Numerical Analysis of Heat and Mass Transfer From Horizontal Cylinders in Downward Flow of Air-Water Mist

1990 ◽  
Vol 112 (2) ◽  
pp. 472-478 ◽  
Author(s):  
T. Aihara ◽  
W.-S. Fu ◽  
Y. Suzuki
Keyword(s):  
Mass Transfer ◽  
Numerical Analysis ◽  
Size Distribution ◽  
Heat And Mass Transfer ◽  
Droplet Size ◽  
Droplet Size Distribution ◽  
Water Mist ◽  
Circular Cylinders ◽  
Two Phase ◽  
Downward Flow

A numerical analysis is made of heat and mass transfer from horizontal circular cylinders in a downward flow of air/water mist of polydisperse droplets, taking into account the far-upstream droplet size distribution and the blockage effect of the gas phase flow. The effects of the droplet size distribution, temperatures, and liquid-to-gas mass flow ratio upon the liquid film thickness and wall shear stress, velocity, and temperature of the air-water interface, two-phase Nusselt numbers, etc., are examined.

Water droplet condensation and evaporation in turbulent channel flow

2014 ◽  
Vol 749 ◽  
pp. 666-700 ◽  
Author(s):  
E. Russo ◽  
J. G. M. Kuerten ◽  
C. W. M. van der Geld ◽  
B. J. Geurts
Keyword(s):  
Mass Transfer ◽  
Nusselt Number ◽  
Size Distribution ◽  
Water Vapour ◽  
Channel Flow ◽  
Droplet Size ◽  
Droplet Size Distribution ◽  
Turbulent Channel Flow ◽  
Phase Changes ◽  
Cold Wall

AbstractWe propose a point-particle model for two-way coupling of water droplets dispersed in the turbulent flow of a carrier gas consisting of air and water vapour. We adopt an Euler–Lagrangian formulation based on conservation laws for the mass, momentum and energy of the continuous phase and on empirical correlations describing momentum, heat and mass transfer between the droplet phase and the carrier gas phase. An incompressible flow formulation is applied for direct numerical simulation of differentially heated turbulent channel flow. The two-way coupling is investigated in terms of its effects on mass and heat transfer characteristics and the resulting droplet size distribution. Compared to simulations without droplets or those with solid particles with the same size and specific heat as the water droplets, a significant increase in Nusselt number is found, arising from the additional phase changes. The Nusselt number increases with increasing ambient temperature and is almost independent of the heat flux applied to the walls of the channel. The time-averaged droplet size distribution displays a characteristic dependence on position expressing the combined effect of turbophoresis and phase changes in turbulent wall-bounded flow. In the statistically steady state that is reached after a long time, the resulting flow exhibits a mean motion of water vapour from the warm wall to the cold wall, where it condenses on average, followed by a net mean mass transfer of droplets from the cold wall to the warm wall.

scholarly journals Dinamika tetes dalam kolom isian

2018 ◽  
Vol 7 (1) ◽  
pp. 710
Author(s):  
Danu Ariono ◽  
Dwiwahju Sasongko ◽  
Priyono Kusumo
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Size Distribution ◽  
Droplet Size ◽  
Droplet Diameter ◽  
Mass Transfer Rate ◽  
Packed Column ◽  
Droplet Size Distribution ◽  
Droplet Dynamics

To date, evaluation of the performance of liquid-liquid extraction in packed columns has not been able to produce satisfactory results, because the correlations used in this evaluation are empirical in nature, with a very limited range of validity. One of the causes of this limitation is the use of the assumption that the dynamics of liquid dispersed in droplets is constant (in terms of shape, dimensions, and numbers), so that the mass transfer interfacial area and mass transfer coefficient in the column are assumed to be constant. In reality, dynamics of droplets in a column is not constant, due to the imbalance between droplet coalescence and disintegration. For a given droplet diameter, there is an increase in numbers of droplets due to coalescence of smaller droplets, and a  decrease in numbers of droplets due to disintegration into smaller droplets. These coalescence and disintegration phenomena may be caused by various factors, including the existence of packings which impede the flow of droplets. These phenomena impact the mass transfer rate from continuous to dispersed phase, and vice versa, due to a variation in the interfacial contact area and mass transfer coefficient. The observation of droplet dynamics from droplet formation until its motion through void spaces between packings is a critical factor in developing a model that can describe the performance of the packed column. The dynamics of droplets is influenced by various operational and physical variables.  A droplet dynamics experiment has been undertaken, aimed at obtaining the droplet size distribution at specific heights along the column. This distribution is to be used to develop mass transfer coefficient correlations in the continuous and dispersed phases.Keywords: droplet size distribution, packed column Abstrak Evaluasi unjuk kerja ekstraksi cair-cair dalam kolom isian (packed column) hingga saat ini belum dapat memberikan hasil yang memuaskan karena korelasi-korelasi yang  digunakan  masih  bersifat  empiris serta daerah keberlakuannya sangat terbatas. Salah satu penyebab keterbatasan berlakunya korelasi tersebut ialah penggunaan anggapan bahwa dinamika cairan yang terdispersi dalam bentuk tetesan bersifat konstan (bentuk, ukuran serta jumlahnya), sehingga harga luas perpindahan massa dan harga koefisien perpindahan massa dalam kolom dianggap tetap. Kenyataannya dinamika tetesan dalam kolom tidak konstan akibat adanya tetesan yang bergabung dan pecah dalam jumlah yang  tidak sama. Pada suatu harga diameter tetesan tertentu, ada penambahan jumlah tetesan akibat penggabungan tetesan­ tetesan yang ukurannya lebih kecil serta adanya pengurangan jumlah tetesan akibat pecahnya tetesan menjadi tetesan-tetesan yang lebih kecil. Peristiwa penggabungan dan pemecahan tetesan dapat disebabkan berbagai faktor temasuk adanya isian yang menghalangi gerakan tetesan. Kejadian tersebut akan mempengaruhi laju proses perpindahan massa dari fasa kontinyu ke fasa  terdispersi  atau sebaliknya, karena adanya variasi luas permukaan kontak serta koefisien perpindahan massanya. Pengamatan dinamika tetesan mulai saat pembentukan tetes hingga pergerakannya saat melewati sela-sela isian merupakan faktor penting dalam  membangun model  yang  dapat menggambarkan unjuk kerja kolom isian. Dinamika tetesan tersebut dipengaruhi oleh berbagai variabel operasi dan variabel fisik. Eksperimen dinamika fetes yang dilakukan diarahkan untuk memperoleh distribusi ukuran tetes pada posisi ketinggian tertentu dan distribusi tersebut akan digunakan untuk pengembangan  korelasi koefisien perpindahan massa difasa  dispersi danfasa kontinyu.Kata kunci: distribusi ukuran tetes, kolom isian.

Study on atomization particle size characteristics of two-phase flow nozzle

2021 ◽  
pp. 1-12
Author(s):  
Haoqi Lilan ◽  
Junbin Qian ◽  
Nan Pan
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Droplet Size ◽  
High Speed ◽  
Droplet Size Distribution ◽  
Average Diameter ◽  
Spray Atomization ◽  
Two Phase ◽  
Nozzle Pressure ◽  
Local Observation

Nozzle spray atomization is widely used in industrial and agricultural production processes and is a very complicated physical change. The spray atomization of the nozzle is a process in which the droplets are continuously broken into finer particles under the action of force, in order to study the effect of nozzle atomization, that is, droplet size distribution characteristics. The experimental average mathematical model of droplet size distribution was established by introducing the average diameter of Sutter (SMD). The droplet size distribution in the atomization field of the nozzle is studied by simulation. In the experimental study, the high-speed camera, external mixing air atomizing nozzle platform experimental device and image processing were used, and the atomization field was divided into multiple observation areas. Through the measurement of several local observation areas, the droplet size distribution of the whole atomization field is constructed. It provides a reference for the study of the atomization field of the nozzle and a basis for the intuitive understanding of the droplet size distribution in the atomization field of the nozzle. The effective atomization area of the nozzle atomization was selected to study the influence of the liquid flow rate, the liquid temperature and the nozzle pressure on the atomized particle size distribution of the externally mixed atomizing nozzle. The internal law is obtained, which provides a basis and reference for effectively controlling the atomization effect in the atomization field.

scholarly journals Numerical simulation of high-pressure gas atomization of two-phase flow: Effect of gas pressure on droplet size distribution

2019 ◽  
Vol 30 (11) ◽  
pp. 2726-2732 ◽  
Author(s):  
Kalpana Hanthanan Arachchilage ◽  
Majid Haghshenas ◽  
Sharon Park ◽  
Le Zhou ◽  
Yongho Sohn ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Size Distribution ◽  
Droplet Size ◽  
Droplet Size Distribution ◽  
Gas Pressure ◽  
Phase Flow ◽  
Gas Atomization ◽  
Two Phase ◽  
Flow Effect
Sign in / Sign up

Export Citation Format

Share Document