experimental report processes in food engineering i bf2571e

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+p2γ+2v22 g + hw1−where: z1, z2 -

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY SCHOOL OF CHEMISTRY AND LIFE SCIENCES

-EXPERIMENTAL REPORT Processes in Food Engineering I – BF2571E

Lecturer:

 MSc Lê Ngọc Cương

Student name: Trịnh Duy Tùng

Student ID: 20221322

Class: BF- E12 01 K67

Class ID: 738145

Hanoi, 2024

The food industry is the primary source of energy and nutrition for humans, and it plays a crucial role 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 basis

of 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 B

3 C

While making the report, I may have made some errors I would appreciate any feedback that can help 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

LESSON 1

DETERMINE THE COMPONENTS IN THE

BERNOULLI 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 The Bernoulli equation for the entire incompressible real fluid, steady flow from cross-section 1-1

to cross-section 2-2 (figure 1) is as follows:

z1+p1

γ+

1v1

2 g =z2+p2

γ+

2v2

2 g + hw 1−

where:

z1, z2 - represent the potential energy of the flow at the center of the wet cross-sections surface 1-1 and 2-2 to any standard plane 0-0, referred to as unit potential energy or geometric height

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 cross-sections surface 1-1 and 2-2 is called unit potential energy or pressure-measured height

γ , z1+p1

γ – unit potential energy of a static water column at cross-sections surface 1-1 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

α1v1

2 g ,

α1v1

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

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

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 the corresponding cross-sections using the formula:

vi= i

S=

4 Qi

π 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] respectively

in Table 1

4 According to the heights of pressure gauges I, II, III, IV, and V, determine the value zi+ pi/γ

at the corresponding cross-sections (see Figure 2) (If the standard surface is chosen through the axis of the tube, then we have z = 0) Record the found values into columns [4], [7], [11], [15],i and [19] respectively of Table 1

5 The loss of column pressure values in columns [9], [13], [17], and [21] in Table 1 are given by Bernoulli’s equation (Need to calculate hw1-2 in column [9] we take the sum of column [7] and column [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), draw the energy line and the pressure line

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

Note: To acquire high accuracy of the experimental results, it is necessary to adjust valve 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

LESSON 2

LIQUID MIXING EXPERIMENT

1 INTRODUCTION

Stirring in a liquid environment is a common practice in the chemical and food industries It is used to create colloidal solutions and emulsions, and to enhance processes such

as dissolution, heat transfer, mass transfer, and chemical reactions

Mechanical stirring, which involves the use of various types of stirring blades, is a popular method The type of stirring blade used can vary depending on the specific requirements

of 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 stirring efficiency When the stirring blade rotates, the energy consumed is used to overcome the friction between the stirring blade and the liquid

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

Eu = f (Re, Fr,…) (1)

Here: Eu =

ΔΡ

ρω2

Euler number

Re =

ωdρ

μ Reynolds number

Fr =

ω2

gd Froude number

- pressure difference

ρ - liquid density, kg/m3

ω- flow velocity, m/s

d - diameter, m

μ - viscosity, N.s/m2

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



Eu = K

Ν

ρn3d5

; Re = K

ρnd2

μ ; Fr = K

n d2 g

Here: n – revolutions of paddle, rev/s

d – paddle diameter, m

N – shaft power, W

Eu = f (Re , Fr )K K K

Through 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 the liquid, so the effect of gravitational acceleration can be ignored

We have :

Ν

ρn3d5

= C ( ρ nd2

μ )m

(3)

2 EXPERIMENTAL PURPOSE

1 Get acquainted with the structure of the stirrer and various types of paddle impellers,

propeller

2 Determine the power consumption when stirring, the number of rotations, and the mixing

time

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

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 of

experi-ment

Number of

stirring

blade’s

revolution-s

(rev/s)

Capa-city N (W)

EuK lgEuK ReK lgReK m lgC C

1

2

3

4

5

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

Eu = K

Ν

ρn3d5

(4)

N – capacity, W

n – number of stirring blade’s revolution, vòng/s

d – stirrring blade diameter, m

ρ - liquid density, kg/m3

2 Determine Reynolds number

Re = K

ρnd2

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 the straight line, we have the equation:

lgEu = lgC + m.lgRe (6)K K

or Eu = C K ReKm

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

lgEuK

(with two different stirring speeds) Draw conclusions

Conclusion :………

………

Bx

t (mins)

LESSON 3

Calculate the settling velocity of particles in a liquid environment.

1 THEORETICAL BACKGROUND

In production and in the chemical industry, environmental technology, settling methods are often used to separate solids and suspended particles from liquid, gas environments, such as dust separation from air, sludge separation from wastewater, etc Therefore, the study of the sedimentation of these particles plays an important role In this experiment, students conduct sedimentation of glass particles in a cooking oil environment, measure sedimentation velocity, calculate Reynolds number, drag coefficient, and sedimentation velocity The difference between actual and theoretical sedimentation velocity is compared and discussed

In a liquid environment, according to Archimedes’ law, the gravity of a spherical particle KS

is calculated as follows

KS=π d3

6 (ρ1−ρ2)g ,( N )(1)

ρ1: density of spherical particle (kg/m )3

ρ2: density of liquid (kg/m )3

g: gravitational acceleration (m/s )2

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

S=ξ F ρ2u2

2,( N )(2)

F: cross-sectional area of the particle in the direction of motion

With spherical particle:

S=ξπd 2

4 ρ2u2

2, ( N)(3)

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

ξπd 2

4 ρ2u2

2=

π d3

6 (ρ1−ρ2)g (4 )

u=√4 gd(ρ1−ρ2)

3 ρ2ξ (5)

The drag coefficient ξ is a function of Reynolds, meaning it depends on the settling velocity, particle size, specific gravity of the liquid, and viscosity of the liquid The dependence ξ = f(Re) is determined experimentally, specifically as follows:

ℜ≤ 0,2 ξ=ℜ24

0,2<ℜ<500 ξ=18,5ℜ 500<ℜ<15.104

ξ=0,44 with:

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 honey environment (dynamic viscosity ν = 65mm2/s) The size of the glass particles is determined

by a caliper or according to the manufacturer’s specifications, then they are dropped into a glass tube containing honey with a height of h = 35cm The falling time of the glass particles

t (s) is measured

Steps to conduct the experiment

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 time using a stopwatch t (s)

Repeat the experiment 5 times

3 RESULT CALCULATION AND COMMENT

Calculate the specific gravity of glass particles and honey ρ 1 ρ 2

Determine the actual settling velocity: utt = h/t From this velocity and the measured size of

the glass particles, calculate the Reynolds number, from which the drag coefficient (6) is determined

Calculate the theoretical settling velocity according to formula (5)

Compare the actual and theoretical settling velocities, and make comments

Data table:

No Settling time t (s) Actual settling

velocity u (m/s) tt

Theoretical settling velocity u (m/s)

1

2

3

4

5