Flow meters and Flow Measurement
By:
Arates, Marielle Valencia Besa, Leo Catulay, Almie Jane Rubio, Rochelle Marie
6 March 2018 School of Technology Dennis Ong
Table of Contents
Page
No.
Title
1
Introduction
3
2
Objectives
4
3
Scope and limitations
4
4
Methodology
4
5
Data Sheet
5
6
References
6
no.
Introduction Flow, defined as volume per unit of time at specified temperature and pressure conditions, is generally measured by positive displacement or rate meters (Perry, 20 08). Flow measurement is the quantification of the bulk fluid movement (vlab, 2018). Differential pressure type of flow meters have been introduced to measure flow rate through a constriction in the flow. The most common of the flow meters are the Venturi Ventu ri and Orifice meters.
Figure 1. Orifice flow meter. (From Geankoplis (1995) Figure 3.2 -4) An orifice plate is a restriction with an opening smaller than the pipe diameter which is inserted in the pipe; the typical orifice plate has a concentric, sharp edged opening, as shown in Figure 1. Because of the smaller area the fluid velocity increases, causing a corresponding decrease in pressure. The flow rate can be calculated from the measured pressure drop across the orifice plate, P1-P2. The orifice plate is the the most commonly used flow sensor, but it creates a rather large non-recoverable pressure due to the turbulence around the plate, leading to high energy consumption (Foust, 1981).
Figure 2. Venturi flow meter. (From Geankoplis (1995) Figure 3.2-2) The venturi tube shown in Figure 2 is similar to an orifice meter, but it is designed to nearly eliminate boundary layer separation, and thus form drag. The change in cross-sectional area in the venturi tube causes a pressure change between the convergent section and the throat, and the flow rate can be determined from this pressure pressure drop. Although more expensive that an orifice plate; the venturi tube introduces substantially lower non-recoverable pressure drops (Foust, 1981).
Objectives The main objective of the experiment is to determine discharge coefficient for both the venturi meter and the orifice meter at varying va rying flowrates for different orifice plates.
Scope and Limitations The scope of the experiment involves the use of the venturi meter and different orifice plates at three (3) different flow rates. The experiment is limited to the hydraulic pipe set-up in SOTECH unit operations laboratory, UPV, Miag-ao, Iloilo city.
Methodology Apparatus: • • • • • •
Venturi meter Orifice meter Pressure gauge Orifice plates with various opening Storage container for discharge Graduated cylinder for volume measurement
Procedure:
Open the flow control valve. Let the flow of water stabilize. stabilize. Record the pressure difference for the venturi meter. Record measurements at different flowrates. Flow rates will be calculated by how much water will be discharged at a given time. Do the same for the orifice meter, test three orifice plates at three different flow rates.
Data Sheet
Venturi meter Trial
H2
H1
Time
Volume
H2
H1
Time
Volume
1
2 3
Orifice Meter
Trial
1
2
3
References
Foust, A. S., et al.(1981). Principles of Unit Operations, 2nd ed. New York: John Wiley & Sons, Inc. Geankoplis Christi J. (1995). Transport Processes and Unit Operations, 3rd ed. S ingapore: Prentice-Hall, Inc. Perry Robert H., Green Don W. (2008). Perry’s Chemical Engineer’s Handbook, 8th ed. New York: McGraw-Hill Book Company. iitb.vlab.co.in,. (2011). Flow measurement by orificemeter and venturimeter. Retrieved 6 March 2018, from iitb.vlab.co.in/?sub=8&brch=116&sim=952&cnt=1
