Heat Exchanger Technology Q&A I

1. Q: How to classify the heat exchanger?

A:(1) Shell And Tube Heat Exchanger                  (2) Casing-type heat exchanger

(3) water immersion heat exchanger                  (4) spray type heat exchanger

(5) rotary (snake tube) type heat exchanger       (6) Plate Heat Exchanger

(7) plate fin heat exchanger                              (8) Tube and fin heat exchanger

(9) Waste heat boiler                                       (10) Other

2. Q: How does the heat exchanger transfer heat?

A: In the most common partition heat exchangers, there are mainly two heat transfer modes, conduction and convection. The thermal fluid first transfers heat to one side of the tube wall by convection, and then transfers heat from one side of the tube wall to the other side by conduction, and finally the other side of the tube wall transfers heat by convection. The heat is transferred to the cold fluid, thus completing the heat transfer process of the heat exchanger.

3. Q: What is the effect of media flow rate on heat transfer?

A: The greater the flow rate of the medium, the greater the heat transfer coefficient. Therefore, increase the media flow rate can greatly improve the heat transfer effect, but the negative impact of increasing the flow rate is to increase the pressure drop through the heat exchanger, increasing the energy consumption of the pump, so there must be a certain appropriate range.

4. Q: What is the effect of the Heat Exchanger Tube surface structure on the heat transfer effect?

A: The use of specially designed heat Exchanger Tube surface structure, such as finned tubes, nailhead tubes, threaded tubes, etc., it increases the heat transfer area, and the special surface of the turbulence greatly increases the degree of fluid turbulence outside the tube, both of which can improve the overall heat transfer effect of the heat exchanger, so these surface structures than the performance of the bare tube surface.

5. Q: What are the common methods for descaling the surface of tubes?

A:Mechanical descaling: manual descaling of steel brazing, descaling with pressure water

Chemical descaling

6. Q: What are the methods of anti-fouling on the surface of tubes?

A: Nickel-phosphorus plating

Chemical coating, 847 coating

7. Q: What are the common methods for enhancing heat transfer?

A: (1) Enlarge the structure of heat transfer surface:

Use Finned Tube, nail head tube, threaded tube, corrugated tube, etc.

Machining the surface of the pipe: spiral pipe, spiral groove pipe, etc.

Use small diameter pipes, increase the quantity of pipes on the same Tube Sheet area to increase the heat transfer area.

(2)Increase the flow rate to greatly improve its heat transfer coefficient:

Add a spoiler, such as inserting a spiral belt in the pipe, setting baffle, etc.

Increase the number of tube or shell passes.

In addition, producing heat exchangers from materials with good thermal conductivity, taking anti-corrosion and anti-scaling measures, and timely cleaning are all ways to improve the heat transfer effect.

8. Q: What are the requirements for the number of blocked tubes when the tube heat exchanger is serviced?

A: Corrosion and perforation of individual pipes in the tube bundle can be blocked with a processed metal plunger with a taper of 3 to 5°. Generally in the same pipe pass, the number of blocked pipes does not exceed 10% of the total number of pipes, but it can be appropriately increased according to the requirements of the process.