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4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009

作者： Bi, Shengshan Guo, Kai Liu, Zhigang Wu, Jiangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9868509610

In this work, an experimental work was investigated on the nano-refrigerant. A domestic R600a refrigerator was selected and instrumented with 19 resistance thermometers and three pressure transducers. R600a/TiO 2 nano-refrigerants were used as working fluid without any system reconstruction. The refrigerator performance was then investigated using energy consumption test and freeze capacity test. The results indicate that R600a/TiO2 nano-refrigerant works normally and safely in the refrigerator. The refrigerator performance was better than the pure R600a system, with 9.6% less energy used with 0.5 g/L nano-refrigerant. Thus, using R600a/ TiO2 nano-refrigerant in domestic refrigerators is feasible.

关键词： Refrigerators

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Equations for the thermophysical properties of dimethyl carbonate

Equations for the thermophysical properties of dimethyl carb...

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2009 AIChE Annual Meeting, 09AIChE

作者： Zhou, Yong Wu, Jiangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

Dimethyl carbonate (DMC) is a nonirritating and nontoxic chemical, further more;it can be used as a fuel additive. In this work, the thermophysical properties formulations for dimethyl carbonate has been developed based upon a selection of available experimental thermophysical property data. In determining the coefficients of the equation of state, multi-property fitting methods were used;including single-phase pressure-volume-temperature (pVT), heat capacity, vapor pressure, and saturated liquid density data. The equation of state has been developed to conform to the Maxwell criterion for two-phase liquid-vapor equilibrium states and is valid for temperatures from 280 K to 400 K and pressure to 60 MPa, and the extrapolation behavior of the equation of state at high temperatures and high pressures is reasonable. The deviation of the density (100x(ρcal-ρexp)/ρexp) is generally less than 0.1% and does not exceed 0.2% except for very few data points in liquid region. The uncertainty of the vapor pressure of the equation of state is generally less than 2.0%. The deviation of viscosity equation developed is generally less than 2.0%, and the absolute average deviation (AAD) between experimental and calculated values is 1.03%. In additional, the extended corresponding states (ECS) model with R134a as the reference fluid was used to represent viscosities and thermal conductivities, and the absolute average deviations are 1.34% and 1.47%, respectively. Detail comparisons between experimental and calculated data have been performed in the work.

关键词： Hydrostatic pressure

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Numerical study of heat transfer characteristics in the solar receiver tube combined with MCRT method

Numerical study of heat transfer characteristics in the sola...

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Cheng, Z.D. He, Y.L. Xiao, J. Tao, Y.B. Xu, R.J. State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaan xi China

ISBN: (纸本)9780791802908

The solar energy flux distribution on the outer wall of the inner absorber tube of parabolic solar collector receiver is calculated successfully by a homemade code adopting Monte Carlo Ray-Trace Method (MCRT Method). It is revealed that the non-uniformity of the solar energy flux distribution is very large. Three-dimensional numerical simulation of coupled heat transfer characteristics in the receiver tube is calculated and analyzed by combining the MCRT Method and the FLUENT software, in which the heat transfer fluid and physical model are Syltherm 800 liquid oil and LS2 parabolic solar collector from the testing experiment of Dudley et al., respectively. Temperature- dependent properties of the oil and thermal radiation between the inner absorber tube and the outer glass cover tube are also taken into account. Then three typical testing conditions are chosen from the experiment to validate the reliability of the simulation code. Numerical results show that the predicted results agree well with the experimental data, the average relative error is within 2%. And then the mechanism of the coupled heat transfer in the receiver tube is further studied. Copyright © 2009 by ASME.

关键词： Numerical methods

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Numerical study on the coupled heat transfer performance of the parabolic solar absorber tube

Numerical study on the coupled heat transfer performance of ...

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Tao, Y.B. He, Y.L. State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9780791802908

In present paper, a two-dimensional numerical model for the coupled heat transfer process in the solar collector tube was developed and the unified dimensionless governing equations were derived. The full field computation method was adopted to deal with the fluid-solid conjugated heat transfer problem. The effects of Ra numbers and tube diameter ratio on the heat transfer and fluid flow performance were numerically analyzed under the constant heat flux conditions. The distributions of flow field, temperature field, local Nu and local temperature gradient were examined. The results show that when Ra is larger than 105, the effects of nature convection must be taken into account. Due to the effect of the nature convection, along the θ direction, the temperature in the cross-section decreases and the temperature gradient on the inner tube surface increases at first. When θ is near to π, the temperature and temperature gradients would present a converse variation. The local Nu on the inner tube surface increases along θ direction until it reaches a maximum then it decreases again. Due to the existing of the nature convection vortexes, the temperature distributions in some cross-sections present fluctuations along the r direction. Copyright © 2009 by ASME.

关键词： Heat flux

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Experimental study of nitrogen oxide emissions in a circulating fluidized bed

Experimental study of nitrogen oxide emissions in a circulat...

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20th International Conference on Fluidized Bed Combustion

作者： Liu, R.W. Zhou, Q.L. Hui, S.E. Xu, T.M. State Key Laboratory of Power Engineering Multiphase Flow Department of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

The experimental study was carried out on the emission characteristics of nitrogen oxide in a 0.3MW circulating fluidized bed as well as analysis of the formation and destruction mechanism of nitrogen oxide. Several variables associated with the combustion system were investigated in the experiment, which include bed temperature, excess air, primary-to-secondary air ratio, and coal species. It is found that the NOx emissions decrease along the height of the furnace, while the N2O emissions increase continuously. More NOx emissions and less N2O emissions are generated as the bed temperature increases. It is also illustrated that an increase of air stoichiometry leads to a significant NOx increase and an obvious N2O increase. And air staging is proved to be an effective way to control the nitrogen oxide emissions in the fluid bed. Besides, it is also shown in the experiment that the concentration of NOx and N2O is higher during the combustion of anthracite than that during the combustion of bituminous.

关键词： Nitrogen oxides

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Lattice Boltzmann method and its applications in engineering thermophysics

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Chinese Science Bulletin 2009年第18期54卷 4117-4134页

作者： HE YaLing LI Qing WANG Yong TANG GuiHua School of Energy and Power Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049 China

The lattice Boltzmann method (LBM), a mesoscopic method between the molecular dynamics method and the conventional numerical methods, has been developed into a very efficient numerical alternative in the past two decades. Unlike conventional numerical methods, the kinetic theory based LBM simulates fluid flows by tracking the evolution of the particle distribution function, and then accumulates the distribution to obtain macroscopic averaged properties. In this article we review some work on LBM applications in engineering thermophysics: (1) brief introduction to the development of the LBM; (2) fundamental theory of LBM including the Boltzmann equation, Maxwell distribution function, Boltzmann-BGK equation, and the lattice Boltzmann-BGK equation; (3) lattice Boltzmann models for compressible flows and non-equilibrium gas flows, bounce back-specular-reflection boundary scheme for microscale gaseous flows, the mass modified outlet boundary scheme for fully developed flows, and an implicit-explicit finite-difference-based LBM; and (4) applications of the LBM to oscillating flow, compressible flow, porous media flow, non-equilibrium flow, and gas resonant oscillating flow.

关键词：格子玻尔兹曼方法工程热物理格子Boltzmann 麦克斯韦分布函数分子动力学方法可压缩流动应用数值方法

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Experimental study on air-staged combustion in a W-shaped boiler furnace 9

Experimental study on air-staged combustion in a W-shaped bo...

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9th International Conference on power engineering, ICOPE 2009

作者： Liu, Ruwei Zhou, Qulan Hui, Shien Zhao, Qinxin Fan, Qingwei Xu, Tongmo Yu, Zhanying State Key Laboratory of Power Engineering Multiphase Flow Department of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaan xi710049 China

The experimental study was carried out on the air-staged combustion of different coal in a 1 MW W-shaped furnace. The combustion process occurred in two zones: the pre-stage combustion zone and the primary combustion zone. A variable SR was introduced to represent the air stoichiometric ratio in the pre-stage combustion zone. It is found that as SR decreases in the test range, the flame penetration depth is lengthened, and the temperature at the exit of the furnace decreases. Meanwhile, the maximum temperature in the central of the furnace first increases and then decreases, whereas the combustible loss and nitrogen oxides (NOx) emissions first decrease and then increase. The value of SR corresponding to the optimal combustion performance is 0.67 for lean coal and 0.65 for anthracite. Besides, it is also indicated that the effects of air-staging method are more significant on the lean coal than that on the anthracite.

关键词： Furnaces

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Hydrogen production by biomass gasification in supercriticor subcritical water with Raney-Ni and other catalysts

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中国高等学校学术文摘·能源与动力工程 2009年第4期3卷 456-464页

作者： Aixia PEI Lisheng ZHANG Bizheng JIANG Liejin GUO Ximin ZHANG Youjun LV Hui JIN Zhongyuan Petroleum Company Puguang Natural Gas Treating Plant Sinopec Dazhou 636156 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor with the presence of a series of Raney-Ni and its mixture with ZnCl2 or Ca(OH)2. The main gas products were hydrogen, methane, carbon dioxide, and a small amount of carbon monoxide. Different types of Raney-Ni, containing different metal components such as Fe, Mo or Cr, have different influences on the gasification yield and hydrogen selectivity. The catalysis effect can be improved obviously by adding ZnCl2 or Ca(OH)2 Increasing the reaction temperature or adding ZnCl2 and Ca(OH)2 could improve the mass of H2 in gas products and reduce the mass of CH4 and CO2 at the same time. The possible mechanism is that ZnCl2 can decompose the biomass particle by accelerating cellulose hydrolyzation in high-temperature water, increasing more specific surface to admit catalysts, while Ca(OH)2 can absorb CO2 to produce CaCO3 deposit, which can drop out from the reactant system, and which will drive the reaction to get more hydrogen. With respect to the biomass conversion to gas product and selectivity of H2 at low temperature, the series of Raney-Ni has shown many advantages over other catalysts; thus, this kind of catalyst has great potential to be utilized in the hydrogen industry for the gasification of biomass.

关键词： biomass catalyst gasification Raney-Ni supercritical water hydrogen

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Numerical simulation of entire pulse tube refrigerators

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2009年第3期43卷 1-9页

作者： He, Yaling Gao, Fan Tao, Yubing Liu, Yingwen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A one-dimensional and two-dimensional combined computational model (1-D and 2-DCC model) was set up to simulate the performances of the basic type, orifice type and double inlet type pulse tube refrigerators (PTRs). The Darcy-Brinkman-Forchheimer model and the thermally non-equilibrium model were adopted to depict the flow and heat transfer in the regenerator which was modeled by taking the mesh as a porous medium. Parameter communicating algorithms were defined to calculate velocity and temperature at the junctions between the 1-D and 2-D computational regions. Then the simulation codes for the whole PTRs were developed. The working process and complex flow phenomena such as velocity and temperature annular effects and DC flow in PTRs were revealed. The results show that a close loop in the PTR can be formed by using a double-inlet valve which leads to the occurrence of DC flow. For the case studied, the DC flow rate accounts for 4.66% of the total mass flow rate under the present parameters and working conditions.

关键词： Porous materials

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Experimental investigation of turbulent bubbly mixing layer using swirling strength method

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Huagong Xuebao/CIESC Journal 2009年第4期60卷 872-877页

作者： Ning, Tao Chen, Bin Guo, Fude Zhang, Ximin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent bubbly mixing layer was experimentally investigated by PIV and analyzed by using the swirling strength method. The velocity ratio between high speed and low speed was 4:1 and the Reynolds number based on the velocity difference of two streams and hydraulic channel diameter ranged from 4400 to 132000. Bubbles with a diameter from 0.5 mm to 2 mm were injected into the flow field at the end of the splitter and in the low speed side separately. By using the swirling strength method, the vortex structures excluded the effect of shear were shown clearly, and were concentrated in the coniform area of the central mixing flow field. With increasing Reynolds number, swirling strength increased and the coniform area became narrow. Swirling strength first increased and then decreased along the downstream direction at the same Reynolds number. When injected at the end of the splitter, most of the bubbles were distributed in the downstream area of the mixing layer where swirling strength was larger. However, when the bubbles were injected in the low speed side, bubbles were mainly concentrated in the low speed side, but some of them could also be trapped by the vortex structures and move to the central part of the mixing layer. Compared with the single phase case, the results indicated that swirling strength was strengthened when the bubbles were injected at a low Reynolds number, while it was weakened at a high Reynolds number. © All Rights Reserved.

关键词： Reynolds number

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