Spray Effect on the Thermal Performances of a Dry Cooling Tower

Pre-cooling the inlet air of a dry cooling tower by means of a spray can improve the tower performance during periods of high temperature.To study the spray effect on the thermal performance of natural draft dry cooling towers(NDDCTs),in this study 3-D numerical simulations of such a process have been conducted using Fluent 16.2(a two-way coupled Eulerian-Lagrangian approach).The considered NDDCT is 120 m high and only half system is simulated due to its structural symmetry.Three different spray strategies have been investigated at a typical crosswind speed of 4 m/s,which is the most frequent wind speed.The results have shown that:(1)The three implemented spray strategies can improve the thermal performance of the studied NDDCT with a vary-ing degree of success.In one case,the heat rejection rate can be increased by 35.2%,and the tower outlet water temperature can be decreased by 2.1℃ when compared with the no spray case;(2)To improve the thermal per-formance of the NDDCT using a small amount of water,the design of the spray pre-cooling system must include more nozzles on the windward and fewer or even no nozzles on the leeward sides of the NDDCT.

Full scale experimental study of a small natural draft dry cooling tower for concentrating solar thermal power plant

Concentrating solar thermal power system can provide low carbon,renewable energy resources in countries or regions with strong solar irradiation.For this kind of power plant which is likely to be located in the arid area,natural draft dry cooling tower is a promising choice.To develop the experimental studies on small cooling tower,a 20 m high natural draft dry cooling tower with fully instrumented measurement system was established by the Queensland Geothermal Energy Centre of Excellence.The performance of this cooling tower was measured with the constant heat input of 600 kW and 840 kW and with ambient temperature ranging from 20 ℃ to 32 ℃.The cooling tower numerical model was refined and validated with the experimental data.The model of 1 MW concentrating solar thermal supercritical CO2 power cycle was developed and integrated with the cooling tower model.The influences of changing ambient temperature and the performance of the cooling tower on efficiency of the power system were simulated.The differences of the mechanism of the ambient temperature effect on Rankine cycle and supercritical CO2 Brayton cycle were analysed and discussed.

THERMAL DESIGN FOR HARMON DRY-COOLING SYSTEM IN LARGE POWER STATION

Based on the analysis of air flow and heat transfer in the dry-cooling towerfor Harmon system, a combined iteration method is presented to solve the coupled heat transfer anddraft equations derived from theoretical and empirical formulas, with the size of the exchangers andthe cooling tower or the systematic parameters being determined. Taking the 686 MW unit as anexample, the present calculating results are well agreed with those of the real case, and thus themethod presented is practical and feasible for reasonable design of Harmon system.

Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens： SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3（only a quarter of that of the grade B mullite brick）,and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^（-1）coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

Study on Operating Characteristics of Power Plant with Dry and Wet Cooling Systems

The represent paper will study the performance of the power plant with the combination of dry and wet cooling systems in different operating conditions. A thermodynamic performance analysis of the steam cycle system was performed by means of a program code dedicated to power plant modeling in design operating condition. Then the off-design behavior was studied by varying not only the ambient temperature and relative humidity but also several parameters connected to the cooling performance, like the exhaust steam flow rate, the air cooling fan load and the number of operating cooling water pumps and cooling towers. The result is an optimum set of variables allowing the dry and wet cooling system be regulated in such a way that the maximum power is achieved and low water consumption.

地下进风系统对间接空冷塔性能的影响

削弱环境风对间接空冷塔散热器性能的不利影响,有助于其安全和经济运行。该文提出一种新型间接空冷塔地下进风系统,将空冷散热器整体布置在低于地表平面的地下空间内。建立配置地下进风系统的间接空冷塔数值计算模型,得到间接空冷塔的空气流场特性和热力特性。基于凝汽器和空冷散热器协同调节、相互制约的作用机制,采用机理模型和数值模拟相结合的方法建立排汽压力的计算模型,在此基础上计算地下进风系统的热经济性。结果表明,在4 m/s风速下,虽然迎风扇段空气流量减少14.5%,热负荷降低12.4%,但侧风扇段和背风扇段冷却空气量分别增加46.0%、8.0%,热负荷分别提升30.9%、3.2%。在高风速工况下,地下进风系统削弱环境风对排汽压力的影响,具有抵御自然大风的能力。某660 MW间接空冷机组,采用地下进风系统全年可节约标煤9554.3 t,节省燃料费1094.0万元。

自然冷却下干式变压器的温度场仿真分析

采用试验与仿真相结合的方法,对干式变压器在自然冷却条件下的温度场特性展开了系统的研究。首先,采用高低压绕组同时施加额定直流电流的试验方法,排除了涡流效应对高低压绕组损耗结果的影响,准确地获得了绕组损耗与温升的对应关系。同时,利用STAR-CCM+软件,分析了达到热平衡后,变压器内部温度场和流场的分布情况以及不同的湍流模型选取和绕组等效建模方法对温升模拟结果的影响规律。研究结果表明,由于空气自然对流的影响,高低压绕组的温度场分布规律基本相同,即:底端温度最低且温度随绕组高度的增加逐渐升高。此外,采用k-ε低雷诺湍流模型和柱坐标等效建模法所得到的变压器自冷温升的仿真结果与试验结果的误差最小,且具有最快的收敛速度。所提出的仿真方法能够准确、快速地对自冷条件下干式变压器的温度场特性进行分析,可为变压器的设计与优化提供一定的指导与参考。

干冰颗粒射流冷却铣削Inconel 718切削性能评价研究

镍基高温合金Inconel 718以高韧性和低导热性等物理力学性能使其成为典型难加工材料,在切削过程中易产生大量切削热,导致刀具磨损加剧并影响加工表面质量。干冰作为一种清洁冷却介质,具有临界温度低、潜热高、升华后无残留等特点,在难加工材料高效准干式切削中具有重要应用潜力。本文将干冰颗粒射流冷却辅助方法应用于Inconel 718切削加工,通过降低切削温度对改善Inconel 718切削性能的有益效果探索该绿色工艺。开展了干冰颗粒射流冷却辅助铣削试验,分析了干冰颗粒冷却工艺对Inconel 718加工过程中铣削温度、铣削力以及加工表面粗糙度的影响规律。结果表明,在干冰颗粒射流冷却条件下,Inconel 718加工过程中铣削温度和铣削力得到显著降低,同时加工表面粗糙度减小,证明干冰颗粒射流冷却辅助加工能够有效改善高温合金材料的切削性能。

基于热负荷均匀分配原则的直接空冷系统轴流风机转速灵活调节策略

在直接空冷电站中,轴流风机功耗占厂用电比例较高。为获得更为高效的风机运行调整策略,以某典型2´600 MW直接空冷机组为例,基于热负荷均匀分配原则,采用数值模拟方法,研究轴流风机转速灵活调节策略。获得不同环境温度和风速条件下,各轴流风机转速分布规律以及通过空冷凝汽器单元的冷却空气质量流量分布规律。最终,计算得到不同环境气象条件下不同轴流风机转速调节策略风机总功耗变化规律。结果表明,基于热负荷均匀分配原则的轴流风机转速灵活调整策略明显优于轴流风机转速整体调节策略,结果可为直接空冷机组优化运行和深层次节能提供参考。

微肋板表面干冰升华喷雾冷却传热数值模拟

针对高度集成化和微型模块化高热载荷电子元器件温度控制问题,基于CFD两相求解器,采用数值实验研究了微肋板表面干冰升华喷雾冷却传热特性。结果表明微肋板表面和热源上表面的温度、传热系数、冷却热通量基本呈环形分布,越靠近中心干冰颗粒越多,温度越低,冷却性能越高。热源上表面中心线上中心温度最低,并且其冷却热通量和传热系数呈M形分布。当喷嘴入口速度和干冰占比增大时,模拟热源表面的传热系数和冷却热通量也随之增大,而温度则整体降低。在喷嘴入口速度为20 m/s,干冰占比为40%时得到相对最优的冷却热通量170 W/cm^(2)和相对最优的传热系数12500 W(/m^(2)·K)。

涡流冷却静电润滑复合干式钻削技术研究

为降低机械加工过程中切削液对环境造成的污染以及处理切削液时高昂的成本,提出一种兼有涡流冷却效应和静电润滑效应的干式钻削技术与装置。将气体离子化、臭氧化后吹到切削加工区域,代替切削液实现润滑、冷却的作用,获得良好的断屑效果,同时延长刀具的寿命。基于结构参数对系统放电性能、臭氧浓度以及冷却效果的影响规律,优化装置结构,形成干式辅助钻削装置。实验结果表明:当电极锥度为15°、电极直径为1 mm、铜帽内径为3 mm、气体流量为20 L/min、驱动电压为6 kV时,臭氧浓度达到峰值34.2×10^(-6)。通过与纯干式切削对比发现:所提技术的切削温度降低40.9%,刀具刃口基本没有损伤,切屑微观表面切痕分布清晰、条理均匀。所设计的涡流冷却静电润滑干式钻削技术在切削效应、冷却效果、刀具磨损以及切屑形态等方面均优于传统的干式钻削技术,可以用于六系铝材的钻削加工。

Thermo-Flow Performances for the Main-Auxiliary Integrated Natural Draft Dry Cooling System

Recently,natural draft dry cooling system with the main-auxiliary integrated air-cooled heat exchangers in the up and lower layers,has drawn attention to the electric power industry.This research firstly develops two physical models for the integrated cooling system,namely Case A and Case B.In Case A,the main air-cooled heat exchanger is arranged in the upper layer and the auxiliary air-cooled heat exchanger arranged in the lower layer,while in Case B,the two heat exchanger systems are arranged in the opposite way.And then,directing at the engineering TMCR and TRL 1 working conditions,the unit-local-overall thermo-flow characteristics of Case A and Case B are obtained and compared by numerical simulation.The findings show that,for the auxiliary air-cooled exchanger,Case A has obviously higher cooling performances than Case B,with the difference varying from 5.46%to 7.55%.Whereas,for the main air-cooled exchanger,Case B shows the recovered cooling performances,with the difference changing from 1.15%to 2.99%.Case A is preferably recommended to the engineering application in consideration of more strict cooling demand of the auxiliary cooling system.Conclusively,this research will provide some theoretical guidelines for the design and construction of the main-auxiliary integrated natural draft dry cooling system.

风冷式干除渣系统在1×330 MW机组中的应用与优化改造

东海热电330 MW机组采用传统的水力除渣方式,存在水资源浪费、能耗高、安全性差、维护费用高等问题。对电厂生产过程中炉渣的排放方式及提高炉渣的综合率方面进行研究论证,将水力除渣系统改造成风冷式干除渣系统,改造后简化了排渣系统,提高了能源利用率及锅炉的效率。风冷式干除渣系统灰渣燃烧充分、含碳量低,保留了炉渣的活性,利于灰渣综合的利用,提高了社会效益及经济效益,对提高整个电厂的经济运行水平具有非常重要的意义。

风冷干式变压器的热仿真分析及优化

对绕组温升和热点温度的有效预测与分析,是确保干式变压器安全、稳定运行的重要前提。模拟了一台8000 kVA干式变压器在强迫风冷条件下的温度场分布情况,并通过风冷温升试验验证了仿真结果的准确性及可靠性。在此基础上,讨论了模型简化方法和结构优化设计对温升模拟结果的影响规律并进行了误差分析。结果表明,所采用的数值仿真方法能够有效地预测变压器的温度分布规律,可为此类变压器的设计、优化和评估提供参考依据。

碎煤加压气化固态排渣系统工艺技术分析比较

固定床碎煤加压气化是一种重要的煤气化技术,根据其灰渣特性采取适当排渣技术是一个重要环节,目前主要有水力湿法排渣、水冷干法排渣及风冷干法排渣等排渣方式。从灰渣收集、冷却方式、综合利用、节水节能等方面对三种排渣方式进行了分析比较,认为水力湿法排渣技术成熟,但已相对落后,水冷干法排渣技术介于风冷干法和水力湿法排渣两者之间,风冷干法排渣技术具有诸多优势,但目前没有在碎煤加压气化系统的应用业绩,煤化工项目在碎煤加压气化排渣技术选择中,应综合考虑各种因素,选择与项目匹配的排渣技术。

聚晶金刚石刀具低温冷却铣削SiC/SiC复合材料磨损试验研究

采用超硬聚晶金刚石(PCD)刀具对SiC/SiC陶瓷基复合材料进行干式和低温液氮冷却铣削试验研究,获得PCD刀具在干式和低温液氮冷却铣削条件下的前刀面和后刀面磨损形貌;分析PCD刀具在干式和低温液氮冷却铣削条件下的主要磨损形式,测得PCD刀具在干式和低温液氮冷却铣削条件下的刀具使用寿命。研究表明:在干式铣削条件下,PCD刀具前刀面的主要磨损形式为刀尖磨钝和崩刃;而在低温液氮冷却铣削条件下,PCD刀具前刀面的主要磨损形式为刀尖磨钝和微剥落;与干式铣削条件相比,PCD刀具在低温液氮冷却铣削条件下寿命提高约71.4%。

立管间接蒸发冷却器与机械制冷复合空气处理机组干湿工况运行模式能耗分析

在达到同样送风要求的前提下,为了研究立管间接蒸发冷却与机械制冷复合机组在数据中心运行时干湿两种模式的运行能耗,搭建了实验台,在室外干球温度为3-7℃范围内,对其不同干湿模式的运行能耗进行了测试并分析。实验结果表明,在达到同样送风要求的前提下,且干湿模式产生的制冷量相同的情况下,湿模式的能效比明显大于干模式的能效比,建议加大湿模式的运行时长。

急冷系统运行问题与优化措施探讨

某石化80万t·a^(-1)乙烯装置采用美国S&W公司专利技术,前脱丙烷前加氢,设计年操作时间为8000 h,装置的操作弹性60%~110%。介绍了急冷系统中的裂解汽油干点过高、稀释蒸汽发生器频繁泄漏以及急冷水一级冷却器泄漏的问题,通过数据建模、压力和p H值分析、扫描电子显微镜分析、金相分析等手段找出其导致问题产生的原因,并提出了调整急冷油塔侧线采出量、增加pH值APC调节系统、增加工艺水甲苯萃取装置、外管壁渗硼工艺处理、对换热器设置阳极保护等技术建议以解决这些问题,来提高急冷系统的稳定性和长期运行性。

半干面高焓杀菌工艺优化及装备设计

传统半干面加工依靠添加防腐剂来延长保质期,但却影响了其口感和外观色泽。高焓杀菌作为一种物理杀菌技术,具有高效杀菌、保持营养、无污染和延长保质期等优点,在半干面加工中逐渐得到应用。介绍了半干面高焓杀菌工艺原理及特点,对高焓杀菌工艺进行了优化,设计了半干面高焓杀菌装备,指出存在的问题,并提出了发展建议,对半干面高焓杀菌工艺及装备后续研发提供借鉴。

超强吸湿速干复合功能运动面料开发

文章采用聚乙烯(PE)与细旦高F数涤纶交织,通过组织结构设计开发具有超强吸湿速干、凉感复合功能的针织面料,最终成品的布面外观良好,耐摩擦色牢度4级、耐水洗色牢度3~4级以上;吸湿速干和吸湿排汗性能满足GB/T 21655.1—2008《纺织品吸湿速干性的评定第1部分:单项组合试验法》、GB/T 21655.2—2019《纺织品吸湿速干性的评定第2部分:动态水分传递法》的要求,特别是蒸发速率达到0.38g/h,单向传递指数达到633.7,性能优异。此外,针对染整生产过程中可能会遇到的布面发硬、单向导湿效果差以及如何保证面料弹性等问题,文章还提供了对应的解决方案。