Role of Bouncing Potential in Molten Ash Impaction

doi:10.1080/00986445.2014.927358

Home
/
Papers
/
Role of Bouncing Potential in Molten Ash Impaction

Journal Article•DOI•

Role of Bouncing Potential in Molten Ash Impaction

Soundaravalli Balakrishnan¹, Rajarathinavelu Nagarajan¹•Institutions (1)

Indian Institute of Technology Madras¹

18 May 2015-Chemical Engineering Communications (Taylor & Francis)-Vol. 202, Iss: 10, pp 1360-1367

TL;DR: In this article, the authors developed a model to predict the outcome of a molten ash particle impacting a heat transfer surface, where the main driving force for a splat at maximum spread state to recoil is the difference in surface energies of the splat and its equilibrium sessile drop state.

read less

Abstract: The aim of the present study is to develop a model to predict the outcome of a molten ash particle impacting a heat-transfer surface. The main driving force for a splat at maximum spread state to recoil is the difference in surface energies of the splat and its equilibrium sessile drop state. If the difference in surface energies is significant, a vigorous recoiling then leads to rebounding. During the travel from splat to equilibrium state, the viscous dissipation in the rim opposes the recoiling process. By overcoming the dissipation loss, the splat reaches sessile drop state. If the drop possesses energy greater than the adhesion energy, it will detach itself from the surface; otherwise, it will deposit. A bouncing potential model based on this concept is derived and compared with models and experimental data in literature.

...read moreread less

Citations

PDF

Open Access

More filters

Journal Article•DOI•

Modeling of ash formation and deposition processes in coal and biomass fired boilers: A comprehensive review

[...]

Yongtie Cai¹, Kun Lin Tay¹, Zhimin Zheng¹, Wenming Yang¹, Hui Wang², Guang Zeng¹, Zhiwang Li¹, Siah Keng Boon, Prabakaran Subbaiah - Show less +5 more•Institutions (2)

National University of Singapore¹, Harbin Institute of Technology²

15 Nov 2018-Applied Energy

TL;DR: In this article, a comprehensive review on the development of the modelling of ash deposition with particle combustion, sticking, rebound and removal behaviors is presented, including the modeling of ash deposit morphomology.

...read moreread less

117 citations

Journal Article•DOI•

Mechanistic modeling, numerical simulation and validation of slag-layer growth in a coal-fired boiler

[...]

Soundaravalli Balakrishnan¹, Rajarathinavelu Nagarajan¹, K. Karthick²•Institutions (2)

Indian Institute of Technology Madras¹, Bharat Heavy Electricals²

01 Mar 2015-Energy

TL;DR: In this paper, a mechanistic bouncing potential model, incorporating the phenomenon of recoiling of molten ash droplets after impaction, is employed to determine the outcome of slag-layer impaction.

...read moreread less

34 citations

Journal Article•DOI•

Ultrasonic coal washing to leach alkali elements from coals.

[...]

Soundaravalli Balakrishnan¹, V. Midhun Reddy¹, Rajarathinavelu Nagarajan¹•Institutions (1)

Indian Institute of Technology Madras¹

01 Nov 2015-Ultrasonics Sonochemistry

TL;DR: Ulasonic water-washing and chemical-washing, in comparison with agitation, are studied in order to estimate the intensification of the alkali removal process by sonication.

...read moreread less

26 citations

Journal Article•DOI•

Mechanistic Model for Ash Deposit Formation in Biomass Suspension Firing. Part 1: Model Verification by Use of Entrained Flow Reactor Experiments

[...]

Stine Broholm Hansen, Peter Arendt Jensen, Flemming Frandsen, Bo Sander, Peter Glarborg - Show less +1 more

16 Mar 2017-Energy & Fuels

TL;DR: In this article, two models for deposit formation in suspension firing of biomass have been developed: model #1 employs a reference viscosity in the description of the sticking probability, while model #2 combines impaction of viscoelastic particles on a solid surface with particle capture by a viscous surface.

...read moreread less

Abstract: Two models for deposit formation in suspension firing of biomass have been developed. Both models describe deposit buildup by diffusion and subsequent condensation of vapors, thermophoresis of aerosols, convective diffusion of small particles, impaction of large particles, and reaction. The models differ in the description of the sticking probability of impacted particles: model #1 employs a reference viscosity in the description of the sticking probability, while model #2 combines impaction of viscoelastic particles on a solid surface with particle capture by a viscous surface. Both models were used to describe the deposit formation rates and deposit chemistry observed in a series of entrained flow reactor (EFR) experiments using straw and wood as fuels. It was found that model #1 was not able to describe the observed influence of temperature on the deposit buildup rates, predicting a much stronger influence of this parameter. Model #2 was able to provide a reasonable description of the influence of temp...

...read moreread less

21 citations

Journal Article•DOI•

Influence of Chemical Leaching on Rheology and Ash Reduction of Indian Coal

[...]

Puneet Juneja¹, Satish Kumar¹, Saroj Kumar Mohapatra¹•Institutions (1)

Thapar University¹

04 Jul 2018-International Journal of Coal Preparation and Utilization

TL;DR: The quality and calorific value of Indian coal are very low. as discussed by the authors The objective of the present study was to reduce the ash content and to produce ultraclean coal (UCC).

...read moreread less

Abstract: The quality and calorific value of Indian coal are very low. The objective of the present study was to reduce the ash content and to produce ultraclean coal (UCC). The low-ash-content coal was then...

...read moreread less

3 citations

References

PDF

Open Access

More filters

Journal Article•DOI•

Impact, recoil and splashing of molten metal droplets

[...]

S. D. Aziz¹, Sanjeev Chandra¹•Institutions (1)

University of Toronto¹

15 Aug 2000-International Journal of Heat and Mass Transfer

TL;DR: In this paper, the impact and solidification of molten tin droplets on a stainless steel surface was studied and a simple energy conservation model was used to predict the maximum spread of droplets during impact.

...read moreread less

390 citations

"Role of Bouncing Potential in Molte..." refers methods in this paper

...In order to prove the presence of rim at the edge of the splat at maximum spread stage, the image of tin droplet impacting the stainless steel surface at 240 C with velocity 2 m s 1 is documented by Aziz and Chandra (2000)....
[...]

Journal Article•DOI•

Normal impact of a liquid drop on a dry surface: model for spreading and receding

[...]

Ilia V. Roisman¹, Romain Rioboo¹, Cameron Tropea¹•Institutions (1)

Technische Universität Darmstadt¹

08 Jun 2002-Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences

TL;DR: In this paper, a strictly theoretical model is introduced, which predicts the evolution of the drop diameter by the motion of a rim appearing at the edge of the liquid film (lamella) due to the surface-tension forces.

...read moreread less

Abstract: The normal impact of a liquid drop on a dry solid surface is studied experimentally and theoretically. In this paper a strictly theoretical model is introduced, which predicts the evolution of the drop diameter. The spreading and receding phases of the impact are described by the motion of a rim appearing at the edge of the liquid film (lamella) due to the surface-tension forces. The mass and the momentum equations of the rim are considered, taking into account the effects of inertial, viscous and surface forces, and wettability. Also, simplified approximations for the maximum spreading diameter of the drop and for the velocity of the merging of the rim in the receding phase are obtained. The theoretical predictions agree well with available experimental data.

...read moreread less

384 citations

"Role of Bouncing Potential in Molte..." refers background or methods in this paper

...It can also be extended to derive the maximum spread diameter as explained by Roisman et al. (2002)....
[...]
...The thickness of the film (hf) is calculated by the expression derived by Roisman et al. (2002) (their Equation no. 3.14), and the initial height (ho) of the rim is determined from the volume balance by knowing the splat diameter....
[...]
...The mass and momentum balance of the rim in the radial direction at Ar are, respectively (Roisman et al., 2002):...
[...]
..., 2007; Kim and Chun, 2001), and boundary-layer approximation to model the flow in lamella (Pasandideh-Fard et al., 1996; Roisman et al., 2002)....
[...]
...The mass and momentum balance of the rim in the radial direction at Ar are, respectively (Roisman et al., 2002): dur dt ¼ 2pArhf Vl Vsð Þ ð1Þ and qur dVs dt ¼ 2p qArhf Vl Vsð Þ2þArFs Arclv ArFv ð2Þ where ur, hf, Vl, q, clv, and t are volume of fluid in rim, height of the lamella, velocity of…...
[...]

Journal Article•DOI•

The recoiling of liquid droplets upon collision with solid surfaces

[...]

Ho-Young Kim, Jung-Hoon Chun

15 Feb 2001-Physics of Fluids

TL;DR: In this article, an empirically determined dissipation factor is used to estimate the viscousfriction of liquid droplets and the model closely predicts the experimental results obtained for varying dynamic impact conditions and wetting characteristics.

...read moreread less

Abstract: Although the spreading behavior of liquid droplets impacting on solid surfaces has been extensively studied, the mechanism of recoiling which takes place after the droplet reaches its maximum spread diameter has not yet been fully understood. This paper reports the study of the recoiling behavior of different liquid droplets (water, ink, and silicone oil) on different solid surfaces (polycarbonate and silicon oxide). The droplet dynamics are experimentally studied using a high speed video system. Analytical methods using the variational principle, which were originated by Kendall and Rohsenow (MIT Technical Report 85694-100, 1978) and Bechtel et al. [IBM J. Res. Dev. 25, 963 (1981)], are modified to account for wetting and viscous effects. In our model, an empirically determined dissipation factor is used to estimate the viscousfriction. It is shown that the model closely predicts the experimental results obtained for the varying dynamic impact conditions and wetting characteristics. This study shows that droplets recoil fast and vigorously when the Ohnesorge number decreases or the Weber number increases. Droplets with a large equilibrium contact angle are also found to recoil faster. Here the Ohnesorge number scales the resisting force to the recoiling motion, and is shown to play the most important role in characterizing the recoiling motion.

...read moreread less

186 citations

"Role of Bouncing Potential in Molte..." refers result in this paper

...With this definition of BP, unlike in the Mao et al. (1997) model, the Hsiao et al....
[...]

Journal Article•DOI•

Viscous bursting of suspended films.

[...]

G. Debregeas¹, Pascal Martin¹, Françoise Brochard-Wyart¹•Institutions (1)

Curie Institute¹

20 Nov 1995-Physical Review Letters

TL;DR: These are the first observations on freely suspended films of long-chain polymers, where viscous effects are dominant and no surfactant is present, and a simple model is developed to explain this growth law.

...read moreread less

Abstract: Soap films break up by an inertial process. We present here the first observations on freely suspended films of long-chain polymers, where viscous effects are dominant and no surfactant is present. A hole is nucleated at time 0 and grows up to a radius $R(t)$ at time $t$. A surprising feature is that the liquid from the hole is not collected into a rim (as it is in soap films): The liquid spreads out without any significant change of the film thickness. The radius $R(t)$ grows exponentially with time, $R\ensuremath{\propto}\mathrm{exp}(\frac{t}{\ensuremath{\tau}})$ [while in soap films $R(t)$ is linear]. The rise time $\ensuremath{\tau}\ensuremath{\propto}\frac{\ensuremath{\eta}e}{2\ensuremath{\gamma}}$ where $\ensuremath{\eta}$ is viscosity, $e$ is thickness (in the micron range), and $\ensuremath{\gamma}$ is surface tension. A simple model is developed to explain this growth law.

...read moreread less

180 citations

"Role of Bouncing Potential in Molte..." refers background in this paper

...Interestingly, highly viscous polymeric films (viscosity 600 Pa S) are observed to have variable dewetting velocity (Debrégeas et al., 1995)....
[...]

Journal Article•DOI•

An energy balance approach of the dynamics of drop impact on a solid surface

[...]

P. Attané, F. Girard, V. Morin

09 Jan 2007-Physics of Fluids

TL;DR: In this article, a semi-empirical description of viscous dissipation taking into account the rolling motion near the contact line is proposed, where dissipation due to rolling motion is added to the calculated dissipation in the core of the droplet.

...read moreread less

Abstract: The description of physical mechanisms involved in the impact of a drop upon a dry, partially wettable substrate is still a matter of debate. One way to analyze the balance of these mechanisms is the development of an analytical one-dimensional (1D) model based upon the energy equation. The assimilation of the drop to a cylinder allows a reduction of the energy equation to a second-order differential equation. This paper proposes a semi-empirical description of viscous dissipation taking into account the rolling motion near the contact line. The dissipation due to the rolling motion is added to the calculated dissipation in the core of the droplet. We compare our model to previous ones using a large set of literature data covering a wide range of viscosity, velocity impact, and equilibrium contact angle values. The new dissipation description proposed is shown to supersede those described in previous 1D models. Our model closely predicts the maximum spread factor and the time at which it is obtained on the whole range of Ohnesorge and Weber numbers considered. It also distinguishes between deposition with a steady variation in the wetted area from deposition with advancing and receding phases. The main limitations of the model lie in its inability to reproduce the spread factor at the very beginning of the impact and the rebounding observed after a receding phase for very high values of the equilibrium contact angle.

...read moreread less

162 citations

"Role of Bouncing Potential in Molte..." refers background or methods or result in this paper

...With this physical insight, Attané et al. (2007) have concluded that the cylindrical shape assumption provides reliable predictions when the spread ratio is greater than 1....
[...]
..., 1981; Kim and Chun, 2001), cylindrical model (Attané et al., 2007; Kim and Chun, 2001), and boundary-layer approximation to model the flow in lamella (Pasandideh-Fard et al., 1996; Roisman et al., 2002). Assuming a cylindrical or spherical shape for the rim is highly debatable. Initially, it is clear that the spherical cap approximation is a close fit for a spreading drop. Such an assumption, however, is applicable only for a low-velocity impact. Immediately after impact, the rim takes the shape of a spherical cap, and later a cylindrical disk as time approaches di=Vi. This implies that for long-time spreading, the free surface of the rim is far from spherical. With this physical insight, Attané et al. (2007) have concluded that the cylindrical shape assumption provides reliable predictions when the spread ratio is greater than 1. Also, Kim and Chun (2001), based on experimental studies and theoretical models derived with cylindrical and truncated sphere assumptions, observed that with an increase in We, the cylindrical model captures the spreading and recoiling dynamics better than the truncated sphere model. With these evidences, and given the high velocity associated with fly ash impaction ( 20 m s (1)), the rim is approximated as a cylinder, with height and width equal to a spherical cap, to calculate viscous dissipation (refer Figure 3). While estimating the maximum spread diameter, Jung and Hutchings’s (2012) observation that the rimmed cylinder with a dent at the center gives accurate predictions compared to flat disc model for small droplet size less than 30mm further substantiates our assumption....
[...]
...Studies confirmed the presence of a rim at the edge (Attané et al., 2007), and fluid motion in the rim dissipates energy as the rim accumulates the disappearing portion of the liquid film (de Gennes, 1985)....
[...]
..., 1981; Kim and Chun, 2001), cylindrical model (Attané et al., 2007; Kim and Chun, 2001), and boundary-layer approximation to model the flow in lamella (Pasandideh-Fard et al....
[...]
...Studies confirmed the presence of a rim at the edge (Attané et al., 2007), and fluid motion in the rim dissipates energy as the rim accumulates the disappearing portion of the liquid film (de Gennes, 1985)....
[...]