Pre Board Powerplant Set B 2011

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INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by marking the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil No.2 only. MULTIPLE CHOICE 1.

A gas is heated at a constant temperature of 550 C until the entropy increases by 3.00 x 10 6 J/K. How much heat is added? A. 2.5 GJ * C. 2.7 GJ B. 2.9 GJ D. 3.1 GJ


What would be the resistance of the scale deposit if the overall heat transfer coefficient for a tube reduced from 1,500 W/m2 K to 1,100 W/m2 K? A. 2500 W/m2 K C. 3500 W/m2 K 2 B. 4125 W/m K * D. 5550 W/m2 K


Two different types of heat exchangers are being considered – parallel flow and counter flow. The heating fluid is water at a rate of 4.0 kg/min. which enters at 60 C and leaves at 40 C. The heated fluid is also water at a rate of 8.0 kg/min. It enters at 10 C and leaves at 20 C. What would be the relative sizes of the two types of heat exchanger? A. They would be equal in size B. The counter flow heat exchanger would be 10 % larger C. The parallel flow heat exchanger would be 5 % smaller D. The parallel flow heat exchanger would be 6 % larger *


A dam 15 m high has a water behind it to a depth of 10 m. What is the overturning force per meter of width? A. 1.6 MJ * C. 2.0 MJ B. 1.8 MJ D. 2.3 MJ


A two meter I.D. pipe is flowing half full. What is the hydraulic radius? A. 1.00 m C. 1.50 m B. 0.50 m * D. 1.75 m


Why must instrumentation and measurement equipment be maintained to provide accurate measurements? A. It is in the union contract B. The insurance company requires it C. To keep tabs on the manufacturing process D. To ensure part replacement compatibility *


A large paper plant uses its own cogeneration power plant to generate its electricity because A. it permits the use of a more efficient generator B. the company can better control the voltage C. it does away with high power lines leading to the plant D. it provides a more efficient conversion of fuel *


A large municipal power plant produces 1,000 MW of power. The overall plant efficiency is 32 %. Coal with a heating value of 24 MJ/kg is used to heat the boilers. How much coal is burned each day? A. 10,500 metric tons C. 12,000 metric tons B. 11,250 metric tons * D. 12,500 metric tons


An office air conditioning system drew in a quantity of hot air from outside, cooled it to 1 C, and mixed it with the internal air of a building. Care was taken to supply enough fresh air to eliminate objectionable odors. The temperature of the space was maintained constant, and yet some people became uncomfortable in the afternoon. Why? A. The relative humidity had dropped * B. When a person spends a long time at a constant temperature that person becomes uncomfortable C. Radiant heat from others in the office made the space uncomfortable D. The complainers were not really uncomfortable, they were just bored


What would be the cooling requirement due to the emission of a body heat to maintain a comfortable temperature in a dance hall that had an attendance of 1500 people if it has been determined that 75 % of the people will be dancing and the others will be seated. Tests have

shown that an adult will give off 71.8 W of sensible heat while engaging in moderate dancing, and 57.1 W of sensible heat while sitting. The latent heat emissions for similar situations have been found to equal 177.3 W for dancers, and 45.4 sitters. A. 200 kW C. 267 kW B. 301 kW D. 319 kW * 11.

A refrigerator is rated at USA one ton capacity. It maintains a cooling temperature of 4.4 C (evaporator temperature). A refrigerant with a refrigerating effect of 136 kJ/kg is in the condenser just ahead of the expansion valve. If the refrigerant vapor has a density of 19.80 kg/m3 what should be the capacity of the compressor? A. 0.078 m3/min * C. 0.091 m3/min 3 B. 0.102 m /min D. 0.113 m3/min


The volumetric output of a centrifugal pump is reduced by closing a valve part way on the intake side of the pump, throttling the intake. The reduction of flow is accompanied by “ popping “ noises which seem to come from inside the case. What is the probable cause? A. The impeller has broken B. Dirt particles have got into the pump intake C. The intake valve flow seal is loose and vibrates D. The fluid is cavitating *


A centrifugal pump pumps water at the rate of 1000 L/min against a head of 10 m. What is the power requirement? A. 1.59 kW C. 1.98 kW B. 1.63 kW * D. 1.07 kW


A fan delivers 225 m3 of standard air per minute against a back pressure of 10.0 cm of water to a coal burning furnace. What power is required to operate the fan if it is 85 % efficient? A. 4.33 kW * C. 3.95 kW B. 3.68 kW D. 4.87 kW


Compute the available power if a hydropower station has an average flow of 1,500 cubic meters per second and a head of 420 meters. A. 8420 MW C. 63 MW B. 45 MW D. 6174 MW


A turbine with an overall efficiency of 85% is supplied with 8 cubic meters per second of water under a net head of 200 meters. Calculate the power developed by the turbine. A. 15696.0 kW C. 17585.5 kW B. 13341.6 kW D. 11230.4 kW


An engine operating on a Carnot cycle between temperatures of 500 C and 30 C produces 50 kJ of work. What change in entropy occurs during the heat rejection process? A. -0.1064 kJ/K * C. -0.2128 kJ/K B. -0.1340 kJ/K D. -0.2056 kJ/K


Water flows through a pipe of 10 mm diameter at a velocity of 1 m/s. Determine the velocity of water if the pipe diameter gradually increases to 15 mm. A. 0.55 m/s C. 0.44 m/s * B. 0.33 m/s D. 0.66 m/s


Water in an insulated container is heated by 3 kW electric heater. In order to maintain a uniform temperature inside the container, a 200 W capacity mechanical stirrer is used. Assuming heat and work transfer to the water only, determine the change in internal energy of the water in 10 minutes of time. A. 120 kJ C. 1800 kJ B. 1200 kJ D. 1680 kJ * In an Otto cycle, the initial volume of 50 cc of air and petrol mixture is compressed to 10 cc isentropically with index of compression k = 1.4 . Calculate the thermal efficiency. A. 47.5 % * C. 45.7 % B. 37.5 % D. 57.7 %



A reversed Carnot cycle absorbs heat at the rate of 1 kW from cold chamber maintained at 250 K and discharges it to the atmosphere at 300 K. Find the work required for the cycle. A. 1 kW C. 0.2 kW * B. 1.5 kW D. 0.5 kW


A steel plate of 10 cm thickness and 1 sq. m area is maintained at temperature of 600 C at one face and 100 on the other side. The thermal conductivity of steel is 20 W/m K. Calculate the conduction heat transfer rate through this plate.

A. 100 kW * B. 300 kW

C. 200 kW D. 400 kW


A composite wall is made of 2 slabs with outermost surface temperatures maintained at 1300 C and 115 C. The first slab has a thickness of 500 mm and thermal conductivity 0f 1.4 W/m K and the thickness and the thermal conductivity of the second slab are 161 mm and 0.35 W/m K respectively. Calculate the conduction heat transfer through this composite wall per sq. m area. A. 2.45 kW C. 3.45 kW B. 4.45 kW D. 1.45 kW *


A hollow cylinder of 2 m length has inner and outer radius as 50 mm and 100 mm. The inner surface and outer surface temperatures of this cylinder are 300 C and 200 C. Determine the conduction heat transfer rate through this cylinder. Assume thermal conductivity of this cylinder as 70 W/m K. A. 126.9 kW * C. 192.6 kW B. 196.2 kW D. 162.9 kW


Steam is carried in a steel pipe having inner radius 5 cm and outer radius 5.5 cm. This pipe is covered with two layers of insulation each 5 cm thick. The thermal conductivity of steel pipe, first and second layers of insulation are 50, 0.06 and 0.12 W/m K respectively. The temperature of steam is 225 C and the temperature of the outermost surface is 25 C. Calculate the intermediate temperatures. A. 224.97 C, 79.2 C C. 224.97 C, 72.9 C * B. 201.67 C, 79.2 C D. 201.97 C, 72.9 C


A coal fired steam power plant has to generate 1000 MW of electricity. The efficiency of boiler, turbine and generator are 85 %, 80 % and 90 % respectively. If the calorific value of coal is 20 MJ/kg, calculate the fuel required for the plant per day. A. 7059 tons * C. 8001 tons B. 6543 tons D. 6666 tons


A four stroke single cylinder IC engine develops 5 kW of brake power with mechanical efficiency of 80 % running at 1500 rpm. If the mean effective pressure is 7 bar, find the diameter of the cylinder assuming stroke and diameter are equal. A. 97 mm * C. 79 mm B. 58 mm D. 85 mm


A petrol engine develops 20 kW of brake power. If the brake thermal and mechanical efficiency are 25 % and 80 % respectively, calculate the indicated thermal efficiency. A. 35.21 % C. 32.51 % B. 33.25 % D. 31.25 % *


An IC engine works with thermal efficiency of 28 % with a fuel having a calorific value of of 40,000 kJ/kg. If its relative efficiency is 50 %, find the specific fuel consumption in kg/kW hr. A. 0.28 C. 0.32 * B. 0.45 D. 0.25


A 75 MW power plant has an average load of 35,000 kW and a load factor of 65%. Find the reserve over peak. A. 21.15 MW * C. 25.38 MW B. 23.41 MW D. 18.75 MW


A hydraulic turbine receives water from a reservoir at an elevation of 100 m above it. What is the minimum water flow in kg/s to produce a steady turbine output of 50 MW. A. 50,247 C. 50,672 B. 50,968 * D. 59,465


A reaction turbine develops 500 BHP. Flow through the turbine is 50 cfs. Water enters at 20 fps with a 100 ft pressure head. The elevation of the turbine above the tailwater level is 10 ft. Find the effective head. A. 130.2 ft C. 110.2 ft B. 120.2 ft D. 116.2 ft *


A hydro-electric plant discharges water at the rate of 0.75 m3/s and enters the turbine at 0.35 mps with a pressure of 275 kPa. Runner inside diameter is 550 mm, speed is 520 rpm and the turbine efficiency is 88%. Find the turbine speed factor. A. 0.638 * C. 0.836 B. 0.386 D. 0.386


During sensible heating, the absolute humidity remains constant but the relative humidity: A. increases C. remains constant

B. decreases *

D. zero


A 2.2 kW refrigerator or heat pump operates between –17 C and 38 C. The maximum theoretical heat that can be transferred from the cold reservoir is nearest to A. 7.6 kW C. 15.6 kW B. 4.7 kW D. 10.2 kW *


The isentropic compression of 1 m3 of air, cp /cv = 1.4, from 20 kPa to a pressure of 100 kPa gives a final volume of A. 0.16 m3 C. 0.32 m3 * 3 B. 0.20 m D. 0.40 m3


The relative humidity become 100 and where the water vapor starts to condense A. critical point C. dew point * B. saturated point D. cloud point


A property of lubricating oil that measure the thickness of the oil and will help determine how long oil will flow at a given temperature is known as A. viscosity * C. pour point B. flash point D. cloud point


The Westphal balance is a laboratory instrument used to measure which of the following ? A. volume C. weight B. mass D. specific gravity *


If the initial volume of an ideal gas is allowed to expand to twice its original volume and lower its temperature by half, the pressure A. doubles C. remains B. is reduced to one fourth * D. is indeterminate


A solidified form of carbon dioxide is termed as A. clear ice C. pure ice B. white ice D. dry ice *


What is the Chemical formula of Ozone? A. O3 * C. O2 B. D2O D. O1


The temperature at which oil will vaporize and burn continuously A. Cloud point C. Critical point B. Dropping point D. Fire point *


Which of the following is the chemical composition of fuel ? A. 65 carbon, 35 hydrogen C. 75 carbon, 25 hydrogen B. 85 carbon, 15 hydrogen * D. 90 carbon, 5 hydrogen


In a standard Otto cycle, when the compression ratio is increased, then the thermal efficiency A. will decrease C. will not change B. will increase * D. cannot be determined


If a man touches two metals which were kept together at room temperature, why would one metal feel colder than the other? A. One has a high temperature coefficient B. One has a lower temperature C. One has a high thermal conductivity * D. One has a high temperature


Find the kinematic viscosity of oil having a specific gravity of 0.8 and a viscosity of 0.01 poise. A. 1.25 x 10-6 m2/s * C. 2.25 x 10-6 m2/s B. 3.25 x 10-6 m2/s D. 0.25 x 10-6 m2/s


A combustion equipment which is used for firing solid fuels A. Stoker * C. Fuel igniter B. Burner D. Air combustion


The ratio of the internal thermal resistance of a solid to the boundary layer thermal resistance is described by A. Biot number * C. Prandtl number B. Nusselt number D. Reynolds number


For a fuel-rich mixture, the equivalence ratio for a given mass of air is always A. greater than one * C. less than one

B. equal to one

D. less than or equal to one


In heat transfer by conduction, due to symmetry the heat flow at a point is perpendicular to the isothermal surface through the point. This mode of conduction is a characteristic of A. non - isotropic C. insulators B. isotropic solid * D. conductors


In Diesel power plants, its purpose is to reduce the weight to A. supercharging * C. turbo-charging B. lubricating D. rubber brushing


Indicator used to determine the anti-knock characteristics of gasoline A. octane number * C. heptane number B. cetane number D. dodecane number


Why should you avoid bending or twisting of fan blades in an air conditioning unit? A. It will not cause ice build-up B. It will wear out the motor bearings & cause noise * C. It may not slice suction line D. It decreases the volume flow of refrigerant


The total stack flow loss is usually less than what percentage of calculated draft ? A. 4 C. 6 B. 5 * D. 7


An improved steam power cycle in which steam are extracted from the turbine for feedwater heating. A. Rankine cycle C. Topping cycle B. Binary cycle D. Regenerative cycle *


The carbon dioxide (CO2) percentage in the flue gas of an efficiency fired boiler should be approximately. A. 6 C. 18 B. 12 * D. 24


What kind of heat exchanger where water is heated to a point that dissolved gases are liberated ? A. Evaporator C. Deaerator * B. Intercooler D. Condenser


When water inside a beaker is heated; over a hot plate, the mechanism of heat transfer through the water is considered to be A. conduction C. natural convection * B. forced convection D. radiation


An ideal surface that absorbs all incident radiation, regardless of wavelength and direction and is also considered to be perfect emitter is referred to as a A. gray body C. black body * B. black hole D. pin hole


Which of the following controls flow of water to boiler in one direction ? A. Globe valve C. Gasket B. Check valve * D. Steam trap


Generally steam turbines in power stations operate at A. 3000 rpm * C. 400 rpm B. 1000 rpm D. 500 rpm Quality is a measure of which of the following ? A. Volatility C. Dryness * B. Moisture D. Wetness


power ratio


The property of the solid that provides a measure of the rate of heat transfer relative to the energy storage is referred to as A. thermal conductivity C. thermal diffusivity * B. heat capacity D. viscosity


Most people are comfortable with the relative humidity of A. 30 % to 70 % * C. 10 % to 40 % B. 20 % to 30 % D. 40 % to 80 %


What is the minimum factor of safety of a re-installed or second hand boiler ? A. 4 C. 6 *

B. 5

D. 7


Which of the following is not an instrument used to measure flow rates ? A. Anenometer C. Flowmeter B. Rotameter D. Velometer *


When the movement of a gas vapor is effected at a low pressure i. e., up to 0.1 kg/cm 2, the equipment used is A. jet C. blower * B. compressor D. fan


The heat transferred radially across insulated pipe per unit area A. remain constant B. inversely proportional to the thermal conductivity C. decrease from pipe wall to insulated surface * D. increase from pipe wall to insulated surface


Under normal operating conditions, when a solid material to be dried is placed inside a batch tray dryer, the material is usually subjected A. under constant drying conditions * B. under variable drying conditions C. under high temperature drying D. under low temperature drying


States that the external pressure applied to a confined fluid increases the pressure of every point in the fluid by an amount equal to the external pressure. A. Archimedes principle C. Bernoulli’s principle B. Pascal’s law * D. Dalton’slaw


A heat exchange device used to provide heat transfer between the exhaust gases and the air prior to its entrance to the combustor. A. Economizer C. Regenerator * B. Reheater D. Heat exchanger


A change of phase directly from vapor to solid without passing through the liquid state is called as A. Sublimation C. Solidification B. Vaporization D. Deposition *


In terms of heat transfer, the use of a cooling tower is said to be more efficient and more economical compared to an ordinary heat exchanger since A. large volume of air is available and free B. temperature profiles of air and water can cross each other * C. large amount of water can be processed D. a cooling tower is much smaller and cheaper than a heat exchanger


A boiler where the water passes through inside the tube while the hot gases surround the outside surface of the tube is A. fire-tube boiler C. stoker B. water-tube boiler * D. Scotch boiler


The simultaneous on-site generation of energy and steam from the same plant output is A. Regeneration C. Binary cycle B. Waste heat recovery D. Co-generation *


Which of the following indicates the water level inside the boiler ? A. Baffles C. Water walls B. Fusible plug D. Water column*


A line that shows the relation of the steam consumption and the load of steam turbinegenerator. A. Dalton’s line C. Jonval’s line B. Willan’s line * D. Rankine line


In boilers, what is the maximum distance of any smokestack from any woodwork or framing ? A. 405 mm C. 305 mm * B. 505 mm D. 205 mm


What is the temperature of a pure substance at a temperature of absolute zero ? A. Unity C. Infinity

B. Zero *

D. Undefined


In cooling cycle, the dry bulb temperature (db) of the air is lowered. When this happens the relative humidity A. increases * B. decreases C. remains constant D. increases or decreases depending on the temperature at which it is cooled


A pipe with an outside diameter of 2 ½ in. is insulated with a 2 in. layer asbestos ( k = 0.12 ) followed by a layer of cork 1 ½ in thick ( k = 0.03 ). If the temperature of the outer surface of the pipe is 290 oF and that of the outer surface of the cork is 90 oF, calculate the heat loss per hour per 100 ft of insulated pipe. A. 6,190 Btu/hr * C. 7869 Btu/hr B. 4560 Btu/hr D. 3678 Btu/hr


Which of the following converts energy of water to mechanical energy ? A. Pump C. Generator B. Turbine * D. Draft tube


In gas compressors, when the volumetric efficiency increases, then the piston displacement is A. increased C. constant B. decreased * D. defined


Which of the following smoothens the flow due to the nature of flow of the liquid from a reciprocating pump ? A. Air filter C. Strainer B. Air chamber * D. Foot valve


Pump whose purpose is to increase the effective water pressure by sucking water from a public service main or private use water system A. Submersible pump C. Horizontal split-case pump B. Booster pump * D. Vertical shaft turbine pump


When a solid material is said to be “dry” it means that A. the solid does not contain any moisture B. the solid still contains very small amount of moisture * C. the solid contains equilibrium moisture D. the weight of the solid is the same as the bone dry weight


In case of axial flow compression for minimum fluid friction and blade tip clearance losses, the blades of an axial flow compressor are designed for A. 80 reaction C. 60 reaction B. 85 reaction D. 53 reaction *


This is the temperature of a vapor - gas mixture as ordinarily determined by the immersion of a thermometer in the mixture. A. Wet bulb temperature C. Dew point temperature B. Dry bulb temperature * D. Saturation temperature


A hot block is cooled by blowing cool air over its top surface. The heat that is first transferred to the air layer close to the block is by conduction. It is eventually carried away from the surface by A. convection * C. conduction B. radiation D. thermal


When drying banana chips under the sun, the rate of drying is faster A. on a slightly breezy day C. on a cloudy day B. on a calm day D. on a hot and windy day *


As a liquid changes phase to a solid , its entropy_____ A. increases C. remains the same B. decreases * D. constant


As a gas is cooled in an isobaric process, its volume___ A. increases C. remains the same B. decreases * D. constant


During the compression process, the internal energy of the refrigerant vapor A. increases * C. remains the same

B. decreases

D. none of the above


As the saturation pressure of the refrigerant in the evaporator increases, the refrigeration effect of the process ____ A. increases * C. remains the same B. decreases D. none of the above


The type of compressor that uses ring valves is a ____compressor A. roller C. rotary vane B. scroll D. reciprocating *


A receiver tank is used to___ A. hold the excess refrigerant during lighter loads * B. collect oil from the base of a riser C. separate liquid from vapor refrigerant D. all of the above


As the refrigeration receiver_____ A. increases B. remains the same










C. decreases * D. varies

If the specific heat for a certain process is given by the equation c = 0.2 + 0.00005T Btu per lb – deg, how much heat should be transferred to raise the temperature of 1 lb from 500 R to 2000 R? A. 394 Btu/lb * C. 590 Btu/lb B. 788 Btu/lb D. 187 Btu/lb

100. If the volumetric efficiency of a pump is 95%, what is the slip? A. 0.05 * C. 0.00005 B. 0.005 D. 0.0005

*** END***


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