Comparison of plate heat exchanger and shell and tube heat exchanger

Comparison of plate heat exchanger and shell and tube heat exchanger

The plate heat exchanger is a new type of high-efficiency heat exchanger composed of a series of metal sheets with a certain corrugated shape. Many flow channels with small flow sections are formed between the plates, and heat exchange is performed through the plates. Compared with conventional shell and tube heat exchangers, its heat transfer coefficient is much higher under the same flow resistance and pump power consumption. There is a tendency to replace shell and tube heat exchangers within the scope of application.

Comparison of plate heat exchanger and shell and tube heat exchanger

1. High 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, and turbulent flow can be generated at a low Reynolds number (generally Re=50~200), so the heat transfer coefficient High, 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, and the overall flow is cross-flow, and the logarithmic average temperature difference correction coefficient is small. 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 liquids 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 between water and water can be lower than 1 °C, while the shell and tube Type heat exchanger is generally 5 ℃.

3. Small footprint

The structure of the plate heat exchanger is compact, and the heat exchange area per unit volume is 2 to 5 times that of the shell-and-tube type. The area occupied by the heat exchanger is about 1/5 to 1/10 of that of the shell-and-tube heat exchanger.

4. It is easy to change the heat exchange 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. Light weight

The plate thickness of the plate heat exchanger is only 0.4-0.8mm, and the heat exchange tube thickness of the shell-and-tube heat exchanger is 2.0-2.5mm. The frame is much heavier, and the plate heat exchanger is generally only about 1/5 of the weight of the shell and tube type.

6. Low price

With the same material and the same heat exchange area, the price of plate heat exchanger is about 20% to 40% lower than that of shell and tube heat exchanger.

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. Easy to clean

As long as the compression bolts of the frame type plate heat exchanger are loosened, the plate bundle can be opened, and the plates can be removed for mechanical cleaning. It is very convenient to use in occasions that require frequent cleaning of equipment.

9. 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, so it must be kept warm.

10. Small capacity

It is 10% to 20% of the shell and tube heat exchanger.

11. The pressure loss per unit length is large

Since the gap between the heat transfer surfaces is small and there are bumps on the heat transfer surface, the pressure loss is larger than that of the traditional smooth tube.

12. Not easy to scale

Due to the turbulent internal water flow, it is not easy to scale, and its scaling coefficient is only 1/3 to 1/10 of that of the tubular heat exchanger.

13. The plate heat exchanger is sealed with a gasket

Generally, the working pressure should not exceed 1.6Mpa, and the temperature of the medium should be lower than 150°C, otherwise there may be leakage.

14. Due to the narrow channel between plates

Generally, it is only 2-5mm. When the heat exchange medium contains large particles or fibrous substances, it is easy to block.