(a)A 12-V battery for an aircraft is completely discharged. It is then placed on a quick-charger,...

 

Transcribed Image Text:

(a)A 12-V battery for an aircraft is completely discharged. It is then placed on a quick-charger, and a current of 10 A is fed to the battery for a period of 1 hour. The battery, which has a mass of 10 kg, is then loaded aboard an aircraft for delivery. The aircraft flies at 194.4 m/s at an altitude of 2000 m above the ground. (i) What is the change in the total energy E of the battery from its discharged state on the ground to its state aboard the aircraft during flight? [6 marks] (ii) What percentage of the energy change is due to potential energy? [2 marks] (iii) How much work was done on the battery during the charging process? [2 marks] (b) As shown in Fig. QSB 25b, a steam turbine at steady state is operated at part load by throttling the steam to a lower pressure before it enters the turbine. Before throttling, the pressure and temperature are, respectively, 1.5 MPa and 320 °C. After throttling, the pressure is 1 MPa. At the turbine exit, the steam is at .08 bar and a quality of 90%. Heat transfer with the surroundings and all kinetic and potential energy effects can be ignored. Determine (a) the temperature at the turbine inlet, in °C and the power developed by the turbine, in kJ/kg of steam flowing. [15 MARKS] P₁ = 1.5 MPa T₁ = 320°C Valve BERTYA P₂ = 1 MPa Fig. QSB 25b 3 SA BEN Power out P3.08 bar x3 = 90% * (a)A 12-V battery for an aircraft is completely discharged. It is then placed on a quick-charger, and a current of 10 A is fed to the battery for a period of 1 hour. The battery, which has a mass of 10 kg, is then loaded aboard an aircraft for delivery. The aircraft flies at 194.4 m/s at an altitude of 2000 m above the ground. (i) What is the change in the total energy E of the battery from its discharged state on the ground to its state aboard the aircraft during flight? [6 marks] (ii) What percentage of the energy change is due to potential energy? [2 marks] (iii) How much work was done on the battery during the charging process? [2 marks] (b) As shown in Fig. QSB 25b, a steam turbine at steady state is operated at part load by throttling the steam to a lower pressure before it enters the turbine. Before throttling, the pressure and temperature are, respectively, 1.5 MPa and 320 °C. After throttling, the pressure is 1 MPa. At the turbine exit, the steam is at .08 bar and a quality of 90%. Heat transfer with the surroundings and all kinetic and potential energy effects can be ignored. Determine (a) the temperature at the turbine inlet, in °C and the power developed by the turbine, in kJ/kg of steam flowing. [15 MARKS] P₁ = 1.5 MPa T₁ = 320°C Valve BERTYA P₂ = 1 MPa Fig. QSB 25b 3 SA BEN Power out P3.08 bar x3 = 90% *