# Relationship between flowrate and pressure in a pipe How would I go about predicting the flow rate at , , and kpa through the same pipe? I think it's a linear relationship but want to. This is what gives, in your words, "pressure is inversely proportional to velocity." .. Flow rate indeed is constant, but somehow velocity may be reduced. When fluid is passing through the pipe having constant area of cross section then that. According to Poiseuille's law, the flow rate through a length of pipe varies Volume flow rate = π X pressure difference X pipe radius 4 X liquid.

### fluid dynamics - Relation between pressure, velocity and area - Physics Stack Exchange

On Moody diagram friction factor can be determined based on the value of Reynolds number and relative roughness. The pressure drop is the function of internal diameter with the fifth power. With time in service, the interior of the pipe becomes encrusted with dirt, scale and it is often prudent to make allowance for expected diameter changes. Also roughness may be expected to increase with use due to corrosion or incrustation at a rate determined by the pipe material and nature of the fluid. Static, dynamic and total pressure, flow velocity and Mach number Static pressure is pressure of fluid in flow stream. Total pressure is pressure of fluid when it is brought to rest, i. Total pressure can be calculated using Bernoulli theorem. Imagining that flow is in one point of stream line stopped without any energy loss Bernoulli theorem can be written as: Dynamic pressure for liquids and incompressible flow where the density is constant can be calculated as: For compressible flow calculation gas state equation can be used. Keep in mind that the stated size of a pipe is a measure of its diameter, and you need the radius to apply Poiseuille's law.

### Relationship between Flow Rate and Pressure | Physics Forums

The radius is half the diameter. Suppose you have a length of 2-inch water pipe, and you want to know how much the flow rate will increase if you replace it with 6-inch pipe.

Demonstrate the Flow Rate Characteristic Change as Pressure Change in a System

That's a change in radius of 2 inches. Assume the length of the pipe and the pressure are constant. The temperature of the water should also be constant, because the viscosity of water increases as the temperature decreases. If all these conditions are met, the flow rate will change by a factor of 24, or Flow rate varies inversely to length, so if you double the length of the pipe while keeping the diameter constant, you'll get roughly half as much water through it per unit of time at constant pressure and temperature. References Anaesthesia, Volume He began writing online in with the goal of exploring scientific, cultural and practical topics, and at last count had reached over a hundred million readers through various sites.