Answer 0.072 6 What are the relative advantages of using a venturi meter to measure flow compared with an orifice meter? A venturi meter has a main diameter of 65 mm and a throat diameter of 26 mm. When measuring the flow of a liquid of density 898 kg/m³ the reading of a mercury differential-pressure gauge was 71 mm. Working from first principles or proving any formula used, calculate the flow through the meter in m³/h. Take the coef- ficient of the meter as 0.97 and the sp. gr. of mercury as 13.6. Answer 8.36 m³/h 7 A venturi meter in a horizontal 300 mm diam water pipe has a throat diameter of 100 mm and a discharge coefficient of 0.98. A mercury U-tube was used to measure the difference of head between the pipe inlet and the throat at points 0.6 m apart. If the mercury gauge reading was 760 mm, find the flow through the pipe in dm³/s. The connections to the U-tube are filled with water. If the meter had been placed vertically with the flow upward, what would have been the gauge reading for the same rate of flow? Answer 106.2 dm³/s, 760 mm 8 A sharp-edged orifice of 48.2 mm diam is employed to mea- sure the supply of air to an oil engine. Prove that the volume in m³/min passing through the orifice is 0.92√(h/p) where h is the drop of pressure between the two sides of the orifice in cm of water and p is the density of the air, assumed uniform, in kg/m³, and the coefficient of discharge for the orifice is 0.602. Calculate the volume of air in m³/min if h = 2.16 cm of water, the pressure of the atmosphere 775 mm of mercury and the tem- perature 15.8°C. For air pV: Answer 1.2 m³/min = 2877 in SI units.