In this article let’s try to understand that, what is the heat exchanger and why to consider it, the former definition of that says it is a device that channelizes the heat from one medium to other medium, either by direct contact or by means of the induction. Virtually all major industrial processes such as heating, refrigeration, air conditioning, power plants, chemical processing plant , plastic, rubber, pharmaceutical, petroleum refineries, natural gas processing, and sewage treatment finds the application of the heat exchanger some or the other way. The efficiency and the rate of the transfer of the thermal energy of heat exchanger plays very critical role in the performance of the heating, drying and cooling. The heat exchangers are generally of three basic classifications based on the heat flow Parallel flow: where the fluids runs in same direction, parallel to each other. Counter flow: where the fluid runs in opposite direction. Cross flow: where the fluids travel per