Monitoring of Corrosion Under Insulations by Acoustic Emission and Humidity Measurement

We simultaneously monitored humidity and AE from active corrosion under insulation (CUI). For humidity monitoring, we developed an optical fiber sensor based on the moisture dependency of absorption of laser light by connecting coating of polyvinyl alcohol and CoCl₂ coating and pullulan coating in series on the fiber as a cladding layer. The sensor could be used to measure humidity of 65–95% RH at 80°C. The temperature dependence of the sensor was as small as 2.5% RH/10°C. We monitored active CUI by the acoustic emission technique and humidity sensing under wetting and drying cycles. Most AE signals were produced during the drying process in each wetting and drying cycle, and the AE rate increased with the time of wetness (period of humidification).     

Design and Characterisation of a Temperature Compensated Relative Humidity Measurement System with On Line Data Logging Feature

A method of relative humidity (RH) measurement with on line temperature correction and data logging feature is described here. The RH sensor is a thermoset polymer capacitive type with on chip conditioning. Output voltage of RH to voltage converter is digitised using a 12-bit A/D converter and it is interfaced with an 8-bit microcontroller. Temperature correction of RH in real time is done using a temperature to digital converter interfaced with the microcontroller. The corrected data is displayed in a liquid crystal display and transmitted for on line monitoring and logging via RS232C. Calibration of the system is performed using standard saturated binary salt solutions. Accuracy and precision are found out. Hysteresis and ageing effect is discussed. The system performance is also compared with a dry/wet bulb psychrometer at different ambient conditions. The performance of the system in an industrial environment is presented.     

Development of an Online Heat Index Measurement System for Thermal Comfort Determination

This paper presents the development of a reliable heat index (HI) measurement system for evaluating the thermal comfort of a particular building or a particular area. The HI is an index that combines air temperature and relative humidity (RH) to determine the human-perceived equivalent temperature. To measure the air temperature and RH, temperature to digital converter and RH to voltage converter is used. HI is calculated online with the help of embedded firmware of the microcontroller. This calculated value is then transferred to the computer through standard RS 232 serial port. The same sensor node is tested with the RS 485 network standard by changing the transceiver of the node. The system is calibrated using four standard saturated binary salt solutions.     

CFD modelling of moisture evaporation in an industrial dispersed system

A methodology is presented here for the mathematical modelling of moisture evaporation in a dispersed system in an industrial tower. An empirical model using characteristic drying curves was applied to calculate moisture evaporation from a droplet and particle. A simple method was developed to calculate the agglomeration process of the dispersed phase in the drying towers, using transient functions between the initial and final particle size distributions, at the nozzle and in the final product. The developed model and simulation results were validated on the basis of industrial spray tower experiments. High instability of the airflow due to the geometry of the dryer and the construction of the air inlets was observed. The general methodology applied within this CFD model is universal, and can be applied to the scaling-up of installations for dewatering in dispersed systems in order to determine configurations of feeding systems and control the product quality and safety of the process.     

Digital Ventilated Psychrometer

A digital ventilated psychrometer for direct reading of the relative humidity (RH) from the digital indicator by means of two identical type thermistors is described. The method is based on the temperature to linear voltage converter, the calculator of the dry and wet bulb temperature ratio, the converter from the ratio to the voltage proportional to RH, and the analog to digital (A/D) converter. The experimental result by the digital ventilated psychrometer shows that the apparatus makes the direct indication of RH possible. The accuracy of the apparatus is estimated to contain an RH error of less than 2 percent and it is almost the same as that of the Assmann psychrometer. The principal advantage of the apparatus is the direct indication of RH and the capability to use the data directly for the input of the digital data processor.     

蜂窝纸板烘干过程的分析

蜂窝纸板的干燥是蜂窝纸板成型及保证蜂窝纸板质量的重要步骤.在烘干机理分析的基础上,用有限元软件对烘干机模型进行温度场、速度场、压力及热空气流向的分析,得到蜂窝纸干燥过程的     

A solid-state relative humidity measurement system

The implementation of a solid-state capacitive relative humidity (RH) sensing system which employs a polymer as the moisture-sensitive material is discussed. The sensing mechanism is based on the fact that the dielectric permittivity of the insulating polymer, polyimide (PI), is linearly related to the ambient relative humidity. Therefore, the capacitance of a parallel-plate device using PI as the dielectric is a linear function of ambient RH (because PI does not swell during moisture absorption). Standard IC processing techniques are used to fabricate the PI-based integrated sensor capacitor. In order for such as sensor to be useful in the field, a voltage, current, or frequency output is desirable. A discrete capacitance-to-voltage converter circuit using this sensor capacitor has been constructed. The performance of this system is reported     

基于TRNSYS的茯砖茶生产工艺能源系统节能环保特性研究

茯砖茶发酵、干燥过程中,烘房内温湿度稳定性和能源系统低能耗是保证茯砖茶品质与成本的重要因素。本文采用TRNSYS仿真与实验研究相结合的方法,对咸阳某茯砖茶厂实际使用的空气源热泵系统进行建模,通过研究各季节典型代表月烘房温湿度的波动情况,确定该空气源热泵系统在全年的运行状态是否满足工艺要求,在此基础上,对比了该系统在全年可运行季节代表月与该生产厂房早期使用的燃气锅炉系统的能耗仿真结果,对空气源热泵系统的节能与环保特性进行研究。结果表明：由于夏季送风质量流量过大且室外空气含湿量较高,7月烘房温湿度不满足工艺要求。热泵系统在1、4、10月的总标煤消耗量的平均值是锅炉系统的44.42%,平均CO2、SO2、NOx排放量分别为锅炉系统的34.13%、44.1%、40.60%。在茯砖茶发酵、干燥的过程中,相比于燃气锅炉系统,空气源热泵系统具有更好的节能与环保特性。     

热泵干衣机仿真与优化

本文建立了热泵干衣机数学模型,包括稳态的热泵系统模型和动态的衣物干燥过程热质交换模型。利用模型仿真研究了各部件大小的匹配关系对单位能耗除湿量SMER和干燥时间的影响,并对重要的系统参数如循环风量、新风比例和制冷剂充注量进行了优化研究。将模型结果与实验结果进行了对比,干衣时间的误差小于3 min,耗电量的误差为-2.3%。结果表明,循环风量180 m~3/h、新风比例9%~10%时SMER最大;在冷凝温度限值之内,增加充注量有利于SMER的提高。研究结果可供热泵干衣机设计参考。     

CFD simulations of droplet and particle agglomeration in an industrial counter-current spray dryer

In this study, CFD simulations of particle and droplet agglomeration in an industrial counter-current spray dryer are presented. For this purpose, a modified form of the stochastic collision agglomeration model is proposed. This model takes into account droplet–droplet collision as well as wet and dry particle interaction. These events are coupled with heat, mass and momentum transfer. A comprehensive moisture evaporation model based on the concept of characteristic drying curve (CDC) was applied to predict the drying kinetics of the detergent slurry. Due to high instability in air flow inside the drying chamber, simulations were carried out under transient condition. A comparison between time-averaged simulation results and measurements, which were performed on an industrial spray drying installation, shows a good agreement. This finding proves the correctness of the developed agglomeration and drying models. The presented methodology of CFD simulations of agglomeration can be used to design or optimise spray-drying installations and to predict the final particle size distribution of the product.     

Particle velocity profiles and residence time distribution in mixed-flow grain dryers

Non-uniform moisture content distribution of grains at the discharge of Mixed-Flow Grain Dryers is one of the sources of product quality loss during subsequent storage. Unfavorable design of this kind of dryers may cause uneven residence times of single grain portions resulting in non-uniform drying. It is then of paramount importance to understand the physical phenomena that control the flow of grains in a mixed-flow dryer to guarantee their quality and minimize the risk of quality loss and waste of energy, thereby optimizing the process drying condition. With this objective, a two dimensional simulation model for the grain mass flow in a mixed-flow dryer based on Discrete Element Method (DEM) has been developed. The influences of the side walls and air ducts on solids mass flow were studied by evaluating the residence time distribution (RTD), particle velocity profiles and particle trajectories. The simulation results were validated with experiments using a semi-technical dryer test station with transparent Plexiglas front wall. The obtained results revealed the complexity of the drying process, the influences of the wall friction and half air ducts positioned directly on the wall on the bulk particle movement. Grains in mixed-flow dryers have different vertical velocities resulting in different residence times of every single portion of grains. The experimental validation confirms and verifies the DEM calculation ability for predicting particle flow.     

食品红外辅助冷冻干燥技术的研究进展

目的概述红外辅助冷冻干燥技术在食品干燥中的研究进展,旨在为红外辅助冷冻干燥技术的选用以及工业化应用提供借鉴和理论支持。方法通过归纳总结国内外的最新研究进展,对红外辅助冷冻干燥技术的机理、红外辐射器波长和温度、食品干燥过程的预测以及对最终品质的影响等进行论述,并且提出改进措施。结果红外辅助冷冻干燥技术的发展潜力巨大,目前研究还处于初级阶段,其中控制红外辐射器温度、波长,监测干燥过程,以及建立适当的动力学模型是实现工业生产规模化的最新研究方向。结论红外辅助冷冻干燥技术可以有效地降低系统能耗,提高产品质量,具有很大的研究价值,新的研究方向具有很大的发展前景。     

On-line monitoring of vacuum drying of theophylline using NIR spectroscopy: solid-state transitions,water content and semi-empirical modeling

The aim of this work was to monitor in-line and at a real time, the solid-state forms during pharmaceuticals manufacturing. It concerns the dehydration behavior and the solid-state transitions of theophylline in an agitated vacuum contact dryer. First, a near infrared spectroscopy (NIRS) method was performed using a reflectance diffuse probe to measure the in-line and in-situ exact composition of the mixture of different forms of theophylline and water content during drying. A multivariate modeling has been investigated to build a robust model which can predict four components at the same time during drying process. The XRPD analysis was used as a reference method in the process of calibration of NIRS. The indicators of the accuracy in quantitative spectral analysis confirm the robustness of the model and the efficiency of the method of calibration. Second, the kinetics of solid state transformations were investigated. It was shown that the dehydration advanced first by the formation of the metastable anhydrate and after a lag time of the stable one. Once the stable form appeared, formation of the metastable form came to an end. The temperature was found out to be the main factor controlling the overall process rate but also the final contents of the stable and metastable anhydrates for the considered dryer and operating conditions range. Finally, a semi-empirical drying model was proposed and significant quantitative differences were found, particularly at the product temperature which was probably caused by the excessive simplicity of the model.     

CO_2热泵干燥机的性能分析

介绍了干燥机的发展,分析了CO2的特性以及CO2热泵干燥机的原理,给出了干燥机评价指标,并以一台CO2热泵干燥机与传统电干燥机进行了比较分析,得出了热泵干燥机与传统电干燥机相比具有入口空气温度低、单位除水量大、节能潜力大以及干燥时间短等优势。最后提出了干燥机性能优化措施。     

新型热泵干燥系统的金丝皇菊干燥实验

目的 为研究热泵在中药材干燥中的性能,并针对批式干燥器干燥不均匀的问题,设计开发一套能够均匀干燥物料的热泵干燥系统.方法 以金丝皇菊为干燥材料,对热泵干燥设备进行实验研究,并对系统的送风温湿度均匀性、系统能效和物料品质进行分析.结果 该系统干燥过程的温湿度、物料含水率的均匀性和温度控制精度都很高,主机室的温度、湿度稳定,且显著高于外界环境,这不仅避免了热泵系统受外界环境因素的影响,且提供了稳定的运行环境.热泵干燥机组的能效约为5.88,系统能效约为1.32,除湿能耗约为0.66 kg/(kW·h).干燥后的金丝皇菊花瓣未出现明显的色差、卷曲和破损现象,干花的完整度高.结论 新型热泵干燥系统能够满足金丝皇菊的工艺要求,最终得到的金丝皇菊的干燥品质较高.该研究为热泵技术在中药材干燥领域的应用提供实际案例和技术参考.     

Studies on the effects of physical properties of feed samples on the performance of fluidized bed dryer

The physical properties of grains are analysed at different levels of moisture contents using a fluidized bed dryer. The performance of fluidized bed dryer measured in terms of its efficiency is determined by using different grains as feed samples in the present work. The effects of various system parameters on the moisture content of the samples in turn on the dryer performance are studied. Again, effects of moisture content on different properties of sample, namely, grain volume, surface area, sphericity, bulk density, true density and porosity are studied. These properties of feed sample which determine the flow characteristics of the sample in a fluidized bed dryer are found to affect the dryer efficiency, in turn, the drying quality. An attempt is made to correlate the performance of the dryer against these physical properties of the materials. Thus, the efficiencies of the dryer calculated through the developed correlation and as per the literature are compared with each other. The comparison results show good agreement, thereby implying that the proposed correlation can be used for estimating the dryer performance over a wide range of parameters. With this study, the dryer can be designed properly in a cost-efficient manner.     

基于RBF神经网络的诺西肽发酵过程菌体质量浓度软测量

针对诺西肽发酵过程中菌体质量浓度的估计问题,提出了一种基于RBF神经网络的软测量建模方法.在诺西肽发酵过程非结构模型的基础上,根据隐函数存在定理确定出辅助变量,从而使其选择有严格的理论依据;根据每批样本数据对被预测对象的预估能力,自适应地为各个批次的训练样本分配权值,并进而实施加权RBF神经网络建模.实际应用表明,所提出的软测量建模方法是有效的.     

Real-time process control of powder bed fusion by monitoring dynamic temperature field

This study aims to optimize the uniformity of the temperature field during sintering to improve part performance. A temperature-field monitoring system is established based on an infrared thermal imager and the temperature field data obtained during the sintering of a part can be measured in real time. The relationship among the sintering temperature field, sintering process parameters, and part performance is established experimentally. Subsequently, a temperature field monitoring and analysis system is constructed, and various sintering temperaturefield control strategies are established for various part sizes. Finally, a dynamic control strategy for controlling the temperature field during sintering is proposed, experimentally validated, and fully integrated into a developed powder bed fusion (PBF) equipment. For eight-shaped standard parts, the range of sintering temperature field is optimized from 44.1 C to 19.7 C, whereas the tensile strength of the parts increased by 15.4%. For large-size H parts, localized over burning is eliminated and the final quality of the part is optimized. This strategy is critical for the optimization of the PBF process for large-sized parts, in particular in the large-sized die manufacturing industry, which offers promise in the optimization of part performance.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00317-y     

Electronic Nose for Black Tea Classification and Correlation of Measurements With “Tea Taster” Marks

Tea is an extensively consumed beverage worldwide with an expanding market. The major quality attributes of tea are flavor, aroma, color, and strength. Out of these, flavor and aroma are the most important attributes. Human experts called ldquotea tastersrdquo conventionally evaluate tea quality, and they usually assign scores to samples of tea that are under evaluation on a scale of 1 to 10, depending on the flavor, the aroma, and the taste of the sample. This paper presents a study where, first, the selection of appropriate sensors was carried out based on sensitivity with the major aroma-producing chemicals of black tea. Then, this sensor array was exposed to black tea samples that were collected from the tea gardens in India, and the computational model has been developed based on artificial neural network methods to correlate the measurements with the tea taster's scores. With unknown tea samples, encouraging results have been obtained with a more than 90% classification rate.     

Monitoring of the temperature modes of operation of autonomous objects

The problems of constructing a measuring converter for a system for monitoring the temperature based on a thermoresistor sensor using programmable logic circuits are considered.