1. Koya University
Faulty of Engineering
School of Chemical & Petroleum Engineering
Chemical Engineering department
EXPERIMENT NUMBER FOUR
Marcet Boiler
Thermodynamics
Marcet Boiler
Instructor: Mr.Rebwar & Mr.Omer
Author Name: Aree Salah Tahir
Experiment Contacted on: 21/Jen/2013
Report Submitted on: 28/Jen /2013
Group:A

2. List of content:
Abstract ………………………………….….2
Objectives……………………………….…...3
Introduction …………………………………4
Background Theory ……………………...….5
Method ………………………………………6
Equipment and components used……………7
Calculation…………………………………...8
Discussion …..…………………....……9 &10
References …………………………………11

3. Abstract:
This experiment was carried out to determine the relationship between the pressure
and the temperature of saturated steam in equilibrium. Besides that this experiment
was also done to demonstrate the vapor pressure curve. The market Boiler was
used for this experiment. When the pressure increases, the temperature also increases.
Therefore, the relationship of pressure and temperature is directly proportional. The
derived formulae and the data were used to calculate the slope. The dT/dP measured
was compared with the data in the steam table. Theoretically, the values measured
should be almost the same with the predicted values. However, at certain points, the
values are not the same. This may because of the errors made in the experiment.{1}
2

4. OBJECTIVE:
The main aim of this experiment is to obtain a slope of saturated temperature and
pressure of steam, in equilibrium with water, between 0 and 14 bars. These results
are then compared to the theoretical values obtained from published steam tables.
A value for the constants as well as the maximum temperature if heating were
continued miscalculated. Moreover, after an expression for the time taken for the
temperature to reach ascertain value is derived.{2}
3

5. Introduction:
Thermodynamics deals with the interchange of energies such as heat and work
between system and the surroundings which occurs when the system undergoes a
process (heating or cooling). The loss or gain of energy in a system has a direct
impact on its thermodynamic properties. Two of the most important thermodynamic
properties of fluids (being investigated in this experiment) are pressure and
temperature that both vary in response to changes in the energy of a system i.e. when
energy is lost or gained by the system. The theoretical values obtained from published
steam tables are to be compared to the readings obtained while conducting the market
boiler experiment, while giving further analysis for the divergence of the two values.
For the purpose of this experiment, a Cussons P5700 Marcet Boiler unit was used to
heat the fluid and measure the temperature and pressure of water vapor inside its
vessel. Thus, conclusions about the change in thermodynamic properties of water
undergoing different processes where drawn. Marcet boiler units are usually used in
classroom demonstrations and lab experiments to understand the relationship between
the changes of temperature and pressure and their effects on the boiling point of water
(equilibrium state). However industry applications vary widely as such an
arrangement can be used in power plants, different cooking utilities, gasifies as well
as utilizing the market boiler as a water boiler{3}
4

6. BACKGROUND THEORY:
An ideal gas obeys the equation of state that the pressure, specific volume or
density, and absolute temperature with mass of molecule and the gas
constant, R.
PV = mRTM
Where, P = Absolute pressure
V = Volume
n = Amount of substance (moles)
R = Ideal gas constant
T = Absolute temperature (K)
However, real gas does not absolutely obey the equation of state. A few
changes on the ideal gas equation of state allow its application in the
properties of 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.
The Marcet Boiler is used to investigate the relationship between the pressure
and temperature of saturated steam in equilibrium with water at all
temperature levels between the atmospheric pressure and 8 bars. The
experimental slope (dT/dP)SAT obtained is compared to the theoretical value
determined through calculation from the steam table.{4}
5

7. Method:
1/Prepare the bench top unit as described in section 2.2.
2/Switch on the unit at the master switch.
3/Switch on the heater at the heater switch and heat up the boiler.
4/Log the boiler pressure and temperature values in increments of approximately
0.5 bar.
5/Enter the measured values in the diagram.
6/Compare your own measurements with the values from the literature.
6

8. EQUIPMENT & COMPONENTS USED:
1/ safety valve,
2/ boiler with insulating jacket,
3/ Bourdon tube pressure gauge,
4/ switch cabinet with temperature display,
5/ drain valve,
6/ heater,
7/ overflow,
8/ temperature sensor
{5}
7

9. Calculation:
NO.
Temperature
(K)
Pressure
(kpa)
1
378
383
181.3
4
388
201.3
5
393
(Hfg ) KJ/kg
151.3
3
Latent heat of evaporation
373 131.3
2
Specific volume
(Vg) m3 /kg
241.3
Temperature and Pressure Plot
300
241.3
250
Pressure (KPa)
201.3
181.3
200
151.3
131.3
150
100
50
0
370
375
380
385
390
395
Teperature (K)
8

10. Discussion:
In the experiment the pressure and temperature are compared by the graphs
and tabulated results as for the pressure and temperature are compared and
it was almost constant throughout the experiment. The result showed that by
comparing each test, error made during the experiment can be analyzed and
support the discussion effetely.
The error percentage should be around 10 - 20 % because there`s small
difference between the actual and ideal value`s we got.
Source of experiment error



Measurement reading accuracy
Room temperature and pressure
The stability of the materials
We put the air in the vessel out If the air is not expelled the correct equilibrium
measurements between the steam and boiling water will not be obtained. Due
to the partial pressure of air a lower water temperature will be required to
raise the pressure.
We use distilled water in this experiment because distilled water prevents corrosion
in the vessel and impurities in other water increase boiling point (D.W boiling point is
100c0 but other water with impurity reaches 110c0 ).
we use over flow valve to pure extra water in the vessel
9

11. Temperature-pressure diagram of water
red: sublimation curve, green: boiling point curve, blue: melting point curve;
1 triple point, 2 boiling point, 3 critical point
{6}
10

12. References:
1/http://www.slashdocs.com/pwxyx/marcet-boiler-lab-report.html
2/http://www.academia.edu/4916263/Marcet_Boiler_Lab_Report_Shahda_Mazin_
Abduljabbar_Al-Taie_H00113228_Mechanical_Engineering__2nd_year_Supervised_by_Dr._Mehdi_Nazarinia
3/http://www.academia.edu/4916263/Marcet_Boiler_Lab_Report_Shahda_Mazin_
Abduljabbar_Al-Taie_H00113228_Mechanical_Engineering__2nd_year_Supervised_by_Dr._Mehdi_Nazarinia
4/http://www.studymode.com/essays/Boiler-Experiment-1059371.html
5/http://www.gunt.de/networks/gunt/sites/s1/templates/scripts/picDetail.php?actEntry
=3436&lang=1&dir=06020400&src=Zeichnung.jpg&color=FF6633&software=0
6/http://answers.yahoo.com/question/index?qid=20071016234129AAM7qEX
http://yoursteacher.blogspot.com/2012/05/marcets-boiler.html
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