Ammonium Salt Deposition Characteristics in an Air Cooler System Based on the Coupling of Fluid Flow and Heat Transfer Simulation

The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations were performed by using the mixture model, the heating transfer model, and the particles tracking model. The results show that the differences between the temperature and the velocity at each cross section of the first-row and second-row tubes are small. The inertia of the particles plays an important role in the particle’s deposition, and the smaller particles distribute more uniformly in the air cooler. However, for larger particles, they prefer falling from the inner side of the vertical elbow, and preferentially depositing at the inlet header and pipes before saturation. In the heat exchanger tubes, the particle deposition number is larger in the second-row tubes than that in the first-row tubes, and the high-risk tubes mainly concentrate on the middle and right side of the air cooler. The kinetic parameters of the particles are in accordance with the blocking-prone position in many real operating conditions.

Functional Link Neural Network for Predicting Crystallization Temperature of Ammonium Chloride in Air Cooler System

The air cooler is an important equipment in the petroleum refining industry.Ammonium chloride(NH4 Cl)deposition-induced corrosion is one of its main failure forms.In this study,the ammonium salt crystallization temperature is chosen as the key decision variable of NH4 Cl deposition-induced corrosion through in-depth mechanism research and experimental analysis.The functional link neural network(FLNN)is adopted as the basic algorithm for modeling because of its advantages in dealing with non-linear problems and its fast-computational ability.A hybrid FLNN attached to a small norm is built to improve the generalization performance of the model.Then,the trained model is used to predict the NH4 Cl salt crystallization temperature in the air cooler of a sour water stripper plant.Experimental results show the proposed improved FLNN algorithm can achieve better generalization performance than the PLS,the back propagation neural network,and the conventional FLNN models.

Influence of syngas components and ash particles on the radiative heat transfer in a radiant syngas cooler

Radiant syngas cooler(RSC)is widely used as a waste heat recovery equipment in industrial gasification.In this work,an RSC with radiation screens is established and the impact of gaseous radiative property models,gas components,and ash particles on heat transfer is investigated by the numerical simulation method.Considering the syngas components and the pressure environment of the RSC,a modified weighted-sum-of-gray-gases model was developed.The modified model shows high accuracy in validation.In computational fluid dynamics simulation,the calculated steam production is only 0.63%in error with the industrial data.Compared with Smith's model,the temperature decay along the axial direction calculated by the modified model is faster.Syngas components are of great significance to heat recovery capacity,especially when the absorbing gas fraction is less than 10%.After considering the influence of particles,the outlet temperature and the proportion of radiative heat transfer are less affected,but the difference in steam output reaches 2.7 t·h^(-1).The particle deposition on the wall greatly reduces the heat recovery performance of an RSC.

Analysis of the Erosion-Corrosion Mechanism of the Air Cooler in a Hydrocracking Unit:A Numerical and Experimental Study

Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirmed that the damage was caused by erosion-corrosion(E-C).Numerical and experimental methods were applied to investigate the E-C mechanism in the air cooler.Computational fluid dynamics(CFD)was used to calculate the hydrodynamic parameters of the air cooler.The results showed that there was a biased flow in the air cooler,which led to a significant increase in velocity,turbulent kinetic energy and wall shear within 0.2 m of the tube entrance.A visualization experiment was then performed to determine the principles of migration and transformation of multiphase flow in the air cooler tubes.Various flow patterns(pure droplet flow,mist flow,and annular flow)and their evolutionary processes were clearly depicted experimentally.The initiation mechanism and processes leading to the development of E-C in the air cooler were also determined.This study provided a comprehensive explanation for the E-C failures that occur in air coolers during operation.

Experimental Investigation of Capacity Control Scheme on System Performance for a Machine Tool Cooler

Highly accurate manufacture in machining industry can only be obtained with precise temperature control of the coolant （oil or water）.Machine tool with more accurate,stable and advanced the precision of the working component cannot be developed without appropriate cooling.However,the machine tool coolers are facing the control hunting of cooling temperature and the dramatic variation of heat load in high-accuracy machining.The main objective of this study is to evaluate the influence of the hot-gas by-pass scheme and suction regulation for capacity control of a machine tool cooler system.In this study,experimental investigation on both hot-gas by-pass scheme and suction valve regulation for capacity control has been proposed.Effects of using capillary tube and thermostatic expansion valve along with different capacity control scheme have been investigated extensively in an environmental testing room.Cooling performance and power consumption of the cooler system have been measured and analyzed as well by comparing with different opening percentage of throttling valve under specific coolant temperature.The experimental results reveal that the power consumption will reduce slightly by capacity control using the hot-gas by-pass scheme but the coefficient of performance （COP） of the overall system will decrease.Lower coolant temperature will result in higher compressor power consumption as well.While conducting suction valve regulating for capacity control,energy-saving at 10%-12% can be obtained by using thermostatic expansion valve under different evaporator load.It also reveals that suction valve regulation along with adequate choice of thermostatic expansion valve can provide alternative choice for steady capacity control and substantial energy-saving.The proposed cooler systems with different capacity control schemes are not only more cost-effective than inverter driven system,but also can perform energy-saving and precise temperature control specific for high-accuracy machine tool cooling.

Experimental Study on the Thermal Performances of a Tube-Type Indirect Evaporative Cooler

The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need to be addressed to make this technology more reliable and easy to implement.This experimental study deals with the performances of a tube-type indirect evaporative cooler based on an aluminum tube with a 10 mm diameter.In particular,the required tests were carried out considering a range of dry-bulb temperatures between 16℃ and 18℃ and a temperature difference between the wet-bulb and dry-bulb temperature of 2℃∼4℃.The integrated convective heat transfer coefficient inside the tube in the drenching condition has been found to lie in the range between 36.10 and 437.4(W/(m^(2)⋅K)).

“链-回-环”系统能质平衡核算及优化

文章以某球团厂200万t“链—回—环”系统为例,根据现场采集到的生产数据,核算得到该系统的热利用率为22.36%,余热回收率为71.62%。优化后得到当喷煤量在5.00~5.40 t/h,煤粉固定碳含量在76%~82%,煤粉燃尽率在97.5%以上时,预热Ⅱ段氧含量可以稳定在14.0%~16.0%,有利于球团矿的氧化且能有效抑制氮氧化物的生成。

Design calculation of porous ceramics tube type dew point indirect evaporative cooler

To improve the wall surface hydrophilicity of a tube type indirect evaporative cooler,a new method adopting porous ceramics is proposed.This method realizes the combination of porous ceramics and the evaporative cooling technique.The design calculation of the porous ceramics tube type dew point indirect evaporative cooler are carried out from such aspects as the volumes and status parameters of the primary and secondary air,the cooler structure,the heat transfer of the solid porous ceramic tubes and the resistance of the cooler.The calculation results show that the design is reasonable.Finally,based on the design calculation,the porous ceramics tube type dew point indirect evaporative cooler is successfully manufactured.

Influence of regenerator flow resistance on stability of pulse tube cooler

Based on the fluid network theory,the possibility of utilizing regenerator flow resistance to suppress the direct current （DC） flow induced by the introduction of a double-inlet in a pulse tube cooler is investigated theoretically. The calculation results show that increasing regenerator flow resistance can lead to a smaller extent of DC flow.Therefore,a better stability performance of the cooler can be realized.On this basis,the stability characteristics of the cooler with various regenerator matrix arrangements are studied by experiments.By replacing 30% space of 247 screens of stainless steel mesh at the cold part of the regenerator by lead balls of 0.25 mm diameter,a long-time stable temperature output at 80 K region is achieved. This achievement provides a new way to obtain stable performance for pulse tube coolers at high temperature and is helpful for its application.

Multi-Pollutant Formation and Control in Pressurized Oxy-Combustion:SO_(x),NO_(x),Particulate Matter,and Mercury

Oxy-combustion is a promising carbon-capture technology,but atmospheric-pressure oxy-combustion has a relatively low net efficiency,limiting its application in power plants.In pressurized oxycombustion(POC),the boiler,air separation unit,flue gas recirculation unit,and CO_(2)purification and compression unit are all operated at elevated pressure;this makes the process more efficient,with many advantages over atmospheric pressure,such as low NO_(x)emissions,a smaller boiler size,and more.POC is also more promising for industrial application and has attracted widespread research interest in recent years.It can produce high-pressure CO_(2)with a purity of approximately 95%,which can be used directly for enhanced oil recovery or geo-sequestration.However,the pollutant emissions must meet the standards for carbon capture,storage,and utilization.Because of the high oxygen and moisture concentrations in POC,the formation of acids via the oxidation and solution of SO_(x)and NO_(x)can be increased,causing the corrosion of pipelines and equipment.Furthermore,particulate matter(PM)and mercury emissions can harm the environment and human health.The main distinction between pressurized and atmospheric-pressure oxy-combustion is the former’s elevated pressure;thus,the effect of this pressure on the pollutants emitted from POC—including SO_(x),NO_(x),PM,and mercury—must be understood,and effective control methodologies must be incorporated to control the formation of these pollutants.This paper reviews recent advances in research on SO_(x),NO_(x),PM,and mercury formation and control in POC systems that can aid in pollutant control in such systems.

采煤工作面空冷器位置及风流参数优化研究

针对济宁二号煤矿10303采煤工作面高温热害问题,采用数值分析方法,建立了工作面物理模型,分析了风筒长度、风筒的出风口距离及温度等多因素对降温系统的影响,确定了不同工况(生产和停产)的温度控制参数;通过自动启闭控温设施控制空冷器出风温度,实现了不同作业下采煤工作面所需的制冷量,解决了工作面高温热害问题。结果表明:100 m风筒长度、50m风筒出风距离的降温效果最好;当工作面正常开采作业时,出风温度设置应小于16.5℃,工作面的平均温度将降低3.7℃;当停采作业时,出风温度设置应小于20.5℃,此时工作面的平均温度将降低3.5℃;2种工况下的参数均能达到采煤工作面的温度控制目标。

基于改进PSO的蝶形半导体激光器温控系统的设计

提出了基于改进粒子群优化算法(Particle Swarm Optimization,PSO)的蝶形半导体激光器温度控制系统。利用蝶形半导体激光器内部热电冷却器(Thermo-Electric Cooler,TEC)作为被控对象求出其传递函数,并在Simulink仿真工具中搭建温度控制系统仿真模型,分析温度对激光器工作的影响。基于改进PSO算法来优化比例积分微分(Proportional-Integral-Derivative,PID)控制器参数以达到良好的温度控制效果。实验结果表明,通过将改进PSO算法优化后的PID控制器参数应用到温控电路,可以保证激光器在安全平稳运行的前提下,达到激光器TEC温控系统稳定性高、响应速度快的目标,2 h内温度最大浮动误差为0.13℃,温度稳定性提升至0.52%。

35 K空间深低温热传输系统性能天地差异

为了解决空间红外探测系统的深低温散热问题,保证红外探测器的低温工作环境,基于脉冲管制冷机和深冷环路热管,设计研制了一套35 K温区的深低温获取与热传输集成系统.该系统由一套35 K温区氖工质深冷环路热管、两台35 K温区脉冲管制冷机、一台150 K温区脉冲管制冷机、隔热冷屏、测温/加热组件、控制系统等组成.完成了地面单机级、整星级热真空测试,并于2020年完成空间飞行测试.在地面单机试验中开展了水平姿态和逆重力恶劣姿态下的传热测试,保证了空间微重力下必定能稳定工作;整星级测试验证了系统在卫星平台散热工况下的工作特性,空间飞行测试获得了系统的空间微重力下的工作性能.本文分析了系统在上述不同阶段的热性能,包括超临界启动特性,稳态运行性能等,验证了相关设计的正确性,重点对比了不同阶段的性能差异,分析其可能的原因.

主变冷却器系统铂热电阻温度传感器应用分析及故障对策探讨

本文通过研究铂热电阻温度传感器(PT100)测温原理,统计分析某水电厂主变冷却器系统铂热电阻温度传感器运行数据及运行工况,总结提炼出铂热电阻温度传感器测量不准确的原因,针对存在的问题,提出相应对策。

空分装置空冷塔分布器堵塞在线处理方法

针对空分装置空冷塔在长期运行过程中出现的因塔内分布器堵塞导致水流量不足,造成空冷塔出口空气温度升高及下游分子筛出口水分和CO_(2)含量超标等问题,通过对堵塞的空冷塔分布器采取在线反吹处理的方法,解决了堵塞问题。

基于TEC的石英挠性加速度计组件一体化温控结构热设计

在高精度惯性导航系统和捷联惯导重力测量系统中,石英挠性加速度计组件的温控精度直接影响系统的导航和重力测量精度。为保证加速度计工作环境的温度稳定性,设计了基于半导体制冷器(Thermoelectric Cooler, TEC)的石英挠性加速度计一体化温度控制系统。对系统硬件结构和热特性进行了分析,完成了相关组件的热力学建模、仿真分析和结构优化,并设计了常温及变温环境下的温控实验。相关结果表明,一体化温控系统在2 h室温环境下,加速度计组件温度波动峰-峰值优于0.006℃;在最高10℃/h的快速变温环境下,系统3 h温度控制波动峰-峰值优于0.006℃,加速度计表头温度波动峰-峰值优于0.03℃。对比温控关闭状态下的实验结果,温控开启时,加表输出稳定性及输出精度分别得到了34.2倍和37.6倍的提升。相关结果表明系统有较好的鲁棒性和温控精度,可以满足多种应用环境下的加速度计组件温控应用需求。

Effect of sinter layer porosity distribution on flow and temperature fields in a sinter cooler

When sinters are filled into the sinter cooler from the sintering machine, it is commonly seen that, due to segregation effects, sinters of larger size usually accumulate closer to the inner wall of the sinter cooler, whereas those of smaller size are to the outer wall. This nonuniform distribution of sinters has led to uneven cooling effect throughout the cooler. This causes the sinters leaving the cooler at a large temperature difference. This undesired temperature difference leads to the deformation and even the destruction of the conveyors. The computational fluid dynamics （CFD） technique was used in the present work to investigate the heat and fluid flow phenomena within the sinter cooler corresponding to the different distribution of sinter layer porosity, which was highly dependent on the arrangement and orientation of sinters within the sinter cooler. It is confirmed that a high mass flow rate within the sinter layer causes a low temperature region and vice versa. The flow fields for vertically reducing porosity distribution and random distribution are almost identical indicating the relative insignificance of convective heat transfer mechanism.

油冷却器及热虹吸油冷却系统设计

热虹吸油冷却系统被广泛应用于螺杆式压缩机组,为更好地指导热虹吸油冷却系统设计,本文采用HTRI对热虹吸油冷却系统和管壳式油冷却器进行设计计算,搭建热虹吸油冷却系统测试试验台,并进行试验验证。结果表明:利用HTRI计算油冷却器换热量的误差为4.6%,计算压降的误差为3.6%;随进液管内径和回气管内径的增大、静压头的升高,油冷却器的换热量逐渐增大,但是换热量的增大幅度逐渐减小。

空压机冷却系统节能改造

针对空压机冷却系统存在水泵、风机功率大,用电、水单耗高和冷却器易结垢堵塞,运行风险、成本高问题,采用将原来水(自来水)—风露天集中式冷却塔(一用一备),改造升级为一台空压机配置一台小型水(纯水)—水(自来水)闭式冷却塔的措施,达到空压机正常运行时一级、二级排气温度小于35°C,用电量节约40000 kWh/月,用水量节约3000m^(3)/月的效果,每年可节约用电、用水和冷却器更换成本共计约73.2万元。

基于半导体制冷的光模块高低温测试系统

5G网络建设和大规模数据中心建设带来了大量光模块需求。在光模块生产制造中,为了保障光模块在环境温度变化情况下能够长时间正常工作,需要检测模块在不同温度下的性能,而进行高低温测试。高低温测试在光模块制造成本中占了很大比重。设计了一种基于半导体制冷器(Thermo Electric Cooler)的光模块高低温测试系统,相较传统基于热流仪的方案,不需要压缩空气,能够大幅降低功耗、噪声和整体成本,且能够实现与热流仪相当的升降温时间。该系统对于节能减排、降低光模块制造成本有重要意义。