提高管式加热炉处理能力的技术改造措施

针对早期建造的炼油厂和化工厂在役管式加热炉热负荷和热效率低的状况 ,提出了若干技术改造措施包括 ,增大对流管表面积以增大对流段的热负荷 ;增加辐射管的换热面积 ;修正烟囱高度 ;换用新型燃烧器 ,变自然通风为强制供风 ,以增大燃烧器的发热量 ,减小过剩空气系数 ,节省燃料 2 %～ 3% ;在对流段和烟囱之间增设空气预热器以提高空气入炉温度 ;采用高温辐射涂料增强辐射换热效果 ,从而增加热源对炉壁的辐射传热量和炉管的传热量等     

费托合成产物预测模型的构建及选择性影响因素分析

 构建包含动量、能量、质量传递以及化学反应动力学方程的多物理场耦合数值模型,用以分析管式固定床反应器的管径、催化剂填充长度、催化剂孔隙率以及冷却工质对流换热系数等影响因素对Fe费托合成产物选择性的影响。结果发现,低碳烃的选择性随着管径的增大而提高,而长链烃的选择性则有所减小;增加催化剂段填充长度使得中间物发生链增长反应生成长链烃的概率增加,从而使C5+的质量选择性增加;较低的催化剂孔隙率会带来更高的C5+产物选择性,但是管内压降也会急剧增加;此外,冷却工质对流换热系数的增大可以降低管内温度“热点”的峰值,同时也可以得到更多C5+类产物。     

Impact of the method chosen for measuring temperatures on the efficacy of rapid cooling of foods in catering facilities

Cooked dishes must be cooled rapidly after cooking to avoid significant growth of Clostridium perfringens. French regulations require that produce be cooled from 63 °C to 10 °C in less than 2 h.Cooling is a critical phase for central cooking facilities that need to cool large quantities of food. The food is cooled in blast-chillers before being placed in cold storage. We observed that in France the blast-chiller is usually switched off by operators as soon as a measured temperature is equal to or below 10 °C. This temperature measurement may be taken at any place in the batch. We studied the consequences of this procedure on the distribution of temperatures at the time when cooling is stopped. We did this by monitoring the core temperatures of the foodstuffs during 52 cooling operations carried out in seven central cooking facilities for hospitals or schools. The data allowed us to estimate the characteristics of the distribution of temperatures within batches. Simulations suggest that, when the blast-chiller is switched off after cooling, there can be significant differences between random temperature readings in the batch and the highest temperatures. For 5% of simulations, the difference could be greater than 17 °C. We propose alternative rules to reduce this discrepancy. If such a single measurement was replaced by three measurements, with each of them taken at the centre of a container, this difference would be less than 3.8 °C in 95% of the simulations. The improvement of methods for measuring temperatures is necessary to achieve the cooling durations recommended by the official organizations.     

Real-time estimation of slowest heating point temperature and residual cooking time by coupling multipoint temperature measurement and mathematical modelling: Application to meat cooking automation

In this work, an innovative procedure for real-time heat transfer modelling and dimensional change estimation during meat cooking was presented. By using a multipoint temperature probe, a punctual calculation of slowest heating point (SHP) temperature was obtained at each time from the radial temperature distribution inside the product. Experimental temperature data from the multipoint probe was combined with a mathematical algorithm previously validated to perform a real-time estimation of SHP temperature and residual cooking time on the basis of the data stored at each instant. The developed procedure and algorithm were validated by cooking pork loin and roast beef samples at 180 and 200 °C both under natural and forced convection regimes. Real-time predicted cooking time and SHP endpoint temperature values were very close to those experimentally obtained: at the 85% of the cooking process, the maximum percentage errors for SHP endpoint temperature and cooking time prediction were 1.72 and 1.67%, respectively. In addition, SHP location inside the meat samples was also obtained at each time instant and used to estimate dimensional changes during cooking: calculated final characteristic dimensions were very similar to those experimentally obtained for all cooking trials. The developed approach could be useful for the automatic cooking operations planning in food-service with microbial safety assurance.     

武钢X80级热轧厚板卷的试制与生产

介绍了武钢X80级热轧厚板卷的生产设备、生产工艺控制。分析了X80级钢的化学成分和金相组织。对X80级热轧板卷及用其所试制的螺旋埋弧焊管的拉伸、冷弯、硬度、系列温度冲击韧性、DWTT等性能进行了测试。结果表明，武钢采用控轧和强制加速冷却工艺生产的17．5mm和15、3mm厚X80级热轧板卷强韧性高，焊接性能良好；组织为针状铁素体加少量弥散分布的岛状组织，其性能和组织符合API 5L和中国石油天然气集团公司对X80级管线钢的标准要求，可满足X80钢级螺旋焊管的制管要求。     

Modeling the growth rates of Escherichia coli spp. and Salmonella Typhimurium LT2 in baby spinach leaves under slow cooling

After field harvest, baby spinaches are transported to the packing shed where they are cooled by forced air systems. If contaminated, the temperature of spinaches will affect the number of pathogens in the leaves, and effective temperature control is critical to restrict their growth. Hence, the need to assess the impact of cooling practices on the growth of pathogens in leafy greens. The Baranyi model was used to describe the experimental data and build a dynamic model to predict microorganism growth rate in baby spinach leaves as function of temperature.Baby spinach leaves, inoculated with 10⁴ CFU/ml of Salmonella Typhimurium LT2 or 10² CFU/ml of an Escherichia coli cocktail, and were maintained at temperatures ranging from 10 to 37 °C for 30 h. At 10–30 °C, the E. coli strains grew significantly more (～2–4 log cycles) than the Salmonella strain (～0.11–2.4 log cycles) while at 37 °C, both bacterial populations increased by ～6 log cycles for 30 h. The growth kinetics of each microorganism followed the Baranyi model. The maximum bacterial population increased with temperature and the values were similar for both bacteria. The theoretical minimum temperature for growth was 5.88 °C and 4.76 °C for Salmonella and E. coli, respectively. The dynamic model was validated with an experimental linear cooling profile (slow cooling) and could be incorporated into a risk assessment tool to evaluate the growth of pathogens in baby spinach during processing and distribution.     

考虑湿润比和横向对流的降膜吸收过程的数值模拟及分析

针对以溴化锂水溶液为工质的水平管吸收器，考虑湿润比和横向对流作用，建立了描述水平管外表面的降膜流动吸收传热传质耦合过程的数学模型。采用涡量流函数法求解，得到了考虑横向对流和湿润比时的液膜内部参数分布。模拟计算及分析的结果表明，横向对流可以强化传热传质效果；湿润比降低则吸收性能变差；吸收器传热系数和换热量随溶液喷淋密度增大而增大，而传质系数和吸收速率则先增大后减小，存在最佳喷淋密度。     

聚磷酸铵填充聚丙烯的非等温结晶动力学

用差示扫描量热法测定了聚丙烯／聚磷酸铵复合材料在不同冷却速率时的非等温结晶行为,并与纯聚丙烯的非等温结晶行为进行比较。分析了结晶峰温、结晶起始温度和结晶峰的半峰宽等结晶峰参数,发现在聚丙烯中加入质量分数为5％的聚磷酸铵后,其结晶速率加快,晶粒分布变窄;继续增加聚磷酸铵含量,结晶速率略有降低。对所得数据分别用修正Avrami方程的Jeziorny法、Ozawa法和莫志深法进行处理。结果表明,用Jeziorny法和莫志深法处理非等温结晶过程比较理想,而用Ozawa法处理不太适合;用Jeziorny法求出的参数Zc随冷却速率的加快而增加,复合材料Zc的值大于聚丙烯;用莫志深法求出的所有试样的参数F(T)均随结晶度的增加而增加,而α值(Avrami指数n与Ozawa指数m的比值)几乎不变。     

厚板管线钢DWTT性能的影响因素

为了进一步研究轧制工艺对厚板管线钢DWTT性能的影响,以X70、X80管线钢为研究对象,在不同板坯加热制度、控制轧制工艺和控制冷却工艺条件下,对厚板管线钢进行了DWTT性能试验,统计分析了轧制工艺参数对DWTT韧性剪切面积SA的影响规律。结果表明,要保证剪切面积SA在85%以上,板坯加热温度为1 150～1 180 ℃,板坯加热时间控制在5～8 h较为合理;在高温变形的粗轧阶段,必须保证在较低的粗轧温度下采用大变形量,单道次变形量大于5%较好;在低温控轧阶段,开轧温度为740～820 ℃,终轧温度为740～780 ℃为较优选择;冷却工艺根据实际情况与控轧工艺相匹配,冷却速度为25～30 ℃/s或45～50 ℃/s,开冷温度为720～800 ℃,终冷温度为450～550 ℃较为合理。     

甲醇-生物柴油体系单液滴的蒸发特性

基于传热传质理论,建立了二组分体系单液滴在对流热空气环境中的蒸发模型。通过对比实验数据,验证了模型的正确性。以甲醇 生物柴油混合燃料为研究对象,分析了环境温度、环境压力、甲醇掺混比例、气流强度对液滴蒸发特性的影响。结果表明,甲醇 生物柴油体系液滴的蒸发过程可以分为甲醇先蒸发和生物柴油后蒸发两个阶段。当环境温度从400 K上升到600 K时,液滴的蒸发时间缩短951%;当甲醇的掺混比例从10%增加到50%时,液滴的蒸发时间缩短177%;当空气速度从1 m/s增加到5 m/s时,液滴的蒸发时间缩短295%;随环境压力的升高,液滴蒸发时间延长。在液滴蒸发过程中,液滴表面温度迅速上升到环境温度,且随着环境温度的升高明显上升,但受环境压力、甲醇比例、气流强度的影响不大。     

Probabilistic evaluation of Clostridium perfringens potential growth in order to validate a cooling process of cooked dishes in catering

The cook-chill operation, a widely used process within central cooking facilities, implies that cooked dishes have to be quickly cooled down immediately after cooking in order to prevent any food-borne diseases due to Clostridium perfringens. The food service operators are obliged to validate the efficiency of the cooling process in the context of their HACCP plan. To perform this cooling process, they can either ensure compliance with some reference criterion (maximal cooling duration) or demonstrate that the cooling operation is safe by carrying out prior tests.This document presents an experimental method to validate the sanitary efficiency of the cooling process. In the studied kitchen the food was cooked and, successively, distributed into plastic containers, cooled down in blast-chiller and then stored in cold room.The tests consisted in monitoring food temperature at the center of the containers from the end of cooking until the beginning of cold room storage. The measurements were performed during 6 cycles of food preparation.From the monitored time–temperature profiles, thermal cooling equations were established for modeling.Each parameter of these thermal equations was linked with a distribution fitted with the experimental data. Then these thermal equations were coupled with predictive microbiology equations. A probabilistic calculation of the C. perfringens potential growth was carried out by using @Risk software. The proposed method required only simple monitoring equipments and could be easily implemented in central kitchens under the usual working conditions.The cooling conditions in the studied kitchen could be considered as satisfactory because the calculations give only a 0.4% probability that the C. perfringens potential growth was equal or greater than 1 log10 cfu/g.     

钻机绞车刹车系统强制冷却装置的研制

鉴于常规钻机绞车刹车系统靠风冷或普通水罐循环冷却,冷却效果差,不能满足钻机绞车刹车系统的要求,设计制造了ZJ-50D和ZJ-70/4500D电驱动钻机绞车刹车系统强制冷却装置;该装置由冷却水罐、循环水泵、散热器、进回水管线及水位和水温控制冷却装置组成。在分析钻机绞车刹车系统强制冷却装置工作原理的基础上,介绍了该装置的设计计算、结构设计及设计方法。研制的强制冷却装置在长庆油田使用中,显示了冷却效果好和工作可靠等许多优点。     

Cold chain maintaining in food trade

The concept of food safety has lately acquired a new approach due to globalization and free trade in food. Introducing a HACCP system in the production and trade in food has become a necessity. The term “food trade” indicates all the postproduction procedures, from storage, transport and distribution to retail, including export and import. The aim of our 2002 survey was to analyse the situation of cold chain maintaining in food trade in Ljubljana, the capital of Slovenia. The research was based upon two hypotheses: in the first one we supposed that a cold chain is interrupted in retail and in the second one we supposed that the handling of food in retail varies. Seventeen stores were divided in three groups, according to sales area of the store: large ones, medium ones and small ones. Temperature conditions in cooling appliances for storage of 1688 perishable food products were measured. Products were inspected by two criteria, by the “best before” date and by the storage temperature. The results confirmed both of the hypotheses. The storage conditions were properly labelled on the packages of the products inspected. In most of the cases the temperatures measured differed from the required ones, even for up to 10 °C. The biggest differences were detected between temperatures indicated on cooling appliances and temperatures measured by our calibrated thermometers. Conditions during food storage and in retail stores were not documented and there was no system to control the cold chain. Our findings have shown that retailers are not familiar with the importance of maintaining a cold chain. The result of that can be a shorter durability of highly perishable foodstuffs and their safety for consumers is questionable.     

大型重整加热炉的设计与优化

介绍了重整加热炉的设计特点。通过区域法模拟分析,对大型侧烧U形管重整加热炉传热影响因素(如炉膛宽度、火焰长度、燃烧器的布置、空气流速及入炉温度等)进行了分析。研究结果表明:①炉膛越宽,传热均匀度越差,管壁峰值温度越高,管内工艺介质温度分布越不均匀;②改进燃烧器的能量分布可以改善炉膛温度场分布,显著降低最高管壁温度;③火焰越长,炉膛温度场分布越均匀,传热均匀度越好;④在强制通风条件下,燃烧器空气流速越高,炉膛温度场分布越均匀;⑤空气预热温度对传热均匀度的不利影响有限,但在较高的燃烧器空气流速下,传热均匀度改善,最高管壁温度降低。指出重整加热炉采用高温预热器在技术上是可行的。     

Hydrochloric acid diffusion coefficients at acid-fracturing conditions

The reaction of a 15% HCl solution with Indiana Limestone was investigated at 93 °C and 34.5 MPa using an annular flow reactor that was erected vertically. The laminar flow conditions were such that both free and forced convections contributed to the overall mass-transfer rate. The experimental results correlated well with theory when the forced and free convections were in the same direction (assisting flow) and when free-convection mass transfer dominated the mass-transfer process. Deviation from theory, however, occurred when free convection was in the opposite direction to forced convection (opposing flow). Correlating the experimental results with theory provided a method for the determination of the effective diffusion coefficient of HCl at the high temperature, pressure and acid concentrations encountered in acid-fracturing treatments. An HCl effective diffusion coefficient of 5.25 × 10⁻⁵ cm²/s was found from correlating the present experimental results with theory.Recent trend in designing acid-fracturing treatments is to use computer models to predict and optimize the etched length of the created fracture. The accuracy and reliability of such computer model predictions depend heavily on the accuracy of the values used for physical parameters such as reaction rate and diffusion coefficient of HCl. The annular flow reactor and the correlations discussed here provide a way to obtain reaction rates and diffusion coefficients at practical conditions for use in computer models and design of acid-fracturing treatments.     

深层页岩气水平井钻进中井筒-地层瞬态传热模型

目前深层页岩气井常用的旋转导向工具服役环境温度为135 ℃,准确预测深层页岩气水平井钻进中循环温度对延长井下测量工具使用寿命与有效延伸水平段长度非常重要。基于能量守恒原理,考虑井筒-地层各控制区域——钻柱内流体、钻柱壁、环空流体及近井壁地层在径向与轴向传热机理,建立了井筒-地层瞬态传热模型,应用全隐式有限差分法对数学模型求解,分析了各敏感因素对井筒温度的影响。研究表明:页岩气水平井流体循环初期环空流体温度高于原始地层温度;增加循环时间、流体比热容与密度、降低入口温度可以降低井底温度;排量过高引起摩阻生热,使得井筒温度非降反升;通过地面降温装置降低入口温度能抵消水平段延伸产生的热量,增加水平段钻进距离;结合Y101H26-1井数据,当入口温度为35、65 ℃,对应钻进井深分别为5 650、5 250 m时,不超过旋转导向工具服役环境温度,计算误差在3%以内。该研究成果可避免井筒降温技术应用的盲目性和低效性。     

钢管3PE防腐生产线水冷过程有限元分析

介绍了钢管3PE防腐涂层生产过程水冷作用的有限元分析,建立了水冷过程传热数学模型,并运用ANSYS分析软件对?准1 219 mm×20.6 mm钢管进行模拟分析,得出了钢管经水冷后的温度分布图,并绘制出沿钢管轴向8个节点的温度变化曲线图。与实际生产数据比较分析后,得出了模拟的温度分布和实际生产数据相吻合的结论,为钢管3PE防腐生产工艺及设备的优化提供依据。     

工程机械用低成本高强钢Q690D的研制与开发

为了开发低成本Q690D高强钢,在C-Mn-Nb-V成分基础上,设计含Mo及不含Mo的2种成分试验钢,并对比研究不同成分不同工艺条件下钢板力学性能及微观组织的变化。试验结果显示,在轧制工艺相同条件下,随终冷温度降低,含Mo钢强度上升,断后伸长率基本不变,当终冷温度在350~400℃时,-20℃冲击功可达到200 J以上。在轧制工艺及终冷温度相同条件下,冷却速度对不含Mo钢强度影响不大,断后延伸率及冲击功变化规律同含Mo钢;降低钢板始冷温度,强度有一定程度降低,冲击韧性及断后伸长率变化不明显。回火前后,含Mo的1#钢,终冷温度在450℃以上(工艺1)时的力学性能,与不含Mo的2#钢终冷温度在350~400℃(工艺5及工艺6)时的力学性能结果相近。研究表明,在不添加合金Mo的前提下,适当降低终冷温度及淬火+回火工艺,钢板性能完全可以满足Q690D要求。     

蒸发式冷凝器管束中强制对流空气CFD模拟

运用FLUENT软件对圆管、椭圆管及交变曲面波纹管管束中强制对流空气热力过程进行了模拟,模拟数据经过Tecplot.10处理后直观地表征了3种管型管束中空气的速度场、压力场及温度场。结果表明,交变曲面波纹管在提高流体湍动程度及强化传热温差方面优于其它两种管型。     

东辛油田稠油举升井筒保温对策研究及现场试验

稠油在井筒举升过程中,由于热损失造成温度下降,致使其黏度迅速增大,举升负荷较大。因此,研究稠油举升中的井筒保温对策具有现实意义。基于传热学的基本原理,采用计算稠油井井筒温度场的Hansan模型,以东辛油田Y12X2X3井为例对井筒温度分布进行了计算分析,并对影响稠油井井筒温度的油管类型、油管长度和产液量等3项参数进行了优化,提出了采用长度1 000 m的D级隔热油管和普通油管组合、产液量由11 m3/d提高到20 m3/d的井筒保温措施。现场试验显示,井口温度由调整前的20.5℃升高至41.5℃,井深1 000 m以浅井段原油黏度大幅度降低,原油流动性增强,有杆泵充满程度增加,泵效提高了47%。研究结果表明,采用稠油井筒温度场计算模型能准确描述井筒温度的分布情况,并能有针对性地制订稠油井井筒保温措施。