Measures to improve the heat transfer capability of tube bundle heat exchangers
The heat transfer capacity of the tube bundle heat exchanger is determined by the shell side heat transfer coefficient, the tube heat transfer coefficient and the average temperature difference between the logarithm of the cold medium
and the heat medium of the heat exchanger, therefore, the heat transfer capability of the tube bundle heat exchanger
The measures include the following.
(1) to improveThe average logarithmic temperature difference of the cold and hot medium of tube bundle heat exchanger. In addition to being affected directly by the temperature of the cold and hot medium inlet and outlet, the average logarithmic temperature difference of the cold medium and the hot medium is also affected by the flow direction of the cold medium and the heat exchange medium and the heat exchange process.
When the temperature of the cold and hot fluid in 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 the design of the actual heat exchangers, the cold and hot fluid is mostly in staggered flow, and the average logarithmic temperature difference is between the reverse flow and the downstream flow.
Therefore, it is necessary to increase the countercurrent proportion of the cold and hot fluids in the heat exchanger as much as possible to increase the logarithmic average temperature difference of the cold and hot fluids and to improve the heat transfer capability of the heat exchanger.
(2) reasonable to determine the tube and shell media.
In heat exchanger design, installation for shell side baffle heat exchanger, Re > 100, shell side medium of turbulence, as a result, small or medium viscosity of the priority for flow as the shell side heat transfer medium;
Because the pipe cleaning is relatively easy compared to the shell process, it is suitable for the medium with easy scaling, precipitation and sundries.
Considering the economical efficiency, it is more reasonable to heat the medium with high temperature, high pressure or corrosive power.
If the rigid structure of heat exchanger, cold and hot medium temperature difference is big, because of the wall temperature and heat transfer coefficient of the medium temperature is close to, to reduce the expansion of the tube bundle and shell, the shell side of the heat transfer coefficient of the medium walk more reasonable,
However, the temperature difference between the two media is large, and the heat transfer coefficient is more reasonable.
(3) the structural measures for heat transfer of shell heat exchanger are adopted. In the design of heat exchanger, it is usually used to improve heat transfer ability of heat exchanger.The commonly used measures to enhance heat transfer are: high efficiency heat transfer surface, electrostatic field strengthening heat transfer, rough wall surface, stirring, etc.