Classification of heat exchangers according to heat transfer principle 
Heat exchanger is a device that transfers part of the heat of hot fluid to cold fluid, also known as heat exchanger. Heat exchanger is a common 
equipment in chemical, petroleum, power, food and many other industrial sectors, which plays an important role in production. In chemical 
production, heat exchangers can be used as heaters, coolers,condensers, evaporators and reboilers, and are more widely used. 
1.Surface heat exchanger Surface heat exchanger is two kinds of fluids with different temperatures flowing in the space separated by the wall. 
Through the heat conduction of the wall and the convection of the fluid on the wall surface, the heat transfer between the two fluids is carried out. 
Surface heat exchangers include shell and tube, casing and other types of heat exchangers. 
2.Regenerative heat exchangerThe regenerative heat exchanger transfers heat from high-temperature fluid to low-temperature fluid through the 
regenerator composed of solid materials. The thermal medium first reaches a certain temperature by heating the solid material, and then the cold 
medium is heated by the solid material to achieve the purpose of heat transfer. Regenerative heat exchangers have rotary, valve switching, etc. 
3.Fluid connection indirect heat exchanger Fluid connection indirect heat exchanger is a heat exchanger that connects two surface heat exchangers 
with heat carriers circulating in them. The heat carrier circulates between the high-temperature fluid heat exchanger and the low-temperature fluid, 
receives heat in the high-temperature fluid, and releases heat to the low-temperature fluid in the low-temperature fluid heat exchanger. 
4, direct contact heat exchanger direct contact heat exchanger is two kinds of fluid directly contact heat transfer equipment, such as cold water tower, 
gas condenser, etc.