科创中国

An experimental rig was constructed for the study of low temperature corrosion of heat exchangers. The experimental rig can simulate flue gas environment and control multiple factors quantitatively. H-type finned tube heat exchangers widely used in waste heat utilization was used for the experimental study on the influencing factors of low temperature corrosion of H-type finned tube heat exchangers. The changes of surface morphology and corrosion products of H-type finned tube heat exchangers under different tube wall temperatures were observed and analyzed, and the condensation rates of sulphuric acid under different flue gas flux rates, flue gas temperatures, sulphuric acid volume fractions and tube wall temperatures were obtained. The results showed that H-type finned tube heat exchangers are corroded relatively badly when the tube wall temperature is lower than water vapor dewpoint and the corresponding corrosion mechanism is oxygen absorption corrosion. Flue gas flux rate, flue gas temperature, flue gas sulphuric acid volume fraction and tube wall temperature can influence the condensation rate of sulphuric acid but in different degrees. As flue gas sulphuric acid volume fraction increased from 10×10^-6 to 50×10^-6, the condensation rate of sulphuric acid increased almost linearly from 2.50×0^-7 mol·m^-2·s^-1 to 7.03×10^-7 mol·m^-2·s^-1; as tube wall temperature decreased from 80℃ to 50℃, the condensation rate of sulphuric acid increased from 3.06×0^-7 mol·m^-2·s^-1 to 1.75×0^-6 mol·m^-2·s^-1. When tube wall temperature decreased further, the measured condensation rate of sulphuric acid decreased because of the heat dissipation of condensed water. The formation of sulphuric acid fog and it's adhesion to the tube wall have a great impact on the condensation rate of sulphuric acid. The research results have some guiding significance for developing novel techniques to alleviate low temperature corrosion and improving flue gas waste-heat utilization systems.

Yong Pei;雅玲 何

Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University

2017-3-10

Membrane electrode assemble (MEA) design is one of the crucial component of MFC. Therefore, the MEA design is critical to improving MFC's performance. In this work, effects of the presence of the cathode microporous layers and the distance between anode and cathode electrodes on MFC's performance are investigated. The experimental result indicates that the peak power density first decreases from 973 to 797 mW/m2 when decreasing the distance from 2 to 1 cm, and then increases to 955 mW/m2 when further reducing the distance to 0 cm. Meanwhile the ohmic resistance of the MFCs decreases from 34 to 14 and to 4.6 Ω with the reduced distance. This is because that the peak power density is improved by increasing the anode potential and decreasing the ohmic loss due to the reduced distance. However, when distance reduced from 1 to 0 cm, the decrease of cathode potential becomes the predominant factor. It is also found that the aerobic heterotrophic microorganism growing on the surface of both the proton exchange membrane and the anode electrode lowers the coulomb efficiency by consuming the organic substance. In addition, the presence of aerobic bacteria is the possible factor that induces the non-linear correlation between the ohmic polarization and electrodes distance.

Sen Yao;雅玲 何;印实 李;Huan Xi

Energy Procedia

2014

From aspect of energy consuming to pump heat transfer fluid, there is no sound basis on which to create an optimum design of a thermal energy storage unit. Thus, it is necessary to develop a parameter to indicate the energy efficiency of such unit. This paper firstly defines a parameter that indicates the ratio of heat storage of phase change thermal energy storage unit to energy consumed in pumping heat transfer fluid, which is called the energy efficiency ratio, then numerically investigates the characteristics of this parameter. The results show that the energy efficiency ratio can clearly indicate the energy efficiency of a phase change thermal energy storage unit. When the fluid flow of a heat transfer fluid is in a laminar state, the energy efficiency ratio is larger than in a turbulent state. The energy efficiency ratio of a shell-and-tube phase change thermal energy storage unit is more sensitive to the outer tube diameter. Under the same working conditions, within the heat transfer fluids studied, the heat storage property of the phase change thermal energy storage unit is best for water as heat transfer fluid. A combined parameter is found to indicate the effects of both the physical properties of phase change material and heat transfer fluid on the energy efficiency ratio.

Wei Wei Wang;Liang Bi Wang;雅玲 何

Applied Energy

2015-1-5

The equivalent thermal conductivities of 50 kinds of hollow clay bricks with the size of 240 × 115 × 90 (in mm) and different hole number and arrangement have been predicted numerically by the finite volume method. The influences of the hole surface radiation and the indoor-outdoor temperature difference are also considered. The results reveal that the hole surface radiation can not be neglected. The hole number and arrangement have significant effects on the equivalent thermal conductivity. There is an optimal configuration for which the equivalent thermal conductivity is the lowest. For this optimum configuration its equivalent thermal conductivity does not vary with the indoor-outdoor temperature difference. The simulation results provide valuable data for the hollow brick design in the building engineering.

Lin Ping Li;Zhi Gen Wu;增耀 李;雅玲 何;文铨 陶

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

2008-5

This paper proposes an improved lattice Boltzmann scheme for incompressible axisymmetric flows. The scheme has the following features. First, it is still within the framework of the standard lattice Boltzmann method using the single-particle density distribution function and consistent with the philosophy of the lattice Boltzmann method. Second, the source term of the scheme is simple and contains no velocity gradient terms. Owing to this feature, the scheme is easy to implement. In addition, the singularity problem at the axis can be appropriately handled without affecting an important advantage of the lattice Boltzmann method: the easy treatment of boundary conditions. The scheme is tested by simulating Hagen-Poiseuille flow, three-dimensional Womersley flow, Wheeler benchmark problem in crystal growth, and lid-driven rotational flow in cylindrical cavities. It is found that the numerical results agree well with the analytical solutions and/or the results reported in previous studies.

Q. Li;雅玲 何;G. H. Tang;文铨 陶

Physical Review E

2010-5-27

A two-dimensional two-phase non-isothermal mass transport model for liquid feed direct methanol fuel cells (DMFCs) is presented in this paper. The heat and mass transfer across the membrane electrode assembly (MEA) is formulated based on the classical multiphase flow theory in the porous media. The effects of methanol crossover and non-equilibrium evaporation/condensation of methanol and water at the gas-liquid interface on the cell performance are considered. Results of this model show that the methanol feeding concentration and cell operation temperature have great effects on the cell performance. The distribution of cell temperature is non-uniform and the highest temperature appears in the cathode catalyst layer (CL). The effects of open-ratio of the flow field plate and the thermal conductivity of diffusion layers, catalyst layers and membrane are also investigated in this work.

Zheng Miao;雅玲 何;Xiao Yue Li;Jin Qiang Zou

2009

This paper presents an investigation of the non-periodic boundary condition (NPBC) which is often used in multiscale molecular-continuum simulations. The relationship between the boundary force exerted by the atoms outside the atomistic domain and the density and temperature at the boundary is studied. Fitting formulas of the boundary force as function of the fluid state has been proposed based on the relationship. The accuracy of fitting formulas is verified by the equilibrium MD simulation results. Poiseuille flow is then simulated using the proposed fitting formulas. The elimination of density oscillation near the boundary of atomistic region further confirm the correctness of our fitting formulas.

Wen Jing Zhou;Hui Bao Luan;Jie Sun;雅玲 何;文铨 陶

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

2012-12

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.

于兵 陶;雅玲 何

2009

This paper is concerned with the shape reconstruction of a bounded domain with a viscous incompressible fluid driven by the Oseen equations. For the approximate solution of the ill-posed and nonlinear problem we propose a regularized Gauss-Newton method. A theoretical foundation for the method is given by establishing the differentiability of the boundary value problem with respect to the boundary in the sense of the domain derivative. The results of several numerical experiments show that our theory is useful for practical purpose, and the proposed algorithm is feasible.

Wenjing Yan;雅玲 何;Yichen Ma

Applied Mathematical Modelling

2012-1

This paper summarized the development of the effective thermal conductivity models for the nanoporous silica aerogel insulation material. Firstly, the nanoscale heat transfer characteristics inside aerogel material was introduced. Secondly, the existing models and methods to calculate the thermal conductivity of each heat transfer mode at the nanoscale were reviewed. Next, the advances and developments of the effective thermal conductivity models for the nanoporous silica aerogel materials as well as its composite insulation material were also discussed. Then the procedure of establishing the effective thermal conductivity model of the aerogel insulation material from nanoscale to macroscale was introduced by taking our previous work as an illustration. Finally, it should be noted that for the nanoporous silica aerogel insulation material, there are still some key issues that need to be investigated to get deep understanding of the mechanism of nanoscale heat transfer inside the material, such as the coupled heat transfer behavior at the gas-solid contact interface, the influence of scale effect/interfacial effect on the thermal conductivity of nanoscale solid particles, etc. Thus it is necessary to keep on investigating these questions thoroughly to provide help for establishing more accurate heat transfer model as well as optimizing the insulation performance of the material.

雅玲 何;Tao Xie

Applied Thermal Engineering

2015-4-25