Lab 7 - Marcet Boiler-1
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MEHB 471: Heat Transfer & Applied Thermodynamics Lab. Lab 7: Marcet Boiler 7.1 Objective: The main goal of this experiment is to obtain a balance relationship between temperature and pressure of saturated steam for water at all pressure levels between atmospheric pressure and 10 bars (150 lb/in 2 ). Then, the experimental value for the slope of the graph (dT/dP) SAT is compared to the theoretical value found in the steam table. 7.2 Introduction: Thermodynamics is defined as a study related to the transfer of heat and work between a system and its surrounding, undergoing a process causing any of the properties of the system change. 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. 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. 20
Transcript of Lab 7 - Marcet Boiler-1
MEHB 471: Heat Transfer & Applied Thermodynamics Lab.
Lab 7: Marcet Boiler
7.1 Objective:The main goal of this experiment is to obtain a balance relationship between temperature
and pressure of saturated steam for water at all pressure levels between atmospheric pressure and 10 bars (150 lb/in2). Then, the experimental value for the slope of the graph (dT/dP)SAT is compared to the theoretical value found in the steam table.
7.2 Introduction:Thermodynamics is defined as a study related to the transfer of heat and work between a
system and its surrounding, undergoing a process causing any of the properties of the system change.
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.
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. Clausius-Clapeyron states:
and hf + hfg = hg hfg = hg - hf
as vg >> vf
in which, vf = specific volume of saturated liquid
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vg = specific volume of saturated vaporhf = enthalpy of saturated liquidhg = enthalpy of saturated vaporhfg = latent heat of vaporization
7.3 Procedures:1. Connect the unit to the power supply to provide a heating rate of 2kW to the electrical
heater.2. Open the level valve open and switch on the power supply.3. Set the temperature 'setpoint' to 1800C.4. Wait for the steam output through the level valve to ensure that there is no air trapped in the
boiler.5. Close the level valve and continue heating until the maximum gauge pressure reaches 8 bars.6. Warning: Don't remove filler plug or open level valve when the device is pressurized.7. Decrease the temperature 'setpoint' to room temperature in which the electrical heater will be
off.8. Record all temperature readings at different pressure settings of the boiler when the boiler is
heated and cooled.
7.4 Questions:
1. Complete Table 1 attached.2. Plot the graph of temperature, T, versus absolute pressure, P.3. Plot dT/dP versus P and Tvg/hfg versus P on a same graph.4. Compare and discuss the graph plotted from experiment data to that of the calculated data.5. Discuss any discrepancy and sources of error of the experiment.6. Why is it necessary to ensure no air trapped within the device at the beginning of the
experiment?7. Discuss the liquid and vapor behavior observed through the experiment and list some
examples of its industrial applications.
Attachments:
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Atmospheric pressure : _____________ barAtmospheric temperature : _____________ (0C)
Table 1: Data Collected and Calculated Results
Pressure, P (bar) Temperature, T Measured
Slope, dT/dP
Calculated Slope, Tvg/hfgabsolute Gauge Increase
(0C)Decrease
(0C)Average Tavc (0C)
Average Tavc (K)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
Table 2: Saturated Water and Steam Tables
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PressureP
Bars (Abs)
TemperatureT
0C
Specific Volumeof Steam, vg
m3/kg
Latent Heat ofVaporization, hfg
kJ/kg
1.0 99.6 1.694 2258
2.0 120.2 0.8856 2202
3.0 133.5 0.6057 2164
4.0 143.6 0.4623 2134
5.0 151.8 0.3748 2109
6.0 158.8 0.3156 2087
7.0 165.0 0.2728 2067
8.0 170.4 0.2403 2048
9.0 175.4 0.2149 2031
10.0 179.9 0.1944 2015
11.0 184.1 0.1774 2000
12.0 188.0 0.1632 1986
13.0 191.6 0.1512 1972
14.0 195.0 0.1408 1960
15.0 198.3 0.1317 1947
16.0 201.4 0.1237 1935
17.0 204.3 0.1167 1923
18.0 207.1 0.1104 1912
19.0 209.8 0.1047 1901
20.0 212.4 0.09957 1890
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