AN ANALYSIS OF HEAT AND MASS TRANSFERPHENOMENON IN WOOD DURING DRYING

According to modeling simulation and experiments study, the heat and mass transtfer phenomenon.in wood during dring processes was analyzed. The results indicate: at initial stage of drying, moisture movement in wood is due to capillary force, heat transfer is major effect, at end stage, moisture movement in wood is due to diffusive transport, heat transfer is less

Research on vacuum drying process and internal heat conduction of Li-ion battery core

In this research, an innovative cylindrical automatic battery core oven was designed to avoid the structural deformation that frequently occurs in traditional ovens. The oven could be automatically connected with the electrolyte injection process after baking, achieving improvement in a battery's baking consistency. This contributed to the feasibility of studying the internal heat conduction process of batch battery cores during actual baking processes. A mathematical model of a certain plate battery cell during the baking process was established. The simulation results of the temperature change inside the battery core during the baking process were consistent with the calculation results of the mathematical model. The temperature distribution at each point inside the battery core could be fitted through the thermal conductivity at different temperatures and the temperature distribution between the layers of the battery core.Finally, based on the thermodynamic balance energy conservation method, the relationship between the temperature change inside the battery core and the entire baking process was established. A feasible algorithm for studying the thermal conduction of complex material and internal structure objects in the baking process was obtained.

Theoretical Modeling and Experimental Analysis of Drying Process in Electromagnetic Field

The effects of electromagnetic waves in drying processes of solid materials are investigated theoretically and experimentally. Modified model of mass transfer being constituted by the effect of electromagnetic waves which have different frequency has been obtained. Modeling of the drying process with a two-port electric circuit for the determination of diffusion coefficients is designed. The frequency limits of electromagnetic wave which will be able to hasten the drying process are determined. The effects of the electromagnetic wave in the potato slice drying process by the influence of different frequencies and temperatures are experimentally examined. The results obtained are compared with theoretical calculations. Moisture concentration curves in drying process have been commented by drawing. Theoretical and experimental results which have been obtained are identified as a well adaptation.

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.

An empiric equation for the latent heat of vaporization of moisture in bananas during its isothermal drying

In order to determine the energy needed to artificially dry a product, the latent heat of vaporization of moisture in the product, hfg, must be known. Generally, the expressions for hfg reported in the literature are of the form hfg = h(T)f(M), where h(T) is the latent heat of vaporization of free water, and f(M) is a function of the equilibrium moisture content, M. But expressions of this type contain a simplification because, in this case, the ratio hfg/h would only depend to the moisture content. In this article a more general expression for the latent heat of vaporization, namely hfg = g(M,T), is used to determine hfg for banana. To this end, a computer program was developed which fits automatically about 500 functions, with one or two independent variables, imbedded in its library to experimental data. The program uses nonlinear regression, and classifies the best functions according to the least reduced chi-square. A set of executed statistical tests shows that the generalized expression used in this work given by hfg = g(M,T) produces better results of hfg for bananas than other equations found in the literature.

Intensification of the Banana Drying Processes by Using EFL Electromagnetic Waves

Drying of the banana in the hot water has a negative impact on the quality of the product and drying effect. The purposes of this study are increasing the drying rate, using the relatively low temperature to improve the quality (40℃, 50℃ and 60℃) and investigate the use of electromagnetic waves to increase the drying speed. Therefore, experiments are performed using 5 kHz,10 kHz and 15 kHz low frequency electromagnetic waves in the air velocity values of 0.5 m/s, 1 m/s, 1.5 m/s and 2 m/s and 40℃, 50℃, 60℃ centigrade degrees of air blast in a special compartment. Mathematical model of the drying process has been created as using the electrical circuits methods and experimental results. As a result, a simple equation describing the drying process has been obtained. Nonlinear expression of the diffusion coefficient for a different situation in this equation has been identified for the first time. The obtained theoretical results and experimental results have been provided a good agreement. This study is considered to be useful for all studies in the drying area.

Research on Constant-Speed Rapeseed Drying Mechanism

This paper presents research on constantspeed rapeseed drying mechanism and the mathematical model established for constant speed drying period.

Non-equilibrium thermodynamic analysis of coupled heat and moisture transfer across a membrane

Non-equilibrium thermodynamics theory is used to analyze the transmembrane heat and moisture transfer process,which can be observed in a membrane-type total heat exchanger(THX).A theoretical model is developed to simulate the coupled heat and mass transfer across a membrane,total coupling equations and the expressions for the four characteristic parameters including the heat transfer coefficient,molardriven heat transfer coefficient,thermal-driven mass transfer coefficient,and mass transfer coefficient are derived and provided,with the Onsager’s reciprocal relation being confirmed to verify the rationality of the model.Calculations are conducted to investigate the effects of the membrane property and air state on the coupling transport process.The results show that the four characteristic parameters directly affect the transmembrane heat and mass fluxes:the heat and mass transfer coefficients are both positive,meaning that the temperature difference has a positive contribution to the heat transfer and the humidity ratio difference has a positive contribution to the mass transfer.The molar-driven heat transfer and thermal-driven mass transfer coefficients are both negative,implying that the humidity ratio difference acts to reduce the heat transfer and the temperature difference works to diminish the mass transfer.The mass transfer affects the heat transfer by 1%–2%while the heat transfer influences the mass transfer by7%–14%.The entropy generation caused by the temperature difference-induced heat transfer is much larger than that by the humidity difference-induced mass transfer.

Experimental and numerical study on the shrinkage-deformation of carrot slices during hot air drying

In order to further understand the mechanism of material volume change in the drying process,numerical simulations(considering or neglecting shrinkage)of heat and mass transfer during convective drying of carrot slices under constant and controlled temperature and relative humidity were carried out.Simulated results were validated with experimental data.The results of the simulation show that the Quadratic model fitted well to the moisture ratio and the material temperature data trend with average relative errors of 5.9%and 8.1%,respectively.Additionally,the results of the simulation considering shrinkage show that the moisture and temperature distributions during drying are closer to the experimental data than the results of the simulation disregarding shrinkage.The material moisture content was significantly related to the shrinkage of dried tissue.Temperature and relative humidity significantly affected the volume shrinkage of carrot slices.The volume shrinkage increased with the rising of the constant temperature and the decline of relative humidity.This model can be used to provide more information on the dynamics of heat and mass transfer during drying and can also be adapted to other products and dryers devices.

Analysis of Entropy Generation of Combined Heat and Mass Transfer in Internal and External Flows with the Assumption of Local Thermodynamic Equilibrium

In this paper, the control volume method is used to establish the general expression of entropy generation due to combined convective heat and mass transfer in internal and external fluid streams. Theexpression accounts for irreversibilities due to the presence of heat transfer across a finite temperaturedifference, mass transfer across a finite difference in the chemical potential of a species, and due toflow friction. Based on the assumption of local thermodynamic equilibrium, the generalized form ofthe Gibbs equation is used in this analysis. The results are applied to two fundamental problems offorced convection heat and mass transfer in internal and external flows. After minimizing the entropygeneration, useful conclusions are derived that are typical of the second law viewpoint for the definitionof the optimum operation conditions for the specified applications, which is a' valuable criterion foroptimum design of heat and fluid flow devices.

Sublimation-condensation phenomenon in microwave freeze-drying

A sublimation condensation model is developed for microwave freeze drying of unsaturated porous media. The transport properties in the model are analyzed and the model is calculated numerically for the microwave freeze drying of unsaturated porous media. The results show that the effects of sublimation condensation region on drying processes are significant as compared with the traditional sublimation interface model.

Study on the Irreversible Thermodynamics of a Marine Engine Exhaust-powered Adsorption Refrigerating System

This study investigates the heat and mass transfer mechanism of a marine engifie exhaust-powered adsorption refrigerating system by using irreversible thermodynamics. The equations of entropy-production rate and the linear phenomenological equations of thermodynamic flux and force are established. The conventional experimental facilities of unit tube are developed and the phenomenological coefficients are obtained by fitting the experimental data. It is concluded that the thermodynamic process in the adsorbent bed is determined by the coupling effect of the heat and mass transfer; furthermore, the mass transfer is determined by the heat transfer. Taking some measures to increase heat transfer can improve the performance of the adsorption refrigerating system. The conclusions presented in this paper may be of value to the engineering applications of the system.

轴向柱塞泵热特性及热力学建模实验研究

针对轴向柱塞泵在高压和高速工况下发热过快的问题,对柱塞泵热特性和热力学建模进行了仿真分析与实验研究。首先,在摩擦副发热理论基础上,考虑了泵内油液搅动摩擦与轴承摩擦发热源,研究了柱塞泵内发热机理和传热分析的热特性理论;然后,根据柱塞泵部件复杂和固流态域区分度高的特点,阐述了所采用的控制体积法原理,将泵划分为5个控制体积后,建立了以各个控制体温度变化为导向的热力学模型;最后,采用光纤光栅温度传感器和蓝牙无线温度传感器,针对不同的控制体节点设计了传感器封装结构和布置方法,共同组成了轴向柱塞泵在线热监测系统,并进行了在不同压力条件下的对照实验,对理论模型进行了有效性验证与分析。研究结果表明:对比实验和仿真结果,模型温度变化与实际误差值在5%左右,验证了该模型能准确地反映和预测泵热力学变化过程。该结果为柱塞泵热力学状态监测提供了故障诊断基础,并为液压系统热管理系统设计提供了理论基础和设计依据。

木材干燥过程的热质迁移及其耦合关系

应用不可逆过程热力学研究木材干燥过程热质迁移及其耦合效应。根据不可逆过程的熵的产生率推导出含有耦合效应的传热传质关系式 ,提出湿度梯度不仅引起水分物质流 ,也引起热流 ,以及驱动水分物质流的力应是扩散势梯度。

多孔介质对流干燥外部传热传质的非平衡热力学理论

从非平衡热力学理论出发，以广义热力学力作为传质过程驱动势，建立了描述多孔介质恒速干燥阶段外部对流传热传质过程的热力学理论模型，并进行了数值计算，计算值与已有的实验数据吻合较好；同时，还将计算结果与传统的理论进行了比较，结果表明，非平衡热力学理论更能反映过程的物理本质。

含湿多孔生物材料干燥过程的传热传质分析

建立了用以描述含湿多孔生物材料干燥过程传热传质特性的数学模型 ,并以马铃薯片为实验材料 ,采用有限差分法进行了干燥工况下的温度和湿度分布数值模拟计算。模拟值与实验值吻合较好 ,表明该模型具有较好的精确性。

H形对流传热脉管的熵产率最小构形优化

针对H形对流传热脉管,以脉管区域面积和通道总表面积为约束,在线热流密度恒定时,基于熵产生最小化进行了构形优化,给出了无量纲总熵产量和无量纲单位传热负荷的总熵产率与脉管组合级数、无量纲质量流量和无量纲泵功率的完整解析关系式及优化算例。结果表明:给定通道总表面积与文献中给定通道总体积约束的优化结果是不同的;无量纲单位传热负荷的总熵产率随组合级数增大而减小,脉管综合性能得到改善,且增加脉管组合级数以改善脉管性能存在阈值;流阻最小化的优化结果为结果特例。

空间飞行器内结露的理论分析及模拟实验

目的探讨防止载人空间飞行器舱内结露的方法。方法从热力学和传热学的角度分析和研究了空间飞行器舱内壁面的结露条件及过程 ,对影响舱内结露的几个因素进行了探讨。结果壁面隔热有利于防止结露 ,局部通风有可能抑制结露。但单独采用隔热或通风的方法均存在一定的局限性。降低外壁黑度有利于防止舱内结露。结论采用壁面隔热和局部通风相结合的方法 ,可以有效地达到防止结露的目的。

多孔介质干燥的非平衡热力学模型

从非平衡态热动力学和相平衡的角度,建立了多孔介质干燥的非线性数学模型.该模型充分考虑了多孔介质内部传热传质之间的相互耦合现象,从化学势的定义出发,进一步从理论上分析了温度、含湿量对各唯象系数的影响,并通过与实验数据的对比分析,验证了模型的正确性,为干燥过程的实施提供了理论依据.

空气温度和湿度对稻谷增湿效果的影响

利用多分子层吸附理论、多孔介质传热传质理论及应力学说并结合相关实验分析温度和湿度对稻谷增湿过程和稻谷吸湿裂纹产生的影响。结果表明:空气相对湿度变化对稻谷整个增湿过程均有影响,而空气温度变化只对稻谷的表层增湿影响显著;当固定空气温度、提高空气相对湿度时,稻谷籽粒的增湿进程加快;当固定空气相对湿度、提高空气温度时,稻谷籽粒的增湿进程减缓;在固定空气温度、提高空气相对湿度的情况下,或固定空气相对湿度、提高空气温度的情况下,吸湿裂纹形成的进程加快。