Dr. Afshin J. Ghajar is a Regents Professor, John Brammer Endowed Professor, and Director of Graduate Studies in the School of Mechanical and Aerospace Engineering at Oklahoma State University, Stillwater, Oklahoma, USA and a Honorary Professor of Xi'an Jiaotong University, Xi'an, China. His expertise is in experimental heat transfer/ fluid mechanics and development of practical engineering correlations. His current research is in two-phase flow heat transfer/pressure drop studies in pipes with different orientations, heat transfer/pressure drop in mini/micro tubes, and heat transfer/pressure drop in the transition region (plain and enhanced tubes). Dr. Ghajar and his co-workers have published over 200 reviewed research papers. He has delivered numerous keynote and invited lectures at major technical conferences and institutions. He has received several outstanding teaching/research/service awards. Dr. Ghajar is a Fellow of the American Society of Mechanical Engineers (ASME), Heat Transfer Series Editor for CRC Press / Taylor & Francis (he has edited five books to date) and Editor-in-Chief of Heat Transfer Engineering, an international journal published fifteen times per year by Taylor and Francis. Dr. Ghajar is also the co-author of the 4th Edition of Cengel and Ghajar, Heat and Mass Transfer – Fundamentals and Applications, McGraw-Hill, February 2010.