The diameter of the compressed air pipe calculated using the formula is much larger than the diameter obtained by referring to a table. What’s going on?
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This post was last edited by woshinn on 2019-10-12 at 13:54. For compressed air, according to the flow velocity formula: d=18.8 x (Q/V) 1/2. For example, if Q= 25 m3/h and V=10 m/s, then d=29.7 mm. However, according to the tables in the Simplified Power Piping Manual, a pipe diameter of DN15 is sufficient. I’m a bit confused; I don’t know why. Could an expert explain it?
Note that the flow rate indicated in the table is under free conditions
What is the difference between working status and normal status, and how do I switch between them? Thank you
Please take a close look at the content in the parentheses on the right side above… Don’t try to apply it mechanically; your calculations are correct, but you’ve overlooked the pressure factor……
So how should we consider stress? If pressure is taken into account, how should it be calculated? Please give some guidance. Thank you!
The general gas equation of state is multiplied by the compression coefficient to convert it to a certain pressure, after which results can be obtained from tables or directly based on the flow velocity.
So, with Q= 25 m3/h and V=10 m/s, the calculated value for d is 29.7 mm. According to the table, this corresponds to a DN15 pipe; should I go with the DN15 pipe as you suggested? Could you give an example, please?
This post was last edited by symc on 2019-10-17 at 13:42. What’s the pressure of your compressed air? 25 m3/h is the flow rate; what about the pressure? How can results be achieved without pressure? The graph shows three flow rates of 8 m/s, 10 m/s, and 12 m/s, corresponding to six pressures of 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 MPa. There are also flow rate values, which are expressed in m3/min
25 should be Nm3/h, which is the volume under standard conditions. rather than the volume in a compressed state.
d=18.8 (Q/v) v^0.5; here, Q=25 represents the volumetric flow rate under standard conditions, and it is necessary to convert this value to the flow rate under pressure conditions. For the calculation process, refer to the expert on floor 10