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  • Experimental and numerical study of CO2 adsorption on Ni/DOBDC metal-organic framework

    • 摘要:

      Metal-organic frameworks show promising applications for carbon capture and storage. In this research, CO2 adsorption on a Ni/DOBDC metal-organic framework was experimentally studied at a pressure range of 0 kPa-100 kPa and a temperature range of 25°C-115°C. The adsorption of CO2 and selectivity for CO2/CH4 were also numerically examined through the grand canonical Monte Carlo method. The adsorbed amount increased significantly at the initial stage and then rose in a steady manner with increased pressure. In contrast, the isosteric heat of adsorption gradually decreased. As the temperature increased, the adsorbed amount decreased linearly, but the isosteric heat of adsorption remained nearly unchanged. The sites and density profiles of the adsorbate provided insight into the formed Ni2+⋯O=C=O at the molecular level. The selectivity for CO2/CH4 was sensitive to pressure and temperature. The electronic contribution could reach 62.0%-68.3% in the 0 kPa-100 kPa pressure range and 40.7%-68.3% in the 25°C-115°C temperature range.

    • 作者:

      H. Wang;治国 屈;W. Zhang;Y. X. Chang;雅玲 何

    • 刊名:

      Applied Thermal Engineering

    • 在线出版时间:

      2014-12-22

  • Coupled optical and thermal performance of a fin-like molten salt receiver for the next-generation solar power tower

    • 摘要:

      The receiver temperature for the next-generation concentrated solar power will be increased from about 560 °C to more than 700 °C, which increases heat losses and decreases receiver efficiency. To meet the challenge, coupled optical and thermal performance of a fin-like molten salt receiver is numerically evaluated by combining Monte Carlo Ray Tracing method and Finite Volume method. The numerical model is firstly validated by comparing the calculated results with the experimental results of the Solar Two plant. After validation, the model is used to obtain the optimal configuration of the fin-like receiver by parametric optimization. Then, efficiencies of the optimal fin-like receiver are compared with those of two cylindrical receivers under different time and weather conditions. In the end, solar flux distribution of the optimal fin-like receiver is analyzed. The results show that when the receiver diameters are the same, the efficiency of the optimal fin-like receiver, with a fin number of 12 and an inner diameter of 1.0 m, has an improvement of 3.8% compared with that of the cylindrical receiver at noon of spring equinox. Besides, the fin-like receiver can also achieve higher efficiencies than the two cylindrical receivers under different time and weather conditions. Moreover, the peak solar flux of the fin-like receiver is also reduced, which is smaller than that of the cylindrical receiver by 38.6% at noon of spring equinox under the same receiver diameter.

    • 作者:

      Wen Qi Wang;Yu Qiu;Ming Jia Li;雅玲 何;Ze Dong Cheng

    • 刊名:

      Applied Energy

    • 在线出版时间:

      2020-8-15

  • Numerical study on performance and fin efficiency of wavy fin-and-tube heat exchangers

    • 摘要:

      Three-dimensional numerical studies were performed for the performance of wavy fin-and-tube heat exchangers in Body-Fitted Coordinates (BFC) system. Effects of geometric parameters on air-side heat transfer and fluid flow characteristics and fin efficiency were examined. The results showed that with the increase in Reynolds number, wavy angle, fin thickness and the decrease in fin pitch and transverse tube pitch, the heat transfer performance are enhanced; however, pressure drops are also increased. So, in practical applications, the wavy angle had better be located between 10° and 20° and the fin pitch should be located between 1.2 mm and 2.0 mm. The fin efficiency and average fin surface temperature decrease with the increase of Reynolds number, wavy angle, fin pitch and transverse tube pitch. With the increase of fin thickness, the fin efficiency and average temperature on fin surface also increase.

    • 作者:

      于兵 陶;雅玲 何;治国 屈;文铨 陶

    • 刊名:

      Progress in Computational Fluid Dynamics

    • 在线出版时间:

      2011-6

  • Analysis and numerical tests of lifting relations to reconstruct LBM distribution functions for coupling simulations

    • 摘要:

      The reconstruction operator (RO), which calculates the distribution functions of the lattice Boltzmann method (LBM) by the macroscopic variables, is important for the information exchange in the coupling simulation between LBM and macroscopic numerical methods. In the present work, different ROs are derived based on the first- and second-order expansions. The derivations show that the second-order ROs can conserve the momentum but the first-order ROs fail. The first-order models can be modified to guarantee the momentum conservation. The numerical tests are employed to evaluate the precisions of different models. The results demonstrate that the multiple-relaxation-time LBM is more stable than the single-relaxation-time LBM, and the first-order models are more stable than the second-order models. The second-order models give better reconstructions of the non-equilibrium parts of the distribution functions than the first-order models. However, the modified first-order models have similar accuracy to the second-order models when they are employed as boundary conditions or used in coupling simulations. Therefore, the second-order models are suggested for the initial conditions. The modified first-order models are suggested for the boundary conditions and the coupling simulations. Moreover, CPU time for coupling simulation decreases with the increase of the ratio between the time steps of finite volume method and LBM, and an optimized time ratio exists to minimize the errors. Finally, the flow past a porous medium is simulated by both the coupling methods and the multi-block LBM. The results show that the coupling methods are more efficient when using a large time step for the finite volume method.

    • 作者:

      Zi Xiang Tong;Ming Jia Li;雅玲 何;文铨 陶

    • 刊名:

      International Journal of Heat and Mass Transfer

    • 在线出版时间:

      2017-4-1

  • Experimental study on two kinds of heat sinks of CPU

    • 摘要:

      The heat transfer characteristics of two kinds of heat sinks, plain plate fins and sub-sectioned plain plate fins, are experimentally measured to investigate the forced cooling capacity of the heat sinks under different power input and approaching velocity. It is concluded that heat transfer coefficient mainly depends on the approaching velocity, and not much of the power input. The sub-sectioned plain plate fin has higher heat transfer coefficient at the cost of a little friction increasing.

    • 作者:

      Zheng Yu Lu;Jian Yin Xiong;Zhi Guo Qu;Hui Zhen Li;雅玲 何;文铨 陶

    • 刊名:

      Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

    • 在线出版时间:

      2004-9

  • The reduction of indoor temperature fluctuation by using phase changing materials included in some building components

    • 摘要:

      Under periodic outdoor temperature fluctuation, unsteady two-dimensional numerical simulation for a room with phase change materials in walls is performed to assess the effects of phase change materials on the room temperature fluctuation. The primary affecting factors such as the thermo-physical properties and thickness of PCMs are investigated. The results show that the daily temperature fluctuation is reduced by using PCMs. To resist the outdoor climate in summer, the function of the lateral wall with PCMs is better than that of the ceiling and ground with PCMs. To keep small temperature fluctuation for a long period in winter it is better to adopt a ground with PCMs. The present work is helpful to the application of PCMs in buildings for reducing indoor temperature fluctuation in both summer and winter.

    • 作者:

      Zhi Gen Wu;雅玲 何;文铨 陶

    • 刊名:

    • 在线出版时间:

      2011

  • Étude expérimentale de l'évaporation du film tombant de r134a et de r123 sur un tube horizontal amélioré

    • 摘要:

      Falling film evaporation is an efficient heat transfer mode in refrigeration and air conditioning industries. In this paper, the falling film evaporation performances of R134a and R123 outside four enhanced tubes and a smooth tube are tested. The results reveal that: with the decrease of film flow rate the falling film heat transfer coefficients of both R134a and R123 on the five tubes exhibit two general stages (a plateau stage and a sharp drop stage); for R134a the plateau is quite uniform while for R123 a mild decrease occurs with the decrease in film flow rate. The four enhanced tubes behave differently in heat transfer performances for R134a and R123. R134a provides around 2–3 times of heat transfer coefficients of R123 for all tubes.

    • 作者:

      Chuang Yao Zhao;Pu Hang Jin;Wen Tao Ji;雅玲 何;文铨 陶

    • 刊名:

      International Journal of Refrigeration

    • 在线出版时间:

      2017-3-1

  • A two-phase non-isothermal mass transport model for direct methanol fuel cells

    • 摘要:

      A two-phase non-isothermal mass transport model is presented in this paper. The heat and mass transfer across the membrane electrode assembly (MEA), coupled with the electrochemical reactions in the catalyst layers (CLs), are calculated based on the classical two-phase flow model in the porous media. The effect of methanol crossover on the cell performance and the non-equilibrium evaporation/condensation of water are considered in this model. The modeling results show that the distribution of temperature in the MEA is not uniform, and the highest temperature appears in the cathode CL. The non-uniform distributed methanol concentration leads to the non-uniform distributed methanol oxidization reaction (MOR) rate while the oxygen reduction reaction (ORR) rate mainly depends on the distribution of the local overpotential in the cathode CL. The increase in the open ratio of the flow field plate results in more uniform distribution of physical fields in the fuel cell and the cell performance is also improved with a larger open ratio.

    • 作者:

      Zheng Miao;雅玲 何;Xiang Lin Li;Jin Qiang Zou

    • 刊名:

      Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

    • 在线出版时间:

      2009-12

  • Experimental study of compressibility, roughness and rarefaction influences on microchannel flow

    • 摘要:

      The existing experimental data in the literature on friction factor in microchannels are analyzed. Flow characteristics for nitrogen and helium in stainless steel microtubes, fused silica microtubes and fused silica square microchannels are studied experimentally. The data in fused silica microtubes with diameters ranging from 50 to 201 μm and the data in fused silica square channels with hydraulic diameter ranging from 52 to 100 μm show that the friction factors are in good agreement with the theoretical predictions for conventional-size channels. The friction factors in stainless steel tubes (D = 119-300 μm) are much higher than the theoretical predictions for tubes of conventional size. This discrepancy is resulted from the large relative surface roughness in the stainless steel tubes. From the literature review and the present test data it is suggested that for gaseous flow in microchannels with a relative surface roughness less than 1% the conventional laminar prediction should still be applied. A positive deviation of the friction factor from the conventional theory is observed due to the compressibility effect. In addition, smaller friction factors in fused silica microtubes with inner diameters ranging from 10 to 20 μm are obtained and the decrease in friction factor from the rarefaction effect is observed.

    • 作者:

      G. H. Tang;Zhuo Li;雅玲 何;文铨 陶

    • 刊名:

      International Journal of Heat and Mass Transfer

    • 在线出版时间:

      2007-6

  • Pore-scale study of multiphase reactive transport in fibrous electrodes of vanadium redox flow batteries

    • 摘要:

      The electrode of a vanadium redox flow battery generally is a carbon fibre-based porous medium, in which important physicochemical processes occur. In this work, pore-scale simulations are performed to study complex multiphase flow and reactive transport in the electrode by using the lattice Boltzmann method (LBM). Four hundred fibrous electrodes with different fibre diameters and porosities are reconstructed. Both the permeability and diffusivity of the reconstructed electrodes are predicted and compared with empirical relationships in the literature. Reactive surface area of the electrodes is also evaluated and it is found that existing empirical relationship overestimates the reactive surface under lower porosities. Further, a pore-scale electrochemical reaction model is developed to study the effects of fibre diameter and porosity on electrolyte flow, VII/VIII transport, and electrochemical reaction at the electrolyte-fibre surface. Finally, evolution of bubble cluster generated by the side reaction is studied by adopting a LB multiphase flow model. Effects of porosity, fibre diameter, gas saturation and solid surface wettability on average bubble diameter and reduction of reactive surface area due to coverage of bubbles on solid surface are investigated in detail. It is found that gas coverage ratio is always lower than that adopted in the continuum model in the literature. The current pore-scale studies successfully reveal the complex multiphase flow and reactive transport processes in the electrode, and the simulation results can be further upscaled to improve the accuracy of the current continuum-scale models.

    • 作者:

      Li Chen;雅玲 何;文铨 陶;Piotr Zelenay;Rangachary Mukundan;Qinjun Kang

    • 刊名:

      Electrochimica Acta

    • 在线出版时间:

      2017-9-10

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