Question 1

A steam power cycle with regeneration as shown below on the T-s diagram employs a single open feedwater heater for efficiency improvement. The fluids mix with each other in an open feedwater heater. The turbine is isentropic and the input (bleed) to the feedwater heater from the turbine is at state 2 as shown in the figure. Process 3-4 occurs in the condenser. The pump work is negligible. The input to the boilder is at state 5. The following information is available from the steam tables?

Question 2

In the Rankine cycle for a steam power plant the turbine entry and exit enthalpies are 2803 kJ/kg and 1800 kJ/kg, respectively. The enthalpies of water at pump entry and exit are 121 kJ/kg and 124 kJ/kg respectively. The specific steam consumption (in kg/kWh) of the cycle is, The pressure ratio across a gas turbine (for air, specific heat at constant pressure, cp = 1040 J/ kg K and ratio of specific heats = 1.4) is 10. If the inlet temperature to the turbine is 1200 K and the isentropic efficiency is 0.9, the gas temperature at turbine exit is?

Question 3

In a steam power plant operating on a ideal Rankine cycle, superheated steam enters the turbine at 3 MPa and 350C. The condenser pressure is 75 kPa. The thermal efficiency of the cycle is ________%. Given data: For saturated liquid, at p = 75 kPa, hf = 384.39 kJ/kg, vf= 0.001037 m3/kg, sf= 1.213 kJ/kgK. At 75 kPa, hfg= 2278.6 kJ/kg, sfg= 6.2434 kJ/kgK At P = 3 MPa and T = 350C (superheated steam), h = 3115.3 kJ/kg, s = 6.7428 kJ/kgK.?

Question 4

The following data pertain to a single stage impulse steam turbine: Nozzle angle = 20 Blade velocity = 200 m/s Relative steam velocity at entry = 350 m/s Blade inlet angle = 30 Blade exit angle = 25 If blade friction is neglected the work done per kg steam is, A steam power plant has the boiler efficiency of 92%, turbine efficiency (mechanical) of 94%, generator efficiency of 95% and cycle efficiency of 44%. If 6% of the generated power is used to run the auxiliaries, the overall plant efficiency is?

Question 5

If one mole of H2gas occupies a rigid container wi t h a capaci t y of 1000 l i t er s and t he temperature is raised from 27C to 37C, the change in pressure of the contained gas (round off to two decimal places), assuming ideal gas behavior, is, The Vander Waals equation of state is {P + (a / c)} (v - b)= RT, where p is pressure, v is specific volume, T is temperature and R is characteristic gas constant. The SI unit of a is?

Question 6

2 moles of oxygen are mixed adiabatically with another 2 moles of oxygen in a mixing chamber, so that the final total pressure and temperature of the mixtures become same as those of the individual constituents at their initial states. The universal gas constant is given as R. The change in entropy due to mixing, per mole of oxygen, is given by?

Question 7

Water has a critical specific volume of 0.003155 m3/kg. A closed and rigid steel tank of volume 0.025 m3contains a mixture of water and steam at 0.1 MPa. The mass of the mixture is 10 kg. The tank is now slowly heated. The liquid level inside the tank, A tank of volume 0.05 m3contains a mixture of saturated water and saturated steam at 200C. The mass of the liquid present is 8 kg. The entropy (in kJ/kgK) of the mixture is ________ (correct of two decimal places) Property data for saturated steam and water are: At 200C [Psat= 1.5538 MPa] vf= 0.001157 m3/kg, vg= 0.12736 m3/kg sfg= 4.1014 kJ/kgK, sf= 2.3309 kJ/kgK?

Question 8

Water flowing at the rate of 1 kg/s through a system is heated using an electric heater such that the specific enthalpy of the water increases by 2.50 kJ/kg and the specific entropy increases by 0.007 kJ/kg.K. The power input t o t he electric heater is 2.50 kW. There is no other work or heat interaction between the system and the surroundings. Assuming an ambient temperature of 300 K, the irreversibility rate of the system is, One side of a wall is maintained at 400 K and the other at 300 K. The rate of heat transfer through the wall is 1000 W and the surrounding temperature is 25C. Assuming no generation of heat within the wall, the irreversibility (in W) due to heat transfer through the wall is.?

Question 9

The pressure, temperature and velocity of air flowing in pipe are 5 bar, 500 K and 50 m/s, respectively. The specific heats of air at a constant pressure and at constant volume are 1.005 kJ/kgK and 0.718 kJ/kgK, respectively. Neglect potential energy. If the pressure and temperature of the surroundings are 1 bar and 300 K, respectively, the available energy in kJ/ kg of the air stream is?

Question 10

During a non-flow thermodynamic process (1- 2) execut ed by a per fect gas, t he heat interaction is equal to the work interaction (Q1.2= W12) when the process is, A vehicle powered by a spark ignition engine follows air standard Otto cycle ( = 1.4). The engine generates 70 kW while consuming 10.3 kg/hr of fuel. The calorific value of fuel is 44000 kJ/kg. The compression ratio is (correct to two decimal places).

Question 12

A gas turbine with air as the working fluid has an isentropic efficiency of 0.70 when operating at a pressure ratio of 3. Now, the pressure ratio of t he t ur bi ne i s i ncr eased t o 5, whi l e maintaining the same inlet conditions. Assume air as a perfect gas with specific heat ratio = 1.4. I f the specific work output remains the same for both the cases, the isentropic efficiency of t he t ur bi ne at t he pr essur e r at i o of 5 is?

Question 13

Consider a simple gas turbine (Brayton) cycle and a gas turbine cycle with perfect regeneration. In both the cycles, the pressure ratio is 6 and the ratio of the specific heats of the working medium is 1.4. The ratio of minimum to maximum temperatures is 0.3 (with temperatures expressed in K) in the regenerative cycle. The ratio of the thermal efficiency of the simple cycle to that of the regenerative cycle is?

Question 14

In a Rankine cycle, the enthalpies at turbine entry and outlet are 3159 kJ/kg and 2187 kJ/ kg, respectively. If the specific pump work is 2 kJ/kg, the specific steam consumption (in kg/ kWh) of the cycle based on net output is,

Steam with specific enthalpy (h) 3214 kJ/kg enters an adiabatic turbine operating at steady state with a flow rate 10 kg/s. As it expands, at a point where his 2920 kJ/kg, 1.5 kg/s is extracted for heating purposes. The remaining 8.5 kg/s further expands to the turbine exit, where h = 2374 kJ/kg. Neglecting changes in kinetic and potential energies, the net power output (in kW) of the turbine is?

Question 15

For a gas turbine power plant, identify the correct pair of statements. P. Smaller in size compared to steam power plant for same power output Q. Starts quickly compared to steam power plant R. Works on the principle of Rankine cycle S. Good compatibility with solid fuel, In an ideal Brayton cycle, atmospheric air (ratio of specific heats, c/cv= 1.4, specific heat at constant pressure = 1.005 kJ/kgK) at 1 bar and 300 K is compressed to 8 bar. The maximum temperature in the cycle is limited to 1280 K. If the heat is supplied at the rate of 80 MW, the mass flow rate (in kg/s) of air required in the cycle is?r