Fan series connection problem
Thread Content
As shown in the figure, this is a spray tower; air enters at point A, passes through two stages of absorption towers, and is then discharged by fan 2. The air intake volume at point A is very low, less than 100 m3/h. A new duct has been introduced; fan 1 draws air from the room and connects it to the spray tower at point B. This air passes through a second stage of spraying before being discharged by fan 2. It is known that fan 1 has a capacity of 5000 m3/h at 500 Pa ； Fan 2 has a capacity of 5000–7000 m3/h and an air pressure of 1300–1800 Pa; a slight negative pressure is desired at point A. The problem now is that, since point B is supplied with air from the outlet of fan 1 and the wind pressure there is positive, the air at point A blows outward; how can we make the wind direction at point A be inward toward the tower?
Cancel fan 1; use pipes to connect point B to the room, so that both the room and point A can maintain a negative pressure
The key is the location of point B; it’s best to connect it directly to the second absorption tower, and valves should be installed on all the pipes.
Fan 1 has been removed; only Fan 2 is used for extraction, with control at point B via a three-way valve
At point B, a downwardly angled pipe tee should be installed; it’s best if the diameter of the main pipe is larger than that of the air inlet pipe – the larger, the better – so that negative pressure can be created at point A. In other words, by orienting the pipe coming from fan 1, this problem is resolved.
I don’t understand your description. First, if point A has an air intake of 100 cubic meters, how does fan two manage to achieve an air flow rate of 5000? Second, was it only after the modification and the introduction of point B that the wind direction at point A changed?
This post was last edited by arpcd on 2017-3-17 00:13. The outlet pressure of Fan 1 is too high; this can be resolved by installing an expansion device at the outlet of Fan 1. The design is quite simple. China’s chimney design standards clearly state that in such cases, an expansion device must be installed at the chimney inlet (which, in your case, is the outlet of Fan 1). This device works by reducing the flow velocity, thereby offsetting the static pressure of the gas exiting Fan 1 (through the conversion between kinetic energy and static pressure energy). . Refer to this post http://bbs.hcbbs.com/thread-1432972-1-1.html; it shows the structure of the expander. It’s quite cheap to create a large-bellied version in your own factory. Calculate the size yourself; just install it on the vertical section at the outlet of your fan. The key factor is the exit flow velocity. There is a static pressure of 500 Pa at the outlet of your fan, which is too high – this pressure needs to be reduced to zero. The air volume of this unit is roughly around 12,000 cubic feet per hour, which is more than twice that of the original unit; it’s sufficient to counteract a positive pressure of 700–1000 Pa. As long as the height remains unchanged, reducing the size of this unit by half should work fine. Would you like to give it a try? :lol
Add a device similar to an ejector vacuum pump before tube 2 of fan 1 enters tower 1, to increase speed and reduce pressure; the outlet tube of tower 1 should be connected at the point where the ejector pump creates vacuum!