Calculation problems for compressed air pipelines
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1. The allowable flow velocity for compressed air is 10–15 m/s (with a pressure ranging from 0.6 to 1 MPa). Using the formula d = 18.8√(q/v), and given that the pressure is P = 0.7 MPa and the volume flow rate under standard conditions is V = 9952 Nm³/h, the pipe diameter should be DN200. 2. According to Table 2-24 of the \"Concise Plumbing Manual\" (3rd edition, Mechanical Industry Press), for a nominal diameter of DN200, with a flow velocity of 8 m/s and a gauge pressure of 0.7 MPa, the volumetric flow rate is 117 m³/min = 7020 m³/h. For the same nominal diameter but with a flow velocity of 16 m/s and a gauge pressure of 0.7 MPa, the volumetric flow rate is 231 m³/min = 13860 m³/h. Question: Is the volumetric flow rate listed in the hydraulic calculation table for compressed air pipelines the flow rate under standard conditions or the flow rate under actual operating conditions? If it is the flow rate under standard conditions, the calculations for 1 and 2 are roughly consistent. But if it’s not a flow rate under standard conditions, then the difference between 1 and 2 is significant. I’m new to pipeline design; I would appreciate any advice. Thank you all.
The flow rate given at the end of this post was edited by *lihuagong on 2016-1-6 09:51; it is, of course, the flow rate under operating conditions, not under standard conditions. However, the flow rates provided are all under standard conditions. The flow rate values for compressors provided by manufacturers are all in m3/min, and these are actually values under standard conditions. What is the difference between 1 and 2 that you mentioned? ?
It is the standard condition; the formula refers to the actual operating conditions. When calculating the pipe diameter, the value corresponding to the standard condition must be converted into the flow rate under the actual operating conditions.
If the flow rate is given at standard conditions, 1 and 2 will be quite close to each other. Thank you for clarifying.
Well, it has been converted already. Thank you for your reply.