Lab Report

Topics: Fluid dynamics, Orifice plate, Mass flow rate Pages: 6 (1380 words) Published: June 27, 2013
INTRODUCTION
The measurement of fluid flow is very important in our daily life from measurements of blood-flow rates in human artery to the measurement of liquid oxygen in a rocket. In this experiment, students are to adapt to various ways to measure the flow of essentially incompressible fluids by using the flow measuring apparatus. Students will also be able to understand the application of Bernoulli’s equation in this experiment. The flow is measured by using a venture meter, an orifice meter and a rotameter respectively. The head losses in each meter will be calculated and compared with each other alongside those arising in a rapid enlargement and a 90o elbow. The Hydraulic bench will be used along with the flow measuring apparatus to provide the essential liquid service and the gravimetric evaluation of flow rate.

Experimental Design

Figure 1.1: the flow measuring apparatus

Figure 1.2: The explanatory diagram of flow measuring apparatus APPARATUS
!. Flow measuring apparatus
2. Volumetric Hydraulic Bench
3. Water
4. Stopwatch
METHODS
Water is allowed to enter from the hydraulic bench into the flow measuring apparatus through the venturi meter which consists of a gradually converging section, a throat and a gradually diverging section. The flow continues through the orifice plate meter for some distance after experiencing a change in cross-section and a rapidly diverging section. After that the flow continues into a further settling length and a 90o bend and finally reaches the rotameter. The rotameter consist of a transparent tube where the float takes up a stable position. This stabilized position is the measure of flow rate. Lastly, the water from rotameter will make its way back to the Hydraulic bench and the weigh tank through a control valve. There are up to nine pressure tappings as shown in Fig 1.2, each of them is connected to its respective manometer in order to enable immediate record of readings. EXPERIMENTAL PROCEDURE

1. The apparatus valve is closed fully and then it is opened with the air purge closed. 2. The Hydraulic bench is switched on and its valve is opened until the point where the water starts to flow, the apparatus is allowed to be filled with water and the bench valve is opened until it is opened completely. 3. The apparatus valve is then completely closed.

4. All the manometers are pumped down until it is approximately 280mm by coupling the hand pump to the purge valve. 5. The manometers are then gently tapped in order to eliminate any trapped air. 6. The water levels in the manometers are kept constant. When the purge valve is leaking there will be a constant rise in water levels. 7. The apparatus valve is opened until the rotameter gives a reading of about 20mm. The flow is measured when it reaches a steady state with the Hydraulic Bench. 8. The readings of manometers is recorded in a table of the form of Fig 2. 9. Repeat the above procedures for different numbers of rotameters up to a maximum of approximately 140mm. RESULTS AND DISCUSSION

 | Manometric Level (mm)| Rotameter (cm)|
No. of Test| A| B | C | D| E| F| G| H| I| |
1| 293| 284| 290| 290| 290| 281| 285| 282| 182| 2| 2| 295| 278| 290| 291| 291| 273| 278| 272| 172| 4| 3| 298| 269| 290| 291| 292| 262| 269| 261| 160| 6| 4| 300| 256| 290| 293| 293| 248| 257| 247| 145| 8| 5| 304| 241| 291| 295| 298| 230| 243| 230| 126| 10| 6| 309| 223| 292| 298| 300| 209| 225| 208| 100| 12| 7| 313| 200| 293| 300| 304| 180| 206| 180| 70| 14|

Water mass, m (kg)| Time, t (s)| ṁ(kg/s)|
| | Venturi (4)| Orifice (8)| Rotameter Calibration Curve| Weight Tank (m/t)| 5| 68| 0.091| 0.086| 0.0531| 0.074|
5| 49| 0.125| 0.122| 0.0931| 0.102|
5| 39| 0.164| 0.158| 0.1331| 0.128|
5| 35| 0.202| 0.193| 0.1731| 0.143|
5| 33| 0.241| 0.237| 0.2131| 0.152|
5| 31| 0.282| 0.275| 0.2531| 0.161|
5...
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