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51.
Wax deposition rate model for heat and mass coupling of piped waxy crude oil based on non-equilibrium thermodynamics 总被引:1,自引:0,他引:1
Yang Liu Chenlin Pan Bing Wang Xuxu Wang Yifan Gan 《Journal of Dispersion Science and Technology》2018,39(2):259-269
In this paper, wax deposition in waxy crude oil transportation process was regarded as an irreversible process. Based on the entropy production rate equations, the linear phenomenological equations for the diffusion of wax molecules were derived by using the theory and method of non-equilibrium thermodynamics and heat-mass transfer. Combined with the mass and energy conservation laws, the differential equations of heat and mass transfer in the process of pipeline transportation were established, and the molecular diffusion rate of dissolved wax was solved. On the basis of this, the mathematical model of actual wax deposition rate was established by considering the attachment process and scouring process of the wax molecules. Taking an oil pipeline in Daqing as an example, the change law and influencing factors of the wax molecular diffusion coefficient, the wax deposition rate, and the net wax deposition rate were studied by numerical simulation. The wax deposition rate test results of the laboratory loop test were compared with the theoretical calculation results in order to analyze the accuracy and the adaptability of heat and mass coupling mechanism and to provide a theoretical basis for further study of wax deposition in the process of waxy oil pipeline transportation. 相似文献
52.
Santhanamoorthi Nachimuthu Yi-Hui Kuo Dang Hoai Khanh Zhan-Jun Zhu Jyh-Chiang Jiang 《中国化学会会志》2023,70(3):349-358
The ability of the polymer-based graphitic carbon nitride (g-C3N4) as a gas sensor toward NO, NO2, CO, CO2, SO2, SO3, and O2 gasses is assessed using density functional theory (DFT) calculations in terms of energetic and electronic transport characteristics. In particular, this study is aimed to explore the role of zigzag and armchair edges of the g-C3N4 sheet on sensing performances. The electronic properties of adsorption systems, such as Bader charge analysis, band gaps, work function, and density of states (DOS), are used to understand the interaction between the adsorbed gas molecules and the g-C3N4 sheet. Our calculated results indicate that SOx (SO3 and SO2) gasses have higher adsorption energies on the g-C3N4 sheet than other gasses. Furthermore, the transport properties, such as current–voltage (I-V) and resistance-voltage (R-V) curves along the zigzag and armchair directions are calculated using the non-equilibrium Green's function (NEGF) method to understand the performance of the g-C3N4 sheet as a prominent conductive/resistive sensor. The I-V/R-V results indicate that the zigzag g-C3N4 sheet has excellent sensing ability toward SOx gasses at low applied voltages. However, the presence of H2O degrades the sensing performance of the armchair g-C3N4 sheet. Theoretical recovery time has also been calculated to evaluate the reusability of g-C3N4 sheet-based gas sensors. Our results reveal that the zigzag g-C3N4 sheet-based sensing device has a remarkably high sensitivity (>300%) and selectivity toward SOx gasses and has the potential to work in a complex environment. 相似文献
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Matthias Morasch Prof. Dieter Braun Dr. Christof B. Mast 《Angewandte Chemie (International ed. in English)》2016,55(23):6676-6679
DNA phase transitions are often induced by the addition of condensation agents or by dry concentration. Herein, we show that the non‐equilibrium setting of a moderate heat flow across a water‐filled chamber separates and gelates DNA strands with single‐base resolution. A dilute mix of DNA with two slightly different gel‐forming sequences separates into sequence‐pure hydrogels under constant physiological solvent conditions. A single base change in a 36 mer DNA inhibits gelation. Only sequences with the ability to form longer strands are concentrated, further elongated, and finally gelated by length‐dependent thermal trapping. No condensation agents, such as multivalent ions, were added. Equilibrium aggregates from dry concentration did not show any sequence separation. RNA is expected to behave identically owing to its equal thermophoretic properties. The highly sequence‐specific phase transition points towards new possibilities for non‐equilibrium origins of life. 相似文献
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Borisover M. D. Zakharychev D. V. Solomonov B. N. 《Journal of Thermal Analysis and Calorimetry》1999,55(1):85-92
Human serum albumin (HSA) immersed in pyridine-n-hexane mixtures was analyzed using differential scanning calorimetry (DSC).
State of the solid HSA in organic solvent mixtures is the non-equilibrium state which is seen as the exothermic peak on the
DSC curves. The enthalpy change corresponding to this exothermic peak approaches zero when going from pure pyridine to pure
n-hexane. Dependence of the enthalpy change on the pyridine concentration is suggestive that the non-equilibrium state of
the immersed HSA results from the HSA-pyridine interactions 'frozen' at the lower temperature. Most likely the temperature-initiated
exothermic peak observed on the DSC curves reflects the swelling of HSA by pyridine.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
58.
打破将散度演化分析局限于水平动力学框架内的传统认识思维,针对大气的斜压性与层结特征将对大气运动散度场演化产生显著影响的事实,从湿斜压原始方程出发,将大气的斜压热力作用通过热力学方程引入散度方程,在替换平衡近似(alternative balance)下,导出了显式包含湿非地转Q矢量与垂直风切变耦合强迫作用的新型散度方程.阐明了潮湿大气中非地转斜压强迫激发散度场演化的物理机制,为利用常规观测资料诊断散度场演化提供了一种有效的数学工具.通过对流层中低层气柱内总体辐合增长影响因子的分
关键词:
暴雨天气
散度演变
正压非平衡强迫
湿斜压热动力耦合强迫 相似文献
59.
A non-equilibrium steady state can be characterized by a nonzero but stationary flux driven by a static external force. Under a weak external force, the drift velocity is difficult to detect because the drift motion is feeble and submerged in the intense thermal diffusion. In this article, we employ an accurate method in molecular dynamics simulation to determine the drift velocity of a particle driven by a weak external force in a one-dimensional periodic potential. With the calculated drift velocity, we found that the mobility and diffusion of the particle obey the Einstein relation, whereas their temperature dependences deviate from the Arrhenius law. A microscopic hopping mechanism was proposed to explain the non-Arrhenius behavior. Moreover, the position distribution of the particle in the potential well was found to deviate from the Boltzmann equation in a non-equilibrium steady state. The non-Boltzmann behavior may be attributed to the thermostat which introduces an effective "viscous" drag opposite to the drift direction of the particle. 相似文献
60.