CO2水冷气体冷却器理论与实验研究

针对自然工质CO2热泵热水器中套管式气体冷却器进行理论分析与实验研究。选取不同的换热关联式,分析管径和流量对CO2侧和水侧换热的影响,理论分析CO2和水的温度匹配情况,设计套管式气体冷却器并进行实验研究,实验结果表明所进行的理论分析在误差允许范围内,满足设计要求,理论和实验结果对于CO2热泵热水器的产业化应用起到了很好的技术支持作用。     

改进型脉冲管制冷机的机理分析

通过分析脉冲管热端气体的变化而得到热端温度变化和热量交换的结果,提出了改进型脉冲管制冷机的理论制冷量的计算方法和公式。在计算中首次提出了气库系数的概念来模拟气体活塞的特征,且它成为理论制冷量公式的一个关键参数。此外,分析获得了估算压力波动大小的方法,为脉冲管完整制冷系统的模拟分析与计算奠定了基础。     

腔体内的热声研究

在Arnold和Crandall建立的腔体内箔电热片两侧均为气体媒质的热声理论的基础上,本文引入了复数方法,建立了这种情况下复数形式的热声理论,重点改变了与电热片相接触的媒质,采用复数方法和一维热传导理论导出了腔体内电热片一侧为气体,另一侧为固体材料时的热声理论,并用自己设计的热声腔和实验装置,对当与电热片接触的固体材料为热学上厚时(材料的厚度远大于该材料中热波波长)进行了实验验证。实验结果和推导的理论符合得很好,进而,作者提出了用热声理论测定固体材料热常数的具体方法。腔体内的热声研究@路志坚$同济大学物理系 @赵松龄$…     

影响热分离机等熵效率的主要因素及改进方法

根据多年来实验研究和推广应用,综合分析了影响旋转式热分离机效率的若干因素,并就脉冲管各主要能量损失与结构参数、运行参数之间的相互关系进行了讨论,提出了改进措施,同时在实验的基础上导出了最佳管长的半经验公式。     

热导式气体分析器校准方法

提出了针对不同种类气体含量分析的热导式气体分析器校准方法。使用该校准方法对不同型号的分析器进行了校准实验,并对校准结果进行了不确定度评定。研究结果表明,该校准方法适用于不同种类气体热导式气体分析器的校准,能够实现对热导式气体分析器示值误差、重复性、响应时间等主要测量性能的综合评价。     

改进的行波型热声发动机的初步实验研究

介绍了新型行波热声发动机的实验装置,并与原有的实验装置进行了比较,对试验结果进行了分析和讨论.在工作气体为氮气,压力为1.56 MPa,热端气体温度615℃时得到压比1.083.     

校准喷嘴系统的不确定度分析方法

介绍了热线／热膜流速仪的基本原理和用于热线／热膜流速仪校准用的校准喷嘴系统的气体速度确定方法，分析和推导了用不确定度理论全面分析系统不确定度的方法。     

真空玻璃内部残余气体热导计算

真空玻璃中心区域热导由辐射热导、支撑物热导及残余气体热导三部分构成,当Low-E玻璃、支撑物材料及间距确定后,真空玻璃热导主要受真空腔内部残余气体热导影响。根据稀薄气体导热理论,确定了真空玻璃内部残余气体热导计算公式。该公式中气体热适应系数α的取值相当重要,使用不同封边材料时,内部残余气体成分不同。目前的计算结果是基于真空玻璃中残余气体主要成分是空气而得出的。今后还应做进一步的实验来测量残余气体中各气体α值,从而精确计算真空玻璃内部残余气体热导。     

碟式分离机转鼓组装体不平衡的原因分析

简述了碟式分离机整机动平衡方法，分析了转鼓组装体不平衡的原因，指出必须进行转鼓组装体的动平衡，并根据在整机平衡过程中的测试数据分析和排除引起分离机振动的隐患。     

行波型热声发动机的试验研究

介绍子新型行波热声发动机的试验装置,对试验结果进行了分析和讨论,在工作气体为氮气、压力为1．56MPa、热端气体温度615℃时获得压比1．083。     

隧道内热环境模型试验的相似关系

运用流体力学和热力学原理,建立了列车在隧道内运行状态和隧道内热环境的数学模型,并运用模型试验相似理论对该数学模型进行分析,获得了针对隧道内热环境进行模型试验时要遵守的相似关系。     

Thermal conductivity of mixtures with interpenetrating components

The basic principles of investigation of transport processes used in generalized conduction theory are formulated. Studies in which a structure with interpenetrating components has been used for determining electrical and thermal conductivity are analyzed. It is shown that using models of such structures it is possible to calculate the thermal conductivity of gas mixtures, liquid solutions, solid disperse systems, certain alloys, and granular and fibrous materials.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 3, pp. 562–577, September, 1970.     

Thermophysical measurements during thermal cycling of gas turbine engine blades with ceramic coatings

A design-experiment method is proposed for high-frequency induction heating of turbine blades and models of combustion chamber flame tubes of gas turbine engines with heat-resistant ceramic coatings. The proposed method has been developed taking into account the electrophysical and thermophysical properties exhibited by the materials in thermal cycling tests. The results of thermophysical measurements, design-experiment studies of the nonstationary thermal state of the parts with coatings with the use of a thermal vision system, and thermal cycling tests of rotating blades and models of flame tubes with heat-resistant ceramic coatings are presented.     

Direct numerical simulation of particulate flows with heat transfer in a rotating cylindrical cavity

The purpose of this work was the direct numerical simulation of heat and fluid flow by granular mixing in a horizontal rotating kiln. To model particle behaviour and the heat and fluid flow in the drum, we solve the mass conservation, momentum and energy conservation equations directly on a fixed Eulerian grid for the whole domain including particles. At the same time the particle dynamics and their collisions are solved on a Lagrangian grid for each particle. To calculate the heat transfer inside the particles we use two models: the first is the direct solution of the energy conservation equation in the Lagrangian and Eulerian space, and the second is our so-called linear model that assumes homogeneous distribution of the temperature inside each particle. Numerical simulations showed that, if the thermal diffusivity of the gas phase significantly exceeds the same parameter of the particles, the linear model overpredicts the heating rate of the particles. The influence of the particle size and the angular velocity of the drum on the heating rates of particles is studied and discussed.     

The Effect of Rotation on a Fiber-Reinforced Medium under Generalized Magneto-Thermoelasticity with Internal Heat Source

In the present article, we discussed the transient waves caused by a line heat source with a uniform velocity inside a rotating half-space fiber-reinforced thermoelastic media permeated into a uniform magnetic field. The formulation of the problem is applied under the coupled theory (CD), Green-Lindsay (G-L) theory, and Lord-Shulman (L-S) theory. The normal mode analysis is used to obtain expressions for the temperature, displacement components, and thermal stresses. Numerical results are given and illustrated graphically. A comparison is made with the results predicted by three theories in the presence and absence of magnetic field and rotation as well as fiber-reinforced.     

Recent Development in Separators for High‐Temperature Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs) are promising energy storage devices for integrating renewable resources and high power applications, owing to their high energy density, light weight, high flexibility, slow self‐discharge rate, high rate charging capability, and long battery life. LIBs work efficiently at ambient temperatures, however, at high‐temperatures, they cause serious issues due to the thermal fluctuation inside batteries during operation. The separator is a key component of batteries and is crucial for the sustainability of LIBs at high‐temperatures. The high thermal stability with minimum thermal shrinkage and robust mechanical strength are the prime requirements along with high porosity, ionic conductivity, and electrolyte uptake for highly efficient high‐temperature LIBs. This Review deals with the recent studies and developments in separator technologies for high‐temperature LIBs with respect to their structural layered formation. The recent progress in monolayer and multilayer separators along with the developed preparation methodologies is discussed in detail. Future challenges and directions toward the advancement in separator technology are also discussed for achieving remarkable performance of separators in a high‐temperature environment.     

Nonisothermal Simulation of Flows in the Hot-Gas Filter Vessel at Wilsonville

A numerical simulation of nonisothermal gas flows in the hot-gas filter vessel at the Power Systems Development Facility in Wilsonville, Alabama is presented. The gas velocity and thermal simulations are based on the Reynolds stress transport turbulence model of the FLUENT TM commercial CFD computer code. While earlier modeling studies were limited to isothermal conditions, in this study, the energy transport equation was solved in addition to the mass and momentum equations. The gas flow and temperature field inside the filter vessel were also studied. Results reveal that the gas flow shows strong rotating flow regions outside the shroud and in the upper and lower parts of the body of the vessel. It is also shown that the temperature distribution is nonuniform with somewhat higher temperatures in the upper part of the filter. The simulated results qualitatively agree with the experimental field observations of the filter vessel.

filter vessel numerical simulation nonisothermal FLUENT     

Effect of SiO2 coating on polyethylene separator with different stretching ratios for application in lithium ion batteries

To enhance the properties of polyethylene separators in lithium ion batteries, we tested separators with uni-axial stretching ratios of 180% and 300%. We also tested stretched separators coated with SiO₂ ceramic substance to increase ionic conductivity and thermal stability without sacrificing mechanical properties. To test the thermal and tensile properties, thermomechanical analyzer (TMA) is employed. CR 2032-type coin cells are prepared by sandwiching pristine and coated stretched separators, respectively, between the Li anode and Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode to evaluate the AC impedance and cycling performance. The coated separators are observed with superior ionic conductivity, thermal and tensile properties. The cells prepared with coated separator have slightly higher discharge capacity and a better capacity retention ratio than the cells with pristine separators. These results suggest that the coated separator is a better option for lithium ion batteries.     

The Effect of Rotation on Two-Dimensional Problem of a Fiber-Reinforced Thermoelastic with One Relaxation Time

In this article, the Lord–Shulman (L–S) theory with one relaxation time and coupled theory are applied to study the influence of reinforcement on the total deformation of a rotating thermoelastic half-space and the interaction with each other. The problem of a thermal shock has been solved numerically using normal mode analysis. Numerical results for the temperature, displacement, and thermal stress components are given and illustrated graphically for both L–S and coupled theories.     

Thermo-mechanical vibration analysis of rotating nonlocal nanoplates applying generalized differential quadrature method

In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines.