This book provides a , student oriented investigation to numerical convective heat transfer analysis. basic ideas are discussed in detail and full devlopement of all importent results is provided. the assumptions on which studies of convective heat transfer problems are thoroughtly discussed. The book contains many worked examples that explained the numerical methods of cooling by natural and mixed convection. Highlights of the book include: 1. A literature review concerning different enclosures shows that some several works have considered the problem of natural and mixed convection . 2. Mathematical and numerical procedure for convective heat transfer 3. A detailed discussion of the numerical investigations of natural and mixed convetion. This book, which can use to support of courses on natural and mixed convection phenomena.