(Comparison of plate heat exchanger and shell and tube heat exchanger)
a. High heat transfer coefficient;
Because the different corrugated plates are inverted to each other to form a complex flow channel, the fluid flows in a rotating three-dimensional flow in the flow channel between the corrugated plates, which can generate turbulent flow at a low Reynolds number (generally Re=50~200), so heat transfer The coefficient is high, generally considered to be 3 to 5 times that of the shell-and-tube type.
b. The logarithmic average temperature difference is large, and the terminal temperature difference is small.
In the shell-and-tube heat exchanger, the two fluids flow in the tube side and the shell side respectively, which is generally a cross-flow flow, and the logarithmic average temperature difference correction coefficient is small, while the plate heat exchanger is mostly co-current or counter-current flow. , and its correction coefficient is usually around 0.95. In addition, the flow of cold and hot fluids in the plate heat exchanger is parallel to the heat exchange surface and there is no side flow, so the temperature difference at the end of the plate heat exchanger is small, and the heat exchange to water can be Below 1°C, while shell and tube heat exchangers are generally 5°C fff.
Plate Heat Exchanger
Plate Heat Exchanger
c. Small footprint.
The plate heat exchanger has a compact structure, and 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, it is not necessary to reserve the maintenance site for drawing out the tube bundle. Therefore, the same heat exchange can be achieved. The area of ​​the heat exchanger is about 1/5~1/8 of that of the shell and tube heat exchanger.
d. It is easy to change the heat exchange area or process combination;
As long as a few plates are added or reduced, the purpose of increasing or reducing the heat exchange area can be achieved; by changing the arrangement of the plates or replacing a few plates, the required process combination can be achieved and the new heat exchange conditions can be adapted. It is almost impossible to increase the heat transfer area of ​​the shell heat exchanger.
e. Light weight;
The thickness of the plate 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, and the shell of the shell and tube is much heavier than the frame of the plate heat exchanger. , The plate heat exchanger is generally only about 1/5 of the weight of the shell and tube type.
f. Low price;
Using the same material and 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.
g. 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.
h. Easy to clean;
As long as the pressing bolts are loosened, the frame plate heat exchanger can loosen the plate bundle and remove the plates for mechanical cleaning, which is very convenient for the heat exchange process that requires frequent cleaning of the equipment.
Plate Heat Exchanger
Plate Heat Exchanger
i. Small heat loss;
In the plate heat exchanger, only the shell plate of the heat transfer plate is exposed to the atmosphere, so the heat dissipation loss can be ignored, and no insulation measures are required. The shell and tube heat exchanger has a large heat loss and requires an insulating layer.
j. Smaller capacity;
It is about 10%~20% of the shell and tube heat exchanger.
k. The pressure loss per unit length is large;
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.
l. Not easy to scale;
Because the interior is fully turbulent, it is not easy to scale, and the scaling coefficient is only 1/3~1/10 of the shell and tube heat exchanger.
m. The working pressure should not be too large, and the temperature of the medium should not be too high, and leakage may occur;
The plate heat exchanger is sealed with a gasket. Generally, the working pressure should not exceed 2.5MPa, and the medium temperature should be below 250℃, otherwise it may leak.
n. Easy to block;
Because the channel 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 channel between the plates.