This volume provides a comprehensive overview on the vast amount of literature on solidification heat transfer. Chapter one develops important basic equations and discusses the validity of considering only conductive heat transfer, while ignoring convection, in the large class of materials which make up the porous media. Chapters 2 to 4 deal with problems that can be expressed in plane (Cartesian) coordinates. These problems are further divided into boundary conditions of temperature, prescribed heat flux, and surface convection. Chapter 5 examines some plane geometries involving three-dimensional freezing or thawing. Problems in the cylindrical and spherical coordinate systems are covered in chapters 6 and 7. Chapter 8 is an introduction to solidification in porous media.Many of the applications have been directed to water/ice soil-systems, but it should be clear that the basic techniques and solutions can be applied to such diverse areas as metallurgy, biological systems, latent heat storage, and the preservation of food.

Freezing time and freezing heat load are the two most important factors determining the economics of food freezers. This Brief will review and describe the principal methods available for their calculation. The methods can be classified into analytical methods, which rely on making physical simplifications to be able to derive exact solutions; empirical methods, which use regression techniques to derive simplified equations from experimental data or numerical calculations and numerical methods, which use computational techniques such as finite elements analysis to solve the complete set of equations describing the physical process. The Brief will evaluate the methods against experimental data and develop guidelines on the choice of method. Whatever technique is used, the accuracy of the results depends crucially on the input parameters such as the heat transfer coefficient and the product's thermal properties. In addition, the estimation methods and data for these parameters will be reviewed and their impacts on the calculations will be evaluated. Freezing is often accompanied by mass transfer (moisture loss, solute absorption), super cooling and nucleation and may take place under high pressure conditions; therefore methods to take these phenomena into account will also be reviewed.

Freezing of water or melting of ice are phenomena that underlie many important scientific and engineering studies of cold regions. Mathematical methods of treating these phase-change heat transfer problems are critical to understanding and dealing with the problems that freeze-thaw causes. While convection may be an important heat transfer mode, it can often be neglected without significant error. This report deals only with problems for which conduction is the basic heat transfer mode or for which the solutions can be obtained in terms of conduction-like problems. Where possible, exact solutions are presented, but since these are quite limited for phase-change problems, approximate solutions are examined in some detail. The approximate methods are 1) the perturbation method, which leads to quasi-stationary techniques, 2) the heat balance integral method, and 3) Biot's variational principle. THe theory associated with these methods is discussed in the appendixes. THe available exact solutions are derived and explained. Graphical solutions are used to generate design curves-such as those for phase-change depth, temperature, and heat flow vs time. The results are presented so as to be easily accessible to practicing engineers without recourse to elaborate calculations. This is especially true for application to soil systems. Keywords: Conduction, Freezing, Heat transfer, Melting, Phase change, Thawing. (mjm).