LABORATORY MODULE
ERT 216/4
HEAT AND MASS TRANSFER
SEMESTER 2
(2012/2013)
LECTURER:
MRS AZDUWIN KHASRI
MISS MISMISURAYA MEOR AHMAD
MR LEE BOON BENG
PM DR KASSIM
GRA:
MR MOHYUDDIN
MRS MAIZATUL
SCHOOL OF BIOPROCESS ENGINEERING
UNIVERSITI MALAYSIA PERLIS
CONTENTS
CONTENTS
PREFACE
LABORATORY SAFETY
FORMAT OF LAB REPORT
EXPERIMENT 1: Thermal Conductivity of Liquid and Gas
EXPERIMENT 2: Linear and Radial Heat Conduction
EXPERIMENT 3: Free and Force Convection Heat Exchanger
EXPERIMENT 4: Plate Heat Exchanger
EXPERIMENT 5: Liquid Diffusion Coefficient
LAB REPORT TEMPLATE
PREFACE
This module is to serve as a guidance and reference material for students who are
registering for Heat and mass transfer subject. It will be used by students for laboratory
practices and it will help them to understand the subject in an effective manner.
There are five (5) experiments that need to be performed by the students. All of the
experiments are being designed to help student in comprehending the subject of Heat and
Mass transfer.
It is hoped the module is user friendly and that students would enjoy the
laboratory work thereby increasing their awareness of the importance of the subject.
LABORATORY SAFETY MANUAL
Safety in the laboratory requires the same kind of continuing attention and effort
that is given to research and teaching. The use of new and/or different techniques,
chemicals, and equipment requires careful preparation. Reading, instruction, and
supervision may be required, possibly in consultation with other people who have special
knowledge or experience. Each individual who works in a laboratory has a responsibility
to learn the health and safety hazards associated with the materials to be used or
produced, and with the equipment to be employed. It is important for you to know what is
expected of you and what your responsibilities are with regard to safety to yourself, your
colleagues and our environment. In addition, there are safety practices and safety
equipment with which you must be thoroughly familiar if you are to work safely in the
laboratory. This manual should be used as a guide to the general types of hazards. Some
of the more basic safety practices that you are expected to follow is:
1. Do not perform unauthorized experiments.
2. Upon entering the laboratory note the location of the closest fire extinguisher, first aid
kit, eye wash station and chemical shower. Their location will be specified on the
laboratory door.
3. DO NOT TOUCH MOVING COMPONENTS while the machine is in operation
4. Use a hood for hazardous, volatile, and noxious chemicals.
5. A laboratory coat or apron should be worn while working in the laboratory. In general,
shorts, skirts, brief tops, and sandals are not safe. Further clarification of clothing
requirements should be directed to the person(s) in charge of the laboratory in which you
are working. Confine all loose clothing, ties, and long hair. Leave your jewellery at
home.
6. Do not wear contact lenses in the laboratory. Fumes, gases, and vapors can easily be
absorbed by the lens or trapped between the lens and eyes resulting in chemical burns or
abrasive injury.
7. Do not work alone in a laboratory. It is unsafe and not recommended.
FORMAT OF LABORATORY REPORT
The purpose of the laboratory report is to provide information on the obtained results,
analysis and interpretation and discussion of the results. The discussion and conclusions
are definitely significant in a report because these sections deliver the knowledge you
gained upon doing the experiments. For this particular laboratory, the following format is
suggested:
1. Cover page
2. Objective
3. Introduction
4. Theory
5. Procedure
6. Results/Calculation
7. Discussion
8. Conclusion
The template of the lab report is attached in the lab module. Detailed descriptions of
every item are given below:
1. Cover page
It should have the course name and number, the number and title of the experiment,
group number and names of the team members and as well as the date of the report
delivery.
2. Objective
It should state main objective of this experiment.
3. Introduction
Some of the background of this experiment needs to be stated. DO NOT REPEAT OR
COPY INTRODUCTION FROM LAB MODULE.
4. Theory
Complete analytical development of all important equations and concepts. DO NOT
REPEAT OR COPY INTRODUCTION FROM LAB MODULE.
5. Procedure
Schematic drawing of the experimental setup including all equipment. Outline step by
step procedure how experiment was performed.
6. Results/Calculation
This section deals with the management of data obtained after experiment. Data can be
presented as a series of figures, tables, etc with descriptive text and numbered but no
discussion. The best presentation of some data is graphical. Figures should be numbered.
Each figure must have a caption following the number. ALL GRAPHS, BESIDE
CAPTIONS, SHOULD HAVE CLEARLY LABELED AXES.
7. Discussion
This section must emphasize on discussing the outcome of the experiment. It can be
written in two ways:
a) Compare the expected outcome of the experiment with theory or
b) Make an appropriate graph on which the theory is represented and experimental data
by points.
A critical part of discussion is error analysis. In comparison of theory and experiment you
may not get a perfect agreement. It does not necessarily mean that your experiment was
failed. The results will be accepted, provided that you can account for discrepancy.
Precision and accuracy of the instrument or your ability to read the scales may be one
limitation. A part from this, data analysis requires you to open your mind and critical
approach to your work and that routine methods may not be sufficient.
8. Conclusion
The conclusions should contain several shorts statements closing the report. They should
inform the reader if the experiments agreed with the theory. If there were differences
between measured and expected results, explain possible reasons for these differences.
You may also say what could have been done differently, how experiments may be
improved, or make other comment on the laboratory report.
EXPERIMENT 1
THERMAL CONDUCTIVITY OF LIQUID AND GAS
1.0 OBJECTIVE
1.1 To calibrate the unit by establishing the incidental heat transfer.
1.2 To determine the thermal conductivity of air and acetone.
2.0 INTRODUCTION
The SOLTEQ® Thermal Conductivity of Liquid and Gas Unit (Model HE 156) has
been designed for students to determine the thermal conductivity of various liquid and
gas. Thermal conductivity data is of prime importance in designing heat exchangers.
Heat transfer coefficients in these equipments are usually computed using correlations,
which require thermal conductivity data. The thermal conductivity measurement unit for
liquid and gas has been designed for student to determine the thermal conductivity of
various liquid and gas by injecting the test fluid to the unit.
3.0 THEORY
Conductivity is the ability of the given substance to transfer energy, in this case the
thermal energy. Basically, the thermal conductivity can be measured by knowing the
temperature difference between two known points of which heat flow is known.
The basis of conduction heat transfer is Fourier’s Law. This law involves the idea that
the heat flux, q, is proportional to the temperature gradient, ∂T in any direction, ∂n.
Thermal conductivity, k, is the constant of proportionality; a property of materials that is
temperature dependent, and A is the cross-sectional area normal to the heat flow,
q  kA
T
n
(1)
There are several experimental techniques used to determine the thermal
conductivity of gas and liquid at steady state such as the hot wire method, the
coaxial-cylinder method, the horizontal parallel flat-plate method, and the concentric
sphere and sphere-cylinder method. The main principle of these methods is the
employment of a thin layer of a test fluid enclosed between two surfaces that maintained
at different temperatures. The apparatus is consists of two coaxial cylinders vertically
placed and leaving a very small annular gap that is charged with the test fluid. The inner
cylinder is heated with the electrical heater. As the thermal low across the gap is fairly
radial, the governing equation is the Fourier equation, which relates heat output, Q, the
inner cylinder temperature,T1, and outer cylinder temperature, T2
with the thermal
conductivity, k, of test fluid :
R 
ln 2 
 R1  Q
k
T1  T2 2L
(2)
where R1 and R2 are radius of the annulus, filled with the gas (R2> R1), and L is the
length of cylinder.
Figure 1: Heat conduction in coaxial cylinders method
From the explanation, to find the thermal conductivity coefficient we must use
Fourier’s Law as stated in equation (1). Solving for k we get,
k
qc dx
A dT
(3)
For radial heat conduction in a cylinder, dx become dr , and area A , is the cross
sectional area of a conducting path. At the steady state conditions across the small
radial gap, dr become Δr, dT become ΔT and we get,
k
qc r
A T
(4)
In order to find the heat by conduction (qc) we can use the conservation of energy
equation. When we applied it to this system we will get,
qc  q gen   qlost   Q  qlost 
(5)
By substituting equation (4) into equation (5), we get the following expression for
qlost
 T 
qlost  q gen  qc  Q   kA

 r 
(6)
We may assume qlost to be proportional to the temperature difference between
the plug and the jacket. This assumption will be tested with a linear regression
analysis, and estimate qlost from the calibration graph of incidental heat transfer
versus the plug and jacket temperature difference. This analysis used the known
thermal conductivity of air,kair . The thermal conductivity coefficient can then be
calculated for other fluids by the temperature difference across the fluid.
4.0
MATERIALS AND EQUIPMENTS
4.1
Thermal conductivity of liquid and gas unit
Figure 2: Thermal Conductivity for Liquid and Gas Unit
1. Thermocouple Sensors
5. Cooling water intlet
2. Sample Port (Top)
6. Heater
3. Cooling water Control Valve
7. Sample Port (Bottom)
4. Cooling water outlet
Figure 4
Figure 3: Construction of Thermal
Conductivity of Liquid and Gas Unit
5.0
PROCEDURES
5.1 Experiment 1: Calibration of the thermal conductivity study unit
5.2.1 Use air as the sample for the calibration.
5.2 Experiment 2: Determination of thermal conductivity of liquids
and gases
5.2.1 Use air as the sample of the experiment.
5.2.2 The power regulator to about 25 watt.
5.2.3 Record the power and temperature readings (T1 to T2)
5.2.4 Repeat the experiment by substituting the air with acetone with the heating
power of 100 watt.
6.0
RESULTS AND CALCULATIONS
6.1 Plot a calibration graph of incidental heat loss, qlost versus temperature
difference (Data of Experiment 1). Make sure to draw the straight line at
zero intercept.
6.2 Use slope of the graph to calculate qlost in Experiment 1 for both air and
acetone:
6.3 Calculate thermal conductivity of air and acetone and compare the value
with the theoretical.
7.0
QUESTIONS
7.1 Explain why the gap between the two cylinders is small?
8.0
CONCLUSION
8.1 Based on the experimental procedure done and the results taken draw
some conclusions to this experiment.
EXPERIMENT 2
LINEAR AND RADIAL HEAT CONDUCTION
1.0 OBJECTIVES
1.1 To investigate the thermal conductivity and thermal contact resistance of
brass in linear direction.
1.2 To investigate the thermal conductivity of brass in radial direction.
2.0 INTRODUCTION
The Linear and Radial Heat Conduction Apparatus is designed for students to study
the principles of conduction heat transfer. The student is able to determine the
relationship between the rate of heat transfer and temperature gradient, the crosssectional area and length of the conducting path and thermal conductivity of the material.
3.0 THEORY
3.1 Heat Distribution in a Plane Wall
The temperature distribution in the wall can be determined by solving the heat equation
with the proper boundary conditions. For steady state conditions with no distributed
source or sink within the wall, the form of the heat equation is:
d  dT 
 kt
0
dx  dx 
(1)
For one-dimensional, steady-state conduction in a plane wall with no heat generation
and constant thermal conductivity, the temperature varies linearly with x:
q x   kt A
dT kt A
TA  TB 

dx
L
(2)
Where;
k - thermal conductivity
A - cylindrical area of specimen
L - heat traveling distance
TA - temperature near heater
TB - temperature further heater
Thermal Resistance
Thermal resistance for conduction in a plane wall is given as:
Rt ,cond 
TA  TB
L

qx
kt A
(3)
Contact Resistance
Although neglected until now, it is important to recognize that, in composite systems, the
temperature drop across the interface between materials may be appreciable. This
temperature change is attributed to what is known as the thermal contact resistance.
Rt",c 
TA  TB
q"x
(4)
where
q”x = qx/A
(5)
3.2 LINEAR HEAT CONDUCTION
The rate of linear conduction heat transfer for the system is shown in equation (2).
3.3 RADIAL HEAT CONDUCTION
The rate of radial conduction heat transfer for this system ;
qr 
2Lkt TA  TB 
l n rB / rA 
Where;
L - specimen cylinder thickness
rA - radius further heater
rB - radius near heater
(6)
4.0 EQUIPMENT AND SPECIFICATIONS
4.1 Equipment
A
L
K
B
J
C
I
D
E
F
G
H
Figure 1 : Linear and Radial Heat Conduction Apparatus
A = Extra 30mm test length
B = Thermocouples
C = Linear heat conduction tester
D = Thermocouple ports
E = Temperature meter
F = Selector switch
G = Power meter
H = Power regulator
I = ON/OFF switch
J = Heater cable
K = ON/OFF switch for linear or
radial selection
L = Radial heat conduction
tester
4.2 Specifications
4.2.1 Linear Heat Conduction
You might need this information for calculation:
A = πD2/4, D = 0.0254 m
Measuring Point
Distance from Heater (mm)
1
15
2
25
3
35
4
45
5
55
6
65
4.2.2 Radial Heat Conduction
You might need this information for calculation:
L = 0.003 m
Measuring Point
Radius, (mm)
1
0
2
10
3
20
4
30
5
40
6
50
5.0 EXPERIMENTAL PROCEDURES
5.1 Experiment 1 :To investigate the thermal conductivity and thermal contact
resistance of brass in linear direction.
5.1.1 Set the power of the heater to 15 W.
5.1.2 Wait for 25 to 30 minutes until the temperature achieved at every measuring point
is stable.
5.1.3 Record the respective final temperature values at every point.
5.2 Experiment 2 : To investigate the thermal conductivity of brass in radial
Direction.
5.2.1 Set the power of the heater to 15 W.
5.2.2 Wait for 25 to 30 minutes until the temperature achieved at every measuring point
is stable.
5.2.3 Record the respective final temperature values at every point.
6.0 RESULTS AND CALCULATIONS
6.1
Determine the thermal conductivity of both experiments.
6.2
Determine the thermal contact resistance for experiment 1.
6.3
Show the temperature profile (graph) of both experiments.
7.0 CONCLUSIONS
7.1
Discuss /compare the thermal conductivity values obtained for linear and radial
heat conduction.
EXPERIMENT 3
FREE AND FORCE CONVECTION HEAT EXCHANGER
1.0 OBJECTIVES
2.1 To demonstrate the relationship between power input and surface
temperature in free and force convection.
2.2 To demonstrate the use of extended surface to improve heat transfer from
the surface.
2.0 INTRODUCTION
Heat transfer by simultaneous conduction and convection, whether free or force,
forms the basis of most industrial heat exchangers and related equipment. The
measurement and prediction of heat transfer coefficients for such circumstances is
achieved in the Free and Force Convection Heat Exchanger Apparatus by studying the
temperature profiles and heat flux in an air duct with associated flat and extended
transfer surfaces. The vertical duct is so constructed that the air temperature and
velocity can be readily measured, and a variety of “plug-in” modules of heated solid
surfaces of known dimensions can be presented to the air stream for detailed study. A
fan situated at the top of the duct provides the air stream for forced convection
experiments. Using the instrumentation provided, free and forced convective heat
transfer coefficients may be determined for: 1. A flat surface
2. An array of cylinders (pinned heat sink)
3. An array of fins (finned heat sink)
3.0 THEORY
3.1 Free Convection
A heated surface dissipates heat primarily through a process called convection.
Heat is also dissipated by conduction and radiation, however these effects are not
considered in this experiment. Air in contact with the hot surface is heated by the
surface and rises due to a reduction in density. The heated air is replaced by cooler
air which is in turn heated by the surface and rises. This process is called free
convection. The hotter the temperature of the surface, the greater the convective
currents and more heat (power) will be dissipated. If more power is supplied to a
surface, the temperature of the surface must rise to dissipate this power.
3.2 Forced Convection
In free convection the heat transfer rate from the surface is limited by the small
movements of air generated by this heat. More heat is transferred if the air velocity is
increased over the heated surface. This process of assisting the movement of air over
the heated surface is called forced convection. Therefore a heated surface experiencing
force convection will have a lower surface temperature than that of the same surface in
free convection, for the same power input.
3.3 Extended Surface
Heat transfer from an object can be improved by increasing the surface area in
contact with the air. In practice it may be difficult to increase the size of the body to suit.
In these circumstances the surface area in contact with the air may be increased by
adding fins or pins normal to the surface. These features are called extended surfaces.
A typical example is the use of fins on the cylinder and head of an air cooled petrol
engine. The effect of extended surfaces can be demonstrated by comparing finned and
pinned surfaces with a flat plate under the same conditions of power input and airflow.
4.0 MATERIALS AND EQUIPMENTS
4.1 DESCRIPTION OF APPARATUS
Figure 1: Free and Force Convection Heat Exchanger Apparatus.
1. Fan
3. RTD sensors
5. Panel
2. Air flow column
4. Portable Anemometer
6. Exchangeable Heat Transfer System
5.0 PROCEDURES
5.1
Experiment 1: To demonstrate the relationship between power
input and surface temperature in free convection.
5.1.1
Place the flat finned heat exchanger in to the duct.
5.1.2
Record the ambient air temperature (tA),
5.1.3
Set the heater power control to 20 Watts. Allow sufficient time to achieve
steady state conditions before noting the heated plate temperature (tH).
5.1.4
Repeat the procedure at 40, 60 and 80 Watts.
5.2 Experiment 2 : To demonstrate the relationship between power
input and surface temperature in force convection (finned heat
exchanger)
5.2.1
Set the heater power control to 50 Watts. Allow sufficient time to achieve
steady state conditions before noting the heated plate temperature (tH).
5.2.2
Set the fan speed control to give a reading of 0.5m/s on the thermal
anemometer. Record the heated plate temperature (tH).
5.2.3
Repeat this procedure at 1.0m/s and 1.5m/s.
5.3 Experiment 3: To demonstrate the use of extended surface to
improve heat transfer from the surface.
5.3.1
Place the tube bundle plate heat exchanger into the duct.
5.3.2
Set the heater power control to 75 Watts. Allow the temperature to rise to
80°C, and then adjust the heater power control to 15 Watts until a steady
reading is obtained. Record heated plate temperature (tH).
5.3.3
Set the fan speed control to give 1m/s.
5.3.4
Repeat this procedure at 2.0 and 2.5m/s.
6.0 RESULTS AND CALCULATION
6.1 For experiment 1, based on the data recorded, plot the graph of power
against temperature (tH – tA).
6.2 For experiment 2 and 3, based on data recorded, plot the graph of air velocity
against temperature (tH – tA).
7.0 QUESTIONS
7.1 Why is it necessary to set the fan speed to maximum before switch OFF the
apparatus?
7.2 How does the extended surface for the plate heat exchanger will improve the
heat transfer process?
7.3 Differentiate between free and forced convection.
7.4 Discuss the relationship between air velocity and surface temperature.
7.5 Discuss the relationship between powers dissipated and surface
temperature.
8.0 CONCLUSION
8.1 Based on the experimental procedure done and the results taken draw some
conclusions to this experiment.
EXPERIMENT 4
PLATE HEAT EXCHANGER
1.0 OBJECTIVE
1.1
To determine of the effect of the parallel flow and counter flow arrangement to the
system efficiency.
1.2
To determine the effect of flow rate variation on the plate heat
exchanger.
2.0 INTRODUCTION
The SOLTEQ® Heat Transfer Service Unit (Plate Heat Exchanger) (Model: HE104-P
& HE104-P-A) has been designed specifically to demonstrate the working principles of
industrial heat exchangers in the most convenient way possible in the laboratory
classroom. The equipment consists of a plate heat exchanger mounted on a support
frame. The external surface of the piping is insulated. Two temperature measuring
devices are installed in both the inside and outside tubes to measure the fluid
temperatures accurately. The flow rates are measured using independent flowmeters
installed in each line.
3.0 THEORY
Plate heat exchangers are used extensively in the food and beverage industries due to
the fact that they are easily taken apart for cleaning and inspection.
The general equation for heat transfer across a surface is:
Q = U A ∆Tm
(1)
where,
Q
U
A
∆Tm
=
=
=
=
heat transfer per unit time, W
the overall heat transfer coefficient, W/m2°C
heat transfer area, m2.
the mean temperature difference, the temperature driving force,
°C
The mean temperature difference is normally expressed in terms of log-mean
temperature difference,
For counter-current flow:
Tlm 
T1  t 2   T2  t1 
T  t 
ln 1 2
T2  t1 
(2)
For co-current flow:
Tlm 
∆Tlm
T1
T2
t1
t2
=
=
=
=
=
T1  t1   T2  t 2 
T  t 
ln 1 1
T2  t 2 
log mean temperature difference
inlet hot water temperature
outlet hot water temperature
inlet cold water temperature
outlet cold water temperature
From the energy balance principle:
Power Emitted = Power Absorb + Power Loss
Where,
Power Emitted, WE  QH H CpH (TH ,in  TH ,out )
Power Absorbed, WA  QC C CpC (TC ,out  Tc,in )
Efficiency for the system can be calculated by applying the following equation:

Power Absorbed
100%
Power Emitted
Overall heat transfer coefficient, U 
Power Absorbed
t m  Area
Where,
Area = surface of contact area
= (width x length) x (number of plates – 1)
(3)
An example of schematic diagram for the flat plate heat exchanger, which is described in
detail is shown as below:
Figure 1: Counter Current Flow
Figure 2: Parallel
4.0 EQUIPMENT AND SPECIFICATIONS
4.1 Equipment
8
9
8
7
6
1
2
3
5
4
7
8
Figure 3: Rear view of the Heat Transfer Service Unit
1.
2.
3.
4.
5.
6.
7.
8.
Pump
Circulation Valve, V2
Pump Inlet Valve, V1
Water Tank
Heater
Level Switch
Drain Valve
Water Tank Cover
21
15
23
14
16
9
10
20
18
25
11
19
24
22
17
Figure 4: Front view of the Heat Transfer Service Unit
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Temperature Controller
Temperature Selector
Main Switch
Water Outlet
Water Inlet
Temperature Indicator
Flow Meter ,FI1
Flow Meter, FI2
Flow Meter Control Valve, V7
Flow Meter Control Valve, V8
Control Valve
Plate Heat Exchanger
Temperature Sensor, T1
Temperature Sensor, T2
Temperature Sensor, T3
Temperature Sensor, T4
Temperature Sensor, T5
12
5
13
4.2
Specifications
Area
= Surface of contact area
= (width x length) x ( number of plates – 1)
= (0.1245 x 0.3099) x (4-1)
= 0.116 m2
5.0 EXPERIMENTAL PROCEDURES
5.1
General Start-up Procedures
5.1.1 Heat up the water in the storage tank.
5.1.2 Open pump inlet valve, V1
5.1.3 V2 should be open partially for the water circulation to the storage tank.
( Do not switch on the pump without water SUPPLY as it will damage
the pump)
5.2
Experiment 1: Parallel Flow Arrangement
5.2.1 Set hot water inlet temperature on the temperature controller at 60 C.
5.2.2 Position of the valves for parallel flow.
5.2.3 The cold water flow rate is set constant at 3 LPM.
5.2.4 Vary the hot water flow rate QH at 3, 6,9,11 LPM.
5.2.5 Record the hot and cold water temperatures at inlet and outlet once
conditions have stabilized.
5.3
Experiment 2: Counter Current Flow Arrangement
5.3.1 Set hot water inlet temperature on the temperature controller at 60 C.
5.3.2 Position of the valves for counter current flow.
5.3.3 The cold water flow rate is set constant at 3 LPM.
5.3.4 Vary the hot water flow rate QH at 3, 6,9,11 LPM.
5.3.5 Record the hot and cold water temperatures at inlet and outlet once
conditions have stabilized.
6.0 RESULT AND CALCULATION
1. Determine the system efficiency of parallel and counter current flow arrangement.
2. Show your calculations.
7.0 CONCLUSION
1. Compare the system efficiency of parallel and counter current flow.
2. Discuss the effect of flow rate variation on the plate heat exchanger operating
performance.
8.0 APPENDIX
Table 1: Properties of water (saturated liquid)
°C
21.11
26.67
30.00
31.00
32.00
32.22
34.00
34.30
34.65
35.15
35.65
35.90
36.20
36.40
37.25
47.20
48.89
50.00
51.50
54.44
54.65
55.00
55.05
55.50
56.50
57.00
57.25
59.70
60.00
65.00
65.55
Cp
kJ/kg. K
4.179
4.179
4.176
4.175
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.174
4.175
4.176
4.179
4.179
4.179
4.179
4.179
4.180
4.180
4.180
4.181
4.179
4.183
4.183
ρ
kg/m3
997.40
995.80
995.26
995.10
994.94
994.90
994.23
994.14
993.99
993.83
993.61
993.53
993.38
993.35
993.02
989.42
988.80
988.18
987.36
985.70
985.61
985.46
985.42
985.22
984.71
984.48
984.41
983.16
983.30
980.60
980.30
EXPERIMENT 5
LIQUID DIFFUSION COEFFICIENT
1.0 OBJECTIVE
1.1 To determine the liquid diffusion coefficient of NaCl solution in distilled / de-ionized
water.
2.0 INTRODUCTION
®
The SOLTEQ Liquid Diffusion Coefficient Apparatus (Model: BP 09) has been
designed for students experiment on the technique of determining diffusivity of sodium
chloride solution in distilled water. A known concentration of sodium chloride solution is
placed in a diffusion cell immersed in distilled water. A magnetic stirrer and a
conductivity meter are provided to monitor the progress of diffusion over time. A plot of
conductivity against time will allow for the determination of the liquid diffusivity.
3.0 THEORY
When a concentration gradient exists within a fluid consisting of two or more
components, there is a tendency for each constituent to flow in such a direction as to
reduce the concentration gradient. This is called mass transfer. Mass transfer takes
place in either a gas phase or a liquid phase or in both simultaneously.
The rate of diffusion is given by:
The –ve sign indicates that flow is from high to low concentration.
The appropriate units shall be:
The concentration at the lower ends chosen and taken to be constant and the
concentration at the top end is effectively zero during the experiment.
Therefore,
Where,
The slope obtained from the plot of conductivity as a function of time can be used to
calculate the diffusivity.
4.0 EQUIPMENT AND SPECIFICATIONS
4.1 Equipment
Figure 1: Diagram for liquid diffusion coefficient apparatus
4.2 Description and Assembly
Before operating the unit and running the experiments, students must familiarize
themselves with every components of the unit. Please refer to Figure 1 to understand
the process.
5.0 PROCEDURES
PART A : LIQUID DIFFUSION COEFFICIENT
5.1
Experimental Procedure
5.1.1
Prepare 1M, 2M, and 4M NaCl solutions.
5.1.2
Fill the diffusion cell with 1M NaCl solution.
5.1.3
Immersed the cell into the distilled water.
5.1.4
Take readings every 5 minute intervals until 30 minutes.
5.1.5
Repeat steps 5.2.1 to 5.2.6 for 2M and 4M NaCl solutions.
6.0 RESULTS AND CALCULATIONS
6.1
Plot Conductivity against Time.
6.2
Determine the liquid diffusivity of sodium chloride solution from the obtained
slope, s.
You need the information below to calculate the diffusivity:
Volume of water,V = volume of water in diffusion vessel, L
Length of capillaries, x = 0.5 cm
Diameter of capillaries, d = 0.1 cm
Number of capillaries, N = 97
6.3
Show your calculations.
7.0 CONCLUSIONS
7.1 Based on the experimental procedure done and the results taken draw some
conclusions to this experiment.
SCHOOL OF BIOPROCESS ENGINEERING
UNIVERSITY MALAYSIA PERLIS
ERT216: HEAT AND MASS TRANSFER
TITLE OF EXPERIMENT:
NAME:
___________________________________
MATRIX NO.:___________________________________
GROUP MEMBERS: ___________________________
____________________________
____________________________
____________________________
DATE OF EXPERIMENT: _______________________
DATE OF SUBMISSION: ________________________
1.0 OBJECTIVES
2.0 INTRODUCTION (Not Repetition from Lab Module.)
3.0 THEORY (Not Repetition from Lab Module.)
4.0 PROCEDURE (Simplify In Schematic Drawing)
5.0 RESULTS/CALCULATION
6.0 DISCUSSION
7.0 QUESTION
8.0 CONCLUSION