A heat exchanger is a device designed to transfer heat between two or more fluids without mixing them. It is widely used in industries such as HVAC, power generation, chemical processing, and automotive cooling systems. Common types include shell-and-tube, plate, and finned-tube heat exchangers, each suited for specific applications. Made from materials like stainless steel, copper, or aluminum, heat exchangers ensure efficient thermal energy transfer while minimizing energy loss. The design considers factors like flow rate, temperature, and pressure to optimize performance. Proper maintenance, including cleaning and inspection, is essential to prevent fouling and ensure long-term efficiency.