heat exchanger

A heat exchanger is a device that transfers part of the heat from a hot fluid to a cold fluid, also known as a "heat exchange device". Heat exchangers play a crucial role in chemical engineering, petroleum, power generation, food processing, and many other industrial sectors. In chemical production, they are widely used as heaters, coolers, condensers, evaporators, and reboilers, among other applications.

Heat exchangers are designed for different media, operating conditions, temperatures, and pressures, and thus come in various structural types. Their specific classification is as follows:

Classification by Heat Transfer Principle

Recuperative heat exchangers (also called "divided-wall heat exchangers"): Two fluids with different temperatures flow in separate spaces separated by a wall. Heat transfer between the two fluids occurs through heat conduction through the wall and convection of the fluids on the wall surface. Recuperative heat exchangers include shell-and-tube heat exchangers, double-pipe heat exchangers, and other types. They are the most widely used category of heat exchangers.

Regenerative heat exchangers (also called "storage heat exchangers"): These transfer heat from a high-temperature fluid to a low-temperature fluid via a heat storage medium made of solid materials. First, the hot medium heats the solid material to a specific temperature; then, the cold medium passes through the solid material and is heated, thereby achieving heat transfer. Regenerative heat exchangers include rotary regenerators and valve-switching regenerators.

Indirect heat exchangers with fluid connection: These consist of two surface heat exchangers connected by a heat carrier that circulates between them. The heat carrier circulates between the high-temperature fluid heat exchanger and the low-temperature fluid heat exchanger: it absorbs heat from the high-temperature fluid and releases heat to the low-temperature fluid in the low-temperature fluid heat exchanger.

Direct contact heat exchangers (also called "mixed heat exchangers"): In these exchangers, two fluids come into direct contact and mix with each other to achieve heat transfer. Examples include cooling towers and gas condensers.

Compound heat exchangers: These integrate two heat transfer methods: indirect heat transfer between steam and water (surface-type) and direct mixed-flow heat transfer between water and water. Compared with steam-water indirect surface heat transfer, they have higher heat transfer efficiency; compared with direct steam-water mixed heat transfer, they offer greater stability and lower unit noise.