The present book is a generalization of works on research of power processes, executed by the author in Saint–Petersburg state polytechnic university. As the tool of researches the method of the mathematical modeling is chosen, allowing defining the basic laws of processes with the minimum expenses of means. The developed mathematical model allows calculating temperature fields in products and also expenses of energy necessary to create corresponding thermal conditions, proceeding from the general characteristics of the phenomenon. Numerical methods of research of the power processes, developed in the present work, have found successful application in hydrodynamics and heat exchange calculations in nuclear power installations. The heat exchange analysis in a skin of warm-blooded animals and people became not less important appendix of numerical methods.