scholarly journals Numerical Investigation of Influence of Nanoparticles Presence on Water Vapor Condensation Process inside a Vertical Channel

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Mustapha Ait Hssain ◽  
Sara Armou ◽  
Kaoutar Zine-Dine ◽  
Rachid Mir ◽  
Youness El Hammami
Keyword(s):  
Water Vapor ◽  
Volume Fraction ◽  
Vertical Channel ◽  
Vapor Condensation ◽  
Film Condensation ◽  
Condensation Process ◽  
Cu Nanoparticles ◽  
Humid Air ◽  
Noncondensable Gas ◽  
Maximum Improvement

This paper is aimed at investigating the nanofluid film condensation by mixed convection in the presence of water vapor, Cu nanoparticles, and air treated as a noncondensable gas (NCG) on the inner walls of a vertical channel. In this simulation, the flow is laminar, stationary, two dimensional, and axisymmetric. The coupled governing equations for the liquid film with the nanoparticles and the mixture air-humid-nanoparticles are solved together using the finite volume method. Since the application of humid air condensation is one of the most applicable methods of phase change processes that is observed in different industrial fields such as heating, ventilation, and air conditioning (HVAC) or cooling systems, for this purpose, the influence of injecting a uniform volume fraction of nanoparticles on improving heat and mass transfer is determined as a function of the variation in relative humidity, velocity, temperature, pressure, and volume fraction of Cu nanoparticles at the channel inlet. The numerical results indicate that under the best conditions in the range of variation studied RH in = 100 % , Re in = 2000 , T in = 50 ° C , P in = 0.5     atm , and φ in = 0.1 % , the use of nanoparticles has a greater impact, and the maximum improvement in the condensation film thickness, the local Nusselt number, and the accumulated condensation rate has an effective ratio strictly greater than one compared with the case of pure humid air.

The Study on Flow Patterns of Condensation of Superheated Vapor in Nanochannels

2010 ◽  
Author(s):  
Hualing Zhang ◽  
Liu Chao
Keyword(s):  
Water Vapor ◽  
Flow Patterns ◽  
Vapor Condensation ◽  
Condensation Process ◽  
Vapor Flow ◽  
Bubble Flow ◽  
Superheated Water ◽  
Injection Flow ◽  
Two Phases ◽  
Solid Walls

The model of two phases of liquid and vapor flow and vapor condensation under the condition of exerted force was established in parallel nanochannel. Fluid was water molecular and the solid walls are composed of Pt atoms. The process of vapor condensation in nanochannel wall was simulated by molecular dynamic simulation. The different flow patterns of the condensation process of superheated water vapor, which mainly were annular flow, injection flow, slug flow, bubble flow and shrinking bubble flow, were observed under different conditions. For low pressure of water vapor, a new flow pattern which was named as fluctuation flow appeared during condensation process. The simulation results agreed very well with the experimental results provided by references.

scholarly journals Numerical Analysis of Laminar Convective Condensation with the Presence of Noncondensable Gas Flowing Downward in a Vertical Channel

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Mustapha Ait Hssain ◽  
Youness El Hammami ◽  
Rachid Mir ◽  
Sara Armou ◽  
Kaoutar Zine-Dine
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Relative Humidity ◽  
Liquid Film ◽  
Vertical Channel ◽  
Dimensionless Temperature ◽  
Condensation Process ◽  
Inlet Temperature ◽  
Mixture Flow ◽  
Noncondensable Gas

The purpose of this paper is to study and perform a numerical analysis of the simultaneous processes of mass and heat transfer during the condensation process of a steam in the existence of noncondensable gas (NCG) inside a descending vertical channel. In this study, the flow of the vapor-air mixture is laminar and the saturation conditions are prevailing at the inlet of the channel. The coupled control equations for liquid film, interfacial conditions, and mixture flow are solved together using the approach of finite volume. Detailed and valuable results are presented both in the liquid condensate film and in the mixing regions. These detailed results contain the dimensionless velocity and dimensionless temperature profiles in both phases, the dimensionless mass fraction of vapor, the axial variation of the dimensionless thickness of the film liquid δ⁎, and the accumulated condensate rate Mr as well the local Nusselt number Nuy. The relative humidity at the inlet varies from 60% to 100% and the inlet temperature from 40°C to 80°C. The results confirm that a decrease in the mass concentration of NCG by the increasing the inlet relative humidity has a direct influence on the liquid film layer, the local number of Nusselt, and the variation of condensation rate accumulated through the channel. The results also designate that an increase of the inlet relative humidity and the inlet temperature ameliorates the condensation process. The comparison made for the coefficient of heat transfer due to condensation process and the condensate liquid film thickness with the literature results is in good concordance which gives more credibility to our calculation model.

Numerical Investigation of Laminar Filmwise Condensation of Water Vapor in Horizontal Tube With VOF Method in the Presence of Air

2014 ◽  
Author(s):  
Zhan Yin ◽  
Jianjun Wen ◽  
Min Zeng ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Horizontal Tube ◽  
Vof Method ◽  
Film Condensation ◽  
Interface Temperature ◽  
Condensation Process ◽  
Laminar Film Condensation

A steady three-dimensional numerical simulation of laminar film condensation of vapor in the presence of air inside a 1 mm horizontal tube is presented. The volume of fluid (VOF) method is used to capture the liquid-vapor interface with a phase change model. According to a generally accepted flow regime map, annular flow pattern is to be expected. Uniform wall temperature and interface temperature are assumed to be boundary condition. The influence of gravity is obvious while the effect of surface tension is neglected. At inlet, the liquid film is thin and evenly distributed around tube wall. Moving downstream the tube, film at the bottom half becomes thicker under the influence of gravity, while film on upper half remains almost constant. Correspondingly, local heat transfer coefficient on bottom half declines gradually and global average heat transfer coefficient shows little difference along axial direction. Existence of air makes heat transfer coefficient decrease sharply compared with that of pure vapor condensation, caused by an existed air layer which increases the thermal resistance during condensation process. As inlet volume fraction of air increases from 0.5% to 3%, the decline trend of heat transfer coefficient slows down.

Free Convection Film Condensation of Steam in the Presence of Non-Condensing Gases Using CFD Based Approach in a Room Filled With Humid Air

2014 ◽  
Author(s):  
Aliihsan Koca ◽  
Sevket Ozgur Atayilmaz ◽  
Ozden Agra
Keyword(s):  
Relative Humidity ◽  
Film Condensation ◽  
Condensation Process ◽  
Condensation Rate ◽  
Humid Climate ◽  
Humid Air ◽  
Ansys Fluent ◽  
Mass Fluxes ◽  
Mass Fractions ◽  
New System

In this paper, transient natural convection combined heat and mass transfer in enclosures filled with humid air, including condensation to the walls, which are subjected to time varying prescribed temperatures, was studied numerically. Ansys Fluent CFD code implemented to the model for wall condensation from a vapor and non-condensable gas mixture. User-Defined Function (UDF) has been used to predict the condensation rate for a mixture of air and water vapor flowing past a cooled surface. The effect of the condensation process on the flow and species distribution in the vapor phase is incorporated into the flow calculations through a customized source term applied in wall-adjacent cells. The condensation phenomenon is modeled from first principles as sink terms for the mass, momentum, species and energy conservation equations. The condensation rate is obtained by requiring the condensate–gas interface to be impermeable to the non-condensable gas. The Computational Fluid Dynamics (CFD) program was used to calculate the value of condensation rates, latent and sensible heat transfer rates as well as the relative humidity rates and mass fractions of species. In the study, the effects of different initial relative humidity ratios and the characteristic lengths of the condensation plate on the condensation mass fluxes were studied. The results indicated that the new system could reduce the risk of condensation on the cooling panels and provide a more comfortable indoor environment. The new system has a great potential for use in hot and humid climate regions with radiant cooling systems.

Effects of Heterogeneous Nucleation of Water Vapor in Nozzles

1970 ◽  
Vol 92 (4) ◽  
pp. 689-694 ◽  
Author(s):  
A. A. Pouring
Keyword(s):  
Water Vapor ◽  
Heterogeneous Nucleation ◽  
Laval Nozzle ◽  
Vapor Condensation ◽  
Condensation Process ◽  
Particle Sizes ◽  
Metallic Ions ◽  
De Laval Nozzle ◽  
Quantitative Results ◽  
Competitive Nature

Condensation initiated by heterogeneous nucleation, which is surface dependent, is examined experimentally for the case of rapid nozzle expansions of water vapor. In contrast to previous de Laval nozzle steam experiments for vapor condensation initiated by homogeneous nucleation, the present results are for flows seeded with inorganic smoke and metallic ions. The influence of heterogeneous seeding materials on the condensation process is readily observable by comparison of seeded and unseeded experiments which are otherwise identical. Quantitative results for temperature and other properties, as well as condensation rates, follow based on pressure distribution. The results indicate that the prolonged isentropic expansion of a seeded flow gives a substantial decrease in entropy production for 1/10 micron and below particle sizes determined by electron microscopy. An attempt is made at determining the relative influence of ions and smokes. The competitive nature between heterogeneous and homogeneous processes is clearly evident.

Condensation of water vapor in a vertical channel by mixed convection of humid air in the presence of a liquid film flowing down

Desalination ◽  
2007 ◽  
Vol 204 (1-3) ◽  
pp. 471-481 ◽  
Author(s):  
A. Belhadj Mohamed ◽  
J. Orfi ◽  
C. Debissi ◽  
S. Ben Nasrallah
Keyword(s):  
Water Vapor ◽  
Mixed Convection ◽  
Liquid Film ◽  
Vertical Channel ◽  
Humid Air

scholarly journals An Experimental Investigation of Water Vapor Condensation from Biofuel Flue Gas in a Model of Condenser, (1) Base Case: Local Heat Transfer without Water Injection

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 844
Author(s):  
Robertas Poškas ◽  
Arūnas Sirvydas ◽  
Vladislavas Kulkovas ◽  
Povilas Poškas
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Flue Gas ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Water Injection ◽  
Vapor Condensation ◽  
Base Case ◽  
Water Vapor Condensation ◽  
Condensing Heat Exchanger

Waste heat recovery from flue gas based on water vapor condensation is an important issue as the waste heat recovery significantly increases the efficiency of the thermal power units. General principles for designing of this type of heat exchangers are known rather well; however, investigations of the local characteristics necessary for the optimization of those heat exchangers are very limited. Investigations of water vapor condensation from biofuel flue gas in the model of a vertical condensing heat exchanger were performed without and with water injection into a calorimetric tube. During the base-case investigations, no water was injected into the calorimetric tube. The results showed that the humidity and the temperature of inlet flue gas have a significant effect on the local and average heat transfer. For some regimes, the initial part of the condensing heat exchanger was not effective in terms of heat transfer because there the flue gas was cooled by convection until its temperature reached the dew point temperature. The results also showed that, at higher Reynolds numbers, there was an increase in the length of the convection prevailing region. After that region, a sudden increase was observed in heat transfer due to water vapor condensation.

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