module ii energy conversion devices ktunotes

BME : MODULE II ©Compiled by AVK©Compiled by AVK

MODULE II

Energy Conversion Devices

AMAL V K

Asst. Professor

UEC, Vallivattom

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Steam Boilers

• Device in which steam is generated from water byapplication of heat.

• Also known as steam generator• Function is to convert chemical energy of fuel into

heat by combustion & to transfer this heat towater to produce steam

• Purposes– Generate power in steam turbines or steam engines– Textile industries– For producing hot water

Energy conversion devicesDept of ME, UEC Vallivattom 2

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Steam boiler - Classification

• According to flow of water & hot gases

– Fire tube boiler: Hot gases pass through tubes which aresurrounded with water. Simple vertical boiler, cochran boiler.

– Water tube boilers - Water circulates through large numberof tubes & hot gases pass around them. Babcock & Wilcoxboiler.

• According to the axis of the shell

– Vertical boiler: Axis of the shell is vertical. Simple verticalboiler, Cochran boiler

– Horizontal boiler: Axis of the shell is horizontal. Babcock &Wilcox boiler


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Steam boiler - Classification

• According to location furnace

– Externally fired boilers: Separate furnace built outside theboiler shell & usually below it. Water tube boilers areexternally fired

– Internally fired boilers: Furnace forms an integral part ofboiler structure. Furnace is located inside boiler shell. Most offire tube boilers are internally fired.

• According to the application

– Stationary boiler: Installed permanently on l& installation.Used in power plants & in industrial process work.

– Mobile boilers: Can be moved from one place to another.These are locomotive & marine boilers


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Comparison between water tube

boiler & fire tube boilerParticulars Fire tube boiler Water tube boiler

Position of

water & hot

gases

Hot gases inside the tubes &

water outside the tubes.

Water inside the tubes &

hot gases outside the tubes.

Mode of firing Generally internally fired. Externally fired.

Rate of steam

productionLower. Higher.

SuitabilityNot suitable for large power

plants.

Suitable for large power

plants.

Floor areaFor a given power, it

occupies more floor area

For a given power, it

occupies less floor area.

Operating cost Less HighEnergy conversion devicesDept of ME, UEC Vallivattom 5

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Cochran Boiler


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Cochran Boiler

• Vertical multi-tubular low pressure fire tubeboiler.

• Consist of cylindrical shell with dome shapedtop for collecting steam.

• Fuel is burnt on grate & ash collected isdisposed of from ash pit.

• Hot gases from fire box passes through flue tubeto combustion chamber.


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Cochran Boiler

• From there hot gases pass through horizontaltubes, during which it transfers heat to thesurrounding water.

• Water is already heated by fire box.

• Water gets converted into steam & getsaccumulated at top of shell.

• Hot gases after reaching smoke box are dischargedto atmosphere through chimney

• Steam is taken out through steam stop valve.


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Babcock & Wilcox boiler


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• Horizontal, externally fired, water tube boiler.• Consist of cylindrical longitudinal drum mounted at

top.• Fed with water by feed water inlet.• Connections are made with uptake & down take

headers from each end of drum.• Headers are joined to each other by no. of inclined

tubes (150).• Mud collector is provided at bottom of down take

header.• Furnace is arranged below uptake header.


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• Fuel is supplied to grate through fire door.

• Hot gases are forced to move upwards &downwards b/w the tubes by baffle platesprovided.

• This provides maximum heating of water tubes.

• Cold water from drum flows into down take header,gets heated & become warm water.

• Warm water moves upwards to uptake header dueto its low density, from where it goes back to drum

• This cycle repeats & finally water in drum becomessteam.


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Benson Boiler


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Benson boiler

• High pressure, drum less, water tube boiler

• Forced circulation

• Designed to withstand critical pressure

• Entire process of heating, steam generation &super heating is done in single tube.

• Comparatively smaller floor area

• Steam generation is quick.


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Benson boiler

• Feed water is supplied to economizer & gets heated byflue gases going out.

• Heated feed water receives heat by radiation & partlygets evaporated in radiant evaporator.

• Water steam mixture is converted into steam inconvective evaporator section

• Steam is superheated in super-heater.

• Economizer, evaporator, super-heater are arranged inpath of flue gases.

• Air for combustion is preheated by flue gases byindirect contact heat transfer


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Steam boiler - Components

• Boiler shell: Exterior of steam boiler, forming acase to contain water & steam. Made up of steelbent into cylindrical form.

• Combustion chamber: Space generally below theboiler shell, meant for burning fuel.

• Grate: Platform in the combustion chamber uponwhich the fuel (coal or wood) is burnt.

• Furnace: Space above the grate & below the boilershell, in which the fuel is actually burnt. Furnace isalso called fire box.


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Steam boiler - Mountings

• Water level indicator: Safety device upon whichworking of boiler depends. Indicates water level insidethe boiler.

• Safety valves: Devices attached to steam chest forpreventing explosions due to excessive internalpressure of steam. Function is to blow off steam whenthe pressure of steam inside the boiler exceeds theworking pressure.

• Feed check valve: Regulates supply of water, which ispumped into the boiler, by feed pump. Fitted below thenormal level of water in the boiler.


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Steam boiler - Mountings

• Pressure gauge: Measures pressure of steam insideboiler.

• Steam stop valve: Fitted to highest part of shell.Function is to control the flow of steam from boiler tosteam pipe.

• Blow-off- cock: Fitted to bottom of a boiler. Function isto empty the boiler when required & to discharge mud,sediments, etc, which are accumulated at bottom ofboiler.

• Fusible plug: Function is to put-off fire in the furnaceof boiler when water level falls below an unsafe level.


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Steam boiler - Accessories

• Boiler feed pump: Used to supply water to boilerwith sufficient pressure.

• Super heater: Used to increase temperature ofsteam without raising pressure. Placed in the pathof hot flue gases from furnace.

• Economiser: Used as a heat exchanger to preheatfeed water by utilizing heat from exhaust flue gases.

• Air pre-heater: Used to recover heat from exhaustgases. Preheats air required for combustion


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Turbine

• Mechanical device in which pressureenergy/ kinetic energy of working fluid isconverted into mechanical energy ofrotation of turbine shaft.

• Steam turbine, Hydraulic turbine, Gasturbine.


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Steam turbine

• Pressure energy of steam is transformed intomechanical energy of rotation of turbine shaft.

• Impulse turbine– High velocity steam from nozzle moves over turbine

blades thereby rotating the turbine shaft.– Here kinetic energy of steam is used to rotate turbine

shaft

• Reaction turbine– Pressure change in steam imparts a reactive force over

turbine, thereby rotating turbine shaft.– Kinetic energy imparts momentum to turbine


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Impulse turbine


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Impulse turbine

• Shaft along with disc forms the rotating part calledrotor.

• High pressure steam flows through nozzle therebydecreasing pressure.

• Decrease in pressure is converted to kinetic energy.

• High velocity steam impinges on blades therebyrotating turbine shaft.

• Velocity of steam decreases when it flows throughmoving blades.

• Eg. De lavel turbine


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Impulse turbine disadvantages

• Velocity of rotor is too high for practical purposes.

• Velocity of steam leaving is considerably high.


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Reaction turbine

• Consist of rotor, fixed & moving blades, casing.• Fixed & moving blades are attached alternatively to

casing & rotor respectively.• Function of fixed blade is same as that of nozzle, i.e.

pressure decreases & velocity increases• Diameter of turbine is increased after each group of

blades because volume of steam increases due toexpansion.

• Due to expansion there will be a continuous drop ofpressure, which produces a reaction force on theblades which cause it to rotate.


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Reaction turbine


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Impulse turbine VS Reaction turbine

IMPULSE TURBINE REACTION TURBINE

•Rotation of rotor is due to impulsive force

•Due to reaction force

•Steam expands in nozzle•Expands when it flows over fixed & moving blades

•Cross sectional area of steam passage is constant

•Cross sectional area increases

•Speed of rotation is high •Not very high

•Comparatively small size for same power output

•Comparatively larger size


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Gas turbines

• Device that converts thermal energy of aworking fluid into useful mechanical power

• Based on Brayton cycle

• Used to generate electricity

• Used in aviation as gas turbine engines.

– Open cycle gas turbines

– Closed cycle gas turbines


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Open cycle gas turbine


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Open cycle gas turbine

• Compressor takes atmospheric air, compresses tohigh pressure.

• High pressure air moves to combustion chamber &gets heated by combustion of fuel.

• High pressure & high temperature gas expands overturbine, thereby doing work.

• Compressor & turbine are directly coupled.

• Part of work done is used to run compressor.

• Products of combustion after expansion is rejectedto atmosphere.


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Advantages & Disadvantages

Advantages• Simplicity• Low weight & size• No warm up period• Low capital costDisadvantages• Air flow rate cannot be varied effectively.• Efficiency of compressor & turbine may vary due

to deposit of mud or dirt.• Requires high air rate.


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Closed cycle gas turbine


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• Working fluid whose properties superior thanair is used. Helium, argon

• Same working fluid is continuously recirculated.

• Working fluid is compressed in compressor & ismoved to heating chamber.

• In Heating chamber heat of combustion istransferred to working fluid.

• High pressure & high temperature fluid expandsover turbine, thereby doing work.


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• Compressor & turbine are directly coupled.

• Part of work done is used to run compressor.

• After expansion, working fluid moves tocooling chamber, where it exchanges heat tocooling water.

• This working fluid is again fed into compressor


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Advantages• Reduced size of components.• Improved part load performance.• No contamination.• Can use inexpensive fuels.Disadvantages• Heating & cooling chambers are required.• Requires cooling water• Complexity


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Open cycle gas turbine Closed cycle gas turbine

Only air can be used as the

working medium.

Any gas with better

thermodynamic properties can be

used.

Working medium is replaced

continuously.

Same working medium is

circulated continuously.

Combustion chamber is used in

which fuel is directly added to the

compressed air.

Heating chamber is used in place

of combustion chamber in which

heat is transferred to the

compressed air.

Expanded product of combustion

is exhausted into atmosphere.

Expanded working medium is

exhausted into a cooling

chamber.

Working medium is contaminated

with carbon & other foreign

materials.

Working medium is not

contaminated.


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Energy conversion devices

Open cycle gas turbine Closed cycle gas turbine

Corrosion of turbine blades is

more due to carbon deposits

No corrosion since working

medium is free from carbon

deposit.

Maintenance cost is low. Maintenance cost is high.

Capital & running cost per

kW is less.

Capital & running cost per

kW is more

Requires only less space per

kW.

More space per kW is

required.

Cooling water is not required. Cooling water is required.

Dept of ME, UEC Vallivattom 37

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Hydraulic turbines

• Device which converts hydraulic energy into mechanical energy of rotation of turbine shaft.


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Hydraulic turbines

• Impulse turbines– Water posses only kinetic energy at inlet of turbine

– Impeller rotates due to impulsive force of water

– Eg. Pelton turbine

• Reaction turbines– Water posses both kinetic energy & pressure energy

at inlet

– Impeller rotates due to reaction force formed bychange in pressure energy of water.

– Eg. Francis turbine, kaplan turbine


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Impulse turbine : Pelton wheel


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Pelton wheel• Tangential flow impulse turbine

• High head turbine (>250m)

• Low discharge or low flow rate type

• Energy available at turbine inlet is kinetic energy

• Major parts

– Nozzle

– Flow regulating arrangement

– Runner & buckets

– Casing

– Breaking jet


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Pelton wheel

• Water is directed to the buckets of runner througha nozzle which increases kinetic energy of water.

• Needle spear inside nozzle controls flow of water.

• When water impinges on buckets, runner rotatesdue to impulsive force

• Breaking jet is provided, which directs water atback of vanes in order to stop the runner.


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Reaction turbine : Francis turbine


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Reaction turbine : Francis turbine

• Mixed flow reaction turbine

• Water enters radially & leaves axially

• Medium head(60m-250m) & medium discharge

• Water enters turbine through a spiral casing

• Water is directed to runner by guide vaneswhich act as nozzle.

• A part of pressure energy gets converted tokinetic energy by the time it reaches runner.


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Francis turbine

• As water pass through runner, its pressure changesgradually.

• Pressure at inlet of runner is greater than outlet.• This pressure difference is known as reaction

pressure which cause rotation of runner.• Water from runner is discharged to tail race

through a draft tube.• Draft tube is a long tube with increasing cross

sectional area, used to decrease the velocity ofoutgoing water.


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Reaction turbine : Kaplan turbine

• Axial flow reaction turbine

• Low head, high discharge

• Water from penstock enters scroll casing &moves to guide vanes

• Guide vanes are fixed, which direct waterthrough 900 to enter runner in axial direction.

• Water flows over the hub or boss which rotatesthe hub.


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Reaction turbine : Kaplan turbine


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Pump

• Mechanical device used to convert mechanicalenergy into pressure energy of a liquid.

• Used for raising liquid from low level to high level.

• This is achieved by creating low pressure at inlet& high pressure at outlet of the pump.

• Positive displacement pump

– Reciprocating pump, gear pump

• Rotodynamic pump

– Centrifugal pump


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Reciprocating Pump


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Reciprocating Pump

• Movement of piston towards right creates avacuum inside cylinder which pulls waterupwards from sump to cylinder.

• Movement of piston towards left pushes water todelivery pipe from cylinder.

• Cylinder is provided with inlet & outlet vales, bothof which are one way valves.

• These valves allow water to flow only in onedirection.

• Reciprocating motion of piston is achieved byconnecting rod-crankshaft mechanism.

• Crankshaft is rotated by an electric motor.


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Centrifugal Pump


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Centrifugal pump

• Required low pressure at inlet & high pressure atoutlet is obtained mainly by centrifugal action.

• Filling the suction pipe & casing with liquid to bepumped so as to remove air is known as Priming.

• Removal of air is required because vacuumcreated in eye of impeller is directly proportionalto density of liquid which is in contact withimpeller.


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Centrifugal pump

• Rotation of impeller in casing full of waterincreases pressure energy of liquid.

• When delivery valve is opened, liquid flows out ofimpeller through the casing whose cross sectionalarea increases towards delivery pipe.

• Increase in area decreases kinetic energy of fluidthereby converting it into useful pressure energy.

• Flow of liquid to delivery valve creates a vacuumat eye of impeller, which pulls water from sump toimpeller.


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Centrifugal pump vs Reciprocating pump

Centrifugal pump Reciprocating pump

Flow is smooth Flow is pulsating

Suitable for large discharge & low head

Suitable for low discharge & high head

Initial cost is less Initial cost is more

Occupies less floor space More floor space required

Needs priming No need of priming

Viscous fluids can be handled Trouble in handling viscous fluids

Due to no reciprocating parts wear & tear is less

Wear & tear more

Maintenance cost is low Maintenance cost is high


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Rotary pump : Gear Pump

• Positive displacement pumpwhich can pump thick &viscous liquids.

• Consist of 2 identicalintermeshing spur gearsworking in side a casing.

• One gear is keyed to drivingshaft of a motor & otherrevolves idly.

• Liquid entrained in spacesbetween teeth & casing iscarried round gears fromsuction to discharge side.

• Can build up high pressure.


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Internal Combustion Engine

• IC engines are heat engines in which, air istaken from atmosphere & combustion offuel & air occurs in the engine whichconverts thermal energy into mechanicalenergy.


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IC Engine Components


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Classification of IC Engines

• BASED ON TYPE IGNITION

– Spark ignition engines

– Compression ignition engines

• BASED ON TYPE FUEL USED

– Petrol engines

– Diesel engines

– Gas engines

– Duel fuel engines


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• BASED ON WORKING CYCLE

– Otto engine

– Diesel engine

– Dual combustion engine

• BASED ON NUMBER OF STROKES/CYCLE

– Four stroke engines

– Two stroke engines


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• BASED ON THE COOLING SYSTEM– Air cooled engines– Water cooled engines

• BASED ON THE NUMBER OF CYLINDERS– Single cylinder engines

– Multi cylinder engines

• BASED ON THE ENGINE SPEED– Low speed engines (up to 350 rpm)– Medium speed engines (350 to 1000 rpm)– High speed engines (above 1000 rpm)


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Four Stroke Diesel Engine


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• Suction stroke

– Inlet valve open, Exhaust valve closed

– Piston moves from TDC to BDC

– Air is sucked inside through inlet valve

• Compression stroke

– Both valves will be closed

– Piston moves from BDC to TDC

– Air gets compressed to high pressure & temperature


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• Expansion/Working/Power stroke

– Towards end of compression stroke, fuel is injectedin the cylinder by fuel injector

– Both valves remains closed

– Combustion takes place thereby pushing pistonfrom TDC to BDC

• Exhaust stroke

– Exhaust valve open, Inlet valve closed

– Piston moves from BDC to TDC, pushing exhaust gasout of cylinder through exhaust valve.


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Four Stroke Petrol Engine


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• Suction stroke

– Inlet valve open, Exhaust valve closed

– Piston moves from TDC to BDC

– Air-fuel mixture is sucked inside through inlet valve

• Compression stroke

– Both valves will be closed

– Piston moves from BDC to TDC

– Air-fuel mixture gets compressed to high pressure &temperature


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• Expansion/Working/Power stroke

– Towards end of compression stroke, Spark pluginitiates a spark

– Both valves remains closed

– Combustion takes place thereby pushing pistonfrom TDC to BDC

• Exhaust stroke

– Exhaust valve open, Inlet valve closed

– Piston moves from BDC to TDC, pushing exhaust gasout of cylinder through exhaust valve.


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Four Stroke Engine

• 4 strokes of piston = 1 cycle of operation.

• Each stroke is 1800 of crankshaft rotation.

• So 4 strokes = 7200 crankshaft rotation.

• Each revolution is 3600 of crank shaft rotation.

• 2 revolution of crank shaft for 1 cycle ofoperation.

• One power stroke in every 2 revolution ofcrank shaft.


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Two Stroke Diesel Engine


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• Suction & Compression Stroke

– Piston moves from BDC to TDC, compressing air tohigh pressure & temperature inside the cylinder

– At the same time, Inlet port opens, air enters crankcase

– All other ports remains closed

• Expansion & Exhaust Stroke

– At end of compression stroke, fuel is injected into thecylinder by fuel injector.

– Combustion takes place, thereby pushing piston fromTDC to BDC


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– At the beginning of this stroke, Inlet port will be inopen position

– As piston moves to BDC, exhaust port opens & inletport is closed

– Burned gases escape through exhaust port

– Air in crank case gets partially compressed

– Further downward movement of piston uncoverstransfer port & partially compressed air from crankcase move to cylinder


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Two Stroke Petrol Engine


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Two Stroke Petrol Engine• Suction & Compression Stroke

– Piston moves from BDC to TDC, compressing air-fuelmixture to high pressure & temperature inside thecylinder

– At the same time, Inlet port opens, air-fuel mixtureenters crank case

– All other ports remains closed


– At end of compression stroke, spark is fired by sparkplug into the cylinder.

– Combustion takes place, thereby pushing pistonfrom TDC to BDC


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Two Stroke Petrol Engine


– At the beginning of this stroke, Inlet port will be inopen position

– As piston moves to BDC, exhaust port opens & inletport is closed

– Burned gases escape through exhaust port

– Air-fuel mixture in crank case gets partiallycompressed

– Further downward movement of piston uncoverstransfer port & partially compressed air-fuelmixture from crank case move to cylinder


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Two Stroke Engine

• 2 strokes of piston = 1 cycle of operation

• Each stroke is 1800 of crankshaft rotation

• So 2 stroke = 3600 of crank shaft rotation

• Each revolution is 3600 of crank shaft rotation

• 1 revolution of crank shaft for 1 cycle of operation

• One power stroke in every 1 revolution of crank shaft


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Two Stroke Engine


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Fuels

• Substance which produces heat energy whenburned in presence of air.

• Amount of heat generated when 1kg of fuel iscompletely burned is called calorific value ofthe fuel.

• Fuels are mainly classified as solid, liquidand gaseous.


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Solid fuels

• Either natural solids like wood, bituminous coal orprepared solid fuels such as charcoal, coke, pulverizedcoal.

• Advantages

– Can be stored with out any risk of explosion.

– Transportation is easy

– Low cost.

• Disadvantages

– Ash content is more and produces large quantity of smoke.

– Combustion rate cannot be easily controlled.

– Calorific value is low compared to liquid and gaseous fuels.


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Liquid fuels• Derived from natural crude petroleum.

• Crude oil contains 83-87% carbon, 10-14% hydrogen, smallpercentage of sulphur, nitrogen, oxygen & metallic derivatives.

• Useful fuels from crude oil are obtained by distillation process.

Advantages

• Air required for complete combustion is less, compared to solid fuels.

• Combustion efficiency is high

• Rate of burning of fuel can be easily controlled.

• Storage space required is much less.

• No problem of ash disposal.

Disadvantages

• Cost of liquid fuel is much more than solid fuel.

• Storage and transportation are risky.Energy conversion devicesDept of ME, UEC Vallivattom 80

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Gaseous fuels

• Classified as natural gas & prepared gas. Natural gas mainlycontains 85% methane along with some hydrogen & small % ofother hydrocarbons.

• Advantages

– Complete combustion is possible.

– Gaseous fuels do not produce ash or smoke.

– Air required for complete combustion is minimum comparedwith solid and liquid fuels.

• Disadvantages

– Gaseous fuels are highly inflammable

– Storage & transportation are difficult because of possibleleakage of gas from pipe & tank.


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Recent Developments in

Automotive Field

• CRDI

• MPFI

• Hybrid Engines


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Common Rail Direct Injection

(CRDI) System


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(CRDI) System

• In conventional diesel engines, fuel pressure had to begenerated repeatedly during each time of injection.

• Hence fuel injection pressure was too low (35-40 bar).

• CRDI system maintains fuel at constant pressure in arail through out the working of engine.

• An ECU along with different sensors controls thepressure & amount of fuel in the rail, injection pressure,fuel injection timing, amount of fuel to be injected etc.

• Fuel from the tank is pumped to the common rail byhigh pressure pump.


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(CRDI) System

• Pressure inside the Common rail is maintained constant& is monitored by ECU with the help of rail pressuresensor.

• Any decrease in pressure actuates the fuel pump byECU, thereby pumping more fuel to the rail.

• Fuel injection timing is determined by ECU with thehelp of signals from various sensors mounted on crankshaft, cam shaft, accelerator pedal etc.

• Fuel is injected at extremely high pressure(upto1800bar) with the help of ECU controlled piezoelectricinjectors.


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(CRDI) System

• CRDI engines maintain constant pressure duringinjection.

• ECU also controls amount of fuel to be injected.

• Fuel that is injected atomizes easily & burns cleanly,reducing exhaust emissions & increasing efficiency.

• Common rail engines require no heating up time, &produce lower engine noise & lower emissions thanolder systems.

• This technique allows fuel to be injected as needed,saving fuel consumption.


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• Advantages– CRDI equipped engines deliver 25% more power &

torque than direct injection engine

– It also offers superior pick up

– Lower levels of noise & vibration

– Higher mileage

– Lower emissions, lower fuel consumption &improved performance

• Disadvantages– Costly spare parts

– More maintenanceEnergy conversion devicesDept of ME, UEC Vallivattom 87

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Multi Point Fuel Injection

System(MPFI)

• It is used in SI engines

• MPFI system assures proper air fuel ratio to theengine by electrically injecting fuel in accordance withvarious driving conditions

• MPFI system injects fuel just upstream of eachcylinder’s intake valve, based on commands from ECU.

• In MPFI system, each cylinder has one injector placednear the intake valve to supply fuel to the cylinders ascompared to one injector located centrally to supplyfuel in case of single point injection system.


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System(MPFI)


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System(MPFI)

• The use of MPFI technology results not only inbetter power but also in higher output fromeach one of the cylinders.

• MPFI system supplies optimized air/fuelmixture under widely varying drivingconditions.

• Using MPFI, uniform air fuel mixture will besupplied to each cylinder.


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Advantages of MPFI• Advantages

– Higher fuel economy

– Lower exhaust emissions

– Power delivered from all cylinders is uniformlybalanced

– Supply of fuel to each cylinder is uniform

– Less vibrations

– Long engine life.

• Disadvantages– MPFI set up is expensive.

– MPFI installation is complex


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Hybrid Vehicles

• Uses two or more distinct power sources to movevehicle.

• Usually an IC engine along with high voltage Electricmotor with battery is used.

• IC engines have lower efficiency & high fuelconsumption at lower rpm.

• At lower speeds, Hybrid vehicles uses electric motoras power source & from medium to higher speed,motor is replaced by IC engine.

• Thus it improves overall fuel consumption &reduces emission.


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Hybrid Vehicles

Series Hybrid• Engines turns a generator, producing current,

which is used to charge batteries• Batteries run the electric motor that drives

transmission.• Thus engine never directly powers the vehicle.


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Hybrid VehiclesParallel Hybrid

• Electric motor as well as Engine is engaged to the transmission.

• So any of the two power plants can be used to drive the transmission.

• Battery for the electric motor is charged during the running time byutilising engine power.

• New technology uses Regenerative braking for charging batteries.

• This converts kinetic energy lost during braking into electric energyfor charging batteries


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Thanks…


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module ii energy conversion devices ktunotes

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