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.

Online Fault Detection Configuration on Equipment Side of a Variable-Air-Volume Air Handling Unit

With the development of the technology of the Internet of Things,more and more operational data can be collected from air conditioning systems.Unfortunately,the most of existing air conditioning controllers mainly provide controlling functions more than storing,processing or computing the measured data.This study develops an online fault detection configuration on the equipment side of air conditioning systems to realize these functions.Modbus communication is served to collect real-time operational data.The calculating programs are embedded to identify whether the measured signals exceed their limits or not,and to detect if sensor reading is frozen and other faults in relation to the operational performance are generated or not.The online fault detection configuration is tested on an actual variable-air-volume(VAV)air handling unit(AHU).The results show that the time ratio of fault detection exceeds 95.00%,which means that the configuration exhibits an acceptable fault detection effect.

Fault isolation of air handling unit based on neural network

Aiming at various faults in an air conditioning system,the fault characteristics are analyzed.The influence of the faults on the energy consumption and thermal comfort of the system are also discussed.The simulation results show that the measurement faults of the supply air temperature can lead to the increase in energy consumption.According to the fault characteristics,a data-driven method based on a neural network is presented to detect and diagnose the faults of air handling units.First,the historical data are selected to train the neural network so that it can recognize and predict the operation of the system.Then,the faults can be diagnosed by calculating the relative errors denoting the difference between the measuring values and the prediction outputs.Finally,the fault diagnosis strategy using the neural network is validated by using a simulator based on the TRNSYS platform.The results show that the neural network can diagnose different faults of the temperature,the flow rate and the pressure sensors in the air conditioning system.

Novel Approach for Fault Detection and Diagnosis of Sensors in Air Handling Units Using Wavelet Energy Entropy

A novel fault diagnosis method for sensors in air handling unit（AHU） using wavelet energy entropy was presented. Instead of directly comparing the numerous data under noise conditiom, the wavelet energy entropy residual was compared in the proposed method. Three.level wavelet analysis was used to decompose the measurement data under both fault-free and faulty operation conditions. The concept of Shannon entropy was referred to define wavelet energy entropy of the wavelet coefficients. The sensor faults were diagnosed by comparing the deviation of the wavelet energy entropy of the measured signal and the estimated one with the preset threshold. Testing results showed that the wavelet energy entropy was sensitive to diagnose the biased faults. The wavelet energy entropy residuals exceed the threshold significantly when faults occur. In addition, the severer the faults were, the larger the residuals would be. The results prove that the proposed method is feasible and effective for the fault detection and diagnosis of the sensors.

An Air Mass Based Approach to the Establishment of Spring Season Synoptic Characteristics in the Northeast United States

The Northeast United States spring is indicative of major meteorological and biological change though the seasonal boundaries are difficult to define and may even be changing with global climate warming. This research aims to obtain a synoptic meteorological definition of the spring season through an assessment of air mass frequency over the past 60 years. The validity of recent speculations that the onset and termination of spring have changed in recent decades with global change is also examined. The Spatial Synoptic Classification is utilized to define daily air masses over the region. Annual and seasonal baseline frequencies are identified and their differences are acquired to characterize the season. Seasonal frequency departures of the early and late segments of the period of record are calculated and examined for practical and statistical significance. The daily boundaries of early and late spring are also isolated and assessed across the period of record to identify important changes in the season’s initiation and termination through time. Results indicate that the Northeast spring season is dominated by dry air masses, mainly the Dry Moderate and Dry Polar types. Prior to 1975, more polar air masses are detected while after 1975 more moderate and tropical types are identified. Late spring is characterized by increased variability in all moist air mass frequencies. These findings indicate that, from a synoptic perspective, the season is dry through time but modern springs are also warmer than those of past decades and the initiation of the season is likely arriving earlier. The end of the season represents more variable day-to-day air mass conditions in modern times than detected in past decades.

Experimental Study of Air Conditioning Unit of Evaporative Cooling Assisted Mechanical Refrigeration

The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analyzed.The test shows that making full use of the evaporative cooling "free cooling" in Spring and Autumn seasons can fully meet the requirements of air-conditioned comfort through the switch of the function in different seasons.Taking into account the evaporative cooling fan and pump energy consumption,compared with the traditional mechanical refrigeration system,more than 80 percent of energy can be saved,and the energy efficiency ratio of the Unit(EER)is as high as 7.63.Using the two stages of indirect evaporative cooling to pre-cool the new wind in summer,under the conditions of the same air supply temperature requirements,0.83 kg/s chilled water saved can be equivalent to the traditional mechanical refrigeration system,and when the new wind ratio up to 50 percent,more than 10 percent load was reduced in mechanical refrigeration system.The overall EER increased about 35 percent.

Characteristics and management strategy of the devices configured in Baosteel's domestically-integrated 60000 m^3/h air separation unit

Baosteel＇ s No. 8 air separation unit（ASU） is the first domestically-integrated 60 000 m^3/h ASU. This paper describes the mechanical equipment, the design and the configuration characteristics of this unit. The potential failure modes of the mechanical devices are deduced via analyses on the failure history of similar devices in other ASUs. Finally, this paper also brings up suggestions on daily maintenance, overhaul and purchases of spare parts.

Independent integration and innovation of the first domestically-integrated 60000 m^3/h air separation unit

Baosteel＇s 60000 m……3/h air separation unit （ASU）, the first domestically-integrated unit of its class, is a milestone in the Chinese air separation industry. In this paper,the process characteristics of the unit and the application of the original techniques are expatiated. Some difficulties in the process design, the risk control, the quality control, the control system integration and the system commissioning are analyzed and appraised. The mode of the project integration and innovation, the cooperation among industries and the user-orientated project management mode are introduced. Finally,the successful experiences in innovation are summarized with the focus on the integration of the project.

Baosteel's No.8 air separation unit and the practice of its system commissioning

This paper introduces the process flow, technical parameters and relevant features of Baosteel＇s No. 8 air separation unit （ASU） with a capacity of 60000m^3/h. It summarizes the commissioning work, which includes the adjustment of the air compressor,the system＇s naked cooling,the precooling system and the operation adjustment. It also provides detailed analyses on some failures which occurred in the commissioning. Through the modification of the design and the interlocks, the tripping probability of the air compressor was greatly reduced. Through the heating of the system and the control of the water cooler＇s nitrogen flow,the overproof content of carbon dioxide and fluctuation of oxygen flow were avoided. Nitrogen-block in the argon system was eliminated by the precise control of the argon rectification flow and argon content. All these solutions have been proved to be effective by practice.

Characteristics and experience in the electrical design of the first domestically-integrated large-scale air separation unit

The first domestically-integrated large-scale air separation unit （ASU） with a capacity of 60 000 m^3/h was successfully built and put into operation at Baosteel. Compared with the electrical design of the imported equipment of the same type,this ASU has an electrical protection interlink that is independent from the distribution control system （DCS）. With the design idea of simplicity, the ASU features a simplified configuration and an audio alarm system for electrical failures. It helps reduce the failure rate of the electrical equipment and detect failures quickly and accurately. It will effectively enhance safe and stabilized production. The ASU can not only reduce the cost of investment, but also ensure a smooth and stable running of the whole electrical equipment. This study focuses on the experience and understanding of the unit design and commissioning.

Type selection and maintenance of the control system of large-scale air separation units

Based on the practice of Baosteel＇ s 60000 m3/h air separation unit （ASU） ,which is the first domestically- integrated unit of such a scale, this paper studies the principles of type selection of the distribution control system （DCS）. It discusses the design of the unit＇s control system,which involves a compressor system,a purification system （molecular sieving）, a turbo expansion system and an air separation system. The final part of the paper discusses the maintenance and future development of the ASU control system at Baosteel.

Influence of Surrounding Structures upon the Aerodynamic and Acoustic Performance of the Outdoor Unit of a Split Air-Conditioner

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics（CFD） and computational aerodynamic acoustics（CAA） simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures（i.e. the heat sink, the bell-mouth type shroud and the outlet grille） upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring＇s size and throat＇s depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %（i.e. 100 m3·h～（-1）） at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

The Impact of Thermal Desorption Unit Associated with Remediation of Hydrocarbon Impacted Soils on Air Quality at Beneku, Ndokwa East, Delta State, Nigeria

The study is on the use of thermal desorption unit in the remediation of contaminated soils located at Beneku in Ndokwa East local government area of Delta state. This method uses heat to vaporize the contaminants, and as such only works for volatile contaminants. Air quality samples around the thermal desorption Unit (TDU), used for the treatment of hydrocarbon impacted soils were taken at six (6) different sampling points (Stations). The sampling points were 100 m apart beginning from 0 m which was the closest to the TDU. The results showed that the mean values of SO2 were 0.01 ppm for both the dry and wet seasons and it is within the FMEnv limit of 0.01. The mean concentration of NO2 in the dry season was 0.25 μg/m3 and in the wet season it was 0.18 μg/m3, which were above the FMEnv limit of 0.06 μg/m3. It is a strong oxidizing agent that reacts with air/water to form corrosive nitric acid, as well as toxic organic nitrates. The mean concentration of CO2 recorded in the dry season was 11.52 ppm and that for the wet season was 10.53 ppm, which were slightly above the FMEnv limit of 10.00 ppm. The levels of SPM 2.5 recorded in the study show a concentration of 132.07 μg/m3 in the dry season and 95.93 μg/m3 in the wet season while those for SPM 10 had 102.17 μg/m3 in the dry season and 91.33 μg/m3 in the wet season. The level of the VOC recorded across the study area was significantly low (0.11 μg/m3). The mean H2S concentration recorded across the study area was low (0.01 μg/m3). Several health risks have been associated with SPM. Inhaling SPM affects respiratory and cardiovascular systems in both children and adults. Fine SPM (such as PM 2.5 particulate) can penetrate into the lungs and blood streams when inhaled, resulting to respiratory problems, heart attack, lung cancer and even death, while exposure to low levels of H2S can induce headaches as well as breathing difficulties in some asthmatic patients.

Indoor Surveillance of Airborne Fungi Contaminating Intensive Care Units and Operation Rooms in Assiut University Hospitals, Egypt

Mycoflora of atmospheric air and dust samples collected from air conditioning systems in 12 of each I.C.U. （intensive care units） and O.R. （operation rooms） were tested using settle and dilution plate methods on four types of agar media and incubated at 25℃. Forty-five fungal species representing 23 genera were isolated and identified. The most prevalent genera recorded were Cladosporium, Aspergillus, Penicillium and Fusarium. The total colony forming units of airborne fungi recovered in I.C.U. and O.R. ranged between 31.13-49.61 colonies/m3 on the four types of media usedl The fungal total catch of the dust samples collected from the air conditioning system filters in I.C.U. and O.R. were ranged from 65.5-170 colonies/mg dust. Since, the interest to replace synthetic xenobiotics by natural compounds with low environmental persistence and biodegradable to control such airborne fungal contaminants is needed. In this respect, essential oils showed to possess a broad spectrum of antifungal activity. Fungal static ability of six oils was tested on 30 different fungal isolates. Vapors of common thyme oil exhibited the strongest inhibitory effects on the tested isolates, whereas the headspace vapors of blue gum and ginger had no inhibitory effects on the tested fungal isolates. These data revealed that the air conditioning systems may be an important source of contamination in I.C.U. and O.R. of Assiut university hospitals. Thus, patients may be in risk of being exposed to contaminated atmospheric air by opportunistic fungi and the use of essential oils as an alternative option to control hospital wards from fungal contaminants needs further studies.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

基于ConvGRU的空气污染预测可视分析系统

预测细颗粒污染物浓度是制定防污减排措施的主要途径之一.针对传统的用于预测的大规模数值模拟需要在超级计算机上计算数小时乃至数天,成本高、效率低,甚至影响实效性的问题,提出一种基于卷积门控循环单元(ConvGRU)的细颗粒物污染预测方法.首先设计一个全面损失函数(C-Loss),综合考虑预测结果与实况之间的绝对误差和相对误差,通过与常用的均方损失函数对比,证明C-Loss可以使预测模型更适合细颗粒物;然后根据领域专家需求,设计一个可交互的可视分析系统,领域专家可以高效地获取一系列时刻的预测结果,从而交互式地深入探索大气污染的形成过程与气象因素之间的相关性,为进一步制定防污减排方案提供了科学依据.通过一系列应用示例全面地分析了污染物的形成原因,并验证了预测模型的有效性.

卧式紧凑型旋流气浮装置旋流筒结构优化数值模拟研究

由于油田开发采出液含水率上升和海上平台空间的限制,亟需紧凑型污水处理设备用于对海上油田含油污水处理。对此设计了卧式紧凑型旋流气浮装置,通过Fluent数值模拟方法对该装置旋流筒区域的流场分布及油水分离性能开展了系统研究,探究了旋流筒结构、入口管径、含油污水入口速度和入口含油率等因素对油水分离效果的影响。结果表明,在入口管径为20 mm,含油污水入口速度为2 m/s时,采用导流叶片的旋流筒结构能获得较好的流场分布;含油污水入口速度越大切向速度衰减越严重;旋流筒在高度为100~300 mm时切向速度衰减较大,在高度为300~650 mm内衰减较小;相同含油污水入口速度下,增大入口管径能使旋流筒内油相体积分数增大;增大含油污水入口速度反而会导致旋流筒内油相体积分数减小;旋流筒内油相体积分数呈“U”型分布,且随入口含油率增大而增大,与入口含油率成正比。

火电耦合压缩空气储能技术研究进展及展望

火电耦合压缩空气储能技术作为一种提升传统火电机组灵活性和经济性的有效手段,近年来受到了广泛关注。该文从分析火电耦合压缩空气储能技术在提升电网调峰能力、促进可再生能源整合等方面的重要意义出发。首先,介绍典型耦合系统的结构组成与工作原理;然后,探讨耦合系统中关键设备的技术现状和面临的挑战;之后,梳理火-储耦合系统的集成方案设计、调峰运行优化以及经济性评估的研究现状;最后,针对当前技术难点,展望未来火电耦合压缩空气储能技术的研究方向与重点。该文旨在为今后相关领域研究提供参考与借鉴,推动其持续发展和创新。

贫数据中基于模型自训练的空气处理设备故障诊断

针对空气处理设备(AHU)故障贫数据,基于深度置信网络(DBN)模型对4种特征选择算法进行对比研究,结果表明最大相关最小冗余算法的特征子集在诊断准确率及子集元素稳定性上表现最优。提出将DBN嵌入自训练框架的故障诊断模型,发现DBN自训练的诊断准确率较单纯DBN最高可提升19.5%。提出均匀抽样及按比例抽样2种自训练伪标签抽样策略,二者的诊断准确率均随抽样数减小而增大,在不同抽样数中的最大差异为3.42%;在所有贫数据样本中,均匀抽样策略始终优于按比例抽样,诊断准确率最大相差1.39%,表明在故障标签匮乏时,采用均匀抽样策略及较小的抽样数有利于提升DBN自训练的诊断性能。

基于反步法的空气处理机组温湿度跟踪控制

针对空气处理机组室内湿负荷和进回水温差不确定的情况,提出一种带有多参数的反步控制器,可以实现温度和湿度的跟踪控制。为了设计方便,先将空气处理机组的动态模型转换为状态空间表达形式,通过引入带增益的状态变换,将原系统的跟踪控制问题转换为变换后所得新系统的稳定控制问题;利用反步法逐步设计了控制器,并通过选择合适的设计参数,实现了温度和湿度的跟踪控制目标;分析了闭环系统的稳定性并给出了证明过程。结果表明:仿真实验验证了所研控制器的有效性,通过与PID控制器对比可知,所设计控制器的跟踪效果更好。