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About this book

This SpringerBrief presents a recent advancement in modeling and measurement of the effect of surface wettability on the defrost process. Carefully controlled laboratory measurements of the defrosting of cooled surfaces are used to reveal the effect of surface wetting properties on the extent and speed of frost removal by melting or slumping. The experiments are accompanied by visualization of frost removal at several defrosting conditions. Analysis breaks the defrost process into three stages according to the behavior of the meltwater. Surface wetting factors are included, and become significant when sufficient meltwater accumulates between the saturated frost layer and the surface. The book is aimed at researchers, practicing engineers and graduate students.

Table of Contents

Frontmatter

Chapter 1. Introduction

This chapter describes the nature of frost removal as it affects the thermal performance of refrigeration systems. The overall scope of the research reported in this monograph is discussed and the defrost process is cast as a coupled heat and mass transfer problem. The effect of surface wettability on defrosting is introduced. The goal of obtaining conditions under which frost slumping occurs is discussed.
Yang Liu, Francis A. Kulacki

Chapter 2. Prior Research

A review of the relevant literature on frost formation and the defrost process is presented. Key elements of the frost formation process are first described and summarized, and the role of surface wettability is highlighted. The effect of surface wettability, melt water behavior and ice adhesion on the defrost process is then discussed, and several experimental and analytical investigations are reviewed.
Yang Liu, Francis A. Kulacki

Chapter 3. A Model of the Defrost Process

A model of frost melting is developed from fundamental analysis of the heat and mass transfer. The melting model envisions three stages as the frosted surface is heated: absorption of the melt water by diffusion, accumulation of the melt water, and draining of the melt water along the surface. The three stages of melting are connected physically, but the analysis of each involves a particular set of assumptions and use of a wide range parameters and physical laws. Surface wettability enters the analysis as a factor in the draining stage. The possibility of frost slumping is expressed through a criterion based on a static force balance in which contact angel is an implicit factor.
Yang Liu, Francis A. Kulacki

Chapter 4. Solution Methods

The melting stages of Chap. 3 describe the behavior of the meltwater during different time periods of the defrost process: absorption and permeation, accumulation, and draining. Meltwater accumulation reduces the strength of ice adhesion and promotes the possibility of slumping. The rate of meltwater draining depends on the boundary conditions at the interfaces of the liquid layer. A large draining rate reduces defrost time and improves defrost efficiency. Solution methods of the governing transport equations of these stages of defrost are described in this chapter.
Yang Liu, Francis A. Kulacki

Chapter 5. Experimental Design

We report the design of a laboratory experiment in a frost layer is built in a controlled environment on a vertical surface. The objective is investigate defrost mechanisms on test surfaces with a given contact angle. The procedure generally involves creating a frost column with a certain thickness and bulk density and then melting it to determine defrost time, efficiency and conditions under which slumping is observed.
Yang Liu, Francis A. Kulacki

Chapter 6. Results

Results of the analysis developed in Chaps. 3 and 4 and measurements obtained with the experimental design of Chap. 5 are presented and discussed in the chapter. Variation of the parameters describing the several underlying physics of the absorption, accumulation and draining stages of melting are graphically summarized. Visualization of the frost slumping is presented.
Yang Liu, Francis A. Kulacki

Chapter 7. Conclusion

Key findings of the analysis and experiments reported in this monograph are summarized. The overarching context of the three-stage melting process and the observations of frost slumping is discussed. Pathways for future fundamental investigation are included.
Yang Liu, Francis A. Kulacki

Backmatter

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