This paper is an attempt to study the concept of laws of thermodynamics and heat exchanging process. The heat exchanger is a device which obeys the thermodynamic laws for exchanging heat and temperature from one substance to another. In last few decades, the technology used in heat exchanger is traditional and less efficient. But advancement in technology has given new designs of heat exchanger. Plate-fin heat exchanger is in use in power plants and other thermal plants nowadays. These heat exchangers are made up of corrugated plates which increase its efficiency and performance as compared to shell and tube heat exchanger. Plate heat exchangers can be easily assembled and split. Because of which inspection, maintenance, and cleaning are easy. Due to presence of shear rates and shear stresses, high turbulence, secondary flow and mixing and plate corrugation pattern in plate type heat exchangers fouling is reduced about 10 to 25% as compared to shell and tube exchangers heat transfer. In this heat exchanger friction factor is less due to rectangular shape plate and it is more efficient.