The plate heat exchanger is a kind of high-efficiency heat exchanger made of a series of metal sheets with a certain corrugated shape. Thin rectangular channels are formed between various plates, and heat is exchanged through the plates. What are the advantages and disadvantages of plate coolers?
1. Large logarithmic average temperature difference, small end temperature difference. In the shell-and-tube heat exchanger, the two fluids flow in the tube-side and the shell-side respectively, and the logarithmic average temperature difference correction coefficient is small. Plate heat exchangers are mostly co-current or counter-current, and their correction factors are usually around 0.95. The temperature difference at the end of the plate heat exchanger is small, and the heat transfer to water can be lower than 1 ° C, while the shell and tube heat exchanger is generally 5 ° C.
2. High heat transfer coefficient. Because different corrugated plates are inverted to form a complicated flow channel, the fluid flows in a three-dimensional rotation in the flow channel between the corrugated plates. It can generate turbulence at a low Reynolds number, so the heat transfer coefficient is high, which is generally considered to be 3 to 5 times that of the shell and tube type.
3. 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 is much heavier than the frame of the plate heat exchanger, and the plate heat exchanger generally only weighs about one fifth of the shell and tube weight.
4. 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. The shell-and-tube heat exchanger has a large heat loss and requires a heat insulation layer.
5. Large pressure loss per unit length. Because the gap between the heat transfer surfaces is small and the heat transfer surfaces have irregularities, the pressure loss is greater than that of a conventional smooth tube.
6. Easy to make. The heat transfer plate of the plate heat exchanger is stamped, has high standardization, and can be produced in large quantities. The shell and tube heat exchanger is generally handmade.
7. The working pressure should not be too high, and the medium temperature should not be too high. The working pressure should generally not exceed 2.5 MPa, and the medium temperature should be below 250 ℃, otherwise it may leak.
8. Easy to block. Because the channels between the plates are very narrow (2 ~ 5mm), when the heat exchange medium contains large particles or fibrous substances, it is easy to block the channels between the plates.