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Analysis on the Thermal Behaviour of the Latent Heat Storage System Using S-Co2 and H-Pcm

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SSRN 2022年

作者： Nan, Wenguang Ming, Zhu Wang, Yueshe School of Mechanical and Power Engineering Nanjing Tech University Nanjing211816 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Energy storage and utilization of CO2 have attracted increasing attention due to international zero carbon plan. Here, the latent heat storage system using high-temperature phase change material (H-PCM) and supercritical CO2 (S-CO2) is analysed by using CFD simulation, in which the tube containing S-CO2 is submerged in a tank containing the salt with high melting temperature. A new and combined phase transition model is developed to describe the dynamics of PCM in different phase state, and it is validated against experimental data in literature. The dynamics of natural convection is focused, and its effects on the heat storage system are analysed, including maximum natural convection velocity, phase interface, and melting pattern. The results show that natural convection has a great influence on the melting process of the H-PCM in the charging process. The melting pattern of H-PCM could be contrary between the cases with and without considering natural convection. During the discharging process, natural convection has little effect on the heat transfer of energy release due to its short duration. With the increase of ratio between the S-CO2 tube and H-PCM tank, the strength of the natural convection of melting H-PCM is enhanced, especially the duration of natural convection. © 2022, The Authors. All rights reserved.

关键词： Natural convection

Prediction of Pressure Drop in Heavy Oil-Water Ring Two-Phase flow Based on Modified Two-Fluid Model

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SSRN 2024年

作者： Fu, Jiqiang Du, Mingjun Jing, Jiaqiang Sun, Jie Liu, Huichao Chen, Yongjiu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China China Petroleum Engineering & Construction Corp North Company Heibei Renqiu062552 China School of Oil & Natural Gas Engineering Southwest Petroleum University Sichuan Chengdu610500 China

Accurate prediction of pressure drop of the heavy oil-water ring flow in pipeline is of great significance for establishing an optimal drag reduction model and ensuring safe production. The effects of different factors on the flow pattern and pressure drop of heavy oil-water annular two-phase flow were systematically analyzed, and a standard two-fluid pressure drop prediction model for annular flow was established. By modifying the shear stress equation of oil-water interface and introducing the wave-flow theory to modify the shear stress equation of water wall, a pressure drop prediction model for the generalized concentric water ring was obtained to calculate the periodic fluctuations of oil phase. Furthermore, by introducing the comprehensive Reynolds number expression of eccentric water ring, the pressure drop prediction model for the generalized eccentric water ring was obtained to calculate the periodic fluctuations of oil phase. The results show that the pressure drop prediction accuracy of the concentric water ring for ultra-heavy oil is improved by 80 % by using the modified pressure drop prediction model. The comprehensive Reynolds number expression of eccentric water ring can effectively reflect the influence of eccentric effect on shear stress of water wall and the calculation error is less than 20 % by predicting the pressure drop of the generalized eccentric water ring with different density differences. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

Thermodynamics analyses on a novel CHP system integrated with multi-grade thermal energy storage

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Journal of Energy Storage 2025年 106卷

作者： Liu, Rongtang Zhang, Kezhen Qin, Yuanzhi Wan, Kaidi Xu, Can Liu, Ming Ningbo Institute of Technology Beihang University Ningbo315800 China Xi'an Thermal Power Research Institute Co. Ltd. Xi'an710054 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Dongfang Boiler Co. Ltd. of Dongfang Electric Group Chengdu611731 China

The high penetration level of intermittent renewable power necessitates the crucial requirement for combined heat and power systems to possess both high efficiency and flexibility. However, the heat-controlled operation modes of traditional combined heat and power systems impose limitations on their efficiency and flexibility. Therefore, it is of great significance to develop a heat-power decoupling technology that exhibits exceptional efficiency and flexibility. A novel combined heat and power system integrated with multi-grade thermal energy storage is proposed in this study. Thermodynamic analysis models of all operational conditions are developed, and the comprehensive characteristics of efficiency and operational flexibility for the proposed system are assessed by taking a 330 MW system as an example. Results show that the proposed system can decrease/increase 1..05 MW/30.96 MW power loads comparing with the reference system during the charging/discharging periods under the design condition. Energy efficiency of the proposed system can reach 49.40 %, which is improved by 1.66 percentage points. Exergy analysis reveals the exergy destruction order for the proposed system, and shows that the combustion and heat transfer in the boiler are the major process of exergy dissipation. Moreover, operation strategies of the proposed system during charging-discharging cycle are explored and formulated under off-design condition, suggesting that thermodynamic performances of the novel system under various conditions even extreme conditions exhibits exceptional properties. The maximum heat load of the proposed system can be improved by 46.78 % comparing with the reference system, and the maximum improvement of power load capacity during charging-discharging cycle is 1..58 percentage points. This study provides a promising approach for multi-grade thermal energy storage to improve the comprehensive characteristics of combined heat and power systems. © 2024

关键词： Charge storage

Catalytic Conversion of Toluene by Biochar Modified with Kmno4

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SSRN 2022年

作者： Jin, Xiaoling Zhang, Kai Jiang, Jiahao Zhu, Zhengrong Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Kunming Institute of Physics Kunming650223 China

This study aims to investigate the effects of biomass species, modification treatment, experimental time and atmosphere on the catalytic conversion of toluene (model tar compound) by the biochar from gasification of oak, wheat straw and Enteromorpha. The gas and liquid phase products are detected by GC and GC-MS, respectively. The physical and chemical characteristics of biochar samples are analyzed by SEM-EDS, XRD and XPS. The results show that the activity of oak char modified by KMnO 4 (Mn-OC) is higher than that of other biochar samples. The KMnO 4 modification improves the pore structure, increases oxygen-containing groups and enhances the activity of biochar. The relatively high toluene conversion rate (53.96%) and low carbon deposition rate (3.41.) of Mn-OC indicates that KMnO 4 is more suitable for the modification of oak char. H 2 and aromatic hydrocarbons (especially biphenyl and their derivatives) are the main components of gas and liquid products, respectively. The proportion of H 2 in the total volume of H 2 , CO, CH 4 and CO 2 of Mn-OC reaches 56.94%. The addition of water vapor is helpful to the formation of oxygen-containing groups, more uniform distribution of inorganic salt particles and the improvement of biochar surface structure. Thus, adding moderate water vapor is beneficial to promote the catalytic activity of biochar. The toluene conversion rate and the total volume fraction of four main gases decrease with the increase of experimental time. They reduce significantly when the experimental time is longer than 1.0 min, from 44.51. (1.0 min) to 24.86% (1.0 min), which might be due to the damage of pore structure and the consumption of oxygen-containing functional groups. © 2022, The Authors. All rights reserved.

关键词： Toluene

Experimental Study on Supported MnO2-Based Catalysts for No Oxidation

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SSRN 2022年

作者： Wang, Denghui Li, Hui Wu, Feng Hui, Shien State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University No. 28 Xianning West Rd. Xi’an710049 China

The selective catalytic oxidation (SCO) of NO in the flue gas to easily soluble NO2 has received extensive attention. In this paper, a single-phase supported MnO2/Al2O3 catalyst and Ce-doped MnCe/Al catalyst system were used for the NO-SCO experiment with MnO2 as the main active component. Combined with XRD, BET, XPS, SEM, O2-TPD, and H2-TPR characterization methods, the physicochemical state of the catalyst surface was analyzed. Furthermore, the effect of loading and Ce doping on active oxygen species and the important factors related to catalyst activity was revealed. The MnO2 catalyst obtained the best activity at 300 °C, corresponding to a NO conversion rate of 79.4%. After MnO2 was loaded on the γ-Al2O3, the activity of the Mn/Al catalysts was not as good as that of the MnO2 catalyst, and the temperature window of Mn/Al shifted to the high-temperature region with the increase of the loading ratio. The relative content of adsorbed oxygen Oα of Mn/Al catalysts was lower than that of MnO2, resulting in poor activity. Ce-doped Mn0.23Ce0.023/Al catalysts exhibited good low-temperature activity. The introduction of the Ce element enhanced the dispersion of Mn species on the catalyst surface, the relative content of surface adsorbed oxygen Oα increased, and the low-temperature activity and mobility of surface oxygen species were enhanced. The Mn0.23Ce0.023/Al catalyst was endowed with both a high specific surface area and good pore structure, as well as a large oxygen storage capacity and excellent surface oxygen species. © 2022, The Authors. All rights reserved.

关键词： Manganese oxide

Corrosion Effect Analysis on Thermal-Hydraulics of Lbe/Water Spiral Tube Steam Generator Under Oxygen-Controlled Environment

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SSRN 2023年

作者： Lu, Dingsheng Yang, Yupeng Wang, Chenglong Zhang, Dalin Qiao, Pengrui Tian, Wenxi Qiu, Suizheng Su, Guanghui H. School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology Xi'an Jiaotong University Xi'An710049 China China Institute of Atomic Energy Beijing102413 China State Key Laboratory of Multiphase Flow in Power Engineering China

In order to explore the flow and heat transfer characteristics of spiral tube steam generators under Lead-Bismuth Eutectic (LBE) corrosion, the accelerated removal effect of LBE corrosion flow was perfected, and a bidirectional coupling model of LBE corrosion and flow heat transfer was established. Computational fluid dynamics (CFD) method was used to simulate the corrosion and flow heat transfer of helical tube steam generator under saturated oxygen concentration and oxygen-controlled environment. The results indicate that the corrosion of liquid LBE forms an oxidation layer, which hinders the heat transfer in the spiral tube steam generator. This leads to a significant increase in the wall friction coefficient and a decrease in the surface Nusselt number. However, it does not have a significant effect on the water side evaporation process of the spiral tube steam generator. The implementation of an oxygen-controlled environment can effectively reduce the influence of LBE corrosion on the flow heat transfer of the spiral tube steam generator. Especially under high temperature conditions, it can reduce the near wall temperature of LBE change by up to 57.5% and the outlet temperature change by up to 61.5%. The oxygen-controlled environment results in prolonged local hypoxia time, with a more pronounced effect at higher temperatures. © 2023, The Authors. All rights reserved.

关键词： Oxygen

Simulation study of channel structural design for direct internal reforming methane solid oxide fuel cell

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Applied Thermal engineering 2025年 274卷

作者： Wu, Wenzhao Bi, Xiaobing Lv, Xuecheng Li, Yang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

Reasonable designs on channels could effectively improve cell performance. This study established a 3D model of planar solid oxide fuel cell directly fueled by methane to investigate the impacts of three independently designed channel structures. This includes modifications to the channel cross-sectional shape (trapezoid and bow), inserting petal-shaped obstacles (single-layer and double-layer), and the study of deflector sheets embedded into the anode channel to address the highly endothermic nature of the methane steam reforming reaction. The research results indicated that, whether trapezoidal or bowed cross-sections are used, the current density achieves the largest growth rate at L_a = 1.5W_CH (1..06 % for bow and 1..53 % for trapezoid). Additionally, double-layer obstacles provide a greater enhancement of current density than single-layer obstacles (1. % for single-layer, 1. % for double-layer) and result in smaller and more uniform fuel flow velocity distribution in the channel. Embedding two or three deflector sheets into the anode channel significantly reduces the maximum temperature difference (by 7 K for two sheets;by 1. K for three sheets, representing a nearly 48 % reduction) and notably improves the temperature distribution uniformity. The study provides a novel perspective on channels alteration which could contribute to the advancement of researches on high-efficiency SOFCs. © 2025 Elsevier Ltd

关键词： Deflection (structures)

Transient Cooling Performance of R1.4a Flash-Evaporation Spray Enhanced by Cold Air Jet: A Novel Heat Transfer Enhancement Method in Laser Dermatology

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SSRN 2022年

作者： Li, Bufa Wang, Junfeng Tian, Jiameng Chen, Bin Xu, Haojie School of Energy and Power Engineering Jiangsu University Zhenjiang212013 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Nevus of Ota is a dermal hyperplastic pigmented disease with a morbidity rate of 0.1.–0.6% in the Asian population. Laser surgery with the assistance of cryogen spray cooling (CSC) is a potential clinical treatment for nevus of Ota. However, for Asians with high melanin content, it is necessary to enhance cooling capability without the increment of refrigerant amount. In this study, a R1.4a flash-evaporation cryogen spray cooling coupled with cold air jet (CSC-CAJ) was developed to improve the cooling capacity. Epoxy resin was employed as a skin phantom to investigate the heat transfer characteristics of CSC-CAJ with different air jet parameters. Air jet parameters of CSC-CAJ are recommended to be T a = -7 °C, V a = 3 m 3 /h Z a = 1. mm and Φ a = 30°. Compared to CSC, CSC-CAJ could reduce the minimum surface temperature from -39 °C to -42.1.°C, and the average value of convection heat transfer coefficient ( h ) of CSC-CAJ could increase from 8 W/(m 2 ·k) to 1..9 W/(m 2 ·k) or 61.3% for the recommended parameters. The liquid film residence time ( τ ) decreases from 301.ms to 234 ms or 23.3%. In addition, based on the visualization observation and surface heat transfer measurement, the frost formation phenomenon on the surface and the heat transfer enhancement mechanisms are well understood. Four modes, including Leidonfrost mode, no runoff mode, runoff mode and evaporation mode, are proposed to describe the four stages of CSC-CAJ. A non-dimensional correlation of normalized Nusselt number ( Nu *) and time ( t *) is summarized. The primary heat transfer enhancement mechanism of CSC-CAJ is found to be the increase in cryogen evaporation rate and the ratio of heat removal from the phantom surface to phase change latent heat. © 2022, The Authors. All rights reserved.

关键词： Evaporation

Numerical simulation of condensation of supercritical water gasification products in a supersonic nozzle

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International Journal of Fluid Engineering

International Journal of Fluid engineering 2024年第4期1卷 76-88页

作者： Hongtu Wu Miso Jurcevic Henrik Ström Muhammad Shahzad Khurram Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong University28 Xianning West RoadXi’an 710049ShaanxiChina LTEF—Laboratory for Thermodynamics and Energy Efficiency Faculty of Electrical EngineeringMechanical Engineering and Naval Architecture(FESB)University of SplitRudjera Boskovica 3221000 SplitCroatia Chalmers University of Technology GöteborgSweden COMSATS LahorePakistan

The clean and efficient separation of supercritical water gasification products(SCWGP)has emerged as a significant challenge in supercritical water gasification *** paper proposes the use of a supersonic nozzle for the condensation and separation of H2and CO_(2)from SCWGP,leveraging the high-pressure characteristics of these *** establishing a flow model and a condensation model for the supersonic nozzle,the effects of inlet pressure and inlet temperature on the condensation process are *** analysis reveals that the latent heat released during condensation causes an abnormal distribution of pressure and temperature within the *** the inlet pressure of the nozzle is increased from 7.0 to 9.0 MPa,the liquid phase mass fraction at the outlet rises from 5.3×1.^(-3)to ***,when the inlet temperature is lowered from 300.0 to 290.0 K,the liquid phase mass fraction at the outlet also rises from 5.3×1.^(-3)to *** increase in inlet pressure leads to the condensation location shifting toward the throat by~8.5×1.^(-3)m·MPa^(-1.,while the impact of inlet temperature is approximately-2.3×1.^(-3)m·K^(-1..The nucleation rate in the nozzle is always concentrated in a small region.

关键词： condensation separation outlet