In recent years, thousands of numerical and experimental studies have been performed on heat exchangers with different configurations. Mainly heat transfer and frictional characteristics have been studied in detail with respect to different geometrical parameters in various ranges of Reynolds number. Further, these studies have been cross-verified with researches already performed in this field. With the advent of new tools like CFD for the study of thermo-hydraulic characteristics, it has become easier to understand flow phenomena around the tubes for different rows and also in rest of flow regions. These studies also bring about some correlations so as to easily find the values of colburn and friction factor for various different geometrical parameters so as to suit the different industrial conditions and requirements. An overview of the work already done on plate-fin heat exchangers is presented in this paper.