This book describes an experimental and theoretical analysis of the heat transfer in a direct contact evaporator with desalination purposes. During the experimental work were analysed process parameter as inlet and water flow rate and ainlet air temperature. The measured variables were temperature profile inside the column, exit air and water temperature, and exit humidity. The data were analysed both in dynamic and steady state conditions. The results were analysed and a simple mathematical model able to predict the inlet air temperature and the exit amount of extracted water were developed.