Case 22 in the morning of 2013
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22. A certain project requires 20 tons of oil per hour, and pipeline transportation is planned to be used for supply. The density of the oil is 900 kg/m3, and its viscosity is 72×10-3 Pa·s. Seamless steel pipes with a diameter of φ108×4 mm are to be used for horizontal transportation, over a total length of 45 km. Due to the long length of the pipeline, the local resistance can be ignored. However, the maximum pressure designed for the pipeline is 5.0 MPa (G). Determine whether it is necessary to install additional pressure boosting stations along the transmission route. Which of the following options is correct? A No additional ones are needed. B Add 1. C Add 3. D Add 2. Where can I find this information? It’s not in the books of the Ten Da He Association either!
First, calculate u using the flow rate: u = 20/0.9/0.785/3600/0.1^2 = 0.786 m/s. Re = duρ/μ = 983, and λ = 64/Re = 0.065. ΔP = λlρu^2/2d = 8.15 Mpa, which is greater than 5.0 Mpa but less than 10 Mpa; therefore, only one pressure boosting station is required.
This question requires some thinking: if the pressure at one point is 5 units, then the pressure that needs to be reduced is 8, so an additional pressurization step is necessary to ensure that the pressure reaches the destination!
So two booster stations are needed? Hehe~
Another approach is to calculate the number of booster stations by determining the distance that can be transported based on a pressure drop of 5 MPa. The question asks whether additional pressure stations need to be installed along the way; in other words, the first one at the start is not included.
There’s something wrong with this question; as long as it’s an increase, any number of increases will do