Marcet Boiler 3w1u5

Chemical Engineering laboratory II

SEGi University

MARCET BOILER

Candidate’s Name:

Yaser Hasan Murshed

Candidate’s ID:

SCM-022930

Group :

1- Mohammed Ameen 2- Hemyar Ahmed 3- Ameen

Supervisor’s Name: Mr. Ir Choo Date of Submission: 12/Aug/2014

1.0 Abstract : There were two objectives of this experiment. The first was to find the relationship between pressure and temperature of saturated steam in equilibrium. The second objective of the experiment was to find out the vapor curve. In this experiment Marcet boiler was used as the apparatus. The Marcet boiler filled with water was heated first, until a certain absolute pressure reached. Then the heater was turned off and was allowed to cool down to its initial temperature. The increasing and decreasing temperature were recorded for further use and calculation of the experiment. 2.0 Introduction: The Marcet boiler is the unit for demonstration of basic principle in thermodynamics studies which is the boiling phenomenon. Initially the discovery of the phenomenon was founded by Rudolf clausius, A German physicist that was a thermodynamics icon. Marcet boiler is also a device that is used for the understanding of the basic properties of saturated steam to superheated steam. It consists of cylinders surrounded with isolated substance in electrically heated boiler which is used to heat up water and to measure both the temperature and pressure. Marcet boiler also contains thermometer, Barometer and safety valve. The saturation pressure curve can be determined at the pressure within 10bar. Thermodynamics is a part of physics, which deals with work, energy and power of a system. Thermodynamics mainly works with large-scale system, which can be measured by experiment study of liquid or gas. The properties of fluid is also a part of thermodynamics. Most thermodynamics substance such as gasses and vapors are often referred as p-v-t substance which is absolute pressure (p),volume (V) and absolute temperature (T). An ideal gas obeys the equation of state that relates the pressure, specific volume or density, and absolute temperature with mass of molecule and the gas constant, R.

PV 

mRT M

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 10 bars. The experimental slope (dT/dP) SAT obtained is compared to the theoretical value determined through calculation from the steam table. ClausiusClapeyron states:

 dT     dP   dT     dP 



Tv fg h fg

SAT



T (v f  v g ) h f  hg

SAT

Where,

h f +hfg =hg h fg =hg −h f  dT     dP 

 SAT

T (v f  v g ) h fg



Tv g h fg as vg >> vf

In which, vf = specific volume of saturated liquid vg = specific volume of saturated vapor hf = enthalpy of saturated liquid hg = enthalpy of saturated vapor hfg = latent heat of vaporization

3.0 Apparatus: HE169 Marcet boiler which shown in Figure 1

a. Pressure transducer b. Temperature controller/Indicator c. Pressure indicator d. Control e. Bench f. Bourdon tube pressure gauge g .Temperature sensor h. Pressure relief valve i. Water inlet port & valve j. Heater

F

a h b g c

i

d

j e

Figure 1: HE169 Marcet boiler

4.0 Procedures: 1. The power supply switch was turned on. 2. The boiler was initially filled with water; the valves were opened at the level side tube to check the water level. No additional distilled water was filled. Then, the valves were closed. 3. The temperature controller was set to 185°C, which was slightly above the expected boiling point of the water at 10 bar (abs). 4. The valve at feed port was opened and the heater was turned on. 5. The steam temperature rising was observed as the water boiled. 6. Steam was allowed to come out from the valve for about 30 seconds, and then the valve was closed. 7. The steam temperature and pressure was recorded when the boiler was heated until the steam pressure reached 10 bar (abs). 8. After that, the heater was turned off and the steam temperature and pressure began to drop. The boiler was allowed to cool down to room temperature. 9. The steam temperatures at different pressure readings were recorded when the boiler was heated and cooled. 10. The heater was switched off and the boiler temperature was allowed to drop.

5.0 Results: Pressure, P Absol ute (bar)

Gauge (kgf/c m2)

1.0

0.0

1.5

0.25

2.0 2.5

0.75 1.4

3.0

2.0

3.5

2.5

4.0

3.2

4.5

3.5

5.0

4.0

5.5

4.25

Temperature, T Incre ase 0

( C) 100. 1 111. 3 120. 5 127. 6 133. 5 138. 9 143. 6 148. 0 152. 0 155. 5

Decre ase 0

( C)

100.1 111.5 120.5 127.3 133.5 138.9 143.6 148.0 151.9 155.5

Measu

Avera Avera ge Tavg(

ge 0

Tavg(K

C) ) 100.1 373.1 0 0 111.4 384.4 0 0 120.6 393.6

red slope

Calculate

Error

d slope

percent

Tvg/hfg

age %

dT/dP

0.226

0.2768 0.2008 11.15

0.184

0.1573

0 0 127.4 400.4

0.137

0.1323

5 5 133.5 406.5

0.121

0.1143

0 0 138.9 411.9 0 0 143.6 416.6 0 0 148.0 421.0 0 0 151.9 424.9 5 5 155.5 428.5 0

0

14.51 3.43 5.53 0.108

0.1010 6.48

0.094

0.0906 3.61

0.088

0.0823 6.47

0.079

0.0756 4.30

0.071

0.0702 1.13

6.0 6.5

5.0 5.5

7.0

6.0

7.5

6.5

8.0

7.0

159.

158.9

0 162.

162.0

0 165.

165.0

1 167.

167.8

7 170.

170.3

3

158.9 431.9

0.069

0.0654

5 5 162.0 435.0

0.061

0.0620

0 0 165.0 438.0

0.061

0.0579

5 5 167.7 440.7 5

5 443.3

170.3

5.22 0.02 5.08 0.054

0.0549 1.66

0.051

0.0523

0

2.55

5.1 Calculations :

 Sample calculation for absolute pressure of 200 kPa: For error prcentage:

Error Percentage=

Measured Slope−Calculated Slope ×100 Measured Slope

Error Percentage=

0.184−0.1573 ×100 =14.51 0.184

For measured slope:

|¿|

¿

|¿|

¿ 1¿ 2¿ P¿ T 2 ( K )−T 1 ( K ) dT = ¿ dP SAT

( )

( dTdP )

=

SAT

393.6 K −384.40 K =0.184 200 kPa−150 kPa

For calculated slope:

( dTdP )

SAT

=

T vg hfg

T v g 393.6 K ×0.88578 = =0.1573 h fg 2706.59−505.698

5.2 Graphs:

Absolute Pressure (Bar) 460 440 420 400

Tempreture (K)

Tempreture

380 360 340 320

0

1

2

3

4

5

6

7

8

Absolute Temperature, T versus Absolute Pressure, P

Figure 2: Absolute pressure vs. Temperature gas behavior

9

Absolute Pressure 0.3 0.25 0.2 Measured slope and Calculated slope

Measured

0.15

Calculated

0.1 0.05 0

0

1

2

3

4

5

6

7

8

9

Measured Slope, (dT/dP)SAT and Calculated Slope, (Tvg/hfg) Vs. Absolute Pressure, P

Figure 3: Absolute Pressure vs. Measured and Calculated lopes

6.0 Discussions: From the results obtained it was noted when pressure increased, temperature also increased. Slopes calculation on the other hand, was calculated to understand the behavior of temperature as pressure changed. Before the conduction of the experiment it was important to remove air from the boiler. The reason lies on inaccuracy that may occur if air was to be inside the boiler. Air may also results in the corrosion of the boiler. Water was initially at liquid phase. When water accumulated enough energy, it will turn into vapor phase via evaporation. This is the reason why Marcet boiler is used as water boiler, gasifier and also power plant in the industries. Figure 2 illustrates the trend of the behavior of the gas. It was noted that when the temperature increased the pressure also increased thus, a proportional relationship. This was due to the faster movement of gas

particles disassociated that therefore, escaped to gas form caused by the increased temperature. While figure 3 showed an inverse relationship between pressure and the slopes, as pressure increased, measured and calculated slopes decreased. Since the experiment was conducted under closed system condition thus, error percentage is said to be less than 10% however, at the second point error was above that and that owed to the procedures error. The discrepancy shown in figure 3 between both slopes is related to the fact that for calculated slope energy loss occurred however, it is always neglected when talking theoretically. There are few things that must be taken in order to avoid such errors. Firstly, the valve at the level sight tube must always be closed before turning on the heater as the sight tube is not designed to endure high pressure and temperature. Another important thing to keep in mind is to wait for 30 seconds to remove the air from the boiler as the accuracy of the experimental results will be affected when air is present. Some more, the steam should not be released during the experiment as it will greatly affect the results obtained. It will cause an increase in pressure and thus causing an increase in temperature. Last but not least, the valve should not be opened when the boiler is heated as pressurized steam can cause severe injury. 7.0 Conclusion: After this experiment, we concluded that the temperature of saturated steam is directly proportional to pressure in equilibrium with water. Both the measured slope and calculated slope were almost the same except for a few deviations. These deviations can be minimized by taking precautions. 8.0 References:



Scribd. 2012. Marcet Boiler. [ONLINE] Available at: http://www.idoub.com/doc/93324504/Marcet- Boiler. [Accessed 21



November 14] Water-tube boiler - Wikipedia, the free encyclopedia. 2014. Water-tube boiler Wikipedia, the free encyclopedia. [ONLINE] Available at:http://en.wikipedia.org/wiki/Water-tube_boiler. [Accessed 21 November



2014]. Marcet boiler . 2014. Marcet boiler . [ONLINE] Available at:http://www.slideshare.net/ShwanSarwan/marcet-boiler. [Accessed 21



November 2014] This Experiment Marcet Boiler Engineering Essay. 2014. This Experiment Marcet Boiler Engineering Essay. [ONLINE] Available at:http://www.ukessays.com/essays/engineering/this-experiment-marcetboiler-engineering-essay.php. [Accessed 22 November 2014].