For long-distance transmission pipelines, how is the pressure loss in such pipelines calculated?
Thread Content
Assume a horizontal pipeline 10 kilometers long with an inner diameter of 100 mm, used to pump water from one end to the other. The flow rate at the outlet is 25 cubic meters, 50 cubic meters, and 100 cubic meters respectively. What pressure is required at the inlet for each of these flow rates?
The pressure loss in pipelines is commonly expressed using the Darcy-Weisbach formula: ΔP = λ*(L/D)*(v^2/2g), where ΔP represents the pressure loss, measured in Pa； λ is the friction coefficient, which is obtained by looking up a table based on the Reynolds number and relative roughness ； L is the pipe length, in meters ； D is the pipe diameter, in meters ； v is the flow velocity, in units of m/s ； g is the acceleration due to gravity, typically taken as 9.81 m/s². However, the information you provided does not specify the material of the pipe (which affects the friction coefficient λ), and the calculation of actual pressure loss also requires taking into account factors such as local resistance and pump efficiency; therefore, more information is needed to calculate the pressure loss accurately. It is recommended that you find a specific hydraulic case or use some hydraulic calculation software to obtain more accurate results. As for the pressure required at the water inlet, more practical parameters are also needed, such as water temperature, altitude (which affects the density and viscosity of water), and whether there is a pump or not. All of these parameters will affect the final result. .
The pipeline is made of PE pipe, and the water temperature is at room temperature. Assuming the water inlet is a lake with the water level always maintained 1 meter above the pipeline, can the inlet pressure be considered to be 0.01 MPa? In that case, can the water flow automatically to the outlet? So, what is the flow rate of water at the outlet? Will the flow rate decrease as the pipeline gets longer?