Process Area Event – [I See Now-52] How fast are the air and steam streams emitted into the atmosphere?
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Having experienced shutdown purging in the workshop, everyone might have a strong impression of the harsh noise. Blowing pipeline equipment with steam or air is one of the steps during shutdown. The noise comes from the gases being emitted, but I wonder if anyone has thought about just how fast those gas streams are moving. Let me tell you that the flow velocity at the pipe end generally reaches the speed of sound. Why the speed of sound? It turns out that when a compressible fluid passes through a pipeline valve, its velocity increases as the pressure downstream decreases, and the flow rate increases accordingly. Once the pressure downstream drops further, the flow rate no longer increases; at this point, a critical flow state is reached, and the ratio of the downstream pressure to the upstream pressure at this point is known as the critical pressure ratio. The critical pressure ratios for steam and air are 0.54 and 0.53, respectively, and the pressure discharged to the atmosphere during purging is 1 atm; therefore, as long as the pressure of steam and air in the pipeline is greater than 1.9 atm, the flow velocity at the pipe ends will reach the speed of sound.
Suppose there’s a small stone in the pipe, could it kill someone?
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The flow velocity at the pipe end will reach the speed of sound. How is this speed of sound measured? Please provide further explanation, expert.
What is the relationship between critical flow and the speed of sound? If the speed of sound is reached, can the upstream flow keep up?
It’s winter now, and when the windows are closed tightly enough, there is noise – does this also reach the speed of sound?
This post was last edited by cjgj008 on 2016-11-28 at 10:47. This critical state is one in which the gas reaches exactly the pressure wave (sound speed) condition; the pressure ratio before and after this point is then the critical pressure ratio. Once the compressed gas reaches the pressure wave condition, that is, the speed of sound, at the discharge end, increasing the pressure difference further will not increase the flow velocity. It is not impossible to exceed the speed of sound, but this requires the use of devices such as Laval nozzles.
That can’t be the case; this can definitely be calculated