This Experiment Marcet Boiler Engineering Essay

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In This experiment Marcet boiler was used to conduct the relationship between a saturated pressure and temperature of water in the range of 0-14 bar indicating in the gauge and also to determine the temperature of a body when being heated or cooled. When the temperature increases pressure also increases in this case the relationship between pressure and temperature is directly proportional. Assumption was made that the temperature is uniform throughout the boiler and the outside surface temperature of the boiler is the same as the steam temperature. Theoretically, the values from the steam table should almost be the same with the recorded values. In this case, if the values are not the same then this is due to error that was made in the experiment.

The experiment was performed carefully and all procedure was followed to get accurate result. First of all the startup procedure is to fill water in Marcet boiler and the water level is half of the boiler's height. Then the supply switch was turned on. It is important to remove the air in the boiler in this case the valve would be open from the start up of the experiment When the temperature increases to 100°C, the steam is allowed to come out from the valve for few seconds and close the valve. Record the steam temperature and pressure reaches 14 bars.

Introduction

Thermodynamics is the study of heat and in relation in other form of work and energy between a system and its surrounding; in this case the property in the system will change.

Generally ideal gas obeys the equation of state which is showed below.

PV=

When energy is increased in the water .the molecules in the water that is increasing will enable the molecules to escape from the surface until it is in equilibrium (boiling point). The state of equilibrium depends on the pressure in the surface of the water. When the pressure is low it is easier for the molecules to leave the water with less energy.

The Marcet boiler is used to investigate the relationship pressure and temperature in saturated steam for comparison with the steam table .the experiment slope (dT/dp) is obtained water at saturated temperature

Theory

The Marcet boiler is used to investigate the between pressure and temperature of saturated steam, in equilibrium with water, at all pressures between atmospheric and a 14bar 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.

and hf + hfg = hg  hf

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

Equipment

Procedure

Fill up water half the height of the boiler

Ensure the valve is opened

Connect the boiler to the electrical switch

The boiler is heated up to 100°c and the steam will come out of the open valve

Close the valve after 1 minutes to ensure that the air in the boiler is out and continues heating

When the pressure start rising , start the stop watch

Record all the temperature readings at different pressure with time

Pressure must not exceed 14 bar

Result

Original table from the lab

20121108_130229.jpg

Temperature

Pressure

TIME

Average

TEMPRETURE

MEASURED SLOPE

CALCULATED SLOPE

ERROR

PERCENTAGE

T (°c) increase

P(bar) gauge

P(bar)

absolute

vg

dp

dT

dt/dp

Tvg

hfg

%

107.2

1.3

2.3

0.777188

98.06

0

83.31

2238

0.0372

0

120.3

2.0

3

0.605864

98.06

0

72.88

2202

0.0331

0

138.8

2.5

3.5

0.524266

98.06

0

2164

0

133.6

3.0

4.0

0.462456

98.06

0

61.78

2164

0.0286

00

151.9

5.0

6.0

0.315626

98.06

0

47.94

2108

0.0227

0

155.5

5.5

6.5

0.292629

98.06

0

45.50

2097

0.0216

0

158.9

6.0

7.0

0.272810

98.06

0

43.35

2086

0.0207

0

162.0

6.5

7.5

0.255547

98.06

0

41.39

2076

0.0199

0

165.0

7.0

8.0

0.240370

98.06

0

39.66

2066

0.0192

0

167.8

7.5

8.5

0.226918

98.06

0

38.07

2057

0.0185

0

170.5

8.0

9.0

0.214912

98.06

0

36.64

2048

0.0179

0

173.0

8.5

9.5

0.204126

98.06

0

35.31

2039

0.0173

0

175.4

9.0

10.0

0.194383

98.06

0

34.09

2031

0.0168

0

177.7

9.5

10.5

0.185536

98.06

0

32.97

2023

0.0162

0

179.9

10.0

11.0

0.177466

98.06

0

31.93

2015

0.0158

0

182.1

10.5

11.5

0.170074

98.06

0

30.97

2008

0.0154

0

184.1

11.0

12.0

0.163277

98.06

0

30.05

2000

0.0150

0

186.1

11.5

12.5

0.157005

98.06

0

29.22

1993

0.0147

0

188.0

12.0

13.0

0.151199

98.06

0

28.425

1986

0.0143

0

189.9

12.5

13.5

0.145808

98.06

0

27.688

1979

0.0130

0

191.7

13.0

14.0

0.140789

98.06

0

26.989

1973

0.0137

0

196.7

13.5

14.5

0.136104

98.06

0

26.772

1953

0.0137

0

195.1

14.0

15.0

0.131721

98.06

0

25.69

1960

0.0131

0

Calculation

Formula used

Pv=

m = mass

M = molecular weight

P = pressure

V = volume

R = molecular gas constant

T = temperature

Plot the graph for T and P

Discussion

The theory can be compared with the experiment where pressure and temperature are directly proportional to each other

When a water is heated in a container to a boiling point the tempreture increases and presussre also increase in the case where the steam is closed in a cylinder, Their will be internal pressure in the container and also internal forces. it is shown in the graph that tempreture is relatively proportional to pressure

In the table error was zero because the decreasing tempreture of the boiler was not noted down therefore erro is unknown . assuming the decreasing tempreture is considered the the error percentage would now exceed 10% because the experiment was done in a closed system so no amount of volume will escape

It was important to remove the air from the boiler to avoid flaws of readings .

Marcet boiler is used in plant steam industries, power plant, cooking utensil and so on

Conclusion

in the experiment, it shows from the table and theory that temperature and pressure is relatively proportional in balance with water

Disgracing some negligible faults, this experiment can be consider successful, to improve the result of the experiment, it should be carried out at room temperature switching off all the air-conditions, and also by repeating the experiment and taking the average value. If some insulation were kept on theMarcet boiler to reduce heat loss, the experiment could be more accurate

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