What is a tube bundle?
The heat transfer capacity of the tube bundle heat exchanger is determined by the shell-side heat transfer coefficient, the tube-path heat transfer coefficient, and the logarithmic mean temperature difference of the heat and cold medium of the heat exchanger. Therefore, the heat transfer ability of the tube bundle heat exchanger is improved. The measures include the following points.
1. Increase the average logarithmic temperature difference between the cold and hot medium of the tube bundle heat exchanger.
The average logarithmic temperature difference between cold and hot media, in addition to being directly affected by the temperature of the inlet and outlet of cold and hot media, is also affected by the flow direction of the cold and hot media and the heat transfer process. When the temperature of the cold and hot fluids of the heat exchanger changes along the heat transfer surface, the average temperature difference between the two fluids is the largest, and the average temperature difference between the two fluids is the smallest. In actual heat exchanger design, cold and hot fluids mostly use staggered flow mode, and the average logarithmic temperature difference is between countercurrent and forward flow. Therefore, the countercurrent ratio of the heat and cold fluid should be increased as much as possible to increase the logarithmic average temperature difference between the hot and cold fluids and improve the heat transfer capacity of the heat exchanger.
2. Reasonably determine the tube and shell media.
In the design of heat exchangers, for the heat exchangers with baffle shells installed on the shell side, when Re>100, the shell-side medium reaches turbulent flow. Therefore, for medium with small flow or high viscosity, it is preferred to consider it as shell-side heat exchange medium. Because the tube cleaning is easier than the shell cleaning, it is better to use the tube for easy fouling, sedimentation and debris. From the economical point of view, for high temperature, high pressure or corrosive medium, it is more reasonable as a heat transfer medium. For a heat exchanger with a rigid structure, if the temperature difference between the cold and hot medium is large, the temperature of the wall surface is close to the temperature of the medium with a large heat transfer coefficient, In order to reduce the difference between the expansion of the tube bundle and the shell, the medium heat transfer coefficient of the shell is more reasonable. The cold and hot medium temperature difference is small, the two mediums have large differences in heat transfer coefficient, and the heat transfer coefficient of the medium is more reasonable.
3. Structural measures to enhance the heat transfer of shell and tube heat exchangers.
In heat exchanger design, heat transfer enhancement measures are usually used to increase the heat transfer capacity of the heat exchanger. The commonly used measures to enhance heat transfer include: high-efficiency heat transfer surface, electrostatic field enhancement heat transfer, rough wall surface, stirring, etc.