R10 II B. Tech I Semester Supplementary Examinations, September THERMODYNAMICS (Com. to ME, AE, AME, MM)

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1 jn SET - 1 II B Tech I Seester Suppleentary Exainations, Septeber THERMODYNAMICS (Co to ME, AE, AME, MM) Tie: 3 hours Max Marks: 75 Anser any FIVE Questions All Questions carry Equal Marks ~~~~~~~~~~~~~~~~~~~~~~~~~ Note: Stea Tables, Refrigeration Tables ith Psychroetric Chart are alloed a) What is the ncept of ntinuu? Ho ill you define density usi this ncept? b) An elastic sphere initially has a diaeter of 1 and ntains a gas at a pressure of 1 at Due to heat transfer the diaeter of the sphere increases to 11 Duri the heati process the gas pressure inside the sphere is proportional to the sphere diaeter Calculate the ork done by the gas 2 a) Explain hy only in nstant pressure non flo process, the enthalpy chae is equal to heat transfer b) An LPG cylinder, initially evacuated, as filled ith 15 kg of LPG (specific enthalpy =625 kj/kg-1) fro the supply ain in a gas bottli plant After filli, the gas pressure rose to 10 bar, its specific enthalpy increased to 750kJ/kg and the specific volue becae /kg Deterine the quantity of heat that got into the cylinder duri the filli 3 a) Ho does the energy value provide a useful easure of the quality of energy? b) One kg of ice at -500C is exposed to the atosphere hich is at 200C The ice elts and es into theral equilibriu ith the atosphere i) Deterine the entropy increase of the universe ii) What is the iniu aount of ork necessary to nvert the ater back into ice at -50C? Cp of ice is 2093 kj/kg K and the latent heat of fusion of ice is 3333 kj/kg (5M+10M) jn 1 a) What is critical point? Explain the ters critical pressure, critical teperare and critical volue of ater? b) 10 kg of ater is heated at a nstant pressure of 15 bar and fro teperare of 400C Calculate the chae in entropy and enthalpy hen ater is nverted into the folloi qualities of stea in each case i) et stea at x = 090 ii) Super heated stea at 3000C 4 1 of 2 jn

2 jn SET - 1 a) What is pressibility factor? What is the physical significance of pressibility factor? b) i) The specific heats of a gas are given by cp = a + kt and cv = b + kt, here a, b, and k are nstants and T is in Kelvin Sho that for an isentropic expansion of this gas Tbva-bekT = nstant ii) 15 kg of this gas occupyi a volue of at 56 MPa expands isentropically until the teperare is 2400C If a = 0946, b = 0662, and k = 10-4, calculate the ork done in the expansion 6 a) Consider a ixre of several gases of identical asses Sho hether all ass fractions and ole fractions ill be identical or not? b) Write short notes on psychoetric chart 7 a) Copare ith the help of P-V and T-S diagra air standard Otto, Diesel and Dual cycles ith respect to i) sae pression ratio and sae heat input ii)sae axiu pressure and sae heat input b) A Diesel eine has a pression ratio of 14 and cut-off takes place at 6% of the stroke Find the air standard efficiency 8 A siple R-12 plant is to develop 5 tonnes of refrigeration The ndenser and evaporator teperares are to be 400C and -100C respectively Deterine: i) the refrigerant flo rate in kg/s, ii) the volue flo rate handled by the pressor in 3/s, iii) the pressor discharge teperare, iv) the pressure ratio, v) the heat rejected to the ndenser in kw, vi) the flash gas percentage after throttli, vii) the COP, and viii) the poer required to drive the pressor Ho does this COP pare ith that of a Carnot refrigerator operati beteen 400C and -100C? (15M) jn 5 2 of 2 jn

3 jn SET - 2 II B Tech I Seester Suppleentary Exainations, Septeber THERMODYNAMICS (Co to ME, AE, AME, MM) Tie: 3 hours Max Marks: 75 Anser any FIVE Questions All Questions carry Equal Marks ~~~~~~~~~~~~~~~~~~~~~~~~~ Note: Stea Tables, Refrigeration Tables ith Psychroetric Chart are alloed a) Explain the siilarities and dissiilarities beteen heat and ork b) A fluid, ntained in a horizontal cylinder fitted ith a frictionless leak proof piston, is ntinuously agitated by eans of a stirrer passi through the cylinder ver The cylinder diaeter is 040 Duri the stirri process lasti 10 inutes, the piston sloly oves out a distance of 0485 against the atosphere The net ork done by the fluid duri the process is 2 kj The speed of the electric otor drivi the stirrer is 840 rp Deterine the torque in the shaft and the poer output of the otor 2 a) Define internal energy Ho is energy stored in olecules and atos? b) The stea supply to an eine prises to streas hich ix before enteri the eine one strea is supplied at the rate of 001kg/s ith an enthalpy of 2952 kj/kg and a velocity of 20/s the other strea is supplied at the rate of 01kg/s ith an enthalpy of 2569kJ/kg and a velocity of 120 /s At the exit fro the eine the fluid leaves as to streas, one of ater at the rate of 0001kg/s ith an enthalpy of 420 kj/kg and the other of stea; the fluid velocities at the exit are negligible The eine develops a shaft poer of 25kW The heat transfer is negligible Evaluate the enthalpy of the send exit strea 3 a) Explain the stateent: The energy of an isolated syste can never increase Ho is it related to the principle of increase of entropy? b) Air expands through a rbine fro 500 kpa, 5200C to 100 kpa, 3000C Duri expansion 10 kj/kg of heat is lost to the surroundis hich is at 98 kpa, 200C Neglecti the KE and PE chaes, deterine per kg of air i) the decrease in availability, ii) the axiu ork, and iii) the irreversibility For air, take cp = 1005 kj/kg K jn 1 1 of 2 jn

4 jn SET - 2 a) Dra and explain the phase diagra for a pure substance on P-T chart Why does the fusion line for ater have negative slope? b) Ten kg of ater at 450C is heated at a nstant pressure of 10 bar until it bees superheated vapor at 3000C Find the chae in volue, enthalpy, internal energy and entropy (7M+8M) 5 a) Derive an expression of ork transfer for an ideal gas in a polytrophic process of the gas in i) Closed syste and ii) Steady flo syste b) Fro an experiental deterination the specific heat ratio for acetylene (C2H2) is found to (10M+5M) 126 Find the to specific heats 6 a) State Daltons la of partial pressures Ho is the partial pressure of a ponent in a gaseous ixre related to the ole fraction of that ponent? b) Explain hat you understand by adiabatic saration (9M+6M) 7 Sho that efficiency of Lenoir cycle depends on the pressure ratio and specific heat ratio Also find the expression for Mean Effective Pressure (15M) 8 An air refrigerator operates in a Bell-Colean cycle Copressor inlet: air is at 1 bar/270 K Copressor outlet: air pressure = 5 bar Cooler outlet: air teperare 290 K After the air is oled to 290 K at a nstant pressure in the oler, it is alloed to expand polytropically (Pv125 = C) to 1 bar in the expansion cylinder hereupon the air teperare falls to the loest teperare liit of the cycle The ld air is then sent to the ld chaber (refrigerated space) to extract heat (refrigerati effect) Deterine the a) Refrigerati effect and air circulation rate b) Copressor ork c) COP of the refrigerator d) Capacity of the plant in ters of tons of refrigeration if the ass flo rate of the air is 100 kg/h Assue isentropic pression Neglect friction losses, and clearance in the pressor and expander (15M) jn 4 2 of 2 jn

5 jn SET - 3 II B Tech I Seester Suppleentary Exainations, Septeber THERMODYNAMICS (Co to ME, AE, AME, MM) Tie: 3 hours Max Marks: 75 Anser any FIVE Questions All Questions carry Equal Marks ~~~~~~~~~~~~~~~~~~~~~~~~~ Note: Stea Tables, Refrigeration Tables ith Psychroetric Chart are alloed a) Is the state of the air in an isolated roo pletely specified by the teperare and pressure Explain? b) A ilk chilli unit can reove heat fro the ilk at the rate of 4187 MJ/h Heat leaks into the ilk fro the surroundis at an average rate of 4187MJ/h Find the tie required for oli a batch of 500kg of ilk fro 450C to 50C Take the cp of ilk to be 4187kJ/kg K 2 a) Define enthalpy Why does enthalpy of an ideal gas depend only on teperare? b) A reciprocati air pressor takes in 2 3/in at 011MPa, 200C hich it delivers at 15MPa, 1110C to an after oler here the air is oled at nstant pressure to 250C The poer absorbed by the pressor is 415kW Deterine the heat transfer in i) the pressor, and ii) the oler State your assuptions 3 a) The Carnot cycle assures axiu efficiency for a heat eine Still it cannot be ipleented in practice Why? b) A heat eine operati beteen to reservoirs at 1000 K and 300 K is used to drive a heat pup hich extracts heat fro the reservoir at 300 K at a rate tice that at hich the eine rejects heat to it If the efficiency of the eine is 40% of the axiu possible and the COP of the heat pup is 50% of the axiu possible, hat is the teperare of the reservoir to hich the heat pup rejects heat? What is the rate of heat rejection fro the heat pup if the rate of heat supply to the eine is 50 kw? jn 1 a) What do you understand by degree of superheat and degree of sub oli? b) A rigid vessel of volue ntains 1 kg of stea at a pressure of 2 bar Evaluate the specific volue, teperare, dryness fraction, internal energy, enthalpy, and entropy of stea 4 1 of 2 jn

6 jn SET - 3 a) Express the chaes in internal energy and enthalpy of an ideal gas in a reversible adiabatic process in ters of pressure ratio b) Sho that for an ideal gas, the slope of the nstant volue line on the T-s diagra is ore than that of the nstant pressure line 6 a) Usi the definitions of ass fraction and ole fraction, derive a relation beteen the b) A closed rigid cylinder is divided by a diaphrag into to equal partents, each of volue 01 3 Each partent ntains air at a teperare of 200C The pressure in one partent is 25 MPa and in the other partent is 1 MPa The diaphrag is rupred so that the air in both the partents ixes to bri the pressure to a unifor value throughout the cylinder hich is insulated Find the net chae of entropy for the ixi process 7 a) Mention the erits and deerits of Stirli and Ericsson cycles? b) A perfect gas undergoes a cycle hich nsists of the folloi processes taken in order: i) Heat rejection at nstant pressure ii) Adiabatic pression fro 1 bar and 270C to 4 bar iii) Heat addition at nstant volue to a final pressure of 16 bar iv) Adiabatic expansion to 1 bar Calculate: A) Work done/kg of gas; B) Efficiency of the cycle Take: cp = 092kJ/kgK, cv = 075 kj/kgk 8 a) Define ork ratio Derive an expression for efficiency of a ideal Brayton cycle in ters of pressure ratio? b) Air enters the pressor of a gas rbine plant operati on Brayton cycle at 1 bar, 270C The pressure ratio in the cycle is 6 If WT=25WC, here WT and WC are the rbine and pressor ork respectively, calculate the axiu teperare and the cycle efficiency jn 5 2 of 2 jn

7 jn SET - 4 II B Tech I Seester Suppleentary Exainations, Septeber THERMODYNAMICS (Co to ME, AE, AME, MM) Tie: 3 hours Max Marks: 75 Anser any FIVE Questions All Questions carry Equal Marks ~~~~~~~~~~~~~~~~~~~~~~~~~ Note: Stea Tables, Refrigeration Tables ith Psychroetric Chart are alloed a) Distiuish beteen stored energy and energy in transit b) It is required to elt 5 tonnes/h of iron fro a charge at 150C to olten etal at 16500C The elti point is 15350C, and the latent heat is 270 kj / kg The specific heat in the solid state is 0502 and in the liquid state( 2993 /atoic eight) kj/kg K If an electric furnace has 70% efficiency, find the kw rati needed If the density in olten state is 6900 kg/3 and the bath volue is three ties the hourly elti rate, find the diensions of the cylindrical furnace if the leth to diaeter ratio is 2 The atoic eight of iron is 56 2 a) When you ind a spri up in a toy or stretch a rubber band, hat happens in ters of ork, energy and heat transfer? Later hen they are released, hat happens then? b) A roo for four persons has to fans, each nsui 018kW poer, and three 100W laps Ventilation air at the rate of 80 kg/h enters ith an enthalpy of 84 kj/kg and leaves ith an enthalpy of 59 kj/kg if each person puts out heat at the rate of 630kg/h deterine the rate at hich heat is to be reoved by a roo oler, so that a steady state is aintained in the roo 3 a) What do you understand by internal irreversibility and external irreversibility b) A reversible eine operates beteen teperares T1 and T(T1>T) The energy rejected fro this eine is received by a send reversible eine at the sae teperare T The send eine rejects energy at teperare T2(T2<T) Sho that (i) teperare T is the arithetic ean of teperare T1 and T2 if the eines produce the sae aount of ork output, and (ii) teperare T is the geoetric ean of teperares T1 and T2 if the eines have the sae cycle efficiencies jn 1 4 a) Dra a neat sketch of throttli calorieter and explain ho dryness fraction of stea is deterined Clearly explain its liitations b) A vessel of volue 0043 ntains a ixre of sarated ater and sarated ste at a tep of 2500C The ass of liquid present is 9 Kg Find the pressure, the ass the specific volue, the enthalpy, the enthalpy and the internal energy 1 of 2 jn

8 jn SET - 4 a) Explain hy do the specific heats of an ideal gas depend only on the atoic strucre of the gas b) A nstant volue chaber of 03 3 capacity ntains 1 kg of air at 50C Heat is transferred to the air until the teperare is 1000C Find the ork done, heat transferred, and the chaes in internal energy, enthalpy and entropy 6 a) Explain the differences beteen dry bulb, et bulb and de point teperares? b) Consider a gas ixre that nsists of 3 kg of O2, 5 kg of N2, and 12 kg of CH4Deterine i) the ass fraction of each ponent, ii) the ole fraction of each ponent, and iii) the average olar ass and gas nstant of the ixre 7 a) Discuss the effect of pression ratio and specific heat ratio on the efficiency of otto cycle b) In an air standard Diesel cycle, the pression ratio is 16, and at the beginni of isentropic pression, the teperare is 150C and the pressure is 01 MPa Heat is added until the teperare at the end of the nstant pressure process is 14800C Calculate i) the cut-off ratio, ii) the heat supplied per kg of air, iii) the cycle efficiency, and iv) the ean effective pressure 8 a) Describe the various operations of a Siple Ranne cycle Derive its expression for theral efficiency b) A stea poer plant operates ideally in the siple ideal Ranne cycle Stea (3MPa/623K) enters the rbine and after expansion is exhausted to a total ndenser operati at a pressure of 75kPa Deterine the theral efficiency of this cycle jn 5 2 of 2 jn