Considerations about mass and energy flow in discontinuous evaporating crystallizers

2016 ◽  
pp. 514-516
Author(s):  
Martin Bruhns
Keyword(s):  
Energy Flow ◽  
Static Pressure ◽  
Bubble Formation ◽  
Boiling Temperature ◽  
Vapor Bubbles ◽  
Local Pressure ◽  
Heating Steam ◽  
Flow Changes ◽  
Local Superheating ◽  
Local Supersaturation

The massecuite circulates in a loop within the evaporating crystallizing vessel. The massecuite flows upwards through the heating tubes. In the room above the calandria the massecuite flow changes its direction to radial inwards and then to vertical downwards. An impeller in the central tube forces the circulation. Below the calandria the main direction of flow is radially outwards until threads of the massecuite stream enter the heating tubes in upwards direction. Within the tubes heat is transferred to the massecuite. At low temperature differences between heating steam and massecuite and higher levels of the massecuite in the crystallizer vapor bubbles are not found in the tubes. Vapor bubbles can be formed at a massecuite level in the crystallizer where the temperature of the massecuite is higher than the local boiling temperature of water, which depends on the local pressure (including the static pressure of the massecuite at this point) and the boiling point elevation of the mother liquor. The surface tension of the liquid is a resistance against the bubble formation, which has to be overcome by the local superheating i.e. the part of the enthalpy of the massecuite exceeding the local boiling temperature. The formation and the flow of the bubbles change the density of the massecuite/bubbles mixture and has an influence on the massecuite flow. The formation of a vapour bubble is connected with a local drop of the massecuite temperature which changes the local supersaturation. Today the heat transfer into the magma is quite well known but the process of bubble formation is quite unknown. Some basic considerations about the formation of bubbles and its influence on local supersaturation based on calculation of heat and mass balances and models of bubble formation are be given and discussed. Experiments for basic investigations are proposed.

Energetic Asymmetry Connected with Energy Flow Changes in Response to Eutrophication: A Study of Multiple Fish Species in Subtropical Shallow Lakes

2020 ◽  
Vol 67 (4) ◽  
pp. 305
Author(s):  
Hong Fu ◽  
Huan Zhang ◽  
Liang He ◽  
Yongcui Sha ◽  
Kangshun Zhao ◽  
...  
Keyword(s):  
Fish Species ◽  
Shallow Lakes ◽  
Energy Flow ◽  
Flow Changes

scholarly journals Numerical simulation of superheated jets using an Eulerian method.

2017 ◽  
Author(s):  
Konstantinos Lyras ◽  
Siaka Dembele ◽  
C. Madhav Rao Vendra ◽  
Jennifer Wen
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Bubble Formation ◽  
Ambient Conditions ◽  
Local Pressure ◽  
Two Phase ◽  
Rapid Phase ◽  
Droplet Sizes ◽  
Flash Boiling ◽  
Fully Eulerian Approach

Flash boiling is the rapid phase change of a pressurised fluid that emerges in ambient conditions below its vapourpressure. Flashing can occur either inside or outside the nozzle depending on the local pressure and geometry and the bubble formation leads to interfacial interactions that eventually influence the emerging spray. Lagrangian methods which exist in literature to simulate the flash atomisation and inter-phase heat transfer employ many sim- plifying assumptions. Typically, sub-models used for the break-up, collisions and evaporation introduce an extensive empiricism that might result in unrealistic predictions for cases like flashing. In this study, a fully Eulerian approach is selected employing the Σ − Y model proposed by Vallet and Borghi. The model tracks liquid structures of any shape and computes the spray characteristics comprising a modified version for the transport equation of the sur- face density. The main goal of this study is to investigate the performance of this model in flash boiling liquids using the Homogeneous Relaxation Model (HRM) developed by Downar-Zapolski, a model capable of capturing the heat transfer under sudden depressurisation conditions accounting for the non-equilibrium vapour generation. The model in this present study considers that the instantaneous quality would relax to the equilibrium value over a given timescale which is calculated using the flow field values. A segregated approach linking the HRM and Σ − Y is implemented in a compressible formulation in an attempt to quantify the effects of flash boiling in the spray dynamics. The developed model is naturally implemented in RANS in a dedicated solver HRMSonicELSAFoam. Results from simulations of two-phase jets of different subcooled fluids through sharp-edged orifices show that the proposed approach can accurately simulate the primary atomisation and give reliable predictions for the droplet sizes and distribution. Strong effects of the flashing and turbulent mixing on the jet are demonstrated. The model istested for turbulent flows within small nozzles and was developed within the open source code OpenFOAM.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4667

Application of Minute-Bubble Technique to Reactive Crystallization of Hydroxyapatite

2014 ◽  
Vol 625 ◽  
pp. 217-222 ◽  
Author(s):  
Yoshinari Wada ◽  
Hiroaki Takahari ◽  
Hiroaki Tamai ◽  
Masakazu Matsumoto ◽  
Kaoru Onoe
Keyword(s):  
Residence Time ◽  
Main Product ◽  
Bubble Formation ◽  
Concentration Field ◽  
Interfacial Area ◽  
Liquid System ◽  
Bulk Liquid ◽  
Reactive Absorption ◽  
Reactive Crystallization ◽  
Local Supersaturation

Minimizing bubble formation in gas-liquid system helps achieve the following: i) acceleration of mass transfer and reactive absorption with an increase in the gas-liquid interfacial area, ii) increase in the average residence time of the bubbles with a decrease in buoyancy, and iii) occurrence of interactions at the gas-liquid interface1,2). Thus, by increasing the residence time of bubbles in the liquid phase, a quasi-homogeneous gas-liquid system can be obtained. Furthermore, attention is focused around minute-bubble interface which is higher concentration field compared with bulk liquid, an increase in the yield of main product can be achieved by the variations in the local supersaturation, which acts as the driving force for crystallization.

Bubble Formation at Impingement of a Liquid Droplet on a Solid Surface

2000 ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Tomoyuki Ogino ◽  
Osamu Takahashi ◽  
Hirohiko Takuda ◽  
Natsuo Hatta
Keyword(s):  
Solid Surface ◽  
Liquid Droplet ◽  
Droplet Diameter ◽  
Bubble Formation ◽  
Liquid Droplets ◽  
Vapor Bubbles ◽  
Experimental Conditions ◽  
Video Cameras ◽  
The Moment ◽  
The Impact

Abstract The collision of liquid droplets with a solid has been studied experimentally. The time evolution of the liquid/solid contact area as well as the shape of droplets has been observed by means of a flash-photographic method using two video cameras. It has been found that some air between the solid surface and the incoming droplet is entrapped at the moment of impact. In the case where the solid temperature is high (= 450 °C), numerous vapor bubbles appear at the liquid/solid interface after the collision. The bubble formation due to the entrapment of air has been examined for various experimental conditions. Water, and ethanol are used as test liquid. The droplet diameter is 2.4 mm for water and 1.9 mm for ethanol. The impact velocity varies from 0.8 to 3.1 m/s. The entrapment of air has been observed for both liquids under all conditions in the present study.

MHD simulations of cold bubble formation from 2/1 tearing mode during massive gas injection in a tokamak

2021 ◽  
Author(s):  
Shiyong Zeng ◽  
Ping Zhu ◽  
Valerie A Izzo ◽  
Haolong Li ◽  
Zhonghe Jiang
Keyword(s):  
Cold Front ◽  
Causal Relation ◽  
Bubble Formation ◽  
Gas Injection ◽  
Mode Number ◽  
Temperature Structure ◽  
Tearing Mode ◽  
Local Pressure ◽  
Bubble Structure ◽  
Impurity Ion

Abstract Massive gas injection (MGI) experiments have been carried out in many tokamaks to study disruption dynamics and mitigation schemes. Two events often observed in those experiments are the excitation of the m = 2, n = 1 magnetohydrodynamic (MHD) mode, and the formation of cold bubble structure in the temperature distribution before the thermal quench (TQ). Here m is the poloidal mode number, n the toroidal mode number. The physics mechanisms underlying those phenomena, however, have not been entirely clear. In this work, our recent NIMROD simulations of the MGI process in a tokamak have reproduced the main features of both events, which has allowed us to examine and establish the causal relation between them. In these simulations, the 3/1 and 2/1 islands are found to form successively after the arrival of impurity ion cold front at the corresponding q = 3 and q = 2 rational surfaces. At the interface between impurity and plasma, a local thin current sheet forms due to an enhanced local pressure gradient and moves inward following the gas cold front, this may contribute to the formation of a dominant 2/1 mode. Following the growth of the 2/1 tearing mode, the impurity penetration into the core region inside the q = 2 surface gives rise to the formation of the cold bubble temperature structure and initiates the final TQ. A subdominant 1/1 mode developed earlier near the q = 1 surface alone does not cause such a cold bubble formation, however, the exact manner of the preceding impurity penetration depends on the nature of the 1/1 mode: kink-tearing or quasi-interchange.

Measurement of Cloud Perturbation Pressures Using an Instrumented Aircraft

2013 ◽  
Vol 30 (2) ◽  
pp. 215-229 ◽  
Author(s):  
Thomas R. Parish ◽  
David Leon
Keyword(s):  
Static Pressure ◽  
Pressure Field ◽  
Base Station ◽  
Cloud Formation ◽  
Cloud Base ◽  
High Plains ◽  
Local Pressure ◽  
Convective Clouds ◽  
Horizontal Pressure ◽  
Pressure Perturbations

Abstract Vertical accelerations during the early stages of convective cloud formation are often the result of buoyancy and the perturbation vertical pressure gradient forces. Convection modifies the local pressure field surrounding the cloud. Measurement of the cloud perturbation pressure field is challenging over distance scales on the order of the convective elements, since the signals are often small and the turbulent environment complicates the measurement of static pressure. A technique is described that enables detection of the horizontal pressure perturbations associated with evolving convective clouds using global positioning system measurements on an airborne platform. Differential kinematic processing of data from dual-frequency, carrier-phase-tracking GPS receivers on research aircraft with static base station receivers enables the three-dimensional aircraft position to be resolved within decimeters. Vertical positioning and precise measurement of static pressure allow horizontal pressure perturbations to be determined to an accuracy of roughly 10 Pa. Errors in the static pressure measurement, rather than the GPS-derived altitude, are the largest source of error. A field experiment was conducted in May–June 2008 to demonstrate measurement of perturbations in the horizontal pressure field associated with summertime cumulus congestus clouds over the high plains. Observations of growing convective clouds show negative pressure perturbations on the order of 100 Pa near cloud base linked to updraft regions. Growing cumulus show a high degree of variability between subsequent passes that demonstrate that the horizontal pressure fields evolve rapidly along with attendant vertical circulations and cloud microphysical characteristics.

Pressure gradient induced generation of microbubbles

2015 ◽  
Vol 778 ◽  
pp. 653-668 ◽  
Author(s):  
A. Evangelio ◽  
F. Campo-Cortés ◽  
J. M. Gordillo
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Rate Ratio ◽  
Bubble Formation ◽  
Reynolds Numbers ◽  
Flow Rate Ratio ◽  
Physical Situation ◽  
Pressure Gradients ◽  
Local Pressure ◽  
Physical Description

We provide a detailed physical description of the bubble formation processes taking place in a type of flow where the liquid pressure gradient can be straightforwardly controlled. The analysis, which is supported by an exhaustive experimental study in which the liquid viscosity is varied by three orders of magnitude, provides closed expressions for both the bubbling frequencies and the bubble diameters. Different equations are obtained depending on the values of the three dimensionless parameters characterizing this physical situation, namely the Weber and Reynolds numbers and the gas to liquid flow rate ratio. Since both the inertia dominated and viscous dominated bubbling regimes are simply described in terms of the local pressure gradient and the flow rate ratio, the same types of ideas can be applied in the design of bubble makers in which the pressure gradients are controlled in completely different ways.

scholarly journals Coupling Model of Energy Flow and Material Flow in SKS Lead Smelting

2014 ◽  
Vol 8 (1) ◽  
pp. 131-135
Author(s):  
Hongcai Wang ◽  
Zhangming Shi ◽  
Liufang Lin ◽  
Bo Chen
Keyword(s):  
Mathematical Model ◽  
Material Flow ◽  
Energy Flow ◽  
Optimization Problems ◽  
Coupling Model ◽  
Flow Angle ◽  
Energy Saving Potential ◽  
Lead Smelting ◽  
Flow Changes ◽  
The Mathematical Model

This paper studied the coupling model of material flow and energy flow in the production process of lead smelting enterprises, and established the mathematical model for material flow and energy flow to resolve optimization problems. From the point of energy flow, the paper analyzed three kinds of energy flow changes which have an effect on the enterprise products. Through calculation and analysis, it has been found that there is 38.42% energy-saving potential in this enterprise. Separately from the material flow and energy flow angle, the paper put forward five aspects suggestions to reduce the energy consumption of the enterprise products.

Inert gas transport in the microcirculation: risk of isobaric supersaturation

1979 ◽  
Vol 46 (6) ◽  
pp. 1157-1163 ◽  
Author(s):  
R. S. Tepper ◽  
E. N. Lightfoot ◽  
A. Baz ◽  
E. H. Lanphier
Keyword(s):  
Gas Transport ◽  
Bubble Formation ◽  
Diagnostic Procedures ◽  
Inert Gas ◽  
Transport Models ◽  
Theoretical Approaches ◽  
Diffusion Limited ◽  
Order Of Magnitude ◽  
Potential Benefits ◽  
Local Supersaturation

This paper is concerned with the theretical background and implications of isobaric supersaturation and bubble formation in the microcirculation following an abrupt shift from one inspired inert gas to another. The use of more than one inert gas, simultaneously or sequentially, has become common in diving and presents risks as well as potential benefits. A review of microcirculatory model useds, theoretical approaches to decompression, and order of magnitude calculations indicates that present empiricisms are inadequate for predicting such supersaturation phenomena. This is true whether based on the familiar assumption of perfusion-limited behavior or its diffusion-limited counterpart. The “chromatographic” model used here, which considers both perfusion and axial diffusion in tissue cylinders, shows that these combined effects can produce unexpectedly high local supersaturation. The implications include new possibilities for the experimental evaluation of gas transport models as well as practical risks of inert gas shifts in diving and certain diagnostic procedures.

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