Regarding the selection of the positions for the inlet and outlet of the heat exchanger
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Our company plans to add a fixed-tube-sheet heat exchanger that will be placed horizontally. The hot fluid in this exchanger is in gaseous form, and phase change occurs during the cooling process; it contains a small amount of non-condensable gases such as air. The original plan was to have the fluid flow in from the top and out from the bottom, thereby enabling counterflow heat exchange with the cold fluid. Could this arrangement lead to the accumulation of non-condensable gases, affecting the heat exchange process? Are there any good suggestions?
Your considerations are reasonable. As the gas cools, the density of the non-condensable gases within it (such as air) decreases, causing them to tend to rise. If the heat exchanger is designed with flow from top to bottom, these non-condensable gases may accumulate at the top of the heat exchanger, resulting in poor local flow and reduced heat exchange efficiency. To avoid this situation, it is possible to consider placing the inlet of the gas-phase medium at the bottom of the heat exchanger and the outlet at the top. This not only takes advantage of the natural tendency of non-condensable gases to rise, but also promotes complete vertical flow of the gases, thereby improving heat exchange efficiency. At the same time, the counterflow method is continued to maintain high heat exchange efficiency. Therefore, it is recommended to change the flow direction of the gas phase medium, adopting a configuration with an inlet at the bottom and an outlet at the top. This can effectively prevent the accumulation of non-condensable gases and may improve the overall heat exchange performance. .
I have this thought: if fluid flows from top to bottom, then no liquid phase should accumulate inside the heat exchanger. To maintain flow, the heat exchanger should be in a state of being mostly gas-phase. If fluid flows from bottom to top, there is a concern that the pressure difference might become too high
It is possible to arrange them in a top-to-bottom configuration; a tube box is placed below the heat exchanger, with two outlets provided. Non-condensable gases flow out through the openings in the tube box, while condensate is discharged through the openings in the end caps
……It doesn’t seem right to have flow in from below and out from above; it should be flow in from above and out from below. Connecting a device similar to a gas-liquid separator at the outlet should work:)
:victory: Common practices in fine chemical processing
Consider gas inlet on the side, liquid outlet and vent at the bottom, and non-condensable gas and gas outlet at the top
In this case, the flow direction of the hot medium at the inlet and outlet has absolutely nothing to do with whether non-condensable gas accumulates; it flows from top to bottom. Make sure that the direction of the baffle plates is parallel to the inlet and outlet pipes in the shell side, and provide an exhaust port for non-condensable gas on the shell side.