Hello friends in this post we are going to discuss about Introduction & Thermal Power Plant MCQ with Answers | Introduction & Thermal Power Plant Multiple choice questions | Introduction & Thermal Power Plant Objective type questions
1 Which of these is an output of a ‘Furnace’?
a) Fuel gas b) Air c) Flue gases d) Water Vapor
Explanation: A furnace takes in a Fuel gas, Air & Water Vapour while it gives off Flue Gases.
2 Which of these is a ‘working fluid’ in liquid phase?
a) Water b) Steam c) Mercury d) Oxygen
Explanation: The working fluid is water in liquid phase & steam in gas phase.
3 What kind of energy output is obtained from a ‘Steam Power Plant’?
a) Heat energy b) Sound energy c) Electricity d) Thermal energy
Explanation: A ‘Steam Power Plant’ is used primarily for electricity generation.
4 What kind of a process does a ‘Steam Power Plant’ undergoes?
a) Adiabatic b) Cyclic c) Irreversible d) Expansion
Explanation: As the internal energy change in the ‘Steam Power Plant’ is ZERO. Hence, the entire plant obeys a Cyclic Process.
5 The product of efficiency & heat transferred to the working fluid is?
a) Net temperature change b) Net work done c) Net enthalpy change d) None of the mentioned
Explanation: The formula of efficiency of a steam power plant is, Efficiency=net work done/net heat transferred
6 The components of a Steam Power Plant are?
a) Evaporator, Condenser, Boiler, Expansion valve b) Evaporator, Condenser, Boiler, Turbine c) Boiler, Turbine, Condenser, Pump d) Boiler, Turbine, Pump, Expansion valve
Explanation: A Steam Power Plant has the sequence, Boiler, Turbine, Condenser, Pump
7 Shaft work is fed to __________ for getting an electrical output.
a) Motor b) Generator c) Rotor d) Accelerator
Explanation: The flow in a Steam Power Plant follows the sequence, Source-Shaft-Generator
8 Ideal ‘Rankine Cycle’ is a __________ process.
a) Reversible b) Irreversible c) Both of the mentioned d) None of the mentioned
Explanation: Ideal Rankine Cycle is a reversible process.
9 For analytical purposes, the Rankine Cycle is assumed to be in?
a) Unsteady flow operation b) Turbulent flow operation c) Steady flow operation d) Laminar flow operation
Explanation: For analytical purposes , always steady flow operation is considered, as in unsteady flow, the various fluid properties vary considerably which remain same when the steady flow operation is assumed.
10 The net work done in a Rankine Cycle is the difference of?
a) Condenser work & Boiler work b) Boiler work & Pump work c) Turbine Work & Pump work d) Condenser work & Pump work
Explanation: The net work done in a Rankine Cycle is given by, Wnet = Wt – Wp.
11 In a Rankine Cycle, heat input is provided to?
a) Condenser b) Pump c) Turbine d) Boiler
Explanation: As the heating of the liquid working fluid occurs in the Boiler, the heat input is provided to the Boiler for the same.
12 In a Rankine Cycle, heat output is obtained from?
a) Condenser b) Boiler c) Turbine d) Pump
Explanation: As the heated water comes to the condenser, it loses its heat & gets condensed. The heat output is obtained from Condenser.
13 The water that flows from the Pump is?
a) Compressible b) Incompressible c) Unsteady d) None of the mentioned
Explanation: The water flowing through the pump is incompressible so as to extract work from the turbine.
14 Steam Rate is the reciprocal of _________
a) Net work done b) Heat extracted from condenser c) Heat given to reciprocal d) Work done by turbine. Answer: a
Explanation: Steam Rate is given by, Steam Rate = 1/Wnet.
15 Which of these is sometimes neglected?
a) Turbine work b) Pump work c) Condenser heat d) Boiler heat
Explanation: Pump Work is very small as compared to Turbine Work & so is often neglected.
16 Efficiency of a Rankine Cycle is also expressed as__________
a) Capacity Ratio b) Heat Rate c) Heat Ratio d) Steam Rate
Explanation: The relation between Heat Rate & Efficiency is, Heat Rate = Efficiency of a Rankine Cycle
17 Steam Power Plants are more popular in electric power generation because
a) Work output of turbine is very large than work input to the pump b) Work output of turbine is very small than work input to the pump c) Work output of turbine is equal to work input to the pump d) None of the mentioned.
Explanation: In a Steam Power Plant, the positive difference of turbine work & pump work makes it useful in electricity generation.
18 The most common type of Evaporator is?
a) Flooded Evaporator b) Plate Evaporator c) Coil Evaporator d) Brine Evaporator
Explanation: The most common type is a coil winding on a plate & so the name ‘plate evaporator’
19 In Rankine Cycle, water is converted to saturated liquid in ___________
a) Evaporator b) Economizer c) Superheater d) Preheater
Explanation: The saturation of water occurs in an Economizer in a Rankine Cycle.
20 If Evaporator & Condenser pressures are p & q, the intercooler pressureP is given as?
a) P=pq b) P=p/q c) P=(pq)(1/2) d) P=p2q
Explanation: The relation between Intercooler pressure, Evaporator & Condenser is, P = (pq)(1/2).
21 Phase change at constant pressure takes place in?
a) Economiser b) Evaporator c) Superheater d) Air-Preheater
Explanation: Superheater undergoes a change in phase at constant pressure.
22 Which of these factors don’t cause Internal Irreversibility of a Rankine cycle?
a) Throttling b) Mixing c) Fluid Friction d) Fluid flow
Explanation: The Rankine cycle is an Irreversible cycle. For a cycle to be irreversible naturally throttling, mixing & friction in fluids are the factors that cause this Irreversibility.
23 What is the unit of Heat rate?
a) kJ/KW b) KW/kJ c) kJ d) KW
Explanation: Heat rate is the rate of input required to produce unit shaft output.
24 Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2
a) has higher thermal efficiency than the Carnot cycle operating between same pressure limits b) has lower thermal efficiency than Carnot cycle operating between same pressure limits c) has same thermal efficiency as Carnot cycle operating between same pressure limits d) may be more or less depending upon the magnitudes of p1 and p2
Explanation: Area under P-V curve for Rankine will be more as compared to Carnot cycle
25 Rankine efficiency of a Steam Power Plant
a) improves in Summer as compared to that in Winter b) improves in Winter as compared to that in Summer c) is unaffected by climatic conditions d) none of the mentioned
Explanation: In winters, temperature of cooling water is low, which increases Condenser’s efficiency.
26 Rankine cycle comprises of
a) two isentropic processes and two constant volume processes b) two isentropic processes and two constant pressure processes c) two isothermal processes and two constant pressure processes d) none of the mentioned
Explanation: Rankine cycle is a reversible cycle which have two constant pressure and two constant temperature processes
27 In Rankine cycle, the work output from the turbine is given by
a) change of internal energy between inlet and outlet b) change of enthalpy between inlet and outlet c) change of entropy between inlet and outlet d) change of temperature between inlet and outlet
Explanation: Work output(turbine) = h1-h2.
28 Rankine cycle efficiency of a good Steam Power Plant may be in the range of?
a) 15 to 20% b) 35 to 45% c) 70 to 80% d) 90 to 95%
Explanation: Efficiency of Rankine cycle in actual working condition is found to be between 35 to 45%.
29 A simple Rankine cycle operates the Boiler at 3 MP a with an outlet temperature of 350°C and the Condenser at 50 kPa. Assuming ideal operation and processes, what is the thermal efficiency of this cycle?
a) 7.7 b) 17.7 c) 27.7 d) 37.7
Explanation: Fixing the states; h1 = 340.5 kJ/kg, h2 = h1 + v1 (P2 – P1) = 343.5 kJ/kg, h3 = 3115.3 kJ/kg, s3 = 6.7428 kJ/kg – K, x4 = 0.869, and h4 = 2343.9 kJ/kg. Thus, η = 1 – Qout / Qin = 1 – (h4 – h1) / (h3 – h2) = 27.7%.
30 A simple Rankine cycle produces 40 MW of power, 50 MW of processheat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?
a) 50 b) 60 c) 70 d) 80
Explanation: Application of the first law to the entire cycle gives Qin = Qp + Qreject + W = 150 MW. The utilization factor is then = (Qp + W) / Qin = 60%.
31 Pulverized coal is
a) coal free from ash b) non-smoking coal c) coal which bums For long time d) coal broken into fine particles
Explanation: Pulverized coal also known as powdered coal or coal dust since it is as fine as face powder in cosmetic make-up.
32 Critical pressure of water is
a) 1 kg / cm2 b) 100 kg / cm2 c) 155 kg / cm2 d) 217.7 kg / cm2
Explanation: The critical pressure of a substance is the pressure required to liquefy a gas at its critical temperature.
33 Coal used in power plant is also known as
a) steam coal b) charcoal c) coke d) soft coal
Explanation: Because this coal is used to generate steam.
34 The maximum temperature of steam that can be used is fixed from metallurgical considerations. This temperature limit is called?
a) Mining Limit b) Metallurgical Limit c) Metallic Limit d) None of the mentioned
Explanation: ‘Metallurgical Limit’ is defined as the lowest temperature limit of usable steam fixed by metallurgical considerations.
35 Most of the turbine expansion takes place in?
a) Liquid Region b) Solid Region c) Vapour Region d) Plastic Region
Explanation: Most of the turbine expansion should take place in the vapour region, so as to increase the life of the blades of the turbine
36 Which of the following diagrams are used while analyzing the effect of superheat & Inlet Pressure on mean temperature of heat addition?
a) P-V diagram b) T-S diagram c) P-T diagram d) V-T diagram
Explanation: Using the T-S diagram gives us an overview as to where a particular process occurs, i.e., it is within the solid region, the gaseous region or the vapour region. So, here, we prefer T-S diagram for analysis process.
37 The cycle efficiency ________________ with the _____________ of condenser pressure.
a) decreases, decrease b) increases, decrease c) remains same, decrease d) does not vary, decrease
Answer: b Explanation: As the decrease in condenser pressure mainly depends on the available cooling water temperature & thus on the climatic conditions of the place. Hence, cycle efficiency being a function of condenser pressure has an inverse relation with the condenser pressure.
38 An increase in inlet steam temperature ___________ the heat rate.
a) lowers b) increases c) does not have any effect on d) temperature has no significance in heat rate
Answer: a Explanation: An increase in inlet steam temperature, i.e. an increase in superheat at constant inlet steam pressure & condenser pressure gives a steady improvement in cycle efficiency & lowers the heat rate due to an increase in the mean temperature of heat addition
39 For the given values of efficiency, inlet steam pressure and quality ofsteam, pressure limits can be determined by ?
a) Mollier Charts b) Gantt Charts c) Both of the mentioned d) None of the mentioned
Explanation: The pressure limits can be readily determined by drawing the corresponding expansion line of the turbine om a Mollier Diagram
40 Why Reheating of steam is used?
a) to increase efficiency b) to increase work output c) to increase Turbine Inlet Temperature d) to reduce amount of fuel used
Explanation: Work output = work done by turbine – work done by compressor.
41 Reheating of steam
a) decreases steam rate b) increases steam rate c) no effect on steam rate d) none of the mentioned
Explanation: Since work output increases the steam rate decreases.
42 Why don’t we use more than two reheats?
a) not economical b) increased mechanical stresses c) net efficiency is decreased d) all of the mentioned
Explanation: The mechanical stresses increases in much higher proportion than the pressure pressure because of the prevailing high temperature.
43 The cycle efficiency in a single reheat plant is influenced by
a) pressure at tubine inlet b) pressure at which steam is reheated c) temperature at which steam is reheated d) temperature at tubine inlet
Explanation: The cycle efficiency is a function of the ratio of reheat to initial pressure.
44 The optimum reheat pressure for the most of the modern power plants is___________ of the initial steam pressure
a) 0.1-0.5 b) 0.2-0.3 c) 0.2-0.25 d) 0.25-0.3
Explanation: In this range of reheat pressure efficiency is maximum.
45 What is the effect of reheat on steam quality?
a) increases b) decreases c) does not change d) depends on several parameters
Explanation: Because this steam is undergoing expansion two times.
46 Reheat is preferred for the plants having efficiency greater than
a) 150MW b) 200MW c) 100MW d) 250MW
Explanation: For producing power less than this reheat will not be economical.
47 What is the basic principle of regeneration?
a) Steam after coming out of condenser is circulated to boiler b) Steam after coming out of condenser is circulated to turbine c Steam after coming out of turbine is circulated to boiler d) Two stage turbine is used
Explanation: In regeneration steam from condenser is circulated through turbine to increase steam temperature before it enters boiler.
48 What is the effect of increase in regeneration on steam rate?
a) decreases b) remains same c) increases d) none of the mentioned
Explanation: More steam has to circulate per hour to produce unit shaft output.
49 The heat transfer taking place in the turbine is?
a) irreversible b) reversible c) both of the mentioned d) none of the mentioned
Explanation: At each point the temperature of the vapour is only infinitesimally higher than the temperature of the liquid.
50 The heat transferred when the H2O in the products is in the liquid state is called?
a) HCV b) LCV c) LHV d) None of the mentioned
Explanation: The heat transferred when the H2O in the products is in the liquid state is called HCV [Higher Calorific Value].