CEBU INSTITUTE OF TECHNOLOGYN. Bacalso Avenue, Cebu City

Chemical Engineeing Department

FINAL REPORTChE Lab 1

Title of Experiment

Juphil A. LamanilaoBSChE-5

Engr. Lyda P. Abellanosa

Instructor

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.

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.

Tabulated Data & Result:

Speed ofRotation

Trials PowerWith baffles Without baffles

Slow1 0.000258 0.0006442 0.000274 0.0006933 0.0003063 0.000673

Moderate1 0.00767 0.073112 0.00767 0.07383 0.007384 0.0745

Fast1 0.0427 0.07652 0.03872 0.07783 0.0404 0.0799

Sample Computations:

For liquid water:

Unbaffled VesselSlow:

Trial 1:N = 692 rev/min x 1 min/60 s = 11.53 rev/s

NRe = NDi2ρ / µ = (11.53 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 28416.021

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(11.53 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.4802 J/s = 6.44x10 -4 hp

Trial 2:N = 690 rev/min x 1 min/60 s = 11.5 rev/s

NRe = NDi2ρ / µ = (11.5 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 28342.09

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(11.5 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 6.39x10 -4 hp

Trial 3:N = 702 rev/min x 1 min/60 s = 11.7 rev/s

NRe = NDi2ρ / µ = (11.7 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 28835

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(11.7 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 6.73x10 -4 hp

Moderate:

Trial 1:N = 3350rev/min x 1 min/60 s = 55.83 rev/s

NRe = NDi2ρ / µ

= (55.83 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 137594.66

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(55.83 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.07311 hp

Trial 2:N = 3360rev/min x 1 min/60 s = 56 rev/s

NRe = NDi2ρ / µ = (56 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 138013.63

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(56 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0738 hp

Trial 3:N = 3370rev/min x 1 min/60 s = 56 .17rev/s

NRe = NDi2ρ / µ = (56.17 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 138432.60

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(56.17 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0745 hp

Fast:

Trial 1:N = 3400rev/min x 1 min/60 s = 56.67 rev/s

NRe = NDi2ρ / µ = (56.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 139664.87

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(56.67 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0765 hp

Trial 2:N = 3420rev/min x 1 min/60 s = 57 rev/s

NRe = NDi2ρ / µ = (57 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 140478.16

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(57 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0778 hpTrial 3:N = 3450rev/min x 1 min/60 s = 57.5 rev/s

NRe = NDi2ρ / µ = (57.5 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 141710.43

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(57.5 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0799hp

Baffled Vessel

Slow:

Trial 1:N = 510 rev/min x 1 min/60 s = 8.5 rev/s

NRe = NDi2ρ / µ = (8.5 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 20948.50

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(2.67 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 2.58x10 -4 hp

Trial 2:N = 520 rev/min x 1 min/60 s = 8.67 rev/s

NRe = NDi2ρ / µ = (8.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 21367.47

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(8.67 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 2.74x10 -4 hp

Trial 3:N = 540 rev/min x 1 min/60 s = 9 rev/s

NRe = NDi2ρ / µ = (9 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 22180.76

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(9 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 3.063x10 -4 hp

Moderate:

Trial 1:N = 1580rev/min x 1 min/60 s = 26.33 rev/s

NRe = NDi2ρ / µ = (26.53 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 658383.96

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(26.53rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 7.67x10 -3 hp

Trial 2:N = 1580rev/min x 1 min/60 s = 26.33 rev/s

NRe = NDi2ρ / µ = (26.53 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 658383.96

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(26.53rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 7.67x10 -3 hp

Trial 3:N = 1560rev/min x 1 min/60 s = 26rev/s

NRe = NDi2ρ / µ = (26 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 64077.76

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(26 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 7.384x10-3 hp

Fast:

Trial 1:N = 2680rev/min x 1 min/60 s = 46.67rev/s

NRe = NDi2ρ / µ = (46.67 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 115019.58

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(46.67 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0427 hp

Trial 2:N = 2710rev/min x 1 min/60 s = 45.17 rev/s

NRe = NDi2ρ / µ = (45.17 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 111322.78

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(45.17 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.03872 hpTrial 3:N = 2750rev/min x 1 min/60 s = 45.83 rev/sCont. Trial 3 (fast):

NRe = NDi2ρ / µ = (45.83 rev/s)(0.047 m)2(997.08 kg/m3) / 0.0008937 kg/m·sNRe = 112949.37

NPo = 1.37

NPo = Pgc / N3Di5ρ

P = NPoN3Di5ρ / gc

= (1.37)(45.83 rev/s)3(0.047 m)5(997.08 kg/m3) / 1 kg·m/s2/NP = 0.0404hp

Given: T@25oC

u = 0.8937x10-4 Pa-sP = 997.08 kg/m3

Da = 0.047 mE = 0.06 mDt = 0.16 mH = 0.16 mW (impeller) = 0.01 mJ = 0.025 m

Unbaffled VesselAverage:Slow = (0.000644 +0.000693+0.000673)/3 = 0.00067Moderate = (0.07311+0.0738+0.0745)/3 = 0.0738Fast = (0.0765+0.0778+0.0799)/3 = 0.0781Baffled VesselAverage:Slow = (0.000258 +0.000274+0.0003063)/3 = 0.0002794Moderate = (0.00767+0.00767+0.007384)/3 = 0.007575Fast = (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.