correct report

The experimental results are shown on Figure 2.

The pressure drop tends to increase as the superficial velocity of air increases. This was expected from the mathematical correlations and is common to all four conditions observed in this experiment.

The range of Reynolds numbers is 239-318. The flow regime was intermediate for the entire experiment, because Reynolds numbers are greater than 10 (laminar regime) and less than 2000 (turbulent regime).

The experimental graphs of pressure drop versus superficial velocity of air are curves. This proves that flow regime is indeed intermediate. Laminar flow supposed to have a straight line with a negative slope, while turbulent flow results in horizontal line as shown on figure 3.

The results for dry trial are presented in Table 1. Ergun equation is working only for Dry regimes; hence it is missing from this section. The graph of pressure drop versus superficial fluid velocity is shown on Figure 4. The experimental pressure drop values are smaller than the ones predicted by Ergun equation. Such difference may result from errors. The sources of errors will be discussed later on.

Table 1 above presents the numerical results obtained for the dry regime. By analyzing the dry regime, it can be noticed that the pressure drop, obtained experimentally, across the packed column increases with increasing air velocity during different conditions.

As shown above, represents the results obtained for the dry regime. The reason for the difference between the Erqun pressure drop and the experimental one, that Erqun is theoretical and used at steady state conditions, hence there will be error and difference between them. From the above figure we notice that the experimental and theoretical pressure drop increase with increasing the airflow.

Table 2 and Figure 5 show the results for irrigated condition at 40% of maximum flow rate. Both Robbin and Leva equations does not fit experimental values equally. On the other hand, leva equation will be more accurate with the experimentally date by comparing the distance between the graphs.

Moreover, by comparing Robbins data dose not consistent with the experimental data. The sources of error will be discussed later on. In comparison with dry column irrigated condition results in higher pressure drop at corresponding flow rates. This happens because the stream of air meets more resistance from the counter-current flow of water. This results in more pressure building up inside the column.

Figure 5and 6 along with tables 2and 3, show the results for the 40% and 60% irrigated bed. The experimental pressure drop was increasing as the flows of water and air were gradually increasing. For 60% irrigated flow, the pressure drop increased significantly compare to the pressure drop of 40% irrigated flow.

This trial has potential for flooding. When the velocity of air is low enough, the water does not meet enough resistance and can freely flow through the packed bed. However, when both water and air streams run at high velocities, the resistance may become great enough to stop water from flowing downwards. Now that water is stuck in the middle of the column by air resistance, it can only move upwards until the column is overflown. The flooding occurred when the velocity of air was 2.19 m/s.,only five data points were obtained.

Due to a higher resistance caused by higher flow rate of water the pressure drop is expected to be greater than in the previous trial. In fact, as shown on Figure 2, this trial has the largest pressure drop in the entire experiment.

The experimental results fit Ergun equation better than Leva. At higher velocity the difference suddenly rises up, resulting in a much greater error. The main source of error in this trial is flooding.

Figure 6: Pressure Drop vs. Fluid Velocity for 60% Irrigated Flow

As you can see the percentage difference for the results in the tables is much higher than we would like. This is a clear indication that the Robin equation is not an optimal method of calculating the pressure drop through packed beds while irrigated.

I would guess this is due to the fact that the robin equation does not account for the added flow of water through the column. This is evident due to the much smaller pressure drops across the column resulting from the robin calculation relative to the actual experimental data.

Comparing the results obtained in this section of the experiment with the results for the dry run it is clear that the irrigation largely increases the pressure drop through the column. This makes sense as the water would increase resistance to the air flow upward through the bed. Error in experimentation could have occurred due to fluctuating water flows as it was difficult to keep the rotameter at a constant level. Calculation error could have occurred due to large amounts of unit conversions.

In this trial the air stream experienced much less resistance, since there was no counter-current stream of water in the column. That is the reason pressure drop is lower than in irrigated trials. However, a significant amount of the water remained on Raschig rings because combined together they create large surface area. This resulted in notable increase in pressure drop, comparing to dry column. Leva correlation works better for this trial resulting in less error.

Moreover From the presented figure below for air flowing through wet packing, the experimental pressure drop in the packed column are lower compared to the theoretical pressure drop obtained from Leva equation. However, the two methods of calculation proved the same point which is: as the flow of the air increases, the pressure drop in the packed column increases because of the high friction between air, the pack and column walls which poses a significant impact on the pressure in the column

Figure 7: Pressure Drop vs. Fluid Velocity for Wet Column

The main source of error is unstable reading from the manometers. The fluid level in manometers oscillated with an amplitude of 5-10 mm. This indicates that the flow rate of air was not constant. The amplitude was larger at higher velocities of supplied air. That’s the main reason all graphs have more error at the right side.

Irrigated conditions have more error, because there were two streams. The flow rate of water varied even more than the flow rate of air. The flooding at the end of 60% irrigated run added even more error to the trial.

Some errors may result from correlations. For example, Ergun equation does not account for friction forces. This may explain that experimental results are generally lower than theoretical. On the other hand, using Robbin equation on the irrigated column is not a good idea because the high difference in the pressure drop comparing with the theoretical result moreover Robbin equation dose have a lot of terms involved in it so that one of the major sources of error Also the unit conversion is kind of tricky to get it in SI unit

· The pressure drop is directly proportional to the superficial fluid velocity for packed columns.

· The packed column in this experiment operated under intermediate flow regime.

· Dry column has the lowest pressure drop.

· Irrigated column at 60% of maximum flow rate has the highest pressure drop.

· The pressure drop of other trials increases in this order: wet 40% irrigated

· Overall, Ergun equation works better than Leva and Robbin equations, because it accounts for both laminar and turbulent regimes.

· Leva works better for wet condition, because it was specifically designed for that.

· Both equations yield rather equal error under irrigated conditions. Leva seems to work slightly better than Robbin , however, more trials are required to identify which equation is more suited for irrigated conditions.

I would like to acknowledge the efforts of my teammates Adam and Joshua in helping me to conduct this experiment and prepare this formal report. I would also like to thank theTA Andrew and Mr. Jamie for their help in pre-lab and supervision of this experiment

Works Cited A. Di Corcia, R. S. (1978). Gas Chromatographic analysis of gasoline and pure naphtha using packed column. Chao, j. T. (1981 ). Analysis of packed bed process . Lieberman, N. P. (2008). A Working Guide to Process Equipment. New York: R. R. Donnelley & Sons Company. M, Y. A. (2006). Fluid mechanics fundamentals and applications. Perry, R. H., & Chilton, C. H. (1973). Perry's Chemical Engineers' Handbook. New York: McGraw-Hill. Rhodes, M. (2008). Introduction to Particle Technology, second edition. Australia: John Wiley & Sons,Ltd.

Appendix A

Appendix B

Appendix C

Dry 1.891987421407068 2.037301686117801 2.1423853287384413 2.247441316287428 2.3431195459666698 651.34954954016825 754.7359145115048 834.24206648207246 917.70631491625238 997.18181887082471 Wet 2.247441316287428 2.5795607297579863 2.8925903323832713 3.1714449808656635 3.44047831698238 811.33565846222609 1068.8465413654544 1343.9951559743836 1615.6162242421726 1901.3474778745215 Irrigated 40% 1.7721172834288601 1.932185876293975 2.0210679478380094 2.1114094524353004 2.2179331480446343 24953.023370066734 49016.046224068334 69831.192083280897 98645.224580308641 145697.82415837058 Irrgated 60% 1.73454162396 48723 1.891987421407068 2.0047027558463251 2.0746864866879973 2.18802706295754 21139.138197940934 41565.510284641503 65495.846664083278 85866.223184380608 130824.89427363624

Dry Column

Velocity m/s

Pressure Drop Pa

Irrigated Packing- Low flow rate (40%)

Velocity m/s

Pressure Drop Pa

Irrigated Packing- high flow rate (60%)

Velocity m/s

Pressure Drop Pa

Wet Column

Velocity m/s

Pressure Drop Pa

10

Tubrulent

Laminar

+

=

D

-

H

P

2

2

t

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U

C

P

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2

3

10

t

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D

CA

Q

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æ

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=

2

1

4

0

0

T-1

Bolwer

V-1

P-1

P-2

T-2

Packed Column

T-5

Water supply

F-1

P-3

T-4

Drain Water

T-3

Drin Air

Exhaust

Air

P-12





3

2

3

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2

)

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(

75

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1

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150

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