Diffusimetry Renounces Graham’s Law, Achieves Diffusive Convection, Concentration Gradient Induced Diffusion, Heat and Mass Transfer

2021 ◽  
Vol 407 ◽  
pp. 173-184
Author(s):  
Abul Khair ◽  
Nilay Kumar Dey ◽  
Mohammad Harun-Ur-Rashid ◽  
Mohammad Abdul Alim ◽  
Newas Mohammad Bahadur ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Concentration Gradient ◽  
Saline Water ◽  
Hot Water ◽  
Gradient Force ◽  
Self Diffusion ◽  
Diffusive Convection ◽  
Low Mass ◽  
Diffusion Rates ◽  
Concentration Diffusion

Absolute diffusion rates of KMnO4 in vertical and flattened diffusimeters show the concentration gradient force as being stronger than the gravitational force. Hot water molecules move downward on self-diffusion against buoyancy. Diffusive convection (DC) in warm water and double-diffusive convection (DDC) in warm, saline water take place inside the diffusimeter with DDC transferring more heat than DC. In the diffusing medium the original reagents change or retain their compositions to give the diffusate molecules to diffuse. In water, the change is mostly hydration. The syngener BaCl2.2H2O separately with congeners 3CdSO4.8H2O, ZnSO4.7H2O, and ZnSO4.H2O presents two distinct pairs of overlapping concentration versus rate curves, first for having very close MWs of BaCl2 and CdSO4 and second for having ZnSO4.H2O as the common congener for both the zinc sulfates. Chlorides of Li, Na, and K diffusing at hindered rates in glucose solution show the least rate for LiCl inevitably on grounds of low mass and high Li+ hydration radius. Diffusion blocking occurs at higher glucose concentration. Diffusion of 0.6M AgNO3-0.6M NH4Cl standardizes this diffusimeter. Mass transfer of HCl, H2SO4, and H2C2O4 show oxalic acid diffusing as hydrate and 88 percentage transfer of sulfuric acid in 5 minutes. The Superdiffusive Anti Graham’s Law, Vd , is further consolidated by Ca (NO3)2-M2CO3(M = Na, K, NH4+) and Ca (NO3)2-Na2HPO4 diffusions. Odd and even diffusions are illustrated by AgNO3-NH4Cl and AgNO3-BaCl2 diffusions.

scholarly journals On the Origin of the Magnetic Concentration Gradient Force and Its Interaction Mechanisms with Mass Transfer in Paramagnetic Electrolytes

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 114
Author(s):  
Magne Waskaas
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Diffusion Layer ◽  
Concentration Gradient ◽  
Homogeneous Magnetic Field ◽  
Diffusion System ◽  
Gradient Force ◽  
Interaction Mechanisms ◽  
Magnetic Circuits ◽  
Magnetic Concentration

The objective of this work is to analyze the origin of the magnetic concentration gradient force. The force will be studied in a diffusion system where a paramagnetic electrolyte diffuses through a thin, inert membrane under the influence of a homogeneous magnetic field. The force will be analyzed using the theory of magnetic circuits, i.e., by the concept of minimum reluctance principles. In addition, based on some previous studies, it will be discussed whether the minimum reluctance principle can be applied to mass transfer into and out of the diffusion layer at electrode/electrolyte interfaces. The results show that the magnetic concentration gradient force arises as a consequence of the minimum reluctance principle. Applied to the diffusion system, the magnetic concentration gradient force arises in the membrane as a consequence of the concentration gradient and hence, the reluctance gradient. The force acts on the flow in such a way that the reluctance in the membrane is minimized. The force implies two interaction mechanisms: attraction of the paramagnetic electrolyte flowing into the membrane in order to decrease the reluctance, and hindrance of the paramagnetic electrolyte flowing out of the membrane in order to hinder an increase in the reluctance. Based on previous studies, it is shown that the minimum reluctance principle can be applied to mass transfer into or out of the diffusion layer at electrode/electrolyte interfaces as well.

Experimental investigation of a pyramid type solar still with porous material: productivity assessment

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Naresh Yarramsetty ◽  
Naveen Sharma ◽  
Modumudi Lakshmi Narayana
Keyword(s):  
Porous Material ◽  
Saline Water ◽  
Base Plate ◽  
Hot Water ◽  
Feed Water ◽  
Solar Still ◽  
Absorber Plate ◽  
Content Type ◽  
Water Distillation ◽  
Clay Pots

Purpose This study aims to investigate the effect of porous material (clay pots) and it is facing on the productivity performance of a pyramid type solar still. The clay pots are placed in the basin facing up and facing down. The numbers of clay pots considered were 9 and 25, and its performance was compared with normal (0 clay pots) solar still. Design/methodology/approach The pyramid solar water distillation system has been designed, fabricated and tested under the actual environmental conditions of Kanchikacherla (16.6834 0N, 80.3904 0E), Andhra Pradesh, India. The solar still is used to produce the fresh water and hot water simultaneously from the brackish (i.e. containing dissolved salts) feed water for domestic applications. From open literature, it was established that the rate of evaporation is higher when the flowing water is held for a longer duration on the black color absorber plate, thereby leading to an increase in productivity of freshwater. Therefore, the pyramid solar still has been tested for smooth absorber plate and the absorber plate with porous heat storage material. Findings The porous material increases the production rate of freshwater compared to a base plate. However, the pyramid still with clay pots has higher productivity at a lower temperature because of the porosity effect. Originality/value The total dissolved solids, electrical conductivity and pH of the distilled water and the saline water have also been measured and compared.

scholarly journals Circulating Jet for Enhancing the Mass Transfer in a Gas-liquid Stirred Tank Reactor

2021 ◽  
Author(s):  
Lei Wang ◽  
Xiao Xu ◽  
Hualin Wang ◽  
HongLai Liu ◽  
Qiang Yang
Keyword(s):  
Mass Transfer ◽  
Scale Up ◽  
Input Power ◽  
Stirred Tank ◽  
Exhaust Gas ◽  
Stirred Tank Reactor ◽  
Tank Reactor ◽  
Mass Transfer Efficiency ◽  
Low Mass ◽  
Liquid Mass Transfer

A gas-liquid stirred tank reactor (STR) has some problems, such as low mass transfer efficiency, high exhaust gas oxygen concentration, and low product conversion rate, due to limitations of stirring speed and input power. This article proposes a method to enhance the gas-liquid mass transfer in a STR using circulating jet internals. When a circulating jet is added, the average bubble size in the reactor is reduced to 1.26 mm, and the overall gas holdup is increased to 8.23%, which is an increase of 3.62 times of the original STR. The gas-liquid volumetric mass transfer coefficient is increased to 0.05556 s-1, which is 4.84 times of the original STR. The unit volume power is increased by only 1.4 times. These data provide references for the design and scale-up of new jet STRs.

NUMERICAL STUDIES ON VERTICAL TUBULAR GENERATOR IN VAPOR ABSORPTION REFRIGERATION SYSTEM

2011 ◽  
Vol 19 (02) ◽  
pp. 121-129 ◽  
Author(s):  
PASUPATHY BALAMURUGAN ◽  
ANNAMALAI MANI
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Computer Code ◽  
Vertical Tube ◽  
Hot Water ◽  
Convective Boiling ◽  
Model Equations ◽  
Absorption Refrigeration System ◽  
Problem Solvers ◽  
Vapor Absorption Refrigeration

A model has been developed based on Colburn–Drew type formulation to analyze a vertical tube in tube stainless steel generator with forced convective boiling. Desorption of refrigerant vapor from refrigerant–absorbent solution takes place in the inner tube of the generator, when hot water through the annulus is used as heating medium. Simultaneous heat and mass transfer phenomena of desorption are described mathematically using the mass and energy balances, considering the heat and mass transfer resistances in liquid as well as vapor phases. Model equations are solved simultaneously by means of initial value problem solvers using explicit Runge–Kutta method with 4th order accuracy. A computer code has been developed in MATLAB to obtain the results. A parametric analysis has also been performed to study the effect of various parameters on the performance of the generator.

Constraining Progenitors of Observed Low-mass X-ray Binaries Using Convection and Rotation-Boosted Magnetic Braking

2021 ◽  
Vol 922 (2) ◽  
pp. 174
Author(s):  
Kenny X. Van ◽  
Natalia Ivanova
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Formation Rate ◽  
Mass Transfer Rate ◽  
Population Synthesis ◽  
X Ray ◽  
Synthesis Technique ◽  
Low Mass ◽  
Magnetic Braking ◽  
X Ray Binaries

Abstract We present a new method for constraining the mass transfer evolution of low-mass X-ray binaries (LMXBs)—a reverse population synthesis technique. This is done using the detailed 1D stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics) to evolve a high-resolution grid of binary systems spanning a comprehensive range of initial donor masses and orbital periods. We use the recently developed convection and rotation-boosted (CARB) magnetic braking scheme. The CARB magnetic braking scheme is the only magnetic braking prescription capable of reproducing an entire sample of well-studied persistent LMXBs—those with mass ratios, periods, and mass transfer rates that have been observationally determined. Using the reverse population synthesis technique, where we follow any simulated system that successfully reproduces an observed LMXB backward, we have constrained possible progenitors for each observed well-studied persistent LMXB. We also determined that the minimum number of LMXB formations in the Milky Way is 1500 per Gyr if we exclude Cyg X-2. For Cyg X-2, the most likely formation rate is 9000 LMXB Gyr−1. The technique we describe can be applied to any observed LMXB with well-constrained mass ratio, period, and mass transfer rate. With the upcoming GAIA DR3 containing information on binary systems, this technique can be applied to the data release to search for progenitors of observed persistent LMXBs.

Brownian Motion

2018 ◽  
pp. 1-24
Author(s):  
Giovanni Zocchi
Keyword(s):  
Brownian Motion ◽  
Statistical Mechanics ◽  
Concentration Gradient ◽  
Nonequilibrium Statistical Mechanics ◽  
Thermal Fluctuations ◽  
Nonequilibrium System ◽  
Individual Particle ◽  
Equilibrium Concept ◽  
Self Diffusion ◽  
Main Ideas

This chapter provides an introduction to the main ideas of Brownian motion. Brownian motion connects equilibrium and nonequilibrium statistical mechanics. It connects diffusion—a nonequilibrium phenomenon—with thermal fluctuations—an equilibrium concept. More precisely, diffusion with a net flow of particles, driven by a concentration gradient, pertains to a nonequilibrium system, since there is a net current. Without a concentration gradient, the system is macroscopically in equilibrium, but each individual particle undergoes self-diffusion just the same. In this sense, Brownian motion is at the border of equilibrium and nonequilibrium statistical mechanics.

scholarly journals Highly Saline Water Desalination Using Direct Contact Membrane Distillation (DCMD): Experimental and Simulation Study

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1575 ◽  
Author(s):  
Noor A. Mohammad Ameen ◽  
Salah S. Ibrahim ◽  
Qusay F. Alsalhy ◽  
Alberto Figoli
Keyword(s):  
Mass Transfer ◽  
Direct Contact ◽  
Saline Water ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Water Desalination ◽  
System Of Nonlinear Equations ◽  
Transfer Model ◽  
Transfer Resistance ◽  
Direct Contact Membrane Distillation

The path for water molecules transported across a membrane in real porous membranes has been considered to be a constant factor in the membrane distillation (MD) process (i.e., constant tortuosity); as such, its effect on membrane performance at various operating conditions has been ignored by researchers. Therefore, a simultaneous heat and mass transfer model throughout the direct contact membrane distillation (DCMD) module was developed in this study by taking into account the hypothetical path across the membrane as a variable factor within the operating conditions because it exhibits the changes to the mass transfer resistance across the membrane under the DCMD run. The DCMD process was described by the developed model using a system of nonlinear equations and solved numerically by MATLAB software. The performance of the poly-tetra-fluoroethylene (PTFE) membrane was examined to treat 200 g/L NaCl saline at various operating conditions. The simulation results in the present work showed that the hypothetical proposed path across the membrane has a variable value and was affected by changing the feed temperature and feed concentration. The results estimated by the developed model showed an excellent conformity with the experimental results. The salt rejection remained high (greater than 99.9%) in all cases. The temperature polarization coefficient for the DCMD ranged between 0.88 and 0.967, and the gain output ratio (GOR) was 0.893. The maximum thermal efficiency of the system was 84.5%.

scholarly journals Super-Eddington Accretion in the Formation of Low-Mass X-ray Binaries and Millisecond Pulsars

1997 ◽  
Vol 163 ◽  
pp. 828-829 ◽  
Author(s):  
R. F. Webbink ◽  
V. Kalogera
Keyword(s):  
Mass Transfer ◽  
Initial Phase ◽  
Transfer Rate ◽  
Birth Rate ◽  
Mass Transfer Rate ◽  
Millisecond Pulsars ◽  
X Ray ◽  
Low Mass ◽  
Orbital Periods ◽  
X Ray Binaries

AbstractConsiderations of donor star stability, age, and mass transfer rate show that low-mass X-ray binaries and binary millisecond pulsars with orbital periods longer than a few days must have survived an initial phase of super-Eddington mass transfer. We review the physical arguments leading to this conclusion, and examine its implications for the apparent discrepancy between the death rate for low-mass X-ray binaries and the birth rate of binary millisecond pulsars.

Sign in / Sign up

Export Citation Format

Share Document