Application of SFEE

Q. A blower handles 1 kg/s of air at ${20}^o$C and consumes a power of 15 kW. The inlet and outlet velocities are 100 m/ s and 150 m/ s respectively. The exit air temperature, assuming adiabatic conditions is ________${}^{o}C$

(Take $c_p$ of air as 1.005 kJ/ kgK

1. ${28.70}^{\circ }C$
2. ${23.70}^{\circ }C$
3. ${58.50}^{\circ }C$
4. ${18.90}^{\circ }C$

Q. In an oil cooler, oil flows steadily through a bundle of metal tubes submerged in steady stream of cooling water. Under steady conditions oil enters at ${90}^o$C and leaves at ${30}^o$C. Water enters at ${25}^o$C and leaves at ${70}^o$C. Enthalpy of oil, $h=1.68t+10.5\times {10}^{-4}{t}^2$ kJ/kg (temperature is taken in ${}^o$C). The cooling water required for cooling 2.78 kg/s of oil is _________ $kg/s$.

1. 1
2. 2.6
3. 1.6
4. 2

Q. Two streams of air, one at 1 bar, ${27}^{o}C$ and velocity of 30 m/ s and the other at 5 bar, 227°C, and velocity of 50 m/s, are mixed in equal proportion in a chamber from which heat at the rate of 100 kJ/ kg is removed. The mixture is then passed through an adiabatic nozzle. If the temperature of the air leaving the nozzle is 27°C and its $C_p=1.005$ kJ/ kg-K then, the velocity of steam issuing out of the nozzle is _______ m/s.

1. 50.05
2. 58.76
3. 51.96
4. 41.96

Q. In a steady flow, adiabatic turbine, the change in the internal energy, enthalpy, kinetic energy, and potential energy of working fluid from intel to exit are -200 kJ/kg, -340 kJ/kg, -40 kJ/kg, and 0 kJ/kg. The work developed by turbine is ________ kJ/kg.

1. 280
2. 300
3. 380
4. 200

Q. A compressor receives 0.2 kg/s of R-134a at 250 kPa, -10${}^{\circ }C$ (h=393 kJ/kg) and delivers it at 1100 kPa. 90${}^{\circ }C$n (h=418 kJ/kg). The power input is measured to be 8 kW. The compressor has heat transfer to air at 100 kPa coming in at 20 ${}^{\circ }C$ and leaving at ${26}^{\circ }C$. The mass flow rate of air is _____ kg/s.

1. $4.975kg/s$
2. $0.4975kg/s$
3. $0.6975kg/s$
4. $2.4975kg/s$