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Analysis of Different Control Strategies Considering Individual Regulation of Heat User

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Analysis of Different Control Strategies Considering Individ...

Electrical engineering and Mechatronics Technology (ICEEMT), IEEE International Conference on

作者： Zhiwei Xun Huijie Wang Liyuan Wang Long Yang Yunfang Gao Ming Liu Guoneng Jinjie Energy Co. Ltd Yulin China Xi’an Jiaotong University Xi’an China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

In the process of outdoor temperature change, it is beneficial to improve the comfort of thermal users to formulate adjustment and control strategies according to the actual needs of each user. In this paper, different adjustment modes are established according to the thermal comfort of users, and the control strategies of rising and cooling within 0, 30 and 60 minutes are proposed, and the indoor temperature control effect and heating energy consumption of each adjustment mode under different control strategies are analyzed. The results show that: in different modes, when the rise and cooling time increase, compared with the design room temperature, the indoor temperature difference under the control mode is smaller, but the time needed to reach stability is longer. At the same time, the total heat load is unchanged, but the total pump work decreases.

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The Enriched-Embedded Discrete Fracture Model (Nedfm) for Fluid flow in Fractured Porous Media

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SSRN 2023年

作者： Jiao, Kaituo Han, Dongxu Chen, Yujie Bai, Bofeng Yu, Bo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development Beijing Institute of Petrochemical Technology Beijing102617 China

The embedded discrete fracture model (EDFM) is widely adopted for fluid flow in fractured porous media, but it cannot be employed for blocking fractures due to the assumption of symmetric and linear pressure distribution around fractures. To improve it, this work presents a novel numerical framework named the enriched-embedded discrete fracture model (nEDFM). It is based on the non-conforming grid and discretized by the mass-conservative finite volume method. Attractively, the nEDFM applies to both conductive and blocking fractures, as well as isotropic and anisotropic matrix permeability, while maintaining a low computational cost. The local shape function, which introduces two enriched degrees of freedom for every fracture cell, is developed to model the discontinuities of pressure and its gradient on two sides of the fracture. Correspondingly, two equations for coupling the matrix and reduced fracture are supplemented to close the system and improve the accuracy of mass exchange between the matrix and fracture. The performance of nEDFM is compared with the classical EDFM and projection-based EDFM (pEDFM). The results show that the nEDFM outperforms the EDFM for conductive fractures and can obtain better pressure distribution inside blocking fractures than the pEDFM. For anisotropic matrix permeability with conductive or blocking fractures, the nEDFM can get solutions comparable to those obtained by the reference solution. Hence, the nEDFM is an accurate and flexible method for fluid flow simulation in fractured porous media. © 2023, The Authors. All rights reserved.

关键词： Fracture

Highly ductile hypereutectic Al-Si alloys fabricated by selective laser melting

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Journal of Materials Science & Technology 2022年第15期110卷 84-95页

作者： Yafeng Yang Kang Geng Shaofu Li Michael Bermingham R.D.K.Misra State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China School of Mechanical and Mining Engineering University of QueenslandSaint LuciaQueensland 4072Australia Department of Metallurgical Materials and Biomedical EngineeringUniversity of Texas at El Paso500 W University AvenueEl PasoTX 79968USA

In the endeavor to maximize the refinement effect of primary Si and alleviate the inherent brittleness of hypereutectic Al-Si alloy,the approach of coating P as a modifier on powder was *** ultimate aim was to create more heterogeneous fine Al P nucleus and enhance the nucleation efficiency of primary Si on Al P to refine the coarse primary Si to nano-scale during 3D *** the combination of large undercooling and high density of nucleation sites,the size of primary Si was successfully refined to 200–300 nm and the divorced eutectic was also induced to modify the microstructure of *** the presence of nano-scale primary Si,the melting pool boundary(MPB)feature disappeared and the fracture mechanism also changed from load transfer to interfacial *** with the pristine alloy,the ductility was increased four times without significantly changing the ultimate tensile strength(UTS)and wear *** improvement of ductility is attributed to the refinement of primary Si,the disappearance of MPB features and the formation of divorced *** optimal tensile properties were:UTS-482 MPa,yield strength-320 MPa and ductility of 8.1%at 0.05 wt.%*** are comparable to those for high-strength Al alloys.

关键词： Al-Si alloys Heterogeneous nucleation Ductility Powder processing Selective laser melting

Hierarchical Heterojunctions of Metal Sulfide Nanosheets/ Metal Oxide Nanofibers for an Efficient Detection of Formaldehyde

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SSRN 2024年

作者： Zhu, Lei Zhang, Jiaxin Wang, Jianan Liu, Jianwei Wang, Ze Yan, Wei Xi’an Key Laboratory of Solid Waste Resource Regeneration and Recycling State Key Laboratory of Multiphase Flow Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China School of Physics and Electrical Engineering Weinan Normal University Chaoyang Street Weinan714099 China School of Chemistry and Chemical Engineering Xi’an University of Science & Technology Xi’an710054 China

The construction of transition metal dichalcogenides (TMDs) heterojunctions for high performance gas sensors has garnered significant attention due to their capacity to operate at low temperature. Herein, we realize two-dimensional (2D) WS2 nanosheets in situ grown on one-dimensional (1D) In2O3 nanofibers to form heterostructures for formaldehyde (HCHO) gas sensors. Capitalizing on the p-n heterojunctions formed between WS2 and In2O3, coupled with the high surface-to-volume ratio characteristic of 1D nanostructures, the WS2/In2O3 NFs sensor demonstrated a high gas response value of 12.6 toward 100 ppm HCHO at operating temperature of 140 ℃, two times greater than that of the pristine In2O3 sensor. Meanwhile, the sensor presents remarkable repeatability, rapid response/ recovery time, and good long-term stability. The superior sensing capabilities of WS2/In2O3 NFs heterojunction are attributed to the combined impact of the increased charge transfer and the presence of more sites for gas adsorption. The research endows a potent approach for fabricating TMDs heterojunctions to significantly improve the performance of gas sensors. © 2024, The Authors. All rights reserved.

关键词： Tungsten compounds

Experimental study on dynamic mechanism of vortex evolution in a turbulent boundary layer of low Reynolds number

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Journal of Hydrodynamics 2020年第5期32卷 807-819页

作者： Yan-ang Guo Xiang-rui Dong Xiao-shu Cai Wu Zhou School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering Shanghai 200093China

The dynamic mechanism of the vortex generation and evolution process in a fully developed turbulent boundary layer with Reθ=97-194 is experimentally *** this study,a moving single-frame and long-exposure(MSFLE)imaging method and a moving particle image velocimetry/particle tracing velocimetry(M-PIV/PTV)are designed and implemented for measuring the temporal and spatial evolution of vortex cores in both qualitative and quantitative ways,*** the other hand,the Liutex vector,which is a new mathematical definition and identification of the vortex core proposed by Liu’s group,is first applied in the experiment for the structural visualization and quantitative analysis of the local fluid *** results show that an intuitional process of vortex evolution can be clearly observed by tracking the vortex using MSFLE and verify that the roll-up of the shear layer induced by shear instability is the origin of vortex formation in ***,a quantitative investigation in terms of the critical vortex core boundary(size)and its accurate rotation strength is carried out based on the Liutex vector field analysis by M-PIV/*** to statistics of the relation between vortex core size and the rotation strength during the whole process,the physical mechanism of vortex generation and evolution in a turbulent boundary layer of low Reynolds number can be summarized as a four-dominant-state course consisting of the“synchronous linear segment(SL)-absolute enhancement segment(AE)-absolute diffusion segment(AD)-skewing dissipation segment(SD)”.

关键词： Turbulent boundary layer high-and low-speed fluid vortex generation moving single-frame and long-exposure moving particle image velocimetry/particle tracing velocimetry Liutex vector

Experimental study on flow characteristics of rectangular narrow channel

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International Journal of Advanced Nuclear Reactor Design and Technology 2020年 2卷 60-68页

作者： Song, Gongle Sun, Rulei Zhang, Dalin Su, G.H. Tian, Wenxi Qiu, Suizheng School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Plate fuel elements is gradually used in advanced reactor structure design because of its advantages of high fuel consumption and high safety. The flow channel of the plate fuel element is a typical rectangular narrow channel, and accurately obtaining the flow characteristics of the rectangular narrow channel has become the most basic problem in the thermal and hydraulic research of the rectangular narrow channel. The flow characteristics of a rectangular narrow channel with cross-section of 3 × 67 mm and length of 745 mm are studied experimentally. The mass flow range is 50–650 kg/h, the pressure is 0.1–1 MPa, and the range of the inlet temperature is 283.15–333.15 K. The Reynolds number obtained experimentally in the laminar-turbulent transition region is in the range of 2700–4000, which has a significant delay compared to round channels. Laminar flow is modeled theoretically, and the Fourier sine transform method is used to solve the momentum Navier-Stocks equation, and the expression of the friction coefficient is obtained through the velocity distribution. However, due to the particularity of the test section, the error of the theoretical solution is large compared with experimental data. Five empirical correlations commonly used in rectangular narrow channels are evaluated. The Leon correlation is applicable to the experimental laminar flow area, and the Blasius correlation is applicable to the turbulent flow area. In order to further reduce the error, the friction correlation applicable to this experimental condition is fitted, making the prediction of friction coefficient more accurate. For subsequent experimental research on heat transfer, flow pattern, CHF, flow instability, etc., these works are of great significance. © 2020 Xi'an Jiaotong University

关键词： Laminar flow

Jet Impingement Boiling Heat Transfer Performance of Refrigerant Hp-1 in Micro-Pin-Finned Surfaces for High-Power Chips

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SSRN 2023年

作者： Ma, Xiang Gui, Liangxin Song, Gege Hu, Chengyu Yang, Xiaoping Zhang, Yonghai Wei, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

In this paper, jet impingement boiling heat transfer performance was studied using a novel new environmentally friendly refrigerant medium (HP-1) based on a high-power chip heat sink. A series of experimental investigations of jet impingement boiling were conducted on smooth and micro-pin-finned surfaces (PF0.5-0.5-1, PF0.5-0.5-2 and PF0.3-0.3-1). Heat transfer performances were evaluated over the saturated pressures from 450 to 590 kPa, liquid subcoolings from 2 to 15 K, nozzle sizes from 1 to 2 mm, mass fluxes from 71 to 858 kg/(m2s). The results show that critical heat flux (CHF) and heat transfer coefficient (HTC) increases with the increase of mass flux and saturated pressure. At ΔTsub=15 K, the CHF of the micro-pin-finned surfaces can be increased by 63% compared with smooth surface, in which the CHF of PF0.5-0.5-2 surface is up to 1532 kW/m2. Boiling heat transfer coefficient first increases and then decreases with the increase of heat flux. Due to the increase of the inlet liquid subcooling, leading to a large temperature difference, so the heat transfer coefficient is smaller at a high liquid subcooling. Several factors, such as mass flux, saturated pressure and liquid subcooling, have a great impact on pressure drop. With the increase of vapor quality, the shear action between the vapor-liquid phase is enhanced, and the pressure drop will gradually increase. Bubble behaviors have also been captured by a high-speed camera to help analyze the mechanism of jet impingement boiling heat transfer in a confined space for high-power chips. © 2023, The Authors. All rights reserved.

关键词： Heat flux

Investigation on the Mechanism of Co2 Hydrate Formation by Synergistic Action of Kinetic Promoters

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SSRN 2023年

作者： Liu, Ni Leng, Jing Cui, Mengxue Yang, Liang School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

CO2 hydrate technology has a promising application in carbon neutralization through carbon capture. In this paper, the effect of different mass concentrations of fullerene C60 and sodium lignosulfonate (SL) on the gas storage performance of CO2 hydrate was investigated. C60 can promote the best results at the concentration of 0.01 wt%. The induction time was 168 minutes, and the gas storage capacity was 56.60 V/V, which is 112.22% higher than that of pure water. This is due to the large specific surface area of C60 nanoparticles, which reduces the surface tension of the solution and increases the gas-liquid mass transfer rate. SL can promote the best results at the concentration of 0.1 wt%. The induction time was 1,908 minutes, and the gas storage capacity was 89.98 V/V, which is 2.37 times higher than that in the pure water system. This is because SL molecules possess abundant functional groups, high chemical reactivity, high elasticity and surface activity. The best compounding pair was in the experimental group of 0.01 wt% C60 with 0.1 wt% SL. The induction time was 60 minutes, and the gas storage capacity was 108.87 V/V. Therefore, both C60 and SL have a positive effect on CO2 hydrate formation. © 2023, The Authors. All rights reserved.

关键词： Carbon dioxide

Mild Combustion of a Premixed Nh3/Air Jet Flame in Hot Coflow Versus its Ch4/Air Counterpart

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SSRN 2023年

作者： Li, Pengfei Wang, Guochang Liu, Xiangtao Shi, Guodong Cai, Xiao Liu, Zhaohui Mi, Jianchun State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology Wuhan430074 China College of Engineering Peking University Beijing100871 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Dalian Maritime University China

MILD combustion is very suitable for solving the problems of unstable flame and high NOx emission (ENOx ) for ammonia fuel, but the related studies are rare. This work numerically investigates the MILD combustion characteristics of a premixed NH3/air jet flame in hot coflow (JHC) under different jet equivalence ratio (ΦJ), coflow temperature (TC) and oxygen level (XO2,C). For comparison, the similar CH4/air MILD-JHC flames are also calculated. Results show that the NH3 flame generally has lower temperature rise and heat release as well as larger reaction zone than CH4. This may suggest that the former flame can develop to the MILD regime more easily. ENOx is two orders higher from the NH3 than CH4 flame at all TC and XO2,C for ΦJ 1, ENOx of the NH3 flame quickly drops to near zero, but ENH3 and EH2 are very high (~1000 ppm) and the combustion efficiency is low. Moreover, ENOx increases quickly (slowly) with XO2,C (TC) while ENH3 and EH2 are quite low at TC ≥ 1300 K and XO2,C ≥ 1% for the NH3 flame. ENOx mainly comes from NO but N2O is also important at low ΦJ and TC. Therefore, considering all ENOx , ENH3, EH2 and the burning efficiency, the optimal conditions for NH3 MILD combustion are ΦJ =1, TC ≥ 1500 K and XO2,C =1%-3%. In addition, compared to the conventional flame, the NH3 MILD combustion can reduce ENOx by 1-2 orders. © 2023, The Authors. All rights reserved.

关键词： Ammonia