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Tuesday, July 21, 2020 | History

2 edition of Precoalescence droplet growth in dropwise condensation. found in the catalog.

Precoalescence droplet growth in dropwise condensation.

Basoor Thammaiah Nijaguna

Precoalescence droplet growth in dropwise condensation.

by Basoor Thammaiah Nijaguna

  • 2 Want to read
  • 13 Currently reading

Published in [Toronto] .
Written in English

    Subjects:
  • Condensation,
  • Thermodynamics

  • Edition Notes

    ContributionsToronto, Ont. University.
    The Physical Object
    Pagination1 v. (various pagings)
    ID Numbers
    Open LibraryOL18883851M

    MACROSCOPIC GROWTH MECHANISMS IN DROPWISE CONDENSATION R. L. Reisbig pages DOI: /IHTC $ THE EFFECT OF SURFACE THERMAL PROPERTIES ON DROPWISE CONDENSATION J. S. Horowitz, Borivoje B. Mikic pages DOI: /IHTC $ PRECOALESCENCE DROP GROWTH RATES IN DROPWISE CONDENSATION .   Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of.

    During condensation, the droplet size grows linearly with time as V ∝ t, and the coalescence between small droplets can affect the resultant wetting mode of large droplets. The results indicate that the cooperation between spatially ordering nucleation and dropwise growth endows hybrid nanopillar surfaces with better heat and mass transfer. Dropwise condensation is not possible in the condensing regions of capillary driven heat pipes because the fluid must be able to wet the heat pipe wick surface. Implementing dropwise condensation in orientation insensitive heat pipes is not straight forward as dropwise condensation only occurs on non-wetting surfaces.

    been attained, the process begins again from initial drop growth at specific nucleation sites. This constant cycle ranging from drop formation to drop departure deems dropwise condensation a quasi-cyclic process. Furthermore, research suggests that a higher frequency of the cycle leads to a higher heat transfer rate []. Dropwise Condensation on Hydrophobic Microporous Powder and the Transition to Intrapowder Droplet Removal Sean Hoenig and Richard W. Bonner, III, 3rd Thermal and Fluids Engineering Conference (TFEC), Fort Lauderdale, FL, March ,


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Precoalescence droplet growth in dropwise condensation by Basoor Thammaiah Nijaguna Download PDF EPUB FB2

Dropwise condensation is a phenomenon of common occurrence in everyday life, the understanding and controlling of which is of great interest to applications ranging from technology to nature.

Scalable superhydrophobic textures on metals are of direct relevance in improving phase change heat transport in realistic industrial applications. Here we reveal important facets of individual droplet Cited by: Most of the theoretical studies in dropwise condensation have based their analysis on the principle that the heat transfer rate limiting mechanism in latent heat of condensation.

drop growth constant. Nusselt number. Nijaguna, B. T., Precoalescence Droplet Growth in Dropwise Condensation, Ph.D. Thesis, Dept. Mech. Engg., Univ. of Cited by: 4. Droplet Growth by Condensation It was shown before that a critical size r and saturation ratio S must be ex-ceeded for a small solution droplet to become a cloud droplet.

Before the droplet reaches the critical size, it grows by diffusion of water molecules from the vapor onto its surface. The rate of diffusional growth of a single droplet File Size: KB. W. Westwater, Drop dynamics and heat transfer during dropwise condensation of water vapor on a horizontal surface.

Chem. Engnci. Proa. S(). Nijaguna and A. Abdelmessih. Precoalescence drop growth model for dropwise condensation: in- fluence of condensing surface properties on precoale- scence drop by:   The droplet growth processes during dropwise condensation are simulated with the help of computer.

We focus on instantaneous and time-averaged characteristics of droplet size distributions. Based on the simulation results, the shift of a single peak from a small to a large size represents a significant characteristic for the instantaneous Author: Maofei Mei, Feng Hu, Chong Han, Yan Sun, Dongdong Liu.

The critical aspects in dropwise condensation considering NCG include the coupled heat and mass transfer during droplet growth, the multi-scale feature of droplet.

Dropwise condensation yields higher heat transfer coefficients by avoiding the thermal resistance of the condensate film, seen during filmwise condensation.

This work explores further enhancement of dropwise condensation heat transfer through the use of electrowetting to achieve faster droplet growth via coalescence of the condensed droplets.

A single droplet model is developed to describe the droplet growth during dropwise condensation of moist air on a cold substrate. The condensation process is divided by the droplet surface into.

Dropwise condensation caused by interfacial effects plays a crucial role in the thermal effciency and integration of power production. It is important to understand the effect of droplet dyanmic characteristics on heat transfer perfromace for the controlling mechanism of dropwise condensation heat transfer at low steam pressure and the development of efficient heat.

Heat transfer equations for condensation growth of single droplet. A heat transfer model for condensation growth of a single droplet on the superhydrophobic surface has been developed.The model is a combination of all thermal resistances between the vapor and the condensing surface, including the vapor-liquid interfacial resistance, the liquid.

Miljkovic, R. Enright, and E. Wang, “ Effect of droplet morphology on growth dynamics and heat transfer during condensation on superhydrophobic nanostructured surfaces,” ACS Nano 6(2), – (). Knowledge of droplet growth rates during dropwise condensation is necessary for accurate predictions of heat transfer rates.

This includes both the heat transfer rate during droplet growth as well as following droplet sweeping—where large droplets sweep away other droplets on an inclined surface. Droplet growth rates on a given. Drop nucleation, growth, and condensation have important practical consequences.

Significantly, heat transfer rates in dropwise condensation can be much higher than in filmwise condensation. 2, 3 Thus dropwise condensation is often preferred to filmwise condensation in heat exchangers. 4, 5 The more general problem of liquid drops interactions.

For nonmetal vapors, dropwise condensation gives much higher heat transfer coefficients than those found with film condensation. For instance, the heat transfer coefficient for dropwise condensation of steam is around 10 times that for film condensation at power station condenser pressures and more than 20 times that for film condensation at.

The chapter on condensation covers most aspects of this topic of interest to the well informed condenser designer, starting from droplet nucleation, through accommodation coefficients, Nusselt's laminar film theories and so forth to dropwise condensation. The section on 'Pressure Drop in Condenser Tube Banks' seemed too superficial, but I write.

In particular, the model comprised of a droplet departure, and droplet distribution in which heat transferred occurred through a single droplet for different flow conditions.

They purposed to determine the heat transfer rates of single droplets and condensation surfaces and also develop various correlations to predict the dropwise condensation. Dropwise condensation is complex process, involving drop formation at the atomic scale, growth of drops by direct condensation, coalescence of drops, drop instability and movement, followed by fresh nucleation.

Hence, the dropwise condensation process is hierarchical in the sense that it occurs a wide range of length and timescales. atomic scale nucleation, progressing towards the growth of individual droplets, coalescence, and drop instability, thus closing the dropwise condensation cycle [].

Though the model is quite comprehensive, the drop-level treatment is simplified in the sense that its shape is determined by the 2-circle approximation.

Although microtextured superhydrophobic surfaces have shown advantageous droplet growth dynamics, precise heat transfer measurements are underdeveloped at high heat flux. Sintered copper powder diameters from 4 μ m to μ m were.

Controlling dropwise condensation is fundamental to water-harvesting systems 1,2,3, desalination 4, thermal power generation 4,5,6,7,8, air conditioning 9, distillation tow and numerous. The dropwise condensation of liquid droplets can frequently be described in terms of a four-stage scenario: (1) Nucleation and growth.

(2) Growth and coalescence. (3) Growth and coalescence with renucleation in exposed regions. (4) Growth, coalescence and renucleation with removal of larger droplets.When a droplet grows large enough to contact with adjacent droplets, they merge and speed up droplet growth, stabilizing the surface coverage to a constant value, known as the self-similarity in dropwise condensation [14, 15, 17, 33, 34].

On a vertical or inclined hydrophobic surface, condensed droplets are generally removed by the gravity.INTRODUCTION. Droplet nucleation and condensation are ubiquitous phenomena in nature and industry. Over the past century, research has shown that heat transfer rates during steam dropwise condensation on nonwetting (e.g., hydrophobic) surfaces can be 10× higher than widely accepted filmwise condensation on wetting substrates (1–4).However, the need for .