太阳能集热器的热流气体对砾石的蓄放热特性研究(英文)

太阳能的蓄放热特性的研究对清洁能源太阳能的开发和利用具有重要意义。该文利用冬季太阳能集热器的热流气体,对砾石的蓄放热特性进行了研究。以居民居住的标准房间(4m×2.7m)为依据进行了模拟;利用太阳能集热器的热能与直径为50～100mm的砾石铺设成150mm厚度的地下蓄热系统进行蓄热和放热试验,研究昼夜之间室内砾石的蓄热和放热特性;通过测试太阳能集热器的内部温度、砾石层内部及室内地表面的温度,研究了太阳能集热器的蓄热效率和转换效率,同时分析了蓄热层及室内地表面的热传递特性;为进一步开拓针对冬季寒冷地区太阳能蓄热型居民建筑物内部热环境方面的基础研究提供了科学的依据。

气体弹簧式喷嘴热流道在医用导管模具生产中的应用

在工作实践中时常面对着如何提高注塑模的生产效率和产品质量以及在满足客户需求的情况下尽可能地简化模具结构的情况,针对气体弹簧式喷嘴热流道在医用导管产品中的应用,论述了气体弹簧式喷嘴热流道在实际生产中的设计、制造及生产特点。

CFD modeling of gas−liquid flow phenomenon in lead smelting oxygen-enriched side-blown furnace

A validated numerical model was established to simulate gas−liquid flow behaviors in the oxygen-enriched side-blown bath furnace.This model included the slip velocity between phases and the gas thermal expansion effect.Its modeling results were verified with theoretical correlations and experiments,and the nozzle-eroded states in practice were also involved in the analysis.Through comparison,it is confirmed that the thermal expansion effect influences the flow pattern significantly,which may lead to the backward motion of airflow and create a potential risk to production safety.Consequently,the influences of air injection velocity and furnace width on airflow behavior were investigated to provide operating and design guidance.It is found that the thin layer melt,which avoids high-rate oxygen airflow eroding nozzles,shrinks as the injection velocity increases,but safety can be guaranteed when the velocity ranges from 175 to 275 m/s.Moreover,the isoline patterns and heights of thin layers change slightly when the furnace width increases from 2.2 to 2.8 m,indicating that the furnace width shows a limited influence on production safety.

船用隐极无刷发电机混合通风和温度场仿真计算研究

该文针对船用隐极发电机混合通风风路的结构 ,建立多元二次非线性回路压降方程组 ,引入函数风阻使之降幂成为多元一次非线性方程组 ,以解算出各等效风路的空气流量 ;引入气体热流 ,构造非线性节点热流方程组 ,以解算出求解域中各节点的温度。

电机三维温度场的综合分析

运用稳定导热问题的有限差分法分析电机三维温度场，对电机内的对流换热系数采用ｈ＝ ｃ ｖ~ｎ的计算公式，引入气体热流的概念，对电机温度场与电机内空气温度场使用耦合边界条件，实现了两者的同时迭代求解。

Air interaction around outdoor air-cooled condensers

In order to increase cooling or heating efficiency,a porous computational fluid dynamics（CFD）model is employed to predict the thermo-fluid status and optimize the placement of outdoor units.A full scale model is established to validate the accuracy of CFD simulation in terms of velocity and temperature distributions.The comparison between the measurement and the simulation shows a good agreement.By evaluating the condensers＇ sucked air temperature with CFD for three units installed in a row,it is found that the minimum separation distance among neighboring units is 0.2 m;a vertical wall should be apart from the unit line by at least 0.8 m;and large different operating pressures among units do not impact the flow rate and the heat transfer of the other units meaningfully.

A Two-Layer Model for Superposed Electrified Maxwell Fluids in Presence of Heat Transfer

Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of the linearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfaciaJ stability has been studied. The stability criteria are performed theoreticaily in which stability diagrams are obtained. In the limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time.

Response of Mode Water and Subtropical Countercurrent to Greenhouse Gas and Aerosol Forcing in the North Pacific

The response of the North Pacific Subtropical Mode Water and Subtropical Countercurrent (STCC) to changes in greenhouse gas (GHG) and aerosol is investigated based on the 20th-century historical and single-forcing simulations with the Geo-physical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3). The aerosol effect causes sea surface temperature (SST) to decrease in the mid-latitude North Pacific, especially in the Kuroshio Extension region, during the past five decades (1950-2005), and this cooling effect exceeds the warming effect by the GHG increase. The STCC response to the GHG and aerosol forcing are opposite. In the GHG (aerosol) forcing run, the STCC decelerates (accelerates) due to the decreased (increased) mode waters in the North Pacific, resulting from a weaker (stronger) front in the mixed layer depth and decreased (increased) subduction in the mode water formation region. The aerosol effect on the SST, mode waters and STCC more than offsets the GHG effect. The response of SST in a zonal band around 40?N and the STCC to the combined forcing in the historical simulation is similar to the response to the aerosol forcing.

Theoretical Model of the Tropospheric Pressure Variation on the Height

In the study and the research of the troposphere, the knowledge about its pressure variation on the height is necessary and important. Of course, exist the sounding to make this work, but not always it is possible to access to sounding data when is necessary, so then, it is important to has others alternatives methods in order to replace it. The troposphere is basically a fluid, susceptible to be studied under the fluid mechanics and thermodynamics of the ideals gases without loss generalities. So, it is possible to study of the atmospheric air like as a continuous perfect gas. These facts are important questions to study the troposphere under the laws and beginning Physics, using its respective equations, in order to get a theoretical model to simulate the behavior of its thermodynamics variables and parameters. Working on this line, it was developed a model in order to simulate the tropospheric pressure variation on the height from its measure on surface data.

Design and parametric optimization of thermal management of lithium-ion battery module with reciprocating air-flow

Single cell temperature difference of lithium-ion battery(LIB) module will significantly affect the safety and cycle life of the battery. The reciprocating air-flow module created by a periodic reversal of the air flow was investigated in an effort to mitigate the inherent temperature gradient problem of the conventional battery system with a unidirectional coolant flow with computational fluid dynamics(CFD). Orthogonal experiment and optimization design method based on computational fluid dynamics virtual experiments were developed. A set of optimized design factors for the cooling of reciprocating air flow of LIB thermal management was determined. The simulation experiments show that the reciprocating flow can achieve good heat dissipation, reduce the temperature difference, improve the temperature homogeneity and effectively lower the maximal temperature of the modular battery. The reciprocating flow improves the safety, long-term performance and life span of LIB.

Prediction of Thermophoretic Deposition Efficiency of Particles in a Laminar Gas Flow along a Concentric Annulus： A Comparison of Developing and Fully Developed Flows

Thermophoresis is an important mechanism of micro-particle transport due to temperature gradients in the surrounding medium.It has numerous applications,especially in the field of aerosol technology.This study has numerically investigated the thermophoretic deposition efficiency of particles in a laminar gas flow in a concentric annulus using the critical trajectory method.The governing equations are the momentum and energy equations for the gas and the particle equations of motion.The effects of the annulus size,particle diameter,the ratio of inner to outer radius of tube and wall temperature on the deposition efficiency were studied for both developing and fully-developed flows.Simulation results suggest that thermophoretic deposition increases by increasing thermal gradient,deposition distance,and the ratio of inner to outer radius,but decreases with increasing particle size.It has been found that by taking into account the effect of developing flow at the entrance region,higher deposition efficiency was obtained,than fully developed flow.

Non-Thermal Plasma Assisted Reforming of Ethanol in Dynamic Plasma-Liquid Systems

The paper presents experimental and theoretical studies of non-thermal plasma assisted reforming of liquid ethanol into hydrogen-rich syngas in dynamic plasma-liquid systems （PLS） using electric DC and pulsed discharges in a gas channel with liquid wall （DGCLW） and DC discharge in a reverse vortex gas flow of Tornado type with ＂liquid＂ electrode （TORNADO-LE）. Results of experiments show the energy efficiency of plasma-chemical conversion of ethanol in studied systems. Results of model calculations explain the kinetic mechanism of non-equilibrium plasma-chemical transformations in different conditions. The proposed technique of plasma-fuel reforming can be used in alternative biofuels combustion technologies in advanced diesel engines and power plants.

Temperature distribution of the incompletely mixed fluid flowing in the tubes and the unmixed fluid crossing over the tubes

A new model is established to describe heat exchanging of the incompletely mixed fluid flowing in the tubes and the unmixed fluid crossing out of the tubes in the heat-exchangers especially in air cooler. In the model, a new method of analyzing volume is proposed to develop the temperature distribution equations of the two fluids --tw（x） and ta（X,,7＂）. With tw（x） and ta （x, ,7）, the curves of the temperature distribution of the two fluids can be obtained. Also tw（x） and ta（x,n） can be used to calculate parameters of structure of an air cooler and to improve performances of it.

Numerical investigation of optimal geometry parameters for ejectors of premixed burner

An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.

Preheating Characteristics of Datong Coal in O2/CO2 and Air Atmospheres

Experimental studies were carried out to find the difference of preheating characteristics of Datong coal in O_2/CO_2 and air atmospheres by a circulating fluidized bed. It is found that pulverized coal could be both steadily preheated to above 800°C in the two different atmospheres, but the temperature distribution was more uniform along the riser in O_2/CO_2 atmosphere. During the preheating, the content of CO in the flue gas can reach 12.32% under the O_2/CO_2 atmosphere, far higher than that in air(5.94%). Simultaneously, the conversion rate of fixed carbon was higher in O_2/CO_2 atmosphere compared with that in air. It can be inferred the higher oxygen concentration and higher partial pressure of CO_2 have greatly accelerated the gasification reaction. The BET analysis indicated a number of large pores were transformed into micropores during the preheating progress, and the major contributors for overall pore volume of chars and specific surface area are the micro-pores and the mesopores with diameter ranging from 2 nm to 10 nm. The inner pore structure was more developed in O_2/CO_2 atmosphere.

Numerical Simulation of Flow and Heat Transfer from Slot Jets Impinging on a Cylindrical Convex Surface

Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental data.Flow structures are described and impingement heat transfer characteristics are discussed.The effects of Re,H/B and D/B on single-slot jets impingement heat transfer are analyzed and heat transfer characteristics of multiple-slot jets are investigated.The results show that:Gas flows along the convex surface and boundary layer separation occurs in both single and multiple-slot jets impingement.A maximum stagnation Nu appears at H/B=8 and the local Nu decreases with increasing H/B in the region far away from the stagnation.The Nu in the stagnation region decreases with increasing D/B but the Nu is nearly the same in the region far away from the stagnation.Pressure gradient is an important factor on heat transfer enhancement.Correlations of the Num for single-slot,double-slot and quadric-slot jets impinging on a convex surface are obtained.It indicates the effects of Re and D/B on Num could become more important in less slot jets impingement.

Numerical and Experimental Studies of an Arc-heated Nonequilibrium Nozzle Flow

The arc-heated high-temperature gas is rotationally and vibrationally excited, and partially dissociated and ionized. When such gas flows inside a nozzle, energy transfers from rotational and vibrational energy modes to translational energy mode, and, in addition, recombination reactions occur. These processes are in thermal and chemical nonequilibrium. The present computations treat arc-heated nonequilibrium nozzle flows using a six temperature model (translational, rotational, N2 vibrational, O2 vibrational, NO vibrational and electron temperatures), and nonequilibrium chemical reactions of air. From the calculated flow properties, emission spectra at the nozzle exit were re-constructed by using the code for computing spectra of high temperature air. On the other hand, measurements of N2+(1-) emission spectra were conducted at the nozzle exit in the 20 kW arc-heated wind tunnel. Vibrational and rotational temperatures of N2 were determined using a curve fitting method on N2+(1-) emission spectra, with the vibrational and rotational temperatures for N2 and N2+ being assumed equal. Comparison of the measured and computed results elucidated that the experimental temperatures were larger than the computed ones. At present, we are trying to reveal the main reason for the discrepancy between the computed and measured N2 vibrational and rotational temperatures.

Convective heat transfer for incompressible laminar gas flow in micropassage with constant wall temperature

Theoretical investigations have been performed on the convective heat transfer for incompressible laminar flow of gases through microtube and parallel-plates micropassages with constant wall temperature. Considering the change in thermal conductivity and viscosity of gas in wall adjacent region from the kinetic theory, mathematical models are built for both of the micropassages. The dimensionless temperature distribution and the corresponding heat transfer characteristics are simulated numerically, and the results discussed briefly.

Analysis of Particle Behavior in High-Velocity Oxy-Fuel Thermal Spraying Process

This paper analyzes the behavior of coating particle as Well as the gas flow both of inside and outside the High-Velocity Oxy-Fuel (HVOF) thermal spraying gun by using quasi-one-dimensional analysis and numerical simulation. The HVOF gun in the present analysis is an axisymmetric convergent-divergent nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. In the present analysis it is assumed that the influence of the particles injected in the gas flow is neglected, and the interaction between the particles is also neglected. The gas flow in the gun is assumed to be quasi-one-dimensional adiabatic flow. The velocity, temperature and density of gas in the jet discharged from the barrel exit are predicted by solving Navier-Stokes equations numerically. The particle equation of motion is numerically integrated using three-step Runge-Kutta method. The drag coefficient of the particle is calculated by linear interpolation of the experimental data obtained in the past. Particle mean temperature is calculated by using Ranz and Marchalls' correlation for spherical particles. From the present analysis, the distributions of velocity and temperature of the coating particles flying inside and outside the HVOF gun are predicted.

Nonlinear Ramsey Interferometry of Fermi Superfluid Gases in a Double-Well Potential

The nonlinear Ramsey interferometry of Fermi superfluid gases in a double-well potential is investigated in this paper. We found that the frequency of the Ramsey fringes exactly reflects the strength of nonlinearity, or the scattering length of the Fermi superfluid gases. The cases of sudden limit, the adiabatic limit and the general case are studied. The analytical result is in good agreement with the numerical ones. The adiabatic condition is proposed. In general situation, the zero-frequency point emerge. Finally the possible applications of the theory axe discussed.