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A Comprehensive Study of a Low-Grade Heat-Driven Cooling and Power System Based on Heat Current Method

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Journal of thermal science 2024年第4期33卷 1523-1541页

作者： ZHAO Tian XU Ronghong XIN Yonglin HE Kelun MA Huan YUAN Mengdi CHEN Qun School of energy Storage science and engineering North China University of Technology Key Laboratory for thermal science and Power engineering of Ministry of Education Department of Engineering MechanicsTsinghua University

Combined cooling and power(CCP) system driven by low-grade heat is promising for improving energy efficiency.This work proposes a CCP system that integrates a regenerative organic Rankine cycle(RORC)and an absorption chiller on both driving and cooling fluid sides.The system is modeled by using the heat current method to fully consider nonlinear heat transfer and heat-work conversion constraints and resolve its behavior accurately.The off-design system simulation is performed next,showing that the fluid inlet temperatures and flow rates of cooling water as well as RORC working fluid strongly affect system performance.The off-design operation even becomes infeasible when parameters deviate from nominal values largely due to limited heat transfer capability of components,highlighting the importance of considering heat transfer constraints via heat current method.Design optimization aiming to minimize the total thermal conductance is also conducted.RORC efficiency increases by 7.9% and decreases by 12.4% after optimization,with the hot fluid inlet temperature increase from 373.15 to 403.15 K and mass flow rate ranges from 10 to 30 kg/s,emphasizing the necessity of balancing system cost and performance.

关键词： combined cooling and power system organic Rankine cycle absorption chiller cascade heat utilization heat current method off-design analysis

Spectral Selectivity of CdTe Cells with Substrate Configuration for Photovoltaic/thermal Applications

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Journal of thermal science 2024年第4期33卷 1542-1553页

作者： CHEN Ken HU Kongfu ZHAO Bin CHEN Tao HAO Yong PEI Gang department of thermal science and energy engineering University of Science and Technology of China Key Laboratory of Solar thermal Conversion of Anhui Province Hefei National Laboratory for Physical sciences at Microscale Department of Materials Science and EngineeringUniversity of Science and Technology of China Institute of engineering Thermophysics Chinese Academy of Sciences University of Chinese Academy of sciences

Existing photovoltaic cells with high infrared emissivity generate huge radiative heat loss in photovoltaic/thermal applications and degrade the photothermal performance.The purpose of this work is to evaluate the full spectral absorptivity of CdTe cells to find a spectrally selective photovoltaic cell for photovoltaic/thermal applications.To this end,the solar absorptivity and mid-infrared thermal emissivity of CdTe cells were tested by ellipsometry,UV-Vis-NIR spectrophotometer,and Fourier transform infrared spectrometer.The experimental results show that the AM 1.5 solar spectrum weighted absorptivity of the substrate configuration CdTe cell reaches 0.91,and the mid-infrared emissivity is only 0.29,while the superstrate configuration cell emissivity is as high as 0.9.Further research shows that substrate configuration with a transparent conductive layer on top can be flexibly grown on metal foils and has spectral selectivity with high solar absorptivity and low mid-infrared emissivity should be considered in the future for photovoltaic/thermal applications.

关键词： photovoltaic/thermal spectral selectivity substrate configuration CdTe cell ITO

The feasibility analysis of the application of TPV system in reentry

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science China(Technological sciences) 2010年第12期53卷 3310-3315页

作者： YE Hong & GENG Xue department of thermal science and energy engineering, University of science and Technology of China, Hefei 230027, China department of thermal science and energy engineering University of Science and Technology of China Hefei China

A fundamental design of using thermophotovoltaic (TPV) system to convert the huge aerodynamic heat into electricity during the reentry process was described. The influences of heat conducting way, spectral filter and selective radiating surface on the system performance were analyzed in detail. The results showed that as a thermal conducting component, SiC is better than ablation material, with more electricity output but a larger cooling load, and that the adoption of spectral filter and selective radiating surface could lower the power output to some extent, yet diminish the cooling load prominently.

关键词： TPV reentry process spectral filter selective radiating surface

Review on heat-to-power conversion technologies for hypersonic vehicles

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Chinese Journal of Aeronautics 2024年第5期37卷 148-179页

作者： Yinke QI Xiaofeng MA Peixue JIANG Yinhai ZHU Key Laboratory for thermal science and Power engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Beijing Key Laboratory of CO_(2)Utilization and Reduction Technology Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and duration.Converting the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the vehicle.This paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined conversion.For the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the system.However,its work capacity is limited by the flow rate of the supplied fuel.The closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion efficiency.The Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about 0.88.The thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power demand.This review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.

关键词： Hypersonic vehicles Heat-to-power conversion Brayton cycle Rankine cycle Thermoelectric materials

Promoting effect of FeOx addition on the mechanochemically prepared vanadium-based catalyst for real PCDD/Fs removal and mechanism insight

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Journal of Environmental sciences 2024年第3期137卷 478-487页

作者： Minghui Tang Ling Wang Hongxian Li Xinlei Huang Cuicui Du Shengyong Lu State Key Laboratory for Clean energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou 310027China

Industrial-use VOx-based catalysts usually have a higher active temperature window (>250-300℃),which becomes a“bottleneck”for the practical application of PCDD/Fs catalytic degradation technology.In this work,VO_(x)-FeO_(x)/TiO_(2) catalyst prepared via mechanochemically method was investigated for the catalytic removal of PCDD/Fs.The removal efficiency of 1,2-DCBz,pure PCDD/Fs gas generated in the lab,PCDD/Fs from actual fue gas,long-term were studied,and the degradation mechanism was explored using FTIR and TOFMS.The degradation efficiency of 1,2-DCBz and PCDD/Fs on VO_(x)-FeO_(x)/TiO_(2) were higher than that of VO_(x)/TiO_(2)catalyst,and the optimal FeOx addition ratio was 3 wt.%.The characterization results show that the addition of FeOx can effectively improve the pore structure,surface acidity,and VOx dispersion of the catalyst,thus contributing to increasing the V^(5+)content and surface-active oxygen,which is conducive to the improvement of adsorption and redox performance of the catalyst.Under the actual MSWI (municipal solid waste incineration)fue gas,the PCDD/Fs removal efficiency over VTi-3Fe-MC maintained long-term stability,higher than 85%for 240 min.This result was not significantly reduced compared with the data obtained in the laboratory.According to the analysis results of intermediate products by FTIR and GC-TOFMS,it can be inferred that the epoxidation fracture of benzene ring is the rate-limiting step of dioxin catalytic degradation reaction.This work gives an in-depth view into the PCDD/Fs removal over VO_(x)-FeO_(x)/TiO_(2) catalysts and could provide guidelines for the rational design of reliable catalysts for industrial applications.

关键词： PCDD/F removal MSWI fue gas VO_(x)-FeO_(x)/TiO_(2) Mechanochemical GC-TOFMS

Optimization of the inhibition of atmospheric window emission using photonic crystals

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science China(Technological sciences) 2010年第5期53卷 1315-1319页

作者： LI Jin & YE Hong department of thermal science and energy and engineering,University of science and Technology of China,Hefei 230026,China department of thermal science and energy and engineering University of Science and Technology of China Hefei China

Transfer matrix method is used to discuss the effect inhibition of photonic crystals on atmospheric window emission(ε-14 μm).According to the optical characteristics of the materials,germanium and zinc sulfide are used as the composing materials.The structure of the photonic crystals is optimized,and the optimal thickness values of the germanium and zinc sulfide are 0.63 and 1.11μm respectively while the ratio of optical thickness is 1:1 and the period is 8.The photonic crystals are prepared by evaporation coating method,and the optical properties of the photonic crystals are measured,the inhibition of the photonic crystals to atmospheric window emission is verified.

关键词： photonic crystals emission at atmospheric window inhibition

Design and performance investigation of modified dual reflector parabolic trough collector with double planar mirrors

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science China(Technological sciences) 2024年第3期67卷 902-918页

作者： LI Peijing LIU TaiXiu QIN YuanLong LI JiChao LIU QiBin School of energy Powerand Mechanical EngineeringNorth China Electric Power University Beijing 226China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of sciences Beijing 100049China department of thermal science and energy engineering University of Science and Technology of ChinaHefei 230027China

In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.

关键词： solar thermal energy parabolic trough collector secondary reflector solar flux distribution optical optimization

Effective temperature and exergy of monochromic blackbody radiation

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Progress in Natural science:Materials International 2007年第10期17卷 1250-1254页

作者： Chen Zeshao and Mo Songping(department of thermal science and energy engineering, University of science and Technology of China, Hefei 230027, China) department of thermal science and energy engineering University of Science and Technology of China Hefei 230027 China

A new parameter named monochromic effective temperature Tλ is proposed, which represents the thermodynamic quality of monochromic blackbody radiation. The exergy of the monochromic blackbody radiation is expressed by Tλ. The monochromic effective temperature equation is developed, which shows that the product of Tλ and the wavelength is constant, which equals 5.33016×10-3 m·K. The exergy function of monochromic blackbody radiation is presented. The cause of the view that there is negative entropy production in photosynthesis can be explained by the results of this work.

关键词： photon monochromic effective temperature exergy of monochromic radiation.

Demonstration of a small‐scale power generator using supercritical CO_(2)

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Carbon energy 2024年第4期6卷 269-290页

作者： Ligeng Li Hua Tian Xin Lin Xianyu Zeng Yurong Wang Weilin Zhuge Lingfeng Shi Xuan Wang Xingyu Liang Gequn Shu State Key Laboratory of Engines Tianjin UniversityTianjinChina department of thermal science and energy engineering University of Science and Technology of ChinaHefeiChina State Key Laboratory of Automotive Safety and energy Tsinghua UniversityBeijingChina

The supercritical CO_(2)(sCO_(2))power cycle could improve efficiencies for a wide range of thermal power plants.The sCO_(2)turbine generator plays an important role in the sCO_(2)power cycle by directly converting thermal energy into mechanical work and electric power.The operation of the generator encounters challenges,including high temperature,high pressure,high rotational speed,and other engineering problems,such as leakage.Experimental studies of sCO_(2)turbines are insufficient because of the significant difficulties in turbine manufacturing and system construction.Unlike most experimental investigations that primarily focus on 100 kW‐or MW‐scale power generation systems,we consider,for the first time,a small‐scale power generator using sCO_(2).A partial admission axial turbine was designed and manufactured with a rated rotational speed of 40,000 rpm,and a CO_(2)transcritical power cycle test loop was constructed to validate the performance of our manufactured generator.A resistant gas was proposed in the constructed turbine expander to solve the leakage issue.Both dynamic and steady performances were investigated.The results indicated that a peak electric power of 11.55 kW was achieved at 29,369 rpm.The maximum total efficiency of the turbo‐generator was 58.98%,which was affected by both the turbine rotational speed and pressure ratio,according to the proposed performance map.

关键词： generator performance map power generation supercritical CO_(2) turbine