Question 5

Question 1

An ideal Brayton cycle, operating between the pressure limits of 1 bar and 6 bar, has minimum and maximum temperatures of 300 K and 1500 K. The ratio of specific heats of the working fluid is 1.4. The approximate final temperature in Kelvin at the end of the compression and expansion processes are respectively?

Question 2

The values of enthalpy of steam at the inlet and outlet of a steam turbine in a Rankine cycle are 2800 kJ/kg and 1800 kJ/kg respectively. Neglecting pump work, the specific steam consumption in kg/kW hour is

Question 3

A compressor undergoes a reversible, steady flow process. The gas at inlet and outlet of the compressor is designated as state 1 and state 2 respectively. Potential and kinetic energy changes are to be ignored. The following notations are used: v = specific volume and P = pressure of the gas. The specific work required to be supplied to the compressor for this gas compression process is?

Question 5

An engine working on air standard Otto cycle is supplied with air at 0.1 MPa and 35C. The compression ratio is 8. The heat supplied is 500 kJ/kg. Property data for air: cp= 1.005 kJ/ kgK, cv= 0.718 kJ/kgK, R = 0.287 kJ/kgK. The maximum temperature (in K) of the cycle is, An air-standard Diesel cycle consists of the following processes: 1-2: Air is compressed isentropically. 2-3: Heat is added at constant pressure. 3-4: Air expands isentropically to the original volume. 4-1: Heat is rejected at constant volume. If and T denote the specific heat ratio and temperature, respectively, the efficiency of the cycle is?

Question 6

For the same values of peak pressure, peak temperature and heat rejection, the correct order of efficiencies for Otto, Duel and Diesel cycles is, Air enters a diesel engine with a density of 1.0 kg/m3. The compression ratio is 21. At steady state, the air intake is 30 10-3kg/s and the net work output is 15 kW. The mean effective pressure (kPa) is?

Question 7

In a compression ignition engine, the inlet air pressure is 1 bar and the pressure at the end of isentropic compression is 32.42 bar. The expansion ratio is 8. Assuming ratio of specific heats () as 1.4, the air standard efficiency (in percent) is, A diesel engine has a compression ratio of 17 and cut-off takes place at 10% of the stroke. Assuming ratio of specific heats () and the air standard efficiency (in%) is?

Question 8

In an air-standard Otto cycle, air is supplied at 0.1 MPa and 308 K. The ratio of the specific heats () and the specific gas constant (R) of air are 1.4 and 288.8 J/kgK, respectively. If the compression ratio is 8 and the maximum temperature in the cycle is 2660 K, the heat (in kJ/kg) supplied to the engine is, The crank radius of a single-cylinder IC engine is 60 mm and the diameter of the cylinder is 80 mm. The swept volume of the cylinder in cm3is?

Question 9

In an air-standard Otto cycle, the compression ratio is 10. The condition at the beginning of the compression process is 100 kPa and 27C. Heat added at constant volume is 1500 kJ/kg, while 700 kJ/kg of heat is rejected during the other constant volume process in the cycle. Specific gas constant for air = 0.287 kJ/kgK. The mean effective pressure (in kPa) of the cycle is?

Question 10

A thermal power plant operates on a regenerative cycle with a single open feedwater heater, as shown in the figure. For the state points shown, the specific enthalpies are: h1= 2800 kJ/kg and h2= 200 kJ/kg. The bleed to the feedwater heater is 20% of the boiler steam generation rate. The specific enthalpy at state 3 is?

Question 11

In a gas turbine, hot combustion products with the specific heats cp= 0.98 kJ/kgK, and cv= 0.7538 kJ/kgK enters the turbine at 20 bar, 1500 K and exits at 1 bar. The isentropic efficiency of the turbine is 0.94. The work developed by the turbine per kg of gas flow is?

Question 12

Consider an actual regenerative Rankine cycle with one open feed water heater. For each kg steam entering the turbine, if m kg steam with a specific enthalpy of h1is blade from the turbine, and the specific enthalpy of liquid water entering the heater is h2, then h3the specific enthalpy of saturated liquid leaving the heater is equal to, A rigid container of volume 0.5 m3contains 1.0 kg of water at 120C (vf= 0.00106 m3/kg, vg= 0.8908 m3/kg). The state of water is?

Question 13

For water at 25C, dps/dTs= 0.189 kPa/K (psis the saturation pressure in kPa and Tsis the saturation temperature in K) and the specific volume of dry saturated vapour is 43.38 m3/ kg. Assume that the specific volume of liquid is negligible in comparison with that of vapour. Using the Clausius-Clapeyron equation, an estimate of the enthalpy of evaporation of water at 25C (in kJ/kg) is, A pure substance at 8 MPa and 400C is having a specific internal energy of 2864 kJ/kg and a specific volume of 0.03432 m3/kg. Its specific enthalpy (in kJ/kg) is?

Question 14

1.5 kg of water is in saturated liquid state at 2 bar (vf= 0.001061 m3/kg, uf= 504.0 kJ/kg, hf= 505 kJ/kg). Heat is added in a constant pressure process till the temperature of water reaches 400C (v = 1.5493 m3/kg, u = 2967.0 k J/kg, h = 3277.0 kJ/kg). The heat added (in kJ) in the process is, A steel billet of 2000 kg mass is to be cooled from 1250 K to 450 K. The heat released during this process is to be used as a source of energy. The ambient temperature is 303 K and specific heat of steel is 0.5 kJ/kgK. The available energy of this billet is?

Question 15

Considering the relationship TdS = dU + pdV between the entropy (S), internal energy (U), pressure (p), temperature (T) and volume (V), which of the following statements is correct, A heat pump absorbs 10 kW of heat from outside environment at 250K while absorbing 15 kW of work. It delivers the heat to a room that must be kept warm at 300 K. The Coefficient of Performance (COP) of the heat pump is?t