one year temporal and vertical profiles of aerosol and cloud over Yaoundé (11.51°E, 3.83°N). It appears that the direct influence of aerosols on the surface compared to the TOA can be 3 times larger. Annual mean value obtained at 559 mb altitude is +27.74 W/m2 with range from 0 to +43 W/m2. At 904 mb, we obtained an annual mean of ﹣46.22 W/m2 with range from ﹣65 to ﹣9 W/m2. Frequency distribution indicates that more than 95% of ARF are between +10 and +70 W/m2 at 559 mb (upper limit of UL), and more than 85% of ARF are between ﹣70 and ﹣10 W/m2 at 904 mb (upper limit of PBL). This sign change is explained by the fact that the backscattering peaks at the upper limit of the aerosol PBL layer. The maximum CRF is noted at TOA where it reaches ﹣600 W/m2 based on the time interval and the structure of clouds. The highest values occur between 11.50 and 13.50 LST. Clouds lead to a general heating of the entire atmospheric column with a much greater effect near the surface. Aerosols effect on the heating rate profile show strong cooling during the day for the lower atmosphere, with slight heating at the upper atmosphere. This cooling contribution generally increases from the surface and peacks at the upper boundary of aerosol layer where reflectivity is the most important. Depending on the moment of the day, average heating effect of clouds peacks at surface or within the middle troposphere due to the absorption by clouds particles. Vertical profiles deeply evolve exhibiting differences that exceed ﹣3 K/day according to altitude from one hour to another during a given mean solar day.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金supported by the National Natural Science Foundation of China(Grant No.52476206)the Key R&D Program of Shandong Province,China(Grant No.2025CXGC010203)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515012123)the Shandong Natural Science Foundation(Grant No.ZR2022ME008).
文摘This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.
基金supported by the Henan Provincial Key Research and Development Special Project(251111220200)Natural Science Foundation of Henan Province Project(252300420446).
文摘To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.
基金supported by the National Natural Science Foundation of China(Nos.52275299,52105313)R&D Program of Beijing Municipal Education Commission(No.KM202210005036)+1 种基金Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-MSX0701)National Defense Basic Research Projects of China(No.JCKY2022405C002).
文摘Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.
文摘The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.
基金National Natural Science Foundation of China,Grant/Award Number:52003248Henan Province Youth Health Science and Technology Innovation Talent Training Program,Grant/Award Number:YQRC2023007+1 种基金Henan Province Excellent Youth Science Fund,Grant/Award Number:242300421064Joint Fund Predominant Discipline Cultivation Project of Henan Province,Grant/Award Number:232301420036.
文摘Switchable radiative cooling/heating holds great promise for mitigating the global energy and environmental crisis.Here,we reported a cost-effective,high-strength Janus film through surface optical engineering waste paper with one side decorated by a hydrophobic polymeric cooling coating consisting of micro/nanopore/particle hierarchical structure and the other side coated with hydrophilic MXene nanosheets for heating.The cooling surface demonstrates high solar reflectivity(96.3%)and infrared emissivity(95.5%),resulting in daytime/nighttime sub-ambient radiative cooling of 6℃/8℃with the theoretical cooling power of 100.6 and 138.5Wm^(−2),respectively.The heating surface exhibits high solar absorptivity(83.7%)and low infrared emissivity(15.2%),resulting in excellent radiative heating capacity for vehicle charging pile(~6.2℃)and solar heating performance.Impressively,the mechanical strength of Janus film increased greatly by 563%compared with that of pristine waste paper,which is helpful for its practical applications in various scenarios for switchable radiative thermal management through mechanical flipping.Energy-saving simulation results reveal that significant total energy savings of up to 32.4MJm^(−2) can be achieved annually(corresponding to the 12.4%saving ratio),showing the immense importance of reducing carbon footprint and promoting carbon neutrality.
文摘This paper introduces a thermodynamically grounded framework that replaces conventional energy-centric building simulation with a heat-based reconstruction method,enabling the use of standard-year weather data without bespoke weather files.High-accuracy predictive models are developed to estimate seasonal heating and cooling loads and to derive convective heat transfer coefficients for transitional seasons.Models are calibrated against extended AMeDAS records for Kurume,Fukuoka Prefecture,demonstrating improved capture of local climatic variability compared with standard practice.Methodologically,the study establishes time-series regression relationships linking outdoor air temperature,incident solar radiation,and wind speed to instantaneous thermal demand and surface convective rates.These empirical relations feed a reconstruction algorithm that adjusts simulation outputs to standardized climatic conditions by rescaling heat flows and convective parameters rather than altering meteorological inputs.Results indicate that reframing simulation inputs in terms of heat enhances reliability and transferability of performance predictions and reduces uncertainty associated with variable weather.The paper examines essential assumptions affecting applicability,including the assumed linearity of convective correlations,representativeness of the reference building envelope,and the use of virtual walls for parameter identification.It further proposes a novel procedure to compute a physical adjustment coefficient for the convective heat transfer coefficient,addressing a parameter gap in macro-scale models while acknowledging challenges for conventional comparative validation.The authors recommend future work on automated calibration routines and on extending the method to tropical and arid climates to broaden applicability and support foundational reform of building energy simulation.
文摘The aim of the present analysis concerns the magnetohydrodynamic flow of fluid which is natural convective and electrically charged through two vertical insulated walls.Influences of radiative heat flux,induced magnetic field,and the Newtonian heating/cooling are taken.We found exact expressions for the temperature field,the velocity field,and the induced magnetic field by solving the set of dimensionless coupled governing equations.Further,we obtained the equations for induced current density,Nusselt number,skin frictions as well as mass flux.The influences of the several constraints like the magnetic,the radiation and the Newtonian heating/cooling on the profiles of the velocity,the temperature field,the induced magnetic field as well as the current density display with graphics.Moreover,the influence of these non-dimensional parameters on the skin frictions,the Nusselt number,and the mass flux is explored in tabular form.The outcome of the radiation raised the velocity,the temperature field,the induced magnetic field and the current density field in view of enhancing the thickness of the boundary layer.Also,the impact of Newtonian heating is to raise the velocity,temperature,induced magnetic field and induced current density,whereas all these fields have opposite behaviors in case of Newtonian cooling.
文摘The knowledge representation mode and inference control strategy were analyzed according to the specialties of air-conditioning cooling/heating sources selection. The constructing idea and working procedure for knowledge base and inference engine were proposed while the realization technique of the C language was discussed. An intelligent decision support system (IDSS) model based on such knowledge representation and inference mechanism was developed by domain engineers. The model was verified to have a small kernel and powerful capability in list processing and data driving, which was successfully used in the design of a cooling/heating sources system for a large-sized office building.
基金Financially supported by the Doctoral Fund of Ministry of Education of China(No.20126101120015)Natural Science Foundation of Education Department of Shaanxi Provincial Government(2013JK0619)
文摘An advanced control concept, Predictive Functional Control （PFC）, is applied for temperature control of a bench-scaled batch reactor equipped with monofluid heating/cooling system. First principles process models are developed. Based on achieved models, significant process variables, which are difficult or impossible to measure online, are estimated from easily measured variables, and cascade PFC control strategy has been projected and implemented in Matlab RI 4. The dynamics of individual subunits is explicitly taken into consideration by internal model in the control algorithms, and model uncertainty, various process disturbances are compensated by modifi- cation of internal model. The experimental results present an excellent capability of tracking the set point, and the success of PFC technique as a process control paradigm is illustratively demonstrated.
基金financial support from the National Natural Science Foundation of China(Grant No.52273067,52233006)the Fundamental Research Funds for the Central Universities(Grant No.2232023A-03)+3 种基金the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(Grant No.23SG29)the Natural Science Foundation of Shanghai(Grant No.24ZR1402400)the Shanghai Scientific and Technological Innovation Project(Grant No.24520713000)Innovation Program of Shanghai Municipal Education Commission(Grant No.2021-01-07-00-03-E00108).
文摘Radiative cooling textiles with spectrally selective surfaces offer a promising energy-efficient approach for sub-ambient cooling of outdoor objects and individuals.However,the spectrally selective mid-infrared emission of these textiles significantly hinders their efficient radiative heat exchange with self-heated objects,thereby posing a significant challenge to their versatile cooling applicability.Herein,we present a bicomponent blow spinning strategy for the production of scalable,ultra-flexible,and healable textiles featuring a tailored dual gradient in both chemical composition and fiber diameter.The gradient in the fiber diameter of this textile introduces a hierarchically porous structure across the sunlight incident area,thereby achieving a competitive solar reflectivity of 98.7%on its outer surface.Additionally,the gradient in the chemical composition of this textile contributes to the formation of Janus infrared-absorbing surfaces:The outer surface demonstrates a high mid-infrared emission,whereas the inner surface shows a broad infrared absorptivity,facilitating radiative heat exchange with underlying self-heated objects.Consequently,this textile demonstrates multi-scenario radiative cooling capabilities,enabling versatile outdoor cooling for unheated objects by 7.8℃ and self-heated objects by 13.6℃,compared to commercial sunshade fabrics.
基金National Natural Science Foundation of China(11875039)Shanxi Scholarship Council of China(2023-033)+2 种基金Fundamental Research Program of Shanxi Province(202303021221071)China Baowu Low Carbon Metallurgical Innovation Foundation(2022)2023 Anhui Major Industrial Innovation Plan Project。
文摘The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.
基金supported by the Science and Technology Projects of Xizang Autonomous Region,China (Grant No.XZ202501ZY0080)。
文摘An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature uniformity. To address the high energy consumption of secondary cooling loops in vehicles for cooling immersion oil, this paper proposes a method of immersion coupled cooling tubes. Battery heat is directly absorbed by the immersion liquid and rapidly dissipated via cooling water in the S-type cooling tube(SCT). This work investigated the effects of structural parameters, immersion fluid medium, and operating parameters on the cooling performance of the BTMS. The results showed that the fin height(h_(f)) has no significant effect on the cooling performance. Both Transformer Oil and HFE-7100 delivered outstanding thermal management, reaching a maximum of 36.73℃ and 41.39℃ while maintaining narrow temperature differences of only 3.70℃ and 2.09℃ apart, respectively. When the ambient temperature reached 40℃ and HFE-7100 was used as the immersion liquid, the maximum temperature difference remained consistently below 3℃. Subsequently, a sensitivity analysis was conducted on the respective influential parameters. It was found that inlet water temperature(T_(in)) and immersion fluids exert the most significant influence on the system performance. Finally, different immersion cooling schemes were compared, which demonstrated the advantages of the system proposed in this study under harsh condition, thereby supporting the application of different schemes under various scenarios. It can be directly integrated with the vehicle-mounted cooling circuit system, thereby reducing energy consumption and weight, and offering new insights for research on thermal management systems for EVs.
基金supported by the Jiangsu Association for Science and Technology,grant number SKX 0225089the National Natural Science Foundation of China,grant number 52476027.
文摘In this study,a Gaussian Process Regression(GPR)surrogate model coupled with a Bayesian optimization algorithm was employed for the single-objective design optimization of fan-shaped film cooling holes on a concave wall.Fan-shaped holes,commonly used in gas turbines and aerospace applications,flare toward the exit to form a protective cooling film over hot surfaces,enhancing thermal protection compared to cylindrical holes.An initial hole configuration was used to improve adiabatic cooling efficiency.Design variables included the hole injection angle,forward expansion angle,lateral expansion angle,and aperture ratio,while the objective function was the average adiabatic cooling efficiency of the concave wall surface.Optimization was performed at two representative blowing ratios,M=1.0 and M=1.5,using the GPR-based surrogate model to accelerate exploration,with the Bayesian algorithm identifying optimal configurations.Results indicate that the optimized fan-shaped holes increased cooling efficiency by 15.2%and 12.3%at low and high blowing ratios,respectively.Analysis of flow and thermal fields further revealed how the optimized geometry influenced coolant distribution and heat transfer,providing insight into the mechanisms driving the improved cooling performance.
基金support of the National Natural Science Foundation of China(grant 22508184 to X.Q.Y.,grant 21736006 to S.C.,and grant 22278225 to S.C.)supported by the Natural Funding Program of Jiangsu Province(grant BK20250610 to X.Q.Y.).
文摘Methods allowing passive daytime radiative cooling(PDRC)to be carried out in an energy-efficient and scalable way are potentially important for various disciplines.Here,we report a sustainable strategy for scalable-designed and color-regulating PDRC coating based on high-crystallinity photonic metamaterial(crystallinity:71.5%;enhanced assembly efficiency:72%),that is derived from the as-prepared 55 wt%solid content poly(methyl methacrylate-butyl acrylate-methacrylic acid)P(MMA-BA-MAA)monodispersed latexes(approaching theoretical limit:59 wt%).Robust meter-scale PDRC coatings are constructed by various industrial modes onto diverse surfaces,addressing bottlenecks like dull appearance,high cost,low efficiency,and hard construction.Notably,the solar reflectance,long-wave infrared emittance,and calculated theoretical cooling power of the designed PDRC coating,respectively,reach~0.94,~0.97,and~95.5 W m^(-2)under solar radiation,which can achieve an average 5.3℃sub-ambient daytime temperature drop in the summer in Nanjing.The cooling performance,scale preparation,and cost-effectiveness of the PDRC coating have extended into leading position compared with those of state-of-the-art designs.This work provides promising route to reduce carbon emissions and energy consumption for global sustainability.
文摘This paper presents an experimental analysis of a solar-assisted powered underfloor heating system,designed primarily to boost energy efficiency and achieve reliable desired steady-state temperature in buildings.We thoroughly tested the system’s thermal and operational features by subjecting it to three distinct scenarios that mimicked diverse solar irradiance and environmental conditions.Our findings reveal a strong correlation between variations in solar input and overall system performance.The Solar Fraction(SF),our key energy efficiency metric,varied significantly across the cases,ranging from 63.1%up to 88.7%.This high reliance on renewables resulted in a substantial reduction in backup power;consequently,the auxiliary electric heater was only required to supply between 1.82 and 3.00 kWh over the test periods.The circulation pump operated on a precise control logic,engaging below 20℃ and disengaging at 21℃.Crucially,the experiments verified the system’s ability not only tomeet the air temperature setpoint but also to ensure the floor surface temperature stayed within required international comfort criteria.These robust results directly support the study’s main objective.For practical application,we advise increasing the total length of the embedded pipe network.This crucial adjustment would allow for a reduction in the required circulating water temperature,which in turn maximizes the utilization of low-grade solar heat and optimizes radiant heat delivery toward achieving the desired steady-state temperature.Ultimately,the study confirms that solar-assisted underfloor heating offers a technically viable,sustainable,and energy-efficient solution with the potential to significantly cut fossil fuel consumption.
基金National Natural Science Foundation of China Excellent Youth Fund(No.52222509)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.52021003)+3 种基金National Key Research and Development Program of China(No.2018YFA0703300)National Natural Science Foundation of China(No.52105298)Science and Technology Development Program of Jilin Province(No.SKL202402005)"Fundamental Research Funds for the Central Universities".
文摘Radiative cooling passively emits heat to outer space without energy input,offering promise for energy-efficient thermal management.It is an important solution to promote the low-carbon environmental protection strategy.With the continuous development of radiative cooling technologies,the material selection,preparation process,structural design,and applica-tion fields have also made more diverse progress.Therefore,this review aims to systematically introduce the fundamental concepts and underlying principles of radiative cooling.A summary of the commonly used materials for radiative cooling is provided.In addition,the advanced fabrication processes and structural designs of radiative cooling materials are further explored and discussed.Subsequently,the unique functions of radiative cooling materials are highlighted to enhance their applicability and usefulness across various fields.An overview of combining radiative cooling materials with different fields is also provided.In reality,these applications hold the potential to improve thermal management across a range of fields.Finally,it summarizes the shortcomings and great potential of radiative cooling materials in various fields.It also looks forward to the future,aiming to promote the progress and widespread adoption of radiative cooling technologies.
基金supported by the Jing-Jin-Ji Regional Integrated Environmental Improvement-National Science and Technology Major Project(No.2024ZD1200400).
文摘Based on the Fluent numerical simulation method,this study systematically analyzed the structural parameters of the spiral tube heat exchanger and the influence of the external baffle on its heat transfer performance.The results show that when the equivalent diameter of the spiral tube increased from 16.68 to 21.23 mm,its surface heat transfer coefficient decreased from 22,040 to 17,230 W/m^(2)⋅K,and the outlet air temperature dropped from 822.3 to 807.3 K.However,the pressure loss decreased from 2.692 to 0.958 kPa.which reveals the contradiction between the heat transfer efficiency and the flow resistance.By adding a baffle to enhance the turbulent disturbance,the wall heat flux density is increased by 21.17%,the surface heat transfer coefficient is increased by 12.1%,and the outlet temperature is optimized,which verifies the significant improvement of the heat transfer performance by the countercurrent design.Comprehensive research shows that the collaborative optimization of spiral tube equivalent diameter parameters and baffle flow control is the key to improve the comprehensive performance of heat exchanger.Theresearch results provide a theoretical basis for energy-saving design of industrial heat exchangers.
