脉动热管激励机制强化传热数值研究

文章以脉动热管内传热传质为出发点,利用数值模拟方法,建立二维模型,采用混合模型(Mixture model)和欧拉模型(Euler model)对脉动热管内传热传质进行了研究,通过对计算结果的比较分析确定哪种模型更适合用于研究脉动热管内传热传质的流动过程。     

二次流旋风分离器的数值模拟与优化设计

利用CFD软件FLUENT6．3模拟三维稳态流动。对引入二次流的旋风分离器各项参数进行了优化设计,采用RSM模型模拟气相有旋流动,利用DPM离散模型进行颗粒相跟踪。通过比较优化前后流场特性,证明二次流有助于提高旋风分离器的分离效率及流场稳定性,不同的进风角度和速度会得到不同的分离效率,为新一代旋风分离器的开发与制造提供了参考依据。     

薄膜蒸发器流场特性的数值模拟研究

针对自行设计的薄膜蒸发器,在FLUENT软件平台上,由于蒸发过程的复杂性,为了简化计算,采用GAMBIT建立二维模型,选用RNG κ-ε湍流计算模型对蒸发器内液膜湍流流场进行数值模拟.结合已有的生产数据,设定进料量分别为3.00、3.50、3.55、4.00m3/h,得到不同进料量下液膜流场分布.结果显示,随着进料量的增加,刮膜器附近的湍流流场明显增加,提高了蒸发效率.模拟验证了先前的理论计算.     

水泥砂浆包装机中混合料在料仓内自由流动的数值模拟

为认知水泥砂浆混合物料靠重力自由流出的流动状态,对包装机出口处料仓内的水泥砂浆混合物的三维定常流场进行了数值模拟。考虑到物料在料仓内流动时是密实状态,因此简化为流体模型进行分析,同时综合考虑了混合物料所受重力和内摩擦力对流动性能的影响。模拟结果直观显示了料仓内的速度和流线等特征,研究结果对研究背压式水泥砂浆包装机的设计与改进提供了一定的理论指导。     

改进型INTER-MIG桨搅拌槽内流场的PIV实验研究

针对二维粒子图像测速技术(particle image velocimetry,PIV)的局限性,利用三维粒子成像测速技术(PIV)对改进型INTER-MIG桨搅拌槽流的轴向速度、径向速度、切向速度的分布进行研究,介绍了三维PIV系统的结构组成,再利用二维PIV对流场进行流线分析。结果表明:无挡板时,槽内的流体受到了较强的剪切作用,而轴向速度与径向速度相对较小,整体的混合效果较差;有挡板时,流体的轴向和径向速度明显提高,增加了流体湍动效应。挡板破坏了流体内部的有序流动,桨叶前端的涡流也明显减弱。     

表面张力驱动下挡板对微通道混合效果的影响

微流控系统由于微通道尺寸变得越来越小,所以原先传统的外力驱动方式遇到了很大的困难。而表面张力驱动微流体不需要任何外部能量源,对于设备小型化和集成化非常有优势。课题组通过对微混合通道内设置挡板,改变挡板的结构参数,通过数值模拟来研究表面张力驱动下挡板结构参数对混合效果的影响。研究结果表明:设置了挡板后微通道的混合效果显著提高;同时随着挡板结构参数的改变,微通道的混合效果也随之呈现出一定的变化规律。挡板的设置扰乱了微流体的流动,使得流体间的界面接触变多,混合效果得到提高。     

不同挡板结构的浆料搅拌罐流场仿真与分析

为了研究挡板对搅拌罐流场的影响,利用流体分析软件FLUENT6.3.26对两个搅拌罐进行了仿真分析,采用多重参考系模型（MRF）模拟叶轮区转动,湍流项选用双方程RANSk-ε模型,模拟得到了流场内的重要参数。通过对分析结果进行比较,发现挡板的设置可减小漩涡,增强流场湍动性,在工程应用中,根据介质的不同设计合理的挡板结构,不仅可以提高搅拌混合效率,还可以降低成本,减少能源消耗。     

防止汽轮机油污秽

汽轮机油污染的问题较多,因运行油是在复杂环境下工作而易被污染,有油循环系统中杂质秽入,油品氧化、油品乳化、油品中秽入空气等而成污染物,所以要油务人员、化验人员掌握油品污秽的状况。 防止杂质、水汽秽入油系统,必须使水封、汽封、汽动油泵和冷油器等部件的结合处保持严密;为了防止灰尘、盐雾及潮气秽入油系统,油箱应加盖,油系统应密闭循环;为了防止油与橡胶反应而成为污秽物,油系统中应严禁使用普通橡胶衬和橡胶管等措施。 防止油品氧化成为污染物。油品是一种     

一种关于焦炭塔展开后的二维平面温度场的重构方法

在求解焦炭塔的整体温度场的问题时,对焦炭塔模型进行了结构简化,将焦炭塔展开为二维平面矩形,并通过重构二维矩形面的温度场来得到焦炭塔的整体温度场。文章通过采用的11个温度传感器在焦炭塔上进行布置,并对简化的焦炭塔进行展开,通过找到相邻节点间的温度关系式建立方程组,进而求解出矩形面内的所有的节点温度。所求节点温度即为划分网格后的各个小矩形面的顶点温度。最后,采用形函数内插的方式,得到各个小矩形面内的温度并进行拼接可以得到最终所需要的焦炭塔的二维平面矩形温度场。     

喷气涡流纺喷嘴内气流流动的二维数值模拟

 为探讨喷嘴内部气流流动特征对纤维加捻成纱的作用,建立计算流体动力学(CFD)模型,对喷气涡流纺喷嘴中的气流流动进行二维数值模拟,并根据计算结果分析喷嘴内高速气流的速度场和压力场分布。模拟结果表明:气流的最大速度可达超音速,由于切向速度所产生的离心力和加捻作用,纤维的尾端从纤维束中分离出来,并旋转加捻到纤维束上,形成具有真捻的纱线;喷嘴入口区域的压力小于外界气压,这有利于由前罗拉钳口处输出的纤维束吸入喷嘴。研究还表明CFD技术是研究喷气涡流纺喷嘴内气流流动的重要手段。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press