MULTIPOINT FIBEROPTIC HUMIDITY MONITOR

Spectral Sciences, Inc. is developing a multipoint humidity monitor for drying application in the pulp and paper industry. The humidity is measured by monitoring near-infrared optical absorption in the process stream atmosphere. An array of sensor heads distributed throughout the plant is linked by fiber optic cables to a single source/readout device which can be located in a control room hundreds of meters away. The sensor heads and cables are modular. allowing for raid installation and reconfiguration of a distributed sensor system in process control applications. The method used for quantifying the optical absorption provides substantial stability, accuracy, and signal processing advantages over standard wavelength scanning or band pass techniques. The laser diode's output wavelength is actively locked to the center of a water absorption line, thereby providing a constant monitor of water vapor concentration which is insensitive to all other species in the process stream. Wavelength modulation and second harmonic detection techniques are used to quantify the water vapor concentration. A simultaneous temperature measurement then permits an output of the absolute humidity or humidity ratio for process monitoring or control     

How coating/polymer properties affect fiber/cable performance

The selection of the coatings/polymers used to fabricate optical fibers has been shown to be very important in determining their optical, mechanical, and connectorization performance. Material properties such as refractive index, optical transmission, and thermal coefficient of linear expansion are critical for coatings functioning as cladding materials. Coating adhesion to the glass surface, water absorption and water vapor permeation, as well as the ability to passivate the glass surface, have strong affects on the strength and fatigue behavior of fibers. Hard, thin, adhesive primary coatings are beneficial in making connectorization easier and more reliable. Many of the preferred properties for the fiber coating are different from those preferred for electrical wire, not only because light must be transmitted rather than electricity, but also because of the brittle nature of the silica substrate and the coupling between physical displacements and light transmission within the guiding material (microbend effects). The selection of cable materials is quite similar to that employed in the electrical wire and cable field. Much more attention must be given to cable design than for the latter. Designs/applications requiring tight jacketed or filled cables put special constraints on the selection of materials for the optical cables, which are more restrictive than for electrical cables.     

NIR‐laser based detection of the photopolymerization state of acrylate coatings suitable for in situ measurements

The present article describes a method for the determination of the radical photopolymerization conversion of acrylic coatings suitable for an in situ monitoring during the coating process. Acrylate based coatings are increasingly used in many kinds of industrial coating processes, because of advantages of the solvent‐free application process. The applied method is based on 1620 nm light absorption of the acrylate. To overcome the disadvantages of a common NIR spectrometer, only the diffuse reflection of the relevant discrete wavelength at 1620 nm and of a reference wavelength is measured. A sophisticated sensor setup including an optical spatial filter and lock‐in amplified signal processing is used to achieve a sufficient signal to noise ratio. The capability of the sensor to discriminate between polymerized and unpolymerized coatings on metal substrates down to a coating thickness of 16 μm is demonstrated. Furthermore, the information on polymerization from larger depth in TiO₂ pigmented coatings is investigated. The results can be analytically modeled in analogy to the Lambert–Beer's law, resulting in a detection limit of a maximum pigment concentration of 15 wt % with 100 μm coating thickness. The presented sensor design is suitable to be used in an industrial production environment for example in screen printing applications as a monitoring and quality control tool. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ultrasensitive and reversible room-temperature resistive humidity sensor based on layered two-dimensional titanium carbide

The nanostructured two-dimensional (2D) materials for humidity sensing applications have become increasingly attractive. However, 2D materials have negative aspects of easily stacking and agglomerating multilayers. Here, a novel resistive-type humidity sensor utilizing multi-layer titanium carbide (Ti₃C₂T_x) films as sensitive material is demonstrated. The humidity sensor exhibits an ultrasensitive and reversible sensing performance in a wide relative humidity range. Furthermore, the ultrafast response and recovery properties are achieved at room temperature. The Fourier transform infrared spectroscopy is used to investigate the adsorption of water vapor on Ti₃C₂T_x surfaces. A rapid capillary condensation of water vapor on the unique accordion-like microstructures and the hierarchical nanostructures of hydroxyl-riched Ti₃C₂T_x surface are supposed to be responsible for the super adsorption capability for water vapor. The electrostatic field induced by adsorbed water molecules is proposed to explain the resistance change of the titanium carbide humidity sensor. This work highlights the unique advantages of humidity sensor with layered 2D materials of Ti₃C₂T_x MXenes, including ultrasensitive, good reversibility and fast recovery at room temperature.     

Determination of key sensor locations for non-point pollutant sources management in sewer network

As the importance of watershed management has emerged for water systems, non-point pollutant sources have been blamed as the main problem of water pollution. To control non-point pollutant sources, it is necessary to monitor sewers connected to the watershed and to analyze their effects on the sewer network. As the cost to monitor a sewer network depends on the number of sensors installed, the monitoring stations should be decided with proper guide of the installation location rule. In present paper, a new method to select the proper sensor location is proposed by combining monitoring information with data mining techniques. To estimate the amount of pollutants by wash-off and to find the sensor locations in a sewer network, three scenarios are considered based on rainfall intensity, influent concentrations and flow rate. The optimal locations of the sensor were selected based on the proposed method to facilitate the management of non-point pollutant source in sewer network. The presented approach can be extended to a complex sewer network system to design a minimum number of sensors and optimum locations for the sensors.     

Influence of Temperature and Humidity on Dynamic Fatigue of Optical Fibers

The influence of temperature and humidity on dynamic fatigue characteristics of silicone resin-coated optical glass fibers is examined. Dynamic fatigue is shown to result from subcritical crack growth. Test results verify that subcritical crack growth during dynamic loading is a thermally activated process and that the effect of humidity on crack growth is a function of water vapor pressure.     

基于STM32的分布式多参数监测仪

采用STM32主控器采集并处理数据,设计制作分布式多参数监测仪,由相关传感器检测温湿度、烟雾浓度和气体浓度。分布式多参数监测仪设有CAN接口和无线接口,可实现多监测仪组网,实现数据远程传输和监控。该监测仪具有精度高、响应快及稳定性好等优点,并能通过CAN网络或无线网络进行可靠的数据传输。     

HIGH INTENSITY DRYING

A mathematical model simulating the heat and mass transfer process during high intensity drying of paper and board has been developed. The model is successful in predicting the vapor pressure developments, pressure driven bulk flow of liquid and vapor, and increased drying rates during high-intensity drying, closely matching the experimental determination.

The model predicts substantial amounts of water removal in the liquid form during high-intensity drying being pushed out of the web by pressurized vapor zone. Water removal by pressure flow of liquid could account for as much as one-third of the total water removed.

Similar to drying under conventional conditions, the existence of a dry zone, wet zone and an intermediate zone with accompanying advancing heat pipe has also been shown for drying under high intensity conditions.     

二氧化钛陶瓷的湿敏特性

介绍了用锁相放大器来研究金红石相ＴｉＯ２陶瓷的电导，介电损耗，介电常数的实部和虚部的湿度响应，以及表面处理对该湿度响的影响。提出的“ＴｉＯ２陶瓷－水分子薄膜”模型能很好地解释实验结果。     

An extended Kalman filter for in situ sensing of yttria-stabilized zirconia in chemical vapor deposition

Chemical vapor deposition is widely used in integrated circuit fabrication. With the increasingly stringent requirements for product quality and yield, it is necessary to apply process monitoring, fault detection and eventually closed-loop control to the deposition process. The implementation of these tools requires an in situ sensor that can measure film properties in real time. This paper discusses an extended Kalman filter (EKF) based in situ sensor and its application in chemical vapor deposition of yttria-stabilized zirconia (YSZ) on a silicon substrate. The sensor measures reflectance from the film surface at 950 and 470 nm. The measurements were processed by the EKF to estimate film thickness, growth rate and surface roughness. The challenge with estimation of film microstructure like roughness lies in the process dynamic model for microstructure evolution at small scales, which in general is high-dimensional and nonlinear. In this work a simple but adaptive process dynamic model and a detailed optical sensor model were used to study how a simple process model could aid in estimation. Based on these models the observability of the process was discussed. The estimated film properties were verified with ex situ characterization using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Finally sensitivity and robustness of EKF were discussed, along with our perspectives on future work on in situ sensing for thin film deposition.     

光纤传感及其在管道监测中应用的研究进展

管道安全关系到人类生命和财产安全,及时掌握管道结构健康状态是确保管道安全运行的重要前提。光纤传感技术的不断发展,使其在各个领域得到广泛研究与应用,特别是为管道结构的安全监测提供了技术保障。介绍了分布式光纤传感、光纤光栅传感、阵列复用传感、以及光纤智能传感的基本原理及关键技术,对其性能和特点进行了对比分析。在此基础上,阐述了各种光纤传感技术在管道监测中的具体应用,包括管道结构监测、管道泄漏监测以及管道腐蚀监测。通过对传感技术的不同应用进行比较分析,总结了各传感技术应用的特点和进一步研究发展的方向,指出光纤传感技术在管道监测方面具有的巨大优势和广泛的应用前景。     

Real-time monitoring of peanut drying parameters in semitrailers

Knowledge of peanut drying parameters, such as temperature and relative humidity of the ambient air, temperature and relative humidity of the air being blown into the peanuts, and kernel moisture content, is essential in managing the dryer for optimal drying rate. The optimal drying rate is required to preserve quality and desired flavor. In the current peanut-drying process, such parameters are elusive in real time and are either not measured or only measured periodically by an operator. A peanut-drying monitoring system, controlled by an embedded microcontroller and consisting of relative humidity and temperature sensors and a microwave peanut moisture sensor, was developed to monitor drying parameters in real time. It was deployed during the 2014 peanut harvest season at a peanut buying point in central Georgia, USA. It was placed in 45-ft (13.7-m) drying semitrailers to monitor in-shell kernel moisture content, temperature of the drying peanuts, temperature, and relative humidity of the exhaust air from the peanuts and relative humidity of the air being blown into the peanuts in real time. In-shell kernel moisture content was determined with a standard error of performance of 0.55% moisture content when compared to the reference oven-drying method. Data from drying parameters were time-stamped and stored on a CompactFlash card every 12?s and were used to assess the efficiency of dryer control settings. Ambient air conditions were measured by an on-site weather station. Results of the study support the value of such a monitoring system and show that implementation of the system for dryer control has the potential for saving a buying point, in the current economical context, as much as $22,000 annually in costs of electric energy and propane.     

DRYING BEHAVIOR OF MUSHROOM SLICES

Drying of mushroom slices is an unsteady-state process under the control of diffusion race of water through the mushroom hyphae. Therefore, temperature, thickness of the mushroom slices and the ratio of the air film to mushroom resistance toward the diffusion of water control the drying rate. In this work, the initial thickness of mushroom slices was kept constant at 2 mm and the effects of structural parameters, temperature and humidity were investigated. Through the measurements of weight, center and surface temperatures of the mushrooms, and variation of the surface area, actual drying behavior of mushrooms under different dryer conditions were determined. Color of the dried mushroom slices were used as criteria for the evaluation and determination of the optimum conditions.     

DRYING BEHAVIOR OF MUSHROOM SLICES

Drying of mushroom slices is an unsteady-state process under the control of diffusion race of water through the mushroom hyphae. Therefore, temperature, thickness of the mushroom slices and the ratio of the air film to mushroom resistance toward the diffusion of water control the drying rate. In this work, the initial thickness of mushroom slices was kept constant at 2 mm and the effects of structural parameters, temperature and humidity were investigated. Through the measurements of weight, center and surface temperatures of the mushrooms, and variation of the surface area, actual drying behavior of mushrooms under different dryer conditions were determined. Color of the dried mushroom slices were used as criteria for the evaluation and determination of the optimum conditions.     

DRYING KINETICS AND PARTICLE RESIDENCE TIME IN SPRAY DRYING

A unique experimental equipment for extensive trials on the spray drying kinetics and particles residence time involving “in situ” analysis of the properties of continuous and dispersed phases was designed, built, and tested. Advanced experimental techniques (including laser techniques) to determine current parameters of spray drying process (temperature, humidity, moisture content) and current structure of spray (particle size distribution, particle velocities, etc.) were employed. Full scale spray drying tests of baker's yeast and maltodextrin enabled identification of the effect of process parameters on drying kinetics and spray residence time in the tower. Quantitative relationship describing spray drying kinetics as a function of atomization ratio and drying agent temperature were determined. The experimental results proved that spray residence time was controlled by atomization ratio and airflow rate. Drying kinetics in spray drying process is presented for the first time in the literature.     

DRYING 84

ABSTRACT

A need exists for a simple device to measure the psychrometric properties of high temperature and high humidity air. To meet this need, a small laboratory double-wick psychrometer was developed and tested which showed good results to 175°C dry bulb temperature and 100°C wet bulb temperature. Based on the results of the laboratory unit, a portable prototype psychrometric system was designed and built. The overall design provided quick measurement and indication of wet bulb temperature, dry bulb temperature, humidity, and enthalpy of a high temperature air stream.     

阻隔性薄膜透湿性能的电解法和红外法测试分析

采用电解法和红外法研究了不同温度、湿度下阻隔性塑料薄膜的水蒸气透过率,分析了温度、薄膜类型对透湿性能的影响。结果表明, 12 μm聚对苯二甲酸乙二酯（PET）薄膜的透湿性能最大,其次是25 μm的PET薄膜,25 μm聚偏二氯乙烯(PVDC)薄膜和12 μm PET/铝箔（PET/Al）复合薄膜的水蒸气透过率相近且最小;这4种薄膜的水蒸气透过率均随温度的升高而增大,温度对12 μm PET/Al、25 μm PVDC薄膜的水蒸气透过率影响较小,水蒸气透过率的对数形式与热力学温度的倒数呈线性关系;红外法的测试结果基本都大于电解法,对于25 μm PVDC薄膜和12 μm PET/Al薄膜,2种测试结果的差异较大,而对于12 μm PET薄膜和25 μm PET薄膜,2种测试结果的差异较小。     

SIMULATION OF SPRAY DRYING OF A SOLUTION ATOMIZED IN A PULSATING FLOW

Spray drying of NaCl solution was carried out under an intense oscillating flow field generated by a pulse combustor. A pulse combustion spray drying system was constructed. An optical analyzer was used to measure the particle diameter distribution of droplets atomized by a pulsating flow. The momentum, heat and mass transfer in both gaseous and particulate phases during spray drying inside the drying chamber were simulated using the computational fluid dynamics method. The simulated profiles of flow field, temperature and humidity of the gaseous phase, as well as the particulate phase, in the drying chamber were presented. The simulation showed changes of the flow field and particle trajectories in the drying chamber during one pulsating period. A large-scale vortex was observed in the upper part of the drying chamber because of the unstable state of flow field and particle trajectories. Short drying time and large evaporation rate are characteristics of pulsating spray drying. The influence of gas stream pulsation frequency on the drying process is also analyzed.     

Measurement Techniques to Monitor and Control Fluidization Quality in Fluidized Bed Dryers: A Review

Fluidized bed dryers (FBD) are commonly employed in many industries to dry particulate solids. FBDs provide good solids mixing, high rates of heat and mass transfer, and relative ease of material handling. For efficient operation, it is important to be able to monitor and control the fluidization regime, particle size distribution (PSD), moisture content, and bulk density as well as product chemical properties. This review provides an overview of the trends in the application of different experimental techniques to monitor and control the hydrodynamic conditions of FBDs which influence the particle physiochemical properties. This review covers a wide range of measurement techniques, including infrared moisture sensor (IR), near infrared (NIR) spectroscopy, analysis of pressure fluctuations, optical imaging techniques, acoustic emission (AE), electrical capacitance tomography (ECT), spatial filter velocimetry (SFV), Raman spectroscopy, focused beam reflectance measurement (FBRM), microwave resonance technology (MRT), triboelectric probes, positron emission particle tracking (PEPT), and some novel techniques for monitoring and control of FBDs. The present review summarizes the use of the diverse techniques and outlines their merits and limitations. Prospects for future research in this area are also identified. The measurement techniques can be used for research, development, and operation of fluidized bed equipment used in non-drying applications as well.     

基于分布式布里渊光纤散射传感的海底动力电缆监测技术研究

针对海底动力电缆出现故障而寻找电缆监测的技术与方法,分析渤海湾不稳定海域的海底动力电缆多次出现短路和断路故障的原因与机理,提出基于布里渊散射原理的分布式光纤传感技术监测电缆所受外力变化和监测电缆内部温度变化的方案和方法,进行三相高压电缆截面温度场和电缆外部受力变形的数值模拟分析,通过室内模拟实验和海堤沉降段电缆敷设后的光纤传感监测数据及水准仪观测监测数据对比分析,得出光纤传感器检测数据趋势与水准仪器测量结果吻合。模拟和现场测试结果表明,基于光纤布里渊散射原理的分布式光纤传感技术可有效实现海底动力电缆的温度和变形监测。