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 constant head tanks. The flow rates are most easily measured in this arrangement by timing liquid accumulation in calibrated beakers. An alternative method (and likely more accurate) is to weigh the mass accumulated during a given time interval. This eliminates uncertainties in the calibration of the beaker. Higher mass flow rates can be obtained by pumping through a feed block and measuring the volume of liquid via the volume gauge mounted on the hydraulics bench. Care should be taken to take data at Reynolds numbers far from the Critical Region in both the laminar and turbulent flow regions. Theory: The frictional pressure drop in a straight pipe segment can be correlated in terms of the Darcy friction factor according to the equation
∆Pf = fL ρv 2 De 2 gc

(1)

where: f = L = De = v = ρ = gc =

Darcy friction factor Pipe length Equivalent diameter Fluid velocity Fluid density Conversion factor.

The friction factor is in general a function of Reynolds number and pipe roughness. The local pressure drop due to flow obstructions (elbows, valves, fittings, etc.) is usually correlated in the form
∆Plocal = K

ρv 2
2 gc

(2)

where K is the local loss coefficient.