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ChE Laboratory Exp't, Agitation - Final Report

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- 1. CEBU INSTITUTE OF TECHNOLOGY N. Bacalso Avenue, Cebu City Chemical Engineeing Department FINAL REPORT ChE Lab 1 Title of Experiment Juphil A. Lamanilao BSChE-5 Engr. Lyda P. Abellanosa Instructor
- 2. Abstract: This experiment only utilizes the agitator equipment. Before the start of the experiment a couple of measurement is made – the diameter of the vessel and impeller, which are vital in the computations later on. Due to its similarities with the properties of water, assumptions are made for fluids densities and viscosities. The fluid is liquid water. The data are obtained with and without the baffled vessel. Efficient mixing is obtained when correct answers are available to such questions as (1) size of motor required to drive the mixing equipment; (2) speed of the unit for quality of mixing desired; & (3) type of impeller and used of baffles. The paddle and the impeller are fixed on the shaft at near the bottom of the tank. The faster the rate of revolution of the shaft, the more the vortex becomes distinctive. With an increase of the rotating velocity, much more air is sucked into water. Doubling the impeller diameter will quadruple Reynold’s Number. This follows, as the impeller will sweep an area four times larger when the diameter is doubled. Temperatures and pressures are accounted for in Reynold’s Number as they affect both density and viscosity. These factors are useful for sizing and selections of tanks, impellers, and the associated driving equipment. It is clear that major variables in the problem will be the size of the impeller and its speed. The presence of the baffles will affect the energy consumption materially.
- 3. Objectives: 1.) Effect of speed of rotation on power requirement for baffled and unbaffled tanks. To show the relationship between the power number against Reynold’s number for baffled and unbaffled tanks 2.) Effect of impeller diameter on power requirement of agitation on baffled and unbaffled tanks. Materials & Equipment: Agitator; 2-blade paddle or square-pitch propeller (3 sizes), baffle strips (removable), dynamometer, tachometer, container (10”dia, 18” deep transparent) Sketch of the Set-up: Without Baffles With Baffles Procedure: 1. The container was filled to almost 16 cm (tank is without baffles). 2. The impeller was attached to the agitator. 3. The impeller was immersed in water inside the container such that its elevation was about 4 in. 4. The power requirement was measured with the dynamometer being attached to the shaft for different speed of rotation. The speed was measured using tachometer. 5. Steps (3) & (4) were repeated.
- 4. Tabulated Data & Result: Speed of Trials Power Rotation With baffles Without baffles 1 0.000258 0.000644 Slow 2 0.000274 0.000693 3 0.0003063 0.000673 1 0.00767 0.07311 Moderate 2 0.00767 0.0738 3 0.007384 0.0745 1 0.0427 0.0765 Fast 2 0.03872 0.0778 3 0.0404 0.0799 Sample Computations: • For liquid water: NPo = 1.37 Unbaffled Vessel NPo = Pgc / N3Di5ρ Slow: P = NPoN3Di5ρ / gc Trial 1: = (1.37)(11.5 rev/s)3(0.047 m)5(997.08 kg/m3) N = 692 rev/min x 1 min/60 s = 11.53 rev/s / 1 kg·m/s2/N P = 6.39x10-4 hp NRe = NDi2ρ / µ = (11.53 rev/s)(0.047 m)2(997.08 kg/m3) / Trial 3: 0.0008937 kg/m·s N = 702 rev/min x 1 min/60 s = 11.7 rev/s NRe = 28416.021 NRe = NDi2ρ / µ NPo = 1.37 = (11.7 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s NPo = Pgc / N3Di5ρ NRe = 28835 P = NPoN3Di5ρ / gc NPo = 1.37 = (1.37)(11.53 rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N NPo = Pgc / N3Di5ρ P = 0.4802 J/s = 6.44x10-4 hp P = NPoN3Di5ρ / gc Trial 2: = (1.37)(11.7 rev/s)3(0.047 m)5(997.08 kg/m3) N = 690 rev/min x 1 min/60 s = 11.5 rev/s / 1 kg·m/s2/N P = 6.73x10-4 hp NRe = NDi2ρ / µ = (11.5 rev/s)(0.047 m)2(997.08 kg/m3) / Moderate: 0.0008937 kg/m·s NRe = 28342.09 Trial 1: N = 3350rev/min x 1 min/60 s = 55.83 rev/s
- 5. Fast: 2 NRe = NDi ρ / µ = (55.83 rev/s)(0.047 m)2(997.08 kg/m3) / Trial 1: 0.0008937 kg/m·s N = 3400rev/min x 1 min/60 s = 56.67 rev/s NRe = 137594.66 NRe = NDi2ρ / µ NPo = 1.37 = (56.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s NPo = Pgc / N3Di5ρ NRe = 139664.87 P = NPoN3Di5ρ / gc NPo = 1.37 = (1.37)(55.83 rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N NPo = Pgc / N3Di5ρ P = 0.07311 hp P = NPoN3Di5ρ / gc Trial 2: = (1.37)(56.67 rev/s)3(0.047 m)5(997.08 kg/ N = 3360rev/min x 1 min/60 s = 56 rev/s m3) / 1 kg·m/s2/N P = 0.0765 hp NRe = NDi2ρ / µ = (56 rev/s)(0.047 m)2(997.08 kg/m3) / Trial 2: 0.0008937 kg/m·s N = 3420rev/min x 1 min/60 s = 57 rev/s NRe = 138013.63 NRe = NDi2ρ / µ NPo = 1.37 = (57 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s NPo = Pgc / N3Di5ρ NRe = 140478.16 P = NPoN3Di5ρ / gc NPo = 1.37 3 5 3 = (1.37)(56 rev/s) (0.047 m) (997.08 kg/m ) / 1 kg·m/s2/N NPo = Pgc / N3Di5ρ P = 0.0738 hp P = NPoN3Di5ρ / gc Trial 3: = (1.37)(57 rev/s)3(0.047 m)5(997.08 kg/m3) / N = 3370rev/min x 1 min/60 s = 56 .17rev/s 1 kg·m/s2/N P = 0.0778 hp 2 NRe = NDi ρ / µ Trial 3: = (56.17 rev/s)(0.047 m)2(997.08 kg/m3) / N = 3450rev/min x 1 min/60 s = 57.5 rev/s 0.0008937 kg/m·s NRe = 138432.60 NRe = NDi2ρ / µ = (57.5 rev/s)(0.047 m)2(997.08 kg/m3) / NPo = 1.37 0.0008937 kg/m·s NRe = 141710.43 NPo = Pgc / N3Di5ρ NPo = 1.37 3 5 P = NPoN Di ρ / gc = (1.37)(56.17 rev/s)3(0.047 m)5(997.08 kg/ NPo = Pgc / N3Di5ρ m3) / 1 kg·m/s2/N P = 0.0745 hp P = NPoN3Di5ρ / gc
- 6. = (1.37)(57.5 rev/s)3(0.047 m)5(997.08 kg/m3) = (9 rev/s)(0.047 m)2(997.08 kg/m3) / 2 / 1 kg·m/s /N 0.0008937 kg/m·s P = 0.0799hp NRe = 22180.76 NPo = 1.37 Baffled Vessel NPo = Pgc / N3Di5ρ P = NPoN3Di5ρ / gc Slow: = (1.37)(9 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/N Trial 1: P = 3.063x10-4 hp N = 510 rev/min x 1 min/60 s = 8.5 rev/s NRe = NDi2ρ / µ Moderate: = (8.5 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s Trial 1: NRe = 20948.50 N = 1580rev/min x 1 min/60 s = 26.33 rev/s NPo = 1.37 NRe = NDi2ρ / µ = (26.53 rev/s)(0.047 m)2(997.08 kg/m3) / NPo = Pgc / N3Di5ρ 0.0008937 kg/m·s NRe = 658383.96 P = NPoN3Di5ρ / gc = (1.37)(2.67 rev/s)3(0.047 m)5(997.08 kg/m3) NPo = 1.37 / 1 kg·m/s2/N P = 2.58x10-4 hp NPo = Pgc / N3Di5ρ Trial 2: P = NPoN3Di5ρ / gc N = 520 rev/min x 1 min/60 s = 8.67 rev/s = (1.37)(26.53rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N NRe = NDi2ρ / µ P = 7.67x10-3 hp = (8.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s Trial 2: NRe = 21367.47 N = 1580rev/min x 1 min/60 s = 26.33 rev/s NPo = 1.37 NRe = NDi2ρ / µ = (26.53 rev/s)(0.047 m)2(997.08 kg/m3) / NPo = Pgc / N3Di5ρ 0.0008937 kg/m·s NRe = 658383.96 P = NPoN3Di5ρ / gc = (1.37)(8.67 rev/s)3(0.047 m)5(997.08 kg/m3) NPo = 1.37 / 1 kg·m/s2/N P = 2.74x10-4 hp NPo = Pgc / N3Di5ρ Trial 3: P = NPoN3Di5ρ / gc N = 540 rev/min x 1 min/60 s = 9 rev/s = (1.37)(26.53rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N NRe = NDi2ρ / µ P = 7.67x10-3 hp
- 7. NPo = 1.37 Trial 3: N = 1560rev/min x 1 min/60 s = 26rev/s NPo = Pgc / N3Di5ρ NRe = NDi2ρ / µ P = NPoN3Di5ρ / gc = (26 rev/s)(0.047 m)2(997.08 kg/m3) / = (1.37)(26 rev/s)3(0.047 m)5(997.08 kg/m3) / 0.0008937 kg/m·s 1 kg·m/s2/N NRe = 64077.76 P = 7.384x10-3 hp Cont. Trial 3 (fast): Fast: NRe = NDi2ρ / µ = (45.83 rev/s)(0.047 m)2(997.08 kg/m3) / Trial 1: 0.0008937 kg/m·s N = 2680rev/min x 1 min/60 s = 46.67rev/s NRe = 112949.37 NRe = NDi2ρ / µ NPo = 1.37 = (46.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·s NPo = Pgc / N3Di5ρ NRe = 115019.58 P = NPoN3Di5ρ / gc NPo = 1.37 = (1.37)(45.83 rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N NPo = Pgc / N3Di5ρ P = 0.0404hp P = NPoN3Di5ρ / gc Given: T@25oC = (1.37)(46.67 rev/s)3(0.047 m)5(997.08 kg/ m3) / 1 kg·m/s2/N u = 0.8937x10-4 Pa-s P = 0.0427 hp P = 997.08 kg/m3 Da = 0.047 m E = 0.06 m Trial 2: Dt = 0.16 m N = 2710rev/min x 1 min/60 s = 45.17 rev/s H = 0.16 m NRe = NDi2ρ / µ W (impeller) = 0.01 m = (45.17 rev/s)(0.047 m)2(997.08 kg/m3) / J = 0.025 m 0.0008937 kg/m·s NRe = 111322.78 Unbaffled Vessel Average: NPo = 1.37 Slow = (0.000644 +0.000693+0.000673)/3 = 0.00067 NPo = Pgc / N3Di5ρ Moderate = (0.07311+0.0738+0.0745)/3 = 0.0738 P = NPoN3Di5ρ / gc Fast = (0.0765+0.0778+0.0799)/3 = (1.37)(45.17 rev/s)3(0.047 m)5(997.08 kg/ = 0.0781 m3) / 1 kg·m/s2/N Baffled Vessel P = 0.03872 hp Average: Trial 3: Slow = (0.000258 +0.000274+0.0003063)/3 N = 2750rev/min x 1 min/60 s = 45.83 rev/s = 0.0002794 Moderate = (0.00767+0.00767+0.007384)/3
- 8. = 0.007575 Fast = (0.0427+0.03872+0.0404)/3 = 0.04061 Data Analysis : In the experiment, agitation process with baffles requires greater power because with more power vortex does not occur hence proper mixing is attainable. Baffles are often included to reduce tangential motion. Without baffles, the liquid is simply swirled around with little actual mixing since the flow is uniform in the same direction. Changing the impeller would affect the power requirement of the agitation process because with different types of impellers, mixing effectiveness varies. By increasing its power the impellers efficiency increases. From the following data, it is now possible to compute for the Reynold’s number to be used from the constant value of power number which is 1.37. Using the power number formula, power was computed. Recommendation: When using the tachometer to determine the speed in rev/min, it is not as accurate as it is. Once it’s already placed on the spindle, timings are necessary before triggering it by the experimenter such that there should be a stable place of such not just by holding it. The shaft must be placed in the middle of the tank to lessen the error occurred. There should be another fluid instead of just water alone for comparison purposes in order to observe the effects of the agitated fluids. Application to ChE: One application to ChE involves the line of pilot plant and with such type of small commercial size propeller agitators may be used for slurry applications for the mineral, chemical and other industries in which the units have axial flow type propellers that are specifically designed for leaching, dissolution, reactors, reagent conditioning, gas diffusion, storage and scrubbing processes involving coarse or fine slurries. These are also available for solvent extraction and other solution applications involving mixing or shear.

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