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91.
针对国内某炼油厂延迟焦化加热炉三点注汽问题,采用热负荷自动调节的算法进行了研究。运用该模型方法,分析了三点注汽量对加热炉热负荷和炉管结焦系数的影响,发现三点注汽量的改变均会对热负荷和炉管结焦系数产生影响,主要表现为提高注汽量将会提高热负荷,同时降低结焦系数;第1点注汽量和第2点注汽量对热负荷和结焦系数的影响较强,第3点注汽量对热负荷和结焦系数的影响较弱。在实际操作中,加热炉中的结焦程度既不能太强也不能太弱,合适的结焦系数能够保证正常开工周期里炉管不结焦,也能保证瓦斯、注汽量等参数的合理分配。通过对热负荷、注汽量的智能分配,可得到不同原料油加工负荷条件下更加合理的装置运行方案。 相似文献
92.
High accuracy mass flow measurement is an enabling technology at the base of many industries. HORIBA STEC Co., Ltd. developed its own primary gas mass flow measurement system. We employed the dynamic gravimetric method in a vacuum chamber, and we use only mass and time information for mass flow rate calculation, with no correction for temperature, pressure and humidity. The system achieved 0.036% uncertainty as lowest of results with satisfactory performance of proficiency testing with NIST (National Institute of Standards and Technology). Then the laboratory has been granted ISO/IEC 17025 accreditation since 2017. This paper describes the system details and uncertainty analysis. 相似文献
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The present study analyzes the effect of chemical reaction on an unsteady magnetohydrodynamic boundary layer viscous fluid over a stretching surface embedded in a porous medium with a uniform transverse magnetic field. A Darcy‐Forchheimer drag force model is employed to simulate the effect of second‐order porous resistance. Dissipative heat energy based on both viscous and Joule dissipation along with a heat source/sink is considered to enhance the energy equation. Similarity analysis is imposed to transform the governing differential equations into a set of nonlinear coupled ordinary differential equations. These sets of equations are solved numerically using the Runge‐Kutta fourth‐order scheme followed by the shooting algorithm. The effects of physical parameters such as magnetic field, Prandtl number, Eckert number, Schmidt number, unsteadiness parameter, and chemical reaction parameters have been discussed on velocity, temperature, and concentration fields. Computation for the coefficient of skin friction, rate of heat and mass transfer is done and presented in a table for validation of the present outcomes. 相似文献
96.
环路热管作为一种高效的相变传热装置,其性能与位于蒸发器和储液槽之间的毛细芯结构密切相关。为了更深入研究双层毛细芯对环路热管传热性能的影响,利用不同颗粒直径铜粉制备双层毛细芯,在毛细芯总厚度为5 mm的条件下,通过调整大粒径和小粒径层的相对厚度来改变毛细芯厚度比,对平板型蒸发器环路热管启动和变工况运行进行实验测试。实验结果表明:在同一工况下,不同厚度比的双层毛细芯启动特性存在显著差异,启动过程中出现小粒径层蒸发效率低引起的温度过冲和环路热管中气液两相流变化导致的温度振荡;同时存在一个较优的双铜层毛细芯厚度比,大粒径(180~280μm)铜层厚度为3 mm可提高蒸发效率,小粒径(56~71μm)铜层厚度为2 mm可提供足够毛细抽吸力保证环路热管稳定运行。搭载该厚度毛细芯的环路热管不仅启动速度快(125 s),而且总热阻和蒸发器壁面温度均最低,最大加热功率达到120 W(21.10 W/cm~2),对应热阻为0.17 K/W。 相似文献
97.
《International Journal of Hydrogen Energy》2020,45(54):29848-29860
Dynamic contact angle (DCA) is of crucial importance in the numerical investigation of water management problems in proton exchange membrane fuel cells (PEMFCs). In order to well predict the gas-liquid two-phase flow in the complex flow field in PEMFCs, first, it is very critical to build a robust DCA model that is capable of simulating droplet behaviors on a single surface under various conditions. In our previous research work, an advancing-receding DCA (AR-DCA) model is developed and has been successfully validated against a series of experiments from the available literature for droplet impact on surfaces. In this study, the AR-DCA model is further applied to simulate droplet behaviors on inclined surfaces with different droplet impact velocities, impact angles and viscosities. It is found that the droplet spreading and deformation from the simulations have excellent agreement with those captured in the corresponding experiments. The results also indicate that higher impact velocity and impact angle can facilitate the spreading trend at the droplet trailing edge and have no notable effects on the leading edge. In addition, the increase of droplet viscosity leads to a transition from droplet deposition phenomenon to partial rebound on the surface. 相似文献
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99.
针对短期日负荷预测的精度问题,本文提出一种基于数据驱动理念的电力负荷预测方法。在建立预测模型前对所给数据采取一定的预处理:首先提取所收集的海量数据的负荷特征,对负荷特征进行分析,然后进行负荷数据与影响负荷值的因素之间的相关性分析,以此确定对负荷影响较密切的因素,随后建立分类器得到各主要影响因素与各负荷类别之间的关系为后续预测模型奠定基础。对预处理后得到的不同类型的负荷数据采用最小二乘支持向量机方法建立不同的负荷预测模型。以南方某发达城市2008年的负荷数据作为算例验证数据,将本文所提负荷预测方法所得结果与未经数据预处理的负荷预测方法所得结果进行比较,结果表明本文提出的方法得到的预测结果精度较传统方法提高约6%。 相似文献
100.
《International Journal of Hydrogen Energy》2020,45(22):12565-12576
Electrospun carbon fibers are featured with abundant electroactive sites but large mass transport resistances as the electrodes for vanadium redox flow battery. To lower mass transport resistances while maintaining large specific areas, electrospun carbon fibers with different structural properties, including pore size and pore distribution, are prepared by varying precursor concentrations. Increasing the polyacrylonitrile concentration from 9 wt% to 18 wt% results in carbonized fibers with an average fiber diameter ranging from 0.28 μm to 1.82 μm. The median pore diameter, in the meantime, almost linearly increases from 1.32 μm to 9.05 μm while maintaining the porosity of higher than 82%. The subsequent electroactivity evaluation and full battery testing demonstrate that the mass transport of vanadium ions through the electrode with larger fiber diameters are significantly improved but not scarifying the electrochemical activity. It is shown that the flow battery with these electrodes obtains an energy efficiency of 79% and electrolyte utilization of 74% at 300 mA cm−2. Hence, all these results eliminate the concern of mass transport when applying electrospun carbon fibers as the electrodes for redox flow batteries and guide the future development of electrospun carbon fibers. 相似文献