LABORATORY

MODULE

PTT 251/3

THERMODYNAMICS FOR CHEMICAL ENGINEERING

SEMESTER 1 (2017/2018)

Dr Rosniza Hamzah Miss Nor Munirah Rohaizad

Faculty of Engineering Technology University Malaysia Perlis

PTT 251 LABORATORY MODULE

Dr Rosniza Hamzah Miss Nor Munirah Rohaizad

Faculty of Engineering Technology

University Malaysia Perlis

2

TABLE OF CONTENTS

CONTENTS PAGE

CLEANLINESS AND SAFETY 4

EXPERIMENT 1: INTRODUCTION TO THE LABORATORY SAFETY 8

DEMONSTRATION OF THE BOYLE’S LAW

EXPERIMENT 2: 12

OF GAS SYSTEM

DEMONSTRATION OF THE PERFECT GAS LAW EXPERIMENT 3: 15

OF GAS SYSTEM

DEMONSTRATION OF SATURATED VAPOUR EXPERIMENT 4: 25

PRESSURE CURVE OF WATER

CONSTRUCTION OF VAPOUR-LIQUID EXPERIMENT 5: 29

EQUILIBRIUM OF BINARY COMPONENT

EXPERIMENT 6: DETERMINATION OF STEAM QUALITY 37 EXPERIMENT 7 MEASUREMENT OF TEMPERATURE USING DIFFERENT TYPE OF TEMPERATURE MEASURING 41

DEVICES

APPENDICES 48

3

SAFETY AND CLEANLINESS

4

5

6

CLEANLINESS

The Thermodynamics Laboratory contains equipment that uses water or air as the fluid.

In some cases, performing an experiment will inevitably allow water to get on the

equipment and/or on the floor.

There are “housekeeping” rules that the user of the laboratory should be aware and abide

by. If no one cleaned up their working area after performing an experiment, the lab would

not be a comfortable or safe place to work in. Consequently, students are required to

clean up their area at the conclusion of the performance of an experiment. Cleanup will

include

removal of spilled water (or any liquid)

wiping the table top on which the equipment is mounted

The lab should always be as clean as or cleaner than it was when you entered.

Cleaning the lab is your responsibility as a user of the equipment.

SAFETY FIRST

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EXPERIMENT 1

INTRODUCTION TO THERMODYNAMICS LABORATORY

SAFETY

1.0 OBJECTIVES

1.1 To understanding of basic laboratory safety.

1.2 To identify and assess laboratory hazards and introduce safety precautions.

2.0 INTRODUCTION

Every place and work processes, has many and all kinds of hazards. Each of these

hazards does not necessarily have the same risk level. This risk level difference can exist

either between types of hazards and the hazards of the same but in different places. The

fact of the existence of various hazards, and different risk levels and the possibility of

these two changed with changes in working conditions require it be managed and not

solely controlled only.

In principle, the management of occupational safety and health require that hazards

are identified in advance. Further, the hazard risk is assessed, controlled and finally

monitoring and checking the status of the overall management is done to ensure hazard-

hazard and risk is always at levels as low as practicable. At the same time, the dynamics

of risk management is expected to also identify and control hazards and new risks, in line

with the change of process, how to work and time.

3.0 THEORY

3.1 Safety

Safety is defined as a freedom from whatever exposes one to danger or from

liability to cause danger or harm; safeness; hence, the quality of making safe or secure,

or of giving confidence, justifying trust, insuring against harm or loss.

Safety can also be defined to be the control of recognized hazards to achieve

an acceptable level of risk. This can take the form of being protected from the event or

from exposure to something that causes health or economical losses. It can include

protection of people or of possessions.

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3.2 Hazard

Hazard is anything on their own or interacts with one another that can cause

harm. This injury is different levels of severity, from minor injuries resulting in up to death.

Occupational Health and Safety Assessment of Standards Malaysia Series 18001 and

Occupational Safety and Health MS1722 Management System defines the hazard as a

source or, in circumstances which have resulted in potential harm, injury and disease to

humans, property damage, environmental damage, or its combinations.

3.3 Category of Hazard

3.3.1 Physical Hazard

Physical hazards associated with energy hazard. This includes falling

objects, slips, collisions, pressure, explosion, noise, vibration and radiation.

Figure 1.1: Example of physical hazards

3.3.2 Mechanical Hazard

Mechanical hazards are hazards associated with mechanical power on

the machine. Some examples of these hazards include moving parts, cut, pinch,

rotate fast, stomping and crushing.

9

Figure 1.2: Example of mechanical hazards of machinery.

3.3.3 Chemical Hazard

Chemical hazards are hazards that affect their chemical and physical

properties and chemical reactions. Chemical hazards expressed in term of

flammable, explosive, radioactivity, corrosiveness and toxicity.

Figure 1.3: Example of chemical hazards.

3.3.4 Biological Hazard

Biological hazard or biohazard is due to the hazards of life for example,

pathogenic organisms such as bacteria, viruses, fungi and yeast infections.

Biohazard is not limited to the area hospitals and medical laboratories only.

Among biohazard that highly monitored in the workplace are HIV and hepatitis

viruses.

10

3.4 Risk

Risk is defined as a combination of likelihood and consequences of a hazard

event occur. MS1722 define risk as the probability of a combination of hazard events with

a certain period, or in certain circumstances and severity of injury or damage to people,

property, environment or any of its combinations

. In short, risk is a combination of factors, the probability of an occurrence and

severity of the accident.

Risk = Probability (Likelihood) x Severity

4.0 PROCEDURES

4.1 Safety Briefing

4.1.1 Attend for a safety briefing which will be conducted within 1 hour.

4.1.2 Listen carefully to the briefing given. Briefing note also included.

4.1.3 List the important matters arising from the briefing.

4.2 Laboratory Assessment

4.2.1 In the group that has been determined, go to the Thermodynamics

Laboratory.

4.2.2 Perform an assessment of the lab and the equipment available in the lab.

4.2.3 Identify the hazards as possible and determine risk.

4.2.4 Record the hazards and risks identified.

4.2.5 Suggest precautions to ensure safety is maintained.

5.0 RESULTS

5.1 Record your result into a table in Appendix 1.

6.0 DISCUSSION

6.1 Suggest a most critical hazard identified and discuss preventive actions that shall

be implemented to eliminate or reduce the hazard risk.

7.0 CONCLUSION

Based on the experimental procedure done and the results taken, draw some

conclusions to this experiment.

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EXPERIMENT 2

DEMONSTRATION OF THE BOYLE’S LAW OF GAS

SYSTEM 1.0 OBJECTIVE

1.1 To understand the concept of Boyle’s gas law.

1.2 To analyze the relationship between pressure and volume of an ideal gas

2.0 INTRODUCTION

Boyle’s law describes the inversely proportional relationship between pressure

and volume of a gas, if the temperature is kept constant within a closed system.

The mathematical equation for Boyle’s law is:

PV = constant

As long as the temperature remains constant the same amount of energy given

to the system persists throughout its operation. By forcing the volume V of the

fixed quantity of gas to increase, keeping the gas at the initially measured

temperature, the pressure P must decrease proportionally. On the contrary,

reducing the volume of the gas will increase the pressure.

The Boyle’s law is used to predict the result of introducing a change, in volume

and pressure, to the initial state of a fixed quantity of gas. The volumes and

pressure of gas before and after expansion is related by:

3.0 MATERIAL AND EQUIPMENTS

3.1 Boyle’s gas law experiment apparatus

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4.0 PROCEDURES

4.1 GENERAL START-UP PROCEDURES

1. Make sure all on/off button is in off position and all valves are close before starting

experiment.

2. Add 4L of water into the pressure cylinder.

3. To ensure an ideal atmospheric pressure, both cylinders will be vacuumed using the

vacuum pump.

4. Use fast coupling tubing to connect pressure cylinder to vacuum pump.

5. Set vacuum to 0.1 Bar and regulate globe valve, V3 to ensure water level drop to zero

scale on measuring cylinder.

6. Switch off vacuum pump immediately when water level is on 0 scales. Close the

control globe valve, V3.

7. Open V1 and V2 until pressure in the pressure and measuring cylinders until reach

atmospheric pressure

8. The equipment is ready for experiment.

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4.2 EXPERIMENTAL PROCEDURES

PRECAUTIONS:

When carrying out the experiment, pump pressure should not exceed 2 bar as

excessive pressure may result in glass cylinder breaking.

1. Disconnect vacuum tubing from pump.

2. Make sure all valves are close and connect compressed air tubing to the

pressure cylinder. Make sure pressure inside the measuring cylinder is 1 bar.

3. Start compressive pump, set the pump to 2 bar.

4. Slowly open the globe valve, V3 and observe the rise of level in measuring

cylinder.

5. Regulate globe valve, V3 to take readings at every intervals of 0.1bar in

measuring cylinder.

6. Close globe valve tightly and record level of water in the measuring cylinder.

7. Record the reading of temperature and pressure inside the measuring cylinder.

8. Repeat step 1 to 7 until the pressure in the measuring cylinder reach 3 bar

(Maximum pressure level).

4.3 GENERAL SHUT-DOWN PROCEDURES

1. Switch off the pump and remove both pipes from the

chambers.

2. Switch off the main switch and power supply.

5.0 RESULTS AND DISCUSSION

5.1 Record the data by using the table in Appendix 2. 5.2 Tabulate results and plot 1/V (Volume) versus P (Pressure). 5.3 Calculate the PV value and prove the Boyles’ Law. 6.0 CONCLUSION 6.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment.

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EXPERIMENT 3

DEMONSTRATION OF THE PERFECT GAS LAW OF GAS

SYSTEM

1.0 OBJECTIVE

1.1 To understand the concept of perfect gas law.

1.2 To measure the ratio of volume and compares it to the theoretical value

1.3 To examine the relationship between pressure and temperature of an ideal gas

1.4 To demonstrate the isentropic expansion process

1.5 To calculate the ratio of heat capacity

2.0 INTRODUCTION

The “Perfect Gas Law” expresses the relationship between pressure, volume, and

temperature where students can apply and understand more on the basic thermodynamic

process. It has been formulated in the 18th and 19th centuries. These correlations were

developed under conditions of temperature and pressure so that the average distance

between gas molecules was great enough to counteract the effect of intramolecular

forces, and the volume of the molecules themselves could be neglected. Under this

condition, a gas became known as an ideal gas. This term now in common use refers to

a gas which obeys certain simple physical laws, such as Boyle, Charles and Dalton.

Pressure is defined as force per unit area. It is usually more convenient to use

pressure rather than force to describe the influences upon fluid behavior. The standard

unit for pressure is the Pascal, which is a Newton per square meter. For an object sitting

on a surface, the force pressing on the surface is the weight of the object, but in different

orientations it might have a different area in contact with the surface and therefore exert

a different pressure.

Temperature and pressure are directly proportional to each other. This means that

as the temperature decreases, the pressure also decreases, and as the temperature

increases, the pressure increases. By increasing their temperature- the force of the

molecules hitting their container increases and this increases the pressure. This

relationship is called Gay-Lussac’s Law and makes up part of the ideal gas law.

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3.0 THEORY

An ideal gas is a gas that conforms, in physical behavior, to a particular, idealized

relation between pressures, volume, and temperature called the ideal gas law. This law

is a generalization containing both Boyle’s Law and Charles’s Law as a special cases

and states that for a specified quantity of gas, the product of the volume,V, and pressure,

P is proportional to the absolute temperature, T; i.e., in equation form, PV = kT, in which

k is a constant. Such a relation for a substance is called its equation of state and is

sufficient to describe its gross behavior.

3.1 The Perfect Gas

Perfect gas is also known as ideal gas. An ideal gas is defined as one in which all

collisions between atoms or molecules are perfectly elastic and in which there are

no intermolecular attractive forces. The ideal gas equation of state is given as:

PV = nRT (1)

where R is the universal gas constant, P is the absolute pressure, T is the absolute

temperature, V is volume, and n is number of mole of gas. Any gas that obeys

this law is called an ideal gas. The properties of ideal gas at two different states

are related to each other by:

P1V1 = P2V2

T1 T2 (2)

It has been experimentally observed that ideal gas relation closely approximate

the behaviour of real gases at low density. At low pressure and high temperature,

the density of gas decreases, and the gas behaves as an ideal gas under these

conditions.

Besides of ideal gas equation of state, perfect gas also obeys the following law:

a. Charles’s Law

b. Gay-Lussac’s Law

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3.1.1 Charles’s Law

Charles’s law is a gas law which states that:

At constant pressure, the volume of a given mass of an ideal gas increases or

decreases by the same factor as its temperature increases or decreases.

The formula for this law is:

V

T (3)

At constant pressure, the same substance under two different sets of condition is

related by:

V1 = V2

T1 T2 (4)

3.1.2 Gay-Lussac’s Law

Gay-Lussac’s law states that the pressure of a fixed quantity of gas at constant

volume is directly proportional to its temperature, therefore:

P

T (5)

Temperature is a measure of the average kinetic energy of a substance; as the

kinetic energy of a gas increases, its particles collide with the container walls more

rapidly, and therefore exert increased pressure. The same substance under two

different sets of condition is related by:

P1 = P2

T1 T2 (6)

3.2 Specific Heats

The specific heat is defined as the energy required to raise the temperature of a

unit mass of a substance by one degree. In thermodynamics, two kinds of specific

heats are commonly used, which is specific heat at constant volume (Cv) and

specific heat at constant pressure (Cp). The definition for Cv and Cp are as follow:

(7)

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= constant

= constant

(8)

Equations (9) and (10) show that Cv is a measure of the variation of internal

energy (U) of a substance with temperature, and Cp is a measure of the variation

of enthalpy (H) of a substance with temperature.

For an ideal gas:

Cp = Cv + R (9)

The ratio of specific heat is the ratio of the specific heat at constant pressure (CP)

to specific heat at constant volume (CV). It is sometimes also known as the

isentropic expansion factor. The specific heat ratio, k, is defined as:

Cp

Cv (10)

The specific heat ratio for an ideal gas can be related to the degrees of freedom

of a molecule. Values of specific heat ratio for some gases are given below:

Gas specific heat ratio Carbon Dioxide 1.3

Helium 1.66

Hydrogen 1.41

Methane 1.31

Nitrogen 1.4

Oxygen 1.4

Standard air 1.4

3.3 Isentropic Process

An isentropic process takes place from initiation to completion without an increase

or decrease in the entropy of the system, i.e., the entropy of the system remains

constant throughout. A reversible adiabatic process is an isentropic process.

During the adiabatic expansion process:

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k =

(11)

The internal energy can be expressed as:

(12)

Substituting equation (12) into equation (11):

(13)

From ideal gas law

Integrating between two different set of conditions

(14) 3.4 Determination of the Specific Heat Ratio

The specific heat ratio can be determined for air near standard pressure and

temperature by a two-step process:

1) A reversible adiabatic expansion (isentropic process) from initial temperature (Ti)

and pressure (Pi), to an intermediate temperature (Tm) and pressure (Pm).

2) A return of the temperature to its original value(Ti) at constant volume (isochoric

process), attaining a final pressure (Pf)

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For step 1, a reversible adiabatic process:

(15)

For step 2, an isochoric process

(16)

Substitute (16) into (15)

(17)

3.5 Determination of Ratio of Volumes using an isothermal process

To determine the ratio of volumes using an isothermal process, a pressurized

vessel is allowed to leak slowly into another vessel of different size. At the end of

the process, the two vessels are equilibrated and the final pressure is the same

in both vessels. The final equilibrium pressure, Pf, can be determined using the

ideal gas equation:

(18)

where subscripts 1 and 2 represent vessels one and two respectively. Using

ideal gas law, the number of moles of each vessel can be calculated:

20

(19)

(20)

Substituting equations (19) and (20) into equation (18) yields:

(21)

The ratio of the two volumes can then be expressed as:

(22)

4.0 MATERIAL AND EQUIPMENTS

4.0.1 Perfect gas experiment apparatus 4.1 DESCRIPTION OF APPARATUS

1 2

4

3

5 6

7

8

9

Figure 3.1: Unit Construction for Perfect Gas Apparatus

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1 Pressure Relief Valve 4 Temperature Indicator 7 Main Switch

2 Pressure Sensor 5 Pressure Indicator 8 Pump Switch

3 Pressure Chamber 6 Vacuum Chamber 9 Vacuum / Pressure Pump

Given: V3 = 0.025m3 V6 = 0.01237m3

5.0 PROCEDURES

5.1 GENERAL START-UP PROCEDURES

1. Connect the equipment to single phase power supply and then switch on

the unit.

2. Fully open all valves and check the pressure reading on the panel. This is

to make sure that the chambers are under atmospheric pressure.

3. Then, close all the valves.

4. Connect the pipe from compressive port of the pump to pressurized

chamber or connect the pipe from vacuum port of the pump to vacuum

chamber.

5. Now, the unit is ready for use.

5.2 EXPERIMENTAL PROCEDURES

PRECAUTIONS:

When carrying out the experiment, pump pressure should not exceed 2 bar as

excessive pressure may result in glass cylinder breaking.

Experiment 1: Gay-Lussac Law Experiment

1. Perform the general start up procedures in section 5.1. Make sure all valves

are fully closed.

2. Connect the hose from compressive pump to pressurized chamber.

3. Switch on the compressive pump and records the temperature for every

increment of 0.1 bar in the chamber. Stop the pump when the pressure PT

1 reaches about 1.6 bar.

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4. Then, slightly open valve V 01 and allow the pressurized air to flow out.

Records the temperature reading for every decrement of 0.1 bar.

5. Stop the experiment when the pressure reaches atmospheric pressure.

6. The experiment is repeated for three times to get the average value.

Experiment 2: Isentropic Expansion Process

1 Perform the general start up procedures in section 5.1. Make sure all

valves are fully closed.

2 Connect the hose from compressive pump to pressurized chamber.

3 Switch on the compressive pump and allow the pressure inside chamber

to increase until about 1.6 bar. Then, switch off the pump and remove the

hose from the chamber.

4 Monitor the pressure reading inside the chamber until it stabilizes. Record

the pressure reading PT 1 and temperature TT 1.

5 Then, slightly open valve V 01 and allow the air flow out slowly until it

reaches atmospheric pressure.

6 Record the pressure reading and temperature reading after the expansion

process.

Experiment 3: Determination of Heat Capacity Ratio

1 Perform the general start up procedures in section 5.1. Make sure all

valves are fully closed.

2 Connect the hose from compressive pump to pressurized chamber.

3 Switch on the compressive pump and allow the pressure inside chamber

to increase until about 1.6 bar. Then, switch off the pump and remove the

hose from the chamber.

4 Monitor the pressure reading inside the chamber until it stabilizes. Record

the pressure reading PT 1 and temperature TT 1.

5 Fully open valve V 01 and bring it back to the closed position after few

seconds. Monitor and records the pressure reading PT 1 and TT1 until it

becomes stable.

5.3 GENERAL SHUT-DOWN PROCEDURES

1. Switch off the pump and remove both pipes from the chambers.

2. Fully open the valves to release the air inside the chambers.

3. Switch off the main switch and power supply.

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6.0 RESULTS AND DISCUSSION

Experiment 1 6.1 Record the data by using the table in Appendix 3.1. 6.2 Plot graph of pressure versus temperature. 6.3 Discuss the graph and prove the Gay-Lussac Law.

Experiment 2 6.1 Record the data by using the table in Appendix 3.2. 6.2 Calculate the ratio of temperature and pressure and prove it is the isentropic process.

Experiment 3 6.1 Record the data by using the table in Appendix 3.3. 6.2 Determine the ratio of heat capacity and compare with the theoretical value.

7.0 CONCLUSION Based on the experimental procedure done and the results taken draw some conclusions to this experiment.

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EXPERIMENT 4

DEMONSTRATION OF SATURATED VAPOUR PRESSURE

CURVE OF WATER

1.0 OBJECTIVES

1.1 To demonstrate and construct saturated vapour pressure curve of water.

2.0 INTRODUCTION

Marcet Boiler is a bench top unit designed for the demonstration of the basic principal

in thermodynamics studies which is the boiling phenomenon. Students will be able to

study the relationship between the pressure and temperature of saturated steam in

equilibrium with water. The saturation pressure curve can be determined at the pressure

within 10 bar (150 lb/in2).

3.0 THEORY

Marcet Boiler has been developed for investigating the relationship between the

pressure and temperature of saturated steam, in equilibrium with water, at all pressures

between atmospheric and 10 bar (abs) (147 lb/in²). Thermodynamics is a branch of

physics, which deals with the energy, and work of a system. Thermodynamics deals only

with the large-scale response of a system that we can observe and measure in

experiments. Small-scale gas interactions are described by the kinetic theory of gasses,

which is a compliment to thermodynamics.

An ideal gas can be characterized by three state variables: absolute pressure (P),

volume (V), and absolute temperature (T). The relationship between them may be

deduced from kinetic theory and is called the Ideal Gas Law. The Ideal Gas Law was

originally determined empirically and is simply.

P V = n R T Where,

P = Absolute pressure

V = Volume

n = Amount of substance (moles)

R = Ideal gas constant

T = Absolute temperature (K)

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If a gas behaves exactly as the ideal gas, the Ideal Gas Laws would predict it to

behave in terms of volume, pressure, moles, and temperature, then the gas is said to be

an ideal gas. On the other hand, the gas deviates from ideal gas behavior, then the gas

is said to be acting like a "real gas".

When energy increases within water, the increasing of activities among the

molecules enables the increase in the number of molecule escape from the surface until

an equilibrium state is reached. The state of equilibrium depends on the pressure

between the water surface and steam. At lower pressure, the molecules become easier

leaving the water surface while less energy required in achieving the state of equilibrium

(boiling point). The temperature where equilibrium occurs at a given pressure level is

called saturated temperature.

4.0 MATERIALS AND EQUIPMENTS

Unit construction for Marcet Boiler

4.1 DESCRIPTION OF APPARATUS

The unit consists of a stainless steel pressure vessel fitted with high pressure

immersion electrical heater. The unit also comes together with a safety relief valve,

temperature and pressure measuring devices. Water feed port is installed to allow water

charging. The unit comes with comes with temperature and pressure transducers so that

students will be able to read the respective values on the digital indicators easily. The

water heater is protected from burnout by setting the maximum operating temperature

with a temperature controller.

Figure 4.1: Unit Construction for Marcet Boiler

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1. Pressure Transducer 6. Bourdon Tube Pressure Gauge 2. Temperature Controller/Indicator 7. Temperature Sensor 3. Pressure Indicator 8. Pressure Relief Valve 4. Control Panel 9. Water Inlet Port & Valve 5. Bench 10. Heater

5.0 PROCEDURES

5.1 Perform a quick inspection to ensure that the unit is in proper operating

condition.

5.2 Connect the unit to the nearest power supply.

5.3 Open the valves at the feed port and the level sight tube.

5.4 If the boiler is initially filled with water, open the valves at the level side

tube to check the water level. Make sure that the water level is at about

the half of the boiler’s height. Pour in additional distilled water if

necessary. Then, close the valves.

5.5 Turn on the power supply switch.

5.6 The temperature controller is already set to 185.0 °C which is slightly

above the expected boiling point of the water at 8.0 bar (abs).

5.7 Open the valve at feed port and turn on the heater.

Important: Always make sure that the valves at the level sight tube are

closed before turning on the heater as the sight tube is not designed to

withstand high pressure and temperature.

5.8 Observe the steam temperature rise as the water boils.

5.9 Allow steam to come out from the valve for about 30 seconds, and then

close the valve. This step is important to remove air from the boiler as the

accuracy of the experimental results will be significantly affected when air is

present.

Warning : Do not touch the hot components of the unit. Be extremely

careful when handling liquid at high temperature.

5.10 Record the absolute pressure and temperature when the water start boiling

at 1.0 bar and continue the readings until the pressure reaches 8.0 bar

(abs).

Warning: Never open the valve when the boiler is heated as pressurized

steam can cause severe injury.

5.11 Then, turn off the heater and the steam temperature and pressure will begin

to drop. Allow the boiler to cool down to room temperature.

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Warning: Do not open the valve at the water inlet port as it is highly

pressurized at high temperature.

5.12 Record the steam temperature and pressure readings when the boiler is

cooled.

5.13 After finished the experiment and let the water cool below 100oC and turn

off the main switch.

6.0 RESULTS

6.1 Record the data by using the table in Appendix 4.

6.2 Plot graph of Temperature against Pressure.

6.3 Plot the graph of (dT/dP)sat against Pressure and TVfg/hfg against Pressure

on a same graph.

(dT/dP)sat = T(Vf –V g)

hf - hg

And hf + hfg = hg

Hence, hfg = hg – hf

(dT/dP)sat = T(Vf –V g) = TVg

hfg hfg

As Vg >> Vf

In which

Vf = specific volume of saturated liquid.

Vg = specific volume of saturated vapour.

hf = enthalpy of saturated liquid.

hg = enthalpy of saturated vapour.

hfg = latent heat of vaporization. (Refer Appendix 8)

7.0 DISCUSSION

7.1 Discuss the finding of the graphs and results.

8.0 CONCLUSION

Based on the experimental procedure done and the results taken draw some

conclusions to this experiment.

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EXPERIMENT 5

CONSTRUCTION OF VAPOUR LIQUID EQUILIBRIUM OF

BINARY COMPONENT

2.0 OBJECTIVE

1.1 To construct vapour-liquid equilibrium curve for a binary component at

atmospheric pressure.

1.2 To investigate vapour-liquid equilibrium compositions at different temperature

and concentration.

2.0 INTRODUCTION

Many processes in chemical engineering do not only involve a single phase but a

combination of two immiscible liquids, or a steam containing both gas and liquid. It is very

important to recognize and be able to calculate when these phase are in equilibrium with

each other, and how much is in each phase. This knowledge will be especially useful

when we are study separation processes, for many of these processes work by somehow

distorting the equilibrium so that one phase is especially rich in one component, and the

other is rich in the other component.

Vapor-liquid equilibrium (VLE) data especially are very important in the design and

operation of separation processes in chemical industry. Such information can be obtained

experimentally or estimated by using generalized methods for calculation of the

properties of mixtures. For ideal system, it is relatively easy to estimate vapor-liquid

equilibrium. However, most systems of industrial interest show deviations from the ideal

behavior.

1.0 THEORY

3.1 Vapour Liquid Equilibrium (VLE)

Vapour liquid equilibrium is established when the liquid and vapour have both

reached an equilibrium state. In this state, the rate of evaporation and condensation are

same on a molecular level. Equilibrium state can be reached when the liquid and the

vapour are in contact with each other for a period of time with minimal external

interference. Vapour pressure is the pressure of vapour when it is at an equilibrium

29

state. It depends significantly on the surrounding temperature. It is the partial pressure of

a component when there a mixture gases present within the vapour.

A vapour with components at certain concentration will have a corresponding

equilibrium liquid concentration. The concentration or partial pressure of the liquid

components will have certain set of values depending on the vapour component

concentrations and the operating temperature. Similarly, this also applies to liquid with

components. The equilibrium concentration of each component in the liquid and vapour

phases are different and the data can be determined experimentally with various

components or can be approximated using certain theories, for example Dalton’s Law,

Henry’s Law and Raoult’s Law.

For an ideal gas the partial

equation as follow:

P 1

pressure, P1 can be determined by Dalton’s Law

Y1 P

For ideal mixture, the partial pressure is given by Raoult’s Law as follow:

Where,

P1

P

P1o

x1,y1

P X P

0

1 1 1

= Partial pressure of component 1. = Total pressure of the mixture. = Vapour pressure of pure component 1. = mole fraction in liquid and vapour phase respectively.

VLE data is important and useful in the process of designing distillation

plant/column. Distillation is a thermal separation process used to separate components

in a mixture by boiling and condensation.

3.2 T-x-y Diagram

Temperature has an effect on the VLE of a system since at different temperature;

there will be a corresponding set of liquid and vapour composition under constant

pressure. These two composition are in equilibrium with one another at that particular

point. For an ideal binary mixture, the relationship between T-x-y at a constant pressure

can be presented in a plot called the phase diagram, as depicted in Figure 6.1 and 6.2

below:

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B

A

Figure 5.1: (a) P-x-y, (b) T-x-y diagrams

Figure 5.2: T-xy diagram of Bezene-Toulene mixture

3.3 X-Y Diagram

For binary mixture boiling point under a constant pressure, the variation of one

component’s equilibrium liquid and vapour compositions can be represented in a plot

known as x-y diagram. Figure X shows a typical x-y diagram for an ideal mixture which

obeys Raoult’s law. An example for such system is the mixture between methanol and

isopropanol boiling at 1 atm.

Figure 5.3: Vapour liquid equilibrium diagram for methanol-isopropanolat 1 atm.

31

4.0 MATERIALS AND EQUIPMENT

4.0.1 Vapour Liquid Equilibrium Unit

4.0.2 Refractometer

4.0.3 Methanol Solution

4.0.4 Distilled water

Figure 5.4: Vapour Liquid Equilibrium Unit

1. Condenser 6. Pressure Relief Valve

2. Evaporator 7. Control Panel

3. Bottom Sample Collector 8. Top Sample Collector

4. Cooling Water Supply 9. Rotameter

5. Cooling Water Drain 10. Heater

32

5.0 PROCEDURES

5.1 REFRACTIVE INDEX CALIBRATION CURVE

To obtain the refractive index data for ethanol-water solution:

5.1.1 Prepare 10ml distilled water.

5.1.2 Obtain 10ml of ethanol.

5.1.3 Measure the refractive index for both distilled water and ethanol by digital

handheld refractor meter.

5.1.4 Record the refractive index for each.

5.1.5 Dilute 10ml of methanol with 1ml of distilled water in a beaker. Then

measure the refractive index by refractor meter. Repeat the same

procedures using the volume of methanol-distilled water mixture state in

Table 6.1 (Appendix 6).

5.2 EXPERIMENT

5.2.1 General Start-up Procedures

1. Check that the evaporator and condenser is empty of liquid.

2. Ensure all valves are initially closed and the heater power switch is

turned off.

3. Switch on the main power at the control panel. Check all sensors and

indicators are functioning properly.

5.1.2 Experiment Procedures

1. Perform the general start-up procedures as described in Section 5.2.1.

2. Prepare about 4-L of pure methanol and 4-L of deionized water.

3. Open valve V8.

4. Pour 0.2 L methanol and 2 L water into the evaporator through valve

V1. Close valve V1.

5. Open valves V13 and V14 at the level sight tube. Make sure that the

liquid level is above the safety line on the level sight tube. Close back

valves V13 and V14.

6. Open and adjust valve V10 to allow about 2 L/min of cooling water to

flow through the condenser.

33

7. Set the temperature controller TIC-01 to about 100°C. Switch on the

heater. Observe the temperature rise in TIC-01. 8. When the temperature at TI-02 starts to increase sharply, the liquid in

the evaporator has begun to boil. Observe the pressure at PI-01. Wait

for all temperatures and pressure to stabilize at a steady state value.

Whenever the pressure increases, open V8 to release the pressure. 9. Record the evaporator pressure as wel as liquid and vapour

temperatures. 10. Collect a liquid and vapour sample from the unit as described in

Section 5.2.4. Analyze the samples to determine their compositions by

using a refractometer. 11. Switch off the heater and open valve V11 to allow cooling water to flow

through the cooling coil in the evaporator. 12. Wait for the temperature at TI-02 to drop significantly (at least below

50 °C) to signify that boiling has stopped. Close valve V11. 13. Collect all the liquid from the condenser by opening valve V5 and V7

and pour it back into the evaporator through valve V1. Close valves

V1, V5 and V7. 14. Collect all the liquid from the bottom sample collector by opening valve

V3 while closing V2 and pour it back into the evaporator through valve

V1. Close valves V1 and V3. 15. Pour an additional 0.4 L methanol into the evaporator through valve

V1. Close valve V1. There is now about 0.6 L methanol and 2L water

in the evaporator. Repeat steps 5 to 14 above. 16. Pour an additional 0.4 L methanol into the evaporator through valve

V1. Close valve V1. There is now about 1.0 L methanol and 2.0 L water

in the evaporator. Repeat steps 5 to 14 above. 17. Pour an additional 1.0 L methanol into the evaporator through valve

V1. Close valve V1. There is now about 2.0 L methanol and 2.0 L water

in the evaporator. Repeat steps 5 to 14 above. 18. Open valves V2 and V3 to drain all liquid from the evaporator. 19. Pour 2.0 L methanol and 0.2 L water into the evaporator through valve

V1. Close valve V1. Repeat steps 5 to 14 above. 20. Pour an additional 0.4 L of water into the evaporator through valve V1.

Close valve V1. There is now about 2.0 L methanol and 0.6 L water in

the evaporator. Repeat steps 5 to 14 above.

34

21. Pour an additional 0.4 L of water into the evaporator through valve V1.

Close valve V1. There is now about 2.0 L methanol and 1.0 L water in

the evaporator. Repeat steps 5 to 14 above.

22. Perform the general shut-down procedures as described in Section

5.2.3.

5.2.3 General Shut-down Procedures

1. Switch off the heater.

2. Open valve V10 to increase the cooling water flow rate through the

condenser.

3. Open valve V11 to allow cooling water to flow through the cooling coil

in the evaporator.

4. If the unit is pressurized, slowly open valve V8 to depressurize the unit.

5. Wait for the temperature at the unit to drop to below 50°C.

6. Open valves V2 and V3 to drain all liquid from the evaporator.

7. Open valves V5 and V7 to drain all liquid accumulated at the

condenser.

8. Close all valves and switch off the main power at the control panel.

5.2.4 Sampling Procedures

Both vapour and liquid samples can be taken from the unit for analysis.

1. Vapour sampling from the condenser

i) Ensure that vent valve V6 is opened and drain valve V7 is closed.

ii) Slowly open valve V5 to allow some condensed vapour from the

condenser to flow into the top sample collector. Close valve V5.

iii) Open valve V7 to collect the sample in a sampling vial.

iv) Immediately close the cap on the vial and immerse it in cold water.

2. Liquid sampling from the evaporator

i) Ensure that vent valve V4 is opened and drain valve V3 is closed.

ii) Open valve V12 to allow cooling water to flow through the bottom

sample collector.

35

iii) Then, slowly open valve V2 to allow some liquid from the

evaporator to flow into the sample collector. Close valve V2.

iv) Open valve V3 to collect the sample in a sampling vial.

v) Immediately close the cap on the vial and immerse it in cold water.

6.0 RESULT

6.1 Record the data by using the table in Appendix 5.1 and Appendix 5.2.

6.2 Plot the graph of refractive index vs. mole fraction of methanol.

6.3 Plot the vapour temperature against vapour and liquid compositions

6.4 Construct the equilibrium curve by plotting the vapour composition against the

liquid composition.

7.0 DISCUSSION

7.1 Discuss the finding of the graphs and results.

7.2 Discuss on the T-x-y and x-y diagrams.

7.3 Compare between the composition plot and equilibrium curve obtained from the

experiment to the literature data.

8.0 CONCLUSION Based on the experimental procedure done and the results taken draw some conclusions to this experiment.

36

EXPERIMENT 6

DETERMINATION OF STEAM QUALITY

1.0 OBJECTIVES

1.1 To determine the quality of steam exiting a pressurized vessel with throttling

calorimeter.

2.0 INTRODUCTION

The saturation vapor pressure is the static pressure of a vapor when the vapor phase of

some material is in equilibrium with the liquid phase of that same material. The saturation

vapor pressure of any material is solely dependent on the temperature of that material. As

temperature raises the saturation vapor pressure rises nonlinearly. An example is water vapor

when air is saturated with water vapor. It is the vapor pressure usually found over flat surface

of liquid water, and is a dynamic equilibrium where the rate of condensation of water equals

of evaporation of water. In general, the higher the temperature, the higher the vapor pressure.

When air is at the saturation vapor pressure, it is said to be at the dew point. Thus, at saturation

vapor pressure, air has a relative humidity 0f 100% and condensation occurs with any increase

of water vapor content or a reduction in temperature.

3.0 THEORY

3.1 Saturated Liquid & Saturated Vapour

When a liquid is heated at any constant pressure there is one fixed temperature at

which bubbles of vapour form in the liquid; this phenomenon is known as boiling. The

higher the pressure of the liquid then the higher the temperature at which boiling occurs.

When a liquid at boiling-point is heated further at constant pressure the additional heat

supplied changes the phase of the substance from liquid to vapour. A liquid that is about

to vaporize is called a saturated liquid. Once boiling starts, the temperature will stop rising

until the liquid is completely vaporized.

37

That is, the temperature will remain constant during the entire phase-change process if the

pressure is held constant. During a boiling process, the only change we will observe is a

large increase in the volume and a steady decline in the liquid level as a result of more

liquid turning to vapour.

Lines of constant temperature, called isothermals, can be plotted on a P-V diagram as

shown in Figure 3.1. A substance at states between these lines is often referred to as a

saturated liquid-vapour mixture since the liquid and vapour phase coexist in equilibrium at

these states. The temperature lines become horizontal between the saturated liquid line

and saturated vapour line. Thus there is a corresponding saturation temperature for each

saturation pressure. At pressure PP the saturation temperature is T1, at pressure PQ the

saturation temperature is T2, and at pressure PR the saturation temperature is T3.

3.2 Saturation Temperature & Saturation Pressure

If probably came as no surprise to that water started to boil at 100°C. Strictly speaking

this statement is incorrect. The correct statement is “water boils at 100°C at 1 atm pressure.”

The only reason the water started boiling at 100°C was because we held the pressure constant

at 1 atm (101.325 kPa). That is, the temperature at which water starts boiling depends on the

pressure: therefore, if the pressure is fixed, so is the boiling temperature.

At a given pressure, the temperature at which a pure substance changes phase is

called the saturation temperature. Likewise, at a given temperature, the pressure at which a

pure substance changes phase is called the saturation pressure.

During a phase-change process, pressure and temperature are obviously dependent

properties, and there is a definite relation between them, that is, Tsat = f(Psat). A plot of Tsat

versus Psat is called a liquid-vapour saturation curve. A curve of this kind is characteristic of

all pure substances. Thus a substance at higher pressures will boil at higher temperature.

38

Figure 6.1: Isothermals for a vapour plotted on a P-V diagram.

5.12 Throttling Calorimeter

A throttling calorimeter is used to throttle saturated steam from its original vapor pressure

to the atmosphere causing it to become superheated. Throttling devices are any kind of flow

restricting devices that cause a significant pressure drop in the fluid. Examples are partially

opened valves, porous plugs, and capillary tubes.

To determine the quality, suppose a small quantity of the two-phase liquid-vapor mixture

in the line is steadily diverted through the throttling calorimeter, as indicated in the Figure 3.2.

If the pressure of the flowing stream is reduced sufficiently by the restriction, the stream would

pass into the superheated vapor region. With P2 the same as atmospheric pressure (the valve

on the calorimeter is fully open) and the measured temperature T2, the enthalpy h2 can be

found in the superheated vapor table. Taking into account that for the throttling process

enthalpy h1=h2, the quality of the steam in the main line (boiler) can be determined.The quality

of steam in the boiler is derived as:

X = (h2 – hf1) / hfg1

where x = the steam quality

h2 = the enthalpy of superheated steam at atmospheric pressure

hf1 = the enthalpy of saturated liquid in the boiler at high pressure

hfg1 =the enthalpy of vaporization at high pressure

39

Figure 6.2: T-V diagram.

4.0 MATERIALS AND EQUIPMENTS

4.1 4.1 Description of Apparatus

Figure 6.3: Saturation vapor pressure measurement apparatus.

5.0 PROCEDURES

5.1 Set up the system as the previous experiment instructions.

5.2 Make sure both the upper and lower valves are fully shut.

5.3 Set the system temperature to 100°C for the first reading.

40

5.4 Once the unit reaches 100°C and stabilizes, slowly open the upper valve with the

protective glove provided. (Ensure that the upper valve is connected to a water hose

to direct the steam away from any student or operator.)

5.5 Allow a small amount of steam to flow through the throttling calorimeter for

approximately 15 seconds.

5.6 Observe if the temperature and pressure of the system are able to be maintain within

the controlled values. This can be controlled with the opening of the upper valve.

5.7 Record the corresponding temperature after the throttling calorimeter (Temp 2).

5.8 Repeat the above procedures by increasing the system temperature (Temp 1) in

5°C per step. For every increment of 5°C, record the corresponding value of

saturation pressure from the digital pressure meter until 140°C is achieved.

5.9 Turn off the heater.

5.10 Release the steam.

5.11 When the pressure reading is low, shutdown the equipment.

Precautions:

1. Do not stand behind the machine when the experiment is carried on.

2. Beware of hot pipes. Do not attempt to touch!

6.0 RESULTS

6.1 Record the data by using the table in Appendix 6.

6.2 Based on the data recorded, plot the graph of steam quality against vessel

temperature. (Refer Appendix 9)

7.0 DISCUSSION

7.1 Discuss the finding of the graphs and results.

7.2 Discuss the relationship between saturation pressure and temperature.

8.0 CONCLUSION

8.1 Based on the experimental procedure done and the results taken draw some

conclusions to this experiment.

41

EXPERIMENT 7

MEASUREMENT OF TEMPERATURE USING DIFFERENT TYPE OF

TEMPERATUREMEASURING DEVICES

1.0 OBJECTIVES

1.1 To understand the different type of temperature measuring devices.

1.2 To measure and compare the result of water temperature using different temperature

measuring devices.

1.3 To measure and compare the result of air temperature using different temperature

measuring devices.

2.0 INTRODUCTION

Temperature is a difficult concept to understand and describing it as the degree of hotness

or coldness of a body is not sufficient where measurement is concerned. Technically, it is

defined as an indication of intensity of molecular activity. This means that a rise in temperature

of a material results in an increase in the vibration of the material‟s molecules. The

temperature of a „cold‟ body is raised by the introduction of energy which increases the

vibration of the molecules, like the body is becoming hotter.

In simpler terms, the temperature of a body is a measure of the thermal potential of that

body and determines whether heat energy is supplied to or rejected from the body when in

contact with a body at a different temperature. Bodies at the same temperature are in

equilibrium and no exchange of energy occurs.

3) THEORY

3.1 Expansion Thermometers (The Liquid Filled Thermometer)

This type of thermometer depends on the expansion of a liquid associated with an

increase in temperature. The most common type is the mercury-in-glass thermometer.

Clean, dry mercury is introduced and the thermometer heated to drive off the air. The end

is then scaled leaving mercury and mercury vapor only. The mercury-in-glass thermometer

is an accurate device but is very fragile and care should be exercised in use. The mercury

42

may be replaced by other fluids according to the application. For example, alcohol is

cheaper and may be used at lower temperature than mercury.

3.2 The Vapor Pressure Manometer

Vapor pressure thermometer consists of a metal bulb partially filled with fluid, which is

connected to the sensing element of a Bourdon gauge. The space above the fluid is filled

with vapor of the fluid, the pressure of which is displayed on the Bourdon gauge. The

gauge is calibrated directly in units of temperature corresponding to the equivalent,

pressure of the vapor but calibration is far from linear due to the pressure increasing more

and more rapidly as the temperature increases. For this reason, the vapor pressure

thermometer is suitable only for operation over short ranges of temperature and suffers

from lack of sensitivity at low readings.

3.3 The Bi-Metal Thermometer

Expansion of solids may be used to measure temperature but direct measurement is

impractical due to the very small movements involved. However, if two thin metal strips,

having different coefficients of linear expression, are mechanically fastened together, the

result is a strip which bends significantly when heated. This combination is called a Bi-

metal strip and the sensitivity may be increased by coiling the strip into a spiral. One end

of the strip is fixed to the case and a pointer is attached to the other end. Linear scale may

be obtained by suitable choice of metals.

This type of thermometer is very robust and has many applications throughout industry

where accuracy of measurement is not important.

3.4 Thermocouples

A thermocouple consists of two wires of dissimilar metal joined together at one end.

When the metallic junction is heated an e.m.f is generated known as the Peltier E.M.F. By

suitable connection of junctions and instrumentation, a circuit can be created which may

be used to determine temperature differences.

44

3.5 Thermistor

The thermistor is a thermally sensitive, variable, resistor which is made from

semiconducting material. The change in resistance with temperature is far greater than in

the case of metals, which means less sensitive instrumentation may be used. In addition,

the miniature bead thermistors may be manufactured which are so small that the thermal

response is virtually instantaneous and effects on the system being measured are

negligible.

4.0 MATERIAL AND EQUIPMENTS

4.1 Description of Apparatus

Figure 2.1: Temperature measurement apparatus.

5.0 PROCEDURES

5.1 Experiment 1: Measurement of Water Temperature using Different Types of

Temperature Measuring Devices.

5.1.1 Plug the 3 pin plug to 220VAC main power supply. Switch ON the power supply.

5.1.2 Switch ON the main power supply (K) for the apparatus.

5.1.3 Put a beaker on a hot plate and pour tap water into the beaker. The water level

must at least half of the beaker.

45

5.1.4 Place all type of temperature measuring sensor into the beaker.

5.1.5 State down the initial temperature reading and record it into the table.

5.1.6 Turn ON the hot water plate and set knob to the maximum.

5.1.7 For every 2 minutes interval, state down the temperature reading and record it

into the table.

5.1.8 Repeat the step 5.1.7 until the water boiled.

5.1.9 Plot the graph of temperature against time for all temperature measuring

devices.

5.1.10 Compare the results and state the finding from the graph plotted.

5.2 Experiment 2: Measurement of Air Temperature using Different Types of

Temperature Measuring Devices.

5.2.1 Plug the 3 pin plug to 220VAC main power supply. Switch ON the power

supply.

5.2.2 Switch ON the main power supply (K) for the apparatus.

5.2.3 Connect the hot air blower to the apparatus and switch ON.

5.2.4 Turn the speed of the hot air blower to low speed.

5.2.5 Choose the desirable temperature measuring device, state down the initial

temperature reading and record it into the table.

5.2.6 Place the temperature measuring device to the test point on the hot air

blower (A).

5.2.7 Take the temperature reading and record it into the table.

5.2.8 Repeat the experiment with different type of temperature measuring

devices.

5.2.9 Compare the result and state the finding.

6.0 RESULTS

Experiment 1

6.1 Record your result into a table in Appendix 7.1.

6.2 Plot a bar chart of temperature versus time for each device.

Experiment 2

6.3 Record your result into a table in Appendix 7.2.

6.4 Plot a bar chart of temperature versus air speed for each device.

46

7.0 DISCUSSION

7.1 By comparison the temperature readings using different measuring devices, which

gives the highest accuracy and why?

7.2 State the effect of air speed regulator towards the temperature? Which devices affect

the most?

8.0 CONCLUSION

8.1 Based on the experimental procedure done and the results obtained, draw some

conclusions to this experiment.

47

Appendix 1

No. Activity/ Work Process Hazard Risk

Safety

Precaution

Appendix 2

Total height of cylinder = 40 cm

Diameter of cylinder = 13 cm

Pressure (bar) Height of water in the

cylinder (cm) Volume of water in the

cylinder (cm3) Temp (T) (°C)

48

Appendix 3.1

Trial 1 Trial 2 Trial 3

Pressure Temperature (°C) Temperature (°C) Temperature (°C)

(bar)

Pressurizing Depressurizing Pressurizing Depressurizing Pressurizing Depressurizing

1.11

1.21

1.31

1.41

1.51

1.61

Appendix 3.2

Before expansion After expansion

PT 1 (bar)

TT 1 (°C)

Appendix 3.3

Initial Intermediate Final PT 1 (bar) TT 1 (°C)

Appendix 4

Pressure, P (bar) Temperature (oC) Measured Calculated

Slope, Slope,

Gauge Absolute Increase Decrease Average Average

(oC) (oC) (oC) (K) dT/dP TVg/hfg

49

Appendix 5.1

Volume of Volume of

Mol fraction

Refractive index

methanol wt%

water (mL) of methanol (RI)

(mL)

0 10

1 9

2 8

3 7

4 6

5 5

6 4

7 3

8 2

9 1

10 0

Appendix 5.2

Pressure Volume Volume Temperature (°C) Refractive Index Mole Fraction

of of (RI) Methanol

Methanol

Water

Liquid Vapor Liquid Vapor Liquid Vapor

(L) (L)

1 atm

50

Appendix 8 Steam Table of Water

52

Appendix 9 Enthalpy of Saturated Water

53

Appendix 10 Vapour Point of Saturated Water

54

Appendix 6

Temperature, T1 (oC)

Absolute Temperature,

Tabs (K)

Pressure, P1 (kN/m2)

Temperature, T2 (oC)

Absolute Temperature

Tabs (K)

Pressure, P2 (kN/m2)

Enthalpy of Saturated Liquid, hf

Enthalpy of Saturated Vapour, hg

Enthalpy of Steam Sample,

h2

Quality of Steam, x

Appendix 7.1

Appendix 7.2

51