Fash: 15ME35 (To be filled by the candidate) (2015 batch onwards) COIMBATORE INSTITUTE OF TECHNOLOGY (Government Aided Autonomous Institution) COIMBATORE 641 014 B.E. DEGREE EXAMINATIONS, APRIL 2017 (Third Semester) MECHANICAL ENGINEERING BRANCH 45ME35 APPLIED THERMODYNAMICS Time: 3 hours Max: 75 Marks INSTRUCTIONS. Answer all questions in Part A and as per choice in Part B. Part A and Part B questions should be answered separately in the same answer sheet Question No. 11 is compulsory Use of Steam Tables, Mollier chart, refrigeration table, p-h charts permitted, ve ae PART —A (10x 2= 20) 4. Whatis the significance of Valve Timing Diagram? How to draw valve timing diagram for Four Stroke Petrol Engine? 2. Asingle cylinder, Cl engine with a brake power efficiency of 30 % uses diese! oll having ‘2 calorific value of 42000 ki/kg. If it's mechanical efficiency is 80%. Calculate thermal efficiency. 3, The vapour compression refrigeration cycle is represented as shown in the figure below, ‘with state | being exit of the evaporator. What coordinate system is used in this figure? 4. The operaling temperature of cold storage is -2°C. Heat leakage from the surrounding is 30 KW for the ambient temperature 40°C. The actual COP of the refrigeration plant used js %4th that of an ideal plant working between the same temperatures. Estimate power required to drive the plant. 5. __ ina three stage compressor, air is compressed from 98 kPa to 20 bar. Calculate work under ideal condition for per m® of air per second. Assume nn = 1.3. 6. __ Differentiate between intercooler and after cooler. 7. Steam at3 MPa, 300°C leaves the boiler and enters the high pressure reheat turbine and itis expanded to 300 kPa, the steam then reheated to 300°C and expanded in the Second stage turbine to 10 kPa, Estimate the total work done. (use only Moller chart) Contd.8. The Brayton cycle operating temperatures between 300 K and 1000 K. Estimate the maximum pressure ratio, 9. Compare fire-tube boiler with water tube boiler, 10. The Camot cycle operating between two pressure limits. Ifthe same pressure limit, the Rankine cycle thermal efficiency will be increased or decreased. Explain valid reasons, PART-B (5x11 = 55) 11. a) Steam enters a C-D nozzle at 2 MPa and 400°C with a regligibie velocity and mass flow rate of 2.4 ka/s and it exits at a pressure of 300 kPa. The flow is isentropic between the nozzle entrance and throat and overall nozzle efficiency is 93%. Estimate throat and exit areas.(use only steam tables) (8) ») Draw the Lamont boiler and label it the important components. ) 12. Bring out the derivation of thermal efficiency and mean effective pressure of Diesel cycle with the help of p-V and T-s diagram. (1) (OR) 13. A single cylinder, 4-stroke Diesel engine works on the following date: Cylinder bore = 15m, stroke= 25cm, — speed = 250 mpm, area of indicator Giagram = 6 cr’, tength of the indicator diagram = 9 em, spring constant = 7.5 bar/em, BSF Consumption = 0.24 kg/kWh, CV of fuel = 42000 kikg, diameter of brake Wheel = 70 om, rope diameter = 3.5 cm and brake load = 40 kg. Calculate brake power, indicated power, indicated mean effective power. Friction power, mechanical efficiency and indicated thermal efficiency. (11) 14, The steam is the working fluid in an ideal Rakine cycle with superheat and reheats. ‘The Steam enters the first stage turbine at 8 MPA, 480°C and expands to 0.7 MP8, itis the reheated to 440°C before entering the second stage turbine. Where itexpands (OR) 18a) 4 large stationary Brayton cycle gas-turbine power plant delivers a power output of 100 MW to an electric generator. The minimum temperature in the eycle is 300 K and the maximum temperature is 1600 K. The minimum pressure in the cycle is 100 kPa, thermal efficiency of the cycle? @) ®) Find out the By-Pass factor ofthe cooling coil from the following cooling and Dehumidification figure. @) Contd...ASME35 16, a) ANH3 refrigerator produces 100 tons of ice from water at 0°C in a day. The cycle operates between 25°C and -15°C. The vapor is dry saturated at the end of compression. If the COP is 50% of theoretical cOP, calculate the power required to drive the compressor. ® b) A camot refrigerator using R 12 as working fluid operates between 40°C and -30°C. Determine the work of the compression and cooling effect produced by the cycle. (Use p-h chart) @) (OR) 47. a) An air conditioning plant is handling 30 m? of air per minute at 32°C DBT and 22°C WBT. If the final conditions of air are 22°C DBT and 50% RH. Calculate the heating capacity of the dehumidifier. © ) One of the major applications of the Psychrometric Chart is in air conditioning, and we find that most humans feel comfortable when the temperature is between 22°C and 27 °C, and the relative humidity g between 40% and 60%. This defines the “comfort zone” which is portrayed on the Psychrometric Chart as shown below. Thus with the aid of the chart, discuss either heat or cool, add moisture or dehumidify as required in order to bring the air into the comfort zone. 6) 18. Atwo stage, single acting, reciprocating air compressor receives atmospheric air at 45°C, compresses it isentropically in the LP cylinder to intermediate pressure, where air cools to its initial temperature and then again compresses _polytropically (n=1.3) in the HP cylinder. The clearance volume and pressure ratio on both cylinders are 5% of the swept volume and 2, respectively. Determine the stroke volume of HP cylinder for 60 lit swept volume of LP cylinder. ay (OR) 19. Derive an expression for indicated work of a reciprocating air compressor by considering its clearance. (ty