Common Data for Question 01 & 02 & 03
In the figure shown, the system is a pure substance kept in a piston-cylinder arrangement. The system is initially a two-phase mixture containing 1 kg of liquid and 0.03 kg of vapour at a pressure of 100kPa. Initially, the piston rests on a set of stops, as shown in the figure. A pressure of 200kPa is required to exactly balance the weight of the piston and the outside atmospheric pressure. Heat transfer takes place into the system until its volume increases by 50%. Heat transfer to the system occurs in such a manner that the piston, when allowed to move, does so in a very slow(quasi-static / quasi-equilibrium) process. The thermal reservoir from which heat is transferred to the system as a temperature of 4000C. Average temperature of the system boundary can be taken as 1750C. Heat transfer to the system is 1kJ, during which its entropy increases by 10 J/K
Specific volume of liquid (vf) and vapour (vg) phases, as well as values of saturation temperatures, are given in the table below.
|
Pressure (kpa)
|
Saturation temperature, (Tsat(0C)
|
vf (m3/kg)
|
Vg (m3/kg)
|
|
100
|
100
|
0.001
|
0.1
|
|
200
|
200
|
0.0015
|
0.002
|
- At the end of the process, which one of the following situations will be true?
(a) superheated vapor will be left in the system
(b) no vapour will be left in the system
(c) a liquid + vapour mixture will be left in the system
(d) the mixture will exist at a dry saturate vapour state
2 . The net entropy generation (considering the system and the thermal reservoir together) during the process is closest to
(a) 7.5 J/K (b) 7.7 J/K
(c) 8.5 J/K (d) 10 J/K
3 . Steam enters a turbine at 30bar, 3000C (u=2750 kJ/kg, h=2993 kJ/kg) and exists the turbine as saturated liquid at 15 kPa (u=225 kJ/kg, h=226 kJ/kg). Heat loss to the surrounding is 50 kJ/kg of steam following through the turbine. Neglecting changes in kinetic energy and potential energy, the work output of the turbine (in kJ/kg of steam) is__________