屋面通风对抑制高温季粮堆升温影响的实验与模拟研究

为了研究高温季节粮食平房仓屋面架空层隔热性能的主要影响因素,采用计算流体力学对具有架空层通风结构的粮食平方仓进行数值模拟,并采取实验仓实验对模型进行了验证。实验结果表明,模拟结果与实验数据有较好的一致性,模型较为合理。在粮堆初始温度和储藏时间相同的条件下,基于所建立的数学模型,对具有不同空气层厚度、不同架空层通风气流速度的粮食平房仓进行了模拟,并研究了架空板表面高反射涂层的影响。结果表明,在主导风向上利用湍流换热入口段效应,可以提高架空层散热速率,减少仓内热量积聚,使上层粮温与"闷顶"式架空层相比降低了2. 1℃,扩大了粮堆内部"冷心"区域;在0. 2 m空气层厚度下,外界风速约为5 m/s时,架空层内形成的流动即可有效带走由架空板传入的积热,有效阻隔屋面向仓内的传热;而当架空层气流速度为2 m/s时,架空层的最佳厚度为δ=0. 3 m。在高温季节自然对流风速范围内(1～5 m/s),根据湍流入口段长径比来设置架空层空气厚度较提高气流速度或单一采用高反射涂层更有利于改善架空层隔热效果。     

不同运行参数下平房仓粮堆表层控温系统的隔热性能试验

该研究以粮食平房仓为研究对象,建立了粮堆控温试验系统,进行了不同工况下的隔热试验,研究在炎热气候下影响系统隔热效果的因素。结果表明:粮堆由外界传入热量引起的温升集中在装粮线以下10 cm的表层粮堆,粮堆表层控温系统可以有效减少外界突发高温对于表层粮温的影响,最优工况下,表层粮堆温度降低1.67℃。在送风温度、风速和层间高度诸因素中,系统送风温度对粮堆表层温升影响较大,而系统送风风速与层间高度影响较小。工程中可采取低风速、低风温的送风形式,使吨粮单位成本降低至5.6元,同时可减少能源消耗。由特征长度定义的努谢尔特数(Nu=hl/λ)表示了系统换热的强弱,无量纲过余温度Θ位于0.4～1时,Nu随Θ的增加而增加,变化范围为45～85。Nu受无量纲高度H影响不大,当H位于0.05～0.09之间时,Nu的变化范围仅为82～89。试验期间送风温度22℃,靠近系统上表面的仓内空气湿度与初始值相比下降13%,高于外界湿度5%,粮堆内部未发生结露情况。     

平房仓保温隔热性能分析及改善

低温储粮的关键是仓房的保温隔热条件,仓房保温隔热条件的优劣直接影响低温储粮的效果。所以低温储粮的先决条件,是仓房要具有良好的保温隔热性能。本文以我国海南某地区的平房仓为例对粮仓的保温隔热结构进行分析,探讨控制仓内上部粮堆和仓壁四周的温度和湿度,以提高粮食储藏的稳定性。     

平房仓内环流均衡温湿度储粮试验

在仓房隔热密闭的条件下,研究了平房仓内环流均衡温湿度对储粮的影响。试验结果表明：内环流控温系统可有效控制仓内粮堆温湿度,减缓玉米品质的陈化速度,推迟虫害发生时间,且降低储粮成本、操作简单,适用于高温高湿地区储粮应用。     

平房仓综合隔热改造技术研究

针对新建高大平房仓在使用中所出现的隔热、气密性差的现象,采用隔热涂料、高强度绝热板、PEF隔热板、新型保温通风口、积热排除软管等材料对墙体、仓顶、门窗、通风道口等处进行了综合隔热气密改造.应用效果表明经改造后增加了仓房气密性,提高了仓房整体储粮性能,试验仓从改造前的54s,综合隔热改造后增加到65s;试验仓在常规储存下常年使最高粮温控制在22℃以下,各层平均粮温控制在19℃以下,达到了准低温储粮;粮食温度得到了有效的控制,抑制了储粮害虫的发生,试验仓在试验阶段没有进行化学药剂熏蒸处理;试验仓粮食品质各项指标均优于对照仓,储粮品质陈化速度远远低于对照仓;在准低温条件下储藏,达到了水分基本不散失.     

屋面聚氨酯发泡与仓内吊顶综合隔热控温储粮的应用效果

高大平房仓进行屋面聚氨酯发泡、仓内吊顶等隔热处理后,5月中旬至9月底间最高仓温降低3.5℃,仓温平均降低2.8℃;最高上层平均粮温降低3.9℃,平均降低2.7℃;最高全仓平均粮温降低2.1℃,平均降低1.1℃.经过秋冬季机械通风降温,粮堆度夏整仓平均粮温低于16.7℃,上层平均粮温低于27.8℃.     

新建高大平房仓机械通风储粮技术应用

根据机械通风储粮技术的条件，结合高大平房仓实际设计技术要求，充分利用冬季有利时机。对高大平房仓的粮堆通过地上笼通风系统进行通风降温试验，试验结果表明在春季初至冬季前加强仓房的隔热保冷工作。从而有效地改善储粮品质，延长储粮轮换周期，延缓粮食陈化，同时对现行高大平房仓在结构等储粮技术上的应用进行了探讨，总结出高大平房仓粮堆内温差大，易形成热核心型粮堆以及易出现结露等特点。     

平房仓仓顶隔热保温性能改造方法初探

国家500亿斤粮库项目建设期间,德州直属库共建平房仓12栋。在近几年的使用过程中,发现所有平房仓均存在保温隔热性能差等弊端,对"低温储粮"极为不利。通过对已建平房仓仓顶隔热保温性能改造方法和途径的探索,使仓顶隔热保温改造能有效降低仓温和粮堆表层温度,从而减少粮食"热皮"厚度,增加粮食"冷心"的体积,使所储存粮食常年处于低温之下,有效延缓粮食陈化速度,更好保持粮食的储存品质,此技术2006年已获国家专利。     

高大平房仓综合控温储粮技术探讨

对高大平房仓的门窗、通风口、环流熏蒸管道等易导热部位用 PVC 发泡塑料作隔热保温处理,以提高仓房的隔热性能,进一步改善仓房的储粮条件;地坪用糠壳铺垫,防止底层结露;秋冬季节进行机械通风降温;春季对粮面进行薄膜密闭、泡沫板压盖保冷;在膜下铺设环流熏蒸回流管网,并均匀预留若干个风口,可进行膜下环流熏蒸和全仓不揭膜通风,还可利用环流风机平衡堆内粮温;高温季节,在环流熏蒸管道上串接小功率制冷机组对粮堆进行辅助制冷,使粮堆长期保持在低温状态;夜间合理利用轴流风机适时排除仓内空间积热,降低仓温,延缓粮温上升。实践证明,粮食在储藏过程中综合运用这些储粮技术,减少了外界环境因素对粮堆的影响,可达到明显的控温效果,使高大平房仓储粮度夏时,平均粮温控制在15℃,表层最高粮温不超过23℃,确保了粮食储存安全,延缓了粮食品质陈化,降低了保管费用,取得了良好的综合效益。     

粮仓专用空调控温储粮实仓测试报告

对铁岭粮食集团直属储备库9号平房仓安装的1台粮仓专用空调,开展了控温储粮实仓应用试验与测试工作。结果表明,在经过隔热处理的平房仓上应用粮仓专用空调,可以有效控制夏季粮堆上层粮食温度升高,实现全仓粮食安全储藏过夏,并且可以有效保持粮食水分。     

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