Applied Thermodynamics Question Papers


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Applied Thermodynamics Question Papers

  1. 1. USN 06M843 Fourth Semester B.E. Degree Examination, December 2011 Applied Thermodynam ics Time: 3 hrs. Max. Marks:100 Note: 1. Answer any FIYE fuII questions, selecting at least TWO questions from esch part. 2. Use of thermodynamic data handbook/eharts/tables is permitted. o C) 3. Any missing data may be assumed suitably. i) PART -A CO I a. Distinguish between: i) Theoretical air and excess air (! ii) Higher calorific value and lower calorific value. (04 Marks) o () b. Define the terms: i) Enthalpy of formation ii) Enthalpy of combustion !!o cFindthestoichiometr#l,l$?if::ffi,1#1T1tr""Jl?fi ::",Uii:fiXJlffi H]y- molar basis. (04 Marks) 6U-o .. ll d. 4.4 kg propane gas is burnt completely with 3.0 kmol of air. Find the excess air and theooc€ molar analysis of the dry combustion products. (08 Marks).=NI-. boYa){)l 2 a. With the help of P-V and T-S diagrams, derive an expression for the air standard efficiencyE0) ofa diesel cycle. (08 Marks)o b. Compare the Otto and Diesel sycles, on the basis of same compression ratio and same heat3s inputs, with the help of T-S and P-V diagrams. (04 Marks)39 c. A four stroke, four cylinder petrol engine of 250mm bore and 375mm stroke works on thebU Otto cycle. The clearance volume is 0.01052m3. The initial pressure and temperature are6do 1 bar and 47oC.If the maximum pressure is limited to 25bar, find the following:bocct cd i) Air standard efficiency ii) Mean effective pressure. (08 Marks)-€ Grod 3a. Derive an expression for the optimum pressure ratio, for the maximum network output, in an4o Brayton cycle. What is the corresponding cycle efficiency? (06 Marks)5;; b. What are the methods of improving the efficiency of Brayton cycle? {02 Marks)pr o.tro. c. ln a reheat gas turbine cycle, comprising one compressor and two turbines, air is compressedoj from t bar,27oC to 6 bar. The highest temperature in the cycle is 900oC. The expansion in9Eto the frst stage turbine is such that the work from it just equals the work required by theqtEE.I compressor. Air is reheated between the two stages of expansion to 850C. Assume that theLOo,- isentropic efficiency of the compressor, the first stage and the second stage turbines are 85%>tboeto0 each and that the working substance is air. Calculate the cycle efficiency. (12 Marks) O=.*otr>:in 4a. Discuss the effect of i) Boiler pressure and ii) Condenser pressure, on the performance of a5E Rankine cycle. (04 Marks)U< b. Explain the working of the regenerative Rankine cycle with one feed-water heater. (04 Marks)i c..i c. ln a reheat cycie, steam a-t 500"C expands in a- HP tr-rrbine till it is sa,tura-ted vapour. It is then()o reheated at c.onstant pressure to 400oC and then expanded in a LP tr:rbine to 40oC. If theZ maximum moisture content at the turbine exhaust is limited to 15Yo find, i) the reheat pressure, ii) the pressure of steam at the inlet to the HP turbine. iii) the net specific workaga output iv) the cycle efficiency v) the steam rate. Assume all the ideal processes. (r2 Marks,y- -- lof2
  2. 2. r 06ME43 5a. what are the drawbacks of , ,rru,.lt}l;*rr"rro, for producing hish pressure? How are these overcome by multistage compression? (0s Marks) b. Derive an expression for the condition for the minimum work input, required for a two stage compressor, with perfect intercooling. (07 Marks) c. A two stage, single acting reciprocating air compressor, with complete intercooling atmospheric air at 1 bar and l5oc, compresses itpolytropically (n = 1.3) to 30 bar. If both cylinders have the same stroke, calculate the diameter of the HP cylinder. The diameter of the LP cylinder is 300mm. (08 Marks) 6 a. Explain the effect of superheat and subcooling on the vapour compression cycle with the help 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 evaporator temperature of -1OoC and a condenser temperature of 40oC, the enthalpy of the refrigerant, Freon-l2 at of compression is 220 kJkg. Show the cycle on f-S ana p-h-planes. lhg_end Calculate i) COP ii) refrigerating capacity and compressor power assuming a refriglrating flow rate of 1 kg/min (07 Marks) 7 a. Define: i) humidity ii) Specific humidity iii) Dew point temperature R.el{ive iv) Enthalpy of humid air v) Degree of saturation. (05 Marks) b. With a schematic diagram, explain the summer air conditioning system, for hot and wet weather. (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/min per person. If the required condition is achieved first by adiabatic humidification and then by cooling, estimate i) the capacity of the cooling coil in tones and ii) the capacity of the hurnidifier in kglh. (08 Marks) 8a. Describe the principle of conducting Morse test on IC engines. (04 Marks) b. 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 fuei consumption : 0.24 kglkwhr, calorific value : 42A00 kJ/kg, diameter of brake wlreel--= 709m, rope diameter : 3.5cm, brake load : 40kg. calculate i) brake power ii) indicated mean effective pressure iii) Indicated power iv) Mechanical efficiency v) Indicated thermal efficiency. (0E Marks) The following data were obtained from a Morse test on a 4-cylinder, 4-stroke cycle SI engine 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 N Brake load with cylinder No.2 not firing = 206 N Brake load with cylinder No.3 not firing = 192 N Brake 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 the brake load in Newtons and N is the speed of the engirr. in rpm. calculate i) Brake power ii) Indicated power iii) Friction po*"r iv) Mechanical efficiency. (08 Marks) t,f*!** 2 of?
  3. 3. USN ME43 Fourth Semester B"E. Degree Examination, Dec.09/Jan.10 Applied Thermodynamics @ Time:3 hrs. Max. Marks:100 .() (J Note: l.Answer any FIYEfull questions. cl o- 2. Use of thermodynamics dsta hand book is permitted. 6 E i. Use of Mollier diagram and Psychrometric chart permitted. 6(! 4. Use co: 1.005 kil kg K, cu= 0.718 kJ/ kg K, R: 0.287 kJ /kg K, E (1, K : bco /cu : 1.4 for Air. .(E(/,o)oEEco-s I a. Deduce an expression for available energy from a finite energy source at temperature T-vEc= when the environmental temperature is To. (06 Marks)(u--EO b. Define second law efficiency and derive the equation for second law ef,ficiency for a solar s,?.= co water heater. (06 Marks) E+E$E- c. Calculate the deuease in available energy when 30 kg of water at 85oC,is mixed with 35 kgo6) of water at25"C, with the pressure being constant and temperature of the surounding being a-!g 15C (co of water:4.2kJ lkg K). (08 Marks)3; 2 a. Distinguish between higher and lower heating values and define combustion efficiency.0J9,EO (06 Marks)3=g9+()(1) b. Define the following terms :6;ic< , Enthalpy of combustion ii) lntemal energy of combustion iii) Adiabatic flameoE temperature. (06 Marks)EE eO >(E c. The products of combustion of an unknown feel C* H, have the following composition as gf, measured by an orsat apparatus COz lZ.lyo, CO 0.9yo, C23.8% and Nz 83.2%. determine -!(5::B i) Chemical equation for the actual reaction ii) Composition of the fueI iii) The air fuel ratiob9U_ iv) Theoretical excess air. (08 Marks)?(EF8_Eo-8.- 3 a. Derive an expression for the air standard efficiency of,an otto cycle in terms of compression;*, ratio. Show the cycle on PV and TS diagrams. (06 Marks)=(E4oq b. Sketch the flow diagram and T*S diagram of a gas turbine plant having 2-stage compression(I,e . with intercooling, 2-stage expansion with reheating and regeneration indicating the statesO:, Eo- points clearly on both diagrams (No description required) (06 Marks)>b c. An air standard dual cycle has a compression ratio of 15 and compression beings at 0.1 MPa 9ora.= and 40oC. The maximum pressure is limited to 6 MPa and the heat added is 1.675 MJ /kg.oEcL(,E> compute i) Work done per kg of air ii) The cycle efficiency iii) mep. (08 Marks)= 0.)o>o< 4 a. With the help of T-S diagrams, explain the effect of the following parameters on the-(ri efficiency of Rankine vapour power cycle.iu i) Increase in boiler pressure ii) Superheating of vapour iii) Decreasing condenser pressure.ozc(EE b. What is a feed water heater? Distinguish clearly between open and ctrosed {::-il[}oo- heaters. (06 Marks).E c. A steam power plant operates on a Reheat Rankine cycle and.has a net power output of 80 MW. Steam enters the high pressure turbine at 100 bar and 500C and the low pressure turbine at 10 bar and 500oC after being reheated. [t Ieaves the low pressure turbine at 0.1 bar. Using the Mollier chart and assuming ideal processes detennine - i) The quality of steam at exit of LP turbine ii) Therma, *O?.:? iii) Mass flow rate of steam. (08 Marks)
  4. 4. f ME43 5 a. Show that for minimum work of coinpression in a multistage Reciprocating air compressor the 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 extend the result to obtain an expression for m stages. (12 Marls) 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 at I bar and l5oC find the power required to compress the air when running at 350 rpm. The process of compression is given by PVI3 : conit. Determine also the .treigy rejected in the intercooler. (08 Marks) 6a. What are the desirable properties of refrigerants? List out a few refrigerants that are used. (06 Marks) b. Give a brief description of a vapour absorption refrigeration system with a neat sketch (06 Marks) c. A vapour compression refrigerator works between temperature limits of 25"C and -15oC with Freon - 72 as refrigerant. The liquid is cooled to l7"C before entering the expansion valve. If the condition at the end of compression is dry saturated, calculate the power required to drive the compressor for a 10 ton capacity refrigerator if the relative C. O. P is 0.75. (08 Marks) 7. a. Define the following terms as applied to psychrornetrics i) DBT ii) WBT iii) Relative humidity iv) Specific humidity. (06 Marks) b. Briefly explain the following processes by representing each on psychrometric chart i) 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 of dry 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 were obtained. cylinder dia:20 cm, Stroke : 40 cm, mep : 6 bar, Torqte : 407,Nm, Speed : 250 rpm, oil consumption: 4 kg /h calorific value of fuel : 43 mJ /kg, cooling water flow rate : 4.5 kgl min, 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 = 1.0 kJ lkg K specific heat of water: 4.18 kJ /kg K. find the IP, BP indicated thermal efficiency and draw up an energy balance sheet for the test in kJ/h. (12 Marks) b. In a test on a 4 cylinders, 4 stroke engine, 7 .5cm bore and 10 cm stroke, the following results were obtained at full tltoffle at a particular constant speed and with fixed setting of fuel supply of 6.0 kg lhr. B.P with all cylinders working : 15.6 kW B.P with cylinders no.1 cut out: 11.1 kW B.P with cylinders no. 2 cut out : 11.03 kW B.P with cylinders no. 3 cut out: 10.88 kW B.P with cylinders no. 4 cur out: 10.66 kW If the calorific value of the fuel is 83600 kJ /kg and clearance volume is 0.0001 m3, calculate i) Mechanical efficiency ii) Indicated thermal efficiency iii) Air standard efficiency. (08 Marks) rl.rl.**{.
  5. 5. USN 2OA2 SCHEME ME43 Fourth Semester B.E. Degree Examination, June-July 2009 Applied Thermodynamics Time:3 hrs. Max. Marks:100 Note: 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 closed system. (05 Marks) c. Calculate the decrease in available energy when 90kg of water at 90oC mix with 30kg of water at 30oC, the pressure being taken as constant and the temperature of the surroundings being 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) Internal energy of combustion. (12 Marks) b. Calculate the amount of theoretical air required for the complete combustion of I kg of acetylene (CzHz) to COz and HzO. (08 Marks) 3a. Represent the following gas power cycles on P-V and T-S diagrams: i) Carnot cycle ii) Otto cycle iii) Diesel cycle iv) Duel cycle v) Stirlingcycle vi) Brayton cycle (06 Marks) b. Compeire the Otto and Diesel cycles for the same ma:rimum pressure and same heat input. (04 Mark) c. An indicator diagram taken on a diesel engine shows that the compression curve follows the law PVra : Constant. At two points lying on the compression curve at l/8ff and 7/8th of the stroke the pressures are 1.6 bar and 16 bar respectively. Find the compression ratio of the engine. If cut off occurs at 6%o of the stroke, calculate air standard efficiency of the engine. (I0 Marks) 4a. Draw the flow diagram of steam power plant with regeneratior, *itf, two stage bleeding and two open feed water heaters. Represent the processes on T-S diagram and explain. Write down energy balance across each feed water heater and derive an expression for regenerative cycle efficiency. (10 Marks) A Rankine cycle operates between a pressure of 80 bar and 0.1 bar. The maximum cycle temperature is 600C. If the steam turbine and condensate pump efficiency are 0.9 and 0.8 respectively , calculate the net specific work output and thermal efficiency. Relevant steam is gtven below: tables extract rs eiven below l0 Marks Pin toc Specific volume Specific enthalpy Specific Entropy bar in m3/ke in k}ke in 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 8.1494 80 295.1 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 without clearance volume and with perfect intercooling. Also, derive an expression for intermediate intercooler pressure for minimum work required. (08 Marls) 1 of2
  6. 6. 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. Determine the indicated mean effective pressure and the ideal power required !q_ run it when compression is (i) isothermal (ii) compression follows the law PVr25 : Constant (iii)PVta=Constant and (iv) PVr5 : 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 its working. 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 ofF-12. P bar TOC hr kJ/ke h, kJlkg s" kJ/ke-K 7.85 32 130.5 264.5 t.542 2.61 -5 249.3 1.557 (10 Marks)7a. 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) b. Explain in brief (i) Enthalpy of moist air and (ii) Adiabatic saturation temperature. (06 Marks) .c. Draw the flow diagramfor summer air conditioning system for hot and dry outdoor conditions. Sketch and represent the processes on psychrometric chart, explain its working and write the formula for the components. (08 Marks)8a. Sketch the apparatus and write how air supply to internal combustion engine is measured in laboratory. (08 Marks) b. 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 = 7.05kg Calorific value of fuel:44000 kJ&g, Area of indicator diagrarn= 322mm2 Length of indicator diagram: 62mm, spring index: 1.1 bar/mm Net load on brakes: 1324.35 N, Brake drum diameter: 1600mm Total mass ofjacket cooling water :495kg, : Temperature rise ofjacket cooling water 38oC, : Temperature of exhaust gas 300"C, Air consumption : 31 lkg Assumptions: Specific heat of exhaust gasses: 1.004 kJ/kg K Specific heat of water = 4.186 kJlkg K, Room temperature =20oC Determine: i) Power available at brakes ii) Indicated power developed iii) Mechanical effi ciency iv) Brake thermal efficiency v) Indicated thermal efficiency Also draw a heat balance sheet of trial for one hour basis. (12 Marks) *:[*** 2 of2
  7. 7. Y ME43 USN ZOOE SCHEME Fourth Semester B.E. Degree Examination, Dec.08/Jan.09 Applied Thermodynamics Time: 3 hrs. Max. Marks:100 Note: IAnswer any FIVE full questions 2.[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 ofsystem 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. (04 Marks) 2 a. Define the following: i. Enthalpy of formation ii. Heat of reaction iii. Calorific value iv. Adiabatic flame temperature v. Stoichiometric AirlFuel ratio. (10 Marks) b. 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) a. 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) b. 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/kg0K and r:1.333 for expansion process. (08 Marks) c. Explain the use of regenerator in gas turbine plants. (02 Marks) a. Explain clearly with the help of a T-S diagram, the working of a Rankine cycle with regeneration using open feed water heater system. Also briefly comment upon the effect of pressure 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) 54. 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) b. With the help of a diagram show the effect of intercooling on a 2 stage compressor. (04 Marks) c. 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
  8. 8. ],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) c A simple vapour compression plant p.Jdu".. 5 tonnes of refrigeration. The (04 Marks) enthalpies of the working flll"d at-i{et to compressor, at exit of compressor and at exit from the condensor arel81 j9kJkg,2094lkJlkg ^d 7a.:?.? lykg respectively. Estimate (i) The refrigerant flow rate (ii)The coP of the plant and (iii) the fowei required to drive tire compressor (iii)The rate 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. Specific humidity 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 and dehumidifuing. c with a neat slietch briefly describe summer Air-conditioning system. ffi ffi:[]8 a the estimation of the indicated power of a multi-cylinder engine using ff#,3fcribe b. Explain one method of determining B.p. of an I.c. engine. c During a test on an oil engine *oikirg on 4-stroke cycle the following data ll:ffi:[i MEP:56 bar, stroke volume:l4 fiGs, speed:4O0rpm, load:o.75KN, were obtained. Radius of brake drum:07m Fuel consumed:0.002kg/sec. ialorific ,rulu" of oil:46000kJ/kg, cooling water circulated:0.l5kg/sec, rise in temperiture of cooling *;;";33€. currrru,. 1. B.P. 2, I.P. 3. Mech. Efflrciency 4. Indicated thermal efficiency Also draw the heat balance sheet. (08 Marks) ,r * *.* * 2 of2
  9. 9. V USN ME43 Fourth Semester B.E. Degree Examination, June/July 08 Applied Thermodynam ics Time:3 hrs. 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 data hundbook permitted. I a. Define the terms- - i) Availability ii) Reversible work iii) Irreversibility iv) Second law efficiency. (SB Marks) b. Derive a general expression for irreversibility in i) Non-flow process ii) Steady flow prooesses. 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 follows: 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 effective pressure 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 500C .The reheat is at 3 bar and to the same temperature. i) Given that the efficiency of the first turbine is 80% how much 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? (12 Marks) I of2
  10. 10. F ME 43 Derive an expression for the condition for minimum work required in a fwo-stage air compressor with perfect intercooling with the help of a P-V diagram. (06 Marks) b. 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 and 7.5cm 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 in both cylinders, compute i) The intermediate pressure P; ii) The power required to drive each cylinder, if the mechanical efficiency is 0.75 iii) The speed of crank driving the compressor in RPM iv) The energy rejected at the intercooler as heat. (14 Marks) a. Derive an expression or theoretical COP of an absorption system. (06 Marks) b. List the desirable properties of refrigerant. (04 Marks) c. An ammonia vapour compression refrigerator works between an evaporator pressure of 1.2 bar and a condenser pressure of 12.0 bar. The refrigerant leaves the evaporator at -200C and leaves the condenser at+200C. Determine the COP of the system and the power required per ton of refrigeration. Determine also the bore and stroke of the compressor cylinder if the speed is 200 rpm, volumetric efficiency is 0.8 and stroke is 1.5 times the bore. (10 Mark$ a. Define i) Saturated air ii) Dry bulb ternperature. iii) Dew point temperature. iv) Relative humidity 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 refrigeration in tons and the heating required in kW. (07 Marks) a. Briefly explain how the I P of a multi-cylinder engine is measured. (04 Marks) b. Write a short note on heat balance sheet. (04 Marks) c. The follo*ing observations .arere made during a trial of a single cylinder four-stroke cycie gas engine having cylinder diameter of 18cm and stroke Z4cm. Duration of trial :30min, total number of revolution:90OO, total no. of explosions :445A MEP:5 bar, Net load on the brake drum:40kg, effective diameter of brake wheel: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.z9 kg/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. Take R:287 J/I(g k. (12 Marks) ?t ?t ,( ,r r!
  11. 11. ME43USN Fourth semester B.E. Degree Examination, Dec. 07 / Jan 08 Applied Thermodynamics Max. Marks:100Time:3 hrs. Note : l.Answer any FIVE full questions is permitted z. ise of theimodynimici datu land book , charts, tubles for the availability of a steadily a. Explain the term Availability and derive an expression (06 Marks) flowing stream Explain the terms ineversibility and second law of thermodynamics (04 Marks) b. i50 m/sec to i00 kPa c. Air expands in a turbine adialatically fro1 i91kll.100 K and per kg of air : Calculate 300K and 70 m/sec. The environment is at 100 kPa, 170C i)The rraximum work output ii) The actual work output iii) The irreversibility (10 Marks) iv) Second law efficiency a. Distinguish between : i) Theoretical air and excess air iil Higher heating value and lower heating value (04 Marks) lLt- LL^^-^ CsHrs uith theoretical amount of b. Balance the chemicai equation for combustion of octane (06 Marks) air, also find the theoretical air-fuel ratio r, air supply is 75N of- -:- - 1"3v" Hz The c. The fuel used in petrol engine contains 87x carbon and that all Hz is burned and that theoretically required-for complete combustion.,Assuming there is no free curbon left. f,inci the volumetric anallsis 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 ratio and explosion ratio of a semi diesel c1-cle in terms ofiompression ratio, cut-off (08 Marks) on constant pressure b. The minimum and maximum temperatures in an engine working is 500 kJ/kg of air cycle are 300 K and 1500 K and the heat addition durlng combustion temperature limits of 300 Another *.rglrr. *orking on semi diesel cycle between the same equally between the K and 1500 K has a heat addition of 500 kJ/kg of air which is shared two heat addition processes" Cornpare their - i) Efficienciesand ii) Work outputs (12 Marks) the working of a a. With the help of a schematic diagram and T-S diagram, explain. for its overall efficiency regenerative vapour power cycle and derive an expression (08 Marks) to the following b. An ideal Rankine cycle with reheat is designed to operate according 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 ii)Ratio of pump work to turbine work iii; Ratio of heat rejection to heat addition iv) Cycle thermal efficiency. (12 Marks) 1 nf ?
  12. 12. T ME43 a. Obtain an expression for the volumetric efficiency of a single stage air compressor in terms of the pressure ratio, clearance and n the exponent of expansion u.r-d compression. (06 Marks) b. Why intercooling is necessary in multistage compression? (04 Marks) c. A single stage, double acting air compressor is required to deliver 14 m3of air per minute measured at i.013 bar and l5C. 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."**punrion index of n: 1.3. Calculate the swept volume of the cylinder, the delivery temperature and the indicated power. (10 Marks) Explain the effect of super heat and subcooling on the vapour compression refrigeration cycle. (06 Marks) b. What is an absotption refrigeration cycle? How does it differ from a vapour compression cycle? (08 Marks) c. A 5 ton R - 12 refrigeratiol plant has saturated suction temperature of -50C. The condensation takes place at 320C. Assuming isentropic ,o*pr"rrion, find i)COP of the plant ii) Mass flow rate of refrigerant iii) power required to run the compressor in kW. Take the following properries of R - 12 Pbu, Toc hft.rrte Hgtyre Sguruer 7.85 32 130.5 264.5 t.542 2.61 -5 249.3 1.557 Take C, (super heated vapour) : 0.615 kJ/kgK (06 Marks) Distinguish between : i) Specific humidity and relative humidity ii) Dry bulb temperature and wet bulb temperature iii) Dry air and atmosphere air. (06 Marks) b. With a neat sketch describe the working of summer air conditioning system for hot and dry weather. (07 Marks) The dry and the wet bulb temperatures of atmosphere air at 1 atm (101.325 kPa) pressure are measured with a sling psychrometer and determined to be 25 and 150C respectivell,. Determine - i) Specific humidity ii) relative humidity iii) The enthalpy of air. (07 Marks) a. A four stroke four cylinder petrol engine rvas tested at full throttle speed. The following were the power measured during N4orse test. With all cylinders r.r,orking : 14.7 kW With nurnber 1 cylinder cutoff : 10.1 kW With number 2 cylinder cutoff : 10.3 kW With number 3 cylinder cutoff 10.2 kw With number 4 cylinder cutoff 10.4 kw The bore and stroke of each of the cylinder are 80 mm and 100 mm respectively. The Clarence 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 with reference to brake thermal efficiency. (10 Marks) 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 : 200 N-m, indicated mean effective pressure :7 bar, fuel consumption: 204 kghr, cooling water follow rate : 5kg/min, cooling water temperature rise : 300C, Air-fuIl ratio : 22 exhaust gas temperature : 4100C, Specific heaf of exhaust gases : 1.0 kJ/kg oC, room temperature:200C. calorific value of fr"l :42lr/.Ilko T)efermine i) Mechanical effinienn, temperature:20C, fuel :42MJlkg. Determine i Mechaninel efficiency ii) BSFC and draw the heat balance sheet on minute basis and percent basis. (10 Marks) 2 af2
  13. 13. Page lto ... I ME43 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 the availability at initial and final states, maximum useful w.ork and change in availability. Take To: 300k, p": 100kpa. (10 Marks)2 a" Define the terms : i) Stoichiometric Air ii) Enthalpy of combustion iii) Percent excess 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.Sak i) 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 for the 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) Reheating on Bralton cycle efficiency with r - S diagrams" {06 Marks) c An Air standard iislited pressure^ cycle has a con:Ipression ratio of 15 and compressian begins at 0.1 IvfPa,400C. The maxi-*. pr.rrure is timitect to 6 Mpa and the heat added is 1.675 MJ/kg. Compute i) the heat supplied at constant volume per kg of air. ii) the heat supplied at constant pressure per kg of air. ii| the work doneperkgofair iv) thecycleefficiency v) thecut -offratio vi) them.e.p.of the cycle. (06 Marks)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 type which 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 rate as cornpared to the Rankine cycle with out regenerations. Purnp work may neglected (08 Marks) Contd...2
  14. 14. Page No...2 ME43 S a. Derive the condition for minimum work input to a two stage compressor with perfeet 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 in botl stages is PVI3 : 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 300 rpm" (10 lVIarks) a. 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) b. 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) la. What do you understand by dry bulb, wet bulb and dew point temperatures? ((!3 Marks) b. Expiain briefly the follouing : i) Specifichumidity ii) Relativehumidity iii) Degreeof satuiation {06lvnarks) LJ. It is required to desigi"r an air conditioning plaqt for a office room with tire following conditions: Outdoor conditions - 140C DBT and 100C WBT ; Required correiitions - 200C DBT and 600,6 ; Amolrni of Air ircuiation - 0.3Om3/minperson ; 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. ii) The capacity of the humidi{ier. (11 Marks) a. What do you understand by Heat balance sheet? Enumerate the importance of the same_ (05 Marks) b. Describe the principle of conducting Morse test on IC engines. On what type of engine it is conducted? What is the important precaution to be taken while conducting 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 of cooling water through engine jacket: 13.65 kg/min; Rise in temperature of cooling water = 100C ; Fuel consumption = 2 kglh, ; Calorific value of the fuel used : 43,000 kJlkg; A.F. ratio :32:1; Cp, (gases) = 1006 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