result and conclusion

Results & Discussion (Schaun Mohan)

Experimental Data

Two test were completed using apparatus that generates high air speed through a pipe. The general findings of this experiment showed that the pressure drop as the probe gets closer to the center of the pipe. For the 1.5 inch diameter orifice plate, the air flow is nearly uniform across the pipe. Table 1 shows the raw data obtained for this experiment. We observed that when the probe was in the center of the pipe, the pressure drop was the largest. When the probe was closer to the edge of the pipe, the pressure drop was the lowest.

Table 1 – Raw data

3 inch diameter Orifice plate
Kiel Probe Location (in)	Pressure Drop (in)
0.125	0.625
0.5	0.725
0.875	0.75
1.25	0.75
1.625	0.75
2	0.7
2.375	0.75
2.75	0.775
3.125	0.8
3.5	0.8
3.875	0.675
1.5 inch diameter Orifice plate
Kiel Probe Location (in)	Pressure Drop (in)
0.125	0.125
0.5	0.1
0.875	0.1
1.25	0.125
1.625	0.125
2	0.125
2.375	0.125
2.75	0.15
3.125	0.15
3.5	0.15
3.875	0.125

Analytical Data

Figure 1 shows the vertical velocity profile at the exit of the pipe. This is achieved by plotting the Kiel probe location against the vertical velocity.

Figure 1 – The Vertical Velocity Profile

In Figure 1, the Kiel probe location relative to the vertical velocity at the exit of the pipe is linear in the beginning. However, as the Kiel probe location started increasing from approximately 0.02m to 0.041m, the vertical velocity is constant. The vertical velocity dropped when the Kiel probe location increased to 0.05m before increasing exponentially. At the edge of the pipe, the velocity dropped from approximately 0.89 to 0.82. Figure 2 shows the horizontal velocity profile at the exit of the pipe. This is achieved by plotting the Kiel probe location against the horizontal velocity.

Figure 2 – The Horizontal Velocity Profile

In Figure 2, the relationship between the horizontal velocity and the Kiel probe location is relatively constant. Initially, the velocity dropped as the Kiel probe location increased. However, the velocity starts to increase from there. The velocity stays constant from 0.03m to 0.06m then increases again from 0.06m to 0.07m. Finally it drops at the edge of the pipe.

Table 2 – Flow rate, Average and Maximum Velocities in the pipe

	Flow Rate by Velocity (kg/s)	Flow Rate by Pressure (kg/s)	Average Velocity (m/s)	Maximum Velocity (m/s)	Percent Difference (%)
Orifice Plate 3”	0.188	0.144	23.187	25.733	30.104
Orifice Plate 1.5”	0.077	0.044	9.510	11.143	75.25

Table 2 shows the flow rate, the average velocity ad the maximum velocity in the pipe. The flow rate was obtained through two different methods. The first method was using the velocity equation and the second method was using the volumetric flow rate equation. We observed that the flow rate achieved by pressure is higher than the flow rate obtained by velocity in orifice plate 3” and 1.5”. However, the average velocity in orifice plate 3” is higher than orifice plate 1.5” due to the size of the diameter. Also the maximum velocity is higher at orifice plate 3” compared to orifice plate 1.5”. This is also due to the size of the diameter of the plates. The strength of obtaining the velocity using 11 measurement is an indication that we have a more precise and accurate measurement compared to the flow rate calculated using pressure that was achieved only through 1 measurement.

The characteristic of the flow was fully developed, steady, incompressible and turbulent. We calculated whether it’s fully developed by using 10 multiplied by the diameter of the pipe. We measured the Kiel probe was 42”-43” away from the entrance of the pipe meaning that the flow was fully developed by the time it reaches the Kiel probe. The flow was steady from an observation of the orifice meter. The meter wasn’t fluctuating, therefore the flow is steady.

Table 3 – Mach number & Reynold’s number for both plates

Plate	Mach Number	Reynold’s number
Orifice plate 3”	0.086	187729.529
Orifice Plate 1.5”	0.037	76997.133

The presence of the orifice meter affects the velocity profile by having the flow converge and then diverge after it leaves the orifice plate. Table 3 shows the Mach number and the Reynold’s number for the 3” orifice plate and the 1.5” orifice plate. The Mach number for the 3” orifice plate is higher than the 1.5” orifice plate because there’s a higher pressure from the flow in the 3” orifice plate. The Reynold’s number for the 3” orifice plate is significantly higher than the 1.5” orifice plate because the average velocity at the 3” orifice plate is higher than the 1.5” orifice plate.

In the hypothesis, we stated first, that the flow rates would be 15% percent between each other and second, the flow is steady, turbulent, incompressible and fully developed. However, our findings contradicts the first part of our hypothesis. The reason being that the flow rates in the 3” orifice plate are significantly higher than the 1.5” orifice plate. Thus, a higher percent difference. For the second part, our findings supports the hypothesis. From a simple observation, the flow was steady because the orifice meter wasn’t fluctuating. It is fully developed because we measured the Kiel probe was 42”-43” away from the entrance of the pipe meaning that the flow was fully developed by the time it reaches the Kiel probe.

Conclusion (Mansour Alajemi)

The orifice meter’s presence has significant effects to the velocity profile by making the flow to converge then later diverge once leaving the orifice plate. The Reynold’s number in the 3 inch orifice place can be viewed to be higher compared to the 1.5 inch plate due to the average velocity being nearly double in the larger orifice plate. The different figures show the velocity profile with respect to the location of the Kiel probe. The sizes of the orifice play a significant role in determining the pressure and velocity of air within the pipes. The larger orifice plate has a higher velocity while the smaller of the orifice has a lesser velocity. At the beginning of the experiment, it was indicated that the rate of flow would be fifteen percent between each other. Further, it was indicated that the flow will be steady, incompressible, turbulence, and fully developed. The findings from the experiment concluded these statements were incorrect. Instead, the percent differences between the flow rates as obtained by pressure and velocity were 30% and 75% for the larger and smaller orifice plates, respectively. The Kiel probe measured 42 to 43 inches away from the entrance of the pipe, which meant that the flow of air was fully developed when it reached the Kiel probe. Based on the finding, the size of the orifice had major impact on the flow of air through the pipes.

Y-Direction Velocity Field 0.003175 0.0127 0.022225 0.03175 0.041275 0.0508 0.060325 0.06985 0.079375 0.0889 0.098425 22.74521718753702 24.49734862579106 24.9161370579365 24.9161370579365 24.9161370579365 24.07127527774999 24.9161370579365 25.32800193631952 25.7332757005892 25.7332757005892 23.63752307880182

Probe Location (m)

Velocity (m/s)

0.003175 0.0127 0.022225 0.03175 0.041275 0.0508 0.060325 0.06985 0.079375 0.0889 0.098425 10.17197035886588 9.098086875014814 9.098086875014814 10.17197035886588 10.17197035886588 10.17197035886588 10.17197035886588 11.14283523964952 11.14283523964952 11.14283523964952 10.17197035886588

Probe Location (m)

Velocity (m/s)