experimental report processes in food engineering i bf2571e

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HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGYSCHOOL OF CHEMISTRY AND LIFE SCIENCES

---EXPERIMENTAL REPORTProcesses in Food Engineering I – BF2571ELecturer:

 MSc. Lê Ngọc CươngStudent name: Trịnh Duy TùngStudent ID: 20221322

Class: BF- E12 01 K67Class ID: 738145

Hanoi, 2024

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The food industry is the primary source of energy and nutrition for humans, and it plays a crucialrole in our lives. To meet the ever-increasing global demand for food, science and technology must continue to advance and grow.

Processes in Food Engineering I provides with the basic knowledge of hydrody-namics, the basisof the principles of mechanic processes.

In addition, it also provides structure, operation, calculation and selection of food processes and equipment systems such as transportation process, the technological pipelines in food factory, mechanical separation process (sedimentation, filtration, centrifugation), stirring process... Students can apply knowledge in the fields of mathematics, physics and informatics to calculate machines and equipment in food industries.

I had the chance to experiment with tools and learn about the basic theory and operation of food processed. Based on all these lessons, this experimental report will point out …

This experimental report contains three main parts:1. A

2. B3. C

While making the report, I may have made some errors. I would appreciate any feedback that canhelp me improve the report’s accuracy and completeness.

Finally, I want to send special thanks to Mr. Cương for his support and guidance throughout the lessons at B4 Centre and C4-5-301.

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LESSON 1

DETERMINE THE COMPONENTS IN THEBERNOULLI EQUATION

Purpose: To plot the energy line and the hydraulic grade line after determining the

components in Bernoulli’s equation through an experiment

1.

THEORETICAL BACKGROUND

Bernoulli equation is an energy equation written for a unit weight of fluid. TheBernoulli equation for the entire incompressible real fluid, steady flow from cross-section 1-1to cross-section 2-2 (figure 1) is as follows:

1v12 g =z2+p2

γ+2v22 g + hw1−where:

z1, z2 - represent the potential energy of the flow at the center of the wet cross-sectionssurface 1-1 and 2-2 to any standard plane 0-0, referred to as unit potential energy or geometricheight.

Figure 1. Diagram of flow through pipe sections of different sizes.

 - specific weight of liquid

p1 , p – pressure at 2 the center of the wet cross-sections surface 1-1 and 2-2.p1

γ , p2

γ – The potential energy of a unit weight of liquid caused by pressure at sections surface 1-1 and 2-2 is called unit potential energy or pressure-measured height.

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cross-z1+p1γ , z1+p1

γ – unit potential energy of a static water column at cross-sections surface1-1 and 2-2.

1, 2 – Coriolis frequency at cross-sections surface 1-1 and 2-2.v1, v – average velocity at cross-sections surface 1-1 and 2-2.2

α1v12 g ,

2 g – unit kinetic energy or velocity height at cross-sections surface 1-1 and2-2.

hw1-2 – unit energy loss in the fluid segment cross-sections surface 1-1 and 2-2.at

2.

EXPERIMENT EQUIPMENT DESCRIPTION

The experimental apparatus is depicted in Fig 2. Water is supplied through a valve into regulator A and flows through Bernoulli’s tube 1 into regulator B. The water level in regulators A and B is maintained stable. Bernoulli’s tube 1 are attached pressure gauges I, II, III, IV, and V corresponding to the 5 selected cross-sections surface. The diameters of the tube are d1 = 1,5 cm; d = 0,8 cm2 . Use valve 2 to adjust the flow velocity through Bernoulli’s tube 1, and the corresponding flow rate for each flow velocity will be displayed on flow meter 3.

Fig 2: Bernoulli experimental tube diagram

A, B. Water containers; 1. Bernoulli experimental tube;2. Flow control valve; 3. Flow meter; I, II, III, IV và V. Pressure gauges.

1. Study the theoretical basis of Bernoulli’s equation for the entire real, incom-pressible, steady flow of fluid.

2. Familiarize yourself with the experimental equipment and measuring devices.

3. Open the supply valve to provide water to regulators A and B under the guidance of the practical experiment instructor and wait until the regulators are supplied with enough water to proceed with the experiment.

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on the rulers (i.e., the value zi+ pi/γ )).

6. Conduct the experiment with five different flow velocities.

1. Record the flow values Qi displayed on flow meter 3 into column [2] of Table 1.

2. For each measured flow value Qi, calculate the average velocity vi of the flow at thecorresponding cross-sections using the formula:

vi= iS=

4 Qiπ d2

where d is the diameter of the cross-section of tube 1. Record the calculated values into column[3] of Table 1.

3. From the vi values just found, calculate the components α1v1

2 g of Bernoulli’s equation (here,we take α = 1). Record the values i α1v1

2 g into columns [5], [8], [12], [16], and [20] respectivelyin Table 1.

4. According to the heights of pressure gauges I, II, III, IV, and V, determine the value zi+ pi/γat the corresponding cross-sections (see Figure 2) (If the standard surface is chosen through theaxis of the tube, then we have z = 0). Record the found values into columns [4], [7], [11], [15],iand [19] respectively of Table 1.

5. The loss of column pressure values in columns [9], [13], [17], and [21] in Table 1 are given byBernoulli’s equation (Need to calculate hw1-2 in column [9] we take the sum of column [7] andcolumn [8] minus the value of column [4] and column [5])

6. From the data in Table 1 and the diagram of Bernoulli’s experimental tube (in Figure 2), drawthe energy line and the pressure line.

Table 1- Experimental results of the components in the Bernoulli equation

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Note: To acquire high accuracy of the experimental results, it is necessary to adjustvalve 2 so that the flow through the Bernoulli tube is turbulent.

5.REVIEW, EVALUATE EXPERIMENTAL RESULTS

Compare the accuracy of the energy curves and pressure measurement lines drawn according to experimental results with the theory.

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Mechanical stirring, which involves the use of various types of stirring blades, is apopular method. The type of stirring blade used can vary depending on the specific requirementsof the process. Common types of stirring blades include paddle type, duck foot or windmill type,turbine type, and other special types.

The stirring process is characterized by the power required and the stirringefficiency. When the stirring blade rotates, the energy consumed is used to overcome the frictionbetween the stirring blade and the liquid.

The movement of the liquid in the stirring machine can be considered a special case ofliquid movement. Therefore, to describe the stirring process in a stable mode, the standardequation of liquid movement can be used. This equation would take into account factors such asthe velocity and pressure of the liquid, the geometry of the stirring machine, and the properties ofthe liquid:

Eu = f (Re, Fr,…) (1)

Here: Eu =

ω- flow velocity, m/s

d - diameter, mμ - viscosity, N.s/m2

For a mixing device, ‘d’ is the diameter of the impeller, the velocity of the liquid motion isreplaced by the number of rotations of the impeller (ω=π dn), and the pressure difference is



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Eu = K

; Re = K

μ

; Fr = K

n d

2

g

Here: n – revolutions of paddle, rev/s d – paddle diameter, m N – shaft power, W

Eu = f (Re , Fr )K KKThrough experiment we have: Eu = C. K ReK. FrKn

(2)Where : C, m, n – quantities determined by experiment.

They depend on the size of the impeller, the liquid level, the shape of the mixing tank,the smoothness of the tank wall, and other structures.

If no funnel is formed on the surface, then the impeller is deeply immersed in theliquid, so the effect of gravitational acceleration can be ignored.

We have :

= C.

(ρ nd

2

μ)

m

3. Determine Euler, Reynolds number and their relationship.

4. Draw a graph representing the relationship between Brix concentration and stirring time.

3.EXPERIMENT GRAPH

4.EXPERIMENTAL PROCEDURE

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3. Pour 5 liters of water into the barrel, add 1 or 2kg of sugar.4. Select the number of rotations of the stirrer on the control panel.5. Turn on the machine for the motor to operate, the stirrer rotates.

6. Start counting the stirring time, take a sample to measure the Brix concentration every minute (read accurately to 0.1).

7. Record the data in table 1 and table 2.

8. Measure until the Bx concentration does not change, then stop stirring. Determine the stirring time.

9. After taking all the data, turn off the machine, clean the experiment area, and report the experiment results to the supervising staff.

Table 1: Table of experiment

No. ofexperi-ment

Number ofstirringblade’srevolution-s

EuK lgEuK ReK lgReK m lgC C

Table 2: Results of Brix concentration measurement

Stirring time t (min) 1 2 3 …..Brix concentration (Bx)

5.Calculate experimental results, plot the graph

1. Determine Euler number

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Eu = K

(4)N – capacity, W

n – number of stirring blade’s revolution, vòng/sd – stirrring blade diameter, m

ρ - liquid density, kg/m32. Determine Reynolds number

Re = K

μ

(5) μ - liquid viscosity, N.s/m2

Do 5 experiments with different values of ReK.

On the lgEuK - lgReKaxis system, we draw a straight line through the points. Based on thestraight line, we have the equation:

lgEu = lgC + m.lgRe (6)KK or Eu = C. K ReKm

(7)Determine value of m, C of equation (7).

lgEuK

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(with two different stirring speeds). Draw conclusions

Conclusion :………...………

t (mins)

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In a liquid environment, according to Archimedes’ law, the gravity of a spherical particle KSis calculated as follows

KS=π d3

(

ρ1−ρ2

)

g ,( N )(1)ρ1: density of spherical particle (kg/m )3

ρ2: density of liquid (kg/m )3g: gravitational acceleration (m/s )2

When a spherical particle falls (settles) at velocity u, it experiences a drag force caused bythe liquid environment. This drag force depends on the physical properties of the liquidenvironment (density, viscosity), depends on the size and shape of the object, and depends onthe falling velocity and gravitational acceleration. According to Newton, the drag force S isdetermined as follows:

S=ξ F ρ2u22,( N )(2)

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F: cross-sectional area of the particle in the direction of motionWith spherical particle:

S=ξπd24 ρ2u2

2, ( N)(3)

Assume that a spherical particle settles at a constant velocity. In that case S = KS:ξπd

24 ρ2u2

2=π d3

ℜ≤ 0,2 ξ=ℜ24

0,2<ℜ<500 ξ=18,5ℜ500<ℜ<15.104

ξ=0,44with: ℜ=ρ2ud

μ (6)μ: liquid dynamic viscosity, Pa.s

2. EXPERIMENT DESCRIPTION AND PROCEDURE

Students conduct an experiment on the sedimentation of spherical glass particles in a honeyenvironment (dynamic viscosity ν = 65mm2/s). The size of the glass particles is determinedby a caliper or according to the manufacturer’s specifications, then they are dropped into aglass tube containing honey with a height of h = 35cm. The falling time of the glass particlest (s) is measured.

Steps to conduct the experiment

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Step 2: Determine the mass of 1l of cooking oil using an electronic scale: m (kg).2

Step 3: Carry out the sedimentation of the glass particle, measure the sedimentation timeusing a stopwatch t (s).

Repeat the experiment 5 times.