Shell-and-tube (or shell-and-tube) heat exchangers are the most widely used conventional heat exchangers. The most basic structure is to add a lot of small tubes for heat exchange in a circular casing. When the heated heat medium is steam, it is called a shell-tube steam-water heat exchanger; when the heated heat medium is high-temperature water, it is called a shell. Pipe-water-water heat exchanger, water-water heat exchanger is water due to heat exchange inside and outside the small pipe, because the water flow rate on both sides of the small pipe is close, the diameter of the circular casing can not be too large, when the heating area requires a large amount, often several segments Connected together, it is also called a segmented water-water heat exchanger. Their specific construction is shown below. This type of heat exchanger is commonly used in hot water heating systems, low temperature water air conditioning systems and some process water for continuous hot water production.