Heat exchangers are systems used to transfer heat between two or more fluids. They are used in both heating and cooling processes. The liquids, gases or plasmas in these systems are either in direct contact, or are separated by a solid wall to prevent mixing. Heat exchangers are extensively used in refrigerators, space heaters, power plants, air conditioners, chemical and petrochemical plants, oil refineries, sewage treatment plants and in natural gas processing. Cooling in internal combustion engines is also an example of heat exchange. The engine coolant flows through the radiator coils and air flows past it, cooling the coolant and heating the air. Heat sinks in electronic or mechanical devices are another example of heat exchangers. There has been rapid progress in this field and its applications are finding their way across multiple industries. The objective of this book is to give a general view of the different areas of heat exchangers. It will prove to be immensely beneficial to students and researchers in this field.