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Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube

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AIP Conference Proceedings 2013年第1期1547卷 390-399页

作者： Shouxu Qiao Haijun Wang Hongfang Gu Yushan Luo Lei Zhang Wei Xiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1,500t⋅h−1 and the heat flux on test tubes ranges from 10 to 40 kW⋅m−2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8∼5.7 times of that in smooth tube and the pressure drop of the porous surface tube is 0.99∼1.007 times of that in the smooth tube. The physical mechanisms of the enhanced heat transfer characteristics of flow boiling in the porous surface tube are analyzed. By the regression analysis of the experimental data, correlations predicting the flow boiling heat transfer coefficient and pressure drop of glycol-water solution within the error range of ±20% are established. The experimental results can be used to guide the design of heat exchange equipment using the porous surface tube as heat transfer elements under these test conditions.

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Investigation on the impact of the environment wind velocity on the indirect air-cooling tower performance

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AIP Conference Proceedings 2013年第1期1547卷 469-476页

作者： Yongbo Qin Hongfang Gu Haijun Wang Guoyong Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerical simulation method was used to analyze the relative influence of the wind speed, ranging from 4m/s to 18m/s, on the outlet water temperature of cooling tower, the outlet air temperature of radiator, the facing wind speed of the fan segment and on the outlet air speed of the cooling tower. The result shows that the impact of the natural wind speed on the cooling tower efficiency varies greatly and this impact increases as the wind speed increases.

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Study on heat transfer characteristic of ethanol-water mixture condensation on a vertical micro-tube

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AIP Conference Proceedings 2013年第1期1547卷 362-372页

作者： Xiping Chen Jinshi Wang Junchao Qin Daotong Chong Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.16kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW⋅m−2⋅K1, which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from −20% to 20%.

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Optimization research on the structure of horizontally-arranged indirect air-cooling tower under strong wind condition

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AIP Conference Proceedings 2013年第1期1547卷 454-462页

作者： Guoyong Chen Hongfang Gu Haijun Wang Yongbo Qin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

Strong wind has a significant impact on the heat radiation of the air-cooling system. In this research, a numerical calculation model of 2×1000MW horizontally arranged air-cooling tower is established to simulate the flow distribution and heat exchanging capability of three different structures-horizontally-arranged indirect air-cooling tower, tower with guide wall outside, and tower with a cross wall inside-under high-speed wind and extreme-speed wind conditions. The result reveals that the structure with the guide wall outside the tower only works under strong wind condition while the structure with cross wall inside shows the anti-wind capability under both high-speed wind and extreme-speed wind conditions.

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A kinetic modeling study of high temperature chemistry of n-pentanol 8

A kinetic modeling study of high temperature chemistry of n-...

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8th US National Combustion Meeting 2013

作者： Li, Qianqian Merchant, Shamel S. Green, William H. Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'n Jiaotong University Xi'an710049 China Department of Chemical Engineering Massachusetts Institute of Technology CambridgeMA02139 United States

ISBN: (纸本)9781627488426

With increasing environmental deterioration and energy demand, studies on new alternative fuels have been attracting more attention. N-pentanol is a five carbon, straight-chain alcohol, which can be produced through natural microbial fermentation and/or engineered microorganisms. It has many advantages over lower carbon alcohols, including higher energy density, lower vapor pressure and better fuel compatibility. In this study, a detailed reaction mechanism of n-pentanol, on the basis of a previously proposed n-butanol mechanism, is generated using the open-source software Reaction Mechanism Generator (RMG). High temperature chemistry of the mechanism was validated against recently published laminar flame speeds and ignition delays. Encouraging results between simulations and experiments were observed under most conditions. Simulations were also conducted using a recently developed n-pentanol oxidation mechanism (NUI model) by Heufer et al. For lean mixtures, the two mechanisms show similar results, while the RMG model yields better predictions for rich mixtures and at an elevated pressure. Reaction pathways and sensitivity analysis reveal the key differences between the two mechanisms in terms of intermediates formed and fuel consumption.

关键词： Alternative fuels

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Experimental study on performance and emissions of diesel/n-pentanol blends on a DI diesel engine

Experimental study on performance and emissions of diesel/n-...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Wei, Liangjie Cheung, C.S. Huang, Zuohua Department of Mechanical Engineering Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this work, experiments were conducted on a diesel engine fueled with n-pentanol/diesel blends to examine the effect of n-pentanol addition on the engine performance and emissions. Results show that, the addition of n-pentanol to diesel increases the brake specific fuel consumption and has little effect on the brake thermal efficiency. Additionally, the emissions of HC, CO and NOx are slightly increased with the increase of n-pentanol in the fuel blends, however, the particulate matter emission is significantly reduced.

关键词： Brakes

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Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

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AIP Conference Proceedings 2013年第1期1547卷 432-441页

作者： Zhuqiang Yang Qincheng Bi Yong Guo Zhaohui Liu Jianguo Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

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Stability analysis of a square rod bundle sub-channel in supercritical water reactor

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AIP Conference Proceedings 2013年第1期1547卷 181-189页

作者： Wang Hai-jun You Ting Zhang Lei Gu Hong-fang Luo Yu-shan Bian Ji-lian State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University Xi'an 710049 China

Extensive investigations on the flow and heat transfer behavior in SCWR fuel assembly have been undertaken worldwide. However, stability analysis of supercritical water in the sub-channels of tight lattices is still lacking. In this paper, the flow stability of a fuel bundle channel with square pitches has been analyzed using commercial CFD code-ANSYS Fluent. Typical dynamic instability of Density Wave Oscillation (DWO) has occurred in heated channel containing fluids at supercritical pressure. A further discussion about the impacts of various operational parameters (e.g. power input, system pressure, mass velocity, inlet temperature, etc) shows that the system becomes more stable as system pressure and/or mass flow rate increases. An increase in inlet temperature also has a stabilizing effect on the system.

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Numerical simulation of the multi-component slurry gasification with the non-premixed combustion model

Numerical simulation of the multi-component slurry gasificat...

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2013 Spring International Conference on Material Sciences and Technology, MST-S 2013

作者： Li, Xing Xing Yi, Chun Hai Yang, Bo Lun Zhang, Yong Men, Chang Gui He, Gen Liang Xu, Hong Dong Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Northwest Research Institute of Chemical Industry Xi'an Shaanxi 710049 China

ISBN: (纸本)9783037857090

Considering the volumetric reactions and particle surface reactions in an entrained flow gasifier, the non-premixed combustion model based on the wet particles combustion method is adopted to simulate the multi-component slurry gasification process with FLUENT software. The velocity, temperature and concentration profiles of the gas products in the gasifier are obtained. Simulated results agree well with the commercial data, which verified the validity and applicability of the present model. Simultaneously, the reaction subarea in the gasifier has turned out to be obvious, the water evaporation, volatiles cracking and combustion reactions mainly appear in the jet region of the gasifier, the char gasification mainly appear in the freeboard region, but few reactions appear in the recirculation region. Moreover, with the increase of the mass fraction of the multi-component slurry, the content of the syngas at the gasifier outlet increases, while with the oxygen carbon atom ratio increasing, the syngas yield is rising early but declining later. © (2013) Trans Tech Publications, Switzerland.

关键词： Surface reactions

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Sensitive measurement of trace mercury using low pressure laser-induced plasma

Sensitive measurement of trace mercury using low pressure la...

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作者： Wang, Zhenzhen Deguchi, Yoshihiro Kuwahara, Masakazu Zhang, Xiaobo Yan, Junjie Liu, Jiping State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China Graduate School of Advanced Technology and Science University of Tokushima Tokushima 770-8501 Japan

The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results. © 2013 The Japan Society of Applied Physics.

关键词： Laser induced breakdown spectroscopy

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