Views: 1 Author: Site Editor Publish Time: 2023-01-06 Origin: Site
Whether the performance of the shell and tube heat exchanger is good or not, the baffle is very important
The shell and tube heat exchanger is composed of shell, heat transfer tube bundle, tube sheet, baffle (baffle) and tube box and other components. Among them, the baffles have a great influence on the heat transfer efficiency and performance of the heat exchanger, and there are many kinds of baffles, each with its own advantages. Their form, height, and spacing are different, and the overall performance of the heat exchanger is different. The following shell and tube heat exchanger manufacturers will explain to you in detail:
1. Influence of baffle notch height
The bow-shaped baffle is the most widely used baffle structure, and the chord height of the notch should be 0.20 to 0.45 times the inner diameter of the shell-side cylinder. The change of the chord height of the notch of the baffle will definitely change the flow state of the fluid, thereby affecting the heat transfer efficiency.
It is found that the shell-side pressure drop and heat transfer coefficient decrease with the increase of the baffle gap height. The shell-side heat transfer coefficient of the heat exchanger with the vertical cut of the baffle is the largest, and the heat transfer coefficient is the smallest when the horizontal cut is made; the shell-side pressure drop is the largest when the baffle is cut at 45°, and the shell-side pressure drop is the smallest when the vertical cut is made.
2. Influence of baffle spacing
The minimum spacing of the baffles should not be less than 1/5 of the inner diameter of the shell and not less than 50mm. The baffles at both ends of the tube bundle should be arranged at the inlet and outlet of the shell as far as possible, and other baffles should be arranged equidistantly.
The smaller the baffle spacing, the higher the natural vibration frequency of the heat exchange tube, the greater the shell side pressure drop, and the higher the heat exchange efficiency.
It is found that the pressure loss of spiral baffles is smaller than that of arched baffles, and the flow rate increases, and the heat transfer coefficient of spiral baffles and arched baffles increases. The larger the baffle spacing, the smaller the shell-side heat transfer coefficient and the smaller the pressure drop.
3. Influence of baffle structure
Common baffle structures include bow baffles, spiral baffles, disc-ring baffles and fan-shaped baffles. With different baffle structures, the flow and heat transfer performance of the heat exchanger are also different.
The research found that the shell-side heat transfer coefficient and comprehensive performance of the spiral baffle heat exchanger are higher than those of the bow-shaped baffle heat exchanger, and the shell-side pressure loss of the bow-shaped baffle heat exchanger is greater than that of the spiral baffle heat exchanger. . The shell-side velocity distribution is more uniform in the spiral baffle heat exchanger.
Under the same working conditions, the fan-shaped baffle heat exchanger has the most reasonable pressure distribution, and the disc-annular baffle heat exchanger has a more uniform velocity distribution, which is beneficial to slow down the vibration and wear of equipment. The bow-shaped baffle heat exchanger The temperature range varies greatly.
4. Material selection and manufacture of baffles
Although baffles generally do not consider corrosion allowance, improper material selection will also affect the use of heat exchangers. For example, changes in toughness and brittleness of baffle materials at low temperature, creep of baffle materials at high temperatures, electrochemical corrosion between baffles, media, and heat exchange tubes will all cause damage to baffles .
When the baffles are manufactured, in order to prevent damage to the outer surface of the heat exchange tubes, the holes of the baffles need to be chamfered to remove burrs. In order to facilitate pipe threading and ensure concentricity, baffles, support plates, tie rod holes, etc. should be drilled together, and the drilling direction should be consistent with the pipe threading direction.
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