Simulation and heat exchanger network designs for a novel single-column cryogenic air separation process

To realize the industrialization of the novel single-column air separation process proposed in previous work,steady-state simulation for four different configurations of the single-column process with ternary(nitrogen,oxygen and argon)is developed.Then,exergy analysis of the single-column processes is also carried out and compared with the conventional double-column air separation process at the same capacity.Furthermore,based on the steady-state simulation of single-column processes,the different heat exchanger networks(HENs)for the main heat exchanger and subcooler in each process are designed.To obtain better performance for this novel process,optimization of process configuration and operation is investigated.The optimal condition and configuration for this process is consisted as:feedstock is divided into two streams and the reflux nitrogen is compressed at the approximate temperature of 301 K.In addition,HEN is optimized to minimize the utilities.HENs without utilities are obtained for the four different configurations of single-column process.Furthermore,capital costs of the HEN for different cases are estimated and compared.

Combined heat and mass transfer by mixed convection MHD flow along a porous plate with chemical reaction in presence of heat source

An exact and a numerical solutions to the problem of a steady mixed convective MHD flow of an incompressible viscous electrically conducting fluid past an infinite vertical porous plate with combined heat and mass transfer are presented.A uniform magnetic field is assumed to be applied transversely to the direction of the flow with the consideration of the induced magnetic field with viscous and magnetic dissipations of energy.The porous plate is subjected to a constant suction velocity as well as a uniform mixed stream velocity.The governing equations are solved by the perturbation technique and a numerical method.The analytical expressions for the velocity field,the temperature field,the induced magnetic field,the skin-friction,and the rate of heat transfer at the plate are obtained.The numerical results are demonstrated graphically for various values of the parameters involved in the problem.The effects of the Hartmann number,the chemical reaction parameter,the magnetic Prandtl number,and the other parameters involved in the velocity field,the temperature field,the concentration field,and the induced magnetic field from the plate to the fluid are discussed.An increase in the heat source/sink or the Eckert number is found to strongly enhance the fluid velocity values.The induced magnetic field along the x-direction increases with the increase in the Hartmann number,the magnetic Prandtl number,the heat source/sink,and the viscous dissipation.It is found that the flow velocity,the fluid temperature,and the induced magnetic field decrease with the increase in the destructive chemical reaction.Applications of the study arise in the thermal plasma reactor modelling,the electromagnetic induction,the magnetohydrodynamic transport phenomena in chromatographic systems,and the magnetic field control of materials processing.

Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

Experimental study on heat exchange of several types of exchangers

Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.

Measurement of thermal conductivity of materials using single-side TPS technique

Based on the traditional measurement theory of transient plane source (TPS) technique, single-side TPS method is proposed for measuring the thermal conductivity of single specimen. The problem of transient heat conduction in a semi-infinite boundary condition is studied and the theoretical formula of single-side TPS method is deduced. During the measurement, the influence of the probe heat capacity on the results is analyzed and the corresponding mathematical compensation model is established, and a series of experiments on different materials are conducted by hot disk probe at normal temperature and pressure. The results show that the relative error with the single-side TPS method is less than 5% and the relative standard deviation is no greater than 3%. This method has high accuracy and good reproducibility, which provides a feasible measuring method for single material that does not meet the requirements of the standard TPS theory.

A deep neural network surrogate modeling benchmark for temperature field prediction of heat source layout

The thermal issue is of great importance during the layout design of heat source components in systems engineering,especially for high functional-density products.Thermal analysis requires complex simulation,which leads to an unaffordable computational burden to layout optimization as it iteratively evaluates different schemes.Surrogate modeling is an effective method for alleviating computation complexity.However,the temperature field prediction(TFP)with complex heat source layout(HSL)input is an ultra-high dimensional nonlinear regression problem,which brings great difficulty to traditional regression models.The deep neural network(DNN)regression method is a feasible way for its good approximation performance.However,it faces great challenges in data preparation for sample diversity and uniformity in the layout space with physical constraints and proper DNN model selection and training for good generality,which necessitates the efforts of layout designers and DNN experts.To advance this cross-domain research,this paper proposes a DNN-based HSL-TFP surrogate modeling task benchmark.With consideration for engineering applicability,sample generation,dataset evaluation,DNN model,and surrogate performance metrics are thoroughly investigated.Experiments are conducted with ten representative state-of-the-art DNN models.A detailed discussion on baseline results is provided,and future prospects are analyzed for DNN-based HSL-TFP tasks.

油田联合站水源热泵能效比软测量方法及节能效果研究

油田联合站水源热泵的应用既有效减少了以天然气为燃料的加热炉碳排放量,又解决了采暖伴热和机泵冷却的问题。但如何能精准方便测量和提高其能效比(COP)值,对水源热泵在油田推广应用有着重大意义。为此,采用BP神经网络对油田在运水源热泵的COP进行建模,测得与实际运行参数平均相对误差均小于1%,证明这种基于BP神经网络建模的水源热泵COP值软测量方法是可行的;另外,通过仿真模型分析,提出将水源热泵间接式单蒸发工艺改进为直进式双蒸发工艺,水源热泵COP值由3.6~4.2提高到4.5~4.8,年节约电耗174.1×104 kWh。研究结果对油田水源热泵的推广应用和系统节能降耗起到了积极作用。

基于热源网络法的永磁式电磁制退机热特性研究

永磁式电磁制退机以磁场为能量传输介质,有望彻底解决传统液压式制退机液体泄漏、阻力规律稳定性差等问题。然而电磁制退机工作过程中的热特性变化规律尚未探明,限制了电磁制退机的进一步发展。依据电磁制退机的结构,建立了热源网络温度场分析模型,计算了电磁制退机各主要部件的热参数,结合热路传播路径编写了温度场计算程序,得到了火炮后坐过程中电磁制退机不同时刻的瞬态节点温度,探究了电磁制退机瞬态工作过程中的温度传播规律与分布特性。同时建立有限元模型,对热源网络分析模型进行了验证。最后充分利用热源网络模型计算效率高的优势,开展了连发射击工况下电磁制退机的热特性研究、失效预测和冷却措施探究,为电磁制退机的工程设计提供了参考。

计及网络动态特性的电-热互联系统仿射优化法

热网动态特性带来能量传输延时的同时,使得空间上的源荷不确定性对系统造成的影响存在时序上的先后差异,导致电-热互联系统日前调度转变为复杂的时空耦合问题。为此,该文提出一种计及网络动态特性的仿射优化法。首先,利用流量分段法与节点网络模型,构建计及能量传输延时且适用于环网的热网动态模型。在此基础上,利用仿射算法与牛顿-拉夫逊能流计算原理,通过线性化建模方式与模型凸化方法,构建仿射凸优化模型。其次,利用仿射优化法解决电-热互联系统不确定性优化调度问题,实现对源荷不确定性传播轨迹的跟踪及其影响的量化分析。最后,33节点电-热互联系统仿真算例证明,所提方法能够揭示网络动态特性下源荷不确定性影响机理,并获得具有低保守性、高经济性的调度方案。

大庆乘银集中供热系统多热源联网优化运行研究

为了增强乘银地区集中供热系统运行可靠性,最大限度地降低供热企业成本,原大庆油田矿区服务事业部通过对乘银集中供热系统4座热源和热网进行规划整合,实现了乘银地区供热系统4座热源联网运行,4座热源相互备用,避免了因单一热源故障而造成局部地区大面积停暖的问题。依据热源择优投运、全网集中调控原则,供热初末期以宏伟热电厂作为基础热源,实施宏伟热电厂、八百垧燃煤锅炉房的双热源联网运行模式;供热中期实施宏伟热电厂、八百垧燃煤锅炉房、乘风燃气锅炉房的三热源联网运行模式;供热高峰期实施宏伟热电厂、八百垧燃煤锅炉房、乘风燃气锅炉房和银浪燃煤锅炉房的四热源联网运行模式。同时尽可能延长效率高、能耗少的宏伟热源运行时间,充分发挥宏伟热电厂热电联产优势,在满足供热需求的前提下,提高了供热系统的经济性。

可控储热负荷参与电网调峰的系统特性与经济性研究

为解决当前可再生能源装机量大但出力相对较小及电力系统调峰能力低下的问题,通过新兴的固态电制热储热技术,充分挖掘电力系统用户侧的潜力。以系统消纳的风电量最多及用户侧运行的经济性最优为目标,建立了含电力需求侧响应的用户侧配置固态电制热储热设备的系统模型。采用改进多目标粒子群算法对模型进行优化求解,针对电力系统的源侧、网侧、荷侧,对比不同运行方式下的风电消纳能力、负荷曲线峰谷差及经济成本。仿真结果表明,在电力需求侧响应的基础上用户侧配置固态电制热储热设备,可以大大提高系统的风电消纳能力及调峰水平,并具有一定的经济价值。

基于ABAQUS的单丝双面气电立焊数值模拟

基于有限元软件ABAQUS,建立了单丝双面气电立焊焊接温度场和应力场的有限元模型。热源模型选取圆柱体热源与面热源的组合,并采用生死单元技术来进行焊缝的填充加载,采用试验测定的EH40钢高温热物性参数模拟了焊接过程。模拟计算结果表明:焊后试板的横向残余应力在板中间区域为拉应力,在其余区域为压应力;纵向残余应力在焊缝及其附近区域表现为较大的拉应力,而在远离焊缝的位置拉应力迅速衰减并过渡为压应力;通过与试验结果对比,计算得到的热循环曲线及焊缝形状与实际试验吻合度较高,验证了所建立的模型的准确性。该模型可以用于预测气电立焊焊接过程中的温度场、应力场和残余应力分布,为焊接工艺优化和结构设计提供理论依据。

集中供热系统节能技术研究

现代城市的发展和壮大,离不开集中供热系统的运行能力。集中供热系统的建设,包括供热热源、热力网、热力站、庭院供热管网及室内采暖系统的规划、设计、施工、调试、验收、运行管理中与能耗有关的部分都应该从节能角度去考虑。提出了企业供热系统优化策略,降低了能源损耗,提高了温度和水力平衡性,减少了污染物排放量,取得了显著的成效。

动热源摆式单轴MEMS热加速度计敏感机理的研究

该文揭示了一种动热源摆式单轴微机电系统(MEMS)热加速度计的敏感机理。在给出敏感结构原理的基础上,通过建立二维物理研究模型、划分网格、加载加速度等方法对敏感结构内的温度场进行了计算。结果表明,开机1.8 s后在敏感结构内形成了一个稳定的以动热源为中心的温度场;输入加速度a时,动热源沿着加速度方向偏移,温度场随之偏移,敏感轴方向上对称设置的两个热线温差ΔT X随着输入加速度a的加大而呈线性增长,温度灵敏度为7.1×10^(-2)mK/g。根据输入-输出(a-V X OUT)特性曲线给出数学模型,得到该加速度计灵敏度为0.5 V/g,非线性度为2.8%,从而揭示了敏感机理。

基于SOFM神经网络的水源热泵故障诊断方法研究

本研究针对水源热泵机组常见的6种热力故障,尝试使用SOFM神经网络进行故障诊断。利用水源热泵机组试验台人为制造制冷剂充注量过多、制冷剂泄漏、膨胀阀开度过大与过小、冷却水管路阻塞、系统含不凝性气体共计6种热力故障,记录机组带故障运行时的运行参数,将收集到的参数进行归纳整理,提取出部分特征值制作成数据集。将数据集划分为训练集合与测试集合,前者用于神经网络的训练,后者用于验证神经网络故障的诊断效果。结果表明,SOFM神经网络对于本次实验人为制造出的6种水源热泵热力故障具有较高的诊断正确率,网络迭代500次,用时2.7 s,在有效诊断的同时具有较快的响应速度。

分布式“源汇一体”太阳能供暖新系统探索

集中太阳能供暖系统需要大面积空地安装集热器阵列,在土地资源紧缺地区应用受限。单体建筑太阳能供暖系统虽能够有效利用建筑屋面进行集热,但其供暖稳定性相对较差。针对现有太阳能供暖系统应用的局限性,提出了一种分布式“源汇一体”太阳能供暖新系统。本文介绍了该系统的工作原理,定性分析了该系统与传统系统的特征区别,探讨了该系统在热用户节点、输配管网形式、蓄热设计等方面亟待解决的关键问题。

基于自适应BPNN-GIS耦合的地下水源热泵适宜性分区研究

基于石家庄市的地质条件构建了地下水源热泵适宜性评价指标体系。利用自适应Back Propagation(BP)神经网络与(GIS)耦合的方法进行地下水源热泵适宜性分区评价,同时与模糊层次分析法评价结果进行对比。结果表明,两者适宜性分区除了面积略有差异,适宜性分布情况基本相同,BP神经网络与模糊层次分析法适宜区评价结果面积占比仅相差3.80%,较适宜区面积占比相差8.06%,不适宜区面积占比相差11.86%。采用自适应BPNN-GIS的评价方法解决了传统人工手动调参以及主观赋权的弊端,同时评价效率更高、精度更高,更能反映研究区单点适宜性程度。

空气源热泵冷热水机组应用于长江流域供暖的适应性分析及节能性提升

针对空气源热泵冷热水机组在长江流域的供暖应用,从气候特征、供暖水温需求、负荷需求等方面进行了适应性分析,从系统设计及识霜、抑霜控制等方面提出了节能性提升方案,并通过实验验证了提升效果。结果表明:出水温度35~50℃可有效满足供暖要求,同时能效较佳;模块化变频单级压缩系统能够较好地满足实际使用需求,可有效提升综合性能系数;基于最佳效率的压缩机加、卸载调度控制及基于最小换热温差的识霜、抑霜控制,可以较好地应对负荷需求,使机组运行在最佳效率点,制热工况性能系数最大提升20%。

基于混合神经网络的短期供热负荷预测模型研究

短期供热负荷预测对促进节能减排以及建设智慧供热系统有着重要意义。由于热负荷数据呈现较强的非线性、滞后性和耦合性,常规预测模型难以取得令人满意的效果。针对传统的长短时记忆(LSTM)神经网络的研究,提出了1种以小波分解(WD)和卷积神经网络(CNN)为基础的混合神经网络模型。首先,采用WD将序列分解为不同的子序列;其次,采用CNN提取局部特征,对输入变量进行解耦合;然后,采用LSTM对时间子序列分别进行预测;最后,通过融合计算子序列预测结果得出预测序列。试验结果表明,与LSTM、CNN、CNN-LSTM等网络相比,WD-CNN-LSTM的平均绝对误差、决定系数、均方根误差等指标都更好,能够满足换热站对供热负荷高精度预测的要求。

空气源热泵结霜量预测技术及试验研究

空气源热泵“监测外管温变化及运行时间”的化霜判断方法,利用了结霜现象对热泵系统运行参数的时空累积影响效应,需要累积到一定结霜量时才能准确识别,无法实时判断当前换热器的结霜情况。基于此痛点问题,提出一种结霜量预测技术,通过分析结霜过程相关原理,利用神经网络和空气源热泵系统特性,搭建结霜量预测模型,从而对结霜量进行准确识别。试验结果表明,搭建的结霜量预测模型能够实时计算室外换热器的结霜量,且与实际结霜量相比误差在15%以内,对探索更精细更灵敏更智能的化霜判断方式具有参考意义。