Fluid FlowBERNOULLI’S EQUATIONTherefore the flow velocity at the throat of the venturi and the volumetric flow rate are directlyproportional to the square root of the differential pressure.The pressures at the upstream section and throat are actual pressures, and velocities fromBernoulli’s equation without a loss term are theoretical velocities. When losses are consideredin the energy equation, the velocities are actual velocities. First, with the Bernoulli equation (thatis, without a head-loss term), the theoretical velocity at the throat is obtained. Then bymultiplying this by the venturi factor (Cv), which accounts for friction losses and equals 0.98 formost venturis, the actual velocity is obtained. The actual velocity times the actual area of thethroat determines the actual discharge volumetric flow rate.The pressure drop, P1-P2, across the venturi can be used to measure the flow rate using a U-tubemanometer as shown in Figure 6. The reading, R’, of the manometer is proportional to thepressure drop and thus the velocity of the fluid.Rev. 0 Page 29 HT-03
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business