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Question and answer to the most complete heat exchanger technology

1. how can the heat exchange equipment be classified?
Answer: can be divided into:
(1) tube shell heat exchanger
(2) casing heat exchanger
(3) water immersion heat exchanger
(4) spray heat exchanger
(5) rotary (snake tube) heat exchanger
(6) plate heat exchanger
(7) plate fin heat exchanger
(8) tube fin heat exchanger
(9) heat exchanger tubes
(10) other
2. how does the heat exchanger heat the heat?
Answer: in the most common wall type heat exchangers, there are mainly two ways of conduction and convection. The heat transfer is first passed to one side of the tube wall by convection heat transfer, then the heat passes through the side of the tube wall through the way of conduction, and the heat transfer is passed to the cold fluid on the other side of the tube wall, and the heat transfer process of the heat exchanger is completed.
3. medium velocity on the heat transfer effect?
Answer: the greater the velocity of the medium in the heat exchanger, the greater the heat transfer coefficient. Therefore, increasing the velocity of the medium in the heat exchanger can greatly improve the heat transfer effect, but the negative effect of increasing the flow rate is to increase the pressure drop through the heat exchanger and increase the energy consumption of the pump, so it is necessary to have a certain suitable range.
4. how does the surface structure of the heat exchanger affect the heat transfer effect?
Answer: the special design of heat transfer tube surface structure, such as fin tube, nail head tube, thread tube and so on, on the one hand increase the heat transfer area, on the other hand, the disturbance of the special surface greatly increases the turbulence level of the fluid outside the tube, which can increase the overall heat transfer effect of the heat exchanger in two aspects, so these surface structures are better than light. The performance of the tube surface is excellent.
5. what are the usual ways to remove fouling on the surface of heat exchanger tubes?
Answer: the common methods of descaling on the surface of heat exchange tube are:
Mechanical descaling: manual cleaning of steel drill and scaling of pressure water
Chemical descaling
6. are there any methods for anti scaling on the surface of the heat exchange tube?
Answer: (1) nickel phosphorus plating
(2) chemical coating, 847 coating
7. what are the commonly used methods to enhance heat transfer in heat exchangers?
Answer: the main method of heat transfer enhancement in heat exchange equipment
One is to use the structure of increasing the heat transfer surface, such as
1 use finned tube, nail head pipe, screwed pipe, bellows and so on.
2 the surface of the pipe is machined: spiral pipe, spiral grooved tube, screwed pipe, etc.
3 small tube diameter can increase the number of tubes on the same tube plate area and increase the heat transfer area.
The two is to increase the flow rate of fluid in the heat exchanger, which can greatly improve its heat transfer coefficient, such as:
1 adding spoiler, such as inserting spiral belt in the tube, setting baffle outside the tube, false pipe, etc.
2 increase the number of tube or shell process.
In addition, the use of materials with good thermal conductivity to make heat exchangers, good heat and corrosion prevention measures, and timely scaling are all means to improve the heat transfer effect.
8. what is the requirement for the number of pipe plugging when the tubular heat exchanger is overhauled?
Answer: the tube holes are allowed to be blocked by a metal plunger with a conical degree of 3~5 degrees. Generally speaking, the number of tubes that are blocked in the same pipe range will not exceed 10% of the total number of pipes, but can be appropriately increased according to the technological requirements.
9. why does the gasket on both sides of the tubesheet have to choose the same material?
Answer: because the flange bolts on both sides of the tubesheet are the same bolts, the specific pressure applied to the gaskets on both sides of the tubesheet is the same. If the gaskets on both sides of the two sides choose different materials, it will cause the sealing failure of one side gasket not enough and the sealing failure of the gasket on the other side is too large, so the gasket on both sides of the tube must choose the same material.
Why does the 10. cooling water heat exchanger produce scale?
Answer: the scale is formed by the crystallization of dissolved salts in the water and attached to the wall of the heat exchanger tube. Its characteristics are dense and hard, firmly attached and difficult to remove. A large number of suspended particles in water can become crystal species. Other impurity ions, bacteria and rough metal surface all have a strong catalytic effect on the crystallization process, which greatly reduces the supersaturation required by the crystallization. Therefore, the cooling water heat exchanger is very easy to produce scale.
What are the main components of the 11. float heat exchanger?
Answer: the main components are: tube bundle, baffle plate, drawing bar, fixed distance pipe, shell, tube box, tube plate, inlet flange, outlet flange, floating head flange, float head cover, float head hook ring, float head gasket, outer cover flange, outer lid flanges, outer cover, outer lid gasket, exigents, draining mouth Pipe box flange, pipe box side flange, pipe box gasket, pipe box side gasket, fixed saddle, movable saddle.
12. what are the main components of the fixed tube sheet heat exchanger?
Answer: the main components are: tube bundle, baffle plate, pull rod, fixed distance pipe, shell, tube box (top cover), tube plate, inlet flange, outlet flange, pipe box flange, tube box gasket, fixed saddle, active saddle, ear type support, expansion joint.
What are the main components of the 13.U tube heat exchanger?
Answer: the main components are: U tube bundle, baffle plate, punching plate (inner guide tube), pull rod, fixed distance pipe, shell, tube box, tube plate, inlet flange, outlet flange, pipe box flange, tube box flanges, tube box gasket, tube box side gasket, fixed saddle, moving saddle.
What are the main components of the 14. casing heat exchanger?
Answer: the main components of the sleeve type heat exchanger are: inner tube, outer pipe and back elbow.
15. what are the main components of a water immersion heat exchanger?
Answer: the main components of the water flooding heat exchanger are: inlet pipe, outlet pipe, collecting pipe, snake pipe and cooling water tank.
What are the main components of the 16. spray heat exchanger?
Answer: the main components of the spray heat exchanger are: tube bundle, fan, water nozzle, drainage pipe, feed water pump.
What are the main components of the 16. spray heat exchanger?
Answer: the main components of the spray heat exchanger are: tube bundle, fan, water nozzle, drain pipe and feed water pump.
17. what are the characteristics of fixed tube sheet heat exchangers, U tube heat exchangers and floating head heat exchangers?
Answer: the characteristics of the fixed tube plate heat exchanger are compact, simple, low cost, the largest number of tubes in the same shell diameter, convenient maintenance of the single tube, convenient cleaning in the tube, but difficult to clean out of tube, and the high stress of tube and shell body temperature. The U type tube heat exchanger is characterized by its simple structure, no temperature difference stress problem, high flow velocity, low metal consumption and high temperature and high pressure fluid. The tube bundle can be easily removed to clean the shell and pipe, but the elbow is not easy to sweep, the tube number is few, the tube spacing is large, the tube center has gap, and the fluid outside the tube is easily short circuited. . The float head type heat exchanger is characterized by the free movement of the tube bundles, no temperature difference stress problem, the free extraction of the tube bundles, the convenience of cleaning the pipe and the tube bundle, but the structure of the float head is complex, the cost is high, the sealing requirement of the float head is more strict, the float head is easy to leak and is not easy to check and find in operation.
18. where are the fixed tube sheet heat exchangers applicable?
Answer: fixed tube sheet heat exchangers are suitable for occasions where shell side medium is clean, it is not easy to scale, and medium temperature difference is relatively small.
Where is the 19.U type tube heat exchanger?
Answer: U type tubular heat exchangers are suitable for high temperature and high pressure applications in the tubes.
20. where do the float heat exchangers apply?
Answer: floating head heat exchangers are suitable for occasions where the temperature difference between the shell and tube is large, the medium is not clean and needs frequent cleaning.
21. the arrangement of tubular heat exchangers is arranged in triangle and square to 45 degrees. Why?
Answer: triangle arrangement and square rotation to 45 degree angle have their advantages and disadvantages. The advantages of triangle arrangement are compact and high heat transfer efficiency. The number of pipe rows on the same tube plate area is the most, which is about 15% more than square arrangement, but it is not easy to clean the outer surface of the tube, while the square to 45 degree angle is more convenient to arrange the surface of the tube, but the number of pipe row is much less than that of the triangle row.
22. what are the materials commonly used in tubular heat exchangers?
Answer: materials commonly used for pipes are: 10#, 20#, 12CrMo, 15CrMo, 0Cr13, 1Cr13, 1Cr5Mo, 0Cr18Ni9Ti, 1Cr18Ni9Ti, titanium tube, 410321, etc.
23. in tube heat exchangers, why are diameters of 32, 25, 19 and 16?
Answer: the size of the pipe will directly affect the performance of the heat exchanger. The diameter of the tube is small, the heat transfer coefficient is large, and the effective heat transfer area is large in the same volume. This can not only make the structure compact, but also save the material. The smaller the diameter of the fluid with the same flow rate, the smaller the diameter, the greater the resistance to the flow and the increase of the pressure loss. In addition, the thin tubes are also easily blocked by the dirt, making the cleaning difficult, so the diameter of the heat exchanger is usually 16 mm to 32 mm.
24. why does the bolt hole of the heat exchanger support have circular and long circular ones?
Answer: the bolt hole on the fixed support is circular, so that the shell can be firmly fastened to the foundation. The bolt holes on the movable support are long and round, the purpose is to make the shell free and telescopic when the temperature changes, and avoid the large stress to protect the equipment.
25. what are the commonly used heat exchanger gaskets?
Answer: commonly used heat exchanger gaskets are oil resistant asbestos mats, iron pads, wave tooth mats, metal mats.
26. what should we pay attention to when choosing the bolts for floating heads of floating head heat exchangers?
(1) length
(2) wet H2S stress corrosion
(3) temperature
27. what is the function of baffles (baffles) in tubular heat exchangers?
Answer: the baffle (baffle) in the heat exchanger can change the flow direction of the fluid in the shell, increase the flow velocity in the shell, increase the turbulence level of the medium, improve the heat transfer efficiency and support the function of the tube bundle.
28. why does tube heat exchanger have single tube, two tube, four tube, six tube, eight pipe?
Answer: when the number of heat exchangers is at the same time, increasing the number of tubes can increase the flow rate in each pipe, so it can increase the heat coefficient and reduce the required heat transfer area. But at the same time, the pressure drop is also increased, and the fluid can not be completely reheated by countercurrent, and the heat exchanger structure is more complicated. Therefore, the general number of pipe runs should be no less than 2, not greater than 8, and should be chosen according to the actual process requirements.
29. what are the causes of leakage in tubular heat exchangers?
Answer: there may be the following reasons for the leakage in the heat exchanger:
Corrosion perforation, or fracture of heat transfer tube
Leakage of pipe mouth cause leakage
Loosening of heat transfer tube and tube plate expansion joint
Cracks, holes or corrosion holes on the weld of heat exchanger tubes and tubesheet.
Loosening or breaking of small float bolt
Small float gasket damage
Seal damage of small float or floating tube plate
30. why should the water pressure be tried after the heat exchanger is overhauled?
Answer: the purpose of the test water pressure of the heat exchanger is to check whether the heat exchanger has the ability to withstand the design pressure (i. e. pressure strength), tightness, the quality of the interface or joint, the quality of the welding and the tightness of the sealing structure. In addition, the residual deformation of the welding seam of the parent material and the pipe after pressure can be observed, and the problems existing in the material can be found in time.
31. what are the installation positions of tubular heat exchangers, some of them are upright, and others are horizontal (horizontal)?
Answer: the tubular heat exchangers are set up and some are lying, mainly from the following aspects: (1) the production process requirements: if some reboiler needs a certain height of the medium liquid level, if the displacement heater is used, that is, the height of the liquid level can not be reached, so the selection of the replacement heat exchanger must be selected; 2. A process unit needs thousands of square meters of heat exchange area. If a heat exchanger with a heat pipe length of 6 meters is selected, a number of heat exchangers may be needed. It occupies a large area and is not conducive to the space effective arrangement of the device. If a vertical replacement heat exchanger with a length of 12 meters of heat transfer tube is selected, 1 sets can solve the problem; 3. Reduce the pressure drop: some students reduce the pressure drop. The production process is required to minimize the pressure drop in the medium transport process, select the vertical displacement heat exchanger and arrange it together with the tower, so that it can shorten the connection line with the tower and reduce the pressure drop.
32. why do some places choose casing heat exchangers and water immersed heat exchangers, while others use tubular heat exchangers?
Answer: at present, most of the heat exchanger selected for oil refining and chemical production equipment are tubular heat exchangers, but in some production devices, there are still a small amount of casing heat exchangers and water immersed heat exchangers. Although tubular heat exchanger has compact structure and high heat exchange efficiency, it is easy to cause blockage if it is used in medium containing solid particles due to its smaller heat exchanger tubes. Therefore, in the medium containing solid particles, the casing heat exchanger or the water immersion heat exchanger is usually selected.
Source: China Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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