scholarly journals Simplified Layer Model for Solid Particle Clusters in Product Oil Pipelines

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4809 ◽  
Author(s):  
Dongze Li ◽  
Lei Chen ◽  
Qing Miao ◽  
Gang Liu ◽  
Shuyi Ren ◽  
...  
Keyword(s):  
Equilibrium State ◽  
External Disturbance ◽  
Fixed Bed ◽  
Force Balance ◽  
Normal Operation ◽  
Particle Cluster ◽  
Balance Principle ◽  
Proposed Model ◽  
Oil Pipelines ◽  
Non Equilibrium

Pipe corrosion caused by the pressure tests using water before starting the normal operation occurs often in Chinese product oil pipelines because of remaining water. To explore the migration of the corrosion impurities in the product oil pipelines, this study started from the force balance principle and considered the entire particle cluster as the research object. This paper established a one-dimensional migration model, and proposed the Froude number equality criterion to calculate the particle cluster length in the equilibrium state. The proposed criterion was verified by experiments. A loop was built to conduct the tests and obtain the migration velocities of the particle cluster from the non-equilibrium state to the equilibrium state in the pipeline. The proposed model was verified using the experimental data. Verification results demonstrate that the model can describe the development process from the non-equilibrium state to the equilibrium state of particle clusters after sudden external disturbance and accurately predict some important parameters, including the velocity of the particle cluster in the equilibrium state and the critical velocity that leads to the transition from fixed bed flow to moving bed flow. The model provides the theoretical basis and calculation method to remove corrosion impurities from product oil pipelines.

Ostwald´s Rule and the Principle of the Shortest Way

2010 ◽  
Vol 224 (06) ◽  
pp. 929-934 ◽  
Author(s):  
Herbert W. Zimmermann
Keyword(s):  
Melting Point ◽  
Equilibrium State ◽  
Entropy Production ◽  
Thermodynamic Stability ◽  
Lagrange Equation ◽  
Classical Mechanics ◽  
Geodesic Line ◽  
Final Equilibrium State ◽  
Relevant Variables ◽  
Non Equilibrium

AbstractWe consider a substance X with two monotropic modifications 1 and 2 of different thermodynamic stability ΔH1 < ΔH2. Ostwald´s rule states that first of all the instable modification 1 crystallizes on cooling down liquid X, which subsequently turns into the stable modification 2. Numerous examples verify this rule, however what is its reason? Ostwald´s rule can be traced back to the principle of the shortest way. We start with Hamilton´s principle and the Euler-Lagrange equation of classical mechanics and adapt it to thermodynamics. Now the relevant variables are the entropy S, the entropy production P = dS/dt, and the time t. Application of the Lagrangian F(S, P, t) leads us to the geodesic line S(t). The system moves along the geodesic line on the shortest way I from its initial non-equilibrium state i of entropy Si to the final equilibrium state f of entropy Sf. The two modifications 1 and 2 take different ways I1 and I2. According to the principle of the shortest way, I1 < I2 is realized in the first step of crystallization only. Now we consider a supercooled sample of liquid X at a temperature T just below the melting point of 1 and 2. Then the change of entropy ΔS1 = Sf 1 - Si 1 on crystallizing 1 can be related to the corresponding chang of enthalpy by ΔS1 = ΔH1/T. Now it can be shown that the shortest way of crystallization I1 corresponds under special, well-defined conditions to the smallest change of entropy ΔS1 < ΔS2 and thus enthalpy ΔH1 < ΔH2. In other words, the shortest way of crystallization I1 really leads us to the instable modification 1. This is Ostwald´s rule.

Extended Thermodynamic Approach for Non-Equilibrium Gas Flow

2013 ◽  
Vol 13 (5) ◽  
pp. 1330-1356 ◽  
Author(s):  
G. H. Tang ◽  
G. X. Zhai ◽  
W. Q. Tao ◽  
X. J. Gu ◽  
D. R. Emerson
Keyword(s):  
Heat Transfer ◽  
Equilibrium State ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Characteristics ◽  
Bimodal Distribution ◽  
Thermodynamic Approach ◽  
Navier Stokes ◽  
Extended Thermodynamic ◽  
Non Equilibrium

AbstractGases in microfluidic structures or devices are often in a non-equilibrium state. The conventional thermodynamic models for fluids and heat transfer break down and the Navier-Stokes-Fourier equations are no longer accurate or valid. In this paper, the extended thermodynamic approach is employed to study the rarefied gas flow in microstructures, including the heat transfer between a parallel channel andpressure-driven Poiseuille flows through a parallel microchannel andcircular microtube. The gas flow characteristics are studied and it is shown that the heat transfer in the non-equilibrium state no longer obeys the Fourier gradient transport law. In addition, the bimodal distribution of streamwise and spanwise velocity and temperature through a long circular microtube is captured for the first time.

Adaptive Integrated Control for Omnidirectional Mobile Manipulators Based on Neural-Network

2011 ◽  
pp. 310-325
Author(s):  
Xiang-min Tan ◽  
Dongbin Zhao ◽  
Jianqiang Yi ◽  
Dong Xu
Keyword(s):  
Neural Network ◽  
Large Scale ◽  
Integrated Control ◽  
External Disturbance ◽  
Torque Control ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Modeling And Control ◽  
Control Approach ◽  
Proposed Model

An omnidirectional mobile manipulator, due to its large-scale mobility and dexterous manipulability, has attracted lots of attention in the last decades. However, modeling and control of such systems are very challenging because of their complicated mechanism. In this paper, an unified dynamic model is developed by Lagrange Formalism. In terms of the proposed model, an adaptive integrated tracking controller, based on the computed torque control (CTC) method and the radial basis function neural-network (RBFNN), is presented subsequently. Although CTC is an effective motion control strategy for mobile manipulators, it requires precise models. To handle the unmodeled dynamics and the external disturbance, a RBFNN, serving as a compensator, is adopted. This proposed controller combines the advantages of CTC and RBFNN. Simulation results show the correctness of the proposed model and the effectiveness of the control approach.

Basic laws of thermodynamics

2005 ◽  
Author(s):  
Boris S. Bokstein ◽  
Mikhail I. Mendelev ◽  
David J. Srolovitz
Keyword(s):  
Physical Chemistry ◽  
Equilibrium State ◽  
General Scheme ◽  
Thermodynamic Description ◽  
External Disturbance ◽  
The State ◽  
System Parameters ◽  
Laws Of Thermodynamics ◽  
Small Set ◽  
State Functions

In this chapter, we first introduce the basic laws of thermodynamics and R17the most important thermodynamic functions. Even though many of the concepts introduced here will be familiar to many readers with a background in elementary physics, this chapter should not be ignored as it presents these concepts in the language of physical chemistry. Since these concepts form the basis of physical chemistry, this subject will make no sense without a firm footing in these fundamentals. Thermodynamics focuses on the thermal behavior of macroscopic systems (i.e. systems containing a very large number of particles). Thermal processes include both heat exchange between a system and its surroundings and work. The general scheme of a thermodynamic description of such processes can be described as in the picture: Thermodynamic descriptions are usually based upon experimental observations. Experiments can characterize the thermodynamic state of the system in terms of a small number of measurable parameters (e.g. temperature T and pressure p). The generalization of these measurements yields thermodynamics laws. Thermodynamic laws identify state functions that describe the system behavior solely in terms of the system parameters and not on how the system came to be in a particular state. Changes in the state functions during some process depend on only the intial and final states of the system but not on the path between them. Therefore, these changes can be determined from calculations based on a very small set of data. Thermodynamics can be used to answer such questions as (1) is a particular process possible? (2) can the system spontaneously evolve in a particular direction?, and (3) what is the final or equilibrium state? all under a given set of conditions. Equilibrium can be understood as the state in which the system parameters no longer evolve, there are no fluxes of matter or energy through the system, and for which all small disturbances decay. According to the zeroeth law of thermodynamics any isolated system will eventually evolve to an equilibrium state and will never spontaneously leave this state (without a substantial external disturbance).

Vibration suppression for large-scale flexible structures based on cable-driven parallel robots

2020 ◽  
pp. 107754632096194
Author(s):  
Haining Sun ◽  
Xiaoqiang Tang ◽  
Senhao Hou ◽  
Xiaoyu Wang
Keyword(s):  
Large Scale ◽  
Vibration Suppression ◽  
Control Method ◽  
External Disturbance ◽  
Flexible Structures ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Lyapunov Theory ◽  
Normal Operation ◽  
Control Methods

Specific satellites with ultralong wings play a crucial role in many fields. However, external disturbance and self-rotation could result in undesired vibrations of the flexible wings, which affect the normal operation of the satellites. In severe cases, the satellites would be damaged. Therefore, it is imperative to conduct vibration suppression for these flexible structures. Utilizing fuzzy-proportional integral derivative control and deep reinforcement learning (DRL), two active control methods are proposed in this article to rapidly suppress the vibration of flexible structures with quite small controllable force based on a cable-driven parallel robot. Inspired by the output law of DRL, a new control method named Tang and Sun control is innovatively presented based on the Lyapunov theory. To verify the effectiveness of these three control methods, three groups of simulations with different initial disturbances are implemented for each method. Besides, to enhance the contrast, a passive pretightening scheme is also tested. First, the dynamic model of the cable-driven parallel robot which comprises four cables and a flexible structure is established using the finite element method. Then, the dynamic behavior of the model under the controllable cable force is analyzed by the Newmark-ß method. Finally, these control methods are implemented by numerical simulations to evaluate their performance, and the results are satisfactory, which validates the controllers’ ability to suppress vibrations.

Cluster mean-field dynamics in one-dimensional TASEP with inner interactions and Langmuir dynamics

2019 ◽  
Vol 33 (02) ◽  
pp. 1950012 ◽  
Author(s):  
Yu-Qing Wang ◽  
Zi-Huan Zhang
Keyword(s):  
Statistical Physics ◽  
Interacting Particle Systems ◽  
Research Work ◽  
Mean Field ◽  
Exclusion Process ◽  
Driven Diffusive Systems ◽  
One Dimensional ◽  
Proposed Model ◽  
Asymmetric Simple Exclusion ◽  
Non Equilibrium

In the area of statistical physics, totally asymmetric simple exclusion process (TASEP) is treated as one of the most important driven-diffusive systems. It contains profound non-equilibrium statistical physics mechanisms due to being the paradigm model like Ising model. Different with previous work, a one-dimensional TASEP coupled with inner interactions and Langmuir dynamics is taken into account. Weak coupled binding and unbinding rates are introduced in the proposed model. Bond breaking and making mechanisms of self-driven particles illustrating the unidirectional movement of protein motors are investigated by means of performing cluster mean-field analyses. Dynamics in the proposed system dominated by the competition between the attraction effect and the repulsion one are found to depend on the specific value of the interaction energy of these active particles. The research work will be helpful for understanding non-equilibrium statistical behaviors of interacting particle systems.

Sign in / Sign up

Export Citation Format

Share Document