Heat Exchanger Technology Q&A III

1. Q: What are the characteristics of fixed tube Plate Heat Exchanger, U-typed tube heat exchanger and Floating Head Heat Exchanger?

A: The fixed tube plate heat exchanger is characterized by compact structure, simplicity, low cost, the largest number of tubes in the same shell diameter, easy replacement and maintenance of a single tube, and easy cleaning inside the tube, but it is difficult to clean the outside of the tube. The temperature difference is large.

The U-tube heat exchanger is characterized by simple structure, no temperature difference stress problem, large fluid flow rate, low metal consumption, suitable for high temperature and high pressure fluid, and the tube bundle can be drawn out to clean the shell side and inter-tubes, but the elbow in the tube is not easy to clean. The number of tubes on the tube plate is small, the distance between the tubes is large, there is a gap in the center of the tube bundle, and the fluid outside the tube is easy to short-circuit.

The characteristics of the floating head heat exchanger are that the tube bundle can move freely, without temperature difference stress. The tube bundle can be freely drawn out, which is convenient for cleaning the outside of the tube and the tube bundle. Leaks are not easy to detect by inspection.

2. Q: Where is the fixed tube plate heat exchanger suitable for?

A: For the case where the medium on the shell side is clean, not easy to scale, and the temperature difference of the medium is relatively small.

3. Q: Where is the U-tube heat exchanger suitable for?

A: For the occasions where the temperature difference between the shell and the tube’s wall is large and the high temperature and high pressure of the cleaning medium is carried in the tube.

4. Q: Where is the floating head heat exchanger suitable for?

A: For occasions where the temperature difference between the shell and the tube is large, the medium is not clean, and it needs to be cleaned frequently.

5. Q: Why the arrangement of the tubular heat exchanger is triangular or square with a 45° angle?

A: The triangle arrangement and the square arrangement with a 45° angle have their own advantages and disadvantages.

The advantages of the triangular arrangement are compactness and high heat transfer efficiency. The number of tubes in the same Tube Sheet area is the largest, which is about 15% more than that of the square arrangement, but it is not easy to clean the outer surface of the tube; while the square is arranged at a 45° angle to clean the outer surface of the tube It is more convenient, but the number of pipes is much less than that of the triangular arrangement.

6. Q: What are the common materials for Shell&Tube heat exchanger?

A: 10#, 20#, 12CrMo, 15CrMo, 0Cr13, 1Cr13, 1Cr5Mo, 0Cr18Ni9Ti, 1Cr18Ni9Ti, titanium tube, 410, 321, etc.

7. Q: In the Shell And Tube Heat Exchanger, why choose φ32, φ25, φ19, φ16 for the pipe diameters?

A: The size of the pipe diameter will directly affect the performance of the heat exchanger. The heat supply coefficient of small diameter pipe is large, and its effective heat transfer area is also large in the same volume. This not only makes the structure compact, but also saves material.

However, if the pipe diameter is too small, it will also bring adverse effects. For the fluid with the same flow rate, the smaller the pipe diameter, the greater the resistance to flow, and the pressure loss will also increase. In addition, too thin pipes are easily blocked by dirt. Makes cleaning difficult, so the diameter of the heat exchanger is generally 16 mm to 32 mm.

8. Q: Why are the bolt holes of the heat exchanger support bound or elongated?

A: The bolt holes on the fixed support are round, the purpose is to fix the shell tightly on the foundation. The bolt holes on the movable support are long and round, and the purpose is to allow the shell to expand and contract freely when the temperature changes, so as to avoid large stress and protect the equipment.