Optimization of Dividing Wall Column with Heat Transfer Process Across the Wall for Feed Properties Variation

This paper investigates the thermal-coupled effect across the wall and the optimal heat transfer region of the wall for enhancing the energy saving effect of dividing wall column (DWC), and also studies the effects of feed thermal condition (q) and middle component composition of feed (cB) on the heat transfer process, the optimal heat transfer region, and the maximum heat transfer quantity across the wall. The simulation results show that the maximum heat transfer quantity across the wall and the potential for energy saving increase with the increase of q, while with the limitation of temperature difference across the wall, the beneficial heat transfer effect between certain range of stages, which are involved in the optimal heat transfer region, cannot be realized completely for a specific value of q. Besides, compared with q, a changing cB does not change the degree of realizing the beneficial heat transfer effect, but can bring about the variation of liquid split ratio (RL) and vapor split ratio (Rv). Thus, for achieving a maximum energy-saving effect of DWC, different q and cB need to find its own corresponding suitable heat transfer process across the wall.

Analysis Process of Finite Element Method in Heat Transfer through Fabrics

According to heat transfer principle and the process of solving engineering problems by finite element method, examples were given to demonstrate how finite element analysis can be used to describe transient heat transfer through fabrics. Details were given to describe how conduction and convection affect temperature distribution and heat loss during heat transfer processes by taking advantage of the quick calculation of FEA software MSC.Marc. Experimental results show good agreement with the theoretical results.

Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

Analysis of prompt supercritical process with heat transfer and temperature feedback

The prompt supercritical process of a nuclear reactor with temperature feedback and initial power as well as heat transfer with a big step reactivity (ρ0>β) is analyzed in this paper. Considering the effect of heat transfer on temperature of the reactor, a new model is set up. For any initial power, the variations of output power and reactivity with time are obtained by numerical method. The effects of the big inserted step reactivity and initial power on the prompt supercritical process are analyzed and discussed. It was found that the effect of heat transfer on the output power and reactivity can be neglected under any initial power, and the output power obtained by the adiabatic model is basically in accordance with that by the model of this paper, and the analytical solution can be adopted. The results provide a theoretical base for safety analysis and operation management of a power reactor.

Numerical analysis on solidification process and heat transfer of FGH95 superalloy droplets during PREP

In order to understand the relation between microstructure of superalloypowders and its solidification progress, the processing parameters are optimized during plasmarotating electrode processing (PREP). It was predicted from the results that the droplet velocities,droplet temperature, and fractional solidification with flight time about FGH95 superalloy droplethave been carried out based on Newtonian heat transfer formulation coupled with the classicalheterogeneous nucleation and the specific solidification process. It has been found that the dropletdynamic and thermal behavior is strongly affected by the distribution of droplet diameters, theproportion of cooling atmosphere, but is relatively unaffected by the droplet superheat.

Heat Transfer between Casting and Die during High Pressure Die Casting Process of AM50 Alloy-Modeling and Experimental Results

A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density （HFD） and interfacial heat transfer coefficient （IHTC） during the high pressure die casting （HPDC） process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.

ANALYSIS OF THE THERMOPHYSICAL PARAMETERS OF MOIST WOOD PARTICLE MATERIAL IN A COUPLED HEAT AND MASS TRANSFER PROCESS OF FREEZING BY USING FINITE ELEMENT METHOD

The coupled heat and moisture transfer in a freezing process of wood particle material was mathematically modeled in the paper. The models were interactively solved by using the numerical method(the finite element method and the finite difference method). By matching the theoretical calculation to an experiment, the nonlinear problem was analyzed and the variable thermophysical parameters concerned was evaluated. The analysis procedure and the evaluation of the parameters were presented in detail. The result of the study showed that by using the method as described in the paper, it was possible to determine the variable (with respect to temperature, moisture content and freezing state) thermophysical parameters which were unknown or difficult to measure as long as the governing equations for a considered process were available. The method can significantly reduces the experiment efforts for determining thermophysical parameters which arc very complicated to measure. The determined variable of the effective heat conductivity of wood particle material was given in the paper. The error of the numerical calculation was also estimated by the comparison with a matched experiment.

STUDY OF THE HEAT AND HUMIDITY TRANSFER PROCESSES BETWEEN AIR AND WATER IN THE AIR WASHER

The processes of heat and humidity transfer between air and water are what to be studied mainly in the paper, we put forward some main factors which influence the processes of heat and humidity transfer in the air washer. We come to the conclusion that we can change these main factors to achieve different heat and humidity transfer processes and decide processes of heat and humidity transfer of air and water with the initial temperature of spraying water in the air washer. All these results can make things convenient for the air conditioning management.

HEAT TRANSFER ANALYSIS DURING ROLLING OF THIN SLAB IN CSP

A mathematical model has been built to numerically predict the thermal history of thin slab during CSP （compact strip process） rolling. To estimate the temperature distribution in the slab mare accurately, the mathematical model combines heat transfer in the slab, in the roll, and at the roll-slab interface during bite. The numerical results agree with on-site running data, which proves the reliabili~, of the mathematical model. The results show that roll chilling has a significant effect on the temperature distribution in the slab.

An Efficient Acceleration of Solving Heat and Mass Transfer Equations with the First Kind Boundary Conditions in Capillary Porous Radially Composite Cylinder Using Programmable Graphics Hardware

With the latest advances in computing technology, a huge amount of efforts have gone into simulation of a range of scientific phenomena in engineering fields. One such case is the simulation of heat and mass transfer in capillary porous media, which is becoming more and more necessary in analyzing a number of eventualities in science and engineering applications. However, this procedure of numerical solution of heat and mass transfer equations for capillary porous media is very time consuming. Therefore, this paper pursuit is at making use of one of the acceleration methods developed in the graphics community that exploits a graphical processing unit (GPU), which is applied to the numerical solutions of such heat and mass transfer equations. The nVidia Compute Unified Device Architecture (CUDA) programming model offers a correct approach of applying parallel computing to applications with graphical processing unit. This paper suggests a true improvement in the performance while solving the heat and mass transfer equations for capillary porous radially composite cylinder with the first type of boundary conditions. This heat and mass transfer simulation is carried out through the usage of CUDA platform on nVidia Quadro FX 4800 graphics card. Our experimental outcomes exhibit the drastic overall performance enhancement when GPU is used to illustrate heat and mass transfer simulation. GPU can considerably accelerate the performance with a maximum found speedup of more than 5-fold times. Therefore, the GPU is a good strategy to accelerate the heat and mass transfer simulation in porous media.

An Efficient Acceleration of Solving Heat and Mass Transfer Equations with the Second Kind Boundary Conditions in Capillary Porous Composite Cylinder Using Programmable Graphics Hardware

With the recent developments in computing technology, increased efforts have gone into simulation of various scientific methods and phenomenon in engineering fields. One such case is the simulation of heat and mass transfer in capillary porous media, which is becoming more and more important in analysing various scenarios in engineering applications. Analysing such heat and mass transfer phenomenon in a given environment requires us to simulate it. This entails simulation of coupled heat mass transfer equations. However, this process of numerical solution of heat and mass transfer equations is very much time consuming. Therefore, this paper aims at utilizing one of the acceleration techniques developed in the graphics community that exploits a graphics processing unit (GPU) which is applied to the numerical solutions of heat and mass transfer equations. The nVidia Compute Unified Device Architecture (CUDA) programming model caters a good method of applying parallel computing to program the graphical processing unit. This paper shows a good improvement in the performance while solving the heat and mass transfer equations for capillary porous composite cylinder with the second kind of boundary conditions numerically running on GPU. This heat and mass transfer simulation is implemented using CUDA platform on nVidia Quadro FX 4800 graphics card. Our experimental results depict the drastic performance improvement when GPU is used to perform heat and mass transfer simulation. GPU can significantly accelerate the performance with a maximum observed speedup of more than 7-fold times. Therefore, the GPU is a good approach to accelerate the heat and mass transfer simulation.

寒区相变蓄热墙体多因素热特性研究

在墙体中应用相变材料可以显著改善墙体的保温蓄热能力,但相变材料厚度和墙体构造的选择尚需科学论证。基于寒区气象特点,选择适用于寒区建筑外墙的相变储能材料,从墙体的传热特性角度出发,通过建立不同相变材料层厚度和多种构造的相变墙体模型,研究多种情况相变墙体的热特性。结果表明,相变墙体在冬季的保温蓄热能力受相变材料层位置和厚度影响,夏季效果主要受相变材料厚度影响;相变材料厚度为40 mm的中间型相变墙体和相变材料厚度为60 mm的内侧型相变墙体比较适合寒区建筑应用。研究所得结论可为寒区相变墙体的结构设计优化提供参考。

影响工业还原罐内铝热法炼镁过程还原效率的因素

在工业还原罐内进行铝热还原炼镁试验,分析影响还原效率的因素。结果表明:结晶镁的氧化和燃烧以及原料混合不均匀是导致还原效率降低的主要原因;原料混合不均匀导致贫铝区和MgO剩余,促进生成12CaO·7Al_(2)O_(3)和CaO·Al_(2)O_(3);对于富铝区域,MgO和CaO同时被还原,生成Mg_(2)Ca相。辐射传热和化学反应吸热是影响还原速率的关键因素;提高加热温度能够迅速提高球团层的温度,进而使球团获得足够的反应速度;此外,球团中含镁量越高,需要的反应时间越长。

微尺度下润湿性表面对双气泡传热特性的影响

为探究混合润湿表面双气泡生长过程的特点和传热特性,利用格子Boltzmann方法研究混合润湿性表面不同因素对生长和传热过程的影响规律。结果表明:对于纯润湿性表面,随着润湿性的降低,气泡成核时间减少,气泡脱离表面时间呈增加趋势,双气泡生长过程的平均热流密度呈减少趋势。混合表面可以实现相比纯润湿性表面更高的脱离频率和更好的换热效果,混合润湿表面整体脱离频率在(L_(q)/△x)>0.37(△x<30)时呈增加趋势,在(L_(q)/△x)≤0.37(△x≥30)时呈降低趋势;同一距离L_(q)/△x不同疏水尺寸的脱离频率在(L_(q)/△x)>0.37(△x<30)时呈先降低后增加趋势,在(L_(q)/△x)≤0.37(△x≥30)时呈增加趋势;同一距离L_(q)/△x不同疏水尺寸的平均热流密度在(L_(q)/△x)>0.37(△x<30)时呈降低趋势,L_(s)=3(L_(s)/L_(q)=0.27)是最佳换热尺寸,在(L_(q)/△x)≤0.37(△x≥30)时呈先增加后降低趋势,L_(s)=5(L_(s)/L_(q)=0.45)为最佳换热尺寸。

制造氢气瓶内胆的电加热滚塑工艺参数的优化研究

在static bed模型的基础上为在PID控制模式下制造氢气瓶内胆的电加热滚塑工艺建立了一个传热模型,并通过FLUENT软件来仿真计算模具表面温度和模内温度以及加热时间和加热电能。这些仿真值与实测值都吻合得较好,从而验证了本文传热模型的准确性。然后应用该传热模型计算了在16种情形下停止加热时的模内温度以及加热时间和加热电能,并通过灰色关联度方法分析了PID模式的触发温度和初始加热功率的百分比对加热时间和加热电能的影响程度。结果表明,停止加热时的模内温度随初始加热功率的百分比变化较小,但随PID模式触发温度的升高而降低。加热时间和加热电能都是随着PID模式的触发温度的升高而减少。最优化的工艺参数是PID模式的触发温度取250℃且初始加热功率的百分比取90%。另外,PID模式的触发温度对加热时间和加热电能的影响程度都要大于初始加热功率的百分比对它们的影响程度。

恒温下相对湿度对果蔬热风干燥特性和品质的影响及调控

相对湿度作为干燥介质的重要参数,对干燥热质传质过程和干燥品质具有显著影响。但由于相对湿度对干燥过程的影响机理及优化调控机制尚不明确,导致相对湿度的调控方式多依靠经验,造成干燥效率低、品质差、能耗高等问题。对于传质过程,降低相对湿度能够增大对流传质系数,加快物料表面水分蒸发;而对于传热过程,升高相对湿度能够增大对流传热系数,加快物料升温速率。相对湿度较高时,物料升温速率快,内部水分迁移量增大,但表面水分蒸发量较小;而当相对湿度较低时,物料升温速率较慢,内部水分迁移量较小,但表面水分蒸发量较大。相对传热和传质过程的影响此消彼长,互相耦合。高相对湿度主要体现为对传热过程的影响,低相对湿度主要体现为对传质过程的影响。高相对湿度能够抑制物料表面的结壳,并能够提高复水性,降低收缩率。阶段降湿及多阶段降湿干燥方式下物料表面形成和保持了蜂窝状多孔结构,能够提高干燥效率和品质。基于监测物料温度的相对湿度调控方式被验证为较优的相对湿度控制方式。阶段降湿干燥方式适用性的实质为:干燥过程中所体现出的对流传热热阻和内部导热热阻的相对大小,及对流传质阻力和内部传质阻力的相对大小,不同干燥条件和物料种类、厚度会影响以上传热传质阻力的大小,从而呈现出不同适应性的结果。当阶段降湿干燥过程中传热毕渥数>1且传质毕渥数>0.1时,说明阶段降湿干燥过程适用于此物料的干燥。该文综合论述了相对湿度对果蔬热风干燥过程中热质传递及干燥品质的影响,优化调控策略及适用性范围4个方面内容,明确了果蔬热风干燥过程中相对湿度的影响机理,为相对湿度的优化调控提供理论依据和技术支持。

基于床层传热的皮江法炼镁过程优化

球团在还原罐内传热导致的温度梯度是限制皮江法还原反应的关键因素.本文采用数值方法研究了球团尺寸、装料方式、还原罐外壁温度等因素对床层温度分布、还原率分布的影响.结果表明:在球团直径为22.3 mm、还原时间相同时能够获得最大的还原率;生产过程中应尽量提高还原罐外壁温度;床层中心区域温度低,还原反应速率慢,反应滞后;通过中心留空的方法能够有效缩短还原周期,提高原料利用率;以单位体积、单位时间镁的产量为依据,对于内径为270 mm的还原罐,当中心留空区域的直径小于27 mm时,可获得最大生产效率.

微波加热强化闪蒸工艺的科学基础及发展趋势

利用微波加热具有选择性、快速性、整体性等优点,对基于能量源补充热量实现蒸发浓缩、分离纯化的料液处理过程而言,利用微波加热实现过程强化具有现实意义。本文综述了液体闪蒸过程的蒸发特性与传热传质特性、微波加热液体蒸发的研究现状,提出了微波加热强化闪蒸工艺,首先指出闪蒸工艺过程中料液面临难以直接加热提供热量而提高蒸发速率的难题,原因是传统热量传递方法无法在真空条件下向闪蒸过程中的料液传递热量。进而分析了微波加热蒸发工艺的研究现状,总结出微波加热蒸发过程中的影响因素,简述了微波加热蒸发工艺的应用。最后,提出可将微波加热与闪蒸工艺相耦合的微波加热强化闪蒸工艺,简述了设备设计、应用开发方面的相关进展。总结了微波加热强化闪蒸面临的相关难题并提出建议,期望对微波加热强化蒸发工艺应用和设备设计的发展提供参考。

EP/IFR环氧膨胀型防火涂层燃烧与传热过程研究

涂覆在钢结构表面的膨胀型防火涂层隔热效果对钢结构建筑免受高温致灾意义重大。通过向环氧树脂(EP)中添加聚磷酸铵(APP)、季戊四醇(PER)、茶皂素(TS)以及氢氧化铝(ATH),制备了EP/IFR环氧膨胀型防火涂层。基于锥形量热仪燃烧实验和热重分析,通过实时测量涂层表面的温度变化,研究了涂层的燃烧与传热过程。结果表明:ATH协效TS能提高涂层的热稳定性;TS添加质量分数1.33%、ATH添加质量分数5.33%时,温升速率最低,阻燃隔热效果最好,峰值热释放速率(pHRR)仅为362.52 kW/m^(2),比纯EP降低了59.32%;热辐射功率对传热过程有显著影响。

A novel method based on entransy theory for setting energy targets of heat exchanger network

A T-Q diagram based on entransy theory is applied to graphically and quantitatively describe the irreversibility of the heat transfer processes.The hot and cold composite curves can be obtained in the T-Q diagram.The entransy recovery and entransy dissipation that are affected by temperature differences can be obtained through the shaded area under the composite curves.The method for setting the energy target of the HENs in T-Q diagram based on entransy theory is proposed.A case study of the diesel oil hydrogenation unit is used to illustrate the application of the method.The results show that three different heat transfer temperature differences is 10 K,15 K and 20 K,and the entransy recovery is 5.498×10~7k W·K,5.377×10~7k W·K,5.257×10~7k W·K,respectively.And the entransy transfer efficiency is 92.29%,91.63%,90.99%.Thus,the energy-saving potential of the HENs is obtained by setting the energy target based on the entransy transfer efficiency.