[Q&A] 2017.7.1

The tube bank refers to the channels through which the fluid flows within the heat exchanger and the parts that are connected to them. The shell side refers to the channel through which the fluid flows outside the heat exchange tubes and the parts connected to it. This relates to the fluid selection for shell-and-tube heat exchangers, with the main considerations being the operating pressure and temperature of the two fluids, the available pressure drop, structural and corrosive factors, as well as equipment-related aspects. Generally, water, water vapor, or highly corrosive fluids ； Toxic fluids ； Fluids that tend to form scale, as well as those handled at high pressures, flow through the tube side ； And the condensed steam at the top of the tower ； Hydrocarbon condensation and reboiling ； For fluids where key pressure drop control is required, those with high viscosity flow through the shell side. In addition to the conditions mentioned above, it is also necessary to take into account the heat transfer coefficient and the optimal utilization of the pressure drop; from the perspective of the pressure drop, it is more reasonable to use the shell side when the Reynolds number is low. In general, in tower top coolers, the bulk of the material flows through the shell side, while the cooling water flows through the tube side. In reboilers, the material flows through the tube side, and steam and condensate flow through the shell side. This is the case for most systems, but there are exceptions: usually, the main material flows through the shell side, while the auxiliary heating and cooling media flow through the tube side. The best approach for on-site decision-making is to have the fluid in the tube side enter and exit from one end of the heat exchanger, while the fluid in the shell side enters and exits from a point near the middle; moreover, a certain amount of space should be reserved at the tube side inlet and outlet ends for removing the heat exchanger core. Simply put, the tube side refers to the inside of the tubes, while the shell side refers to the outside of them. In the case of fixed-tube-sheet heat exchangers, the selection of fluids for the tube side and shell side is based on the following criteria: 1) Fluids that are dirty or prone to scaling should be used on the tube side, as it is easier to clean the inside of the tubes; corrosive fluids should also be placed on the tube side to prevent both the tube bundle and the shell from being corroded, and it is also easier to clean and maintain such systems. Fluids with high pressure should be used on the tube side to avoid putting stress on the shell. Toxic fluids should be located on the tube side to reduce the risk of leaks. Fluids that need to be cooled should be on the shell side, as this facilitates heat dissipation and improves the cooling effect. Saturated steam should be used on the shell side, as it makes it easier to remove condensate and non-condensable gases, and the steam remains clean and does not cause contamination. Fluids with low flow rates or high viscosity should be on the shell side, as baffle plates can help achieve turbulence at lower Reynolds numbers; however, multiple tube passes can also be used inside the tubes. To facilitate cleaning, fluids with a high viscosity should be placed on the shell side, thereby reducing the temperature difference between the tube walls and the shell walls. In practice, it is often not possible to take all of these principles into account simultaneously, as they may conflict with each other. In such cases, it is necessary to focus on the most important factors based on the actual situation. Moreover, different heat exchangers require different considerations; for example, in U-tube heat exchangers, fluids that are dirty or prone to scaling cannot be used on the tube side. The tube side refers to the inside of the tubes, while the shell side refers to the area outside the tubes and between them. The tube side and shell side represent the two areas where fluids flow in a shell-and-tube heat exchanger. Such heat exchangers generally consist of an outer shell, gaskets, end caps, etc. In short, the inside of the tubes is called the tube side, while the outside is called the shell side. Generally, fluids that are easy to clean flow on the shell side, while fluids that are dirty, prone to scaling, crystallization, or clogging flow on the tube side, which makes it easier to remove dirt, crystals, and other obstructions. Generally speaking, there is nothing absolute, but there are several patterns that can serve as a guide. 1. Those with high pressure should be in the tube side. 2. The cooled shell side.

(1) Fluids that are dirty or prone to scaling should flow in the tube side, as cleaning inside the tubes is easier. (2) Toxic fluids should also flow in the tube side to reduce the risk of leaks. (3) Fluids with high pressure should be sent through the tube side to avoid stress being applied to the shell as well. (4) Corrosive fluids ought to flow in the tube side, so as to prevent both the tube bundle and the shell from being corroded, and it also makes cleaning and maintenance easier. (5) The fluid that needs to be cooled should flow in the shell side, as this facilitates heat dissipation and improves the cooling effect. (6) If there is a large temperature difference between the two fluids, the fluid with a higher thermal expansion coefficient should be routed to the shell side, thereby reducing the temperature difference between the tube walls and the shell walls. (7) Fluids with low flow rates or high viscosity should flow in the shell side; the baffle plates can help achieve turbulence at low Reynolds numbers (Re>100), and multiple tube passes can also be used inside the tubes. (8) Saturated steam should flow in the shell side, as this makes it easier to remove condensate and non-condensable gases, and the steam remains clean and does not cause contamination. In practical applications, it is often not possible to take all of these principles into account simultaneously, as they may conflict with each other. In such cases, it is necessary to consider the actual situation and focus on the most important factors as the basis for making a decision.

In terms of heat transfer efficiency, the material to be heated or cooled should flow through the tube side. However, considering that the tube side is easier to clean than the shell side, materials prone to scaling are generally chosen for the tube side

Fluids that are high in pressure, toxic, corrosive, unclean, or prone to scaling should flow through the tube side, while fluids with low flow rates, high viscosity, or those that need to be cooled should flow through the shell side

For relatively pure fluids, use the tube side; for high pressure and high temperature conditions, use the shell side

The selection principle is: in terms of heat transfer efficiency, the material to be heated should be in the tube side. However, considering that the tube side is easier to clean than the shell side, materials prone to scaling are generally chosen for the tube side.

In terms of heat transfer efficiency, the material to be heated or cooled should flow through the tube side. However, considering that the tube side is easier to clean than the shell side, materials prone to scaling are generally chosen for the tube side.

(1) Fluids that are dirty or prone to scaling should flow in the tube side, as cleaning inside the tubes is easier; (2) Toxic fluids should also flow in the tube side to reduce the risk of leaks; (3) Fluids with high pressure should be sent through the tube side to avoid stress being applied to the shell as well; (4) Corrosive fluids ought to flow in the tube side, so as to prevent both the tube bundle and the shell from being corroded, and it also facilitates cleaning and maintenance; (5) The fluid that needs to be cooled should flow in the shell side, as this helps with heat dissipation and improves the cooling effect; (6) If there is a large temperature difference between the two fluids, the fluid with a higher α value should flow in the shell side, thereby reducing the temperature difference between the tube walls and the shell walls; (7) Fluids with low flow rates or high viscosity should flow in the shell side, as the baffle plates can help achieve turbulence at low Reynolds numbers (Re>100), although multiple tube passes can also be used inside the tubes; (8) Saturated steam should flow in the shell side, as this facilitates the removal of condensate and non-condensable gases, and the steam remains clean and does not cause contamination. In practical applications, it is often not possible to take all of the above principles into account simultaneously, as they may conflict with each other. In such cases, it is necessary to consider the actual situation and focus on the most important factors as the basis for making a decision.

The selection principle is: in terms of heat transfer efficiency, the material to be heated or cooled should flow through the tube side. However, considering that the tube side is easier to clean than the shell side, materials prone to scaling are generally chosen for the tube side