This experiment aims to plot the friction factor against the Reynolds Number for a fixed bed and determine the critical velocity and superficial velocity of particles. Fluidization occurs when the upward drag force from the fluid equals the apparent weight of particles, lifting them. The experiment obtains bed expansion, pressure drop, and flow rate at different superficial velocities. The fanning friction factor is then plotted against the Reynolds number. Results show the friction factor was around 0.15, with 0.16 in the first trial and 0.14 in the second as the pressure drop increased and critical velocity and superficial velocity rose proportionally to the gas supply rate.

1. FLUIDIZATION
ELECCION, NICELY JANE R.
Department of Chemical Engineering
College of Engineering and Architecture
Cebu Institute of Technology – University
N. Bacalso Ave., Cebu City 6000
This experiment aims to plot the friction factor against the Reynolds Number for fixed
bed and to determine the critical velocity and the superficial velocity of the particle.
Fluidization is an operation by which a bed of solid particles acquires fluid-like
properties by passing a gas or liquid through it. Fluidization converts a bed of solid
particles into an expanded mass that has many properties of a liquid. As a fluid is
passed upward through a bed of particles, pressure loss due to frictional resistance
increases as fluid flow increases. At a point, whereby the upward drag force exerted
by the fluid on the particle equal to apparent weight of particles in the bed, fluidization
occurs. From this experiment, we can obtain the bed expansion, bed pressure drop
and the flow rate of the fluid. Superficial gas velocity, critical velocity, and ε for all cases
can be calculated. Then only, we plotted fanning friction factor versus the Reynolds
number of the particle and the bed.
Engr. Jennifer M. Fernandez
Instructor
Jan. 16, 2018

2. 1. Introduction
Fluidization is a process where a bed of solid particles acquires fluid-like
properties by passing a gas or liquid through it. This phenomena can be visibly
seen in a fluidized bed. A fluidized bed is a state of a two-phase mixture of
particulate solid material and fluid, (relatively new tool in the chemical
engineering field). The term "fluidized bed" is unavoidably connected to the
term "particulate solid material". Particulate materials are mechanical mixtures
of multitude of solid particles. Natural particulate materials originate from many
long-term natural processes: heating, cooling, thermal dilatation, colliding,
crushing, and chopping up, atmospheric changes, river erosion and erosion
caused by sea waves.
Fluidized beds provide a large surface area for contact between solids
and a liquid or a gas that is conducive for heat and mass transfer. In this
environment, nearly uniform temperatures can be maintained in the reactor even
with highly exothermic reactions. This is important because a temperature
gradient can form in a poorly mixed bed, leading to equipment failure, product
degradation, and decreased efficacy of the reaction. A fluidized bed also
provides uniform mixing, which is important for product quality and efficiency.
Fluidized bed reactors are often a continuous process, meaning they are also
very efficient compared to batch processes.
According to Cocco, R. et al. (2014), particles become fluidized when an
upward-flowing liquid imposes a high enough drag force to overcome the
downward force of gravity. The drag force is the frictional force imposed by the
liquid on the particle, wherein the particle imposes an equal and opposite drag
force on the liquid. Thus, as the particle becomes more fluidized, it affects the
local liquid velocity around it because of its drag forces.
This experiment aims to plot the fanning friction factor versus the
Reynolds number and in doing so, several values must be acquired from the
experiment such as getting the critical velocity of the fluidized bed and its
superficial velocity.

3. 2. Materials and Methods
2.1 Equipment and Materials
 Fluidization Apparatus
 Tap water
 Tape Measure
 Graduated Cylinder
 Stopwatch
2.2 Methods
1. The weight of the bed and the average diameter of the particle were
noted.
2. The water container was filled with water sufficient enough to operate
the apparatus.
3. Before operating, the height of the mercury was ensured to be of the
same level by removing the clip and adjusting the pressure in the
manometer slowly.
4. The valve was ensured to be closed before turning on the pump.
5. The pump was turned on.
6. Initial height of the particle was recorded.
7. The pressure drop across the bed was measured starting with the lowest
possible flow rate of water.
8. By simultaneously collecting liquid sample in the exit tube using
graduated cylinder, the volumetric flow rate and the time of collection
was recorded.
9. The volume of the liquid sample was measured and recorded.
10. The flow rate of water was increased and the corresponding pressure
drop across the bed was recorded.
11.The new height of the bed was measured when the bed expanded.
12. Steps 10 and 11 was repeated until the maximum allowable flow rate
was reached.

4. 3. Results
Table 3.1 Tabulated Data and Results of Fluidization
Time
(sec)
Pressure (mm
H2O)
∆P in
manometer
∆P in
bed
Volume
Volumetric
flow rate
Left Right (mm H2O) (Pa) mL m3/s
1. 750 428 193 235 22.63 850 1.13x10-6
2. 683 490 212 278 32.47 830 1.22x10-6
Bed
height (m)
Porosity
(Ɛ)
Velocity v,
(m.s)
Superficial
velocity v’,
(m/s)
Fanning
friction (f)
NRe, bed NRe, particle
0.145 0.8 0.035 0.16 0.16 105.32 157.98
0.155 0.8 0.038 0.14 0.14 113.05 169.58
Initial Pressure in Manometer - Left: 260 mm H2O Right: 260 mm H2O
Initial height of the bed: 0.110 m
Volume of bed – 2.2471x10-4 m3
Volume of particle – 6.5x10-8 m3
No. of particles – 681
Area of the pipe – 0.32 cm2
ρ - 0. 99708 g/cm3
𝜇 – 0. 8937x10-3 kg / m s

5. Figure 3.1 Friction Factors for fluids inside pipes. (Plotting the friction factor
against Reynolds number)
Trial 1
Trial 2
0.16
0.14
105.32
113.05

6. 4. Discussion
Fluidization is an operation in which the fluid is passed upward trough a bed of
particles, the pressure in the fluid will be loss due to the frictional resistance
which increases with increasing fluid flow. A point is reached when the upward
drag force exerted by the fluid on the particles is equal to the apparent weight
of particles in the bed. At this point the particles are lifted by the fluid, the
separation of the particle increases, and the bed become fluidized. The
superficial fluid velocity at which the packed bed becomes a fluidized bed is
known as the minimum fluidization velocity. This velocity increases with particle
size and particle density and is affected by fluid properties.
5. Conclusion
Thus, the fanning friction factor can be plotted and read by getting first
Reynold’s number of the bed using the formula, 𝑁 𝑅𝑒,𝑏𝑒𝑑 =
4𝐷𝑝𝑣′𝜌
6(1−𝜀)𝜇
. The average
fanning friction factor undergone by the experiment is 0.15, with 0.16 in Trial 1
and 0.14 in Trial 2 when the pressure drop is changed. With a critical velocity
increasing as the pressure drop is increased so as its superficial velocity, it is
concluded that the bed expansion and the pressure drop of the particle are
proportional to the superficial velocity of the gas supply.
Figure 5.1 Graph of fanning friction factor versus Reynolds Number

7. 6. Appendix
Figure 6.1 Sketch on the Fluidization Apparatus

8. 7. Calculations

9. 8. References
[1] Geankoplis, C.J. (2009) Principles of Transport Processes and Separation
Processes. 1st edition. Pearson Education South Asia PTE. LTD. page 94
9. Web References
[1] Fluidized bed. (2010, September 7). Retrieved January 14, 2018, from
http://www.thermopedia.com/content/46/
[2] Cocco, R., Karri, R., & Knowlton, T. (2014).
Https://www.aiche.org/sites/default/files/cep/20141121.pdf. Https://www.aiche.
org/sites/default/files/cep/20141121.pdf, 2-3. Retrieved January 15, 2018, from
https://www.aiche.org/sites/default/files/cep/20141121.pdf.