-The concept of heat exchangers plays a major role in the refrigeration and air conditioning system.This project discusses about the parallel flow and counter flow heat exchanger using LMTD and NTU effectiveness method. The main objective of this project is to calculate theoretical parameters of heat exchanger like Effectiveness, Area, Inlet and outlet temperatures, Log mean temperature difference (LMTD), Number of Transfer units (NTU), by using concepts of OOPs & java. To calculate this all parameters java program is done on the parallel and counter flow heat exchanger.