冷藏集装箱温度场均匀性改善研究进展

综述了货物堆码、送风速度、送回风形式、风机位置等因素对冷藏集装箱温度分布的影响,阐述了箱体内温度场的空间分布特性,进而对影响箱体内温度分布的相关因素进行了对比分析,并对其未来发展方向进行了展望。     

大型冷库内温度场的数值模拟与优化

以典型大型冷库作为研究对象,对冷库内外环境(包括空气幕在内)进行三维数值建模,并利用计算流体力学软件对冷库内温度场进行模拟研究,并将计算结果进行了实验验证。通过对结果分析可得:在稳态条件下,库内流场温度虽达到了要求的范围,但堆垛货物附近的温度场分布并不均匀,货物之间与库内其他区域存在着较明显的温差;在非稳态条件下,空气幕的送风速度对温度场的影响很大,当送风速度为8m/s时,库内温度场的波动较小,空气幕性能较好。在该基础上提出了今后可进一步优化的建议:改变库内空气的流动方式,改变货物的堆垛方式,降低货物堆垛高度,对影响空气幕性能的其他参数进行研究优化。     

易腐食品冷藏运输车内温度场影响因素仿真研究

运用k-ε湍流模型,对不同厚度的车厢隔热材料、不同送风口位置、不同送风温度及不同送风速度条件下冷藏运输车厢内温度场进行数值模拟。结果表明:冷藏运输车车厢聚氨酯隔热材料合理厚度为100～120mm;制冷设备送风口位于车厢内正前下方位置时,车厢内各个不同典型断面温度均匀性最好,并且厢内各处温度更接近于设定值,送风口位于车厢中间位置次之,送风口位于车厢内正前上方最差;冷藏运输温度要求不同,对制冷设备的最佳送风速度要求也不同,冷藏运输车厢内温度要求高,其合理的送风速度也相应要求高,并且每种冷藏运输温度条件下都有与之对应的最佳风速。     

基于装配式周转箱的甘薯气调贮藏环境仿真

目的：减少果蔬盛装、运输及贮藏时的不利因素,以循环、绿色理念为前提设计出一种装配折叠式塑料周转箱。方法：将甘薯看作长旋转椭球体,以标准化周转箱盛装甘薯并对气调贮藏库进行建模,通过多孔介质模型、组分输运模型、局部非热平衡模型研究愈伤升温、愈伤后降温,以及贮藏阶段货物区的温度、湿度、速度、O₂体积分数、CO₂体积分数分布情况。结果：较佳的愈伤送风温度为40 ℃,所需时间为5.85 h;较佳的愈伤后降温送风速度为10 m/s,所需时间为8.47 h。送风速度（4.0~6.0 m/s）对O₂、CO₂体积分数分布影响不大;当送风速度为4.5 m/s时,贮藏效果较佳,与目标贮藏条件（12 ℃,90.00% RH）相比,偏差率依次为1.24%,0.48%。甘薯呼吸热的产生使得货物区内部温度达到目标愈伤温度所需的时间较短,达到目标贮藏温度所需的时间较长,相较于导热,对流换热占主导作用,造成贮藏过程中货物区内部温度与外部温度变化存在滞后。增大送风温度、送风速度分别有利于缩短达到目标愈伤、贮藏温度所需的时间,货物区贮藏甘薯的物理性质以及贮藏量决定了后续升温、降温过程。结论：货物区表面速度场与相对湿度场分布关联性较小,温度场与相对湿度场呈负相关且分布状态相似。送风速度可以改变货物区箱体内部的流体流向,送风速度大小以及箱体内流体流向对货物区内部温度分布影响较大。     

苹果差压预冷均匀性的实验研究

通过搭建差压预冷实验台研究送风速度、送风温度、开孔大小以及开孔方式4个因素对差压预冷冷却均匀性的影响。利用混合正交试验分析法研究以上4个因素对冷却均匀性的影响程度。结果表明:送风速度越大、送风温度越高预冷均匀性越好,预冷过程中均匀度峰值最低;对于圆形开孔,孔径越大,均匀度越好;对于椭圆形开孔,孔径越小,均匀度越好;孔径大小不同时,均匀性变化过程相似,峰值出现所需预冷时间相同(峰值出现的位置相同);不同送风速度、送风温度、开孔大小和开孔方式,均匀度均呈先增大后减小的趋势;不同送风速度、送风温度、开孔大小和开孔方式对均匀度影响程度大小依次为送风温度、送风速度、开孔大小、开孔方式。     

卷烟材料暂存高架库温湿度场的优化控制研究

卷烟材料暂存高架库内的空调系统实际运行效果不理想,室内空气温湿度达不到工艺要求,对暂存材料质量造成不利影响.为此,对高架库的空调系统进行了改造,并对改造后空调系统的运行效果进行了测试和分析.改造后高架库空调系统增加了两台空调机组负责新回风的混合与送风,气流组织方式由原来的侧送、侧回改为顶部送风、底部回风.空调系统改造后各平面温湿度分布表明,水平方向温湿度场的均匀性提高;垂直方向的温度场存在分层现象,但温湿度场基本分布在要求范围内.利用CFD软件对高架立体仓库构建了物理数学模型,对不同风量、送风参数条件下仓库内的温湿度场进行了模拟研究,结果显示:①对于需要保持均匀温湿度场的高架立体库,带有静压箱和送风孔板的上送下回气流组织方式是可行的;②对于该高架库的夏季工况,送风量的变化对库内温度场的影响较小,送风温差的改变则对库内温度场影响较大.因此,通过调节送风风量和送风温度,可保持卷烟材料高架库内温湿度的恒定与均匀性.     

计算流体力学在冷库优化中的应用研究进展

对中国冷库的发展进行论述并列举冷库运行中存在的一些问题,对计算流体力学技术在冷库中的应用研究进行综述,介绍国内外该技术在冷库模拟中所取得的进展,尤其是如何使气流均匀、不同货物最适储存温度和湿度、货物储存中合适的堆码形式和堆码尺寸等方面的研究成果,并对今后计算流体力学技术在冷库中的进一步应用进行展望。     

多温区冷藏车回风导轨对厢内温度场的影响分析

通过冷藏车多温区影响因素分析,建立多温区冷藏车的传热模型,利用计算流体力学方法研究回风导轨对车厢内温度场分布均匀性的影响规律。依靠Fluent软件,采用标准K-ε模型,开展空仓和载货两种状态下的数值模拟试验。结果表明:回风导轨的变化能够改变车厢内温度场分布;其对冷藏区温度场分布影响较大,对常温区温度分布影响较小。空仓状态下,导轨高度与温度不均匀系数近似呈"凸型曲线"分布;载货状态下,导轨高度与温度不均匀系数近似呈正比例线性分布。相比于X方向导轨,冷藏车采用Y方向导轨可以有效提高车厢温度分布均匀性。     

液氮充注气调对运输厢体内流场均匀性的影响

为了掌握液氮充注气调对厢体内流场的影响,搭建液氮充注气调试验平台,研究不同汽化器的翅片间距、回风道风速和初始温度条件下厢体内的温度场和相对湿度场的均匀性变化。结果表明,翅片间距对厢体内的温度场及相对湿度场的均匀性有一定影响,翅片间距为7 mm时均匀性相对较好,翅片间距为4 mm时均匀性相对较差;回风道风速越大,厢体内温度场的均匀性越好,相对湿度场均匀性越差;初始温度越高,温度场和相对湿度场越均匀。研究结果为气调保鲜装备的进一步开发提供了参考依据。     

保鲜运输用超声波加湿的数值模拟

为掌握保鲜运输用超声波加湿流场的分布特性,本文针对压差原理的保鲜运输厢体结构,以脐橙为试验物料,建立厢体的1/4等比例三维紊流模型,借助有孔模型和组分传输模型,结合SIMPLE算法和壁面函数法,运用Fluent软件进行超声波加湿的数值模拟,分析了厢体内温湿度场的变化。模拟结果表明:采用超声波加湿可以在212 s内将厢体内的相对湿度自70%升高至90%;厢体内温度场和湿度场分布均匀,厢体内温差不超过1℃,相对湿度差小于3.5%;加湿过程对温度场的影响较小;货物表面的相对湿度差不超过3%;货物区水蒸气扩散较快。经试验验证,试验结果与模拟结果相吻合。该研究结果对于保鲜运输加湿装置的结构优化具有一定的参考价值。     

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