Fluid Flow Through Packed Beds

Heat Transfer To a Fluid in a CSTR University Of Illinois

Heat Transfer to a Fluid in a CSTR

Final Report Unit Operations Lab 1 February 2, 2011 Group 3

Russel Cabral Jay Gulotta Scott Morgan Brian Mottel Mrunal Patel Frank Perez Sukhjinder Singh

1 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

1. Summary

The purpose of this experiment is to measure the heat transfer coefficient between the fluid and the inside vessel wall. These measurements can then be examined to determine its dependence on impeller speed and fluid properties. The agitated tank is important for various processes including chemical reactions, blending, dispersions, and leaching. The apparatus used in this experiment, includes a jacketed agitated vessel with a recirculation stream and internal cooling coil. This apparatus is used to study a range of heat transfer processes in the two-part procedure.

The results in the steady state experiment show the heat transfer coefficient increases with an increase in temperature. This definitely shows when comparing runs one and two during steady state. Run one had a vessel temperature of 143 °F leading to a heat transfer coefficient of 46.47 kJ/min*m2*K. Likewise, run two had a vessel temperature of 157 °F leading to a heat transfer coefficient of 71.49 kJ/min*m2*K. In the unsteady state experiment, the overall heat transfer coefficient increases exponentially with an increase in temperature and an increase in time. An increase in impeller speed results in the heat transfer coefficient increasing faster with time. This trend can be seen by the Temp vs. RPM graph. In an increase in impeller speed resulted in an increase in temperature. As far as the baffles are concerned, the experimental data did not show any significant improvement in the heat transfer rate with or without the baffles. Even though the baffles should theoretically enhance the mixing and lead to an increase the heat transfer rate. This was most likely due to the fact that the top of the tank is not insulated. There is definitely a significant amount of heat loss through

2 Heat Transfer To a Fluid in a CSTR University Of Illinois the top of the tank and by fixing this problem will lead to better relationships and results.

2. Results

The purpose of this lab was to study a range of heat transfer processes involving a stirred tank reactor. From performing various experiments and gathering appropriate data, the measurement of the heat transfer coefficient between the inner vessel wall and fluid was obtained in this experiment. This experiment also allowed the dependence of the heat transfer coefficient on the impeller speed, fluid properties, and the presence of baffles to be experimentally determined and analyzed.

For the first part of the experiment the heat transfer coefficient was measured from data gathered for an un-baffled agitated tank. . For the unbaffled portion of the experiment increasing the impeller speed caused the heat transfer coefficient at inner wall to increase. The trend seems to be linear if run number three is discarded, shown in the attached graphs. As it can be seen from figure 2.1 below, adding baffles to the agitated tank and increasing the impeller speed had a small effect on the heat transfer coefficient at inner wall.

Figure 2.1 hi vs. Impeller speed for trials 1-6 at steady state.

During this experiment it was observed that increasing the impeller speed in the un-baffled tank caused the temperature inside the tank to increase. Adding the baffles to the tank increased the temperature inside the vessel but increasing the impeller speed caused very little change. This trend in the heat transfer coefficient as can be seen in figure 2.2 below.

Figure 2.2 Temperature vs. Impeller speed for trials 1-6 at steady state.

For the third part of the experiment the unsteady state heat transfer was measured as a function of time. For this part three different impeller speeds were used

4 Heat Transfer To a Fluid in a CSTR University Of Illinois but the temperature of the tank was kept the same throughout the three runs. From the data gathered, three graphs of temperature as a function of time were obtained. As it can be seen from figure 2.3 below, the R2 value for run 1 is .9982 and the slope is 0.1997.

The slope for run 2 and run 3 are 0.2008 and 0.2065 respectively. Since the three slopes seem to be close, it can be safe to assume that the impeller speed has little effect on the rate of heat transfer from the steam to the fluid. Run 2 and run 3 are shown as figures

2.4 and 2.5 respectively, below.

Figure 2.3 Temperature vs. time for run 1.

From the three runs it can be seen that the overall heat transfer coefficient increases almost exponentially as temperature increases. Figure 2.6 represents the overall heat transfer coefficient as a function of temperature for a unsteady state tank. It can be seen that as the temperature of the tank increase and smooth exponential increase in the heat transfer coefficient occurs.

Figure 2.6 Overall heat transfer coefficient vs. Temperature at unsteady state. 3. Discussion

In the first section of this experiment, the apparatus was run under steady state conditions in an un-baffled agitated tank. Overall, the trends from the data and the calculated heat transfer coefficient seemed to be in general agreement. The

5 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois trends of the experimental values showed slight increases with temperature. The overall heat transfer coefficient had values which ranged from 37.12 to 51.24 kJ/min*m^2*K. The increase due to temperature is because the specific heat of the water will increase with increasing temperature, while the density and viscosity decrease. Impeller speed had little to no effect on the temperature of the unbaffled tank. The impeller speed, however, did seem to have an effect on the heat transfer coefficient, which increased with increasing impeller speed up to about 350 rpm, then slightly dropped off.

In the second section of the experiment, the first part was repeated with baffles placed in the tank. The data taken from this section didn’t change much from the data taken from the un-baffled tank. It was shown, however, that the temperature within the tank did increase almost linearly with increasing the impeller speed. This could be because the baffles helped to better stir the system, so increases in the impeller speed greatly increased the turbulence of the system, which allowed for better heat transfer.

In the final section of the experiment, the unsteady state heat transfer was measured. The baffles were removed, the starting temperature for each run was the same, the cooling coil and recirculation valves were closed, and the impeller speed was changed. The data showed that the impeller speed had little effect on the temperature of the system because the temperature vs. time graphs all appear essentially the same although the impeller speed was changed for each of the three runs, from 128.6 to 450 rpm. The heat transfer coefficient in this section increased exponentially as a function of temperature.

6 Heat Transfer To a Fluid in a CSTR University Of Illinois

There were some issues with the apparatus, which could have significantly affected the data and results of the experiment. It was difficult to control the impeller speed using the speed controller. The motor, which drives the impeller would often speed up to a level quite different from that which it was originally set.

It was discovered that there is a brake lever on the motor, which we used to control the variance within the voltage sent by the controller. This greatly improved the accuracy of the impeller speed. We also encountered issues with the inlet flow rate to the cooling coil. It was difficult to set the flowrate because slight adjustments of the valve would show great changes in the rotameter. We were unable to determine whether it was due to the valve or the rotameter, and therefore, we cannot be certain that the cooling coil flowrates were the correct values.

3.Conclusions

During this lab the heat transfer coefficient’s dependence on temperature as well as impeller speed was calculated for a constantly stirred tank reactor (CSTR). The CSTR used in this lab has an internal cooling coil inside of a jacketed agitated vessel with surrounding steam to supply the wall heat. This apparatus will be utilized to gain information on various heat transfer processes conducted during the two-part procedure.

During the steady state portion of the procedure, it was found that as the temperature increases, so too does the heat transfer coefficient. This can be seen in the first two runs for the steady state portion of the lab. For the first run the temperature 7 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois was 143 °F and the heat transfer coefficient was calculated to be 46.47 kJ/min*m2*K.

The difference can be seen when comparing the values obtained for the second run where the temperature was 157 °F leading to a heat transfer coefficient of 71.49 kJ/min*m2*K. During the unsteady state portion of the lab the heat transfer coefficient increased exponentially as temperature increased. Also an increase in impeller speed increases the heat transfer coefficient. This trend is seen on the temperature versus

RPM (impeller speed) graph.

As for the baffles that are used in conjunction with the steady state portion of the lab, the data did not show any significant change with their use. Although theoretically it should allow for better mixing and thus increase the heat transfer coefficient, thus the hypothesis was not supported with experimental data, possibly due to the lack of insulation for the tank.

All the changes made in lab made the heat transfer coefficient increase, whether it be increasing the temperature or impeller speed.

5. References

1. Bird, R. B., Warren E. Stewart, and Edwin N. Lightfoot. Transport Phenomena. 2nd ed. New York, NY: Jonh Wiley & Sons, Inc., 2002

2. "Heat Transfer Coefficient." Wikipedia. 19 Jay. 2011

3. Perry, Robert H., and Don W. Green. Perry's Chemical Engineers' Handbook. New

York: McGraw-Hill Professional, 2007.

4. University of Illinois at Chicago - UIC. Web. 13 Sept. 2010. .

6. Appendix I: Data Tabulation/Graphs

Measured Constants Height of Tank (cm) 41 (+/- 1) Diameter of Tank (cm) 22.8 (+/- 1) Radius of Tank (cm) 11.4 (+/- 1) Volume of tank (cm^3) 16739 (+/- 1) Diameter of Impeller (cm) 10 (+/- 0.5) 9 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

Figure 6.1 Measured Constants for CSTR

Experimental Data for Part 1 of 2 No Baffles Steady State With Baffles Steady State Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 (+/- 1) (+/- 1) (+/- 1) (+/- 1) (+/- 1) (+/- 1) Height of water (cm) 35.5 35.5 35.5 35.5 35.5 35.5 RPM (rev/min) 128.6 360 460 128.5 360 497 Flow rate of steam (%) 48 48 44.5 44.4 47 46 Flow rate of cooling water (%) 26 21.5 22.5 22.5 23 23 T1 (°F) 143 157 161 161 160 160 T2 (°F) 31 31 31 31 31 31 T3 (°F) 99 121 123 123 120 120 T4 (°C) 38 42 42 42 42 41 T5 (°C) 64 70.5 73 73 70 71 T6 (°F) 40 39 38 38 40 40 T7 (°F) 31 31 31 31 31 30 Condensate volume (mL) 100 100 100 100 100 100 Time (sec) 22.1 20.8 18.75 28.95 20.13 19.45 Figure 6.2 Measured data for part 1 of 2 for a baffled and un-baffled CSTR.

Calculated Experimental Data Part 1 of 2 No Baffles at Steady State With Baffles at Steady State Run 1 Run 2 Run 3 Run 4 Run 5 Run 6

Mc (kg/min) (+/- 0.01) 0.78 0.65 0.68 0.68 0.69 0.69

Mhx (kg/min) (+/- 0.01) 1.45 1.45 1.34 1.34 1.42 1.39

Mst (kg/min) (+/- 0.01) 0.27 0.28 0.31 0.20 0.29 0.30 T1 (K) (+/- 1) 334.82 342.59 344.82 344.82 344.26 344.26 T2 (K) (+/- 1) 272.59 272.59 272.59 272.59 272.59 272.59 T3 (K) (+/- 1) 310.37 322.59 323.71 323.71 322.04 322.04

T4 (K) (+/- 1) 311.15 315.15 315.15 315.15 315.15 314.15 T5 (K) (+/- 1) 337.15 343.65 346.15 346.15 343.15 344.15 T6 (K) (+/- 1) 277.59 277.04 276.48 276.48 277.59 277.59 T7 (K) (+/- 1) 272.59 272.59 272.59 272.59 272.59 272.04

Qhx (kJ/min) (+/- 1) 148.63 172.36 172.73 172.34 179.01 181.22

Qc (kJ/min) (+/- 1) 128.51 140.65 150.46 150.46 148.79 148.79 U (kJ/min*m^2*K) (+/- 1) 37.12 51.25 50.13 50.07 48.30 48.63

H0 (kJ/min^2*K) (+/- 1) 184.65 180.96 174.80 202.04 178.99 176.95

hi (kJ/min*m^2*K) (+/- 1) 46.47 71.49 70.28 66.56 66.15 67.05 Figure 6.3 Calculated data for part 1 of 2 for a baffled and un-baffled CSTR.

RPM (rev/min) Ht of water (cm) (+/- 15) (+/- 1) Run 1 128.6 36 Run 2 370 36 Run 3 450 36 Figure 6.4 Experimental Data for Part 2 of 2

Experimental Data and Calculated U for Un-baffled CSTR at Unsteady State Temperature in Tank (K) U (KJ/min*m^2*K) Time (sec) Run 1 Run 2 Run 3 Run 1 Run 2 Run 3 0 294.26 294.82 294.26 1.51 1.52 1.51 30 297.59 298.71 298.71 1.57 1.60 1.60 60 300.93 302.04 301.48 1.64 1.67 1.66 11 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

90 304.26 304.82 305.93 1.72 1.74 1.77 120 308.71 308.71 309.26 1.84 1.84 1.86 150 311.48 312.04 313.71 1.93 1.94 2.00 180 314.82 316.48 316.48 2.04 2.10 2.10 210 318.71 319.82 320.37 2.18 2.23 2.25 240 322.04 323.15 323.71 2.33 2.38 2.40 270 325.93 327.59 327.59 2.52 2.61 2.61 300 329.82 330.37 330.93 2.74 2.78 2.82 330 332.59 333.15 334.26 2.93 2.97 3.06 360 335.93 336.48 337.59 3.20 3.25 3.35 390 338.71 339.26 342.04 3.46 3.51 3.83 420 342.04 343.15 344.26 3.83 3.97 4.12 450 344.82 345.93 347.59 4.21 4.38 4.67 480 348.71 349.26 350.37 4.88 4.99 5.24 510 350.37 351.48 353.15 5.24 5.51 5.97 540 354.26 355.37 356.48 6.33 6.72 7.18 570 356.48 358.15 359.82 7.18 7.98 8.99

Figure 6.5 Experimental and Calculated U for Part 2 of 2 for a Un-baffled CSTR

7. Appendix II: Error Analysis

There are 5 readings taken, each with varying errors.

The first reading is from the water flow meter. The readings go from 0 to 100 percent. The meter seemed inaccurate at times. When adjusting the flow rate the flow had to be shut down completely, or to 0, then increased in order to get an accurate

12 Heat Transfer To a Fluid in a CSTR University Of Illinois reading. After setting the flow rate it was still difficult to get an accurate reading because of the bobble of the meter. At high flow rates (greater than 50 percent) the bobble occurred even more. It is then concluded that the flow rate error is + 2% for readings less than 50 % and + 3% for readings greater than 50%.

The second reading is from the temperature gauge. There are three different

o o temperature gauges used in this experiment: 1) Reads 0 to 300 F in intervals of 2 F, 2)

o o o o Reads from 0 to 250 F in intervals of 2 F, 3) Reads from 0 to 105 C in intervals of 1 C.

o These gauges were easy to read and measurements could be taken every 1 C, with a

o o estimated error is + .5 F/ C.

The next reading is from the display box that gives the RPM of the impeller.

Although it displays one significant figure and the accuracy should be ± 0.05, although during the measurements, the reading was constantly fluctuating. Therefore a estimated error ±15 RPM associated with this instrument.

The next reading is from the 500 mL graduated cylinder used to calculate the volumetric flow rate of the fluid. It has markings every 5mL and they are far apart to take the reading every 2mL, so we estimated an error associated with this instrument to be ±1mL. The volumetric flow rate of the fluid was used to calculate the maximum flow rate of the recycled water and the flow rate of the steam. These readings are important as they are used to calculate the experimental and overall heat transfer coefficients.

The last reading is from the ruler used to measure the length and the diameter of the tank and the impeller. The ruler has markings every 0.001 m and the grading’s are

13 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois too close to take readings every 1mm so we estimated an error associated with this instrument to be ±0.001 m. The dimensions of the tank and the impeller are important because they will be used in many calculations throughout the experiment.

8. Appendix III: Sample Calculations

Sample Calculations for Unbaffled CSTR Run1

Temperature of the fluid entering the cooling coil : Tincc = 334.8 ±1 K

Temperature of the fluid leaving the cooling coil: Toutcc = 272.6 ±2 K Temperature of the tank = 310.3 ±1 K

Mass flow rate of the heat exchanger mhx = 1.44 kg/min

Mass flow rate of the cooling coil mcc = 0.78 kg/min

error (+/- 1) Height of tank 41cm Diameter(inner) 22.8 cm Diameter(outer) 30 cm Diameter of impeller 10 cm

The maximum flow rate of the recycled water was calculated using data collected at 26% flow. In 1 minute 100 mL of water was collected. Volumetric flow rate = 270.8 mL/min

0.342GPM at 26% with a max cooling for the rotometer of 0.810GPM from the manufacturer.

Calculation of QHX ( heat exchanger)

Qhx=mhxCp(Thx-TR), where Cp = 4.34kJ/kg*K

Qhx=mhxCp(Thx-TR)== 147.8kJ/min

Calculation of Qcc (cooling coil)

Qcc=mcCp(Tout-TRin), where Cp = 4.34kJ/kg*K

Qcc=mcCp(Tout-Tin)== 128.5kJ/min

Calculation of U i, wall

Ui, wall=(Qhx-Qc)/A(T3-T1) 2 Ui, wall=(Qhx-Qc)/A(T3-T1)= = 37.12 kJ/((min*m *K)

Calculation for h0

(1/3) 2 h0 = (DT,o/mst)=2960*(0.3/0.266) (W/m K)(1kJ/1000J)(60s/1min)

2 h0=184.7(kJ/min*m K)

Calculation for hi,(experimental) 15 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

hi,exp =

2 2 2 hi,exp = 37.12 kJ/((min*m *K)/(1-((37.12 kJ/((min*m *K))/( 184.7(kJ/min*m K))

2 hi,exp= 46.45(kJ/(min*m *K)

Calculation of U using run 1 data at 294.26 K. with a mass of 46 kgs of fluid;

U = U = 1.50(kJ/(min*m2*K)

9. Appendix IV: Individual Team Contributions

Name: Jay Gulotta Time Description (hours) Operator (both Lab days) 3 Basic understanding Pre-Lab Editing 3.5 Proofreading, Editing, and Formatting Final Lab Editing 4 Proofreading, Editing, and Formatting Summary - Introduction - Literature Review/Theory 6 Research and Derivations Apparatus - Materials And Supplies - Procedure - Anticipated Results - Results - Discussion - Conclusions -

References .5 References Data Tabulation/ Graphs - Error Analysis - Sample Calculations 2 Sample Calculations for Part 1 and 2 Job Safety Analysis - Power Point Presentations 2 Objective, measured variables, safety, etc.. Total Hours 21

Name: Mrunal Patel Time Description (hours) Operator (both Lab days) 7 Helped conduct the experiment during the two lab periods Pre-Lab Editing Final Lab Editing Summary Introduction Literature Review/Theory Apparatus Materials And Supplies Procedure Anticipated Results 3 Based on the equations given in the lab manual, made Results Discussion Conclusions 2 Concluded the data found during the lab 17 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

References Data Tabulation/ Graphs Error Analysis Sample Calculations Job Safety Analysis Power Point Presentations Total Hours 13

Name: Frank Perez Time Description (hours) Operator (both Lab days) 7 Pre-Lab Editing Final Lab Editing Summary Introduction Literature Review/Theory Apparatus Materials And Supplies Procedure Anticipated Results Results 2 I wrote the results section.

Discussion Conclusions References Data Tabulation/ Graphs 1 I graphed some of the graphs used in the results section. Error Analysis Sample Calculations Job Safety Analysis .5 I wrote the safety analysis section of the prep lab. Power Point Presentations Total Hours 10.5

Name: Sukhjinder Singh Time Description (hours) Operator (both Lab days) 7 Helped both days with operation of lab Pre-Lab Editing Final Lab Editing Summary 2 Wrote Section Introduction 2 Wrote Section Literature Review/Theory Apparatus Materials And Supplies Procedure Anticipated Results Results Discussion Conclusions References 19 Unit Operations CHE-381 Group No. 3 Spring 2011 2/02/2011 Cabral, Gulotta, Morgan, Mottel, Patel, Perez, Singh Heat Transfer To a Fluid in a CSTR University Of Illinois

Data Tabulation/ Graphs Error Analysis Sample Calculations Job Safety Analysis Power Point Presentations Total Hours 11

Name: Russ Cabral Time Description (hours) Operator (both Lab days) 7 Helped to operate flow rate, temperature, and impeller speed. Pre-Lab Editing Final Lab Editing Summary Introduction Literature Review/Theory Apparatus Materials And Supplies 1 Created table that included materials and supplies and they’re uses. Procedure Anticipated Results Results Discussion Conclusions

References Data Tabulation/ Graphs Error Analysis 2 Analyzed possible error. Sample Calculations Job Safety Analysis Power Point Presentations Total Hours 10

Name: Scott Morgan Time Description (hours) Operator (both Lab days) 7 Pre-Lab Editing Final Lab Editing Summary Introduction Literature Review/Theory Apparatus 4 Materials And Supplies Procedure Anticipated Results Results Discussion 3

Conclusions References Data Tabulation/ Graphs Error Analysis Sample Calculations Job Safety Analysis Power Point Presentations 2 Total Hours 16

Name: Brian Mottel Time Description (hours) Operator (both Lab days) 7 In charge of running equipment Pre-Lab Editing 0 Final Lab Editing 0 Summary 0 Introduction 0 Literature Review/Theory 0 Apparatus 0 Materials And Supplies 0 Procedure 1.5 Wrote the procedure for this experiment Anticipated Results 0 Results 0 Discussion 0 Conclusions 0 References 5 Wrote down all the data collected in lab, completed all necessary calculations, and constructed the graphs Data Tabulation/ Graphs 0 Error Analysis 0

Sample Calculations 0 Job Safety Analysis 0 Power Point Presentations 13.5 Total Hours 7 In charge of running equipment

I have read relevant background material for the Unit Operations Laboratory entitled: “

Heat transfer to a Fluid in a CSTR” and understand the hazards associated with conducting this experiment. I have planned out my experimental work in accordance to standards and acceptable safety practices and will conduct all of my experimental work in a careful and safe manner. I will also be aware of my surroundings, my group members, and other lab students, and will look out for their safety as well.

Signatures: First & Last Name 1____electronic_signature______

Jay Gulotta______

Mrunal Patel ______

Brian Mottel______

Frank Perez______

Sukhjinder Singh______

Russell Cabral______

Scott Morgan______