Effects of Steam Heat Treatment on the Surface Contact Angle of Chinese Fir

The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.

Transient Heat Transfer Study of Direct Contact Condensation of Steam in Spray Cooling Water

We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 1045 mm. We applied a new analysis method for the steam state equation to analyze the molar quantity change in steam over the course of the experiment and determined the transient steam variation. We also investigated the influence of flow rates and temperatures ofcooling water on the efficiency ofsteam condensation. Our experimental results show that appropriate increasing of the cooling water flow rate can significantly accelerate the steam condensation. We achieved a rapid increase in the total volumetric heat transfer coefficient by increasing the flow rate of cooling water, which indicated a higher thermal convection between the steam and the cooling water with higher flow rates. We found that the temperature ofcooling water did not play an important role on steam condensation. This method was confirmed to be effective for rapid recovering ofsteam.

Performance Optimization of Dual Pressure Heat Recovery Steam Generator (HRSG) in the Tropical Rainforest

This work evaluates the performance optimization of heat recovery steam generator system in Afam VI power plant, Rivers State. Nigeria. Steady state monitoring and direct collection of data from the plant was performed including logged data for a period of 12 months. The data were analysed using various energy equations. Hysys software was used to model the temperature across the heating surfaces, and MATLAB software was used to determine the heat transfer coefficient, heat duties, steam flow, effectiveness of the HRSG. The optimization technique was carried out by varying the exhaust gas flow, exhaust gas temperature, steam pressure and the theoretical introduction of duct burner for supplementary firing. The results show that between 490℃ and 526℃, the percentage increase in the overall heat absorbed in the HRSG is 37.39%. It also show that for an increase in the exhaust gas mass flow by 80 kg/s, the steam generation increase by 19.29% and 18.18% for the low and high pressure levels respectively. The overall result indicates an improvement in the HRSG energy efficiency and steam generation. As the exhaust gas mass flow and temperature increases, the steam generation and system effectiveness greatly improved under the various considerations, which satisfy the research objective.

Dynamic simulation of drum level sloshing of heat recovery steam generator

Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level controlling, influence factors on the drum level sloshing were investigated. Firstly, drum sub-modules were developed using the method of modularization modeling, and then the model of drum level sloshing was set up as well. Experiments were carried out on the experimental rig, and the model was validated using the obtained experimental results. Dynamic simulation was made based on the model to get a 3-D graph of drum level sloshing, which shows a vivid procedure of drum level sloshing. The effect of feed-water flow rate, main-steam flow rate and heating quantity on the drum level sloshing was analyzed. The simulation results indicate that the signals with frequency higher than 0.05 Hz are that of drum level sloshing, the signals with frequency of 0.0-0.05 Hz are that of drum level trendy and "false water level", and variation of the feed-water flow rates, main-steam flow rates and heating quantities can change the frequency of drum level sloshing, i.e., the frequency of sloshing increases with the increase of feed-water flow rate, or the decrease of the main-steam flow rate and the heating quantity. This research work is fundamental to improve signal-to-noise ratio of drum level signal and precise controlling of drum level.

A Study of the Jet System of the Recovery Concerning Waste Heat of Steam Condensate

This paper presents a frame figure of the recovery system concerning waste heat of steam condensate. When steam phase changes into liquid state in the condenser, the heat equilibium equation, gas state equation, mass flow calculating equation of the jet steam and incondensable gas equation are established. The coupling function between condensate unit and recovery pump of the hot condensate with ejector is studied. The paper sets up the fluid continuity equation, heat equilibium equation and efficiency equation of the ejector and points out the technical key how the prevent hot condensate change into steam phase. When fluid passes from circulation loop through pump to export, the energy equations are obtained here. At last, signal figure of the applied examples are given and settle the techanical questions of the jet system are discussed.

The Research of Heat Transfer Area for 55/19 Steam Generator

A calculation method of heat transfer area for vertical natural circulated steam generator was introduced. According to the design requirements of steam generator 55/19 of CPR1000, its heat transfer area was calculated based on this method. The results show that the accuracy of partitional and overall calculation method is almost the same, but the result is different when using different calculation models. And the results are compared with the foreign companies for 55/19 steam generator.

The Calculation of Heating Radius and Determination of Parameters in Heavy Oil Steam Stimulation

在稠油吞吐过程中,加热半径是热采中的重要指标,对注汽参数和生产制度起到了指导性作用。运用能量守恒原理,从热量注入方面考虑了蒸汽相变释放的气化潜热,从热量损失方面考虑井筒热量损失和顶底盖层热量损失,最终得到了新的加热半径计算公式。计算结果表明,加热半径受注汽参数、焖井时间、储层参数等因素影响,并系统阐述了岩层各物性参数的计算及选择方法。最后通过实例验证了该方法的计算值和试井解释出的值较为相符,为现场实际应用提供了可靠的方法。

自然对流下蒸汽凝结表面传热系数测定实验装置研制

自然对流下蒸汽凝结表面传热系数测定实验是将蒸汽通过一组表面状态各不相同的管道,测定管道在大空间空气介质中自然冷却过程中的蒸汽凝结表面传热系数。由于管道的材质、几何形状、接触方式及管外空气流动状况都会不同程度地影响换热效果,因此测定每根管道的表面传热系数值,可条理性和系统性地分析影响传热过程的各因素。该文设计了自然对流下蒸汽凝结表面传热系数测定实验装置,可开展管道材质、肋片结构、管道横截面几何形状、管道保温材料对传热系数的影响实验研究。应用实践表明,实验项目内容全面,提高了学生的课堂积极性,具有良好的教学效果。

高温气冷堆热态功能试验中一回路加热动态特性研究

高温气冷堆反应堆压力容器堆内构件由石墨和碳化硼烧结陶瓷材料组成,热态功能试验过程中需对一回路堆内构件进行加热除湿。针对高温气冷堆一回路热试系统特点,采用COMSOL Multiphysics 5.4计算软件构建了压力容器、蒸汽发生器和主氦风机三维数值模型,并通过示范工程加热试验值验证了模型的可靠性,并获得了一回路加热过程中温度场动态特性。为了解决高温气冷堆示范工程一回路首次加热效率低的问题,提出了将辅助蒸汽通入到蒸汽发生器,并动态调整辅助蒸汽运行参数来加热一回路氦气的方法,结果表明:相较于主氦风机单独加热方式,外加辅助蒸汽热源可节省加热时间约31.3 h,同时可将堆芯最终平衡温度由250℃提高至265℃;在满足运行准则的前提下,更有利于碳砖和石墨堆内构件的除湿。该研究结果为高温气冷堆一回路热试提供了有力支持。

量子电炉烟气余热回收发电设计与实践

介绍了量子电炉高温烟气余热回收发电项目,其中高效余热锅炉以及省煤器的设置充分回收了电炉高温烟气中的热量,急冷塔的设置保证了整个发电系统的安全性,切换式母管制蒸汽管以及蓄热器的设置保证了发电系统的稳定和连续运行,余热锅炉对二噁英再生的遏制以及活性炭对二噁英的去除保证了发电系统的环保性。

纳米C-S-H/PCE对蒸养UHPC力学性能增强机理研究

目前超高性能混凝土(UHPC)制品的力学性能有待进一步提升,采用纳米C-S-H/PCE对UHPC进行增强在理论上是一种可行的技术途径。本文研究了蒸养条件下掺入以聚羧酸(PCE)为分散剂的纳米水化硅酸钙(C-S-H/PCE)对UHPC力学性能的影响,通过测试水化热、水化产物、微观形貌和孔结构等对其机理进行了分析。结果表明,掺入3.0%(质量分数)纳米C-S-H/PCE可以显著提高蒸养UHPC的抗压强度和抗折强度。掺入纳米C-S-H/PCE可以促进UHPC的早期水化,生成更多的水化硅酸钙(C-S-H)凝胶,使水化放热温峰增高,并缩短达到水化温峰的时间。掺入纳米C-S-H/PCE可有效改善蒸养UHPC的孔结构,在掺量为3.0%(质量分数)时总孔隙率最小,有害孔比例最低。该研究可为纳米C-S-H/PCE在蒸养UHPC中的应用提供参考。

多相流阻垢热泵蒸发系统特性研究

为验证多相流热泵蒸发系统的在线阻垢及强化换热性能,以蒸氨废液为液相工质、氧化铝及聚甲醛粒子为阻垢颗粒进行实验研究。结果表明,氧化铝颗粒的加入可有效去除蒸发器已有垢层,换热系数由结垢后的392.5 W/(m^(2)·K)提升至1 712.2 W/(m^(2)·K),且连续运行130 h换热系数未降低;蒸发器换热系数受颗粒物性参数影响较大,随着颗粒直径、密度、体积分率增加换热系数逐渐增大,但增加过量时导致流动不畅,换热系数降低;颗粒自身材质导热系数越高强化换热效果越好;循环流量、颗粒分布形式对换热系数也有较大影响,提高循环流量有助于强化换热;不同分布形式在一定程度上均可提高换热系数,双层多孔分布器可实现颗粒逐级输运,增加其进入换热管比例,强化换热效果最佳。

直流余热锅炉蒸发段长度和位置变动特性的仿真分析

在直流余热锅炉变工况运行过程中蒸发段长度和位置的改变会造成锅炉管壁温度分布、工质出口参数等产生较大的波动,影响锅炉安全运行。以某立式直流余热锅炉为研究对象,建立其动态仿真模型,研究锅炉烟气流量、入口烟温、高压给水流量和给水温度分别发生阶跃扰动后蒸发段长度及相变点位置的变化规律。仿真结果表明:余热锅炉在设计工况下运行,锅炉入口烟温对锅炉蒸发段长度的影响程度最大,入口烟温阶跃升高10℃后,蒸发段迅速缩短,相变点均向锅炉管内工质入口方向移动,蒸发段长度和相变点位置恢复稳定所需时间相对较短;烟气流量阶跃升高5%后,蒸发段长度迅速缩短而后缓慢增长,沸腾点向管内工质入口方向移动距离大于蒸干点,恢复稳定所需时间较长;给水流量阶跃升高5%后,蒸发段长度迅速增长而后缓慢缩短,蒸干点向管内工质出口方向移动距离大于沸腾点,恢复稳定所需时间最长;给水温度阶跃变化20℃对蒸发段长度和相变点位置的影响很小。

湿热处理对杂豆馒头淀粉消化特性及风味品质的影响

目的研究湿热处理对杂豆馒头消化特性及风味品质的影响。方法选取湿热处理豌豆、红豆、白芸豆3种杂豆制作杂豆馒头,对湿热杂豆馒头的色度、比容、感官评分等进行评价,通过固相微萃取-气相色谱-质谱法(solid phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS)分析湿热粉杂豆馒头挥发性风味物质变化规律,并对馒头进行体外淀粉消化实验。结果湿热处理杂豆粉的添加降低了馒头的比容,改变了馒头的色度。对豌豆馒头和白芸豆馒头感官评分没有影响,但可显著提高红豆馒头的感官评分(P<0.05)。SPME-GC-MS从湿热杂豆馒头中共检出47种挥发性成分,主要为醛类、醇类、酯类、酮类、芳香族类、烷烃类及杂环类。淀粉体外消化特性表明3种杂豆馒头的抗性淀粉含量显著高于小麦馒头,淀粉水解率低于小麦馒头。结论湿热处理可使杂豆馒头风味品质改善,使红豆馒头和白芸豆馒头抗性淀粉含量提高和淀粉水解率降低,但对豌豆馒头没有影响。研究结果为淀粉基杂豆营养健康食品的加工提供数据支撑。

不同热处理方式对小麦粉特性及其蒸饼品质的影响

目前蒸饼的制作大多采用传统的半烫面工艺,工序较为复杂,为解决这一问题,该研究采用不同热处理方式(蒸汽处理、微波处理、干热处理)对小麦粉进行热处理,研究了不同处理方式对小麦粉的糊化特性、热机械学特性、微观结构等的影响,并将处理后的小麦粉添加到未处理的小麦粉中制成蒸饼,考察了所制得的蒸饼的水分分布、质构特性及感官品质。结果表明:3种热处理的适当处理时间都可以提高小麦粉的黏度和回生值;经干热处理和微波处理后的小麦粉的破损淀粉含量高于经蒸汽处理的小麦粉。3种热处理小麦粉的添加均可以提高面团的吸水率,蒸汽处理小麦粉的添加使面团耐揉性降低、蒸煮稳定性提高,微波和干热处理小麦粉的添加使面团的耐揉性和内部结构稳定性提高。适当处理时间的热处理小麦粉的添加可以提高蒸饼的结合水含量、硬度、弹性和咀嚼性等。其中,经蒸汽处理40 min、微波处理2 min和干热处理30 min后的小麦粉的添加制得的蒸饼有相对适中的强韧性、较高的结合水含量和感官评分。该研究结果表明添加热处理后的小麦粉代替传统的烫面工艺制作高品质蒸饼具有可行性,同时能够为蒸饼的工业化生产提供相应的基础数据和一定的理论指导。

基于水蓄热的热源厂蒸汽调峰技术

基于工业供汽负荷波动大、昼夜偏差显著的现状,将水蓄热技术与热源厂热力生产工艺相结合,提出采用蒸汽-除盐冷水的间接换热技术、环氧富锌漆防腐技术和硬质聚氨酯发泡保温技术,并对形状、容积和高径比等罐体结构优化设计,旨在开发一种适用于工业供热的蒸汽调峰技术。实践应用表明,基于水蓄热的热源厂蒸汽调峰技术具有稳定高效、简单易操和投资收益显著等优点。本技术还可应用于燃煤机组实现深度调峰、消纳新能源发电等场景,具有重要的现实意义。

双循环蓄热式导热油加热系统在工业领域的应用探究

当今工业领域中有很多间歇式生产流程,在工作时需要过热蒸汽进行生产运转。而随着国内企业节能环保意识的逐步加强,将厂区内低品质蒸汽更清洁、高效地利用起来成为各企业研究的方向。本文通过建立一种双循环蓄热式导热油加热系统,将清洁的电能转换为热能,间接加热蒸汽,将一个工作周期内的间断供汽所需最大热负荷需求转变为该周期内连续平均的电加热负荷,避免电加热器频繁启停,延长电加热器寿命,同时降低对电网的影响。由此对于下一步大规模工业实践提供了参考和借鉴。

危废焚烧锅炉饱和蒸汽驱动有机朗肯循环系统热力学分析

危险废弃物焚烧处理过程中产生的热量通常用于生产饱和蒸汽以供应工业园区的蒸汽、热量等需求,也可以用于低温发电。分析了饱和蒸汽驱动有机朗肯循环(ORC)系统做功时的热力学特性。通过基本工况下蒸汽潜热型热源与ORC系统的热匹配特性分析,提出3种优化措施,并研究了单一优化和组合优化措施下以及不同工况下的系统热力学性能。结果表明,组合优化可使系统获得更优的性能,相对于基本工况,优化后的工况下最大净输出功为3 193.81 kW,提高了170.46%;热效率为23.34%,提高了30.25%;总[火用]效率为66.25%,提高了41.80%。

蒸汽加热垂直矩形窄通道内流型与局部换热特性研究

为了明确竖直矩形窄通道内各阶段流动沸腾的换热特性,优化换热器性能,以去离子水为工质,对尺寸为1400 mm×250 mm×2.75 mm(高×宽×深)的蒸汽加热垂直矩形窄通道内流动沸腾流型与局部换热特性进行实验研究。将由实验数据得到的流型图与不同加热条件下的现有流型图进行了对比分析。结合流型变化分析了进口温度、质流密度、加热功率对局部换热特性的影响,并基于对实验数据的参数分析,得到适用于该实验工况下的新流动沸腾传热关联式。结果表明:入口温度的升高对提升核态沸腾段的换热有积极作用,而在进入搅拌流阶段后,其对局部传热系数的影响很小;质流密度增加会降低核态沸腾阶段的局部传热系数,提升液膜流动蒸发区的局部传热系数;随着加热功率的增加,局部传热系数的峰值呈现左移的趋势;新的传热关联式能很好地预测该实验工况下蒸汽加热垂直矩形窄通道内流动沸腾的局部传热系数。