Shell and tube heat exchanger (shell and tube heat exchanger), also known as tube heat exchanger. Is closed in the shell of the wall of the tube bundle as the heat transfer surface of the wall type heat exchanger. This heat exchanger structure is relatively simple, reliable operation, can be used in a variety of structural materials (mainly metal materials) manufacturing, can be used at high temperatures and high pressures, is currently the most widely used type.

framework

Shell and tube heat exchanger consists of shell, heat transfer tube bundle, tube plate, folding plate (baffle) and tube box and other components. The shell is mostly cylindrical, with tube bundles inside, and the ends of the tube bundles are fixed on the tube plate. Heat transfer of cold and hot two kinds of fluids, one in the tube flow, known as the tube course fluid; another in the tube outside the flow, known as the shell course fluid. In order to improve the heat transfer coefficient of the fluid outside the tube, usually installed in the shell of a number of baffles. Baffle can increase the shell process fluid velocity, forcing the fluid to pass through the tube bundle according to the specified distance several times laterally, to enhance the degree of fluid turbulence. Heat exchanger tubes in the tube plate can be arranged according to the equilateral triangle or square. Equilateral triangle arrangement is more compact, high degree of fluid turbulence outside the tube, heat transfer coefficient; square arrangement is easy to clean outside the tube, suitable for easy scaling of the fluid.

typology

Shell and tube heat exchangers have different temperatures of the fluid inside and outside the tubes, so the temperature of the heat exchanger shell and the tube bundle are also different. If the difference between the two temperatures is very large, the heat exchanger will produce a large thermal stress, resulting in tube bending, fracture, or pull off from the tube plate. Therefore, when the temperature difference between the tube bundle and the shell exceeds 50°C, appropriate compensation measures need to be taken to eliminate or reduce the thermal stress. According to the compensation measures adopted, shell and tube heat exchangers can be divided into the following main types.

① fixed tube and plate heat exchanger tube bundles at both ends of the tube plate and shell into one, simple structure, but only for hot and cold fluid temperature difference is not large, and the shell process does not require mechanical cleaning of the heat transfer operation. When the temperature difference is slightly larger and the shell pressure is not too high, can be installed in the shell with elastic compensation ring to reduce thermal stress.

Floating head heat exchanger tube bundle at one end of the tube plate can float freely, completely eliminating the thermal stress; and the entire tube bundle can be withdrawn from the shell, to facilitate mechanical cleaning and maintenance. Floating head type heat exchanger is more widely used, but the structure is more complex, higher cost.

③ U-tube heat exchanger Each heat exchanger tube are bent into a U-shape, the ends were fixed in the same tube plate up and down the two areas, with the help of the tube box into the import and export of the two rooms of the partition. This heat exchanger completely eliminates thermal stress, the structure is simpler than the floating head type, but the tube course is not easy to clean.

④ Vortex heat film heat exchanger Vortex heat film heat exchanger adopts the latest vortex heat film heat transfer technology to increase the heat transfer effect by changing the state of fluid movement, when the medium passes through the surface of the vortex tube, the surface of the tube is strongly flushed to improve the heat transfer efficiency. It can reach up to 10000W/m2℃. At the same time, this structure realizes corrosion resistance, high temperature resistance, high pressure resistance and anti-scaling function. Other types of heat exchangers have fluid channels in the form of fixed directional flow, forming a winding flow on the surface of the heat exchanger tube, and the convection heat transfer coefficient is reduced.

According to the information of [heat exchanger equipment promotion center], the biggest characteristic of vortex heat film heat exchanger lies in the unity of economy and safety. As a result of the consideration of the flow relationship between the heat transfer tube, heat transfer tube and shell, no longer use the folding plate forced blocking way to force out the turbulence, but by the natural induction between the heat transfer tube to form alternating vortex flow, and to ensure that the heat transfer tube does not friction with each other under the premise of maintaining due to the strength of the flutter. Rigidity and flexibility of the heat exchanger tube configuration is good, will not collide with each other, not only to overcome the floating coil heat exchanger collision between each other to cause damage to the problem, but also to avoid the ordinary shell and tube heat exchanger easy to scale the problem.

performances

specificities

1. High efficiency and energy saving, the heat transfer coefficient of this heat exchanger is 6000-8000W/m2.0C.

2. All stainless steel production, long service life, up to 20 years or more.

3. Change laminar flow into turbulent flow, improve the heat transfer efficiency, reduce the thermal resistance.

4. Fast heat exchange, high temperature resistance (400℃), high pressure resistance (2.5Mpa).

5. Compact structure, small footprint, light weight, easy to install, saving civil investment.

6. Flexible design, complete specifications, practical and targeted, saving money.

7. Wide range of application conditions, applicable to a wide range of pressure, temperature and a variety of media heat exchange.

8. Low maintenance costs, easy to operate, long scale cycle, easy to clean.

9. Adopting nano thermal film technology, significantly increasing the heat transfer coefficient.

10. Wide range of applications, can be widely used in thermoelectricity, factories and mines, petrochemical industry, urban centralized heat supply, food and medicine, energy and electronics, machinery and light industry.

performance comparison  

Non-metallic materials heat exchanger chemical production of highly corrosive fluid heat transfer, the need to use ceramic, glass, PTFE, graphite and other non-metallic materials to make shell and tube heat exchanger.

One of the main material of silicon carbide as the ceramic heat exchanger has the following characteristics.

The production process of ceramic heat exchanger is basically the same as that of kiln furniture, and thermal conductivity and oxidation resistance are the main application properties of the material. It is the principle of the ceramic heat exchanger placed in the flue outlet closer to the higher temperatures, do not need to be mixed with cold air and high temperature protection, when the kiln temperature of 1250-1450 ℃, the flue outlet temperature should be 1000-1300 ℃, ceramic heat exchanger recovery of waste heat up to 450-750 ℃, will be recycled to the hot air into the kiln and the gas to form a mixture of gas for combustion, can save energy! 25% -45%, which directly reduces production costs, increase economic efficiency.

Ceramic heat exchanger in the use of metal heat exchanger under the limitations of the development of a good, because it is a better solution to the corrosion resistance, high temperature and other issues, and has become the recovery of high-temperature waste heat recovery of the best heat exchanger. After years of production practice, shows that ceramic heat exchanger effect is very good. Its main advantages are: good thermal conductivity, high-temperature strength, oxidation resistance, good thermal shock resistance. Long life, small maintenance, reliable and stable performance, easy to operate. It is the best device for recovering high temperature flue gas waste heat.

At present, ceramic heat exchanger can be used in metallurgy, non-ferrous, refractory, chemical, building materials and other industries, the main thermal kiln, is making a great contribution to the world's energy saving and emission reduction cause.

Flow path selection for heat transfer of hot and cold two fluids, according to the following principles of selection of flow path: ① unclean and easy to scale the fluid should be taken to the tube, because the tube cleaning is more convenient; ② corrosive fluid should be taken to the tube, so as to avoid corrosion of the bundles and shells at the same time; ③ high pressure fluid should be taken to the tube to avoid the shell to withstand the pressure; ④ saturated steam is appropriate to go to the shell process, because of the condensation of steam and flow rate of heat transfer coefficients have nothing to do with the condensate is easy to discharge; ⑤ if the temperature difference between the two fluids, the temperature difference between the two fluids is not as large as in the heat exchange, the condensate can easily discharge; ⑤ if the temperature difference between the two fluids. ⑤ If the temperature difference between the two fluids is large, the selection of fixed tube plate heat exchanger, it is desirable to make the heat transfer coefficient of the fluid to go to the shell process, in order to reduce the thermal stress.

Operation strengthening when the difference between the two sides of the tube wall heat transfer coefficient is very large (such as small viscosity of the liquid and gas heat transfer), should try to reduce the heat transfer coefficient of the low side of the thermal resistance. If the heat transfer coefficient outside the tube is small, you can use the external threaded tube (low finned tube), in order to increase the heat transfer area outside the tube and fluid turbulence, reduce the thermal resistance. If the tube heat transfer coefficient is small, can be set up in the tube twisted iron, spiral ring and other additives to enhance the tube perturbation, strengthen the heat transfer, of course, this time the resistance of the fluid flow will also increase.

Heat exchanger unit
 

Thermal sensing heat exchanger unit is a cold and hot direct mixing type heat exchanger unit, heat transfer efficiency can reach the limit of 100 percent, which is essentially different from the traditional between-wall heat exchanger, such as shell and tube heat exchanger, as we all know, the traditional between-wall heat exchanger because of its own fatal flaws - noise and vibration, it is difficult to get the market to promote the wide range of customers and customers agree. Due to various reasons caused by the system pressure fluctuations will trigger the type of heat exchanger strong operating noise, to the user to use a great inconvenience.

Thermal sensing heat exchanger unit has successfully overcome the technical defects of the above heat exchanger, through the combination of mass and heat transfer and injection principle, completely eliminated the huge noise source caused by the system pressure fluctuations, not only realizes the zero thermal resistance heat exchange of thermal and cold sensing, but also makes full use of the sensible calorific value of the condensate, so that the heat exchanger efficiency reaches a very high level, in addition to the full use of this product to take full advantage of the internal and external kinetic energy of the steam itself, to promote the circulation of the whole system, greatly reducing the electrical energy consumed for promoting the system circulation, while the condensate can be 100% recycled. In addition, the product makes full use of the internal and external kinetic energy of the pressurized steam itself to promote the circulation of the whole system, which greatly reduces the consumption of electric energy due to the promotion of the system circulation. The product fully achieves the energy-saving effect of saving steam, electricity and water, and creates considerable energy-saving benefits for the users and the society, which further increases the value of the product. As the condensate is recycled by the system, the water used in the whole system is completely replaced by pure condensate, thus completely eliminating the possibility of scaling in the whole system at the source, from the main heat exchanger to the user's radiator panels are all operating under an ideal working condition, which greatly enhances the operating efficiency of the whole heat exchanger system as well as the service life of heat exchanger unit.

Technical features.

1, rapid heat transfer, heat transfer efficiency, heat transfer efficiency up to 100%.

2, condensate recovery, recycling, the entire system water self-cleaning anti-scaling, heat exchangers, radiators and heat transfer system can maintain long-term stable and efficient heat exchange performance, minimize system scaling phenomenon, will not be difficult to overcome the scaling drawbacks and reduce the efficiency of the system heat transfer.

3, the heat exchanger is made of stainless steel, the product structure is scientifically designed, well-made, long service life, up to 20 years or more.

4, the key components of the German advanced technology and order processing, so the host is not affected by the steam pressure and system pressure, effectively eliminating the noise, the phenomenon of vapor strike, the whole machine running smoothly.

5, condensate is completely absorbed and utilized, the system has no special reasons, no need to set up water replenishment device, greatly saving the system water and operating costs.

6, the whole set of compact structure, covers an area of small, greatly saving the investment in civil engineering, at the same time, due to the heat transfer efficiency is very high, the system does not need to replenish water during operation, the whole set of steam-saving, power-saving, water-saving trinity, for the user to create considerable energy-saving benefits.

7, the unit has a highly intelligent automation control function, can realize the overpressure, over-temperature protection, power outage steam automatic cut-off and outdoor temperature automatic compensation function and can realize remote monitoring and control, to provide users with a worry-free operation platform.

8, the application field is broad, can be widely used in thermoelectricity, factories and mines, food and medical, machinery and light industry, civil construction and other fields of heating, hot water bathing and other purposes.

9、Wide application conditions, can be used for heat exchange of larger pressure and temperature range.

Cooling characteristics

1. The heat transfer tube adopts copper tube with rolled fins on the outer surface, which has high thermal conductivity and large heat transfer area.

2. The guide plate guides the shell fluid to flow continuously in the heat exchanger in the form of a folded line, the distance between the guide plate can be adjusted according to the optimal flow rate, the structure is sturdy, to meet the large flow or even large flow rate, high pulsation frequency of the shell fluid heat transfer.

3. When the shell fluid is oil, it is suitable for low viscosity and cleaner oil heat exchange.

control parameter

1.The main control parameters of shell and tube heat exchanger are heating area, hot water flow rate, heat exchange capacity and heat medium parameters.

Points of Selection

1), according to the known cold and hot fluid flow, initial and final temperature and specific heat capacity of the fluid to determine the required heat transfer area. Preliminary estimate of the heat transfer area, generally assume the heat transfer coefficient, determine the structure of the heat exchanger, and then calibrate the heat transfer coefficient K value.

2), the selection of heat exchanger should pay attention to the pressure level, the use of temperature, interface connection conditions. In the pressure drop, under the premise of installation conditions allow, shell and tube heat exchanger to choose a small diameter of the elongated type, is conducive to improving the heat transfer.

3), the pressure drop of the heat exchanger should not be too large, generally controlled between 0.01 ~ 0.05MPa;.

4), the size of the flow rate should take into account the viscosity of the fluid, viscosity of the flow rate should be less than 0.5 ~ 1.0m / s; general fluid tube flow rate should be taken 0.4 ~ 1.0m / s; easy to scale the fluid should be taken 0.8 ~ 1.2m / s.

5), high-temperature water into the heat exchanger before the appropriate filter.

6), the heat exchange station in the heat exchanger of a single unit to deal with and configure the number of units combined results should meet the total heat exchange station heat load and the requirements of regulation. Under the premise of meeting the user's heat load regulation requirements, the number of heat exchanger units in the same heating coefficient should not be less than 2 units, should not be more than 5 units.

Installation points

1), the heat exchanger should be 1.5 times the maximum working pressure to do hydraulic test, the steam part should not be less than the steam supply pressure plus 0.3MPa; hot water part should not be less than 0.4MPa. In the test pressure, keep the pressure does not fall for 10min.

2), shell and tube heat exchanger front end should be left to extract the bundle of space, that is, its head in the wall or roof distance shall not be less than the length of the heat exchanger, equipment operation channel net width should not be less than 0.8m.

3), all types of valves and meters should be installed at a height that facilitates operation and observation.

4), the upper part of the heater accessories (generally refers to the safety valve) of the highest point to the lowest point of the building structure of the vertical clearance should meet the requirements of the installation test, and shall not be less than 0.2m.

Implementation standards

Product standard

Shell and tube heat exchanger GB151-1999

Infusion type volumetric water heater and semi-volumetric water heater (U-type tube bundle)" CJ/T 163-2002

Engineering Standards

Code for Quality Acceptance of Construction of Building Water Supply, Drainage and Heating Works GB50242-2002

Related Standard Drawings

05R103 Heat exchange station engineering design and construction drawing set

01S122-1~10 Water Heater Selection and Installation

corrosion analysis

Shell and tube heat exchanger materials are generally based on carbon steel, stainless steel and copper, the carbon steel material of the tube plate in the use as a cooler, the tube plate and tube weld often corrosion leakage, leakage into the cooling water system to pollute the environment and cause material waste.

Shell and tube heat exchanger in the production, tube plate and tube welding generally use manual arc welding, weld shape there are different degrees of defects, such as depression, porosity, slag, etc., weld stress distribution is not uniform. When in use, the pipe plate part is generally in contact with industrial cooling water, and the impurities, salts, gases, microorganisms in the industrial cooling water will constitute the corrosion of the pipe plate and weld seam, which is often referred to as galvanic corrosion. Studies have shown that industrial water, whether freshwater or seawater, will have a variety of ions and dissolved oxygen, of which the concentration of chloride ions and oxygen changes, the corrosion shape of the metal plays an important role. In addition, the complexity of the metal structure will also affect the corrosion pattern. Therefore, the corrosion of the weld seam between the tube plate and the column pipe is dominated by pore corrosion and crevice corrosion. From the outside, there will be many corrosion products and deposits on the surface of the tube plate, distributed with pits of different sizes. With seawater as the medium, it will also produce galvanic corrosion. Chemical corrosion is the medium of corrosion, heat exchanger tube plate contact with a variety of chemical media, will be subject to chemical media corrosion. In addition, the heat exchanger tube plate will also produce a certain bimetallic corrosion between the heat exchanger tube.

In summary, the main factors affecting shell and tube heat exchanger corrosion are.

(1) media composition and concentration: the effect of concentration varies, for example, in hydrochloric acid, generally the greater the concentration of corrosion is more serious. Carbon steel and stainless steel in the concentration of about 50% of sulfuric acid corrosion is the most serious, and when the concentration increases to more than 60%, the corrosion instead of a sharp decline;.

(2) impurities: harmful impurities including chloride ions, sulfur ions, cyanide ions, ammonia ions, etc., these impurities in some cases can cause serious corrosion

(3) temperature: corrosion is a chemical reaction, the temperature is raised every 10 ℃, the corrosion rate of about 1 ~ 3 times, but there are exceptions; (4) temperature: corrosion is a chemical reaction, the temperature is raised every 10 ℃, the corrosion rate of about 1 ~ 3 times, but there are exceptions.

(4) ph value: generally the smaller the ph value, the greater the corrosion of the metal.

(5) flow rate: in most cases, the greater the flow rate, the greater the corrosion.

Anti-corrosion protection

For cooling tower corrosion problems, the traditional method to fill welding-based, but fill welding easy to make the internal stress of the tube plate, difficult to eliminate, may cause the cooling tower tube plate weld leakage again. Western countries now use polymer composite materials for protection. It has excellent adhesion properties and temperature and chemical resistance, can be safely used in a closed environment without shrinkage, especially good isolation of bimetallic corrosion and resistance to scouring performance, fundamentally eliminate the repair parts of the corrosion leakage, provide a long-lasting protective coating for the cooling tower.