Calibration of Flow Meters
Objective:
The objective of this experiment is to calibrate four flow meters that have different operating
... [Show More] principles.
System and Theory:
The flow meters to be calibrated include:
(i) A venturi meter
(ii) A sharp-edged orifice meter
(iii) A rotameter
(iv) A turbine flow meter
The calibration curve will be the instrument reading (the dependent variable, i.e. plotted on the y-axis)
versus the volume flow rate out of the system (the independent variable, i.e. plotted on the x-axis). The
volume flow rate will be determined using a bucket and stopwatch.
The meters are mounted in a system of pipes through which water is circulated. Two of the flow meters
require the measurement of the pressure drop across the meter. Two U-tube manometers containing
different Meriam oils are available to measure the pressure drop. The specific gravity, SG, of the Meriam
oil for the manometer connected to the venturi meter is 1.75, while for the oil in the manometer connected
to the orifice meter, SG = 2.95. The venturi and orifice meters both have throat diameters of 0.625 inches.
The pipe diameter upstream of the flow meters is D1 = 1.025 inches. Single pressure taps are located 1.5
pipe diameters upstream of the inlet and at the throat for the venturi meter, as well as ¾ pipe diameter
upstream and downstream of the orifice plate.
(i) Venturi meter
Venturi meters are made in a variety of ways depending on the application and precision of the
measurement desired. Most commercial venturi meters consist of a casting with flanges, and an insert or
liner which provides a relatively sharp contraction followed by a considerably more gradual expansion. In
the best meters many pressure taps are located around the circumference of the liner just upstream of the
contraction and at the throat. In quality instruments the taps are connected to circumferential rings and a
differential manometer is attached to the two rings. The rings provide a means for mechanically averaging
the pressure along the circumference of the measurement station. Only single pressure taps are used in the
current setup due to the small size of the flow meter. The size of a venturi meter is denoted by its entrance
and throat diameters. A schematic of a venturi meter is presented in Figure 1. For steady incompressible
flow of an ideal fluid, Bernoulli’s equation, written between stations 1 and 2 in Figure 1 i [Show Less]