The main contradiction should be grasped when selecting the medium in the tube and shell side of the heat exchanger to determine whether some medium goes through the tube side or the shell side. Comprehensive consideration should be given to conditions such as the nature of the medium, temperature or pressure, allowable pressure drop, fouling, and increasing the heat transfer coefficient of the heat exchanger.
(1) Corrosive, toxic, high temperature or pressure media, as well as media that are prone to fouling, should go through the tube side, mainly because: the shell side of the heat exchanger with corrosive media, the tube and shell side material Both are subject to corrosion. Therefore, the general corrosive medium can reduce the requirements on the shell side material; the toxic medium can reduce the chance of leakage; the high temperature and pressure of the heat exchanger can reduce the requirements on the shell side material. , And the fouling is easy to clean in the pipe pass.
(2) It is beneficial to improve the total heat transfer coefficient of the heat exchanger and make full use of the pressure drop. The cross-section and direction of the flow channel in the shell side of the fluid are constantly changing and a baffle plate can be set to easily achieve turbulent flow. Re>100 means turbulent flow, and tube side Re>10000 means turbulent flow. Therefore, if the viscosity is high or the flow is small, the Re is low. The fluid in the shell side is selected; on the contrary, if the turbulent flow condition can be reached in the tube side of the heat exchanger, it is more reasonable to arrange it on the tube side. It is also advantageous to choose the shell side from the pressure drop angle.
(3) Determined according to the heat transfer coefficient of the films on both sides of the heat exchanger. If the difference is very large, the film heat transfer coefficient can be small to go to the shell side, so as to use external heat transfer enhancement facilities, such as threaded tubes or finned tubes.
