Views: 2 Author: Site Editor Publish Time: 2023-01-31 Origin: Site
Plate Heat Exchanger VS Shell and Tube Heat Exchanger
(1) Heat transfer coefficient. Since different corrugated plates are inverted to each other to form a complex flow channel, the fluid flows in a three-dimensional rotation in the channel between the corrugated plates, which can generate turbulent flow at a low Reynolds effect (generally Re=50~200), so the plate heat exchange The heat transfer coefficient of the device 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, and the temperature difference at the end is small. In the shell-and-tube heat exchanger, the two fluids flow in the shell side and the tube side respectively. Generally, it is a cross-flow flow, and the logarithmic average temperature difference correction coefficient is small, while the plate heat exchanger mostly flows in parallel or countercurrent flow. Its correction factor is usually around 0.95.
In addition, the flow of cold and hot liquids in the plate heat exchanger is parallel to the heat exchange surface. There is no bypass flow, so the temperature difference at the end of the plate heat exchanger is small, and the heat exchange between water and water can be lower than 1°C, while the shell-and-tube heat exchanger is generally 5°C.
(3) Floor area. The structure of the plate heat exchanger is compact, and the heat exchange area per unit volume is 2-5 times that of the shell-and-tube type, and it does not need to reserve a maintenance site for pulling out the tubes like the shell-and-tube type. The floor area of the heat exchanger is about 1/5-1/10 of that of the shell-and-tube heat exchanger.
(4) Change the heat transfer area or process combination. The purpose of increasing or reducing the heat transfer area can be achieved by adding or reducing a few plates; changing the arrangement of plates or replacing a few plates can achieve the required process combination and adapt to new heat transfer conditions. It is almost impossible to increase or decrease the heat transfer area of the shell and tube heat exchanger.
(5) Weight. The plate thickness of the plate heat exchanger is only 0.4-0.8mm, the thickness of the heat exchange tube of the shell-and-tube heat exchanger is 2.0--2.5mm, and the shell-and-tube shell is much heavier than the frame of the pull-type heat exchanger , The plate heat exchanger is generally only about 1/5 of the weight of the shell and tube type.
(6) PRICE. Using the same material, under the same heat transfer area. The price of the plate heat exchanger is about 40% to 60% lower than that of the shell and tube type.
(7) Easy to make. 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) cleaning. As long as the frame-type plate heat exchanger is loosened and tightened, the plate can be opened and the plate can be removed for mechanical cleaning. It is very convenient to use in occasions that require frequent cleaning of equipment.
(9) Heat loss. In the plate heat exchanger, only the shell plate of the heat transfer plate is exposed to the atmosphere, so the loss of heat dissipation is negligible, and no insulation measures are required. The shell and tube heat exchanger has a large heat loss, so it must be kept warm.
(10) CAPACITY. The plate heat exchanger is 10% to 20% of the shell and tube heat exchanger.
(11) Pressure loss per unit length. Due to the small gap between the heat transfer surfaces and the unevenness on the heat transfer surface, the pressure loss is larger than that of the traditional smooth tube.
(12) Fouling. Due to the turbulent internal water flow, it is not easy to scale, and the scaling coefficient of the plate heat exchanger is only 1/3 to 1/10 of that of the tube heat exchanger.
(13) Working pressure. The plate heat exchanger is sealed with a gasket, the working pressure should generally not exceed 2.5MPa, and the medium temperature should be lower than 250~C, otherwise it may leak.
(14) CLOCK. Because the channel between the plates is very narrow, generally only 2-5mm, when the heat exchange medium contains large particles or fibrous substances, it is easy to block.
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