改善CO_2膨胀烟丝结构的探讨

为降低膨胀烟丝的造碎率 ,从改善膨胀烟丝结构的角度出发 ,对美国AIRCOCO2 烟丝膨胀生产线影响膨胀烟丝结构的有关工艺进行了试验分析。结果表明 :①适宜的工艺气体温度和饱和蒸气流量是影响膨胀烟丝结构的重要因素。试验条件下 ,当工艺气体温度为 355℃ ,饱和蒸气流量为 60 0kg/h时 ,膨胀烟丝结构最佳。②适当加大膨胀前的烟丝水分 ,有利于增强膨胀后烟丝的抗碎性 ,膨胀前烟丝水分以 2 2 %为宜。③试验范围内 ,回潮滚筒转速越低 ,膨胀烟丝的造碎率越低。④在膨胀烟丝中施加保润剂 ,能明显增强烟丝的抗碎性     

提高CO2膨胀烟丝内在质量的技术研究

为了提高CO2膨胀烟丝的内在质量,采用正交试验设计法分析膨胀热端工艺(气体温度、气体风速、蒸汽流量)对膨胀烟丝内在质量的影响;根据热端优化结果,分析来料烟丝水分、浸渍时间对膨胀烟丝内在质量影响。结果表明:在试验范围内,来料烟丝水分22.0%、浸渍时间80s、工艺气体温度240℃时,膨胀烟丝内在质量最佳,应用到配方中,感官质量明显提高。因此,较低的工艺气体温度,较低的来料烟丝水分、较短的浸渍时间对膨胀烟丝的内在质量是有利的。     

钛管换热器的换热管与管板焊接工艺介绍

文章介绍了以海水作为冷却介质的换热器中一种以爆炸复合钛钢板作管板、以钛管作换热管的换热管与管板焊接的工艺评定及生产制作中的焊接工艺。文章为钛制换热器的生产制造提供可借鉴经验。     

膨胀工艺对烟丝质量的影响

以烟丝为研究对象,分别以感官评价和气质联用测定烟丝香味成分,判定不同碳膨胀工艺技术条件对膨胀烟丝物理加工质量、感官质量的影响及其变化趋势。结果表明,烟丝经不同温度二氧化碳膨胀、HT处理和塔管板烘丝后,其香味成分的变化趋势和感官质量的变化基本一致,但二氧化碳膨胀后的烟丝香味成分和感官质量降低趋势更明显。二氧化碳膨胀后烟丝的含水率有一定的提高,进而促进了烟丝膨胀效果的提高。烟丝二氧化碳膨胀最佳温度为250℃,较佳浸渍时间为120s,烟丝填充值为6.8cm3/g。     

蒸汽喷射预回潮出料装置的设计应用

为解决在传统CO2膨胀烟丝加工过程中,升华后的膨胀烟丝耐加工性差、造碎大等问题,采用蒸汽预回潮工艺,在升华器后增设了蒸汽喷射预回潮出料装置。该装置既有蒸汽预回潮功能又能保证正常出料,蒸汽经过均匀分布的加湿喷管释放到气锁刮板的腔体内,把经过转网分离进入出料气锁刮板内的膨胀烟丝均匀加湿,并对物料进行松散。应用效果表明,采用预回潮工艺进行设备改造后,膨胀烟丝整丝率提高1.5百分点,出丝率提高0.75百分点,避免了在加湿过程中产生水渍烟丝,有效提高了膨胀烟丝的耐加工性,降低了烟丝造碎。     

基于层次分析和响应面设计的烟丝膨胀工艺优化

选用干冰法膨胀烟丝,采用层次分析法确定膨胀烟丝各项质量指标权重,对数据规范化处理后进行综合评价得到综合质量得分。选取浸渍时间、工艺气温度、热风风速、蒸汽施加量为主要考察因素,研究其对综合质量得分的影响,并使用响应面法优化膨胀烟丝加工工艺条件。结果表明,优化后的烟丝膨胀工艺条件为浸渍时间42s、工艺气温度291℃、热风风速38 m/s、蒸汽施加量500kg/h,该条件下膨胀烟丝的综合质量得分为1.052。     

干冰膨胀烟丝加工过程参数优化研究

针对干冰膨胀烟丝生产及应用过程中存在的造碎严重和耐加工性差等问题,采用正交试验法对膨胀过程的循环气流初始温度、气流流速及蒸汽消耗量进行了优化研究,系统分析了各主要工艺参数对烟丝膨胀质量的影响,并对参数优化前后的膨胀烟丝质量进行了测试对比.结果表明,循环气流初始温度对膨胀后烟丝含水率、回潮烟丝结构及填充值等工艺指标的影响最大;其次是气流风速;再次是蒸汽量.确定的最佳工艺参数为循环气流初始温度260℃;气流风速36 m/s;蒸汽量2000 kg/h.在此条件下,可明显提高膨胀烟丝的含水率,降低造碎,提高其耐加工性能.     

焊接式板式换热器带管板片的研制

为更加直观的分析焊接式板式换热器的换热效果并提高其换热效率,研制了一种焊接式板式换热器带管板片。带管板片在焊接式板式换热器中应用后,可协助测量换热器在换热过程中板间流道的温度分布情况和介质的相关数据,通过对测量数据的分析,以期达到优化产品流程组合形式,为合理选择换热方案起指导作用。     

烟丝在水平管气力输送过程中起动速度研究

利用高速摄像机和水平管气力输送系统研究了不同种类烟丝在水平管气力输送过程中的起动速度.通过捕获烟丝起动瞬间的运动图像,描述了在水平管气力输送过程中烟丝由静止状态开始旋转、翻滚直至达到悬浮状态的起动现象.考察了烟丝物理性质及输送管道性质对起动速度的影响,结果表明,烟丝起动速度随烟丝密度、当量直径、输送管道直径的增加而增大,其规律可由烟丝物理性质、输送气体性质及管道特性等组成的雷诺数Re和弗鲁德数Fr之间的关系式进行表征.通过对试验结果的回归分析,获得了计算烟丝起动速度的经验公式.     

烟丝承压预膨胀装置的设计与应用

烟草制丝线中采用加温加湿机和干燥设备构成的烟丝干燥膨胀处理工艺系统,结构和控制方式复杂,能耗大,烟丝容易被过度干燥,干燥膨胀后的烟丝理化指标存在差异,从而影响成品烟支的感官质量.为此,研究设计了烟丝承压预膨胀装置.该装置主要由进料罩、承压气锁及蒸汽系统组成,蒸汽喷射至气锁壳体内,使气锁壳体内产生一定的压力,从而使连续进入的烟丝快速完成增温增湿的膨胀过程.应用效果表明,该装置可完全取代传统加温加湿设备,对于采用气流式干燥设备的系统,可直接取代原来的普通气锁进料系统,简化了烟丝干燥膨胀工艺,占地面积小,能耗低;防止了烟丝过度干燥膨胀,增温增湿时间由原来的1 min左右减少为2～3 s,改善了烟丝膨胀效果,提升了烟丝的内在品质.     

失效钛换热器的修复

分析了钛换热器管板与换热管焊接接头补焊失效的原因,提出了实施修复的可靠措施。     

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。     

含芯棒水平换热管冷凝传热数值模拟

为提高蒸汽换热器换热效率,提出了一种在水平换热管中插入芯棒的含芯棒蒸汽换热管结构,并通过采用Fluent中两相流模型分析了该结构中芯棒直径对换热管管内冷凝换热特性的影响规律。研究结果表明,由于芯棒的插入使得管内两相流流体的平均流速与管道壁面附近速度梯度增大,故换热管的换热效率得到有效提升;定量而言,换热管的换热效率在棒径比值处于0.52~0.57区间范围内时,换热管内蒸汽冷凝率最高及通流截面内速度梯度最大,此时换热效率达到最高,可确保较低的换热管出口温度和稳定的换热效率。此外,场协同性能分析结果还表明,协同角与棒径比值?呈正相关性,且当棒径比值?>0.52后,芯棒对水平换热管的强化传热效果明显。     

Modelling the gas exchange rate in perforation-mediated modified atmosphere packaging: Effect of the external air movement and tube dimensions

Perforation-mediated modified atmosphere packages control the gas exchange rate and thus the internal atmosphere composition by judicious choice of dimensions of small tubes in perforations in an otherwise hermetic container. The aims of this work were (i) to study the effect of external turbulence on the gas exchange rate through small perforations, (ii) to develop a mathematical model to predict the effect of tube dimensions and hydrodynamic conditions on gas exchange coefficients, and (iii) validate the model developed during the storage of shredded carrots. Different hydrodynamic conditions in the controlled temperature room due to the storage temperature settings (5, 10 and 15 °C) and PVC tubes dimensions (diameter from 1.5 to 4.5 mm length from 2.0 to 6.0 mm) were tested. Results showed that, as expected, hydrodynamic conditions (induced turbulence) and tube diameter had a significantly positive effect on the mass transfer values, whereas tube length had a negative effect. The permeability ratio between CO₂ and O₂ was 0.83 ± 0.01 and did not show any pattern with the factors tested. The gas exchange coefficients increased with decreasing temperature, as the establishment of lower temperatures implied a frequent air movement. A mathematical model to estimate changes of gas composition over time as a function of tube dimensions and hydrodynamic conditions was developed and found to have good predictive abilities. The model was validated during the storage of shredded carrots at 5 °C in PM-MAP, showing a good agreement between the experimental and predicted gas exchange of O₂ and CO₂. The results obtained in this work showed that hydrodynamic conditions of the cold storage room affected the gas exchange rate in PM-MAP.     

降膜蒸馏强化换热管的研究进展

降膜蒸馏具有传热温差小、能源利用效率高等优点,在海水淡化等方面有广泛的应用前景。换热管是降膜蒸馏工艺的核心部件,其表面性质是制约蒸馏效率与实用性最关键因素之一。文章综述了目前强化换热管的类型与强化方法,指出了这些换热管的优点以及存在的问题。纳米技术的引进使得换热管表面形成超疏水或超亲水特性,提高了换热管表面的传热性能,是未来强化换热管的重要研究方向。     

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。     

OVERALL HEAT TRANSFER COEFFICIENTS AND AXIAL TEMPERATURE DISTRIBUTION IN A TRIPLE TUBE HEAT EXCHANGER

Computation of overall heat transfer coefficients in a triple tube heat exchanger (TTHE) is more complicated than in the case of a double tube heat exchanger (DTHE) as the two overall heat transfer coefficients are not independent of one other. A new procedure was developed to calculate these overall heat transfer coefficients and an effective overall heat transfer coefficient value for known inlet and outlet temperatures, and heat capacities of the fluids (product and heating/cooling medium). In this study, this newly developed procedure was utilized and the overall heat transfer coefficients and axial temperature distribution of fluids were computed for a cooling process for different flow rates and inlet temperatures of the fluid streams. The effectiveness of the TTHE was compared to that of a DTHE of identical length. It was observed that when the fluids were flowing in a cocurrent manner, the temperature of the cooling medium with lower heat capacity exceeded the temperature of the product before the fluids exit the TTHE, which caused a decrease in the effectiveness of the TTHE.     

氯化钾车间150m~2管壳式换热器的设计改进

天津长芦海晶集团有限公司化工厂氯化钾车间现有的150 m2管壳式换热器,在生产过程中多次出现管板与换热管接口处渗漏以及换热能力略显不足等问题。文章分析了原管壳式换热器出现问题的原因,并在更新改造设计中进行了有针对性的设计改进。     

HXD气流干燥过程工艺气流传热分析

为研究RCC-HXD气流干燥过程的运行规律,在热工原理分析的基础上,设定试验方案并进行数据采集处理,通过使用在线数据采集系统RSSQL并运用理论推导和统计分析方法对试验结果进行了分析。结果表明:①在干燥过程中,HXD喂料点前工艺气流与烟丝间的换热量可用干燥前后工艺气流温差的倒数来衡量;②在其它控制参数不变,只改变排潮模式(手动与自动)的情况下,设置为手动控制排潮时,干燥过程的换热量总是较低;③当设置为自动排潮且HXD蒸气注入量超过1800kg/h时,工艺气流的干燥能力随着注入量的增大而降低。     

The role of heat exchangers in the contamination of milk with Bacillus cereus in dairy processing plants

In the dairy industry microbiological contamination may arise from equipment used for handling or processing. In this study it was demonstrated that Bacillus cereus spores could adhere stainless steel, germinate and/or multiply in a tube heat exchanger. The levels of B cereus detect in the tubes, after 24 h at 20°C, varied from less than 1 to 2600 cm^-2. Adhering cells and/or spores were more resistant to cleaning with K500 and sodium hydroxide, determined by laboratory suspension tests and surface tests on stainless steel. This was confirmed in a field trial with a tube heat exchanger after cleaning B cereus could still be isolated from all tubes determined by swab samples of individual tubes. The identity of the isolates was checked by polymerase chain reaction/randomly amplified polymorphic DNA typing to confirm that the organisms found on the surfaces were the same as the bacteria in the ingoing milk.