ESO201A: Thermodynamics First Semester 2015-2016 Mid-Semester Examination Instructor: Sameer Khandekar Time: 120 mins Marks: 250 Solve sub-parts of a question serially. Question #1 (60 marks): One kmol of an ideal gas, initially at T 1, P 1 and V 1 (State #1), is allowed to expand to twice its initial volume in a reversible isothermal process. (a) What is the amount of heat added to the system during this process? Subsequently, the system is brought back to its initial State #1, by first undergoing a constant volume process, followed by a reversible adiabatic process. (b) Will the constant volume process be one of cooling or of heating (give reasons for your answer)? (c) Draw a P-v diagram of the entire cycle. (d) Find the work done by the system in the entire cycle if γ = 2.0. Question #2: 80 marks A nuclear reactor core containing 1 m 3 of saturated water at 20 MPa is enclosed inside a containment room, as shown in the figure. The room is well insulated and evacuated with valve closed. Due to a severe accident, the reactor core ruptures and water fills the containment. Find the containment room volume so that the final pressure is 300 kpa. insulated Containment room (Initially evacuated) valve Question #3: 70 marks Reactor core with 1 m 3 of water An adiabatic air compressor is to be powered by a directcoupled adiabatic steam turbine that is also driving a generator. Steam enters the turbine at 12.5 MPa and 500 C at a rate of 25 kg/s and exits at 10 kpa and a quality of 0.92. Air enters the compressor at 98 kpa and 295 K at the rate of 10 kg/s and exits at 1 MPa and 620 K. Determine the net power delivered in MW to the generator by the turbine. State all assumptions you have made while solving. (Take C p of air = 1.005 kj/kgk) 1 MPa 620 K Air Compressor 98 KPa, 295 K 10 kg/s 12.5 MPa, 500 C 25 kg/s Steam Turbine 10 kpa Gen Set
Question #4: 40 marks (02 marks for the correct answer and -1 mark for the wrong answer.) For the statements below, write /, as the case may be. Solve this question in the regular answer sheet; not here, by clearly writing Answer #1: or, as the case may be. 1. A constant volume ideal gas process is equivalent to a polytropic process with the exponent n (PV n = constant) tending to infinity. 2. For a closed system undergoing a cycle, entire amount of heat supplied can be converted to net work output. 3. For an ideal gas, ( h T ) p ( u T ) v = 0 4. Enthalpy of an ideal gas is a function of temperature only. 5. In general, for all common solids, the term (vdp) is significant. 6. For monoatomic gases, the value of gamma, the specific heat ratio, is equal to 1.4. 7. The specific heat of gases, for noble gases, such as Ar, He, Ne, Kr, etc., is independent of temperature. 8. For steady incompressible flows, the conservation of volume flow rate is equivalent to conservation of mass flow rate. 9. The exit velocity of a diffuser is usually small as compared with the inlet velocity (for usual engineering systems operating with subsonic flows). 10. A positive Joule-Thomson coefficient indicates that the gas will cool down when it passes through a throttling device. 11. The density ratio ρ vapor / ρ liquid of a pure substance approaches a value equal to unity when approaching the critical conditions. 12. If air pressure is continuously increased inside an adiabatic chamber filled with leafy vegetables, they will eventually cool down. 13. The correction term a/v 2 in the van der Waals equation, accounts for intermolecular forces in real gases. 14. If energy and mass, both cannot cross a system boundary, it is called as a stationary system. 15. A gas turbine produces net work at the expense of the kinetic energy of the working fluid. 16. If the product PV of a gas decreases during a throttling process, its internal energy and temperature will decrease due to throttling. 17. A high temperature (T R > 2), ideal gas behavior can be assumed with good accuracy regardless of pressure (except when P R >> 1) 18. If shear stress exerted by a flowing fluid on the wall is proportional to the velocity gradient at the wall, the SI units of the proportionality constant is (Pa/s) 19. For substances that have a triple point pressure above the atmospheric pressure, sublimation is the only way to change from solid to vapor phase at atmospheric pressure. 20. The principle of corresponding states stipulates that the Z-factor of all the gases is the same at a given reduced pressure and temperature.