采用落差式浓缩机提高经济效益

目前我国造纸行业在制浆流程中采用不同的浓缩机。这里我们将落差式浓缩机与刮板式浓缩机在结构、工艺流程、纸浆洗净度、回收纤维量、节电及经济效益诸方面进行比较，从而说明落差式机的优越性。     

刮板式换热器的研究

刮板式换热器借助刮板搅动料液并清洁传热面以加快传热效率,不仅适合低粘度料液,尤其适合高粘度或含颗粒料液快速换热.高粘度料液由于粘度大或流动慢,在超高温杀菌处理中,一般换热器的传热面易生成焦化膜,采用刮板式换热器最适合.在乳品、蕃茄酱、豆乳和果汁等无菌包装食品生产中,常将数台刮板式换热器串联,输送泵将料液连续通过换热器进行预热、杀菌和冷却,然后无菌包装.进行     

拖链刮板式浸出器的应用研究

为了进一步提高油厂对拖链刮板式浸出器的认识,介绍了拖链刮板式浸出器的结构,着重阐述了其设计、制造过程中的要点及运行中应注意的问题。通过生产实践,利用该浸出器对大豆坯进行浸出,可使粕中残油达到0.6%~0.8%。     

垂直式埋刮板输送机设计方法探讨

从散体结构力学理论出发,分析了垂直式埋刮板输送机的工作原理,并推导出刮板间距与其它结构参数之间的关系式,是垂直式埋刮板输送机设计计算的一种理论方法。     

控制埋刮板输送机中物料滑移和翻滚的研究

通过对埋刮板输送机中物料运动状态的仔细观察和分析，发现料槽内物料经常有滑移和翻滚现象，因而降低了输送效率。并对单元内物料的不同运动状态进行划分，建立相应的力学模型来分析物料区的受力情况，最终得到了刮板冀的１／ｈ值是影响埋刮板输送机中物料滑移和翻滚和重要参数的结论。     

刮板输送机的维护和使用

刮板输送机在饲料厂和其他粮食加工厂使用很多，它可以水平或一定角度传输原料或成品，其类型包括水平刮板输送机、倾斜刮板输送机和自清式刮板输送机。刮板输送机看起来简单，但在实际生产中，它是故障频率最高的设备之一。笔者借鉴一些国外的先进经验，结合国内饲料厂的实际，探讨了这方面的问题。     

刮板机行之有效的改造方法

刮板机是一种散状物料运输设备 ,在粮食加工储运工程中广泛使用 ,它在流程中负责物料的分流转向等。其主要结构有链条、链轮、刮板、机头、机身 (底板、侧板、盖板 )和托轨。1　原理一般刮板机内槽与刮板间均有 10～ 15mm间隙 ,利用这一间隙选用板厚 5mm的锰钢板内衬刮板机底板侧板。使其物料在运输过程中没有机会直接磨损刮板机底板和侧板 ,从而达到保护刮板机机身的目的。2　方法2 .1　内衬底板制作选用板厚 5mm的锰钢板 ,将其切割成与刮板机内空一样的宽度 (最好小 1mm)。长度按所购钢板的实际长度 ,要求方正平滑。总长则按刮板机尾到出…     

水平型埋刮板输送机物料整体移动的条件分析

运用散体结构力学理论，以新的方法分析水平型埋刮板输送机“物料整体移动”的条件。刮板推动物料实际是给予物料一个局部压力，如果刮板面积过小或刮板的间距过大都会导致刮板对物料的压力过大，从而破坏物料的整体性，结果是只有极少部分的物料随刮板链条移动，大部分的物料则停滞不前。因此，根据物料受压的稳定条件导出了刮板面积及刮板间距与物料整体输送条件之间的关系，并结合实例作进一步的验证和说明，为水平埋刮板输送机的设计提供理论参考。     

用于稻壳输送的埋刮板输送机设计

稻壳是酿酒的主要辅料,在酿酒工艺中需要短距离封闭输送。基于稻壳的物理特性以及酿酒工艺对稻壳的破损率要求,从埋刮板输送机的安装倾斜角度、刮板链条、导轨结构、防尘措施、卸料口位置等方面对"L"形埋刮板输送机的设计进行了阐述,旨在为开发适用于稻壳输送的埋刮板输送机提供参考。     

浅谈通用型埋刮板输送机的选型与设计

对埋刮板输送机的输送原理进行了简述,重点对埋刮板输送机选型的基本设计与计算及主要技术参数的确定进行了较为详细的论述,并对设计与计算中存在的问题进行了探讨,以期科学合理地设计和使用埋刮板输送机。     

Firmness and crystallization of milk fat in relation to processing conditions

We studied the influence of different processing conditions on the crystallization and firmness of milk fat. Liquid milk fat was quickly cooled with a scraped surface heat exchanger to several temperatures ranging from 10 to 20 degrees C to initiate crystallization, and in some cases subsequently passed through an agitated working unit, in which the crystallizing fat was subjected to high shear. Samples of the crystallizing fat were taken directly after either the scraped-surface heat exchanger or the agitated working unit. Crystallization and development of firmness were monitored by a number of techniques that were applied simultaneously. Crystallization was monitored by temperature measurement, nuclear magnetic resonance, differential scanning calorimetry, and microscopic imaging. Firmness was measured by penetrometry. The development of firmness of milk fat produced by a Votator line at temperatures encountered in practice, ranging from 10 to 20 degrees C, can be explained by the kinetics of crystallization into the beta'-form of high-melting and middle-melting triglyceride fractions of milk fat and subsequent recrystallizations. The new insights allow better control of the firmness by adjusting the processing conditions.     

HEAT TRANSFER IN A VERTICAL, LIQUID-FULL SCRAPED-SURFACE HEAT EXCHANGER. APPLICATION OF THE PENETRATION THEORY AND WILSON PLOTS MODELS

Heat transfer characteristics of a scraped-surface heat exchanger (Contherm Model 6 × 2) were evaluated at ultra high temperatures using water and soybean water extracts as model systems. The resistance equation was used to calculate internal (scraped-side) heat transfer coefficients (h_i) from the overall heat transfer coefficient, the wall coefficient and the external (steam-side) coefficient (calculated from the Nusselt Theory using an iteration procedure). The Penetration Theory of Harriot (1958) predicted h_i values quite well at low axial mass flow rates, where laminar flow conditions prevail. However, turbulent axial flow resulted in experimental higreater than predicted by the theory. A correction factor based on Prandtl number suggested by Trommelen et al. (1971) did not improve the prediction. The Wilson Plots method was useful for explicitly accounting for axial and rotational velocity effects, both of which significantly affected heat transfer, especially at high values of either variable.     

The effect of pre-denatured whey proteins on the textural and micro-structural properties of model processed cheese spreads

Whey proteins (WP) were heated in a scraped-surface heat exchanger to produce products with different levels of denaturation. Model processed cheese spreads containing the WP were prepared. Rheological measurements showed that higher levels of denaturation in the WP produced softer (lower elastic modulus) cheeses. Temperature scans indicated that the cheeses prepared with high levels of native whey proteins did not melt (the elastic modulus was higher than the viscous modulus at all temperatures), whereas those prepared with high levels of denatured whey proteins melted on increasing the temperature. Microstructural examination of selected cheeses indicated that, when denatured whey proteins were used in processed cheeses, the whey proteins were incorporated as large aggregates dispersed within the cheese matrix. These aggregates did not contribute to, and may disrupt the structure of the cheese. When native whey proteins were used, they were incorporated into the cheese matrix, producing a denser network structure.     

Performance of a Scraped-Surface Heat Exchanger Under Ultra High Temperature Conditions: A Dimensional Analysis

Performance characteristics of a pilot-scale scraped-surface heat exchanger (Contherm Model 6 × 2) under UHT operating conditions were evaluated. Outlet temperature and overall heat transfer coefficient (U) were significantly affected by rotational speed of the blades, mass flow rate of feed, feed inlet temperature, steam pressure and solids content of the model low-acid liquid food (soy extracts). The scraping action of the blades greatly improved the performance up to about 350 rpm; higher blade speeds had little or no effect and sometimes decreased U values. Application of dimensionless models showed that the effect of axial Reynolds number (Re_A) on the Nusselt number was more significant in the turbulent regime (Re_A > 1800), while rotational Reynolds number above 10⁵ had a significant effect at all values of Re_A between 1200 and 3700. At very high values of the Taylor number (> 10¹⁰) when laminar axial flow conditions prevailed, Nusselt number decreased with increase in rotational Reynolds number.     

Edible table (bio)spread containing potentially probiotic Lactobacillus and Bifidobacterium species

A prototype of a reduced fat (60% w/w) edible table biospread, with an added viable, nongrowing, mixed-strain and potentially probiotic culture was developed. Conventional commercial aqueous-phase ingredient and reduced fat spread processing technologies were modified to achieve acceptable strain viability ( ≥   10⁵ cfu/mL) during scraped-surface heat exchange emulsion processing and biospread shelf life. The modifications consisted of:

• 1

   spilt-stream pasteurization of the aqueous and lipid phases (thereby obviating the need for in-line pasteurization of the water-in-oil emulsion during processing);

       
  
  

油脂精炼脱臭中高温油油换热器的应用实践

对植物油精炼脱臭中的几种高温油油换热器进行对比,分析了各自的特点。在考虑不同工艺要求、投资成本以及脱臭油品质的情况下,降膜换热器适用范围最广,真空热回收换热器适用于大豆油、菜籽油等油品的冷热油热交换,Compabloc全焊型板式换热器适用于玉米油、葵花籽油的冷热油热交换。     

批式循环粮食干燥机板式换热器优化设计

基于前人研究得出的高效小型批式粮食干燥工艺,将批式循环粮食干燥机用列管式换热器设计为板式换热器,以更易得到的100℃高温蒸汽代替800℃烟气,将板式换热器采用更为高效的材料,最后在保证换热效率不变的情况下利用matlab优化工具箱优化换热器的尺寸。研究表明:改善之后的换热器具有更高的换热效率,减少了换热器占地面积以及材料的浪费。     

新型空心内管换热器

介绍了一种新型空心内管换热器。该换热器的核心结构就是在管壳式换热器换热管束中的每个换热管内。各内置1根封闭的空心内管。在该内管外固定有小螺旋导流叶片．并将内管的一端或两端固定于管板或壳体上。该结构可以改善管内循环状态,提高换热强度。具有该结构形式的换热器,同时具备管壳式换热器结构强度高和板式换热器换热系数高的优点,是综合性能较为优越的换热器形式。     

Indirect Heating of Alfalfa Juice in Steam-Filled Heat Exchangers

Alfalfa juice, a highly proteinaceous liquid, was heated in steamfilled shell and tube and rotating coil heat exchangers to effect protein coagulation. The juice could be preheated prior to entering the heat exchanger by use of a recycle system. Lower fouling rates were obtained when the protein was denatured prior to contacting the exchanger surfaces and when the rotating coil exchanger was used. Chemical cleaning treatments could restore the heat transfer coefficient of a fouled exchanger to the original value.     

微管道阵列流体流动及其耦合传热的数值模拟

针对一种阵列式微管道换热器,利用FLUENT软件对其进行了数值模拟。将恒壁温、恒热流和流固耦合计算方法的模拟结果进行对比,结果表明:采用流固耦合传热边界条件更有助于揭示换热器局部温度场变化的实际情况,模拟结果与实际情况吻合较好,能够为微管道换热器结构优化设计提供参考依据。