A heat exchanger is a device that transfers heat between two or more fluids without mixing them. It is commonly used in various applications, such as in heating systems, refrigeration, and power plants. The main goal is to efficiently transfer thermal energy to either heat or cool a fluid, improving energy efficiency. Heat exchangers come in different designs, including shell and tube, plate, and air-cooled types. Each design has its advantages depending on the specific application and required heat transfer efficiency. By optimizing heat transfer, these devices help reduce energy consumption and lower operational costs in many industries.