Question no 1 1) What is a quasi characteristic features?
static
process?
what
are
its
2) Compare work transfer and heat transfer. 3) Unde Underr what what cond condiition tions s is the the work work done done equal qual to ∫12Pdv? 4)A mass of gas is compressed in a quasi static process from 80Kpa, 0.1m3 to 0.4Mpa, 0.03m 3 Assuming that the pressure and volume are related by PV n = Constant, find the work done by the gas system. 5) How does homogeneous heterogeneous system?
system
differ
from
a
6) What is the need for the inter ternational practical temperature scale? 7)A gas undergoes a thermodynamic cycle consisting of thr three proc proce esses begi beginn nniing at an initia itiall stat state e wher here P1=1bar ,V1=1.5m3 and U1=512KJ.The processes are as follows (i)process 1-2: compression with PV=constant to P2=2Bar ,U2 =690KJ ii) Process 2-3: W 23 =0, Q23 = -150KJ and iii) Process 3-1: W 31=+50KJ, neglecting KE and PE changes, determine the heat interactions Q 12 and Q31 8)The properties of a system during a reversible constant pre pressure non non flow flow proce roces ss at 1. 1.6 6 bar bar chan change ged d from from V1=0.3m3/kg.T1=200C to V2=0.55m3/kg,T2=2600C.The specific heat of the fluid is given by Cp=[1.5+(75/T+45)]KJ/kg0C. Where T is in 0C.Determine
(i) heat added/kg,(ii)work done/kg(iii)change of internal energy/kg,(iv)change in enthalpy/kg.
9)A 5Kg piston in a cylinder with diameter of 100mm is loaded with a linear spring and outside atmospheric pressure of 100KPa.The spring exerts no force on the piston when it is at the bottom of the cylinder and for the state shown the pressure is 400KPa with volume 0.4L. The valve is opened to let some air in , causing the piston to rise 2cm find (i)the new pressure (ii)The boundary work done from the point at which the valve is first opened C piston resting at the bottom of the cylinder to the final state
po g
AIR SUPPLY LINE AIR
QUESTION NO 2
1) How does Bernoulli’s equation and Euler’s equation compare with SFEE?
2) State the first law for a closed system undergoing a change of state and show that energy is a property of a system. 3) Show that energy is a property of a system. What are the modes in which energy is stored in a system? 4) Define enthalpy. Why does the enthalpy of an ideal gas depends only on temperature? 5) A nozzle is a device for increasing the velocity of a steadily flowing steam .At the inlet to a certain nozzle ,the enthalpy of the fluid passing is 3000KJ/kg and the velocity is 60 m/sec. At the discharge end, the enthalpy is 2762KJ/kg. The nozzle is horizontal and there is negligible heat loss from it. (i)Find the velocity at exit from a nozzle, (ii)If the inlet area is 0.1 m 2 and the specific volume at the inlet is 0.187 m 3/kg. Find the mass flow rate. (iii) If the specific volume at the nozzle exit is 0.498 m 3/kg. Find the exit area of the nozzle. 6)Air flows steadily at the rate of 0.4kg/sec through an air compressor, entering at 6 m/sec with a pressure of 1bar and a specific volume of 0.85 m 3/kg and having at 4.5 m/sec with a pressure of 6.9 bar and a specific volume of 0.16 m3/kg, The internal energy of the air leaving is 88KJ/kg greater than that of the air entering. Cooling water in a jacket , surrounding the cylinder absorbs heat from the air at the rate of 59W.Calculate the power required to drive the compressor and the inlet and outlet cross sectional areas.
7) A reciprocating air compressor takes in 2m 3/min at 0.11Mpa,200C which it delivers at 1.5 Mpa ,111 0C to an after cooler where the air is cooled at constant pressure to 250C .The power absorbed by the compressor is 4.15KW. Determine the transferred in (i)the compressor (ii)the cooler. 8) State the first law of thermodynamics for a cyclic process and prove that for a non flow process,it leads to the energy equation Q=∆U+W. 9) Air enters an isentropic nozzle steadily at 300KPa,2000C and 30m/sec and leaves at 100KPa.The inlet area of the nozzle is 80x10- 4m2.Determine: i)the mass flow rate through the nozzle, ii)the exit temperature of the air, iii)the exit velocity and iv)the exit area of the nozzle. 10) Obtain the steady state flow energy equation for a flow system(open System). List all the assumptions made? 11) Explain clearly the difference between a non flow and steady flow process. 12) Show that general energy equation for a variable flow process for a variable flow process for a closed system dQ= dE+dW X 13)Derive an expression for the rate of energy and mass transfer into and out of control volume in case of unstable flow process for filling a tank and emptying a tank. 14)The following is the equation which connects u, p and v for several gases:u=a+bv, where a and b are constant. prove that for a reversible adiabatic process: PV γ=constant, where γ=b+1/b
QUESTION NO 3 1) Show that the efficiency of reversible engine operating between two given constant temperature is maximum. 2) Show that the COP of a heat pump is greater than the COP of a refrigerator by unity. 3) A heat pump working on the Carnot cycle take in heat from a reservoir at 5˚C and delivers heat to a reservoir at 60˚C. The heat pump is driven by a reversible heat engine which takes in heat from a reservoir at 840˚C and rejects heat to a reservoir at 60˚C. The reversible heat engine also drives a machine that absorbs 30 KW. If the heat pump extracts 17 KJ/S from the reservoir. Determine a) The rate of heat supply from the 840˚C source b) The rate of heat rejection to the 60 0C sink. 4) What is the absolute temperature scale? Why is it called absolute? How is the absolute scale independent of the working substance? 5) Two reversible heat engines A and B are arranged in series ,A rejecting heat directly to B. Engine A receives 200KJ at a temperature of 4210C from a hot source , while engine B is in communication with a cold sink at a temperature of 4.4 0C .If the work output of A is twice that of B. find (i)the intermediate temperature between A and B,(ii) the efficiency of each engine and (iii)the heat rejected to cold sink. 6) A heat pump is to be used to heat a house in winter ,and then reversed to cool the house in summer .The interior temperature is to be maintained at 200C .Heat transfer through the walls and roof is estimated to be 0.525KJ/sec per degree temperature difference between the inside
and outside.(i)If the outside temperature in winter is 5 0C ,What is the minimum power required to drive the pump?(ii)If the power output is the same as in part(i) What is the maximum outer temperature for which the inside can be maintained at 20 0C? 7) Show that a definite zero point exists the absolute temperature scale but this point cannot be reached without a violation of second law. 8) Three Carnot engines operate in series between two reservoirs are at temperature of 1200Kand 300K.Calculate the temperature of intermediate reservoirs and the efficiencies of the engines if the amount of work produced by these engines is in the proportion of 5:4:3
9) Establish the equality of ideal gas temperature and Kelvin temperature 10) What is an irreversible process? Give some examples of irreversible process. 11) A reversible heat engine operates between two reservoirs at a temperature of 700 0C and 500C .The engine drives a reversible refrigerator which operates between reservoirs at a temperature 50 0C and -250C.The heat transfer to the engine is 2500KJ and the net work output of the combined engine refrigerator plant is 400KJ. Determine the heat transfer to the refrigerant and the net heat transfer to the reservoir at 500C QUESTION NO 4 AND 5
1) Show that entropy is a property of a system. 2) State and prove the Clausius Inequality theorem
3)A reversible engine as shown in fig below during a cycle of operation draws 5MJ form the 400K reservoir and does 840KJ of work. Find the amount and direction of heat interactions with other reservoir
200K
300 K
400K
5M J
E
W=840KJ
4)Derive the expression for a maximum work of an open system which exchanges only heat with the surroundings. 5) 2 kg of air at 360 0K and 0.6MPa expands adiabatically in a closed system until its volume is thrice the initial volume till the final temperature reaches 300 0K AT 0.101MPa .Assuming air as a perfect gas determine a) Maximum work b) Change in availability
c) The irreversibility Take Ta=280K
6) Show that the adiabatic mixing of two fluids is irreversible. 7) A lump of ice with a mass of 1.5 kg at an initial temperature of 260K melts at the pressure of 1 bar as a result of heat transfer from the environment . After some time has elapsed the resulting water attains the temperature of the environment 293K.calculate the entropy production associated with this process. The latent heat of fusion of ice is 333.4KJ/Kg. The specific heat of ice and water are 2.07 and 4.2 KJ/Kg.K respectively. and Ice melts ay 273.15K 8) Eighty Kg of water at 100 0C are mixed with 50 Kg of water at 600C,while the temperature of the surrounding is 15 0C. Determine the decrease in available energy due to mixing. 9)Derive the expressions for availability in a non flow system and steady flow systems. 10) 2 kg of air at 90 0Cexpands adiabatically in a closed system until its volume is doubled and its temperature becomes equal to that of surrounding which is at 1bar ,5 0C for this process determine a) Maximum work b) Change in availability c) The irreversibility For air take C V =0.718 kJ/kg , R= 0.287 kJ/kg
11)15 Kg of water is heated in an insulated tank by a churning process from 300K to 340K .If the surrounding temperature is 300K find the loss in availability for the process. 12) What do you understand by exergy and energy? How does the exergy value provide useful measure of the quality of energy? 13) What is available energy and unavailable energy?
14) Show that equal amount of work is done in all reversible processes between the same end states of a system if it exchanges energy only with the surroundings. 15) Derive and explain the maximum work obtainable from two finite bodies at temperature T1and T2 16)
What is available energy referred to a cycle? Show that there is
a decrease in available energy when heat is transferred through a finite temperature 17)Air at 200C and 1.05 bar occupies 0.025m 3.The air is heated at constant volume until the pressure is 4.5 bar and than cooled at constant pressure back to original temperature calculate (i)the net heat flow from the air (ii)the entropy change. Sketch the process on T-S diagram. 18)calculate the decrease in available energy when 25Kg of
water at 950C mix with 35Kg of water at 35 0C ,The pressure being taken as constant and the temperature of the surroundings being 15 0C .Take C p of water as 4.2 KJ/kg-k .
QUESTION NO 6
1) What is the critical state? Explain the term critical pressure, critical temperature and critical volume of water. 2) Steam initially at 0.3Mpa, 250 0C is cooled at constant volume:a) At what temperature will the steam becomes saturated vapour? b) What is the availability at 800C c) What is the heat transferred per Kg of steam in cooling from 2500C to 800C. 3) What do you understand by degree of superheat and degree of sub cooling? 4) A pressure cooker contains 1.5Kg of saturated steam at 5 bar. Find quantity of heat which must be rejected so as to reduce the quality to 60% dry. Determine the pressure and temperature at new state. 5) What is quality of steam? 6) What are the different methods of measurement of quality of steam? Explain any one with a neat diagram.
QUESTION NO 7
1) State Dalton law of partial pressure. How is the partial pressure in a gas mixture related to the mole fraction? 2) Derive the Maxwell relations and explain their importance in thermodynamics. 3) Write down the first and second Tds equation and derive the expression for the difference in heat capacities C p and Cv. What does the expression signify? 4) Define the coefficient of(i)volume expansion (ii)Isothermal compressibility.(iii)Adiabatic compressibility 5) What is joule Thomson co efficient? Why is it zero for an ideal gas? 6) Show that for an ideal gas the internal energy depends only on its temperature 7) What are viral coefficients? Why do they become zero? 8) A certain gas as C p =1.968 kJ/kg and C v =1.507 kJ/kg. Find its molecular weight and gas constant. A constant volume chamber of 0.3
capacity contains 2kg of
this gas at 50 C. Heat is transferred to the gas until the temperature is 1000 C . Find the work done, heat transferred and change in internal energy, enthalpy and entropy.
8) Differentiate between compressibility factor and compressibility chart. 9) The analysis by weight of a perfect gas mixture at 20 0C and 1.3 bar is 10%O2, 70%N2,15%CO2 and 5%CO ,for a reference of 0 0C and 1bar .determine i)partial pressures of the constituents ii)Gas constant of the mixture. 10) Find the increase in entropy when 2 kg of oxygen at 60 0C are mixed with 6 kg of nitrogen at same temperature. The initial pressure of each constituent is 103 KPa and is same as that of the mixture. 11) Show that for a reversible adiabatic process executed by an ideal gas, the following relations holds good. (i) Pvγ=constant, (ii)Tvγ-1=constant
QUESTION NO 8 Write short notes on the following (i)Psychrometer (ii)Cooling and dehumidification of air (iii)Enthalpy of formation (iv) Gibbs function (v)Clausis clapeyron equation (vi)Joule Kelvin effect (vii)Actual vapour compression cycle
(viii)Refrigerants (ix)Law of corresponding states
