I: heat exchanger classification
1, Classified according to the use of heat exchanger
(1) Heater: The heater is used to heat the fluid to the desired temperature and the fluid being heated does not undergo phase change during the heating process.
(2) Preheater: Preheater is used to preheat the fluid to improve the efficiency of the whole process unit.
(3) Superheater: The superheater is used to heat the saturated vapour to a superheated state.
(4) Evaporator: The evaporator is used to heat the liquid to evaporate and vaporise it.
(5) reboiler: reboiler is the distillation process of special equipment, used to heat the liquid that has been condensed so that it is re-heated and vaporised.
(6) Cooler: the cooler is used to cool the fluid so that it reaches the required temperature.
(7) condenser: condenser used to condense saturated vapour so that the release of latent heat and condensation liquefaction.
2, according to the heat exchanger heat transfer surface shape and structure classification
(1) Tubular heat exchanger: Tubular heat exchanger heat transfer through the wall of the tube, according to the structure of the heat transfer tube is different, can be divided into column tube heat exchanger, casing type heat exchanger, snake tube heat exchanger and finned tube heat exchanger and so on several kinds of heat exchanger. The tube heat exchanger is the most widely used.
(2) plate heat exchanger: plate heat exchanger heat transfer through the plate, according to the structural form of the heat transfer plate, can be divided into flat plate heat exchanger, spiral plate heat exchanger, plate-fin type heat exchanger and hot plate heat exchanger.
(3) special form of heat exchanger: this type of heat exchanger is designed according to the special requirements of the process with a special structure of the heat exchanger. Such as rotary heat exchangers, and heat pipe heat exchangers.
3, Classified according to the materials used in the heat exchanger
(1) Metal materials heat exchanger: A metal materials heat exchanger is made of metal materials, commonly used metal materials are carbon steel, alloy steel, copper and copper alloy, aluminium and aluminium alloy, and titanium and titanium alloy. Because of the thermal conductivity of metal materials, the heat transfer efficiency of this type of heat exchanger is higher, the production is mainly used in metal materials heat exchangers.
(2) non-metallic materials heat exchanger: non-metallic materials heat exchanger made of non-metallic materials, commonly used non-golden materials such as graphite, glass, plastic and ceramics. This type of heat exchanger is mainly used for corrosive materials due to the thermal conductivity of non-metallic materials is small, so its heat transfer efficiency is low.
Plate heat exchanger structure and performance characteristics
1. Plate heat exchanger
Flat plate heat exchanger referred to as plate heat exchanger, its structure is shown in Figure 4-46. It is a set of rectangular thin metal plates arranged in parallel, clamped assembly in the bracket above the composition. The edge of the two neighbouring plates is lined with gaskets and pressed between the plates to form a sealed fluid channel, and the thickness of the gasket can be used to adjust the size of the channel. The four corners of each plate, each open a round hole, of which two round holes and the flow channel on the surface of the plate, the other two round holes are not connected. Their positions are staggered on neighbouring plates to form separate channels for the two fluids. Cold and hot fluids flow alternately on both sides of the plates, and heat is exchanged through the metal plates.
The plate is the core component of the plate heat exchanger. To make the fluid flow uniformly through the plate surface, increase the heat transfer area, and promote fluid turbulence, often the plate surface is stamped into concave-convex corrugated, corrugated shapes there are dozens of kinds of commonly used corrugated shapes are horizontal corrugated, herringbone corrugated and arched corrugated and so on.
Plate heat exchanger has the advantages of compact structure, unit volume of equipment to provide a large area of heat transfer; assembly flexibility, according to the need to increase or decrease the number of plates to regulate the heat transfer area; plate ripples to make the cross-section changes in the complexity of the fluid to enhance the perturbation effect, with a high heat transfer efficiency; easy to disassemble, conducive to maintenance and cleaning. The disadvantage is that the processing capacity is small; operating pressure and temperature by the sealing gasket material performance limitations and should not be too high. The plate heat exchanger is suitable for frequent cleaning, the working environment is very compact, the working pressure is below 2.5 MPa, and the temperature is -35 ℃ ~ 200 ℃ occasions.
