Regarding the location of the non-condensable gas extraction port on the condensing evaporator
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Neon and helium extraction ports (i.e., non-condensable gas extraction ports) need to be installed in the main cooler, the crude argon condenser, and the refined argon condenser. In the questions and answers on oxygen production, it is mentioned that neon and helium accumulate at the upper part of the condenser; therefore, the non-condensable gas extraction port is usually located at the upper part of the condenser. However, nowadays most manufacturers of plate-fin heat exchangers place the non-condensable gas extraction port at the outlet head of liquid nitrogen (or liquid argon), that is, at the lower part of the condenser; a few manufacturers still locate it at the upper part. Is it better to place the non-condensable gas vent at the top or at the bottom? Please ask an expert to answer.
In my opinion, the non-condensable gases from the main cooler should be discharged from the upper part of this cooler, while the non-condensable gases from the crude argon condenser and the refined argon condenser can be discharged from above the liquid outlet pipes at the lower part. This is because the main cooler generates a large amount of non-condensable gases, and discharging them from the upper part facilitates this process. The crude argon and refined argon condeners produce less non-condensable gas and have a lower load, making it easier to discharge those gases. Additionally, the crude argon condenser may not require a separate non-condensable gas discharge system; the gases can be discharged through the exhaust gases from the refined argon condenser. Discharging from the lower part may be intended to reduce potential leakage points in the heat exchanger. The purpose of setting up non-condensable gas discharge is to prevent such gas from occupying the heat transfer surfaces, thereby increasing the heat transfer area; therefore, it can be discharged from anywhere as long as it does not interfere with the heat exchange process.
Reply to 2# zhaozhen1234: I have a question. Nitrogen enters the main cooler at a certain speed; in other words, the non-condensable gas also moves at a certain speed. Moreover, nitrogen does not fully liquefy until it reaches the bottom of the main cooler. Thus, there is a downward flow of gas throughout the nitrogen flow channels in the main cooler, and the internal channels of plate-fin heat exchangers are relatively narrow. It is debatable whether non-condensable gases will accumulate at the upper part of the main cooler. As you said, the main cooler should draw air from above, but I’ve seen that in foreign systems the main cooler draws non-condensable gas from below. So, is it better to draw the gas from below rather than from above? Could drawing it from above also result in nitrogen being drawn out as well? ?
Nitrogen will be drawn out no matter where it is extracted from
Reply to 4# zhaozhen1234. . . . . . . . . It’s not possible to draw from below; everything has already liquefied
Times are advancing, and technology is also progressing. Nowadays, most systems use bottom discharge for non-condensable gases, indicating that this approach is the standard and represents progress. Previously, condensers generally took in air from the bottom (or sides), so non-condensable gases were discharged from the top; nowadays, most condensers take in air from the top, so non-condensable gases are discharged from the bottom.
Regarding this issue, it is recommended that those in the design field explain it to everyone
We don’t have this exhaust opening at all, but the heat exchange is still very good. . . . . . . . . .
Have you seen a steam trap? It works on the same principle as a non-condensable gas venting system~~ When liquid nitrogen is liquefied, what remains are non-condensable gases such as neon and helium, which are then vented from the lower part~~