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.

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 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.

Heat Transfer of Boiling R134a and R142b on a Twisted Tube with Machine Processed Porous Surface

这个工作的目的是调查起核心作用有机器的一个扭曲的试管上的 R134a 和 R142b 的水池沸腾传热性能和机制处理了多孔的表面(T-MPPS 试管) 象一样决定它的潜在的申请到充满的致冷的蒸发器。在试验性的范围，一个 T-MPPS 试管上的 R134a 的沸腾传热系数是光管上的 R134a 的比那些大的 1.8-2.0 时间。另外，发达试验性的关联证实以试验性的条件在一个 T-MPPS 试管上煮 R134a 和 R142b 的传热系数的预言是更加精确的。

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 simulation of temperature distribution and heat transfer during solidification of titanium alloy ingots in vacuum arc remelting process

In order to get a better understanding of the vacuum consumable arc remelting(VAR) processes and thus to optimize them,a 3D finite element model was developed for the temperature fields and heat transfer of titanium alloy ingots during VAR process.The results show that the temperature fields obtained by the simulation are well validated through the experiment results.The temperature distribution is different during the whole VAR process and the steady-state molten pool forms at 329 s for d100 mm × 180 mm ingots.At the initial stage of remelting,the heat dissipation of crucible bottom plays an important role in the whole heat dissipation system.At the middle of remelting,the crucible wall becomes a major heat dissipation way.The effect of cooling velocity on the solidification structure of ingots was investigated based on the temperature fields and the results can well explain the macrostructure of titanium alloy ingots.

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.

Coupled models of heat transfer and phase transformation for the run-out table in hot rolling

Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occurring on the run-out table(ROT) in a hot strip mill. A variational method is utilized for the discretization of the governing transient con-duction-convection equation,with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling,a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations,thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties,including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.

Heat Transfer Investigation and Modeling of Heat Integrated Distillation Column

The high degree of reversibility of heat integrated distillation column(HIDiC) has been thermodynamically interpreted by the entropy method. In this paper, a heat transfer model and a more universal method were proposed, through which the overall heat transfer coefficient at different height of column under different operating conditions could be obtained before the experiment. Then the separation of a binary ethanol-water system was carried out experimentally as a case study to verify the heat transfer model and the aforementioned calculation method. The close results between the calculation, the simulation, and the experiments suggested that the proposed model and the calculation method in this paper were accurate and applicable. Meanwhile, it was demonstrated that the HIDiC shows obvious effect of reducing entropy increase and improving thermodynamic efficiency as compared to conventional distillation column.

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.

Modeling Hydrothermal Transfer Processes in Permafrost Regions of Qinghai-Tibet Plateau in China

Hydrothermal processes are key components in permafrost dynamics; these processes are integral to global warming. In this study the coupled heat and mass transfer model for(Coup Model) the soil-plant-atmosphere-system is applied in high-altitude permafrost regions and to model hydrothermal transfer processes in freeze-thaw cycles. Measured meteorological forcing and soil and vegetation properties are used in the Coup Model for the period from January 1, 2009 to December 31, 2012 at the Tanggula observation site in the Qinghai-Tibet Plateau. A 24-h time step is used in the model simulation. The results show that the simulated soil temperature and water content, as well as the frozen depth compare well with the measured data. The coefficient of determination(R2) is 0.97 for the mean soil temperature and 0.73 for the mean soil water content, respectively. The simulated soil heat flux at a depth of 0–20 cm is also consistent with the monitored data. An analysis is performed on the simulated hydrothermal transfer processes from the deep soil layer to the upper one during the freezing and thawing period. At the beginning of the freezing period, the water in the deep soil layer moves upward to the freezing front and releases heat during the freezing process. When the soil layer is completely frozen, there are no vertical water exchanges between the soil layers, and the heat exchange process is controlled by the vertical soil temperature gradient. During the thawing period, the downward heat process becomes more active due to increased incoming shortwave radiation at the ground surface. The melt water is quickly dissolved in the soil, and the soil water movement only changes in the shallow soil layer. Subsequently, the model was used to provide an evaluation of the potential response of the active layer to different scenarios of initial water content and climate warming at the Tanggula site. The results reveal that the soil water content and the organic layer provide protection against active layer deepening in summer, so climate warming will cause the permafrost active layer to become deeper and permafrost degradation.

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.

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。

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.