STUDENT NAME STUDENT ID COURSE LECTURER SUBMISSION DATE SUBJECTMD ATIQUR RAHMAN FAISAL SCM-012154 BACHELOR IN MECHANICAL ENGINEERING DR. THAM 7th May 2012 THERMODYNAMICS (EAT 106) Marcet Boiler Experiment Title Introduction : Marcet Boiler Experiment : 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 or the properties of fluid is also a part of thermodynamics. : The experiment is going to be carried out to demonstrate the relationship between the pressure and temperature of saturated steam in equilibrium. Marcet boiler is going to be used as apparatus. The Marcet boiler filled with water is to be healed first, until a certain absolute pressure reached. Then the heater will be turned off and will be allowed to cool down to its initial temperature. The increasing and decreasing temperature will be recorded for further use and calculation of the experiment. Abstract Objective : Demonstrating the relationship between pressure and temperature of a saturated steam in equilibrium with water and determining the pressure vapor curve. : As we know about ideal gas law and how they behave. The ideal gas equation states that, relates the pressure, specific volume or density and absolute temperature with the mass of molecule and gas constant “R”. = Theory Where, P= absolute pressure. V=volume. n= amount of substance in moles. Where, n= R= ideal gas constant. T= absolute temperature in Kelvin. In real life, real gas never exactly follows or obeys the equation. If a few changes are allowed on the ideal gas equation of state, then it can be applied on the properties of real gas. When energy increases within water, the water molecules with the water gets excited and try to escape from the water in the form of steam. It’s easier for the molecules to escape, if the pressure is low. MD Atiqur Rahman Faisal Page 2 Marcet Boiler Experiment The temperature at which the equilibrium state is reached (boiling point) at a given pressure is called saturated temperature, and the pressure where saturated equilibrium occurs at given temperature is called saturated pressure. Marcet boiler is used to investigate the relationship between the pressure and the temperature of saturated steam in equilibrium with water at all temperature levels between the atmospheric pressure and 8 bars. The measured value of the slope of the graph * + obtained from the practical result can be compared with corresponding values calculated from the data in steam tables. Clausius-clapeyron states: * + * + Where, = = as, ( ) In which, specific volume of saturated liquid. specific volume of saturated vapor. latent heat vaporization. enthalpy of saturated liquid. enthalpy of saturated vapor. MD Atiqur Rahman Faisal Page 3 Marcet Boiler Experiment Apparatus : The unit consists of a stainless steel pressure vessel fitted with highpressure immersion electric heater. The unit also comes with a safety relief valve, temperature and pressure measuring devices. Water feed port is installed to allow water charging. The unit also includes temperature and pressure transducer, so that it is easy to read the respective valves on the digital indicator. The water heater is protected from burnout by setting the maximum operating temperature with temperature controller. Figure: Marcet Boiler MD Atiqur Rahman Faisal Page 4 Marcet Boiler Experiment Procedure : 1. A quick inspection is performed before starting the experiment to ensure the units is in proper operating condition. 2. The Marcet boiler is connected to the nearest power supply. 3. The valves at the feedport are now opened. 4. The boiler is filled with distilled water at about half of boiler’s height through the feedport. 5. The valve at the level sight tube is then closed. 6. The power supply is then turned on, to start the experiment. Precaution : 1. The temperature controller is set to 185.0oc, that is slightly above the expected boiling point of water at 10bars (abs). 2. The valve at the feed port was opened while the heater was turned on. 3. The valve at the level sight tube are made sure to be closed before turning on the heater as the sight tube is not designed to withstand high pressure and temperature. 4. The rise of the steam temperature could be observed when the water boils. 5. The steam from the valve was allowed to come out for 30 seconds before the valve was closed (this step is very important to remove the air from the boiler as the accuracy of the experiment results would be significantly affected if air is present). 6. The steam temperature, gauze pressure at 1.00bar (abs) and time taken for steam to reach until 8.00bar (abs) is recorded. 7. After the experiment, the heater is allowed to cool down to room temperature. 8. The time taken for the heater or boiler to cool down is also recorded. 9. All the readings of result are recorded and tabulated on a table. 10. Graph is plotted at absolute temperature “T” against absolute pressure “P”. 11. The slope of the graph is measured using certain points. 12. Another graph* + vs. P, [ ] vs. P, is plotted. 13. The graph plotted from experiment data is compared to that of the calculated data. MD Atiqur Rahman Faisal Page 5 Marcet Boiler Experiment Obtained data : Pressure, P(bar) Absolute 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 Gauze 0 0.5 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 (abs) 101 150.03 199.06 248.09 297.12 346.65 395.18 444.21 493.24 542.27 591.3 640.3 689.36 738.39 787.42 Increase, 0C 100.0 111.2 120.1 127.4 133.6 138.9 143.7 148.0 152.1 155.9 159.3 162.5 165.4 168.2 170.8 Temperature, T Decrease, 0C 99.7 111.3 120.2 127.9 134.1 139.5 144.3 148.6 152.6 156.2 159.6 162.7 165.6 168.4 170.8 Average, 0C 99.85 111.25 120.15 127.65 133.85 139.20 144.00 148.30 152.35 156.05 159.45 162.60 165.50 168.30 170.80 Average, K 372.85 384.25 393.15 400.65 406.85 412.20 417.00 421.30 425.35 429.05 432.45 435.60 438.50 441.30 443.80 Measured Slope. (dT) (dP) [ ] 0.20 0.17 0.14 0.12 0.10 0.09 0.08 0.08 0.07 0.07 0.06 0.06 0.05 626.42 447.65 348.99 287.35 244.76 214.43 191.19 173.03 157.76 145.06 134.58 125.84 118.18 111.52 105.81 2256.8 2226.28 2190.82 2180.47 2162.46 2146.67 2132.22 2119.04 2106.37 2094.64 2083.76 2073.47 2063.92 2054.17 2046.06 Calculated Slope. [ 0.28 0.20 0.16 0.13 0.11 0.10 0.09 0.08 0.08 0.07 0.07 0.06 0.06 0.05 0.05 ] Error Percentage % 20.3 16.40 13.70 11.55 10.15 9.10 8.35 7.75 7.10 6.55 6.05 5.70 5.30 98.06 98.06 98.06 98.06 98.06 98.06 98.06 98.06 98.06 98.03 98.06 98.09 98.10 0 5.88 7.14 8.33 0 0 0 0 0 0 0 0 0 Calculation Equation used : m mass(grams) M molecular weight(grams/mol) P Pressure(Kpa) V volume(m3) R molar gas constant(J/mol K) T temperature(K) Things to do : Plotted graph, T vs P. Calculate gradient of graph. Graph * + vs P, and [ ] vs P. Compare graph plotted from experiment data to that of calculated data. MD Atiqur Rahman Faisal Page 6 Marcet Boiler Experiment T vs P 500 450 400 350 300 250 200 150 100 50 0 0 200 400 600 800 1000 y = 0.0965x + 374.09 R² = 0.953 T vs P Linear (T vs P) Gradient = 0.0965 0.3 0.25 0.2 0.15 0.1 0.05 0 0 200 400 600 800 1000 (dT/dP)sat vs P (Tvfg/hfg) vs P MD Atiqur Rahman Faisal Page 7 Marcet Boiler Experiment Sample calculation: Taking the values of fourth row, Calculation, For the temperature 127.650C (from the saturated water- Temperature table) Calcultion, For the temperature 127.650C (from the saturated water- Temperature table) Calculation, MD Atiqur Rahman Faisal Page 8 Marcet Boiler Experiment [ ] Calculation, [ ] Calculating the value of P(abs) at the temperature 120.150C, Calculating the values of P(abs) at the temperature 133.850C, Calculating the value of Calculating the value of T(K) at 120.150C Calculating the value of Calculating the value of * + [ ] and [ ], error percentage. Calculating the difference between * + MD Atiqur Rahman Faisal Page 9 Marcet Boiler Experiment Discussion : Marcet boiler was made by Nathan Chamberlain, Boston, USA, in the year 1850. He made this boiler for measuring the vapor pressure of saturated liquid. Later this Marcet boiler was used to study the evaporation filtration of water. Pressure and temperature are two fundamental quantities of materials in thermodynamics. These two factors have relation directly proportional to each other. When a container contains saturated liquid and are heated to it’s boiling temperature, the liquid will be changing it’s state from liquid to steam. If the steam are not allowed to escape from the container, their internal pressure will increase. Because, when the liquid becomes gas by heating, the internal molecular energy will increase and the atoms will be more excited. All the excited atoms will hit each other and split with more speed or velocities. As their mass remains constant, so their forces on each other will increases. And when their forces on them increases, and are not allowed to occupy more area, they exerts pressure on the container, which gradually increases with temperature. Hence it is calculated and proved from the graph, that temperature is directly proportional to the pressure. The error percentage should not cross or exceed 10%, as the experiment was done in enclosed surface and no volume of experimenting samples are allowed to escape from the system. That is done in closed system. It is important to remove gas at the beginning to avoid the flaws of reading due to pressure difference. Marcet boiler is being used as water boiler, gasifier, powerplant, cooking utensils, steam plant industries, etc. Conclusion : From the experiment, it is found from the graph and calculation, temperature of a saturated steam is directly proportional to the pressure in equilibrium with water. The percentage error on the experiment for first two values were found higher than those third value and onward. This happened due to take improper reading from the pressure gauze and some technical fault. The rest of the result for percentage error are found “O” zero percent, which is also not practically possible. This happened due to taking the two figure after decimal, which reduce the contrast of the reading. 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 the Marcet boiler to reduce heat loss, the experiment could be more accurate. MD Atiqur Rahman Faisal Page 10