Hello All,
Let's say I have a pipeline connecting to the outlet of a blower. The pressure at the blower outlet and thus the inlet of pipeline is 1500Pa. The pipeline is only subject to major and minor head loss and the loss due to change of elevation. The diameter of the pipeline is constant.
When I calculate the pressure drop along the pipeline, I found the pressure drop is 2500Pa. Meaning to say, the pressure at the end of pipeline is around -1000Pa. Is this possible to happen? Does gas able to flow along the pipeline and flow out at the outlet? What is the impact to the gas and pipeline?
What are you specifying in the calculation? Did you measure blower outlet pressure and flow rate? I assume you are working in gauge pressure, since you can't have a negative absolute pressure. If using gauge pressure, a loss of 2500 Pa is okay, as long as the outlet of the pipeline is at a pressure of -1000 Pag. Maybe it's elevation is higher, since you are considering elevation head?
The typical way such a problem is solved is to use the pressure at the inlet side of the blower and at the pipeline outlet along with the blower curve to solve for the pressure at the outlet of the blower and the flow rate it will operate at. On a graph of pressure vs flow rate, where the blower curve and the head loss curve intersect is the blower operating point.
If the pressure at the end is below the atmosphere means the atmospheric air will flow in. Check your calculation if it is correct either need to increase the output pressure of the blower or change the material or length of the pipe to reduce pressure losses. The height also is a problem, in that case, you may consider erecting the blower at a height, based on calculation, to reduce the pressure drop. If you can specify the application and your situation better, either I or anyone else can give an apt solution.
Without knowing how you are performing the calculation it's not possible to give a definitive answer. However, assuming your medium is air or another gas, your negative outlet pressure could be correct and due to the Bernoulli effect.
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