MEB 420 - THERMAL ENGINEERING - I QUESTION BANK UNIT-I Each question carries 1 mark. PART-A 1. Define temperature. 2. Define intensive property 3. Explain the term absolute zero of temperature 4. State first law of thermodynamics 5. State the three types of thermodynamics systems. 6. State Boyle s law. 7. Define enthalpy. 8. Write the relationship between C p C v and R. 9. Define change in entropy. 10. Derive the characteristic gas equation. 11. What is the significance of adiabatic process? 12. What is the significance of isothermal process? 13. Write down the expression for change in internal energy. 13. Define absolute zero temperature. 14. State the three types of thermodynamics system with examples. 15. What are intrinsic and extrinsic properties? Give examples. 16. State and explain first law of thermodynamics. 17. State and explain the clausius statement. 18. Compare isothermal and isentropic processes. 19. Explain the adiabatic process of expansion of gases on PV and TS diagrams. Each question carries 12 marks. PART-B 1. Determine the final temperature, external work done, change in internal energy, and change in enthalpy and change in entropy in the case of 2kg of gas at 50 0 C being heated at constant volume until the pressure is doubled. 2. A mass of 2.25 kg of nitrogen occupying 1.5m 3 is heated from 25 0 C to 200 0 C at constant volume. Molecular weight of nitrogen is 28 and universal gas constant is 8314 J/kg mole k. calculate the initial and final pressure of the gas. 3. A gas whose pressure, volume and temperature is 5 bar, 0.23 m 3 and 185 0 C respectively has changed its state at constant pressure until its temperature becomes 70 0 C. Determine (i) workdone (ii) change in internal energy (iii) the heat transferred during the process. Take R = 290 J/kg K and C p = 1.005 KJ/kg K.
4. 0.2 kg of air at a pressure of 1.1 bar and 15 0 C is compressed isothermally to a pressure o 5.5 bar. Calculate (i) final volume (ii) heat rejected (iii) change in entropy (iv) change in internal energy. Assume R=0.292 KJ/kg K 5. Air at 1 bar and 40 0 C is compressed to 1/10 th the original volume isentropically. Determine the final pressure and temperature and the workdone on 1m 3 of air. Assume R = 0.287KJ/kg and = 1.41 6. 0.5 kg of air at 180 0 C expands adiabatically to 3 times its original volume. During the expansion the temperature is decreased to 20 0 C. workdone during the expansion is 53 KNm. Find C p C v and R. 7. 1 kg of air at 11 bars and 80 0 C is expanded to 10 times the original volume by i) Isothermal process (ii) isentropic process. Determine the workdone in each of the cases. Plot these two processes on a common P-v diagram. R = 287 J/Kg.k and = 1.4 8. A gas at a pressure of 700KN/m 2 and 15 0 C expands from a volume of 0.075 m 3 to 0.36 m 3 according to the law PV 1.2 = C, Determine, i) final temperature (ii) worksdone (iii) Heat transferred. Take = 1.4 and R = 0.29 KJ/Kg.k. 9. 0.25 Kg of air at a pressure of 140KN/m 2 occupies 0.15 m 3 and from this condition it is compressed to 1.4 MN/m 2 according to the law PV 1.25 = C, Determine, i) change in internal energy (ii) workdone on or by the air (iii) the heat received or rejected by the air (iv) change in entropy. Take C p = 1.005 KJ/kg. k, C v = 0.718 KJ/Kgk.
UNIT-II Each question carries 1 mark. PART-A 1. Write the expression for air standard efficiency of diesel cycle. 2. Write the expression for air standard efficiency of Otto cycle. 3. Define air standard efficiency. 4. What is meant by reversible process? 5. State any two conditions of reversibility. 6. Define compression ratio. 7. What is the effect of compression ratio on efficiency Otto cycle? 8. Define the term air - standard efficiency. 9. State the conditions of reversibility. 10. State the assumptions made in thermodynamics cycle. 11. Write the SFEE for (a) steam boiler 12. What is meant by control volume? 13. Write the non-flow energy equation. 14. Mention few applications of SFEE. 15. What is meant by control surface? 16. Write down the steady flow energy equation. PART-B Each question carries 12 marks. 1. The temperature limits for a Carnot cycle using air as working fluid are 500 0 C and 10 0 C. Calculate the efficiency of the cycle and the ratio of adiabatic expansion. Assume = 1.4 for air. 2. Calculate the air standard efficiency of an engine working on Otto cycle, if the pressure at the beginning and the end of compression are 1 bar and 10 bar respectively. Take = 1.4. 3. Derive an expression for air standard efficiency of Otto cycle in terms of temperatures. 4. Derive an expression for air standard efficiency of Joule s cycle in terms of pressure ratio. 5. Derive an expression for air standard efficiency of a diesel cycle. 6. In a gas turbine, air flows at the rate of 5kg/sec. The velocity and the enthalpy of air at the entrance are 200m/sec and 7000 KJ/kg respectively. The exit velocity and enthalpy are 160m/sec and 5000 KJ/kg. As the air passes through the turbine a heat loss of 40KJ/kg. As the air passes through the turbine a heat loss of 40KJ/kg occurs. Find the power developed by the turbine. 7. Steam enters a turbine at velocity of 12m/s and specific enthalpy is 2900 KJ/kg. At the exit of the turbine, the steam velocity is 30 m/s and the specific enthalpy is 2400 KJ/kg. The heat lost during the flow through the turbine is 20 KJ/kg and the steam flow rate is 85 kg/s. Determine the power output from the turbine. 8. In a steady flow air through a Nozzle, the enthalpy decreases by 40KJ between two sections. Assuming that there are no other energy changes than kinetic energy, determine the increase in velocity at section 2, if the velocity at the section 1, is 100m/sec. 9. Air expands from 3 bars to 1 bar in a nozzle. The initial velocity is 90m/sec and the temperature 150 0 C. Calculate the final velocity of the air, if C p = 1.005 KJ/kg k.
UNIT-III Each question carries 1 mark. PART-A 1. What is an air compressor? 2. Name the various types compression processes used in air compression. 3. What is the purpose of intercooler? 4. What are the uses of compressed air? 5. Classify air compressors. 6. Explain with P-v diagrams, the various types of compression in a single stage compressor. 7. Sketch the three types of compression processes in a p-v diagram. Which process requires minimum work input. 8. Define the term free air delivered. 9. What is the effect of clearance in volumetric efficiency of a compressor? Explain briefly with P-v co-ordinate. 10. Explain with a line diagram a two stage air compressor. 11. Mention the types of rotary compressor. 12. Explain roots blower. 13. What is a gas turbine? 14. What is an open cycle gas turbine? 15. Mention the types of jet engines. 16. How gas turbines are classified? 17. How are gas turbines classified? With the help of neat sketch explain the working of a closed cycle gas turbine. 18. What is open cycle gas turbine? Each question carries 12 marks. PART-B 1. A single acting, single stage reciprocating air compressor has a bore of 200mm and a stroke at 300mm. It runs at a speed of 500 rpm. Air is compressed according to the law Pv 1.3 = C from a pressure of 97 KN/m 2 and compression pressure is 550 KN/m 2. Air is delivered at this pressure. The initial temperature is 20 0 C. Determine (i) The delivery temperature (ii) The amount of air delivered (iii) The power required to drive the compressor. Neglect clearance and assume R = 0.29 KJ/Kg.k. 2. A compressor is required to deliver 30m 3 /hr of free air at 1 bar and 32 0 C to a pressure of 5 bars. The law of compression is Pv 1.3 = C. Determine the power required. 3. A single stage acting reciprocating air compressor has a bore of 200mm and a stroke at 300mm. It receives air at 1 bar and 20 0 C and delivers it at 5.5 bars. If the compression follows
the law Pv 1.3 = C and clearance volume is 5 percent of the stroke volume, determine the power required to drive the compressor, if it runs at 500 rpm. 4. Find the percentage saving in work by compressing air in two stages from 1 bar to 8 bars instead of in one stage. Assume compression index as 1.3 in both the cases and complete intercooling in two stage compressor. 5. Derive an expression for the power required to drive a single acting single stage air compressor when the air is compressed polytropically. 6. Derive an expression for the theoretical power required to drive a single acting single stage reciprocating compressor when the air is compressed isentropically. 7. Derive and expression for the air standard efficiency of Brayton cycle in terms of compression ratio. 8. Explain with neat sketch the working of turbo-jet engine. 9. With a neat sketch explain the working of a turbo jet engine and state the advantages and disadvantages of turbo jet. 10. Explain the working of ram jet with a neat sketch.
Unit-IV Part - A 1. What for an Orsat apparatus is used? 2. Write the expression for theoretical minimum air required for complete combustion of 1kg of a fuel? 3. Write down Delong s formula to determine H.C.V of fuels 4. What are non-fossile fuels? 5. Define calorific value of fuel? 6. What is the use of bomb calorimeter? 7. Name some prepared solid fuels? 8. Mention few merits of liquid fuels over solid fuels 9. What is meant by excess air? 10. State any two requirement of good fuel 11. Name the four strokes of a petrol engine 12. What is the main function of a carburetor? 13. What is meant by valve liming diagram? 14. State the different types of cooling systems used in IC engines 15. What is the other name of petrol engine? 16. Name the type of injection nozzles used in diesel engine 17. What is meant by scavenging? 18. State the different methods of lubricating IC engine 19. State any two advantages of super charging? 20. What is the function of connecting rod of IC engine? PART B 1. Explain the bomb calorimeter with neat sketch 2. Explain the Junker s calorimeter gas with neat sketch 3. Explain the Orsat apparatus with neat sketch 4. A fuel contains 92% carbon, 4% hydrogen, 2% sulphur, 1.5% oxygen and ash 0.5%. It is supplied with 50% excess air. Determine the total air supplied and also gravimeter composition of the products of combustion. 5. Hydrocarbon fuel has the following composition Carbon-90%, Hydrogen-6%, Sulphur-2%, Oxygen-1% Ash-1%. Find the theoretical air required to burn 1kg of the above fuel completely. What is the gravimetric composition of the products of composition? 6. Explain the working of a 4-stroke and 2-stroke cycle petrol engine 7. Compare four stroke and two Stroke engine 8. Explain the working of AC mechanical fuel pump with neat sketch. 9. Explain the working of a simple carburetor and point out is short coming for use in car engine 10. Explain with a neat sketch the working of inline (CAV) fuel injection pump used in diesel engine
Unit - V PART - A 1. State the difference between indicated power and brake power. 2. Define mechanical efficiency. 3. Define indicated thermal efficiency 4. Define specific fuel consumption 5. Define indicated mean effective pressure. 6. Name of the various methods of measuring brake power. 7. What is the significance of Morse test? 8. Define volumetric efficiency. 9. What is meant by heat balance heat losses? 10. Define indicated thermal efficiency. 11. State Fourier s law. 12. Write the modes of heat transfer. 13. Define convention. 14. Define radiation 15. Define black body 16. Define white body 17. What is thermal resistance of plance wall? 18. What are the types of heat exchanger 19. What is meant by LMTD? 20. Define thermal conductively. PART - B 1. Explain the Prony brake dynamometer and Rope brake dynamometer with neat sketch 2. Briefly explain the Morse test. 3. Briefly explain the method of heat transfer. 4. Explain the morse test for finding out the indicator power of a mult-icylinder engine 5. Discuss about the conduction heart transfer through a plane wall and composite wall. 6. Discuss about LMTD for parallel flow and counter flow. 7. Discuss about the conduction heat transfer through hollow cylinder. 8. Explain black, white, opaque, transparent and grey bodies.