ME742A

BOILING AND CONDENSATION



Updated Syllabus:
Introduction: Applications of boiling and condensation. Difference between evaporation and boiling. Comparison of Nucleate and Convective (or Flow) boiling. Pool boiling: Nukiyama Experiment. Theory of vapour bubble formation: Homogeneous and Heterogeneous Nucleation. Bubble Growth Models. Mechanism of Critical Heat Flux (CHF). Various models and correlations. Pool Boiling of Binary Mixture. Flow Boiling: homogeneous and heterogeneous models. Flow Boiling in Microchannels. Flow Boiling of Binary Mixtures. Boiling enhancement techniques. Film and dropwise condensation. Nusselt’s analysis of laminar film condensation on vertical plate, single horizontal tube and vertical array of tubes. Laminarwavy and turbulent film condensation. Film condensation inside horizontal tubes. Condensation enhancement techniques. Special topics (Suggested): Boiling in Microgravity Environment. Boiling of Nanofluids. Liquid Metals Boiling. Boiling on Structured Surfaces. Effect of Noncondensable Gases in Vapour on Condensation. Numerical Modelling of Boiling and Condensation Heat Transfer. Special topics: Boiling of Nanofluids. Computer Simulation of Pool Boiling by the Coupled Map Lattice Method.
LecturebyLecture Breakup (Three 50 min lectures per week)
Lecture # 1: Introduction:
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Review of Thermodynamics of Phase Change of Pure Substances: subcooled liquid, saturated liquid, saturated liquidvapour mixture, saturated vapour, superheated vapour, critical point. Psat vs. Tsat plot: Clapeyron Equation and ClausiusClapeyron Equation. Triple Point. Superheated liquid: Definition. Application in boiling. Concept of metastable equilibrium of vapour bubble and superheated liquid.
Lecture # 5:
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Expression for the rate of bubble growth (completed). Example Problem. Bubble Departure Diameter and the Frequency of Bubble Release: Definition of the frequency of bubble release. Various mechanisms of bubble release. Sample Correlations for Departure Diameter: Fritz (1935), Zuber (1959) and Cole (1967).
Lecture # 9:

Frequency of Bubble Release: Influencing factors. Correlations for frequency of bubble release (valid in the intermediate regime between inertia and heattransfer controlled growth): Jacob and Fritz (1931), Peebles and Garber (1953), Zuber (1963). Basic forms of correlations given by Ivey (1967) for inertia controlled growth and heattransfer controlled growth. Favourable conditions for inertia controlled growth and heattransfer controlled growth. Example Problem.
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Stephan and Abdelsalam Correlation (1980): Basis. Correlations for water, hydrocarbons, cryogenic fluids, and refrigerants. Unified correlation valid for all fluids (lower accuracy). Simpler and easytouse correlations. Surface roughness correction. Comparison of q//vs.∆Tw graphs on loglog plot for boiling of water at 1 bar using Rohsenow (1952) and, Stephan and Abdelsalam (1980) correlations.
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Lecture # 21:

Minimum Heat Flux: Zuber(1959) theory and correlation, and modification by Berenson (1961) for Infinite Plate. Lienhard and Wong (1963) Correlation for Horizontal Cylinder. Film Boiling: Bromley (1950) Correlations for horizontal cylinder and sphere. Berenson (1961) Correlation for Infinite Horizontal Surface. Effect of Radiation on Film Boiling: Correction by Bromley (1950). Film Boiling on Finite Horizontal Surface.
Lecture # 22:
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Basic Terms and Definitions in TwoPhase Flows. Basic Model and Governing Equations (Conservation of Mass and Momentum) for Onedimensional TwoPhase Flow: Assumptions and derivations. Expression of total axial pressure gradient in terms of frictional effect at the wall, gravitational head effect and acceleration (or deceleration) of the flow.
Lecture # 26:

Calculation of Frictional Pressure Gradient:Definition of TwoPhase Multipliers, φl ,φlo ,φv . Homogeneous Flow: Basic definition and idealizations. Derivation of the expression for φlo2 . Heterogeneous Flow: Basic definition. Method of Lockhart and Martinelli (1949): Basic philosophy. Concept of Correction factor or Martinelli parameter, X. To be continued.
Lecture # 27:
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Expression for mass rate of condensation. Effect of Subcooling: Derivation of the expression for modified latent heat of condensation h/fg . Turbulent Film Condensation over a Vertical Plate: Definition of film condensation Reynolds number. Various regimes of film condensation flow such as laminar, laminarwavy and turbulent and transition criteria. Experimental correlations for average heat transfer coefficient for laminarwavy and turbulent regimes. Basic method of solution of film condensation problems: Why are iterations required? Example Problem (to be continued).
Lecture # 35:
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Lectures # 3740:
Reference Books:

Stephan K, 1992, Heat Transfer in Condensation and Boiling, SpringerVerlag, Berlin.

Carey, V.P., 2008, LiquidVapor PhaseChange Phenomena, 2nd edn, Taylor & Francis, New York.
