Natural convection of a binary liquid in cylindrical porous annuli/rectangular porous enclosures with cross-diffusion effects under local thermal non-equilibrium state

2022 ◽  
Vol 184 ◽  
pp. 122294
Author(s):  
K.M. Lakshmi ◽  
D. Laroze ◽  
P.G. Siddheshwar
Keyword(s):  
Natural Convection ◽  
Equilibrium State ◽  
Cross Diffusion ◽  
Binary Liquid ◽  
Diffusion Effects ◽  
Non Equilibrium

Numerical Study of Heat and Mass Transfer by Laminar and Turbulent Natural Convection With Cross Diffusion Effects in Square Cavity

2008 ◽  
Author(s):  
Wenguang Geng ◽  
Baoming Chen ◽  
Maocheng Tian ◽  
Fang Liu
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Soret Effect ◽  
Solute Concentration ◽  
Square Cavity ◽  
Component System ◽  
Turbulent Natural Convection ◽  
Cross Diffusion ◽  
Diffusion Effects

Laminar and turbulent natural convection flow in a two-dimensional square cavity filled two component system with compensating horizontal thermal and solute concentration gradients is investigated in this paper. The temperature gradient and volatile organic compounds (VOCs) concentration gradient are kept uniform in horizontal direction, while horizontal surfaces are kept adiabatic and impermeable within a square cavity. According to the principle of irreversible thermodynamics, with thermal-diffusion (Soret) effect and diffusion-thermo (Dufour) effect, a commercial computational fluid dynamics (Fluent) code is used to simulate heat and mass transfer numerically in present work. After validation of the method with available measurements, the range of the cross diffusion coefficients are analyzed firstly. Furthermore, the thermal field and solute concentration fields are presented for various conditions. Finally, the average Nusselt number and Sherwood number at the vertical wall are presented graphically. The numerical results show that the present work would help to know about the convective diffusion and distribution of VOCs indoor environment accurately. Also, it gives the more accurate characteristics of heat and mass transfer in multi-component system with cross diffusion effects.

A thermal non-equilibrium model for predicting LNG boil-off in storage tanks incorporating the natural convection effect

Energy ◽  
2021 ◽  
pp. 121162
Author(s):  
Zhongdi Duan ◽  
Hongxiang Xue ◽  
Xueru Gong ◽  
Wenyong Tang
Keyword(s):  
Natural Convection ◽  
Equilibrium Model ◽  
Storage Tanks ◽  
Non Equilibrium

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.

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