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S.No Question Option A Option B Option C Option D Answer Solution Comments Status Action
1 Under what condition is an inclined manometer used? In small pressure changes When surface of measurement is inclined In high pressure range When u – tube manometer is not available a Inclined column manometer:
In an inclined column manometer the column is inclined at some angle with the horizontal axis.
Due to inclination, the distance moved by the heavy liquid in the right limb is more.
This manometer is more sensitive so measure in small pressure change		 Comments Active
2 ____is also called spheroidal graphite cast iron. Malleable cast iron Ductile cast iron White cast iron Gray cast iron b Nodular (spheroidal graphite) cast iron: Nodular iron is also called ductile iron. The graphite is present as tiny balls or spheroids. Because the spheroids interrupt the matrix much less than graphite flakes, nodular cast iron has higher strength and toughness than gray cast iron. The formation of nodules or spheroids occurs when eutectic graphite separates from the molten iron during solidification. Comments Active
3 In the context of moving control volume, which of the following statement is more relevant? Absolute velocity of fluid carries fluid across the control volume Control volume is considered as a fixed volume in space Relative velocity of fluid carries fluid across the control surface of moving control volume Difference between absolute and relative velocities of fluid is the velocity across moving control volume c In the Reynolds Transport Theorem, when dealing with a moving control volume (as in many practical fluid systems like turbines, nozzles on moving vehicles, etc.), the flow across the control surface is analyzed based on the relative velocity of the fluid with respect to the moving control volume. Comments Active
4 With respect to the term kinematic viscosity, which of the following statements is more relevant? Numerator represents property of the fluid to maintain its momentum Denominator represents propagation of disturbance Denominator represents physical property of the fluid to maintain its momentum It is an indicator of absolute tendency of the fluid. c Kinematic viscosity: Kinematic viscosity is defined as the ratio of dynamic viscosity and density of the fluid.
Kinematic viscosity \(=\frac{dynamic viscosity}{density of fluid}\)
\(ϑ=\frac{μ}{ρ}\)
“Denominator represents physical property of the fluid to maintain its momentum"
ρ (Density) is a physical property of the fluid.
Density essentially represents the fluid's inertia — i.e., how much it resists changes in motion or maintains momentum.		 Comments Active
5 An ideal constant pressure gas turbine works on the ____cycle. Atkinson Lenoir Stirling Brayton d The Brayton cycle is a theoretical cycle for a simple gas turbine. The ideal Brayton cycle consists of two isentropic and two constant pressure processes. Comments Active
6 In a triple fluid vapour absorption refrigeration system, hydrogen gas is used to: provide vapour seal reduce partial pressure of refrigerant in evaporator improve system performance circulate the refrigerant b Generally in NH3 - H2 vapour absorption system the hydrogen is added in to NH3 before it pass through the evaporator. The main function H2 is to reduce the partial pressure of the NH3 gas as low of dalton's partial pressure so the Nh3 is evaporate at low temp. Comments Active
7 Define a machine in terms of its basic objective. A device to transfer load of source A device to transfer and transform motion and force from source to load. A device to transform force. A device used to transfer force b A machine is a human-made device that uses power to apply forces and control movement to perform an action.Machine: an assemblage of parts that transmit forces, motion and energy in a predetermined manner.Simple Machine: any of various elementary mechanisms having the elements of which all machines are compose(d) Included in this category are the lever, wheel and axle, pulley, inclined plane, wedge and screw.A machine is a combination of rigid or resistant bodies, formed and connected so that they move with definite relative motions and transmit force from the source of power to the resistance to be overcome. A machine has two functions: transmitting definite relative motion and transmitting force Comments Active
8 Identify the method by which steel is NOT classified. Based on chemical composition Based on notch toughness Manufacturing method Based on heat treatment b Based on notch toughness: Notch toughness refers to the material's ability to absorb energy when a stress concentrator (like a notch) is present, and is not a method of classification but a property measurement. While notch toughness affects the performance of the steel under certain conditions (like low temperatures), it is more of a performance criterion than a classification method. Comments Active
9 Which of the following is NOT considered as external loads? Those arising from environment Those arising from cohesion of material Those arising from fluid pressure Those arising from service conditions b Type of force Definition:
Internal force: A force that acts between the molecules of a material.
External force: A force that acts on a material from the outside environment.
Examples of internal forces :Cohesion force,Adhesion force,Elastic force,Plastic force,Frictional force
Examples of external forces: Gravity force,Drag force,Viscous force,Electromagnetic force,Fluid pressure		 Comments Active
10 For a static fluid, the increase of pressure at any point inside the fluid, in a vertically downward direction must be equal to the product of the _______of the fluid and depth from the free surface. density viscosity specific gravity specific weight d law which is given by –
\(\frac{Dp}{dz}=-ρg\)
\(∴P=-ρgz\)
\(∴P=-ρgh\)
Where P = pressure above atmospheric pressure and h = height of the point from the free surface.
Specific Weight is the weight of a substance per unit volume.
Specific weight, w = \(\frac{mg}{V} or ρg\)
Where m = mass, V = Volume
The correct answer is specific weight. \(∴\)		 Comments Active
11 Which of the following is NOT a projectile motion? A stone thrown in any direction A stone thrown horizontally from a building A car moving in a straight line A bullet fired from a gun c Projectile motion: A kind of motion that is experienced by an object when it is projected near the Earth's surface and it moves along a curved path under the action of gravitational force.• Projectile motion is the motion of an object thrown or projected into the air, subject to only the acceleration of gravity. The object is called a projectile, and its path is called its trajectory.• In case of a stone thrown in any direction, a stone thrown horizontally from a building, and a bullet fired from a gun are subjected to only gravitational force. But in case of a car moving in a straight line is a rectilinear type of motion Comments Active
12 Another name for the Bell-Coleman cycle is: reversed Carnot cycle ideal reverse Brayton cycle Carnot cycle Rankine cycle b Bell Coleman cycle is also known as Reversed Brayton cycle or Reversed Joule cycle. The working fluid of the Bell Coleman refrigeration cycle is Air. This system of refrigeration is used for Air Craft refrigeration and it has light weight. Comments Active
13 How is a high-pressure boiler classified? When pressure >50 bar When pressure >80 bar When velocity of water is very low When it operates, high amount of steam is required for the operation of the cycle b Boilers that produce pressure above 80 MPa are considered to be high pressure. Comments Active
14 With respect to the first law of thermodynamics, which of the following statements is the most relevant? There is a natural tendency for any system to degenerate into a disordered state Energy can be created or destroyed depending on the source of input At process that involves transfer of heat energy is irreversible Energy is always conserved d First law of thermodynamics states that total energy of an isolated system is constant, energy can neither be created nor be destroyed but can be transformed from one form to another. Comments Active
15 What is sonic speed? It is the speed at which disturbance propagates at higher velocity. It is speed at which disturbance propagates through an inelastic medium it is the speed at which disturbance propagates through a medium. It is the speed of air. c sonic speed is the speed at which a disturbance propagates through a medium.
In gases, it is given by: \(V=γRT\)
Where:
ratio of specific heats (Cp/Cv) \(γ=\)
R = specific gas constant
T = absolute temperature
It depends on the medium's properties, like compressibility and density.
In air at 20°C, the sonic speed is approximately 343 m/s.		 Comments Active
16 For a Kaplan turbine, the value of speed ratio is _________. 2 0.5 0.1 0.9 d  
Turbine Type
Speed Ratio Range
Remarks
Pelton
0.43 – 0.47
Impulse turbine
Francis
~0.6 – 0.9
Mixed flow reaction turbine
Kaplan
~0.8 – 1.0 (commonly ~0.9)
Axial flow reaction turbine		 Comments Active
17 The Lagrangian description of fluid field is more computational because: It is required to track movement of a large number of fluid particles with time variation of velocity is expressed in Cartesian coordinates velocity field is a continuous function distribution with position and time velocity of the fluid particle is the same as the local velocity a In fluid mechanics, there are two primary ways to describe fluid motion:
Lagrangian Description: Follows individual fluid particles as they move through space and time.
Requires tracking position, velocity, and acceleration of each particle at all times.
Eulerian Description: Focuses on specific locations in the flow field and observes fluid properties changing with time at those fixed points.
Much more commonly used in CFD (Computational Fluid Dynamics).		 Comments Active
18 Which of the following is the characteristics of an isochoric process? Process during which specific volume remains constant Process applied to impure substances Process during which no heat is transferred Process during which no mass is transferred a A process is said to be isochoric when the volume is held constant. In any Isochoric process, the work done by the system is always zero. Comments Active
19 In Lancashire boilers, the feed water tube is: open channel type perforated thin conduit solid b Lancashire Boiler: It is a horizontal drum axis, natural circulation draft, medium pressure, fire tube boiler with a perforated feed water tube. The Lancashire boiler consists of a cylindrical shell inside which two large tubes are placed.
Purpose of the Perforated Tube: The perforations allow feed water to be evenly distributed into the boiler drum. This helps avoid thermal stresses due to sudden temperature differences (cold feed water hitting hot metal surfaces).Promotes uniform mixing and better efficiency.		 Comments Active
20 Which of the following statements is more relevant in the context of IC engines? Compression ratio of the fuel-air mixture is in the range of 6 to 10 in Spark Ignition (SI) engines Compression ratio for air in the range of 16 to 20 for SI engines Walls of the engine cylinder of SI engines need to be thicker than CI engines Compression Ignition (CI) engines have lesser weight than SI engines a
Compression ratio (r): it is defined as the ratio of volume before compression (Total volume) to the volume after compression (Clearance Volume).
\(r=\frac{(V_{c}+V_{s})}{V_{c}}=1+\frac{V_{s}}{V_{c}}=1+\frac{1}{C} \)
Where are clearance and s		 Comments Active
21 What is a degree of freedom in the context of kinematics? Minimum dependent coordinates to describe the configuration Maximum independent coordinates to describe the configuration Maximum dependent variables specified to describe the configuration Minimum independent variables specified to fix the configuration d Degree of Freedom: The degree of freedom (DOF) of a mechanical system is the minimum number of independent variables required to define the position or motion of the system. Comments Active
22 In a flow – measuring device, what is velocity head? Free rise of liquid column in an open-ended tube Vertical distance through which a column of the flowing liquid would rise in an open-ended tube Free fall of liquid column to attain a given velocity freely Difference in elevation in the flow direction c Velocity Head: It is a fundamental concept of fluid mechanics representing the bulk motion. i.e. the fluid’s kinetic energy. It can also be transformed into the pressure that the fluid would obtain where it to be held without any energy loss.
It is measured as
Velocity head = \(\frac{v^{2}}{2g} m\)
Where v = velocity of fluid; g = acceleration due to gravity;
From the expression, it is clear that it is that height which is required to attain a velocity v in under free fall.		 Comments Active
23 Which of the following statement is INCORRECT with reference to the first law of thermodynamics? Work done by a system on its surroundings is a positive quantity Energy transfer to a system from its surroundings is a positive quantity Heat interaction is a path function Energy transfer is a point function d First Law of Thermodynamics for a closed system undergoing a process neglecting kinetic and potential energy. δQ = dU + δW Work done  on the system = sign convention is -ve Work done by the system = sign convention is +ve Heat or energy transfer to the system = sign convention is +ve and Heat rejected by the system = sign convention is -ve Comments Active
24 What is the unit of absolute viscosity? Centipoise Saybolt universal unit Viscosity index Centistoke a Viscosity: The property that represents the internal resistance of a fluid to motion (i.e. Fluidity (is called viscosity. There are two ways to write viscosities:
(1) Dynamic viscosity: This is also termed as absolute viscosity. A common unit of dynamic viscosity is poise.
1 Poise = 0.1 Pa.s =0.1 N.s/m2
(2) Kinematic Viscosity: The ratio of dynamic viscosity to density appears frequently and this ratio is given by the name kinematic viscosity. Its unit is Stoke or m2/s (1 stoke = 0.0001 m2/s).
C.G.S unit of kinematic viscosity is cm2/s. \(∴\)		 Comments Active
25 Which of the following statements is INCORRECT in the context of static fluid pressure? At any particular depth, it changes with direction. It exerts force normal to the walls of the container It is independent of shape or area of the container It is directly proportional to depth of fluid. a Pascal’s law: According to Pascal’s Law, the pressure or intensity of pressure at a point in a static fluid is equal in all directions. Fluid pressure is always perpendicular to the wall of the container
This law is valid for the cases of fluid flow where shear stresses do not exist. The cases are
Fluid at rest
No relative motion exists between different fluid layers. For example, fluid at a constant linear acceleration in a container fluid pressure is always
Ideal fluid flow where viscous force is negligible.		 Comments Active
26 Define pure substance. A single substance without any mixture Substance which is available in the purest form in nature Substance with non-uniform composition Substance with fixed chemical composition throughout d A pure substance always has a definite and constant composition. Comments Active
27 ________ states that “pressure of a gas mixture is equal to the sum of the pressure each gas would exert if it existed alone at the mixture temperature and volume”. Amagat’s law of additive volumes Hooke’s law Dalton’s law of additive pressures Ideal gas law c Dalton’s law of partial pressures is a gas law which states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures exerted by each individual gas in the mixture.
 Comments Active
28 According to Kelvin-Plank’s statement of the second law of thermodynamics which of the following statements is correct? Heat from a source should be rejected to a high temperature sink. It restricts the mechanical efficiency of the heat engine to be lesser than unity Thermal efficiency of the heat will be unity It restricts the thermal efficiency of the heat engine to be lesser than unity. d Kelvin-Planck statement: It is impossible for a system to accept a given amount of heat from a high-temperature medium and to deliver an equal amount of work output, meaning that a heat engine cannot have a thermal efficiency of 100% or unity. Comments Active
29 What is a diffuser? It is a duct which decreases the velocity and increases pressure. It is a type of nozzle. It is a type of valve that decreases pressure. It is voltage regulator a Diffuser purpose is to reduce the velocity of the flow leaving the impeller resulting in an increase in pressure. Comments Active
30 In the context of the Reynolds transport theorem, which of the following statements is the most appropriate? It uses fixed control volume It links system and control volume approaches. It does not use control volume approach It uses deforming control volume. b Reynolds Transport Theorem: Reynold theorem gives the relation between the system equations and corresponding control volume equations which relates the change in extensive property of a system and control volume. Comments Active
31 In actual compressors, there is a clearance between the cylinder head and piston to take care of thermal expansion. Identify the correct expression from the given options, where C is the clearance (in mm) and L is the stoke length (in mm) C = (0.005L + 0.05) C = (0.005 + 0.5L) C = (0.005L + 0.5) C = (0.05L + 0.5) c The relation between the clearance and stroke length for a compressor in the practical case is given by C = (0.005L+ 0.5) mm
Where C = clearance provided between cylinder head and piston, L = stroke length.		 Comments Active
32 What is the flow called if the velocity at a given instant is the same in both magnitude and direction throughout the flow domain? It refers to external work done on a bar. It refers to change in length of a bar. It is the potential energy stored by an elastic body when deformed It is the energy released by bar during loading process. c Strain energy is defined as the energy stored in a body due to deformation under elastic region. Comments Active
33 Aircraft engines use ____for cooling engines. a forced cooling system a water-cooled system a thermo-syphon cooling system an air-cooled system d Air – cooled system: In an air – cooled system, a current of air is made to flow past the outside of the cylinder barrel, the outer surface area of which has been considerably increased by providing cooling fins.
* This method is mainly applicable to General aviation aircraft, Lawn motors, Generators, pump sets and Motorcycles. Where the motion of the vehicle gives a good velocity to cool the engine.
* In bigger units, a circulating fan is also used.
* The value of the heat transfer coefficient between metal and air is appreciably low.
* As a result of this, the cylinder wall temperature of the air – cooled cylinders are considerably higher than those of the water – cooled type.		 Comments Active
34 Under what condition of fluid flow does shear stress NOT exist? Fluid in low velocity motion Fluid in high velocity motion Negligible viscosity Relative motion exists between fluid layers c This type of fluid is called an ideal fluid and the resulting motion is called an ideal or inviscid flow. In an ideal flow, there is no existence of shear force because of vanishing viscosity. Comments Active
35 In isentropic compression, similar to aircraft refrigeration cycle, what is ram efficiency? It is proportional to mass flow rate Ratio of input to output ram pressure Ratio of aircraft velocity to sonic velocity Ratio of actual pressure rise to isentropic pressure d Ram efficiency is a measure of the effectiveness of the compressor in converting the kinetic energy of the incoming air into pressure energy. It is defined as the ratio of actual pressure rise to the ideal (isentropic) pressure rise that would be achieved under the same operating condition. Comments Active
36 The COP (Coefficient of performance) of a heat pump is always _______the COP of a refrigerator. greater than less than equal to less than or equal to a COP of Heat pump=1+COP of Refrigerator. So COP of Heat Pump is always greater than cop of refrigerator. Comments Active
37 The major function of a steam nozzle is to: produce high viscosity steam produce high velocity jet of steam produce low velocity jet of steam produce low viscosity steam b A steam nozzle is a passage of varying cross-sections that converts the heat energy of steam into kinetic energy. The main application of the steam nozzle is in a steam turbine which produces a jet of steam with high velocity. Comments Active
38 What is a gauge pressure? It is pressure measured relative to a perfect vacuum. It is an alternate name of datum pressure. It is pressure measured relative to local atmospheric pressure. It is the same as local atmospheric pressure. c Gauge Pressure is measured after taking atmospheric pressure as a datum, i.e. atmospheric pressure is marked as zero. Thus it can be concluded that the gauge pressure is relative to local atmospheric pressure. Comments Active
39 The benchmark pressure above which a boiler is considered to be a high- pressure boiler is: 60 bar 50 bar 80 bar 70 bar c A high pressure boiler is a type of boiler that operates at 80 bars or higher and is used in thermal power plants to generate power. Comments Active
40 If compression is achieved by trapping a refrigerant vapor in an enclosed space and then reducing its volume then it is roto-dynamic type compressor open type compressor radial-flow type compressor positive – displacement type compressor d In positive displacement type compressors, compression is achieved in an enclosed space by reducing its volume. Comments Active
41 Which of the following is the working fluid in an air-cycle refrigeration system? Air at high Mach number Saturated air Compressed air Gas c Air cycle refrigeration systems belong to the general class of gas cycle refrigeration systems, in which a air is used as the working fluid it does not undergo any phase change during the cycle, consequently, all the internal heat transfer processes are sensible heat transfer processes. Comments Active
42 In a compressor, work is done by: the fluid on the rotor the rotor on the fluid element the rotating part called stator a static component known as impeller b In the compressor, the rotating part is called the rotor. With the help of this rotor, the gases are generally fed into the less volume zone. As we know that pressure and volume both are inversely related to each other. When the same amount of gas is fed from a large volume to a less volume zone. Its pressure get increase Comments Active
43 Which of following is NOT a phase in steel? Pearlite Austenite Limonite Martensite c
From iron- carbon diagram it is clear that limonite is not a phase in steel.		 Comments Active
44 What is the functions of a fly wheel in IC engines? To absorb energy during suction stroke To circulate air in the engine for cooling To increase the speed To maintain constant speed d
Solutions: In a four – stroke engine, combustion occurred only once every four cycles. As a result, power is only available for one cycle. However, this does not imply that the engine should work for that cycle. This is where a flywheel comes in h		 Comments Active
45 The air fuel ratios used in a compression ignition engine lie in the range of 6 to 14 18 to 25 40 to 48 28 to 36 b In compression ignition (CI) engines, commonly known as diesel engines, the air-fuel ratio varies significantly depending on the load conditions. At full load, the air-fuel ratio may be as low as 18:1 to 25:1, and during lighter load conditions or idle, it can rise to much higher values.
The air-fuel ratio in CI engines is generally higher than in spark ignition (SI) engines, which typically operate with an air-fuel ratio around 14.7:1 under normal conditions. Diesel engines are designed to run with excess air to ensure complete combustion of the fuel and to reduce the formation of undesirable emissions like carbon monoxide and hydrocarbons.		 Comments Active
46 Which of the following helps to increase efficiency of the Rankine cycle? Increasing average temperature at which heat is rejected from the working fluid Increasing average temperature at which heat is transferred to the working fluid Increasing the condenser pressure Operating at constant temperature b To increase the efficiency one should increase the average temperature at which heat is transferred to the working fluid in the boiler, and/or decrease the average temperature at which heat is rejected from the working fluid in the condenser. Comments Active
47 Which of the following is NOT a maintenance method of a boiler? Dry lay-up Wet lay-up Short-term lay-up Chemical lay-up d A steam boiler layup is a maintenance procedure that helps to prevent corrosion within the boiler on both the waterside and fireside when you plan to have the boiler out of operation for an extended period of time. Comments Active
48 Identify the complete and correct statement of the first law of thermodynamics. During a process, extracting work without supplying heat, while sacrificing the energy of the system. Difference between the heat and work interactions during a process, which is property of the system When a closed system execute a complete cycle the sum of heat interactions is equal to the sum of work interaction. When a system undergoes a cycle, the integral of heat is equal to the integral of work. Comments Active
49 Which of the following statements is INCORRECT with respect to water tube boilers? They are suitable for high steam pressure They are suitable for large gas flows They cannot handle high steam pressure They are smaller and lesser in weight c Water tube boilers are preferred for high pressure and high output while shell boilers are preferred for low pressure and low output. Comments Active
50 With respect to reaction turbines, which of the following statements is relevant? Guide blades are not connected to the regulating ring. Water does not flow through a scroll casing. Governing of reaction turbines is done by altering position of the guide vanes. Flow rate cannot be controlled by changing the gate openings to the runner. c • In a reaction turbine, only some amount of the available energy is converted into kinetic energy before the fluid enters the runner.
• Both pressure and velocity change as the fluid passes through a runner. Pressure at the Inlet is much higher than at outlet.
• The runner must be enclosed within a watertight casing.
• Water is admitted over the entire circumference of the runner.
• Water completely fills at the passages between the blades and while flowing between inlet and outlet sections does work on the blades.
• Reaction turbines are generally connected to the tail race through a draft tube which is a gradually expanding passage. It may be installed below or above the tail race.
• The flow regulation in the reaction turbine is carried out by means of guide-vane assembly. Other component parts are scroll casing, stay ring runner, and the draft tube.  		 Comments Active
51 Intercooling is multistage compression reduces ______. the work input to compressor the volume of free air delivered the pressure of air at delivery the index of compression a Intercooling is used in a multistage compressor to reduce compressor work. In other words, multistage compression is effective at the same higher pressure ratio. The pressure ratio of each stage is decreased through multiple staging. As a result, the cylinder's air leakage past the piston is likewise decreased. Comments Active
52 Which of the following is NOT a water-tube boiler? Stirling boiler Cornish boiler Loeffler boiler LaMont boiler b Cornish boiler is a fire tube boiler. Comments Active
53 ________is the ability of steel to resist stresses that are reversal in nature. Impact strength Fatigue strength Toughness Hardness b Fatigue strength is the ability of steel to resist stresses that are a reversal in nature. Comments Active
54 Why do engines need to be cooled? To regulate mass transfer To reduce ignition temperature To avoid pre-ignition and knocking To improve compression volume C Engines need to be cooled to prevent excessive temperatures that can lead to pre-ignition and knocking. Here’s why:
Pre-ignition occurs when the fuel-air mixture ignites prematurely due to contact with hot surfaces like spark plugs or exhaust valves. This early ignition can cause engine damage, and cooling helps to maintain components at safe temperatures to prevent this.
Knocking happens when the fuel ignites before the spark plug fires, causing abnormal combustion. This can happen when the engine temperature and pressure are too high. Keeping the engine cool ensures that the combustion process remains under control, and knocking is minimized.		 Comments Active
55 Heat and work both are: point and path functions both path functions point funtions state functions b Both heat and work depend on the path followed during the process So, heat and work are path functions .Heat and work are independent of their physical properties .So, both are not considered as the case of intensive or extensive properties. Comments Active
56 Which is the most practical fluid for the Rankine cycle? Fuel Air Air-fuel mixture Water d The efficiency of the Rankine cycle is limited by the high heat of vaporization by the flui(d) The fluid must be cycled through and reused constantly, therefore, water is the most practical fluid for this cycle. Comments Active
57 When water is about to vaporize it is called? super-heated vapor saturated vapor sub-cooled liquid saturated liquid d The water which is about to vaporize is called Saturated liquid.
 Comments Active
58 What is radiant heating in the context of boilers? Heating process carried out using radiation effect Heating done on radial tubes Saturated steam is re-circulated and super- heated Heating done on external walls only reflecting radiant energy a Some super heaters are radiant type absorb heat by radiation heat transfer. This radiation type heat energy released by the boiler furnace along with convection heat transfer. This is called radiant heating. Comments Active
59 Which refrigeration system is driven by low-grade energy? Gas cycle refrigeration Steam jet refrigeration Vortex tube systems Thermo-electric refrigeration b Steam jet or Ejector refrigeration system uses water as a refrigerant. It uses the basic principle of boiling liquid at a lower temperature by reducing pressure on its surface. This system employs a steam ejector or booster instead of a mechanical compressor. It has the capability to produce refrigeration using waste heat or solar energy as a heat source at temperatures above 80°C Comments Active
60 An appurtenance whose length generally does NOT exceed three times of its diameter is called ______. non-return valve a diffuser an orifice a mouthpiece d Mouthpiece: A mouthpiece is a short length of pipe or tube attached to the tank or vessel, used to determine the rate of flow of flui(d) It is an extended form of an orifice with a length equal to 2 to 3 times the diameter of the orifice. By fitting the mouthpiece, the discharge through an orifice of the tank can be increased. Comments Active
61 A member of length 200 mm and diameter 25 mm is subjected to a tensile load of 20kN. The final length of the member is formed to be 220 mm. the percentage increase in the length of the member is: 2% 1% 5% 10% d \(Percentage change in the lenth=\frac{L_{f}-L_{i}}{L_{f}}×100\)
\(=\frac{220-200}{200}×100=10%\)		 Comments Active
62 Lithium bromide is used as an absorbent in ____. vapour compression refrigeration vapour absorption refrigeration steam jet refrigeration Electrolux refrigerators b In the vapour absorption system, the water is used as the refrigerant while lithium bromide (Li Br) is used as the absorbent. Comments Active
63 One ton of refrigeration is equal to _______ kW. 5 2.5 3.5 1 c 1 TR = 210 kJ/min = 3.5 kW. Comments Active
64 Which of the following is the best example of a thixotropic fluid? Tooth paste Minerals in suspension Fly ash Printing ink d Thixotropic: Apparent viscosity for thixotropic fluids decreases with time under constant applied shear stress.
Example: Crude oil, lipstick, certain paints, and Printing Ink.		 Comments Active
65 The fourth stage of the compression ignition process is: burning on the expansion stroke ignition delay period period of controlled combustion period of rapid or uncontrolled combustion a Stages of combustion in compression ignition engine:
1. Ignition Delay Period
2. Period of Uncontrolled combustion
3. Period of Controlled combustion
4. Burning on the Expansion stroke
Burning on the expansion stroke:
This is the last stage of the four stages of combustion in CI engine.
Naturally, the combustion process is completed at the point when the maximum pressure is obtained in the combustion chamber at point E as shown in figure.
Practically, the burning of the fuel in the combustion chamber remains to continue during the expansion stroke. The main reason behind it is the re association of dissociation gases and unburnt fuel.
Therefore, the last phase of combustion is also called after burning.		 Comments Active
66 At sea level, under normal conditions, what is the atmospheric pressure? 101.32 kPa 100.043 kPa 100.1 kPa 104.013 kPa a Atmospheric Pressure: Standard atmospheric pressure at sea level is defined as:
=101.325 kPa
= 1 atm
= 760 mmHg
= 1.01325 bar
= 14.696 psi		 Comments Active
67 For a carburizing flame, the flow of _______is kept higher. argon nitrogen oxygen acetylene D “A carburizing flame is obtained by supplying acetylene in excess of the amount required for complete combustion. This flame is used where addition of carbon to the weld is desired or where oxidation must be avoided.” Comments Active
68 A thermoelectric refrigeration system requires: low voltage DC input high voltage DC input high voltage AC input low voltage AC input a A thermoelectric refrigeration system requires Low voltage DC input.
“Thermoelectric refrigeration works on the Peltier effect and utilizes low-voltage DC power to operate. It is commonly used in portable refrigerators, electronic cooling systems, and where compact and vibration-free operation is required.”		 Comments Active
69 Which of the following links does NOT undergo any deformation while transmitting motion? Rigid link Flexible link Resistance link Fluid link a Rigid link: A rigid link is one which does not undergo any deformation while transmitting motion. For examples , connecting rod, crank etc Comments Active
70 Which of the following pairs is NOT an example of a lower pair? Prismatic pair Helical and cylindrical pair Revolute pair Rolling ball on a flat surface d Some of the types of lower pair are:
Revolute Pair
Prismatic Pair
Screw Pair
Cylindrical Pair
Planar Pair
Rolling ball on a flat surface is an example of higher pair because it has point contact.		 Comments Active
71 The specific gravity of water at standard atmospheric conditions is: greater than 1 less than 0 1 0 c • Specific gravity is also termed as relative density.
• The relative density/specific gravity of a substance is defined as the ratio of the density, mass or weight of the substance to the density, mass or weight of water at 4°C (Standard atmospheric conditions)
• Specific gravity is the ratio of the specific weight of the liquid to the specific weight of a standard flui(d)
• In the case of liquids standard fluid is taken as water with specific gravity 1.
\(γ=\frac{Density of Substance}{Density of same volume of water}=\frac{ρ}{ρ_{w}}\)		 Comments Active
72 Which of the following statements is relevant? Fluid deforms continuously under the action of shear stress of even very low magnitude. Fluid deforms under constant shear stress. Fluid can sustain shear stress when at rest. Fluid does not deform continuously under the action of shear stress. a Fluid:
A fluid is a substance that deformed continuously when shear stress is applied to it irrespective of the magnitude of the shear stress. Because of the continuous deformation flow of the liquid can be seen. In other words, we can also tell that liquid cannot sustain any shear load.		 Comments Active
73 While loading, ___________material undergoes fracture after large amount of deformation. isotropic plastic brittle ductile d Ductile material is the type of material that shows the large deformation before undergoing fracture Comments Active
74 According to TBR regulations, boilers exceeding __________need regular inspection and certification. capacity of more than 15 litres capacity of more than 5 gallons capacity lesser than 5 gallons capacity of more than 50 gallons b Any closed vessel exceeding 25 liters or 5 gallons in a capacity that is used expressly for generating steam under pressure, including any mounting or other fitting attached to such vessel that is wholly or partly under pressure when the steam is shut off, is referred to as an IBR boiler. Comments Active
75 With respect to head loss of flowing fluid, select the most appropriate statement. Energy loss is not caused by change in velocity Increase in velocity is a flow induces large scale turbulence Energy loss is not due to formation of eddies Portion of energy loss will not be dissipated as heat b • Head loss of the piping system is divided into two main categories:
Major Head Loss due to friction in pipes and ducts.
Minor Head Loss-due to components as valves, fittings, bends and tees.
• In most engineering flows, the major head loss is roughly proportional to the square of the flow rate and is given by Darcy-Weisbach equation.
\(\frac{∆h}{L}=\frac{fV^{2}}{2gD}\)
where h is the head loss in m. f is Darcy friction factor, L is the pipe length. D is the hydraulic diameter and V is the mean flow velocity. \(∆\)
• An Increase in velocity causes the flow to transition to turbulent flow and this turbulence causes the formation of eddies of many different length scales these formations come at the expense of the available energy loss of the flow
• The large-scale eddies contain the majority of the kinetic energy of turbulent motion. Some portion of n of this energy is dissipated when these large scale eddies are converted into small scale due to the viscous effects.		 Comments Active
76 Which of the following statements is correct with reference to perpetual motion machines of the first kind? It violates the second law of thermodynamics It is a reversible process. It produces work without receiving work input. It produces work without receiving heat. d PMM1: A machine that produces works continuously without energy input.
PMM2: A machine that has 100% efficiency		 Comments Active
77 Which of the following is an inferential type of flow meter? Purge flow regulator Rotameter Laser Doppler Magnetic flowmeter b According to Fluid Mechanics by Modi & Seth, inferential flow meters are those that measure the rate of flow (or flow velocity) rather than the total quantity of flui(d) These meters infer the flow rate based on some other measurable parameter like pressure, velocity, or other factors related to the flow behavior.
Rotameter: A Rotameter is a variable area flow meter where the flow rate is inferred from the position of a float inside a tapered tube. The float rises and falls in response to changes in flow rate, and this position is used to infer the flow rate.
Why it's inferential: The flow rate is not directly measured but inferred from the relationship between the float position and the flow rate, making it an inferential flow meter.		 Comments Active
78 Nominal volume generated by the working piston when travelling from one dead centre to the next is called _________. clearance volume swept volume total volume stroke volume b Swept Volume: The volume swept by the piston in cylinder during its suction stroke or movement from TDC to BDC is called Swept Volume. \((V_{s})\)
The volume swept by the piston in cylinder during its suction stroke and is given by
\(V_{s}=AL=\frac{Ï€}{4}d^{2}L\)
Where, d = Inner diameter of cylinder, L = stroke length.		 Comments Active
79 Boilers in the Rankine cycle are used: to allow expansion of steam to store working fluid for steam generation to maintained heat in the process c The Rankine cycle system consists of a pump, boiler, turbine, and condenser. The pump delivers liquid water to the boiler. The boiler heated by the solar heat converts water to superheated steam. This steam is used to run the turbine which powers the generator. Comments Active
80 What is dilatant? It is a fluid with suspended colour pigments. It is a shear thickening fluid. It is a fluid that sustains shear stress without any deformation It is a shear thinning fluid. b Dilatant fluids: It is one of the Non-Newtonian fluids which do not obey the Newtonian equation
• The value of n > 1 and B = 0 for these fluids
• The viscosity () is not constant and depends on how fast the fluid is deforming \(μ\)
• These are called shear thickening fluids because the faster the deformation occurs the more the viscosity increases
Examples: quicksand, corn starch, sugar syrup, automobile oils, etc.		 Comments Active
81 In air standard cycle analysis of IC engine, Which of the following statements is correct? Specific heats (Cp, Cv) of air vary with temperature. There will be a sudden change in chemical equilibrium of the working fluid. There are no intake or exhaust processes. Compression and expansion processes are considered as irreversible c There are three standard cycles that are used to perform analysis of IC engine:
1. Constant volume combustion (Otto) cycle
2. Constant pressure combustion (Diesel) cycle
3. Combination of constant volume and constant pressure combustion (Duel) cycle
Assumption during analysis:
The working fluid throughout the cycle is air and it is treated as an ideal gas.
The compression and expansion processes are taken as frictionless and adiabatic (no heat loss) i.e. they are reversible.
The chemical equilibrium of the working fluid is taken as constant.
The combustion process is replaced by well – defined heat addition processes.
The exhaust process is replaced by a heat rejection process that return the air of the cycle to intake conditions
Since the gas is assumed as ideal the specific heats at constant volume and pressure are taken as constant.
∴ there are no intake and exhaust processes because they are replaced by heat addition and heat rejection processes.		 Comments Active
82 For a single cylinder four-stroke oil engine indicated is 15 kW, calorific value of fuel is 40000 kJ/kg and fuel consumed is 0.001 kg/s. What will be the indicated thermal efficiency? 40% 37.5% 62.5% 75% b Indicated thermal efficiency:
It is the ratio of indicated power (I.P.) and energy in fuel per second.
\(η_{ith}=I.\frac{P}{m_{f}×C.V}\)
Where amd C.V. = calorific value of fuel (kJ/kg) \(m_{f}=mass flow rate of fuel (kg/s)\)
I.P. = 15 kW, C.V. = 40000 kJ/kg, \(m_{f}=0.001 kg/s\)
Indicated thermal efficiency
\(η_{ith}=\frac{I.P.}{m_{f}×C.V.}=\frac{15}{0.001×40000}×100 \)
\(η_{ith}=37.5%\)		 Comments Active
83 Which of the following characteristics of a centrifugal pump is vital? Slip will decrease with the increase in flow rate Fluid is considered to have friction while flowing inside the pump Fluid moves normal to the blade There will be no whirl component of velocity at the entry to impeller d  The figure shows an impeller of a centrifugal pump with the velocity triangles drawn at the inlet and outlet. The blades are curved between the inlet and outlet radius. A particle of fluid moves along the broken curve shown in the figure. Hence fluid moves along the blade and not normal to the blade.

The impeller blades are considered to have a smooth surface finish to avoid losses due to skin friction. Hence fluid is considered to have negligible friction while flowing inside the pump.
Slip: A difference in pressure and velocity during the course of clockwise flow through the impeller passage can be observed between the trailing and leading faces of the impeller blades. High pressure and low velocity are observed at the leading face of the impeller's blade as compared to lower pressure with high velocity at the trailing face of the blade. This results in circulation in the direction of w around the impeller blade which prevents the fluid from acquiring the whirl velocity equivalent to impeller speed with non-uniform velocity distribution at any radius		 Comments Active
84 Fans and blowers of turbo machines: a higher static pressure will prevail spiral casing decreases the static pressure deliver air at a higher desired velocity deliver air at a lower mass flow rate c Fans and blowers are turbo machines that deliver air at a desired high velocity (and accordingly at a high mass flow rate) but at a relatively low static pressure. Comments Active
85 In the context of aircraft refrigeration cycle, what is temperature of air at the exit of cooling turbine in the absence of moisture condensation? Saturated temperature Dry air rated temperature (DART) Super-saturated temperature Dry air temperature (DAT) b Dry air rated temperature (DART):
The concept of Dry Air Rated Temperature is used to compare different aircraft refrigeration cycles. Dry Air Rated Temperature is defined as the temperature of the air at the exit of the cooling turbine in the absence of moisture condensation. For condensation not to occur during expansion in the turbine, the dew point temperature and hence moisture content of the air should be very low, the air should be very dry. The aircraft refrigeration systems are rated based on the mass flow rate of air at the design DART. The cooling capacity is then given by:
Q = mcp(Ti - TDART)
where, m = Mass flow rate, TDART = Dry Air Rated Temperature, Ti = Cabin temperature.		 Comments Active
86 Select the most appropriate definition of a turbine from the following statements: Turbine is a fluid machine It is device in which kinetic energy held by a fluid is converted to mechanical energy of a rotating member. It is a device where potential energy is transferred to a fluid It is a device where mechanical energy from moving parts is transferred to a fluid b hydraulic turbine is a prime mover which converts hydraulic energy into mechanical energy. Comments Active
87 The refrigerant used in the VCRS based refrigerant cycle rejects heat in _________. the expansion valve the evaporator the condenser the compressor c The refrigerant in vapour form enters the compressor where temperature and pressure increased by compressing vapour. In Condensor due to temperature difference heat rejected to the atmosphere. In Expansion device due to throttling process temperature and pressure drops by maintaining constant enthalpy. Comments Active
88 Which of the following statements is more relevant? In kinematics of fluid flow, pressure is a vector field. In the Lagrangian approach, a fluid particle of fixed mass is considered Fluid kinematics deals with the action of the forces in producing or changing motion of fluid. In the Eulerian method, control volume approach is not used. b Pressure is a scalar quantity, it has intensity but no direction.
Lagrangian Description:
• The Lagrangian Description is one in which individual fluid particles are tracked, much like the tracking of billiard balls in a high school physics experiment
• The Lagrangian description of fluid flow, individual fluid particles in t are "marked," and their positions, velocities, et(c) are described as a function of time.
• The physical laws, such as Newton's laws and conservation of mass and energy, apply directly to each particle.
• If there were only a few particles to consider, as in a high school physics if the experiment with billiard balls, the Lagrangian description would be desirable.
• However, fluid flow is a continuum phenomenon, at least down to the molecular level it is not possible to track each "particle" in a complex flow fiel(d)
• Thus, the Lagrangian description is rarely used in fluid mechanics.
Eulerian Description:
• The Eulerian Description is one in which a control volume is defined, within which fluid flow properties of interest are expressed as field
• In the Eulerian description of fluid flow, individual fluid particles are not identifie(d) Instead, a control volume is define(d)
• Pressure, velocity, acceleration, and all other flow properties are described as fields within the control volume,
• In other words, each property is expressed as a function of shown for the velocity field in the diagram.
• In the Eulerian description of fluid flow, one is not concerned about the location or velocity of any particular particle, but rather about the velocity, acceleration, et(c) of whatever particle happens to be at a particular location of interest at a particular time.
• Since fluid flow is a continuum phenomenon, at least down to the molecular level, the Eulerian description is usually preferred in fluid mechanics.
• Note, however, that the physical laws such as Newton's laws and the laws of conservation of mass and energy apply directly to particles in a Lagrangian description. Hence, some translation or reformulation of these laws is required for use with an Eulerian description.		 Comments Active
89 A single stage impulse turbine is also known as: Curtis stage turbine reaction turbine de Laval turbine Rateau turbine c The single-stage impulse turbine is also called the de Laval turbine after its inventor. The turbine consists of a single rotor to which impulse blades are attached. Comments Active
90 A continuity equation for two dimensional compressible flow is given by: \(\frac{∂u}{∂x}+\frac{∂v}{∂y} (ρuv)=0\) \(u\frac{∂u}{∂x}+v\frac{∂v}{∂y}=0\) \(\frac{∂(ρu)}{∂x}+\frac{∂(ρv)}{∂y}=0\) \(\frac{∂u}{∂y}+\frac{∂v}{∂x}=0\) c
Solution General Continuity Equation:
The equation is based on the principle of conservation of mass which means mass can neither be created nor be destroyed.
\(\frac{∂ρ}{∂t}+\frac{∂}{∂x}(ρu)+\frac{∂}{∂y}(ρv)+\frac{∂}{∂z}(ρ		 Comments Active
91 The Rankine cycle is an ideal cycle for vapor power plants because: it does not allow isentropic expansion steam is not condensed in the condenser it includes reversible process water enters the pump at unsaturated state c The Rankine cycle is an ideal cycle because that has two constant pressure and two isentropic processes and all processes are reversible. The working fluid is pumped from low to high pressure. Comments Active
92 A fusible plug must be used primarily for safety purpose in which of the following types of boilers? Oil-fired boiler High-pressure boiler Fire-tube boiler Marine type boiler c A fusible plug must be used primarily for safety purposes in Fire-tube boilers. Comments Active
93 A centrifugal pump: flow is radially outwards in this pump fluid gain is through constant head flow is tangential in this pump works on the same principle as that of a Francis turbine a In a centrifugal pump, the impeller imparts centrifugal force to the fluid, pushing it radially outward from the center (eye) toward the casing. Comments Active
94 In the context of fluid mechanics, which of the following statements is INCORRECT? Fluid continues in motion under the application of shear stress. Fluid does not deform continuously under shear stress. Fluid cannot sustain any shear stress when at rest Fluid deforms under very small shear stress. b Fluid:
• A fluid is a substance that continually deforms or flows under applied shear stress or external force,
• Fluids are a phase of matter and include liquids, gases, and plasmas.
• The main difference between fluids and solids in terms of mechanical behavior is that when shear stress is applied to a fluid, it undergoes a continuous and permanent distortion.
• Fluids have no permanent resistance to shearing and are only elastic under direct compression; unlike solids, which have all three elastic moduli, fluids only have a bulk modulus.
• The inability of fluids to resist shearing stress gives them their characteristic ability to change shape or to flow.
• As a result, a fluid can be defined explicitly as a substance that deforms continuously and permanently under shearing stress, regardless of how small.		 Comments Active
95 The compression ratio of a Compression Ignition (CI) engine is: <5 12 to 22 10 to 15 5 to 10 B SI engine
CI engine
Petrol is used as fuel.
Diesel is used as fuel.
A petrol engine draws a mixture of petrol and air during the suction stroke.
A diesel engine draws only air during the suction stroke.
The pressure at the end of the compression is about 10 bar.
The pressure at the end of the compression is about 35 bar.
The Charge (i.e. petrol and air mixture) is ignited with the help of spark plug.
The fuel is injected in the form of a fine spray. The temperature of the compressed air is about 600℃ at a pressure of about 36 bars.
A carburettor is used to atomize, vaporize and meter the correct amout of fuel accoridng to the requirement.
Fuel injection pumps and atomizers are used to inject metered quantities of fuel at high pressure according to the requirement.
A petrol engine has a compression ratio approximately from 6 to 10.
A diesel engine has a compression ratio of approximately 12 to 22.
The combustion of fuel takes place approximately at a constant volume. In other words, it works on the Otto cycle.
The combustion of fuel takes place approximately at constan pressure, in other words, it works on the Diesel cycle.
Less vibration and hence, smooth running.
More vibration, and hence, rough running and noisier.
Engine weight is less.
Engine weight is more
It emits carbon monoxide. (CO)
It emits carbon dioxide. \((CO_{2})\)		 Comments Active
96 Which of the following does NOT result in poor performance of boilers? Surface fouling Poor combustion Boiler mounting Poor water quality c Boiler mounting: These are essential safety and operational devices (e.g., safety valve, water level indicator, pressure gauge). They do not degrade boiler performance—rather, they are necessary for safe and proper operation. Not a cause of poor performance. Comments Active
97 What is the unit of surface tension? kg/m N/m N-m N b Surface Tension: It is defined as force per unit length in the plane of the liquid surface at right angles to either side of an imaginary line drawn to the surface.
Mathematically,
Surface Tension = \(\frac{Force }{Lenth}\)
• It is the tendency of the liquid surface to shrink into a minimum surface area.
• The SI Unit of surface tension is N/m or Nm-1
• It allows insects to float and slide on the water surface, usually denser than water
• The molecules at the surface have unbalanced force rather than molecules at deeper and the resultant force moves downward this is surface tension.		 Comments Active
98 What happens when a fluid is at rest? There is no shear component Internal deformation is considerable Fluid element will not be subjected to normal and shear component Frictional force is present a In a real fluid, the following forces are present
Gravity force (Fg) due to gravity
Pressure force (Fp) due to the pressure of the fluid
Viscous force (Fv) due to viscosity
Tension force (Fs) due to viscosity
Turbulent force (Ft) due to turbulence.
and (Fc) due to compressibility.
\(∴F_{net}=F_{g}+F_{p}+F_{v}+F_{s}+F_{t}+F_{c}\)
• If \(F_{net}=F_{g}+F_{p}+F_{v}+F_{t} this is knwon as Reynold^{'}s equations of motion.\)
• If this is known as the Navier – Stokes equation of motion. \(F_{net}=F_{g}+F_{p}+F_{v}\)
• If this is known as Euler’s equation of motion. \(F_{net}=F_{g}+F_{p}\)
the fluid is in rest i.e. the velocity gradient is zero, therefore no shear stress/force will be acting and no external force is acting on it, the only force present is due to gravity (Fg) and pressure of the fluid (Fp) i.e. normal force only \(∴\)
 Comments Active