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Applied Thermodynam ics

Time: 3 hrs. Max. Marks:100Note: 1. Answer any FIYE fuII questions, selecting

at least TWO questions from esch part.2. Use of thermodynamic data handbook/eharts/tables is permitted.3. Any missing data may be assumed suitably.

PART - AI a. Distinguish between: i) Theoretical air and excess air

ii) Higher calorific value and lower calorific value.b. Define the terms: i) Enthalpy of formation ii) Enthalpy of combustion

cFindthestoichiometr#'l,l$?if:':ffi,1'#1T1tr""'Jl?fi ::",Uii:'fiXJlffi H]molar basis. (04 Marks)

d. 4.4 kg propane gas is burnt completely with 3.0 kmol of air. Find the excess air and themolar analysis of the dry combustion products. (08 Marks)

2 a. With the help of P-V and T-S diagrams, derive an expression for the air standard efficiencyofa diesel cycle. (08 Marks)

b. Compare the Otto and Diesel sycles, on the basis of same compression ratio and same heatinputs, with the help of T-S and P-V diagrams. (04 Marks)A four stroke, four cylinder petrol engine of 250mm bore and 375mm stroke works on theOtto cycle. The clearance volume is 0.01052m3. The initial pressure and temperature are

1 bar and 47oC.If the maximum pressure is limited to 25bar, find the following:i) Air standard efficiency ii) Mean effective pressure. (08 Marks)

Derive an expression for the optimum pressure ratio, for the maximum network output, in anBrayton cycle. What is the corresponding cycle efficiency?What are the methods of improving the efficiency of Brayton cycle?ln a reheat gas turbine cycle, comprising one compressor and two turbines, air is compressed

from t bar,27oC to 6 bar. The highest temperature in the cycle is 900oC. The expansion inthe frst stage turbine is such that the work from it just equals the work required by the

compressor. Air is reheated between the two stages of expansion to 850'C. Assume that theisentropic efficiency of the compressor, the first stage and the second stage turbines are 85%each and that the working substance is air. Calculate the cycle efficiency. (12 Marks)

Discuss the effect of i) Boiler pressure and ii) Condenser pressure, on the performance of aRankine cycle. (04 Marks)Explain the working of the regenerative Rankine cycle with one feed-water heater. (04 Marks)

ln a reheat cycie, steam a-t 500"C expands in a- HP tr-rrbine till it is sa,tura-ted vapour. It is thenreheated at c.onstant pressure to 400oC and then expanded in a LP tr:rbine to 40oC. If themaximum moisture content at the turbine exhaust is limited to 15Yo find, i) the reheatpressure, ii) the pressure of steam at the inlet to the HP turbine. iii) the net specific workoutput iv) the cycle efficiency v) the steam rate. Assume all the ideal processes. (r2 Marks,y- --

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06ME43

what are the drawbacks of , ,rru,.lt}l;*rr"rro, for producing hish pressure? How arethese overcome by multistage compression? (0s Marks)Derive an expression for the condition for the minimum work input, required for a two stagecompressor, with perfect intercooling. (07 Marks)A two stage, single acting reciprocating air compressor, with complete intercoolingatmospheric air at 1 bar and l5oc, compresses itpolytropically (n = 1.3) to 30 bar. If bothcylinders have the same stroke, calculate the diameter of the HP cylinder. The diameter ofthe LP cylinder is 300mm. (08 Marks)

6 a. Explain the effect of superheat and subcooling on the vapour compression cycle with thehelp of r-s and p-h diagrams. (06 Marks)

b. With a neat sketch, explain the working of vapour absorption refrigeration system. (07 Marks)c. In a saturated vapour compression refrigeration cycle operating between an evaporatortemperature of -1OoC and a condenser temperature of 40oC, the enthalpy of the refrigerant,Freon-l2 at

lhg_end of compression is 220 kJkg. Show the cycle on f-S ana p-h-planes.Calculate i) COP ii) refrigerating capacity and compressor power assuming a refriglratingflow rate of 1 kg/min (07 Marks)

7 a. Define: i) R.el{ive humidity ii) Specific humidity iii) Dew point temperatureiv) Enthalpy of humid air v) Degree of saturation. (05 Marks)b. With a schematic diagram, explain the summer air conditioning system, for hot and wetweather. (07 Marks)c. For a hall to be air-conditioned, the following conditions are given:

Outdoor conditions: 40o DBT, 20"C WBT, required comfort condition - 2O.C WBT.60% RH. Seating capacity of the hall is 1500, amount of outdoor air supplied: 0.3 m3/minper person. If the required condition is achieved first by adiabatic humidification and then bycooling, estimate i) the capacity of the cooling coil in tones and ii) the capacity of thehurnidifier in kglh. (08 Marks)

Describe the principle of conducting Morse test on IC engines. (04 Marks)A single cylinder four stroke diesel engine works on the following data:cylinder bore : l5cm, stroke :25cm, speed :250 rpm, area oflnd,icator diagram : 6 cm3,length of the indicator diagram : 9 cm, spring conitant : 7.5 bailcm, brakJ specific fueiconsumption : 0.24 kglkwhr, calorific value : 42A00 kJ/kg, diameter of brakewlreel--= 709m, rope diameter : 3.5cm, brake load : 40kg. calculate i) brake powerii) indicated mean effective pressure iii) Indicated power iv) Mechanical efficiencyv) Indicated thermal efficiency. (0E Marks)The following data were obtained from a Morse test on a 4-cylinder, 4-stroke cycle SIengine coupled to a hydraulic dynamometer, operating a constant ipeed of 1500 rpm.

Brake load with all four cylinders firing = 296 ][Brake load with cylinderNo.l not firing:201 NBrake load with cylinder No.2 not firing = 206 NBrake load with cylinder No.3 not firing = 192 NBrake load with cylinder No.4 not firing :200 N

The brake power in kW is calculated using the equation BP : WN/42300, where W is thebrake load in Newtons and N is the speed of the engirr. in rpm. calculatei) Brake power ii) Indicated power iii) Friction po*"r iv) Mechanical efficiency.

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ME43USN

Fourth Semester B"E. Degree Examination, Dec.09/Jan.10

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Applied Thermodynamics

Time:3 hrs. Max. Marks:100Note: l.Answer any FIYEfull questions.

2. Use of thermodynamics dsta hand book is permitted.i. Use of Mollier diagram and Psychrometric chart permitted.4. Use co: 1.005 kil kg K, cu= 0.718 kJ/ kg K, R: 0.287 kJ /kg K,

K : bco /cu : 1.4 for Air.

I a. Deduce an expression for available energy from a finite energy source at temperature Twhen the environmental temperature is To. (06 Marks)

b. Define second law efficiency and derive the equation for second law ef,ficiency for a solarwater heater. (06 Marks)

c. Calculate the deuease in available energy when 30 kg of water at 85oC,is mixed with 35 kgof water at25"C, with the pressure being constant and temperature of the surounding being15'C (co of water:4.2kJ lkg K). (08 Marks)

2 a. Distinguish between higher and lower heating values and define combustion efficiency.(06 Marks)

b. Define the following terms :

, Enthalpy of combustion ii) lntemal energy of combustion iii) Adiabatic flametemperature. (06 Marks)

c. The products of combustion of an unknown feel C* H, have the following composition as

measured by an orsat apparatus COz lZ.lyo, CO 0.9yo, C'23.8% and Nz 83.2%. determine -i) Chemical equation for the actual reaction ii) Composition of the fueI iii) The air fuel ratioiv) Theoretical excess air. (08 Marks)

3 a. Derive an expression for the air standard efficiency of,an otto cycle in terms of compressionratio. Show the cycle on PV and TS diagrams. (06 Marks)

b. Sketch the flow diagram and T*S diagram of a gas turbine plant having 2-stage compression

. with intercooling, 2-stage expansion with reheating and regeneration indicating the statepoints clearly on both diagrams (No description required) (06 Marks)

c. An air standard dual cycle has a compression ratio of 15 and compression beings at 0.1 MPaand 40oC. The maximum pressure is limited to 6 MPa and the heat added is 1.675 MJ /kg.compute i) Work done per kg of air ii) The cycle efficiency iii) mep. (08 Marks)

4 a. With the help of T-S diagrams, explain the effect of the following parameters on theefficiency of Rankine vapour power cycle.i) Increase in boiler pressure ii) Superheating of vapour iii) Decreasing condenser pressure.

b. What is a feed water heater? Distinguish clearly between open and ctrosed {::-il[}heaters. (06 Marks)

c. A steam power plant operates on a Reheat Rankine cycle and.has a net power output of80 MW. Steam enters the high pressure turbine at 100 bar and 500'C and the low pressure

turbine at 10 bar and 500oC after being reheated. [t Ieaves the low pressure turbine at 0.1bar. Using the Mollier chart and assuming ideal processes detennine - i) The quality ofsteam at exit of LP turbine ii) Therma, *O?.:? iii) Mass flow rate of steam. (08 Marks)

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ME43

5 a. Show that for minimum work of coinpression in a multistage Reciprocating air compressorthe interstage pressure must be the geometric mean between the initial and final pressures.Hence deduce an expression for work of iompression in a two stage compressor and extendthe result to obtain an expression for 'm' stages.

b. The following particulars apply to a two stage single acting air compressor.Stroke 28.5 cm, L.P. cylinder dia 23 cms, final pressure - 25 bar intermediate pressure 5 bar,temperature of air leaving the intercooler 35oC. If the air is drawn into the compressor atI bar and l5oC find the power required to compress the air when running at 350 rpm. Theprocess of compression is given by PVI'3 : conit. Determine also the .treigy rejected in the

(12 Marls)

6a.b.

c.

0.75.

7. a. Define the following terms as

humidity iv) Specific humidity.

(08 Marks)

applied to psychrornetrics i) DBT ii) WBT iii) Relative(06 Marks)

intercooler. (08 Marks)

What are the desirable properties of refrigerants? List out a few refrigerants that are used.(06 Marks)

Give a brief description of a vapour absorption refrigeration system with a neat sketch(06 Marks)

A vapour compression refrigerator works between temperature limits of 25"C and -15oCwith Freon - 72 as refrigerant. The liquid is cooled to l7"C before entering the expansionvalve. If the condition at the end of compression is dry saturated, calculate the powerrequired to drive the compressor for a 10 ton capacity refrigerator if the relative C. O. P is

b. Briefly explain the following processes by representing each on psychrometric charti) Heating and humidification ii) Cooling and dehumidification. (06 Marks)

c. A room 6m x 4m x 4m contains air at 25oC and 1 atm at a relative humidity of 80%.Determine i) partial pressure of dry air ii) specific humidity iii) the enthalpy per unit mass ofdry air and iv) the masses of dry air and water vapour in the room. (08 Marks)

8 a. During a trial of a single cylinder, four stroke oil engine, the following results wereobtained.cylinder dia:20 cm, Stroke : 40 cm, mep : 6 bar, Torqte : 407,Nm, Speed : 250 rpm, oilconsumption: 4 kg /h calorific value of fuel : 43 mJ /kg, cooling water flow rate : 4.5 kglmin, Air used per kg fuel = 30 kg, Rise in cooling water temperature : 45"C, Temperafure.of exhaust gases : 420"C, Room tempr. : 20"C, Mean specific heat of exhaust gases = 1.0kJ lkg K specific heat of water: 4.18 kJ /kg K. find the IP, BP indicated thermal efficiencyand draw up an energy balance sheet for the test in kJ/h. (12 Marks)In a test on a 4 cylinders, 4 stroke engine, 7 .5cm bore and 10 cm stroke, the following resultswere obtained at full tltoffle at a particular constant speed and with fixed setting of fuelsupply of 6.0 kg lhr.B.P with all cylinders working : 15.6 kWB.P with cylinders no.1 cut out: 11.1 kWB.P with cylinders no. 2 cut out : 11.03 kWB.P with cylinders no. 3 cut out: 10.88 kWB.P with cylinders no. 4 cur out: 10.66 kWIf the calorific value of the fuel is 83600 kJ /kg and clearance volume is 0.0001 m3, calculatei) Mechanical efficiency ii) Indicated thermal efficiency iii) Air standard efficiency.

(08 Marks)

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USN 2OA2 SCHEME ME43

iii) Diesel cycle iv) Duel cycle(06 Marks)

Fourth Semester B.E. Degree Examination, June-July 2009Applied Thermodynamics

Time:3 hrs. Max. Marks:100Note: I.Answer any FIVE full questions.

2.Use of steam tables, refrigerant tables/charts,Mollier ch arts, Psych rometric c h art p ermitte d

I a. What do you mean by (i) high grade energy (iil) low grade energy (iii) available energy(iv)Unavailable energy and (v) dead state? (05 Marks)

b. Define the term availability. Derive an expression for the availabiiity of a non cyclic closedsystem. (05 Marks)

c. Calculate the decrease in available energy when 90kg of water at 90oC mix with 30kg ofwater at 30oC, the pressure being taken as constant and the temperature of the surroundingsbeing 15oC. Take Coof water:4.2 kJ/kg K. (10 Mahsl

2 a. Describe in brief (i) Enthalpy of formation (ii) Enthalpy of combustion and (iii) Internalenergy of combustion. (12 Marks)

b.

3a.

b.

c.

Calculate the amount of theoretical air required for the complete combustion of I kg ofacetylene (CzHz) to COz and HzO. (08 Marks)

Represent the following gas power cycles on P-V and T-S diagrams:i) Carnot cycle ii) Otto cyclev) Stirling cycle vi) Brayton cycle

4a.

Compeire the Otto and Diesel cycles for the same ma:rimum pressure and same heat input.(04 Mark)

An indicator diagram taken on a diesel engine shows that the compression curve follows thelaw PVr'a : Constant. At two points lying on the compression curve at l/8ff and 7/8th of thestroke the pressures are 1.6 bar and 16 bar respectively. Find the compression ratio of theengine. If cut off occurs at 6%o of the stroke, calculate air standard efficiency of the engine.

(I0 Marks)

Draw the flow diagram of steam power plant with regeneratior, *itf, two stage bleeding andtwo open feed water heaters. Represent the processes on T-S diagram and explain. Writedown energy balance across each feed water heater and derive an expression forregenerative cycle efficiency. (10 Marks)A Rankine cycle operates between a pressure of 80 bar and 0.1 bar. The maximum cycletemperature is 600'C. If the steam turbine and condensate pump efficiency are 0.9 and 0.8respectively , calculate the net specific work output and thermal efficiency. Relevant steam

extract rs gtven below: l0 MarksPinbar

toc Specific volumein m3/ke

Specific enthalpyin k}ke

Specific Entropyin kYke K

Vr V, hr hr" hn S1 sfs Ss

0.1 45.84 0.00r013 14.68 191.9 2392.3 2584.2 0.6488 7.5006 8.149480 295.1 0.001385 0.0235 t3t7 1440.5 2757.5 3.2473 2.5351 5.7424

5 a. Derive an expression for work required per cycle by a two stage compression withoutclearance volume and with perfect intercooling. Also, derive an expression for intermediateintercooler pressure for minimum work required.

tables is eiven below

1 of2

(08 Marls)

ME43

A single stage single acting air compressor 30cm bore and 40cm stroke runs at 200rpm. The

suction pressure is 1 bar and temperature is l5oC and delivery pressure is 5 bar. Determinethe indicated mean effective pressure and the ideal power required !q_ run it whencompression is (i) isothermal (ii) compression follows the law PVr'25 : Constant(iii)PVt'a=Constant and (iv) PVr'5 : Consknt. Determine isothermal efficiency for (ii), (iii)and (iv) and adiabatic efficiency for (iv). (12 Marks)

6 a. Draw the flow diagram of a simple vapour compression refrigeration system and explain itsworking. Represent the processes on T-S and P-H diagrams and write an expression for(i)Mass of refrigerant required per second (ii) Power required to run the compressor (iii)C.O.P. and (iv) Mass of cooling medium required in kg per second. (10 Marks)

b. A 5 ton Freon-I2 refrigeration plant has saturated suction temperature of -5oC. The

condensation takes place at 32oC and there is no under cooling of refrigerant liquid.Assuming isentropic compression, find (i) COP of the plant (ii) Mass flow rate of refrigerant(iii) Power required to run the compressor in kW.Take Co (S ur):0.615 kJ/ke K. ke the tbllowi tes

P bar TOC hr kJ/ke h, kJlkg s" kJ/ke-K7.85 32 130.5 264.5 t.5422.61 -5 249.3 1.557

ofF-12.

(10 Marks)

Define the following and describe a theoretical method for determining their values:i) Specific humidity ii) Relative humidity and iii) Degree of saturation (06 Marks)

Explain in brief (i) Enthalpy of moist air and (ii) Adiabatic saturation temperature. (06 Marks)Draw the flow diagram'for summer air conditioning system for hot and dry outdoorconditions. Sketch and represent the processes on psychrometric chart, explain its workingand write the formula for the components. (08 Marks)

7a.

b..c.

8a.

b.

Sketch the apparatus and write how air supply to internal combustion engine is measured inlaboratory. (08 Marks)During the trial of a single cylinder engine, the following observations were recorded:Engine data : Bore: 300mm, Suoke = 400mm, Speed:200rpm, Cycle four stroke.Experimental Observations :

Duration of trial = t hour, Fuel consumption = 7.05kgCalorific value of fuel:44000 kJ&g, Area of indicator diagrarn= 322mm2Length of indicator diagram: 62mm, spring index: 1.1 bar/mmNet load on brakes: 1324.35 N, Brake drum diameter: 1600mmTotal mass ofjacket cooling water :495kg,Temperature rise ofjacket cooling water : 38oC,

Temperature of exhaust gas : 300"C, Air consumption : 31 lkgAssumptions: Specific heat of exhaust gasses: 1.004 kJ/kg K

Specific heat of water = 4.186 kJlkg K, Room temperature =20oCDetermine:i) Power available at brakesii) Indicated power developediii) Mechanical effi ciencyiv) Brake thermal efficiencyv) Indicated thermal efficiency

Also draw a heat balance sheet of trial for one hour basis. (12 Marks)

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ZOOE SCHEMEME43

(04 Marks)

(08 Marks)(02 Marks)

Fourth Semester B.E. Degree Examination, Dec.08/Jan.09

Applied ThermodynamicsTime: 3 hrs. Max. Marks:100

Note: IAnswer any FIVE full questions2.[Jse of thermodynamic charts and tables permitted.

I a. Define (i) Availability (ii)unavailable energy and (iii)Ineversibility applied to a closed

system undergoing a process. (06 Marks)

b. Explain the significance of second law of thermodynamics. (06 Marks)

c. Show that the availability of system decreases because of heat transfer with finite

temperature difference. ^ (04 Marks)

d. A hiat engine receives heat from a source at 15000K atarate of 700kW, and rejects wa^ste

heat at 32i0K. If the measured power output is 320kW and the environment is at 25oC.

Calculate the reversible power, irreversibility and the second law efficiency.

2 a. Define the following:i. Enthalpy of formationii. Heat of reaction

b.

iii. Calorific valueiv. Adiabatic flame temperaturev. Stoichiometric AirlFuel ratio. (10 Marks)

The sample of coal has the following mass based analysis. C:800%, H:l2o/o and ash:S%o.

Compute the stoichiometric A/F ratio and the analysis of products by volume. (10 Marks)

Derive the expression for the Air standard efficiency of a Diesel cycle with usual notations.

State the assumptions made and represent the process on P-V and T-S diagrams (10 Marks)

A gas turbine unit has a pressure iatio of 10:i and a maximum cycle temperature of 7000C.

The isentropic efficiencies of the compressor and turbine are 0.82 and 0.85 respectively.

Compute thi porver output of the turbine when air enters the compressor at 150C at the rate

of 15kgisec. iake for air Co:1.005kllkg0K and r:1.4 for compreision and Cp:1.l1kJ/kg0Kand r:1.333 for expansion process.

c. Explain the use of regenerator in gas turbine plants.

a. Explain clearly with the help of a T-S diagram, the working of a Rankine cycle withregeneration using open feed water heater system. Also briefly comment upon the effect ofpressure and temperature on the performance, (10 Marks)

b. On a Rankine cycle, the steam at inlet to turbine is saturated at a pressure of 35 bar and the

exhaust pressure is 0.2 bar. Calculate (i)The pump work (ii)The turbine work (iii)Rankine

efficiency (iv)Condensor heat flow (v)The dryness fraction at the end of expansion. Assume

mass flow rate of steam to be 9.5 kg/sec. (10 Marks)

b.

a.

54.

b.

c.

Derive with usual notations the expression for the polytropic work done by a single stage-

reciprocating compressor with clearance volume. Also show the Indicator diagram.(10 Marks)

With the help of a diagram show the effect of intercooling on a 2 stage compressor.(04 Marks)

A single stage reciprocating air compressor takes 1 mt3 of air per minuJg at i.013 bar and

150C and delivers the same at7 bar.If the law of compression is PV'":constant and the

clearance is negligible compute the indicated power. (06 Marks)

I of2

]\,IE436 a with a neat sketch describe clearly the working of a vapour absorption refrigerator system

b. write a brief note on properties of refrigerants. ::9 y"F)(04 Marks)c' A simple vapour compression plant p.Jdu".. 5 tonnes of refrigeration. The enthalpies of theworking flll"d at-i{et to compressor, at exit of compressor and at exit from the condensorarel81 j9kJkg,209'4lkJlkg

^d 7a.:?.? lykg respectively. Estimate (i) The refrigerant flowrate (ii)The coP of the plant and (iii) the fowei required to drive tire compressor (iii)Therate of heat rejection in the condensor. (08 Marks)

7 a. Define the following clearly.1' Dty bulb temperature 2. wet bulb temperature 3. Dew point temperature 4. Specifichumidity 5. Relative humidity.

(10 Marks)b. Represent the following p.o..rr"s on a psychrometric chart.(i)Heating and humidi&ing (ii)Sensible heating (iii)sensible cooling (iv) Cooling anddehumidifuing.

c' with a neat slietch briefly describe summer Air-conditioning system. ffi ffi:[]8 a'

ff#,3fcribe the estimation of the indicated power of a multi-cylinder engine using

b. Explain one method of determining B.p. of an I.c. engine. ll:ffi:[ic' During a test on an oil engine *oikirg on 4-stroke cycle the following data were obtained.MEP:5'6 bar, stroke volume:l4 fiGs, speed:4O0rpm, load:o.75KN, Radius of brakedrum:0'7m' Fuel consumed:0.002kg/sec. ialorific ',rulu" of oil:46000kJ/kg, cooling watercirculated:0.l5kg/sec, rise in temperiture of cooling *;;";33€. currrru,.1. B.P.2, I.P.3. Mech. Efflrciency4. Indicated thermal efficiency

Also draw the heat balance sheet.(08 Marks)

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USN

ii) Reversible work

ME43

iii) Irreversibility(SB Marks)

Time:3 hrs.

I a. Define the terms- - i) Availabilityiv) Second law efficiency.

Fourth Semester B.E. Degree Examination, June/July 08

Applied Thermodynam ics

Max. Marks:100

Note : I. Answer any FIVE full questions.2. (Jse of steam tables, refrigerant tables/charts, Mollier

ch art/psychrometric ch urt, on d Th ermo dy n amic datahundbook permitted.

b. Derive a general expression for irreversibility in i) Non-flow process ii) Steady flowprooesses. t04 F1arks)

c. A lead storage battery used in an automobile is able to deliver 5.2 Mi of electrical energy.

This energy is available for starting the car. Let compressed air be considered for doing an

equivalent amount of work in starting the car. The compressed air is to be stored at 7 MPa,

250 C. What is the volume of the tank that would be required to let the cornpressed air have

an availability of 5.2}ix1? (08 Marks)

2 a. Explain the following terms with reference to a combustion plocess.

i) Theoretical and excess air ii) Stoichiometric air fuel ratio iii) Enthalpy of reaction. ir,)

Enthalpy of formation. v) Adiabatic flanretemperature. (10 Marks)

b. Methane (CH+) is burned rvith atmospheric air. The analysis of the products cn a dry basis

is as follow's:COz:7TYa, Oz:2.37o/o, CO:0.53% and N2:87.1A%. Calculate the air fuel ratio and the

percent theoretical air and write the combustion equation. (10 Marks)

3 a. Compare Otto, diesel and dual combustion cycles on the basis of same compression ratio

and same heat input with the help of T-S and P-V diagrams. (06 Marks)

b. A mass of 1 Kg of air is taken through a diesel cycle and a joule cycle closed initially the

air is at 288 K and i.01325 bar. The compression ratio for both cycles is 15, and the heat

added is 1850 kJ in each case. Calculate the ideal cycle effrciency and mean effectivepressure for each cycle. Comment on the results. (14 Marks)

4 a. Explain the effect of i) Maximum pressure ii) Exhaust pressure iii) Superheat on the sirnple

rankine cycle. (06 Marks)

b. List the methods of improving the performance of a rankine cycle. ^ (02 Marks)

c. A reheat cycle has the first stage supply conditions of 70 bar and 500'C .The reheat is at 3

bar and to the same temperature. i) Given that the efficiency of the first turbine is 80% howmuch energy is added per Kg of steam in the reheat coils? ii) Assume that the same

expansion efficiency exists in the second turbine. What is the thermal efficiency if the

condenser pressure is 0.03 bar?

I of2

(12 Marks)

F

b.

ME 43

Derive an expression for the condition for minimum work required in a fwo-stage aircompressor with perfect intercooling with the help of a P-V diagram. (06 Marks)The following data refer to a two-stage, single acting air compressor.Air compressed:4 kg/min, Pressure rise:l bar to 25 bar, cylinder diameters: 15cm and7.5cm stroke leng-rh in each stage: 20cm compression index: 1.2, Air inlet temp:250c.

Assuming perfect intercooling and a clearance volume equal to ll25rh stroke volume inboth cylinders, compute i) The intermediate pressure P; ii) The power required to driveeach cylinder, if the mechanical efficiency is 0.75 iii) The speed of crank driving thecompressor in RPM iv) The energy rejected at the intercooler as heat. (14 Marks)

a.

b.c.

Derive an expression or theoretical COP of an absorptionList the desirable properties of refrigerant.

refrigeration in tons and the heating required in kW.

Briefly explain how the I P of a multi-cylinder engine is measured.Write a short note on heat balance sheet.

system. (06 Marks)(04 Marks)

(07 Marks)

(04 Marks)(04 Marks)

An ammonia vapour compression refrigerator works between an evaporator pressure of 1.2bar and a condenser pressure of 12.0 bar. The refrigerant leaves the evaporator at -200Cand leaves the condenser at+200C. Determine the COP of the system and the powerrequired per ton of refrigeration. Determine also the bore and stroke of the compressorcylinder if the speed is 200 rpm, volumetric efficiency is 0.8 and stroke is 1.5 times thebore. (10 Mark$

a. Define i) Saturated air ii) Dry bulb ternperature. iii) Dew point temperature. iv) Relativehumidity v) Specific humidity. (05 Marks)

b. Explain briefly i) Summer air conditioning ii) Winter air conditioning. (08 Marks)c. Moist air enters a humidifier heater unit at 260C and 80 percent ,*l*tir. humidity. It is to

leave at 26aC and 50 percent relative humidity. For an flow rate of 0.47m3ls,"find the

a.

b.

c. The follo*'ing observations .arere made during a trial of a single cylinder four-stroke cyciegas engine having cylinder diameter of 18cm and stroke Z4cm.Duration of trial :30min, total number of revolution:90OO, total no. of explosions :445AMEP:5 bar, Net load on the brake drum:40kg, effective diameter of brakewheel:lm.Total gas used at NTP:2.4m', CV of gas at NTp :19 MJim3, totul air used:36m', Pressure of air= 720mm^Hg, temp of air :170c, Density of air at NTp : L.z9kg/m3, temp of exhaust gas :3500c,ioorn iemp :170g, Sp heat, oi exhaust gas :1kJ/kgK;cooling water circulated:80 kg, Rise in temperatue of cooling water: 300c.Draw up a heat balance sheet on minute basis in kJ and indicated thermal effrciency. TakeR:287 J/I(g k. (12 Marks)

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USNME43

Max. Marks:100

Fourth semester B.E. Degree Examination, Dec. 07 / Jan' 08

Time:3 hrs.

Applied Thermodynamics

Note : l.Answer any FIVE full questions'z. ise of theimodynimici datu land book , charts, tubles is permitted'

a. Explain the term 'Availability' and derive an expression for the availability of a steadily

flowing stream' (06 Marks)

b. Explain the terms ineversibility and second law of thermodynamics' (04 Marks)

c. Air expands in a turbine adialatically fro1 i91kll.100 K and i50 m/sec to i00 kPa'

300K and 70 m/sec. The environment is at 100 kPa, 170C' Calculate per kg of air :

i)The rraximum work output ii) The actual work output iii) The irreversibility

iv) Second law efficiency' (10 Marks)

a. Distinguish between :

i) Theoretical air and excess air

iil Higher heating value and low'er heating value' lLt- LL^^-^

(04 Marks)

b. Balance the chemicai equation for combustion of octane CsHrs u'ith theoretical amount of

air, also find the theoretical air-fuel ratio' r, -:- - (06 Marks)

c. The fuel used in petrol engine contains 87x carbon and 1"3v" Hz The air supply is 75N of-

that theoretically required-for complete combustion.,Assuming that all Hz is burned and

there is no free curbon left. f,inci the volumetric anall'sis of dr}- exhaust gases' (10 Marks)

a. With the help of P-V and T-S diagrams, derive an expression for the air standard efficiency

of a semi diesel c1-cle in terms ofiompression ratio, cut-off ratio and explosion ratio(08 Marks)

b. The minimum and maximum temperatures in an engine working on constant pressure

cycle are 300 K and 1500 K and the heat addition durlng combustion is 500 kJ/kg of air'

Another *.rglrr. *orking on semi diesel cycle between the same temperature limits of 300

K and 1500 K has a heat addition of 500 kJ/kg of air which is shared equally between the

two heat addition processes" Cornpare their - i) Efficiencies'and ii) Work outputs'(12 Marks)

a. With the help of a schematic diagram and T-S diagram, explain. the working of a

regenerative vapour power cycle and derive an expression for its overall efficiency'(08 Marks)

b. An ideal Rankine cycle with reheat is designed to operate according to the following

specification. Pressure of steam at high pressule turbine inlet 20 MPa

Temperature of steam at higi pr.rrrrr. turbine inlet 5500c

Temperature of steam at the end of reheat 5500C

Pressure of steam at the turbine exhaust 15 kPa

Determine:i) The pressure of steam in the condenser

iii; Ratio of heat rejection to heat additionii) Ratio of pump work to turbine work

iv) Cycle thermal efficiency. (12 Marks)

1 nf ?

T

ME43

Obtain an expression for the volumetric efficiency of a single stage air compressor in termsof the pressure ratio, clearance and 'n' the exponent of expansion u.r-d compression.

a.

b.c.

Why intercooling is necessary in multistage compression?A single stage, double acting air compressor is required to deliver 14 m3of air per minutemeasured at i.013 bar and l5'C. The delivery pressure is 7 bar and the speed is 300 rpm.Take the clearance volume as 5N of the swept volume with a compression-and."**punrionindex of n: 1.3. Calculate the swept volume of the cylinder, the delivery temperature and

(06 Marks)(04 Marks)

(06 Marks)

(06 Marks)for hot and dry

(07 Marks)kPa) pressure

respectivell,.(07 Marks)

the indicated power. (10 Marks)

Explain the effect of super heat and subcooling on the vapour compression refrigerationcycle. (06 Marks)

b. What is an absotption refrigeration cycle? How does it differ from a vapour compressioncycle? (08 Marks)

c. A 5 ton R - 12 refrigeratiol plant has saturated suction temperature of -50C. Thecondensation takes place at 320C. Assuming isentropic ,o*pr"rrion, find i)COP of theplant ii) Mass flow rate of refrigerant iii) power required to run the compressor in kW.Take the following properries of R - 12

Pbu,

7.85

2.61

Toc

32

-5

hft.rrte Hgtyre Sguruer130.5 264.5 t.542

249.3 1.557Take C, (super heated vapour) : 0.615 kJ/kgK

Distinguish between :

i) Specific humidity and relative humidity

b. With a neat sketch describe the working of summer air conditioning systemweather.The dry and the wet bulb temperatures of atmosphere air at 1 atm (101.325are measured with a sling psychrometer and determined to be 25 and 150CDetermine - i) Specific humidity ii) relative humidity iii) The enthalpy of air.

ii) Dry bulb temperature and wet bulb temperature iii) Dry air and atmosphere air.

a. A four stroke four cylinder petrol engine rvas tested at full throttle speed. The followingwere the power measured during N4orse test.

With all cylinders r.r,orkingWith nurnber 1 cylinder cutoffWith number 2 cylinder cutoffWith number 3 cylinder cutoffWith number 4 cylinder cutoff

The bore and stroke of each of the cylinder are 80 mm and 100 mm respectively. TheClarence volume of the cylinder is 100cc. The fuel is consumed at the rate of 5.44kgltr.If the calorific value of the fuel is 41900 kJ/kg, determine -i) Mechanical efficiency ii) Indicated thermal effrciency iii) Relative efficiency withreference to brake thermal efficiency. (10 Marks)

: 14.7 kW: 10.1 kW: 10.3 kW

10.2 kw10.4 kw

The following data were recorded during a test on a single cylinder four stroke oil engine.Bore : l50mm, stroke : 300mm, Speed : 18000 revolutions per hour, Brake torque : 200N-m, indicated mean effective pressure :7 bar, fuel consumption: 204 kghr, coolingwater follow rate : 5kg/min, cooling w'ater temperature rise : 300C, Air-fuIl ratio : 22exhaust gas temperature : 4100C, Specific heaf of exhaust gases : 1.0 kJ/kg oC, roomtemperature:200C. calorific value of fr"l :42lr/.Ilko T)efermine i\ Mechaninel effinienn,temperature:20'C, calorific value of fuel :42MJlkg. Determine i) Mechanical efficiencyii) BSFC and draw the heat balance sheet on minute basis and percent basis. (10 Marks)

2 af2

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USN

NEW SCHEME

Fourth Semester ts.E. Degree Examination, July ZA}?AU IIn/I/IP/ME/MA

Applied ThermodynamicsTime:3 hrs.l [Max. iVfarks:100

Note z 1. Answer ony FIVE full questions.2. Assume any missing data suitably.3. Use of Thermodynamic datu lfand book / Moilier churt /

. Psyehrometric chart I Stuam Tables is permitted.L a. Explain the term availability and derive expression for availability for a Non -flow

process with usual notations. (10 Marks)b. Calculate the maximum work cl:veloped when air expands in a piston - cylinder

arrangement from 600 kPa, 1500C to a final state of f5C kPu, S00C. Also find theavailability at initial and final states, maximum useful w.ork and change inavailability. Take To: 300k, p": 100kpa. (10 Marks)

2 a" Define the terms : i) Stoichiometric Air ii) Enthalpy of combustion iii) Percentexcess Air ir') Adiar:atic flame temperafure v) Enthalpy- oi formation (10 Marks)

b' A sarnple cf flrel has the foliorving percentage composition by rveight :

carbon = 84oh:ox-vgen :3.5ok; Hydrogen : l0%o; Ash :lo/o ; Nitrog.n : l.Saki) Deterrnine the stcichiometric Air - fuel ratio bv mass.ii) If 2A% excess air is supplied, find the perceniug. ,o*position of dry flue gases

by volume. (lo Marks)

3 a. What do you understand by the 'Air standard efficiency'? Derive an expression forthe air standard effici*ncy of a diesei cycle with usual notations. (08 Marks)

b. Explain briefly the effbcts of i) Regeneration ii) Intercooiing and iii) Reheatingon Bral'ton cycle efficiency with r - S diagrams" {06 Marks)

c' An Air standard iislited pressure^ cycle has a con:Ipression ratio of 15 andcompressian begins at 0.1 IvfPa,400C. The maxi-*. pr.rrure is timitect to 6 Mpaand the heat added is 1.675 MJ/kg. Compute i) the heat supplied at constant volumeper kg of air. ii) the heat supplied at constant pressure per kg of air. ii| the workdoneperkgofair iv) thecycleefficiency v) thecut -offratio vi) them.e.p.of

(06 Marks)the cycle.

4 a. Why is Carnot cycle not practicable for a steam po\.ver plant? Explain briefly"(04 Marks)b. Give the flow and T-S diagrarns of the ideal regenerative cycle. Derive and

expression for the regenerative cycle efficiency. (08 Marks)c. In a single heater regenerative cycle, the steam enters the turbine at 30 bar, 400cC

and the exhaust pressure is 0.10 bar. The feed water heater is a direct contact typewhich operates at 5 bar. Find i) the efficiency and the steam rate of the cycle.ii) the increase in mean temperature of the heat addition, efficiency and steam rateas cornpared to the Rankine cycle with out regenerations. Purnp work mayneglected (08 Marks)

Contd...2

S a. Derive the condition for minimum work input to a two stage compressor withperfeet inter cooling between stages. Also derive an expression for the ideal

intermediate plessure for the same. (10 Marks)

b. In a single acting two stages rcciprocating air compressor 4.5 kg of air per minute

are €ompressed from 1.013 bar and 15uC through a pressure ratio of 9 to 1. Both

stages have the same pressure ratio and the law of compression and expansion inbotl stages is PVI'3 : constant. If intercooling is complete, calculate the indicated

power and the cylinder swept volumes required. Assurne that the clearance volurne

of both stages are 5,k of their respective swept volumes and the compressor runs at

Page No...2

la.

b.

LJ.

ME43

300 rpm" (10 lVIarks)

With the help of T-S and h-S diagrams, explain the working principle of vapour

compresslon refrigeration plant. What is the effect of superheating and sub - cooling

on the vapour compression refrigeration cycle. (10 Marks)

A vapour compression plant uses R - 12 and is to develop 5 tonnes of refrigeration.

The iondensoi and evaporator temperatures are to be 400C and -100C respectively.

Determine i) the refiigerant flow rate jn kg/sec ii) the volume flow rate handled by

the compressor is m'/sec. iii) the compressor discharge temperature iv) the

pressure ratio v) the heat rejected to the condenser in kW. vi) COP and vii) the

power required to drive the compressor. (ls Marks)

What do you understand by dry bulb, wet bulb and dew point temperatures?((!3 Marks)

Expiain briefly the follou'ing :

i) Specifichumidity ii) Relativehumidity iii) Degreeof satuiation {06lvnarks)

It is required to desigi"r an air conditioning plaqt for a office room with tire followingconditions: Outdoor conditions - 140C DBT and 100C WBT ;

Required correiitions - 200C DBT and 600,6 R.fi ; Amolrni of Air ircuiation -0.3Om3/min'person ; Seating capacity of office - 60.

The required condition is achieved first by heating and then by adiabatic

humidifying. Determine the following :

i) Heating capacity of the coil in kW and the surface temperature required if the by

pass factor of coil is 0.4.

a.

b.

ii) The capacity of the humidi{ier.

a. What do you understand by Heat balance

same_

(11 Marks)

sheet? Enumerate the importance of the(05 Marks)

b. Describe the principle of conducting Morse test on IC engines. On what type ofengine it is conducted? What is the important precaution to be taken whileconducting this test? (05 Marks)

c. The following readings were recorded during atrial on a single cylinder, 2 - stroke

diesel engine. Power supplied by electric motor: 1.5 kW; Rated speed: 500 rpm;

Net load on brake :225 N; Diameter of Brake wheel : 100 cm ; Rate of flow ofcooling water through engine jacket: 13.65 kg/min; Rise in temperature of coolingwater = 100C ; Fuel consumption = 2 kglh, ; Calorific value of the fuel used :43,000 kJlkg; A.F. ratio :32:1; Cp, (gases) = 1'006 kJfkg0C ; Exhaust gas

temperature = 3450C ; Ambient temperature:250C and ambient pressure = 1 bar

Take L: D : 30 mm.Determine : i) Mechanical efficiency iD Thermal efficiency iii) Brake specific

fuel consumption iv) Brake mean effective pressure.

Draw heat balance sheet on 7o basic' (10 Marks)

**)k,lrs