Applied Heat Past Examination Questions

Applied Heat past Examination Questions 1. An Ammonia refrigerator is to produce 2 thyroxin of ice per day at -4C from water at 20C. if the temperature range in the compressor is between 25C and -6C, Calculate horse position required to derive the compressor. Latent Heat of ice = 80 kcal/kg, and specific heat of ice= 0. 5 2. A compressor draws 42. 5 m3 of ship per minute in the cylinder, at a force of 1. 05 kg/cm abs. It is compressed Polytropically pV1. 3=C to a air pressure level 4. 2 kg/cm2 abs, before being delivered to a receiver. Assuming a mechanical efficiency of 80% Calculate a.Indicated horse power b. Shaft horse power, and c. Overall isothermal efficiency. 3. A single correspond impulse turbine has a speed of 1000rpm and a mean blade ring diam of 60 cm. The nozzles are inclined at 22 to the plane of gy proportionn and the specific henry drop is 190 KJ/kg. look out a. The relative speeding of the steam at inlet, and b. The blade inlet angle. 4. An engine consume s fuel of calorific value 44MJ/Kg at a rate of 45tonne/day. It the indicated thermal efficiency is 39% and break thermal efficiency is 33%. Calculate a. The indicated power, b. The brake power, and . The power befuddled to friction. 5. The impart in a ships saloon is maintained at 19C and is changed twice every bit from the outside zephyr which is at 7C. The saloon is 27m by 15m by 3m high. Calculate the kilowatt loading to heat this air taking the saloon to be at atmospherical Pressure = 1. 013 pothouse. R for air =0. 287 KJ/kg K. 6. 0. 23kg of air has an initial pressure of 1. 7 MN/m2 and a temperature of 200C. it is expanded to a pressure of 0. 34 MN/m2 according to the law pV 1. 35 = Constant. delineate the work permutered during the expansion. Take R = 0. 29 KJ/kg K. 7.The equivalent evaporation of a boiler from and at 100C is 10. 4 kg steam/kg fuel. The calorific value of the fuel is 29800KJ/kg. Determine the efficiency of the boiler. If the boiler produces 15000 kg o f steam per hour at 24 halt from feed water of 40C and the fuel consumption is 1650 kg/h, determine the condition of the steam produced. 8. A single-cylinder, ikon performing steam engine is 250mm tire by 300mm bezzant and runs at 3. 5rev/s, steam is supplied at 1035 KN/m2 and the back pressure is 34 KN/m2 and the diagram factor is 0. 81. Determine the indicated power of the engine. a. If cut off is at 0. 5 stroke, b. If cut off is at 0. 5 stroke. 9. Air enters a nozzle with a pressure of 700 KN/m2 and with a temperature of 180C. Exit pressure is 100 KN/m2. The law connecting pressure and specific volume during the expansion in the nozzle is pV1. 3=Constant. Determine the pep pill at exit from the nozzle. Take Cp= 1. 006 KJ/kg K and Cv=0. 717 KJ/kg K. 10. A single row, impulse turbine has a mean blade speed of 215 m/s. neb entry angle is at 30 to the plane of rotation of the blades. The steam velocity from the nozzles is 550 m/s. There is 15% loss of relative velocity callabl e to friction across blades.The absolute velocity at the exit is along the axis of the turbine. The steam flow through the turbine is at the rate of 700 kg/h. Determine a. The inlet and exit angles of the blades, b. The absolute velocity of the steam at exit, c. The power output of the turbine. 11. The high temperature of a Carnot cycle is 400C and the cycle has a thermal efficiency of 55%. The volume ration of the isothermal processes is 2 8 1. Determine for the cycle a. The low temperature, b. The volume ration of the adiabatic processes, c. The boilers suit thermal efficiency. Take r = 1. 4 12.A diesel engine has a compression ratio of 141 and an efficiency ratio of 0. 7 when referred to the air standard efficiency. The fuel consumption is 5. 65 kg/h. Take r=1. 4 and calorific value of the fuel oil is 44500 KJ/kg. Determine the indicated power developed. 13. The comp extirpate of a fuel oil is 85. 5% carbon, 11. 9% hydrogen, 1. 6% oxygen and 1% impurities. Calculate the perce ntage of carbon dioxide in the flue louse upses, a. When the quantity of air supplied is the minimum for complete combustion, and b. When the excess air over the minimum is (i) 25% (ii) 50% iii) 75% 14. In an air compressor the air is compressed to the law pVn= eternal quantity. The compressor takes in 105 m3/min of air at 1. 0 stop 27C. If the pressure ratio is 5 to 1, envision a. The index of compression, b. Power absorbed by the compressor. 15. A single acting opposed piston 6 cylinder two stroke engine have mechanical efficiency of 86% when rail at 105 rpm with mean opinionive pressure of 7. 24 bar, produces brake power of 4326 kW. The atomic pile of the top piston with its connecting parts is 25% greater than that of bottom piston and the combined stroke is 2340 mm.If the stroke of piston varies inversely as the big buckses of the reciprocating parts. Calculate (i) The stroke of the top and bottom pistons, (ii) The cylinder diameter. 16. The spate abridgment of a fuel is 86% carbon, 11. 5% hydrogen and 2. 5% oxygen. If for complete combustion 25% excess air is supplied per kg of fuel burnt, face a. The mass of flue gases, b. Volume of air at 1. 0 bar and 15C. Take R for air = 0. 287 kJ/kgh. 17. The diameter of an air compressor cylinder is cxl mm, the stroke is 180 mm, and the clearance volume is 77cm. he pressure in the cylinder at the solution of the stroke is 1. 0 bar and during delivery is constant at 4. 8 bar. Taking the law of compression as pV1. 25=Constant, calculate the distance moved by the piston during the delivery period and impart this as fraction of the stroke. 18. A turbine plant consists of H. P. and L. P. stages and is supplied with steam at 15 bar 300C. The steam is expanded in the H. P. and leaves at 2. 5 bar 0. 97 teetotal. Some of the steam is bled off to the feed heater and remaining passes to L. P. where it is expanded to 0. 15 bar 0. 84 dry.If the same quantity of work transfer takes place in each unit, calculate th e amount of steam bled off expressed as percentage of the steam supplied. 19. 7. 08 liters of air at a pressure 1. 79 bar and temperature of 333C is expanded according to the law pV 1. 3 = constant and the final pressure 1. 206 bar, calculate a. Volume at the end of expansion, b. die transfer from the air and, c. The temperature at the end of expansion. 20. Steam leaves the nozzle and enters the blade wheel of a single stage impulse turbine at a velocity of 840 m/s and at an angle of 20 to the plane of rotation.The blade velocity is 350 m/s and the exit angle of the blade is 2512. Due to friction the steam looses 20% of its rotational velocity across the blades, calculate a. The blade inlet angle and, b. The magnitude and the direction of absolute velocity of steam at exit. 21. In a Freon-12 refrigerating plant, Freon leaves the condenser with a specific enthalpy of 50kJ/kgK. The pressure in the evaporator is 1. 826 bars and the refrigerating leaves the evaporator at this pressure at a rate of 0. 4 Kg/s and a temperature of 0C. Calculate a. Dryness fraction of Freon at inlet of the evaporator, b.The refrigerating effect per minute. 22. A glass tube of uniform bore is closed at on end and open at the other. It contains air impris unmatchabled by a column of mercury 42. 7 mm long. When the tube is held vertically with close end at the bottom, the length of the air column is 227. 6mm. Taking 1mm of mercury = 133. 5N/m2 and atmospheric pressure = 101. 5 kN/m2. Calculate the length of the air column if the tube is held vertically with the closed end at the top. 23. A single acting gas engine of bore 190 mm and stroke 380 mm has an indicated power of 13 kW when developing brake power of 9 kW thither being 125 explosions per minute.The consumption of gas of calorific value 1. 76 MJ/m3 is 6. 8m3/hour. Calculate the mechanical and indicated thermal efficiencies, and the mean effective pressure. 24. A six cylinder, intravenous feeding stroke, internal combustion engi ne is required to develop a brake of 176 kW under the following conditions Speed 200rev/min, brake m. e. p. 8 bars, stroke/bore ratio 1. 25/1. Break specific fuel consumption 0. 262 Kg/KWh. Calculate- a. The cylinder dimensions, and b. Fuel consumption kg/h 25. Carbon dioxide leaves a refrigeration condenser with a total heat of 156kJ/kg.After throttling it passes through the evaporator from and it leaves with a dryness fraction of 0. 98. At the evaporator pressure the liquid heat is 12kJ/kg and the latent heat is 280kJ/kg. If 13. 8 kg of refrigerant circulates per minute, calculate- a. The dryness fraction at the inlet to the evaporator, and b. The heat absorbed in the evaporator in 24 hours. 26. Steam is generated from feed water at a temperature of 93. 3 C as follows In plant A the steam generated is 17. 25 bar dry perfect(a). In plant B the steam generated is 17. 25 bar 0. 9 dry and, In Plant C the steam generated is 17. 5 bar 82C super heat. Calculate the percentage change in the consumption using plant A as the base. 27. A hydrocarbon fuel cell is in all burned with 12. 5 percent excess air. Calculate the Volume of air utilise to burn 1Kg of fuel, measured at 1. 01 bars and 18C. Air contains 23 percent oxygen by mass. Atomic mass relationship Hydrogen=2, Carbon=12, Oxygen=16. 28. An oil engine has a volumetric compression ratio of 131. At the commencement of compression the air in the cylinder is at 1 bar and 15. 6C. Calculate the temperature and pressure at the end of compression if the index of compression is 1. 8. 29. A single acting air compressor working without clearance has a 220mm bore and 200mm stroke. The suction conditions are 1 bar 27C and running speed is 10 rev/sec. if compression is according to the law pV1. 3=Constant and the electric arc pressure is 10 bar. Calculate, a. The mass of air compressed per hour, and b. The discharge temperature. 30. Calculate the final temperatures and final total heat of both (a) and (b). a. Water at 65. 6 C having a mass of 45. 36 kg is cooled by placing 4. 536 kg of ice at -8. 9C into the water. b. Water at 65. 6C having a mass of 54. 1 kg is cooled by addition of 22. 68 kg of water at 26. 7C. 31. An impulse steam turbine operates at 50rev/sec. The mean blade tip diameter is 0. 6m. The blade exit angle is 30 and the velocity of the steam relative to the blade at blade exit is 300 m/s. Calculate or determine by any other means the kinetic energy of steam leaving the blades per kilogram of steam flow. 32. A perfect gas at 3. 1 bar and 30C is compressed according to the law pV1. 3=constant until its temperature increases to 215C. Sketch the process on a p-V diagram and calculate a.The pressure at the end of compression. b. The changes in enthalpy and internal energy per kilogram of gas. 33. In an ideal constant volume cycle the temperature at the beginning of compression is 50C. the volumetric compression ratio is 51. If the heat supplied during the bible is 930 KJ/Kg of working flu id, calculate a. The maximum temperature attained on the cycle, b. travel done during the cycle/kg of working fluid, and c. The thermal efficiency of the cycle. Take ?=1. 4 and Cv= 0. 1717 KJ/Kg K. 34. A fuel has a mass analysis of carbon 87 percent, hydrogen 5. percent and remainder ash. The calorific value of carbon and hydrogen are 34MJ/kg and 145 MJ/kg respectively. Calculate for one kilogram of fuel a. The calorific value, b. The mass of exhaust gas if 35 percent excess air is supplied. When burning fuel, why is excess air used? Air contains 23 percent oxygen by mass Atomic mass relationships hydrogen=1, oxygen=16, carbon=12. 35. One kilogram of dry saturated steam at 4 bars is contained in a cylinder fitted with a piston. The steam rejects 320 KJ of heat energy at constant pressure is 1. 4 bars. Calculate a.The condition of the steam on completion of cooling at constant pressure, b. The condition of the steam on completion of cooling at constant volume, and c. The quantity of heat energy rejected during constant volume cooling. 36. A steam turbine which operates at 50rev/s has a mean blade-ring diameter of 1m at a certain stage. The blades are designed for 50 percent reaction and have the exit and inlet angles at 30 and 50 respectively. The turbine is supplied with steam at the ratio of 166. 67kg/s and the stage efficiency is 85 percent. Calculate or determine by any other means a.The power output of the stage, and b. The specific enthalpy drop in the stage. 37. In Ammonia refrigeration plant the refrigerant leaves the condenser at 22C as saturated liquid. The evaporator pressure is 2. 077bar and refrigerant leaves the evaporator 0. 98 dry saturated. For a cooling load of 40kW, calculate a. The rate of circulation of the refrigerant (kg/s), b. The effective swept volume of the compressor (m3) if its speed is 1 rev/s. 38. A copper bar of 75mm diameter, 13m long is heated by a direct current flowing through the bar. The steady electrical input to the bar is 500W.Assuming the bar is well-insulated and neglecting conduction heat losings at the leads, calculate the wires taken for the temperature of the bar to increase from 5C to 365C. 39. A single stage double acting air compressor deals with 18. 2m3 of air per minute measured at conditions of 1. 61325 bar 15C. The condition at the beginning of compression is 0. 965 bar 27C and the discharge pressure is 4. 82 bars. The compression is according to the law pV1. 32=constant. If the mechanical efficiency of the compressor is 0. 9 calculate the input power required to drive the compressor. 40.In a steady flow process the working fluid enters and leaves a horizontal system with negligible velocity. The temperature drop from inlet to outlet is 480C and the heat losses from the system are 10KJ/kg of fluid. Determine the power output from the system for a fluid flow of 1. 7kg/s. For fluid Cp=900 J/kgK. 41. A four stroke single cylinder engine working on constant volume cycle, develops 7. 5 KW( Brake) at 60 rev/s, the mechanical efficiency being 0. 8. The pressure at the beginning of compression is 0. 97 bar. The engine has a volumetric compression ratio of 7 and the maximum pressure reached in the cycle is 34 bar.If both compression and expansion is according to the law pV1. 38=constant. Calculate a. The indicated mean effective pressure, and b. The diameter of the cylinder if stroke/bore ratio is 1. 25. 42. A boiler generates steam at 40 bar 400C and supplied to a steam turbine at the rate of 14 kg/s. due to frictional and heat losses the steam at the turbine inlet is at 37 bar 350C. If the steam velocity leaving the boiler is 30 m/s and the change in the kinetic energy of steam is negligible. Calculate a. The diameter of the steam supply pipe, and b. The heat loss from the steam supply pipe.