BME-A PREVIOUS YEAR QUESTIONS

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BME-A PREVIOUS YEAR QUESTIONS CREDITS CHANGE ACCHA HAI TEAM UNIT-1 Introduction: Introduction to Thermodynamics, Concepts of systems, control volume, state, properties, equilibrium, quasi-static

1 BME-A PREVIOUS YEAR QUESTIONS CREDITS CHANGE ACCHA HAI TEAM UNIT-1 Introduction: Introduction to Thermodynamics, Concepts of systems, control volume, state, properties, equilibrium, quasi-static process, reversible & irreversible process, cyclic process. Zeroth Law and Temperature, Ideal Gas. Heat and Work. 1. Define and classify thermodynamic system and thermodynamic properties ( 2015) 2. Explain the similarities between work transfer and heat transfer. ( 2015) 3. What is thermodynamic system and explain the various types of thermal equilibrium. (2013) 4. If a gas of volume 6000 cm 3 and a pressure of 100 kpa is compressed quasi statically according to PV 2 = constant until the volume becomes 2000 cm 3. Determine the final pressure and work transfer. (2013) 5. Differentiate between (i) microscopic viewpoint and macroscopic viewpoint (ii) reversible process and irreversible process.(2012) 6. Explain the following: I) concept of continuum Ii) point function and path function Iii) gauge pressure (2012) 7. I) define thermodynamic equilibrium(2010,2011,2012) ii) what is a quasi-static process? What are the causes of irreversibility in a process? (2011,2010) 8. A fluid at a pressure of 3 bar and with specific volume of 0.18 m 3 /kg is contained in a cylinder behind a piston. The fluid expands reversibly to a pressure of 0.6 bar according to law p=c/(v 2 ) where c is constant. Calculate the work done by the fluid on the piston.(2011) 9. I) define thermodynamic system, surrounding and boundary. ii) state the difference between extensive and intensive property of a thermodynamic system. (2010) 10. A gas undergoes a reversible non-flow process according to relation p=(-3v + 150) where V is the volume in m 3 and p is the pressure in bar. 11. Determine the work done when volume changes from 3 to 6 m3.(2010)

2 END SEM 1. Show that energy is a property of a system.(2015) 2. What is the qualitative difference between heat and work? Why are heat and work not completely interchangeable forms of energy? (2015) 3. Define: a) Concept of available and unavailable energy.(2010) UNIT-2 First Law of Thermodynamics for closed & open systems. Non Flow Energy Equation. Steady State, Steady Flow Energy Equation. Second Law of Thermodynamics-Kelvin and Plank's Statements, Clausius inequality, Definition of Heat Engines, Heat pumps, Refrigerators. Concept of Energy and availability. Carnot Cycle; Carnot efficiency, Otto, Diesel, Dual cycle and their efficiencies. 1. Starting from the first law of thermodynamics, derive expressions for specific heat at constant volume and specific heat at constant pressure. (2015) 2. A turbine operates under steady flow conditions, receiving steam at following state: pressure- 1.2 MPa, temperature-188 O C, enthalpy-2785 kj/kg, velocity-33.3 m/s and elevation-3m. The steam leaves the turbine at following state: pressure-20 kpa, enthalpy-2512 kj/kg, velocity-100 m/s and elevation-0m. Heat is lost to the surrounding at the rate of 0.29 kj/s. If the rate of steam flow through is 0.42 kg/s, what is the power output of the turbine in kw? (2015) 3. Explain the first law of thermodynamics for a closed system undergoing a cycle.(2013) 4. Explain the first law of thermodynamics for a closed system undergoing change of state. (2013) 5. Derive the expression for enthalpy and explain that enthalpy of an ideal gas depends only on temperature. (2013) 6. Derive and explain expression for specific heat at constant volume and specific heat at constant pressure. (2013) 7. Show from 1 st law of thermodynamics that work in an adiabatic process is given by: W 1->2 = P1V1-P2V2 γ1 (2012) 8. Show from first law of thermodynamics the work in a polytropic process is given by: W 1->2 = P1V1-P2V2 n-1 (2012) 9. A closed rigid vessel containing 10kg of oxygen at 290K is supplied heat until its pressure becomes two-fold that of initial value. Identify the process and calculate the final temperature, change in internal energy and enthalpy and heat interaction across the system boundary. Take Cv=0.65kJ/kgK (2011)

3 10. A centrifugal air compressor delivers 15kg of air per minute. The inlet and outlet conditions are given: At inlet Velocity=5 m/s, enthalpy=5 kj/kg At outlet Velocity=7.5 m/s, enthalpy=173 kj/kg. Calculate the power of motor required to drive compressor.(2011) 11. State the Kelvin-plank and Clausius statements of the second law of thermodynamics. (2011) 12. A reversible heat engine receives heat from two thermal reservoirs at 870K and 580K and rejects 50kW of heat to a sink at 290K. If the engine output is 85kW. Calculate the engine efficiency and heat supplied by each reservoir.(2011) 13. Show that internal energy is a property of the system. 14. A perfect gas undergoes the following three separate and distinct processes to execute a cycle. i)constant volume during which 80kJ of heat is supplied ii) constant pressure during which 85kJ of heat is lost to the surroundings and 20kJ of work done on it. iii) adiabatic process which restores the gas back to initial state. Evaluate the work done during adiabatic process and value of internal energy at all the state points if initially its value is 96kJ.(2010) 15. A nozzle is device for increasing velocity of a flowing stream. At inlet of nozzle, the fluid parameters are: Enthalpy=2850kJ/kg, velocity=50 m/s At discharge end the enthalpy is 2650kJ/kg. Calculate the velocity of fluid at exit from nozzle.(2010) END SEM 1. Show that the efficiency of a reversible engine operating between two given constant temperatures is maximum.(2015-nov. And may) 2. Show that the COP of a heat pump is greater than COP of a refrigerator by unity.(2015,2011) 3. Prove that the efficiency of the Otto cycle depends only on the compression ratio.(2015-no. And may) 4. a) a domestic refrigerator is loaded with food and the door is closed. During a certain period, the machine consumes 1kWh of electricity and internal energy of the system drops by 5000kJ. Find the net heat transfer for the system.(2015) 5. a) a certain water heater operates under steady flow conditions receiving 4.2 kg/s of water at 75 O C temperature, enthalpy 2676 kj/kg. The mixture leaves the heater as liquid water at temperature 100 O C and enthalpy 419 kj/kg. How much steam must be supplied to the heater per hour?

4 b) using SFEE, What will be the velocity of a fluid leaving a nozzle, if the velocity of approach is very small.(2015) 6. What are refrigerators and heat pumps? Show that COP of a heat pump is greater than the COP of refrigerator by unity.(2015) 7. A) What is a steady flow process. State all the assumptions made for such a flow process, explain the concept of flow work.(2012) b) A centrifugal pump delivers 2750kg of water per minute from initial pressure of 0.8 bar absolute to a final pressure of 2.8 bar absolute. The suction is 2m below and the delivery is 5m above the centre of pump. If the suction and delivery pipes are 15cm and 10cm diameter respectively, make calculation for the power required to run the pump.(2012) 8. A)Explain thermal efficiency of a heat engine. Can it be 100%? Deduce the concept of clausius inequality. b) define entropy. What are the two requirements for a process to be isentropic? Also prove the entropy is a point function.(2012) 9. A) Derive an expression for the air standard efficiency of the diesel cycle in terms of the compression ratio, cut off ratio and the adiabatic index. b) an air standard Otto cycle is designed to operate with the following data: Maximum cycle pressure and temperature: 5MPa and 2250K. Minimum cycle pressure and temperature: 0.1 MPa and 300K. Determine the net work output per unit mass of working fluid and the thermal efficiency.(2012) 10. A) explain and give expression for mass balance and energy balance equation in a simple steady flow process. b) explain the equivalence of Kelvin-Planck statement and Clausius s statement of second law of thermodynamics. c) explain the operation of a refrigerator and define its COP.(2011) 11. A) explain the Carnot s theorem with block diagram. b) a reversible engine during a cycle of operation draws 5 MJ from 400K reservoir and does 840 kj of work. It also interacts with other two reservoirs at 200K and 300K. Find the amount and direction of heat interaction with the two reservoirs.(2011) 12. Derive the expression for efficiency of Otto cycle.(2011) 13. Define: a) Second law of thermodynamics. b) Clausius inequality.(2010) 14. Air flows steadily at the rate of 0.5 kg/s through an air compressor, entering at 7 m/s velocity, 100 KPa pressure and 0.96 m 3 /kg volume and leaving at 5 m/s, 700KPa and 0.19 m 3 /kg. The internal energy of air leaving is 90kJ/kg greater than that of air entering. Cooling water in compressor jackets absorb heat from inlet air at the rate of 58kW. I)Compute the rate of shaft work input by air in kw. Ii)find the ratio of inlet pipe diameter to outlet pipe diameter.(2010) 15. A) A reversible heat engine operates between two reservoirs at temperatures of 600 and 40 O C. The engine drives reversible refrigerator which operates between reservoirs at

5 temperatures of 40 and -20 O C. The heat transfer to heat engine is 2100kJ and net work output of combined engine refrigerator plant is 350kJ. Evaluate the heat transfer to the refrigerant and the net heat transfer to reservoir at 40 degree Celsius. b) In a diesel cycle, the pressure and temperature at beginning are 1 bar and 303K respectively. The compression ratio is 16. The cut-off ratio is 2.5. calculate maximum pressure and maximum temperature in the cycle also calculate efficiency of cycle. Assume Cp= 1kJ/kgK and Cv=0.715 kj/kgk.(2010) 16. A) prove that entropy is a property of a system. Air of 5kg at a temperature of 300K and 2 bar pressure is compressed at constant volume to a pressure of 5 bar. Calculate the change in entropy. Given Cp= 1.005kJ/kgK, Cv=0.718kJ/kgK.(2010) UNIT-3 Principles of power production, basic introduction about thermal power plant, hydroelectric Power plant and nuclear power plant. 1. Write short notes on: a) Thermal power plant.(2015) END SEM UNIT-4 Properties & Classification of Fluids, Ideal & real fluids, Newton's law of viscosity, Pressure at a point, Pascal's law, Pressure variation in a static fluid, General description of fluid motion, stream lines, continuity equation, Bernoulli's equation, Stead and unsteady flow. END SEM 1. An oil film of thickness 1.5mm is used for lubrication between a square plate of 0.9mm x 0.9mm and on an inclined plane having 20 O inclination from the horizontal. The weight of the square plate is N and it slides down the plane with a uniform velocity of 0.2 m/s. Find the dynamic velocity of the oil. (2015) 2. State and prove the Pascal s law.(2015-nov. And may) 3. Water is flowing through a pipe of 5cm diameter under a pressure of N/cm 2 and with mean velocity of 2 m/s. Find the total head of the water at a cross section which is 5m above the datum line.(2015) 4. Write short note on b) steady flow mass and energy balance equation(2015) 5. State the Newton s law of viscosity and give examples of its application.(2015,2010)

6 6. The water is flowing through a pipe having diameter 20cm and 10cm at 1 and 2 respectively. The rate of flow through pipe is 35 litre/sec. The section 1 is 6m above datum and section 2 is 4m above the datum. If the pressure at the section 1 is N/cm 2. Find the intensity of pressure at section 2.(2015) 7. A) obtain an expression for total pressure and corresponding centre of pressure on a plane surface immersed in a fluid vertically.(2010,2012) b) a cubical block weighing 4.5 N and having a 40cm edge is allowed to slide down an inclined plane surface making an angle of 30 O with the horizontal on which there is a uniform layer of oil cm thick. If the expected steady state velocity of the block is 12.5 cm/s, determine the viscosity of the oil. Also express the kinematic velocity in stokes if the oil has a mass density of 800 kg/m 2. (2012) 8. A 15cm diameter vertical cylinder rotates concentrically inside another cylinder of diameter 15.10cm. both cylinders are 25cm high. The space between the cylinders is filled with a liquid whose viscosity is unknown. If a torque of 12N-m if required to rotate the inner cylinder at 100 rpm. Determine the viscosity of the fluid.(2011) 9. A) prove that the intensity of pressure at a point in a static fluid is equal in all direction. b) calculate the pressure due to a column of 0.3m of i)water ii)an oil of specific gravity 0.08 and iii)mercury of specific gravity take density of water= 1000kg/m 3. (2011) 10. B) the dynamic viscosity of an oil for lubrication between a shaft and sleeve is 6 poise. The shaft is of diameter 0.4m and rotates at 190 rpm. Calculate the power lost in bearing for a sleeve length of 90mm. The thickness of an oil film is 1.5mm.(2010) 11. The water is flowing through a pipe having diameter 20cm and 10cm at 1 and 2 respectively. The rate of flow through pipe is 40 litre/sec. The section 1 is 7m above datum and section 2 is 3m above the datum. If the pressure at the section 1 is 40 N/cm 2. Find the pressure at section 2.(2010)

UNIT I Basic concepts and Work & Heat Transfer

UNIT I Basic concepts and Work & Heat Transfer SIDDHARTH GROUP OF INSTITUTIONS :: PUTTUR Siddharth Nagar, Narayanavanam Road 517583 QUESTION BANK (DESCRIPTIVE) Subject with Code: Engineering Thermodynamics (16ME307) Year & Sem: II-B. Tech & II-Sem