Venturi meter consists of three sections that is converging section, throat section and diverging section. The flow is introduced to the meter through the inlet with diameter ‘D’. The inclined angle of the converging section is α1 which may be between 19o to 23o. The flow is then passed through the throat section which have the diameter‘d’. Two pressure taps (one at inlet section and second is at middle of throat section) are provided to measure the pressure difference by using U-tube manometer as shown in figure. The diversion section has inclined angle α2 which may be between 5o to 15o. Flow rate is proportional to the square root of the differential pressure. Flow rate α √P1 – P2
It is a primary element of differential pressure Flow meters. 1) It consists of a straight inlet section, a converging conical inlet section, a cylindrical throat and diverging recovery cone. 2) Straight inlet section has same diameter as pipe. In converging conical inlet section, the cross-section of stream decreases & velocity increases. 3) In cylindrical throat, flow velocity will be maximum & static pressure will be minimum 4) In diverging recovery cone flow velocity decreases taps are located at. 5) The pressure taps are located at straight edge section and at cylindrical throat where pressure is minimum thus the maximum Pressure Gauges across this point. 6) As it have no sharp edges or warner and does not project into fluid stream. It can be used to handle fluids with solid, slurries, etc. 7) The cross sectional area of fluid does not increase or decreases. Abruptly, so permanent pressure loss or energy loss is very low as compared to orifice plate. 8) Venture tube are usually made up of cast iron or steel and built up in several forms such as. a) Long from or classic venture tube. b) Short from where outlet cone is shortened. c) Eccentric from to minimize the buildup of heavy materials. d) Rectangular from which is used in air-duct work.