The plate heat exchanger has a good heat exchange effect, and the plates can be removed for easy cleaning. For shell and tube heat exchangers, the heat exchange tubes cannot be split, which will bring some inconvenience to cleaning. Plate heat exchangers have limitations in terms of heat transfer conditions. They are only suitable for heat transfer within 150 degrees Celsius, while shell-and-tube heat exchangers have no restrictions on the temperature in heat transfer conditions. , No matter the degree of heat can be used shell-and-tube heat exchanger. From the perspective of price, the plate heat exchanger has a lower cost than the shell-and-tube heat exchanger.
1. High heat transfer coefficient: Because different corrugated plates are turned upside down to form a complicated flow channel, the fluid flows in a rotating three-dimensional flow in the flow channel between the corrugated plates, which can be at a low Reynolds number (generally Re=50~200) Turbulent flow is generated, so the heat transfer coefficient is high, which is generally considered to be 3 to 5 times that of the shell-and-tube type.
2. The logarithmic average temperature difference is large: the end temperature difference is small. In the shell-and-tube heat exchanger, the two fluids flow in the tube side and the shell side respectively, and the flow is generally cross-flow. The logarithmic average temperature difference correction coefficient is small, while the plate type heat exchanger Heat exchangers are mostly co-current or counter-current flow, and the correction coefficient is usually about 0.95. In addition, the flow of cold and hot fluid in the plate heat exchanger is parallel to the heat exchange surface without bypass flow, so the plate heat exchange The temperature difference at the end of the heat exchanger is small, and the heat transfer to water can be lower than 1℃, while the shell-and-tube heat exchanger is generally 5℃.
3. Small footprint and compact structure: The heat exchange area per unit volume is 2 to 5 times that of the shell-and-tube type. Unlike the shell-and-tube type, there is no need to reserve a place for the maintenance of the tube bundle, so the same heat exchange can be achieved. The area of the plate heat exchanger is about 1/5~1/8 that of the shell-and-tube heat exchanger.
4. It is easy to change the heat exchange area or process combination: the plate heat exchanger can achieve the purpose of increasing or reducing the heat exchange area by adding or reducing a few plates; changing the plate arrangement or replacing several plates can achieve the goal The required process combination is adapted to the new heat exchange conditions, and the heat transfer area of the shell-and-tube heat exchanger is almost impossible to increase.
5. Light weight: The plate thickness of the plate heat exchanger is only 0.4~0.8mm, while the thickness of the heat exchange tube of the shell-and-tube heat exchanger is 2.0~2.5mm. The shell-and-tube shell is better than the plate heat exchanger. The frame is much heavier, generally only about 1/5 of the shell-and-tube weight.
6. Low price: Using the same material, under the same heat exchange area, the price of the plate heat exchanger is about 40%~60% lower than that of the shell-and-tube type.
7. Convenient production: The heat transfer plate of the plate heat exchanger is processed by stamping, which has a high degree of standardization and can be mass-produced. The shell-and-tube heat exchanger is generally made by hand.
8. Easy to clean: The plate heat exchanger can loosen the plate bundle and remove the plates for mechanical cleaning as long as the compression bolts are loosened. This is very convenient for the heat exchange process that requires frequent cleaning of the equipment.
9. Small heat loss: only the shell plate of the heat transfer plate is exposed to the atmosphere, so the heat dissipation loss can be neglected, and no heat preservation measures are required. The shell-and-tube heat exchanger has a large heat loss and requires a thermal insulation layer.
10. The smaller capacity is 10%-20% of the shell-and-tube heat exchanger.
11. The pressure loss per unit length is large. Because the gap between the heat transfer surfaces is small and the heat transfer surface has unevenness, the pressure loss is greater than that of the traditional smooth pipe.
12. Not easy to scale: due to the full turbulence inside, it is not easy to scale, and the scale coefficient is only 1/3~1/10 of the shell-and-tube heat exchanger.
13. The working pressure should not be too high, and the medium temperature should not be too high. It may leak. The plate heat exchanger is sealed with gaskets. The working pressure should not exceed 2.5MPa. The temperature of the medium should be below 250℃, otherwise it may leak.
14. Easy to block. Because the passage between the plates is very narrow, generally only 2~5mm, when the heat exchange medium contains larger particles or fibrous substances, it is easy to block the passage between the plates.
