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Inverse analysis of radiative properties of internal medium and surface for cylindrical system using CSM-CGM approach

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2023年第1期190卷

作者： Zhang, Chao Li, Ben-Wen Zhou, Rui-Rui Li, Pan-Xin Huang, Ling-Yun Dalian Univ Technol Sch Energy & Power Engn Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Kunming Univ Sci & Technol Fac Land Resource Engn State Key Lab Complex Nonferrous Met Resources Cle Kunming 650093 Peoples R China

An inverse analysis is conducted to simultaneously estimate the radiative properties in a 2D cylindrical system including the extinction coefficient, scattering albedo, and the wall emissivity from the knowledge of the radi-ative heat flux over different boundaries. In which the collocation spectral method (CSM) is developed to solve the forward problem, the conjugate gradient method (CGM) is employed to solve the inverse problem, and the complex-variable-differentiation method is used to treat the sensitivity problem, separately. Meanwhile, the effects of measurement errors, initial values, and imaginary values of complex variables on the precision of the inverse analysis are investigated. Results show that the proposed inverse analysis can successfully retrieve the unknown radiative physical properties of 2D cylindrical system. Under the same physical properties, good inversion results can be obtained by using different wall (end walls and side wall) radiative heat fluxes, but the inversion efficiency from sidewall radiative heat flux is higher. Besides, it is found that, the inversion for the scattered participating medium is more efficient than that for the non-scattered participating medium;the true values and iterative convergence values have little effect on the inversion result;the influence of the initial values and the imaginary values of the complex variable on the inversion cannot be ignored.

关键词： Inverse analysis Radiative physical properties Collocation spectral method Conjugate gradient method Complex-variable-differentiation method 2D cylindrical system

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An experimental investigation on the frosting and defrosting process of an outdoor heat exchanger in an air conditioning heat pump system for electric vehicles

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APPLIED THERMAL engineering 2022年第PartA期201卷 117766-117766页

作者： Li, Kang Xia, Dingyu Luo, Shuxian Zhao, Yugang Tu, Ran Zhou, Xuejin Zhang, Huiqi Su, Lin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai 200093 Peoples R China Huaqiao Univ Coll Mech Engn & Automat Xiamen 361021 Fujian Peoples R China

The heat pump air conditioning system is a promising solution for energy conservation and ensuring a good driving range can be maintained. Micro-channel heat exchangers are used as outdoor heat exchangers to improve the heat transfer efficiency. A heat pump system introduces frosting problems to the outdoor heat exchanger, especially in a low temperature and high humidity environment. This study conducted an experiment on the frosting and defrosting process of the outdoor heat exchanger of a heat pump air conditioning system for electric vehicles. The surface of the outside heat exchanger had an uneven distribution of the frost layer owing to the variation in the liquid-phase refrigeration occupation. Thermal parameters of the system were obtained. The suction pressure was sensitive to the frosting process, decreasing from (0.15-0.25) to (0.02-0.1) MPa, and it can be used as a frosting monitoring parameter. The frosting and defrosting behavior was also studied at a micrometer scale on the surface of the heat exchanger. The ice bridge phenomenon was observed in the frosting process. Hydrophilic and hydrophobic treatments of the heat exchanger surface were conducted for compassion and it was found that the hydrophilic treatment of the surface of the outdoor heat exchanger of the vehicle heat pump effectively slows frosting. Future experimental research should investigate the effects of superhydrophobic and superhydrophilic surface treatments, in addition to hydrophilic and hydrophobic surface treatments on the performance of the heat exchanger, to improve the performance of the overall heat pump system.

关键词： heat pump Frosting and defrosting Outside heat exchanger Frost coverage rate Electric vehicle

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Numerical simulation of non-Fourier heat conduction in fins by lattice Boltzmann method

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APPLIED THERMAL engineering 2020年第0期166卷 114670-000页

作者： Liu, Yi Li, Ling Zhang, Yuwen Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China Univ Missouri Dept Mech & Aerosp Engn Columbia MO 65211 USA

The addition of fin to the surface of microelectronic elements is a very effective way to enhance their heat transfer rate. Since the heat generation of the microelectronic elements is very fast, the Fourier law is no longer valid and the non-Fourier effect must be considered when designing a fin. Cattaneo - Vemotte model (CV model) is the most common model that is used to describe the non-Fourier effect in heat conduction. The mathematical expression of the CV model is essentially a wave equation. The lattice Boltzmann method (LBM) can be used to solve the wave equation in the CV heat conduction problem. In this paper, LBM is used to solve the non-Fourier heat conduction in a fin under periodic boundary conditions. Effects of relaxation time, shape and the frequency of the base temperature oscillations on heat transfer efficiency are analyzed.

关键词： Lattice Boltzmann method Non-Fourier heat conduction heat transfer and efficiency of fin

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Hydrochar prepared from municipal sewage sludge as renewable fuels: Evaluation of its devolatilization performance, reaction mechanism, and thermodynamic property

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JOURNAL OF ENVIRONMENTAL CHEMICAL engineering 2022年第5期10卷

作者： Liu, Weike Zheng, Xiaoyuan Ying, Zhi Feng, Yuheng Wang, Bo Dou, Binlin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Tongji Univ Thermal & Environm Engn Inst Sch Mech Engn Shanghai 200092 Peoples R China

Hydrothermal treatment (HT) of sewage sludge (SS) is a promising method to improve its dewaterability. Effect of HT on devolatilization performance, kinetic parameters, and thermodynamic property during the pyrolysis of SS was investigated by thermogravimetric analysis (TGA), isoconversional method, and master plots method. Derivative thermogravimetry (DTG) curves showed two distinct devolatilization peaks #1 at 283.21 ? and #2 at 327. 43 ? along with a shoulder between 400 and 600 ?. HT temperature influenced peak #2 more significantly as its peak devolatilization rate decreased consecutively from 4.25 % to 1.70 %center dot min(-1). Meanwhile it moved towards higher temperature and overlapped with the shoulder ultimately. The value of comprehensive pyrolysis index (CPI) decreased greatly from 3.37 x 10(-5) to 1.24 x 10(-6) %3 center dot?(-3)center dot min(-2) with HT temperature. Activation energy was determined by Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Starink, and Friedman methods. It generally increased against conversion with diverse variation patterns. Its average value reduced obviously after HT. Despite HT, all samples followed identical Avrami-Erofeev model with decreased order of reaction from 7.60 to 6.56. The variation trends of enthalpy, Gibbs free energy, and entropy verified that HT improved the thermal stability of SS, which coincided with CPI. Pyrolysis process of SS evolved from ordered state to disordered state, indicating increased reactivity due to the probable catalytic effect of inorganics in the ash. The work provides guidance for the design, optimization, and upscale of pyrolysis reactors and operation parameters when SS is utilized as renewable fuels.

关键词： Hydrothermal treatment Pyrolysis Kinetics Isoconversional method Master plots

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Aerodynamic performance of horizontal axis wind turbine with application of dolphin head-shape and lever movement of skeleton bionic airfoils

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ENERGY CONVERSION AND MANAGEMENT 2022年 267卷

作者： Huang, Shengxian Qiu, Huihe Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Hong Kong Univ Sci & Technol Dept Mech & Aerosp Engn Clear Water Bay Hong Kong Peoples R China

In order to continuously develop the special airfoil for wind turbine and further improve the energy efficiency of wind turbine, based on the bionic airfoil Dol-Rot 24 degrees that was proposed by the streamline contour of the Phocoenoides Dalli, another novel bionic airfoil is constructed combined with the lever movement shape of the dolphin skeleton, and the airfoil is named Dol-Rot 24 degrees-2. For the cross section of NREL phase VI horizontal axis wind turbine blade (S809 airfoil), Dol-Rot 24 degrees, and Dol-Rot 24 degrees-2 are adopted and numerically simulated to quantitatively analyze from both aspects of aerodynamic performance and noise characteristics. Using the above two novel airfoils profiles, two 3D bionic blades named Dol-Blade-1 and Dol-Blade-2 suitable for NREL phase VI HAWT are established. The results show that: compared with S809 airfoil, Dol-Rot 24 degrees-2 airfoil can greatly improve the lift coefficient, while Dol-Rot 24 degrees airfoil can more effectively inhibit the flow separation on the suction surface. In terms of noise characteristics, compared with S809 airfoil, the noise of the two types of dolphin airfoils does not increase significantly. In addition, Dol-Blade-1 can comprehensively improve the low-speed shaft torque of the blade, while the load of the wind turbine hardly changes. The low-speed shaft torque of Dol-Blade-2 is even better than that of Dol-Blade-1. However, the blade root bending moment of Dol-Blade-2 increases obviously, which inevitably increases the load of the wind turbine. In this paper, the new bionic method is proposed to improve the wind energy utilization of wind turbine on the premise of strictly controlling the aerodynamic noise and load level of blade. The research results of this paper can provide a reference for the optimization of energy efficiency and noise research of NREL phase VI HAWT.

关键词： CFD Airfoil HAWT engineering bionics Aerodynamic performance Aerodynamic noise

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Enhanced transformation of phosphorus (P) in sewage sludge to hydroxyapatite via hydrothermal carbonization and calcium-based additive

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SCIENCE OF THE TOTAL ENVIRONMENT 2020年 738卷 139786-139786页

作者： Zheng, Xiaoyuan Ye, Yutong Jiang, Zhengwei Ying, Zhi Ji, Shasha Chen, Wei Wang, Bo Dou, Binlin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shanghai Urban Construct Design & Res Inst Shanghai 200125 Peoples R China

Phosphorus (P) recovery from sewage sludge is one of the promising substitutes to the phosphate ores to alleviate the shortage of P supply in the future. In this study, how hydrothermal carbonization (HTC) temperature functioned in the migration and transformation of P from sewage sludge during HTC process was clarified. The enhancement effect of Ca-based additive on the transformation of P to hydroxyapatite via HTC was systematically studied. Additionally, leaching characteristics of P in the hydrochars with Ca-based additive were analyzed to assess their P-bioavailability. Results indicated that favoring by increased pH in the process water, HTC temperature played a significant role in the migration and transformation of P during HTC. Therefore, higher HTC temperature was beneficial for P enrichment and transformation to apatite phosphorus in the hydrochars. Both alkaline environment and existence of sufficient calcium ions were essential for enhanced formation of apatite phosphorus during HTC. Adding CaO could stimulate almost complete transformation of non-apatite inorganic phosphorus to apatite phosphorus such as hydroxyapatite, causing a maximum increase of apatite phosphorus by 252%. Concurrently, P-bioavailability by 2% (w/w) formic acid extraction of the hydrochars increased by 233% at CaO=4%. These findings were confirmed by XRD analyses. Ca-associated apatite phosphorus such as Ca-5(PO4)(3)OH and Ca2P2O7 center dot 2H(2)O, was detected in the hydrochars. With the assistance of thermochemical calculation, transformation pathways of P after CaO addition have been proposed, which coincided with our experimental results well. The stable P-containing minerals of hydroxyapatite (Ca-5(PO4)(3)OH) was calculated at equilibrium state. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Sewage sludge Hydrothermal carbonization Hydrochar Phosphorus bioavailability Hydroxyapatite Thermochemical equilibrium

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Efficient anchoring of nanoscale Pd on three-dimensional carbon hybrid as highly active and stable catalyst for electro-oxidation of formic acid

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APPLIED CATALYSIS B-ENVIRONMENTAL 2020年 263卷 1页

作者： Yang, Liang Wang, Xin Liu, Daoping Cui, Guomin Dou, Binlin Wang, Juan Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Sch Energy & Power Engn 561 Jungong Rd Shanghai 200093 Peoples R China Shanghai Univ Elect Power Sch Environm & Chem Engn 2588 Changyang Rd Shanghai 200090 Peoples R China

The commercialization of fuel cells requires the design and development of novel effective electrocatalysts. Thus, considerable efforts have been directed at the synthesis of supported electrocatalyst particles with an optimum size of < 6 nm and controlled shape/size. To date, although most studies have focused on the exploitation of supports facilitating charge/mass transfer and capable of inhibiting catalyst sintering/detachment during the catalytic process, comprehensive and straightforward investigation of the anchoring effect and the stabilization mechanism of complex hybrid supports with tunable electronic properties and tuned morphologies remain challenging. Herein, we prepare nanoscale Pd supported by a three-dimensional hybrid of boron-doped graphene with carbon nitride (Pd/BG-CN). The results show that the mass (2215 mA mg(-1)) and specific (31.7 mA cm(-2)) activities of Pd/BG-CN for formic acid oxidation are 2.8- and 2.5-fold higher than those of commercial Pd/C, respectively. This enhanced activity was ascribed to the electronic effect of the BG-CN substrate and the high content of surface metallic Pd-0 (55.2 at%). Moreover, identical-location transmission electron microscopy imaging show that the stabilization of Pd particles on BG-CN and the strong anchoring effect of this support reduced the extent of active Pd detachment, whereas the weakening of metal-carbon support interactions in commercial Pd/C resulted in remarkable performance degradation. Theoretical calculations of the intrinsic stabilization mechanism of Pd/BG-CN reveal that BG-CN could efficiently trap Pd atoms, which could accumulate and form Pd clusters at trapping (nucleation) sites.

关键词： Carbon hybrid Formic acid oxidation Anchoring effect Stabilization mechanism

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Molecular dynamics simulation of explosive boiling of the H2O-Cu nanofluid

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JOURNAL OF MOLECULAR LIQUIDS 2021年 332卷 115847-115847页

作者： Wang, Zhao Li, Ling Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

In this paper, molecular dynamics simulations are used to study the effect of the Cu nanoparticle and wall surface wettability on the explosive boiling of H2O-Cu nanofluids. The influence of the nanoparticle wettability, the wall surface wettability and the size of nanoparticles on explosive boiling is analyzed. The results show that when the wall superheat is the same, the hydrophilic nanofluid will explode fastest on the hydrophilic surface. The nanoparticle enhances the heat transfer during the boiling process, and the enhancement is more significant on the hydrophobic surface. The increase in the wettability of the nanoparticle reduces the thermal resistance of the solid-liquid interface, thereby enhancing heat transfer. The potential energy of the solid-liquid interface increases with the decrease of the particle size, which also enhances the solid-liquid heat transfer capability. In addition, the temperature gradient, heat exchange and evaporation rate of the hydrophilic surface per unit time are greater than those of the hydrophobic surface. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Explosive boiling H2O-Cu nanofluid Particle diameter Surface wettability

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Non-isothermal kinetics of biomass waste pyrolysis by TG-MS/DSC

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CARBON CAPTURE SCIENCE & TECHNOLOGY 2023年 6卷

作者： Du, Jinbo Dou, Binlin Zhang, Hua Wu, Kai Gao, Daoxing Wang, Yadong Chen, Haisheng Xu, Yujie Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Sch Energy & Power Engn Shanghai 200093 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China

The non-isothermal kinetics and pyrolysis characteristics of biomass waste including camphor wood (CW), pure glycerol (PG) and a blend (1:1 mass ratio) (PG-CW) were studied by coupling TG-MS/DSC techniques. The samples were heated from ambient temperature to 700 degrees C at different heating rates (10, 15, 20 and 25 degrees C/min) in a nitrogen atmosphere. The mass loss during pyrolysis and the evolution of gas products were studied. The improved CoatsRedfern method was used to obtain non-isothermal kinetic parameters for samples pyrolysis, and the activation energies and the pre-exponential factors were estimated iteratively by regression to improve their accuracy. PG had only one main pyrolysis phase, while CW had two main pyrolysis phases. The results showed that adding PG into CW reduced the residue and increased the amount of gas released after co-pyrolysis. The non-isothermal kinetic model based on the improved iterative Coats-Redfern method entirely fitted the pyrolysis phases of CW, PG, and PG-CW. The suitable models for the second, third, and fourth phases of blend were nucleation, nucleation, and one-dimensional diffusion, respectively. Activation energy values for the three phases were 67.47-82.48, 81.13-104.43 and 145.45-204.86 kJ/mol, respectively. The addition of PG promoted the pyrolysis process of CW.

关键词： Camphor wood Glycerol Co-pyrolysis Improved non-isothermal kinetics TG-MS/DSC

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Experimental investigation of the heat transfer performance of an oscillating heat pipe with LiCl salt solution

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INTERNATIONAL JOURNAL OF heat AND MASS transfer 2020年 158卷 120033-120033页

作者： Wang, Peng Cui, Xiaoyu Weng, Jianhua Cai, Ziqiu Cai, Ren Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shanghai Univ Elect Power Coll Energy & Mech Engn Shanghai 200090 Peoples R China

The heat transfer performance of oscillating heat pipes (OHPs) with LiCl solution was investigated experimentally at the concentration of 5wt%, 10wt% and 15wt% with the heat input ranging from 10 to 100 W and the filling ratio (FR) of 45%, 55%, 62%, 70%, 80%, and 90%. OHP with different concentrations of LiCl solution can improve the heat transfer performance compared with deionized water (DW) in most conditions, because of the combined positive effects of bubble characteristics, absorption and generation mechanism, two-phase flow, mass transfer, and other behaviors caused by hygroscopicity of LiCl solution. At an appropriate filling ratio (62% and 70%), the addition of LiCl in DW reduces the thermal resistance of OHP. The thermal resistance of a 62% volume of 10wt% LiCl solution reduces up to 61% compared with DW. At low filling ratio (45% and 55%), LiCl solution can reduce the temperature of the evaporation section and improve the anti-dry-out ability;simultaneously, the higher the concentration, the better the effect. It is due to the low water activity and the characteristics of bubble generation and growth in LiCl solution. At increased filling ratio (80% and 90%), the reduction of the gas phase space inside the OHP and the slowing down of the working fluid make the effect of adding LiCl less on the heat transfer performance, 5wt% LiCl solution performs better than the other concentrations. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Oscillating heat pipe LiCl salt solution Hygroscopicity Phase change Thermal resistance

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