Thermodynamics Questions and Answers PDF

1. For an endothermic reaction, if the temperature is increased, the equilibrium constant A. remains constant B. decreases C. increases D. will depend on initial temperature Answer: C 2. The equilibrium composition of a reaction, taking place in an insulated constant volume vessel, will be obt...

1. For an endothermic reaction, if the temperature is increased, the equilibrium constant A. remains constant B. decreases C. increases D. will depend on initial temperature Answer: C 2. The equilibrium composition of a reaction, taking place in an insulated constant volume vessel, will be obtained when A. gibbs function is maximum B. entropy is minimum C. gibbs function is minimum D. entropy is maximum Answer: B 3. Dulong's formula is used for evaluating the calorific value of a fuel containing A. Oxygen B. Hydrogen C Sulfur D. Carbon Answer: A 4. Which of the following is the chemical formula for methyl chloride? A. CHCI2F B. C2H5Cl C. CCIF3 D. CH3CI Answer: D 5. Which of the following is the chemical formula for butane? A. C4H10 B. C2H5CI C. C3H8 D. C2H4O2 Answer: A 6. Which of the following is a COMMON constituent between water gas and producer gas? A. CO B. CO2 C. N2 D. H2 Answer: D 7. Which of the following is a variety of bituminous or sub-bituminous coal, commonly having a dull luster and grayish-black color, of compact structure often containing a few thin irregular bands with vitreous luster? A. Splint coal B. Cannel coal C. Boghead coal D. Banded coal Answer: A 8. Which of the following is a variety of bituminous or sub-bituminous coal, characterized by a high percentage of algal remains and volatile matter? A. Cannel coal B. Splint coal C. Boghead coal D. Banded coal Answer: C 9. It is a small-scale laboratory test that indicates the caking and coking properties of coal and givens an approximate measure of the material in coal that fuses become plastic when heated. A. Agglutinating-value B. Free-swelling C. Fusibility test D. Plastic Property test Answer: A 10. It is defined as any material which has less than 40% of fixed carbon. A. Bone B. Slate C. Ferrous D. Nonferrous Answer: B 11. It is defined as any material which has 40% or more but less than 75% of fixed carbon A. Bone B. Slate C. Ferrous D. Nonferrous Answer: A 12. Which of the following is caused by the union of coal with oxygen, and is similar to the combustion process in the furnace but progresses at a considerably lower rate? A. Theoretical combustion B. Stoichiometric combustion C. Imperfect combustion D. Spontaneous combustion Answer: D 13. Which of the following feeding and burning method of coal is based on the upward, parallel flows of fuel air? A. Crossfeed method. B. Overfeed method C. Underfeed method D. Gravity feed method Answer: C 14. Which of the following firing method is used exclusively in wet-bottom or slagging-type furnaces? A. Vertical firing B. Horizontal firing C. Impact firing D. Corner firing Answer: C 15. Which of the following is an excellent fuel for hand-fired furnaces and fireplaces? A. Disco B. Coal C. Hog fuel D. Wood Answer: A 50. Equilibrium constant for a chemical reaction depends upon A. total number of moles present at equilibrium B. partial pressure of the constituents C. total pressure D. partial pressure of the constituents and stoichiometric coefficients Answer: D 51. What is the stoichiometric air fuel ratio of gasoline and air? A. 14.15 B. 10 C 15.15 D. 17 Answer: A 52. In an Orsat apparatus, the order of absorption in the three absorption flasks is A. CO2, O2, CO B. CO, CO2, 02 C. CO2, CO, 02 D. O2, CO, CO2 Answer: D 53. Which of the following statement is INCORRECT regarding the maximum temperature attained in a chemical reaction? A. increases if the products of combustion dissociate B. reduces if excess oxygen is supplied for combustion C. reduces if the combustion is incomplete. D. depends upon the type of fuel used Answer: A 54. Coal may be fed into the furnace for combustion in lump pieces or in powder form. The combustion of coal may occur in the following, EXCEPT A. Grate furnaces B. Fuel bed furnaces C. Cyclone furnaces. D. Fluidized bed furnaces Answer: A 55. The following is the advantages of using pulverized coal firing, EXCEPT A. Ease of burning alternately with, or in combination with gas and oil B. Less fan power required C. Lower boiler efficiency D. Less pressure losses and draught need Answer: C 60. Butane is burned with dry air at an air-fuel ratio of 20. Determine the percent excess air. A. 28.29 B. 29.28 C. 29.82 D. 22.89 Answer: B 61. The calorific value of gaseous decane is 69 MJ/kg. Determine the lower heating value of decane gas in MJ/kg if the enthalpy of water at 25 deg. C is 2400 kJ/kg and for decane is 358 kJ/kg. A. 65.65 B. 44.62 C. 68.64 D. 65.29 Answer: A 62. In a particular installation, 30% excess air at 103 kPa and 40 deg. C is needed for the combustion of methane. How much of nitrogen (MW = 28.016) kg/min passes through the furnace if methane is burned at the rate of 31 L/s? A. 22.15 B. 16.15 C. 18.15 D. 20.15 Answer: D 64. A boiler uses fuel represented by C10H20 and is burned with 35% excess air. Determine the percent mass of nitrogen in the product of combustion. A. 76.01 B. 70.01 C. 73.01 D. 79.01 Answer: C 66. Which of the following fuel is defined by ASTM D288-47 as refined petroleum naphta which by its composition is suitable for use as carburetant in internal combustion engines. A. Gasoline B. Kerosene C. Diesel D. Fuel oil Answer: A 67. Which of the following fuel is defined by ASTM D288-47 as refined petroleum distillate having a flash point not below 73 deg. F? A. Fuel oil B. Gasoline C. Diesel D. Kerosene Answer: D 70. A boiler of a power station uses fuel with the following ORSAT analysis: 20% CO2 in the product of combustion. If percent excess air is 30%, calculate the maximum percentage of CO2 attainable. A. 32.34 B. 23.45 C. 29.30 D. 34.94 Answer: A 71. An oil-fired boiler of a Power Station had a fuel analysis by mass: carbon 84%, hydrogen 10%. Sulphur 3.2%, Oxygen 1.6%, remainder incombustible. The analysis of dry flue gas by volume gave: combined CO2 and SO2 15.72%, O2 1%, there being no CO or SOs. Calculate per lbs fuel the mass of water vapor formed. A. 3.98 B. 2.98 C. 1.98 D. 4.98 Answer: C 72. An unknown hydrocarbon fuel, CxHy was allowed to react with air. An ORSAT was made of a representative sample of the product gases with following result: CO2 = 12.1% O2 = 3.8% and CO = 0.9% Determine composition of the fuel. A. C13H23 B. C11 H20 C. C12H21 D. C14 H22 Answer: A 73. Four liters of octane gasoline weigh 3.91 kg. Determine the volume of the air required for complete combustion at STP in li. A. 9604 B. 37,307 C. 7834.40 D. 45,731 Answer: D 74. If the exhaust gases of a hydrogen fueled engine contain 22.3% H2O, 7.44% 02 and 70.2% N2. At what equivalence ratio is it operating? A. 0.598 B. 0.0174 C. 0.0921 D. 0.586 Answer: A 78. In a particular installation, 30% excess air at 103 kPa and 40 deg. C is needed for the combustion of methane. Determine the volume of nitrogen (MW = 28.016) (m ^ 3) / m * in passes through the furnace if methane is burned at the rate of 31L / s ? A. 22.18 B. 20.18 C. 18.18 D. 24.18 Answer: C 80. Which of the following factors is defined as the ratio of the maximum generator demand to the generator capacity A. Plant Capacity B. Utilization C. Plant Use D. Load Answer: B 81. Overtime, the performance of generating power plants is compared by their A. average efficiency B. peak load capacity C. generating capacity D. thermal efficiency Answer: A 82. Which of the following is NOT the performance indicator of a plant? A. Thermal Capacity B. Plant load factor C. Specific fuel consumption D. Heat rate Answer: A 87. A certain small scale power plant operates 4 hours a day, 40 weeks a year. If on average the plant is not available for 5 hours a week for scheduled and unscheduled maintenance, what is the utilization factor of the plant? A. 0.85 B. 0.97 C. 0.13 D. 0.78 Answer: C 89. A certain small scale power plant operates 4 hours a day, 40 weeks a year. If on average the plant is not available for 5 hours a week for scheduled and unscheduled maintenance, what is the availability factor of the plant? A. 0.78 B. 0.13 C 0.85 D. 0.97 Answer: D 90. The cost of electricity can be calculated by A. Fixed cost/electrical energy generated B. Electrical energy generated/(Fixed cost Variable cost) C. (Fixed cost Variable cost)/Electrical energy generated D. Variable cost/electrical energy generated Answer: C 91. Which of the following power plant is preferred as a peak load type? A. Gas Turbine B. Nuclear C. Hydroelectric D. Thermal Answer: A 92. It is a type of load which consists of street lighting, power required for water supply and drainage purposes. A. Industrial B. Municipal C. Irrigation D. Provincial Answer: B 98. Which of the following best describe the Joule's law? A. The change of pressure is proportional to temperature change. B. The sum of all heat transfer is proportional to sum of all work transfer. C. The change of volume is proportional to temperature change. D. The change of internal energy is proportional to temperature change. Answer: B 99. Which one of the following substances has constant specific heat at all pressures and temperatures? A. Mano-atomic gas B. Di-atomic qas C. Tri-atomic gas D. Poly-atomic gas Answer: A 100. Which of the following is INCORRECT about the first-law of thermodynamics? A. The heat transfer equals the enthalpy change for an adiabatic process. B. The internal energy change equals the work of a system for an adiabatic process. C. The heat transfer equals the quasiequilibrium work of a system for a constant-volume. D. The net heat transfer equals the work output for an engine operating on a cycle. Answer: A 101. Which of the following is INCORRECT about the second-law of thermodynamics? A. The entropy of a hot copper block decreases as it cools B. Heat is always rejected from a heat engine C. The entropy of an isolated process must remain constant or increase D. Work must be input if energy is transferred from a cold body to a hot body Answer: D 102. Which of the following phenomena occurs when gas in a piston-in-cylinder assembly expands reversibly at constant pressure? A. Heat is removed from the gas. B. Heat is added to the gas. C. Gas does work from its own stored energy. D. Gas undergoes adiabatic expansion. Answer: B 103. Which is NOT an extensive property? A. Kinetic Energy B. Momentum C. Density D. Mass Answer: C 104. Which would be identified with a control volume? A. The goodyear blimp during flight B. Compression of air in a cylinder. C. Expansion of the gases in a cylinder after combustion. D.. Filling a tire with air at a service station. Answer: D 105. Which is a quasiequilibrium process? A. Mixing paint in a can B. Compression of air in a cylinder. C. Combustion D. A balloon rising Answer: B 106. Which work mode is a nonequilibrium workmode? A. Energizing an electrical resistor B. Compressing a spring C. Transmitting torque with a rotating shaft D. Compressing gas in a cylinder Answer: A 107. Which of the following does NOT transfer work to or from a system? A. An electrical resistance heater B. A moving piston C. The expanding membrane of a balloon D. A membrane that bursts Answer: D 108. Which statement about work for a quasiequilibrium process is INCORRECT? A. Work is a path function. B. The differential of work is inexact.. C. Work is the area under a P-T diagram. D. Work is always zero for a constant-volume process. Answer: C 109. Air undergoes a three-process cycle with a P = \mathbb{C} a T = C and a V = C constant process). Which of the following statement is correct for a piston-cylinder arrangement? A. W = 0 for the V = constant process B. W = 0 for the P=constant process C. Q = 0 for the V = constant process D. Q = 0 for the T= constant process Answer: A 110. What is the key concept in analyzing the filling of an evacuated tank? A. The mass flow rate into the tank remains constant. B. The enthalpy across a valve remains constant. C. The internal energy in the tank remains constant. D. The temperature in the tank remains constant. Answer: B 111. Which of the following can be assumed to be reversible? A. A piston compressing gas B. A paddle wheel C. A burst membrane D. A resistance heater Answer: A 112. Which of the following second-law of THERMODYNAMICS statements is INCORRECT? A. Work must be input if energy is transferred from a cold body to a hot body B. The entropy of a hot copper block decreases as it cools. C. If ice is melted in water in an insulated container, the net entropy decreases D. The entropy of an isolated system must remain constant or increase. Answer: D 113. Why is the exhaust process in the Otto and diesel cycles is replaced with a constant-volume process? A. To ensure that the first law is satisfied. B. To simulate zero heat transfer of the actual exhaust process. C. To restore the air to its original state. D. To simulate zero work of the actual exhaust process. Answer: D 114. Which component in a Rankine cycle that leads to relatively low cycle efficiency? A. The turbine B. The pump C. The boiler D. The condenser Answer: B 115. He defined the thermodynamic efficiency of a heat engine and showed the usefulness of P-v diagrams as related to work. A. Rudolf Julius Emanuel Clausius B. William Jogn Macquorn Rankine C. William Thomson D. Emile Clapeyron Answer: B 116. Which thermodynamic property is evaluated with the help of Maxwell equations from the data of other measurable properties of a system? A. Enthalpy B. Entropy C. Latent Heat D. Specific Heat Answer: A 117. An engineer was steaming siomai using pressure cooker while drinking coffee. Suddenly, he wondered which thermodynamic process would approximate the steaming of the siomai. Which thermodynamic process is illustrated? A. Isobaric B. Isenthalpic C. Isochoric D. Isothermal Answer: C 118. Which of the following is useful in predicting the properties of gases for which more precise data are not available but their critical properties are known. A. Breattie-Bridgeman equation of state B. Van del Waal's equation of state C. Generalized compressibility chart D. Redlich-Kwong equation of state Answer: C 156. A steam Carnot cycle operates between 340°C and 38 deg * C The turbine and compressor efficiencies are 90% and 80%, respectively. Solve for the actual enthalpy of the pump exit in Btu/lb. Enthalpies at each point (corner): h1 = 1594.5KJ /kg h2= 2821.9KJ /kg h3= 1649 KJ/kg, h4 =1128.3. KJ /kg A. 735.55 B. 715.55 C. 725.55 D. 745.55 Answer: A 157. A steam Carnot cycle operates between 340°C and 38 deg * C The turbine and compressor efficiencies are 90% and 80%, respectively. Solve for the actual in Btu/lb at turbine exit. Enthalpies at each point (corner): h1= 1594.5kJ /kg h2= 2621.9KJ /kg, h3= 1649KJ/kg, h4 = 1128.3KJ /kg A. 720.68 B. 750.68 C 730.68 D. 740.68 Answer: B 160. A reversed Carnot uses 1 lb of air is to constitute as refrigerating cycle between temperatures limits of 144 F and 41 F. The isothermal expansion ratio for the cycle is 3.1. The pressure at the start of isothermal expansion is 50 psia. Calculate the heat rejected by the working substance in Btu/lb. A. 31.83 B. 36.83 C. 34.83 D. 32.83 Answer: A 164. Which of the following BEST describe a closed thermodynamic system? A. Both energy and mass transfer take place across the boundary, but the mass transfer is controlled by valves B. There is no energy or mass transfer across the boundary. C. There is no energy transfer, but mass transfer exists D. There is no mass transfer, but energy transfer exists. Answer: D 165. Which of the following BEST describe the zeroth law of thermodynamics? A. When two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. B. Two thermodynamic systems are always in thermal equilibrium with each other. C. If two systems are in thermal equilibrium, then the third system will also be in thermal equilibrium. D. Two systems not in thermal equilibrium with a third system will also not be in thermal equilibrium with each other Answer: A 166. When is a closed thermodynamic system manifested? A. There is transfer of both mass and energy across the system boundaries B. Matter is not allowed to cross the boundary but energy transfer occurs across the boundary C. There is only transfer of mass but no heat and work energy are transferred D. There is absolutely no interaction of the system with surroundings Answer: B 172. A cubical tank, 1 m on a side, contains a mixture of 1.8 kg of nitrogen and 2.8 kg of an unknown gas. The mixture pressure and temperature are 290 kPa and 340 K. Determine the molecular weight of the unknown gas. A. 73 B. 70 C. 77 D. 91 Answer: A 178. The vapor pressure of zinc is given by the equation: In(P (solid)= - 15 ,780/T-0.755 ln(T)+19.25) and In(P) (bquid)= - 15.65 / T - 1.255 * ln(T) + 21.79. where T is absolute temperature in kelvin. What should be the triple point? A. 712 B. 175.44 C 334 D. 484.44 Answer: B 180. The vapor pressure of zinc is given by the equation In( ( 5 olid)=-15,7 B0/T-0.7 55 in(T)+19.25) and In( P)(liquid)=-15, 650 / T - 1.255 * ln(7) + 21.79 , where T the boiling temperature of zinc in deg. C at 5 * 10 raised to -4) atm? A. 468.8 B. 721.12 C. 484.7 D. 924 Answer: A 182. An air standard engine operates on Carnot cycle which have the ratio of maximum and minimum volume of 20. Given that the lower temperature of the cycle is fixed, determine the compression ratio of adiabatic compression if it is variable and the work done of the cycle is maximum. A. 12.3 B. 8.7 C. 5.7 D. 9.28 Answer: C 184. An air standard engine operates on Carnot cycle which have the ratio of maximum and minimum volume of 19. Given that the lower temperature of the cycle is fixed at 100 deg. C. determine the MAXIMUM thermal efficiency of the cycle if the compression ratio of adiabatic compression is variable A. 68.5 B. 49.50 C. 50.2 D. 75.28 Answer: B 186. A facility handling liquid methane at 115 K and 5 MPa needs to reduce its pressure to 1 MPa. Instead of throttling, an engineer proposes using a turbine for this process to generate power. Calculate the maximum amount of power that can be produced by plant in kWh/yr if the turbine operates continuously at a rate of P15.00/kWh. At 5 MPa, 115K: h=232.2 KJ/kg, s= 4.9945KJ / kg-K p = 422.15kg / (m ^3) At 1 MPa: h = 222.8KJ/kg A. 9,346,920 B. 9.237,480 C. 9,437,480 D. 9,146,920 Answer: A 187. A facility handling liquid methane at 115 K and 5 MPa needs to reduce its pressure to 1 MPa. Instead of throttling, an engineer proposes using a turbine for this process to generate power. Calculate the potential annual savings if the turbine operates continuously at a rate of P15.00/kWh At 5 MPa, 115K: h=232.2 KJ/kg, s= 4.9945KJ / kg-K p = 422.15kg / (m ^3) At 1 MPa: h = 222.8KJ/kg A. P145,403,800 B. P140,203,800 C. P147.362,200 D. P147,562,200 Answer: B 188. Which one of the following statements is CORRECT during adiabatic charging of an ideal gas into an empty cylinder from a supply main? A. The specific enthalpy of the gas in the supply main is equal to the specific internal energy of the gas in the cylinder. B. The specific enthalpy of the gas in the supply main is equal to the specific enthalpy of the gas in the cylinder. C. The specific internal energy of the gas in the supply main is equal to the specific enthalpy of the gas in the cylinder. D. The specific internal energy of the gas in the supply main is equal to the specific internal energy of the gas in the cylinder. Answer: A 189. Which of the following statements is CORRECT? A. The increase in entropy is obtained from a given quantity of heat transfer at a low temperature. B. The change in entropy may be regarded as a measure of the rate of the availability of heat for transformation into work. C. The entropy represents the maximum amount of work obtainable per degree drop in temperature.. D. The change in enthalpy of the maximum amount of work obtainable per degree drop in temperature. Answer: A 192. An open vertical cylindrical vessel, 2 m in diameter and 4 m high is filled with water to the top. If rotated on its own vertical axis in order to discharge a quantity of water to uncover a circular area at the bottom of a vessel 1 m in diameter. Find the angular speed in rpm. A. 93.65 B 91 65 C 97.65 D. 99.65 Answer: C 193. An open vertical cylindrical vessel, 2 m in diameter and 4 m high is filled with water to the top. If rotated on its own vertical axis in order to discharge a quantity of water to uncover a circular area at the bottom of a vessel 1 m in diameter. Calculate the volume of water left in the cylinder after rotation A. 157 cu. ft B. 137 cu ft C. 147 cu. ft D. 167 cu. ft Answer: D 194. A conical vessel with sides inclined 30º with its vertical axis is revolved about another axis 1 m from its own and parallel. How many revolutions per minute must it make in order that water poured into it will be entirely discharged by the rotative effect? A. 39.36 B. 37.36 C. 41.36 D. 43.36 Answer: A 195. The prototype vehicle features a hybrid drivetrain with a Stirling engine that operates between the temperature limit of 35 deg. C and 790 deg. C. The pressure of the working medium at the beginning of isothermal compression is 100 kPa with a compression ratio of 6. The heat is supplied at 950 kJ/min with a regenerator efficiency of 78%. Determine the net work done in HP A. 9.127 B. 13.822 C. 8.375 D. 11.71 Answer: D 196. The prototype vehicle features a hybrid drivetrain with a Stirling engine that operates between the temperature limit of 35 deg. C and 790 deg. C. The pressure of the working medium at the beginning of Isothermal compression is 100 kPa with a compression ratio of 6. The heat is supplied at 950 kJ/min with a regenerator efficiency of 78%. Determine the thermal efficiency of the cycle. A. 56.12 B. 55.16 C. 87.30 D 58.23 Answer: B 197. A Camot heat engine converts one-fifth of the heat input into power output. If the temperature of the sink is reduced by 100 deg. C, its thermal efficiency is doubled. Determine the temperature of the source in deg R A. 900.6 B. 400 C. 172 D. 446.0 Answer: A 198. A piston-cylinder device contains 0.05 m³ of gas initially at 200 KPa. At this state, a linear spring that has a spring constant of 150 KN/m is touching the piston but exerting no force on it. Now heat is transferred to the gas, causing the piston to rise and to compress the spring until the volume inside the cylinder doubles. If the cross-sectional area of the piston is 0.25 m², determine the total work done by the gas in Btu. A. 17.22 B. 2.84 C. 12.32 D. 32.32 Answer: C 199. For given compression ratio, which of the following ideal cycles have equal thermal efficiency? A. Stirling and Otto B. Diesel and Stirling C. Otto and Joule D. Joule and Diesel Answer: A 200. Power cycles are idealized Which of the following is NOT an idealization? A. Pressure drops in pipes are neglected B. Friction is absent C. Pipes connecting components are insulated. D. Heat transfer does not occur across a finite temperature difference. Answer: D 201. In the analysis of the Otto power cycle, which we is NOT assumed? A. The exhaust process is replaced by a heat rejection process B. All processes are quasiequilibrium processes C. The combustion process is a constant-pressure process D. The specific heats are assumed constant. Answer: C 202. By higher octane number of SI fuel it is meant that the fuel has A. Longer ignition delay B. higher heating value C. higher flash point D. lower volatility Answer: D 203. The brake power of a diesel engine, keeping other parameters constant, can be increased by A. increasing the pressure of intake air B. decreasing the density of intake air C. increasing the temperature of intake air D. decreasing the pressure of intake air Answer: A 204. In a diesel engine, the duration between the time of injection and ignition, is known as A. periof of ignition B. pre-ignition period C. delay period D. burning period Answer: C 205. Which inversion mechanism is also known as gnome engine? A. Four stroke engine B. Rotary I.C engine C. Two stroke engine. D. Crank and lever mechanism Answer: B 206. Which of the following statement about internal combustion engine is CORRECT? A. Diesel engines take less space than petrol engine for same power output. B. All emissions are reduced by selective catalytic converter. C. Diesel can be filled in petrol engine, but not vice versa. D. Knocking doesn't depend on spark timing. Answer: A 207. The following are CORRECT about the valve of internal combustion engine, EXCEPT A. Exhaust valve diameter is bigger than inlet valve diameter. B. Exhaust valve is made of two different materials. C. Inlet valve diameter is bigger than inlet valve diameter. D. Valve used in 4-stroke diesel engine are called poppet valves. Answer: A 208. Why is an engine piston is usually made of aluminum alloy? A. Because it is cost-effective. B. Because it is stronger C. Because it has less wear D. Because it is lighter. Answer: D 209. When will the exhaust of a vehicle from an internal combustion engine will have a maximum of hydrocarbons? A. Accelerating B Cruising C. Idling D. Running at high speed Answer: C 210. The stroke of an engine is the A. length of the connecting rod B. volume of the cylinder C. distance between TDC and BDC D. internal diameter of cylinder Answer: C 211. The viscosity of most commercially available petroleum lubrication oil change rapidly above,____F. A. 120 B. 180 C. 150 D. 130 Answer: B 212. What air pressure is needed for air starting a Diesel engine in psi? A. 350 B. 250 C. 450 D. 150 Answer: A 213, in a diesel engine, what element in the fuel make the work of the lubricant more difficult? A. High cetane number B. Water and ash content C. High octane number D. Sulphur and asphaltene Answer: D 214. What is a small auxiliary engine in which is usually portable or semiportable and powered by steam? A. Portable B. Steam C. Donkey D. Disk Answer: C 215. Spark plug makes use of which of the following materials for insulation? A. Glass B. Asbestos C. Slate D. Porcelain Answer: D 216. In a valve head, the disk part of a poppet valve gives a tight closure to A. steam valve B. valve seat C. gate valve D. globe valve Answer: B 217. In the 21 century, the design of gasoline engine, the thermal efficiency is which of the following? A. 55% B. 100% C. 40% D. 49% Answer: A 218. It is the maximum pressure and temperature attained in the cycle, the combustion is A. Complete B. Incomplete C. stoichiometric D. Continues Answer: B 219. Inverted engine is an engine in which the cylinders are A. above the crankshaft B. above the camshaft C. below the camshaft D. below the crankshaft Answer: D 220. The typical scavenging efficiency of a four-stroke diesel engine is % A. 97 B. 82 C. 86 D. 95 Answer: A 230. A six-cylinder engine with a compression ratio of 8 and a total volume MTDC of 500 t, intakes atmospheric ar at 20 deg C The maximum temparature during a суcle 1500 deg C. Assuming Otto cycle, calculate the mass of air in kg A 0.004281 B. 0.002481 C. 0.001823 D. 0000273 Answer: A 236. For maximum specific output of a constant volume cycle, the temperature of the working fluid at the end of compression and expansion A. the speed should be high. B. the working fluid should be air. C. should be equal. D. suction temperature should be high. Answer: C 237. In a petrol engine car, which one of the following performance characteristics is affected by the front-end volatility? A. Engine warm-up and spark plug fouling B. Hot starting and vapor lock C. Spark plug fouling and hot starting D. Vapor lock, engine warm-up and spark plug fouling Answer: B 238. In Spark Ignition engine for higher thermal efficiency the compression ratio should be A. surface to volume ratio should be high. B. heat liberation during combustion should be maximum. C. high within the available limits. D. long flame travel distance. Answer: C 239. Why is divided chamber diesel engines use lower injection compared to open chamber engines? A. High air swirl does not require high injection pressures for atomization. B. Pintle nozzles cannot withstand high injection pressures. C. High injection pressures may cause over penetration. D. High injection pressure causes leakage of the fuel at the pintle. Answer: A 240. Which of the following factors increase the tendency for knocking in Compression Ignition engine? A. Increasing both the speed and the injection advance B. Increasing both the compression ratio and the coolant temperature. C. increasing the speed, injection advance and coolant temperature. D. Increasing the compression ratio. Answer: C 250. A single cylinder 4-stroke diesel engine running at 2000 RPM uses 3.8 kg of fuel per hour. It has an injector with a single orifice nozzle and the injection period is 22 deg, crank angle. If the average injection pressure is 150 bar and the average pressure inside the cylinder is 30 bar, calculate the volume (in m³) of fuel injected per cycle. A. 7.2 * 10 ^ - 4 B. 5.3 * 10 ^ - 6 C. 3.6 * 10 ^ - 8 D. 3.5 * 10 ^ - 8 Answer: A 262. The following are properties of air which increase with rise in temperature, EXCEPT A. Thermal conductivity B. Density C. Thermal diffusivity D. Dynamic viscosity Answer: B 263. Which of the following is an example of transient heat flow? A. Cooling of water B. Current carrying conductors C. Spherical conductor carrying superheated steam D. heating and cooling of enclosures due to solar radiation Answer: D 264. The temperature for transient heat conduction in a solid is explained by A. Blot and Fourier number B. Peelet number C. Prandtl and Peelet number D. Mach number and Biot Number Answer: A 265. What is the PRIMARY reason why Heat pipes are widely used nowadays? A. It acts as an insulator B. It acts as superconductor C. It acts as conductor and insulator D. It acts as a fin Answer: B 266. Which of the following has LEAST value of conductivity? A. Water B. Rubber C. Air D. Plastic Answer: C 280. Which of the following is expected to have HIGHEST thermal conductivity? A. Steam B Water C. Melting ice D. Solid ice Answer: D 281. Why are metals a good thermal conductor? A. Because they have free electrons. B. Because their atoms are relatively closer. C. Because their surfaces reflect. D. Because their atoms are of larger size. Answer: A 287. What will happen to the heat loss to surroundings if the thickness of insulation of a round circular pipe is increased? A. Convection and conduction increases B. Convection decreases, while that due to conduction increases C. Convection and conduction increases D. Convection increases, while that due to conduction decreases Answer: D