rep - NOMENCLATURE Symbol m t v D Re f P l Cn Co vmax u Q...

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NOMENCLATURE Symbol Definition SI Units m t v D Re f P l C n C o v max u Q A n A o D n D o ΔP g Mass flow rate Time Average velocity Diameter of pipe Reynolds number Friction factor Pressure Inclıned manometer reading Correction factor of nozzle meter Correction factor of orifice meter Experimental maximum velocity Maximum velocity Volumetric flow rate Cross section area of nozzle meter Cross section area of orifice meter Diameter of nozzle meter Diameter of orifice meterPressre drop Gravitanional accelaration kg/s s m/s m Pa m m/s m/s m 3 /s m 2 m 2 m m Pa m/s 2 1
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Greek Symbols Definition SI Units α ρ μ ε Angle of inclined manometer Density viscosity roughness kg/m 3 N.s/m 2 mm 2
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1.INTRODUCTION 1.1 U-TUBE MANOMETER U-tube manometer is one of the earliest pressure measuring device. It gives more accurate measurements and it is a simple device. As figure 1.1 shows U-tube manometer is a U-shaped glass tube partially filled with liquid. This manometer has no moving parts and requires no calibration. U-tube manometry measurements are functions of gravity and the liquid’s density. Liquid manometers measure differential pressure by balancing the weight of a liquid between two pressures. Light liquids such as water, CCl 4 can measure small pressure differences; mercury or other heavy liquids are used for large pressure differences. 4 2 1 CCl water h P h P γ × + = × + (1.1) 1 P 2 P water h 4 CCl Figure 1.1 U-tube manometer[Ref. ] 3
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1.2 ROTAMETER A rotameter is a type of flow meter which is also called as Variable area meter. It is composed of a tapered, transparent metering tube with a float inside, attached vertically to the pipe line. The fluid flows in meter from bottom to top, through the annular area between the float and the tube wall. Float starts to rise with the pushing force until the net force on it exerted by gravitational, buoyancy and drag forces, is zero. [Ref.3]   As the flow rate increases the movement of float would provide a higher flow area which helps to keep pressure drop nearly constant. The widest cross sectional area of the float indicates the height in the tube. Rotameter is calibrated with flow rate and the relation between the tube reading and flow rate is almost linear. Rotameters can be used for both liquids and gases. It is a simple device which is cheap and easy to set up but it can not be very useful for low flow rates. Figure 1.2 Rotameter[Ref. 5] 4
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1.3 FLOW NOZZLE Nozzle meter is device which is used to measure flow rate. Bended plate which has a hole at middle is put inside pipe. This plate limits the flow of fluids. The operation principle is based on Bernoulli equation. With the help of plate, velocity of fluid increases because cross section area gets narrow. As velocity increases, pressure decreases. This pressure difference is measured by manometer. Flow rate can be calculated by pressure drop and cross section area. [Ref.1 ] Since narrowing in nozzle meter is not severe as orifice meter, there is a slight vena contract and less separated flow occurs. Nozzle meter is more close to ideal situation than orifice meter.
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This note was uploaded on 05/01/2011 for the course CHE che 320 taught by Professor Ahmetarslan during the Spring '11 term at Middle East Technical University.

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rep - NOMENCLATURE Symbol m t v D Re f P l Cn Co vmax u Q...

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