申論題

6. (30%) A team of engineers for a defense contractor are commissioned by the naval force of a global power to build a nuclear submarine. The specs for the submarine, as demanded by the navy in order to designate the submarine as the Los Angeles Class, is as follows,
 ●Weight: 7,000 tones (1 tone =1,000 kg)
●Top speed when submerged: 20 knots (~37 km/hr)
●Acceleration from rest to top speed when submerged: 1 minute
It is also estimated that all the friction experienced by a submarine submerged in sea water is 3.86 x 10⁶ N. Moreover, such a submarine is conventionally propelled by a steam-driven turbine, with the high-pressure steam generated from a boiler heated by the nuclear reaction. Now, you are assigned the most critical part of the project - design the heat exchange system for the power generation system of the submarine - and need to determine the operation condition of the heat exchanger. Before that can be done, several other operation parameters have to be known in advance.

(1) In the steady-state operation, steam leaving the turbine is condensed and recycled back to the boiler. For the sake of efficacy, steam from the outlet of the turbine is set to 1 bar and 100℃. Given the steam fow rate of 20 kgs, determine the minimal temperature and pressure of steam entering the turbine (assuming entropy generation). (4 pts)