Plate heat exchanger
a. High heat transfer coefficient;
Because the different corrugated plates are inverted to form a complicated flow channel, the fluid flows in the three-dimensional flow path between the corrugated plates, and can generate turbulence at a low Reynolds number (generally Re=50~200), so heat transfer is performed. The coefficient is high and is generally considered to be 3 to 5 times that of shell and tube type.
b. The logarithmic mean temperature difference is large and the end temperature difference is small.
In the shell-and-tube heat exchanger, the two fluids flow in the tube and the shell, respectively. The overall flow is cross-flow. The logarithmic mean temperature difference correction coefficient is small, and the plate heat exchanger is mostly cocurrent or countercurrent flow. The correction factor 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 no side flow, so the temperature difference at the end of the plate heat exchanger is small, and the water heat exchange can be Below 1 °C, while the shell and tube heat exchanger is generally 5 °Cfff.
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, and unlike the shell-and-tube type, maintenance sites for drawing out the tube bundles are not reserved, so the same heat exchange amount is achieved, and the plate-type heat exchanger is changed. Heater covers approximately 1/5~1/8 of the shell-and-tube heat exchanger.
d. Easily change the heat exchange area or process combination;
As long as the number of plates is increased or decreased, the purpose of increasing or decreasing the heat exchange area can be achieved; changing the arrangement of the plates or replacing several plates can achieve the required flow combination and adapt to the new heat transfer conditions while the tube The heat transfer area of ??the shell heat exchanger is almost impossible to increase.
e. Light weight;
The plate heat exchanger plate thickness is only 0.4 ~ 0.8mm, and shell and tube heat exchanger heat exchanger tube thickness is 2.0 ~ 2.5mm, shell shell type than the plate heat exchanger frame is much heavier Plate heat exchangers are generally only about 1/5 of the weight of the shell and tube.
f. The price is low;
Using the same material, the plate heat exchanger costs about 40% to 60% lower than the shell and tube under the same heat transfer area.
g. Easy to make;
Plate heat exchanger heat transfer plate is stamping processing, a high degree of standardization, and a large number of production, shell and tube heat exchanger generally used hand-made.
h. Easy to clean;
If the frame plate heat exchanger loosens and presses the bolt, the plate bundle can be released and the plate can be removed for mechanical cleaning. This is very convenient for the heat exchange process that requires frequent cleaning of the equipment.
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 loss is negligible and no insulation measures are required. The heat loss of the shell-and-tube heat exchanger requires a heat insulation layer.
j. Smaller capacity;
About 10% to 20% of shell-and-tube heat exchangers.
k. The pressure loss per unit length is large;
Since the gap between the heat transfer surfaces is small, the heat transfer surface has irregularities and therefore has a greater pressure loss than a conventional smooth tube.
l. not easy to scale;
Because the interior is fully agitated, it is not easy to foul, and its fouling coefficient is only 1/3~1/10 of the shell-and-tube heat exchanger.
m. Work pressure should not be too large, medium temperature should not be too high, leakage may occur;
The plate heat exchanger is sealed with a gasket. The working pressure should not exceed 2.5 MPa in general, and the medium temperature should be below 250°C, otherwise it may leak.
n.Since the channel between the plates is very narrow, it is usually only 2 to 5 mm. When the heat exchange medium contains large particles or fiber materials, it is easy to plug the channels between the plates