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. By allowing hot fluid to transfer its heat to a cooler fluid, heat exchangers help improve energy efficiency and maintain desired temperatures in different processes. There are several types of heat exchangers, including shell and tube, plate, and air-cooled designs. Each type has its own advantages and is chosen based on factors like space, cost, and the specific requirements of the system. Overall, heat exchangers play a crucial role in modern engineering and energy management.