ABSTRACTThere are 3 experiment conducted for this laboratory.The objectives of this experiment is to obtain and compare flow rate measurement by utilizing mass flow meter and rotameter. In experiment 1, the flow rate is obtained from flow meter and rotameter. Then ,in experiment 2 and 3 the overall experimental constant of venturi meter and orifice meter is obtained and compared with the theoretical calculated constant.

In reality,the investigation of a compressible fluid flow is done by using different measuring instrument and techniques including primary flow measurement devices (e.g orifice and venture) as well as secondary flow measurement devices (e.g differential transmitter).Hence, the comparison of different measurement or devices can be accomplished as all the flow measuring devices are strategically arranged in a pipe work which pressure and flow measurement are provided for flow compensation of a compressible fluid.

INTRODUCTION

A flow meter is a device used to measure the flow rate or quantity of a gas or liquid in a pipe. Flow measurement applications are very diverse such as water flow through an open channel, hydraulic valve leakage, fuel measurement through a fuel injector, or respiratory flow through a peak expiratory flow meter. Although there are many technologies used to measure flow, the positive displacement flow meter is unique as it is the only one to directly measure the actual volume. All other types infer the flow rate by making some other type of measurement and equating it to the flow rate.

An orifice meter is simple apparatus consists of a flat plate with a drilled hole inserted into the pipe. This flat plate or commonly known as orifice plate causes restriction in the fluid flow and will create pressure difference before and after the orifice plate. Because of the restriction, the fluid flow will take the form of the restriction and will have a change in cross sectional area depending upon the area of the hole in the restriction. . The orifice plates are simple, cheap and can be delivered for almost any application in any material. The Turn Down Rate for orifice plates are less than 5:1. Their accuracy are poor at low flow rates. A high accuracy depend on an orifice plate in good shape, with a sharp edge to the upstream side. Wear reduces the accuracy.

Due to simplicity and dependability, the Venturi tube flow meter is often used in applications where it's necessary with higher Turn Down Rates, or lower pressure drops, than the orifice plate can provide. In the Venturi Tube the fluid flow rate is measured by reducing the cross sectional flow area in the flow path, generating a pressure difference. After the constricted area, the fluid is passes through a pressure recovery exit section, where up to 80% of the differential pressure generated at the constricted area, is recovered.

The rotameter consists of a vertically oriented glass (or plastic) tube with a larger end at the top, and a metering float which is free to move within the tube. Fluid flow causes the float to rise in the tube as the upward pressure differential and buoyancy of the fluid overcome the effect of gravity.

OBJECTIVES

For experiment 1: Determination of the operation and characteristic of mass flow meter and rotameter1) To obtain the flow rate measurement by utilizing mass flow meter and rotameter2) To compare rate flow measurement by utilizing mass flow rate and rotameter

For experiment 2: Determination of the operation and characteristic of venturi meter1) To determine the overall experiment constant of the venturi meter and compare with theoretical calculated constant

For experiment 3: Determination of the operation and characteristic of orifice meter1) To determine the overall experiment constant of the orifice meter and compare with theoretical calculated constant

THEORYFlowmeters are used in fluid systems (liquid and gas) to indicate the rate of flow of the fluid. They can also control the rate of flow if they are equipped with a flow control valve.

1. Rotameter

Rotameter is a particular kind of flowmeter, based on the variable area principle. They provide a simple, precise and economical means of indicating flow rates in fluid systems.This variable area principle consists of three basic elements, a uniformly tapered flow tube, a float, and a measurement scale. A control valve may be added if flow control is also desired. In operation, the rotameter is positioned vertically in the fluid system with the smallest diameter end of the tapered flow tube at the bottom. This is the fluid inlet. The float, typically spherical, is located inside the flow tube, and is engineered so that its diameter is nearly identical to the flow tubes inlet diameter.

When fluid (gas or liquid) is allow to flow into the tube, the float is lifted from its initial position at the inlet, allowing the fluid to pass between it and the tube wall. As the float rises, more and more fluid flows by the float because the tapered tubes diameter is increasing. Ultimately, a point is reached where the flow area is large enough to allow the entire volume of the fluid to flow past the float. This flow area is called the annular passage. The float is now stationary at that level within the tube as its weight is being supported by the fluid forces which caused it to rise. This position corresponds to a point on the tubes measurement scale and provides an indication of the fluids flow rate.

One way to change the capacity or flow range of a rotameter is to change the float material, and thus its density, while keeping the flow tube and float size constant. Floats which are made from less dense materials will rise higher in the tube and therefore will yield lower flow capacities for the same diameter flow tube.

2. Venturi meter

Venturi meter is the most widely used device to measure the discharge through the pipe. A venturi is a converging-Diverging nozzle ofcircular cross-section.The principle of venture meter is that when a fluid flows through the venture meter,it accelerates in the convergent section and decelerates in the divergent section, resulting in a drop in the static pressure followed by a pressure recovery in the flow direction. By measuring the difference in thepressures at an axial station upstream of the convergent section and at the throat, the volumetric flow rate can be estimated.The flow through the venture meter and hence through the pipe is given by

whereQactual= Actual discharge in m3/sCv=Discharge co-efficient of a venturimeterA1 =area at the inlet side in m2A2 =area at the throat side in m2h =Differential pressure head of liquid in mg =Acceleration due to gravity (9.81 m/s2)

In a venturi meter there is first a converging section in which the cross sectional area for flow is reduced. Then there is a short section at the reduced diameter, known as the throat of the meter. Then there is a diverging section in which the cross sectional area for flow is gradually increased to the original diameter. The velocity entering the converging section is where the pressure is P1. In the converging section the velocity increases and the pressure decreases. The maximum velocity is at the throat of the meter where the minimum pressure P2 is reached. The velocity decreases and the pressure increases in the diverging section. There is a considerable recovery of pressure in the diverging section. However, because of frictional effects in the fluid, the pressure leaving the diverging section is always less than P1, the pressure entering the meter.

The venturi tube has a converging conical inlet, a cylindrical throat, and a diverging recovery cone. It has no projections into the fluid, no sharp corners, and no sudden changes in contour.

3. Orifice meter

Orifice meter is another simple device used for the measuring the discharge through pipes, orifice meter also works on the same principle as that of venturi meter i.e., by reducing the cross-sectional area of flow passage, a pressure difference between the two sections before and after Orifice is developed and the measurement of the pressure difference enables the determination of the discharge through the pipe . An orifice meter is a cheaper arrangement for discharge measurement through pipes and its installation requires a smaller length as compared with venturi meter. As such where the space is limited, the orifice meter may be used for the measurement of discharge through the pipe.

Where,

= volumetric flow rate(at any cross-section), m/s

= cross-sectional area of the orifice hole, m

= diameterof the pipe, m

= diameter of the orifice hole, m

= fluid upstreampressure, Pa with dimensions of kg/(ms )

= fluid downstream pressure, Pa with dimensions of kg/(ms )

= fluiddensity, kg/m

APPARATUS

Model FM 120SOLTEQGas Flow measurement Bench

PROCEDUREGeneral start up procedure1. All the valves are closed2. The compressor was connected to the gas flow measurement bench using PU tubes.3. The compressor pressure was regulated to 1 bar4. The main switch was turned on at the panel5. The desired valves was opened according to the experimental procedure

General Shut-down procedure1. All the pressure in the piping was released 2. The main switch was turned off at the panel

Experiment 1: Determination of the operation and characteristic of mass flow meter and rotameter

1. The pressure tubing was connected and the compressor pressure was set to 1 bar2. The valve V1,V2 and V13 were opened3. The valve V13 was regulate to 10 LPM4. After the reading had stabilized, the temperature reading,(TT1) ,pressure reading (PT1) and mass flow meter reading (FT1) was recorded 5. The step 3 and 4 were repeated with different flow rates.6. The experiment was repeated with different compressor pressure.

Experiment 2: Determination of the operation and characteristics of venture meter

1. The pressure tubing was connected and the compressor pressure was set to 1 bar2. The valve V4,V5,V9 and V10 were opened3. The valve V13 was regulate to 10 LPM4. After the reading had stabilized, the temperature reading,(TT1) ,pressure reading (PT1) and mass flow meter reading (FT1) was recorded5. The step 3 and 4 were repeated with different flow rates.6. The experiment was repeated with different compressor pressure.

Experiment 3: Determination of the operation and characteristic of orifice meter

1. The pressure tubing was connected and the compressor pressure was set to 1 bar2. The valve V7,V8,V11 and V12 were opened3. The valve V13 was regulate to 10 LPM4. After the reading had stabilized, the temperature reading,(TT1) ,pressure reading (PT1) and mass flow meter reading (FT1) was recorded5. The step 3 and 4 were repeated with different flow rates.6. The experiment was repeated with different compressor pressure.