热声制冷效应验证的实验设计

热声制冷技术是一项新的冷制技术。它具有无运动部件、运行可靠、寿命长和环保等优点。在航天、微电子、低温物理及军事等领域有着十分诱人的应用前景。热声制冷机主要由声驱动器、共振管、热声叠和换热器等部件组成。根据热声制冷原理,利用常见的材料和仪器,采用自制的玻璃管状热声叠,设计了一套结构简单的扬声器驱动热声制冷实验验证装置。实验结果表明:以空气作工质,在无冷却措施的情况下,在系统运行较短时间内,实现了13℃的降温及25℃的温跨,热声制冷效应十分明显。该装置可用于研究热声制冷效应的影响因素。     

热声制冷的实验研究

热声制冷作为一种很有前途的制冷方法,在国内外引起了极大的兴趣。介绍了一套热声制冷机实验台。该热声制冷机由声发生器、共振管、板叠、高低温换热器管组成,在此基础上进行了热声制冷的实验研究,重点研究了输入频率、输入电压和平均充气压力对热声制冷机性能的影响,在以氮气工作的情况下,制冷机冷端温度下降了１２℃。     

热驱动热声制冷技术发展现状与展望

热驱动热声制冷技术利用热声发动机输出的高强度声波驱动热声制冷机实现制冷,即实现热—声—冷能源转换,是一种环境友好、近零电耗且热源适应性好的新型绿色制冷技术。热驱动热声制冷系统工作温跨大,可实现室温至液氦温区不同制冷需求,在多个领域具有广阔的应用前景。本文以热驱动热声制冷技术近三十年来的发展为基础,介绍了热驱动热声制冷原理和分类,从热驱动室温热声制冷机和热驱动低温热声制冷机两个方面综述了研究现状和发展方向,对该技术在室温制冷、余热/冷回收、天然气液化和低温制冷等方面的应用及相关研究进行了归纳分析,并指出未来的研究需要在热声新流程、谐振机构、高效热声转换、低品位能源利用、工程样机实用化等方面实现协同突破,形成效率高、功率大、起振温度低、可实现极低温、稳定可靠的热驱动热声制冷技术,从而推动新型绿色制冷技术的科学发展与应用。     

热声驱动脉管制冷机的实验研究

采用热声压缩机驱动脉管制冷机,使彻底消除低温制冷机中的运动部件成为可能。作者研制了热声驱动脉管制冷机实验台,着重研究了加热温度,平均工作压力,小孔开度等主要因素对制冷机性能的影响。初步实验中,以氮作工质,获得了－３８．７℃的无负荷制冷温度,最大温降达５４．７℃。此外,还指出了进一步的改进方向,具有一定参考价值。     

吸附剂型回热器热声热机

介绍了回热器热声制冷机理及发展简况,并对回热器填料为金属网格和吸附剂两种材料的热声特性作了对比,给出强化吸附剂型回热器热声特性的方法,并提出吸附剂型回热器热声制冷机更应能广泛适用于低温热源,无运动部件,清洁制冷的建议。     

热声制冷机

热声制冷是微型低温技术潜在的最佳方法。一台声驱动热声制冷机主要包含一个接在中空管道端部的声波发生器和一个在管道内预选位置处放置的热声器件。声波发生器产生的声波在热声效应作用下可在热声器件两端形成温度梯度。介绍了一种基于高效斯特林循环的热声制冷机的基本原理及主要组成。在此基础之上,可通过对各组成部件结构参数的计算、确认,设计出一台热声制冷机。     

驻波型热声压缩机驱动脉管的最新结果

热声驱动脉管制冷机中由于完全无运动部件,具有运行稳定、寿命长等优点,经过对先前已经达到138K的热声驱动脉管制冷机进行系统的改进,在国内首次使该类型的制冷机进入低温温区,以氦气为工质获得了119.7K的制冷温度,这一温度已经能够液化一个大气压表压下的天然气（主要成分：甲烷）,显示出该制冷方式广阔的应用前景,此外,研究了混合工质对热声驱动脉管制冷系统性能的影响情况,并获得了117.6K的最低制冷温度。     

声功回收型脉管制冷机的分析与研究

对所有的回热式低温制冷机,压力小与质量流之间的相位控制是达到制冷效果的关键。在斯特林制冷机中,这一相位是由压缩活塞和冷头排出器的相对运动来提供来;而在脉管制冷机中,这一相角是由构成脉管制冷机的各个部件：回热器、换热器、脉管、小孔,气库,连管等在几何空间上的合理拓扑结构来实现达到适宜的热声网络阻抗,从而最终实现压力波与质量流之间的适配相角。脉管制冷机的这一结构上的简化及由此带来的寿命长,可靠性高等优     

热声制冷的应用与分析

在环境问题日益突出的今天,热声制冷作为一种对环境无污染的制冷技术,成为一个大有前途的发展方向,本文介绍了热声制冷的原理,分析了热声制冷机的性能影响因素,并提出了性能优化方法。     

基于热声理论对G—M制冷机的热力分析

为了解释低温下制冷功率与膨胀功的非比例关系而从热声理论出发,对G-M制冷机进行了热力分析,阐明了膨胀功和制冷功率的关系及与极限制冷温度相关的因素.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...