707 words - 3 pages

NE 402 Laboratory Pressure Losses in Pipes and Fittings Objective: The Cussons Hydraulic Bench is to be used to measure friction factors and local loss coefficients in selected piping arrangements. These include sudden expansions, sudden contractions and bends. Other flow components to be studied in this lab include a Venturi flow meter and an Orifice flow meter. The theory for using Venturi tubes and orifice plates for flow rate measurement will also be verified. The hydraulics bench can be operated in both the laminar flow (Re < 2300) and turbulent flow regimes by adjustment of the fluid velocity. At low flows, the velocity is controlled by maintaining level (and therefore pressure) in two ...view middle of the document...

In a piping system consisting of both straight pipe segments and local flow obstructions, the total pressure drop is a linear sum of these two components. Flow rate measurement with the Venturi tube is based on application of Bernoulli’s equation and mass conservation at selected points within the component. In the absence of losses, the volumetric flow rate ( Q = VAx ) of a constant density fluid through the venturi can be shown to be

Q = A

2 gc

2

( P1 −

2 1

P2 ) ⎞ ⎟ ⎠

2

⎛ ⎛ A ρ ⎜1 − ⎜ ⎜ ⎝ A ⎝

⎞ ⎟ ⎟ ⎠

where: A1 = inlet area A2 = throat area P1 = inlet pressure P2 = throat pressure. With known Venturi geometry, the system flow rate is found by measuring P1 and P2. In reality, some irreversible losses within the venturi are to be expected. This is accounted for by an experimentally determined discharge coefficient Cd such that the actual volumetric flow rate is

Q = Cd A

2 gc

2

( P1 −

2 1

P2 ⎞ ⎟ ⎠

)

⎞ ⎟ ⎟ ⎠

⎛ ⎛ A ρ ⎜1 − ⎜ ⎜ ⎝

2

⎝ A

The equation for volumetric flow rate given above is also commonly used to determine the flow through orifice plates and nozzles. Procedure: 1) Under...

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