Thermodynamics lab report - This report is meant to be written for a reader who does not have in-depth knowledge of the subject so all working must be included/ all equations must be stated and...

AIM AND THEORY
AIM
The aim of the experiment is to investigate the various factor which affects the efficiency of the Stirling engine during operation
THEORY
Introduction:
Stirling engine is the alternative to the steam engine which falls under heat engine but relatively safer than the steam engine. It was invented by Robert Stirling in the year 1816 which was first working hot air engine. In this engine the heat energy is extracted and converted into mechanical energy by cyclic compression and expansion of gas. It is a closed system where the mass transfer and energy transfer to the environment is zero in an ideal case. The change in pressure causes the motion of piston leading to expansion and compression of the working fluid or gas. The Fig 1 shows the displacer type Stirling engine and naming of parts.
Crank shaft
Flywheel
Power cylinde
Bottom plate
Top plate
Displacement piston
Fig 1. Displacer type Stirling Engine
The four stage of operation are expansion, cooling, compression and heating.
When the gas is near the bottom plate it is heated due to which pushes the displacement piston up and power piston down. In this stage the expansion of gas takes place in return rotating the flywheel. When the flywheel rotates the power piston moves up.
While the displacing piston moves down the hot air is pushed towards the top plate which is relatively colder.
When the air cools down the pressure decreases and while the power piston moves down it compresses the gas resulting in increase in pressure and this gas is transfe
ed to bottom plate where it is again heated.
The Fig 2 shows the step by step process of operation of Displacer type Stirling engine.
Fig 2. Operation of displacer type Stirling engine
The PV diagram for Ideal Stirling engine is shown in the Fig 3 and that of real Stirling engine is shown in the Fig 4.
Fig 3. Ideal Stirling engine Fig 4. Actual Stirling cycle
1-2: Represents Isothermal Expansion
2-3: Represents isochoric Cooling (Heat rejection)
3-4: Represents Isothermal Compression
4-1: Represents Isochoric Heating (heat addition)
Efficiency is the ratio of output energy to the input energy. This indicates what amount of mechanical work (energy) is produced with the given amount of heat.
……………….(i)
As we know energy is conserved hence Heat Input (, Heat Rejected ( and Work output (W) can be linked as follows
· W=……………………….(ii)
Substituting equation (ii) into equation (i) we can also write
= 1-
Carnot cycle is the maximum efficiency cycle and the efficiency of the carnot engine operating between is given by
= 1-
Power output is to be calculated which is the ratio between the work done and time. Which shows the rate of doing work.
Power (P)=
Note: Workdone can also be calculated by the area under the curve since
W=
Guided Activity
We first take all the material and assemble all them with the experiment. The main aim of the experiment is find the factor which effects the efficiency of the sterling operation. In this experiment the software is used to find the pressure of the working piston at different displaced volume in cycle. By using area under the PV diagram we can find the actual heat taken by the system and actual work which helps to find the efficiency of the engine. We try to compare this efficiency with Carnot efficiency and will try to find the energy which is going to waste and which can be used for the betterment of the efficiency of the engine
MATERIALS
1. CASSY board and software used for plotting PV curve and finding area under curve
2. Pump for flow of water to pipes
3. Stirling engine: It is used to get powe
4. Optical Distance Sensor: Used to find the distance between the piston and TDC. It helps to find the volume of the displaced cylinde
5. Thermometer: It is used to measure temperature so that we can find carnot efficiency by find temperature of the hot and cold reservoi
6. Heater: It is used to the heat the water and that hot water helps to transfer to the heat to the bottom element of the displaced piston chambe
7. Transformer: It is used to varies the voltage of the heater so that we can varies the actual heat input
8. Pressure Sensor: To measure pressure inside the working piston cylinde
9. Sensor for reading RPM of flywheel:
The Fig 5. Shows the experimental setup for the Stirling cycle experiment
Fig 5. Experiment setup of Stirling cycle
METHOD
1. Turn on the CASSY board and CASSY software. To check the software has been started a dialogue box must appear, on clicking
2. Manually rotate the flywheel and check the measured path by sensors are lying on the specified range.
3. Check the water pump and temperature of the water initially
4. At 12 Volts turn on the transformer, run the flywheel with your hand and let it reach the steady state.
5. Click on the stopwatch icon and record the data.
6. Record the data by pasting it on notepad.
7. With the help of CASSY software the area enclosed can be found out. To do that choose ‘Calculate Integral’ ‘Peak Area’
8. Do the same for different voltages (6V, 8V, 10V)
9. After the experiment is done turn of the heater and close the power supply. Let the water to flow for around 30 minutes to avoid overheating of the plate
The water pump was switched on helping to circulate the water for heat transfer to the lower plate. The heater was switched on which heated the water. For different voltage of heater the time to reach the higher temperature was noted down. When the flywheel was given initial momentum due to the heated working fluid inside the engine the Engine starts to run. When the engine became steady the reading of pressure, position of working piston and position of displacement piston was plotted in the monitor. With the help of these data’s the plots between PV curve was plotted and the Area under curve was calculated using the same software (CASSY).
The area found out using the...