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Fan Zhao

Bio: Fan Zhao is an academic researcher from Northeastern University (China). The author has contributed to research in topics: Knudsen number & Direct simulation Monte Carlo. The author has an hindex of 3, co-authored 7 publications receiving 30 citations.

Papers
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Journal ArticleDOI
TL;DR: The results show that the changing in the gas physical properties does not affect the distribution of the velocity field, temperature fields, or other fields in the Knudsen pump, and the thermal creep effect is related to the molecular mass of the gas.
Abstract: A Knudsen pump operates under the thermal transpiration effect or the thermal edge effect on the micro-scale. Due to the uneven temperature distribution of the walls in the channel axis direction or the constant temperature of the tips on the walls, directional thermally-induced flow is generated. In this paper the Direct Simulation Monte Carlo (DSMC) method is applied for N2–O2 gas mixtures in the ratios of 4:1, 1:1, and 1:4 with different Knudsen numbers in a classic rectangular Knudsen pump to study the flow characteristics of the gas mixtures in the pump. The results show that the changing in the gas physical properties does not affect the distribution of the velocity field, temperature fields, or other fields in the Knudsen pump. The thermal creep effect is related to the molecular mass of the gas. Even in N2 and O2 gas mixtures with similar molecular masses, N2 can be also found to have a stronger thermal creep effect. Moreover, the lighter molecular weight gas (N2) can effectively promote the motion of the heavier gas (O2).

21 citations

Journal ArticleDOI
TL;DR: In this paper, a comparative study on the thermodynamic performance of two types of GLS vacuum pumps, the MGLS and the constant lead screw (CLS), is presented.

15 citations

Journal ArticleDOI
TL;DR: In this paper, a new online monitoring method is developed to determine the moisture change during the vacuum drying of lithium ion battery powder, which can estimate the moisture content accurately so the predicted value can be used as a reference for optimizing the drying process.

8 citations

Journal ArticleDOI
TL;DR: In this article, the influence of temperature, Knudsen number, surface accommodation coefficient, and geometric parameters of the microchannel on its gas separation efficiency are studied using the controlled variable method.

5 citations

Journal ArticleDOI
01 Apr 2020
TL;DR: Based on the ideal gas laws, a thermodynamics model of the double-blade roots vacuum pump is established and the influence of gas leakage on the pumping process is taken into consideration.
Abstract: As a kind of fluid machinery, the roots vacuum pump is widely used in the metallurgical industry and semiconductor industry. The double-blade roots vacuum pump is widely used in the vacuum system due to its easy manufacture and low cost. The pumping process can be divided into four distinctive processes (i.e. sucking process, transferring process, backlashing process and exhausting process). The characteristics of each process are illustrated sufficiently in this paper. Based on the ideal gas laws, a thermodynamics model of pumping process is established and the influence of gas leakage on the pumping process is taken into consideration. Using this model, quantificational expressions of five gas thermodynamic parameters (volume, mass, pressure, temperature and internal energy) are given. The performance curves are plotted by MATLAB and the pumping characteristics of double-blade roots vacuum pump are discussed at last. This research can provide a theoretical reference on the design of double-blade roots vacuum pump.

4 citations


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01 Jan 2002
TL;DR: In this article, the authors discuss the fluid-dynamic type equations derived from the Boltzmann equation as its asymptotic behavior for small mean free path and the boundary conditions that describe the behavior of the gas in the continuum limit.
Abstract: In this series of talks, I will discuss the fluid-dynamic-type equations that is derived from the Boltzmann equation as its the asymptotic behavior for small mean free path. The study of the relation of the two systems describing the behavior of a gas, the fluid-dynamic system and the Boltzmann system, has a long history and many works have been done. The Hilbert expansion and the Chapman–Enskog expansion are well-known among them. The behavior of a gas in the continuum limit, however, is not so simple as is widely discussed by superficial understanding of these solutions. The correct behavior has to be investigated by classifying the physical situations. The results are largely different depending on the situations. There is an important class of problems for which neither the Euler equations nor the Navier–Stokes give the correct answer. In these two expansions themselves, an initialor boundaryvalue problem is not taken into account. We will discuss the fluid-dynamic-type equations together with the boundary conditions that describe the behavior of the gas in the continuum limit by appropriately classifying the physical situations and taking the boundary condition into account. Here the result for the time-independent case is summarized. The time-dependent case will also be mentioned in the talk. The velocity distribution function approaches a Maxwellian fe, whose parameters depend on the position in the gas, in the continuum limit. The fluid-dynamictype equations that determine the macroscopic variables in the limit differ considerably depending on the character of the Maxwellian. The systems are classified by the size of |fe− fe0|/fe0, where fe0 is the stationary Maxwellian with the representative density and temperature in the gas. (1) |fe − fe0|/fe0 = O(Kn) (Kn : Knudsen number, i.e., Kn = `/L; ` : the reference mean free path. L : the reference length of the system) : S system (the incompressible Navier–Stokes set with the energy equation modified). (1a) |fe − fe0|/fe0 = o(Kn) : Linear system (the Stokes set). (2) |fe − fe0|/fe0 = O(1) with | ∫ ξifedξ|/ ∫ |ξi|fedξ = O(Kn) (ξi : the molecular velocity) : SB system [the temperature T and density ρ in the continuum limit are determined together with the flow velocity vi of the first order of Kn amplified by 1/Kn (the ghost effect), and the thermal stress of the order of (Kn) must be retained in the equations (non-Navier–Stokes effect). The thermal creep[1] in the boundary condition must be taken into account. (3) |fe − fe0|/fe0 = O(1) with | ∫ ξifedξ|/ ∫ |ξi|fedξ = O(1) : E+VB system (the Euler and viscous boundary-layer sets). E system (Euler set) in the case where the boundary is an interface of the gas and its condensed phase. The fluid-dynamic systems are classified in terms of the macroscopic parameters that appear in the boundary condition. Let Tw and δTw be, respectively, the characteristic values of the temperature and its variation of the boundary. Then, the fluid-dynamic systems mentioned above are classified with the nondimensional temperature variation δTw/Tw and Reynolds number Re as shown in Fig. 1. In the region SB, the classical gas dynamics is inapplicable, that is, neither the Euler

501 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview of the whole process in lithium-ion battery fabrication from powder to cell formation, and bridge the gap between academic development and industrial manufacturing.
Abstract: Electrode processing plays an important role in advancing lithium-ion battery technologies and has a significant impact on cell energy density, manufacturing cost, and throughput. Compared to the extensive research on materials development, however, there has been much less effort in this area. In this Review, we outline each step in the electrode processing of lithium-ion batteries from materials to cell assembly, summarize the recent progress in individual steps, deconvolute the interplays between those steps, discuss the underlying constraints, and share some prospective technologies. This Review aims to provide an overview of the whole process in lithium-ion battery fabrication from powder to cell formation and bridge the gap between academic development and industrial manufacturing.

167 citations

Journal ArticleDOI
TL;DR: In this article, the impact of powder technology on electrode microstructure evolution during electrode processing is discussed. And the progress in understanding the basic principles of the materials processing technologies for electrodes in lithium ion batteries is presented, including slurry mixing and coating, electrode drying, and calendering.

60 citations

Journal ArticleDOI
TL;DR: KPs are defined and classified according to the flow mechanisms of the thermally induced flows, and three aspects of configurations, performance, applications, and current problems of KPs in the current state of research are reviewed and analyzed.
Abstract: The Knudsen pump (KP) is a kind of micro-pump that can form thermally induced flows induced by temperature fields in rarefied gas environments. It has the advantages of having no moving parts, simple structure, easy construction and extension, a wide range of energy sources, and low energy consumption. With the development of Micro/Nano Electro Mechanical Systems (MEMS/NEMS), extensive studies have been conducted on KPs, and the applications of KPs have widened. In order to obtain efficient flow fields in KPs, it is necessary to adopt modern computational methods for simulation and analysis. In many circumstances, the simulation and experimental results have good agreement. However, there seems to be no comprehensive review on KPs at present. In this paper, KPs are first defined and classified according to the flow mechanisms of the thermally induced flows. Then, the three aspects of configurations, performance, and applications of KPs in the current state of research are reviewed and analyzed. Finally, the current problems of KP are discussed, and some suggestions are provided for future research and applications. Knudsen pumps are micro-sized, non-mechanical gas pumps that can be useful in a range of biomedical and mechanical fields. Zhang and his team from China’s North-eastern University analyzed Knudsen pumps’ configurations, performance, applications, and current problems. In Knudsen pumps, gas flow is induced by temperature gradients along the walls of the device. They benefit from low energy consumption and ease of manufacture. Different configurations, realized through the placement of variably heated walls, offer multiple mechanisms to transport rarefied gases. Knudsen pumps can be used, amongst other applications, to generate a vacuum, deliver fluids, and separate gases. Micro-channels play a key role in Knudsen pump efficiency and gas flow operation; however, there is a lack of research into efficiency which the authors say should be addressed in future research.

30 citations

Journal ArticleDOI
TL;DR: In this paper, a numerical analysis of a novel configuration of the Knudsen pump for rarefied gas flow is presented, where the authors apply the direct simulation Monte Carlo (DSMC) method to study the influence of the operation conditions and geometric parameters on the gas flow.

23 citations