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Experimental study on the effect of diameter on gas?liquid CCFL characteristics of horizontal circular pipes

NUCLEAR engineering AND DESIGN 2020年 364卷 110645-110645页

作者： Ma, Youfu Shao, Jie Lyu, Junfu Peng, Jiewei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Tsinghua Univ Dept Energy & Power Engn Key Lab Thermal Sci & Power Engn Minist Educ Beijing 100084 Peoples R China

The gas–liquid two-phase countercurrent flow in horizontal pipes is closely related to the safe operation of marine diesel engines with underwater exhausts, and nuclear power plants with pressurized water reactors. A visualization experiment on the effect of the diameter size on the counter current flow limitation (CCFL) characteristics of horizontal pipes was performed in the diameter range of 20–130 mm using air and water as the two phases. The results indicate that with a certain gas flow rate, the flow rate of the backflow liquid significantly increases with increasing diameter. Wallis models and those using the Froude–Ohnesorge numbers can correlate the effect of the change in diameter size when the diameters are greater than 100 mm, whereas they lose normalization capability with diameters less than 100 mm. From an analysis of the physical mechanism of formation of this diameter effect, a novel correlation model based on a new dimensionless group for each phase, consisting of the dimensionless inertia and dimensionless viscous force, was proposed for predicting the CCFL characteristics of small diameter pipes. Meanwhile, another correlation based on the Wallis model was also advanced for predicting the CCFL characteristics of large diameter pipes.

关键词： Gas–liquid flow Countercurrent flow limitation Flooding Horizontal pipe

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Modeling the multi-step discharge and charge reaction mechanisms of non-aqueous Li-O2 batteries

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APPLIED ENERGY 2022年 317卷

作者： Wang, Yuanhui Hao, Liang Bai, Minli Dalian Univ Technol Sch Energy & Power Engn Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Liaoning Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

The modeling study plays a critical role in understanding the reaction mechanisms and predicting the performance of lithium-oxygen (Li-O2) batteries. Although several models have successfully captured the discharge behaviors of the Li-O2 batteries, modeling the charge behaviors of the Li-O2 batteries is a challenge due to lacking a thorough understanding of the related reaction processes. This work proposes a multi-step reversible discharge/charge model for the non-aqueous Li-O2 batteries. Both the surface and solution reaction pathways of lithium peroxide (Li2O2) are taken into account. The proposed model can predict the discharge behaviors well, and more importantly, can accurately capture the charge behaviors of the Li-O2 batteries by considering the following three aspects: the effect of Li2O2 morphology on its decomposition potential, the evolution of interfacial resistance by Li2O2 film collapse, and the different desorption rates of absorbed lithium superoxide (LiO*2) in different electrolytes. Based on this model, the discharge/charge processes of the Li-O2 batteries using dimethoxyethane(DME), tetraethylene glycol dimethyl ether (TEGDME) and dimethyl sulfoxide (DMSO) electrolytes, as well as a redox mediator TEMPO, are simulated and verified. The Li2O2 formation/decomposition through the surface and solution pathways are dominated by the specific surface area of the electrode and the potential, respectively. The Li2O2 generated by the solution pathway is more difficult to be decomposed during charge. The use of redox mediator TEMPO lowers the discharge capacity of the Li-O2 batteries due to the weakened solution reaction, while remarkably reduces the reversible capacity loss. The desorption time constant of LiO*2 in electrolyte is a critical parameter that determines the degree of the reaction through the solution pathway, thus determining the discharge/charge cycling performance of the Li-O2 batteries with various electrolytes.

关键词： Li -O-2 batteries Multi-step reaction mechanism Discharge charge model Surface and solution pathways

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Novel Design of In-Situ Hydrogen Sorption/Storage Integrated Enhanced Hydrogen Production in Supercritical Co2 Gasification, Air Gasification, and Steam Gasification from Biomass

SSRN

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SSRN 2023年

作者： Yang, Tiebing Tie Dou, Binlin Zhang, Hua Wu, Kai Ning, Luo Chen, Haisheng Xu, Yujie Li, Wei Wu, Chunfei School of Energy and Power Engineering Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China Department of Energy Engineering Zhejiang University Hangzhou310027 China School of Chemistry and Chemical Engineering Queen's University Belfast BelfastBT7 1NN United Kingdom

Novel process on in-situ hydrogen sorption/storage during water gas shift (WGS) was proposed and the enhanced hydrogen production in supercritical CO2 gasification (CG), air gasification (AG), and steam gasification (SG) from biomass was integrated. The effects of temperature, pressure, steam-to-carbon (S/C) ratio, and adsorbent content for in-situ hydrogen sorption/storage on the enhanced hydrogen production were determined. The energy and exergy analysises under different thermodynamic conditions were calculated and compared. The results show that as the temperature increases, the hydrogen conversion and yield from water gas shift (WGS) reaction with in-situ hydrogen sorption/storage based on Mg-based sorbent were greatly increased, in which SG has the highest hydrogen yield and AG has the highest hydrogen conversion. The steam-to-carbon (S/C) ratio has a positive effect on the hydrogen production for all the processes, and also presents an effect on in-situ hydrogen sorption/storage during WGS. The methanation reaction was greatly inhibited by AG. The energy requirement order was SG> CG >AG, and the system energy can be supplied by in-situ hydrogen sorption/storage. © 2023, The Authors. All rights reserved.

关键词： Biomass

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Sulfur/water resistance and regeneration of MnOx-CeO2/TiO2 catalyst for low-temperature selective catalytic reduction of NOx

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JOURNAL OF ENVIRONMENTAL CHEMICAL engineering 2022年第2期10卷

作者： Wang, Qiulin Wang, Rui Huang, Xiaoniu Shi, Huancong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Zhejiang Univ Huzhou Inst Huzhou 313000 Peoples R China

Mn-based catalysts present a great prospect for application in selective catalytic reduction (SCR) of NOx with NH3 at low temperatures, due to their high low-temperature catalytic activity. However, poor resistance of Mn-based catalysts to SO2 and H2O restricts their industrial application. This paper investigates the SO2 & H2O resistance of MnOx-CeO2/TiO2 catalyst and discusses the poisoning mechanism based on catalytic character-izations. The results indicate that MnOx-CeO2/TiO2 catalyst exhibit high tolerance to SO2 poisoning mainly because the surface sulfates are preferentially formed on Ce dopants so that protect the main active component (MnOx). Catalytic deactivation become more severe when SO2 & H2O are simultaneously present, which implies that SO2 & H2O exhibit a synergistic toxicity in poisoning catalyst. Interestingly, the presence of H2O can alleviate the formation of surface metal sulfates on catalyst to some extent, for the surface reactive oxygen species and the surface acid sites are preserved to fulfill the low temperature SCR reaction cycle. Thermal regenerations under different atmosphere (e.g., O-2 and H2O) are conducted for the SO2 poisoned catalyst. Effective regeneration of the sulfated catalyst can be realized and their regeneration mechanisms are explored by utilization of several catalytic characterizations.

关键词： key Mn-based catalysts SO2&H2O resistance Regeneration Mechanism

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Knowledge mining for chiller faults based on explanation of data-driven diagnosis

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APPLIED THERMAL engineering 2022年第0期205卷 118032-118032页

作者： Gao, Yu Han, Hua Lu, Hailong Jiang, SongXuan Zhang, Yunqian Luo, MingWen Univ Shanghai Sci & Technol Energy & Power Engn Coll Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China CQ Midea Gen Refrigerat Equipment CO LTD Chongqing 401336 Peoples R China

Data-driven model is considered to be an efficient and convenient diagnosis method for refrigeration systems, especially in Big Data Era, but the black box characteristic has always been a criticism and hindered its application. For this problem, SHapley Additive explanation (SHAP) method is explored to unveil the black box and the knowledge of system-level chiller faults has been mined. Two ensemble models with excellent diagnostic performance have been investigated including Random Forest (RF) and Light Gradient Boosting Machine (LightGBM). Detailed analysis shows that the sub-cooling at the condenser outlet (TRC_sub) and the condenser approaching temperature (TCA) have a great contribution to the detection of refrigerant leakage and overcharge with different margin, which is consistent with but standing out from the prior knowledge. In practical applications, temperature and pressure sensors for lubricating oil are recommended for a refrigeration system with lubricant due to the sensitive variation with system change (failure or condition altering), which can be a supplement to the traditional experience. The data-driven model is, indeed, an effective way to discover the hidden knowledge of a data set from all dimensions to upgrade the traditional experience. Furthermore, the local explanation by individual samples and the explanation comparison between the RF and the LightGBM model show that the primary features on which the model(s) depends to diagnose the same fault are basically the same, while the auxiliary features may vary slightly. The consensus further proves that the primary features and the related rules mined out in this study can be trusted.

关键词： Refrigeration system Data-driven model Explanation Random Forest System-level Fault Refrigerant leakage

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Correlating phosphorus transformation with process water during hydrothermal carbonization of sewage sludge via experimental study and mathematical modelling

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SCIENCE OF THE TOTAL ENVIRONMENT 2022年第Part1期807卷 150750-150750页

作者： Zheng, Xiaoyuan Shen, Mengxuan 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 Shanghai 200093 Peoples R China Tongji Univ Thermal & Environm Engn Inst Sch Mech Engn Shanghai 200092 Peoples R China

Recently, hydrothermal carbonization (HTC) based phosphorus (P) recovery from sewage sludge (SS) has attracted considerable interests worldwide. However, they concentrated on P transformation in the hydrochars, while ignored that the variations of process water (PW) might influence P transformation, since it exposed to water thoroughly during HTC. In this study, correlation of P transformation with PW were examined via experimental study and mathematical modelling. The results showed that statistical significance (p < 0.05) of HTC temperature and feedwater pH on NH4+-N concentration in the PW was observed due to deamination and ring opening reactions of amino acids, confirming by their excellent correlation with R-2 = 0.988. NH4+-N concentration dominated increasing PW pH, which stimulated the transformation of NAIP to AP. Associated model was developed with satisfactory R-2 = 0.938. Although P transformation during HTC was significantly influenced by HTC temperature and feedwater pH, supporting by their strong correlation with R-2 = 0.956, its transformation was PW pH dependent. Ultimately, detailed P transformation pathways during HTC was proposed with incorporation into the impact of PW. This work can provide new insights into HTC-based P transformation in the pristine SS. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Phosphorus recovery Hydrochars Feedwater pH HTC temperature ammonia Apatite phosphorus

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Study on micro-liquid droplets behavior at the expander of the pulse tube cryocooler under 5 K based on molecular dynamics

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JOURNAL OF MOLECULAR LIQUIDS 2022年 346卷 118222-118222页

作者： Lu, Yang Qi, Yingxia Hu, Yuying Chen, Weiyi Zhang, Hua Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Natl Key R&D Program China Shanghai 200093 Peoples R China

The alternating oscillations in the expander of the pulse tube cryocooler at liquid helium temperature level were studied by molecular dynamics method. It is found that the densely atom clusters - namely micro-liquid droplets were formed in the cold part of the pulse tube and mostly close to the wall of the tube. The size and the number of the clusters were increasing with cycle progressing. The mass proportion of the liquid droplets was up to 8.0 % in all the gas. The largest droplets contained up to 275 He atoms. The clusters moved around during the compression and expansion process of the cycles. It is known that the formation of the micro droplets had influences on the oscillating waves of the gas, resulting in the amplitudes of the density, temperature, so that pressure waves decreased greatly. The local lowest expansion temperatures were also increased over 4.2 K with the formation of the droplets. This may be one of the reasons that it is very difficult to obtain the temperature below 4 K in the Stirling pulse tube cryocoolers. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Expansion Liquid helium temperature Alternating oscillations Liquid droplets Molecular dynamics simulation

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Investigation on water injection characteristics and its influence on the performance of twin-screw steam compressor

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ENERGY 2022年第0期259卷

作者： Tian, Yafen Geng, Yanting Yuan, Hao Zhao, Zhaorui 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 Shanghai Marine Diesel Engine Res Inst SMDERI Dept Compressor Shanghai 201108 Peoples R China

Water injected twin-screw steam compressor has great energy-saving potential in mechanical vapor compression, high temperature heat pump and steam production applications. To investigate the water injection characteristics and its influence on compressor performance under different operating conditions, a detailed thermodynamic model was developed for the working process. heat and mass transfer between injected water and compressed vapor were considered, together with leakage of two-phase flow and power consumption of excess liquid water. Comparison between simulated results and experimental results show reasonable agreement with an error of +/- 5%. With the validated model, the effects of operating parameters on compressor performance and optimum injected water flowrate were investigated. Results proves water injection to be an efficient approach to improve compressor performance if properly applied. Compared with no water injection, the volumetric efficiency and isentropic efficiency with injection can be promoted by 11.9% and 17.2% respectively. As the injected water flowrate increases, the compressor efficiency firstly increases to a maximum value and then reduces when the injected flowrate is superabundant. The optimum injected water flowrate is dominated by rotating speed and nearly proportional to the rotating speed, while the optimum mass ratio of the injected water to the compressed vapor varies between 8.9% and 10.4%.

关键词： Twin-screw compressor Water injection Steam compression heat and mass transfer Performance

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Suppressing Condensation Frosting Using Micropatterned Ice Walls

SSRN

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SSRN 2022年

作者： Zuo, Zichao Zhao, Yugang Li, Kang Zhang, Hua Yang, Chun Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Key Laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development Center Sichuan Mianyang621000 China School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore639798 Singapore

Condensation frosting is encountered ubiquitously in our daily life and numerous industrial applications, rooting many detrimental consequences in heat transfer and mechanical stabilities. In latest decades, both active de-frosting and passive anti-frosting methods have been developed. In this work, we adopt the concept of three-dimensional overlapping dry zones by patterning microscopic ice walls on a smooth substrate, engendering a sustainable frost coverage of less than 10%. Patterned ice walls prevent vapor deposition on the substrate base by absorbing all incoming moisture on upper sidewalls, leaving the substrate base free of contaminates from both frost and condensate. To ensure vapor preferentially depositing on upper sidewalls, a critical ice wall height exists, below which fine ice grains initiate in the adjacent of the substrate base and grow substantially faster, compromising the anti-frosting performance. The proposed surface shows reasonable durability when exposed to varying substrate supercooling, and frost coverage may increase due to covering and fracturing of the out-of-plane growth of feather-like ice clusters at large substrate supercooling. Our findings provide an effective anti-frosting surface design that doesn’t require any chemical or mechanical modifications on the targeted surfaces, showing great advantages compared to conventional icephobic surface designs. © 2022, The Authors. All rights reserved.

关键词： Ice

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CaO-assisted hydrothermal treatment combined with incineration of sewage sludge: Focusing on phosphorus (P) fractions, P-bioavailability, and heavy metals behaviors

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CHEMOSPHERE 2022年第Part2期308卷 136391页

作者： 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 Heat Transfer & Multiphase Flow P Shanghai 200093 Peoples R China Tongji Univ Thermal & Environm Engn Inst Sch Mech Engn Shanghai 200092 Peoples R China

Dewatering of sewage sludge (SS) was the prerequisite for saving its drying energy and sustaining its stable combustion. Hydrothermal treatment (HT) has been a promising technology for improving SS dewaterability with high energy efficiency. However, the knowledge of phosphorus (P) transformation and heavy metals (HMs) behaviors in the combined HT and incineration process was still lack. P fractions, P-bioavailability, HMs speciation, and their environmental risk in the ash samples from this combination process were evaluated and compared with those from the co-incineration of SS and CaO. The combination process was superior to the latter one in the light of P and HMs. CaO preferred to enhance the transformation of non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP) initially with enriched P and increased P-bioavailability in the resultant ash samples. The combination process further reduced the values of risk assessment code and individual contami-nation factor with the increment of the stable F4 fraction in HMs. Significant reduction of potential ecological risk was observed with the lowest global risk index of 43.76 in the combination process. Optimum CaO addition of 6% was proposed in terms of P and HMs. The work here can provide theoretical references for the potential utilization of P from SS to mitigate the foreseeable shortage of P rocks.

关键词： Sewage sludge Ash Hydrochar Speciation P -solubility Environmental risk

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