Mathematical Modeling and Effect of Various Hot-Air Drying on Mushroom(Lentinus edodes)

An experimental study was performed to determine the characteristics and drying process of mushroom （Lentinus edodes） by 6 different hot-air drying methods namely isothermal drying, uniform raise drying, non-uniform raise drying, uniform intermittent drying, non-uniform intermittent drying and combined drying. The chemical composition （dry matter, ash, crude protein, crude fat, total sugars, dietary fiber, and energy）, color parameters （L, a＊, b＊, c＊, and h~） and rehydration capacities were determined. Among all the experiments, non-uniform intermittent drying reached a better comprehensive results due to the higher chemical composition, better color quality associated with high bright （26.381＋5.842）, high color tone （73.670＋2.975）, low chroma （13.349a：3.456） as well as the highest rehydration （453.76% weigh of dried body）. Nine kinds of classical mathematical model were used to obtained moisture data and the Midili-kucuk model can be described by the drying process with the coefficient （R2 ranged from 0.99790 to 0.99967）, chi-square （X2 ranged from 0.00003 to 0.00019） and root mean square error （RMSE ranged from 0.000486 to 0.0012367）.

Spray Evaporation of Different Liquids in a Drying Chamber--Effect on Flow, Heat and Mass Transfer Performances

Almost without exception literature data and modeling effort are understandably devoted to water as the sprayed liquid since it constitutes the most common liquid used in spray drying applications. In selected applications, however, the liquid making up the solution or suspension may not be water. The objective of this work is to examine the differences in flow patterns, thermal behavior and drying rates caused by different liquids having different thermo-physical properties spray into a spray dryer using a computational fluid dynamic model.Numerical experiments were carried out for water (base case), ethyl alcohol and isopropyl alcohol-the latter two as model non-aqueous liquids. The chamber geometry was cylinder type with a co-current axial pressure nozzle and also an axial central exit so that the configuration is two dimensional and axi-symmetric. It is shown that the liquid properties can have major influence on the thermal field, droplet trajectories, residence times and overall evaporation capacity when all parameters of the problem are held fixed. Deviations from the single phase turbulent airflow in the same chamber without spray are different for the three liquids examined.

Simulation of Wetting and Drying Processes in A Depth Integrated Shallow Water Flow Model by Slot Method

A particular porosity method named ＂slot method＂ is implemented in a depth-integrated shallow water flow model （DIVAST） to simulate wetting and drying processes. Discussed is the relationship between the shape factors of the ＂slot＂ and the preset depth used in ＂wetting-drying＂ algorithm. Two typical tests are conducted to examine the performance of the method with the effect of the shape factors of the ＂slot＂ being checked in detail in the first test. Numerical results demonstrate that： 1 ） no additional effort to improve the finite difference scheme is needed to implement ＂slot method＂ in DIVAST, and 2） ＂slot method＂ will simulate wetting and diying processes correctly if the shape factors of the ＂slot＂ being selected properly.

Experimental Investigation on Flow and Drying Characteristics of Impinging Stream Drying

Based on the experimental investigation of one-stage semi-circular impinging stream drying, the experiments with the two-stage semi-circular, as well as the vertical and semi-circular combined impinging stream drying were conducted. The variations of system pressure drop, the mean residence time of particles with the mass flow-rate ratio and air velocity etc, were determined. The influences of inlet air temperature, mass flow-rate ratio, initial moisture content of particles and air velocity etc. on drying characteristics were also studied. The results indicate that the vertical and semi-circular combined impinging stream drying can make full use of the advantages of both the vertical and semi-circular impinging stream drying. Reasonable mass flow-rate ratio, air velocity, and higher inlet air temperature should be used for less energy consumption and cost during drying process.

Unsteady RANS and detached eddy simulation of the multiphase flow in a co-current spray drying

A detached eddy simulation(DES) and a k-ε-based Reynolds-averaged Navier–Stokes(RANS) calculation on the co-current spray drying chamber is presented. The DES used here is based on the Spalart–Allmaras(SA) turbulence model, whereas the standard k-ε(SKE) was considered here for comparison purposes. Predictions of the mean axial velocity, temperature and humidity profile have been evaluated and compared with experimental measurements. The effects of the turbulence model on the predictions of the mean axial velocity, temperature and the humidity profile are most noticeable in the(highly anisotropic) spraying region. The findings suggest that DES provide a more accurate prediction(with error less than 5%) of the flow field in a spray drying chamber compared with RANS-based k-ε models. The DES simulation also confirmed the presence of anisotropic turbulent flow in the spray dryer from the analysis of the velocity component fluctuations and turbulent structure as illustrated by the Q-criterion.

Optimal Design of Drying Process of the Potatoes withMulti-Agent Reinforced Deep Learning

Heat and mass transport through evaporation or drying processes occur in many applications such as food processing,pharmaceutical products,solar-driven vapor generation,textile design,and electronic cigarettes.In this paper,the transport of water from a fresh potato considered as a wet porous media with laminar convective dry air fluid flow governed by Darcy’s law in two-dimensional is highlighted.Governing equations of mass conservation,momentumconservation,multiphase fluid flowin porousmedia,heat transfer,and transport of participating fluids and gases through evaporation from liquid to gaseous phase are solved simultaneously.In this model,the variable is block locations,the object function is changing water saturation inside the porous medium and the constraint is the constant mass of porous material.It shows that there is an optimal configuration for the purpose of water removal from the specimen.The results are compared with experimental and analyticalmethods Benchmark.Then for the purpose of configuration optimization,multi-agent reinforcement learning(MARL)is used while multiple porous blocks are considered as agents that transfer their moisture content with the environment in a real-world scenario.MARL has been tested and validated with previous conventional effective optimization simulations and its superiority proved.Our study examines and proposes an effective method for validating and testing multiagent reinforcement learning models and methods using a multiagent simulation.

Experimental and Theoretical Analysis of the Impinging Stream Drying

The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and the mean residence time of particles, and the influence of various factors on drying characteristics were studied. A mathematical model of granular material drying in a semi-circular impinging stream dryer was proposed, in which the flow characteristics as well as the heat and mass transfer mechanisms were considered. Reasonable numerical methods were used to solve the equations. Under various conditions, the calculated results agree well with the experimental data. The unsteady-state drying dynamic equation, as well as the variations of drying rate and moisture content versus time were obtained. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate semi-circular stage number and curvature radius, flow-rate ratio, air velocity, and higher inlet air temperature should be used for enhancing the drying process.

Impacts of native vegetation on the hydraulic properties of the concentrated flows in bank gullies

To quantify the impacts of native vegetation on the spatial and temporal variations in hydraulic properties of bank gully concentrated flows,a series of in situ flume experiments in the bank gully were performed at the Yuanmou Gully Erosion and Collapse Experimental Station in the dry-hot valley region of the Jinsha River,Southwest China.This experiment involved upstream catchment areas withone-and two-year native grass(Heteropogon contortus)and bare land drained to bare gully headcuts,i.e.,Gullies 1,2 and 3.In Gully 4,Heteropogon contortus and Agave sisalana were planted in the upstream catchment area and gully bed,respectively.Among these experiments,the sediment concentration in runoff in Gully 3 was the highest and that in Gully 2 was the lowest,clearly indicating that the sediment concentration in runoff obviously decreased and the deposition of sediment obviously increased as the vegetation cover increased.The concentrated flows were turbulent in response to the flow discharge.The concentrated flows in the gully zones with native grass and bare land were sub-and supercritical,respectively.The flow rate and shear stress in Gully 3 upstream catchment area were highest among the four upstream catchment areas,while the flow rate and shear stress in the gully bed of Gully 4 were lowest among the four gully beds,indicating that native grass notably decreased the bank gully flow rate and shear stress.The Darcy–Weisbach friction factor(resistance f)and flow energy consumption in the gully bed of Gully 4 were notably higher than those in the other three gully beds,clearly indicating that native grass increased the bank gully surface resistance and flow energy consumption.The Reynolds number(Re),flow rate,shear stress,resistance f,and flow energy consumption in the gully beds and upstream areas increased over time,while the sediment concentration in runoff and Froude number(Fr)decreased.Overall,increasing vegetation cover in upstream catchment areas and downstream gully beds of the bank gully is essential for gully erosion mitigation.

Estimating the maximum impact force of dry granular flow based on pileup characteristics

The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing layer.The influence of the interaction between the flowing layer and dead zone on the impact force is ignored.In this study,we classified two impact models with respect to the pileup characteristics of the dead zone.Then,we employed the discrete element method to investigate the influences of the pileup characteristics on the impact force of dry granular flow on a tilted rigid wall.If the final pileup height is equal to the critical value,the maximum NIRF can be estimated using a hydrostatic model,because the main contribution to the maximum NIRF is the static earth pressure of the dead zone.If the final pileup height is less than the critical value,however,the particles in the dead zone are squeezed along the slope surface by the impact ofthe flowing layer on the dead zone,and because of shear effects,the flowing layer causes an entrainment in the dead zone.This results in a decrease in the volume of the dead zone at the moment of maximum NIRF with increases in the slope angle.As such,the maximum NIRF mainly comprises the instant impact force of the flowing layer,so hydro-dynamic models are effective for estimating the maximum NIRF.Impact models will benefit from further study of the components and distribution of the impact force of dry granular flow.

Simplified Calculation of Flow Resistance of Suspension Bridge Main Cable Dehumidification System

To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models.A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula.Additionally,Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values.Based on the actual measured results for a Yangtze River bridge,this study verifies the semi-empirical formula,and indicates that it can be applied in actual engineering.

Mass and heat transfer mechanism in wood during radio frequency/vacuum drying and numerical analysis

The mass and heat transfer mechanisms during radio frequency/vacuum （RF/V） drying of square-edged timber were analyzed and discussed in detail, and a new one-dimensional mathematical model to describe the transport phenomena of mass and heat during continuous RF/V drying was derived from conservation equations based on the mass and heat transfer theory of porous materials The new model provided a relatively fast and efficient way to simulate vacuum drying behavior assisted by dielectric heating. Its advantages compared with the conventional models include： （1） Each independent vari- able has a separate control equation and is solved inde- pendently by converting the partial differential equation into a difference equation with the finite volume method; （2） The calculated data from different parts of the specimen can be displayed in the evolution curves, and the change law of the,parameters can be better described. After analyzing the calculated results, most of the important phenomena observed during RF/V drying were adequately described by this model.

Evaluation of the Impact Force of Dry Granular Flow onto Rock Shed

In the design of rock sheds for the mitigation of risk due to rapid and long landslides, a crucial role is played by the evaluation of the impact force exerted by the flowing mass on the rock sheds. This paper is focused on the influencing factors of the impact force of dry granular flow onto rock shed and in particular on the evaluation of the maximum impact force. The coupled DEM-FEM model calibrated with small-scale physical experiment is used to simulate the movement of dry granular flow coupled with impact forces on the rock-shed. Based on the numerical results, three key stages were identified of impact process, namely startup streams slippery, impact and pile-up. The maximum impact force increases linearly with bulk density, and the maximum impact force exhibits a power law dependence on the impact height and slop angle respectively. The sensitivities of bulk density, impact height, and slope angle on the maximum impact force are: 1.0, 0.496, and 2.32 respectively in the benchmark model. The parameters with high sensitivity should be given priority in the design of the rock shed. The results obtained from this study are useful for facilitating design of shed against dry granular flow.

The Effects of Climate Change and Sea Level Rise on Dry Season Flows in Tien River and Hau River

Tien river and Hau river are two main branches of Cuu Long River which have hydrology regime directly effected by climate change and sea level rise. The flow of the dry season in the Tien and Hau rivers plays a key role in the socio-economic development of the Mekong Delta, especially in agricultural production. The study aims to provide useful information in socio-economic development planning and water use strategies for managers, planners and policymarkers of the provinces/cities in the Mekong Delta. This paper presents the study results in changing of dry season flows in Tien river and Hau river under the impacts of climate change in order to propose measures for protection, substainable development and water security.

Solid Boundary as Energy Source and Sink in a Dry Granular Dense Flow: A Comparison between Two Turbulent Closure Models

Solid boundary as energy source and sink of the turbulent kinetic energy of the grains, and its influence on the mean and turbulent features of a dry granular dense flow, are investigated by using the proposed zero- and first-order turbulent closure models. The first and second laws of thermodynamics are used to derive the equilibrium closure relations, with the dynamic responses postulated by a quasi-static theory for weak turbulent intensity. Two closure models are applied to analyses of a gravity-driven flow down an inclined moving plane. While the calculated mean porosity and velocity correspond to the experimental outcomes, the influence of the turbulent eddy evolution can be taken into account in the first-order model. Increasing velocity slip on the inclined plane tends to enhance the turbulent dissipation nearby, and the turbulent kinetic energy near the free surface. The turbulent dissipation demonstrates a similarity with that of Newtonian fluids in turbulent boundary layer flows. While two-fold roles of the solid boundary are apparent in the first-order model, its role as an energy sink is more obvious in the zero-order model.

Heat and mass transfer of a circular porous moist object located in a triangular shaped vented cavity

Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method.The porous object is considered to be a moist food sample,located in the middle of the cavity with inlet and outlet ports with different configurations of inlet/outlet ports.Convective drying performance is numerically assessed for different values of Reynolds numbers(between 50 and 250),dry air inlet temperature(between 40 and 80℃)and different locations of the port.It is observed that changing the port locations has significant impacts on the flow recirculaitons inside the triangular chamber while convective drying performance is highly affected.The moisture content reduces with longer time and for higher Reynolds number(Re)values.Case P4 where inlet and outlet ports are in the middle of the walls provides the most effective configuration in terms of convective drying performance while the worst case is seen for P1 case where inlet and outlet are closer to the corners of the chamber.There is a 192% difference between the moisture reduction of these two cases at Re=250,T=80℃ and t=120 min.

海上气田生产污水处理系统运行改造优化

海上D气田投产至今已有20年,随着气田开发进入中后期,气田逐步开展降压生产,部分气井出现出砂、出水情况,气井出砂出水造成外输凝析油含水超标、生产污水排海含油升高、聚结分离器/闭式排放罐液位计频繁卡滞故障的情况。气田人员结合生产实际情况,采取上游海管段塞流排液流量控制、生产污水处理装置改造提升优化的方式,成功解决了生产系统含油乳化物堆积、生产污水处理系统效果差、外输凝析油不合格等问题,恢复了生产污水处理系统处理能力,成功将生产污水处理系统排海含油质量分数降至0.0025%左右。

考虑自然风的气辅式喷雾雾滴飘失特性建模与补偿

气流辅助喷雾在雾滴减飘方面确有效果,然而大田作业时,其减飘效果受到自然风、喷雾流量、风筒出口风速、喷雾角等多种工况的严重影响。该文采用多相流计算流体动力学软件,建立三维流场几何模型,依据不同工况参数对雾滴漂移特性的影响,利用均匀设计安排试验方案,研究雾滴在自然风、辅助气流综合作用下在连续相和雾滴粒子离散相的耦合规律,通过流体动力学仿真完成训练样本采集,采用多元相关向量机回归方法建立不同自然风速下减飘模型,并通过模糊决策支持系统对作物茂密程度和喷嘴与冠层间垂直距离进行控制参数修正。试验结果表明:多元相关向量机回归模型预测飘失率的平均绝对百分比误差为2.56%,自然风扰动中实测和预测飘失率平均误差为8.92%,其飘失规律与所建飘失模型基本吻合。研究结果可为面向雾滴沉积效果的喷雾主动控制系统设计提供参考。

黄土丘陵区枣林土壤水分动态及其对蒸腾的影响

为了探明黄土高原半干旱区山地枣林蒸腾和土壤水分间的关系，对山地枣林的土壤水分和枣树茎液流动态进行了连续 3 年的定位监测，结果表明：土壤水分时空变异性显著，土壤水分垂直方向上随着土层深度的增加，变异系数（Cv）逐渐降低。其自上而下可划分为土壤水分变化层（0-2.6m）、土壤水分干层（2.6-6.0m）和土壤水分恢复层（6.0-10.0m）。枣树液流监测的参数在生育期和休眠期间具有显著性差异，根据这一特征可以对枣树生育期进行较为准确的界定。基于液流参数特征确定的生育期与观察树体萌芽落叶确定的生育期时长基本一致，均约为 160d，但基于液流参数确定的生育期较后者约提前 5d。土壤水分的增加会使枣树液流（瞬时蒸腾）的谷值出现时间提前，峰值出现时间推后，“午休”时间缩短，旺盛蒸腾时间延长，反之亦然。枣树生育前期蒸腾均呈逐日增加趋势，而生育中后期蒸腾和土壤水分呈极显著的正相关关系。

岷江上游水电开发对河道减脱水的影响研究

通过对岷江上游水电站以及受影响河道的实地调查,建立了河道减脱水评价指标,分别对岷江干流、一级支流及二级支流河道的减脱水情况进行了分析。在对减脱水河道分析的基础上,分析了调查断面距电站坝址的距离、电站类型、电站装机容量、电站调节性能与河道减脱水的关系。结果表明:水电开发引起河道减脱水现象已非常严重,各级支流上游都有不同程度的断流现象,以二级支流最为严重;河道减脱水严重程度随距电站坝址的距离增加呈减小的趋势;电站的类型、调节性能与河道减脱水存在明显的相关性,而装机容量对河道减脱水的影响不大。在制定流域水电开发以及河流生态系统恢复规划时,应考虑电站类型、调节性能对河道减脱水的影响。

变制冷剂流量制冷系统运行稳定性试验研究

搭建变制冷剂流量制冷循环实验台,分析试验结果,对比影响定容量压缩机制冷系统稳定运行的因素,确定影响变频系统稳定运行的两个主要因素:(1)蒸发器完全蒸干点在蒸发器出口处随机振荡;(2)蒸发器最小稳定过热度。