Flow of films liquid

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PART ONE: INTRODUCTION1

1.1Research Objectives1

1.2Specific Aims of the Research2

1.3 Significance of the Study3

PART TWO: LITERATURE REVIEW4

2.1 Overview of Falling Liquid Films4

2.2 Falling Film Parameters7

2.3 Dynamics of Backflow Films of Liquid8

2.4 Various factors related to films liquid abstraction11

2.5 Equation of the Liquid Flow Films14

PART THREE: CONCLUSION15

REFERENCES16

PART ONE: INTRODUCTION

Research Objectives

The primary aim of this research study is to investigate in detail the flow physics and transport phenomena associated with falling liquid film evaporation. The study focuses on wavy laminar falling films of water and black liquor. Conventional black liquor evaporation is characterized by high rates of soluble scale fouling resulting from precipitation of dissolved black liquor salts on heat transfer surface. Soluble scaling is a concentration and temperature dependent process and for black liquor in particular, the inverse-solubility property makes temperature a critical scaling parameter. In recent times, high energy costs and strict environmental regulatory demands require concentration of black liquor to higher mass fractions of dissolved solids to ensure efficient combustion of the thickened liquor. At high dissolved solids mass fractions, black liquor evaporator scaling becomes erratic and less predictable with rapid fouling of heat transfer surface leading eventually to evaporator shut down.

Falling film evaporation is characterized by high rates of heat transfer and shorter residence time of the process stream, thus making it more suitable for black liquor concentration/evaporation. Nevertheless, with liquors at high dissolved solids mass fraction, its performance still suffers from rapid heat transfer surface fouling albeit to lesser degrees. Studies have shown that soluble scale deposition in high solids black liquor evaporators is controlled by crystallization phenomena, and the influence of fluid flow of and heat transfer associated with the crystallization and evaporation processes. However, relatively little information has been reported about the hydrodynamics and transport phenomena of black liquor falling films and their influence on the crystallization process. More importantly, since falling liquid film free surface deformation significantly influence film transport and consequently the temperature and concentration fields, thorough understanding of the soluble scaling process is incomplete without accurate prediction of falling film flow field and interfacial evolution. The main focus of this research will be on the theoretical part of the topic. Since, it requires a detailed assessment of all the theories presented in the topic. There would not be any discussion regarding the development of a computational framework and numerical solution. Though a formula for the numerical method related to the solutions that satisfies the conservation laws will be mentioned in the essay. For constant property liquid, the study investigates the influence of different interfacial wave regimes on falling film hydrodynamics and stream wise thermal regions that evolve in the liquid film due to interfacial deformation. The impact of wave dynamics on evaporation heat transfer enhancement is also analyzed. The computational model is applied to study falling film evaporation of black liquor mixture with dissolved species enrichment and depletion respectively evaluated based on liquid vaporization and soluble salt crystallization. Therefore, all the issues related to modeling flow of films liquid ...