properties measuremnt pvt experiment

8/10/2019 Properties Measuremnt PVT experiment

1/20

ABSTRACT.

This experiment involves a perfect gas or ideal gas experiment. The equipment; Perfect

Gas Expansion Apparatus had been utilised in order to determine the properties of

measurement and study the relationship between ideal gas and various factor that can propose

an understanding of First and second law of thermodynamics. The objectives of this

experiment successfully achieved. Boyles and Gay-Lussacs law was proven in this

experiment when the ideal gas obey the law. The volume ratio and heat capacity were also

determined. The experiment was successful.

INTRODUCTION.

The Perfect Gas Expansion Apparatus from model TH11 is a sufficient bench top unit

designed in order to expose the student and familiar with the fundamental thermodynamic

processes. This experiment likely safe and more convenient to demonstrate thermodynamic

properties. The apparatus have two vessel, one is for pressurized chamber and the other one is

for vacuum chamber. This apparatus also equip with pressurized pump and vacuum pump and

several valve which can connect between chambers and also to the surrounding. The chamber

is made from glass that can withstand maximum pressure of apparatus can operate.

The apparatus also equipped with temperature and pressure sensors for both tanks

which can be read on the board. These sensors used to monitor and manipulate the pressure

and temperature. The board displays the temperature and pressure in a digital indicator that

dealt with the PVT laws.

Gas particles in the chamber collide with each other and the walls which transfermomentum in each collision. The gas pressure is equal to the momentum delivered to the wall

per unit time. A single particles moves arbitrarily along some direction until it strikes back

and forth with wall and change direction and speeds. Equations are derived directly from the

law of conservation of linear motion of conservation of energy.

This experiment is conducted to improved our understanding about First and

SecondLaw of Thermodynamics and relationship of pressure, volume and temperature. The

Perfect Gas Expansion Apparatus (Model: TH 11) was used in the experiment. The apparatus


2/20

contain 2 chambers. First chamber with bigger volume is pressure vessel (PT 1) and another

chamber is vacuum vessel (PT 2). Both of the chamber is made up from glass. The apparatus

also contain 5 valves and one pressure relief valve if pressure inside the chamber exceed than

2 bar.

AIMS/OBKECTIVES.

i.Experiment 1

The objectives of this experiment is to determine the relationship between pressure and

volume of an ideal gas and to compare the experimental results with theoretical results.

ii.Experiment 2

The objectives of this experiment is to determine the relationship between pressure and the

temperature of an ideal gas.

iii.Experiment 3

The experiment is to demonstrate the isentropic expansion process.

iv.Experiment 4

The experiment is to study the response of the pressurized vessel following stepwise

depressurization.

v.Experiment 5

The objectives of this experiment is to study the response of the pressurized vessel following

a brief depressurization.

vi.

Experiment 6

The experiment is to determine the ratio of volume and compares it to the theoretical value.

vii.Experiment 7

This experiment is to determine the ratio heat capacity.


3/20

THEORY.

Perfect Gas.

Theories of perfect gascan be divided into three which is Charless law, Boyles law

and Gay-Lussacs law. Perfect gas is same with ideal gas where there is none attractive forces

exist in the ideal gas. Since perfect gas is an ideal gas, they collide between atoms or

molecules elastically with no intermolecular attractive forces. Some assumption has been

respect to kinetic theory of ideal gas which is the gasses are made up of molecules that always

move in a constant straight line. An equation had been introduced in 1662 where it has been

named as ideal gas equation of state:

) (1)

The subscript R refer to gas constant where different gas would have different value of

R. Any gas that obeys this law is called an ideal gas. The equation also can be written as:

(2)

The properties of ideal gas at two different state is related to each other as long as they has

one constant property throughout the experiment where:

(3)

Boyles Law

The behavior real gas using parameter of pressure, temperature and volume is

considered at low density. Ideal gas also obeys the law of Boyles, Charless and Gay -

Lussacs. Boyles lawdescribe the relationship between the pressure and the volume of a gas.

This law works when the pressure increase inversely with the volume of gas where the

temperature held constant along the process. The gas inside a system loosely packed and

move randomly. If the volume is reduce, then the pressure become high as the molecules

having less space to move, to hit the wall of container more frequently.


4/20

Figure 1: Graph of Boyle's Law

Charless Law

Second law is Charless Lawwhich involves with the effect of heat on the expansion

of gases. The pressure will remain constant throughout the process and the volume of gas will

go directly proportional to the absolute temperature. The moving molecules increase their

speed and hit the wall more frequently as the temperature getting higher because the

temperature transfer the heat of energy into the molecule. Thus, as the speed increase and the

frequency of collision increase, the volume of the container also increase. Therefore the

equation of Charless law simply show below where the k is a constant. The temperature must

be calculated in Kelvin unit. If the constant value of k is not known then, the equation is

derived as follow:

(4)


5/20

The relationship of volume and temperature of Charless law describe in a graph as follow :

Figure 2: The graph of Charles's Law

Gay-Lussacs Law

The third law involving ideal gas is Gay-Lussacs law where the volume of the

system become constant throughout the process. This law stated that the pressure and

temperature are in direct relation. That means as the pressure increase, the temperature also

increase. Temperature is a parameter for kinetic energy, as the temperature increase, the

kinetic energy also increase, therefore the frequency of collision also increase which causing

the pressure to be increase with the constant volume. The equation below can prove the

relationship between pressure and temperature in a particular system with constant volume.

(5)

Graph below show the relationship of temperature and pressure in the Gay-Lussacs law with

constant volume. The conclusion is that the pressure directly proportional to the temperature.


6/20

Figure 3: Graph of Gay-Lussac's Law

First law of thermodynamics

Based on first law of thermodynamics statement, energy can be neither created nor

destroyed but it can only change in the form of energy. For example the change of energy of

lamp, from electric energy convert to light and heat energy. Therefore, the conservation of

energy principle introduced as the net change in the total energy of the system equivalent to

the difference in the total energy enter the system and total energy leaving the system.

(6)

That equation also referred as energy balance equation that applicable to any kind

system any kind of process. Since the energy has numerous form such as internal, kinetic,

potential, electrical and magnetic and their sum constitutes the total energy of the system.

Simple compressible system has the following equation which the change in the total energy

of a system is the sum of the changes in its internal, kinetic, potential energy can be expressed

as:

(7)

Where internal energy, U

(8)


7/20

Where kinetic energy, KE

(9)

Where the potential energy, PE

(10)

Energy can be transfered in or out of a system in three forms such as heat, work and mass

flow. As there is one of any three form cross the boundary of an open system, it can be

concluded as energy gained or lost during a process. In a closed system, there is only two

form can pass through the boundary which can change the energy which are heat and work.

Temperature difference in a system with its surrounding is not an energy interaction. Work

interactions refer as rising piston and rotating shaft. Commonly sense when the work transfer

into the system, the energy of the system increase and vice versa. As mass transfer in the

system, energy also increase as the mass carries energy with it and vice versa. Equation below

represent the concluded energy balance.

Amount of energy required to raise the temperature of a unit mass of a substance by one

degree is a definition of specific heat. There are two specific heat use widely which is specific

heat at constant volume and specific heat at constant pressure. Cp value larger than Cv as at

constant pressure system is allowed to expand and the energy must supplied to system.

Specific heat capacity at constant pressure is the energy required to raisethe temperature of

the unit mass of a substance by one degree as the pressure remain constant. It can be

concluded that Cv is related to internal energy and Cp involved enthalpy value.

(11)


8/20

(12)

Internal energy is a function of temperature only. As the temperature high, then enthalpy

value also big. Then the enthalpy value is represent with subscript h:

(13)

Where it can combine to become:

(14)

(15)

Since R is a constant and u= u(T), the enthalpy of an ideal gas is also a function of

temperature ony,

h= h(T) (16)

Therefore, at a given temperature of an ideal gas, u, h, Cv, and Cpwill have fic=xed values

regardless of the specific volume or pressure. Thus the differential changes in the internal

energy and enthalpy of an ideal gas can be expressed as:

du= Cv(T)dT (17)

dh= Cp(T)dT (18)

Cp and Cv has special relationships for ideal gas by differentiating the h = u + RT to producedh = du + RT and by replacing dh by CpdT and du by CvdT, the equation come out with:

(19)

Specific heat capacity also has the constant k by the relation of:

(20)


9/20

Ratio of volumes using isothermal process can be determine using isothermal process.

One pressurized vessel is allowed to leak slowly into another vessel of different size. Finally,

the pressure will be same for both vessel. Final pressure in vessel can be calculated by:

Both vessel was placed in room temperature before valve is opened lead the isothermal

process and the initial temperature will be equal to the final temperature. Deriving :

Using these equation, substitute m1 and m2 into equation of Pabsf and become:

Rearrange the equation and cancel the RT to give the ratio of the two volume:

Stepwise Depressurization

Stepwise depressurization is conducted by depressurizing the chamber or tank step by

step slowly or gradually by flowing out the gas which they would expand at every instant

opened and closed in order to identify gradual changes in pressure and temperature within the

contrary decreases with the expansion.


10/20

Brief Depressurization

This is similar to stepwise depressurization but reduced in terms of time. The time

interval increased to a few seconds. This is to make sure that, the effect on the pressure and

temperature can be observe which can be compared later. The graph should be more higher

gradient.

PROCEDURES.

i. General Operating Procedures

A.

General Start-Up Procedures

1.

Equipment was connected to single phase power supply and the unit was switched on.

2. All valves were fully opened and the pressure reading on the panel was checked just to make

sure the pressure was at atmospheric pressure.

3. All valves were closed.

4. Pipe from compressive pump was connected to pressurized chamber or the pipe from vacuum

pump was connected to vacuum chamber.

5.

The unit was ready to use.

B. General Shut-Down Procedures

1. Pump was switched and it was removed from the chamber.

2. The valve was fully open in order to release out the air inside the chamber.

3. The switch and power supply was switched off.

ii.

Experiment 1 : Boyles LawA. Experiment 1.1 : Condition 1

1. All valves were fully closed.

2. Compressive pump, Tank 1 was filled with air until 150kPa.

3. The gas was transferred from tank 1 to tank 2 by opening the valve between tanks.

4.

The temperature and pressure was recorded.


11/20

B. Experimeny 1.2 : Condition 2


2. Tank 2 was filled with air until 50kPa.

3.

The gas was then transferred from tank 2 to tank 1 by opening the valve between tanks.

4. The temperature and pressure was recorded.

C. Experiment 1.3 : Condition 3


2. Both tank 1 and tank 2 filled with air until 150kPa and 50kPa.

3.

The valve between tanks was opened.

4. The pressure and temperature was recorded.

iii. Experiment 2 : Gay-Lussac Law Experiment


2.

The hose from compressive pump was connected to pressurize chamber.

3. Compressive pump was turned on and the temperature was recorded for every increment of

10kPa in the chamber and the pump stopped when the pressure in tank 1 has achieved

160kPa.

4.

The valve was slightly opened and the pressurized air are allowed to flow out. The

temperature was recorded for every decrement in 10kPa.

5.

The experiment stopped when the pressure in tank 1 has reached atmospheric pressure that is

101.3kPa.

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

7. A graph of pressure versus temperature was plotted.

iv.

Experiment 3 : Isentropic Expansion Process


2. Hose was connected from compressive pump to pressurized chamber.

3. Compressive pump was switched on and the chamber was pressurized until 160kP. Pump was

switched off and the hose was removed from the chamber.

4. The pressure was monitored until the reading was stabilized. The pressure and temperature

was recorded.

5.

The valve was slightly opened and the air was flow out slowly until reached the atmosphericpressure.


12/20

6.

The pressure and temperature reading was recorded after the expansion process.

7. The isentropic process was discussed.

v. Experiment 4 : Stepwise Depressurization


2. Tank 1 was filled with air until 160kPa and the data was recorded.

3.

The valve 1 was opened and closed quickly for 5 times.

4. The data was recorded.

vi. Experiment 5 : Brief Depressurization


2.

Tank 1 was filled with air until 150kPa and the data was recorded.

3. Valve 1 was open for 3 seconds.

4. The data was recorded.

vii. Experiment 6 : Determination Of Ratio Volume


2. Tank 1 or pressurized tank was filled with air at about 150kPa.

3.

The data was recorded.

4. Valve 2 was slightly opened and the data was recorded.

5.

The experiment was repeated by passing air from tank 2 to tank 1 and tank 1 to tank 2 by

using the pressure of 150kPa for tank 1 and 50kPa for tank2.

viii. EXPERIMENT 7 : Determination Of Ration Of Heat Capacity

1. General start up was done and the valve was fully closed.

2.

The hose from the compressive pump was connected to the pressurized chamber.

3. Compressive pump was switched on and the chamber was pressurized until 160kPa. Then, the

pump was switched off and the hose was removed from the chamber.

4. C. The pressure and temperature was recorded.

8.

The valve one was fully open and closed after few seconds. The pressure and temperature was

monitored and recorded right after the reading was stabilized.

5. The ratio of heat capacity and the theoretical value was compared.


13/20

APPARATUS.

1) Pressure transmitter.

2) Pressure relief valve.

3)

Temperature sensor.

4) Big glass.

5)

Small glass.

6) Vacuum pump.

7) Electrode.


14/20

DISCUSSIONS.

Boyles law stated that the pressure of gas inversely proportional to the volume of a

container. From the results recorded, some calculation have been made in order to know the

difference value between before and after of the experiment one. For conditions 1, 2 and 3 the

value are 0.030862, 0.0720 and 0.003. These values are very small and close with the

theoretical value, therefore the Boyless Law is verified. According to the data tabulated, it

can been said that the pressure and volume inversely proportional. When the pressure

increase, the volume start to decrease. This is happen because if the gas of the same pressure

with constant temperature injected into small and big container which means have different

volume. The gas molecule in small container have less spacious room and will collide to the

wall and with each other more often which exert more pressure.

Gay-Lussacs Lawstated that pressure is directly proportional to the temperature which

means if the pressure increase, the temperature also increase with constant volume.

Experiment two has been conducted in order to know the relationship between pressure and

temperature. Therefore, from the data tabulated and graph plotted, it can be said that the Gay-

Lussacs Law is verified. The same concept applied here, if the temperature of a gas in a

container increase, the heat energy of the system transfer its energy into the molecule of gas

which actually increase the frequency of collision in that container which exert more pressure.

Isentropic expansionprocess occur when the system are reversible and adiabatic where

no heat will be transferred in or out and no energy transformation occurs. From the data

recorded, a constant k are now known which is equal to 1.814. It was obtained that both

temperature and pressure of the gas before expansion were higher compared to after the

expansion. The process is said to be isentropic since there was no change in the entropy

throughout the process.

Stepwise depressurizationis a strategy to adopt an equal time-stepwise depressurization

approach in this study yield a more reliable result for an example in the production sector in

industries. The molecule in the container affected when the number of them decreasing slowly

as they do not have to collide between them more often. The depressurization shown that

pressure decrease with time and also affecting the temperature. As the pressure decrease, the

temperature also decrease in the system.


15/20

Brief depressurization shown in the graph plotted in result section which is decrease

more linear compared to stepwise. The expansion occur when the pressure of gas increase.

Expansion of gas decrease as the gas is free to flow out time by time.

Ratio volume can be determined by manipulating the equation of Boyles law.

Boyles law proposed an equation P1V1=P2V2 and after manipulate the equation ratio

volume can be determine by V2/V1=P1P2. This experiment test in three different condition

where first condition the gas is flow from tank 1 to tank 2, while gas flow from tank 2 to tank

1 in second condition and both were filled with gas in third condition. The theoretical value is

2.021 in this experiment where the error or percentage difference was between 10 and -10.

There must be environmental factors that affect the stability of pressure and temperature or

random mistake during experiment. Since the percentage error is less than 10%, it can be said

that the experiment is successful.

Determination of ratio of heat capacityusing the expression of the heat capacity ratio

and it gives the 1.102. The theoretical value of this experiment is 1.4. The deviation which

now is equal to 21.28%. The deviation is due to measurement error. The actual intermediate

pressure supposed to be lowered that the measured one. Unfortunately the error occur due to

heat loss and sensitivity of pressure sensors. Supposed, the intermediate pressure taken as the

lowest pressure at the moment the valve is closed. Since the percentage difference is more

than 10%, the experiment can be declared as failed.

COCLUSIONS.

In conclusion, the experiment was aimed at determining the properties of measurement /PVT

according to the Boyles law, Gay-Lussacs Law, isentropic expansion, and heat capacity

equation. In fact, in this experiment, we have proven the Boyles law and Gay-Lussacslaw.

Although our experiment failed, but we have the reason behind the failure. For experiment 7,

the failure was due to the fact that an intermediate pressure was not taken after the valve

closed. However, the experiment was successfully done in final, and the objective of the

experiment was accomplishedly achieved.


16/20

RECOMMENDATIONS.

There are several improvements that can be performed so as to obtain a more satisfying

result in future. Before starting this experiment, we are supposed to do a start-up and shut-

down step in order to make sure there is no gas left in the chamber. Most importantly, during

recording data, keep an eye on the sensor while monitoring the board because the parameter

can increase and decrease really fast and read the procedure carefully.

In addition, obtain an average reading by repeating the experiment for three times in

order to reduce the range of deviation. Handle the valve carefully and try not to make mistake

by choosing the valve because it will affect the data. The place where the experiment is

conducted also must be at stable and no vibration. All the equipment must be handledcarefully in order to avoid explosion because over-pressure in the tank would cause an

explosion.


17/20

REFERENCES.

Engineering Sciences 182: PVT Measurement And Properties Of a Simple Compressible

Substances. (n.d). Retrieved from

http://sites.fas.harvard.edu/~es181/handouts/lab01_PVT_f05_v9.pdf

Charles's Law. (n.d.). Retrieved from how stuff works:

http://science.howstuffworks.com/dictionary/physics-terms/charles-law-info.htm

Charles's Law.(2010). Retrieved from Sparknotes:

http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter5section8.rhtml

Calculating PVT Properties. (n.d). Retrieved from

http://petrowiki.org/Calculating_PVT_properties
http://sites.fas.harvard.edu/~es181/handouts/lab01_PVT_f05_v9.pdfhttp://science.howstuffworks.com/dictionary/physics-terms/charles-law-info.htmhttp://www.sparknotes.com/testprep/books/sat2/chemistry/chapter5section8.rhtmlhttp://petrowiki.org/Calculating_PVT_propertieshttp://petrowiki.org/Calculating_PVT_propertieshttp://www.sparknotes.com/testprep/books/sat2/chemistry/chapter5section8.rhtmlhttp://science.howstuffworks.com/dictionary/physics-terms/charles-law-info.htmhttp://sites.fas.harvard.edu/~es181/handouts/lab01_PVT_f05_v9.pdf


18/20

APPENDIX.

Figure a:Pressure chambers


19/20

Figure b:Pressure pumps.


20/20

Figure c: Electrode

properties measuremnt pvt experiment

Documents